Dissertations / Theses: 'Zirconi'

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LIBERATO. "Stratigraphic, sedimentological and provenance study on the Permian-Triassic sequences of southern Gondwana: comparison between Victoria Land (Antarctica) and Tasmania and paleoenvironmental implications." Doctoral thesis, Università di Siena, 2020. http://hdl.handle.net/11365/1118448.

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La tesi di dottorato è stata svolta seguendo un approccio multidisciplinare che ha riguardato lo studio stratigrafico-sedimentologico, petrografico e geochimico di depositi fluviali Permo-Triassici affioranti in Terra Vittoria meridionale e settentrionale. Con lo scopo di ottenere e comprendere le varie peculiarità di ogni singola unità deposizionale (Permo-Triassica, affiorante ad Allan Hills, Terra Vittoria meridionale), è stato eseguito uno studio di dettaglio multidisciplinare con diverse tecniche e metodologie analitiche. I risultati prodotti sono stati utilizzati per comparare aree limitrofe come il Morris Basin (zona transizionale tra la TVm e TVs), in modo da poter ricostruire l’evoluzione geologico-stratigrafica. I dati sono presentati nella Tesi nell’ordine seguente: 1) comprensione e ricostruzione geologico-stratigrafica dell’area di interesse ad Allan Hills (Terra Vittoria meridionale, TVm, Antartide) 2) analisi sedimentologica (analisi di facies) 3) analisi composizionale delle arenarie di Allan Hills (TVm) e Morris Basin (TVm-TVs, analisi modale con metodo Gazzi-Dickinson) 4) studio dei minerali pesanti presenti in sezione sottile (Allan Hills e Morris Basin, conteggio per clasti) 5) analisi composizionale dei granati e delle muscoviti detritici di Allan Hills (TVm) 6) geocronologia degli zirconi detritici di Allan Hills (TVm) Nella prima parte del dottorato è stato fondamentale reinterpretare ed elaborare circa 800 metri di colonne stratigrafiche ottenute nella fase di campagna dai ricercatori in Antartide, per comprendere i rapporti stratigrafici e la geologia dell’area (punto 1). La sezione geologica del settore nord-est di Allan Hills mostra un andamento degli strati debolmente inclinati verso N-NE (monoclinale) di una decina di gradi. La successione Permo-Triassica affiora in relativa continuità fatta eccezione per aree con diffuse coperture detritiche-nivali e dicchi Giurassici. Il punto 2 è stato acquisito con uno studio ad alta risoluzione (scala decimetrica) eseguendo un’analisi di facies, al fine di ricostruire i paleoambienti della successione di Allan Hills. Seguendo lo schema classificativo ed interpretativo di Miall (2014), più di una decina di litofacies e associazioni di facies sono state interpretate. Il risultato più rilevante sembrerebbe evidenziare fasi trasgressive nel Permiano medio-superiore e nel Triassico medio-superiore, come probabile risposta a cambiamenti morfo-strutturali bacinali dovuti a fattori tettonici e a possibili cambiamenti climatici (come evidenziato nella Formazione Feather Conglomerate). In seguito, a scala microscopica sono state caratterizzate in modo quantitativo le arenarie (punti 3 e 4), al fine di poter individuare differenti petrofacies suddivise per unità formazionali. Differenze rilevanti sono state riscontrate tra le arenarie Permiane e quelle Triassiche; in primis una maggiore maturità composizionale dovuta ad un maggiore trasporto (più cicli di sedimentazione) e ad un clima umido con un weathering index intenso al passaggio PTT (Permian-Triassic Transition). Allo stesso modo, lo studio composizionale del granato e della muscovite (punto 5) sembra evidenziare un maggiore grado metamorfico di provenienza, nel Permiano medio-superiore (Formazione della Weller Coal Measures) e Triassico medio-superiore (Formazione della Lashly), rispetto al Triassico inferiore (Feather Conglomerate). In quest’ultima infatti, le muscoviti sono meno ricche in fengite ed i granati diminuiscono drasticamente (nessun dato composizionale). Questo fenomeno indica probabilmente un repentino cambiamento climatico a favore dell’alterazione. Questo approccio è stato di aiuto nel definire ulteriormente le differenze tra le unità Permiane e Triassiche e le loro provenienze. Con lo stesso scopo, sono state effettuate le datazioni su zirconi detritici di Allan Hills (TVm, punto 6). Tre aspetti fondamentali ne risultano: - nei sedimenti Permiani lo spettro di età è più ampio e si hanno buone percentuali in tutti i range, variabili dal Devoniano all’Archeano. Picchi di età “greenvilliana” sono da evidenziare mentre non sono presenti zirconi Permo-Triassici. - Gli zirconi detritici del Triassico inferiore hanno origine principalmente dall’Orogene di Ross, mostrando forse un unroofing regionale. Con un picco minore, ma pur sempre evidente, ci sono età “greenvilliane”. - Nel Triassico medio-superiore si registra l’attività vulcanica Permo-Triassica del margine meridionale del Gondwana. Sembra evidente come il bacino della Terra Vittoria meridionale fosse, durante il Permiano, morfologicamente separato dal bacino contiguo nelle Central Transantarctic Mountains (CTM). Un processo di cattura fluviale, probabilmente da porsi alla transizione tra il Permiano superiore ed il Triassico inferiore, potrebbe spiegare sia lo spettro composizionale che di età degli zirconi. Una volta ottenuto un quadro completo di ogni singola unità stratigrafica, è stata effettuata una prima comparazione litologico-petrografica con una parte significativa di campioni arenacei sparsi per la Terra Vittoria (Morris Basin e Terra Vittoria settentrionale). Con la missione in Tasmania (febbraio 2019), è stato possibile confrontare in modo preliminare le arenarie delle successioni Tasmane coeve a quelle antartiche. Granulometricamente più fini di quelle del Victoria Group, mostrano rapporti sabbia/fango in alcuni casi confrontabili (dal Triassico inferiore al superiore). Il PTT sembra collocarsi tra superfici di discordanza semplice meno erosivi a sud rispetto al settore nord-nord-est del bacino Tasmano. Questo potrebbe essere attribuito ad una estrema variabilità degli ambienti sedimentari paleozoici e dei processi deposizionali e tettonici. Si rinvengono spessori ingenti di livelli di siltiti argillose rossastre (paleosuoli) con spessori molto variabili. Al contrario, dai dati di questo studio, il PTT ad Allan Hills potrebbe connotarsi per avere caratteri transizionali o di paraconcordanza. Il confronto geologico tra macroregioni diverse e distanti, Terra Vittoria settentrionale e meridionale (TVs TVm), è stato anche rafforzato grazie allo studio analitico di tesi e articoli prodotti negli anni precedenti da altri studiosi. I risultati più importanti provengono dall’analisi di facies e dalle composizioni mineralogiche: - Tutte le petrofacies del Morris Basin sono correlabili con quelle di Allan Hills (TVm) - Una parte dei depositi del Permiano nel bacino della TVs sembra contenere più litici plutonici e metamorfici (circa 5%) rispetto a successioni analoghe ad Allan Hills ed in Terra Vittoria meridionale in generale. - La litostratigrafia di Thern Promontory (TVs) sembra affine, in termini di facies e petrofacies, ad una fase post-glaciale Permiana, come evidenziano alcuni dati in TVm, anche se con spessori notevolmente ridotti. - Le arenarie di Stewart Heights (TVs) e di Pudding Butte (Morris Basin) hanno caratteri sedimentologici e petrologici comparabili con quelle del Triassico inferiore ad Allan Hills (TVm). - Nella Section peak Fm. (simil-Lashly Fm) sono composizionalmente litareniti e litareniti feldspatiche come quelle della SVL. - I bacini della TVs e TVm, in un periodo compreso tra il Triassico medio-Giurassico inferiore, registrano la comparsa di litici vulcanici lavici (Formazioni di Section Peak e Lashly). - Anche per i granati e le miche detritiche triassiche le composizioni sono correlabili tra la TVs e TVm. In conclusione, il presente studio pone nuovi vincoli petro-stratigrafici e paleogeografici in Terra Vittoria meridionale e settentrionale, in quello che era il paleomargine meridionale del Gondwana. In particolare, lo studio sedimentologico e di provenienza dei sopracitati depositi ha consentito di produrre ed apportare una grande mole di nuovi dati, la cui elaborazione consente di evidenziare una storia geologica evolutiva ben più articolata e complessa di quella conosciuta.

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PASTORE, GUIDO. "Sand provenance and dispersal in the Sahara and Kalahari deserts: fluvial aeolian interactions and climatic implications." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2023. https://hdl.handle.net/10281/404096.

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Questa tesi presenta lo studio della composizione delle sabbie dei più grandi deserti africani e dei fiumi limitrofi al fine di illustrare gli effetti dell'interazione tra processi fluviali ed eolici sul trasporto di sedimenti in ambiente arido. Le sabbie del Sahara, del Kalahari e dello Zambesi sono state analizzate mediante petrografia, mineralogia della frazione pesante e geocronologia U-Pb di zirconi detritici. Per il caso di studio dello Zambesi sono stati analizzati anche la geochimica elementare, gli isotopi del Nd e i minerali delle argille. I campi di dune del Sahara sono, con poche eccezioni, composti da pura sabbia quarzosa con suite di minerali pesanti molto impoverite, dominate da minerali ultrastabili. La composizione varia solamente lungo la Valle del Nilo, in prossimità della catena dell'Anti-Atlante e alla provincia vulcanica libica. La sabbia delle dune del Kalahari è costituita principalmente da quarzo associato a minerali pesanti ultrastabili. La composizione varia solo ai margini occidentali e orientali del deserto, riflettendo in parte l’apporto fluviale di primo ciclo dai basamenti cristallini nella Namibia centrale, nello Zimbabwe occidentale e nelle dune vicino alle cascate Vittoria dove i sedimenti sono erosi dalle lave del Karoo. La morfologia segmentata del fiume Zambesi si riflette nella sua mineralogia e geochimica. La sabbia quarzosa erosa dalle dune del deserto del Kalahari viene progressivamente arricchita in frammenti litici basaltici e clinopirosseno. Successivamente nuovo apporto di sedimenti avviene a valle del lago Kariba, documentando una graduale diminuzione del quarzo e dei minerali ultrastabili. La composizione diventa quarzo-feldspatica nel tratto finale. L'abbondanza di feldspato nella sabbia del basso Zambesi non ha equivalenti tra i grandi fiumi sulla Terra e supera di gran lunga quella nei sedimenti del delta e della piattaforma, rivelando che il segnale di provenienza dell’alto Zambezi ha cessato di essere propagato a valle dopo la chiusura delle grandi dighe. La smectite, dominante nei fanghi generati dai basalti del Karoo o nel clima equatoriale delle pianure mozambicane, prevale su illite e kaolinite. La geochimica indica: l'aggiunta di quarzo per riciclo; l'erosione dei basalti del Karoo; l’erosione dei basamenti precambriani. Lo studio di Sahara e Kalahari consente di mettere a confronto deserti dominati dai processi eolici e deserti caratterizzati da una consistente interazione fluvio-eolica. Nel Sahara, la maggior parte della sabbia sembra essere riciclata da arenarie quarzose e il principale meccanismo erosivo e di trasporto è il vento. Nel Kalahari, i sedimenti sono trasportati dai fiumi che, erodendo gli orogeni ai fianchi del deserto, accumulano e omogeneizzano il detrito al centro del bacino grazie all’azione eolica. Lo studio permette di riconsiderare criticamente diversi dogmi della sedimentologia, come il presunto aumento della “maturità” mineralogica durante il trasporto fluviale: i sedimenti dell’alto Zambezi, erosi dalle dune del Kalahari e ricchi di quarzo, vengono progressivamente diluiti da sedimenti lito-feldspatici lungo il corso del fiume. Gli indici geochimici e la composizione dei fanghi sembrano indicare maggiore alterazione chimica nell'arido bacino dell’alto Zambesi rispetto al più umido Zambesi centrale e inferiore, testimoniando che il segnale di “paleo-alterazione del Kalahari” registrato nei sedimenti delle dune viene trasportato a valle fino alla foce.
This thesis presents a study of the composition of sand from desert dunes and adjacent rivers across the African continent to illustrate the effects of the interplay between fluvial and aeolian processes on sediment transport in desertic environments. The Sahara, Kalahari and Zambezi samples were analyzed by bulk-petrography, heavy-mineral, and detrital-zircon U–Pb geochronology. For the Zambezi case study, elemental geochemistry, Nd isotopes and clay minerals were also analyzed. Saharan dune fields are generally composed of pure quartzose sand with very poor heavy-mineral suites dominated by ultrastable minerals. Relatively varied compositions characterize sand along the Nile Valley, the southern front of the Anti-Atlas belt and near a basaltic field in Libya. Kalahari dune sand mostly consists of monocrystalline quartz associated with durable heavy. Composition varies only at the western and eastern edges of the desert, reflecting partly first-cycle fluvial supply eroded from crystalline basements of Cambrian to Archean age in central Namibia and western Zimbabwe. Basaltic detritus from Jurassic Karoo lavas is dominant in dunes near Victoria Falls. The segmented morphology of Zambezi River is reflected by its mineralogy and geochemistry. Pure quartzose sand recycled from Kalahari Desert dunes in the uppermost tract is next progressively enriched in basaltic rock fragments and clinopyroxene. Sediment load is renewed ﬁrst downstream of Lake Kariba, documenting a stepwise decrease in quartz and durable heavy minerals. Composition becomes quartzo-feldspathic in the lower tract. Feldspar abundance in Lower Zambezi sand has no equivalent among big rivers on Earth and far exceeds that in sediments of the northern delta, shelf, and slope, revealing that provenance signals from the upper reaches have ceased to be transmitted across the routing system after closure of the big dams. Irumide ages predominate over Pan-African, Eburnean, and Neoarchean ages. Smectite, dominant in mud generated from Karoo basalts or in the equatorial climate of the Mozambican lowlands, prevails over illite and kaolinite. Elemental geochemistry reflects quartz addition by recycling, supply from Karoo basalts, and first-cycle provenance from Precambrian basements. Sahara and Kalahari case studies allow to study in situ sand generation by wind erosion versus external fluvial supply in arid environment. In the Sahara, most sand appears to be recycled from rocks with high sand-generation potential, and the main transport mechanism is the wind saltation and dune movement. In Kalahari, sediments are fed by rivers by first cycle erosion of exposed orogens at the flanks of the desert and therein homogenised. The contrasting effect of strong recycling by wind and fresh supply from rivers are the key factor for most deserts studied in literature and their identification in terms of mineralogy and provenance is proved to be precious for present and past climatic debate. In addition, evaluating the results from the Kalahari and Zambezi studies allows to critically reconsider several dogmas, such as the supposed increase of mineralogical “maturity” during long-distance ﬂuvial transport. This is strongly affected by provenance factors: quartz-rich recycled Kalahari dune sand is progressively diluted along the Zambezi River by sediment supplied by different crustal domains. Inheritance of the “Kalahari paleo-weathering signal” by Zambezi River is highlighted also by geochemical indexes and mud composition which appear to be oddly more affected by weathering in the arid Uppermost Zambezi catchment than in the wetter Middle and Lower Zambezi.

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Carbonneau, Xavier. "Etude des propriétés thermomécaniques de mullite zircone et de zircon." Lyon, INSA, 1997. http://theses.insa-lyon.fr/publication/1997ISAL0105/these.pdf.

