A study of the effects of heat treatment on the physical properties of the carbon black Vulcan 3

Abstract

The changes which occur in the properties of the carbon black Vulcan 3 upon heat treatment in argon at temperatures up to 2700 °C have been investigated. Two important regions of change have been identified as samples are heated to progressively higher temperatures. A change in the polar properties and wettability of the surface, which occurs during pretreatment at temperatures between 1000 and 1150 °C, is inferred from changes in the shape of the water adsorption isotherms and the enthalpies of immersion in water. An enhancement of the surface area, calculated from the nitrogen adsorption isotherm, was observed for samples heated to temperatures between 1035 and 1050 °C. This previously unreported effect has been attributed to the removal of surface complexes creating a limited porosity. An increase in the crystallographic ordering of the carbon, which is demonstrated by changes in the X-ray powder diffraction pattern, the surface area and the enthalpies of immersion in n-hexadecane, occurs between 1100 and 2000 °C. Ageing of graphitised carbon samples due to exposure to the atmosphere or to water vapour was observed and may be an important consideration in the use of graphitised carbon blacks as reference adsorbents.