Utilizing the cold sintering process for the SiO2-HA glass-ceramics

Hydroxyapatite (HA) ceramics have promising applications in various fields, such as medical and waste treatment. However, traditional high-temperature sintering methods suffer from issues like element volatilization and performance degradation. Additionally, HA ceramics prepared using the cold sintering process (CSP), a low-temperature processing technique, often exhibit low density and poor mechanical properties. In this work, HA ceramics were reinforced with 35 mol% SiO 2 . The SiO 2 -HA glass-ceramic, fabricated at 250 °C under 750 MPa pressure with 35 wt% deionized water via CSP, exhibits a high relative density of 92.4 %, a relatively high Vickers hardness of 5.4 GPa, a fracture toughness of 0.62 MPa m 1/2 , and a high compressive strength of 602 MPa. The hardness value of the glass-ceramic is significantly higher than those of HA ceramics prepared by CSP and is comparable to those of well-sintered HA ceramics via conventional high-temperature sintering. Additionally, we summarize the CSP densification mechanism of SiO 2 -HA glass-ceramics, which includes the dissolution-reprecipitation and plastic deformation of SiO 2 and HA, as well as the fracture and rearrangement of HA nanorods.