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Cette étude porte sur la caractérisation du comportement mécanique de mullite zircone et de zircon entre 1000 et l 300°C. Une caractérisation microstructurale fine des différentes nuances est tout d'abord réalisée, avec notamment de nombreuses observations en microscopie transmission. Ceci a pour but de mieux connaître la localisation et la composition de la phase vitreuse. La propagation des fissures à haute température est ensuite étudiée grâce à des essais de double torsion. La guérison des fissures observée au cours de ces essais est plus particulièrement étudiée dans le cas du zircon. Des mesures de spectrométrie mécanique ont aussi été réalisées pour mettre en évidence des mécanismes liés à la présence de phase vitreuse. Enfin une étude du comportement en fluage a été réalisée par des essais de flexion. Ces résultats sont complétées par une série d'essais sur des éprouvettes préalablement indentées ce qui permet de mieux comprendre le comportement à la rupture, et a montré l'existence d'un seuil dans le mode de propagation des fissures. Ces résultats ont pu être rapprochés de ceux obtenus en double torsion
The high temperature mechanical properties of mullite zirconia obtained by reaction sintering, and zircon have been studied. Numerous transmission electron microscopy observations have been conducted to obtain an accurate microstructural characterization, and a better knowledge of the glassy phase composition and localization. Crack propagation is then measured at high temperature using the double torsion technique. Crack healing observed during these tests is especially studied in the case of zircon. Internal friction measurements have also been conducted to try to characterize the glassy phase. In addition, the creep behavior has been studied using bending tests. These results are completed with others obtained on previously indented specimens to better understand the fracture behavior. A threshold has been observed in the crack propagation in zircon. These results are close to those obtained with the double torsion technique

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Carbonneau, Xavier Fantozzi Gilbert. "Etude des propriétés thermomécaniques de mullite zircone et de zircon." Villeurbanne : Doc'INSA, 1998. http://docinsa.insa-lyon.fr/these/pont.php?id=carbonneau.

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Lê, Đưc Huy Daniel Philippe Laffez Patrick. "Contribution à l'étude structurale et vibrationnelle des couches minces de zircone ZrO2 déposées sur alliage Zy-4." [S.l.] : [s.n.], 2004. http://cyberdoc.univ-lemans.fr/theses/2004/2004LEMA1021.pdf.

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Reproduction de : Thèse de doctorat : Sciences des matériaux : Le Mans : 2004. Reproduction de : Thèse de doctorat : Sciences des matériaux : Ecole Normale Supérieure de Hanoï : 2004.
Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre. Bibliogr. en fin de chapitres.

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Minnaar, Ettiénne Gerald. "Microstructural and analytical characterization of plasma dissociated zircon." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1015972.

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This dissertation focuses on the microstructural and analytical characterization of plasma dissociated zircon (PDZ) which was produced by the South African Nuclear Energy Corporation (NECSA). The techniques used in the analysis of the material include scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy and wavelength dispersive X-ray spectrometry (EDS and WDS), infrared spectroscopy, Raman spectroscopy and X-ray diffraction (XRD). The differences in morphology of the zirconia (ZrO2) crystals observed in the PDZ are related to the thermal history of the material. Large zirconia crystals grow in a spherulitic manner and have the monoclinic crystal structure. Some smaller crystals formed via a rapid cooling process appear to retain the tetragonal or cubic crystal structures rather than relaxing to the monoclinic structure, and this may be because such nanocrystals are stabilised by small surface area or constraints from surrounding materials. Impurity distribution analysis of the PDZ showed that majority of the impurities present in zircon segregates to the silica phase during the dissociation process. The infrared and Raman spectroscopy analysis of the PDZ material indicated that the zirconia is present in the monoclinic and tetragonal polymorphs. X-ray diffraction revealed the presence of monoclinic, tetragonal and cubic zirconia phases. Rietveld refinement of the XRD patterns revealed zirconia to be predominantly found in the monoclinic polymorph followed by the tetragonal and cubic polymorphs. A Fourier transform infrared (FTIR) spectrometer equipped with an attenuated total reflectance (ATR) cell proved to be a viable method for determining the percentage dissociated zircon in PDZ.

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Vickerfält, Amanda. "Investigation of the possibility for using ZrO2 and ZrSiO4 for Zr additions to liquid ferrosilicon." Thesis, KTH, Materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-214009.

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Ferrosilicon containing 50-75% Si and 1.0-5.0% Zr is used as inoculant in the cast iron industry. Zr can be added to liquid ferrosilicon by use of Zr metal or zirconium ferroalloy (FeSiZr). Then the recovery of Zr, i.e. the fraction of Zr transferred from the additive to the ferrosilicon, as well as the hit rate on specification is high. The aim of this study was to investigate the recovery of Zr from zircon sand, ZrSiO4, and zirconia, ZrO2, in comparison to zirconium ferroalloy when added to liquid ferrosilicon with 75% Si at 1600⁰C. Also the refining effect of the different additives on Al was investigated. The experiments were carried out by stirring samples of controlled amounts of ferrosilicon and Zr additive in a graphite crucible at 1600⁰C and under inert Ar atmosphere for certain amounts of time. The reaction between ferrosilicon and Zr additive was stopped by rapid cooling of the samples. ICP-OES provided the concentration of Zr and Al and LECO O/N the concentration of O. SEM-ESD was used to examine the microstructures of ferrosilicon and Zr additive after experiments. It was found that ZrO2 was reduced by Si at the particle surface to yield dissolved Zr and ZrSiO4. The ZrSiO4 additive decomposed via two simultaneous reactions, one yielding ZrO2, Si and O2 and the other Zr, Si and O2. The recovery of Zr from ZrO2 and ZrSiO4 was significantly lower than from FeSiZr. Of ZrO2 and ZrSiO4, ZrO2 yielded the highest Zr recovery; the difference was much bigger than predicted by thermodynamics. It was discussed if that could be due to a higher reaction rate of the ZrO2, caused by the smaller size (APS 1 µm compared to d50 91 µm) and larger surface area of this addition. It was also found that utilization of density differences to separate the ferrosilicon and Zr additive did not work for zirconia under the same conditions as it worked for zircon sand, although zirconia has a higher density than zircon sand. The reason was the smaller particle size of the ZrO2 powder. No refining of Al was observed.

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Manhique, A. J. (Arao Joao). "Optimisation of alkali-fusion process for zircon sands: A kinetic study of the process." Diss., University of Pretoria, 2003. http://hdl.handle.net/2263/27817.

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Giry, Jean-Paul. "Etude du frittage-réaction alumine-zircon préparation et propriétés des céramiques zircone-mullite /." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37605469n.

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Khazeni, Nasser. "Synthesis And Characterization Of Zirconium Tungstate-zirconia Core-shell Composite Particles." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615316/index.pdf.

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Thermal mismatch between different components of a system could cause of problems like residual stress induced cracking, thermal fatigue or even optical misalignment in certain high technology applications. Use of materials with customized thermal expansion coefficient is a counter-measure to resolve such problems. Zirconium tungstate (ZrW2O8) with negative thermal expansion coefficient is capable of being used in synthesis of composites with tailored coefficient of thermal expansion (CTE). In this work, the sol-gel method which had been already set up in our group was characterized and the sources of the factors imposing impurities in the product were distinguished in all the steps of precursor preparation and heat treatment. In the second part of study, zirconium tungstate particles synthesized by the sol-gel method were utilized as core in synthesis of ZrW2O8&ndash
ZrO2 core&ndash
shell composite particles. Shell layer was composed of ZrO2 nanocrystallites and precipitated from an aqueous solution by urea hydrolysis. Volume of the shell was effectively controlled by concentration of the initial zirconium ion in the solutions. The rate of precipitation was a function of the ratio of initial urea concentration to zirconium ion. It is hypothesized that isolation of the ZrW2O8 within a layer of ZrO2, will be a key element in solving problems associated with reactivity of ZrW2O8 towards other components in sintering of ceramic&ndash
ceramic composites with tuned or zero thermal expansion coefficient.

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Orlans, Patrick. "Étude physicochimique des oxydes de zirconium et du dispersoi͏̈de alumine-zircone." Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 1987. http://tel.archives-ouvertes.fr/tel-00845464.

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Le procédé de synthèse et les divers traitements thermiques ou mécaniques modifient les propriétés physicochimiques des zircones industrielles. Cependant, l'origine exacte de ces modifications est difficile à déterminer compte-tenu des imprécisions concernant la préparation des produits industriels. Les oxydes de zirconium sont synthétisés par précipitation de gel. Les propriétés physicochimiques de la zircone sont liées aux modifications des différents paramètres (température, ph de fin de neutralisation, séchage, conditions de calcination). L'obtention du dispersoïde alumine-zircone par coprécipitation de gels permet une bonne homogénéisation des poudres. Selon les conditions de synthèse, l'interaction entre les oxydes peut devenir un phénomène important qui dans certains cas améliore notablement les propriétés mécaniques des matériaux obtenus.

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Orlans, Patrick. "Etude physicochimique des oxydes de zirconium et du dispersoïde alumine-zircone." Grenoble INPG, 1987. http://tel.archives-ouvertes.fr/tel-00845464.

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Le procédé de synthèse et les divers traitements thermiques ou mécaniques modifient les propriétés physicochimiques des zircones industrielles. Cependant, l'origine exacte de ces modifications est difficile à déterminer compte-tenu des imprécisions concernant la préparation des produits industriels. Les oxydes de zirconium sont synthétisés par précipitation de gel. Les propriétés physicochimiques de la zircone sont liées aux modifications des différents paramètres (température, ph de fin de neutralisation, séchage, conditions de calcination). L'obtention du dispersoïde alumine-zircone par coprécipitation de gels permet une bonne homogénéisation des poudres. Selon les conditions de synthèse, l'interaction entre les oxydes peut devenir un phénomène important qui dans certains cas améliore notablement les propriétés mécaniques des matériaux obtenus.

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Orlans, Patrick. "Etude physicochimique des oxydes de zirconium et du dispersoïde alumine-zircone." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37608557n.

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RICCI, DOLORES R. "Otimizacao do processo de obtencao de zirconia via precipitacao do sulfato basico de zirconio." reponame:Repositório Institucional do IPEN, 1989. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10393.

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

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Padovini, David Santos Souza [UNESP]. "Síntese e caracterização de nanopartículas de ZrO2 por rota hidrotérmica." Universidade Estadual Paulista (UNESP), 2013. http://hdl.handle.net/11449/99712.

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Com o crescimento das aplicações dos nanomateriais, as metodologias de síntese têm se tornado importante para pesquisadores e investidores nesse ramo da ciência. A proposta de síntese rápida, com pouco gasto de energia e com reagentes de fácil acesso é o fator principal para pesquisas com nanopartículas. Neste trabalho foram sintetizadas nanoestruturas de ZrO2 utilizando como precursor o butóxido de zircônio pela rota hidrotérmica. Os materiais obtidos foram caracterizados por DRX, FT-Raman, FT-IR, BET, MEV, MET e TG. Os resultados das caracterizações mostraram que a rota de síntese utilizada foi eficiente na produção de nanoestruturas cristalinas de ZrO2 com morfologias diferentes de acordo com a alteração do pH. As amostras apresentaram grande área superficial, consequentemente, houve a formação de partículas muito pequenas, na ordem de 2 nm. A análise de FT-IR e TG mostraram que há uma pequena quantidade de material residual na superfície do material após o tratamento térmico, demonstrando que a técnica hidrotermal mostrou-se eficiente tanto na cristalinização e crescimento do ZrO2 com na eliminação do material orgânico proveniente da síntese. Os estudos de adsorção bem como os espectros de FT-IR mostraram que a rodamina B adsorve quimicamente sobre a superfície da zircônia através do grupo carbonila e do nitrogênio carregado positivamente
With the growth of the applications of nanomaterials, synthesis methodologies have become important for researchers and investors in the science field. The proposed rapid synthesis, with little expenditure of energy and reagents easy access is the main factor for research on nanoparticles. In this study, we synthesized nanostructures using ZrO2 as the the precursor zirconium butoxide by hydrothermal route. The materials were characterized by XRD, FT-Raman, FTIR, BET, SEM, TEM and TG. The results of the characterizations showed that the synthesis route used was efficient in the production of crystalline ZrO2 nanostructures with different morphologies according to the pH change. Samples showed large surface area, therefore, there was the formation if very small particles, on the order of 2nm. Analysis of the FT-IR and TG showed that there is a small amount of residual material on the surface of the material after heat treatment, showing that the hydrothermal technique was effective in both the crystallization and growth of ZrO2 with the elimination of organic matrial from the synthesis. Adsorption studies as well as FT-IR spectra of rhodamine B showed that chemically adsorbed on the surface of the zirconia by the carbonyl group and the positively charged nitrogen

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Sullasi, Henry Socrates Lavalle. "Centros de cor, centros paramagnéticos e centros de luminescência dependentes de defeitos pontuais em zirconita." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-29112006-123818/.

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Ermoluminescência (TL), Ressonância Paramagnética Eletrônica (EPR) e absorção Óptica (AO) de duas amostras de zirconita ou zircão (de cor marrom), de Minas Gerais, de origem exata e desconhecida. As duas curvas de emissão TL mostraram a presença de 4 picos TL visíveis em 140, 215, 270 e 350 ºC, bastante superpostos. Por deconvolução, outros picos foram revelados. A intensidade dos picos TL em 140, 215 ºC em função da dose apresenta um comportamento linear seguido de sublinear. O espectro de emissão TL é composto de duas bandas em 480 e 580 nm, que são devidas à presença do Dy na nossa amostra. Além de Dy muitos outros elementos são encontrados na amostra, porém, não têm influência na emissão TL. Os espectros de EPR da amostra em pó irradiada mostraram a presença de um sinal central em g=2,000, devido ao centro SiO45- que é isotrópico, o que é facilmente observado na amostra policristalina (em pó). Na amostra monocristalina pode-se observar que existem outros centros EPR não isotrópicos, produzidos durante a irradiação da amostra, e que são devidos à perda ou ganho de um elétron por parte do grupo SiO44-. Os estudos de decaimento isócrono do sinal SiO45 e dos picos TL mostraram que existe correlação entre o centro EPR e os centros TL, o que nos levou a um possível mecanismo TL, segundo o qual o Dy3+ perde um elétron passando para Dy4+ durante a irradiação. O elétron liberado é capturado por SiO44- formando o centro EPR, SiO45-. Quando se aquece a amostra para a leitura TL o processo inverso acontece, deixando Dy3+ em estados excitados, e na transição ao estado fundamental duas emissões de luz, uma em 480nm e outra em 580nm são observados. As bandas de AO são devido ao Urânio (1100), H2O (1900nm) e o radical OH (1400nm). Estas bandas não são afetadas pela irradiação gama utilizada neste trabalho.
In the present work the investigation of some properties of Thermoluminescence (TL), Electronic Paramagnetic Resonance (EPR) and Optical Absorption (OA) of two samples of zircon (of brown color) from Minas Gerais, but the unknown exact origin, were carried out. The glow curves of thermoluminescence emission have shown the presence of 4 TL peaks at 140, 215, 270 and 350 ºC although strongly overlaped. By deconvolution more peaks were revealed. The intensity of the TL peaks at 140 and 215 ºC as function of the radiation dose presents linear and sublinear behavior. The TL emission spectrum has shown two bands at 480 and 580 nm, which are due to the Dy content in our sample. Appart from Dy many other elements are found in the sample, however, they do not participate in the TL emission. The EPR spectra of the irradiated powder sample showed a central signal whith g=2,000 that is due to the SiO45- center. This signal is isotropic and easily observed in the polycrystalline sample (in powder). In the monocrystalline sample non-isotropic signals can be observed due to EPR centers produced by irradiation. They are due to the loss or gain of one electron from the SiO44- group. The isocronal decay curves of the SiO45- signal and that of TL peaks are similar indicating a correlation between the EPR and TL centers suggesting us a possible TL mechanism: the Dy3+ looses one electron and converts into Dy4+ during irradiation. The electron liberated is then captured by SiO44- forming the SiO45- EPR center. When the sample is heated in order to read out TL the inverse process takesplace leaving the Dy3+ in excited states. In the transition to the ground state two light emissions are observed, one in 480nm and other in 580nm. In the OA spectrum measuremment two bands due to the Uranium (1100 and 1503nm), one to H2O(1900nm) and one due to the radical OH (1400nm) are observed. These bands are not afected by the irradiation used in this work.

