Bioactivity enhancement by a ball milling treatment in novel bioactive glass-hydroxyapatite composites produced by spark plasma sintering

Hydroxyapatite (HA) and a lab-made bioactive glass (BGMS10) are combined (50/50 wt%) in this work, where the effect produced by a ball milling (BM) treatment (0-120 min) prior SPS consolidation on the characteristics of the resulting products is investigated. An extraordinary improvement of the apatite-forming ability during in -vitro test on SPS samples (800 degrees C/70 MPa/2 min) is obtained using the 30 min BMed mixture. Superior Young's Modulus (122 GPa) and Vickers Hardness (675) were also found compared to unmilled samples (95 GPa and 510, respectively). Microstructural changes induced by BM, with 90 nm HA crystallites size in the bulk composite, and the intimate HA/BGMS10 interfaces established, are the factors mainly responsible for such result. When milling was prolonged to 120 min, samples with relatively lower density, mechanical properties, and in-vitro bioactivity, were produced under the same SPS conditions. The formation of crystalline SiO2 during SPS might be responsible for such behaviour.

Automated summary

In this study, hydroxyapatite and a lab-made bioactive glass were mixed in certain proportion and subjected to ball milling treatment. The effect of ball milling time on the characteristics of the resulting products was investigated. The results showed that using a 30-minute ball milling mixture significantly improved the apatite-forming ability and resulted in higher Young's Modulus and Vickers Hardness. The microstructural changes induced by ball milling and the formation of intimate HA/BGMS10 interfaces were the main factors responsible for these improvements.