交流碳弧法合成碳包碳化铁纳米晶

采用交流碳弧法高效合成碳包碳化铁纳米晶磁性微粉,磁性微粉产率达90%以上.用热重分析法(TG)测得磁性微粉中Fe的质量分数为17.5%.X射线衍射(XRD)分析结果表明,在碳包碳化铁微粉中存在Fe₃C和Fe₅C₂两种结构形式,不含纯Fe晶粒,碳层结构与石墨相似.在透射电镜(TEM)下观察了纳米晶的形貌和粒径分布,碳化铁纳米晶尺寸分布在3～10nm,并呈颗粒状分散在碳层中,碳层为巴基管和巴基葱的堆积体,形状各异,尺寸分布在几十纳米到几微米之间.讨论了碳包碳化铁纳米晶的形成机理.测定了磁性微粉的磁滞回线,其饱和磁感应强度Bs,剩磁Br和矫顽力Hc分别为2.6×10^-2T,2.5×10^-3T和5.52kA/m.

Preparation of Carbon-coated Iron Carbide Nanocrystals by Using AC Carbon Arc Discharge Method

A highly effective method for preparation of carbon-coated iron carbide nanocrystals by AC carbon arc discharge was studied,the yield of magnetic micro powder was over 90％.The result of thermogravometric analyses (TG) (＞800℃,O2,5℃/min) indicated that there was 17.5％ of Fe wrapped by graphite carbon in the magnetic micro powder.The structural characterization by X-ray diffraction(XRD) and transmission electron microscopy(TEM) revealed that Fe3C and Fe5C2 particles were wrapped by graphite carbon,no evidence of α-Fe was observed.The size of the wrapped iron carbide particles was typically in the range 3－10 nm.The formation mechanism of carbon-coated iron carbide nanocrystals was discussed.The magnetic hysteresis loop(B-H) at room temperature was investigated,it showed that Bs=2.6×10-2 T,Br=2.5×10-3 T,Br/Bs=9.7％,Hc=5.52 kA/m.