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  • [May 10, 2017]

    Multifunctional Structural Carbon Foams and Their Application

  • Speaker:
    Kai Li
    Date:
    Wednesday, May 10, 2017
    Time:
    3:30-5:00pm
    Location:
    Room 212, COE Building No.1
    Host:
    Ruqiang Zou
  • Abstract
  • In the past fifteen years, we have been continuously developing multifunctional structural carbon foams from mesophase pitch and bituminous coal with properties of lightweight, high porosity and mechanics, Controllable thermal and electrical conductivity, corrosion and flame resistance, acoustic and vibrational energy absorption, etc. By correlating charactors of the raw materials with properties of two kinds of the carbon foams, we tried to elaborate performance origins of the carbon foams. During foaming of raw materials, the mesophase pitch and bituminous coal, with behaviors like a mixture of macromolecule polymers, both become viscous fluid firstly at high temperature, and with increasing temperature, small molecules decomposed from macromolecules begin to take effect on foaming under pressure, and thus the polymerized macromolecule is converted into coke-like green foams. With further carbonization and/or graphitization, the mesophase pitch-based graphite foams and coal-based carbon foams are obtained from the coke-like green foams respectively. Unlike the non-graphitized hard carbon materials from resins, the carbon materials from mesophase pitch and bituminous coal, called graphitized carbons, both have the same structure model with the basic unit as graphite microcrystallites. The graphite crystallites size and crystalline degree will increase with the increasing temperature of heat treatment, which grants the materials special thermal and electrical conductivity and mechanical performance.
     
    Furthermore, macromolecules of mesophase pitches are layered aromatic macromolecule with highly ordered structure, exhibiting some properties of liquid crystals. Such properties guarantee the graphite microcrystallites to grow adequately and gradually approach  the state of perfect graphite under condition of graphitization temperature above 2800?. The macromolecules in coal are cross-linked extensively in the presence of some heteroatoms like oxygen and nitrogen, which would restrict the growth of graphite crystallites even under the graphitization temperature above 2800?. Therefore, in comparison with graphitized coal-based carbon foam and traditional resin-based carbon foam, the graphitized carbon foams from mesophase pitch have the highest thermal conductivity and are a kind of soft carbons, while the coal-based carbon foams with lower thermal conductivity are kinds of carbon materials between soft carbons like graphite and hard carbons like resin-based carbons.

    Finally, applications of the mesophase pitch-based and coal-based carbon foams in military are reviewed. The multifunction feature makes them ideal military materials, providing unique solutions to many problems and provoking innovations and developments of new concepts and practices in functional device designs for military equipments.
  • Biography
  • Dr. Kai Li is an Assistant Professor in the Department of Protection, Research Institute of Chemical defense, a military academy. He completed his bachelor study at National University of Defense Technology in 1998, and Master and Doctor studies at Research Institute of Chemical defense (1998-2006). His current research focuses are on industrialization and application developments of mesophase pitch-based and the coal-based carbon foams. The carbon foams, developed by Dr. Li and his co-workers, have been used broadly in military functional devices since 2009.