Bioceramic Composite Coating Research Articles

Preparation of bio-ceramic composite coatings on Ti6Al4V titanium alloy by gas-detonation spraying

The paper presents study of a new approach to manufacturing carrier implants with a combination of bioactivity, biocompatibility, and mechanical properties, composite powders of hydroxyapatite and titanium with a mass content of 50:50 % when sprayed by gas detonation spraying. Experimental studies of the surface morphology and cross-section microstructure, phase composition and mechanical properties of HATi composite coatings are obtained. The experimental results showed that the cross-section microstructures of HATi composite coatings are typical plate structures comprising curved strips formed by well-deformed and oxidized Ti plates and limited deformed HA plates. Composite coatings’ morphology and phase states were studied using scanning electron microscopy and X-ray diffractometry. It was found that the deprived coatings mainly consist of the phases HA, Ti and TiO. The elemental composition study results designated that the atomic ratio of calcium and phosphorus in the obtained coatings is Ca/P ~ 1.64, which is close to the value of the initial powder — Ca/P ~ 1.67. This indicates a limited change in the chemical composition during the coating formation.

Electrochemical deposition of HAP/f-MWCNTs and HAP/GO composite layers on 316L SS implant with excellent corrosion resistance performance

Bioceramic composite coatings were deposited on surgical grade 316L stainless steel substrate via in-situ electrolytic method by supplying the voltage of −1.5 V for 30 mins using three electrode arrangements. Formations of pure HAP/GO and HAP/f-MWCNTs composite films were developed and the structure of hydroxyapatite was retained even with incorporation of secondary materials into its matrix. Homogeneously dispersed dense coating was observed for the electrochemically derived HAP composite films on 316L SS. The attachment of GO and f-MWCNTs with hydroxyapatite particles were observed using high resolution transmission electron microscopic (HR-TEM). In-vitro corrosion studies of the fabricated bioceramic composite coatings showed better corrosion protection against the simulated body fluid. Apatite mineralization formed at faster rate for the prepared bioceramic composite films; further which it enhance their bone bonding ability. These results concluded that the electrochemical deposition of bioceramic coatings on implant may be treated as an effective method for orthopedic repair and replacements.

Mechanical properties of warm sprayed HATi bio-ceramic composite coatings

To explore a new approach for fabricating the load bearing implants with the combination of bioactivity, biocompatibility, and mechanical properties, mechanically mixed hydroxyapatite (HA) and titanium (Ti) powders containing 30, 50, and 70 wt% Ti were sprayed onto a 316L stainless steel substrate using a warm spray (WS) process. The microstructures, phase compositions, chemical structures, and mechanical properties of WS HATi composite coatings were comprehensively investigated and compared to those of WS HA coating. Experimental results indicate that the cross-sectional microstructures of WS HATi composite coatings present typical lamellar structures composed of curved stripes formed by well-deformed and oxidized Ti splats and limited deformed HA splats, and are significantly influenced by the Ti content in the original powders. Phase constitutions of the composite coatings mainly consist of HA, Ti, TiO2, and TiO. Chemical structures of HA in the composite coatings deposited using powders with Ti content less than 30% are similar to the structures in the original powder. The microhardness, elastic modulus, and bond strength of the coatings increased from 0.32 ± 0.15 GPa to 1.41 ± 0.31 GPa, from 1.37 ± 0.28 GPa to 23.28 ± 3.45 GPa, and from 17.3 ± 2.2 MPa to 34.8 ± 3.2 MPa, respectively. The abrasive wear weight loss of the coatings on Al2O3 abrasive paper decreased from 2.9 mg to 1 mg, as the addition of Ti particles in original powders increased from 0 to 70%.

