MORPHOLOGICALSTUDYOFDETONATIONSPRAYED 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.PolzunovAltaiStateTechnicalUniversity, Barnaul
1Institute of Strength Physics and Materials Science SB RAS, Tomsk
Biocompatible coatings are effectively formed by spraying of calcium hydroxyapatiteСа10(РО4)(ОН)2 powders on a titanium substrate.Recently, along with the composition, macro- and microstructure development, thesurfacemorphologyof the coatings has receivedincreasingattention. Inanumberofstudies, theroughnessofthecoatings has been shown to significantly influence the induction processes of cells. Asasubstratematerial, titaniumVT1-0 hasbeenchosen, whichhasseveraladvantages 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 titaniumsubstrates 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). Whenhydroxyapatiteparticlesof 20-100 µmin 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). Preliminarytreatmentofthetitaniumsubstratebysandingand chemical etching allows increasing the adhesive strength of the coating up to 20MPa.
Fig.1.SEM images:hydroxyapatite powder (a), detonation sprayed hydroxyapatite coating (b), XRD pattern of the coating (c).
Biologicalstudieshavedemonstratedbiocompatibility and bioactivity of the coatings. Itwasfoundthatthe calciumphosphatedetonationsprayedcoatingsinduce growth of tissue cells with 100% probability, which indicates that the relief of the coatings is optimal for fixation and aging of the cells. Comparativestudiesofcalciumphosphatecoatingsproducedbydetonationsprayingandthoseproducedbymicro-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. Thisopensupapossibilityofmakingtwo-phasecoatings(hydroxyapatite and beta-calcium phosphate) ensuring the closest match in composition to the bone tissue.
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