氧化锆陶瓷的可逆相变及铁弹性畴转变

本文通过对成分（ｍｏｌ％）为８ＣｅＯ２－１Ｙ２Ｏ３－９１ＺｒＯ２陶瓷材料Ｃｅ－Ｙ－ＴＺＰ的应力应变关系的研究，配合Ｘ身线衍射分析，发现材料中ｔ＾→←ｍ的可逆相变及不可逆铁弹性畴转变。在此基础上提出了Ｃｅ－Ｙ－ＴＺＰ陶瓷材料的增韧公式。     

陶瓷中的相变

提出陶瓷中相变的分类，引述ｓｐｉｎｏｄｅｌ分解的热力学判据和动力学判据，评述含ＺｒＯ２陶瓷马氏体相变尺寸效应的热力学推导和象理论在ＭｇＯ－ＰＳＺ，ＣｅＯ２－ＴＺＰ，Ｙ２Ｏ３－ＴＺＰ，ＢａＴｉＯ３；ＫＴＮ，ＰｂＴｉＯ３及ＹＢａ２Ｃｕ３Ｏ７－ｘ马氏体相变中的应用，指出含ＺｒＯ２陶瓷及ＹＢａ２Ｃｕ３Ｏｙ的等温相变可能属扩散机制的贝氏体相变。     

氧化钇含量对Al2O3／Y—TZP复相陶瓷的影响

本文以ＺｒＯＣｌ２．８Ｈ２Ｏ、Ａｌ２Ｏ３及Ｙ（ＮＯ３）３为原料，用共沉淀法合成Ｙ２Ｏ３含量不同的ＺｒＯ２－Ａｌ２Ｏ３复合粉体，并采用热压工艺制备复相陶瓷。研究了氧化钇含量对复相陶瓷力学性能及应力诱导下氧化锆相变能力的影响。     

14mol%Ce-TZP和Al2O3/Ce-TZP层状复合材料的研究

本文主要通过对含有１４ｍｏｌ％ＣｅＯ２的Ｃｅ－ＴＺＰ及不同结构参数的Ｃｅ－ＴＺＰ／Ａｌ２Ｏ３层状复合材料断裂韧性的测试，从力学和材料角度出发分析Ａｌ２Ｏ３层厚及Ａｌ２Ｏ３层中Ｃｅ－ＴＺＰ的含量对材料力学性能的影响。同时通过对ＫＩＣ试样断裂后断面及受力侧面的激光拉曼微区分析，来定性解释Ａｌ２Ｏ３层的引入对Ｃｅ－ＴＺＰ相变区开头及相变量的影响，从而揭示此类材料的增韧机制?     

添加Al2O3对SiC板粒／Y—TZP复合材料力学性能的影响

本以ＳｉＣ板粒、ＺｒＯＣｌ２·８Ｈ２Ｏ、ＡｌＣｌ３和Ｙ（ＭＯ）３为原料，利用共沉淀和热压烧结工艺，制备ＳｉＣ板粒／Ｙ－ＴＺＰ和（含Ａｌ２Ｏ３）ＳｉＣ板粒／Ｙ－ＴＺＰ复合材料。测试了材料的室温和高温力学性能。研究了添加Ａｌ２Ｏ３对ＳｉＣ板粒／Ｙ－ＴＺＯ复合材料的影响。结果表明，ＳｉＣ板粒／Ｙ－ＴＺＰ复合材料与Ｙ－ＴＺＰ复合材料与Ｙ－ＴＺＰ陶瓷相比，其室温强度和韧性出现明显下降，高温强度也没有改善；     

添加Al_2O_3对SiC板粒／Y－TZP复合材料力学性能的影响

本文以ＳｉＣ板粒、ＺｒＯＣｌ２－８Ｈ２Ｏ、ＡｌＣｌ３和Ｙ（ＭＯ）３为原料，利用共沉淀和热压烧结工艺，制备ＳｉＣ板粒／Ｙ－ＴＺＰ和（含Ａｌ２Ｏ３）ＳｉＣ板粒／Ｙ－ＴＺＰ复合材料．测试了材料的室温和高温力学性能．研究了添加Ａｌ２Ｏ３对ＳｉＣ板粒／Ｙ－ＴＺＯ复合材料的影响．结果表明，ＳｉＣ板粒／Ｙ－ＴＺＰ复合材料与Ｙ－ＴＺＰ陶瓷相比，其室温强度和韧性出现明显下降，高温强度也没有改善；而在ＳｉＣ板粒与Ｙ－ＴＺＰ复合的基础上，添加Ａｌ２Ｏ３可明显提高材料的强度和断裂韧性，同时，材料的高温强度也获得显著改善．     

Y2O3含量及制备工艺参数对Y—TZP纳米粉烧结体性能的影响

用化学共沉淀法制备了Ｙ２Ｏ３含量不同的两种Ｙ－ＴＺＰ纳米粉体；采用了不同压力不冷等静压成形制备素坯；研究了Ｙ２Ｏ３含量，素坯成型压力及烧结温度对Ｙ－ＴＺＰ陶瓷体密度，组织结构及机械性能的影响。     