Multifunctional Bioceramic Composite Coatings Deposited by Cold Spray

Bioactive coatings have predominately been explored through plasma spray; but this technique has associated heat and melting of the feedstock materials thereby degrading the novel bioactive properties of hydroxyapatite (HA), as well as deteriorating the adhesion of the coating to the implant. The current study discusses a novel approach to producing biocompatible coatings that have been deposited at temperatures well below their melting point. The cold spray process was used to deposit 100 wt.% titanium (Ti) and composite powders with 80 wt% titanium (Ti) and 20 wt% hydroxyapatite (HA) onto Al6061, 316SS and Ti-6Al-4V substrates with the aim of achieving well-bonded homogeneous coatings; the effect of process parameters and substrate material was investigated. Preliminary results indicate the phase composition of the HA remained the same before and after synthesis of coating. Dense composite coatings were obtained with thicker coatings yielding the least amount of total porosity.

Research on the Fabrication of Bioceramic Composite Coatings Fabricated by Nd-YAG Laser Cladding

Laser surface cladding is a material processing technique to overlay the precursor material with the substrate to form a sound chemical and metallurgical bonding. Recently, laser cladding technique has been introduced in the bioceramic coating field. This paper presents a new technology to obtain bioceramic composite coating on Ti6Al4V substrate by Nd-YAG laser cladding. The microstructures of the mixed powders and cladding layer were investigated by scanning electron microscopy, and the compositions were analyzed by electron diffraction spectroscopy. The phases of the mixed powders and cladding layer were clarified by X-ray diffraction technology. Composite coating including HAP,Ca2P2O7,Ca3(PO4)2 and calcium titanates was successfully obtained by Nd-YAG laser cladding with pre-depositing mixed powders of CaHPO4·2H2O and CaCO3 directly on Ti6Al4V substrate. The average grain size of the mixed powders is 3μm from the image analyse software. The most important parameter that affected the completion of laser cladding was the scanning speed.

Ti6Al4V表面激光熔覆生物陶瓷复合涂层研究

Ti6Al4V表面激光熔覆生物陶瓷复合涂层研究

Degradation behavior of n-MAO/EPD bio-ceramic composite coatings on magnesium alloy in simulated body fluid

The bio-ceramic composite coatings have been fabricated on ZK60 magnesium (Mg) alloy to improve its bio-corrosion resistance in a simulated body fluid (SBF). Firstly, micro-arc oxidation coatings (n-MAO coating) with the addition of zirconium oxide (ZrO2) and cerium oxide (CeO2) nano-particles were prepared by MAO technique on ZK60Mg alloy in alkaline electrolyte. Secondly, nano-hydroxyapatite (HA) was deposited on the surface of n-MAO coatings by using electrophoretic deposition (EPD) technique. The degradation behavior of the coated samples was investigated by means of immersion tests and electrochemical impedance spectroscopy (EIS) in the SBF at 36.5±0.5°C. The variation of phase composition, surface and cross-section morphology of coatings at different immersion stages were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results showed that the precipitation layer with biological activity formed on the surface of coated samples during the SBF immersion, which can inhibit Mg alloys from degrading effectively. The n-MAO/EPD composite coating with HA dense structure has a favorable anti-corrosion effect compared to the n-MAO coating. Degradation mechanism model of the corrosion process at different corrosion stages for two kinds of coatings were proposed. The long-term corrosion protection of the n-MAO/EPD composite coating was governed significantly by the synergistic effect of phase composition stability and micro structural integrity.

Polymer–bioceramic composite coatings on magnesium for biomaterial applications

Magnesium's combination of low weight, biodegradability, and favourable mechanical properties make it an ideal material for a biodegradable orthopaedic implant. However, current magnesium-based materials degrade too quickly to be used. In this work, bioceramic–polymer composite coatings were applied to magnesium in an attempt to improve their corrosion resistance.The coatings were characterised and subjected to mechanical tests and qualitative corrosion tests. All of the coatings provided some resistance to corrosion, however, due to gas evolution (a by-product of magnesium corrosion), the coatings blister and crack, allowing corrosion to increase.The adhesion strength of the coating was seen to correlate with the time until cracking failure (during the corrosion test), which indicates that adhesion strength must be increased in order to provide corrosion protection for a suitable time period.The bioceramic–polymer composite coatings had a lower adhesion strength compared to the polymer only coating, due to poor bonding between the bioceramic layer and the magnesium substrate. This decreased adhesion strength leads to cracking failure occurring earlier during the corrosion test, indicating worse performance.In order to improve mechanical and corrosion properties of this method, work needs to be done on strengthening the bonding between the bioceramic layer and the magnesium substrate.

