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Plasma sprayed hydroxyapatite coatings on titanium substrates Part 2: optimisation of coating properties

Paper ID Volume ID Publish Year Pages File Format Full-Text
13728 895 1998 13 PDF Available
Title
Plasma sprayed hydroxyapatite coatings on titanium substrates Part 2: optimisation of coating properties
Abstract

Heat treatment and the introduction of a Ti bond coat have been applied to hydroxyapatite (HA) coatings sprayed using different plasma powers and gas mixtures. Attempts were made in this way to achieve optimal coating properties for orthopaedic implants. In particular, the effects on the degree of crystallinity, the adhesion, the OH- ion content and the purity were evaluated. Heat treatment at 700°C for 1 h in air proved to be effective in increasing the crystallinity, regaining the OH- ion and removing other non-HA compounds, although it caused a significant decrease in the degree of adhesion (interfacial fracture toughness) for those specimens sprayed at high powers. This heat treatment was found to induce significant transformation of amorphous HA to the crystalline form, while not detrimentally changing the properties of the underlying Ti–6Al–4V substrates. Precoating with a 100 μm Ti layer increased the adhesion of the HA coatings on Ti–6Al–4V substrates, primarily by providing a rougher surface and promoting better mechanical interlocking. Changes in coating properties during immersion in biological fluids were also studied and were found to depend critically on the chemical composition of the fluids. Small precipitates formed on the coating surfaces when immersed in Ringers solution. These might account for the apparent drop in the degree of crystallinity when measured using X-ray diffraction. A significant drop in the interfacial adhesion was found for those coatings sprayed at high powers. This could be offset by prior precoating with a titanium bond coat and suitable heat treatment. In summary, the following processing sequence is suggested in order to achieve optimum coating properties: precoating the substrate with a layer of Ti (∼100 μm), spraying HA at a sufficiently high-power level (depending on particle size and gas mixture) and heat treatment at 700°C for 1 h in air.

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Plasma sprayed hydroxyapatite coatings on titanium substrates Part 2: optimisation of coating properties
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Publisher
Database: Elsevier - ScienceDirect
Journal: Biomaterials - Volume 19, Issue 22, November 1998, Pages 2031-2043
Authors
Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us