Claims
- 1. Process of preparing a ferrite composition with a final ferrous iron content of about 1.5% from ferrite material in a mixture with ranges of 52-55 mole percent Fe.sub.2 O.sub.3, 26-32 mole percent MnO and 15-20 (22) mole percent ZnO, the process comprising the steps of:
- a. weighing powders for setting a desired final ferrite powder composition;
- b. first milling said ferrite powder composition in a stainless steel mill with stainless steel media for intimate mixing of said ferrite powder composition and controlled iron pick-up;
- c. calcining said ferrite powder composition for a first time interval under a flowing inert atmosphere providing for formation of ferrite spinal structures in a ferrite reaction of ferric iron to ferrous iron reduction; and,
- d. second ball milling said calcined ferrite powder composition in a stainless steel mill with stainless steel media for a second time interval providing particle reduction and additional ferrous iron pick-up yielding an optimum final ferrous iron content of about 1.5% in said final ferrite powder composition.
- 2. Process of claim 1 wherein said inert atmosphere is nitrogen.
- 3. Process of claim 1 wherein the temperature of said calcining step is in a range of 900 degrees to 1100 degrees centigrade.
- 4. Process of claim 3 wherein said temperature is lower for larger pick-ups of ferrous iron during said first milling.
- 5. Process of claim 1 wherein said first time interval is one to ten hours.
- 6. The process of claim 1 wherein said second time interval is one to four hours.
- 7. Process of claim 1 comprising the step of cooling said calcined mixture in an inert flowing atmosphere.
- 8. Process of claim 6 wherein said mixture is cooled to a temperature of 150.degree. C. or less.
- 9. Process of claim 7 wherein said atmosphere is nitrogen.
- 10. In process of preparing a desired final ferrite composition with a desired final ferrous iron content from ferrite material of a powder mixture in ranges of 52-55 mole percent Fe.sub.2 O.sub.3, 26-32 mole percent MnO and 15-20 (22) mole percent ZnO including weighing said powders for setting said desired final ferrite composition, an improvement comprising:
- a. incorporating controlled iron pick-up during a first milling of said ferrite composition in a stainless steel mill with stainless steel media during intimate mixing of said ferrite powder composition;
- b. said controlled iron pick-up acting as a catalyst for ferric iron to ferrous iron reduction during calcining of said ferrite composition for a first time interval under a flowing inert atmosphere providing for formation of ferrite spinal structures in a ferrite reaction; and,
- c. providing particle reduction and additional ferrous iron pick-up during a second milling operation yielding an optimum final ferrous iron content of about 1.5% in said final ferrite composition during said second ball milling said calcined ferrite composition in a stainless steel mill with stainless steel media for a second time interval.
CROSS REFERENCES TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. Ser. No. 566,872, filed Dec. 29, 1983.
US Referenced Citations (7)
Foreign Referenced Citations (2)
Number |
Date |
Country |
210820 |
Oct 1956 |
AUX |
2158804 |
Nov 1971 |
DEX |
Continuation in Parts (1)
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Number |
Date |
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Parent |
566872 |
Dec 1983 |
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