Wetting of Solid Iron, Nickel and Platinum by Liquid MnO–SiO2 and CaO–Al2O3–SiO2
Wetting of solid metals-iron, nickel and platinum, by molten MnO-SiO 2 (MS) and CaO-Al 2 O 3 -SiO 2 (CAS) oxide systems was studied by the sessile drop method at 1 350-1 450°C in reducing atmosphere. Terminal contact angles (after 240 min) for MS system were: for iron substrates-5Ϯ2 deg at 1 350°C, 9Ϯ2 deg at 1 390°C, 6Ϯ2 deg at 1 450°C; platinum-15Ϯ2 deg at 1 350°C and 1 390°C, and 12Ϯ2 deg at 1 450°C. Contact angle for the Ni-MS system was close to zero-3Ϯ2 deg at 1 350°C and 1 390°C. Contact
... angles with CAS system were: iron-55Ϯ2 deg (1 350°C (1 390°C) ; and platinum-15Ϯ2 deg (1 350°C, 1 390°C and 1 450°C). Work of adhesion for all substrates with MS system was 910 to 930 mJ/m 2 . Interfacial tension with MS system was 1 480 mN/m for Ni at 1 350 to 1 390°C, and 1 880 to 1 890 mN/m for Pt in the temperature range 1 350 to 1 450°C. For iron, interfacial tension was 1 720 mN/m at 1 350°C; 1 580 mN/m at 1 390°C and 1 450°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. Table 3 . Surface tension of metals and oxides. Table 4. Interfacial tensions for MS and CAS systems with Fe, Ni and Pt (mN/m).