US 8,993,113 titled Graphene Aerogels

The first claim of US 8,993,113 contains an element about covalent bonding:

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A composition comprising at least one graphene aerogel comprising a three-dimensional structure of graphene sheets, wherein the graphene sheets are directly chemically crosslinked with each other by covalent carbon bonds.

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Note separately:

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The United States Government has rights in this invention pursuant to Contract No. DE-AC52-07NA27344 between the United States Department of Energy and Lawrence Livermore National Security, LLC for the operation of Lawrence Livermore National Laboratory.

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LLNL is managed and operated by Lawrence Livermore National Security, LLC (LLNS), a partnership of the University of California, Bechtel, Babcock & Wilcox, URS, and Battelle Memorial Institute in affiliation with the Texas A&M University System.