Abstract: This disclosure sets forth a microwave sintering process for green oxide particles introduced from a source such as a hopper or a container, a downwardly directed funnel and a discharge outlet from the funnel. Particles are introduced into an elongate rotatable tube. The tube is inclined at a controlled angle. Particles traverse the tube, passing through a central heating zone between inlet and outlet. The time interval of the particles in the heating zone is controlled by adjustment of the angle of inclination, particle size, and rotation rate to assure that all particles are processed and converted from green to sintered oxide particles.

Abstract: The present disclosure is directed to a method of converting the preferred hydrated alumina oxide, boehmite, into a green particle which is then sintered to form an abrasive alumina particle. The process involves dispersing boehmite in water at a slightly elevated temperature with an acidic pH, then seeding it with alumina seed particles and drying it, then crushing to desired shapes and sizes, calcining the dried precipitate and sintering the calcined material. This forms high quality alumina abrasive grains. The apparatus used for sintering incorporates an elongate hollow tube, an insulative sleeve thereabout to define an elevated temperature zone, and a microwave generator coupled through a wave guide into a microwave cavity incorporated in the tube. The particles are moved through the tube at a controlled rate to assure adequate exposure to the microwave radiation.

Abstract: The present disclosure is directed to a method of converting the preferred hydrated alumina oxide, boehmite, into a green particle which is then sintered to form an abrasive alumina particle. The process involves dispersing boehmite in water at a slightly elevated temperature with an acidic pH, then seeding it with alumina seed particles and drying it, then crushing to desired shapes and sizes, calcining the dried precipitate and sintering the calcined. This forms a high quality alumina abrasive grains. The apparatus used for sintering incorporates an elongate hollow tube, an insulative sleeve thereabout to define an elevated temperature zone, and a microwave generator coupled through a wave guide into a microwave cavity incorporated in the tube. The particles are moved through the tube at a controlled rate to assure adequate exposure to the microwave radiation.