| 摘要 |
The material is impregnated with an aqueous solution containing the precursors of a phosphate glass base modified by at least the presence of zinc oxide, dried and heat treated to form an internal anti-oxidative coating comprising the modified phosphate glass base. The precursors are fed into the aqueous solution so as to form a glass base wherein the molar ratio of the glass modifying oxides, including zinc oxide and glass-forming oxides, consisting of mainly or only phosphoric anhydride, is sufficiently high, particularly 0.6 or over, preferably 0.9, to make the phosphate glass base resistant to moisture corrosion. The solution is obtained by initially dissolving in water a polyphosphate such as sodium metaphosphate or trimetaphosphate capable of subsequently stably solubilising, by complexing, and without precipitate formation, the required amount of precursor salts of the modifying oxides, comprising at least one zinc salt such as zinc nitrate or sulphate.
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