Surface modification of SiC powders by hydrolysed aluminium coating |
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| Affiliation: | 1. School of Resources and Environmental Engineering, Shandong University of Technology, Zibo 255049, China;2. School of Materials Science and Engineering, Shandong University of Technology, Zibo 255049, China;1. School of Resources and Environmental Engineering, Shandong University of Technology, Zibo, 255049, People’s Republic of China;2. School of Materials Science and Engineering, Shandong University of Technology, Zibo, 255049, People’s Republic of China;3. State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing, 100084, People’s Republic of China;1. Section of Chemistry, Aalborg University, Fredrik Bajers Vej 7H, DK-9220 Aalborg, Denmark;2. Universitá di Torino, Dipartimento di Chimica and NIS Centre, Via P.Giuria 7, 10125 Torino, Italy;1. State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China;2. State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace Engineering, Xi’an Jiaotong University, Xi’an 710049, China;3. Department of Mechanical Engineering, Nagaoka University of Technology, Nagaoka 940-2188, Japan |
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| Abstract: | SiC powders are surface modified to behave like alumina in aqueous suspensions by coating the powders with in situ generated hydrolyzed aluminium from dilute aqueous aluminum nitrate solutions in a pH range of 3–4.5 using hexa-methylene-tetramine as the base generator at ambient temperature. By examining the zeta potential and rheological properties of aqueous suspensions of the powder with different Al-coverage, it was observed that the coated powder begins to show alumina-like surface properties at an Al-coverage of 0.1 mg/m2, in contrast to 0.5 mg/m2 that was the minimum value reported earlier for observing the effect. This is explained by proposing a coating mechanism which proceeds through adsorption of a layer of cationic hydrolysed aluminum molecules, such as Al(OH)(H2O)5]2+ and Al2(OH)2(H2O)8]4+, during which the particles attain alumina-like surface charge properties. The modified powder retained alumina-like surface characteristics when stored under moist conditions and in acidic suspensions. The low value of Al-coverage and the resulting low increase (<10%) of powder surface area are advantageous for preparation of concentrated SiC and SiC–Al2O3 composite suspensions in acidic aqueous medium with rheological properties similar to that of their counterparts containing alumina only. |
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