SO4^2—／ZrO2—SiO2固体酸催化剂的研究

用ＸＲＤ、ＢＥＴ、Ｈａｍｍｅｎｔｔ指示剂法及乙酸乙酯化反应等手段研究了引入ＳｉＯ２对ＳＯ４＾２－／ＺｒＯ２体系的晶化，比表面，酸强度和催化性能的影响。添加ＳｉＯ２会延迟ＺｒＯ２的晶化，减弱ＳＯ４＾２－／ＺｒＯ２的超强酸性，但有利于提高催化剂的酯化反应活性。     

O＇－Sialon－ZrO_2质复合材料与钢水中Al_2O_3的反应

设计了研究钢水中Ａｌ２Ｏ３附着性的高温（１５００～１６００℃）模拟试验装置和方法，对Ｏ＇－Ｓｉａｌｏｎ－ＺｒＯ２复合材料进行了试验，并与Ａｌ２Ｏ３材料作对比。结果表明，Ｏ＇－Ｓｉａｌｏｎ－ＺｒＯ２复合材料的抗Ａｌ２Ｏ３附着能力优于Ａｌ２Ｏ３材料，而Ｏ＇－Ｓｉａｌｏｎ含量越多，抗附着能力越强。探讨了这种复合材料抗Ａｌ２Ｏ３附着的机理，认为主要是Ｏ＇－Ｓｉａｌｏｎ与Ａｌ２Ｏ３在高温下反应生成液相。     

连铸保护渣对O’－Sialon－ZrO_2复合材料侵蚀的研究

研究了保护渣对Ｏ’－Ｓｉａｌｏｎ－ＺｒＯ２复合材料的侵蚀情况，并与ｔ－ＺｒＯ２材料对比。结果表明．保护渣对ｔ－ＺｒＯ２的侵蚀小于Ｏ’－Ｓｉａｌｏｎ－ＺｒＯ２材料；ＺｒＯ２引入量的增多，有利于Ｏ’－Ｓｉａｌｏｎ－ＺｒＯ２制品抗渣性能的提高。这可能是由于ＺｒＯ２在保护渣中的溶解度较小，渣中ＣＯ与Ｏ’－Ｓｉａｌｏｎ的反应及渣中多元成分与Ｏ’－Ｓｉａｌｏｎ共同作用的结果。     

ZrO_2在陶瓷工业中的应用

ＺｒＯ２已应用于陶瓷色料、颜料、耐火材料、分散作和研磨介质、加热管及氧气探测器、陶瓷添加剂等。本文介绍了ＺｒＯ２材料的典型性能以及不同种类的ＺｒＯ２材料在陶瓷工业中的用途。指出一种新的潜在的陶瓷材料是基于ＺｒＯ２－Ａｌ２Ｏ３系统     

复合氧化物固体超强酸SO^2—4／WO3—ZrO2的制备和分析

制备系列复合氧化物固体超强酸ＳＯ＾２－４／ＷＯ３－ＺｒＯ２以流动的Ｈａｍｍｅｔｔ指示剂法测定其酸工，用Ｘ射线衍射法，差热－热重法，吸附吡啶ＩＲ等方法对其酸强度，物相结构与焙烧温度，钨锆原子比的相关性进行分析，结果表明：ＳＯ＾２－４与ＷＯ３的加入，延迟了ＺｒＯ２晶化，稳定了介稳的四方晶相，有利于超强酸中心的形成，该超强酸有Ｌｅｗｉｓ和Ｂｒｏｎｓｔｅｄ两种酸中心。     

MgO－Al_2O_3－ZrO_2质耐火材料的显微结构分析

在方镁石－尖晶石－ＺｒＯ２－硅酸盐相结构中，发现由于ＺｒＯ２的存在，可提高主晶相方镁石与尖晶石的结构完整性。同时ＺｒＯ２又吸收并富集了大量的ＣａＯ成分，形成ＣａＺｒＯ３布于晶间，阻断硅酸盐相的扩散路径，封闭气孔．并有形成原位生长的含有ＣａＯ·ＺｒＯ２高粘弹基质相的趋势，在遇渣侵蚀时这种现象更为明显。     

助烧剂Y2O3对ZrO2（Y—TZP）—Si3N4系统中ZrO2相组成的影响

本文研究了助烧剂Ｙ２Ｏ３对ＧＰＳＺｒＯ２（３ｍｏｌ％Ｙ－ＴＺＰ）－Ｓｉ３Ｎ４系统中ＺｒＯ２相结构的影响。研究结果表明：ＺｒＯ２（Ｙ－ＴＺＰ）－Ｓｉ３Ｎ４系统中不添加Ｙ２Ｏ３助烧剂,ＺｒＯ２相组成主要以ｍ－ＺｒＯ２形式存在,并有少量氮稳定ＺｒＯ２;ＺｒＯ２（Ｙ－ＴＺＰ）－Ｓｉ３Ｎ４系统中添加５ｗｔ％Ｙ２Ｏ３助烧剂,ＺｒＯ２相组成为ｃ－ＺｒＯ２、不能相变的过稳定ｔ－ＺｒＯ２。     

