ZrO2—Y2O3ZrO2—MgO赝二元系相平衡的研究

用双亚点阵模型处理了ZrO_2-Y_2O_3、ZrO_2-MgO系统中的体心立方ZrO_2基固溶体相。用正态分布函数和样条函数相结合的方法,由部分相图数据优化了上述赝二元系中各相的相互作用参数,并用优化的相互作用参数及本工作估计的各氧化物的点阵稳定性参数计算了上述赝二元系相图。此外,还用DTA和X射线衍射方法测定了赝二元系在1300℃以下的固态相关系。计算结果与实验结果符合。     

ZrO2颗粒浓度对钕铁硼Ni-P/ZrO2复合镀层耐蚀性的影响

采用化学镀技术在钕铁硼表面制备出Ni-P/ZrO2复合镀层,并研究了ZrO2颗粒浓度对复合镀层中ZrO2颗粒含量、复合镀层的形貌、孔隙率和耐蚀性的影响.结果表明,ZrO2颗粒浓度在0.5～4.0 g/L范围内时,复合镀层的耐蚀性随着ZrO2颗粒浓度增加逐步改善,在不同腐蚀介质中的平均腐蚀速率都呈现减小的趋势,主要归因于...     

纳米ZrO2应用研究进展

纳米ZrO_2因其特殊的理化性能被广泛应用于材料、医学等多个领域。综述了ZrO_2在催化治污、药物载体、高性能材料和氧传感器等领域的应用研究进展;展望了纳米二氧化锆的发展前景,开发性能优异、应用范围广泛的复合型纳米ZrO_2材料及其高效生产工艺有助于进一步拓展其应用前景和商业化推广。     

ZrO2增韧陶瓷的研究进展

综述了ZrO2陶瓷及添加氧化物稳定剂对四方相氧化锆的稳定性影响，以及ZrO2陶瓷材料的种类，增韧机理及其主要应用领域，并展望了氧化锆增韧陶瓷的研究发展趋势。     

ZrO2复相陶瓷材料的研究

综合近几年来ZrO2复相陶瓷材料的研究情况,发现对ZrO2结构陶瓷的研究主要集中在力学性能的改善方面,本文总结了ZrO2复相陶瓷的研究情况和进展,作为后面对ZrO2复相陶瓷研究的基础和参考。     

ZrO2陶瓷纤维制备及性能研究

通过挤压法制备ZrO_2陶瓷纤维；采用参量变换法研究了PVA和甘油含量分别对纤维密度和收缩率的影响；并且对ZrO_2纤维的前躯体进行热重(TG)和差热(DTA)分析,对ZrO_2纤维进行扫描电镜(SEM)分析。且在实验中用溶胶取代粘结剂制备纤维,提高了纤维密度。     

ZrO2/SiO2复合溶胶稳定性的实验研究

以硅酸乙酯和氧氯化锆为先驱体，制备了ZrO2／SiO2复合溶胶，重点考察了ZrO2的摩尔含量、添加剂DMF和TEABr、陈化温度对ZrO2／SiO2复合溶胶稳定性的影响。结果表明：氧氯化锆的存在不利于ZrO2／SiO2复合溶胶的稳定，且随着氧氯化锆摩尔百分含量的增加，溶胶易于凝胶；随着陈化温度的升高，凝胶时间变短；DMF能明显延长ZrO2／SiO2复合溶胶的凝胶时间；当0．4〈n（TEABr）／n（TEOS）〈1时，TEABr能提高溶胶的稳定性。     

纳米ZrO2的制备

本实验研究了利用ZrOCl2·8H2O为原料,根据不同的醇水配比及氨水配比,采用溶胶-凝胶法,并以超临界干燥法（SCFD）制备纳米ZrO2。得出在一个大气压,温度在15～25℃,采用溶胶-凝胶法,在不同的醇水配比及氨水配比下,对ZrO2颗粒将有一定的影响。     

Hydrothermal Crystallization of Zirconia and Zirconia Solid Solutions

Zirconia as well as yttria-zirconia and calcia-zirconia solid-solution powders were crystallized under hydrothermal conditions from (co)precipitated hydroxides. The morphology of the powder particles is strongly dependent on the crystallization conditions. The powders crystallized in a water solution of Na, K, and Li hydroxides show elongated particles of much larger sizes than those which result from the process carried out in pure water or a water solution of Na, K, or Li chlorides. The shapes of the latter particles are isometric. The growth mechanism of the elongated particles is suggested.     

