Effect of sintering temperature and nanotube concentration on microstructure and properties of carbon nanotube/alumina nanocomposites

Multiwalled carbon nanotube (MWCNT)/alumina (Al2O3) nanocomposites were prepared by simple wet mixing of MWCNT and Al2O3 powder followed by pressureless sintering in static Argon. X-ray diffraction (XRD) line broadening analyses using Williamson-Hall (W-H) technique revealed a polynomial dependence of crystallite size (D-V) on sintering temperature (T-sin) and volume percent CNT added (V-CNT) as D-V approximate to [0.9(T-sin)-770]+[-1.1(T-sin)+1489](V-CNT)+[0.4(T-sin)-547](V-CNT) (2). While the highest increase (similar to 14%) in Vickers hardness (HV) over pure Al2O3 was offered by 0.15 vol% MWCNT/Al2O3 specimen, the highest fracture toughness (K-IC similar to 5 MPa m(0.5)) and flexural strength (sigma(FS)similar to 260 MPa) were obtained for nanocomposite containing 0.3 vol% MWCNT which were similar to 26% and similar to 16% higher, respectively, than those of pure Al2O3. The 0.15 vol% MWCNT/Al2O3 specimen also offered maximum increase (similar to 22%) in thermal conductivity over unreinforced Al2O3 (similar to 39 W/m K). Electrical percolation in nanocomposites was observed between 0.6 and 1.2 vol% CNT loading. (c) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved