VICKERS HARDNESS TESTING OF SUCROSE SINGLE-CRYSTALS

Using a technique developed by Gillespie [BSc Thesis, University of St rathclyde, June 1982], single crystals of sucrose 3-5 mm on an edge we re grown isothermally from high-purity aqueous solution at relatively high supersaturation. The crystal fracture behavior was assessed using Vickers indentation hardness testing to relate to observations from a n earlier compaction study of commercial sucrose powder. Emphasis was given to indenting freshly cleaved +/-(100) surfaces. Chemical etch pi tting studies were attempted to determine the extent of the dislocatio n strain fields around the impressions. Application of indentation fra cture mechanics analyses yielded fracture toughness values for several prominent crack planes. The occurrence of these planes is discussed r elative to their attachment energies calculated using the computer pro gram, HABIT, designed to provide morphological predictions of molecula r crystals.