氧化锆气凝胶研究进展

氧化锆气凝胶以其优异的性能受到人们广泛的关注。本文综述了氧化锆气凝胶的制备工艺、掺杂改性工艺、SiO2-ZrO2复合气凝胶、纤维增强氧化锆气凝胶的研究进展以及氧化锆气凝胶的应用。最后,对氧化锆气凝胶的发展方向进行了探讨。     

铝掺杂纳米氧化锆的合成与改性研究

氧化锆是一种具有特殊作用的氧化物并受到越来越多的关注。作者利用阳离子表面活性剂(CTAB)的辅助途径,通过前期的制备工艺成功实现了金属铝对纳米氧化锆的掺杂改性。借助XRD,TEM,EDS,Uv-vis以及N2吸附-脱附等方法对样品进行了表征分析;研究表明:金属铝离子能成功地进入氧化锆当中,掺杂改性后的氧化锆相对未掺杂的氧化锆有明显的蓝移,热稳定性显著提高,并且有一定的微孔结构。     

沉淀法制备铈掺杂氧化锆陶瓷粉体材料的研究

采用化学沉淀法以ZrOCl2.8H2O和Ce2(CO3).8H2O为反应物,制得铈掺杂氧化锆陶瓷粉体材料,研究了反应温度、氧化铈的摩尔含量、pH、沉淀剂对铈掺杂氧化锆陶瓷粉体的影响。通过XRD谱图表明未掺杂的产品为单斜相,掺杂的产品为单斜与四方相共存,表明在室温下掺杂了的氧化锆可以以亚稳的四方相存在。     

氧化锆基固体电解质的研究进展

综合介绍了氧化锆基固体电解质的粉体制备、成型与烧结、稳定剂及共掺杂的影响,氧化锆基电解质的电性能的老化,力学性能,与电极材料的兼容性、电解质薄膜制备的研究进展以及未来的发展趋势.由于氧化锆基固体电解质的操作温度较高,因此,电解质薄膜的制备工艺及其对电池性能的影响将是氧化锆基固体电解质未来的主要研究内容.此外,氧化锆基固体电解质的烧结性能、力学性能和高温抗老化性能也有待于进一步改善和提高.     

氧化锆基固体电解质研究

电解质是固体氧化物燃料电池（SOFC）的核心部件,其性能的优良直接决定燃料电池的应用前景。氧化锆基陶瓷具有较高的离子电导率、良好的结构和化学稳定性,是理想的固体电解质材料。本文综合介绍了各种掺杂元素对氧化锆基固体电解质性能的影响,电解质薄膜制备方法和研究现状。并对氧化锆基固体电解质的研究方向进行了展望。     

锡掺杂量对介孔氧化锆材料相结构的影响

采用季胺盐作为结构模板剂,在水热条件下合成了Sn掺杂的有序多孔氧化锆材料.通过XRD、FT-IR、HRTEM、UV-Vis吸收、N2吸附等分析手段对材料性能进行了表征.结果表明:金属锡能均匀地掺杂于规则的介孔氧化锆骨架中;锡掺量小于10%(物质的量分数,下同)时,可以提高无机墙体氧化锆的缩合程度,有利于提高材料的比表面积和热稳定性;当锡掺量介于10%～30%之间时,锡也能很好的进入氧化锆骨架中,不会析出氧化锡纳米晶,但随着锡掺量增加,孔道长程有序度、比表面积、热稳定性都会降低.     

氧化锆-碳化硅复合材料性能研究

从稀土氧化物、氧化锆含量、碳化硅含量、温度及制备工艺方面对氧化锆-碳化硅复合材料电阻率的影响进行了讨论,同时探讨了氧化锆-碳化硅复合材料的高温氧化性能,为氧化锆-碳化硅复合材料的制备及其电性能研究提供了依据。     

氧化锆的水热合成及其应用研究进展

介绍了水热合成氧化锆的发展历程以及水热法制备氧化锆的特点和发展趋势。水热合成是一种合成氧化锆的重要方法,自发明以来就是该领域的研究热点。同时,介绍了氧化锆在陶瓷增韧、催化剂及载体、离子导电和生物等方面的应用。由于氧化锆的优异性质,其应用范围将越来越广阔。     

掺杂中孔氧化锆的合成进展

介绍中孔氧化锆的合成机理及国内外研究现状,讨论了影响合成中孔氧化锆的一些因素,特别是对掺杂中孔氧化锆合成的影响。概述了掺杂中孔氧化锆的应用并展望了其发展方向。     

中国氧化锆生产现状及发展前景

介绍了目前中国氧化锆生产，研究及应用市场现状，并结合世界材料发展方向论证了中国氧化锆研究应以高起点入手，同发其在功能陶瓷，精细陶瓷中的应用。     

Oxidative dehydrogenation of ethane over alkali‐metal doped sulfated zirconia catalysts

