Characterisation of boron-doped coal-derived carbon foams and their oxidation behaviour

Abstract

Carbon foams with improved resistance to oxidation were obtained from a bituminous coal and different boron precursors (boron oxide, boron carbide and pyridine–borane complex), by controlled carbonisation under the pressure derived from the release of the volatile matter, which also acts as the foaming agent. The foams were subsequently carbonised at 1100°C and the presence of boron gives rise to an increasing disorder in the carbon structure. After heat treatment at 2400°C, it is confirmed that boron occupies substitutional positions in the graphitic layers, and at high boron loadings (>2.5%), boron clusters, boron carbide and BC2O structures are also observed. The presence of boron has two opposite effects on the oxidation behaviour of the foams. At low B loadings, the foams obtained with boron carbide display lower oxidation temperatures. In the other foams, increases in the temperature of oxidation and the amount of residue remaining after the oxidation tests are observed.