Heat of combustion of tantalum-tungsten oxide thermite composites

The heat of combustion of two distinctly synthesized stoichiometric tantalum-tungsten oxide energetic composites was investigated by bomb calorimetry. One composite was synthesized using a sol-gel (SG) derived method in which micrometric-scale tantalum is immobilized in a tungsten oxide three-dimensional nanostructured network structure. The second energetic composite was made from the mixing of micrometric-scale tantalum and commercially available (CA) nanometric tungsten oxide powders. The energetic composites were consolidated using the spark plasma sintering (SPS) technique under a 300 MPa pressure and at temperatures of 25, 400, and 500 °C. For samples consolidated at 25 °C, the density of the CA composite is 61.65 ± 1.07% in comparison to 56.41 ± 1.19% for the SG derived composite. In contrast, the resulting densities of the SG composite are higher than the CA composite for samples consolidated at 400 and 500 °C. The theoretical maximum density for the SG composite consolidated to 400 and 500 °C are 81.30 ± 0.58% and 84.42 ± 0.62%, respectively. The theoretical maximum density of the CA composite consolidated to 400 and 500 °C are 74.54 ± 0.80% and 77.90 ± 0.79%, respectively. X-ray diffraction analyses showed an increase of pre-reaction of the constituents with an increase in the consolidation temperature. The increase in pre-reaction results in lower stored energy content for samples consolidated to 400 and 500 °C in comparison to samples consolidated at 25 °C.