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Slow crack growth behaviour of hydroxyapatite ceramics

Paper ID Volume ID Publish Year Pages File Format Full-Text
11925 767 2005 7 PDF Available
Title
Slow crack growth behaviour of hydroxyapatite ceramics
Abstract

Among materials for medical applications, hydroxyapatite is one of the best candidates in orthopedics, since it exhibits a composition similar to the mineral part of bone. Double torsion technique was here performed to investigate slow crack growth behaviour of dense hydroxyapatite materials. Crack rate, V, versus stress intensity factor, KI, laws were obtained for different environments and processing conditions. Stress assisted corrosion by water molecules in oxide ceramics is generally responsible for slow crack growth. The different propagation stages obtained here could be analyzed in relation to this process. The presence of a threshold defining a safety range of use was also observed. Hydroxyapatite ceramics appear to be very sensitive to slow crack growth, crack propagation occurring even at very low KI. This can be explained by the fact that they contain hydroxyl groups (HAP: Ca10(PO4)6(OH)2), favouring water adsorption on the crack surface and thus a strong decrease of surface energy in the presence of water. This study demonstrates that processing conditions must be carefully controlled, specially sintering temperature, which plays a key role on V–KI laws. Sintering at 50 °C above or below the optimal temperature, for example, may shift the V–KI law towards very low stress intensity factors. The influence of ageing is finally discussed.

Keywords
Ageing; Crack growth; Fracture toughness; Hydroxyapatite; Mechanical properties
First Page Preview
Slow crack growth behaviour of hydroxyapatite ceramics
Publisher
Database: Elsevier - ScienceDirect
Journal: Biomaterials - Volume 26, Issue 31, November 2005, Pages 6106–6112
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering