Available online at www.sciencedirect.com Journal of the European Ceramic Society 33 (2013) 2049–2051 Short communication Phase-inversion tape casting and synchrotron-radiation computed tomography analysis of porous alumina Hong Fang a , Chunlei Ren a , Yaoge Liu b , Detang Lu b , Louis Winnubst a,c , Chusheng Chen a,∗ a CAS Key Laboratory of Advanced Materials for Energy Conversion and Department of Materials Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, PR China b Department of Mechanical Engineering, University of Science and Technology of China, Hefei, Anhui 230026, PR China c Inorganic Membranes, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands Received 22 January 2013; received in revised form 17 February 2013; accepted 26 February 2013 Available online 19 March 2013 Abstract A variant of tape casting based on the phase inversion phenomenon was adopted for fabrication of porous ceramic wafer. A slurry was prepared by dispersing alumina powder in an N-methyl-2-pyrrolidone (NMP) solution of the polymers polyethersulfone (PES) and polyvinylpyrrolidone (PVP). The slurry was cast using a doctor blade, and immersed in water to solidify the polymer solution via phase inversion. The green tape was dried and sintered at 1500 ◦ C. The as-prepared ceramic wafer was characterized using synchrotron-radiation computed tomography (SR-CT). It was revealed that the ceramic wafer contained typical finger-like macrovoids, and the porosity resulting from these macrovoids was ∼30%. The overall porosity of the wafer was 59%, as derived from the density data measured by Archimedes method in mercury. It is concluded that the phase inversion tape casting is a simple and effective method for preparation of porous ceramics. © 2013 Elsevier Ltd. All rights reserved. Keywords: Tape casting; Phase inversion; Porous ceramics; Synchrotron-radiation computed tomography; Alumina 1. Introduction Porous ceramics have a number of applications owing to their excellent chemical and thermal stability and acceptable mechanical strength. 1,2 In particular, they are used as filters and membranes in separation processes. 3,4 Preparation of porous ceramics usually involves the use of pyrolyzable pore formers such as starch, polymers and graphite. 5 These substances are burned out during sintering of ceramic green bodies, leaving pores in the final ceramics. The porosity and shape of these pores are largely determined by the amount and shape of the pore formers. In some cases, porous ceramics are prepared using the freeze-casting method. 6 In this method a ceramic slurry is solidified by freezing the solvent (water). The removal of the frozen solvent by sublimative drying leaves pores in the ceramic green body, and those pores are largely preserved in the sintered ceramic. ∗ Corresponding author. Tel.: +86 55163600088. E-mail address: ccsm@ustc.edu.cn (C. Chen). Recently, a new forming method based on the phase inver- sion phenomenon has been explored for preparation of porous ceramics especially those with the hollow fiber geometry. 7 This method was originally developed for preparation of polymer membranes. 8 The term phase-inversion here refers to the trans- formation of a polymer from liquid to solid state. For preparation of ceramic hollow fibers, ceramic powders are dispersed in an organic solution of polymers, and then extruded through a tube- in-orifice spinneret into a water bath (coagulation bath). Upon immersion in water, the exchange of the organic solvent with water occurs, resulting in precipitation of the polymer. (Note that water is a relatively poor solvent for polymers, and thus is termed non-solvent.) During this immersion-precipitation pro- cess, the polymer solution demixes, or “phase-separates”, into a polymer-rich and polymer-lean phase, the former functioning as a binder for the ceramic particles, and the latter acting as a pore-former. The as-formed green hollow fibers are converted into ceramic hollow fibers by firing at elevated temperatures. Tape-casting is a well-established ceramic forming method and has been applied to the preparation of porous ceramics through the use of pyrolyzable pore formers. 5 In the present study, tape casting involving phase inversion was used to 0955-2219/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jeurceramsoc.2013.02.032