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Artykuły w czasopismach na temat "Silicatées"
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Baraček, Jan, Martin Palou, Jiří Másilko, Jaromír Wasserbauer, František Šoukal, Tomáš Opravil i Martin Boháč. "Application of Sol-Gel Method to Investigate the Influence of P2O5 on the Course of Reactions in CaO-SiO2 System". Materials Science Forum 851 (kwiecień 2016): 92–97. http://dx.doi.org/10.4028/www.scientific.net/msf.851.92.
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The effect of P2O5 addition on the calcium silicate phase equilibrium during the sol-gel synthesis of dicalcium silicate was investigated using Scanning electron microscope and X-ray diffraction. It is established that phosphorous oxide can form solid solution with dicalcium silicate, but its causes the formation of phosphatic calcium silicate phases such as Ca14.92 (PO4)2.35(SiO4)5.65 and 5CaO.SiO2.P2O5 also. Local analysis has demonstrated the presence of calcium phosphate epicenters containing silicon oxide and calcium silicate zones with minimum content of phosphorous oxide and intermediary areas of various phosphatic calcium silicates. The formation of two distinct islets of calcium silicate and calcium phosphate is due to the affinity between acid oxides (SiO2, P2O5) and basic one (CaO) during sol-gel process. Then, the formation of various phosphatic calcium silicates result from the diffusion of P2O5 towards calcium silicate and that of SiO2 towards calcium phosphate.
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Wooden, Diane H. "Cometary Silicates: Interstellar and Nebular Materials". Highlights of Astronomy 13 (2005): 495–97. http://dx.doi.org/10.1017/s1539299600016403.
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AbstractEvidence for interstellar material in comets is deduced from IR spectra, in situ measurements of Comet Halley, and chondritic porous interplanetary dust particles (CP IDPs). IR spectra of comets reveal the spectrally active minerals: amorphous carbon, amorphous silicates, and (in some comets) crystalline silicates. Evidence suggests amorphous silicates are of interstellar origin while crystalline silicates are of nebular origin.10 μm spectra of comets and sub-micron amorphous silicate spherules in CP IDPs have shapes similar to absorption spectra through lines-of-sight in the ISM. Thermal emission models of cometary IR spectra require Fe-bearing amorphous silicates. Fe-bearing amorphous silicates may be Fe-bearing crystalline silicates formed in AGB outflows that are amorphized through He+ ion bombardment in supernova shocks in the ISM.Crystalline silicates in comets, as revealed by IR spectra, and their apparent absence in the ISM, argues for their nebular origin. The high temperatures (>1000 K) at which crystals form or are annealed occur in the inner nebula or in nebular shocks in the 5 – 10 AU region. Oxygen isotope studies of CP IDPs show only 1% by mass of the silicate crystals are of AGB origin. Together this suggests crystalline silicates in comets are probably primitive grains from the early solar nebula.
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Liang, Jian-Jie, Alexandra Navrotsky, Thomas Ludwig, Hans J. Seifert i Fritz Aldinger. "Enthalpy of Formation of Rare-earth Silicates Y2SiO5 and Yb2SiO5 and N-containing Silicate Y10(SiO4)6N2". Journal of Materials Research 14, nr 4 (kwiecień 1999): 1181–85. http://dx.doi.org/10.1557/jmr.1999.0158.
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The enthalpies of formation of two rare-earth silicates (Y2SiO5 and Yb2SiO5) and a N-containing rare-earth silicate Y10(SiO4)6N2 have been determined using high-temperature drop solution calorimetry. Alkali borate (52 wt% LiBO2·48 wt% NaBO2) solvent was used at 800 °C, and oxygen gas was bubbled through the melt. The nitrogen-containing silicate was oxidized during dissolution. The standard enthalpies of formation are for Y2SiO5, Yb2SiO5, and Y10(SiO4)6N2, respectively, –22868.54 ± 5.34, –22774.75 ± 8.21, and –14145.20 ± 16.48 kJ/mol from elements, and –52.53 ± 4.83, –49.45 6 ± 8.35, and –94.53 ± 11.66 kJ/mol from oxides (Y2O3 or Yb2O3, SiO2) and nitride (Si3N4). The silicates and N-containing silicate are energetically stable with respect to binary oxides and Si3N4, but the N-containing silicate may be metastable with respect to assemblages containing Y2SiO5, Si3N4, and SiO2. A linear relationship was found between the enthalpy of formation of a series of M2SiO5 silicates from binary oxides and the ionic potential (z/r) of the metal cation.
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Kozasa, Takashi, i Hisato Sogawa. "Formation of crystalline silicate around oxygen–rich AGB stars". Symposium - International Astronomical Union 191 (1999): 239–44. http://dx.doi.org/10.1017/s0074180900203124.
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Crystallization of silicate has been investigated within the framework of dust formation in steady state gas outflows around oxygen–rich AGB stars, where silicates are locked not only into homogeneous silicate grains but also into the mantles of heterogeneous grains. Based on the thermal history of dust grains after their formation, the crystallization calculation results in no crystalline silicate for the mass loss rate Ṁ ≤ 2 × 10−5M⊙ yr−1. Only silicate in the mantles of heterogeneous grains can be crystallized for Ṁ ≥ 3 × 10−5M⊙ yr−1, while homogeneous silicate grains remain amorphous. The mass fraction of crystalline silicate increases with increasing Ṁ. The radiation transfer calculations confirm the appearance of an emission feature around 33.5 μm, taking olivine as a representative of crystalline silicates. On the other hand, the 10μm feature appears in absorption, being dominated by homogeneous silicate grains. These trends are consistent with the observations. Thus the crystalline silicate is a diagnostics of high mass loss rate at the late stage of AGB stellar evolution, reflecting the formation process of dust grains.
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DERRIEN, RICHARD, ETHAN MICHAEL SULLIVAN, STEPHEN LIU, ELODIE MOINE i FRANCIS BRIAND. "Silicate Island Formation in Gas Metal Arc Welding". Welding Journal 100, nr 01 (1.01.2021): 13–26. http://dx.doi.org/10.29391/2021.100.002.
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Because formation of silicate islands during gas metal arc welding is undesirable due to decreased productivity and decreased quality of welds, it is important to understand the mechanism of the formation of these silicate islands to mitigate their presence in the weld. The effects of welding parameters on the silicate formation rate were studied. Results showed that the applied voltage and oxidizing potential of the shielding gas were the parameters that most strongly influenced the amount of silicates formed on the surface of the weld bead. High-speed video was used to observe the formation of silicate islands during the welding process, which showed that the silicates were present at each stage of the welding process, including the initial melting of the wire electrode, and grew by coalescence. A flow pattern of the silicate islands was also proposed based on video analysis. An electromagnetic levitation system was used to study the growth kinetics of the silicate islands. Silicate coverage rate was found to increase with increasing oxidizing time, increasing oxidizing potential of the atmosphere, and increasing content of alloying elements except for Ti.
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Niciu, H., Dorel Radu, C. Onose, A. Ioncea, Daniela Niciu, H. Stroescu i C. S. Onose. "The Permanently Bonded Glass Decor from Chemical Precursors". Advanced Materials Research 39-40 (kwiecień 2008): 579–82. http://dx.doi.org/10.4028/www.scientific.net/amr.39-40.579.
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Alkaline earth metal silicates as well as many polyvalent metals silicates can be obtained through aqueous solutions reactions between an alkaline silicate solution and the solutions of metal salts. The vitrifiation of the oxide compositions, established by the necessary molar ratios for the projected glass, is realised by calculating the concentration of chemical precursors, through their reaction directly on the substrate. The sodium silicate viscosity in aqueous solution and the viscosity of nitrogenated compounds or oxalates necessary in the silicates synthesis is compatible with the necessary viscosity for ink-jet cartridges. The necessary silicates forming reactions were studied directly on the deposition support, so that the functional characteristics of the multicompartment ink-jet cartridges were used. Compositions were realised, in which the colouring effect was obtained with ionic colorants. The vitrifiation and the quality of the obtained thin films were studied through Optical Microscopy and Scanning Electron Microscopy.
