Dilip K Das

Author:

Dilip Das

ISBN #:

0773455396

Author:

Dilip Das

ISBN #:

0793185106

Author:

Dilip K. Das

ISBN #:

0195921003

Author:

Dilip K. Das

ISBN #:

0195921283

Author:

Dilip K. Das

ISBN #:

0130309567

Author:

Dilip K. Das

ISBN #:

0130417149

Author:

Dilip K. Das

ISBN #:

0130481998

Author:

Dilip K. Das

ISBN #:

0130872105

US Patent:

48972835, Jan 30, 1990

Filed:

Jul 6, 1987

Appl. No.:

7/070634

Inventors:

Kaplesh Kumar - Wellesley MA
Dilip K. Das - Bedford MA

Assignee:

The Charles Stark Draper Laboratory, Inc. - Cambridge MA

International Classification:

B05D 100
B05D 512

US Classification:

427 34

Abstract:

A highly aligned rare-earth transition metal alloy magnet material such as samarium-cobalt (SmCo. sub. 5). The high degree of alignment is evidenced by an isolated X-ray diffraction pattern peak for Cu. sub. k. alpha. radiation at a interplane "d" spacing of 2. 0 A. degree. and is produced by very high temperature deposition of the material on a hot surface. The surface temperature is maintained well above 800 degrees centigrade and most preferably is initially set at approximately 1020 degrees centigrade or higher at which temperature the isolated diffraction pattern peak dominates. A higher temperature typically occurs during deposition. Deposition of the material on the surface typically takes place by application of the material as a fine, homogeneously sized powder to the plasma flame of a plasma torch. The surface may be preheated by the application of the plasma flame to the surface without the application of the powdered material. A feedback controlled auxiliary heat source may also be used to facilitate maintaining the temperature of the surface at the very high temperature level.

US Patent:

45334072, Aug 6, 1985

Filed:

Mar 30, 1981

Appl. No.:

6/248798

Inventors:

Dilip K. Das - Bedford MA
Kaplesh Kumar - Wellesley MA
Ernest C. Wettstein - Acton MA

Assignee:

The Charles Stark Draper Laboratory, Inc. - Cambridge MA

International Classification:

H01F 102

US Classification:

148102

Abstract:

Apparatus and method for forming radial orientation rare earth-transition metal magnets in continuous arc rings by hot isostatic pressing. A method includes the steps of compacting rare earth-transition metal powders having a particle size up to 40 microns into radially oriented rings in a mold provided with a radially aligning field, stacking a plurality of compacted radially oriented rings within an annular cavity within a sealed, evacuated cannister to form a cylinder of a predetermined height, subjecting the cannister to temperatures in the range of 900. degree. to 1150. degree. C. under a gas pressure of 15 kpsi to densify the compacts, and cooling the cannister and the compacts to room temperature. An apparatus for performing the above-described method, includes a mold for forming green compacts having a central iron core or mandrel, an outer housing forming an annular space between it and the iron mandrel, plungers for compacting into a ring rare earth-transition metal powder within the annular space, and means for forming a radially oriented magnetic field. The magnetic field forming means includes a pair of electromagnetic coils with bucking fields disposed on opposite axial ends of the annular space.

US Patent:

42605822, Apr 7, 1981

Filed:

Jul 18, 1979

Appl. No.:

6/058530

Inventors:

Kaplesh Kumar - Wellesley MA
Dilip K. Das - Bedford MA

Assignee:

The Charles Stark Draper Laboratory, Inc. - Cambridge MA

International Classification:

B29C 100

US Classification:

264111

Abstract:

Method and apparatus for the formation of a molded article from powders and powder compacts of a material by pressure compaction of the powders under the influence of a thermally driven differential volume expansion of first and second elements constraining the powders. The volume expansion achieves a trippling of the compaction effect.

US Patent:

44418744, Apr 10, 1984

Filed:

Nov 5, 1980

Appl. No.:

6/206877

Inventors:

Kaplesh Kumar - Wellesley MA
Dilip K. Das - Bedford MA

Assignee:

The Charles Stark Draper Laboratory, Inc. - Cambridge MA

International Classification:

B22F 300

US Classification:

425 78

Abstract:

Apparatus for the formation of a molded article from powders and powder compacts of a material by pressure compaction of the powders under the influence of a thermally driven differential volume expansion of first and second elements constraining the powders. The volume expansion achieves a trippling of the compaction effect.

