Research Article To Evaluate the Application of Alkoxide Sol-Gel Method in Fabrication of 3YSZ-MWCNTs Nanocomposites, in an Attempt to Improve Its Mechanical Properties Ali Ahmadi, 1,2 Amir Ali Youzbashi, 1 Ahmad Nozad Golikand, 2 Toraj Ebadzadeh, 1 and Amir Maghsoudipour 1 1 Materials and Energy Research Centre, P.O. Box 31878-316, Karaj 31787-316, Iran 2 Materials Research School, NSTRI, P.O. Box 81465-1589, Isfahan 8166184111, Iran Correspondence should be addressed to Amir Ali Youzbashi; a-yuzbashi@merc.ac.ir Received 26 April 2014; Revised 5 August 2014; Accepted 20 August 2014; Published 12 October 2014 Academic Editor: Claude Estourn` es Copyright © 2014 Ali Ahmadi et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In the present research work, fabrication of YSZ-CNTs composite system through alkoxide sol-gel processing was evaluated, in an attempt to improve its mechanical properties. Nanocomposites containing 0.5–2 wt% MWCNTs were then fabricated through the hydrolysis and condensation processing of the solution mixtures containing alkoxide and inorganic precursors along with the functionalized CNTs under basic condition and its fnal sintering by the SPS technique at 1400 ∘ C. Results showed the formation of a nanocomposite powder based on pure 3YSZ matrix, with well dispersion of CNTs and its good adhesion to the matrix particles in composite containing 0.5 wt% CNTs. Te fracture toughness of sintered samples showed around 24% increase for the composite containing 0.5 wt% CNTs. Te fracture toughness, hardness, and density decreased due to the agglomeration of CNTs over 0.5 wt%. Toughening mechanisms including pullout and crack bridging were observed on the polished and fractured surfaces. 1. Introduction Ceramics based on yttria stabilized zirconia have attained much attention, due to their unique mechanical character- istics. However, fracture toughness of these ceramics is not sufciently good to meet the needs of many high performance ceramics. Terefore, many attempts are being made in order to improve their mechanical properties, mainly, through fabrication of their composites with carbon nanostructures. Among them, carbon nanotubes have shown to be the promising nanoscale materials, which have been widely used in reinforcing of various ceramic materials. CNTs can improve the mechanical properties of ceramics through the reduction of grain size and toughening mecha- nism including pull-out, crack bridging, and crack defection [1, 2]. For successful development of CNT/composite materi- als, besides the uniformity in composition, structure, particle size, and shape of the synthesized matrix nanopowder as the efective structural characteristics, a number of the key factors, concerning CNTs, must be challenged. CNTs must be processed in such a way as to ensure its homogeneous dispersion within the ceramic matrix, whilst developing an appropriate degree of interfacial bonding [3]. No doubt, the above structural requirements could be fulflled through proper selection of the techniques, during the synthesis of the composite powder, as well as its sin- tering process. Although, some researchers have attempted to fabricate the ZrO 2 -CNT composite by various methods, the observed mechanical properties could not be adequately explained on the basis of their structural characteristics, and, in most of the cases, the results show inconsistency. Te reason may be due to the complexity of the factors, infuencing the structural and mechanical properties of these composites. For instance, Sun et al. [4] and Duszov´ a et al. [5] fabricated 3Y-TZP/MWCNTs composites through colloidal processing route followed by SPS and hot press sintering techniques. Hardness and fracture toughness of the fabricated composites were found to decrease with increasing CNT weight percent. Te existence of agglomerated CNTs at Hindawi Publishing Corporation Journal of Nanomaterials Volume 2014, Article ID 867367, 8 pages http://dx.doi.org/10.1155/2014/867367