金属铝对氧化锆制品的去稳定化行为

采用物质吉布斯自南能函数法对金属铝造成氧化锆制品的去稳定化行为进行了热力学分析,并结合扫描电子显微镜(SEM)进行了试验验证.结果表明:(1)含锆质制品中,金属铝易与氧化锆的稳定剂氧化钙发生反应,生成层片状六铝酸钙,造成氧化锆中稳定剂脱溶,体积失稳;(2)金属铝易与氧化锆的稳定剂氧化镁进行反应,生成正八面体的镁铝尖晶石,造成氧化锆中稳定剂脱溶,体积失稳;(3)金属铝对氧化锆制品的去稳定化行为,可界定为原始层、脱溶过渡层和反应层三层.     

氧化锆气凝胶研究进展

氧化锆气凝胶以其优异的性能受到人们广泛的关注。本文综述了氧化锆气凝胶的制备工艺、掺杂改性工艺、SiO2-ZrO2复合气凝胶、纤维增强氧化锆气凝胶的研究进展以及氧化锆气凝胶的应用。最后,对氧化锆气凝胶的发展方向进行了探讨。     

氧化锆及掺杂氧化锆的研究进展

介绍了氧化锆的性质、制备方法及国内外研究现状,概述了掺杂氧化锆的研究进展,并对氧化锆及掺杂氧化锆的发展方向进行了分析和讨论。     

掺杂中孔氧化锆的合成进展

介绍中孔氧化锆的合成机理及国内外研究现状,讨论了影响合成中孔氧化锆的一些因素,特别是对掺杂中孔氧化锆合成的影响。概述了掺杂中孔氧化锆的应用并展望了其发展方向。     

沉淀法制备铈掺杂氧化锆陶瓷粉体材料的研究

采用化学沉淀法以ZrOCl2.8H2O和Ce2(CO3).8H2O为反应物,制得铈掺杂氧化锆陶瓷粉体材料,研究了反应温度、氧化铈的摩尔含量、pH、沉淀剂对铈掺杂氧化锆陶瓷粉体的影响。通过XRD谱图表明未掺杂的产品为单斜相,掺杂的产品为单斜与四方相共存,表明在室温下掺杂了的氧化锆可以以亚稳的四方相存在。     

金属共掺杂对树脂炭结构及抗氧化性能的影响

以热固性酚醛树脂和金属铝粉为原料、纳米镍为催化剂,采用机械搅拌法制备了金属铝和纳米镍共掺杂酚醛树脂,研究了金属铝和纳米镍共掺杂对树脂炭结构及其抗氧化性能的影响。结果表明:在埋炭气氛下,树脂材料内部CO分压较高而无氮化物存在,体系属于Al-C-O系统;随着温度的升高,氧分压增大,Al2O3(s)相的稳定区间增大。900℃炭化后体系中生成纳米碳管和Al3C4晶须,1 000℃处理后有Al3C4晶须和Al2O3颗粒同时存在。当温度升高到1 200℃时,Al3C4相消失,Al2O3晶须生成量增加。随着热处理温度升高,纳米碳管的直径从60 nm增大到100 nm。添加金属铝粉和纳米镍后,掺杂改性树脂炭化后炭产物的氧化峰值为664.6℃,相比单一掺杂,氧化峰值温度提高了约122℃,增幅达到22%。     

氧化锆对环氧丙烯酸酯乳液性能的影响

采用γ-氨丙基三乙氧基硅烷(KH-550)对氧化锆(ZrO2)纳米粒子进行表面处理,通过傅里叶变换红外光谱(FT-IR)和X射线衍射(XRD)对改性纳米氧化锆的结构进行了表征,采用扫描电镜(SEM)观察其形貌及分散性.利用改性后的氧化锆对环氧丙烯酸酯乳液进行改性,分析了不同氧化锆添加量的乳液薄膜的热稳定性,并以改性环氧...     

ZrO2基Al2O3-ZrO2-C质高温陶瓷材料抗渣性能研究

以板状刚玉、活性α—氧化铝、氧化锆(PSZ)、碳黑为主要原料,以金属硅和碳化硼作为添加剂,以热固性酚醛树脂作为结合剂,制备了ZrO2基Al2O3-ZrO2-C质材料。实验证明添加稳定氧化锆的Al2O3-ZrO2-C质高温陶瓷材料的抗渣性能优于添加单斜氧化锆、纳米氧化锆、金属铝的Al2O3-ZrO2-C质高温陶瓷材料。     

油酸改性纳米二氧化锆的研究

以水热法自制的纳米氧化锆为原料,用油酸对其进行表面改性。考查了改性温度、油酸用量对改性粉体的分散性的影响。用TEM、SEM对改性粉体进行表征。结果表明,改性后氧化锆从亲水性明显转变为亲油性,在弱极性溶剂中分散效果良好,改性效果明显。     

KH560改性氧化锆粉体及凝胶注模研究

采用硅烷偶联剂KH560对氧化锆粉体进行湿法改性,研究了硅烷偶联剂KH560添加量对凝胶注模成型氧化锆陶瓷性能(抗折强度、硬度和密度)及浆料性能的影响,并研究了添加量对氧化锆粉体、生坯和陶瓷显微结构的影响.结果表明:采用KH560改性氧化锆粉体可改善粉体团聚,烧结后获得高强度高致密性的氧化锆陶瓷.当KH560添加量为0...     

Increase in Phase Transition Temperature of Activated Alumina with Nano-Zirconia Synthesized by Pulsed Wire Discharge

Activated alumina powders have been synthesized by using a novel dry process of pulsed wire discharge. The temperature of phase transition from activated alumina to α-alumina and its variation caused by adding zirconia have been investigated. A mixture of activated alumina and zirconia was formed by mixing zirconium plasma with aluminum plasma and cooling together in an oxygen atmosphere. It was found that the transition temperature increased when the zirconia content ratio was increased. On the other hand, results of X-ray diffraction and X-ray photoelectron spectroscopy analysis indicated no substitution of zirconium in an alumina lattice. Thus, most of the zirconium atoms were located in zirconia particles on the surface and/or the grain boundary of alumina grains. Thus, it appears that the increase in the phase transition was caused by retardation of atomic diffusion at zirconia particles.     

Design and synthesis of 3D ordered macroporous ZrO2/Zeolite nanocomposites

Zeolite NaY nanocrystals (20−50 nm) were hydrothermally grown on polyelectrolyte-coated three-dimensionally ordered macroporous (3DOM) activated zirconia. The zeolite nanocrystallites uniformly coated the macropore walls of 3DOM sulfated zirconia, but sulfate groups were lost during the hydrothermal reaction. 3DOM tungstated zirconia was found to be more stable in the strong basic environment of the zeolite precursor solution. Further, ion-exchange of zeolite NaY with ruthenium followed by hydrogen-reduction formed a composite of RuNaY and 3DOM activated zirconia. The presence of ruthenium was confirmed by X-ray photoelectron spectroscopy and the external shape of zeolite nanoparticles was maintained after ion-exchange, but the zeolite lattice fringes could not be observed by transmission electron microscopy after incorporation of reduced ruthenium. Although the catalytic activity of the materials has not yet been tested, these hierarchical nano- and microstructures bring multiple catalyst components (modified zeolite Y, a typical Fischer–Tropsch catalyst, and activated zirconia, an isomerization catalyst) together in intimate contact for potential multi-reaction processes.     

Chemical synthesis and structural characterization of nanocrystalline powders of pure zirconia and yttria stabilized zirconia (YSZ)

Nanocrystals of pure zirconia and yttria stabilized zirconia (YSZ) are obtained by a simple chemical synthesis route using sucrose, polyvinyl alcohol (PVA) and metal nitrates. The reaction mixture on pyrolysis and calcination gives nanocrystals. These are characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The size of the nanocrystallites for pure zirconia is in the range of about 7.0–45.0 nm and for yttria stabilized zirconia, is in the range of about 5.0–24.0 nm at 200°C and above, according to the preparative condition. At 200°C, pure zirconia forms cubic phase and this cubic phase is stable up to 600°C and then slowly transformed into monoclinic form. For yttria stabilized zirconia, the crystals are tetragonal in the temperature range from 200 to 1200°C.     

