Biodegradable implants are critical for regenerative orthopaedic procedures,but they may suffer from too fast corrosion in human-body environment.This necessitates the synthesis of a suitable coating that may improve ...Biodegradable implants are critical for regenerative orthopaedic procedures,but they may suffer from too fast corrosion in human-body environment.This necessitates the synthesis of a suitable coating that may improve the corrosion resistance of these implants without compromising their mechanical integrity.In this study,an AZ91 magnesium alloy,as a representative for a biodegradable Mg implant material,was modified with a thin reduced graphene oxide(RGO)-calcium carbonate(CaCO_(3))composite coating.Detailed analytical and in-vitro electrochemical characterization reveals that this coating significantly improves the corrosion resistance and mechanical integrity,and thus has the potential to greatly extend the related application field.展开更多
Mg and its alloys have been introduced as promising biodegradable materials for biomedical implant applications due to their excellent biocompatibility, mechanical behavior, and biodegradability. However, their suscep...Mg and its alloys have been introduced as promising biodegradable materials for biomedical implant applications due to their excellent biocompatibility, mechanical behavior, and biodegradability. However, their susceptibility to rapid corrosion within the body poses a significant challenge and restricts their applications. To overcome this issue, various surface modification techniques have been developed to enhance the corrosion resistance and bioactivity of Mg-based implants. PEO is a potent technique for producing an oxide film on a surface that significantly minimizes the tendency to corrode. However, the inevitable defects due to discharges and poor biological activity during the coating process remain a concern. Therefore, adding suitable particles during the coating process is a suitable solution. Hydroxyapatite(HAp)has attracted much attention in the development of biomedical applications in the scientific community. HAp shows excellent biocompatibility due to its similarity in chemical composition to the mineral portion of bone. Therefore, its combination with Mg-based implants through PEO has shown significant improvements in their corrosion resistance and bioactivity. This review paper provides a comprehensive overview of the recent advances in the preparation, characterization, corrosion behavior and bioactivity applications of HAp particles on Mg-based implants by PEO.展开更多
TiO2-hydroxyapatite (HA) nanostructured coatings were produced by atmospheric plasma spray method. The effects of starting powder composition and grain size on their mechanical properties were investigated. The micr...TiO2-hydroxyapatite (HA) nanostructured coatings were produced by atmospheric plasma spray method. The effects of starting powder composition and grain size on their mechanical properties were investigated. The microstructure and morphology were characterized by X-ray diffraction and scanning electron microscopy (SEM). It is found that the coating with 10% HA has the best mechanical properties. Based on Rietveld refinement method, the mean grain size of the as-received powder (212 nm) extensively decreases to 66.4 nm after 20 h of high-energy ball milling. In spite of grain growth, the deposited coatings maintain their nanostructures with the mean grain size of 112 nm. SEM images show that there is a lower porosity in the coating with a higher HA content. Optical microscopy images show that uniform thickness is obtained for all the coatings.展开更多
Air plasma spraying process was employed to fabricate various hydroxyapatite(HA)coatings on titanium substrates.The influence of processing parameters on the phase composition and the microstructure of the obtained co...Air plasma spraying process was employed to fabricate various hydroxyapatite(HA)coatings on titanium substrates.The influence of processing parameters on the phase composition and the microstructure of the obtained coatings was investigated.The effect of heat treatment on as-sprayed coating in terms of the crystallinity and microstructure was also studied.The phase composition of coatings was analyzed by X-ray diffraction(XRD)and FTIR.The surface and cross-section morphologies and microstructure of coatings as well as the morphology of feedstock were evaluated using scanning electron microscope(SEM).The crystallization temperature of amorphous HA phase in as-sprayed coating was examined by using differential thermal analysis(DTA). The results suggest that phase composition and microstructure of as-sprayed HA coatings strongly depend on the spraying parameters,and heat treatment at 760 ℃for 2 h is one of effective means for increasing the crystallinity and improvement in microstructure of as-sprayed HA coatings.展开更多
