Boron ignition and combustion with doped δ-Bi2O3: Bond energy/oxygen vacancy relationships

The purpose of this paper is to extract a clearer relationship between atomic properties of the oxidizer, and ignition temperature and combustion kinetics. Pure Bi2O3 and a series of Y3+ and W6+ doped Bi2O3 nanoparticles with the same crystal structure and morphology were synthesized via aerosol spray pyrolysis and used as oxidizers in boron-based thermites. This enabled us to vary bond energy and oxygen vacancy concentration systematically. The ignition temperatures and the reactivities of different B/Bi2O3 thermites were measured by rapid heating (> 105 K/s) temperature-jump/time-of-flight mass spectroscopy and a confined pressure cell, respectively. With pure Bi2O3, the boron could be ignited at a temperature as low as 520 °C. In-situ high heating rate TEM was used to observe the reaction before/after heating. We find very clear relationships that higher oxygen vacancy concentration and smaller metal-oxygen bond energy lead to lower ignition temperature and higher combustion reactivity.