Gotowa bibliografia na temat „Bi2O3:ZrO2”

Different contents of bismuth oxide doped in 3YSZ material and the mixed powder formed. After press forming,the samples were sintered at 850°C, 900°C, 1000°C and 1100°C respectively. The electrical properties,the thermal shock resistance,the phase components and the microstructure morphology were analyzed to study the solid solution mechanism of Bi2O3-Y2O3-ZrO2 three-phase system. It was found that the Bi2O3 can effectively reduce sintering temperature as a flux. Sintered at 1000°C, t-ZrO2 can be induced into m-ZrO2 by Bi2O3 doped. With the increasing of Bi2O3 content, system shock resistance decreases. The thermal shock resistance of the 2-3mol% Bi2O3-YSZ is the best. In the different content of Bi2O3 system, 3mol% doped materials has the highest conductivity.

Bismuth oxide (monoclinic α-Bi2O3) and zirconium oxide (monoclinic ZrO2) are the most popular radiopacifiers in commercial Portland cement-based endodontic restoratives, yet their effects on the setting and hydration reactions are not fully understood. This study compares the impact of 20 wt.% of Bi2O3 or ZrO2 on the early hydration reactions and C–S–H gel structure of white Portland cement (WPC). Cement paste samples were hydrated at 37.5 °C prior to analysis by 29Si and 27Al magic angle spinning nuclear magnetic resonance spectroscopy at 3 h and 24 h, and transmission electron microscopy at 3 h. Initial and final setting times were determined using a Vicat apparatus and reaction kinetics were monitored by isothermal conduction calorimetry. Bi2O3 was found to prolong initial and final setting times and retard the degree of hydration by 32% at 24 h. Heat evolution during the acceleration and deceleration phases of the hydration process was reduced and the exotherm arising from renewed ettringite formation was delayed and diminished in the presence of Bi2O3. Conversely, ZrO2 had no significant impact on either setting time; although, it accelerated hydration by 23% within 24 h. Increases in the mean silicate chain length and the extent of aluminum substitution in the C–S–H gel were observed in the presence of both radiopacifying agents after 24 h relative to those of the unblended WPC. The Bi2O3 and ZrO2 particles remained intact within the cement matrix and neither bismuth nor zirconium was chemically incorporated in the hydration products.

Mineral trioxide aggregates (MTA) have been widely used in endodontic treatments, but after some time, patients suffer tooth discoloration due to the use of bismuth oxide (Bi2O3) as a radiopacifier. Replacement of Bi2O3 with high energy ball-milled single (zirconia ZrO2; hafnia, HfO2; or tantalum pentoxide, Ta2O5) or binary oxide powder was attempted, and corresponding discoloration improvement was investigated in the present study. Bi2O3-free MTA is expected to exhibit superior discoloration. The radiopacity, diametral tensile strength, and discoloration of MTA-like cements prepared from the as-milled powder were investigated. Experimental results showed that MTA-like cements prepared using Ta2O5 exhibited a slightly higher radiopacity than that of HfO2 but had a much higher radiopacity than ZrO2. Milling treatment (30 min to 3 h) did not affect the radiopacities significantly. These MTA-like cements exhibited superior color stability (all measured ΔE00 < 1.0) without any perceptible differences after UV irradiation. MTA-like cements prepared using ZrO2 exhibited the best color stability but the lowest radiopacity, which can be improved by introducing binary oxide. Among the investigated samples, MTA-like cement using (ZrO2)50(Ta2O5)50 exhibited excellent color stability and the best overall performance with a radiopacity of 3.25 mmAl and a diametral tensile strength of 4.39 MPa.

Powder mixtures of ?-Bi2O3 containing 2, 5 and 10 mole % of TiO2, ZrO2 or HfO2 were homogenized, heated at 820?C for 24 h and quenched in air. X-ray powder diffraction technique was used to characterize the prepared samples. In all cases metastable Bi2O3 polymorphs, ?-Bi2O3 or ?-Bi2O3, are found as single or major phases. Addition of Ti4+ ions stabilizes ?-Bi2O3 polymorph, while either Zr4+ or Hf4+ ions stabilize ?-Bi2O3 polymorph. In the samples with 2 and 5 mole % of TiO2 the presence of even two ?-Bi2O3 phases (Bi12TiO20 compound and a very low Ti-doped ?-Bi2O3) was established. Similarly, in the sample with 2 mole % of HfO2 two ?-Bi2O3 phases were found. Phase composition of prepared samples, values of unit cell parameters and the appearance of two polymorphs with identical crystal structure but different unit cell parameters are discussed and compared with known data.

