Phase relation of ternary system ZrO2CaOAl2O3

The phase relation in the ternary system ZrO₂CaOAl₂O₃ has been studied at 1,380°C in the composition range below 50 mol% CaO. The mixed oxides with various compositions have been prepared from their acidic solutions through evaporation, calcination, and heat-treatment. Nine regions have been found. In the stabilized zirconia with fluorite structure, 4 mol% Al₂O₃ is soluble. The fluorite phase also exists in equilibrium in two-phase regions (fluorite + ZrO₂, and fluorite + CaO·ZrO₂) and in three-phase regions (fluorite + ZrO₂ + CaO·2Al₂O₃, and fluorite + CaO·ZrO₂ + CaO·2Al₂O₃).     

Y2O3稳定ZrO2材料的电导活化能

在313～473K温度范围内测定了一种Y2O3稳定ZrO2材料(YSZ)的交流电导率谱,进而导出了材料的直流电导率并分析了其随温度的变化关系.研究发现:在低温下材料的电导活化能随温度的升高而增大.这一实验现象与在高温下所观察到的活化能随温度升高而降低的规律截然相反.通过分析材料中氧空位的解缔及迁移机制,对YSZ材料中电导活化能随温度的变化关系作出了一个合理的解释.     

New ZrO2Yb2O3 plasma-sprayed coatings for thermal barrier applications

New thermal barrier coatings with improved properties were identified. These ZrO₂Yb₂O₃ coatings were evaluated together with ZrO₂6.1Y₂O₃¹ and ZrO₂8.0Y₂O₃. All ceramic coatings were deposited onto Ni16.2Cr5.9A10.15Y and Ni18.3Cr6.4A10.22Yb bond coatings on MAR-M-200 + Hf substrates. Tests were run in a cyclic furnace at temperatures up to 1120°C. On the NiCrA1Y bond coating the ZrO₂12.4Yb₂O₃, ZrO₂14.7Yb₂O₃ and ZrO₂17.4Yb₂O₃ have respectively 60%, 30% and 15% longer lives than the ZrO₂6.1Y₂O₃ coating. They also have 80%, 50% and 25% longer lives than the ZrO₂8.0Y₂O₃ coating. On NiCrA1Yb bond coating the ZrO₂12.4Yb₂O₃ has about 40% longer life than the ZrO₂6.1Y₂O₃. The optimum Yb₂O₃ concentration in ZrO₂, at which maximum life is obtained, is believed to be between 12.4 and 14.7 wt.%. The ZrO₂Yb₂O₃ coatings fail in a similar fashion to the ZrO₂Y₂O₃ coatings.X-ray diffraction data from the limited study of the ZrO₂Yb₂O₃ system suggest that monoclonic, cubic and tetragonal phases, in addition to Zr₃Yb₄O₁₂ and Yb₂O₃, are present in zirconia-ytterbia powders containing between 2 and 90 wt.% Yb₂O₃. The ZrO₂Yb₂O₃ plasma-sprayed coatings were also found to contain monoclinic, cubic and tetragonal phases in addition to Zr₃Yb₄O₁₂, and they showed a few very weak X-ray diffraction peaks that belong to an unknown phase.     

Zeolite synthesis in the system pyrrolidine-Na2OAl2O3SiO2H2O

Crystallization of zeolites from the system pyrrolidine-Na₂OAl₂O₃SiO₂H₂O was investigated. Five zeolites, ZSM—5, ZSM—35, ZSM—39, ZSM—48 and KZ—1, were synthesized as single phases, whose crystallinity was very high. In this work zeolite ZSM—48 was prepared from the pyrrolidine system for the first time. It was suggested that pyrrolidine might stabilize certain aluminosilicate polyanions which have building units of oxygen five-membered rings. It was also presumed that all zeolites, except ZSM—39, have a pore opening of oxygen ten-membered rings.     

三元系ZrO2—Y2O3—Yb2O3材料的低温电性能

采用复阻抗技术对三元系ＺｒＯ２－Ｙ２Ｏ３－Ｙｂ２Ｏ３材料在５７３－８７３Ｋ内的离子电导率随组成的变化关系进行了研究,发现该材料的低温电导率随Ｙｂ２Ｏ２含量的增加而降低。用Ａｒｒｈｅｎｉｕｓ公式对实验数据进行的分析表明,电导率降低的原因在于Ｙｂ＾２＋与结构中氧空位之间的缔合比Ｙ＾３＋与氧空位之间的缔合更甚,阻碍了氧空位在低温下的定向迁移。     