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Heckmann, W., F. Ramsteiner i Ch Mehler. "Morphology of Poly Amide Nanocomposites Characterized by Transmission Electron Microscopy (TEM) and Electron Spectroscopic Imaging (ESI)." Microscopy and Microanalysis 7, S2 (sierpień 2001): 502–3. http://dx.doi.org/10.1017/s1431927600028580.
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The introduction of organophilic layered silicates into a polyamide matrix significantly improves stiffness and strength [1,2]. Two methods are known to prepare such nanocomposites. For both methods cations such as sodium, potassium, magnesium or calcium, located in the interlayer galleries of the layered silicates must be exchanged by quaternary alkyl ammonium ions containing at least one alkyl chain and so rendering the originally hydrophilic into an organophilic silicate. in the insitu-method monomeric caprolactam is intercalated between the modified silicate interlayers and subsequently polycondensated to polyamide. By this method the silicates can be broken down into their nanoscale building blocks as can be shown by TEM and ESI (Fig. 1). Another more direct possibility to delaminate the silicates is melt mixing in an extruder. with both methods similar degrees of delamination can be achieved.This paper presents some of our morphological results on polyamide containing organically modified montmorillonite.
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Lii, Kwang-Hwa. "High-T, High-P Hydrothermal Synthesis of Uranium Silicates and Germanates". Acta Crystallographica Section A Foundations and Advances 70, a1 (5.08.2014): C759. http://dx.doi.org/10.1107/s2053273314092407.
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Most uranium minerals can be classified as oxidized species in which U is fully oxidized to U(VI), and reduced species, in which U occurs primarily as U(IV). Uranyl silicates are an important group of uranium(VI) minerals in the altered zones of many uranium deposits [1]. Uranyl silicates have also received attention because they form when spent nuclear fuel interacts with water containing silicon under oxidizing conditions. One naturally occurring uranium(IV) silicate exists, namely coffinite (USiO4), which is the most important ore mineral for uranium after uraninite. Numerous synthetic uranium(VI) silicates and germanates containing organic amines or alkali metals as countercations have also been reported [2]. In contrast to the uranium(VI) compounds, the chemistry of materials containing uranium(V) is considerably less developed owing to the tendency of U(V) to either oxidize to U(VI) or disproportionate to U(IV) and U(VI). We have synthesized a pentavalent-uranium silicate and a germanate by a high-temperature, high-pressure hydrothermal method in gold ampoules contained in a high-pressure reaction vessel at ca. 600 °C and 170 MPa [3a,b]. Following the synthesis of the U(V) compounds, a number of mixed-valence uranium silicates and germanates have been synthesized, for example, a mixed-valence uranium(IV,V) silicate, Cs2K(UO)2Si4O12 [3c], a uranium(IV,VI) germanate, Cs8U(UO2)3(Ge3O9)3·3H2O [3d], uranium(V,VI) silicates and germanates, A3(U2O4)Ge2O7 (A = Rb, Cs) and [Na9F2][(UO2)3(Si2O7)2] [3e,f], and a uranium(IV,V,VI) silicate, Na7UO2(UO)2(UO2)2Si4O16 [3g] in which three oxidation states of uranium co-exist in one compound. In addition, tetravalent-uranium compounds, Cs2USi6O15 and Cs4UGe8O20 [3h,i], were also synthesized. All members in the family of uranium silicates and germanates with the oxidation states of uranium from +4 to +6 have been observed. In this presentation the high-temperature, high-pressure hydrothermal synthesis, crystal structures, and XPS spectroscopy of these interesting compounds will be reported.
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Jakobsen, U. H. "A hydrated barium silicate in unmetamorphosed sedimentary rocks of central North Greenland". Mineralogical Magazine 54, nr 374 (marzec 1990): 81–89. http://dx.doi.org/10.1180/minmag.1990.054.374.08.
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AbstractA new occurrence of barium silicates has been found in unmetamorphosed sedimentary rocks of central North Greenland. Two different barium minerals have been identified, the Ba-feldspar hyalophane, and an unknown and hitherto undescribed hydrated Ba-silicate with an anhydrous chemical composition identical to cymrite but with about 4 moles of water in the mineral structure. Both silicates are found in a black organic-rich chert sequence in close association with baryte. No replacement textures are observed between the three Ba-minerals.The hydrated Ba-silicate in the unmetamorphosed rock sequence of the Navarana Fjord area is considered to represent a member in a sequence of Ba-silicates from the unknown Ba-silicate with four H2O in the structure (BaAl2Si2O8·4H2O), through cymrite with one H2O (BaAl2Si2O2O8·H2O) to celsian with none (BaAl2Si2O8). This sequence might reflect the continuous release of water during prograde diagenesis and metamorphism. The association between chert and Ba minerals in the sedimentary rocks of the Navarana Fjord area is believed to reflect an addition of silica and barium by hydrothermal solutions.
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P. C. Bennett, J. R. Rogers, W. J. "Silicates, Silicate Weathering, and Microbial Ecology". Geomicrobiology Journal 18, nr 1 (styczeń 2001): 3–19. http://dx.doi.org/10.1080/01490450151079734.
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Palard, Mickaël. "Synthèse et frittage d’hydroxyapatites phosphocalciques silicatées". Limoges, 2007. https://aurore.unilim.fr/theses/nxfile/default/0a57188a-f515-49eb-b974-67e88f06f89e/blobholder:0/2007LIMO4056.pdf.
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Des poudres d’hydroxyapatites silicatées Ca10(PO4)6-x(SiO4)x(OH)2-x (0 ≤ x ≤ 2) ont été synthétisées par précipitation en milieu aqueux à pH et température contrôlés suivie d’une calcination. Les précipités sont composés d’une phase apatite carbonatée et silicatée (phase principale) et d’une phase secondaire contenant le silicium en excès. Celui-ci n’est incorporé en totalité dans l’apatite que lors de la calcination en substituant les groupements carbonates (CO32-) issus de la synthèse. Pour xSi ≤ 1 mol, les poudres sont monocristallines. Le mécanisme de formation de l’HA silicatée est : Ca10-y(PO4)6-y-w(CO3)y(SiO4)w(OH)2-y-w + y CaSiO3 → Ca10(PO4)6-y-w(SiO4)w+y(OH)2-y-w + y CO2. Au-delà de 1 mol de silicium, les poudres cristallisent dans un système biphasé, hydroxyapatite et phosphate tricalcique alpha. La stabilité thermique des poudres dépend de la teneur en silicium. L’hydroxyapatite silicatée se décompose en deux temps selon les réactions : Ca10(PO4)6-x(SiO4)x(OH)2-x → (1 – x/2) Ca10(PO4)6(OH)2 + (x) Ca3(PO4)2 + (x) Ca2SiO4 (T1) → (1 – x/2) Ca10(PO4)6(OH)2 + (x/2) Ca10(PO4)4(SiO4)2 (T2). L’incorporation de silicium dans l’hydroxyapatite engendre un décalage des températures de début de frittage et de vitesse maximale de densification vers les hautes températures. Les conditions doivent être adaptées à chaque composition afin d’obtenir des matériaux denses (τ > 95%) sans phase secondaire. Ceux-ci ont été testés biologiquement par culture in vitro de cellules ostéoblastes MG-63 en évaluant la prolifération et l’adhésion cellulaire. Le nombre de cellules augmente jusqu’à 5 jours de culture. La présence de silicium dans l’apatite ne modifie pas la biocompatibilité des matériaux mais l’activité cellulaire (prolifération, adhésion) n’est cependant pas amélioréeSilicated hydroxyapatite powders Ca10(PO4)6-x(SiO4)x(OH)2-x (0 ≤ x ≤ 2) were synthesized by a wet precipitation method with control of the pH and temperature, followed by a heat treatment. The raw materials were composed of a partially silicated and carbonated apatite and a secondary minor phase containing the excess silicon. This excess is fully incorporated in the apatite lattice during the calcination by substituting carbonate groups (CO3 2-) from the synthesis. For xSi ≤ 1 mol, powders are pure. The mechanism of formation of the silicated HA is : Ca10-y(PO4)6-y-w(CO3)y(SiO4)w(OH)2-y-w + y CaSiO3 → Ca10(PO4)6-y-w(SiO4)w+y(OH)2-y-w + y CO2. For xSi > 1 mol, the powders crystallize in a biphasic system, alpha tricalcium phosphate and hydroxyapatite. The thermal stability of powders depends on the silicon content. The thermal decomposition of the silicated hydroxyapatite could be written into two steps according to the reactions : Ca10(PO4)6-x(SiO4)x(OH)2-x → (1 – x/2) Ca10(PO4)6(OH)2 + (x) Ca3(PO4)2 + (x) Ca2SiO4 (T1) → (1 – x/2) Ca10(PO4)6(OH)2 + (x/2) Ca10(PO4)4(SiO4)2 (T2). When silicates were incorporated in the hydroxyapatite lattice, the begining of the sintering and the maximum densification rate were shifted to the high temperatures. The conditions must be adaptated to each composition in order to obtain dense materials (τ> 95%) without secondary phase. Dense ceramics made of pure HA and SixHA containing various amounts of silicate (up to x = 0. 6) were biologically tested in vitro with human osteoblast like cells. The proliferation of cells on the surface of the ceramics increased up to 5 days of culture indicating that the materials were biocompatible. But, the silicon content did not influence the cell proliferation
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Coste, Amaury. "Modélisation moléculaire de solutions silicatées en milieux alcalins". Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS144.
