两种氧化铝粉对熔铸AZS耐火材料结构和性能的影响

熔铸Al₂O₃-ZrO₂-SiO₂(AZS)耐火材料是玻璃熔窑的关键筑炉材料。本文分别以煅烧氧化铝粉和普通工业氧化铝粉为原料制备熔铸AZS耐火材料,并采用岩相分析、X射线衍射分析和能谱分析等测试方法,对比分析了两种熔铸AZS耐火材料的结构和性能。结果表明：普通工业氧化铝粉制备的熔铸AZS耐火材料中存在未转化完全的γ-Al₂O₃,导致获得的Al₂O₃-ZrO₂共晶体分布不均匀。煅烧氧化铝粉制备的熔铸AZS耐火材料中,氧化铝物相为α-Al₂O₃,其晶体结构中斜锆石少,Al₂O₃-ZrO₂共晶体多,玻璃相分布均匀。晶体结构的分布影响着玻璃相渗出量和抗玻璃液侵蚀性能。煅烧氧化铝粉制备的熔铸AZS耐火材料玻璃相渗出量比普通工业氧化铝粉制备的熔铸AZS耐火材料玻璃相渗出量降低了0.57个百分点,...     

关于氧化铝粉作焙烧填充料的研究

用氧化铝粉作填充料进行焙烧实验。与传统焙烧工艺产品进行分析比较，得出氧化铝粉是一种优良的填充料。     

微硅粉低成本制备莫来石基陶瓷材料

以工业废弃物微硅粉和工业氧化铝为原料,采用原位反应烧结法制备莫来石基陶瓷材料,主要研究了烧结温度对莫来石的形成和莫来石基陶瓷的显微结构和性能的影响.结果 表明:当微硅粉和工业氧化铝的配比为32∶68时,在1550℃下进行烧结,可制得主晶相为莫来石基的陶瓷材料,其抗弯强度为66 MPa,显气孔率为24％,体积密度为2.25 g/cm3.微硅粉中的金属氧化物杂质使制备莫来石的烧结温度降低100℃.     

氧化铝源对CA6多孔材料相组成和显微结构的影响

用Al(OH)3、Al2 O3微粉(uf-Al2 O3)、工业Al2 O3粉作为氧化铝源,CaCO3为钙源,通过高温固相反应合成了六铝酸钙(CA6)材料,研究了氧化铝原料对材料物相组成、显微结构和性能的影响.结果表明,以Al(OH)3、Al2O3微粉、工业Al2 O3为氧化铝源的试样在1300℃时开始有CA6相生成,各...     

低成本生产白色中高铝瓷球

本文针对目前市场上纯氧化铝粉原料价格昂贵的问题,研究了利用工业废料制备白色中高铝瓷球的工艺,不仅大大降低了生产成本,而且有利于环境保护。     

不同工业氧化铝粉在NH_4F存在下物相转变和微观形貌的差异

以α-Al_2O_3含量不同的两种不同工业氧化铝粉为原料,引入2.0%NH_4F作为添加剂,经过700~1200℃煅烧,采用X射线衍射仪和扫描电子显微镜进行物相分析和微观形貌的观察。XRD结果表明,两种不同工业氧化铝经1200℃煅烧后全部转化为α-Al_2O_3。当2.0%含量的NH_4F存在时,α-Al_2O_3含量较高的工业氧化铝(A)在900℃煅烧后全部转化为α-Al_2O_3,而α-Al_2O_3含量较低的工业氧化铝(B)要在1000℃煅烧后才全部转化为α-Al_2O_3,即NH_4F促进两种不同工业氧化铝转化为α-Al_2O_3的效果是不同的。SEM结果表明,含2.0%NH_4F的两种工业氧化铝粉A和B在900℃烧后有明显差异,而在1000℃煅烧后两者微观形貌没有明显差异,这是因为二者在900℃煅烧后物相有明显不同,而在1000℃煅烧后两者物相基本相同。     

