铝热反应合成法制备β-FeSi_2及Al元素对其相变的影响

Effect of Al Content on Phase Transition of β-FeSi_2 Prepared by Aluminothermic Reaction

利用铝热反应合成方法制备了不同铝含量的FeSi_2粉末材料,采用XRD、SEM和EDS等方法对FeSi_2粉末材料的组成和相结构进行表征,并研究了不同铝含量和退火时间对FeSi_2结构的影响及其作用机制。结果表明,不同铝含量下可一步铝热反应制备出α-FeSi_2,同时还有少量的ε-FeSi和杂质;随铝含量的增加,α-FeSi_2的比重减小,ε-FeSi的比重增大;铝含量为0%,5%,10%,20%的FeSi_2材料粉碎后其粒度分布和颗粒形貌相近,平均粒度分别为997,785,950和1 084 nm。退火处理中,Al元素的存在加速了α-FeSi_2向β-FeSi_2的相转变,并且在退火100 h后,含铝材料中α-FeSi_2相向β-FeSi_2相发生了完全转变,而不含铝材料中仍有20.72%的α-FeSi_2未发生相转变。

FeSi_2 powder with different Al content were synthesized by aluminothermic reaction.Their composition and phase structure have been investigated by a combination of X-ray diffractometry,scanning electron microscopy and energy dispersive spectroscopy.The effects of different Al content and annealing time on the structure of FeSi_2 powder and mechanism of action were studied.The results show that α-FeSi_2with different Al content can be prepared by one step by aluminothermic reaction,as well as it has a small amount of e-FeSi and impurities.The proportion of α-FeSi_2decreases and α-FeSi_2 increases with the increase of Al content Particle size distribution and morphology of FeSi_2with different Al content after crushing are similar and the average particle size for Al content of 0%,5%,10%and 20%is 997,785,950 and 1 084 nm,respectively.In the annealing treatment,the existence of Al element accelerates the phase transition of α-FeSi_2 to β-FeSi_2.And after annealing for 100 h,in materials with Al element,α-FeSi_2 is completely converted into β-FeSi_2,while there is 20.72%α-FeSi_2 in material without Al element,indicating phase transformation is not complete.