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This Defense Intelligence Reference Document from the Defense Intelligence Agency, dated 1 November 2010, was one of a series of advanced technology reports produced in FY 2010 under the Advanced Aerospace Weapons System Applications (AAWSA) Program. It reviews ultracapacitors as energy and power storage devices. It covers how they work, their materials, their commercial and military uses, and new developments such as carbon nanotubes, thin films and magnetic capacitors. It concludes that the U.S. government must understand and adopt advanced ultracapacitors.
“The Advance”13 pages
UNCLASSIFIED/ ,'Pl!li.t l!ll"l"!!!llit tl!II!! l!IHLY Activated carbons are synthesized by a heat treatment of carbon-rich organic precursors in a controlled atmosphere. This carbonization process can be performed from natural sources, such as fruit shells, wood, pitch, or coke. Activated carbons can also be produced from synthetic precursors, such as select polymers. The heat treatment process uses a controlled partial oxidation of the precursor combined with a high-temperature processing. The high-temperature processing can be done in an inert atmosphere, an oxidizing environment, or with a chemical modification. The activated carbons contain a distributed porous network throughout, as shown in Figure 5. 17 These materials can have an extremely high surface area, upward of 3,000 m 2/g, but process conditions to create activated carbons have little control over pore size distribution, resulting in incomplete utilization of the surface area. Carbon cloth electrodes use processing conditions similar to those used to create activated carbons. The advantage with a fabric composed of activated carbon is these materials are directly used as active electrodes, requiring no binder or additional processing. However, these tend to be expensive to produce, which has thus far limited their use to specialized applications. >,',--, ';, -;,. ___ macrnpnrcs >:51Jnm mi,:nip,lls'~ <~nrn Figure 5. Activated Carbon Porosity. These can be produced with a distribution of pore sizes ranging from less than 2 nm to greater than 50 nm. Continued improvements to the carbon electrodes are expected to provide additional performance enhancement to ultracaps. Current research is leading toward carbon materials with higher specific capacitance (F/g). Improved materials, such as carbon nanotubes and tailored porous carbons show promise as the next generation of carbon materials. Graphene is another advanced carbon material that shows promise to providing increased capacitance. One of the key design issues revolves around improved understanding of the relationship between the carbon pore size and the electrolyte ion. The nanostructured materials allow fine tuning of the porous structure to increase capacitance. Carbon nanotubes (CNTs) are commonly produced as powders where they can be cast as a distributed network to form an electrode, and they can be used as an additive to increase conductivity. Additionally, CNTs can be grown as a "forest," where the CNTs are grown perpendicular to a substrate. These forests can be used as is or can be modified or coated to change specific structural or electronic properties. CNTs are grown by a number of methods, but most methods used currently are a derivative of a chemical vapor deposition (CVD) process. The specific properties of the nanotubes are extremely tailorable. CNT length, diameter, the number of tubes, and the electronic properties can all be tailored by growth conditions. The catalysts used to grow CNTs can affect tube properties, as well as CNT temperature and precursor variables. Carbon nanotubes are finding utility in both battery and ultracapacitor applications, where they are used for conductivity enhancement and energy storage. Their capacitive behavior suggests they may have a fundamentally different storage mechanism than traditional carbon. Storage potential includes CNT outer walls, inner diameter, and interwall spaces 10 UNCLASSIFIED/ /P81il 8ffl81.t.k Wlili SU.bl/
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Report, from the dia collection. The PDF is mirrored here; the original link is above. 34 pages are in the text index: search them above, or from the library's search.