INSTITUTE OF PHYSICS PUBLISHING JOURNAL OF PHYSICS: CONDENSED MATTER J. Phys.: Condens. Matter 18 (2006) 2995–3003 doi:10.1088/0953-8984/18/11/006 The mechanism of the solid-state reaction between carbon nanotubes and nanocrystalline silicon under high pressure and at high temperature Yuejian Wang and T W Zerda Department of Physics and Astronomy, Texas Christian University, TCU 298840, Fort Worth, TX 76129, USA Received 23 November 2005 Published 27 February 2006 Online at stacks.iop.org/JPhysCM/18/2995 Abstract An x-ray powder diffraction method was used to study the reaction between carbon nanotubes (CNT) and silicon (Si) nanosize powder at 2 GPa and temperatures varying from 1273 to 1370 K with different sintering times. Samples were obtained using the piston–cylinder system. On the basis of the Avrami–Erofeev model, we found the activation energy of silicon carbide (SiC) formation from CNT and Si to be 96 ± 30 kJ mol −1 . Analysis of x-ray diffraction patterns provided information on the domain sizes and microstrain in SiC. Extending the sintering time increased the grain sizes and decreased the microstrain in SiC, and increasing the temperature resulted in larger crystallites. 1. Introduction Due to the formation of sp, sp 2 , and sp 3 hybridized bonds, carbon (C) exists in numerous phases such as graphite, CNT, and diamond [1]. These different hybridizations lead to the significantly different features of carbon phases, e.g., diamond is the hardest material, but graphite is very soft. All carbon phases can react with Si to form SiC which is an important material and plays a key role in many fields. Sustained efforts have been devoted to studying the reaction between elemental carbon and Si. Gorovenko et al [2] investigated the high temperature interactions in the silicon–graphite system. They found that the activation energy for the reaction between micrometre size Si and graphite particles was 230 ± 20 kJ mol −1 and the process was limited by diffusion of carbon in liquid silicon. Previously, our group studied the kinetics of SiC formation from diamond and Si under high temperature and high pressure conditions. We concluded that the reaction was controlled by the diffusion of carbon atoms through the newly formed SiC layer with activated energy ranging from 170 ± 40 kJ mol −1 for nanodiamond to 260 ± 40 kJ mol −1 for micrometre size diamond [3]. To the best of our knowledge no information on the reaction between CNT and Si is currently available. The carbon nanotube is a particular form of carbon, and since it was observed in 1990s [4], it has attracted extensive attention around the world. Because of its unique properties, it has 0953-8984/06/112995+09$30.00 © 2006 IOP Publishing Ltd Printed in the UK 2995