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Title:	Customized boron and magnesium-based reactive materials prepared by high energy mechanical milling
Author:	Liu, Xinhang
View Online:	njit-etd2019-062 (xviii, 169 pages ~ 3.7 MB pdf)
Department:	Department of Chemical and Materials Engineering
Degree:	Doctor of Philosophy
Program:	Chemical Engineering
Document Type:	Dissertation
Advisory Committee:	Dreyzin, Edward L. (Committee chair) Schoenitz, Mirko (Committee member) Wang, Xianqin (Committee member) Venerus, David C. (Committee member) Guerieri, Philip M. (Committee member)
Date:	2019-12
Keywords:	Biocidal Chemical engineering Energetic material Explosive Heat transfer Milling
Availability:	Unrestricted
Abstract:	New reactive materials need to be developed having biocidal combustion products. When ignited, such material can add chemical biocidal effects to the common effects of high temperature and pressure. Biocidal combustion products are capable of deactivating harmful spores or bacteria, which can be released by targets containing biological weapons of mass destruction. Research showed that halogens, especially iodine, are effective as biocidal components of reactive material formulations. Recently, magnesium combustion product MgO is also found to have a biocidal effect. Thus, advanced formulations containing both magnesium and iodine are of interest; such formulations are prepared and investigated here. Reactive materials for biological agent defeat, despite containing iodine, must be stable at room temperature and in ambient conditions, so that they can be handled, mixed with other components, and stored prior to their deployment. Due to the required properties, thermite systems are often considered. However, it is difficult to develop a suitable fuel for such thermite, which generates a lot of energy, reacts rapidly, while remaining safe to handle. In present work, boron based composites and magnesium are investigated as potential fuels. Thermites are prepared by high-energy mechanical milling the fuels with Ca(IO3)2 as an oxidizer to produce reactive materials with high iodine concentrations. It is found that boron's natural oxide layer, which hinders the boron ignition can be partially removed by washing the powder in acetonitrile and toluene. Such washed boron powders remain stable in room conditions. Up to 30 wt% of iodine can be stabilized in a boron matrix in materials prepared by high-energy milling. For a baseline comparison, combustion of magnesium in different oxidizers is investigated. Air is found to be a more effective oxidizer than mixtures of CO, CO2, and H2O. Mg oxidation occurs very near to the boiling Mg surface and the rate is controlled by both oxygen diffusion and surface kinetics. A binary MgB composite is then prepared by milling; it has a reduced ignition temperature compared to boron. When washed boron serves as a starting material, the composite ignites more readily at high heating rates. Two thermites, a ternary BI2Ca(IO3)2 and a binary MgCa(IO3)2 are prepared and tested. The fuel and oxidizer are mixed on a micron scale. BI2Ca(IO3)2 contains 57.6 wt% of iodine and has a lower ignition temperature than BCa(IO3)2. MgCa(IO3)2 contains 29 wt% of iodine. At low heating rates, iodine release steps in that material correlate with the decomposition of Ca(IO3)2. Both thermites burn more rapidly in air than in air-C2H2 flame. The iodine release behavior of MgCa(IO3)2 in premixed air-C2H2 flame is simulated theoretically and compared with the experimental data using infra-red absorption measurements. The results show that iodine release at a constant rate during the entire particle combustion time is an acceptable assumption for describing the process theoretically. However, the directly measured iodine concentrations are lower than the predictions because of the metastable iodine-bearing combustion products discounted in the calculations.