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Ma thèse porte sur la modélisation moléculaire de solutions silicatées en milieu alcalin. L’originalité de l’approche est d’appliquer une description classique par dynamique moléculaire (sans rupture ni création de liaisons) pour des systèmes connus pour être réactifs. Le but est de comprendre les interactions ion-ion dans ces solutions d’électrolytes. Pour y parvenir, des champs de force polarisables ont été développés pour décrire les propriétés de solvatation de l’anion hydroxyde et des oligomères de silicates. Dans un premier temps, les propriétés structurales et thermodynamiques des solutions concentrées d’hydroxyde d’alcalin MOH (M+ = Li+, Na+, K+ et Cs+) ont été étudiées sur une large gamme de concentrations. Les intensités WAXS théoriques calculées à partir de nos simulations sont en bon accord avec les données expérimentales. De plus, nous avons mis en évidence une faible association des paires MOH même à forte concentration. Cela a été confirmé par le calcul des constantes d’association des paires ioniques (KMOH = 0,1 L mol-1) qui sont en bon accord avec la littérature. Ensuite, nous nous sommes intéressés aux propriétés structurales de solutions alcalines contenant des oligomères de silicates, notamment des monomères (Si(OH)4, SiO(OH)-) et des dimères (Si2O2(OH)5-, Si2O3(OH)42-). Nous avons donc, dans un premier temps, développé un champ de force « universel » permettant de modéliser un très grand nombre d’oligomères de silicates. Ces simulations ont permis de mettre en évidence une adsorption des cations Na+ dépendante de la spéciation en silicates et une faible interaction entre les hydroxydes et les silicates. Enfin, en prenant en compte la connectivité des atomes de silicium (déterminée par RMN du 29Si) et le rayon moyen des oligomères (déterminé par des mesures de diffusion des rayons X), nous avons modélisé le comportement de solutions « réelles » expérimentales et expliqué l’influence de la nature des alcalins sur les propriétés structurales et dynamiquesMy thesis focused on the molecular modeling of alkaline silicate solutions. The originality of our approach is the use of classical molecular dynamics, which is suited to study equilibrium properties, to reactive systems. The aim of this work is to understand ion-ion interactions in of such electrolyte solutions. To this end, polarizable force fields have been developed to describe the solvation properties of the hydroxide anion and the silicate oligomers.First, the structural and thermodynamics properties of concentrated aqueous solutions of alkali hydroxide MOH (M+ = Li+, Na+, K+, and Cs+) have been studied over a wide range of concentrations. Theoretical WAXS intensities calculated from our simulations are in good agreement with the experimental data. In addition, we pointed out a weak association of the MOH ion pairs, even at high concentrations. This was confirmed by the calculations of the association constants of ion pairs (KMOH = 0.1 L mol-1) which are in good agreement with the data available in the literature. Further- more, based on the McMillan-Mayer potentials calculated from the molecular dynamics simulations, Monte Carlo simulations have been performed to calculate the osmotic coefficients of MOH solutions.Then, we focused on the structural properties of alkaline solutions containing silicate oligomers, typically monomers (Si(OH)4, SiO(OH)-) and dimers (Si2O2(OH)5-, Si2O3(OH)42-). Thus, we first developed an "universal" force field allowing for describing a large number of silicate oligomers. These simulations highlighted a Na+ adsorption dependent on the silicate speciation and a low interaction between the hydroxide anions and the silicates.Finally, by taking into account the connectivity of silicon atoms (determined by 29Si NMR) and the average oligomer radius (determined by X-ray scattering measurements), we have simulated the behaviour of "real" experimental solutions, and we have explained the influence of the alkali’s nature on the structural and dynamical properties
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Boussois, Kévin. "Céramiques silicatées à résistance mécanique et ténacité élevées". Limoges, 2013. https://aurore.unilim.fr/theses/nxfile/default/409cf415-f1bf-4a2e-883f-2b79387c362d/blobholder:0/2013LIMO4022.pdf.
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Des céramiques multicouches à microstructure organisée ont été obtenues à partir de kaolin et de fibres silico-alumineuses. Ce type de microstructure permet d’améliorer significativement la contrainte à la rupture et la ténacité, qui sont des propriétés essentielles des céramiques d'utilisation courante. Les deux voies principales qui favorisent l'organisation microstructurale sont (i) l'utilisation d'un procédé de mise en forme favorisant l'orientation préférentielle de particules de forme anisotrope dans le compact de poudre. C'est le cas des mélanges de kaolinite et de fibres mis en forme par pressage et surtout par coulage en bande; (ii), la recristallisation de cristaux aciculaires de mullite au cours du frittage se fait dans des directions préférentielles à partir des feuillets de kaolinite et des fibres qui ont un rôle de templates pour la croissance orientée de la mullite. Il en résulte un processus anisotrope de frittage dans les directions parallèle et perpendiculaire à l'orientation des feuillets de kaolin et des fibres. Simultanément à la densification, la croissance de la mullite est aussi fortement anisotrope, induisant la formation d’une microstructure micro composite organisée dans laquelle la majorité des grands cristaux de mullite sont principalement orientés dans la direction de coulage et perpendiculairement aux fibres. A l'échelle macroscopique, les matériaux présentent des propriétés mécaniques fortement corrélées au degré d'organisation des cristaux de mullite dans la microstructure. Les valeurs de contrainte à la rupture et surtout de ténacité sont significativement améliorées malgré la faible teneur en fibres (entre 1 et 5% volumique), en comparaison des propriétés de céramiques silicatées usuellesMultilayer ceramic materials with organized microstructures were obtained from kaolin and alumino-silicate fibers. This kind of microstructure can significantly improve tensile strength and toughness, which are essential properties for conventional ceramics. The two main ways promoting microstructural organization are (i) the use of an adapted shaping process favoring the preferential orientation of anisotropic particles in the compact powder. This is the case of mixtures composed of kaolinite and fibers shaped by pressing and especially by tape casting; (ii) the recrystallization of mullite needle crystals during sintering occurs in preferred directions from the layers of kaolinite and fibers. This addition of template contributes to impose the mullite growth direction. An anisotropic sintering is then obtained in the directions parallel and perpendicular to the orientation of the layers of kaolin and fibers. Simultaneously to the densification, the growth of mullite is highly anisotropic, inducing the formation of a micro composite with an organized microstructure in which the majority of large mullite crystals are mainly oriented in the casting direction and perpendicular to the fibers. At the macroscopic scale, materials exhibit mechanical properties strongly correlated to the organization degree of mullite crystals in the microstructure. The values of tensile strength and toughness are mostly increased despite the low fiber content (between 1 and 5 vol. %) compared to the properties of usual silicate ceramics
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Boyer, Antoine. "Synthèse, caractérisation et évaluation biologique d'apatites phosphocalciques carbo silicatées". Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2014. http://tel.archives-ouvertes.fr/tel-01068540.
