University of Cambridge > > Department of Materials Science & Metallurgy Seminar Series > Novel Methods of Engineering and Characterizing Carbon Materials for Sustainable Applications

Novel Methods of Engineering and Characterizing Carbon Materials for Sustainable Applications

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The interaction between metals and carbon has been of significant scientific and technological interest for hundreds of years. This work reports novel metallurgical methods to synthesize various carbon architectures for sustainable applications. Porous graphite was prepared by dealloying SiC in molten germanium and then excavating the Ge phase. Dealloying is a technique whereby nanoporous materials are produced via the selective dissolution of one or more components from an alloy. Here, the liquid metal dealloying (LMD) process was extended to non-metal precursors, demonstrating that carbide-derived carbons (CDCs) can be fabricated by this process. The dealloying depth, concentration profile, and length scale of the dealloyed microstructure were examined as they varied with immersion times and temperatures. The dealloying depth h varied with time as h ~ t1/2, and we also observed a buildup of Si concentration in the germanium in front of the dealloying interface. The porous graphite exhibited three-dimensional connectivity and a high degree of crystallinity, with an I(D)/I(G) ratio of 0.3 for samples dealloyed at the highest temperatures, as determined by Raman spectroscopy. Additionally, we have developed the first study on the preparation and characterization of freestanding nanostructured carbon materials produced by melt spinning nickel-carbon alloys with carbon fractions up to 12 at. and iron-carbon alloys with carbon fractions of 17 at. . The carbon was excavated by chemical dissolution of the metal. We performed a detailed study on the precipitation kinetics of carbon in nickel-carbon ribbon. The equilibrium solubility of carbon in Ni is only 2 at. at the eutectic composition, but we attained metastable solid solubility, observing 2 lattice strain for an alloy spun at a linear velocity of 80 m/s; the lattice distortion was reversed via high temperature heat treatments. We also demonstrated the ability to tune the microstructure of carbon precipitated from the rapidly quenched ribbon by varying the carbon content from 4 – 12 at. % in the precursor and annealing the ribbon at temperatures that ranged from 400 – 1200 ℃. By the step-wise variation of these two parameters, we sequentially transformed amorphous carbon nanospheres into thick, highly crystalline flakes of graphite as determined by Raman spectroscopy and transmission electron microscopy.

This talk is part of the Department of Materials Science & Metallurgy Seminar Series series.

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