Combustion synthesis of Ti(C, N)-TiB2 from a Ti-C-BN system

In this paper, a simple way of fabricating TiCxNy-TiB2 ceramics through the combustion reaction of Ti, C and BN powder mixtures in an argon atmosphere is reported with an emphasis on the effects of the C/(C + N) ratio on the SHS reaction behaviors and mechanism. With the increase in the C/(C + N) ratio, the combustion temperature shows a zigzag variation behavior: the combustion wave velocity displays a similar variation tendency as did in the combustion temperature while the ignition delay time increases progressively. XRD results confirmed that TiCxNy-TiB2 could form in all the samples. Microstructural observations revealed that both TiCxNy and TiB2 grains had fine sizes of less than 1 mu m in the products when the C/(C + N) ratio was lower than 0.5. Based on the characterization of quenched samples, the formation mechanism of the titanium carbonitride is proposed. Namely, the formations of TiN0.3 and TiN are followed by the incorporation of C in TiN. to form the titanium carbonitride solid solution. (C) 2009 Elsevier B.V. All rights reserved.