铝热还原法合成TiN／刚玉复合陶瓷的研究

以金属铝粉和钛白粉为原料，在流动氮气和匣钵埋碳保护气氛下采用铝热还原氮化法制备了TiN／刚玉复合陶瓷。采用XRD-SEM和TEM等分析手段，研究了铝热还原氮化法制备TiN／刚玉复合陶瓷在不同气氛和温度下的物相组成、晶格常数、显微结构。研究结果表明：在流动氮气和埋碳气氛下铝热还原法均可以制备TiN／刚玉复合陶瓷；处理温度和气氛明显影响着铝热反应的程度及产物的形貌，在埋碳条件下处理后的产物中TiN含量、晶粒大小、晶格常数明显低于流动氮气氛下处理产物中上述各项值。热力学计算发现埋碳条件下铝除参与铝热还原反应外，还与碳粉床中氧发生反应，导致参与铝热反应的金属铝不足，造成产物中有剩余的金红石存在。     

以白云石和菱镁石的混合物为原料真空铝热还原法炼镁过程的动力学（英文）

研究真空铝热还原煅烧白云石和煅烧菱镁石的混合物炼镁过程的动力学,提出一种满足真空铝热过程的等温还原方法。实验在4 Pa的真空下进行。实验结果表明:还原率随着温度、制团压力和铝粉添加量的提高而增加。对不同还原时间的还原渣进行XRD分析,结果表明,还原过程能够粗略地分为3个阶段:MgAl2O4和Ca12Al14O33的形成阶段;CaAl2O4的生成阶段;CaAl4O7的形成阶段。根据动力学模型将获得的实验数据分为3部分,这3部分的活化能分别为98.2、133.0和223.3 kJ/mol。     

以白云石和菱镁石的混合物为原料真空铝热还原法炼镁的机理(英文)

利用SEM和EDS研究真空铝热还原煅白和煅烧菱镁石的混合物炼镁的反应机理。结果表明,根据在温度T时,t时间的还原率ηt与此温度下实验最终获得的还原率ηf的比,将还原过程分为三个阶段:0≤ηt/ηf≤0.43±0.06、0.43±0.06≤ηt/ηf≤0.9±0.02、0.9±0.02≤ηt/ηf<1。第一阶段为铝分别与煅烧菱镁石和煅白反应,主要产物为12CaO·7Al2O3和MgO·Al2O3,还原速率受化学反应的控制;Ca2+伴随熔融铝的扩散和化学反应速度决定了第二阶段的还原速率,CA相是此阶段的主要产物;CA2相在第三阶段产生,反应速率受Ca2+扩散控制。     

铝酸钠溶液碳酸化分解产品中的Na2O

对高浓度铝酸钠溶液碳酸化分解过程中Na2 O的析出行为和产品中Na2 O的存在形式进行了实验研究。结果表明 :溶液中NaAl(OH) 4的过饱和度是高浓度铝酸钠溶液碳酸化分解的主要动力 ,并直接影响产品中吸附碱和晶间碱含量水平 ;提高分解温度、添加晶种或钾碱均可以明显降低产品的Na2 O含量 ;表面吸附和晶间夹杂存在的可洗碱一般占氢氧化铝产品中Na2 O含量的 2 0 %～ 30 %,而晶格碱和含碱化合物杂质等不可洗碱是产品中Na2 O的主要存在形式。     

铝热还原酸溶性钛渣制备TiAl基多元合金

对含高钛的酸溶性钛渣进行铝热还原制备钛铝基多元合金。为了控制并了解合金的制备,讨论了铝和氧化钙的添加和温度的影响。通过考虑材料的配比计算,可以成功地使合金与渣合金分离。大多数还原元素的回收率表现为高值,在所有实验条件下均为95%。铝的添加主要影响合金的成分,而氧化钙的添加则通过改变渣系成分来影响渣金分离。此外,系统的温度可以提高大部分还原元素的回收率和分配比。     

Microwave permittivity of SiC-Al2O3 composite powder prepared by sol-gel and carbothermal reduction

SiC-Al2O3 composite powder was prepared by sol-gel and carbothermal reduction method. The powder synthesized was characterized by X-ray diffraction（XRD） and scanning electron microscopy（SEM） to confirm the phase formation, and the thermodynamic analysis was performed systematically. Moreover, the variation of its microwave permittivity with different atomic ratio of Al/Si was investigated in the frequency range of 8.2-12.4 GHz. The results show that, the powder obtained consists of spherical particles of 300-400 nm in diameter, which are composed of SiC and Al2O3 microcrystal with the grain size of approximately 45 nm. The results of XRD accord with those of the thermodynamic analysis. It is impossible for Al atoms to dissolve in the lattice of SiC during the carbothermal reduction process. Along with the increase of atomic ratio of Al/Si in the xerogel, the amount of Al2O3 in the powder synthesized increases, which reduces both ε＇, the real part of complex permittivity, and tg δ（ε＂/ε＇）, the dissipation factor, where ε＂ is the imaginary part of complex permittivity.     

Synthesis of ZrO2-SiC composite powder and effect of its addition on properties of Al2O3-C refractories

ZrO2-SiC composite powder was synthesized by carbothermal reduction of zircon in argon atmosphere, and it was used as the additive to prepare Al2O3-C refractories. The effects of heating temperature on the synthesis process and the addition of the synthesized composite powder on the properties of the Al2O3-C refractories were investigated. The results show that the synthesized composite powder can be easily obtained by heating the mixture of zircon and carbon black at 1 873 K for 4 h in argon atmosphere, and the relative contents of ZrO2 and SiC in sample reach about 83.7% and 16.3%, respectively. The bulk density, crushing strength and thermal shock resistance of the Al2O3-C refractories can be improved obviously by the addition of the synthesized ZrO2-SiC composite powder.     

Production of High-Strength Al/Al2O3/WC Composite by Accumulative Roll Bonding

In this study, Al/Al₂O₃/WC composites were fabricated via the accumulative roll bonding (ARB) process. Furthermore, the microstructure evolution, mechanical properties, and deformation texture of the composite samples were reported. The results illustrated that when the number of cycles was increased, the distribution of particles in the aluminum matrix improved, and the particles became finer. The microstructure of the fabricated composites after eight cycles of the ARB process showed an excellent distribution of reinforcement particles in the aluminum matrix. Elongated ultrafine grains were formed in the ARB-processed specimens of the Al/Al₂O₃/WC composite. It was observed that as the strain increased with the number of cycles, the tensile strength, microhardness, and elongation of produced composites increased as well. The results indicated that after ARB process, the overall texture intensity increases and a different-strong texture develops. The main textural component is the Rotated Cube component.     

Al2O3/AC8A复合材料制备工艺的热力学与动力学分析

对原位生成法制备Al2 O3/AC8A复合材料的工艺进行了较深入的热力学与动力学计算及分析 ,结果表明 :原位反应满足热力学条件 ;在反应温度下 ,熔体中Al的浓度以及决定物质配分函数的各物质微观运动状态是影响反应速度的主要因素。