Y2O3添加剂对ZrO2超微粉体性质的影响

添加0-6mol%Y2O3的ZrO2超微粉体由化学共沉淀法制备，系统地研究了添加剂对粉体粒子粒径，表面性质和团聚状态的影响，结果表明，添加Y2O3组元，使制备的ZrO2粉体粒子粒径减小，对粒子的长大趋势可起到抑制作用，但加剧了粉体粒子的团聚，团聚体颗粒变大，团聚强度升高，随着组元添加量的增多，作用加剧。     

2Y2O3—ZrO2陶瓷中t→m相变

用热膨胀分析仪和Ｘ射线衍射仪研究了２＾（ｍｏｌ百分数，下同）Ｙ２Ｏ３－ＺｒＯ２陶瓷中ｔ→ｍ等温和变温相变动力学及相结构。发现其中存在的低温和中温ｔ→ｍ相变。前者发生在液氮温度附近或更低温度，具有爆发性转变特征，不能被快速冷却抑制。后者发生在室温以上，具有等温相变特征。相变过程中仅与温度有关，而且受时间控制，ＴＴＴ曲线具有Ｃ形特征。相变温度范围取决于ｔ相晶粒尺寸和冷速，足够快的冷速可抑制中温相变。Ｘ     

Rapid Solidification of ZrO2–8 mol % Y2O3Melt

This paper deals with the singularities of crystallization of a pool with a melt produced by local heating of ZrO₂–8 mol % Y₂O₃ceramic by concentrated laser radiation. The effect of the semitransparency of the oxide, of the thickness of the melt, and of the rate of its cooling on the behavior of crystallization and on the structure of solidified layer is analyzed. The obtained results are compared with the results of crystallization of the melt of pure ZrO₂.     

(Y2O3,Yb2O3)复合掺杂ZrO2材料的中低温电导率

采用交流复阻抗体技术对（Y2O3，Yb2O3)复合掺杂ZrO2材料在573－873K这一温度范围的离子电导率随组成的变化关系进行了研究，发现在ZrO2-Y2O3系统加入Yb2O3会使得材料在中低温区域电导率降低。用经典的Arrhenius公式对实验数据进行的分析表明，导导率降低的原因在于Yb^3＋与结构中氧空位之间的缔合比Y^3 与氧空位之间的缔合更甚，阻碍了氧空位在中低温下的定向迁移。     

Y2O3稳定ZrO2材料离子电导率与温度的关系

在不同温度下制定了Ｙ２Ｏ３含量不同的几种Ｙ２Ｏ３稳定ＺｒＯ２材料的电导率，发现在所研究的Ｙ２Ｏ３含量范围内，材料的电导率随温度的变化关系可以用有一个改进的Ａｒｒｈｅｎｉｕｓ方程加以描述。由这一改进的Ａｒｒｈｅｎｉｕｓ方程导出的电导活化能数值与其他作者给出的理论计算结果的吻合得很好。     

Mössbauer Study of Tetragonal ZrO2–Y2O3–Fe2O3 Solid Solutions

Tetragonal Zr_0.886Y_0.057Fe_0.057O_{2 –} solid solutions prepared by calcining coprecipitated and successively precipitated hydroxide mixtures were studied by Mössbauer spectroscopy immediately after calcination and after long-term storage. The results indicate that the solid solutions prepared via coprecipitation and successive precipitation contain Fe³⁺ in two (octahedral coordination) and three (octahedral, fivefold, and tetrahedral coordinations) inequivalent sites, respectively. Partial Fe³⁺ substitution for Y³⁺ is shown to prevent or substantially slow down the low-temperature structural degradation of stabilized zirconia.     

ZrO2（Y2O3）纳米粉在超高压下快速烧结

研究了超高压（５ＧＰａ）、高温（１３５０℃）下烧结的ＺｒＯ２（Ｙ２Ｏ３）纳米材料的结构及相关系。结果表明：水解法制备的纳米（９ｎｍ）２．２Ｙ－ＺｒＯ２粉体经超高压烧结１０ｓ，致密度即达９９．５％以上，晶粒迅速长大达６０ｎｍ。在０￣９９ｓ范围内，随烧结时间延长，２．２Ｙ－ＴＺＰ的ｔ相增加，四方度（ｃ·ａ＾－１）减小，表明Ｙ２Ｏ３固溶进入ＺｒＯ２晶格内。     

ZrO2—Y2O3纳米晶的制备及其湿敏性能

以化学共沉淀法为基础，配合高速剪切均质并添加表面活性剂制备了粒径为２０￣４０ｎｍ的ＺｒＯ２－Ｙ２Ｏ３纳米晶，经ＸＲＤ分析为稳定立方相结构。用ＺｒＯ２－Ｙ２Ｏ３纳米晶为感湿材料制作了厚膜型湿敏元件，测试结果表明：（１）元件电阻随相对温度上升而下降。（２）在总电导中，离子电导占主要成分。（３）元件有较快的感湿响应速度。     