US Patent:

46288090, Dec 16, 1986

Filed:

Aug 5, 1985

Appl. No.:

6/762708

Inventors:

Dilip K. Das - Bedford MA
Kaplesh Kumar - Wellesley MA
Ernest C. Wettstein - Acton MA

Assignee:

The Charles Stark Draper Laboratory - Cambridge MA

International Classification:

B30B 1514

US Classification:

100208

Abstract:

Apparatus and method for forming radial orientation rare earth-transition metal magnets in continuous arc rings by hot isostatic pressing. A method includes the steps of compacting rare earth-transition metal powders having a particle size up to 40 microns into radially oriented rings in a mold provided with a radially aligning field, stacking a plurality of compacted radially oriented rings within an annular cavity within a sealed, evacuated canister to form a cylinder of a predetermined height, subjecting the canister to temperatures in the range of 900. degree. to 1150. degree. C. under a gas pressure of 15 kpsi to densify the compacts, and cooling the canister and the compacts to room temperature. An apparatus for performing the above-described method, includes a mold for forming green compacts having a central iron core or mandrel, as outer housing forming an annular space between it and the iron mandrel, plungers for compacting into a ring rare earth-transition metal powder within the annular space, and means for forming a radially oriented magnetic field. The magnetic field forming means includes a pair of electromagnetic coils with bucking fields disposed on opposite axial ends of the annular space.

US Patent:

42645565, Apr 28, 1981

Filed:

Aug 27, 1979

Appl. No.:

6/070147

Inventors:

Kaplesh Kumar - Wellesley MA
Dilip K. Das - Bedford MA

International Classification:

B22F 302
B30B 502
B30B 1100

US Classification:

264314

Abstract:

A method and apparatus for thermally isostatically densifying a sample, including placing the sample to be densified into a pressure vessel filled with a thermally expansive pressurizing medium with the medium intermediate the vessel and sample; and varying the thermal energy of the medium to cause it to expand and exert increased pressure to densify the sample.

US Patent:

42973880, Oct 27, 1981

Filed:

Apr 8, 1980

Appl. No.:

6/138650

Inventors:

Kaplesh Kumar - Wellesley MA
Dilip K. Das - Bedford MA
Ernest C. Wettstein - Acton MA

Assignee:

The Charles Stark Draper Laboratory, Inc. - Cambridge MA

International Classification:

B05D 314

US Classification:

427 47

Abstract:

Process and apparatus for forming plasma sprayed high density, high coercivity permanent magnet material and permanent magnets formed therefrom. The plasma sprayed permanent magnet material is obtained in a substantially amorphous state resulting from specifically controlled plasma spray parameters. The amorphous deposition possesses high coercivity, density and potential residual magnetism. The as-sprayed magnetic material is preferably heat treated and then densified to nearly maximum theoretical density. The amorphous structure permits retention of substantially all of the coercivity after heat treatment as well as densification to well over 95% of maximum theoretical density. In addition, magnetic materials, preferably fabricated in accordance with this plasma spraying technique as an amorphous deposit of permanent magnet material, are aligned in a magnetic field and thermally aged to produce permanent magnets in the presence of a thermal gradient or mechanical strain resulting in a high coercivity permanent magnet. Controlled crystalline deposits may also be utilized as the starting material for fabrication of the aligned magnets. The invention has application primarily with the use of permanent magnets formed of rare earth-cobalt alloys and in particular of samarium-cobalt alloys.

US Patent:

40750426, Feb 21, 1978

Filed:

May 9, 1977

Appl. No.:

5/794879

Inventors:

Dilip K. Das - Bedford MA

Assignee:

Raytheon Company - Lexington MA

International Classification:

H01F 102

US Classification:

148103

Abstract:

Permanent magnets formed from rare earth cobalt compounds have high energy products. One rare earth cobalt composition, formulated by metallurgical sintering techniques, is a composition of a rare earth and cobalt such as samarium and cobalt containing about 37. 2 weight per cent samarium which corresponds to 60 proportions of SmCo. sub. 5 for each 40 proportions of Sm. sub. 2 Co. sub. 7. This composition is an excellent permanent magnet having an energy product at least as high as 15. times. 10. sup. 6 gauss-oersteds and up to 20. times. 10. sup. 6 gauss-oersteds or higher. SmCo. sub. 5 contains roughly 33. 8 weight per cent samarium, and Sm. sub. 2 Co. sub. 7 about 42. 2 weight per cent samarium; I have found that samarium-cobalt materials containing samarium between about 36. 5 weight per cent and about 38 weight per cent are preferred and can be developed into magnets of greatly improved properties. The samarium-cobalt magnet of this invention is basically comprised of crystals of SmCo. sub. 5 and Sm. sub. 2 Co. sub.