Hardness equation for ormosils

Hardness of ormosils coating on various kinds of substrates is important, a nd by considering recent progresses in understanding the hardness of ionic crystals or covalent crystals, new hardness equations for calculating the h ardness of glasses or ormosils from chemical compositions were derived. Whe n we applied an indenter to the surface of glass or sol-gel coatings, the s urface of indenter is a declined one to the flat surface of glass or coatin g, thus the applied force should be analyzed by using the shear modulus, S, and Young's modulus, E. This is now well accepted for the analysis of hard ness of ionic or covalent bonding inorganic materials. For example, by cons idering the binding energy and plastic deformation, Gilman showed that Hv o f NaCl crystal can be calculated by an equation including elastic stiffness which indicated a good agreement between calculated and observed value. Fo r covalent crystals he reported that the strength of chemical bonds could b e correlated with the glide (shear) activation energy for covalent crystals quantitatively. These explanations are basically applied to the hardness o f silicate glasses and ormosils. By considering both shear modulus and Youn g's modulus we have derived equations for calculating the hardness of glass es or ormosils from chemical composition, which includes packing density of atoms and bond energy per unit volume has been taken account. The agreemen ts between calculated and observed hardness values for ormosils were compar atively good.