Bi4Ti3O12 based thick films were prepared by screen printing and firing using Pt bottom electrodes and ZrO2 substrates. The influence of excess Bi2O3 as sintering aid was investigated. Furthermore, substitution of Ti-site and Bi-site for V5+ and Nd3+ was performed. Screen-printable pastes were prepared by kneading the Bi4Ti3O12 based powder and Bi2O3 powder in a three-roll mill with an organic vehicle. The microstructures and ferroelectric properties of the thick films were examined in comparison with bulk ceramics. The remanent polarization of 9.6 μC/cm2 and coercive field of 64 kV/cm were obtained for the Bi3.0Nd1.0Ti2.99V0.01O12 thick film with 10 wt% of excess Bi2O3 fired at 1200OC.

The aim of this study was to explored the effects of Fe2O3 and Bi2O3 on the color properties of a 3Y-TZP zirconia ceramics for dental application. Pigmented dental ZrO2 powders were prepared by mixing different concentration of Fe2O3 and Bi2O3, also in their combinations with 3Y-TZP powders. The mixture was compacted by isostastic pressure, then densely sintered. Color parameters were measured by Minolta CM2600d spectrophotometer. XRD was used to exam the structure of colored 3Y-TZP. Experimental results showed that the hue of the materials shift from yellow-green to yellow-red with the increasing concentration of the Fe2O3 and Bi2O3. Combined use of Fe2O3 and Bi2O3 could further decrease the L* value, which color scope was suitable for dental color matching. The XRD spectra showed only tetragonal phase was detected.

Bi2O3 is a promising sintering additive for YSZ that not only decreases its sintering temperature but also increases its ionic conductivity. However, Bi2O3 preferably grows into large-sized rods. Moreover, the addition of Bi2O3 induces phase instability of YSZ and the precipitation of monoclinic ZrO2, which is unfavorable for the electrical property. In order to precisely control the morphology and size of Bi2O3, a microemulsion method was introduced. Spherical Bi2O3 nanoparticles were obtained from the formation of microemulsion bubbles at the water–oil interface due to the interaction between the two surfactants. Nanosized Bi2O3–YSZ composite powders with good mixing uniformity dramatically decreased the sintering temperature of YSZ to 1000 °C. Y2O3-stabilized Bi2O3 (YSB)–YSZ composite powders were also fabricated, which did not affect the phase of YSZ but decreased its sintering temperature. Meanwhile, the oxygen vacancy concentration further increased to 64.9% of the total oxygen with the addition of 5 mol% YSB. In addition, its ionic conductivity reached 0.027 S·cm−1 at 800 °C, one order of magnitude higher than that of YSZ. This work provides a new strategy to simultaneously decrease the sintering temperature, stabilize the phase and increase the conductivity of YSZ electrolytes.

Pt/CeO2-ZrO2-Bi2O3-PbO/SBA-16 (SBA-16: Santa Barbara Amorphous No. 16) catalysts were synthesized to produce hydroxypyruvic acid by glycerol oxidation. In the catalysts, the introduction of PbO into CeO2-ZrO2-Bi2O3 improved the oxygen release and storage abilities owing to the synergistic redox reaction of Pb2+/4+ and Ce3+/4+, which facilitated the oxidation ability of Pt. In addition, the oxidation of the secondary OH group in glycerol might be accelerated by the geometric effects of glycerol, Pt, and Bi3+ or Pb2+/4+. Furthermore, the moderate reaction conditions such as room temperature and open-air atmosphere enabled the suppression of further oxidation of hydroxypyruvic acid. The highest catalytic activity was obtained for 7 wt% Pt/16 wt% Ce0.60Zr0.15Bi0.20Pb0.05O2−δ/SBA-16, which provided a hydroxypyruvic acid yield maximum of 24.6%, after the reaction for 6 h at 30 °C in atmospheric air.

