Fabrication of Beta-tricalcium Phosphate Bioceramic Scaffolds by Freeze Drying Techniques

Objective: Porous bioceramics can be produced by many methods, such as the polymeric sponge impregnation technique, pore-former, extrusion, sol-gel, freeze-drying process, and so on. Among them, freeze-drying process is a simple and effective fabricating method for its many advantages including small forming shrinkage, widely controllable porosity, relatively good mechanical strength, and environmental friendliness. There are many factors that influence the microstructures and properties of bioceramic scaffolds fabricated by the freeze-drying process, such as the slurry solid loading, freezing rate, sintering conditions , and so on.The freeze-drying process from aqueous ceramic slurries was used to fabricate β-tricalcium phosphate (β-TCP) scaffolds with different morphology and porosity by adjusting the content of the slurries, and analyze the influence factor.

Method: β-TCP slurries with different solid loading and different concentration of polyvinyl alcohol(PVA) were prepared, after freeze-drying and high-temperature calcination, the bioceramic scaffolds were fabricated. The materials component of the scaffolds was analyzed by X-ray diffraction technique. The morphology of the scaffolds was observed by scanning electron microscope. The porosity of the scaffolds was calculated by the Archimedes method.

Result: Freeze-cast β-TCP ceramics with different porous morphologies and properties have been fabricated by adjusting the concentration of PVA addition and the slurry solid loading. The diffraction peak position of the scaffolds was identical with the standard β-TCP; The scaffolds without PVA additive were composed of macroscopic lamellar pores and porous ceramic walls, and as the solid longing of slurry increasing, the pore size and the porosity decrease; With PVA additive, the large lamellar pores gradually change into the interconnected three-dimensional reticulate pores, and the porosity was improved because of the addition of PVA.

Conclusion: In a word, using the freeze-drying process, the pore size,pore morphology and as well as the porosity of the bioceramic scaffolds can be adjusted and modified by adjusting the content of the slurries.