Jean M Berchtold

39897940, Nov 2, 1976

May 18, 1973

5/361698

Jean Berchtold - La Jolla CA

Eastman Kodak Company - Rochester NY

C04B 3560
C04B 3526

264332

A process for preparing ferrite materials exhibiting an excellent combination of physical and magnetic properties is disclosed. In this process a ferrite powder is formed and subsequently sintered while exerting a mechanical pressure of about 5 to about 500 kg. per square centimeter on the ferrite. The oxygen content of the ferrite is maintained substantially stoichiometric throughout the process by controlling the oxygen content of the ambient atmosphere. Temperatures in the range of about 1100. degree. to about 1400. degree. C during sintering are disclosed. New ferromagnetic ferrite compacts which can be prepared by this process are characterized by an oxygen content which is substantially stoichiometric and a porosity no greater than about 0. 4%.

41013484, Jul 18, 1978

Dec 29, 1975

5/645177

Jean Berchtold - La Jolla CA

Spin Physics - San Diego CA

H01F 102

148105

Aluminum-silicon-iron alloys exhibiting an excellent combination of properties are disclosed. The process for preparing these alloys is also disclosed. In this process an aluminum-silicon-iron alloy powder is formed, sintered and hot-pressed simultaneously with or after sintering. The alloy powder can contain 4-9%, by weight, aluminum, 8-11%, by weight, silicon and the remainder iron. Pressures for hot-pressing of at least 1000 psi. and sintering temperatures of at least 1205. degree. C are disclosed. The process can also include the additional step of nitriding the alloy powder prior to sintering. Such nitriding prevents or retards grain growth during sintering and provides increased electrical resistivity and hardness in the end product.

39992160, Dec 21, 1976

Jul 30, 1970

5/059512

Jean Berchtold - La Jolla CA

Eastman Kodak Company - Rochester NY

G11B 522
G11B 514

360125

A magnetic head assembly wherein the material of the pole tips or of the pole pieces comprises a hot-pressed sintered iron-silicon-aluminum alloy, the particles of such alloy preferably being provided with a nitride layer or coating prior to sintering for preventing or retarding grain growth during sintering and to provide increased electrical resistivity and hardness in the end product. The preferred hot-pressed sintered material is characterized by a substantially uniform grain size most preferably of between about 40 microns and 60 microns, a porosity of substantially less than one percent, a Vickers hardness greater than 600, and a resistivity of at least about 100 micro-Ohm-cm. A method of making such a sintered material preferably comprises heating an iron-silicon-aluminum alloy powder in an atmosphere of nitrogen to form a nitride layer thereon, blending 80% of such nitrided alloy powder with from about 10 to 20% of elemental iron, silicon and aluminum powders, without varying the composition from that desired in the final alloy, and heating the mixture to a sintering temperature while applying a pressure of about 1000 pounds per square inch.

39487857, Apr 6, 1976

May 18, 1973

5/361697

Jean Berchtold - La Jolla CA

C04B 3530
C04B 3538

252 6262

A process for preparing ferromagnetic ferrite powder is disclosed. According to this process, solid ferrite forming metal compounds are calcined and subsequently sintered while the oxygen content of the ambient atmosphere is controlled to maintain the oxygen content of the ferrite substantially stoichiometric throughout the process. As disclosed herein, metal oxides can be used as the ferrite forming metal compounds and the oxygen in the ambient atmosphere can be controlled during calcining and sintering by using a flowing stream of nitrogen gas containing 0 to about 1%, by volume, of oxygen. Ferromagnetic ferrite powders obtained by this process exhibit substantially uniform mircostructures and oxygen contents which are substantially stoichiometric. Examples of ferrite powders which are prepared by the process include manganese zinc ferrite and nickel zinc ferrite.