Measurement of Particle Size of Ultrafine (Submicrometre) WC Powders

Abstract

There is an increasing need for size measurement of particles of submicrometre diameter in the hard-metal and ceramic industries, and in associated technologies such as wear evaluation by wear debris sizing. Specific studies of the problem have been made on fine grained WC powders by comparing the results from conventional instrumental techniques with those obtained by two new methods. The advantages and disadvantages of the various techniques are discussed including the Fisher sub-sieve sizer, the Coulter counter, gas adsorption (BET), laser, sedimentation, and new experimental methods which are based on image analysis and on the oxidation of WC powders. All the different measurement procedures gave useful information although some, such as the laser and Coulter counter, were thought to be more limited than, for example, the BET and oxidation techniques. The most informative and accurate results were probably those obtained from semi-automatic image analysis of scanning electron micrographs, and from com-paring the micrographs with a set of computer generated assemblies of similar sized circles randomly positioned within a frame. PM/0386