ISSN:
1551-2916
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
The amorphous phase in hydroxyapatite coatings has been examined by using X-ray diffractometry, Fourier transform infrared spectroscopy, optical microscopy, and thermal analysis methods. The amorphous phase mostly consists of a dehydroxylated calcium phosphate. When heated, crystallization of hydroxyl-rich areas produces hydroxyapatite, followed by diffusion of hydroxyl ions, thus increasing the amount of crystalline phase. Hydroxyl-deficient amorphous areas crystallize to oxyapatite at 700°C. Thus, crystallization occurs over a range of temperatures and is dependent on the hydroxyl content of the amorphous phase and the partial water-vapor pressure. The activation energies of crystallization to hydroxyapatite, diffusion of hydroxyl ions, and crystallization to oxyapatite are 274, 230, and 440 kJ/mol, respectively. Shrinkage from these processes leads to a crack network and decreases the mechanical strength of the coating.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1151-2916.1998.tb02301.x
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