This paper revies the preparation and properties of hard forms of amorphous carbon and hydrogenated amorphous carbon, often known as diamond-like carbon. Properties such as the hydrogen content, sp 3 content, optical gap, refractive index, hardness, elastic modulus and friction and their dependence on the deposition conditions are described. Models of the electronic structure and mechanical properties are used to relate the physical properties to the atomic structure.

Properties of diamond-like carbon

Hard amorphous (diamond-like) carbons

The strength of lightweight mechanical metamaterials, which aim to exploit material-strengthening size effects by their microscale lattice structure, has been limited by the resolution of three-dimensional lithography technologies and their restriction to mainly polymer resins. Here, we demonstrate that pyrolysis of polymeric microlattices can overcome these limitations and create ultra-strong glassy carbon nanolattices with single struts shorter than 1 μm and diameters as small as 200 nm. They represent the smallest lattice structures yet produced--achieved by an 80% shrinkage of the polymer during pyrolysis--and exhibit material strengths of up to 3 GPa, corresponding approximately to the theoretical strength of glassy carbon. The strength-to-density ratios of the nanolattices are six times higher than those of reported microlattices. With a honeycomb topology, effective strengths of 1.2 GPa at 0.6 g cm(-3) are achieved. Diamond is the only bulk material with a notably higher strength-to-density ratio.

Approaching theoretical strength in glassy carbon nanolattices.

In 1903, Alexander Graham Bell developed a design principle to generate lightweight, mechanically robust lattice structures based on triangular cells; this has since found broad application in lightweight design. Over one hundred years later, the same principle is being used in the fabrication of nanolattice materials, namely lattice structures composed of nanoscale constituents. Taking advantage of the size-dependent properties typical of nanoparticles, nanowires, and thin films, nanolattices redefine the limits of the accessible material-property space throughout different disciplines. Herein, the exceptional mechanical performance of nanolattices, including their ultrahigh strength, damage tolerance, and stiffness, are reviewed, and their potential for multifunctional applications beyond mechanics is examined. The efficient integration of architecture and size-affected properties is key to further develop nanolattices. The introduction of a hierarchical architecture is an effective tool in enhancing mechanical properties, and the eventual goal of nanolattice design may be to replicate the intricate hierarchies and functionalities observed in biological materials. Additive manufacturing and self-assembly techniques enable lattice design at the nanoscale; the scaling-up of nanolattice fabrication is currently the major challenge to their widespread use in technological applications.

Nanolattices: An Emerging Class of Mechanical Metamaterials.

HRTEM study of diesel soot collected from diesel particulate filters

The fracture toughness of glassy carbons at elevated temperatures

Effect of air oxidation at 873 K on the mechanical properties of a carbon-carbon composite

Oxidation effects on toughness and slow crack growth in polycrystalline graphites

The subcritical crack growth characteristics of glassy carbons in water were measured and are correlated with their elastic moduli. It is observed that the susceptibility to fatigue varies inversely with the elastic modulus, which is directly related to the crack growth parameter N. Crack propagation characteristics of glassy carbons are compared with those of silicate glasses and amorphous metals.

R.C. Bradt

Papers

The fracture toughness of glassy carbons at elevated temperatures

Effect of air oxidation at 873 K on the mechanical properties of a carbon-carbon composite

Oxidation effects on toughness and slow crack growth in polycrystalline graphites

Subcritical crack growth of glassy carbon in water

Subcritical crack growth in fine grained polycrystalline graphites