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I n this work a systematic study on the phase formation and stability in the system Bi2O3-ZrO2 was realized, the solubility of the Zr4+ ion in Bi12TiO20 (BTO) was investigated and Zr-doped BTO crystals (BTO:Zr) were grown and optically characterized. It was verified that a tetragonal phase was formed in the following wide composition interval: (6-x)Bi2O3:(1+x)ZrO2, with x = 0.5, 0.3, 0.2, 0.1, 0, -0.1, -0.2, -0.3, -0.5, -0.65 e -0.7. The phases were synthesized by solid state reaction and the powders were characterized by Xray diffraction and diferential thermal analysis. The formed tetragonal phase, however, was metastable for all investigated compositions and its preparation was dependent on the sample thermal history. The stable phase at room temperature was a monoclinic one. A low solubility of Zr4+ in BTO was verified, but BTO:Zr single crystals were grown by Top Seeded Solution Growth (TSSG) technique. Good quality crystalline samples were prepared and characterized by chemical compositon and by optical activity, photoconductivity and electro-optical measurements. The results shown that Zr-doping produced a decreasing in the crystal photosensitivity, and almost no changes in the optical activity and electro-optical coefficient were generated.
Neste trabalho foi realizado um estudo sistemático das condições de preparação e estabilidade de fases no sistema Bi2O3-ZrO2, a solubilidade do íon Zr4+ no Bi12TiO20 (BTO) foi investigada e cristais de BTO dopados com Zr4+ (BTO:Zr) foram crescidos e caracterizados opticamente. Verificou-se que uma fase tetragonal é formada no amplo intervalo de composições (6- x)Bi2O3:(1+x)ZrO2, com x = 0,5, 0,3, 0,2, 0,1, 0, -0,1, -0.2, -0,3, -0,5, -0,65 e - 0,7. As fases foram sintetizadas por reação no estado sólido e os pós foram caracterizados por difração de raios-X e análise térmica diferencial. A fase tetragonal formada, no entanto, é metaestável em todo o intervalo de composições investigadas, sendo sua obtenção condicionada à história térmica da amostra. A fase estável à temperatura ambiente é monoclínica. Foi constatado que a solubilidade do Zr4+ no BTO é baixa, mas cristais de BTO:Zr foram crescidos através da técnica Top Seeded Solution Growth (TSSG). Amostras cristalinas de boa qualidade óptica e estrutural foram preparadas e caracterizadas quanto à composição química e através de medidas de atividade óptica, fotocondutividade e coeficiente eletro-óptico. Os resultados demonstram que o Zr produz uma diminuição na fotosensibilidade do cristal, provocando pouca alteração nos valores de atividade óptica e coeficiente eletro-óptico

