High surface area valve metal powder

Abstract

Abstract SOLID PARTICLES OF POTASSIUM FLUOTANTALATE ARE THOROUGHLY DRIED AND THEN COATED WITH MOLTEN FORM SODIUM REDUCING AGENT, THE COATING BEING ACCOMPLISHED UNDER TEMPERATURE CONDITIONS CONTROLLED TO REMAIN BELOW A TEMPERATURE WHICH WILL INITIATE THE EXOTHERMIC REDUCTION REACTION BETWEEN THESE MATERIALS. AFTER COMPLETION OF THE COATING, THE CHARGE OF PREMIXED DOUBLE SALT AND REDUCING AGENT IS THEN HEATED THROUGH THE TEMPERATURE AT WHICH THE EXOTHERMIC REDUCTION REACTION IS INITIATED. THE INITIATION OF THE EXOTHERMIC REACTION CAUSES A RAPID TEMPERATURE RISE. OVER 90% OF THE TANTALUM VALUES OF THE SALT CHARGE ARE FORMED AS ELEMENTAL TANTALUM IN PARTICLE FORM IN THE COURSE OF THE EXOTHERMICALLY DRIVEN TEMPERATURE RISE. THE CHARGE TEMPERATURE IS THEN STABILIZED IN THE RANGE OF 700*11--*C, HELD FOR A TIME AT THIS ELEVATED TEMPERATURE AND THEN SLOWLY COOLED. DURING THE TEMPERATURE RISE, TANTALUM METAL PARTICLES NUCLEATE THROUGHOUT THE MASS OF THE PREMIXED CHARGE TO FORM A CHERENT SKELECAL STRUCTURE. THIS SKELETON RESISTS SETTLING AS THE TEMPERATURE IS RAISED ABOVE THE MELTING TEMPERATURE OF THE SALT MAS, AND A SUBSTANTIALLY HOMOGENEOUS DISTRIBUTION OF TANTALUM VALUES THROUGHOUT THE REDUCTION CHARGE IS FORMED AND HIGHLY STRUCTURED TANTALUM METAL PARTICLES, SO FORMED ARE HIGHLY STRUCTURED AND CAN BE SEPARATED AS A HIGH YIELD OF HIGH SURFACE AREAHIGH CAPACTANCE TANTALUM POWDER.

Inventors

• 👤 T Mahy

Bibliographic Details