Silicon carbide (SiC) foam is an ideal monolith catalyst carrier material for excellent properties such as high strength, high temperature resistance, wear resistance, corrosion resistance, oxidation resistance, high heat transfer coefficient, low thermal expansion factor, good thermal shock resistance and chemical inert. In order to improve the specific surface area, the aluminum film was prepared on the surface of silicon carbide (SiC) ceramic foam by electrophoretic technique and vacuum sintering. After anodic oxidation of the aluminum film, the porous alumina film was obtained on the surface of SiC ceramic foam. The effects of parameters of electrophoretic deposition, sintering and anodic oxidation processes on the final alumina film were investigated. The main results are as follows:
The investigation of electrophoretic deposition process shows: (1) the optimized composition of suspension was ethanol + 3g/L PVB + 3g/L PE+0.6wt% Al; (2) in order to achieve a good aluminum film, the optimized electrophoresis parameters are the current 6mA, electrical field strength less than 150/cm, deposition time less than 5min; (3) the non-uniform phenomenon of the aluminum film can be avoided when the deposition processes were conducted in a device with boundary limited flow field.
The researches of the sintering behavior of aluminum film indicate that: (1) the integral aluminum film and the alumina fiber were detected respectively when the samples were sintered in the vacuum and argon atmosphere. Hence, the vacuum sintering should be chosen for the subsequent anodic oxidation treatment; (2) the sintering temperature should be controlled at 960~1000℃ with the aim to improve the interface between aluminum film and silicon carbide and to obtain high quality aluminum film; (3) NaOH solution treatment can be used for adjusting Si content on the surface of strut of SiC foam and consequently controlling the silicon content in aluminum films.
The investigations of anodic oxidation of aluminum film reveal that: (1) the porous alumina film with 18nm pore diameter and 7×1010/cm2 pore density could be prepared by anodic oxidation, and the specific surface area of SiC foam can be enlarged by a factor of seven; (2) the anodic oxidation voltage is a critical factor to determine the shape of anodic alumina film, porous-type film and barrier-type film can be respectively obtained when the voltage is higher or lower than the critical value. In this experiment, the critical voltage value is between 30~40V.
修改评论