480
Z. Qi and Z. F. Yuan
the metal/ceramic system at high temperature has also been studied extensively, but
it mainly concentrates on the chemical composition of solid or liquid phases, liquidsolid interface reaction, and the experimental furnace conditions. Ma et al. [10]
investigated the wetting between molten tin and CuFeNiCoCr high-entropy alloy
substrate at 573–973 K. The wetting process was divided into three stages. The first
stage occurs in the temperature range of 573–673 K. The wetting between molten
tin and substrate was poor due to the oxidation of the substrate surface. In the second stage, the oxidation film was dissolved by the reaction between molten tin and
the Cu-rich phase in the substrate, which improved the wetting at 673–723 K. The
temperature of the third stage was 723–973 K. Tin atoms passed through the Cu-rich
phase and initiated a variety of chemical reactions; therefore, the equilibrium contact
angle further decreased with the increasing temperature. The surface roughness of
most materials varies greatly in practical application; however, the theory about the
effect of roughness on the wettability of metal/ceramic non-reactive wetting system
is not perfect. Therefore, it is of great significance to study the influence of surface
roughness on interfacial wettability of molten metals at high temperature.
In this paper, lead with low melting point, good stability, and strong anti-oxidation
ability were selected as the research object. The surface roughness of alumina substrate was taken as the variable, and the wetting behavior of liquid lead on the surface
of alumina substrate was studied in detail. The mechanism of roughness affecting
wetting behavior was illustrated on the basis of the Wenzel equation, and the effect
of roughness on surface tension was studied which provided a theoretical basis for
improving the wettability of metal and alumina.
Experimental Materials and Methods
Surface Roughness Measurements of Alumina Substrate
Alumina with a purity of 99.95% was chosen as the substrate to study the relationship between surface roughness and liquid lead wettability. The alumina substrate
was processed into four sets of sheets having different roughness, and the size was
20 × 20 × 2 mm. It was pre-acid cleaned by ultrasonic cleaner for 3–5 min, then
ultrasonically cleaned in acetone, absolute ethanol, and deionized water for 20 min
in sequence, dried and placed in a drying cabinet to remove water vapor from the
surface. The 3D morphology and roughness parameters (Ra indicates the height of
peaks and the depth of valleys along a mean line, which was used as a measure of
surface roughness.) of alumina substrate surface were measured by confocal laser
scanning microscope (CLSM).
Z. Qi and Z. F. Yuan
the metal/ceramic system at high temperature has also been studied extensively, but
it mainly concentrates on the chemical composition of solid or liquid phases, liquidsolid interface reaction, and the experimental furnace conditions. Ma et al. [10]
investigated the wetting between molten tin and CuFeNiCoCr high-entropy alloy
substrate at 573–973 K. The wetting process was divided into three stages. The first
stage occurs in the temperature range of 573–673 K. The wetting between molten
tin and substrate was poor due to the oxidation of the substrate surface. In the second stage, the oxidation film was dissolved by the reaction between molten tin and
the Cu-rich phase in the substrate, which improved the wetting at 673–723 K. The
temperature of the third stage was 723–973 K. Tin atoms passed through the Cu-rich
phase and initiated a variety of chemical reactions; therefore, the equilibrium contact
angle further decreased with the increasing temperature. The surface roughness of
most materials varies greatly in practical application; however, the theory about the
effect of roughness on the wettability of metal/ceramic non-reactive wetting system
is not perfect. Therefore, it is of great significance to study the influence of surface
roughness on interfacial wettability of molten metals at high temperature.
In this paper, lead with low melting point, good stability, and strong anti-oxidation
ability were selected as the research object. The surface roughness of alumina substrate was taken as the variable, and the wetting behavior of liquid lead on the surface
of alumina substrate was studied in detail. The mechanism of roughness affecting
wetting behavior was illustrated on the basis of the Wenzel equation, and the effect
of roughness on surface tension was studied which provided a theoretical basis for
improving the wettability of metal and alumina.
Experimental Materials and Methods
Surface Roughness Measurements of Alumina Substrate
Alumina with a purity of 99.95% was chosen as the substrate to study the relationship between surface roughness and liquid lead wettability. The alumina substrate
was processed into four sets of sheets having different roughness, and the size was
20 × 20 × 2 mm. It was pre-acid cleaned by ultrasonic cleaner for 3–5 min, then
ultrasonically cleaned in acetone, absolute ethanol, and deionized water for 20 min
in sequence, dried and placed in a drying cabinet to remove water vapor from the
surface. The 3D morphology and roughness parameters (Ra indicates the height of
peaks and the depth of valleys along a mean line, which was used as a measure of
surface roughness.) of alumina substrate surface were measured by confocal laser
scanning microscope (CLSM).