Method of purifying carbon nanotubes
Patent 5641466 Issued on June 24, 1997. Estimated Expiration Date: 
June 24, 2014. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
June 24, 2014. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesUncapped and thinned carbon nanotubes and process Patent #: 5346683 InventorsAssigneeApplicationNo. 253168 filed on 06/02/1994US Classes:423/447.2, Product423/445B, Fullerene (e.g., C60, C70, etc.)423/447.1, Fiber, fabric, or textile423/461Recovery or purificationExaminersPrimary: Straub, Gary P.Assistant: DiMauro, Peter Attorney, Agent or FirmInternational ClassesC01B 031/00D01F 009/12 Foreign Application Priority Data1993-06-03 JPAbstractA mixture of carbon nanotubes and impurity carbon materials, which include carbon nanoparticles and may possibly include amorphous carbon, is purified into carbon nanotubes of high purity by utilizing a significant difference in oxidizability between the nanotubes and the nanoparticles. The mixture is pulverized and heated in the presence of an oxidizing agent at a temperature in the range from 600° to 1000° C. until the impurity carbon materials are oxidized and dissipated into gas phase. The nanotubes remain almost unoxidized except for loss of some lengths from the tube tips. It is suitable to perform the heating in air or oxygen.Other References
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