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La substitution ionique apparait comme une des possibilités pour moduler la bioactivité de l'hydroxyapatite (HA), matériau couramment employé comme substitut osseux. L'incorporation simultanée d'ions carbonates et silicates dans la structure apatitique pourrait permettre de coupler les propriétés de résorption et de dissolution des apatites carbonatées avec le rôle métabolique important du silicium dans le tissu conjonctif.Des poudres d'hydroxyapatites phosphocalciques substituées en carbonates et en silicates de formule Ca10 x+y(PO4)6-x-y(CO3)x(SiO4)y(OH)2-x+y (avec 0 ≤ y ≤ x ≤ 2 et x+y ≤ 2, C Si HA), ont été synthétisées par précipitation en milieu aqueux. L'originalité de cette synthèse réside essentiellement dans l'emploi de réactifs parfaitement solubles et miscibles dans l'eau. L'incorporation des carbonates et des silicates en substitution des phosphates a lieu dès la précipitation. Les poudres obtenues sont monophasiques, cristallines et de structure apatitique.Les caractérisations physico-chimiques des poudres ont mis en évidence l'existence d'interactions entre les carbonates (A et B) et les silicates au sein de la maille apatitique. La décarbonatation des sites B, synonyme de décomposition de la phase C-Si-HA, a pu être décalée à de plus hautes températures avec l'emploi du CO2 comme atmosphère de calcination. Le frittage de céramiques denses et monophasiques en C Si HA destinée à une première évaluation biologique a donc été possible. La culture in vitro de cellules souches mésenchymateuses C3H10T1/2 à la surface de céramiques de composition C0,8 Si0,4 HA a mis en évidence leur biocompatibilité et des propriétés ostéoconductives équivalentes à celles de l'HA.
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Houta, Nadia. "Dispersion de phyllosilicates et processus de frittage de céramiques silicatées". Thesis, Limoges, 2015. http://www.theses.fr/2015LIMO0075/document.
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Ces travaux de thèse visent à améliorer la densification et la résistance à la rupture de céramiques silicatées élaborées principalement à partir de kaolin. Cette amélioration est effectuée en substituant une partie du kaolin par de l’halloysite. En effet, cette voie permet également de mettre en évidence l’influence de la morphologie et de l’organisation des particules sur les propriétés microstructurales. Premièrement, la dispersion des suspensions contenant soit du kaolin soit un mélange de kaolin et d’halloysite, a été optimisée en réduisant la taille des agglomérats et en augmentant la valeur absolue du potentiel zêta. Deuxièmement, les paramètres (broyage, rapport liant/plastifiant…) contrôlant le procédé de mise en forme de coulage en bande ont également été optimisés. Enfin, l’influence de deux types de traitement thermique à 1200°C (frittage conventionnel et par voie micro-ondes) sur les propriétés mécaniques (contrainte à la rupture en flexion biaxiale) des matériaux finis a été mise en évidence. Les résultats obtenus montrent que plusieurs compromis entre le taux de porosité, l’organisation de la microstructure et les propriétés mécaniques ont été obtenus i) soit avec un taux d’halloysite de 10 % en masse associée à un traitement thermique par voie micro-ondes à 1200°C ii) soit avec un taux de substitution d’halloysite égal à 50 % en masse associé à un frittage conventionnel à la même températureThis thesis is devoted to improve both densification and stress to rupture values of silicate ceramics mainly elaborated from kaolin. This improvement is achieved by replacing a proportion of kaolin by halloysite. Indeed, this way also allows to highlight the influence of the shape of particles and their organization on microstructural properties. First, the dispersion of suspensions containing only kaolin or a mixture of kaolin and halloysite was optimized by reducing the size of agglomerates and by increasing the absolute value of zeta potential. Second, parameters (milling, ratio binder/plasticizer...) controlling the tape casting shaping process were also optimized. Finally, the influence of two types of thermal treatment at 1200°C (conventional and micro-waves sintering) mechanical properties (stress to rupture determined by bixial bending tests) of final products was studied. Results obtained show that several compromises regarding porosity, the organization of microstructure and mechanical properties i) a proportion equals to 10 mass % of halloysite combined with a micro-waves thermal treatment at 1200°C ii) a substitution content equals to 50 mass % of halloysite combined with a conventional thermal treatment at the same temperature
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Gautron, Laurent. "Minéralogie physique de phases silicatées alumino-calciques du manteau terrestre. Implications géodynamiques". Habilitation à diriger des recherches, Université de Marne la Vallée, 2008. http://tel.archives-ouvertes.fr/tel-00743660.
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La minéralogie physique a permis d'élucider de nombreuses énigmes relatives aux phases minérales du manteau terrestre, leur nature, leur changement de phase. L'expérimentation à haute pression et haute température dans la seconde moitié du 20ème siècle a permis d'apporter des données essentielles sur les matériaux du globe : on a pu alors faire le lien entre ces matériaux et les données obtenues par la sismologie, la géochimie et la géodynamique notamment. Les phases silicatées riches en calcium et aluminium se révèlent avoir des caractéristiques particulièrement intéressantes, avec de grandes implications géodynamiques. L'intérêt majeur de la combinaison de ces deux éléments est que le calcium peut être substitué par des cations volumineux tandis que l'aluminium permet d'assurer les compensations de charges en se substituant au silicium. D'autre part, la minéralogie de Ca et Al est caractérisée par de nombreuses nouvelles phases aux propriétés et structures tout à fait originales. Nous présentons ici les principaux résultats obtenus sur la perovskite calcique alumineuse Al-CaSiO3 : cette phase est capable d'incorporer de très grandes quantités d'actinides uranium et thorium, qui sont les principales sources d'énergie du globe. Ainsi cette phase minérale peut être le véritable moteur thermique du manteau inférieur terrestre. Ces résultats sont énoncés dans la perspective de mieux contraindre les modèles géodynamiques récents : ainsi cette phase pourrait à elle seule contribuer au chauffage par le bas de gros dômes observés dans les coupes du manteau obtenues par tomographie sismique. La relation possible entre nos résultats de minéralogie physique et le volume de matériaux chauds dans le bas du manteau terrestre est également discutée. La deuxième phase alumino-calcique présentée ici est la nouvelle phase appelée CAS et de composition CaAl4Si2O11. Il est maintenant acquis que ce minéral est essentiel dans les basaltes en subduction, notamment lorsqu'ils sont partiellement fondus. Mais plus intéressant, nous montrons que cette phase est caractérisée par une transition isosymétrique permettant à des atomes de silicium d'adopter une coordinence 5 au sein d'une bipyramide trigonale (2 tétraèdres partageant une face). L'importance d'une telle coordinence pour Si, intermédiaire entre les coordinences 4 et 6, est discutée, notamment en termes de processus de diffusion, de déformation par fluage diffusionnel, de viscosité : il apparaît clairement que des espèces telles que les groupes SiO5 favorisent grandement la déformation des matériaux qui les contiennent, et contribuent donc à améliorer leurs propriétés de transport. Ainsi la coordinence du silicium a un effet direct sur les processus dynamiques se produisant dans le manteau profond. A travers ces deux grandes études, on s'aperçoit à quel point les résultats de minéralogie physique peuvent apporter des données essentielles permettant d'alimenter des modèles géodynamiques, des modèles de fonctionnement thermique ou des modèles sismologiques. La sismologie ausculte le globe dans sa totalité, les expériences de géodynamique en laboratoire simulent le comportement rhéologiques du manteau avec des fluides et un chauffage par le bas : il est important d'apporter à ces modèles des informations précises sur les matériaux traversés par les ondes sismiques, ou que l'on essaie de modéliser en dynamique. D'autre part, l'étude de la phase CAS montre que des propriétés macroscopiques observées dans le manteau terrestre peuvent trouver leur origine dans la structure microscopique des phases minérales du manteau.
