2499 Pure Appl. Chem., Vol. 84, No. 12, pp. 2499–2506, 2012. http://dx.doi.org/10.1351/PAC-CON-11-12-01 © 2012 IUPAC, Publication date (Web): 31 March 2012 Tantalum carbide-graphite composite film synthesized by hot-filament chemical vapor deposition* Mubarak Ali 1,‡ and Mustafa Ürgen 2,‡ 1 Department of Physics, COMSATS Institute of Information Technology (CIIT), 44000 Park Road, Islamabad, Pakistan; 2 Department of Metallurgical and Materials Engineering, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey Abstract: A composite film of tantalum carbide (TaC)-graphite was synthesized on etched Si using thermal evaporation of Ta followed by C/H chemical vapor deposition (CVD). In the present study, Ta wire 0.5 mm in diameter was electrically heated without carburizing. Under high current conditions, filaments were thermally evaporated and interacted with chemically decomposed C, forming a composite film of TaC-graphite deposits on the substrates. The influence of chamber pressure, substrate temperature, and methane concentration on the film properties has been studied. By increasing chamber pressure from 25 to 100 torr in a gas mix- ture of H and methane (containing 3 % methane), the morphology of films changed with an increased growth rate and surface roughness. Increasing the methane concentration in the mixture resulted in broadening of X-ray diffraction (XRD) peaks, increase in film thickness, and coarsening of grains, along with formation of clusters. The growth rates of the films pro- duced at a substrate temperature of 950 °C were lower than those deposited at 850 °C. Their grain sizes were bigger and exhibited a dense structure with higher surface roughness. Keywords: chemical vapor deposition; composite materials; crystal structures; interfaces; materials science. INTRODUCTION Tantalum carbide (TaC) is a promising material, particularly in applications where tolerance toward high temperature is an essential requirement. TaC is an extremely high melting point material (3983 °C), and displays high hardness (15–19 GPa) and resistance to chemical attack [1]. Owing to these attractive properties, TaC offers promise for high-temperature applications, such as rocket nozzles and scramjet components. As a stoichiometric compound, TaC is also inert to C up to its melting tem- perature and has high resistance against corrosion [2] and chemical attack [1]. TaC films have been prepared by various methods, for example, reactive dc magnetron sputtering [3], chemical vapor infiltration [4], thin-film solid-state reaction [5], ion-beam-assisted deposition [6], isothermal chemical vapor deposition (CVD) [7], cold-wall low-pressure CVD [8] and pulsed laser ablation [9]. *Pure Appl. Chem. 84, 2499–2675 (2012). A collection of invited papers based on presentations at the 7 th International Conference on Novel Materials and their Synthesis (NMS-VII) and the 21 st International Symposium on Fine Chemistry and Functional Polymers (FCFP-XXI), Shanghai, China, 16–21 October 2011. ‡ Corresponding authors: E-mail: mubarak74@comsats.edu.pk; urgen@itu.edu.tr