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Structural and Chemical Hierarchy in Hydroxyapatite Coatings

  • Hydroxyapatite coatings need similarly shaped splats as building blocks and then a homogeneous microstructure to unravel the structural and chemical hierarchy for more refined improvements to implant surfaces. Coatings were thermally sprayed with differently sized powders (20–40, 40–63 and 63–80 µm) to produce flattened homogeneous splats. The surface was characterized for splat shape by profilometry and Atomic force microscopy (AFM), crystal size by AFM, crystal orientation by X-ray diffraction (XRD) and structural variations by XRD. Chemical composition was assessed by phase analysis, but variations in chemistry were detected by XRD and Raman spectroscopy. The resulting surface electrical potential was measured by Kelvin probe AFM. Five levels of structural hierarchy were suggested: the coating, the splat, oriented crystals, alternate layers of oxyapatite and hydroxyapatite (HAp) and the suggested anion orientation. Chemical hierarchy was present over a lower range of order for smaller splats. Coatings made from smaller splats exhibited a greater electrical potential, inferred to arise from oxyapatite, and supplemented by ordered OH− ions in a rehydroxylated surface layer. A model has been proposed to show the influence of structural hierarchy on the electrical surface potential. Structural hierarchy is proposed as a means to further refine the properties of implant surfaces.

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Document Type:Article
Author:Karlis A. GrossORCiD, Christiane PetzoldORCiD, Liene Pluduma-LaFarge, Maris Kumermanis, Håvard J. HaugenORCiD
Parent Title (English):Materials
Year of first Publication:2020
Release Date:2022/11/18
Tag:biomaterials; design; electrical surface potential; hierarchy; hydroxyapatite coating; implants; self-assembly
Impact:03.623 (2020)
Funding Information:This research was supported by the M-ERA Net project grant named Signalling Implant, ES RTD/2017/4. This study extends the initiative of a previously funded project grant PIRG05-GA-2009-249306 Refined Step.
Groups:Nano Zell Interaktionen
Open Access:Open Access
Signature:INM 2020/115
Licence (German):License LogoCreative Commons - CC BY - Namensnennung 4.0 International