Lo sviluppo di nuovi nanosistemi ibridi organico-inorganici è un campo di ricerca all'avanguardia specifico per le applicazioni biomediche ad alto potenziale. In particolare, l'interazione tra i ligandi organici e le nanoparticelle inorganiche deve essere studiata e adattata in modo specifico al fine di ottenere stabilità e conferire proprietà specifiche ai nano-assiemi. Gli ZrNP sono sottoposti a approfonditi studi e funzionalizzazione per modificare le proprietà superficiali di questi materiali. La chimica superficiale della zirconia non è paragonabile a quella della silice, in particolare a causa della ridotta stabilità chimica del legame silanico da Zr – O – Si – R rispetto a Si – O – Si – R. Vale la pena notare che l'uso di derivati ​​del silano implica una reazione di condensazione con rilascio spesso di alcool o alogenuri come da prodotti. È noto che la zirconia, grazie alla sua struttura superficiale, può interagire efficacemente con ligandi a base di fosfato e fosfonato, come evidenziato anche dall'applicazione della zirconia per rimuovere i fosfati dall'acqua. Abbiamo considerato la reazione dell'estere vinilidenebisfosfonato con nucleofili attraverso Michael o etero-Michael come una reazione versatile che consente la preparazione da un comune scaffold di una vasta gamma di possibili prodotti BP a partire dal dietilfosfito attraverso la formazione di estere metilenbisfosfonato. Nel presente contributo introduciamo un approccio versatile per la modifica delle proprietà superficiali degli ZrNP e, in una certa misura, anche di altri NP di ossido di metallo, basato sull'impiego di una famiglia di BP come specie derivate. La funzionalizzazione è stata ottenuta miscelando semplicemente in soluzione acquosa la zirconia con i BP desiderati in condizioni tampone portando ad una vasta gamma di NP modificate in superficie con maggiore stabilità colloidale a causa della presenza di cariche negative sulla superficie su una vasta gamma di pH, come dimostrato da misurazioni ζ-potenziali. Le nanoparticelle modificate sono state caratterizzate da IR, TGA, XPS per studiare la densità dell'innesto e il carico dell'acido bifosfonico, TEM e SEM per studiare le dimensioni e le morfologie delle nanoparticelle e NMR a stato solido 31P e 1H per studiare il motivo di coordinazione del unità di fosfonati sulla superficie. Tutte queste tecniche analitiche hanno dimostrato la forte affinità della porzione bifosfonica per i centri metallici Zr (IV). L'acido bifosfonico ha mostrato anche un legame efficace con altre nanoparticelle di ossido di metallo come Bi2O3, mentre l'interazione con le nanoparticelle di SiO2 era troppo debole a causa del carattere non metallico dei centri Si. La funzionalizzazione delle nanoparticelle di ossido di metallo con acidi bifosfonici rappresenta un approccio covalente semplice per la derivatizzazione che è complementare ai tipici reagenti tris-alcossi-silano o tricloro-silano ampiamente impiegati per la funzionalizzazione di silice e nanoparticelle di ossido di metallo
TThe development of new hybrid organic-inorganic nanosystems is a cutting-edge field of research specifically for high potential biomedical applications. Specifically, the interaction between the organic ligands and the inorganic nanoparticles need to be specifically investigated and tailored in order to achieve stability and to impart specific properties to the nano-assemblies. ZrNPs are subjected to extensive study and functionalization to modify the surface properties of these materials. The surface chemistry on zirconia is not comparable to that of silica in particular due to the decreased chemical stability of the silane bond from Zr–O–Si–R with respect to Si–O–Si–R. It is worth to notice that the use of silane derivatives implies a condensation reaction with often release of alcohol or halides as by products. It is well known that zirconia, thanks to its surface structure, can efficiently interact with phosphate and phosphonate-based ligands, as evidenced also by the application of zirconia to remove phosphates from water. We considered the reaction of vinylidenebisphosphonate ester with nucleophiles through Michael or hetero-Michael as a versatile reaction enabling the preparation from a common scaffold of a wide range of possible BPs products starting from diethyl phosphite via formation of methylenebisphosphonate ester. In the present contribution we introduce a versatile approach for the modification of the surface properties of ZrNPs and to some extent also other metal oxide NPs, based on the employment of a family of BPs as derivatizing species. The functionalization was obtained by simple mixing in aqueous solution the zirconia with the desired BPs under buffered conditions leading to a wide range of surface modified NPs with enhanced colloidal stability due to the presence of negative charges on the surface over a wide range of pH, as demonstrated by ζ-potential measurements. The modified nanoparticles were characterized by IR, TGA, XPS to investigate the grafting density and the loading of the bisphosphonic acid, TEM and SEM to investigate the size and morphologies of the nanoparticles and 31P and 1H Solid State NMR to investigate the coordination motif of the phosphonate units on the surface. All these analytical techniques demonstrated the strong affinity of the bisphosphonic moiety for the Zr(IV) metal centers. The bisphosphonic acid showed also efficient binding to other metal oxide nanoparticles such as Bi2O3, while interaction with SiO2 nanoparticles was too weak due to the non-metallic character of the Si centers. The functionalization of metal oxide nanoparticles with bisphosphonic acids represents a straightforward covalent approach for derivatization that is complementary to the typical tris-alkoxy-silane or trichloro-silane reagents largely employed for the functionalization of silica and metal oxide nanoparticles.

