Spark plasma sintering of graphene reinforced hydroxyapatite composites

Hydroxyapatite (prepared from eggshell)/graphene (HAP/GNPs) composites were prepared by spark plasma sintering (SPS). Pure HAP does not have good mechanical properties so it is necessary to combine them with other materials, which endow them acceptable strength. Sintering was carried out at various temperatures (700 degrees C and 900 degrees C) and holding times (5 and 10 min). Rapid processing time and low sintering temperatures was of importance to avoid HAP decomposition. Mechanical and structural properties of the sintered bodies were studied with different methods. The highest relative density similar to 96% was obtained at 700 degrees C sintering temperature regardless of the holding time. Composite with the best mechanical properties (hardness similar to 4 GPa, 3-point bending strength similar to 119 MPa) consisted of HAP elongated grains with average length of 300 nm. The GNPs were agglomerated and located on grain boundaries closed to porosities. The structural observation confirmed increased fraction of hexagonal shaped grains, and poorer mechanical properties with increased sintering time and temperature. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.