喷雾干燥法制备球形钨粉及还原过程的研究

Study on Fabrication of Spherical Tungsten Powder by Spray-Dryingand Reduction Process

摘要:

以偏钨酸铵(AMT)为原料，采用喷雾干燥法结合氢气还原方法成功制备出球形钨粉。随后利用SEM、TEM、激光粒度分析仪和XRD等分析方法对粉末微观形貌、颗粒平均粒度、粒度分布和还原过程中的相变情况进行研究。结果表明，前驱粉末为球形，煅烧后，颗粒形貌未发生明显变化，仍保持球形；TEM结果显示粉末是球形中空结构。同时探讨了溶液浓度、鼓风速度、给料速度对粉末粒度的影响。激光粒度分析结果表明，溶液浓度对粉末的平均粒度影响最大，溶液浓度越大，颗粒的平均粒度就越大。粒度分布越集中，而给料速度对颗粒的平均粒度影响不明显。XRD结果显示，氢气气氛下，550 ℃保温2 h，α-W相出现；还原温度升高到750 ℃，保温2 h，WO3被完全还原为α-W

Abstract:

The spherical tungsten powder was fabricated by spray-drying method combined with hydrogen reduction using ammonium metatungstate (AMT) as raw materials. The powder morphology, mean particle size, particle size distribution and phase transformation process of reduction were characterized by SEM, TEM, XRD and laser diffraction particle size analyzer, respectively. Results show that the morphology of the powder prepared by spray drying is hollow sphere, and both of AMT and WO3 powder has similar good spherical structure with smooth surface. TEM results indicate that the process parameters, such as the slurry concentration, compressed air flow rate, and liquid feeding rate, play important roles in controlling the performance of AMT microspheres, such as the size distribution. It is found that calcination has no effect on the particle morphology and phase composition. The mean size is increased with the increase of the slurry concentration and compressed air flow rate, but the size distribution changes slightly with different liquid feed rates. The X-ray diffraction patterns indicate that α-W phase is obtained after reduction at 550 oC for 2 h in hydrogen atmosphere, but WO3 still exists; after reduction at 750 oC for 2 h, WO3 disappears, and α-W phase exists in the powder