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Boyer, Laurent. "Synthèses et caractérisations d'apatites phospho-silicatées aux terres rares : application au nucléaire". Toulouse, INPT, 1998. http://www.theses.fr/1998INPT008C.
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Des matrices apatitiques ont été développées pour le conditionnement des actinides issus des combustibles irradies des réacteurs rep. Des apatites silicatées (britholites) contenant des actinides et des lanthanides, ont été découvertes dans le milieu naturel. Des analogues synthétiques de ces britholites peuvent être obtenus par réaction solide-solide a haute température. Les composes de la solution solide des britholites fluorées sont synthétises par la double substitution de (ca#2#+, po#4#3#) par (ln#3#+, sio#4#4#). Les lanthanides trivalents sont des analogues chimiques des actinides trivalents. La synthèse a été effectuée avec du la, nd et eu. Notre étude permet de montrer que l'immobilisation chimique provient de la fixation à l'échelle atomique des terres rares, du fait de leur participation à l'édifice structural du minéral. Dans la partie i, nous développons nos critères pour la formulation d'une matrice de conditionnement pour des radionucléides sépares comme les actinides. Nous présentons également la structure et les différentes méthodes de préparations des apatites. La partie ii concerne l'étude de la solution solide, l'élaboration de la céramique ca#9nd#1(sio#4)#1(po#4)#5f#2 et sa caractérisation physico-chimique. La dernière partie est consacrée à la localisation des terres rares dans la structure apatitique, déterminée par la luminescence de l'europium et la diffraction x sur monocristal
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Meducin, Fabienne. "Etude des phases silicatées du ciment hydraté sous haute pression et haute température". Paris 6, 2001. http://www.theses.fr/2001PA066337.
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Froment, Aurélien. "Caractérisation structurale d'hydroxyapatites carbo-silicatées par RMN du solide : applications à l'ingénierie du tissu osseux". Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS435.
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Les biocéramiques à base de phosphates de calcium, et plus particulièrement d'hydroxyapatite (HA, Ca10(PO4)6(OH)2) sont très largement plébiscitées pour les applications liées au comblement osseux. Ces biocéramiques macroporeuses ostéoconductrices offrent une fonction de support de la repousse osseuse, mais les volumes sont faibles et uniquement situés sur les berges du tissu hôte. Ces biocéramiques présentent également une capacité limitée à favoriser l’ostéogènèse et l’angiogenèse au cœur de l’implant et ne se dégradent pas selon une cinétique concomitante à celle de la formation des nouveaux tissus. Ces limites ont mis au jour la nécessité de développer une nouvelle génération de biomatériaux pour des applications cliniques de médecine régénérative, des biomatériaux n’ayant plus seulement la capacité d’accueillir la repousse osseuse mais devant la stimuler. Les hydroxyapatites carbo-silicatées dont les connaissances structurales sont très faibles voire quasi inexistantes sont de sérieux matériaux candidats pour cette nouvelle génération de biomatériaux. La double substitution en ion carbonate, favorise les propriétés de biodégradation et d’ostéoconduction, et en ion silicate, qui sous forme soluble favorise la formation osseuse, est source de modifications structurales pouvant mener à la modulation des propriétés biologiques de ces biomatériaux. La connaissance structurale de ces nouveaux matériaux est donc nécessaire avant de pouvoir les classifier comme futur candidats à des applications biomédicales. Le LCMCP possède depuis longtemps une compétence affirmée en "cristallographie RMN" afin de déterminer les propriétés structurales de matériaux à l'aide de techniques de caractérisation classiques et de la RMN en phase solideBioceramics based on calcium phosphates, and more particularly hydroxyapatite (HA, Ca10(PO4)6(OH)2) are widely popular for applications linked to bone filling. These osteoconductive macroporous bioceramics provide a function of supporting bone regrowth, but the volumes are weak and only located on the edges of the host tissue. These bioceramics also have a limited capacity to promote osteogenesis and angiogenesis at the heart of the implant and do not degrade according to a kinetic concomitant with that of the formation of new tissues. These limits have revealed the need to develop a new generation of biomaterials for clinical applications of regenerative medicine, biomaterials no longer only having the capacity to accommodate bone regrowth but must stimulate it. Carbo-silicate hydroxyapatites for which structural knowledge is very weak or almost non-existent are serious candidate materials for this new generation of biomaterials. The double substitution in carbonate ion, promotes the properties of biodegradation and osteoconduction, and in silicate ion, which in soluble form promotes bone formation, is a source of structural modifications that can lead to the modulation of the biological properties of those biomaterials. Structural knowledge of these new materials is therefore necessary before being able to classify them as future candidates for applications. The LCMCP has long had proven expertise in "NMR crystallography" in order to determine the structural properties of materials using characterization techniques. conventional and solid-phase NMR
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Villanova, de Benavent Cristina. "Compositional and structural characterisation of Ni-phyllosilicates in hydrous silicate type Ni-laterite deposits". Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/396616.
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Ni-bearing Mg-phyllosilicates (commonly known as garnierites) are significant ore minerals in many Ni-laterite deposits worldwide. However, the characterisation of these mineral phases is complex, as well as their classification and nomenclature, due to their fine-grained nature, low crystallinity and frequent occurrence as mixtures. The aim of this study is to shed some light to the nature of the Ni-bearing Mg-phyllosilicates occurring at the Falcondo Ni-laterite.
In this deposit, these minerals are found within the saprolite horizon mainly as fracture-fillings, coatings on joints and as breccias. The Falcondo garnierites display easily distinguishable different shades of green and characteristic textures, which correspond to different mineral phases. Five garnierite types were defined by X-ray diffraction (XRD), optical and electron microscopy, and electron microprobe (EMP) analyses: I) Ni-Fe-bearing serpentine-like, II) Ni-(Al)-bearing serpentine-like with minor talc-like, III) Ni-rich mixture of serpentine- and talc-like, IV) talc-like and V) sepiolite-falcondoite. The characterisation was completed with differential thermal analysis and thermogravimetry (DTA-TG), transmission electron microscopy (TEM), Raman spectroscopy, microfocus X-ray absorption spectroscopy (i.tXAS) and dissolution experiments, in order to gain further insight on these mineral phases from different points of view.
EMP oxide totals and DTA-TG indicate that talc-like contain higher H2O than talc sensu stricto (about 4.5% mass loss at 200°C, and up to 5% at 650°C), and therefore the names kerolite-pimelite [(Mg,Ni)3Si4010(OH)2• nH20] should be used instead of talc-willemseite [(Mg,1•103Si401o(OH)21. Compositional data showed continuous Mg-Ni solid solution along the joins lizardite-nepouite/chrysotile-pecoraite (serpentine-like), kerolite-pimelite (talc-like) and sepiolite-falcondoite. The phases with larger amounts of talc-like displayed the highest Ni contents (up to 2.2 apfu out of 3 octahedral atoms). In addition, EMP analyses of the mixed phases showed deviations from the stoichiometric Mg-Ni solid solutions of serpentine and talc. This is best explained by mixing at the nanoscale, which was confirmed by XRD and high resolution TEM imaging. Furthermore, a detailed textural study by means of EMP quantified X-ray element imaging was used to explain the relationships between textural position, sequence of crystallization and mineral composition of the studied Ni-phyllosilicates. These results indicate several stages of growth with variable Ni content, pointing to recurrent changes in the physical-chemical conditions during the precipitation of the different Ni-phyllosilicates.