钛酸铝的工业化合成试验

用工业氧化铝粉、钛白粉及适量的键活性剂、亲和剂、稳定剂合成了较稳定的钛酸铝，并用这种钛酸铝合成了抗热震性好的陶瓷制品。     

纳米级氧化铝粉添加剂对高铝耐火材料性能的影响

介绍了纳米级氧化铝粉的制备方法。纳米级氧化铝粉的特点是活性高、不含碱类物质。此类粉料主要用于制造高温陶瓷及高铝耐火材料。探讨了纳米级氧化铝粉对材料强度的影响。     

原料及热处理制度对合成微孔轻质莫来石骨料性能的影响

研制具有优良隔热性能的耐火骨料对开发高性能轻质浇注料有重要作用。以w(α-Al2O3)=95%,w(β-Al2O3)=3%~5%的工业氧化铝A或w(γ-Al2O3)=70%~80%,w(α-Al2O3)=5%~10%,w(三水铝石)=5%~10%的工业氧化铝B,硅石粉为主要原料,采用烧烬可燃物法制备了微孔轻质莫来石骨料,研究了两种具有不同特性的工业氧化铝和不同热处理制度对合成微孔轻质莫来石骨料性能的影响。结果表明:(1)以工业氧化铝B为原料制得的轻质莫来石骨料的体积密度要普遍低于以工业氧化铝A为原料的,且以工业氧化铝B为原料得到的莫来石骨料的常温耐压强度随热处理温度升高而增加。(2)以不同工业氧化铝为原料合成骨料的莫来石的转化率在1500℃之前大致相当,均为60%(w)左右,得到的微孔轻质莫来石骨料的平均孔径约为3~5μm。(3)以γ相为主的工业氧化铝B更适合作原料,合适的热处理制度为1350℃6h。     

高能球磨预处理工业氧化铝对制备亚微米α-Al_2O_3形貌的影响

为了制备粒度均匀的亚微米α-Al_2O_3粉,以工业氧化铝(Al_2O_3的质量分数为99. 66%)为原料,研究了高能球磨时间(0、5、9和15 h)对工业氧化铝颗粒形貌及1 300和1 450℃煅烧3 h后制备亚微米α-Al_2O_3形貌的影响。结果表明:随着高能球磨时间从5 h延长至15 h,工业氧化铝的颗粒尺寸逐渐细化,聚集体(20～100μm)经高能球磨15 h后,粉碎为1μm左右、分散性较好的小尺寸团聚体; 1 300和1 450℃煅烧所得α-Al_2O_3的颗粒形貌与γ-Al_2O_3形貌密切相关,α-Al_2O_3的晶粒尺寸随γ-Al_2O_3高能球磨时间的延长而细化,粒度分布的均匀性也逐渐提高。综合对比高能球磨不同时间的工业氧化铝经高温煅烧后制备α-Al_2O_3粉的颗粒形貌,高能球磨15 h的工业氧化铝经1 450℃煅烧3 h制备所得亚微米α-Al_2O_3的晶粒分布良好,晶粒尺寸在500 nm左右。     

球形氧化铝粉体制备的研究进展

球形氧化铝粉体是氧化铝产品中不可缺少的一部分,因其特殊的物理化学性质而备受关注。与不规则氧化铝粉体相比,球形氧化铝粉体的形貌和尺寸能极大地提高其产品的使用性能。目前,已有大量文献探讨了制备球形氧化铝粉体的方法,但缺少文献系统性地比较不同含铝原料适用的制备方法和优缺点。本文从不同的含铝原料出发,对已有文献进行总结分析,发现不同的含铝原料决定了不同的制备方法,从而决定了工业化的难易程度,其中无规则氧化铝是球形氧化铝粉体工业化并实现量产的最佳原料。     

Effect of Industrial Alumina Powder Particle Size on Preparation of Active α-Al2O3 Micropowder

To study the effect of the particle size of industrial alumina powder on the properties of active alumina micropowder(α-Al2O3 micropowder),the fine powders with...     