The tribological properties of bioceramic coatings produced on Ti6Al4V alloy by plasma electrolytic oxidation

In this study, hydroxyapatite and calcium apatite-based bio-ceramic composite coatings were produced on Ti6Al4V alloy by plasma electrolytic oxidation (PEO) in the electrolyte consisting of calcium acetate (CA) and β-calcium glycerophosphate (β-Ca-GP) for different treatment times. Coating thickness, phase structure, coating morphology of the cross section, elemental composition, adhesion strength, wear resistance and tribological property of the PEO coatings were analyzed by eddy current method, X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDX mapping), micro scratch tester and tribometer, respectively. The average thickness of the coatings varied from 28 to 52µm with increasing times. The XRD results indicated that anatase (TiO2), rutile (TiO2), TiP2, TCP (Ca3(PO4)2), perovskite – CaTiO3 and hydroxyapatite (Ca10(PO4)6(OH)2) phases were formed on the Ti6Al4V alloy after PEO. According to the EDS mapping results, uniform Ca and P elemental distributions were observed on the surface of PEO coatings. The adhesion strengths of the PEO coatings enhanced with increasing time. The wear resistances and tribological properties of the PEO coatings were greater than those of the uncoated Ti6Al4V alloys, and they were increased with increased time.

Bioceramic Composite Coatings Fabricated by Nd-YAG Laser Cladding Process on Ti6Al4V Substrate

Laser cladding technology was adopted to fabricate hydroxyapatite(HAP) and calcium phosphate compound coating according to the feature that a metallurgical bonding can be formed by laser cladding process. Compared with CO2laser, Nd-YAG laser has different wavelength(the former is 1.06μm and the latter is 10.06μm). Metal and ceramic material has quite different absorbance ability towards them and thus they can generate different laser cladding products by these two laser surface processings with different wavelength. This paper presents a new process and mechanism analysis to obtain bioceramic composite coating on Ti6Al4V substrate by Nd-YAG laser cladding. A bioceramic composite coating including HAP，Ca2P2O7，Ca3(PO4)2and calcium titanates and was successfully obtained by Nd-YAG laser cladding with pre-depositing mixed powders of CaHPO4•2H2O and CaCO3directly on Ti6Al4V substrate. Nd-YAG laser transmits mixed powders of CaHPO4•2H2O and CaCO3and the laser power is absorbed by Ti6Al4V substrate to produce a thin layer of molten region. There are mainly two kinds of chemical reaction systems in the coating during laser cladding processing. When CaHPO4•2H2O and CaCO3react together, they make calcium phosphate bioceramic products; The microstructure of the bioceramic composite coating is even and minute because of the rapid solidification in laser processing. A chemical metallergical bonding is formed between the boceramic composite coating and Ti6Al4V substrate. It can also be expected that Nd-YAG laser cladding technology can be used as a further modification procedure to enhance HAp/metal interface property.

Wetting and in vitro bioactivity of laser processed CaP coating with presence and variation of SiO2 on Ti–6Al–4V

Calcium phosphate bioceramic and SiO2–CaP bioceramic composite coatings were prepared on Ti–6Al–4V substrates by laser cladding method. Surface energy components were calculated and the wettability of the coatings in simulated body fluid (SBF) was investigated. In vitro bioactivity of the coatings were performed by immersing in SBF and analysed for the precipitation of hydroxyapatite (HA). The effects of SiO2 content on the wettability and in vitro bioactivity of the bioceramic composite coatings were investigated. The surface energy values increased as the percentage of SiO2 in the coating precursor increased, resulting in decrease in contact angle with SBF for improved wettability. X-ray diffraction results indicated that after immersion in SBF for more than three days, 17 wt-%SiO2–CaP and 25 wt-%SiO2–CaP samples possessed highly intense peaks of HA than 100 wt-%CaP sample. Furthermore, in vitro bioactivity assays show that the SiO2–CaP bioceramic composite coatings possess a higher HA precipitation rate than CaP coating and Ti–6Al–4V control.