氧化钇含量对Al_2O_3／Y－TZP复相陶瓷的影响

本文以ＺｒＯＣｌ２８Ｈ２Ｏ、Ａｌ２Ｏ３及Ｙ（ＮＯ３）３为原料，用共沉淀法合成Ｙ２Ｏ３含量不同的ＺｒＯ２－Ａｌ２Ｏ３复合粉体，并采用热压工艺制备复相陶瓷．研究了氧化钇含量对复相陶瓷力学性能及应力诱导下氧化锆相变能力的影响．结果表明，氧化钇含量为１．８ｍｏｌ％时，复相陶瓷中氧化锆仍能全部保持为四方相，且在应力诱导下可相交量高达６４．６％，使材料呈现优良的室温和较好的高温力学性能．     

Y_2O_3含量及制备工艺参数对Y－TZP纳米粉烧结体性能的影响

用化学共沉淀法制备了Ｙ２Ｏ３含量不同的两种Ｙ－ＴＺＰ纳米粉体；采用不同压力下冷等静压成形制备素坯；研究Ｙ２Ｏ３含量、素坯成型压力及烧结温度对Ｙ－ＴＺＰ陶瓷体密度、组织结构及机械性能的影响。     

细晶（Mg,Y）—PSZ陶瓷在热蒸汽条件下的腐蚀行为

研究细晶（Ｍｇ，Ｙ）－ＰＳＺ陶瓷在１７５℃（１．２ＭＰａ）热蒸汽环境下的腐蚀行为。研究发现。细晶（Ｍｇ，Ｙ）－ＰＳＺ陶瓷不仅比３Ｙ－ＴＺＰ陶瓷具有良好的抗水热腐蚀能力，而且也比Ｍｇ－ＰＳＺ陶瓷具有更高的常温抗弯强度。相变激活能的计算结果表明，热蒸汽环境下，（Ｍｇ，Ｙ）－ＰＳＺ陶瓷具有与Ｙ－ＴＺＰ及Ｃｅ－ＡＺＰ陶瓷相近的相变激活能。进一步说明水分子与Ｚｒ－Ｏ－Ｚｒ键相互作用大幅度降低了材料的相变激活     

Microstructure of a sintered 16.5 mol% CeO2-ZrO2 alloy at cryogenic temperature

The microstructure of a fine grained 16.5 mol% CeO2-stabilized tetragonal zirconia polycrystal (Ce-TZP) has been investigated by transmission electron microscopy observations. The results show that the samples fractured at 298, 77 and 4.2 K change significantly. At 298 K, there is no stress-induced martensite but a few anti-phase boundaries (APB) in the tetragonal (t) parent phase. With a decrease in testing temperature, monoclinic (m) product, or martensite within retained t phase, appears. Its morphologies are characterized as lenticular and block-like at 77 K and as lenticular and butterfly-like at 4.2 K. The relationship between microstructure and mechanical properties is also discussed. This revised version was published online in November 2006 with corrections to the Cover Date.     

Correlations between flaw tolerance and reliability in zirconia

Interrelations between flaw tolerance and reliability in Y-TZP, Ce-TZP and Mg-PSZ ceramics are investigated. Indentation-strength tests indicate an enhanced flaw tolerance with increasing R-curve behaviour from tetragonal martensite transformation. The Weibull modulus of unindented specimens increases with the enhanced tolerance. However, even the most tolerant zirconias show persistent scatter in strength, implying that variability in material microstructure may be as important a factor in reliability evaluation in these materials as variability in flaw size.     

液相包覆制备Ce-TZP陶瓷的力学性能与稳定行为

采用XRD、SEM、TEM等分析手段对由液相包覆工艺制备的Ce—TZP陶瓷的微结构进行了研究，并和共沉淀粉体制备的Ce—TZP陶瓷进行了对比分析．力学性能表明，同共沉淀粉体制备的Ce—TZP陶瓷相比，由液相包覆工艺制备的Ce—TZP陶瓷虽硬度下降，但断裂韧性改善；液相添加少量Al2O3硬度随之增加、断裂韧性显著提高．电镜分析表明，液相包覆工艺制备的Ce—TZP陶瓷晶粒尺寸分布宽化，一部分晶粒尺寸较大但CeO2含量低、易发生马氏体相转变晶粒的存在是断裂韧性改善的主要原因．陶瓷体中单斜相大晶粒与四方相之间的残余应力、添加少量Al2O3在晶界上易形成薄的非晶包裹层，是增加可相变四方相数量，提高断裂韧性的其它机制。     

Dispersion stability of Y-TZP/Ce-TZP powder system and slip casting

The zeta potential and apparent viscosity measurements of 3Y-TZP, 12Ce-TZP and 3Y-TZP/12Ce-TZP suspensions, has allowed the slip casting conditions for the preparation of multilayer composites have been examined. The influence of heat treatment on the sintered density, microstructure and crystalline phase of multilayer composites was also studied. The isoelectric point of both 3Y-TZP and 12Ce-TZP suspensions was near pH 8 and that of 3Y-TZP/12Ce-TZP was at pH 8.6. The suspensions exhibited pseudoplastic flow, showing a decrease in viscosity with increasing shear stress. A small (0.3 wt%) addition of an organic deflocculant gave 3Y-TZP and 3Y-TZP/12Ce-TZP suspensions with 15 and 20 vol% solid contents an appropriate fluidity for slip casting, but an additional electrolyte was required to reduce viscosity in 12Ce-TZP. Dense (>98% of theoretical) multilayer composites with grain size of 0.3–2.2 m were obtained after sintering at 1500°C.     

