A novel stearic acid/modified expanded vermiculite composite phase change material (PCM) was prepared in this study. Titanium dioxide-loaded expanded vermiculite was treated with nitric acid (aEVT) and then used as stearic acid (SA) supporting matrix. The thermal conductivity and latent heats of the SA/aEVT composite PCM were enhanced simultaneously compared with those of SA/expanded vermiculite (EV) and SA/expanded vermiculite with acid treatment (aEV) composite PCMs. The thermal conductivity of SA/aEVT was 0.58 W/mK, which was 11.4% and 203% higher than those of SA/EV and SA/aEV, respectively. The latent heats of SA/aEVT were 146.8 J/g at the melting temperature of 65.9 degrees C and 141.7 J/g at the freezing temperature of 63.4 degrees C, which were also higher than those of SA/EV and SA/aEV. The results of the thermal cycling test and Fourier transform infrared spectroscopy (FT-IR) indicated that the SA/aEVT composite PCM was thermally stable and chemically inert. Thus, the prepared SA/aEVT is a promising composite PCM for latent heat storage systems. (C) 2016 Elsevier B.V. All rights reserved.