HRTEM and low magnification imaging enabled to measure the characteristic basal spacings of these phyllosilicates and to observe a wide variety of nanotextures, respectively: 15-sectored polygonal serpentine, chrysotile tubes, lizardite lamellae, kerolite-pimelite lamellae and sepiolite ribbons. In accordance with EMP results, chemical analyses by TEM showed that Ni is more concentrated in the kerolite-pimelite lamellae than in the serpentine particles. In addition, the HRTEM revealed that kerolite-pimelite lamellae replace the Ni-poor
serpentine particles. These observations evidence the processes of progressive Ni-enrichment within some Ni-bearing Mg-phyllosilicates.
Characteristic Raman bands were observed for serpentine-, talc- and sepiolite-like phases, and therefore this technique allowed discriminating the different garnierite types.
The synchtrotron radiation-based µXAS analyses were conducted to investigate the speciation of Fe (by Fe K-edge X-ray absorption near edge structure, XANES) and the local environment of Ni (by Ni K-edge extended X-ray absorption fine structure, EXAFS). The XANES results indicate that Fe in the weathered saprolite and in the garnierites is mostly oxidised, whereas in the primary serpentine from the ultramafic protolith it is in the ferrous form. The EXAFS spectra indicate that Ni is homogeneously distributed in the unweathered rock, and is accumulated in discrete domains (clusters) in the weathered saprolite and in all the garnierite types.
Finally, the dissolution experiments of a set of garnierites which cover a wide range of mineral compositions at acidic pH suggest that the dissolution rates are faster in serpentine- dominated garnierites than in talc (kerolite)-dominated garnierites or sepiolite-falcondoite, and that the dissolution is not congruent, being the serpentine component the first to dissolve in the garnierite mixtures of serpentine and talc (kerolite).
In summary, the various analytical techniques applied to the garnierites of this study provide an accurate outlook of their complex mineralogy, structures, textures and chemistry at different scales that provides further details on the formation of these Ni-bearing Mg- phyllosilicates in a lateritic environment.Els fil- losilicats de níquel (comunament anomenats "garnierites") són importants menes en molts jaciments laterítics de Ni del món. La seva caracterització, classificació i nomenclatura és complexa, ja que normalment es troben en forma de mescles íntimes de diferents fil- losilicats de gra molt fi i baixa cristal• linitat. L'objectiu d' aquesta tesi és avançar en el coneixement de la mineralogia dels fil- losilicats de Ni del dipòsit de laterites niquelíferes de Falcondo, a la República Dominicana, per mitjà de l'ús d'un ampli espectre de tècniques analítiques: difracció de pols de raig X, anàlisi tèrmica diferencial i termogravimetria, microscòpia òptica, microscòpia electrònica de rastreig, microsonda electrònica, microscòpia electrònica de transmissió, espectroscòpia Raman, espectroscòpia d' absorció de raigs X (EXAFS i XANES, amb radiació sincrotró) i per mitjà d'experiments de dissolució. Les garnierites de Falcondo es localitzen a la part baixa de l'horitzó saprolftic en forma de rebliment de fractures i vetes, i ciments i clasts en bretxes. Els principals resultats indiquen que hi ha cinc tipus de garnierites, segons el seu color, la seva mineralogia i la química mineral. La majoria són barreges de serpentina i talc hidratat (kerolita-pimelita), tot i que també hi ha fases de la sèrie sepiolita-falcondoita. La fase que concentra més Ni és la kerolita-pimelita, mentre que a la serpentina el Ni és sistemàticament molt baix i a la sepiolita-falcondoita és molt variable. Les imatges d' alta resolució obtingudes amb microscopi electrònic de transmissió indiquen que els fil- losilicats que componen les garnierites formen una gran varietat de textures: serpentina poligonal, tubs de crisòtil, lamel• les de lizardita, lamel• les de talc hidratat i cintes de sepiolita. A més, s'ha observat que la kerolita-pimelita (rica en Ni) reemplaça sistemàticament la serpentina (pobra en Ni). L'espectroscòpia Raman permet distingir els cinc tipus descrits de garnierites i per tant, s'ofereix com una tècnica ràpida, senzilla i no destructiva per analitzar aquest tipus de minerals al camp. L' absorció de raigs X per mitjà de radiació sincrotró ha permès identificar que tot el Fe contingut en les garnierites i en les serpentines de la saprolita està en forma de Fe3+, i que tot el Ni es troba acumulat formant clusters, i no pas en forma de solució sòlida homogènia, a la capa octaèdrica. Finalment, els experiments de dissolució suggereixen que les velocitats de dissolució són més ràpides en les garnierites que contenen molta serpentina, i que la dissolució no és congruent, sent el Mg el primer element en ser posat en solució, seguit del Si i del Ni.
Książki na temat "Silicatées"
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Silicate crystal chemistry. New York: Oxford University Press, 1992.
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Mysen, B. O. Structure and properties of silicate melts. Amsterdam: Elsevier, 1988.
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Webb, Sharon L. Silicate melts: With 33 figures. Berlin: Springer, 1997.
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A Handbook of silicate rock analysis. London: Blackie Academic & Professional, 1987.
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Tagiev, D. B. Kristallicheskie ali͡u︡mosilikaty v katalize. Baku: Ėlm, 1989.
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A handbook of silicate rock analysis. Glasgow: Blackie, 1987.
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L, Perchuk L., Kushiro I. 1934- i Baker Donald R. 1927-, red. Physical chemistry of magmas. New York: Springer-Verlag, 1991.
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Farwell, Stebbins Jonathan, McMillan Paul Francis 1955- i Dingwell D. B, red. Structure, dynamics, and properties of silicate melts. Washington, D.C: Mineralogical Society of America, 1995.
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N, Maslennikova G., Goldin B. A i Rossiĭskai͡a︡ akademii͡a︡ nauk. Komi nauchnyĭ t͡s︡entr., red. Keramika na osnove prirodnykh kalʹt͡s︡iĭ-magnievykh silikatov: Mestorozhdenii͡a︡ Respubliki Komi. Syktyvkar: Komi nauch. t͡s︡entr UrO Rossiĭskoĭ AN, 1993.
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Deer, W. A. An introduction to the rock-forming minerals. Wyd. 2. Harlow, Essex, England: Longman Scientific & Technical, 1992.
Znajdź pełny tekst źródłaCzęści książek na temat "Silicatées"
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Liebau, Friedrich. "Nomenclature and Structural Formulae of Silicate Anions and Silicates". W Structural Chemistry of Silicates, 69–75. Berlin, Heidelberg: Springer Berlin Heidelberg, 1985. http://dx.doi.org/10.1007/978-3-642-50076-3_5.
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Okrusch, Martin, i Hartwig E. Frimmel. "Silicates". W Springer Textbooks in Earth Sciences, Geography and Environment, 157–239. Berlin, Heidelberg: Springer Berlin Heidelberg, 2020. http://dx.doi.org/10.1007/978-3-662-57316-7_11.
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Castroviejo, Ricardo. "Silicates". W A Practical Guide to Ore Microscopy—Volume 1, 819–44. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-12654-3_135.
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Babushkin, V. I., G. M. Matveyev i O. P. Mchedlov-Petrossyan. "The Basic Concepts and Laws of Thermodynamics". W Thermodynamics of Silicates, 1–54. Berlin, Heidelberg: Springer Berlin Heidelberg, 1985. http://dx.doi.org/10.1007/978-3-642-69320-5_1.
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Babushkin, V. I., G. M. Matveyev i O. P. Mchedlov-Petrossyan. "Pyrosilicate Reactions". W Thermodynamics of Silicates, 55–249. Berlin, Heidelberg: Springer Berlin Heidelberg, 1985. http://dx.doi.org/10.1007/978-3-642-69320-5_2.
