In Situ Neutron Powder Diffraction Study of Ti₃SiC₂ Synthesis

Abstract

The synthesis of Ti3SiC2 by pressureless reactive sintering of Ti/SiC/C mixtures under an Ar atmosphere has been studied using in situ neutron diffraction. The intermediate phases TiCx and Ti5Si3Cx (x≤ 1) form first at ∼800–1400°C. These phases are consumed in the formation of Ti3SiC2, at ∼1500°C. After sintering, Ti5Si3Cx disappears but an amount of TiCx remains in the sample primarily as a surface layer. The studies appear to support a suggestion that the intermediate phases react to form Ti3SiC2 through a diffusion‐controlled process. Prolonged stepwise heating under argon in some experiments resulted in decomposition of Ti3SiC2 above ∼1400°C and significant disproportionation of the sample.

Phase reactions associated with the formation of Ti3SiC2 from TiC/Si powders

“…Racault et al [29] were first to observe the decomposition of Ti 3 SiC 2 into TiC x and gaseous Si, which has been confirmed by others [13,20,30]. Racault [13] reported that this reaction was promoted by the presence of carbon.…”

Synthesis of Ti3SiC2 by Reaction of TiC and Si Powders

“…[1][2][3][4][5] Ti 3 SiC 2 is most often prepared from starting powder mixtures including pure titanium, such as Ti/Si/C [6][7][8][9][10][11] , Ti/C/SiC 2,12-15 and Ti/Si/TiC [16][17][18] by use of different powder metallurgical synthesis methods, e.g. hot pressing, 2,8,10 hot isostatic pressing, 12,17 vacuum sintering, 7,11,15,18 pressureless sintering, 6,9,13,14,16 mechanical alloying [19][20][21] and self-propagation high-temperature synthesis. 22 Pure titanium powder is highly oxidizing and thus has to be handled with great care under strict safety precautions.…”

“…Wu et al 13 who observed that the presence of titanium carbide in the sample was deleterious to the thermochemical stability of Ti 3 SiC 2 . Gao et al 17 stated that the stability was related to the vapor pressure of silicon in the furnace.…”

Microstructure evolution of Ti3SiC2 compound cathodes during reactive cathodic arc evaporation

“…The diffusion-controlled solid state reaction of Ti 3 SiC 2 is known to require sufficient time at elevated temperatures. 24 The transition zone, region II, does probably not completely melt during the evaporation process since the observed layered regions resembles the virgin Ti 3 SiC 2 grains in terms of size and shape. Instead, region II is exposed to high temperature spikes during and right after the discharge due to inward heat conductions from the surface.…”