铝合金表面氧化锆转化膜的结构与性能

采用氟锆酸工艺在AA6061铝合金表面制备出氧化锆转化膜,用扫描电镜和能谱仪分析了氧化锆转化膜的组织形貌和结构,采用电化学方法和中性盐雾试验研究了氧化锆转化膜的耐蚀性能。结果表明,制备出的氧化锆转化膜为无色膜,主要由Zr和Al的氧化物组成。氧化锆转化膜的耐腐蚀性能优异。涂覆环氧树脂漆或聚氨酯漆后的涂层可以通过1500h的中性盐雾试验,氧化锆转化膜可以用作铝合金的涂漆前预处理膜。     

Hydrothermal Synthesis and Characterization of Zirconia Nanocrystallites

This work focuses on the synthesis of tetragonal zirconia (ZrO₂) nanocrystallites with diameters of 5 nm by a simple hydrothermal process in the presence of hydrazine hydrate. Structural characterization of the ZrO₂ products using X-ray diffraction and Raman spectroscopy revealed that the predominant crystal phase was the tetragonal phase. High-resolution transmission electron microscopy images further showed that that the diameter of the majority of the tetragonal ZrO₂ nanocrystallites was <5 nm. Furthermore, we discussed the mechanism of the hydrothermal process and the critical roles of hydrazine hydrate in the hydrothermal formation of the small-sized ZrO₂ nanocrystallites.     

Reactivity stabilization and capacity study of fabricated alumina and zirconia-supported CaO-based sorbents for high-temperature CO2 capture in a fixed-bed reactor

Calcium looping process is a promising approach for CO₂ capture from the flue gas of fossil fuel power plants and the cement industry. Even though the advantages of calcium-based sorbents are low cost and high uptake capacity, they suffer from low durability during cycles. Modified sorbents were fabricated by adding alumina and zirconia and the mixture of alumina and zirconia to calcium oxide via the co-precipitation method. The performance of synthesized sorbents in terms of stability and CO₂ capture capacity were evaluated using a fixed bed reactor in various CO₂ sorption/desorption cycles. The sorbents were fabricated by a co-precipitation methodology using 10% binders (alumina and/or silica). X-ray diffraction (XRD), BET/BJH, and scanning electron microscopy (SEM) were conducted for characterization of synthesized sorbents. CaO-10% ZrO₂ showed the best performance among the fabricated sorbents in terms of stability during 5 cycles and CO₂ capacity (14 mmol CO₂/g sorbent). The formation of CaZrO₃ with a perovskite structure and high-temperature resistance could be attributed to well performance of zirconia-supported sorbent. On the other hand, no sign of aluminum zirconate formation was approved in XRD analysis for the fabricated sorbent using mixed binders of zirconia and alumina to enhance its stability during cycles.     

Growth of carbon nanospheres through a building block assembly method at 300 °C

Carbon nanospheres (CNSs) with the diameters of 50–250 nm were synthesized through a one-step solvothermal method at about 300 °C. In this process, benzene and hexachloroethane (C₂Cl₆) served as carbon source for the CNSs. The results showed that the CNSs were composed of a mixture of graphitic nanocrystallites and amorphous carbon. It is believed that they formed through intermolecular Friedel–Crafts alkylation and dehydrogenation reactions in the presence of anhydrous aluminum chloride (AlCl₃). The mechanism of carbonization and the effect of Al particles on the morphology of carbon products are discussed.     

Mesoporous nanocrystalline zirconium oxide: novel preparation and photoluminescence property

A novel strategy involving the combination of soft-templating and solid–liquid method (CSSL) is presented to synthesize mesoporous nanocrystalline zirconia with high specific surface area, that is, the mesostructured zirconia hybrid is firstly synthesized via cooperative assembly between zirconium sulphate as inorganic precursor and 1-hexadecyl-3-methylimidazolium bromide (C₁₆mim⁺Br⁻) as the structure-directing agent, and subsequently ground with solid magnesium nitrate salt followed by heat-treatment in air. The resulting zirconia material after calcination at 600 °C possesses a wormlike arrangement of mesopores surrounded by tetragonal ZrO₂ nanocrystallites of ca. 2.3 nm. The BET surface area is 255 m²/g and the pore size is ca. 4.3 nm. However, no mesoporous structure exists in the obtained zirconia material via the simple soft-templating method at the same calcination temperature. Photoluminescence (PL) spectra of the obtained mesoporous nanocrystalline ZrO₂ show a strong emission peak at ca. 394 nm under UV excitation of 250 nm wavelength.     

The wettability of zirconia refractories with iron and aluminum melts

Conclusions An investigation of the wettability of zirconia refractories with molten aluminum and iron showed that regardless of the amount of stabilizing oxide in the material the refractories are wetted more rapidly with the molten iron. Aluminum and iron melts both wet the refractory more rapidly when the latter is produced from a cubic solid solution containing a large amount of stabilizing oxide.When wetted with the melts of aluminum and iron a zirconia refractory acquires a zonal structure, the ZrO₂ in the reaction zone being partly destabilized.Translated from Ogneupory, No. 8, pp. 35–38, August, 1976.