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The nanocrystalline cubic Phase of zirconia was found to be thermally stabilized by the addition of 2.56 to 17.65 mol % Y2O3 (5.0 to 30.0 mol % Y, 95.0 to 70.0 mol % Zr cation content). The cubic phase of yttria stabilized zirconia was prepared by thermal decomposition of the hydroxides at 400°C for 1 hr. 2.56 mol % Y2O3‐ZrO2 was stable up to 800°C in an argon atmosphere. The samples with 4.17 to 17.65 mol % Y2O3 were stable to 1200°C and higher. All samples at temperatures between 1450°C to 1700°C were cubic except the sample with 2.56 mol % Y2O3 which was tetragonal. The crystallite sizes observed for the cubic phase ranged from 50 to 150 Å at temperatures below 900°C and varied from 600 to 800 nm between 1450°C and 1700°C. Control of furnace atmosphere is the main factor for obtaining the cubic phase of Y‐SZ at higher temperature. Nanocrystalline cubic Fe‐SZ (Iron Stabilized Zirconia) with crystallite sizes from 70 to 137 Å was also prepared at 400°C. It transformed isothermally at temperatures above 800°C to the tetragonal Fe‐SZ and ultimately to the monoclinic phase at 900°C. The addition of up to 30 mol % Fe(III) thermally stabilized the cubic phase above 800°C in argon. Higher mol % resulted in a separation of Fe2O3. The nanocrystalline cubic Fe‐SZ containing a minimum 20 mol % Fe (III) was found to have the greatest thermal stability. The particle size was a primary factor in determining cubic or tetragonal formation. The oxidation state of Fe in zirconia remained Fe3+. Fe‐SZ lattice parameters and rate of particle growth were observed to decrease with higher iron content. The thermal stability of Fe‐SZ is comparable with that of Ca‐SZ, Mg‐SZ and Mn‐SZ prepared by this method. 相似文献
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N. I. Sorokin 《Russian Journal of Electrochemistry》2000,36(3):319-322
The oxygen-ionic conduction in the YSZ|YSZ and YSZ|YSH bicrystals, where YSZ and YSH are single-crystalline solid solutions
of, respectively, ZrO2 and HfO2 with 12 mol % Y2O3 are studied using the impedance method. Bicrystals consist of two single crystals separated by a common intercrystalline
boundary. The direction of the applied electrical field is chosen perpendicular to the intercrystalline boundary. The oxygen-ion
transfer in the bicrystals is determined primarily by the transport processes in the bulk single crystals. This is associated
with a fast exchange by oxygen vacancies between single crystals at the intercrystalline boundary. 相似文献
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Li‐Qin Xiong Chuan‐Min Qi 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(1):m10-m12
The title compound, [La2(C8H3NO6)2(C8H4NO6)2(H2O)6]·2H2O, consists of dimeric units related by an inversion center. The two LaIII atoms are linked by two bridging bidentate carboxylate groups and two monodentate carboxylate groups. Each LaIII atom is nine‐coordinated by six O atoms from five different carboxylate groups and three from water molecules. Hydrogen bonds between the water molecules and between the solvent water and a carboxylate O atom are observed in the structure. In the crystal packing, there are slipped π–π stacking interactions between the parallel benzene rings. Both hydrogen‐bonding and π–π interactions combine to stabilize the three‐dimensional supramolecular network. 相似文献
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L. J. Wang V. L. Stolyarova S. I. Lopatin S. Seetharaman 《Rapid communications in mass spectrometry : RCM》2009,23(14):2233-2239
