Freeze Casting of Porous Hydroxyapatite Scaffolds -- II. Sintering, Microstructure, and Mechanical Behavior


In Part I, the influence of processing parameters on the general microstructure of freeze-cast hydroxyapatite (HA) constructs was explored. This work is an extension of Part I to investigate the effect of sintering conditions on the microstructure and mechanical behavior of freeze-cast HA. For constructs prepared from aqueous suspensions (5-20 vol % HA), sintering for 3 h at temperatures from 1250°C to 1375°C produced a decrease in porosity of <5% but an increase in strength of nearly 50%. Constructs with a porosity of 52% had compressive strengths of 12 ± 1 MPa and 5 ± 1 MPa in the directions parallel and perpendicular to the freezing direction, respectively. The mechanical response showed high strain tolerance (5-10% at the maximum stress), high strain to failure (>20%), and high strain rate sensitivity. Manipulation of the freeze-cast microstructure, achieved by additions of glycerol and 1,4-dioxane to the aqueous suspensions, produced changes in the magnitude of the mechanical response, but little change in the general nature of the response. The favorable mechanical behavior of the porous constructs, coupled with the ability to modify their microstructure, indicates the potential of the present freeze-casting route for the production of porous scaffolds for bone tissue engineering.


Materials Science and Engineering

Keywords and Phrases

Biomaterials; Freeze Casting; Hydroxyapatite; Mechanical Behavior; Scaffolds

International Standard Serial Number (ISSN)

1552-4973; 1552-4981

Document Type

Article - Journal

Document Version


File Type





© 2008 John Wiley & Sons, All rights reserved.

Publication Date

13 Mar 2008