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Babushkin, V. I., G. M. Matveyev i O. P. Mchedlov-Petrossyan. "Hydration Reactions". W Thermodynamics of Silicates, 251–335. Berlin, Heidelberg: Springer Berlin Heidelberg, 1985. http://dx.doi.org/10.1007/978-3-642-69320-5_3.
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Babushkin, V. I., G. M. Matveyev i O. P. Mchedlov-Petrossyan. "Corrosion Reactions". W Thermodynamics of Silicates, 337–53. Berlin, Heidelberg: Springer Berlin Heidelberg, 1985. http://dx.doi.org/10.1007/978-3-642-69320-5_4.
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Babushkin, V. I., G. M. Matveyev i O. P. Mchedlov-Petrossyan. "Thermodynamics of Irreversible Processes". W Thermodynamics of Silicates, 355–68. Berlin, Heidelberg: Springer Berlin Heidelberg, 1985. http://dx.doi.org/10.1007/978-3-642-69320-5_5.
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Edler, Karen J. "Mesoporous Silicates". W Porous Materials, 69–145. Chichester, UK: John Wiley & Sons, Ltd, 2010. http://dx.doi.org/10.1002/9780470711385.ch2.
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Falcone, J. S., i J. G. Blumberg. "Anthropogenic Silicates". W Detergents, 367–82. Berlin, Heidelberg: Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-540-47108-0_14.
Pełny tekst źródłaStreszczenia konferencji na temat "Silicatées"
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Neufuss, K., J. Ilavsky, J. Dubsky, B. Kolman i P. Chraska. "Plasma Spraying of Silicates II". W ITSC 1999, redaktorzy E. Lugscheider i P. A. Kammer. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 1999. http://dx.doi.org/10.31399/asm.cp.itsc1999p0636.
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Abstract Silicates represent a broad group of industrially important ceramic materials. The only silicate that is widely used for plasma spraying is zirconium silicate. Other silicates are generally not used, although they can offer interesting application properties. This paper presents results with other silicates: synthetic wollastonite, stoichiometric mullite, cordierite, and steatite. The input materials were produced in selected sizes from ceramic in industrial quality and applied with the water-stabilized plasma spray system PAL160 to form free-standing panels. The morphology of the microstructure, the thermal expansion, the bulk and filling densities, the open and closed porosity, the phase, and the chemical changes were evaluated. Paper includes a German-language abstract.
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Tan, Bee Chea, Ismail Mohd Saaid, Siti Qurratu'Aini Mahat, Suzalina Zainal, Petrus Tri Bhaskoro i Astriyana Anuar. "Evaluation of Polyamidoamine-Assisted Scale Inhibitors to Mitigate Silicate Scale Formation in Near Wellbore Region". W SPE/IATMI Asia Pacific Oil & Gas Conference and Exhibition. SPE, 2023. http://dx.doi.org/10.2118/215266-ms.
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Abstract Silicate scaling is a concern that could result in formation damage and flow assurance issue. Phosphonates and phosphino-polyacrylates are widely used to treat many types of scale but they are not intended to treat silicate scale. Besides that, these inhibitors may have been considered as harmful substances due to their reported inherent biodegradability. Synergistic silicate scale inhibitors are current trends since cationic or anionic polymers alone is found not effective for silicate scale inhibition. The objective of this work is to assess the performance of polyamidoamine-assisted scale inhibitors for silicates. The experiment settings are simulating the environment in near wellbore region, such that higher temperatures and brine that is mostly pH neutral. The effectiveness of scale inhibitors is investigated through static bottle test and dynamic scale loop (DSL) test. The scale inhibitors are also characterized to determine their functional groups in aqueous state. The tendency of scale inhibitors to impede silicate polymerization process is also determined through the remaining concentration of monomeric silica in water after 72 hours. FTIR revealed that all scale inhibitors exhibit amine characteristic in water. Experimental results show that the polyamidoamine-assisted scale inhibitor, PAMAM G-2/PteGlu, is the most effective in mitigating silicate scale formation. It reduces scaling brine's turbidity as much as 94.8% after 72 hours at 90°C. In addition, it also minimizes silicate polymerization process by retaining almost half of the initial monomeric silica concentration. This also implies that PAMAM G-2/PteGlu inhibitor could reduce the tendency of silicate scale formation to 46% as compared to 97% of silicate scale formation without any inhibition at 95°C. From DSL test, PAMAM G-2/PteGlu inhibitor is also the most effective inhibitor. It prolongs the scaling time from 7 minutes to 339 minutes at 0.01 g/L inhibitor concentration. It is also 7% more effective than PAMAM G-1/PteGlu inhibitor in DSL test. In general, the performance of scale inhibitors for silicates can be arranged as: PAMAM G-2/PteGlu > PAMAM G-1/PteGlu > PteGlu > PAMAM G-2 > PAMAM G-1 from top to bottom. In this work, these environment-friendly products had demonstrated good silicate scale inhibition as well as synergistic effect. They could offer as alternatives to commercial scale inhibitors.
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Quet, A., L. Bianchi, E. Darthout, F. Gitzhofer, J. L. Leluan i F. Rebillat. "Yttrium Silicate Coatings by Sol Precursor Plasma Spraying for Environmental Barrier Applications". W ITSC2011, redaktorzy B. R. Marple, A. Agarwal, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima i A. McDonald. DVS Media GmbH, 2011. http://dx.doi.org/10.31399/asm.cp.itsc2011p0581.
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Abstract Yttrium silicates are among the candidates for protection of silicon-based ceramics in high temperature and moist environments due to chemical and mechanical compatibility with substrate, low volatility and moisture resistance. Here we reported on the development of yttrium silicate coatings by sol precursor plasma spraying. The use of a sol feedstock allowed easy composition flexibility. The microstructure and the structure of as-sprayed and heat-treated coatings were investigated. Finer microstructure was obtained compared to micrometric powder plasma spraying traditionally used to produce environmental barrier coatings (EBC). XRD analyses on as-sprayed coatings revealed amorphous or crystalline layers depending on plasma parameters. In EBC application, a volume change from crystallization or phase transformation was envisaged to be damaging due to induced stresses and fully crystalline phases are a key durability requirement for EBC from conventional plasma spraying. Yttrium silicates are characterized by an important polymorphism and the ability to form amorphous coatings. Therefore, special attention was so paid to the amorphous degree of the coatings.
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Ctibor, P., J. Sedláček, K. Neufuss, J. Dubský i P. Chráska. "Study of Dielectric Properties of Plasma Sprayed Silicates at Low Voltage". W ITSC2002, redaktorzy C. C. Berndt i E. Lugscheider. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 2002. http://dx.doi.org/10.31399/asm.cp.itsc2002p0617.
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Abstract This paper examines the dielectric properties of silicate coatings including mullite (3Al2O3-2SiO2), steatite (MgSiO3), spodumene (Li2O-Al2O3-4SiO2), and olivine with near-forsterite (Mg2SiO4) composition. The materials were sprayed using a water-stabilized plasma gun and the deposits were removed from the substrate, polished, and sputtered with aluminum on both sides. Electrical tests consisting of voltage, resistance, and capacitance measurements showed that the relative conductivity of plasma-sprayed silicates is stable between 200 Hz and 1 MHz, which is suitable for many insulation applications. Paper includes a German-language abstract.
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SUN, Desi. "The alternation of surface electrokinetic characteristics before and after interaction between silicate bacteria and silicates". W 2011 International Workshop on Engineering Application Research. Hangzhou: IEIT Press, 2011. http://dx.doi.org/10.5813/www.ieit-web.org/ips.1.22.
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Martins, Roberto Fernando, Antonio Augusto Couto i Carlos Roberto Camello Lima. "Study on the Attack of Molten Silicates to Thermal Barrier Coatings at Varying Service Temperatures". W ITSC 2023. ASM International, 2023. http://dx.doi.org/10.31399/asm.cp.itsc2023p0647.
