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MORPHOLOGICAL STUDY OF DETONATION
SPRAYED COATINGS OF CALCIUM HYDROXYAPATITE
DEPOSITED ON A NANOSTRUCTURED TITANIUM
SUBSTRATE
A.A. Sitnikov, V.I. Yakovlev, Yu.P. Sharkeev 1,
E.V. Legostaeva 1, A.A. Popova
I.I.Polzunov Altai State Technical University, Barnaul
[email protected]
1
Institute of Strength Physics and Materials Science SB RAS,
Tomsk
Biocompatible coatings are effectively formed by spraying of
calcium hydroxyapatite Са10(РО4)(ОН)2 powders on a titanium substrate.
Recently, along with the composition, macro- and microstructure
development, the surface morphology of the coatings has received
increasing attention. In a number of studies, the roughness of the
coatings has been shown to significantly influence the induction
processes of cells. As a substrate material, titanium VT1-0 has been
chosen, which has several advantages being highly biocompatible,
bioinert, practically non-toxic, corrosion-resistant and possessing low
thermal conductivity and low coefficient of thermal expansion. The
morphology of the gas-detonation sprayed calcium phosphate coatings
deposited on ultrafine-grained and nanostructured titanium substrates
and implant imitations has been studied. The substrates and implant
imitations were produced in the Institute of Strength Physics and
Materials Science SB RAS, Tomsk.
It was shown that the detonation sprayed hydroxyapatite powders
with particles ranging from 1 to 20 µm formed coatings non-uniform in
thickness and phase composition. The roughness of the coatings was
Ra=3,65-4,72 µm (class 5). When hydroxyapatite particles of 20-100
µm in size are sprayed, coatings more uniform in thickness and phase
composition are formed (Fig.1) with an average roughness of Ra = 6,24
µm (class 4). Preliminary treatment of the titanium substrate by sanding
and chemical etching allows increasing the adhesive strength of the
coating up to 20MPa.
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Fig.1. SEM images: hydroxyapatite powder (a), detonation sprayed
hydroxyapatite coating (b), XRD pattern of the coating (c).
Biological studies have demonstrated biocompatibility and
bioactivity of the coatings. It was found that the calcium phosphate
detonation sprayed coatings induce growth of tissue cells with 100%
probability, which indicates that the relief of the coatings is optimal for
fixation and aging of the cells. Comparative studies of calcium
phosphate coatings produced by detonation spraying and those produced
by micro-arc in an electrolyte containing
phosphoric acid,
hydroxyapatite and calcium carbonate have shown the advantages of
detonation spraying for providing the required phase composition of the
coating. This opens up a possibility of making two-phase coatings
(hydroxyapatite and beta-calcium phosphate) ensuring the closest match
in composition to the bone tissue.
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