| 摘要 |
PURPOSE:To obtain the titled powder having excellent whiteness and filling effect in resins and being suitable as a material for plastic teeth in dental use by heating silicon nitride powder having high conversion rate to alpha-form at high temp. in the presence of gaseous chlorine, then heating further at high temp. in the presence of N2. CONSTITUTION:Silicon nitride powder having >=30% rate of conversion to alpha- form, which is prepd. by the nitridation of metallic Na is heated at >=1,100 deg.C in the presence of gaseous chlorine to remove iron contained therein completely and to whiten the product. Then, the treated silicon nitride is heated at >=1,200 deg.C in the presence of gaseous N2 to improve the whiteness further, and target white silicon nitride powder is obtd. Obtd. silicon nitride powder has superior suitability for filling resin and >=ca.80 deg. Hunter whiteness. Therefore, it is suitable for use for other teeth besides the molars when it is used for plastic dental material.
|
