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1.
The effect of rare earth oxides Y203 or Ce02 on sintering properties of Si3N4 ceramics was studied and the mechanism of assisting action during sintering was analyzed. The results in dicate that the best sintering properties appear in Si3N4 ceramics with 5% Y203 or 8% CeO2. Secondary crystallites are formed at grain boundaries after heat treatment,which decreases the amount of glass phase and contributes to the improvement of high-temperature mechanical properties of silicon nitride. 相似文献
2.
Preparation and Properties of Sintering Additives Coated Si3N4 from Heterogeneous Nucleation Processing 总被引:1,自引:0,他引:1
The sintering additives such as Al2O3 and /or Y2O3 were coated on the surfaces of Si3N4 particles via heterogeneous nucleation processing using a buffered pH solution as the precipitation reagent .They nucleated and grew only on the surfaces of Si3N4 and did not form sol particles in solution by TEM observation .The isoelectric point(IEP) of coated Si3N4 was different from that of as-received Si3N4.The IEP of Al(OH)3-coated Si3N4 occurred at pH8.4, which is close to that of alumina .When Al(OH)3-coated Si3N4 particles were coated with Y(OH)3,the IEP of coated Si3N4 powder shifted from pH8.4 to pH9.2 ,similar to that of yttria.In addition ,the rheological data showed that Al2O3 and /or Y2O3 coated Si3N4 suspension is nearly Newtonian and that added Si3N4 suspension shows a shear rate thinning behavior. 相似文献
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秀卢瑟福背散射-沟道技术(RBS-C)和X射线衍射技术(XRD)研究了Pt和注入YSZ(Y2O3稳定的ZrO2)后产生的损伤和退火过程中损伤的恢复及注入Pt的晶化,RBS-C分析表明YSZ室温下的存在较强自退火效应,XRD分析结果示出硫以铂的晶化产生很大影响。 相似文献
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Alumina-doped yttria-stabilized zirconia (ADYSZ) nanopowders were prepared by microwave-assisted peroxyl-complex coprecipitation (MAPCC) using ZrOCl2-8H2O, Y2O3 and AICly6H2O as starting materials, NH2-H2O as precipitant and H2O2 as complexant. The effects of adding H2O2 and microwave drying on the preparation and properties of ADYSZ were investigated. The precursors and nanopowders were studied by EDX, XRD, SEM and TEM techniques. The results show that the uniformity of component distribution within ADYSZ nanopowders is improved by adding appropriate dosage of H2O2. Complexing reaction between H2O2 and Zr^4+ ion restrains the hydrolyzation and precipitation of Zr^4+ ion. With the addition of H2O2, Al^3+, y^3+ and Zr^4+ ions can be precipitated synchronously in a relatively narrow range of pH value. H2O2 also improves the filterability of the wet precipitate. The highly hydrophilic precipitates can be quickly and effectively separated from aqueous solution. During microwave drying process, the moisture of wet precursors is selectively heated. Quick expansion of steam vapor within the wet colloidal particles causes the aggregations burst into numerous tiny lumps. Compared with oven drying, microwave drying can not only shorten drying time but also reduce aggregation intensity of the resultant ADYSZ nanopowders. 相似文献
8.
氮化铝相在SiC-AIN-Y2O3复相陶瓷中起着至关重要的作用。在2050℃高温时,AIN颗粒表面发生固相蒸发现象,并聚集到SiC颗粒周围最终形成固溶体,改善了SiC颗粒周围最终形成固溶体,改善了SiC陶瓷的晶界结构,使该复相材料具有良好的机械性能,其室温抗折强度为610MPa,这一强度可持续至1400℃高温,断裂韧性达到8.1MPa.m^1/2。 相似文献
9.
Y2O3改性的MgO—ZrO2共析陶瓷 总被引:2,自引:0,他引:2
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。 相似文献
10.
采用粉冶法制备了添加Y2O3/CeO2(≤0.6w%)的复合强化钼合金(MYC)丝。用XRD标定合金相组成,用SEM观察合金的显微组织,用万能电子拉伸机测定合金丝的力学性能并将测定结果与纯钼丝进行了对比研究。研究结果表明:添加Y2O3/CeO2复合强化钼合金的相组成为Mo,YMoO4和CeO2;MYC合金断口具有典型的塑性断裂特征,MYC合金丝在1600℃退火后仍然表现明显的纤维状织构组织形态。 相似文献