Tailoring the Surface Morphology and the Crystallinity State of Cu- and Zn-Substituted Hydroxyapatites on Ti and Mg-Based Alloys

Abstract

Titanium-based alloys are known as a “gold standard” in the field of implantable devices. Mg-based alloys, in turn, are very promising biocompatible material for biodegradable, temporary implants. However, the clinical application of Mg-based alloys is currently limited due to the rapid resorption rate in the human body. The deposition of a barrier layer in the form of bioactive calcium phosphate coating is proposed to decelerate Mg-based alloys resorption. The dissolution rate of calcium phosphates is strongly affected by their crystallinity and structure. The structure of antibacterial Cu- and Zn-substituted hydroxyapatite deposited by an radiofrequency (RF) magnetron sputtering on Ti and Mg–Ca substrates is tailored by post-deposition heat treatment and deposition at increased substrate temperatures. It is established that upon an increase in heat treatment temperature mean crystallite size decreases from 47 ± 17 to 13 ± 9 nm. The character of the crystalline structure is not only governed by the temperature itself but relies on the condition such as either post-deposition treatment, where an amorphous calcium phosphate undergoes crystallization or instantaneous crystalline coating growth during deposition on the hot substrate. A higher treatment temperature at 700 °C results in local coating micro-cracking and induced defects, while the temperature of 400–450 °C resulted in the formation of dense, void-free structure.

Zn-Doped CaP-Based Coatings on Ti–6Al–4V and Ti–6Al–7Nb Alloys Prepared by Magnetron Sputtering: Controllable Biodegradation, Bacteriostatic, and Osteogenic Activities

“…Various methods have already been used to produce substituted CaP coatings, including radio frequency (RF) magnetron sputtering (MS) to deposit Zn-doped CaP surfaces [18] onto Ti-based alloys (mainly pure Ti and Ti-6Al-4V) as described, in particular, in [20,21].…”

TOFSIMS and XPS characterisation of strontium in amorphous calcium phosphate sputter deposited coatings

“…Sr substituted CaP coatings have already been manufactured using a range of wellestablished approaches, namely plasma spraying [11][12][13], sol-gel methods [14], pulsed laser deposition [15,16], micro-arc oxidation [17], co-blasting [18] and Radio Frequency (RF) Magnetron Sputtering methods [19][20][21][22][23][24][25]. Each techniques has advantages and disadvantages, but sputtering has already shown significant promise in this area as the operating parameters can be tuned to deliver coatings with specific properties.…”

“…Each techniques has advantages and disadvantages, but sputtering has already shown significant promise in this area as the operating parameters can be tuned to deliver coatings with specific properties. [19][20][21][22][23][24][25].…”

RF Magnetron Sputtering of Substituted Hydroxyapatite for Deposition of Biocoatings

“…The structure of the Zn-HA coating has been recently published [ 62 ]. Figure 17 shows TEM images of polycrystalline Zn-HA coating deposited on a substrate controllably heated up to 400 °C.…”