Knudsen effusion mass spectrometry was used to study vaporization processes and thermodynamic properties of twenty samples of chromium‐containing slags in the CaO‐MgO‐Al2O3‐Cr2O3‐FeO‐SiO2 system in the temperature range 1850–2750 K. Tungsten cells were used and Cr2O3 solid was used as a reference material. The system was calibrated using liquid gold. As FeO was the first emanating vapor species, monitoring of the chromium‐containing species could be carried out only after the complete vaporization of FeO. This, however, was found to have very little impact on the concentration of the slags investigated. During the measurements, the ion current intensities of CrO+ and CrO species in the mass spectra of the vapor over the CaO‐MgO‐Al2O3‐Cr2O3‐FeO‐SiO2 samples were monitored and compared with those corresponding to solid Cr2O3. Data on the partial pressures of vapor species as well as the activities of Cr2O3 as a function of temperature were obtained. The results are expected to be valuable in the optimization of slag composition in high alloy steelmaking processes. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Ming‐Lin Guo Chen‐Hu Guo 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(12):m595-m597
In the title complex, [Zn(C8H3NO6)(H2O)3]n, the two carboxylate groups of the 4‐nitrophthalate dianion ligands have monodentate and 1,3‐bridging modes, and Zn atoms are interconnected by three O atoms from the two carboxylate groups into a zigzag one‐dimensional chain along the b‐axis direction. The Zn atom shows distorted octahedral coordination as it is bonded to three O atoms from carboxylate groups of three 4‐nitrophthalate ligands and to three O atoms of three non‐equivalent coordinated water molecules. The one‐dimensional chains are aggregated into two‐dimensional layers through inter‐chain hydrogen bonding. The whole three‐dimensional structure is further maintained and stabilized by inter‐layer hydrogen bonds. 相似文献
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The nanocrystalline cubic phase of zirconia was found to be thermally stabilized by the addition of 3 to 40 mol % manganese. The nanocrystalline cubic, tetragonal and monoclinic phases of zirconia stabilized with manganese (III)oxide (Mn‐Stabilized Zirconia) were prepared by thermal decomposition of carbonate and hydroxide precursors. Both the crystallization and isothermal phase transitions associated with Mn‐SZ were studied using high temperature x‐ray diffraction and x‐ray diffraction of quenched samples. Cubic Mn‐SZ initially crystallized and progressively transformed to tetragonal, and monoclinic structures above 700°C. The nanocrystalline cubic Mn‐SZ containing 25 mol % Mn was found to have the greatest thermal stability, retaining its cubic form at temperatures as high as 800°C for periods up to 25 hours. Higher than 40 mol %, cubic Mn2O3 was found to coexist with cubic Mn‐SZ. The crystallite sizes observed for the cubic, tetragonal and monoclinic Mn‐SZ phases ranged from 50 to 137, 130 to 220, and 195 to 450 Å respectively, indicating, for ZrO2, that particle size was a primary factor in determining its polymorphs. The classical Avrami equation for nucleation and growth was applied to the observed phase transformations. 相似文献
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γ-Al2O3作为催化剂载体具有较大的比表面积,机械强度高,孔结构适宜,但不耐高温。近年来,氧化锆载体以其耐高温等[1]独特性质引起多方面的关注[2-4],它能与所负载的金属产生强烈的电子相互作用,影响催化剂的吸附、氧化和还原性能。但是ZrO2比表面积较小,且随焙烧温度的升高急剧下降,如单独作为催化剂载体,其应用受到很大限制。若将ZrO2分散到γ-Al2O3表面上,可制得兼备两者优点的复合载体。当ZrO2中加入Y2O3,能产生特殊的氧空穴[5],具有氧离子传导功能和导电性;与活性组分相结合能在很大程度上提高反应速度。我们用Y… 相似文献
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Zilu Chen Huihui Xing Fupei Liang 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(12):m576-m578
In the title compound, [Mn(C5H2N2O4)(H2O)2]n, the MnII ion has a distorted octahedral geometry and the 4‐oxido‐2‐oxo‐1,2‐dihydropyrimidine‐5‐carboxylate (Hiso2−) anion acts as a μ3:η4‐bridging ligand. Two oxo O atoms from different Hiso2− ligands bridge two MnII ions, forming centrosymmetric dinuclear building blocks. Each dinuclear building block interacts with another four by the coordination of the oxide groups and carboxylate O atoms, producing a two‐dimensional framework in the ab plane. Hydrogen bonds further extend the two‐dimensional sheets into a three‐dimensional supramolecular framework. 相似文献
