Comparison of Physical-chemical and Mechanical Properties of Chlorapatite and Hydroxyapatite Plasma Sprayed Coatings

Abstract

Chlorapatite can be considered a potential biomaterial for orthopaedic applications. Its use as plasma-sprayed coating could be of interest considering its thermal properties and particularly its ability to melt without decomposition unlike hydroxyapatite. Chlorapatite (ClA) was synthesized by a high-temperature ion exchange reaction starting from commercial stoichiometric hydroxyapatites (HA). The ClA powder showed similar characteristics as the original industrial HA powder, and was obtained in the monoclinic form. The HA and ClA powders were plasma-sprayed using a low-energy plasma spraying system with identical processing parameters. The coatings were characterized by physical-chemical methods, i.e. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy, including distribution mapping of the main phases detected such as amorphous calcium phosphate (ACP), oxyapatite (OA), and HA or ClA. The unexpected formation of oxyapatite in ClA coatings was assigned to a side reaction with contaminating oxygenated species (O2, H2O). ClA coatings exhibited characteristics different from HA, showing a lower content of oxyapatite and amorphous phase. Although their adhesion strength was found to be lower than that of HA coatings, their application could be an interesting alternative, offering, in particular, a larger range of spraying conditions without formation of massive impurities.

The 2016 Thermal Spray Roadmap

“…As well, studies in biological systems are demanding, as described by some key references (Ref [244][245][246][247][248][249][250][251][252][253][254][255][256][257][258] in the subject area of thermal spray. According to Professor R.B.…”

First Cold Spraying of Carbonated Biomimetic Nanocrystalline Apatite on Ti6Al4V: Physical–Chemical, Microstructural, and Preliminary Mechanical Characterizations

“…[47,48] The average roughness (Ra) of both coatings was in the same range (4 AE 0.2 mm and 7.2 AE 0.6 mm, respectively), whereas the thickness was quite different (60 AE 10 mm and 85 AE 8 mm respectively), which might explain these differences in critical load. [49] …”

Powder bed selective laser process (sintering/melting) applied to tailored calcium phosphate-based powders

“…For this reason, ClA has been studied as a substitute for HA in other manufacturing processes involving high temperatures (e.g. plasma spraying) [13]. The SEM analyses of the circular pattern microstructures produced at the same Ed (96 J.cm 2 ) and using different powder feedstock blends are shown in Figure 9.…”

“…The goal of the present work was to evaluate the performance of different graphite-filled powder blends feedstock with calcium phosphates, such as hydroxyapatite (HA) and chlorapatite (ClA), as main component in a PBSLP process. The use of ClA in addition to HA was explored due to its known higher thermal stability which could be an interesting advantage for processes involving high temperatures [13,14]. Indeed, the ClA conversion into HA has been demonstrated to be feasible through hydrothermal ion exchange of Clby OHif the application requires it [15].…”