The composition, structure and properties of four different glassy carbons

Glassy carbon (GC) is a class of disordered carbon materials that is known to be superelastic and non-graphitizing up to 3000 °C. The maximum heat treatment temperature is often used as a proxy to denote structure and physical properties. GC synthesised at low temperatures (~1000 °C) is often classified as Type I GC which has advantages of higher elastic modulus, resistance to oxidation, and lower permeability to gases. Type II GC is synthesised at higher temperatures (>2000 °C), has fewer impurities, is more electrically conductive, and is rated to a higher service temperature. Here Type I and II GC samples sourced from two suppliers are investigated using Rutherford backscattering spectrometry and elastic recoil detection analysis for composition, Raman spectroscopy, transmission electron microscope imaging, X-ray and neutron diffraction for structure determination, nanoindentation for mechanical properties, and Van der Pauw measurements for resistivity. The results show that the broad classifications of Type I or Type II do not correlate with the physical properties of the samples. We conclude that the quoted maximum heat treatment temperature alone is not sufficient to specify the properties of GC and that a careful microstructural examination of the material should be used to inform materials selection.