Determination of macro-contact angle and line tension at high temperatures for Au/Al₂O₃ system at 1373 K using a micro-scale wetting method

The size effect of a drop on the contact angle was discussed for the Au/Al₂O₃ system. As the size of the drop decreases, the shape of the drop closes to a sphere and the contact angle is obtained by the equation θ = cos^-1 (1 - h/R_Max.), where θ is the contact angle between the drop and substrates, h is the height of the drop and R_Max. is the maximum radius of the drop. The contact angle between liquid gold and alumina polycrystalline substrates having the roughness of 0.141 μm in RA number slightly increased as the sample size decreases to about 10 μm, yielding 134° and 3.50 × 10^-7 N as the macro-scale contact angle and the line tension, respectively.