High-Pressure Phase Transitions in Zirconia and Yttria-Doped Zirconia

Raman spectroscopy has been utilized to characterize the phase transformations and transition pressures in pure and doped zirconia containing 3, 4, and 5 wt% Y₂O₃. The pressure-induced transformations were investigated to over 6 GPa (at room temperature) using a diamond anvil pressure cell. Pure zirconia single-crystal samples transformed to a "new" tetragonal phase (different from the one obtained at high temperatures at atmospheric pressure) at about 4 GPa. The pressure transformation, like the temperature transition, was reversible and exhibited an approximately 0.45-GPa hysteresis at room temperature. The 3 and 4 wt% Y₂O₃ crystals underwent a monoclinic ( P 2_1/b) to tetragonal ( P 4_{2 nmc}) phase transition similar to that observed at high temperatures. This phase change was found to be irreversible on releasing the pressure. The 5 wt% Y₂O₃ at atmospheric pressure consists of a tetragonal modification in a disordered cubic matrix; a gradual, but reversible, disordering transformation of the tetragonal precipitate takes place with pressure.     

Crystal Structure of Orthorhombic Zirconia in Partially Stabilized Zirconia

A neutron powder diffraction investigation confirms that, in tough magnesiapartially-stabilized zirconia cooled to 30 K, most of the tetragonal zirconia transforms to an orthorhombic phase. This phase is retained on heating to room temperature; the lattice parameters at 295 K are a = 0.5068, b = 0.5260, and c = 0.5077 nm. The room-temperature crystal structure (space group Pbc2₁) is determined by multiphase Rietveld refinement from the neutron diffraction pattern. This orthorhombic structure is compared with the parent tetragonal structure and with the structure of monoclinic zirconia, which it closely resembles.     

Zirconia refractories

Results on the thermal conductivity of powders of monoclinic zirconia as a function of the grain size are presented. It is established that of all the investigated sintered powders of monoclinic ZrO₂ the 1 – 0.5-mm and 2 – 1-mm fractions have the lowest thermal conductivity and the least apparent density (2.190 and 2.262 g/cm³). Fused powders of monoclinic and stabilized ZrO₂ have a higher thermal conductivity than their sintered counterparts. Powders prepared from monoclinic ZrO₂ with a burning-off addition of polystyrene have larger pores in the grains, which increases the share of the radiation component in the heat transfer, and hence their thermal conductivity is higher than in powders obtained by sintering pure monoclinic ZrO₂. For the same reason, powders from void granules of the 3 – 0.5-mm fraction have a higher thermal conductivity than sintered monoclinic powders of ZrO₂.Translated from Ogneupory, No. 1, pp. 26 – 29, January, 1995.     

Nitridation of Zirconia

ZrO₂ can be nitrided partially by nitrogen at temperatures >1400°C. It is possible to describe all the synthesized phases with the general formula ZrO_2-2χN_4χ/3 (system ZrO₂-Zr₃N₄). Parameters–such as nitridation time, temperature, nitrogen pressure, and particle size–have a strong effect on the amount of incorporated nitrogen. Variation of these parameters allows the synthesis of Zr-O-N ceramics within a wide range of possible compositions. ZrO_2-2χcN4_χ/3 phases synthesized by reaction of ZrO₂ with nitrogen show ordered anion vacancies (β-type structures). β-type phases are non-transformable under mechanical stress at ambient temperature. Nitrogen-containing ZrO₂ shows very poor oxidation resistance. At temperatures >600°C, stability is found only in the presence of an oxygen getter.     

Phase Stability and Mechanical Properties of Zirconia and Zirconia Composites

Monolithic zirconia materials (3Y‐TZP, 10Ce‐TZP, and 12Ce‐TZP) and their composites with 30 vol% alumina were produced. Low‐temperature aging degradation (LTAD) and mechanical properties of materials were investigated. For assessment of phase stability in the materials, aging experiments were performed in water at 90°C for 32, 64, and 128 days. The aging phenomenon was characterized and monitored using X‐Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Four‐point bending was used to determine the flexural strength of materials before and after aging treatment in water at 90°C for 2, 4, and 6 months. The aging experiments resulted in different phase transformation rates for the materials studied. The 12Ce‐TZP containing materials showed the highest resistance to low‐temperature aging and 3Y‐TZP containing materials showed the highest bending strength. When compared, no change in flexural strength was observed between the materials not exposed to aging and the aged materials.     

'Polymorph Method' Determination of Monoclinic Zirconia in Partially Stabilized Zirconia Ceramics

The polymorph method, which provides phase analysis from a small number of integrated intensities in a powder diffraction scan, is adapted for the determination of monoclinic zirconia in a mixture with cubic, tetragonal. and orthorhombic zirconias and the γ-phase (Mg₂Zr₅O₁₂). Such a mixture is representative of Mg-PSZ after subeutectoid aging. The quantitative determination of the monoclinic depends in principle on a knowledge of the relative amounts of the other phases present in the mixture. It is demonstrated, however, that without this knowledge, even in complex mixtures, the traditional polymorph method analysis gives an acceptable estimate of the monoclinic fraction in the sample.     

High-Strength Zirconia Fibers

Fine-grained polycrystalline zirconia fibers have been formed from an acetate precursor. The fibers contained a Y₂O₃ additive, which inhibited grain growth (grain size ≤0.5 μm) and allowed the tetragonal phase to be retained at room temperature. Fibers with diameters in the range 2 to 5 μm had strengths in the range 1.5 to 2.6 GPa.