Effect of Zircon Addition on Properties of Low Carbon Al2O3-C Refractories

Using tabular alumina as aggregate,tabular alumina fines, reactive alumina ultra-fines, aluminum powders,silicon powders,carbon black,flake graphite,B4C and zircon fines as matrix,low carbon Al2O3- C refractories were prepared. Influences of zircon powders additions( 0,3%,5% and 7%,in mass,the same hereinafter) on properties,phase composition and microstructure were investigated. The results show that the ZrO2- nitride can be in-situ formed through carbothermal reduction and nitridation in Al2O3- C refractories.With the increase of zircon powder,the oxidation resistance of the Al2O3- C refractories improves obviously,the oxidized layer thickness decreases from 7. 94 mm without zircon to 2. 71 mm with 5% zircon. HMOR at 1 400 ℃of the Al2O3- C refractories reaches the maximum 14. 9MPa when zircon addition is 5%. With the increase of zircon powder,the apparent porosity and bulk density change a little,CMOR and CCS increase.     

非水解溶胶-凝胶法制备硅酸锆

以工业纯ZrCl4、Si(0C2H5)4为前驱体,通过非水解溶胶-凝胶法合成了硅酸锆。采用DTA-TG和XRD等测试手段研究了凝胶热处理过程中的物相变化。结果表明：当热处理温度为700℃时,随着缩聚反应温度的不断提高,粉体中m -Zr02晶体衍射峰逐渐增强,但由于煅烧温度较低,此时Si02为非晶态,因此未形成ZrSiO...     

非水解溶胶-凝胶法制备硅酸锆

以工业纯ZrCl<,4>、Si(OC<,2>H<,5.)<,4>为前驱体,通过非水解溶胶-凝胶法合成了硅酸锆.采用DTA-TG和XRD等测试手段研究了凝胶热处理过程中的物相变化.结果表明:当热处理温度为700℃时,随着缩聚反应温度的不断提高,粉体中m-ZrO<,2>晶体衍射峰逐渐增强,但由于煅烧温度较低,此时SiO<,...     

Fabrication and Characterization of Cordierite/Zircon Composites by Reaction Sintering: Formation Mechanism of Zircon

The formation mechanism of ZrSiO₄ in the cordierite-ZrO₂ system was studied in the temperature range of 1250° to 1400°C by X-ray diffraction analysis and discussed by analyzing experimental data using some reported reaction models. Nuclei growth models were found to describe the reaction well, and a satisfactory fit was obtained by applying the Avrami equation to estimate the reaction rate constant κ. Different values of the time exponent m were obtained at different temperatures: 0.32 at 1250°C, 0.34 at 1300°C, 0.39 at 1350°C, and 0.49 at 1400°C. The results indicate that there is a progressive change in reaction mechanism.     

锆英石质研磨体的研制

本文通过对锆英石原料、成型工艺和烧成工艺的研究,确定了锆英石质研磨体的生产工艺。     

锆英石的合成

概述了近年来化学法合成锆英石（ＺｒＳｉＯ４）的典型工艺及合成温度,并对合成过程中的晶相变化,影响锆英石合成的因素及锆英石合成机理进行了综述。     

锆英石脱硅精化技术

以锆英石精矿为原料，加脱硅复合不原剂，外加剂等，经电弧炉一次熔融脱硅并除铁，钛，将熔炼了的富锆液喷式成球。对脱硅反应过程了研究，并对工艺参数的选择进行了优化试验。生产的电熔脱硅锆解决了我国这种原料长期信赖进口的局面，大大改善了玻璃窑用熔铸造耐火制品的产品性能。     

非水解溶胶-凝胶法制备硅酸锆晶须

以无水四氯化锆为锆源、正硅酸乙酯为硅源、氟化锂为矿化剂、乙醇为溶剂、氟化锆为生长助剂,采用非水解溶胶-凝胶法制备硅酸锆晶须。借助综合热分析、X射线衍射分析、扫描电子显微镜和透射电子显微镜等研究了硅酸锆干凝胶在氮气气氛中热处理的物相变化以及成型压力、氟化锆用量对形成硅酸锆晶须的影响,探讨了硅酸锆晶须的形成机理。结果表明:氮气气氛下热处理并不影响硅酸锆的低温合成,成型压力过大或过小、氟化锆用量过多或过少均不利于硅酸锆晶体的一维择优生长,成型压力为2 MPa、氟化锆用量为10%(质量分数)时,硅酸锆晶须直径为0.2~0.4μm、长径比达到15~30。     

