International Business Machines Corporation

Ralph W Scheidecker

Robert R Suchomel

Eugene B Rigby

Process of calcining the ball milling manganese zinc MnZn, ferrite material for achieving a ferrite having a ferrous iron content appropriate for optimum magnetic properties. A first initial ball milling step is very carefully controlled as a small amount of metallic iron is blended into an initial mixture which is a catalyst for the ferrous iron reduction reaction during a calcine step. This provides for a predetermined ferrous iron content to be set in the powder prior to any forming or firing steps. The process includes a controlled atmosphere, time, and temperature for the calcining process step, and a second controlled ball milling step over time where the interaction of the stainless steel balls and milled slurry contributes to final ferrous iron content. These two process steps are balanced yielding a MnZn ferrite powder of a predetermined particle size with a controlled ferrous iron content which is a function of both the calcining and ball milling steps.

Process for controlling ferrous iron content in manganese zinc ferrite

Process of hot isostatic pressing of MnZn ferrite material for producing ferrite close to theoretical density without a significant increase in grain size. Permeability is increased with the increase in theoretical density. The process includes the steps of pressurizing an entire ferrite sample which is surrounded by pieces of similar composition while in alumina crucibles with fused alumina grain there between and an optional oxygen getter on top of the grain, introducing an inert atmosphere, elevating pressure and temperature, the temperature elevated to a value below that previously used for sintering or hot pressing, and maintaining temperature to optimize density without excess grain growth. Density is thereby optimized without excess grain growth, while maintaining or improving the magnetic properties.

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Byron, MN, United States of America

Ralph W Scheidecker