Mapping Boron Dioxide (BO2) Light Emission During Ballistic Initiation of Boron

Abstract : This work describes chemical imaging of boron dioxide (BO2) formed during ballistic initiation of 1:1 by weight powder-mixtures of boron (B) and potassium nitrate (KNO3) contained within a polyethylene spherical projectile (25-mm diameter). Initiation was achieved by impact of the gas-gun-launched B/KNO3-filled projectile with an anvil in a windowed, air-filled chamber. To monitor the subsequent chemical reaction, a 2-camera, optically filtered method to map discrete chemical emission from the BO2 molecule was used. This technique distinguishes incandescence of hot particles produced during the event from discrete chemical emission by BO2 near a wavelength of 546 nm. The dependence of delay in BO2 chemical emission (that exceeded particle incandescence) with impact velocity was investigated, and chemical emission movies, which ratio the intensity of discrete to thermal emission, are discussed. Emission spectra (300- to 1000-nm wavelength) were recorded during the impact event and used to determine a gray-body temperature of the hot particles during the time when BO2 emission was most intense.