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Prado, Pedro Henrique Condé Oliveira. "Cinética de degradação de zircônias odontológicas com alta translucidez." Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/152667.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Com o avanço da ciência e processamento de materiais, a zircônia odontológica deixou de ser um material opaco para apresentar certa translucidez, possibilitando a confecção de peças ultrafinas. Sabe-se que a água em contato com a superfície das zircônias convencionais acarreta na transformação de fase T-M e subsequente decréscimo de resistência, mas esses efeitos nas zircônias translúcidas ainda não foram explorados. Para avaliar, mapear e caracterizar os efeitos da cinética de envelhecimento acelerado em zircônias de alta translucidez, foram cortados 39 blocos de Y-TZP (VITA YZ, VITA HT, InCoris TZI) para cada zircônia comercial, onde posteriormente foram sinterizados (1530 ºC, 2h) e atribuídos a 13 grupos com 3 amostras cada: Um controle e 12 envelhecidos hidrotermicamente a 134 ºC com pressão constante de 2 bars por 6, 10, 14, 18, 22, 26, 30, 40, 60, 80, 100 e 140 horas. A análise em DRX foi utilizada para quantificar a transformação de fase da zircônia (tetragonal-monoclínica) em diferentes profundidades do material ao se trocar o ânodo do tubo irradiador (Cr, Co e Cu). Uma curva cinética de envelhecimento foi feita para cada profundidade para as 3 zircônias comerciais. Para avaliar os efeitos do envelhecimento hidrotermal nas propriedades mecânicas, 270 discos de Y-TZP foram cortados, 90 para cada tipo, sinterizados e atribuídos a 3 grupos: C-Controle; E1- envelhecido até 26h e E2- envelhecido até 140 horas. Os discos foram testados em uma máquina de teste universal (EMIC). A microestrutura dos discos foi avaliada sob MEV. As curvas de cinética do envelhecimento funcionaram de forma semelhante para todas as zircônias utilizadas neste estudo, caracterizadas por uma rápida transformação de fase T-M em função do tempo e estabilização de um platô após uma média de 26 horas. As camadas superficiais apresentam concentrações mais elevadas de fase monoclínica à medida em que essa concentração diminuiu em camadas mais profundas. O envelhecimento hidrotermal através de 140h diminuiu a tenacidade da cerâmica VITA YZ em 17% (681,78 ± 121,18) quando comparado ao seu grupo controle (841,69 ± 56,01), enquanto que as zircônias de alta translucidez não mostraram diferenças estatísticas de resistência flexural após o envelhecimento. O envelhecimento hidrotermal induz a transformação da fase martensítica de fora para dentro do material e não afeta as propriedades mecânicas das cerâmicas VITA HT e INCORIS TZI, enquanto diminui a dureza do material da zircônia VITA YZ.
To evaluate, map and characterize the effects of the accelerated aging kinetics of high translucency zirconias, this study was split into 2 parts: One part evaluating the superficial changes after in vitro hydrothermal aging and the second part aiming the effects of this aging on the mechanical properties of those ceramics. 117 Y-TZP (VITA YZ, VITA HT, InCoris TZI) blocks were cut, 39 for each commercial zirconia, sintered (1530 ºC, 2h) and assigned to 13 groups with 3 samples each: One being a control, aging-free group, and 12 groups that were prematurely aged hydrothermally at 134 ºC and constant pressure of 2 bars through 6, 10, 14, 18, 22, 26, 30, 40, 60, 80, 100 and 140 hours. XRD was used to quantify the amount of zirconia phase transformation (tetragonalmonoclinic) on different depths of the material by swapping the anode tube (Cr, Co, and Cu). An aging kinetic curve was made for each depth for the 3 commercial zirconias. To evaluate the effects of the hydrothermal aging on the mechanical properties, Y-TZP blocks were rounded to a cilindrical shape. 270 discs were cut, 90 for each kind, sintered as mentioned above and assigned to 3 groups: C-Control; E1- Aged through 26h and E2- Aged through 140h. Disks were then tested in a universal testing machine (EMIC) under a load of 1000 kg till fracture of the specimen and the surface was evaluated under SEM. The aging kinetics curves work similarly for all the YTZP used in this study, characterized by phase transformation ascendant and plateau stabilization as far as the aging goes. Superficial layers present higher concentrations of monoclinic phase as it decreases in deeper layers. Hydrothermal aging through 140h decreased VITA YZ toughness by 17% (681,78 ± 121,18) when compared with its control group (841,69 ± 56,01), while high translucency zirconias didn't show any statistical differences after aging.Hydrothermal aging does induce martensitic phase transformation from the outside-to-inside the material and doesn't affect the mechanical properties of VITA HT and INCORIS TZI ceramics, while it decreased the material toughness of VITA YZ zirconia.
FAPESP: 16/03688-1

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BERGAMASCHI, VANDERLEI S. "Influencia de parametros de precipitacao nas caracteristicas fisicas e quimicas do carbonato de zirconio." reponame:Repositório Institucional do IPEN, 2000. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10884.

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

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Lê, Đưc Huy. "Contribution à l'étude structurale et vibrationnelle des couches minces de zircone ZrO2 déposées sur alliage Zy-4." Le Mans, 2004. http://cyberdoc.univ-lemans.fr/theses/2004/2004LEMA1021.pdf.

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Ce travail de thèse entre dans le cadre d'une convention de co-tutelle en partenariat avec l'Ecole Normale Supérieure de Hanoï (Vietnam) selon un financement attribué par l'ambassade de France à Hanoï et complété par l'Université du Maine. Le sujet, qui a été initié en collaboration avec le service des matériaux irradiés du CEA-Saclay, a pour objectif final d'améliorer la durée de vie des gaines de réacteurs nucléaires (réservoir des pastilles combustibles de UO2) constituées d'un alliage à base de zirconium (Zy-4 : zircalloy-4). En effet ces gaines qui sont immergées dans un circuit d'eau primaire, à haute température et sous pression, s'oxydent naturellement ; la formation de couches minces, sur alliage Zy-4, de zircone Zr02 avec apparition d'une modification de variété allotropique (quadratique-monoclinique), sous irradiation, influence largement les propriétés mécaniques de ces gaines. Ainsi notre travail a été consacré à la synthèse de couches minces de ZrO2 déposées sur un alliage identique au cas réel (Zy-4) avec investigation des mécanismes de changements de phases existants dans ces matériaux. Le but est aussi de pouvoir réduire la vitesse d'oxydation du Zy-4 en déposant une couche préliminaire de ZrO2 stable afin de former une barrière protectrice à l'environnement de travail des centrales nucléaires. La première étape de ce travail a donc porté sur l'élaboration des couches minces de ZrO2 sur des substrats en Zy-4 à l'aide de la technique de pulvérisation cathodique magnétron en radiofréquence. Cette pulvérisation a été effectuée sur une cible en ZrO2 de symétrie monoclinique en appliquant différentes conditions de dépôt (paramètres de dépôt) : température du substrat, durée de dépôt, pression partielle d'oxygène. L'ensemble de ces couches a ensuite été étudié et complètement caractérisé selon plusieurs techniques : diffraction des rayons X, diffusion Raman, réflectivité des rayons X et interférométrie en lumière blanche. Ainsi l'épaisseur des couches synthétisées a été déterminée par la réflectivité des rayons X (pour les couches dont l'épaisseur est inférieure à 1500 Å) et l'interférométrie en lumière blanche (pour les couches dont l'épaisseur est supérieure à 5000 Å). Les résultats nous prouvent globalement que cette épaisseur varie linéairement avec la durée de dépôt. L'influence du paramètre " température de substrat " a également été étudié. Nous avons montré dans les couches synthétisées entre 40°C et 300°C, l'existence d'une très forte proportion de ZrO2 en phase quadratique (100-80%), qui normalement correspond à la symétrie métastable qui ne devrait pas exister en dessous de 900°C. Ce taux diminue progressivement pour ensuite rester stable entre 400 et 800°C. La stabilisation de cette phase quadratique a été expliquée par l'existence de particules de taille nanométrique et/ou l'influence du champ de contraintes sur ces particules. Par ailleurs, l'étude menée sur la série de couches déposées pendant différentes durées de dépôt nous montre que le taux de phase quadratique diminue linéairement avec ce temps de dépôt, donc avec l'épaisseur des couches. L'influence de la pression partielle d'oxygène a aussi été étudiée ; les diagrammes de diffraction X et les spectres de diffusion Raman montrent que la pression partielle d'oxygène dans l'enceinte de dépôt favorise la croissance de zircone monoclinique. Nous pouvons conclure que l'ajout d'oxygène réduit la concentration de lacunes favorisant ainsi la croissance de zircone stable. La reproductibilité de couches est aussi un des paramètres les plus importants à contrôler. L'étude sur une série de couches déposées dans des conditions identiques (à 600°C, pendant 30 minutes, dans l'environnement d'argon pur) a justifié cet aspect de notre approche expérimentale. Enfin dans une troisième étape un mécanisme de croissance des couches a pu être proposé sur la base de l'interprétation des données structurales et vibrationnelles. Cette étude permet de vérifier que la croissance des couches commence par la zircone en symétrie quadratique près du substrat (près de l'interface) et termine par la zircone monoclinique stable au voisinage de la surface. Nous avons également justifié l'effet de la taille des cristallites et l'effet des contraintes sur la stabilisation de zircone quadratique à une température inférieure à 900°C par affinements des diagrammes de diffraction X enregistrés sur les deux séries de couches déposées à différentes températures et différentes épaisseurs. Les résultats obtenus constitueront ainsi une base solide d'approche du comportement sous irradiation de ces mêmes couches afin de comprendre les mécanismes se produisant réellement dans les réacteurs.

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Somavilla, Luciana Müller. "Zircônia hidratada nanocristalina obtida a partir do tungstato de zircônio." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2013. http://hdl.handle.net/10183/96984.

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Zircônia hidratada cristalina, ZrO2.2H2O, com tamanho de domínio coerente médio de 1,5 nm foi obtida pela lixiviação do tungstato de zircônio (α-ZrW2O8) em uma solução de NaOH 1M, em ebulição por 5h. A partir do padrão de difração de elétrons das partículas de zircônia hidratada, esta pode ser indexada de acordo com uma rede tetragonal com a = 1,463(4)Å e c = 2,535(6)Å. Após aquecimento a 60ºC sob um vácuo de 10-5mbar, a zircônia hidratada, desidrata de forma reversível. Quando aquecida a 850ºC e 1000ºC, forma-se zircônia tetragonal e monoclínica, respectivamente. A zircônia hidratada nanocristalina produzida a partir do tungstato de zircônio forma aglomerados duros e transparentes, quase sem poros. A formação destes aglomerados e a desidratação observada em baixas temperaturas, sugere a possibilidade de obter-se corpos transparentes de zircônia, com tamanho de grão reduzido, a partir da deposição controlada de nanopartículas de zircônia hidratada a partir de uma suspensão aquosa.
Crystalline hydrous zirconia (ZrO2 .2H2O) with volume weighted average domain size of 1.5 nm was obtained by soaking zirconium tungstate (α-ZrW2O8) in boiling 1M NaOH solution for 5 h. The selected area electron diffraction pattern of hydrous zirconia particles could be indexed according to a tetragonal lattice with a = 1.463(4) Å and c = 2.535(6) Å. Upon heating to 60 oC under a vacuum of 10-5 mbar, hydrous zirconia dehydrates reversibly. Further heating to 850oC and 1000oC resulted in the formation of tetragonal and monoclinic zirconia, respectively. Some of the nanocrystalline hydrous zirconia produced from zirconium tungstate coalesced into transparent, nearly pore-free aggregates. The formation of these almost fully densified aggregates of hydrous zirconia, and the observed dehydration under very mild conditions, suggests that it could be possible to obtain transparent bodies of zirconia, with unprecedented small crystallite size, with the controlled deposition of the extremely small hydrous zirconia nanoparticles from a water-based suspension.

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Le, Coadou Cécile. "Caractérisation de films de zircone yttriée et développement d’un procédé de brasage avec du TA6V pour des applications biomédicales." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI041/document.

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Les maladies neurodégénératives sont en forte progression dans nos sociétés, mais elles sont également mieux connues et mieux soignées. Par exemple, la stimulation cérébrale profonde est de nos jours utilisée pour lutter contre des maladies comme la maladie de Parkinson. Pour cela, un boitier semblable à celui d'un pacemaker, placé sous la clavicule, est habituellement utilisé pour délivrer des impulsions électriques dans des zones spécifiques du cerveau grâce à des électrodes. Afin d'éviter certaines complications, un boitier ultrafin a été imaginé. Il peut être placé directement au niveau du crâne, au plus proche de la zone à traiter. Les matériaux composant ce boitier doivent présenter certaines caractéristiques. Nous avons choisi de travailler avec des feuilles de TA6V et de zircone yttriée et avons réalisé un assemblage hermétique par l'obtention d'une brasure fine en Ti2Ni.Les feuilles de zircone yttriée présentent des propriétés remarquables mais elles sont notoirement dégradées par un vieillissement hydrothermal. Une étude en vieillissement accéléré a été réalisée sur les feuilles de zircone telles que reçues mais également dans des conditions proches de l'utilisation. Le vieillissement mesuré est suffisamment limité pour envisager une utilisation in vivo, avec cependant une réserve concernant les zircones sous-stœchiométriques. Enfin, le profil de vieillissement et sa vitesse de progression ont pu être précisés.L'assemblage TA6V-zircone a été réalisé par brasage réactif in situ via l'apport initial en nickel pur et la création d'un joint de brasage en Ti2Ni. Le système TA6V-Ni-ZrO2 met en jeu plusieurs phénomènes, que nous avons cherché à déconvoluer : diffusion (solide et liquide), formation et croissance d'intermétalliques et réactions d'oxydo-réduction. La croissance des intermétalliques à partir du couple TA6V-Ni a été particulièrement étudiée. Cela a permis de relier certains événements à la température et de préciser les vitesses de croissance du Ti2Ni (selon son état physique). Grâce à l'ensemble des résultats, un procédé de brasage métal-céramique adapté aux matériaux ultrafins a été d'identifié et réalisé sur système avec succès
Neurodegenerative diseases are increasingly present in our society but they are also better known and treated. For example, deep brain stimulation is nowadays used to treat diseases such as Parkinson disease. For this purpose, a pacemaker-like device localized in the infraclavicular region is commonly used to deliver electrical pulses in concerned area of the brain thanks to electrodes. In order to avoid some complications, an ultrathin housing was designed. It could be directly implanted under the scalp, close to the area to be treated. Materials of the housing have to be display some features. TA6V, yttria-stabilized zirconia sheets and a hermetic brazing with a Ti2Ni joint were selected to develop this housing.Yttria-stabilized zirconia sheets have remarkable properties but they undergo a degradation caused by hydrothermal aging. An accelerated aging study was done on pristine sheets but also under near-reality conditions. The observed aging is sufficiently limited to consider an in vivo application, subject to one reservation for the under-stoichiometric zirconia. Finally, the aging profile and the propagation rate were specified.The TA6V-zirconia joining was obtained by an in situ reactive brazing, thanks to a filler metal in pure nickel and the formation of a Ti2Ni joint. Several phenomena occur in the TA6V-Ni-ZrO2 system, which were separately studied: (solid and liquid) diffusion, formation and growth of intermetallic compounds and redox reactions. The intermetallic compounds growth from the TA6V-Ni couple was studied in detail. Thanks to all of the results, a metal-ceramic brazing process for ultrathin materials was identified and successfully achieved on our system

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Aramide, FO, KK Alaneme, PA Olubambi, and JO Borode. "In-Situ Synthesis of Mullite Fibers Reinforced Zircon-Zirconia Refractory Ceramic Composite from Clay Based Materials." International Journal of Materials and Chemistry, 2015. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001844.

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Abstract Understanding the phase transformations/developments that result due to varying the production parameter of engineering materials is vital to development of new materials. The effects of yttria and niobium oxide on the phase changes and mechanical properties of mullite fiber reinforced zircon-zirconia ceramic composites produced by in-situ sintering of raw materials was investigated. Varied amounts of powder zirconia, yttria and niobium oxide were mixed in a turbula mixer with a fixed composition of clay (70% volume) of known mineralogical composition and mechanically milled in a planetary ball mill. The blended powders/clay were compacted into standard sample dimensions, and finally fired at 1400°C and held at varied time of one, two and three hours. The fired samples were characterized using ultra-high resolution field emission scanning electron microscope (UHR-FEGSEM) equipped with energy dispersive spectroscopy (EDX), and X-ray diffractometry (XRD). Various mechanical properties of the sintered samples were also investigated. It was observed that the investigated mechanical properties (with the exception of shrinkages) improved with the amount of raw zirconia initially used in the samples. It was also observed that addition of niobium oxide favours the formation polymignite phase, while the presence of both yttria and niobium oxide in the raw materials resulted in the formation of fergusonite phase in the samples. Both additives favour the phase transformation of zirconia from monoclinic to tetragonal and cubic phases even at temperature as low as 1400°C. It was concluded that the improved mechanical properties of the samples was due to strengthening by both mullite fibers reinforcement and phase transformation strengthening.

