INTERFACE REACTION BETWEEN OXIDE GLASSES AND FE-AL-SI MAGNETIC ALLOY

The interface reactions between oxide glasses and magnetic alloy, Fe-A l-Si (so-called Sendust), were analysed. The oxide glasses used were S iO2-PbO, SiO2-Na2O, SiO2-Li2O and B2O3-Na2O binary glasses. It was obs erved that the lattice constant of the alloy decreases and the saturat ion magnetic-flux density of the alloy increases on reaction with the glasses. It was found that the aluminium atoms in the alloy diffuse to the interface and dissolve into the glass melt as Al3+ ions, leading to the iron-rich composition of the alloy. On the other hand, Pb2+, Na + and H+ ions in the molten glasses were reduced at the interface. Met allic lead particles about 20 mum in diameter were found to be dispers ed in the SiO2-PbO melt. Reduced sodium was thought to evaporate from the SiO2-Na2O melt, and H-2 gas bubbles were observed at the interface between B2O3-Na2O melt and the alloy. These reactions were analysed b ased on the standard free energy diagrams of oxidation-reduction react ion, and expressed as 3Pb(glass)2+ + 2Al(alloy) --> 3Pb + 2Al(glass)3 3Na(glass)+ + Al(alloy) --> 3Na + Al(glass)3+ 6H(glass)+ + 2Al(alloy) --> 3H-2 + 2Al(glass)3