Y2O3-MgO共稳定ZrO2的相含量及形貌研究

用湿化学法制备的Y2O3-MgO共稳定ZrO2固体电解质,分别在1550℃,1600℃,1630℃下烧结,获得了室温下单斜相和四方相含量不同的烧结样品.结果表明:随着氧化钇含量的增加,单斜相含量降低,四方相含量增加.烧结温度对相含量的影响较小.(MgO,Y2O3)-PSZ材料断口组织致密,结构均匀且晶粒大小一致,当Y2O3含量较高(≥2.5mol%)时,材料中出现过烧现象.采用Y2O3和MgO复合稳定剂共同稳定ZrO2,能有效地降低材料的烧结温度,且弯曲强度得到明显提高.从当前实验结果来看,在8.0 mol%MgO-ZrO2的基础上,加入2.0 mol%Y2O3在1600℃烧结,得到的材料弯曲强度性能最佳.     

用保护共沉淀法制备纳米ZrO2(Y2O3)粉体

用Tween-80保护共沉淀法制备了ZrO2(Y2O3）纳米粉体，用差热分析，热重分析，X射线衍射及透射电子显微镜等技术研究所了粉体的特征，结果表明：在700℃燃烧0.5h后ZrO2(Y2O3)粉体的平均粒径为3－9nm，比表面为128.5-134.5m^3g^-1,在1250℃煅烧8h后ZrO2(Y2O3)粉体已完全形成了立方相的ZrO2L大溶体，并且有非常好的烧结性能。     

液相等离子喷涂制备纳米ZrO2/Y2O3涂层的研究

传统的喷涂技术制备的ZrO2/Y2O3涂层存在原料需团聚烧结致密,纳米晶粒不定和物理性能不佳等缺点.采用一种新型的液相等离子喷涂法制备了纳米氧化锆热障涂层,初步分析了液相前驱体液滴在等离子焰流中和基体表面的沉积变化过程,研究了雾化液滴尺寸对纳米氧化锆涂层的显微结构,特别是其相结构的影响;同时分析了纳米氧化锆涂层的抗热震循环性能.结果表明,纳米氧化锆涂层可以承受1 000多次的热循环试验,具有优良的抗热震性能.     

Y2O3掺杂ZrO2基电解质材料的离子传导性能及研究进展

纯二氧化锆掺杂了与锆离子半径相近的低价阳离子后,会产生较多氧空穴,可以实现离子导电.其中Y2O3,掺杂ZrO2基电解质材料有着优越的离子传导能力,它已经被广泛的应用到传感器和固体电解质上.介绍了Y2O3掺杂ZrO2基电解质材料导电的机理,简述了YSZ材料以及多元掺杂的ZrO2基电解质材料的研究进展.     

Stability of ZrO2–Y2O3 t′ phase formed during laser sealing

Abstract

Results are reported concerning the effect of thermal treatments in the temperature range 1050–1500°C for 1–1000 h on the stability of the t′ phase present in laser sealed layers of ZrO₂–8·5 wt-% Y₂O₃. Aging for up to 1000 h at 1050°C is not sufficient to cause significant transformation of the t′ phase. At temperatures >1300°C, the t′ phase is less stable and transforms to mixtures of the t and c phases in proportions which are a function of both the time and temperature of aging. An improvement in the fracture toughness of the sealed layer was found to occur when substantial proportions of t phase were produced by annealing.

MST/1529     

Microstructure and mechanical properties of SiC Whisker reinforced ZrO2–Y2O3 composites

Abstract

The mechanical properties of 20 vol.-%SiC whisker reinforced ZrO₂?V₂O₃ composites containing 2 and 6 mol.-% Y₂O₃ were measured at room temperature and the fracture surface was examined. The results indicate that the mechanical behaviour of the composites is strongly influenced by the Y₂O₃ content. The magnitude of the enhancement of the toughness in composites containing 2 mol.-% Y₂O₃ compared with unreinforced ZrO₂?Y₂O₃ matrix is larger than that for the composites containing 6 mol.-% Y₂O₃. Crack propagation modes were characterised by crack deflection, whisker bridging, and whisker pullout. High resolution electron microscopic observations show that in composites containing 2 mol.-% Y₂O₃ the whiskers are directly bonded to the matrix. However, in composites containing 6 mol.-% Y₂O₃ there is always a thick amorphous layer at the interface, indicating that the high Y₂O₃ content has promoted the formation of interfacial amorphous layers. These interfacial amorphous layers strengthen the interfacial bonding, resulting in a composite with a low fracture toughness.

MST/2043