Processing and characterization of B-based self-sustaining high temperature (SHS) reactive materials and combustion studies

Abstract

B powders are commonly used as fuel in propellants due to their high theoretical gravimetric heat of combustion. However, the formation of viscous B2O3 layer during B combustions acts as a passivating layer that hinders the combustion efficiency.

The aim of this work is to evaluate the SHS (self-propagating high-temperature synthesis) reaction of B-Fe2O3 thermite and B-Fe binary system to improve the efficiency of B’s combustion. The raw materials were processed by suspension mixing and mechanical milling and studies were done by correlating powder samples’ thermal and kinetics properties with crystallographic and morphological properties. Combustion studies on reactants are made to assist in the understanding of the proposed SHS systems to boron’s combustion behavior.

Mechanical milled samples were observed to undergo morphology changes which gave particle size reduction and improved homogeneity. The combustion energy harnessed for both systems falls along the predicted values. B which is predicted to be able to harnessed ~24% of the theoretical energy. B-Fe2O3 thermite system achieved up to 28% while B-Fe binary system up to 27% of this theoretical value. The addition of SHS additives helped to lower the B’s combustion onset temperature. This reduction increases with increased wt% of additives. Mechanical milled samples provide a higher reduction in the onset than suspension mixed samples. The highest combustion onset reduction was achieved by B-Fe2O3 thermite system of 34.6%. B-Fe2O3 thermite system brought about improvement in the B’s kinetics up to 4 times while B-Fe binary system by 2 times.

From combustion studies, both B combustion and B-Fe2O3 thermite reactions were observed from the B-Fe2O3 thermite system while only B combustion was observed in the B-Fe binary system.