Formation of highly orientated graphite from polyacrylonitrile by using a two-dimensional space between montmorillonite lamellae

Abstract

Carbon materials have many attractive physical and chemical properties, because of a wide variety of chemical bonding, crystal structure and microtexture. Carbon properties can be created by selecting a preparation procedure and a raw material. For example, many new carbon materials such as exfoliated graphite, benzenederived fibre and diamond film have come into use recently. The possibility of creating a new carbon material by a new method still remains. Here we report a novel method of preparing a highly orientated graphite from polyacrylonitrile (PAN) by making use of the interlamellar opening of montmorillonite (MONT) as a two-dimensional space for carbonization. A MONT-PAN intercalation compound was prepared and heat-treated at 700 °C to produce carbon from PAN between MONT lamellae. The carbon was then released from MONT by acid treatment and subjected to further heat treatment at various temperatures up to 2,800°C. The interplanar spacing (d₀₀₂) of the carbon treated at 2,800 °C was very close to that of ideal graphite crystal and the crystallite size, L_c and L_a, were ~40 nm and >1μm, respectively. The formation of such a highly orientated carbon is probably a consequence of the orientation of the two-dimensional carbon precursor produced between the lamellae of MONT. When PAN itself is heat-treated, it produces a three-dimensional carbon with a network of intertwined ribbons of stacked graphitic sheets.