Characteristics of microbubbles generated by porous mullite ceramics prepared by an extrusion method using organic fibers as the pore former |
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| Authors: | Kiyoshi Okada Mai Shimizu Toshihiro Isobe Yoshikazu Kameshima Munetoshi Sakai Akira Nakajima Taisuke Kurata |
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| Affiliation: | 1. Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro, Tokyo 152-8552, Japan;2. Materials and Structures Laboratory, Tokyo Institute of Technology, 4459 Nagatsuta, Midori, Yokohama 226-8503, Japan;3. Kanagawa Academy of Science and Technology, 308 East, Kanagawa Science Park, 3-2-1 Sakado, Takatsu, Kawasaki 213-0012, Japan;4. Kurata Refractory Co. Ltd., Hirono, Futaba, Fukushima 979-0402, Japan;1. School of Metallurgy, Key Laboratory for Ecological Metallurgy of Multimetallic Mineral (Ministry of Education), Northeastern University, Shenyang, 110819, PR China;2. State Key Laboratory of Advance Refractories, Sinosteel Luoyang Institute of Refractories Research Co., Ltd., Luoyang, 471039, PR China;3. Electron Microscope Unit, Mark Wainwright Analytical Centre, The University of New South Wales, Sydney, NSW, 2032, Australia;1. The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China;2. School of Materials Science and Engineering, Anhui University of Technology, Ma’anshan 243002, China;3. High Temperature Ceramics Institute, Zhengzhou University, Zhengzhou 450052, PR China;4. College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK;1. College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing, 211106, China;2. Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Nanjing, China;3. The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology(WUST), Wuhan, 430081, China;1. High Temperature Ceramics Institute, Zhengzhou University, Zhengzhou 450052, China;2. College of Materials Science and Engineering, Henan University of Technology, Zhengzhou 450007, China |
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| Abstract: | Porous mullite ceramics with unidirectionally oriented pores were prepared by an extrusion method using rayon fibers as the pore formers and the characteristics of microbubbles generated by these porous ceramics were investigated. The 1200 mm long ceramics were tubular and of thick or thin types of 20–30 mm inner diameter and 30–50 mm outer diameter, respectively. The thin and thick samples had porosities of 47 and 49% and average pore radii of 7.8 μm. The gas permeabilities of the thick and thin samples were 4.1 × 10?14 and 5.4 × 10?14 m2, respectively. Microbubbles were generated by introducing N2 gas through the ceramic tube by immersing it into water. The minimum pressure (bubble point pressure) for generation of microbubbles was 20 kPa, much lower than for other bubble-forming methods. The average microbubble radii ranged from about 70 to 105 μm at flow rates of 0.15–0.25 L/min in the thin sample and 0.3–0.7 L/min in the thick sample. These bubble sizes are much smaller than calculated for a Fritz-type bubble such as generally formed by bubbling from pores and/or orifices. However, the present bubble sizes agree well with the calculated value based on nanobubbles, indicating that bubble formation occurs by mixing the gas with water in small pores. Since microbubbles enhance the dissolution rate of a gas phase in water, they are potentially useful for improving water environments, especially oxygen-deficient water. The effectiveness of gas dissolution in water was confirmed by determining the dissolution behavior of CO2 gas using these porous ceramics. |
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