真空钙热还原法制备金属钛粉的研究

在真空炉中(30~40 Pa)1273 K下,将物料放入螺纹密封的石墨坩埚中进行不同时间下的还原反应。本文采用热力学分析及X射线衍射、扫描电子显微镜及能量弥散X射线谱等方法与手段,系统研究了金属钙(Ca)与反应器中的氧气(O2)、氮气(N2)、二氧化钛(TiO2)的反应和还原时间及还原产物的预处理对得到金属钛粉(Ti)的影响。通过热力学研究,在温度低于钙的熔点(1115 K)时,密封容器内的O2与Ca的反应及N2与Ca的反应满足反应发生的热力学条件。当温度达到1273K时,Ca的饱和蒸气压p*≈p系,有利于整个气固反应进行。实验研究表明,在还原反应发生前,反应器内的O2,N2与Ca反应完全。将在1273 K下还原时间为4 h得到的还原产物在酸洗前真空挥发处理还原产物表面大量的Ca时,金属单质Ti再次被氧化成低价氧化物,最终得不到金属Ti粉。将反应时间延长至6 h时,酸洗过滤后得到形状不规则、纯度达到98.64%的Ti粉。

Ti Powder Preparation by Calciothermic Reduction of TiO2 in Vacuum

A novel technique was developed to produce metal Ti by calciothermic reduction of TiO2 in vacuum.The impacts of the reaction conditions,including the reactions of the metal Ca with O2,N2,and TiO2,pretreatment of TiO2 powder,and reduction time and products,on quality of the Ti metal powder were evaluated with X-ray diffraction,energy dispersive spectroscopy,and scanning electron microscopy.The experimental results show that the newly-developed technique is feasible to produce high quality Ti metal powder(98.64% pure,25~30 μm in grain size),under optimized conditions:a reduction temperature of 1273 K,a pressure of 30~40 Pa,and a reduction time of 6 h.The calciothermic reduction processes and thermodynamics calculation were also briefly discussed.