Effect of different nano-carbon reinforcements on microstructure and properties of TiO2 composites prepared by spark plasma sintering

In this study, Titania (TiO2) based composites reinforced with 2 wt% of various carbon nanomaterials were prepared using spark plasma sintering (SPS). Prior to SPS, the samples were ball milled. The reinforcements used in the composites were graphene nanoplatelets (GNP), carbon nanotubes (CNT) and single walled carbon nanohorns (SWNH). The ball milled powders and SPS compacts were characterized using various techniques. Mechanical and photocatalytic properties of the SPS composites were evaluated and compared for different nano-carbon reinforced TiO2 composites. X-ray diffraction and Raman spectroscopy studies confirmed that the milled powders comprised of Anatase phase which transformed into Rutile phase during SPS. Nano transformation twins were observed in Rutile grains. Fractured surfaces showed that the reinforcements were well bonded with the TiO2 grains and the SWNH reinforcement resulted in comparatively finer grain size. Nanoindentation studies showed that the hardness and elastic modulus of GNP reinforced composites was 78% and 30% respectively higher compared to TiO2 matrix. The hardness and modulus of the CNT reinforced TiO2 increased by 22% and 5.4% respectively while that of the SWNH reinforced TiO2 increased by 11% and 23% respectively. GNP and CNT reinforced TiO2 exhibited superior photocatalytic activity for the degradation of methylene blue dye compared to pure TiO2. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.