Abstract
As the fundamental study of wetting phenomena accompanied by a solid/liquid interface reaction, the contact angle θ of liquid Al drops on sintered MgO (purity: 96.85%) was measured in an atmosphere of He+3%H2 at 1173∼1333 K.
From the changes of θ on a logarithmic scale of time, it has become clear that the wetting of this system has three stages as follows.
(1) Early stage. (2) apparent steady stage, and (3) contact angle decreasing stage accompanied by chemical reaction. And the reaction zone is a spinel structure (MgO·Al2O3).
Further, by investigating the changes of contact angle θ and solid/liquid interface diameter 2x, it has been confirmed that the third stage has the following two cases: (1) with spread (advancing contact angle) and (2) without spread (receding contact angle).
Therefore it is proposed that the condition of wetting extension is defined as
dθ⁄dt<0 and d(2x)⁄dt>0
