| 摘要 |
PURPOSE:To efficiently form a nonconductor film having an excellent insulating characteristic on a substrate contg. Nb in the surface layer to a uniform thickness by subjecting the substrate to a surface treatment with an aq. nitric acid soln. CONSTITUTION:The surface of the substrate 1 having Nb (alloy) as its surface layer is subjected to the surface treatment by using the aq. nitric acid soln. and by a immersion method or spraying method such as spraying or anodic oxidation method using the substrate 1 as an anode. Nb in the above-mentioned treatment is converted to oxide and if iron, Ni, etc., are incorporated as the other materials in the surface layer, the iron and Ni dissolve and the nonconductor film 2 essentially consisting of the oxide Nb2O5 of Nb is formed on the surface of the substrate 1 to a uniform thickness. This method is, therefore, particularly adequate for the efficient formation of the nonconductor film with high efficiency with good insulating property on the thin magnetic core surface having laminated structure.
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