K. Gupta, Shubra Singh, M. Rao
May 2, 2016
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Journal
Crystal Growth & Design
Abstract
In this report, we have evolved a new method to synthesize nanocrystalline calcium sulfate dihydrate (gypsum) via electrochemical oxidation. This method provides a facile, direct way of synthesizing nanocrystalline gypsum at room temperature. Field-emission scanning electron microscopy micrographs present an interesting phenomenon of formation of microcracks in the nano-CaFeO2.5 pellet during electrochemical oxidation leading to nucleation of gypsum within the cracks. A known theoretical model has been invoked to explain the gypsum growth within the cracks. Transmission electron microscopy studies indicate electron beam-induced phase transformation of single-crystalline calcium sulfate dihydrate to polycrystalline CaO nanoparticles. The hardness was found to be improved (63% higher) by the addition of a mere 5 wt % of nano-gypsum to commercial gypsum, which is almost 200% higher than nano-gypsum synthesized earlier via an indirect route of flame synthesis and hydration. Moreover, the compressive strength ...