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Sciasci, Plínio [UNESP]. "Efeito de tratamento de superfície na composição de zircônia e na resistência de união com diferentes cimentos." Universidade Estadual Paulista (UNESP), 2013. http://hdl.handle.net/11449/97311.

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A zircônia tetragonal policristalina estabilizada por ítria (Y-ZTP), em virtude de suas propriedades mecânicas, pode ser indicada para restaurações dento ou implantosuportadas. Porém, em função de sua composição, este material apresenta dificuldade de se unir eficazmente com os cimentos, comprometendo assim a longevidade das restaurações. O objetivo desse estudo foi avaliar a influência de diferentes tratamentos de superfície e cimentos na resistência ao cisalhamento (RC) de uma Y-ZTP, assim como a caracterização química da superfície da zircônia após os jateamentos. Duzentos e quarenta discos de Y-ZTP (5 x 2 mm) foram obtidos e aleatoriamente divididos em 5 grupos (n=40) de acordo com os tratamentos de superfície: 1) jateamento com óxido de alumínio (Al2O3) de 50 μm + silano; 2) jateamento com Al2O3 de 120 μm + silano; 3) jateamento com partículas de Al2O3 modificadas por sílica (Rocatec Soft) (30 μm) + silano; 4) jateamento com Al2O3 de 120 μm seguido do jateamento com partículas de Al2O3 modificadas por sílica (110 μm) (Rocatec Plus) e 5) Rocatec Plus + silano. Discos de resina composta (Filtek Z350 XT) foram confeccionados e imediatamente cimentados sobre a superfície da zircônia com os seguintes cimentos (n=12): 1) RelyX Luting 2; 2) RelyX ARC; 3) RelyX U100; e 4) Panavia F 2.0. Os silanos usados foram: 1) RelyX Ceramic Primer para os cimentos RelyX Luting 2, RelyX ARC e RelyX U100 e 2) Clearfil SE Bond Primer/Clearfil Porcelain Bond Activator para o cimento Panavia F 2.0. Após a cimentação, os espécimes foram armazenados por 6 dias em meio seco à 37ºC antes da ciclagem térmica (10.000 ciclos, 5 – 55ºC, 30 s/banho) para então serem submetidas ao teste de RC em máquina universal de ensaios (EMIC DL2000). Os dados foram analisados por meio de ANOVA 2 fatores e teste de Tukey ( =0,05)...
Due to their excellent mechanical properties, biocompatibility, low thermal conductivity, and chemical stability, Y-TZP (yttria-stabilized tetragonal zirconia polycrystal) ceramics have been used to manufacture metal-free tooth- or implantsupported prostheses. However, the conventional surface treatments (hydrofluoric acid etching and silanization) used for silica ceramics are not effective in promoting suitable bonding between resin-based materials and zirconia. Therefore, the purpose of this in vitro study was to evaluate the effect of different surface treatments on the shear bond strength (SBS) of luting cements to yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) and on its surface chemical characterization. Two hundred and forty Y-TZP discs (5 × 2 mm) were obtained and randomly divided into 5 airborneparticle abraded groups (n=48): 1) 50 μm Al2O3 particles; 2) 120 μm Al2O3 particles; 3) 30 μm silica-modified Al2O3 particles (Rocatec Soft); 4) 120 μm Al2O3 particles, followed by 110 μm silica-modified Al2O3 particles (Rocatec Plus); and 5) Rocatec Plus. After airborne-particle abrasion the surfaces were treated with silane coupling agent. Composite resin discs (Filtek Z350 XT) were produced and bonded immediately to the zirconia-treated surfaces (n=12) with: 1) RelyX Luting 2; 2) RelyX ARC; 3) RelyX U100; or 4) Panavia F 2.0. The silanes used were RelyX Ceramic Primer (RelyX Luting 2, RelyX ARC and RelyX U100) and Clearfil SE Bond Primer/Clearfil Porcelain Bond Activator (Panavia F 2.0). The bonded specimens were stored for 6 days in dry conditions at 37ºC before thermal cycling (10,000 cycles, 5 to 55ºC) and then tested for SBS in a mechanical testing machine (EMIC DL2000). Data were analyzed by two-way ANOVA and Tukey HSD post hoc test ( =.05). Failure mode was determined with a stereomicroscope (×20). The... (Complete abstract click electronic access below)

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Tchikou, Madina. "Propriétés mécaniques et mécanismes d’usure de billes de broyage en zircone." Rennes 1, 2011. http://www.theses.fr/2011REN1S044.

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Les dommages subis par les billes de broyage, dans un broyeur à billes agitées, sont fonction des conditions d’utilisation comme la nature des matériaux à broyer et les conditions de broyage. L’objectif de ce travail était d’étudier les couplages entre l’usure des billes, les conditions d’emploi et les matériaux mis en jeu. Les propriétés intrinsèques (structures, microstructures et propriétés mécaniques) de cinq types de billes à base zircone ou zircon ont été déterminées, ceci dans le but de dégager des tendances permettant de les relier à l’usure en broyeur. Les mécanismes d’usure ont été étudiés à travers une approche multi-échelle : l’échelle macroscopique consistant à observer les billes à l’état initial et final (pertes de masse et observations des surfaces des billes), l’échelle mésoscopique s’intéressant aux contacts entre les billes par simulation numérique, l’échelle microscopique visant à caractériser plus précisément les mécanismes d’usure par découplage expérimentale des contacts. Ces éléments nous permettent de proposer un modèle d’usure en fonction des propriétés des billes et de discuter de sa validité pour différents paramètres expérimentaux
Damage of grinding beads depends on operating conditions as nature of grinding materials and grinding parameters. The aim of this work was to study the correlations between wear of beads, grinding parameters and materials (powders, fluid and beads). Intrinsic properties (structures, microstructures and mechanical properties) of five kinds of zirconia or zircon beads were determined to link them to grinding wear. The wear mechanisms were studied with a multi-scale approach: the macroscopic scale consisted in observing the beads during the initial and final steps (through the mass losing during milling and the observation of surface by SEM). The mesoscopic scale focused on contacts of beads by numerical simulation, and the microscopic scale aimed at characterizing the mechanisms of wear by decoupling experimental contacts during milling. The elements allow proposing a model of wear based on properties of beads, and the validity of the model is observed for several experimental parameters

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Bererd, Nicolas. "Effets d'irradiation sur l'oxydation du zirconium et la diffusion de l'uranium dans la zircone." Phd thesis, Université Claude Bernard - Lyon I, 2003. http://tel.archives-ouvertes.fr/tel-00005944.

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Cette thèse a pour contexte l'entreposage direct des assemblages de combustible usé après fonctionnement en réacteur. Afin d'obtenir des données sur les capacités de la gaine comme barrière à la diffusion de l'uranium, nous avons mené une étude fondamentale visant à modéliser l'évolution de la face interne de la gaine sous et en l'absence d'irradiation.
Le comportement du zirconium en conditions réacteur a tout d'abord été étudié auprès du réacteur à haut flux de l'Institut Laue Langevin (ILL) de Grenoble. Une cible mince d'uranium enrichie en isotope fissile a été placée sur un échantillon de zirconium, l'ensemble étant irradié par un flux de neutrons thermiques induisant la fission de l'uranium du dépôt. Le suivi de l'évolution énergétique des produits de fission formés a permis de mettre en évidence deux phases : l'oxydation du zirconium, puis la diffusion de l'uranium dans la zircone formée à la température de 480°C. Un coefficient de diffusion sous irradiation a été mesuré et vaut 10-15 cm2.s-1.
Afin de pouvoir mettre clairement en évidence l'effet de l'irradiation par les produits de fission sur l'oxydation du zirconium, des mesures d'oxydation thermique et sous irradiation de 129Xe ont été effectuées respectivement à l'Institut de Physique Nucléaire de Lyon (IPNL) et au GANIL à Caen. Elles ont montré que l'oxydation est fortement accélérée par l'irradiation, et que la température joue un rôle négligeable jusqu'à 480°C.
Par ailleurs, la diffusion thermique de l'uranium dans le zirconium et la zircone a été étudiée à l'IPNL par couplage implantation ionique/RBS. Cette étude montre que l'uranium diffuse dans le zirconium alors qu'il se retrouve piégé dans la zircone sous forme UO3.

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Bérerd, Nicolas. "Effets d'irradiations sur l'oxydation du zirconium et la diffusion de l'uranium dans la zircone." Lyon 1, 2003. http://tel.archives-ouvertes.fr/docs/00/04/67/68/PDF/tel-00005944.pdf.

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Cette thèse a pour contexte l'entreposage direct des assemblages de combustible usé après fonctionnement en réacteur. Afin d'obtenir des données sur les capacités de la gaine comme barrière à la diffusion de l'uranium, nous avons mené une étude fondamentale visant à modèliser l'évolution de la face interne de la gaine sous et en l'absence d'irradiation. Le comportement du zirc nium en conditions réacteur a tout d'abord été étudié auprès du réacteur à haut flux de l'Institut Laue Langevin (ILL) de Grenoble. Une cible mince d'uranium enrichie en isotope fissible a été placée sur un échantillon de zirconium, l'ensemble étant irradié par un flux de neutrons thermiques induisant la fission de l'uranium du dépôt. Le suivi de l'évolution énergétique des produits de fission formés a permis de mettre en évidence deux phases : l'oxydation du zirconium, puis la diffusion de l'uranium dans la zircone formée à la température de 480°C. Un coefficient de diffusion sous irradiation a été mesuré et vaut 10 puissance moins 15 cm2. S puissance moins 1. Afin de pouvoir mettre clairement en évidence l'effet de l'irradiation par les produits de fission sur l'oxydation du zirconium, des mesures d'oxydation thermiques et sous irradiation de 129Xe ont été effectués respectivement à l'Institut de Physique Nucléaire de Lyon (IPNL) et GANIL à Caen. Elles ont montré que l'oxydation est fortement accéléreé par l'irradiation, et que la température joue un rôle négligeable jusqu'à 480°C. Par ailleurs, la diffusion thermique de l'uranium dans le zirconium et la zircone a été étudiée à l'IPNL par couplage implantation ionique/RBS. Cette étude montre que l'uranium diffuse dans le zirconium alors qu'il se retrouve piégé dans la zircone sous forme UO3.

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Bererd, Nicolas Chevarier Alain Moncoffre Nathalie. "Effets d'irradiations sur l'oxydation du zirconium et la diffusion de l'uranium dans la zircone." [S.l.] : [s.n.], 2003. http://tel.archives-ouvertes.fr/docs/00/04/67/68/PDF/tel-00005944.pdf.

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Lima, Emilena Maria Castor Xisto. "Caracteristicas de superficies, adsorção de proteinas e aderencia bacteriana em diferentes materiais odontologicos." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/288334.

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Orientadores : Altair Antoninha Del Bel Cury, Pedro Luiz Rosalen, Hyun Koo
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: O uso de implantes osseointegrados para substituição de dentes perdidos é uma alternativa importante na odontologia atual. Uma das condições relacionada ao sucesso nos procedimentos de implante é fornecida pelas propriedades de superfície dos implantes e componentes protéticos que influenciam não só na biocompatibilidade, mas também na adesão bacteriana e colonização. A qualidade de superfície pode ser determinada pela combinação das propriedades física, química, mecânica e de estrutura de superfície. Dentre elas, a energia livre de superfície e rugosidade superficial tem efeito significante no processo de adesão. Considerando que cada biomaterial pode apresentar propriedades físicas/químicas e energias de superfícies diferentes, a adsorção dos componentes salivares/soro sanguíneo presentes na película adquirida é provavelmente específica aquela superfície. Esses componentes mediam a aderência bacteriana inicial nas superfícies dos dentes e materiais restauradores, sendo a aderência reconhecida como primeiro passo para formação do biofilme. O acúmulo de biofilme pode levar ao desenvolvimento de lesões inflamatórias na mucosa adjacente e reabsorção óssea, aumentando o risco de falhas dos implantes. Assim, os propósitos destes trabalhos foram: I) avaliar as características de superfíde de abutments (Ti-6AI-4V e Tilite) e 11) caracterizar o perfil de adsorção dos componentes salivares/ soro sanguíneo e a aderência bacteriana de Streptococcus mutans e Actinomyces naeslundii sobre titânio (Ti) e cerâmica zirconia (Zi) usados na confecção de abutments de implantes. Como resultados das pesquisas observamos que as ligas de Ti-6AI4V e Tilite apresentaram diferenças nas características de superfícies, exceto para dureza de superfície e que o titânio e a cerâmica zírcônia apresentaram propriedades biológicas similares em termos de adsorção de proteínas e aderência bacteriana. Entretanto, esses materiais apresentaram-se diferentes quanto à adesão bacteriana quando comparados com a hidroxiapatita, principalmente para A. naeslundii
Abstract: The use of osseointegrated implants for replacing missing teeth is an important alternative in current dentistry. One of the most important conditions, which relates to the future success of implant procedures, is provided by the surface properties of the implant and its prosthetic abutments. Since these components penetrate through the gingival mucosa and are also exposed to the oral cavity, they play an important role not only for the biocompatibility but also for the bacterial adhesion and stagnation. Surface quality of a biomaterial can be measured by a combination of physical, chemical and mechanical properties and its surface structure. Surface ftee energy and surface roughness have a significant impact in the adhesion processo Since each biomaterial has different physicaVchemical properties and surfaces energies, adsorption of salivary/serum components to each surface is likely to be specific to that surface and they mediate the initial bacterial adherence to the tooth surface and restorative materiaIs. The bacterial adherence is recognized as th~ first step of the biofilm formation, which accumulation may lead to inflammatory lesions in the adjacent mucosa and bone resorption, increasing the risk of implant failure. Thus, the purposes of these studies were: I) evaluate surface characteristics of implant abutments (Ti-6Al-4V and Tilite) and 11) characterize the profile of salivary/serum components adsorption, and Streptococcus mutans and Actínomyces naeslundií adherence on titanium (Ti) and ceramic zirconia (Zi) used for manufacturing implant abutments. The results revealed that the Ti-6Al-4V and Tilite alloys showed differences on the surface characteristics, except to surface hardness and titanium and zirconia ceramic displayed similar biological properties in terms of protein adsorption and bacterial adherence. However, the abutment materials showed subtle, but significant differences on the bacterial binding pattern when compared to HA (surrogate tooth enamel), especially for A. naeslundií
Doutorado
Protese Dental
Doutor em Clínica Odontológica

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Valero, Rémi. "Mécanismes de la synthèse hydrothermale du zircon." Mulhouse, 1997. http://www.theses.fr/1997MULH0501.

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La synthèse hydrothermale du zircon a été principalement envisagée à partir d'un gel de zircone, élaboré à partir de l'oxychlorure de zirconium et d'une silice amorphe de type Aérosil 130 (Dégussa). La première partie du travail concerne l'étude du milieu de synthèse et en particulier l'étude de la solubilité des précurseurs en fonction du pH. A pH acide, les gels de zircone et de silice présentent des solubilités beaucoup plus importantes que le zircon, ce qui laisse entrevoir une possibilité de cristallisation. Toutefois, le gel de zircone étant deux fois plus soluble que la silice amorphe, le zircon contiendra probablement des défauts siliciques. D'autre part, une étude des espèces en solution montre que l'espèce zirconique stable est un complexe renfermant 4 atomes de fluor par zirconium. A pH basique, le gel de zircone est quasiment insoluble alors que le gel de silice présente une solubilité très importante. A ce pH aucune anticipation de synthèse ne peut être faite. L'étude du zircon cristallisé à pH acide montre qu'il contient, en effet, des lacunes siliciques, où les entités (SiO4)4- sont remplacées par des tétraèdres de type [Fn(OH)4-n]4-, où n varie de 0 à 4. Ce matériau est métastable et se détruit après calcination à 500°C avec départ de silice sous la forme SiF4 gazeux. Le résidu de calcination est de la zircone monoclinique en forme de bâtonnets de 100 nm de longueur principale et de 10 nm d'épaisseur. Le zircon cristallisé à pH basique est très stable et ne présente pas de défaut silicique. De plus, il possède une morphologie en forme de sphères microniques feuilletées à l'origine de surfaces spécifiques importantes (200 m2/g), qui laisse entrevoir une possible utilisation de ce matériau comme support de catalyseurs. Pour chaque type de zircon synthétisé un mécanisme est proposé.

