Combustion of a finely divided powder of a subgroup IVA metal in hydrogen

The propagation of a combustion wave in a porous metal specimen burning in a gaseous reagent is largely dependent on the dispersion of the metal particles, the porosity, the gas pressure, and the previous heat treatment. Infiltration combustion of titanium, zirconium and hafnium may burn layerwise or in a surface mode depending on these conditions, and the mode of burning has a decisive effect on the composition of the final product. Samples of titanium powder burned layerwise in hydrogen, regardless of the porosity, pressure or particle size. The same applied to specimens previously heat-treated or dehydrogenated. Hafnium and zirconium powders burn in the surface mode, while dehydrogenated ones burn in layer mode. Measurements show the dehydrogenated zirconium and hafnium to have a permeability 1.5 times as great as that of the initial material, with a commensurate increase in the combustion rate.