Formation of nanodimensional structures in precipitated hydroxyapatite by fluorine substitution
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Formation of nanodimensional structures in precipitated hydroxyapatite by fluorine substitution Ekaterina A. Bogdanova1 · Vladimir M. Skachkov1 · Irina S. Medyankina1 · Hartmuth Schröttner2 · Nail A. Sabirzyanov1 · Andrey A. Rempel3 Received: 30 April 2020 / Accepted: 20 August 2020 © Springer Nature Switzerland AG 2020
Abstract Hydroxyapatite Ca10(PO4)6(OH)2 is a bioactive compound, which is of great interest for medical application as a component of artificial bones and implants. The modification of its composition via anion and cation substitution can strongly affect its properties due to the formation of nanosized particles in the basic structure. In this work the influence of fluorine substitution of hydroxyl groups is examined. The powders of fluorine-substituted hydroxyapatite C a10(PO4)6(OH)2−xFx (x = 1; 1.5; 2) were precipitated by chemical condensation from solutions. Such characteristics of powders as phase composition, morphology, particle size distribution, density, specific surface area have been studied. It was established that partial replacement of hydroxyl groups by fluorine leads to a decrease in the particle size to 10 nm. The degree of substitution affects the mechanical properties of synthesized powders and ceramics after annealing. A comparison of the particle size distribution in the initial samples and the distribution of grains in the sintered ceramics confirmed that the ceramics inherits the structure of the powders, which has a positive effect on its strength characteristics. Keywords Hydroxyapatite · Fluorapatite · Nanopowders · Bioactive ceramics
1 Introduction Dense or porous ceramics based on hydroxyapatite (HAP) is used as an implant material in many fields of medicine [1, 2]. The disadvantage of HAP-based bioceramics is a low mechanical strength, which limits its use for the elimination of defects in bone tissues experiencing regular and significant mechanical stresses [3]. A better durability can be achieved by transition to nanostructured materials, since ceramics based on such powders is characterized by a homogeneous structure, a near-zero open porosity, a small crystal size and increased strength [4, 5]. The small
particle size and narrow size distribution of the initial powder aggregates suggest that it is possible to obtain ceramics with a homogeneous fine crystalline structure [6]. The fact that ceramics inherits the structure in the next technological stage indicates the importance of the production method, which determines the quality of the initial powder and, consequently, the microstructure and properties of final ceramics [6, 7]. In this regard, the "wet" methods of HAP synthesis, in particular, chemical condensation or precipitation from solutions, are of great interest, since they allow one to obtain powders with a high degree of dispersion and a well-developed surface and
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s42452-020-03388-5) contains supplementary material, which is available to authorized us
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