Burning Rate Characterization of Ammonium Perchlorate Pellets Containing Micro- and Nano-Catalytic Additives

Ammonium perchlorate (AP) is a common oxidizer in composite propellants, and its combustion behavior can be tailored by micro- and nano-metal oxide catalysts. Ammonium perchlorate pellets were manufactured with micro- and nano-titanium oxide and iron oxide at several mass loadings (0–3%) to isolate their effects on AP. The samples were burned from 3.45 to 34.5 MPa (500–5000 psi) in a constant-volume strand bomb. Microscopy characterization was completed for both additives and representative pellets. The incorporation of 1% micro- yielded the highest burning rate within the investigated pressure range. All micro-additive formulations increased the burning rate at pressures ranging from roughly 13.45 to 17.24 MPa (1950–2500 psi) and from 4.50 to 8.60 MPa (650–1250 psi) for micro- and micro-, respectively, and these effects were dependent on catalyst mass loading. The burning rates were increased at pressures greater than 11.27 (1620 psi) and 8.27 MPa (1200 psi) for nano- and nano-, respectively. Both nano-additives yielded burning rates that were independent of mass loading within the range of evaluated concentrations (0.25–1%). In all cases, the presence of the catalytic additives removed the negative slope generally observed in the burning rate curve of plain AP. Higher low-pressure deflagration limits were observed for nano-additive formulations, potentially due to radiative heat losses.