Wetting of solid Iron, nickel and platinum by liquid MnO-SiO_2 and CaO-AI_2O_3-SiO_2

摘要

Wetting of solid metals-iron, nickel and platinum, by molten MnO-SiO_2 (MS) and CaO-Al_2O_3-SiO_2 (CAS) oxide systems was studied by the sessile drop method at 1 350-1 450℃ in reducing atmosphere. Terminal contact angles (after 240 min) for MS system were: for iron substrates-5±2deg at 1 350℃, 9±2deg at 1 390℃, 6±2deg at 1 450℃; platinum-15±2deg at 1 350℃ and 1 390℃, and 12±2 deg at 1 450℃. Contact angle for the Ni-MS system was close to zero-3±2 deg at 1 350℃ and 1 390℃. Contact angles with CAS system were: iron-55±2deg (1 350℃), 60±2 deg (1 390℃), 44±2deg (1 450℃); nickel-59±2 deg (1 350℃), 60±2 deg (1 390℃); and platinum-15±2 deg (1 350℃, 1 390℃ and 1 450℃). Work of adhesion for all substrates with MS system was 910 to 930mJ/m~2. Interfacial tension with MS system was 1 480mN/m for Ni at 1 350 to 1 390℃, and 1 880 to 1 890mN/m for Pt in the temperature range 1 350 to 1450℃. For iron, interfacial tension was 1720mN/m at 1 350℃; 1 580 mN/m at 1 390℃ and 1 450℃. 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.