Thermodynamic assessment of the ZrO2-AlO1.5 system

The ZrO₂-AlO_1.5 quasibinary system has been assessed by means of the CALPHAD (CALculation of PHAse Diagram) technique. The liquid phase, cubic (fluorite-type) zirconia solid solution and tetragonal zirconia solid solution are described by a regular solution model. The monoclinic zirconia and α-AlO_1.5 are treated as stoichiometric phase. A consistent set of optimized parameters describing the system have been obtained to agree with almost all of the avaiable experimental data. Comparisons between the assessed and experimental data are presented. It is shown that further studies are needed for equilibrium solubilities of AlO_1.5 in ZrO₂ phases. Project supported by the National Natural Science Foundation of China and the National Key Laboratory of Powder Metallurgy Synopsis of the first author Wang Tao, born in 1972, doctoral student, majoring in phase diagram and materials design.     

Design and Synthesis of Ti-ZrO2 Functionally Graded Materials

Functionally graded materials (FGMs) based on titanium-zirconia system have been prepared by powder metallurgical method. The graded interlayer number and the compositional distribution have been designed by elastic finite element method. The inierfacial microstructure between layers, the combining state of phases between Ti and ZrO2 have been investigated by means of XRD (X-ray dif fraction), SEM (scanning electron microscope), EDS (energy dispersive spectrometer) and so on. The co-existing region of Ti and ZrO2 has been determined by thermodynamic calculation to control the sintering atmosphere. The experimental results show that the joint between Ti and ZrO2 phases is physical in this composite and ZrO2, mainly exists as tetragonal phase. The microstructure of Ti-ZrO2, system FGM exhibits a transition from a zirconia particle dispersion in a titanium matrix to an inverse dispersion of titanium in zirconia. The gradient structure of titanium and zirconia can relieve thermal stress.     

ZrO2掺杂CeO2基电解质材料的研究

在CeO2/Sm2O3体系中加入ZrO2,能降低CeO2基电解质材料的电导率,主要是因为ZrO2的固溶使得CeO2基电解质材料的晶格常数减小,活化能增加;添加ZrO2可提高材料的断裂强度,使材料断裂以穿晶断裂为主,同时可促进致密烧结,使晶界结合紧密。     

热处理对热障涂层材料Y_2O_3部分稳定ZrO_2性能的影响

热障涂层用于燃气轮机的热端部件,可以显著提高其使用温度,延长热端部件的使用寿命,并增大燃气轮机发动机的效率.利用Y2O3和ZrO2为原料,通过固相合成法合成了Y2O3(w(Y2O3)=6%~8%)部分稳定的ZrO2(Y-PSZ)热障涂层陶瓷顶层,并对此陶瓷顶层的微观形貌、相组成进行了研究.同时研究了热处理对热障涂层材料Y-PSZ性能的影响.     

镧对WO3/ZrO2固体超强酸酸强度和结构的影响

通过共沉淀法制备了合适酸强度,比表面积为175.284 3 m2.g-1,最可几孔径在5.99 nm,负载镧的WO3/ZrO2固体超强酸催化剂。用Hammett指示剂法、XRD、N2等温吸附/脱附、DTA等方法考察了负载稀土镧后对催化剂的酸强度、比表面积、孔结构和热稳定性的影响。结果发现：La能均匀掺入WO3/ZrO2固体超强酸中,且适当加入稀土元素镧不但可以提高其酸强度,而且可以稳定结构、增加比表面积。     

电熔MgO-ZrO2原料显微结构的研究

以轻烧氧化镁和锆英石为原料,采用电熔法制备了MgO-ZrO2合成料,利用扫描电子显微镜和能谱仪对材料的显微结构进行了分析,计算了材料中各物相的化学组成,探讨了其显微结构的形成过程.研究结果表明,在电熔过程中锆英石分解产生的S iO2在晶界的低钙区域中以2MgO.S iO2的形式存在,而在高钙区域将生成MgO.S iO2.CaO玻璃相.基体中的MgO和杂质中的CaO将进入ZrO2晶格中形成（MgO＋CaO）ZrO2固溶体,该固溶体在降温过程中会析出MgO,并在其晶粒周围形成富镁的2MgO.S iO2相.     

Synthesis and characterization of pure mesoporous zirconia thin film with two-dimensional hexagonal framework

Sincethediscoveryofanewfamilyofsilica basedmesoporousmaterialsdesignatedasM41Sbyresearchers atMobilOilCorporationin1992[1,2],avarietyofmeso porousmaterialshavebeenpreparedusingstructure di rectingagents,suchasionicornonionicsurfactants,as templates[3-9].M…     

Degration of Partially Stabilized Zirconia Ceramics under an Applied Stress

Partially stabilized zirconia ceramics were sintered using fine powder of ZrO2-3mol % Y2O3 prepared by the chemical co-precipitation method. The tetragonal-to-monoclinic phase transformation in ZrO2 ceramics during the aging in boding water and the effect of an applied stress of 100MPa were mainly investigated.The degradation of ZrO2 ceramics is considered to be caused by the reaction between Y2 O3 and H2O, which leads to a decreasing in the stability of tetragonal phase of ZrO2. It is found that the tensile stress improves the driving force of the phase transformation and acoelerates the degradation while the compressive stress has no obvious effect on the deeradation.     

