Densification and strengthening of silver-reinforced hydroxyapatite-matrix composite prepared by sintering

Abstract

Ductile-phase reinforcement of hydroxyapatite (HA) was achieved by addition of silver particulates (5-30 vol %) in HA powder and subsequent sintering of HA-Ag powder compacts. A composite made by sintering 10 vol% Ag and the balance HA at 1200°C for 1 h in air had flexural strength of 75 4-7 MPa, which was almost double that of pure HA sintered under an identical condition. The density of HA-10 vol% Ag composite was 90 -t-2% of the theoretical density (as calculated from the rule of mixture) and was lower than that (98.7 ___ 0.4%) of pure HA sintered at a similar condition. The X-ray diffraction pattern of the composite did not indicate any decomposition of HA or any reaction between HA and Ag. Ag in the composite melted during sintering, but, due to poor wetting, did not spread in between HA particles. The addition of Ag reduced densification and grain growth during sintering of HA-Ag composites. Indentation cracks in the composites went around Ag inclusions and often stopped at Ag inclusions. The increase in the flexural strength of the composites was thought to be due to crack-bridging and crack-arrest by silver particles.

Calcium orthophosphate-based biocomposites and hybrid biomaterials

“…Luckily, the histological evaluations revealed that HA/Ti biocomposites could be partially integrated with newborn bone tissues after 3 weeks and fully osteointegrated at 12 weeks in vivo [840]. Similar findings had been earlier made for HA bioceramics reinforced by addition of silver particulates (5-30 vol.%) and subsequent sintering of the HA/Ag powder compacts [838,839]. Other studies on calcium orthophosphate/Ti biocomposites are available elsewhere [845][846][847][848].…”

Challenges and Opportunities for Spark Plasma Sintering: A Key Technology for a New Generation of Materials

“…However, HA shows a limited stability at high temperatures and will dissociate into tricalcium phosphate and tetracalcium phosphate at 1300 °C in air or 1000 °C in vacuum [Chaki et al, 1994]. On the other hand, high temperatures and long sintering duration required for consolidation of HA powders by conventional techniques often result in extreme grain coarsening or surface contamination, which can degrade the desired mechanical properties.…”

Biocomposites and hybrid biomaterials based on calcium orthophosphates

“…%) and subsequent sintering of the HA/Ag powder compacts. 1028,1029 The addition of silver also imparts an antimicrobial activity. 1042 Other studies on calcium orthophosphate/Ti biocomposites are available elsewhere in reference 1035-1038. To conclude this section, biocomposites consisting only of calcium orthophosphates should be briefly described.…”

“…1003,1004 Various biocomposites of calcium orthophosphates with metals and alloys have been fabricated as well. 540,928,967,997,[1028][1029][1030][1031][1032][1033][1034][1035][1036][1037][1038][1039][1040][1041][1042][1043][1044][1045] For example, an HA-based biocomposite reinforced with 20 vol.% of Ti particles was fabricated by hot pressing. 1030 Calcium orthophosphate/Ti biocomposites might be prepared by powder metallurgy ©2 0 1 1 L a n d e s B i o s c i e n c e .…”