CERAMICS INTERNATIONAL Available online at www.sciencedirect.com Ceramics International 38 (2012) 6445–6453 Synthesis and reaction mechanism of Ti 3 SiC 2 ternary compound by carbothermal reduction of TiO 2 and SiO 2 powder mixtures Senol Cetinkaya n , Serafettin Eroglu Istanbul University, Engineering Faculty, Department of Metallurgical and Materials Eng., Avcilar 34320, Istanbul, Turkey Received 2 April 2012; received in revised form 7 May 2012; accepted 8 May 2012 Available online 19 May 2012 Abstract The present study aims to investigate synthesis of Ti 3 SiC 2 from TiO 2 and SiO 2 powder mixtures by carbothermal reduction method. Equilibrium TiO 2 –SiO 2 –C ternary phase diagram was used to predict the conditions for the formation of Ti 3 SiC 2 at 1800 K under Ar atmosphere. A reactant mixture with a TiO 2 :SiO 2 molar ratio of 1.5 and a C content of 68.75 mol% (26.86 wt%) was initially selected among the thermodynamically favorable reactant compositions for the experimental studies. Two different C sources, graphite flakes and pyrolytic C coating, were used to synthesize Ti 3 SiC 2 at 1800 K under Ar atmosphere. When graphite flakes were used, the products contained a trace amount of Ti 3 SiC 2 phase along with major TiC and minor SiC phases. Whereas, pyrolytic C coating on the oxide particles resulted in the products with much higher Ti 3 SiC 2 contents owing to the close contact between the reactants. Optimal C concentration for the C coated oxide mixtures with a TiO 2 :SiO 2 molar ratio of 1.5 was determined to be 30.05 wt% under the experimental conditions studied. Ti 3 SiC 2 content of the products obtained from this reactant was observed to increase with reaction time to 31 wt% at 75 min beyond which it gradually decreased. XRD studies indicated that the product with the highest ternary carbide content also contained TiC and a trace amount of SiC. SEM-EDS analyses showed that this sample essentially consisted of spherical fine TiC particles and Ti 3 SiC 2 nanolaminates. Equilibrium thermodynamic analysis of the TiO 2 –SiO 2 –C system suggested that the reaction of solid Ti 2 O 3 with SiO and CO gases may play a dominant role in the formation of Ti 3 SiC 2 . & 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: A. Powders: gas phase reaction; Carbothermal reduction; Ti 3 SiC 2 ternary carbide 1. Introduction Ternary titanium silicon carbide (Ti 3 SiC 2 ) compound with a layered hexagonal structure is the most popular member of the M n þ 1 AX n phases (n ¼ 1, 2 or 3) where M is an early transition metal, A is a group A element and X is C and/or N. Ti 3 SiC 2 has received considerable attention because it offers unusual combination of metallic and ceramic properties. For example, it is readily machinable, thermally shock resistant, electrically conductive and has a low density, a high melting point, good oxidation resis- tance. Hence, Ti 3 SiC 2 has been considered a potential material for high temperature applications such as bearings, engine linings, turbine blades in aircraft and diesel engines [1–4]. Various methods have been developed for the synthesis of Ti 3 SiC 2 including arc-melting [5], chemical vapor deposition [6], hot-isostatic pressing [7], spark plasma sintering [8], pulse discharge sintering [9], mechanically activated sintering [10], plasma spraying [11] and self propagating high temperature synthesis [12]. All these methods, however, use combinations of high cost non- oxide precursors (e.g. Ti, Si, TiC, SiC, TiCl 4 , CH 3 SiCl 3 ). Furthermore, these techniques involve complex, time con- suming processes or corrosive reactants. No report has been published on the synthesis of Ti 3 SiC 2 from oxide precursors (TiO 2 and SiO 2 ) by carbothermal reduction method. In addition, equilibrium thermody- namic analysis has not been carried out in the TiO 2 – SiO 2 –C system. Hence, the objectives of the present study were (i) to synthesize Ti 3 SiC 2 compound from the oxide www.elsevier.com/locate/ceramint 0272-8842/$36.00 & 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved. http://dx.doi.org/10.1016/j.ceramint.2012.05.020 n Corresponding author. Tel.: þ 90 212 473 7070x17759; fax: þ 90 212 473 7180. E-mail address: senol-c@istanbul.edu.tr (S. Cetinkaya).