锆英石系无机色料的工业搭烧

为了降低锆英石系色料的使用成本,可通过在低温快烧陶瓷辊道窑生产线冷却段预留孔进行色料的搭烧,利用通用色差仪对所得产品进行色调测定,并调整配方和工艺,试验结果表明,以钒锆蓝为例,当复合矿化剂添加量质量分数为14%,烧成温度为950℃并恒温2h,烧成气氛为弱还原性时,能够合成发色纯正的锆英石系无机色料,这也为锆英石系无机色料工业性生产提供了另一条生产途径。     

锆英石质耐热瓷的研制

本文利用锆英石天然矿物材料研制了新型锆英石质耐热陶瓷餐具和炊具。该产品热稳定性好,510℃至20℃水中急冷,一次不裂。强度高,抗折强度达184MPa。该产品生产成本低,质量稳定,烧成范围宽,生产控制方便。     

Enthalpy of Formation of Zircon

Using high-temperature solution calorimetry in molten 2PbO. B₂O₃, the enthalpy of reaction of the formation of zircon, ZrSiO₄, from its constituent oxides has been determined: Δ_r H ₉₇₇(ZrSiO₄) =−27.9 (± 1.9) kJ/mol. With previously reported data for the heat contents of ZrO₂, SiO₂, and ZrSiO₄ and standard-state enthalpies of formation of ZrO₂ and SiO₂, we obtain Δ_f H °₂₉₈· (ZrSiO₄) =−2034.2 (±3.1) kJ/mol and Δ_f G °₂₉₈ (ZrSiO₄) =−1919.8 kJ/ mol. The free energy value is in excellent agreement with a range previously estimated from solid-state reaction equilibria. At higher temperature also the data are in close agreement with existing data, though the data sets diverge somewhat with increasing T . The limitations of the data for predicting the breakdown temperature of zircon into its constituent oxides are discussed.     

硅酸锆粉体的制备及其研究进展

对硅酸锆粉体制备技术的研究现状做了系统的概述,着重介绍了目前硅酸锆粉体制备中应用较多的固相法、沉淀法、水热法、溶胶-凝胶法、非水解溶胶-凝胶法等几种方法,简要地分析了这几种方法在硅酸锆粉体制备中的优缺点,指出了非水解溶胶-凝胶法是现阶段低温合成硅酸锆粉体最具潜力的一种合成方法。     

碳纳米管的纯化进展

碳纳米管具有独特的结构和性能,目前生产的碳纳米管均存在有一定的杂质,对其发展应用有很大阻碍,除杂十分必要。本文综述了目前碳纳米管纯化所采用方法及相关机理,分析了各自的利弊,认为简单易行而又有较高收率且成本低廉的碳纳米管纯化方法仍是重要的研究方向。     

Characteristization of Pore Size Distribution for Porous Insulating Refractories by Image Analysis Technique

根据 Sierpinski 地毯模型和分形几何的基本概念,推导了多孔隔热耐火材料中孔径分布的分形模型,借助于该模型并结合图像分析技术研究了漂珠多孔隔热耐火材料气孔孔径分布的分形特征,并分析了不同气孔孔径区间与热导率的相关性。结果表明：漂珠多孔隔热耐火材料中气孔孔径分布的均匀程度可用孔径分布分形维数的大小定量表征,分形维数越大,气孔孔径分布越不均匀,反之亦然。研究发现,漂珠多孔隔热耐火材料气孔孔径分布具有双重分形特征,并可由以下 2 个参数确定：大孔区间的分形维数（1.7～1.9）和小孔区间的分形维数（1.9～2.0）。不同孔径区间与热导率的灰色关联分析表明,孔径〈150μm 范围内的气孔与热导率的关联度最大。     