Gradient Rare-Earths Bioceramic Composite Coating Fabricated by Wide-Band Laser Cladding and its Bioactivity

A gradient bioceramic composite coating was prepared by wide-band laser cladding technique on TC4 alloy surface. The influence of rare earths oxide CeO2 on microstructure of bioceramic coating was studied. The experimental results indicated that CeO2 plays an important role in inducing HA + β-TCP formation. There is almost no HA+β-TCP in bioceramic coating without CeO2. When CeO2 content is higher than 0.2 wt.%, the amount of HA+β-TCP catalyzed by CeO2 gradually increases. The amount of HA+β-TCP becomes largest when CeO2 content is up to 0.4wt%. However, when CeO2 content ranges from 0.6 wt.% to 0.8 wt.%, the amount of synthesizing HA+β-TCP conversely goes down. Through cell culture experiment in vitro, the effect of bioceramic coating with different CeO2 contents on the expression of characteristic protein is investigated. The results show that the largest amount of expression of hydroxyproline(Hyp) at 2d and alkaline phosphatase(ALP) at 6d on coating is complied with 0.4wt.% CeO2, The result indicates that bioactivity of bioceramic coating is dependent on the amount of HA + β-TCP catalyzed by different CeO2 contents.

Microstructure and Bonding Feature of the Bioceramic Composite Coating Obtained by Nd: YAG Laser Cladding

Undesirable phase and microstructure formation, and poor HAP/metal bonding strength restrict the fabrication technique to obtain HAP and other calcium phosphate ceramic coatings. In this paper a bioceramic composite coating, which includes HAP andβ-Ca2P2O7, was obtained by laser cladding with pre-depositing mixed powders of CaHPO4·2H2O and CaCO3 directly on the 316L stainless steel metal substrate. The phases, microstructure and bonding feature of the bioceramic composite coating are characterized by X-ray diffraction(XRD), scanning electron microscopy-energy dispersive spectroscopy(SEM-EDS). The microstructure of the coating consists of minute granular HAP that is distributed among the overlapped club-shapedβ-Ca2P2O7. Uniform presences of Ca, P and O in bioceramic composite coating supplie necessary elements for the synthesis of HAP andβ-Ca2P2O7. Diffusions inwards of P and O into alloying layer help form the chemical metallurgical bonding and composition gradient distributions are present. a chemical metallurgical bonding was formed between the bioceramic composite coating and metal substrate.

Microstructure and Biocompatibility of Gradient Bioceramic Composite Coating Fabricated by Wide-Band Laser Cladding

In this study, microstructure and biocompatibility of gradient bioceramic composite coating fabricated by Wide-Band Laser Cladding is investigated. The experimental results indicate that the coating consists of an alloyed transition layer and the bioceramic coating. The bioceramic coating is mainly comprised of HA, CaTiO3, CaO, α-TCP, β-TCP and TiO. The coral-shaped structure and short-rod piled structure existing on the surface of coating. After the implantation of the bioceramic coatings into dogs’ femur for 6, 12, and 24 weeks, hypersusceptibility, rejection and pathological changes are not found. No fiber cyst, necrosis of bone tissue and chronic inflammation obviously appear through slice observation of hard tissues. The bioceramic coating with different ratios of Ca : P have different abilities to induce osteogenesis. At Ca: P=1.4 and 0.6wt.% Y2O3 (No.3 sample), the bioceramic coating is of best bioactivity and biocompatibility.