Alkali‐metal doped sulfated zirconia catalysts were tested for the oxidative dehydrogenation of ethane into ethene. The effects of metal precursor compounds and acidic anion promoters on the catalytic activity in this reaction were studied. It was found that sulfation of zirconia increases the selectivity of ethane towards ethene. Lithium‐, sodium‐, and potassium‐doped sulfated zirconia catalysts showed quite different activities in this reaction. Sulfated zirconia doped with lithium catalysts were found to be effective for the oxidative dehydrogenation of ethane, giving over 90% selectivity to ethene and 25% ethene yield at 650 °C. © 1999 Society of Chemical Industry     

Bi-colored zirconia as dental restoration ceramics

Machinable zirconia blocks with gradient colors are fundamental for fabrication of full-contour esthetic dental restorations. The aim of this study was to process and evaluate bi-colored zirconia ceramics as a pilot dental material by using well-established techniques. Two commercially available partially stabilized zirconia granules, one undoped and one doped with 0.202 wt% Fe₂O₃, resulted in white and yellow colors after sintering, respectively. Bi-colored zirconia was fabricated by two-step dry pressing of both zirconia granules one above the other to form green bodies, followed by cold isostatic pressing (CIP) and, a two-step pressureless sintering finally at 1450 °C. The dilatometer results showed that the Fe₂O₃ doped zirconia sintered slightly rapid, but the difference of shrinkage between two powders was <1%. Sintered bars achieved full density, 6.018 g/cm³ (～99%TD), without cracks in the ～1 mm color gradient zone. The microstructures were characterized by scanning electron microscopy (SEM) and careful observation of both surface and interior provided no obvious structural difference of either grains or pores among the three distinct regions, comprising white, yellow and color gradient zone. Vickers hardness of bi-colored zirconia was ～13.1 GPa, with no obvious difference in the three regions. The four-point bending strength of the bi-colored zirconia bars was 745.5±159.6 MPa, which appeared noticeably lower than that of the single-colored references being above 1000 MPa. Fractographic analysis revealed that in most of the cases (60%) the fracture was initiated at the color gradient zone, where large voids with high coordination numbers, agglomerates with critical size and concentration of irregular grains with porous surfaces were observed. Above all, bi-colored zirconia ceramics prepared by the improved technique could meet the basic requirements of dental materials. The ways of minimizing the defects within bi-colored blocks should be developed for the production of esthetic zirconia ceramics of high strength and reliability.     

Crystal structure and morphology of CeO2 doped stabilized zirconia ceramics under high-frequency microwave field sintering

Under high-frequency microwave irradiation, zirconia ceramics were prepared by sintering nano-CeO₂ (Ce = 7 mol%) doped zirconia powder. The different effects of temperature environment on the phase structure transformation, surface functional groups, microstructure, growth process, and density of doped zirconia were analyzed, and the optimized microwave sintering process for zirconia was determined. The experimental results reveal that the tetragonal phase of zirconia is positively correlated with the temperature when the temperature reaches about 1100 °C in the studied range. The reason is that the grain grows with the increase of sintering temperature, and the surface energy of grain decreases, which leads to the fluctuation of tetragonal phase content. The density of zirconia reaches 98.03% at 1300 °C, and the growth activation energy is 27.40 kJ/mol. There is no abnormal growth of zirconia particles, and the phase transition temperature decreases, which is attributed to the efficient heating of microwave and the incorporation of nano-ceria stabilizer.     

Transition metals increase hydrothermal stability of yttria-tetragonal zirconia polycrystals (3Y-TZP)

In this paper, the influence of transition metals on phase stability of zirconia in 3?mol% Y₂O₃ doped tetragonal zirconia polycrystals (3Y-TZP) in hydrothermal environments was reported. 3Y-TZP with and without stainless-steel or CoCr metal stains on the sample surface were subjected to different isothermal treatments in water vapor, and their respective monoclinic fractions were quantified by confocal Raman spectroscopy. The outputs of these spectroscopic experiments revealed transition metals conspicuously could stabilize the tetragonal zirconia polymorph in the monolithic zirconia, possibly due to the occurrence of off-stoichiometric chemistry in the presence of metal stains.     

Phase stability in scandia‐zirconia nanocrystals

Scandia‐zirconia system has great technological interest as it has the highest ionic conductivity among doped zirconia ceramics. However, polymorphism is the most important limiting factor for application of this material. Considering that there is a strong grain size dependence on phase transitions in this class of materials, mapping out the stable polymorph as a function of grain size and composition may lead to more efficient compositional design. In this article, the phase stability of zirconia‐scandia nanocrystals was investigated based on experimental thermodynamic data. Exploiting recent advances in microcalorimetry, reliable surface energy data for five polymorphs of scandia‐zirconia system: monoclinic, tetragonal, cubic, rhombohedral β and γ are reported for the first time. Combining surface energy values with bulk enthalpy data obtained from oxide melt drop solution calorimetry allowed us to create a predictive phase stability diagram that shows the stable zirconia polymorph as a function of composition and grain size of the specimen within the range of 0‐20 mol% scandia.     

