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- Nachgewiesen in: USPTO Patent Grants
- Sprachen: English
- Patent Number: 7,276,226
- Publication Date: October 02, 2007
- Appl. No: 10/525939
- Application Filed: August 22, 2003
- Assignees: Tata Institute of Fundamental Research (Mumbai, IN)
- Claim: 1. A substantially pure bulk chromium dioxide (CrO 2) having saturation magnetization of at least 120 emu/gm.
- Claim: 2. The substantially pure bulk chromium dioxide according to claim 1 having saturation magnetization of 126 emu/gm when synthesized in pellet form.
- Claim: 3. The substantially pure bulk chromium dioxide according to claim 1 having saturation magnetization of 132 to 135 emu/gm when synthesized in powder form.
- Claim: 4. The substantially pure bulk chromium dioxide according to claim 1 , which is in polycrystalline form.
- Claim: 5. The substantially pure bulk chromium dioxide according to claim 4 having negative magnetoresistance of at least 2% at about room temperature at 2 Tesla.
- Claim: 6. The substantially pure bulk chromium dioxide according to claim 1 having negative magnetoresistance of at least 0.5% at about room temperature at 2 Tesla.
- Claim: 7. The substantially pure bulk chromium dioxide according to claim 6 having negative magnetoresistance of at least 2% at about room temperature at 2 Tesla.
- Claim: 8. The substantially pure bulk chromium dioxide according to claim 7 having negative magnetoresistance of about 5% at about room temperature at 2 Tesla.
- Claim: 9. The substantially pure bulk chromium dioxide according to claim 1 , wherein said bulk CrO 2 comprises sintered pellets.
- Claim: 10. Bulk composites of chromium dioxide and chromium sesquioxide (CrO 2 /Cr 2 O 3) having negative magnetoresistance of at least 0.5% at about room temperature at 2 Tesla.
- Claim: 11. The bulk composites according to claim 10 , having negative magnetoresistance of at least 2% at about room temperature at 2 Tesla.
- Claim: 12. The bulk composites according to claim 11 , having negative magnetoresistance of at least 5% at about room temperature at 2 Tesla.
- Claim: 13. The bulk composites according to claim 12 , having negative magnetoresistance of 8% at about room temperature at 2 Tesla for a 25% molar Cr 2 O 3 composite, which is cold pressed.
- Claim: 14. The bulk composites according to claim 12 , having negative magnetoresistance of 33% at about room temperature at 2 Tesla for a 40% molar Cr 2 O 3 composite, which is sintered.
- Claim: 15. The bulk composites according to claim 10 , having saturation magnetization of 75 emu/gm at 5K for a sintered 40% molar Cr 2 O 3 composite.
- Claim: 16. The bulk composites according to claim 10 , having saturation magnetization of 103 emu/gm at 5K for a cold pressed composite of 25% molar Cr 2 O 3 .
- Claim: 17. The bulk composites according to claim 10 , which can be obtained in powder form and in pellet form.
- Claim: 18. The bulk composites according to claim 10 , which is homogenous.
- Claim: 19. The bulk composites according to claim 10 , which is obtainable in any ratio of the constituent compounds.
- Claim: 20. The bulk composites according to claim 10 , which has substantial reproducibility in sintered form.
- Claim: 21. Bulk composites of chromium dioxide and Cr 2 O 5 (CrO 2 /Cr 2 O 5) having negative magnetoresistance of at least 0.5% at about room temperature at 2 Tesla.
- Claim: 22. The bulk composites according to claim 21 , having negative magnetoresistance of at least 2% at about room temperature at 2 Tesla.
- Claim: 23. The bulk composites according to claim 22 , having negative magnetoresistance of at least 5% at about room temperature at 2 Tesla.
- Claim: 24. The bulk composites according to claim 23 , having negative magnetoresistance of about 8% at 2T at about room temperature for a sintered composite with 80 emu/g M s .
- Claim: 25. The bulk composites according to claim 23 , having negative magnetoresistance of about 22% at 2T at about room temperature for a sintered composite with 60 emu/g M s .
- Claim: 26. The bulk composites according to claim 21 , which can be obtained in powder form and in pellet form.
- Claim: 27. The bulk composites according to claim 21 , which is homogenous.
- Claim: 28. The bulk composites according to claim 21 , which is obtainable in any ratio of the constituent compounds.
- Claim: 29. The bulk composites according to claim 21 , which has substantial reproducibility in sintered form.
- Claim: 30. A process for manufacture of substantially pure bulk chromium dioxide (CrO 2), or composites of chromium dioxide and chromium sesquioxide (CrO 2 /Cr 2 O 3) or composites of chromium dioxide and Cr 2 O 5 (CrO 2 /Cr 2 O 5) comprising heating an intermediate oxide, primarily Cr 8 O 21 , from about room temperature to a temperature of between 350 and 500° C. for a period of between 1-5 hours whereby substantially pure chromium dioxide (CrO 2), or composites of chromium dioxide or chromium sesquioxide (CrO 2 /Cr 2 O 3) or composites of chromium dioxide and Cr 2 O 5 (CrO 2 /Cr 2 O 5) are formed.
- Claim: 31. The process according to claim 30 , wherein intermediate oxide is converted to said substantially pure chromium dioxide CrO 2 when the temperature is maintained between 390-400° C. or to a composite of chromium dioxide and chromium sesquioxide (CrO 2 /Cr 2 O 3) when the temperature is maintained between 400-500° C. or to a composite of chromium dioxide and Cr 2 O 5 (CrO 2 /Cr 2 O 5) when the temperature is maintained between 350-390° C.