Mechanical Properties on Gradient Bioceramic Composite Coating Produced by Wide-Band Laser Cladding

To eliminate thermal stress during laser cladding and to raise the bonding strength between substrate and coating, composition gradient coatings are designed and fabricated by using wideband laser cladding technique on a Ti alloy. And mechanical properties on coating is studied. The experimental results indicate that the bonding strength between coating and substrate is fairly high, above 38.8MPa. The highest microhardness is obtained for coating containing 0.6wt.% Y2O3 1062HV0.1 and 1405HV0.1, respectively at bioceramic coating and alloyed transition layer. The average tensile strength, bending strength, and elastic modules of coatings are 767.83MPa, 1671.65MPa, and 13.98GPa, respectively.

Structure of calcium titanate/titania bioceramic composite coatings on titanium alloy and apatite deposition on their surfaces in a simulated body fluid

In this study, TiO 2-based coatings containing Ca and P ions were prepared on titanium alloy surfaces by microarc oxidation (MAO). After soaking in aqueous NaOH solution and subsequent heat treatment at 700 and 800 °C, calcium titanate/titania bioceramic composite (CTBC) coatings were obtained. The results show that the outer layers (0–1.5 μm) of the CTBC coatings are mainly composed of Ca, Ti, O and Na constituents with a uniform distributions with increasing the depth near the surfaces. The surface phase compositions of the CTBC coating formed at 700 °C are anatase, rutile and CaTi 21O 38 phases, as well as a few CaTiO 3, while those of the CTBC coating formed at 800 °C are anatase, rutile and CaTiO 3. When incubated in a simulated body fluid (SBF), apatite was deposited on the CTBC coatings probably via formation of hydroxyl functionalized surface complexes on the CTBC coating surfaces by ionic exchanges between (Ca 2+, Na +) ions of the CTBC coatings and H 3O + ions in the SBF. The CTBC coating formed at 800 °C seems to facilitate the deposition of Ca and P probably due to the good crystallographic match between perovskite CaTiO 3 and HA on specific crystal planes.

Research on the In Situ Fabrication of Bioceramic Composite Coatings by Laser Cladding

Hydroxyapatite(HAP) has excellent osteoconductive properties. By controlling the Ca/P ratio better biphasic calcium phosphate ceramics can be produced than pure HAP ceramics. β- calcium pyrophosphate(β-Ca2P2O7) is a new biodegradable ceramic material and its biological response is quite similar to HAP. Obtaining HAP and other bioactive calcium phosphate ceramic coatings has been a popular research field in the past. In our research a new bioceramic composite coating was obtained by laser cladding with pre-depositing mixed powders of CaHPO4·2H2O and CaCO3 directly on the metal substrate. Its main constituents are HAP and β-Ca2P2O7. The microstructure of the coating consists of minute granular HAP that is distributed among the overlapped club-shaped or needle-like β-Ca2P2O7. The hardness distribution in the cladding layer is even and its value is much higher than that in the substrate. There is a bonded structure of the epitaxial planar growth between the substrate and cladding layer, and both a typical cellular microstructure in the middle and an equiaxed microstructure at the top of the cladding layer.

In situ fabrication of bioceramic composite coatings by laser cladding

A bioceramic composite coating was fabricated onto AISI 316L stainless steel in situ by laser cladding with mixed powders of CaHPO 4•2H 2O and CaCO 3 without a bonding agent. The microstructures of the mixed powders and cladding layer were investigated by scanning electron microscopy, and the compositions/phases were analyzed by electron diffraction spectroscopy and X-ray diffraction. The major phases in the coating are β-Ca 2P 2O 7 and Ca 10 (PO 4) 6(OH) 2. The coating consists of the granular HAP that is distributed among the overlapped club-shaped β-Ca 2P 2O 7. It is shown that there is a bonded structure of the epitaxial planar growth between the substrate and cladding layer, and there is evidently a typical cellular microstructure in the middle and an equiaxed microstructure at the top of the cladding layer. The microstructure evolution in the cladding layer was analyzed based on the ratio of temperature gradient to solidification rate ( G / R) produced in laser cladding.