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AssigneeTata Institute of Fundamental Research
InventorsAshna Bajpai, Arun Kumar Nigam
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A novel process for preparing chromium dioxide of substantially high purity as well as composites of CrO2/Cr2O3 and CrO2/Cr2O5 following a sequence of simple steps. The process does not require pressure as a control parameter during the process of synthesis. No chemical modifier has been used to bring down the working pressure during synthesis. Fairly hard sintered pellets of CrO2 can be obtained without introducing any detectable impurity phase that usually appears during the process of sintering. Further, CrO2/Cr2O3 and CrO2/Cr2O5 composites have also been prepared where the fraction of insulating Cr2O3 or Cr2O5 in metallic CrO2 can be easily controlled. Significant negative magnetoresistance is found in pure CrO2 (5% MR) as well as CrO2/Cr2O3 (33% MR) composites near room temperature. The MR studies on the CrO2/Cr2O5 composites have been done and significant negative MR (22%) has been found in CrO2/Cr2O5 composites near room temperature.
A substantially pure bulk chromium dioxide (CrO2) having saturation magnetization of at least 120 emu/gm.
Bulk composites of chromium dioxide and chromium sesquioxide (CrO2/Cr2O3) having negative magnetoresistance of at least 0.5% at about room temperature at 2 Tesla.
Bulk composites of chromium dioxide and Cr2O5 (CrO2/Cr2O5) having negative magnetoresistance of at least 0.5% at about room temperature at 2 Tesla.
A process for manufacture of substantially pure bulk chromium dioxide (CrO2), or composites of chromium dioxide and chromium sesquioxide (CrO2/Cr2O3) or composites of chromium dioxide and Cr2O5 (CrO2/Cr2O5) comprising heating an intermediate oxide, primarily Cr8O21, 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 (CrO2), or composites of chromium dioxide or chromium sesquioxide (CrO2/Cr2O3) or composites of chromium dioxide and Cr2O5 (CrO2/Cr2O5) are formed.
A substantially pure bulk chromium dioxide (CrO2) manufactured by a process for manufacture of substantially pure chromium dioxide (CrO2), or composites of chromium dioxide and chromium sesquioxide (CrO2/Cr2O3) or composites of chromium dioxide and Cr2O5 (CrO2/Cr2O5) comprising heating an intermediate oxide, primarily Cr8O21 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 (CrO2), or composites of chromium dioxide or chromium sesquioxide (CrO2/Cr2O3) or composites of chromium dioxide and Cr2O5 (CrO2/Cr2O5) are formed.
Bulk composites of chromium dioxide and chromium sesquioxide (CrO2/Cr2O3) manufactured by a process for manufacture of substantially pure chromium dioxide (CrO2), or composites of chromium dioxide and chromium sesquioxide (CrO2/Cr2O3) or composites of chromium dioxide and Cr2O5 (CrO2/Cr2O5) comprising heating an intermediate oxide, primarily Cr8O21 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 (CrO2), or composites of chromium dioxide or chromium sesquioxide (CrO2/Cr2O3) or composites of chromium dioxide and Cr2O5 (CrO2/Cr2O5) are formed.
Bulk composites of chromium dioxide and CrO5 (CrO2/Cr2O5) manufactured by a process for manufacture of substantially pure chromium dioxide (CrO2), or composites of chromium dioxide and chromium sesquioxide (CrO2/Cr2O3) or composites of chromium dioxide and Cr2O5 (CrO2/Cr2O5) comprising heating an intermediate oxide, primarily Cr8O21 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 (CrO2), or composites of chromium dioxide or chromium sesquioxide (CrO2/Cr2O3) or composites of chromium dioxide and Cr2O5 (CrO2/Cr2O5) are formed.
Dependencies are inferred from the claim text.