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SUMMARY:Novel Methods of Engineering and Characterizing Carbon Materials f
 or Sustainable Applications  - Dr. Gina Greenidge\, National Physical Labo
 ratory\, Teddington\, UK
DTSTART:20231123T160000Z
DTEND:20231123T170000Z
UID:TALK206923@talks.cam.ac.uk
CONTACT:Julie Smith
DESCRIPTION:The interaction between metals and carbon has been of signific
 ant scientific and technological interest for hundreds of years. This work
  reports novel metallurgical methods to synthesize various carbon architec
 tures for sustainable applications. Porous graphite was prepared by deallo
 ying 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 me
 tal dealloying (LMD) process was extended to non-metal precursors\, demons
 trating that carbide-derived carbons (CDCs) can be fabricated by this proc
 ess. The dealloying depth\, concentration profile\, and length scale of th
 e dealloyed microstructure were examined as they varied with immersion tim
 es 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 fr
 ont of the dealloying interface. The porous graphite exhibited three-dimen
 sional 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 deter
 mined by Raman spectroscopy. Additionally\, we have developed the first st
 udy on the preparation and characterization of freestanding nanostructured
  carbon materials produced by melt spinning nickel-carbon alloys with carb
 on 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. W
 e performed a detailed study on the precipitation kinetics of carbon in ni
 ckel-carbon ribbon. The equilibrium solubility of carbon in Ni is only 2 a
 t. % at the eutectic composition\, but we attained metastable solid solubi
 lity\, 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 carbo
 n content from 4 – 12 at. % in the precursor and annealing the ribbon at
  temperatures that ranged from 400 – 1200 ℃. By the step-wise variatio
 n of these two parameters\, we sequentially transformed amorphous carbon n
 anospheres into thick\, highly crystalline flakes of graphite as determine
 d by Raman spectroscopy and transmission electron microscopy.
LOCATION:Goldsmiths 1 & https://zoom.us/j/96836714124
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