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Phase relationships obtained by heating coprecipitated oxide powders in the HfO2Er2O3Ta2O5 system were investigated by X-ray diffractometry. Partial isothermal sections at 1100 and 1500°C are presented. 相似文献
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Erwann Jeanneau Nathalie Audebrand Daniel Louër 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(9):1012-1013
Crystals of anhydrous cadmium oxalate, β‐[Cd(C2O4)], have been synthesized hydrothermally and the crystal structure solved using single‐crystal X‐ray diffraction data. The Cd and oxalate ions lie about independent inversion centres. The structure consists of a three‐dimensional framework built from sheets of cadmium octahedra linked together by oxalate groups. 相似文献
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Eun‐Ju Kim Chong‐Hyeak Kim Sock‐Sung Yun 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(9):m427-m429
The title complex, [Li2(C6H3N2O5)2(H2O)4], contains two kinds of Li atoms, viz. five‐coordinated and four‐coordinated. The five‐coordinated Li ion has a tetragonal–pyramidal geometry, with a water molecule in the apical position and four O atoms from two 2,4‐dinitrophenolate (2,4‐DNP) ligands in the basal plane. The four‐coordinated Li ion has a tetrahedral geometry, with three water molecules and one phenolate O atom of a 2,4‐DNP ligand. The Li ions are bridged by a phenolate O atom, giving the complex a dinuclear structure. The crystal packing is stabilized by O—H...O hydrogen‐bonding interactions involving the water molecules and nitro O atoms. 相似文献
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Lea Glaar Marjeta Radiek Primo egedin Amalija Golobi
《Acta Crystallographica. Section C, Structural Chemistry》2005,61(12):m526-m528
In the title compound, [Cu2(CHO2)2(C5H4NO)2(C5H5NO)2]·1.02CH3CN, the dimeric unit is centrosymmetric, with two bidentate pyridin‐2‐olate and two bidentate formate syn–syn bridges, and two apical 2‐pyridone ligands coordinated through the O atoms. The N atom from the apical 2‐pyridone ligand is a donor of a hydrogen bond to the O atom of the bridging pyridinolate ligand of the same complex. The coordination polyhedron of the Cu atom is a distorted square pyramid. 相似文献
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Ana María Atria Maria Teresa Garland Ricardo Baggio 《Acta Crystallographica. Section C, Structural Chemistry》2012,68(7):m185-m188
The title ionic compound, (C7H8N3)2[Ho2(C4H5O2)8], is constructed from two almost identical independent centrosymmetric anionic dimers balanced by two independent 2‐amino‐1H‐benzimidazol‐3‐ium (Habim+) cations. The asymmetric part of each dimer is made up of one HoIII cation and four crotonate (crot or but‐2‐enoate) anions, two of them acting in a simple η2‐chelating mode and the remaining two acting in two different μ2:η2 fashions, viz. purely bridging and bridging–chelating. Symmetry‐related HoIII cations are linked by two Ho—O—Ho and two Ho—O—C—O—Ho bridges which lead to rather short intracationic Ho...Ho distances [3.8418 (3) and 3.8246 (3) Å]. In addition to the obvious Coulombic interactions linking the cations and anions, the isolated [Ho2(crot)8]2− and Habim+ ions are linked by a number of N—H...O hydrogen bonds, in which all N—H groups of the cation are involved as donors and all (simple chelating) crot O atoms are involved as acceptors. These interactions result in compact two‐dimensional structures parallel to (110), which are linked to each other by weaker π–π contacts between Habim+ benzene groups. 相似文献
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不同含量Y2O3的ZrO2对Al2O3复合陶瓷热震稳定性的影响 总被引:4,自引:0,他引:4
含2% (摩尔分数) Y2O3的ZrO2 (简称TZP(2Y)) 和3% (摩尔分数) Y2O3的ZrO2 (简称PSZ(3Y)) 分别以15%(体积分数)添加到Al2O3基体中, 经1550 ℃真空烧结.实验表明, Al2O3复合材料的性能均高于单相Al2O3陶瓷, 并且Al2O3/PSZ(3Y)的抗热震性优于Al2O3/TZP(2Y). 提高改善复合材料的抗热震性是ZrO2(Y2O3)多种增韧机制的作用. 理论计算表明, Al2O3陶瓷和Al2O3/TZP(2Y), Al2O3/PSZ(3Y)复合材料的断裂功分别为38, 100.8, 126.2 J·m-2. Al2O3/TZP(2Y) 和 Al2O3/PSZ(3Y)复合材料的裂纹萌生阻力是Al2O3陶瓷的1.41倍和1.57倍, 而裂纹扩展阻力是Al2O3陶瓷的1.38倍和1.46倍, 与热震实验残余强度的结果一致. 相似文献