Elastic Properties of 4–6 nm-thick Glassy Carbon Thin Films

Glassy carbon is a disordered, nanoporous form of carbon with superior thermal and chemical stability in extreme environments. Freestanding glassy carbon specimens with 4–6 nm thickness and 0.5 nm average pore size were synthesized and fabricated from polyfurfuryl alcohol precursors. Elastic properties of the specimens were measured in situ inside a scanning electron microscope using a custom-built micro-electro-mechanical system. The Young’s modulus, fracture stress and strain values were measured to be about 62 GPa, 870 MPa and 1.3%, respectively; showing strong size effects compared to a modulus value of 30 GPa at the bulk scale. This size effect is explained on the basis of the increased significance of surface elastic properties at the nanometer length-scale

Activation Energies for Creep of Pyrolytic and Glassy Carbon

IN an investigation of the high temperature (2,500° to 2,900° C) creep behaviour of glassy (vitreous) carbon, Fischbach1 obtained apparent activation energies for creep in the range 306 to 382 kcalories mol−1. These values are unexpectedly high for a non-graphitizing carbon with a disordered structure, especially when compared with the activation energies of 250 and 260 kcalories mol−1 reported earlier for pyrolytic carbon for creep2,3 and graphitization4, respectively. It is therefore appropriate to examine whether an important contribution to the activation energy may arise through the temperature dependence of the shear modulus5,6