Synthesis and Characterization of Amorphous Nano‐Alumina Powders with High Surface Area for Biodiesel Production

Nano‐alumina powders containing yttrium oxide were synthesized via the sol‐gel method using aluminum chloride hexahydrate as catalyst precursor. Fourier transform infrared analysis showed the presence of Al‐O and Al‐O‐Al bands in the powder structure and X‐ray diffraction spectra proved that the alumina was in the amorphous phase. The amorphous nano‐alumina powders were shown to be mesoporous with a high surface area, and both spherical and slit‐shaped particles were found in the calcined powder. A high percentage of conversion of oil to biodiesel was obtained in the transesterification reaction and the synthesized nano‐alumina powders could be easily regenerated for further use. The amorphous nano‐alumina powder can thus be recommended for use as active catalyst in the transesterification reaction for biodiesel production on the industrial scale.     

Development and mechanical characterization of novel ceramic foams fabricated by gel-casting

Porous ceramic materials are of considerable interest for a variety of chemical and industrial applications in extremely harsh conditions, particularly at very high temperatures for long time periods. A combined gel-casting-fugitive phase process employing agar as a natural gelling agent and polyethylene spheres as pore formers was exploited to produce porous ceramic bodies. Alumina and alumina–zirconia powders were used to prepare samples having a porosity of about 65–70–75 vol%. The composite powder was produced by a surface modification route, i.e. by coating a well-dispersed alpha-alumina powder with a zirconium chloride aqueous solution. On thermal treatment, ultra-fine tetragonal zirconia grains were formed on the surface of the alumina particles. SEM observations and image analysis were used to characterize the microstructure of porous samples and uniaxial compressive tests were carried out to measure their mechanical behavior.     

不同工艺制备ZrO2—Al2O3复合陶瓷超细粉体的研究

采用正滴定工艺，反滴定工艺和水解工艺来制备ＺｒＯ２－Ａｌ２Ｏ３系复合陶瓷超细粉体。研究了制备工艺对水合氧化锆凝胶的包裹状态，煅烧后粉体中ＺｒＯ２颗粒的弥散状态以及烧结体显微结构的影响。结果表明采用水解工艺，ＺｒＯ２颗粒能均匀弥散在Ａｌ２Ｏ３颗粒周围，最终获得均匀细晶的陶瓷烧结体；在反滴定工艺中，虽然水合氧化锆凝胶能较好包裹Ａｌ２Ｏ３颗粒，但由于Ａｌ２Ｏ３颗粒本身得不到有效分散，因此在烧结体中出现了     

Effects of alumina sources on the microstructure and properties of nitrided Al2O3-C refractories

Fused white alumina, tabular alumina with a plate-like morphology, reactive alumina powder with a high specific surface area and industrial alumina composed of 40 to 76% γ-Al₂O₃ and 60 to 24% α-Al₂O₃ were selected as alumina sources and grouped in this work. The effects of alumina sources on the microstructure of nitrided Al₂O₃-C refractories were investigated. A large number of β-Sialon phases and a small number of SiC phases were formed when the alumina source varied, and α-Si₃N₄ phase was only formed when using tabular alumina. The β-Sialon phase was deemed to be the major ceramic bonding phase, which generated the morphologies of column and tabular column. Columned β-Sialon crystals with conical tips were formed by the direct nitriding of liquid silicon following a VLS (vapor-liquid-solid) growth mechanism, the transformation of the VLS growth mechanism into a VS (vapor-solid) growth mechanism was observed when using industrial alumina with smooth tips on the β-Sialon crystals. β-Sialon crystals with a morphology of tabular column were formed through nitriding of SiO _(g) and Si _(g) following the VS growth mechanism. SiC whiskers were formed by the reacting of CO _(g) and SiO _(g) following a CVD (chemical-vapor-deposition) growth mechanism. The physical, mechanical and thermal properties of these groups after the nitriding process were also investigated and compared. When using reactive alumina powder and fused white alumina as the alumina sources, the optimal cold crushing strength (CCS) and cold modulus of rupture (CMOR) were generated due to the dense reticular structure, and also the optimal hot modulus of rupture (HMOR) was achieved due to the formation of large size of O’-Sialon tabular whiskers in the test atmosphere. Improved thermal shock resistance and oxidation resistance were also observed.     