Effect of 10Ce-TZP/Al2O3 nanocomposite particle amount and sintering temperature on the microstructure and mechanical properties of Al/(10Ce-TZP/Al2O3) nanocomposites

A zirconia/alumina nanocomposite stabilized with cerium oxide (Ce-TZP/Al₂O₃ nanocomposite) can be a good substitute as reinforcement in metal matrix composites. In the present study, the effect of the amount of 10Ce-TZP/Al₂O₃ particles on the microstructure and properties of Al/(10Ce-TZP/Al₂O₃) nanocomposites was investigated. For this purpose, aluminum powders with average size of 30 μm were ball-milled with 10Ce-TZP/Al₂O₃ nanocomposite powders (synthesized by aqueous combustion) in varying amounts of 1, 3, 5, 7, and 10 wt.%. Cylindrical-shape samples were prepared by pressing the powders at 600 MPa for 60 min while heating at 400–450 °C. The specimens were then characterized by scanning and transmission electron microscopy (SEM and TEM) in addition to different physical and mechanical testing methods in order to establish the optimal processing conditions. The highest compression strength was obtained in the composite with 7 wt.% (10Ce-TZP/Al₂O₃) sintered at 450 °C.     

Fabrication and sinterability in Y2O3-CeO2-ZrO2

CeO₂-stabilized tetragonal zirconia polycrystal (Ce-TZP) containing 1 to 6 mol % YO_1.5 have been fabricated as fine powders by a coprecipitation technique. The microstructure of the as-sintered surface and fracture surface were examined by electron microscopy. CeO₂ dopants reduced the phase transformation temperature from amorphous to tetragonal and stabilized the tetragonal phase at low temperature. The addition of Y₂O₃ to Ce-TZP inhibited the grain growth. The sintered density reached 99% theoretical for short sintering times at 1440 and 1540° C, but decreased slightly to 97 to 98% theoretical for longer sintering times. The decrease in density is attributed to the morphological development of agglomerates, which induce large pores during sintering. The average grain size decreased significantly as the yttrium content increased from 1 to 3 mol %. Specimens aged in water at low temperatures exhibited no phase transformation. This implies fairly good thermal stability in the Y₂O₃-doped Ce-TZP system.     

14mol?-TZP和Al_2O_3/Ce-TZP层状复合材料的研究

本文主要通过对含有14mol％CeO2的Ce－TZP及不同结构参数的Ce－TZP／Al2O3层状复合材料断裂韧性的测试，从力学和材料角度出发分析Al2O3层厚及Al2O3层中Ce－TZP的含量对材料力学性能的影响．同时通过对KIc试样断裂后断面及受力侧面的激光拉曼微区分析，来定性解释Al2O3层的引入对Ce－TZP相变区形状及相变量的影响，从而揭示此类材料的增韧机制．     

Ceramics Surface Modification by Excimer Laser Metal Coating

Thin metallic layers (~ 2 μm) of Ni were deposited on polycrystalline Al2O3. ZrO2 and (Ce-TZP)+Al2O3 ceramic substrates. and further irradiated with pulsed excimer (Xeno chloride) laser pulses. The laser energy density was varied from 0.21 to 0.81 J / cm2 to optimize bending strength. For ZrO2 ceramic, it was found that the strength increases from 530 to 753 MPa at 0.51 J / cm2 irradiation. For Al2O3 and (Ce-TZP)+ Al2O3 the fracture strength also increases in varying degree. The causes of strength increment were discussed.     

原位Al2O3片晶/Ce-TZP和SrO·6Al2O3棒晶/Ce-TZP复合材料的制备与显微结构

通过在Ce-TZP基体中加入AlOOH及矿化剂TiO₂或反应剂SrCO₃制备了原位Al₂O₃片晶/Ce-TZP复合材料和原位SrO·6Al₂O₃棒晶/Ce-TZP复合材料。在烧结过程中TiO₂促进Al₂O₃晶粒发生显著的各向异性生长原位生成的片晶、Al₂O₃与SrCO₃发生反应,原位生成的高度各向异性的棒晶,它们在基体中分布均匀,具有较大的纵横比。烧结温度对片晶/棒晶的大小和含量有明显影响。通过在基体中原位形成片晶或棒晶,材料的力学性能有明显的改善。