Phase analysis, mechanical properties and in vitro bioactivity of graphene nanoplatelet-reinforced silicon nitride-calcium phosphate composites

• Published in: Journal of Asian Ceramic Societies Vol. 9; no. 2; pp. 471 - 486
• Main Authors: Bozkurt, Dilan, Akarsu, Melis Kaplan, Akin, Ipek, Goller, Gultekin
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 03-04-2021; Taylor & Francis Group
• Subjects: bioactivity; graphene; Silicon nitride; spark plasma sintering; tricalcium phosphate
• ISSN: 2187-0764; 2187-0764
• DOI: 10.1080/21870764.2021.1891664

The aim of this study is to produce highly dense Si
3
N
4
based composites with good mechanical properties and bioactivity. Si
3
N
4
ceramics without using sintering aids, Si
3
N
4
-HA and Si
3
N
4
-HA-GNP based composites have been produced by spark plasma sintering (SPS) at temperatures of 1525-1550°C. The effect of reinforcement type and content on the densification behavior, phase analysis, microstructural development, mechanical properties, and in-vitro bioactivity behavior of Si
3
N
4
were systematically investigated. Monolithic Si
3
N
4
that contains a high amount of β-Si
3
N
4
phase (~87 wt%) was produced by nearly full densification (~99%). Hydroxyapatite (HA) was used as a starting powder during the preparation of binary and triple composites to provide bioactivity to Si
3
N
4
, and after sintering, HA transformed into tricalcium phosphate (β-TCP and α-TCP) polymorphs. The incorporation of GNPs had a positive effect on the stability of β-TCP phases at higher sintering temperatures. The improvement in indentation fracture toughness of the samples with GNP reinforcement was mainly attributable to pull-out and crack deflection mechanisms. In-vitro bioactivity of GNP added composites enhanced with increasing α-TCP content. More calcium phosphate-based particle formation was observed in Si
3
N
4
-HA-GNP composites compared to the Si
3
N
4
-HA.