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Padovini, David Santos Souza. "Síntese e caracterização de nanopartículas de ZrO2 por rota hidrotérmica /." Bauru, 2013. http://hdl.handle.net/11449/99712.

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Orientador: Fenelon Martininho Lima Pontes
Banca: Manoel Lima de Menezes
Banca: Cleocir José Dalmaschio
O Programa de Pós Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi
Resumo: Com o crescimento das aplicações dos nanomateriais, as metodologias de síntese têm se tornado importante para pesquisadores e investidores nesse ramo da ciência. A proposta de síntese rápida, com pouco gasto de energia e com reagentes de fácil acesso é o fator principal para pesquisas com nanopartículas. Neste trabalho foram sintetizadas nanoestruturas de ZrO2 utilizando como precursor o butóxido de zircônio pela rota hidrotérmica. Os materiais obtidos foram caracterizados por DRX, FT-Raman, FT-IR, BET, MEV, MET e TG. Os resultados das caracterizações mostraram que a rota de síntese utilizada foi eficiente na produção de nanoestruturas cristalinas de ZrO2 com morfologias diferentes de acordo com a alteração do pH. As amostras apresentaram grande área superficial, consequentemente, houve a formação de partículas muito pequenas, na ordem de 2 nm. A análise de FT-IR e TG mostraram que há uma pequena quantidade de material residual na superfície do material após o tratamento térmico, demonstrando que a técnica hidrotermal mostrou-se eficiente tanto na cristalinização e crescimento do ZrO2 com na eliminação do material orgânico proveniente da síntese. Os estudos de adsorção bem como os espectros de FT-IR mostraram que a rodamina B adsorve quimicamente sobre a superfície da zircônia através do grupo carbonila e do nitrogênio carregado positivamente
Abstract: With the growth of the applications of nanomaterials, synthesis methodologies have become important for researchers and investors in the science field. The proposed rapid synthesis, with little expenditure of energy and reagents easy access is the main factor for research on nanoparticles. In this study, we synthesized nanostructures using ZrO2 as the the precursor zirconium butoxide by hydrothermal route. The materials were characterized by XRD, FT-Raman, FTIR, BET, SEM, TEM and TG. The results of the characterizations showed that the synthesis route used was efficient in the production of crystalline ZrO2 nanostructures with different morphologies according to the pH change. Samples showed large surface area, therefore, there was the formation if very small particles, on the order of 2nm. Analysis of the FT-IR and TG showed that there is a small amount of residual material on the surface of the material after heat treatment, showing that the hydrothermal technique was effective in both the crystallization and growth of ZrO2 with the elimination of organic matrial from the synthesis. Adsorption studies as well as FT-IR spectra of rhodamine B showed that chemically adsorbed on the surface of the zirconia by the carbonyl group and the positively charged nitrogen
Mestre

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SOLMON, HELENE. "Autodiffusion de l'oxygene, du zirconium et de l'yttrium dans la zircone cubique stabilisee par l'yttrium." Paris 6, 1992. http://www.theses.fr/1992PA066332.

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L'autodiffusion du zirconium, de l'yttrium et de l'oxygene dans des monocristaux de zircone cubique stabilisee par l'yttrium a ete mesure en fonction de la temperature sous une pression de 0,21 atm. D'oxygene. Les coefficients de diffusion de l'oxygene ont ete obtenus par sims apres des experiences d'echange isotopique #1#8o/#1#6o. Les coefficients de diffusion de zr et de y ont ete deduits de l'evolution des profils obtenus par implantation de #9#6zr. Deux mecanismes independants de diffusion de l'oxygene ont ete determines: un du aux lacunes libres d'oxygene (q=78 kj/mol), l'autre du a la presence de microdomaines correles dans lesquels se trouvent des lacunes d'oxygene associees aux cations (q=119 kj/mol). La diffusion du zr et de y est similaire (q460 kj/mol) et est due aux lacunes de zirconium chargees. Les coefficients de diffusion des cations decroissent lorsque le taux d'yttrium augmente

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Ribeiro, Beatriz Regalado Galvão [UNESP]. "Efeito de tratamentos de superfície sobre a adesão de reparo com resina composta em restarações cerâmicas á base de zircônia Y-TPZ envelhecida hidrotermicamente." Universidade Estadual Paulista (UNESP), 2013. http://hdl.handle.net/11449/97272.

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O lascamento e a delaminação da porcelana de cobertura são considerados problemas técnicos frequentes em restaurações cerâmicas com infraestrutura em zircônia Y-TZP. O reparo intraoral com resina composta pode ser uma alternativa de tratamento para solucionar esse problema. Esse estudo avaliou o efeito de diferentes tratamentos de superfície e agentes de união sobre a união entre resina composta e zircônia Y-TZP envelhecida. Corpos-de-prova de zircônia Lava (n=14) foram confeccionados em forma de blocos (7,0 x 7,0 x 1,7 mm). Metade dos espécimes foi submetida ao envelhecimento hidrotérmico em autoclave a 134°C, 3 bar e 8 horas, enquanto a outra metade não sofreu envelhecimento (grupo controle). Difração de raios-X mostrou picos característicos das fases tetragonal e monoclínica, após a zircônia ser submetida ao tratamento em autoclave. As amostras foram subdivididas, de acordo com o tratamento de superfície: jateamento com partículas de alumina 50 μm, deposição triboquímica de sílica 30 μm (Rocatec Soft) ou sem tratamento abrasivo. Microscopia eletrônica de varredura, Espectroscopia por Dispersão de Energia (EDS) e Difração de raios-X foram utilizados para caracterização das amostras após os tratamentos. Clearfil Porcelain Bond Activator + Clearfil SE Bond; fina camada dos cimentos resinosos Panavia F ou RelyX U100 foram utilizados como agentes de união, antes da aplicação da resina composta Filtek Z350 XT, na forma de um cilindro (4,0 x 2,0 mm). Os nove subgrupos experimentais foram submetidos à ciclagem térmica (6.000 ciclos, 5 e 55°C, 30 segundos de imersão) antes do ensaio de resistência de união ao cisalhamento, em máquina de ensaios mecânicos EMIC DL2000 a uma velocidade de 0,5 mm/min. Os valores de resistência de união foram avaliados por meio da Análise de...
Chipping and adhesive failure of the veneer porcelain are considered frequent technical problems in zirconia YTZP-based ceramics restorations. The intraoral repair with composite resin become as an alternative treatment to solve this problem. This study evaluated the effect of different surface treatments, hydrothermal aging and bonding agent about the union Y-TZP zirconia/composite resin. 360 Lava zirconia specimens were made in the form of blocks (7.0 x 7.0 x 1.7 mm). Half of the specimens were subjected to hydrothermal aging by autoclaving at 134°C, 3 bar and 8 hs, while the other half were not subjected to aging (control group). X-ray diffraction analysis showed characteristic peaks of tetragonal and monoclinic phase, after the zirconia be subjected to autoclave treatment. The samples were subdivided according to the surface treatment: Sandblasting with 50 μm alumina particles, tribochemical silica coating 30 μm (Rocatec Soft) or without abrasive treatment. Scanning electron microscopy, Energy-dispersive spectroscopy (EDS) and x-ray diffraction were used for surface characterization. After the surface treatment 3 different bonding agents were applied: Clearfil Porcelain Bond Activator + Clearfil SE Bond; thin layer of luting cements Panavia F or RelyX U100. A cylinder (2.0 x 4.0 mm) of composite Filtek Z350 XT was built on the prepared zirconia to simulate the repairing. The nine experimental subgroups (n = 14) were thermal cycled (6,000 cycles, 5 and 55°C, 30-second dwell time) before the test of shear bond strength in mechanical testing machine EMIC DL2000 (0.5 mm/min). Bond strength values were evaluated using 2-way ANOVA and Tukey’s test (α = 5%). The fracture analyzed as adhesive failure, cohesive or mixed. All specimens without abrasive surface treatment debonded during thermal cycling. The results... (Complete abstract click electronic access below)

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Longhini, Diogo [UNESP]. "Caracterização mecânica de uma porcelana de aplicação convencional e uma prensada para recobrimento de infraestruturas de zircônia e o efeito do método de resfriamento na resistência à flexão biaxial do conjunto zircônia/porcelana." Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/110828.

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Este estudo caracterizou mecanicamente uma porcelana feldspática de aplicação convencional e uma porcelana feldspática prensada, indicadas para infraestrutura em zircônia, quanto a resistência à flexão biaxial, dureza Vickers e tenacidade à fratura. Além disso, foi investigado o efeito da taxa de resfriamento após o ciclo de sinterização do glaze da porcelana na resistência à flexão biaxial de bicamadas zircônia/porcelana. Espécimes monocamada de VM9 (n=15) e Vita PM9 (n=15) (12,0 mm de diâmetro x 1.2 mm de espessura) foram confeccionados conforme as recomendações do fabricante e submetidos ao ensaio de resistência à flexão biaxial (MPa). Um fragmento de cada espécime fraturado foi aleatoriamente selecionado para a mensuração da dureza Vickers (n=15) (VHN). A tenacidade à fratura aparente(MPa.m½) foi determinada pela técnica da indentação Vickers (n=15). Para o ensaio de flexão biaxial dos bicamadas, discos de zircônia (Vita In-Ceram YZ) foram recobertos com porcelana convencional Vita VM9 (n=30) ou com porcelana prensada Vita PM9 (n=30). Após a simulação da queima de glaze, os espécimes foram submetidos a resfriamento rápido (n=15) ou lento (n=15). Após o ensaio de resistência à flexão, os espécimes foram analisados quanto ao tipo de fratura. Teste de T-Student para espécimes monocamada mostrou que Vita PM9 apresentou valores significantemente maiores de resistência à flexão biaxial (p<0,01) e dureza (p=0,017) em relação a Vita VM9, mas não quanto a tenacidade à fratura (p= 0.41). ANOVA a dois fatores (porcelana e método de resfriamento), utilizada para análise dos bicamadas indicou significância apenas para porcelanas, com superioridade para a combinação Vita PM9/zircônia (p<0,01). Porcelanas prensadas parecem ser uma alternativa mais efetiva para recobrimento de zircônia em relação as convencionais.
This study characterized mechanically a conventional and a pressed feldspathic porcelain indicated for zirconia core in terms of biaxial flexural strength, fracture toughness, Vickers hardness. In addition it was investigated the effect of the glaze cooling rate on the biaxial flexural strength of the zirconia/porcelain bilayer. Specimens monolayers of Vita VM9 (n=15) and Vita PM9 (n=15) (12.0 mm diameter x 1.2 mm thickness) were prepared according to manufacturer’s recommendations for the biaxial flexural strength test (MPa). Afterwards, one fragment of each broken specimen was randomly selected for Vickers hardness measurements (n=15) (VHN). Apparent fracture toughness (MPa.m½) was determined by Vickers hardness indentation technique (n=15). For the biaxial flexural strength of bilayers, zirconia discs (Vita In-Ceram YZ) were veneered with the conventional porcelain Vita VM9 (n=30) or with the pressed porcelain Vita PM9 (n=30). After the glaze firing simulation, the specimens were submitted to fast (n=15) or slow cooling method (n=15). After the biaxial flexural test, the specimens were analyzed in relation to fracture pattern. T-Student tests were performed for the monolayer specimens, while two-way ANOVA (porcelain and cooling method) was used for the bilayer ones (α=.05). Vita PM9 exhibited significantly higher biaxial flexural strength (p<0.01) and hardness than VM9 (p=0.017). However, there was no significant difference (p= 0.41) in fracture toughness between the porcelains. The two-way ANOVA indicated significance only for the porcelain, with superiority for the combination Vita PM9/zirconia (p<0.01).The pressed porcelain seems to be a mechanically more effective alternative for zirconia veneering than the conventional one.

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Leidens, Victor Luis. "Preparação do Si'O IND. 2'/fosfato de zirconio (IV) pelo metodo de processamento sol-gel : caracterização e propriedades." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249702.

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Orientador: Yoshitaka Gushikem
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
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Foram obtidos, pelo método de processamento sol-gel, os materiais compósitos SiO2/ZrO2/Fosfato, partindo de tetraetil ortosilicato (TEOS), butóxido de zircônio, e três diferentes precursores H3PO4, Cl3OP e (CH3O)3PO, originando os materiais compósitos designados respectivamente como SZP1, SZP2 e SZP3. Utilizou-se etanol como solvente e catálise ácida para promover a hidrólise do TEOS. A área superficial específica, SBET, apresentou um valor maior para SZP2 (270 ± 10 / m g) e menor para SZP1 (176 ± 10 / mg). No caso de SZP3 a área se mostrou pequena (56 ± 10 / m g), fato considerado normal devido ao precursor de natureza orgânica, empregado na síntese. A espécie fosfato contida na superfície foi determinada como sendo dihidrogênio fosfato para SZP1 e mono hidrogênio fosfato para SZP2 e SZP3. Estudos de RMN P CPMAS e XPS demonstraram este fato. As imagens de SEM mostram uma superfície significativamente lisa das partículas em um aumento de 30.000 vezes. Já as imagens de TEM demonstram que, assim como foi observado pelos dados de difratometria de raios-X, o material é constituído de uma estrutura amorfa, sendo possível avaliar que as partículas são de tamanho nanométrico. As qualidades eletrocatalíticas para a determinação simultânea de ácido ascórbico, dopamina e ácido úrico foram avaliadas e o material SZP1/AM (sílica/fosfato de zircônia/ azul de metileno) demonstrou picos voltamétricos em potenciais suficientemente separados para a quantificação simultânea das três espécies
The synthesis of the ceramic material SiO2/ZrO2/Phosphate were carried out through the sol-gel method, by reaction of tetraethyl orthossilicate (TEOS) with zirconium tetrabuthoxyde and three different reagents (phosphoric acid to SZP1; phosphoryl chloride to SZP2; and methyl phosphate to SZP3) to obtain phosphate group in the surface of solid particles. The solvent used was ethanol, with acid catalysis to start TEOS hydrolisis. The materials were characterized by different techniques and properties of acidity, thermical resistance and electrochemical activity were studied. The specific surface area, SBET, showed a higher value to SZP2 (270 ± 10 / m g) and lower to SZP3 (56 ± 10 / mg). The small specific surface area value for SZP3 was expected due to the use of reagent with organic groups. The phosphate species on surface of the solids were assigned as dihydrogen phosphate to SZP1 and mono hydrogen phosphate to SZP2 e SZP3. This was showed by XPS and NMR P CP MAS studies. The SEM images show a smooth surface on 30.000 times of amplification. TEM images show, as in X ray diffraction experiments, that the materials have an amorfous structure, being possible to say that that particles are of nanometric size. The electrochemical potentials to determination of ascorbic acid, dopamine and uric acid were studied and the material SZP1/MB (silica/zirconium phosphate/ metilene blue) showed voltametric peaks enough disconnected to makes the simultaneous determination of the three substances
Doutorado
Quimica Inorganica
Doutor em Ciências

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Garcia, François. "Elaboration de membranes en zircone sur support métallique." Montpellier 2, 1989. http://www.theses.fr/1989MON20250.

