Shasha Zhang

Inactivation of Aerosolized Bacillus Atrophaeus (BG) Endospores and MS2 Viruses by Combustion of Reactive Materials

Accidental release of biological agents from a bioweapon facility may contaminate large areas, possibly causing disastrous environmental consequences. To address this issue, novel halogen-containing reactive materials are being designed with the added capability to inactivate viable airborne microorganisms. This study determined the efficiency of combustion products of such materials to inactivate aerosolized bacteria and viruses. Spores of Bacillus atrophaeus and MS2 viruses dispersed in dry air were exposed for subsecond time intervals to hydrocarbon flames seeded with different reactive powders so that bioaerosol particles interacted with the combustion products in a controlled high-temperature environment. The experiments were designed to quantify differences in the biocidal effects of different reactive material powders including Al and Mg, a B•Ti nanocomposite, an 8Al•MoO(3) nanothermite, and a novel Al•I(2) nanocomposite. Compared to pure hydrocarbon flame, powder-seeded flame (with no iodine) produced about an order of magnitude greater inactivation of bacterial spores. The iodine-containing material increased the spore inactivation by additional 2 orders of magnitude. The aerosolized MS2 viruses (generally not as stress-resistant as spores) were fully inactivated when exposed to combustion of either the iodinated or noniodinated powders. Overall, the study suggests a great biocidal potential of combustion products generated by novel iodine-containing nanocomposite materials.

Nearly Pure Aluminum Powders with Modified Protective Surface

The thermodynamically predicted benefits of aluminum combustion are rarely achieved because of extended ignition delays associated with protective alumina layer, which is always present on the aluminum surface. This effort focuses on adjusting aluminum combustion dynamics by modifying its surface and structure. Aluminum is cryo-milled with cyclooctane. The prepared material consists of micron-sized, equiaxial, nearly pure Al particles; their external surface and crystal grains are coated with a cyclooctane-modified layer with properties significantly different from those of regular alumina. The materials oxidation kinetics, as observed from thermo-analytical measurements, is different from that of pure aluminum. The powder ignites at substantially reduced temperatures, and produces shorter ignition delays and higher aerosol burn rates compared to a regular spherical Al powder with similar particle sizes. In air, single particles of the prepared composite material burn longer than pure Al and produce reduced molecular AlO emission, but generate nearly the same temperature as pure Al. In the combustion products of an air-acetylene flame, composite particles burn faster than pure Al.