交流碳弧法合成碳包碳化铁纳米晶

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

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 1 7.5% .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 Fe5 C2 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～ 1 0 nm,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× 1 0 - 2 T,2 .5× 1 0 - 3 T和 5.52 k A/m.

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 ℃, O_2, 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 Fe_3C and Fe_5C_2 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 B_s=2.6×10^-2 T, B_r=2.5×10^-3 T, B_r/B_s=9.7%, H_c=5.52 kA/m.