Synthesis of transition metal nitrides and hydrides can be accomplished in the self propagating high temperature regime. A one dimensional model is proposed to study the effects of various operating parameters on the stability of the combustion front, to which gaseous oxidizer is fed by a process of filtration through the permeable solid. Different propagation phenomena can exist depending on the pressure of the gaseous reactant. The stability criteria derived for solid-solid systems can be extended for gas-solid systems at high pressures. At very low pressures filtration combustion is always stable. Systems which show unstable front propagation under adiabatic conditions have been observed to become more unstable due to heat losses.

Transition metal nitrides can be synthesized in the combustion regime using a self-propagating, high-temperature synthesis by the process of filtration combustion. A detailed two-dimensional numerical study for the filtration combustion process in the cross-flow configuration is presented. The process is modeled by a two-dimensional pseudohomogenous model. The model equations, which are very stiff and exhibit varying time and length scales, are solved using finite differences on a two-dimensional orthogonal adaptive mesh. The effects of pressure, bed height and bed porosity on combustion front propagation and final conversion are studied. A series of full simulations for the titaniumnitrogen system shows good agreement between theoretical predictions and experimental observations.

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Simulation of reactive flows often involves resolution of regions of steep gradients as well as varying time scales. A finite-volume formulation on a hybrid generalized moving adaptive mesh grid along with an explicit time integration scheme is presented. The algorithm is tested by simulating the filtration combustion process in three dimensions. lmportaru considerations such as the geometric conservation law for moving grids and its compliance for the finite-volume method are discussed. Applicabitity of this algorithm to vector and coarse-grain parallel architectures is also discussed. Simulation results have for the first time predicted the presence of three-dimensional instabilities in filtration combustion. Good agreement has been found with experimental observations.

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