Materials Chemistry and Physics 128 (2011) 181–186 Contents lists available at ScienceDirect Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys Synthesis of porous chromium carbides by carburization Tingyong Xing a,b , Xinwei Cui b , Weixing Chen b,∗ , Ruisong Yang c,b a State Key Laboratory of Nonferrous Metals and Processes, Grinm, Beijing 100088, PR China b Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, Canada T6G 2G6 c Department of Materials Science and Engineering, Sichuan University of Science & Engineering, Zigong 643000, China article info Article history: Received 17 June 2010 Received in revised form 12 December 2010 Accepted 24 February 2011 Keywords: Chromium Oxide Carburization Porous material Chromium carbide abstract Porous chromium carbide structures have been synthesized through reactive sintering of chromium oxides in carbonaceous reducing environments. The process is simple and can be used to fabricate large size porous structures. It has been characterized that the pores in the porous structure are open in nature and the size of pores in the same porous structure can be controlled within a narrow range. Depending on the processing condition, the porosity in the porous structure was measured to be from 50% to 78%, and pore size varied from 0.5 m to 3 m. It has been determined that the porosity in the process was formed primarily due to volume reduction caused by phase transformation from chromium oxides to chromium carbides. It is believed that similar process can be used to form porous structures of other materials as long as a reactive sintering can occur and is accompanied with volume reduction. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Ceramics are traditionally sintered under high temperatures and pressures to avoid presence of porous defects because of their inherent brittleness. However, an increasing number of appli- cations require porous ceramics. Such applications include, for example, the filtration of molten metal, high-temperature thermal insulation, support for catalytic reactions, filtration of particulates from diesel engine exhaust gases, and filtration of hot corrosive gases in various industrial processes [1–7]. The advantages of using porous ceramics in these applications are usually the high melting point, tailored electronic properties, high corrosion, and wear resis- tance in combination with the features gained by the replacement of solid material by voids in the component. Such features include low thermal mass, low thermal conductivity, controlled permeabil- ity, high surface area, low density, high specific strength, and low dielectric constant [8]. Porous materials are generally categorized into microporous, with pore width (d) less than 2 nm, mesoporous, with pore sizes ranging from 2 nm to 50 nm, and macroporous, having a pore size larger than 50 nm [9]. Microporous materials are used primarily for ion exchange and gas sorption. The former involves the exchange of ions held in the cavity of microporous materials with ions in the external solutions. Gas sorption is the ability of a microporous material to reversibly take molecules into its void volume. Meso- porous materials have huge surface areas, providing a vast number ∗ Corresponding author. Tel.: +01 780 4927706; fax: +01 780 4927706. E-mail address: weixing.chen@ualberta.ca (W. Chen). of sites where sorption processes can occur. These materials have numerous applications in catalysis, separation and many other fields. The synthesis of these materials is of considerable interest and is constantly being developed to introduce different proper- ties. A number of techniques such as sol-gel, templating, and other chemistry routes were developed to fabricate micro- and meso- porous ceramic materials, as have been reviewed in the recent literature [10–12]. The synthesis of macroporous materials has been recently clas- sified into three major routes: replica, sacrificial template and direct foaming. The major features of these methods are summa- rized in Table 1 [8]. Despite many techniques being developed, the reliable methods are still lacking that can fabricate high pore den- sity macroporous ceramics with pore sizes ranging from 500 nm to 5 m [8]. This paper reports a simple reaction sintering process to fabricate macroporous chromium carbide structures with high pore density of open pores in dimensions ranging from 0.5 to 5 m. Chromium carbide has recently been the centre of considerable attention for industrial applications, own to its unique proper- ties, such as high hardness (Vickers, 1834 kg mm -1 mm -1 [13]) and young modulus (373.13 GPa [13]), medium fracture toughness (5.5 MPa √ m, [14]) excellent resistance to oxidation, erosion and wear, low density (6.68 g cm -3 [15]) and high-temperature and chemical stability [16,17]. Several processing techniques have been employed to fabricate chromium carbide in the past. Mechanical alloying and high energy milling are used to synthesize chromium carbide from mixed powders of metal chromium and carbon [18–20]. Although the processes are simple to perform, chromium carbide of high purity can’t be synthesized. Osvaldo etc. proposed a mechanical-thermal method to enhance the reaction between 0254-0584/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.matchemphys.2011.02.056