2009 Volume 49 Issue 6 Pages 788-795
Wetting of solid metals—iron, nickel and platinum, by molten MnO–SiO2 (MS) and CaO–Al2O3–SiO2 (CAS) oxide systems was studied by the sessile drop method at 1350–1450°C in reducing atmosphere. Terminal contact angles (after 240 min) for MS system were: for iron substrates—5±2 deg at 1350°C, 9±2 deg at 1390°C, 6±2 deg at 1450°C; platinum—15±2 deg at 1350°C and 1390°C, and 12±2 deg at 1450°C. Contact angle for the Ni–MS system was close to zero—3±2 deg at 1350°C and 1390°C. Contact angles with CAS system were: iron—55±2 deg (1350°C), 60±2 deg (1390°C), 44±2 deg (1450°C); nickel—59±2 deg (1350°C), 60±2 deg (1390°C); and platinum—15±2 deg (1350°C, 1390°C and 1450°C). Work of adhesion for all substrates with MS system was 910 to 930 mJ/m2. Interfacial tension with MS system was 1480 mN/m for Ni at 1350 to 1390°C, and 1880 to 1890 mN/m for Pt in the temperature range 1350 to 1450°C. For iron, interfacial tension was 1720 mN/m at 1350°C; 1580 mN/m at 1390°C and 1450°C. Lower work of adhesion and higher interfacial tension were found for metals with CAS system. Reduction of MnO from MS system was observed, leading to Mn dissolution in metal substrates. Degree of silica reduction from MS system was much smaller in comparison with MnO reduction (negligible for Pt); it was very minor from CAS system. Reduction of oxides and adsorption of oxygen modify the metal–oxide interface, making wetting dynamic and profoundly affecting interfacial properties.