GRAVITATIONAL EFFECTS ON THE SHS PRODUCTION OF HIGH-POROSITY MATERIALS

We introduce a model of combustion of porous samples in a gravitationa l field, in which the high temperature products can deform, to describ e the synthesis of high porosity materials and its dependence on param eters of the problem. In addition to the main synthesis reaction we al low for the possibility of a gasification reaction of a special additi ve. We derive an equation for the elongation of the sample due to an i ncrease in its porosity, which is caused by the additional gas produce d in the main reaction or in the additive reaction or both. We also ca rry out numerical simulations of the model and compare to existing exp erimental results. We describe ignition, propagation, extinction and s tability of propagating combustion waves and their dependence on vario us factors such as heat loss, gravity, rheological parameters and amou nt of additive. In particular, we show the possibility of synthesizing uniform high porosity materials in a microgravity environment.