Low toughness and wear resistance have limited application of many bioceramics in biomedical applications requiring load bearing capability. Spark plasma sintering (SPS) has widened the envelope of processing conditions available to produce bioceramics with new microstructural architectures. SPS has enabled realisation of transparent hydroxyapatite (HA) by providing the means to consolidate fully dense nanostructured HA. Recently, low-dimensional carbon nanomaterials, including carbon nanotubes (CNTs) and graphene/graphene nanoplatelets (GNP) have gained increasing attention as reinforcements due to their providing superior mechanical properties, favourable biocompatibility, and large specific surface area. Processing of these nanocomposites is done using SPS in order to consolidate the ceramics to full density in short time periods, while retaining the structure and properties of the nanomaterial reinforcements. This review focuses on recent progress on GNP/CNT reinforced HA and alumina nanocomposites, including mechanical properties, tribological behaviour, processing conditions, and mechanisms. Biocompatibility of these promising bioceramics with various cells/tissues are discussed.

Heteroatom-doped graphene is a potential anode material in sodium-ion batteries (SIBs). However, understanding the mechanisms of Na adsorption on the surface and intercalation in the interlayer remains a critical challenge to develop a suitable heteroatom-doped graphene anode. In this work, the structural and electronic influences in B-, N-, Si-and P-doped bilayer graphene (BLG) have been investigated by first-principles calculations. Pyridinic N, graphitic B and Si-doped BLG have preferential adsorption for Na with stronger surface binding than intercalation. The undoped carbon layer of Bdoped BLG can be converted into n-type doping state by inserting Na, and the doped layer remains p-type mainly caused by the different electrons transfer to carbon layers from Na. Additionally, the electronic conductivity and Na diffusions on surfaces and in interlayers during sodiation are improved by doping heteroatoms. However, pyridinic N, graphitic Si and P doping promote the Na storage on surfaces and in interlayers of BLG due to the structural influence of carbon vacancy, which leads to high activation barriers during desodiation. The graphitic N-doped BLG is unsuitable and reduces the numbers of storage sites for Na in/on it. Therefore, B-doped and pyridinic N-doped BLG are promising anodes for SIBs because of stronger attraction and better kinetics of the electronic and cationic transport.