Alumina/zirconia ceramic membranes fabricated by temperature induced forming technique

It is well known that the fabrication technique of porous ceramic composites has a significant effect on their microstructure and properties. In the present study, alumina/zirconia ceramic composites doped with magnesia were fabricated by temperature induced forming technique using tri-ammonium citrate and polyacrylic acid (PAA) as dispersant and gelling agents, respectively. The zirconia content was up to 20 wt% and added at the expense of alumina while the magnesia content was up to 2 wt% over the total mass. The optimum amount of ammonium citrate tribasic needed for dispersing the ceramic slurry was determined by measuring zeta potential of slurries. The prepared green alumina/zirconia composites were subjected for solid state sintering at 1550 °C for 1 h. The densification parameters, phase composition, average pore diameter, microstructure and cold crushing strength of sintered alumina/zirconia ceramics were investigated by the suitable techniques. The results revealed that the addition of tri-ammonium citrate to ceramic slurries enhanced the zeta potential which reached ?28.3 mV by adding 1 wt.-%. The bulk density was decreased while the apparent porosity was increased with the increase of zirconia content. The apparent porosities of sintered porous composites were in the range of 38.8–48.5%. The average pore diameter for the composite containing 15% zirconia was 1.79 μm and pore volume was 0.11 ml/g. The obtained microstructure exhibited zirconia grains located on the grain boundaries of Al₂O₃ matrix. The existence of zirconia in addition to magnesia hindered the growth and deformation of the matrix. The cold crushing strength of porous composites was decreased from 16.0 to 8.5 to MPa by increasing the zirconia content from 5 to 20 wt.-%.     

Preparation and stabilization of high specific area zirconia carriers

Zirconia samples have been prepared by precipitation from an aqueous solution of zirconyl nitrate followed by calcination in flowing air at temperatures up to 970 K. The textural properties (S_BET and pore size distribution) of these zirconia powders were very sensitive to the activation procedure. Calcination in carefully controlled conditions at 770 K yielded crystallized zirconia with surface area (S_BET ≈ 130 m² g⁻¹) and porosity suitable for use as a catalyst carrier.

Zirconia samples doped with yttrium, nickel or aluminium were obtained by impregnation of the amorphous hydrous oxide. For solids calcined at 770–970 K, the surface area and thermal stability were improved, but the porosity was lower.     

Machining performance of phase transformation toughened alumina and partially stabilised zirconia composite cutting tools

Phase transformation toughened zirconia (TTZ) doped with yttria or ceria has excellent properties such as higher order fracture toughness, thermal shock resistance and moderate hardness. With these qualities, they are able to exhibit machining performance comparable to cold-compacted Al₂O₃ cutting tools. With an addition of 20% aluminium oxide to TTZ, i.e. the composites of alumina and partially stabilised zirconia (PSZ) exhibit improved toughness, enhanced thermal shock resistance and hardness. The alumina and PSZ composite ceramic tools exhibit cutting performance better than TTZ tools and comparable to zirconia toughened alumina tools.     

二氧化锆的相稳定及其制备方法

简要地介绍了二氧化锆常见的物理、化学性质及其推广应用受到限制的主要原因.综述了目前国内外二氧化锆相稳定的主要方法--物理稳定方法和化学掺杂稳定方法的机理及研究现状.简单介绍了稳定二氧化锆的分类,同时对国内外稳定二氧化锆的制备方法及工艺进展进行了系统的叙述,并对各种制备方法进行了分析讨论,并作了简要的评述,进而提出了对今后研究方向的展望.     

Mechanical behaviour of yttria- and ferric oxide-doped zirconia at different temperatures

The variation of strengh, deformability, fracture toughness and other characteristics of partially stabilized zirconia ceramics (Y–Fe–PSZ) doped with 3% yttrium and 3% ferric oxide over a temperature range from −140 to 1400°C were investigated. Fracture toughness (K_1c) values obtained by the methods such as SENB, SEPB, IS and IF were compared. Lower temperatures resulted in an increase in fracture toughness by approximately 29%. Using the Vickers indents as stress concentrators for the IS tests we derived the relationship between K_1c values and mean values of radial crack length described by a second-degree polynomial. The data for zirconia (Y–PSZ and Mg–PSZ) and silicon-nitride ceramics, as well as the fractographic data, were used to analyse the results. It was established that the addition of ferric oxide exerted a positive effect on the strengh and fracture toughness of zirconia ceramics.