MgO与ZrSiO_4反应烧结机理研究

应用ＳＥＭ方法观察了ＭｇＯ与ＺｒＳｉＯ_４的反应烧结机理。结果表明,随着ＺｒｓｉＯ_４的分解,ＳｉＯ_２呈不定形态向外扩散,与ＭｇＯ反应生成Ｍｇ_２ＳｉＯ_４,原来的锆英石颗粒中只留下了ＺｒＯ_２,同时ＭｇＯ向ＺｒＯ_２方向移动,与ＺｒＯ_２形成有限固溶体;反应产物之一ＺｒＯ_２大部分聚集成集合体,也有一部分分布比较均匀。     

管式反应制备氧化锆纳米晶微粉的研究

本文采用管式ＳＫ－１０／２０型表态混合反应器对ＺｒＯＣｌ２·８Ｈ２Ｏ·ＹＣｌ３与ＮＨ·Ｈ２Ｏ进行液相共沉淀反应以制备ＺｒＯ２（Ｙ２Ｏ３）纳米晶微粉。研究了表态混合器反应过程中的流速、混合特性和反应浓度对粉体粒径与粒径分布的关系,并进行了分析探讨。     

预烧法制备ZrO_2-SiO_2-V_2O_5绿色颜料

利用预烧法制备出了主反射波长在535nm的ZrO_2－SiO_2－V_2O_5绿色颜料,并用XRD和UV－V光谱对样品进行了表征。结果显示硅酸锆是所制备颜料的主晶相,其结晶越完整,颜料的色度越好;V_2O_5是该颜料生成反应的矿化剂,它的加入极大的降低了硅酸锆的生成温度,原因在于该反应进行的主要途径是液相反应。     

Synthesis of high-purity zircon,zirconia, and silica nanopowders from local zircon sand

High-purity zircon (ZrSiO₄) nanopowder was successfully produced from Indonesian natural zircon sand using a low-cost purification approach via magnetic separation, immersion in HCl, and reaction with NaOH, followed by a top-down nanosizing process using wet ball-milling for 10?h and annealing at 200?°C for 2?h. Furthermore, polymorph zirconia (ZrO₂ – amorphous, tetragonal, and monoclinic) and silica (SiO₂ – amorphous and cristobalite) nanopowders were also successfully derived from the purified zircon powder using a bottom-up method via alkali fusion and co-precipitation processes followed by calcination. The crystallite size of the powders was estimated from X-ray diffraction (XRD) data analysis to give 40, 31, 61, and 149?nm, respectively, for the zircon, tetragonal- and monoclinic-zirconia, and cristobalite. Microstructural characteristics of the zircon, silica, and zirconia nanopowders were revealed in transmission electron microscopy (TEM) images which confirmed that the average sizes of the particles were in a good agreement with the XRD estimated values.     

Effect of Cu and Zr Co-doped SiO<Subscript>2</Subscript> Nanoparticles on the Stability of Phases (Quartz-Tridymite-Cristobalite) and Degradation of Methyl Orange at High Temperature

SiO₂ nanoparticles doped by 10 mol% Zr and 10 mol% Cu were prepared via the sol-gel method in a controled process. The effects of doping and calcination temperature on the structural and photo-catalytic properties of SiO₂ nanopowders were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-Vis absorption spectroscopy. The phases of cristobalite, quartz and tridymite were found at a calcinations temperature range of 800 to 1000 ^°C and only cristobalite phase was formed at a temperature of 1200 ^°C. The degradation of methyl orange was examined under visible light radiation indicating that the effect of doped elements (Zr, Cu) on SiO₂ reduces the band gap effectively.     

预烧法制备ZrO2—SiO2—V2O5绿色颜料

利用预烧法制备出了主反射波长在535nm的ZrO2-SiO2-V2O5绿色颜料，并用XRD和UV－V光谱对样品进行了表征。结果显示硅酸锆是所制备颜料的主晶相，其结晶越完整，颜料的色度越好；V2O5是该颜料生成反应的矿化剂，其加入极大的降低了硅酸锆的生成温度，原因在于该反应进行的主要途径是液相反应。     

Zr4+掺杂TiO2光催化剂的制备与表征

以ZrCl4及TiOSO4为前驱物,用尿素热分解共沉淀法制备了Zr4+掺杂TiO2光催化剂Zr/TiO2,并用XRD, TEM, BET, FT-IR等表征了其物相及光催化性能. 结果表明,Zr4+掺杂使TiO2纳米晶粒细化(粒径14~17 nm),比表面积增大,同时有效抑制了TiO2从锐钛矿到金红石的晶型转变;Zr4+掺杂使TiO2表面的羟基数量增加,改善了对苯酚的吸附性能;Zr4+掺杂提高了TiO2的光催化活性,以4%Zr/TiO2作光催化剂,反应100 min后对苯酚的降解率达100%,TOC去除率超过80%.     

