Mechanochemical Synthesis of Nanocrystalline Hydroxyapatite Coating

Abstract

A novel approach for depositing of hydroxyapatite (HA) films on titanium substrates by using high energy ball milling (HEBM) has been developed. It was demonstrated that a heat treatment of the mechanically coated HA at 800 °C for one hour leads to partial transformation of HA phase to -TCP. It appears that the grain boundary and interface defects formed during MCS reduce this characteristic transformation temperature. Also, it was shown that Ti incorporation into the HA structure causes the lattice shrinkage and reduction of its grain size as compared to pure HA, but also promote the phase transformation of HA to TCP at high temperature. It is important that doping HA by silicon, while also significantly decrease crystallinity of deposited HA layer, results in hindering of the phase transformation process. The Si-doped HA does not show phase transition or decomposition after heat treatment even at<br />900 °C. The samples were investigated by X-ray diffraction, scanning electron microscope, Energy dispersive spectroscopy, Atomic force microscopy, Transmission electron microscopy, inductively coupled plasma (ICP) optical emission spectrometer, Vickers microhardness, Electron paramagnetic resonance.

Calcium orthophosphate deposits: Preparation, properties and biomedical applications

“…Similar results were obtained in another study [666]. According to the authors, the impacts of the milling balls both significantly decreased the dimensions of the HA particles and simultaneously activated the metal surface, which led to the robust cold-welding of HA particles to the metal surface [665,666]. No information on the properties of deposits was disclosed.…”

“…To prevent contamination from the atmosphere, the chamber was sealed. Deposits of ~ 50 μm thick were put down as the result [665]. Similar results were obtained in another study [666].…”

“…A rather unusual mechanochemical deposition of CaPO 4 was proposed [665,666]. In both papers, the authors used a high-energy ball milling to perform CaPO 4 deposition on metallic substrates.…”

Surface Mechanical Attrition Treatment of Commercially Pure Titanium Vt1-0

“…Large amounts of plastic deformation result in the generation of a variety of defect structures (dislocations, vacancies, stacking faults, grain boundaries, etc.) and these destabilize the ordered nature of the lattice leading to the formation of a disordered (crystalline or amorphous) phase [8,9]. The amorphization process starts when the substrate has experienced a certain number of critical collisions which depend on the impact energy.…”

“…SMAT involves repeated multidirectional impact by flying balls to induce surface hardening of bulk samples. The impact causes severe plastic deformation in the surface layer of the treated sample, leading to grain refinement, large grain boundary misorientation, dislocation blocks and microbands [5][6][7][8]. Recent investigations have demonstrated that commercially pure titanium with an ultrafine grain structure in the nanometer range can be processed using severe plastic deformation methods such as equal channel angular pressing and high pressure torsion [3,8].…”