KNOOP MICROHARDNESS OF SINGLE-CRYSTAL SULFUR

The Knoop microhardness of single crystal sulphur was measured as a function of crystallographic orientation and applied test load on the (110) and (111) planes. Microhardnesses were determined to be in the range of 25-35 kg mm(-2). Anisotropy of the microhardness and a normal indentation size effect (ISE) were observed. The ISE was addressed by the application of the traditional power law and the proportional specimen resistance model (PSR) of Li and Bradt. The load-independent hardness was determined, from which it was concluded that the (111) plane is harder than the (110) plane and also that the (111) plane is more anisotropic in microhardness.