Ce_(0.7)Zr_(0.3)/γ-Al_2O_3纳米固溶体的制备及其结构

以氯氧化锆、硝酸铈、硝酸铝为原料,按n(Ce)∶n(Zr)=0.7∶0.3的比例,采用化学共沉淀法与有机物共沸蒸馏法,将CeO2、ZrO2分散到γ-Al2O3表面上使其形成Ce0.7Zr0.3O2/γ-Al23固溶体。用XRD考察纳米固溶体在不同温度下焙烧后的相结构。结果表明:Ce0.7Zr0.3O2/γ-Al2O3纳米固溶体为立方晶型,且随着焙烧温度的升高,样品的衍射峰依次变强,峰宽变窄。     

Microscopic Mechanisms of Oxidation in SiC-Whisker-Reinforced Mullite/ZrO2 Matrix Composites

The oxidation of SiC whiskers, contained in alkoxide-derived mullite-based matrices and exposed in air at 1000–1350°C for up to 1000 h, has been studied by analytical TEM, high-resolution SEM, and XRD. Silicon carbide whiskers were effectively protected from oxidation when embedded in a pure mullite matrix, but oxidized considerably when embedded in mullite/ZrO₂ matrices. The oxidation mechanisms varied with matrix composition and exposure temperature. At 1350°C the amorphous layer first crystallized as cristobalite, then gradually incorporated alumina. At later times, the mullite portion of the mullite/ZrO₂ matrix dissolved extensively into the layer. Also, the zirconia particles reacted with silica to form zircon. At 1200°C less extensive interdiffusion and chemical reaction occurred, and the silica layer devitrified into cristobalite and quartz. At 1000°C no interdiffusion or chemical reaction was seen, and the silica layer tended to devitrify into quartz. The thickness of the oxide layer around a SiC whisker in a particular matrix depended on the morphology and composition of grains abutting it or adjacent to it.     

The role of zircon particle size distribution, surface area and contamination on the properties of silica-zircon ceramic materials

Zircon is used as an additive to silica ceramics for use in investment casting to improve their high temperature properties. However, little is known about the mechanisms by which this occurs. To investigate the effect of zircon addition to a silica ceramic a number of silica-zircon formulations were created utilising three different batches of zircon with different particle size distributions (PSDs), surface areas and contaminant inclusions. The contaminant inclusion of the zircon, present in the zircon from the ball-milling stage of manufacture, appeared to have a large effect on the room temperature flexural strength, high temperature flexural strength and high temperature creep properties. It is also suggested that any increase in post-fired cristobalite content and any change to crystal growth morphology was due to the inherent contaminant inclusions and not because of the zircon itself. Hence, use of silica-zircon materials in ceramics for investment casting should account for variation in the contaminant inclusion of the zircon in order to maintain the specific material properties required.     

Kinetics of Zircon Synthesis

The synthesis of zircon from ZrO₂ and SiO₂ at fixed temperatures from 1200° to 1400°C was studied as a function of time up to 16 h. Quantitative X-ray diffraction was used to estimate the phases in the product. Quartz transforms to cristobalite through an amorphous transitional phase. Assuming a homogeneous reaction model, analog computer simulation of reactions was used to determine the rate constants at different temperatures. In the temperature range studied, the transitional phase is the most reactive form of silica in zircon synthesis, followed by cristobalite.     

Effects of composition and crystallite size on the accuracy of the Rietveld method in determining lattice parameters of polytypes in multiphase SiC ceramics

The accuracy of the Rietveld method in determining the lattice parameters of polytypes in multiphase SiC ceramics was investigated as a function of the polytype composition and of the polytype crystallite size, using as benchmarks two sets of standard X-ray diffraction (XRD) patterns obtained by computer simulation. It was found that the Rietveld method is remarkably accurate, but also that the measurement of lattice parameters is sensitive to the polytype composition and to the polytype crystallite size. In particular, the accuracy of Rietveld-calculated lattice parameters for a given polytype not only decreases with increasing number of polytypes in the SiC ceramics, but also depends on which other polytypes are present. These two findings are interpreted based on the severity of the corresponding peak overlap phenomenon in the XRD patterns. In addition, the accuracy of the Rietveld analyses also decreases with decreasing crystallite size of the polytypes, which is due to the progressive loss of definition in the location of the peak maxima and to the greater severity of the peak overlap, both resulting from the corresponding peak broadening. This identification of the confidence limits of the Rietveld-calculated lattice parameters for a wide range of microstructural features may have important implications for the future characterization of SiC ceramics by XRD.     

Studies on SnO2–ZrO2 solid solution

The solubilities of Sn in ZrO₂ and Zr in SnO₂ are investigated. The X-ray diffraction (XRD) studies show the solubility limit for Sn in zirconia to be 20 mol% whereas Zr in SnO₂ is around 25 mol%. All the compositions were prepared by the coprecipitation method. The average particle size for a typical composition was 25 nm as revealed by the transmission electron microscopy (TEM).