Preparation of ZrO2 nano-particles by the hydrolysis of ZrOCl2 solution in the reverse micelles

Zirconia nano-particles have been produced by the hydrolysis of ZrOCl2 solution in the reverse micelles of a liquid-liquid two-phase system, in which sodium bis（2-ethylhexyl） sulfosuccinite （AOT） and toluene were chosen as the surfactant and organic phase, respectively. The reverse micelles prevented the aggregation of primary particles and reduced the diameters of zirconia nanoparticles. Superfine zirconia powders soft-aggregated by the zirconia nano-particles were obtained. The diameters of zirconia nanoparticles were influenced by the quantity of the surfactant.     

Effect of ZrO2 （9mol % Y2O3） coating thickness on the electronic conductivity of Mg-PSZ oxygen sensors

The ZrO2 (9mol% Y2O3) coating was prepared evenly on the surface of MgO partially stabilized zirconia (Mg-PSZ) tube (oxygen sensor probe) by dipping the green Mg-PSZ tube in a ZrO2, (9mol% Y2O3) slurry and then co-firing at 1750℃ for 8 h. The double-cell method was employed to measure the electronic conductivity parameter and exam the reproducibility of the coated Mg-PSZ tube. The experimental results indicate that the good thermal shock resistance of the Mg-PSZ tube can be retained when the coating thickness is not more than 3.4μm. The ZrO2 (9mol% Y2O3) coating reduces the electronic conductivity parameter remarkably. probably due to the lower electronic conductivity of Y2O3-stabilized ZrO2 than that of MgO-stabilized ZrO2. Moreover, the ZrO2(9mol% Y2O3) coating can improve the reproducibility and accuracy of the Mg-PSZ tube significantly in the low oxygen measurement. The smooth surface feature and lower electronic conductivity of the coated Mg-PSZ tube should be responsible for this improvement.     

Effect of nucleating agents on microstructure and mechanical properties of SiO2-Al2O3-ZrO2 glass-ceramics

SiO2-Al2O3-ZrO2 glasses with different nucleating agents were crystallized under special processing schedule. The microstructure and mechanical properties of the glass-ceramics in SiO2-Al2O3-ZrO2 system were investigated by differential scanning calorimetry, scanning electron microscopy, X-ray diffraction and three-point bending method. The results show that ZrO2 is not an effective nucleating agent in SiO2-Al2O3-ZrO2 system, while TiO2 is effective for the separation of spinel, and P2O5 facilitates solubility of ZrO2 in glass and crystallization. The main crystalline phases of the glass-ceramics are spinel, anorthite and tetragonal zirconia. With the increase of ZrO2 content in the glass, glass-ceramics show higher bending strength （120 MPa） than others.     

Application of the C-Me segregating theory in solid alloys to ceramics

Because of its excellent properties, zirconia ceramics has already been widely applied. Its phase transformation affects its properties. The research on the mechanism of its phase transformation is very important to control the phase transformation as well as its properties. The valence electron structure of cubic zirconia, tetragonal zirconia and monoclinic zirconia are calculated with the em-pirical electron theory in solids and molecules in this paper. The results show that the total numbers of the covalent electron pairs which form their strong bond framework are 3.19184, 3.45528 and 3.79625, respectively. According to the view-point of the C-Me segregating theory in solid alloys, it can be deduced that the phase transformation order of zirconia should be liquid phase→cubic phase→tetragonal phase→monoclinic phase. The deduction from valence electron struc-ture is completely in accordance with the experimental results, so the electron theory of phase transformation in alloys can be expanded to ceramics materials.     

稀土固体超强酸S2O^2- 8／ZrO2-PrO2-TiO2催化合成苯乙酸乙酯

以稀土固体超强酸S2O^2- 8／ZrO2-PrO2-TiO2为催化剂，苯乙酸和乙醇为原料合成了苯乙酸乙酯。考察了催化剂用量、原料配比、反应时间等对酯化反应的影响。其最适宜反应条件：酸醇比为1：5、催化剂用量为1．5g（苯乙酸为0．1 mol）、反应时间为6h，在此条件下酯化率可达88％以上。表明固体超强酸S2O^2- 8／ZrO2-PrO2-TiO2具有良好的催化活性，它的使用可避免用浓硫酸催化所造成的环境污染，并可重复使用。     