The thesis entitled "Structural Characterization of Complex Oxides and Sulfates Towards the Design of Photocatalytic and Sodium Ion Conducting Materials" consists of _ve chapters. Chapter 1 gives a brief introductory note which outlines the various synthesis procedures, characterization techniques and a description of properties like photocatalysis and ionic conductivity. Chapter 2 discusses the solution combustion synthesis of Bi2Zr2O7 using urea, tartaric Acid and glycine as fuels. Only the samples prepared using urea and tartaric acid result in pure compounds and are further characterized by X-ray di_raction studies depicting a disordered uorite type structures. Careful Rietveld re_nements bring out subtle structural di_erences in these two samples as well, a feature which is demonstrated for the _rst time among samples prepared from two di_erent fuels. Di_erence Fourier maps con_rms the structures, and the catalytic behaviour is shown to correlate to these subtle changes in oxygen occupancy. The band gap determined from UV-Vis spectroscopic results conform to the structural di_erences of the compound. Photocatalytic degradation of cation dyes suggest that the compound prepared using urea shows better photocatalytic activity and is comparable to the commercial Degussa P-25. Chapter 3 describes the e_ect of Bi doping on photocatalytic activity of CeO2 (band gap is in the UV range) is evaluated with BixCe1-xO2􀀀_ (x = 0.2, 0.4, 0.6) using solution combustion method using glycine as fuel. These compounds have a band gap in the visible range and the structures are established by Rietveld re_nements clearly establishing that the oxygen vacancies increase with increasing bismuth substitution. Featureless di_erence Fourier maps con_rm the structures and photodegradation experiments on a cationic and an anionic dye clearly establishing that the photocatalytic activity increases with increase in bismuth content leading to increased oxygen vacancies. Chapter 4 describes synthesis, crystal structure, phase transition and ionic conductivity in a family of vantho_te mineral Na6Mn(SO4)4. Single crystal of Na6Mn(SO4)4 are grown from aqueous solution by slow evaporation method at 80°C, crystal grown are analyzed by single crystal X-ray di_raction which depict monoclinic system with space group P21/c at room temperature. Ionic conductivity measurements are carried out by using impedance spectroscopy, and conductivity value is found to be 2.01x10􀀀5 Scm􀀀1 at 490°C and 7.4x10􀀀3 Scm􀀀1 at 505°C. Two order magnitude change in conductivity value on a temperature window of 15°C con_rms a _rst order nature of phase transition. Further, conductivity of the mineral reached of 3.9x10􀀀2 Scm􀀀1 at 600°C which establishes the superionic nature of the mineral.In addition, the nature of phase transition was examined by using thermal analysis such asDSC, DTA and variable temperature powder X-ray di_raction technique. The PXRD after the phase transition at 550°C was also indexed, pro_le _tted with orthorhombic space group. Chapter 5 presents the crystal growth and in situ structural studies of di and tetra hydrate of vantho_te mineral Na6M(SO4)4 (M = Ni and Co). As discussed in Chapter 4, these crystals are grown in aqueous solution by slow evaporation method at 80°C in an oven. Interestingly, di and tetra hydrate of Na6M(SO4)4 (M = Ni and Co) are grow concomitantly. Single crystal X-ray di_raction measurements reveal the structure to be triclinic with space group P_1. Further di-hydrates of Na6M(SO4)4 (M = Ni and Co) are isostructural, and the tetrahydrates also follow the same trend. Thermal Gravimetric analyses and in situ powder di_raction studies were carried out to characterize the step-wise dehydration process in these materials.

Bi2O3 doped scandia stabilized zirconia systems have shown promise for use as electrolytes in IT-SOFCs. Sintering properties, crystal phase transformation, microstructure, as well as electrical conductivity of the Bi2O3 doped Sc2O3-ZrO2 systems were investigated. The effect of Bi2O3 doping from 0 to 2.0mol%, and different sintering temperatures, on the properties and performance of the electrolyte were examined. The presence of Bi2O3 aided the sintering process and better sintering for the doped system was achieved at lower temperatures. The rhombohedral phase in 10ScSZ was successfully stabilized to cubic phase at room temperature with a concentration of 1 mol% and 2 mol% Bi2O3 sintered at 1100°C–1400°C. The achievement of cubic structure depends upon both the Bi2O3 concentration and the sintering temperature. Higher electrical conductivity was achieved with Bi2O3 doped Sc2O3-ZrO2 systems than 10ScSZ below 600°C. A maximum conductivity of 1.68 × 10−2 S/cm at 700°C was obtained for 2 mol% Bi2O3 doped sample sintered at 1100°C.

The data in this paper were compiled from information collected from over 10 individual coating runs to provide the optical designer optical constants for six oxide thin film materials over the 0.6 – 12.0 µm wavelength region. Data are included for bismuth oxide (Bi2O3), chromium oxide (Cr2O3), hafnium oxide (HfO2), tantalum pentoxide (Ta2O5), yttrium oxide (Y2O3), and zirconium oxide (ZrO2). In addition, the durability of each film has also been examined.