Cryptocrystalline graphite chemical-mechanical preparation for subsequent processing stages

Abstract

A combined effect of chemical treatment and mechanical activation upon cryptocrystalline graphite condition was studied. Chemical-mechanical preparation was accomplished by means of sulfuric acid in the presence of potassium bichromate with subsequent activation in planetary centrifugal mill AGO-2 in optimal regimes. By means of optical and scanning electron microscopy, differential thermal analysis and X-ray phase analysis, it was established that consecutive chemical and mechanical treatment of natural cryptocrystalline graphite leads to liberation of graphite intergrowths with impurity minerals, permitting to decrease impurities content in its composition, also providing for decrease in particle average size and increase in nano-size fractions content. Removal of sulfur-containing compounds from graphite composition will hamper oxidation reactions of iron sulfur-containing compounds during crude iron casting into molds, preventing formation of sulfide-containing lowmelting phases in surface layer of antistick coating in cast iron-coating interface, contributing to antistick coating unwettability with molten iron and significantly decreasing burning-on formation on castings.