- Claim: 32. The process according to claim 30 , wherein intermediate oxide, primarily Cr 8 O 21 used in the process of the invention is prepared by heating CrO 3 and maintaining the temperature in the range of 230-320° C.
- Claim: 33. The process according to claim 32 , wherein in the composites of CrO 2 /Cr 2 O 3 and CrO 2 /Cr 2 O 5 , the mass fraction of Cr 2 O 3 or Cr 2 O 5 can be systematically varied by varying the temperature between 350 and 500° C.
- Claim: 34. The process according to claim 30 , wherein said CrO 3 is heated and maintained in the said temperature range for 6-14 hours.
- Claim: 35. The process according to claim 34 , wherein CrO 3 is heated in dry oxygen/air.
- Claim: 36. The process according to claim 34 , wherein CrO 3 is heated at about atmospheric pressure.
- Claim: 37. The process according claim 34 , wherein CrO 3 is heated to raise the temperature to about 250° C. and then maintained in the said temperature range.
- Claim: 38. The process according to claim 30 , wherein intermediate oxide thus formed is cooled to about room temperature at the same rate as it was heated.
- Claim: 39. The process according to claim 30 , wherein the intermediate oxide is crushed into powder form prior to heating.
- Claim: 40. The process according to claim 30 , wherein, prior to heating, the intermediate oxide in powder form is sealed in an inert tube or can be pelletized and sintered before sealing in an inert tube.
- Claim: 41. The process according to claim 30 , wherein the temperature of intermediate oxide is maintained in the temperature range between 350 and 500° C. for 2-3 hrs.
- Claim: 42. The process according to claim 30 , wherein intermediate oxide, primarily Cr 8 O 21 used in the process of the invention is prepared by heating CrO 3 and maintaining the temperature in the range of 250-280° C.
- Claim: 43. The process according to claim 30 , wherein said CrO 3 is heated and maintained in the said temperature range for 8-12 hours.
- Claim: 44. A substantially pure bulk chromium dioxide (CrO 2) manufactured by a process for manufacture of substantially pure chromium dioxide (CrO 2), or composites of chromium dioxide and chromium sesquioxide (CrO 2 /Cr 2 O 3) or composites of chromium dioxide and Cr 2 O 5 (CrO 2 /Cr 2 O 5) comprising heating an intermediate oxide, primarily Cr 8 O 21 from about room temperature to a temperature of between 350 and 500° C. for a period of between 1-5 hours whereby substantially pure chromium dioxide (CrO 2), or composites of chromium dioxide or chromium sesquioxide (CrO 2 /Cr 2 O 3) or composites of chromium dioxide and Cr 2 O 5 (CrO 2 /Cr 2 O 5) are formed.
- Claim: 45. Bulk composites of chromium dioxide and chromium sesquioxide (CrO 2 /Cr 2 O 3) manufactured by a process for manufacture of substantially pure chromium dioxide (CrO 2), or composites of chromium dioxide and chromium sesquioxide (CrO 2 /Cr 2 O 3) or composites of chromium dioxide and Cr 2 O 5 (CrO 2 /Cr 2 O 5) comprising heating an intermediate oxide, primarily Cr 8 O 21 from about room temperature to a temperature of between 350 and 500° C. for a period of between 1-5 hours whereby substantially pure chromium dioxide (CrO 2), or composites of chromium dioxide or chromium sesquioxide (CrO 2 /Cr 2 O 3) or composites of chromium dioxide and Cr 2 O 5 (CrO 2 /Cr 2 O 5) are formed.
- Claim: 46. Bulk composites of chromium dioxide and CrO 5 (CrO 2 /Cr 2 O 5) manufactured by a process for manufacture of substantially pure chromium dioxide (CrO 2), or composites of chromium dioxide and chromium sesquioxide (CrO 2 /Cr 2 O 3) or composites of chromium dioxide and Cr 2 O 5 (CrO 2 /Cr 2 O 5) comprising heating an intermediate oxide, primarily Cr 8 O 21 from about room temperature to a temperature of between 350 and 500° C. for a period of between 1-5 hours whereby substantially pure chromium dioxide (CrO 2), or composites of chromium dioxide or chromium sesquioxide (CrO 2 /Cr 2 O 3) or composites of chromium dioxide and Cr 2 O 5 (CrO 2 /Cr 2 O 5) are formed.
- Current U.S. Class: 423/607
- Patent References Cited: 3117093 January 1964 Arthur, Jr. et al. ; 3449073 June 1969 Balthis, Jr. ; 3979310 September 1976 Montiglio et al. ; 4092439 May 1978 Demazeau et al. ; 4126714 November 1978 Haines ; 4428852 January 1984 Covington et al. ; 5378383 January 1995 Jachow et al. ; 1274880 May 1972
- Other References: The English abstract of GB 1,343,622 A published Jan. 16, 1974. cited by examiner ; P. G. Ivanov et al. “Epitaxial growth of CrO2 thin films by chemical-vapor deposition from a Cr8O21 precursor” Journal of Applied Physics, vol. 89, No. 2 (Jan. 15, 2001), pp. 1035-1040. cited by examiner ; L. Ranno et al. “Production and magnetotransport properties of CrO2 films” Journal of Applied Physics, vol. 81, (8) (Apr. 15, 1997), pp. 5774-5776. cited by examiner ; J. Dai et al. “Junction-like magnetoresistance of intergranular tunneling in field-aligned chromium dioxide powders” Physical Review B, vol. 63 (2001) pp. 054434-1 to 054434-4. cited by examiner
- Primary Examiner: Vanoy, Timothy C.
- Attorney, Agent or Firm: Akerman Senterfitt ; Pendorf, Stephen A.
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