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Single-crystal metals have distinctive properties owing to the absence of grain boundaries and strong anisotropy. Commercial single-crystal metals are usually synthesized by bulk crystal growth or by deposition of thin films onto substrates, and they are expensive and small. We prepared extremely large single-crystal metal foils by “contact-free annealing” from commercial polycrystalline foils. The colossal grain growth (up to 32 square centimeters) is achieved by minimizing contact stresses, resulting in a preferred in-plane and out-of-plane crystal orientation, and is driven by surface energy minimization during the rotation of the crystal lattice followed by “consumption” of neighboring grains. Industrial-scale production of single-crystal metal foils is possible as a result of this discovery.

A new approach to make graphitic thin films from graphene oxide (G-O) is presented. By incorporating small-diameter, reduced GO platelets with GO , graphitized films show improved density and crystalline order when compared with pure GO. Mechanical pressing of the graphitized films increased density but decreased crystallinity. A subsequent high-temperature heat treatment improved atomic order beyond that seen before mechanical pressing. In-plane thermal conductivity is on par with highly oriented pyrolytic graphite and exceeds commercially available graphite-based thermal interface materials.

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