Synthesis of silica-based scaffolds with high porosity and controllable microstructure by a sintering-free sol–gel/freeze-casting hybrid method under mild conditions

• Main Authors: Haw-Kai Chang, Po-Yu Chen
• Format: Article
• Language: English
• Published: Elsevier 2020-11-01
• Series: Journal of Materials Research and Technology
• Subjects: Freeze casting; Sol–gel; Anisotropic; Mechanical property; Composites
• Online Access: http://www.sciencedirect.com/science/article/pii/S2238785420320238

Scaffolds and porous composites synthesized by freeze casting method and polymer infiltration can be applied in the fields of bone grafting materials, implants, filtration, and thermal insulation due to the anisotropic and interconnected porous structure. Freeze casting techniques have been applied to synthesize a wide variety of scaffolds with aligned channels. Typical freeze casting method requires sintering as-casted scaffolds at high temperature which limits the materials selection and its applicability. In this study, a novel sintering-free sol–gel/freeze-casting hybrid method is established. The as-synthesized gel can be shaped by mold more easily compared to powder by the novel mold assisted melting method. This pioneering method surpassed the limitation of freeze-drying under low pressure and temperature, facilitating controllable reaction under mild condition. Another important advantage is that the sintering process at a high temperature is no longer required which broadens the materials selection and potential applications. Besides, microstructural features can be controlled by tuning the water content in the gel and the cooling rate. Moreover, composite scaffolds with high porosity (>90%) and proper mechanical stability are synthesized by mixing gel and polymer. The bio-inspired scaffolds and composites fabricated by this novel sintering-free sol–gel/freeze-casting hybrid method possess advantages and great potentials in various applications.