High-temperature hydrogenation behaviour of bulk titanium silicon carbide

Thermal stability of Ti3SiC2 was investigated at 1200-1400 degrees C in hydrogen atmosphere for 3 hours. The hydrogenation mechanism was clarified by a combination of X-ray diffraction, scanning electron microscope, Raman spectroscopy and first principles calculation. At 1200 degrees C, a dense and uniform TiSi2 layer formed on the sample surface, which originated from both the preferable lose of silicon from the Ti3SiC2 substrate and the dissociation of Ti3SiC2. As temperature increased to 1300 degrees C, TiSi2 layer began to scale off and presented laminated Ti3SiC2 grains beneath this layer, which indicated preferential hydrogenation occurred along the basal planes. This phenomenon was ascribed to the fact that the introduction of H interstitial atom weakened the combination between titanium and silicon interface layer, which was confirmed by first principles calculations. In addition, the formation of TiSi2 owing to the dissociation of Ti3SiC2 caused the volume expansion after hydrogenation, resulting in that majority of TiSi2 layer spelled off at 1400 degrees C.