Some techniques for the characterization of cokes and graphites

Abstract

Methods used at the Coal Research Establishment of the UK NCB for characterizing the structure and physical properties of cokes and graphites are briefly reviewed. These include the use of X-ray diffraction and optical microscopy, and the measurement of a range of mechanical, thermal and electrical properties. Some relations between the structural parameters of graphites and their physical properties are discussed. Examples illustrating the application and practical importance of the results obtained are grouped loosely under three headings: 1. (1) Prediction of graphite properties from tests on cokes (e.g. prediction of coefficient of thermal expansion from coke mosaic texture). 2. (2) Exploration and monitoring of changes in process conditions (e.g. use of graphite crystallite size to monitor the effects of changes in graphitization temperature, use of coke mosaic texture to indicate effects of changes in temperature and time during coal-digestion stage of the solvent-extraction process). 3. (3)Prediction of the performance of graphite electrodes in an arc furnace (e.g. concept of thermal-shock resistance, estimation of thermal-shock resistance parameters from physical properties, and correlation between these and thermal-shock performance in laboratory tests).