Influence of the synthesis conditions of boron carbide on its structural parameters

Resumo

Boron carbide is prepared by self-propagating high-temperature synthesis (SHS) in a composition range from 5 to 30 at % carbon. The introduction of an inert (MgO) and active (Mg(ClO₄)₂) additives into the reaction mixture leads to a variation in process parameters such as the temperature and combustion rate. It is established that the unit cell metrics of boron carbide substantially vary depending on the synthesis conditions. The degree of the effect of the SHS mode on the crystal structure rises with an increase in the carbon fraction in the boron carbide structure. This regularity is associated with the ordering diversity of carbon atoms in nonstoichiometric boron carbide. No influence of the synthesis conditions on the unit cell parameters is observed for stoichiometric boron carbide, which is associated with the structure saturation with carbon. It is shown that the variation in the combustion temperature during SHS of boron carbide of the same composition leads to the variability of the structural parameters, thus reflecting the influence of the synthesis conditions on the material crystal structure.