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Les procedes barbotine et sol-gel ont ete utilises pour preparer des membranes en zircone sur des supports tubulaires en acier inox. La microstructure des couches depend notamment de la stabilite des preparations et des programmes de sechage et de calcination. Le procede barbotine donne, en fonction de la poudre de zircone utilisee, des membranes presentant des diametres de pores compris entre 0,e' et 0,08 microns. Le procede solgel aboutit a des diametres de pores d'une dizaine d'angstroms. Les performances presentees par ces membranes en filtration ainsi que l'etendue importante de leur domaine d'application, en font un materiau de choix pour l'ultrafiltration. L'etude par diffraction des neutrons de la calcination des gels de zirconium q permis de mieux comprendre le role de l'oxygene sur les phenomenes de cristallisation et par consequent, sur la qualite de la couche finale

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Marlot, André. "Synthèse par pulvérisation cathodique magnétron et caractérisation de revêtement d'oxydes biocompatibles pour application aux implants dentaires en alliage de titane." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0319/document.

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Les procédés de dépôt en phase vapeur sont particulièrement performants pour la synthèse de revêtements à propriétés contrôlées. Plus spécifiquement, ce travail de recherche porte sur l'élaboration de revêtements biocompatibles, sur alliage titane TiAl6V4, obtenus par pulvérisation magnétron en conditions réactives. Dans un premier temps, nous avons décrit les procédés de mise en forme des implants commerciaux pour pouvoir les reproduire au niveau du laboratoire. Dans un second, nous avons focalisé notre étude sur l'effet de la structure cristallographique de films de zircone sur leur caractère biocompatible à partir de cultures cellulaires de fibroblastes. Les résultats ainsi obtenus démontrent très nettement des différences de comportement entre des films de zircone monoclinique, quadratique ou cubique. Dans l'objectif d'apporter des éléments d'information permettant de discuter de ces effets, d'autres séries de revêtements céramiques ont été élaborées comme par exemple des oxydes de titane ou de zirconium amorphes, de l'oxyde d'yttrium, de l'oxyde d'aluminium ou encore du carbone amorphe. Les cultures cellulaires pratiquées sur ces échantillons ont permis de démontrer le caractère biocompatible de l'oxyde d'yttrium excluant ainsi tout effet nocif de cet élément dans les zircones dopées
The vapor deposition processes are particularly successful for the synthesis of coatings with tuneable properties. More specifically, this research deals with the development of biocompatible coatings on titanium alloys TA6V obtained by magnetron sputtering in reactive conditions. At first, we described the processes to design the commercial medical implants to be able to reproduce them within the laboratory. In the second, we focused our study on the effect of the crystallographic structure of zirconia-based coatings on their biocompatible character from cell cultures of fibroblasts. The results obtained demonstrate a significant variation of cell behavior for the three the zirconia structures: monoclinic, tetragonal or cubic. In the purpose to bring relevant information that allow discussing these effects, another series of ceramic coatings were developed as for instance amorphous oxides of titanium or zirconium, yttrium oxide,, aluminum oxide or amorphous carbon. The cell response on these samples demonstrates to the biocompatible properties of the yttrium oxide, excluding any harmful effect of this element in the doped zirconia

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Verlet, Romain. "Influence de l’irradiation et de la radiolyse sur la vitesse et les mécanismes de corrosion des alliages de zirconium." Thesis, Saint-Etienne, EMSE, 2015. http://www.theses.fr/2015EMSE0806/document.

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Le combustible nucléaire des Réacteurs à Eau sous Pression (REP), sous forme de pastilles d’oxyde d’uranium UO2 (ou MOx), est confiné dans un gainage en alliage de zirconium. Ce gainage est très important car il représente la première barrière de confinement contre la dissémination des produits de fission, générés par la réaction nucléaire, vers le milieu extérieur. La corrosion par le milieu primaire des alliages de zirconium, en particulier l’alliage Zircaloy-4, est un des facteurs limitant le temps de séjour en réacteur des crayons combustibles (pastilles UO2 + gainage). Afin de permettre aux exploitants de centrales d’optimiser la gestion des cœurs et de prolonger la durée de vie des crayons combustibles en réacteur, de nouveaux alliages à base de zirconium-niobium (M5®) ont été développés. Or, les mécanismes de corrosion de ces derniers ne sont, en l’état, pas complètement élucidés du fait notamment de la complexité de ces matériaux, de l’environnement de corrosion et de la présence de l'irradiation venant du combustible nucléaire. De ce fait, cette thèse porte spécifiquement sur l’effet de la radiolyse et des défauts induits par l’irradiation aux ions dans la matrice métallique et dans la couche d’oxyde sur la vitesse de corrosion de l’alliage Zircaloy-4 et M5®. L’objectif est de déconvoluer la part de l’influence des dommages d’irradiation subis par la matrice métallique, de celle relative aux défauts créés dans l’oxyde et de celle liée à la radiolyse du milieu primaire sur la vitesse d’oxydation des alliages de zirconium en réacteur.1) Concernant l’effet de l’irradiation de la matrice métallique sur la vitesse d’oxydation : des boucles de dislocation de type apparaissent et entrainent une augmentation de la vitesse d’oxydation des deux alliages. Pour le M5®, en plus de ce premier effet, une précipitation d’aiguilles fines de niobium diminue la concentration en niobium en solution solide dans la matrice métallique et in fine dans l’oxyde, ce qui réduit fortement la vitesse d’oxydation de l’alliage.2) Concernant l’effet de l’irradiation de la couche d’oxyde sur la vitesse d’oxydation : les défauts générés par les cascades de déplacement dans l’oxyde augmentent la vitesse d’oxydation des matériaux. Pour le M5®, la germination de zones enrichies en niobium par irradiation de l’oxyde entraine une également diminution de la concentration en niobium en solution solide dans l’oxyde, ce qui réduit une nouvelle fois, la vitesse d’oxydation de cet alliage.3) Concernant l’effet de la radiolyse de l’eau : nous n’avons pas relevé d’effet considérable de la radiolyse sur la corrosion de l’alliage Zy4 ou M5® dans nos conditions expérimentales
The nuclear fuel of pressurized water reactors (PWR) in the form of uranium oxide UO2 pellets (or MOX) is confined in a zirconium alloy cladding. This cladding is very important because it represents the first containment barrier against the release of fission products generated by the nuclear reaction to the external environment. Corrosion by the primary medium of zirconium alloys, particularly the Zircaloy-4, is one of the factors limiting the reactor residence time of the fuel rods (UO2 pellets + cladding). To optimize core management and to extend the lifetime of the fuel rods in reactor, new alloys based on zirconium-niobium (M5®) have been developed. However, the corrosion mechanisms of these are not completely understood because of the complexity of these materials, corrosion environment and the presence of radiation from the nuclear fuel. Therefore, this thesis specifically addresses the effects of radiolysis and defects induced by irradiation with ions in the matrix metal and the oxide layer on the corrosion rate of Zircaloy-4 and M5®. The goal is to separate the influence of radiation damage to the metal, that relating to defects created in the oxide and that linked to radiolysis of the primary medium on the oxidation rate of zirconium alloys in reactor.1) Regarding effect of irradiation of the metal on the oxidation rate: type dislocation loops appear and increase the oxidation rate of the two alloys. For M5®, in addition to the first effect, a precipitation of fines needles of niobium reduced the solid solution of niobium concentration in the metal and ultimately in the oxide, which strongly reduces the oxidation rate of the alloy.2) Regarding the effect of irradiation of the oxide layer on the oxidation rate: defects generated by the nuclear cascades in the oxide increase the oxidation rate of the two materials. For M5®, germination of niobium enriched zones in irradiated oxide also causes a decrease of the niobium concentration in solid solution in the oxide, which once again, reduced the oxidation rate of this alloy.3) Regarding the effect of water radiolysis: We did not identify any significant effect of radiolysis on corrosion of the alloys under our experimental conditions

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Lundberg, Mikael. "Environmental analysis of zirconium alloy production." Thesis, Uppsala universitet, Tillämpad kärnfysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-166178.

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The generation of electricity in light water nuclear power plants uses zirconium alloys as the primary containment and cladding of the nuclear fuel. The environmental impacts of the production of zirconium alloys have been analyzed form a lifecycle perspective. From the mining of the zirconium-bearing mineral zircon to the finished zirconium alloy tube. A qualitative study indentifying the production processes and their potential environmental impacts have been performed. A quantitative study to perform a lifecycle analysis of the zircon mining and mineral separation was carried out. The life cycle analysis for the zircon mining was compared to the current lifecycle analysis (LCA) in Vattenfall's Forsmark nuclear power plant environmental product declaration (EPD). The results showed that the additional impact on Forsmark's EPD, when including the mining of zircon, is below 0.1% of the current levels for all parameters analyzed. A lifecycle analysis for the production of zirconium metal and zirconium alloy tube could not be performed due to lack of data from the zirconium metal industry. The major direct emissions from the zircon mining industry are related to the use of fossile fuels in machinery. The major direct emissions from the zirconium metal manufactoring industry are related to the use of acids.

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Jebrouni, Mostafa. "Elaboration de zircones et de dispersions alumine-zircone par réaction dans les sels fondus et caractérisation." Lyon 1, 1990. http://www.theses.fr/1990LYO10169.

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La zircone pure est obtenue par reaction de l'oxychlorure de zirconium avec des nitrates alcalins fondus. Les differents facteurs pouvant avoir une influence sur la morphologie de la poudre sont etudies et un mecanisme reactionnel est propose. Les transformations allotropiques de la zircone sont analysees par diffraction de rayon x, microscopie electronique et resonance paramagnetique electronique. Des hypotheses sont avancees pour justifier la metastabilite de la phase quadratique. Des poudres de zircone stabilisee a l'yttrium ultrafines, constituees de cristallites de taille inferieure a 100 a et caracterisees par une repartition tres homogene de l'element dopant, sont elaborees par reaction de l'oxychlorure de zirconium et du chlorure d'yttrium avec les nitrates alcalins fondus. L'influence des conditions d'extraction de l'oxyde du milieu fondu sur sa morphologie et son aptitude au frittage est examinee. Des dispersions alumine-zircone sont elaborees par reaction de l'oxychlorure de zirconium, de chlorure d'aluminium et de chlorure d'yttrium avec les nitrates alcalins fondus. Les effets des grains d'alumine sur la stabilisation de la zircone quadratique en absence d'oxyde d'yttrium sont etudies en premier. Les caracteristiques morphologiques et l'aptitude au frittage de dispersions renfermant de l'oxyde d'yttrium sont ensuite precisees

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Corolleur-Thomas, Gae͏̈lle. "Etude multi-échelle de la transformation quadratique monoclinique de la zircone résultant de l'oxydation du zirconium." Limoges, 2000. http://www.theses.fr/2000LIMO0004.

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Le zircaloy est utilise dans l'industrie nucleaire, pour la fabrication de tubes contenant le combustible, ils sont places sous forme d'assemblages dans le cur du reacteur. Dans les conditions d'utilisation (105bars, 400\c, h 2o), le zircaloy s'oxyde en formant la zircone. La zircone est un materiau polymorphe. Sa variete haute temperature, quadratique, peut etre stabilisee, a temperature ambiante, par la taille des grains (<30nm). Dans l'etude de la transformation quadratique/monoclinique, nous utilisons deux types d'echantillons : une poudre nanometrique et la couche d'oxydation developpee en autoclave sur des plaquettes de zircaloy. L'echantillon pulverulent sert de modele pour comprendre le phenomene beaucoup plus complexe qui se produit lors de la croissance de l'oxyde sur les plaquettes. L'etude multi echelle de la transformation correspond : - a une analyse par ir-tf de la surface des grains de poudres quadratique et monoclinique (traitee en autoclave). Nous avons declenche et analyse la transformation q/m dans la cellule ir. Pour chacun des trois echantillons, nous avons attribue, par decomposition du massif d'absorption, les differentes bandes appartenant aux groupements hydroxyles, et analyse l'adsorption de molecules sonde sur la surface (pyridine, dioxyde de carbone, methanol). Nous avons etudie les carbonates presents initialement a la surface, ainsi que ceux crees apres adsorption de co 2. - a une analyse par met et drx en incidence rasante. Nous avons montre que la zircone croit sur le metal en colonnes perpendiculaires au substrat, constituees de cristallites nanometriques. Nous avons etabli (met) que ces cristallites presentent les plans (h00) et (hhh) paralleles (3\) a l'interface metal oxyde. La couche de zircone est majoritairement de phase monoclinique, et ce meme pour une epaisseur de 50nm (drx rasants).

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Antunes, Márjore. "Produção, dispersão e consolidação de zircônia obtida a partir do tungstato de zircônio." reponame:Repositório Institucional da UCS, 2016. https://repositorio.ucs.br/handle/11338/1156.

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O presente trabalho tem por objetivo principal explorar a produção, a dispersão e a consolidação de zircônia (óxido de zircônio – ZrO2), em sua forma hidratada, obtida a partir do tungstato de zircônio (ZrW2O8), em meio alcalino e em condições de temperatura de até 100°C. A produção dos materiais particulados foi realizada sob diferentes condições experimentais (concentração de NaOH, tempo e temperatura) de modo a investigar como as características cristalográficas, morfológicas, químicas e térmicas dos pós produzidos são afetadas e, com base nesses resultados, buscou-se inferir o mecanismo pelo qual o ZrW2O8, pó micrométrico e insolúvel em água, originou partículas nanométricas de zircônia em condições brandas de síntese. Neste trabalho também se explorou a dispersão das partículas de zircônia, no momento de sua síntese, com o uso de trietanolamina (TEOA) como surfactante, de modo a obter soluções coloidais estáveis que pudessem ser ultracentrifugadas visando à obtenção de corpos de zircônia transparentes de forma controlada. Verificou-se, de um modo geral, que os materiais particulados produzidos sem a adição de TEOA são compostos por aglomerados de nanopartículas constituídas majoritariamente por Zr e O, com partículas primárias de tamanho próximo a 5 nm e cristalitos inferiores a 3 nm. Os pós apresentaram uma estrutura cristalina semelhante à da ZrO2 cúbica (ou de uma mistura de fases tetragonal e cúbica dependendo da condição de síntese), que formam aglomerados de elevada área superficial, mesoporosidade e capacidade para adsorção de água e dióxido de carbono em diferentes sítios superficiais. O mecanismo da síntese parece ser constituído, primeiramente, por uma reação química de substituição entre os tetraedros de WO4 e íons hidroxila, com posterior solubilização de parte da estrutura, pelo excesso de hidroxilas no meio, formando íons zircônio coloidais que polimerizam/condensam para a formação de núcleos cristalinos para posterior crescimento, em um processo facilitado por nucleação heterogênea e supersaturação. Além disso, a presença de tungstênio remanescente em todas as amostras parece ser um fator importante para a estabilização do tamanho e da estrutura cristalina dos materiais produzidos. A utilização de TEOA no processo de síntese permitiu a obtenção de corpos amarelados e transparentes, por ultracentrifugação, semelhantes a géis, que podem ser entendidos como um híbrido contendo material orgânico e WOx/ZrO2.
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The aim of the present work is to explore the production, dispersion and consolidation of zirconia (zirconium oxide – ZrO2), in its hydrous form, obtained from zirconium tungstate (ZrW2O8) in alkaline medium using temperatures up to 100°C. The production of particulate materials was carried out under different experimental conditions (NaOH concentration, time and temperature) in order to investigate how the crystallographic, morphological, chemical and thermal characteristics of the powders are affected and, based on these results, it was possible to infer the mechanism by which micrometric ZrW2O8 powder, water insoluble, yielded nanosized zirconia particles under mild synthesis conditions. This work also explored the dispersion of zirconia particles using triethanolamine (TEOA) as a surfactant, to obtain stable colloidal solutions which could be ultracentrifuged in order to obtain transparent zirconia bodies. It was found, generally, that the particulate materials produced without the addition of TEOA are composed of agglomerated nanoparticles composed mainly of Zr and O, with primary particle sizes near 5 nm having crystallites of less than 3 nm. The powders had a similar crystalline structure to cubic ZrO2 (or a mixture of tetragonal and cubic phases depending on the synthesis conditions), which create high surface area agglomerates with mesoporosity and capacity for water and carbon dioxide adsorption onto different surface sites. The mechanism of synthesis seems to be related to a chemical reaction of substitution between WO4 tetrahedra and hydroxyl ions, with subsequent solubilization of some portions of the structure due to the hydroxyl groups excess in the medium, originating colloidal zirconium ions which polymerize/condense to form crystal nuclei for further growth, in a process facilitated by heterogeneous nucleation and supersaturation. Furthermore, the presence of the remaining tungsten in all samples seems to be an important factor for stabilizing the size and crystalline structure of the materials produced. The use of TEOA in the synthesis process was responsible for the production of yellowish and transparent bodies by ultracentrifugation, similar to gels, which can be understood as a hybrid containing organic material and WOx/ZrO2.

