超塑性Y-TZP增韧陶瓷超细粉末的研究

用化学共沉淀法制备了3mol％Y_2O_3-ZrO_2超细粉末。利用热分析,x射线,透射电镜,颗粒粒度分析仪分析了粉料的相组成;颗粒形貌、大小;粉料的团聚状态;化学组成的均一性以及其烧结性能,并结合烧结试样的显微结构和力学性能对粉末的性能做出了评价。实验表明,所制备的粉料组成较为均匀;粒度分布窄;团聚体尺寸小,烧结活性高;颗粒粒度约为200(?)。粉料的相组成主要为四方相和约26％的单斜相。3Y-TZP陶瓷材料三点弯曲强度达1479.14MPa,断裂韧性为13.2MPa·m~(1/2),超塑性压缩变形达190％。     

Al2TiO5-ZrTiO4-ZrO2 Composites: A New Family of Low-Thermal-Expansion Ceramics

The characterization and properties of ceramic composites containing the phases Al₂TiO₅, ZrTiO₄, and ZrO₂ are described. The range of compositions investigated gives very low average thermal expansions (α_24–1000°C as low as −2.0 × 10⁻⁶°C⁻¹) and excellent high-temperature stability. The low thermal expansions are apparently due to a combination of microcracking by the titanate phases and a contractive phase transformation by the ZrO₂. The crystal chemistry and microstructure of the product are processing dependent. Although the composites represent a complex microcracking system, the low thermal expansions and high-temperature stability make them potential candidates for commercial applications requiring thermal shock resistance.     

碳,氮对氧化锆相结构稳定性的作用

利用热处理研究了碳、氮对氧化锆相结构和相变的影响。实验结果表明：碳、氢原子在高温下可以渗入到氧化锆中去，阻止了氧化锆高温相（四方相和立方相）在冷却过程中向低温相（单斜相）的转变。     

Mullitization of Diphasic Aluminosilicate Gels

Recent studies have shown that the mullitization of diphasic aluminosilicate matrices comprising transitional alumina and amorphous silica occurs via a nucleation and growth process. Nucleation is preceded by a temperature-dependent incubation period. Following this incubation period, rapid nucleation of mullite occurs, producing about 1.8 × 10¹¹ nuclei/cm³, which remains constant throughout the rest of the transformation. Both incubation and mullite growth are thermally activated processes with apparent activation energies of 987 ± 63 and 1070 ± 200 kJ/mol, respectively. The growth rate of mullite grains under isothermal conditions is time dependent. An interpretation of these results is proposed on the basis of the nucleation and growth concepts of LaMer and Dinegar which supports the concept that the growth rate of mullite grains is controlled by the dissolution of transitional alumina into the amorphous matrix.     

用于测定钢液低氧含量的双层固体电解质研究

采用“毛坯浆料法”在ＺｒＯ２（９％摩尔含量ＭｇＯ）管状固体电解质基体表面制备了厚度为１－４μｍ的ＺｒＯ２（１０％摩尔含量Ｙ２Ｏ３）固体电解质涂层，并分别对此在本实验室和美国ＬｅｅｄｓａｎｄＮｏｒｔｈｒｕｐ公司进行了钢液低氧含量测试，结果表明：涂层没有破坏基体的抗热震性：氧浓差电池电动势的重现性偏差由原来的±２ｍＶ；电动势的绝对值提高１０ｍＶ左右；而比日本Ｔｏｒａｙ公司的同类产品提高３５ｍＶ，这说明     

Y2O3改性的MgO—ZrO2共析陶瓷

共析ＭｇＯ－ＺｒＯ２陶瓷添加Ｙ２Ｏ３可以获得高温热稳定性和较佳的力学性能，添加２％Ｙ２Ｏ３时断裂韧性为７．６ＭＰａ．ｍ＾１／２，弯曲强度为６１８ＭＰａ，用透射电子显微镜详细研究和讨论了上述材料的时效显微组织和韧化的原因。     

Y-TZP/Al_2O_3超细粉末的研究

用共沉淀法制备了3mol％Y_2O_3-ZrO_2-20Wt％Al_2O_3超细粉末。利用热分析、X射线、粒度分析仪、透射电镜和扫描电镜等研究了粉末的性能。实验结果表明:制备的粉末组分均匀,颗粒粒度为10nm,粒度分布窄,团聚体尺寸小,烧结活性高。粉末的相组成为t-ZrO_2。烧结体显微结构致密细晶,具有优异的力学性能。     

Characterization and Sintering Behavior of Alkoxide-Derived Aluminosilicate Powders

Submicrometer SiO₂-Al₂O₃ powders with compositions of 46.5 to 76.6 wt% Al₂O₃ were prepared by hydrolysis of mixed alkoxides. Phase change, mullite composition, and particle size of powders with heating were analyzed by DTA, XRD, IR, BET, and TEM. As-produced amorphous powders partially transformed to mullite and Al-Si spinel at around 980°C. The compositions of mullite produced at 1400° and 1550°C were richer in Al₂O₃ than the compositions of stable mullite solid solutions predicted from the phase diagram of the SiO₂-Al₂O₃ system. Particle size decreased with increasing Al₂O₃ content. The sintered densities depended upon the amount of SiO₂-rich glassy phase formed during sintering and the green density expressed as a function of particle size.     

Phase Stability and Physical Properties of Cubic and Tetragonal ZrO2 in the System ZrO2–Y2O3–Ta2O5

The cubic ( c -ZrO₂) and tetragonal zirconia ( t -ZrO₂) phase stability regions in the system ZrO₂–Y₂O₃–Ta₂O₅ were delineated. The c -ZrO₂ solid solutions are formed with the fluorite structure. The t -ZrO₂ solid solutions having a c/a axial ratio (tetragonality) smaller than 1.0203 display high fracture toughness (5 to 14 MPa · m^1/2), and their instability/transformability to monoclinic zirconia ( m -ZrO₂) increases with increasing tetragonality. On the other hand, the t -ZrO₂ solid solutions stabilized at room temperature with tetragonality greater than 1.0203 have low toughness values (2 to 5 MPa · m^1/2), and their transformability is not related to the tetragonality.     

Direct Measurement of Transformation Zone Strains in Toughened Zirconia

Residual strains responsible for crack tip shielding have been measured within transformation zones surrounding cracks in Mg-PSZ. Two techniques were used for strain measurement: moiré interferometry and high-resolution image matching. Both methods provide maps of differential in-plane displacements within the specimen surface intersected by the crack, the latter method with the higher resolution. The results are compared with finite-element analysis to assess surface relaxation effects, and the measured strains are used to evaluate the crack tip shielding stress intensity factor. Calculations based on the assumption that the unconstrained transformation strain is hydrostatic dilatation yielded results that were significantly smaller than the measured toughness increases.