Improvement of the mechanical properties of spark plasma sintered hap bioceramics by decreasing the grain size and by adding multi-walled carbon nanotubes

Abstract

Composites based on HAP and oxidized multi-walled carbon nanotubes (o-MWCNT) and monophase HAP materials were processed by spark plasma sintering. Starting from stoichiometric nano-sized HAP powder, monophase bioceramics were obtained with a density close to the theoretical one and with an average grain size of several hundred nanometers to micron dimensions. It was shown that decreasing the sintering temperature resulted in a decrease of the grain size, which affected an increase in the fracture toughness and hardness. The fracture toughness of an HAP/ o-MWCNT bioceramic processed at 900°C for only 5 min was 30 % higher than that of monophase HAP materials obtained under the same conditions. The addition of MWCNT during SPS processing of HAP materials caused a decrease in the grain size to the nano-dimension, which was one of the reasons for the improved mechanical properties. [Projekat Ministarstva nauke Republike Srbije, br. III45019 i FP7-REGPOT-2009-1 NANOTECH FTM, Grant Agreement Number: 245916

Characterization of mechanically milled and spark plasma sintered Al2124-CNT nanocomposites

“…Therefore, the hardness of the material strongly depends on its density and the effect of grain growth will be small. This is more meaningful, specifically with a process such as spark plasma sintering where the heating rate is high, the sintering temperature is low, and the sintering time is short compared to other conventional sintering processes [22,[49][50][51]. The hardness reported in this study for the Al2124 alloy was higher than the hardness of other alloys, processed under similar conditions, such as Al6061 [27], Al-7Si-0.3Mg [52], and Al-12Si-0.3Mg [31].…”

Preparation, spectroscopic and mechanical studies of nano porous HAp loaded with MWCNTs

“…where t is the crystallite size (nm) and d-is the theoretical density of HAp (3.16 g/cm 3 ).The results suggested that in case of (HAp/PVA) blend the apparent average crystal size is the same by increasing the percentage of the PVA before and after burning.as shown in fig.7a-7bIn case of the presence of MWCNTs the outcomes indicated that the apparent average crystal size increased by increasing the share of the MWCNT beforeburning.as shown in fig.9aBut the opposite occurred after burning as shown in fig 9b where the crystallite size of the HAp/.0003 MWCNT are significantly smaller, with average grain size of 85±29 nm (tab.2). This decrease of the crystallite size can be linked to the presence of carbon nanotubes on the grain boundaries during grain growth [27]. The FTIR analysis showed in Figure (10a) HAp/10%PVA/MWCNTs (0.0005, 0.001, 0.002, and 0.003) gm powders before burning.…”

“…So the strategy to overcome this weakness is to introduce materials possess good mechanical properties to enhance mechanical properties with HAP as matrix without impairing its bioactivity. Carbon nanotubes have a lot of interest in most of the areas of nanoscience and nanotechnology because of their high chemical and thermal stability, mechanical resistance, flexibility, electrical and thermal conductivity [27][28][29]. Inclusion of small amounts of CNTs in a ceramic matrix should that producing composites with high rigidity and mechanical properties improved compared to single phase ceramics.…”

Study of nanosized hydroxyapatite material annealing at different retention times

“…The most commonly used method of powder consolidation is conventional sintering method. Densification of hydroxyapatite compacts normally require sintering at 1000 °C or higher temperatures [16,17]. However, low temperatures (400-500 °C) are used to preserve the morphology of initial particles and develop microstructures made by nanosized grains.…”