Formation and reactivity of oxides and basic salts. III. Titanium dioxides and basic titanic salts

Abstract

AbstractMethods of production and application of titanium dioxides and basic titanic salts have been summarised and the appropriate physical properties of the products have been studied. Variations in phase composition, surface area and crystallite and aggregate sizes have been correlated with experimental conditions.When titanic sulphate or chloride is hydrolysed by sodium hydroxide, the basic salts initially formed are decomposed subsequently to hydrous titanium dioxide as the pH becomes stabilised at higher values. The specific surface of the basic sulphate increases considerably when it hydrolyses to anatase. On calcination at temperatures up to about 750°, the anatase crystallites can grow from about 0·006 μm to the requisite 0·1–0·5 μm range, but the aggregate sizes vary widely. Shock‐heating at temperatures between 600° and 900° removes the remaining water and breaks up the larger aggregates.At higher temperatures, the anatase is transformed to rutile which subsequently sinters. The rutile produced by shorter calcinations at 1100°–1150° is similar in crystallite size to that obtained by complete oxidation (‘burning’) of titanic chloride vapour at the same temperatures. Results emphasise the need for close control of residence time in the high‐temperature zone in the production of pigmentary titanium dioxide.