Selection of burning rate modifiers for hydrazinium nitroformate

Species including N2H4, NH3 and N2O are known to be present near the surface of burning hydrazinium nitroformate (HNF). In this paper, planar laser induced fluorescence from the near surface region of burning HNF pellets is reported indicating the presence of NO2. These four species are formed in the upper (foamy) layer of the solid phase. A burning rate modifier might be selected to induce reactions between the gaseous species in this layer. Selective catalytic reduction (SCR) is able to start highly exothermic reactions at relatively low temperatures. The SCR catalyst V2O5 increases the burning rate of HNF by a factor of 11 at 0.1 MPa. The pressure exponent is reduced to 0.28, far below the target value of 0.5 required for practical application of HNF in propellant formulations. As far as SCR catalysts have been tested as burning rate modifiers of HNF, they are effective, yet incompatible. To overcome this incompatibility remedies might possibly be found in high-temperature catalysts, or in coating particles.