Fe/C复合纳米炭粉的制备及其磁学性能研究

以高温煤焦油沥青为原料,以体积比7∶3的浓硫酸和浓硝酸混合酸为氧化剂,制备水性中间相沥青;采用溶胶-凝胶法先形成碳基溶胶,加入FeCl3后进一步形成复合Fe/C凝胶;凝胶经醇水交换、常温干燥和900℃炭化制备出Fe/C复合磁性纳米炭粉。利用FT-IR、XRD、TG和TEM等对水性中间相沥青、磁性纳米炭原粉以及磁性纳米炭粉进行表征。结果表明:采用溶胶-凝胶和常温干燥的方法可以制备出粒度均匀、形状近似于椭圆形的Fe/C复合磁性纳米炭;其磁性纳米炭粉的平均粒径约5 nm,以聚集成粒度为20 nm～30 nm的团聚体形式存在。磁性纳米炭粉中的碳以无定型结构的形式存在,Fe元素以α-Fe、Fe2O3和Fe3C的形式存在,Fe/C复合磁性纳米炭粉具有软磁性和较高的磁响应性。

Preparation and magnetic properties of Fe/C composite powders

Fe/C composite magnetic powders were prepared by a sol-gel method from aqueous-mesophase pitch(AMP) and ferric chloride.The AMP was prepared by the oxidation of coal tar pitch with a mixture of concentrated sulfuric acid and nitric acid(7:3v/v),to which ferric chloride and ammonia were added to form aqueous Fe/C based gels.The gels were displaced by ethanol,dried at ambient temperature and pressure,and carbonized at 900 ℃ to obtain the Fe/C magnetic powders.The powders were characterized by FT-IR,XRD,TG and TEM.Results show that primary particles in the powders have an ellipsoidal shape with a uniform particle size about 5 nm,which are aggregated into secondary particles with a size about 20-30 nm.The carbon has a turbostratic structure and the Fe exists in the form of α-Fe、Fe2O3 and Fe3C.The powders are soft magnetic materials with a saturation magnetization increasing with Fe content.