In order to accommodate an increasing demand for glassy carbon products with tailored characteristics, one has to understand the origin of their structure-related properties. In this work, through the use of high-resolution transmission electron microscopy, Raman spectroscopy, and electron energy loss spectroscopy it has been demonstrated that the structure of glassy carbon at different stages of the carbonization process resembles the curvature observed in fragments of nanotubes, fullerenes, or nanoonions. The measured nanoindentation hardness and reduced Young’s modulus change as a function of the pyrolysis temperature from the range of 600–2500 °C and reach maximum values for carbon pyrolyzed at around 1000 °C. Essentially, the highest values of the mechanical parameters for glassy carbon manufactured at that temperature can be related to the greatest amount of non-planar sp²-hybridized carbon atoms involved in the formation of curved graphene-like layers. Such complex labyrinth-like structure with sp²-type bonding would be rigid and hard to break that explains the glassy carbon high strength and hardness.

Transmission electron microscopy and neutron or X-ray diffraction are powerful techniques available today for characterization of the structure of various carbon materials at nano and atomic levels. They provide complementary information but each one has advantages and limitations. Powder X-ray or neutron diffraction measurements provide structural information representative for the whole volume of a material under probe but features of singular nano-objects cannot be identified. Transmission electron microscopy, in turn, is able to probe single nanoscale objects. In this review, it is demonstrated how transmission electron microscopy and powder X-ray and neutron diffraction methods complement each other by providing consistent structural models for different types of carbons such as carbon blacks, glass-like carbons, graphene, nanotubes, nanodiamonds, and nanoonions.

Carbon can have many different forms and the characterisation of structural features on a length scale of 1 Å to 10 μ m is important in defining its physical and chemical properties for the various forms. The use of either electro-magnetic (x-ray) or particle (neutron) beams plays an important role in determining these characteristics. In this paper, we review the various techniques that are used to determine the structural features by experimental means and how the data are processed to give the required information in a suitable form for detailed analysis by computer simulation. Diffraction methods are used for studies of the atomic arrangement and small-angle scattering techniques are used for studies of microporosity in the sample materials. The experimental data obtained from a wide range of different carbon materials are considered and how these results can be used as a basis for modelling the structures in a quantitative manner is also considered. This information underpins their use as active components in a wide range of functional materials.