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Petroni, Laeticia. "Étude du comportement post-coulée de réfractaires électrofondus à Très Haute Teneur en Zircone : thtz." Paris, ENMP, 2011. http://pastel.archives-ouvertes.fr/pastel-00657812.

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Cette étude, inscrite dans le Programme National de Recherche NOREV (Nouveaux REfractaires Verriers), porte sur la simulation numérique par éléments finis du refroidissement post-coulée de réfractaires électrofondus à très haute teneur en zircone (THTZ). Un modèle numérique thermique du refroidissement d'une dalle a été développé, à partir de mesures thermiques réalisées dans un moule lors d'une coulée en usine. Ce calcul a permis de situer dans le temps, pour les différents points de la dalle, les phénomènes intervenant au cours du refroidissement : solidification, fluage et transformation de la zircone. Des essais mécaniques isothermes et anisothermes ont permis de définir les équations constitutives du comportement en fluage (écrouissage isotrope) et lors de la transformation de phase de la zircone (modèle de plasticité de transformation de Leblond). A partir des chargements thermiques, les contraintes générées au cours du refroidissement ont été calculées, ainsi que les contraintes résiduelles après retour à température ambiante. La transformation de phase de la zircone, qui induit un gonflement volumique de 4%, semble s'avérer être le phénomène physique le plus critique pour ces deux types de contraintes. Les études paramétriques réalisées ont prouvé l'intérêt du modèle numérique en tant qu'outil d'aide à l'amélioration du procédé en jouant sur les propriétés de divers paramètres : propriétés du matériau coulé, géométrie du moule, propriétés de ses constituants,. .
This work has been carried out in the frame of a French national research program on new refractories for glass production (NOREV) and focussed on the numerical simulation of the post-casting cooling of fused-cast refractories with a very high zirconia content (HZ). A numerical model of the cooling-down sequence of a tile has been developed from thermal measurements performed in a mould during a casting on industrial site. This calculation allowed the time positioning, for each location in the tile, of the physical phenomena occurring during cooling: solidification, creep and phase transformation of zirconia. Isothermal and non-isothermal mechanical tests allowed the constitutive equations of creep (isotropic hardening) and during zirconia transformation (Leblond transformation-induced viscoplasticity model). From the thermal loadings, the thermal stresses induced by cooling have been calculated, as well as the residual stresses remaining at room temperature. The phase transformation of zirconia, which induces a 4% volume swelling, seems to be the most critical physical phenomenon for both types of stresses. The performed parametric studies proved the interest of the numerical model as a tool for improving the process by varying different parameters: cast material properties, mould shape, properties of its constituents,. .

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Wei, Chong. "Influence of stress and structural parameters on the hydrothermal ageing of zirconia-based ceramics." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI091/document.

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Cette thèse explore l'influence des contraintes et des paramètres structurels sur la sensibilité au vieillissement de la céramique à base de zircone. Il traite d'abord de l'influence des contraintes externes (appliquées) et des contraintes internes (résiduelles). Des contraintes extérieures sont appliquées par des tests de flexion in situ, tandis que des contraintes internes sont obtenues en contrôlant la microstructure des composites d'alumine durcis à la zircone. Le comportement de vieillissement de différents matériaux (3Y-TZP, 4Y-TZP et ZTA) est étudié par diffraction des rayons X (XRD) et spectroscopie Micro-Raman. Le résultat principal est l'influence principale des contraintes résiduelles sur les contraintes appliquées, principalement dans les matériaux de zircone. Il détruit alors l'effet de différents paramètres microstructuraux sur la cinétique du vieillissement. 3Y-TZP échantillons de même composition nominale mais différentes microstructures (caractérisées par leur taille de grain, la teneur en Y2O3 en phase tétragonale et la proportion de phase cubique) sont obtenues en utilisant différents procédés de frittage (frittage en deux étapes ou frittage normal pour différents temps et à différents moments Températures). En utilisant deux modèles semi-empiriques, on peut d'abord quantifier la relation entre la microstructure et les paramètres de traitement, puis la relation entre la cinétique du vieillissement et la microstructure. Enfin, il qualifie différents traitements de surface pour améliorer la résistance au vieillissement de 3Y-TZP. Les échantillons 3Y-TZP sont recuits sur des poudres de différentes compositions (TZ3YE, TZ4YS, 12ceTZP) et leur comportement de vieillissement est comparé. Les résultats montrent qu'une amélioration significative de la résistance au vieillissement peut être atteinte à 134 °C, sans compromettre la ténacité, mais ce gain n'est pas toujours valable à température ambiante ou corporelle. Étant donné que cette thèse traite de nombreux matériaux et des temps de vieillissement très long (jusqu'à plusieurs milliers d'heures), il était essentiel d'accélérer les tests de vieillissement et de réduire le nombre d'échantillons. Ainsi, nous avons mis en place une méthode rapide permettant d'accéder à l'énergie d'activation du vieillissement, avec une réduction de dix fois de la durée des études vieillissantes (présenté en annexe)
This thesis explores the influence of stresses and structural parameters on the sensitivity to ageing of zirconia-based ceramics. It first addresses the influence of both external (applied) stresses and internal (residual) stresses. External stresses are applied by in-situ bending tests, while internal stresses are obtained by controlling the microstructure of zirconia-toughened alumina composites. The ageing behavior of different materials (3Y-TZP, 4Y-TZP and ZTA) is investigated by X-ray diffraction (XRD) and Micro-Raman spectroscopy. The main result is the primary influence of residual stresses over applied stresses, mainly in zirconia materials. It then discriminates the effect of different microstructural parameters on the ageing kinetics. 3Y-TZP samples of same nominal composition but different microstructures (characterized by their grain sizes, content of Y2O3 in tetragonal phase and proportion of cubic phase) are obtained by using different sintering processes (two step sintering or normal sintering for different times and at different temperatures). Using two semi-empirical models, we are first able to quantify the relation between microstructure and processing parameters, and then the relation between ageing kinetics and microstructure. Finally it qualifies different surface treatments to improve the ageing resistance of 3-TZP. 3Y-TZP samples are annealed on powders of different compositions (TZ3YE, TZ4YS, 12ceTZP) and their ageing behavior are compared. The results show that a significant improvement of the ageing resistance can be reached at 134°C, without compromising the toughness, however this gain is not always valid at room or body temperature. Since this thesis deals with many materials and very long ageing times (up to several thousand hours), it was crucial to accelerate ageing tests and reduce the number of samples. Thus we set up a fast method enabling access to the activation energy of ageing, with a tenfold reduction in the duration of the ageing studies (presented in the appendix)

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Szymanski, Raymond. "Préparation, caractérisation et étude des propriétés catalytiques d'alliages platine-zirconium sur supports de carbone ou de zircone." Lyon 1, 1985. http://www.theses.fr/1985LYO19012.

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Etude de la formation des alliages par diffusion de rx, de la dispersion (tem, stem), du degre d'oxydation (esca), de la composition en surface (esca, iss, auger, chimisorption de h::(2)-o::(2)). Activite pour des reactions d'hydrogenation et hydrogenolyse (benzene, toluene, co, ethane)

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Lungareze, Daniel. "Influência da espessura da infraestrutura em Zircônia (3Y-TZP)na resistência mecânica da porcelana de cobertura /." Araraquara, 2015. http://hdl.handle.net/11449/127971.

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Orientador: Gelson Luis Adabo
Banca: Francisco de Assis Mollo Junior
Banca: Janaina Habib Jorge
Banca: Pedro Cesar Garcia de Oliviera
Banca: Sicknan Soares da Rocha
Resumo: Considerando o efeito das propriedades térmicas da zircônia (3Y-TZP) em infraestruturas anatômicas com maior volume, sobre a taxa de resfriamento da porcelana de cobertura e possível interferência sobre suas propriedades mecânicas, este estudo avaliou a influência da espessura da zircônia na resistência à fratura em coroas, dureza e tenacidade à fratura da porcelana e na resistência adesiva. Para o teste de resistência, foram obtidas infraestruturas em 3Y-TZP de coroas de 1º molar superior com três diferentes espessuras na oclusal: Grupo I - 1 mm, Grupo II - 2 mm e Grupo III - 3 mm. A porcelana VITA VM9 foi aplicada com espessura de 1,1 ± 0,1 mm pela técnica manual. A carga axial foi aplicada na cúspide mésiolingual por máquina de ensaios mecânicos (N=45). Para o teste de resistência de cisalhamento, foi aplicada a porcelana na forma cilíndrica com 1,2 mm de altura X 4 mm de diâmetro sobre placas de 3Y-TZP (5 x 5 mm) nas três espessuras (N= 30). O modo de falha foi analisado por microscopia óptica. Para medida da dureza Vickers e tenacidade à fratura da porcelana na interface com a 3Y-TZP e na superfície, foram usadas placas planas como descrito acima, e a porcelana aplicada, na extensão de uma das faces, com a espessura uniforme de 1,2 mm (N=24). Resultados: As médias e desvio padrão da resistência à fratura por compressão das coroas (N) foi: GI=1979 (523,5), GII=2266 (816,9) e GIII=2316 (672,9). A resistência ao cisalhamento (MPa) foi: GI=18,5 (2,44), GII=15,6 (3,80) e GIII=17,1 (3,17). A tenacidade à fratura (MPa.m1/2) foi: GI=1,53 e 1,48; GII=1,89 e 1,70 - GIII=1,84 e 1,72, respectivamente na interface e na superfície. ANOVA a um fator para resistência das coroas e ao cisalhamento, assim como a dois fatores para dureza e tenacidade a fratura não foram significantes. Concluiu-se que volumes...(Resumo completo clicar acesso eletrônico)
Abstract: Considering the possible effect of the cooling delaying of zirconia (3Y-TZP) in anatomical framework for higher volume, this study evaluated the influence of the framework thickness in the fracture load of porcelain veneered crowns, bond strength between zirconia and porcelain, hardness and fracture toughness of porcelain. For testing fracture load, maxillary first molar were prepared to accomplish three different thicknesses on the occlusal surfaces: Group I - 1 mm, Group II - 2 mm and Group III - 3 mm. The thickness of 1.1 ± 0.1 mm of porcelain VITA VM9 was applied by handmade technical stratification. The axial load was applied to the medial lingual cusp by means of a mechanical test machine (N = 45). The shear test was carried-out in flat plates (5 x 5 mm) in the three thicknesses of zirconia, and the porcelain was applied as cylindrical shape with 1,2 mm high for 4 mm in diameter (N=30). The shear bond strength test was performed by chisel. For measurement of the Vickers hardness and fracture toughness flat plates were fabricated as described above, and the porcelain was applied with uniform thickness of 1.2 mm (N=24). The measurements were done close to the surface and at the interface with zirconia. The mean and standard deviation for the test were: fracture load of the crowns (N) - GI = 1979 (523,5), GII = 2266 (816.9) and GIII = 2316 (672.9); sheer bond strength (MPa) - GI=18.5 (2.44), GII=15.6 (3.80) e GIII=17.1 (3.17); fracture toughness (MPa.m1/2) - GI = 1.53 and 1.48; GII = 1.89 and 1.70 - GIII = 1.84 and 1.72, respectively at the interface and close to the surface. Data from all trials analyzed by ANOVA were not significant for all the tests, revealing that the zirconia thicknesses did not affect the porcelain resistance of the crowns, hardness and fracture toughness and adhesion between the ceramic. Conclusion: The use...(Complete abstrat electronic access below)
Doutor

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Sousa, Priscilla Felício. "Estudos ab initio das propriedades estruturais, energéticas e eletrônicas de clusters de óxidos mistos de Ce15-nZrnO30,(n=0-15)." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/75/75134/tde-07122017-143721/.

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Partículas nanométricas de óxidos têm despertado um grande interesse devido a ampla gama de aplicações, por exemplo em catálise, óptica, sensores de gases, semicondutores, entre outros. Por isso, há vários estudos para uma grande variedade de óxidos com composição MO2, em função do tamanho e terminação da superfície. Também existe um grande interesse no estudo de óxidos mistos devido a possibilidade de combinar dois ou mais óxidos em escala nanométrica, com objetivo de controlar as propriedades físicas e químicas em função da composição. Neste trabalho, utilizou-se os metais Ce e Zr, uma vez que os óxidos desses elementos têm um grande potencial de aplicação na indústria como em células combustíveis, reações catalíticas entre outros. Os óxidos mistos Cem-nZrnO2mpossuem a capacidade de armazenar ou liberar oxigênio ao longo de reações químicas, e portanto, são largamente empregados em catalisadores de três-vias na indústria automobilística. Neste estudo foi empregada a teoria do funcional da densidade (DFT) com o funcional de troca-correlação proposto por Perdew, Burke e Ernzerhof (PBE). Investigou-se as propriedades estruturais, energéticas e eletrônicas dos clusters puros e então, selecionou-se quatro estruturas, as quais foram aplicadas na construção dos clusters de óxidos mistos de céria-zircônia. Por meio dos estudos de eletronegatividade de Mulliken, verificou-se que os clusters de zircônia apresentam uma tendência maior em atrair elétrons, quando comparados aos clusters de céria. Observou-se também que as estruturas de mais baixa energia de céria e zircônia apresentam diferentes números de coordenação (CN), no caso 4 e 3 NNN (vizinhos mais próximos), respectivamente. Isso se deve ao fato de tais estruturas não serem esféricas e também aos diferentes tamanhos atômicos de Ce e Zr. Além disso, notou-se que há uma maior compactação dos clusters de menor energia se comparados aos de maior energia, tanto para o céria quanto para zircônia, obteve-se os seguintes valores de diâmetro 1 nm e 2 nm para essa variação da energia relativa. Com esses resultados tem-se que há uma propensão dos clusters mistos, manterem propriedades semelhantes dos cluster puros, devido a similaridade entre o comportamento das estruturas de céria e da zircônia, os quais foram os agentes geradores dos clusters mistos. Observou-se que as propriedades estruturais dos cluster puros como CN, dav, σ e raio, mantiveram-se com a mesmas tendências nos clusters mistos. Para a obtenção do cluster mais estável analisou-se a energia de formação dos sistemas, sendo que a configuração mais favorável de ser formada é a Ce0,27Zr0,73O2, a qual considerou-se a estrutura pGMC representativa das configurações estudadas. Levando-se em consideração os resultados obtidos, na análise de formação dos clusters mistos delimitou-se a região de maior probabilidade de formação de clusters mistos estáveis entre 25% a 60%, de cério na composição.
Oxide nanomaterials have aroused great interest due to their application in several fields, such as in catalysis, optics, gas sensors, semiconductors, among others. Therefore, there are several studies for a wide variety of oxides with composition, and MO2, depending on the size and surface termination. There is also great interest in the study of mixed oxides due to the possibility of combining two or more oxides on a nanometric scale, in order to control their physical and chemical properties. In this work the metals Ce and Zr were used, since the oxides of these elements have a promising application in the industry as in fuel cells, catalytic reactions among others. The mixed oxides Cem-nZrnO2m present the ability to store or release oxygen during chemical reactions and therefore are widely used in three-way catalysts in the automotive industry. In this study, we used density functional theory (DFT) with PBE for the exchange-correlation functional. To investigate the structural, electronic and energetic properties of clusters, four selected structures were applied to build up the mixed ceria-zirconia oxides. Through the Mulliken electronegativity studies, it was found that zirconia clusters have a greater tendency to attract electrons, than the ceria clusters. Also observed that the lowest energy structures of ceria and zirconia have different coordination numbers, 4 and 3 NNN (Number of Nearest Neighbours), respectively. This is due to the fact that such structures are not spherical and have different atomic sizes. In addition, it was noted that there is a higher compaction of the clusters of lower energy compared to higher energy, for both ceria and zirconia, it was obtained the following values of diameter 1 nm and 2 nm for this variation of relative energy change. These results show that there is a trend in which mixed clusters have similar properties of the pure cluster, due to the similarity between the behavior of the structures of ceria and zirconia, which were the generating agents of the mixed clusters. It was observed that the structural properties of the pure clusters like CN, dav, σ and cluster radii, remained with the same trends in the mixed clusters. To obtain the most stable clusters we analyzed the formation energy of the systems, the most favorable configuration to be obtained is Ce0,27Zr0,73O2, which was considered the representative pGMC structure of the studied configurations. Taking into consideration the results, obtained in the analysis of the formation of the mixed clusters, delimited the higher probability of formation of mixed stable clusters between 25% to 60%, of cerium in composition.

