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 nan ocrystals by AC carbon are discharge was studied, the yield of magnetic mic ro powder was over 90%. The result of thermogravometric analyses(TG) (> 800 degreesC, O-2, 5 degreesC/min) indicated that there was 17.5% of Fe wrappe d by graphite carbon in the magnetic micro powder. The structural character ization by X-ray diffraction(XRD) and transmission electron microscopy(TEM) revealed that Fe3C and Fe5C2 particles were wrapped by graphite carbon, no evidence of alpha -Fe was observed. The size of the wrapped iron carbide p articles was typically in the range 3-10 nm. The formation mechanism of car bon-coated iron carbide nanocrystals was discussed. The magnetic hysteresis loop(B-H) at room temperature was investigated, it showed that B-s = 2.6 x 10(-2) T, B-r = 2.5 x 10(-3) T, B-r/B-s = 9.7 %, H-c = 5.52 kA/m.