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Abstract Thermal barrier coatings have provided a revolution in the industry as they allow a higher operating temperature of equipment, improving the efficiency of gas turbines. However, one of the biggest challenges in terms of increasing the lifespan of TBC systems is the attack of fused silicates or simply CMAS (Calcium-Magnesium-Alumina-Silicate). CMAS are particles from the environment that can penetrate the TBC structure and cause delamination of the coating when exposed to high temperatures during thermal cycling. In this study, a plasma sprayed YSZ coating in the as coated and surface treated condition were given CMAS depositions from various preparation methods, and then subjected to thermal cycles at different evaluation temperatures and exposure times. The permeability of the ceramic layer and the penetration path of CMAS at different temperature levels were evaluated, as well as the penetration characteristics in relation to the microstructure of the ceramic layer. X-Ray diffraction and Scanning Electron Microscopy were used to characterize the applied CMAS and the penetration kinetics and conditions. Samples with longer exposure time had a considerable volume increase. The conditions to guarantee the formation of the silicate and its consequent wettability are also discussed.
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Hussain, Farzana, Derrick Dean i Anwarul Haque. "Structures and Characterization of Organoclay-Epoxy-Vinylester Nanocomposites". W ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-33552.
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The field of polymer-clay nanocomposites has attracted considerable attention as a method of enhancing polymer properties and extending their utility. Layered silicates dispersed as a reinforcing phase in a polymer matrix are one of the most important forms of such inorganic-organic nanocomposites, making them the subject of intense research. We have recently prepared several thermoset-based nanocomposites with improved thermal and mechanical properties. This paper is primarily focused in studying the effects of nano clay particles such as montmorillonite on improving mechanical and thermal properties of the polymer matrix composite. Epoxy and vinyl ester nanocomposites were prepared by adding different weight percentages (0.5%, 1%, 2%, 5% and 10%) of montmorillonite nano clay particles to epoxy and vinyl ester matrices. The results show significant improvements in mechanical and thermal properties of the nanostructured materials with low loading of organo silicates. Thermal property measurement includes dynamic mechanical analysis (DMA). Mechanical properties such as flexural strength and flexural modulus of polymer matrix were improved in nano structured materials owing to their unique phase morphology and improved interfacial interactions. Molecular dispersion of the layered silicate within the cross-linked matrix was verified using Wide Angle X-Ray Diffraction (WAXD) and Transmission Electron Microscopy (TEM) revealing the intercalated nanocomposites were formed.
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Petrov, D. V., A. A. Savushkin i E. A. Zhuzhulina. "10-micron emission feature of nonspherical olivine particles". W Всероссийская с международным участием научная конференция студентов и молодых ученых, посвященная памяти Полины Евгеньевны Захаровой «Астрономия и исследование космического пространства». Ural University Press, 2021. http://dx.doi.org/10.15826/b978-5-7996-3229-8.37.
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Many astronomical objects, from comets to circumstellar disks, contain silicate particles. The spectrum of silicates has a set of emission features, the most characteristic of which is in the spectral range of about 10 microns, and is called a 10-micron emission feature. The 10-micron emission feature is often studied under the assumption that the scattering particles are spherical. In this work, we investigated the contribution of nonspherical particles (elongated and oblate spheroids) of olivine to the 10-micron emission feature. It is shown that enough large non-spherical particles (whose size more than 20 microns) cause a noticeable increasing of scattering cross section Csca in comparison with spheres. Thus, the observed 10-micron emission feature of large particles can be explained by the non-sphericity of the scattering particles.
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Gao, W., H. L. Liao i C. Coddet. "Oxide Ion Conductivity in Dense Apatite-Type Lanthanum Silicate". W ITSC2010, redaktorzy B. R. Marple, A. Agarwal, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima i G. Montavon. DVS Media GmbH, 2010. http://dx.doi.org/10.31399/asm.cp.itsc2010p0791.
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Abstract In order to improve the ionic conductivity of lanthanum silicates, which have been considered as the new electrolyte candidates for intermediate temperature solid oxide fuel cells (IT-SOFCs), the feedstock powders are prepared by sintering the mixed oxide powders in different temperatures and sintering times. The main phase of all the samples is the hexagonal apatite structure. The apatite-type ceramic coatings with a typical composition of La10(SiO4)6O3 are deposited by atmospheric plasma spraying (APS). The influence of sintering time of feedstock powders on the electrical properties of La10(SiO4)6O3 electrolyte coatings is reported here. The highest conductivity of the dense composite electrolyte coatings reaches 6.8×10-6 S·cm-1 at 435 °C in air which is comparable to other apatite-type lanthanum silicate (ATLS) conductors.
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Miniscalco, William J. "Materials for Erbium-Doped Fiber Amplifiers". W Optical Amplifiers and Their Applications. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/oaa.1991.wd1.
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Fiber offers an extremely favorable geometry for optical devices, and fiber lasers [1] and amplifiers [2] were reported only shortly after the first bulk glass laser [3]. The choice of host composition has always been an important consideration. Silicates are the oldest and best understood glasses, and the first glass lasers used silicate compositions selected for high rare earth solubility and long lifetimes for the metastable state. The use of phosphate glass significantly improved the performance of early bulk Er3+ lasers [4] and it has become the most common host for bulk glass lasers doped with Er3+ and Nd3+. Although outstanding performance has been achieved using single-mode silica fiber, silica is a poor host for most activator ions, particularly rare earths. The influence of glass composition on the properties of Er3+ fiber amplifiers will be considered with particular emphasis placed upon silica; a more detailed discussion can be found in Ref. [5].
Raporty organizacyjne na temat "Silicatées"
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Shen, Andy Anda. Analyzing Silicates in Los Alamos’s Water Supply. Office of Scientific and Technical Information (OSTI), lipiec 2019. http://dx.doi.org/10.2172/1557154.
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Wereszczak, Andrew A., Kathryn J. Ham, Yogesh K. Vohra, Georgiy Tsoi, Brian A. Oistad, Brett S. Kuwik, Emily F. Steiner, Osama Jadaan i Benjamin L. Hackett. High-Pressure Mechanical Response of Two Vitreous Silicates. Office of Scientific and Technical Information (OSTI), listopad 2018. http://dx.doi.org/10.2172/1482450.
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James Butz, Thomas Broderick i Craig Turchi. Amended Silicated for Mercury Control. Office of Scientific and Technical Information (OSTI), grudzień 2006. http://dx.doi.org/10.2172/932891.
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Michael G. Nelson. CARBON DIOXIDE SEQUESTRATION BY MECHANOCHEMICAL CARBONATION OF MINERAL SILICATES. Office of Scientific and Technical Information (OSTI), kwiecień 2004. http://dx.doi.org/10.2172/826304.
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Belt, R. F., i J. A. Catalano. Investigation of Single Crystal Silicates for Blue Tunable Lasers. Fort Belvoir, VA: Defense Technical Information Center, czerwiec 1986. http://dx.doi.org/10.21236/ada171823.
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OJI, LN. Conditions Conducive to Forming Crystalline Uranyl Silicates in SRS Evaporators. Office of Scientific and Technical Information (OSTI), kwiecień 2004. http://dx.doi.org/10.2172/823370.
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Kelley, James. Catechol effected dissolution of silicate minerals. Portland State University Library, styczeń 2000. http://dx.doi.org/10.15760/etd.970.
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Mueller, H., i L. M. Perle. Long lifetime silicate laser glass compositions. Office of Scientific and Technical Information (OSTI), sierpień 1985. http://dx.doi.org/10.2172/6730599.
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Glazner, A. F. Activity composition relationships in silicate melts. Office of Scientific and Technical Information (OSTI), styczeń 1990. http://dx.doi.org/10.2172/7031820.
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William B. White, Michael R. Silsbee i B. Joe Kearns. REACTION MECHANISMS OF MAGNESIUM SILICATES WITH CARBON DIOXIDE IN MICROWAVE FIELDS. Office of Scientific and Technical Information (OSTI), luty 2004. http://dx.doi.org/10.2172/826203.
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