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Fauroux, Marie-Alix. "Ostéo-intégration des implants dentaires à partir de l’étude de recherche clinique ZIR-ROC : matériaux, techniques opératoires, limites et perspectives." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT030.

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Introduction : Depuis les premiers implants dentaires Bränemark, les techniques chirurgicales et les matériaux implantaires ont évolué. La référence en terme de matériau implantaire est le Titane. Cependant, d’autres matériaux comme le Zircone ont été proposés pour suppléer le Titane en cas d’allergie au Titane mais aussi pour améliorer la bio-intégration de l’implant dentaire et l’esthétique. Les facteurs de risques d’échec implantaire des implants en Titane incluent, entre autre, l’hygiène orale, la consommation de tabac et la mise en charge immédiate. Objectif : L’étude ZIR-ROC a donc été menée dans le but d’étudier le taux de survie de ces implants zircone après 2 ans de suivi, de recueillir des informations sur l’intégration tissulaire des implants et de rechercher les facteurs de risque d’échec des implants en Zircone. Matériel et méthode : l’étude ZIR-ROC a été menée dans le service de chirurgie orale du CHU de Montpellier sur des implants monobloc en Zircone de la société Paris Implant®. La pose de 43 implants a été déterminée pour permettre l’analyse statistique des résultats. Le forage et l’insertion des implants ont été réalisés à l’aide du système de chirurgie guidée 2ingis®. La variable principale pour évaluer l’ostéo-intégration des implants a été le score délivré par le Periotest®. 22 variables secondaires ont été recueillies tels que les indices gingivaux et de plaque ainsi que l’analyse rétro-alvéolaire. Les données ont été relevées juste avant la chirurgie implantaire, ainsi qu’à 1 semaine, 4 semaines, 5 mois, 1 an et 2 ans. La méthode de Kaplan-Meier, le modèle de Cox et les analyses en composantes principales ont été utilisés pour l’analyse statistique. Résultats : Tous les implants ont présenté une bonne stabilité primaire post-opératoire (valeurs du Periotest comprises entre -8 et +1 ; moyenne à -5,7). Le taux d’échec implantaire a atteint 31% après les 5 premiers mois d’ostéo-intégration. Une mobilité clinique a été observée pour les implants perdus. Les facteurs de risque décrits dans la littérature ont été retrouvés dans le modèle de Cox avec une significativité pour la consommation de tabac et d’alcool et sans significativité statistique pour la densité osseuse ou encore la mise en place d’une couronne provisoire. Par ailleurs, la présence de plaque et d’inflammation gingivale a été observée en faible quantité sur les implants en Zircone. Discussion et conclusion : Le Zircone apparaît comme un matériau biocompatible pour des implants dentaires. Les causes des échecs implantaires précoces observés sont probablement multiples et cette étude n’a pas permis de démontrer l’implication seule de la Zircone dans ces échecs. La recherche des facteurs d’échecs implantaires a conduit à évaluer la technique chirurgicale utilisée pour cette étude mais aussi le dessin de l’implant. De plus, une étude in vitro comparant des implants à base de Zircone et de Titane a été entreprise pour évaluer l’affinité de cellules souches d’origine dentaire pour les 2 matériaux
Introduction: Since first Bränemark dental implants were implanted, operative surgery and materials for implantation have evolved. Titanium was the gold standard for dental implant material. But others materials like Zirconium were studied in replacement of Titanium due to allergy, bio-integration end aesthetic reasons. Contributing risk factors of Titanium implant failure include oral hygiene, tabacco and early loading among others factors. Objective: The aim of this clinical study was to evaluate survival rate of Zircon implants after 2 years, to collect information for tissue integration of Zirconium implant and to identify risk factors for Zircon implant failure. Material and Methods: ZIR-ROC study, conducted in the Oral Surgery Departement in Montpellier University Hospital, used zircon monobloc (ZIR-ROC®) implants (Paris Implant Society®). 43 implants were required for statistical analysis. Drilling and implantation were conducted with 2ingis® surgical guide system. The Periotest® value was the first endpoint for the implant osseointegration analysis. Gingival and dental plaque indices as well as intraoral X-ray analysis were part of the 22 secondary variables. Data were collected just after implantation surgery, and then, 1 week, 4 weeks, 5 months, 1 year and 2 years after implantation. Kaplan-Meier method, Cox regression model and principal component analysis were used for statistical analysis. Results: All implants showed postoperative optimal primary stability (Periotest® values between -8 and +1; mean: -5,7). Implants failure rate reached 31 percent after the 5 initial months of osseointegration. Clinical mobility was observed for the failed implants. Risk factors published in the scientific literature were observed in the Cox regression model with significant statistical effect for tobacco and alcohol consumption but without significant statistical effect for osseous density or even temporary crown insertion. Furthermore, gingival inflammation and dental plaque presence were low on Zircon implant. Discussion and Conclusion: Zirconium remains a biocompatible material for dental implantation but there were probably many reasons for the observed early implant failures and this study could not demonstrate the only involvement of Zirconium based material. Operative surgery used in this clinical study and the design of the implants were studied for researching other risk factors. In addition, an in vitro study comparing Zirconium versus Titanium as gold standard, was conducted for testing affinity of dental stems cells on Titanium and Zirconium-based dental materials

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Longhini, Diogo. "Caracterização mecânica de uma porcelana de aplicação convencional e uma prensada para recobrimento de infraestruturas de zircônia e o efeito do método de resfriamento na resistência à flexão biaxial do conjunto zircônia/porcelana /." Araraquara, 2014. http://hdl.handle.net/11449/110828.

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Orientador: Gelson Luis Adabo
Banca: Renata Garcia Fonseca
Banca: Igor Studart Medeiros
Resumo: Este estudo caracterizou mecanicamente uma porcelana feldspática de aplicação convencional e uma porcelana feldspática prensada, indicadas para infraestrutura em zircônia, quanto a resistência à flexão biaxial, dureza Vickers e tenacidade à fratura. Além disso, foi investigado o efeito da taxa de resfriamento após o ciclo de sinterização do glaze da porcelana na resistência à flexão biaxial de bicamadas zircônia/porcelana. Espécimes monocamada de VM9 (n=15) e Vita PM9 (n=15) (12,0 mm de diâmetro x 1.2 mm de espessura) foram confeccionados conforme as recomendações do fabricante e submetidos ao ensaio de resistência à flexão biaxial (MPa). Um fragmento de cada espécime fraturado foi aleatoriamente selecionado para a mensuração da dureza Vickers (n=15) (VHN). A tenacidade à fratura aparente(MPa.m½) foi determinada pela técnica da indentação Vickers (n=15). Para o ensaio de flexão biaxial dos bicamadas, discos de zircônia (Vita In-Ceram YZ) foram recobertos com porcelana convencional Vita VM9 (n=30) ou com porcelana prensada Vita PM9 (n=30). Após a simulação da queima de glaze, os espécimes foram submetidos a resfriamento rápido (n=15) ou lento (n=15). Após o ensaio de resistência à flexão, os espécimes foram analisados quanto ao tipo de fratura. Teste de T-Student para espécimes monocamada mostrou que Vita PM9 apresentou valores significantemente maiores de resistência à flexão biaxial (p<0,01) e dureza (p=0,017) em relação a Vita VM9, mas não quanto a tenacidade à fratura (p= 0.41). ANOVA a dois fatores (porcelana e método de resfriamento), utilizada para análise dos bicamadas indicou significância apenas para porcelanas, com superioridade para a combinação Vita PM9/zircônia (p<0,01). Porcelanas prensadas parecem ser uma alternativa mais efetiva para recobrimento de zircônia em relação as convencionais.
Abstract: This study characterized mechanically a conventional and a pressed feldspathic porcelain indicated for zirconia core in terms of biaxial flexural strength, fracture toughness, Vickers hardness. In addition it was investigated the effect of the glaze cooling rate on the biaxial flexural strength of the zirconia/porcelain bilayer. Specimens monolayers of Vita VM9 (n=15) and Vita PM9 (n=15) (12.0 mm diameter x 1.2 mm thickness) were prepared according to manufacturer's recommendations for the biaxial flexural strength test (MPa). Afterwards, one fragment of each broken specimen was randomly selected for Vickers hardness measurements (n=15) (VHN). Apparent fracture toughness (MPa.m½) was determined by Vickers hardness indentation technique (n=15). For the biaxial flexural strength of bilayers, zirconia discs (Vita In-Ceram YZ) were veneered with the conventional porcelain Vita VM9 (n=30) or with the pressed porcelain Vita PM9 (n=30). After the glaze firing simulation, the specimens were submitted to fast (n=15) or slow cooling method (n=15). After the biaxial flexural test, the specimens were analyzed in relation to fracture pattern. T-Student tests were performed for the monolayer specimens, while two-way ANOVA (porcelain and cooling method) was used for the bilayer ones (α=.05). Vita PM9 exhibited significantly higher biaxial flexural strength (p<0.01) and hardness than VM9 (p=0.017). However, there was no significant difference (p= 0.41) in fracture toughness between the porcelains. The two-way ANOVA indicated significance only for the porcelain, with superiority for the combination Vita PM9/zirconia (p<0.01).The pressed porcelain seems to be a mechanically more effective alternative for zirconia veneering than the conventional one.
Mestre

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49

Bitencourt, Sandro Basso. "Desenvolvimento e caracterização físico-química de um novo filme de PECVD na melhora da resistência de união entre a Y-TZP e a cerâmica de cobertura /." Araçatuba, 2017. http://hdl.handle.net/11449/149902.

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Orientador: Daniela Micheline dos Santos
Coorientador: Aldiéris Alves Pesqueira
Banca: Marcelo Coelho Goiato
Banca: Valentim Adelino Ricardo Barão
Resumo: A obtenção de uma união duradoura da interface zircônia/cerâmica de cobertura é uma preocupação para sucesso clínico de restaurações livres de metal e ainda não existem evidências que indiquem uma técnica de tratamento dessa zircônia com melhor previsibilidade e durabilidade. Assim, o objetivo desse estudo foi desenvolver e caracterizar fisico-quimicamente um novo filme por vapor químico melhorado por plasma (plasma enhanced chemical vapor deposition - PECVD) na superfície da zircônia tetragonal policristalina estabilizada por óxido de ítrio (Y-TZP) para melhorar sua resistência de união com cerâmica de cobertura. Para isso, um total de 192 amostras de Y-TZP (13×5,4×5 mm) foram divididas em 6 grupos, de acordo com o tratamento de superfície: controle - sem tratamento (C), jateamento com partículas de óxido de alumínio de 27 µm (Al27), jateamento com partículas de óxido de alumínio de 110 µm (Al110), jateamento com partículas de óxido de alumínio de 250 µm (Al250), aplicação de liner para zircônia (L) e o filme por PECVD (P). A superfície da Y-TZP foi caracterizada por meio da microscopia eletrônica de varredura (MEV), espectroscopia de energia dispersiva (EED), microscopia de força atômica (MFA), perfilometria e energia livre de superfície. A resistência de união entre a Y-TZP e uma cerâmica de cobertura foi testada antes e após fadiga térmica (20.000 ciclos de 5 e 55 °C). Os dados foram submetidos à análise de variância e teste Tukey HSD (α=0,05). Como resultados, foi encont... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The obtainment of a durable zirconia/veneer ceramic interface bond is a preoccupation for clinical success of metal-free restorations and did not exist evidence indicates that the technique with the best predictability and durability. Thus, the aim of this study was to develop and to physico-chemically characterize a novel film formed after plasma enhanced chemical vapor deposition (PECVD) on the yttria stabilized tetragonal zirconia (Y-TZP) surface aiming to improve its bond strength to the veneer ceramic. For this, a total of 192 YTZP samples (13×5.4×5 mm) were divided in 6 groups, according the surface treatment: control - no treatment (C), airborne-particle with 27 µm aluminum oxide (Al27), airborneparticle with 110 µm aluminum oxide (Al110), airborne-particle with 250 µm aluminum oxide (Al250), zirconia liner (L) and the film by PECVD (P). The Y-TZP surface was characterized through scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), atomic force microscopy (AFM), surface roughness and surface free energy. The bond strength between Y-TZP and veneer ceramic was tested before and after thermal fatigue (20,000 cycles of 5 and 55ºC). The data were submitted to analysis of variance and Tukey HSD test (α=0.05). The results were that the roughness of Y-TZP surface was not modified in the P group (P>0.05 vs control), while the Al110, Al250 and L groups showed higher roughness values (P<0.05). All the treatments improved the surface free energy of Y-TZP, exc... (Complete abstract click electronic access below)
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Lauriol-Garbey, Pascaline. "Étude de nouveaux catalyseurs pour la valorisation du glycérol en acroléine." Thesis, Lyon 1, 2010. http://www.theses.fr/2010LYO10206.

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Abstract:

La déshydratation du glycérol en acroléine a été étudiée sur de nouveaux catalyseurs à base d'oxydes en vue de mettre au point un nouveau procédé de production de la méthionine. Ces catalyseurs performants sont des zircones niobiées et des zircones tungstées dopées à la silice. Si les catalyseurs proposés dans la littérature jusqu'à présent pouvaient être sélectifs, ils se désactivaient rapidement par cokage. Les nouveaux catalyseurs mis au point sont aussi actifs et sélectifs mais beaucoup plus stables sous flux réactionnel. Les performances des zircones niobiées sont très sensibles à la méthode de préparation; les catalyseurs ont été caractérisés par DRX, spectroscopie Raman, MET, EDX, XPS. Ces analyses ont montré qu'une partie du niobium est incorporée dans la zircone qui est recouverte d'espèces polymères de niobium. Les zircones tungstées performantes sont constituées d'une zircone recouverte de silice et de polytunsgtates. L'acido-basicité des catalyseurs a été étudiée par différentes techniques: réactions modèles de transformation du méthylbutynol et du 2-propanol, TPD-NH3, adsorption de NH3 et SO2étudiée par microcalorimétrie et adsorption de pyridine suivie par IR. Ces études ont permis de montrer que les sites basiques de la zircone sont néfastes pour les performances et que les sites acides de Brönsted avec une large gamme de force acide sont actifs et sélectifs en acroléine. Nous avons montré par microcalorimétrie que même les sites acides très faibles participent à la réaction
Glycerol dehydration to acrolein has been studied over innovative oxide catalysts in order to develop a new methionine production process. These performing catalysts are niobiate zirconia mixed oxides and tungstated zirconia doped with silicium. The catalysts proposed so far in the literature are active and selective but they show fast deactivation under reaction flow due to coke deposition. The new catalysts appear at least as active and selective but much more stable. The niobiate zirconia mixed oxides, which catalytic performances are very sensitive to the preparation method, have been characterized by XRD, Raman spectroscopy, TEM with EDX analyses and XPS. Theses analyses show that niobium cations are partially incorporated into zirconia and covered its surface as polymeric niobium oxide species. The efficient tungstated zirconia catalysts consist of zirconia cover with silicium and polymeric tungstate species. Acid-base properties of the catalysts have been studied by model reaction of methylbutynol and 2-propanol, NH3-TPD, SO2 and NH3adsorption followed by microcalorimetry and IR spectroscopy of pyridine adsorption. These studies show that the zirconia uncovered by silica or containing no niobium are unselective sites and that Brönsted acid sites of the polymeric tungstate or niobium oxide species are the selective sites in acrolein. The strength of these sites does not appear as a key parameter to acrolein selectivity and even weak sites participate to the reaction

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