Nobuyuki Mori1, Shiki Matsuo2, Keisaku \=Ogi1 and Kimio Matsuda3
1Faculty of Engineering, Kyushu University, Fukuoka
The effect of Ni ion plating 0.05~25 μm thick to graphite and of 1~4%Ni addition to Al on the wettability of molten Al to graphite was measured by the sessile drop method in vacuum at temperatures from 973 K to 1273 K.
The wetting angle between molten Al and graphite was hardly changed by the Ni addition to Al, and decreased with increasing temperature.
On the contrary, Ni coating from the thickness of 0.1 μm up to graphite substrates remarkably improved the wettability of molten Al, and Ni coating thicker than 1 μm made the wetting angle below 30°ree at any temperature. With Ni coating of 0.1 to 1 μm thickness the wetting angle showed a tendency to increase with increasing temperature. This abnormal temperature dependence of Ni-coated substrates was considered to be due to the change in structure of the Ni coating layer with temperature. At high temperatures, Ni deposited on the substrate coagulated to produce many pores in the coating, and the wettability could be explained by Cassie's equation for the composite surface of Ni and graphite. The wetting angle became smaller than 20°ree by Ni coating of 4 to 25 μm thickness and decreased with increasing temperature, which was lower than the wetting angle of molten Al to pure Ni substrate. This was explained from the viewpoint of the shape and growth rate of the reaction zone of Ni with molten Al.
wettablity, contact angle, molten aluminum, graphite, aluminum-nickel alloy, ion plating, nickel coating, surface tension
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