Available online at www.sciencedirect.com Journal of the European Ceramic Society 33 (2013) 201–206 Short communication Effects of the alumina matrix on the carbonization process of polymer in the gel-casted green body Takashi Shirai, Tomoaki Kato, Masayoshi Fuji ∗ Advanced Ceramics Research Center, Nagoya Institute of Technology, Japan Received 26 April 2012; received in revised form 10 August 2012; accepted 13 August 2012 Available online 19 September 2012 Abstract We propose a new convenient method for making nanocarbon/ceramic composites, which combines gel casting and firing in an inert atmosphere. The objective of this work was to clarify the effect of the alumina matrix on the carbonization process of the gel content in the gel-casted green body. The presence of the alumina matrix was found to assist the survival of functional groups such as amide groups during the thermal decomposition of the polymers. Consequently, the carbon content was in a form such that it could be easily graphitized at low temperatures. The prevention of the thermal decomposition of amide groups through the interaction between the surface of the ceramic grains and the polymers was found to be important in the graphitization of the carbon content and the attainment of high conductivity during the synthesis of nanocarbon/ceramic composites. © 2012 Elsevier Ltd. All rights reserved. Keywords: Gel casting; Carbonization process; Nano-carbon/Al 2 O 3 ; Graphitizable carbon 1. Introduction In recent years, there have been many attempts, using various methods, to make composites of carbon materials and ceramics with enhanced functionalities. 1–4 One objective is to furnish the ceramics with the excellent electrical and heat conductivities of carbon materials. Nanocarbon materials such as carbon nano- tubes (CNTs) and graphene sheets are attracting attention as filler materials because of their high heat, corrosion, and thermal shock resistances, excellent heat and electrical conductivities, and their advantages for percolation because of their size and anisotropy. 2–4 A typical method for making nanocarbon/ceramic compos- ites involves mixing nanocarbon fillers and ceramic powders, e.g., by using a wet or dry mill. The obtained powder mixture is formed, for example, by press forming, casting, or extruding, and is then fired. In this method, the segregation and aggregation of the carbon content and ceramic powder result in a decrease in the strength and various other properties, so it is crucial to obtain a composite with uniform dispersion. However, when ∗ Corresponding author. E-mail address: fuji@nitech.ac.jp (M. Fuji). nanocarbon fillers are used, the hydrophobicity of the carbon and the high cohesiveness because of the nanometer-scale size become problematic in terms of obtaining a uniformly dispersed composite. Therefore, methods for obtaining uniform composites are currently being investigated, and these include the synthesis of uniform dispersions of nanocarbon materials using organic solvents, 5 polymer electrolytes, 6,7 the introduc- tion of functional groups by acid treatment, 8,9 and mixing of the dispersions with ceramic powders. However, such methods have problems in industry, such as their increased complexity, processing time, and manufacturing costs. We propose a new method combining gel casting and firing in an inert atmosphere as a convenient method for making compos- ites of nanocarbon materials and ceramics. 10–15 In this method, alumina powder is mixed in an aqueous solution including dis- persants, vinyl monomers, and gelling agents, and this mixture is then ball-milled to prepare a slurry. Polymerization initia- tors are added, and the formation and crosslinking of polymers, occurring through polymerization reactions, gel the slurry into a wet green body. This green body is dried and then fired under nitrogen or argon atmosphere to carbonize the polymer in the compact, resulting in the formation of a uniform nanocarbon in an alumina matrix. The formed carbon is known to exist between the grains having sizes of a few tens of nanometers and have 0955-2219/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jeurceramsoc.2012.08.013