The effect of electric spark discharge on graphitization of carbon

The effect of electric spark discharge on graphitization of carbon was investigated using three different types of heat treated carbon such as petroleum coke, pitch-bonded petroleum coke, and Akabira coal carbon. Each cylindrical specimen of 6 mm dia. by 6 mm length was shocked by electric spark discharge between iron electrodes in an iron capsule. The capacity of condenser was 20,000 μF and the charging voltage was 680 V. The pulse duration of spark discharge recorded by synchroscope was 1–2 millisec. The change of the graphitization degree was investigated by determining the inter-layer spacing d and crystallite thickness Lc by X-ray diffraction. The interlayer spacing d of petroleum coke and pitch-bonded petroleum coke pre-heat-treated over the range from 1000° to 2800°C decreases to 3·56–3·57 Å, and their crystallite thickness Lc increases to 400–1000 Å as a result of the electric spark shock. It was found that the increase in degree of graphitization was more remarkable when the carbon is heat treated to lower temperature. X-ray diffraction profiles for Akabira coal carbon also showed an increase in degree of graphitization resulting from the electric spark shock