Current work aimed to predict the flame velocity in aluminum dust clouds by directly solving the energy conservation equations on particles while considering the two scenarios of heat transfer: continuum regime assumption and free molecular regime assumption. Generally, the model shows that the influence of particle diameter (d_p) on the velocity follows the d_p^-m, and the velocity is insensitive to the wide range of dust concentration 200-1000 g･m ^-3. For continuum regime assumption, the calculation has been compared with the reported experimental results in particle sizes range of 5.4-7.1 μm, and the velocity is comparable with the predicted size of 10 μm; however, it failed to predict the velocity as particle decreases to nano-scale resulting in the unpractical high results. These results imply that the heat transfer mechanism in nano-particle transits to free molecular regime assumption. For free molecular regime assumption, particle agglomeration has been taken into account for the flame velocity; however, due to lack of experimental flame velocity in nano dust clouds, the calculations are compared with other numerical predictions. In the last part, a particle burning time was approximated by considering the particle’s residence time in the preheat zone, and the results follow the well-known d_pⁿ-law.

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We have developed a novel welding technique for joining ceramic materials and metals. The technique composes of combustion synthesis, which is an exothermic reaction with very high temperature, and explosive welding. Layered powder bed consisting of raw material powders for TiC-Al₂O₃ ceramic composite and TiNi intermetallics was combustion-synthesized on a copper plate by using the metal heating coil. After that, the explosive was detonated immediately for welding under elevated temperature associated with the combustion synthesis. Consequently, a threelayered clad was obtained with cohesive interface between the dissimilar materials. Hardness value in the ceramics layer increased with the amounts of explosives. The rapid quenching tests using the strip specimen showed no exfoliation at the interfaces of the samples. It is suggested that TiNi with pseudo elastic effect was effective to relax the thermal stress caused between the dissimilar materials.

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The reduction in the impact and frictional sensitivity needed for the ignition of flash and black power while replacing sulfur by fructose (a type of sugar) as a fuel was studied. 23 wt.% and 10 wt.% of sulfur present in flash and black powders, respectively, were gradually replaced by blending varying percentage of fructose in 10 different compositions. Performance characteristics of the resultant mixtures were checked by measuring the flame height, ballistic behaviour, minimum ignition energy, impact energy and frictional load, by following various ASTM standards. The sensitivity of firework mixtures containing fructose is moderate in contrast to conventional fireworks mixtures prepared using sulfur. The thermal characterization of the mixtures was attained through DTA and DSC analysis. The performance of the fructose blended mixtures were evaluated by making banger fireworks and rocket fireworks. The banger fireworks prepared using fructose blended flash powder produces a sound of 120 dB in which the percentage of sulfur was reduced from 23 wt.% to 9.51 wt.%. The rocket fireworks prepared using fructose blended black powder moved to a higher distance with a slower velocity. The advantage of using fructose in flash and black powder for making fireworks is that the percentage of sulfur used was considerably reduced, thereby increasing the handling safety of the mixtures being used for making fireworks as well as a reduction in the release of SO₂.

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To assess the risk of a hydrogen recombination catalyst, its ignition characteristics were experimentally investigated. A layer of catalysts was installed perpendicular to a mixture flow of H₂ and air with controlled flow rates. The temperature on the catalyst and that of the mixture upstream of the catalyst were measured using thermocouples. The density variation of the mixture caused by combustion was observed using shadowgraph visualization. When both the flow velocity of the mixture and the fraction of H₂ were larger than the ignition thresholds, deflagration started and the temperature of the mixture upstream of the catalyst rapidly increased owing to the propagation of the flame front. The catalyst had the potential to ignite the mixture when the temperature of the catalyst, which increased with the amount of H₂ reacting on the catalyst, was sufficiently high. Therefore, it is necessary to maintain the flow velocity of the mixture and the fraction of H₂ below the thresholds while monitoring the surface temperature of the catalyst.

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