Physical characteristics of charcoal for use in gunpowder

Abstract

A series of experiments are described which identify those characteristics of charcoals which are important for gunpowder manufacture. Charcoals from Alder Buckthorn, Alder, Beech and Douglas Fir woods were prepared by carbonization under nitrogen in the heat-treatment temperature range 523 to 1173 K. The charcoals were characterized by elemental analysis, differential thermal analysis, measurement of spontaneous ignition temperature, morphology using scanning electron microscopy, surface-area assessment using carbon dioxide as adsorbate, mercury porosimetry and microstrength analyses. Results indicate that for charcoals with acceptable carbon contents of 70 to 80 wt %, extremely fine control of carbonization conditions is required. The surface area and carbon content of the charcoal increased rapidly on heat treatment. The surface area of the charcoal reached values of −400 m² g⁻¹. Mercury porosimetry indicated that Alder Buckthorn and Douglas Fir charcoals had cumulative pore volumes greater than Alder charcoal and substantially greater than Beech charcoal. The Beech charcoal was the most friable of the three hardwood charcoals tested using microstrength analysis. Alder Buckthorn and Alder charcoals are recommended for gunpowder manufacture.