稀土固体超强酸S2O82-/ZrO2-PrO2-TiO2催化合成苯乙酸乙酯

以稀土固体超强酸S2O82-/ZrO2-PrO2-TiO2为催化剂,苯乙酸和乙醇为原料合成了苯乙酸乙酯。考察了催化剂用量、原料配比、反应时间等对酯化反应的影响。其最适宜反应条件:酸醇比为1:5、催化剂用量为1.5 g(苯乙酸为0.1mol)、反应时间为6 h,在此条件下酯化率可达88%以上。表明固体超强酸S2O28-/ZrO2-PrO2-TiO2具有良好的催化活性,它的使用可避免用浓硫酸催化所造成的环境污染,并可重复使用。     

纳米晶钇稳定氧化锆的制备及表征

以草酸盐为沉淀剂,通过化学共沉淀-高温煅烧法制备了系列钇稳定氧化锆,采用XRD分析技术对样品进行表征。结果表明,不进行钇掺杂时,ZrO2在煅烧温度较低时,晶型以t-ZrO2为主,煅烧温度提高,t-ZrO2向m-ZrO2转变,900℃时晶型已完全转变为m-ZrO2。掺杂钇后低温煅烧产物晶型为四方相,当掺杂钇的含量低于6%(摩尔分数)时,随着煅烧温度提高,少部分四方相转变为单斜相,转变比例随着掺杂量的提高而降低;掺杂钇的含量达到6%(摩尔分数)时,低温煅烧产物的晶型为四方相,随着煅烧温度的提高,晶型保持稳定。Y3+取代Zr4+产生氧缺陷是ZrO2晶体结构稳定化的主要因素。通过该方法制备的钇稳定氧化锆均为纳米晶,晶粒尺寸随着煅烧温度的提高而长大。     

水热法制备固体酸SO4^2-/ZrO2催化合成乙酸正丁酯

通过水热法制备出SO42-/ZrO2固体酸催化剂,对催化剂进行XRD、IR表征,并以冰乙酸和正丁醇的酯化反应为探针,探讨了各个因素对反应的影响.结果表明:当反应时间为2 h,n(正丁醇):n(冰乙酸)=2:1,催化剂用量为0.2%(占总物料的质量分数),酯化率可达99.1%.同时利用未经水热反应制备SO42-/ZrO2做对比实验,结果发现水热法比常规法制备的材料比表面积增加一倍.     

Effect of particle size on phase structure of ZrO2 produced by hydrolysis of ZrOCl2 solution

A method to produce ZrO2 nano-particles is developed and the effect of particle size on the phase structure of ZrO2 is studied. The method is based on the hydrolysis of ZrOCl2 solution in the reverse micelles of a liquid-liquid two-phase system, in which AOT （sodium 2-ethylhexyl sulfosuccinite） and toluene are chosen as the surfactant and organic phase, respectively. The reverse micelles prevent the aggregation of primary particles, the nano-particle size increases as the AOT content decreases. The TEM, XRD and particle-size analysis results show that the occurrence of metastable tetragonal ZrO2 is attributed to the effect of the particle size other than the effect of the crystallite size. The ratio of t-phase to m-phase increases as the particle size decreases, and 28 nm is the critical size for t-phase to m-phase transformation.     

用悬浮液干燥法制备CeO2包覆的ZrO2粉体

讨论了用一种新的表面改性技术制备Al2O3掺杂、CeO2包覆ZrO2纳米粉体的方法。在水-乙醇溶剂中,干燥硝酸铈和单斜相二氧化锆粉体的悬浮液经800℃热分解,可以制备出粒度小于100 nm的Al2O3掺杂、CeO2包覆的单斜相ZrO2粉体。该粉体可以在空气中和1 450℃下无压烧结成致密化Ce-TZP材料,具有KIC=11 MPa m1/2的良好断裂韧性和HV30=750 kg/mm2的硬度。     

Mechanical Properties and Erosive Wear Resistance of Zirconia Toughened Al2O3-TiC Ceramics

The effect of ZrO2, content on the fracture toughness, flexural strength and Vickers hardness as well as the erosive wear resistan properties of zirconia toughened Al2O3-TiC ceramic composites has been investigated. The results showed that the improvement in fracture toughness and flexure strength of composites with the content of zirconia less than 50% and 10% in mass fraction respectively,is primarily attributed to stress-induced transformation toughening by the analyse of X-ray diffraction. The dependance of erosion wear resistance on the attak angle and the content of ZrO2, panicles of the composites was also revealed. It is found that the erosion rate of the composites has a sharp rise at a attack angle over 65°. This phenomenon is due to a brittle response to the erosion test by microsmictural observation on eroded surface.     

沉积压力对磁控溅射Mg薄膜结构的影响

采用直流磁控溅射方法在氧化锆固体电解质表面制备了Mg金属薄膜,利用XRD和SEM研究了沉积压力（0.9～2.1 Pa）对薄膜形貌和结构的影响.结果表明：随着沉积压力的提高,薄膜结晶程度逐渐变差,晶粒尺寸减小,表面粗糙度增大;薄膜呈（002）择优生长的柱状晶结构,且随着沉积压力的提高薄膜厚度先增加后减小.