Drying of Inorganic Particulate Compounds

Inorganic particulates are usually dried in a fixed bed, fluidized bed, or spray dryers. These compounds are easy to dry, once their physical structure, with high porosity, allows moisture content removal with low resistances. For fluidized bed of alumina particle evaluations, a laboratory-scale drying unit was built. The drying experiments were carried out with alumina particles with different diameters to evaluate temperature and air flow rate effects on drying kinetics and bed height. In another case, the dehydration of a mixture of rare-earth chlorides in a fluidized bed was studied, aiming at the production of anhydrous rare-earth chlorides, used to obtain mischmetal by electrolytic and metallothermic processes. The spray drying experiments were carried out in a pilot plant. Spray drying is a technique largely applied in industrial processes to dry solutions or suspensions, converting their solid parts into a dried powder. A set of rare-earth drying experiments was carried out, aiming at the development of techniques to obtain a powder that could satisfy international morphological requirements. The results allowed evaluating the effects of air flow rate, feed concentration, atomizer model, rotation velocity, and atomization pressure on powder density and particle size distribution.     

Drying of Inorganic Particulate Compounds

ABSTRACT

Inorganic particulates are usually dried in a fixed bed, fluidized bed, or spray dryers. These compounds are easy to dry, once their physical structure, with high porosity, allows moisture content removal with low resistances. For fluidized bed of alumina particle evaluations, a laboratory-scale drying unit was built. The drying experiments were carried out with alumina particles with different diameters to evaluate temperature and air flow rate effects on drying kinetics and bed height. In another case, the dehydration of a mixture of rare-earth chlorides in a fluidized bed was studied, aiming at the production of anhydrous rare-earth chlorides, used to obtain mischmetal by electrolytic and metallothermic processes. The spray drying experiments were carried out in a pilot plant. Spray drying is a technique largely applied in industrial processes to dry solutions or suspensions, converting their solid parts into a dried powder. A set of rare-earth drying experiments was carried out, aiming at the development of techniques to obtain a powder that could satisfy international morphological requirements. The results allowed evaluating the effects of air flow rate, feed concentration, atomizer model, rotation velocity, and atomization pressure on powder density and particle size distribution.     

高纯度氧化铝粉体颗粒细化对烧结致密化及透光性能的影响

以法国Baikowski公司高纯度氧化铝粉体为参照,选取大连瑞尔精细陶瓷有限公司产超高纯度氧化铝粉体为研究对象。采用研磨处理,以改善国产氧化铝粉体的形貌、粒径及其分布。分别采用硅钼电炉中常压烧结和真空气氛下在1850℃烧结2种不同的烧结方式评价了研磨后粉体的烧结性能和用于制备半透明氧化铝陶瓷的可行性。结果表明:经过研磨改性处理后,粉体的粒径分布和比表面积接近于法国粉体;在1600℃常压烧结得到的氧化铝陶瓷达到理论密度的97%,具有均一的晶粒尺寸(～5μm)。添加MgO为烧结助剂,在真空下烧结得到了半透明氧化铝陶瓷,在波长为200～1100nm范围直线透过率最大值达到16%。     

Ascorbic acid as a dispersant for concentrated alumina nanopowder suspensions

The stabilization of concentrated nanopowder suspensions is crucial for many industrial applications. Yet, controlling the suspension viscosity is challenging for nanopowder suspension systems. In this study, we examined the adsorption of l-ascorbic acid (Vitamin C) on alumina surfaces and the related reduction in viscosity of the suspensions. Interactions between the ascorbic acid and the alumina surface were investigated by in situ ATR-FTIR and zeta potential measurements. It was shown that ascorbic acid forms complexes with the alumina surface through ligand exchange mechanisms. The optimum concentration of ascorbic acid for minimum suspension viscosity was determined. The maximum achievable solids content could be increased to around 0.35 by the addition of only 1.0 wt.% of dry powder ascorbic acid. Because ascorbic acid is easy to use, inexpensive, and a non-toxic organic additive, it has great potential to be used as a dispersant in a variety of industrial applications, from dilute to concentrated systems of intermediates or products.