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Abstract: The effect of Ni addition on the exothermic reaction in the Ti–C–BN system was investigated using differential thermal analysis (DTA). Based on DTA and X-ray diffraction (XRD) analyses, a reaction path for the formation of TiC x N y and TiB2 in the Ni–Ti–C–BN system was proposed in which the reaction initiated with the solid-state diffusion between Ti and BN. The resultant TiN x then reacted with Ni to form Ni–Ti compounds (e.g., Ti2Ni). With increasing temperature, a Ni–Ti–N eutectic liquid phase formed between the Ni–Ti compounds and TiN x at about 1110°C, enabling the dissolution of C and B in the melt to form Ni–Ti–N–C–B liquid. Finally, TiC x N y and TiB2 formed and precipitated out of the liquid. [Copyright &y& Elsevier]

Abstract: An experimental study on direct formation of TiC x N y –TiB2 ceramics by self-propagating high-temperature synthesis (SHS) was conducted using a Ti–B4C–BN system. The effects of the C/(C+N) ratio on the combustion behavior and reaction products were investigated. Experimental characterizations of quenched samples show that the combustion reaction started with the formation of highly substoichiometric TiN y and TiB due to the solid-state reaction between Ti and BN; and then the TiN y precursor and TiB dissolved back into the titanium melt, forming the Ti–B–N liquid, which in turn transformed to the Ti–B–N–C liquid due to the dissolution of the carbon atoms diffused away from B4C. Finally, the TiC x N y and TiB2 particles are formed from the melt through the dissolution-precipitation mechanism. [Copyright &y& Elsevier]