Freeze Casting of Porous Hydroxyapatite Scaffolds -- I. Processing and General Microstructure
Freeze casting of aqueous suspensions on a cold substrate was investigated as a method for preparing hydroxyapatite (HA) scaffolds with unidirectional porosity. In the present paper, we report on the ability to manipulate the microstructure of freeze-cast constructs by controlling the processing parameters. Constructs prepared from aqueous suspensions (5-20 volume percent particles) on a steel substrate at -20°C had a lamellar-type microstructure, consisting of plate-like HA and unidirectional pores oriented in the direction of freezing. Sintering for 3 h at 1350°C produced constructs with dense HA lamellas, porosity of 50%, and inter-lamellar pore widths of 5-30 m. The thickness of the HA lamellas decreased but the width of the pores increased with decreasing particle concentration. Decreasing the substrate temperature from -20°C to -196°C produced a finer lamellar microstructure. The use of water-glycerol mixtures (20 wt % glycerol) as the solvent in the suspension resulted in the production of finer pores (1-10 m) and a larger number of dendritic growth connecting the HA lamellas. On the other hand, the use of water-dioxane mixtures (60 wt % dioxane) produced a cellular-type microstructure with larger pores (90-110 m). The ability to produce a uniaxial microstructure and its manipulation by controlling the processing parameters indicate the potential of the present freeze casting route for the production of scaffolds for bone tissue engineering applications.
Q. Fu et al., "Freeze Casting of Porous Hydroxyapatite Scaffolds -- I. Processing and General Microstructure," Journal of Biomedical Materials Research - Part B: Applied Biomaterials, John Wiley & Sons, Dec 2007.
The definitive version is available at http://dx.doi.org/10.1002/jbm.b.30997
Materials Science and Engineering
Keywords and Phrases
Biomaterials; Freeze Casting; Hydroxyapatite; Porous Ceramics; Scaffolds
Article - Journal
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