Capillary rise properties of porous mullite ceramics prepared by an extrusion method with various diameters of fiber pore formers
Porous mullite ceramics with unidirectionally oriented pores were prepared by an extrusion method using rayon fibers as the pore formers. Rayon fibers of 8.1, 9.6, 16.8, and 37.6 μm in diameter were used as the pore formers and were kneaded with alumina powder, kaolin clay, China earthen clay, and water to form pastes. These pastes were extruded into cylindrical tubes, dried, and fired at 1500 °C for 4 h. The apparent porosities ranged from 45.7 to 48.2 %. The pore size distributions showed a sharp peak at 9.4, 10.0, 15.6, and 30 μm with increasing fiber diameters. The height of the capillary rise was 1780, 1670, 1320, and 950 mm with increasing fiber diameter. The maximum capillary rise is much higher than previously reported. The contact angle and effective pore radius that determine the capillary rise ability were calculated by fitting the capillary rise curves using the Fries and Dreyer’s equation.
KeywordsContact Angle Fiber Diameter Capillary Rise Porous Ceramic Apparent Porosity
A part of this work was supported by the Grant for Application of Industrial Technology Innovation of the New Energy and Industrial Technology Development Organization of Japan (NEDO) under Contract No. 0827001. The authors thank Professor E. Sakai of the Tokyo Institute of Technology for permitting the use of the instrument for Hg porosimetry. We thank Professor K.J.D. MacKenzie of Victoria University of Wellington for critical reading and editing of this manuscript.
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