| 摘要 |
PURPOSE:To maintain original characteristics of magnesia and contrive reduction in hydrating properties, by specifying powdery MgO and Al2O3 and the total amount of both and converting most of the Al2O3 into MgO.Al2O3 crystals and most of the residual MgO into periclase crystals. CONSTITUTION:This highly heat conductive magnesia based powder consists of 70-95wt.% MgO, 5-30wt.% Al2O3 and >=98.0wt.% MgO+Al2O3. The Al2O3 is mostly MgO.Al2O3 crystals and most of the residual MgO is periclase crystals. If the content of the Al2O3 is <5wt.%, hydration resistance is insufficient. If the content exceeds 30wt.%, deterioration in heat conductivity appears. If the total content of MgO+Al2O3 is <98.0wt.%, increase in dielectric loss and deterioration in heat conductivity appear. Furthermore, this powder can be produced, by e.g. calcining Mg(OH)2 to produce MgO powder, blending the resultant MgO powder with Al2O3 powder so as to provide the target composition, mixing the blend in an alcohol, drying the blend, adding a binder to form granules, firing the granules and classifying the fired granules.
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