Direct ceramic coating of calcium phosphate doped with strontium via reactive growing integration layer method on α-Ti alloy

Abstract

A strontium (Sr)-doped hydroxyapatite-like coating was deposited on α-Ti alloy via the growing integration layer (GIL) method at various applied voltages. We added 0.03 M strontium hydroxide (Sr(oH) 2 •8H 2 o) to a solution containing calcium acetate and sodium dihydrogen phosphate to produce Sr-doped hydroxyapatite (Sr-HA) coatings. The scanning electron microscope (SEM) images of these coatings showed that all various features, such as average pore size, coating thickness, microhardness, and roughness, were similar to those of HA. As the voltage increased from 250 to 300 V, the amount of micro cracks decreased, and there were eliminated at 350 V. The SEM images also showed that the Sr-HA coatings were closely integrated with the alloy: without any gaps between the oxide layers and the alloy. In addition, energy-dispersive X-ray spectroscopy verified the Sr integration from the bottom up. X-ray diffraction patterns confirmed Sr-HA formation instead of calcium phosphate, even at the lowest voltage of 250 V. The value of E corr increased by 6.6% after raising the voltage from 250 to 350 V. The electrochemical impedance spectroscopy analysis confirmed that the adequate corrosion resistance of Sr-HA coatings, especially at the highest voltage of 350 V. In addition, the GIL treatment increased the layer resistance measured by R p /R c. optimally, the GiL method used the highest voltage of 350 V to produce higher quality of Sr-HA-rich coatings. Due to their favorable mechanical properties, titanium (Ti) alloys are considered excellent implant alloys 1,2. Many kinds of Ti alloys were designed for applications in dental treatment and clinical surgery. Ti-Cu alloys have valuable mechanical properties like hardness and yield strength, and chemical properties, such as corrosion resistance and antibacterial effect. It is common belief that Ti-Cu alloy can improve by increasing the Cu contents 3. The higher Cu content and fine Ti 2 Cu phase compounds increase the performance resulting in a stronger antibacterial ability and higher strength. In addition, the Cu ions do not lead to cell cytotoxicity. The alloys particularly exhibit very good cell biocompatibility and do not influence cell proliferation or differentiation even if the Cu ion content is increased to 25 wt% 4-6. However, such alloys still need to be coated with a layer of biocompatible protective bioactive ceramics. Calcium phosphates are essential for such creamics. They improve corrosion protection of mechanical property. In addition, they enhance bone regeneration at the beginning apposition stage, and also regeneration of hard tissues in tissue engineering 7-10. Among various calcium phosphates, HA is a major component of human bones and teeth 11,12. During the past two decades, various surface treatments and deposition techniques for the HA coating of the Ti alloys have been studied. These techniques include plasma sprayed deposition, thermal spraying, ion beam assisted deposition (IBAD), sputtering, micro-arc oxidation (MAO), hot isostatic pressing, dip coat...

Evaluation of osteogenic and antibacterial properties of strontium/silver‐containing porous TiO2 coatings prepared by micro‐arc oxidation

“…Several studies demonstrated that Ag incorporation and Ag nanoparticles may improve corrosion resistance of titanium and its alloys 17,21 . Another study by Huang et al 22 also reported that Sr‐doped hydroxyapatite coating can improve corrosion resistance of α‐Ti alloy. Therefore, it may be speculated that Sr/Ag containing TiO 2 coating, prepared by MAO, may benefit corrosion resistance of titanium implants, although experimental evidence is still absent yet and this should be confirmed in future.…”

Low voltage environmentally friendly plasma electrolytic oxidation process for titanium alloys

“…Non-metallic particles such as SiO 2 , Si 3 N 4 , SiC, Al 2 O 3 and ZrO 2 and graphene nanoparticles reportedly improved the mechanical functionality of Ti-alloyed components for aerospace applications. Literature studies also report incorporating NiO, Fe 2 O 3 , Cr 2 O 3 , and hydroxyapatite 15 microparticles into the electrolytic baths to produce functional ceramic oxide coatings on titanium and/or titanium alloys.…”

Recent Advancements in Materials and Coatings for Biomedical Implants

“…Other remarkable advantages are higher resistance to compressive force, low toxicity, good corrosion resistance, and promotion of the formation of new hard tissues. For example, hydroxyapatite-based ceramics exhibit higher Ca/P ratios, which are desirable due to similar chemical properties of bone and teeth hard tissues [32][33][34][35]. Due to these attractive properties, ceramics are increasingly utilized for bioimplant applications.…”