单颗粒锆石U-Pb同位素测年研究综述

锆石U-Pb同位素测年是目前地质学者探讨岩浆结晶年龄及各期次变质时代的重要方法之一。论述了热电离质谱法(TIMS)、单颗粒锆石蒸发法、离子探针质谱法(SHRIMP)、激光剥蚀电感耦合等离子体质谱法(LA-ICP-MS)和电子探针化学法在单颗粒锆石U-Pb同位素体系定年研究中的进展,并对各方法的局限性和应用前景进行了探讨。     

锆英石质耐火纤维针刺毯开发研究

本研究以Al_2O_3—SiO_2—ZrO_2三元系统相图为依据,确定了ZrO_2>15wt％的锆英石质耐火纤维针刺毯配方。在工厂生产线上,探讨了若干技术关键对成纤的形响。提出了工业化生产控制的工艺参数范围,研制成功了在1430℃下保温6小时,收缩率<2％,长期使用温度可达1350℃的针刺毯。     

Thermal Expansion of Compounds of Zircon Structure

The thermal expansion behavior of 13 members of ABO₄ compounds of the zircon family is examined in terms of crystal chemical (size, charge, and mass of cations) and crystallographic ( a and c ) parameters. The systematic trend in the thermal expansion coefficients, α_a and α_c, with the ionic radii, r _A and r _B, can be explained in terms of the unique arrangement of M-O polyhedra along a and c directions of this lattice. In the zircon structure, edge-sharing ZrO₈ dodecahedra form a chain along the a direction while the chain along the c direction consists of alternate edgesharing SiO₄ tetrahedra and ZrO₈ triangular dodecahedra. Substitution in the A sites affects a and α_a more than c and α_c and the reverse is true for replacements in the B sites. Unequal valencies on the A and B sites affect thermal expansion coefficients, particularly α_c.     

Purification process of phosphoric acid by vertical zone‐melting technique

The efficiency of vertical zone‐melting technique as a function of molten‐zone length, number of zone passes, molten‐zone velocity and phosphoric acid concentration on the purification process of phosphoric acid is studied. The results showed that adopting a relatively long molten‐zone length in the initial passes to effect a rapid movement of impurities and a short molten‐zone length in the later passes to obtain greater purification; additional zone‐passes cannot be made as impurities redistribution approaches limiting distribution; for stirring mechanism is not adopted in the present study and as diffusion is the only mixing process, slow molten‐zone velocity 3–6 mm h^?1 is better; the purification efficiency increases with phosphoric acid concentration, and 94–99.8% concentration of phosphoric acid is better. © 2012 Canadian Society for Chemical Engineering     

Effects of Glass Frit Oxides on Crystallization and Zircon Pigment Dissolution in Whiteware Coatings

In experimental whiteware coatings comprised of zircon pigment and multi-oxide silicate glass frits that incorporated ZrO₂, the quantity, size, and morphology of zircon that precipitated during "fast-firing" were mainly dependent upon the ZnO, SrO, and Al₂O₃:alkali levels. In these frits, little or no zircon pigment dissolution occurred, and zircon crystallization was nearly complete by 1000°C. Microstructures of the coatings were consistent over a range of peak firing temperatures from 1000° to 1100°C. Fritted ZnO in these coatings stimulated zircon crystallization and produced high opacity. Replacing ZnO with SrO in the same frits prevented zircon from precipitating and resulted in transparent coatings. In frits without ZrO₂, significant zircon pigment dissolution and crystallization of calcium-based silicates occurred during firing. In these unstable coatings, crystallization and dissolution increased from 1000° to 1100°C and produced a range of microstructures. Raising the Al₂O₃:alkali ratio caused frits with ZrO₂ to precipitate more zircon, and frits without ZrO₂ to form less of the calcium-based silicates and dissolve less pigment.     

Synthesis of Gray Zirconium Silicate Pigments from Zircon Mineral

Zirconium silicate (zircon) pigments in new gray hues have been prepared from mineral zircon as a low-cost raw material. In the first step this material was deocmposed with a waste mixture of NaOH-KOH. In the second step the pigments were synthesized with addition of manganese, especially manganese(II) carbonate, as the chromophore. The optimum conditions for the syntheses of pigments have been estimated and the properties of products (hues, applicability to ceramic glazes) have been evaluated.