Microstructure and Properties of Hydroxyapatite Coatings Made by Aerosol Cold Spraying–Sintering Technology

Abstract

Hydroxyapatite is a widely used material used for the bioactivation of an implant’s surface. A promising hydroxyapatite coating approach is the kinetic deposition of powder particles. The possibility of solid-state deposition improvement through the merging of Aerosol Deposition and Low Pressure Cold Spraying techniques is a promising prospect for improving the deposition efficiency and the quality of coatings. The objective of the paper is to study the possibilities of hydroxyapatite coating structure modification through changes in the coating process and post-heat treatment. The novel Aerosol Cold Spraying system joining Low Pressure Cold Spraying and Aerosol Deposition was used for the deposition of coatings. The coating’s post-processing was conducted using two techniques: Spark Plasma Sintering and Pressureless Sintering. The coating’s structure was examined using scanning, transmission, and light microscopy, and X-ray diffraction. Substrate–coating bond strength was assessed using a tensile test. Homogenous buildup using Aerosol Cold Spraying of hydroxyapatite was achieved. Various pores and microcracks were visible in the sprayed coatings. The deposition process and the thermal post-processing did not lead to significant degradation of the hydroxyapatite phase. As a result of the Spark Plasma Sintering and Pressureless Sintering at 800 °C, an increase in tensile adhesion bond strength and crystal size was obtained.

There Are over 60 Ways to Produce Biocompatible Calcium Orthophosphate (CaPO4) Deposits on Various Substrates

“…According to the authors, the disadvantages of AD technology, which takes place at ambient temperature, can be overcome by using radial injection into the divergent zone of a Laval-type nozzle, as used in a low-pressure CS. In this case, gas heating of 500-600 • C is possible and the parameters of the fluidized bed aerosol chamber (gas pressure, oscillation amplitude and frequency) can be controlled over a wide range [657].…”

Enhanced Release of Calcium Ions from Hydroxyapatite Nanoparticles with an Increase in Their Specific Surface Area

“…In this paper, we take advantage of our original HAP-synthesis technology [13,62] to precisely determine the effects of GoHAP size and specific surface area on the Ca 2+ concentration in a PBS dispersion. If the relationship between the amount of ions released, the size of the specific surface area, and the sizes of the hydroxyapatite nanoparticles is known, it is possible to program hydroxyapatite resorption [42] and create biodegradable bone grafts [53,63], or layers on titanium implants [64][65][66]. In addition, it is possible to control the degradation rate and the bone-growth-stimulation potential of biodegradable electrospun membranes coated with HAP NPs [67,68], as well as titanium implants coated with HAP NPs.…”

Contribution to Knowledge on Bioapatites: Does Mg Level Reflect the Organic Matter and Water Contents of Enamel?

“…Reducing this scale in of apatites to nanometer scale provides structures that are similar to natural bone in both scale and chemical composition [6]. Furthermore, nanohydroxyapatite (Nano-HA) has been widely investigated due to other potential biomedical applications, such as in drug carriers, as an inhibitor of the growth of various tumor cells [7], and in surface coating [8]. It should be noted that, nowadays, apatites play an essential role in developing composite materials.…”