Ultra-micro-hardness of organic and inorganic crystals

The measurement of ultra-micro-hardness is an attempt to find a physical property which can be used for the description of the so-called abrasion resistance of crystals produced in chemical engineering equipment. Such approaches are necessary in order to compare calculations of the secondary nucleation rates for different substances. Abrasion is the main source of the existing secondary nucleation. The main purpose of the paper is to show that it is possible to obtain ultra-micro-hardness data for organic and inorganic substances, and such data are presented. All of these substances are commonly processed in industrial crystallization processes. The results for the Vickers-hardness measurements of the substances are presented as hardness-indentation force-dependency diagrams. The pictures of indentations at different indentation forces show that measurements of the Vickers hardnesses with indentation forces higher than 0.04-0.1 N (with respect to the substance) lead to cracks at the Vickers pyramid of the indentation and therefore to irreproducible results for the Vickers-hardness measurements.