Globally,vast research interest is emerging towards the development of biodegradable orthopedic implants as it overcomes the toxicity exerted by non-degradable implants when fixed in the human body for a longer period...Globally,vast research interest is emerging towards the development of biodegradable orthopedic implants as it overcomes the toxicity exerted by non-degradable implants when fixed in the human body for a longer period.In this context,magnesium(Mg)plays a major role in the production of biodegradable implants owing to their characteristic degradation nature under the influence of body fluids.Also,Mg is one of the essential nutrients required to perform various metabolic activities by the human cells,and therefore,the degraded Mg products will be readily absorbed by the nearby tissues.Nevertheless,the higher corrosion rate in the biological environment is the primary downside of using Mg implants that liberate H2gas resulting in the formation of cavities.Further,in certain cases,Mg undergoes complete degradation before the healing of damaged bone tissue and cannot serve the purpose of providing mechanical support.So,many studies have been focused on the development of different strategies to improve the corrosion-resistant behavior of Mg according to the requirement.In this regard,the present review focused on the limitations of using pure Mg and Mg alloys for the fabrication of medical implants and how the calcium phosphate conversion coating alters the corrosive tendency through the formation of hydroxyapatite protective films for enhanced performance in medical implant applications.展开更多
A novel biocomposite coating of hydroxyapatite/Al2O3 was fabricated on titanium using a multi-step technique including physical vapor deposition(PVD), anodization, electrodeposition and hydrothermal treatment. Anodic ...A novel biocomposite coating of hydroxyapatite/Al2O3 was fabricated on titanium using a multi-step technique including physical vapor deposition(PVD), anodization, electrodeposition and hydrothermal treatment. Anodic Al2O3 layer with micrometric pore diameter was formed by anodization of the PVD-deposited aluminum film on titanium and subsequent removal of part barrier Al2O3 layer. Hydroxyapatite coating was then electrodeposited onto the as-synthesized anodic Al2O3 on titanium. A hydrothermal process was finally applied to the fabricated biocomposite coating on titanium in alkaline medium. Scanning electron microscopy(SEM), energy dispersive spectrometry(EDS) and X-ray diffractometry(XRD) were employed to investigate the morphologies and compositions of the pre-and post-hydrothermally treated hydroxyapatite/Al2O3 biocomposite coatings. The results show that micrometric plate-like Ca-deficient hydroxyapatite (CDHA) coatings are directly electrodeposited onto anodic Al2O3 at constant current densities ranging from 1.2 to 2.0 mA/cm2 using NaH2PO4 as the phosphorous source. After hydrothermal treatment, the micrometric plate-like CDHA coating electrodeposited at 2.0 mA/cm2 is converted into nano-network Ca-rich hydroxyapatite (CRHA) one and the adhesion strength is improved from 9.5 MPa to 21.3 MPa. A mechanism of dissolution-recrystallization was also proposed for the formation of CRHA.展开更多
Recently,magnesium and its alloys have attracted more and more attention as promising implant materials due to their excellent properties such as good biocompatibility,biodegradation,non-toxicity and comparable mechan...Recently,magnesium and its alloys have attracted more and more attention as promising implant materials due to their excellent properties such as good biocompatibility,biodegradation,non-toxicity and comparable mechanical properties with natural bone.They can be gradually degraded and absorbed so as to avoid the second surgery for implants removal after the tissues are healed completely.In addition,they are also able to prevent the stress shielding effect in human body environment because of the density,elastic modulus and yield strength of magnesium closer to the bone.Unfortunately,the high corrosion rate which causes early mechanical failure of the implants in physiological environment limits the widespread use of magnesium alloys for clinical application in biology.And the high corrosion process usually causes huge hydrogen evolution and alkalinization,resulting in problems against the implants as well as the surrounding tissues.In order to enhance the corrosion resistance of magnesium alloys,in this study,the ZEK100 magnesium alloy was pre-deformed with a highpressure torsion(HPT)process and then fabricated hydroxyapatite(HA)coatings with different contents of Mg(OH)2 nanopowder via hydrothermal method.The specimens were characterized by scanning electron microscope(SEM)and X-ray diffraction(XRD).At the same time,prior and after the HPT procedure,the metallography,microhardness and tensile tests of specimens were characterized.Meanwhile,the corrosion behavior of the specimens was evaluated by electrochemical impedance spectroscopy(EIS)and hydrogen evolution tests.And the interface bonding strength of the HA coating on the magnesium alloy substrate was evaluated by a tape adhesion test/scratch test.Results showed that HPT processing refined the grain size and introduced a great number of twins,resulting in the enhancement of microhardness and Young’s modulus of ZEK100 magnesium alloy,but hardness values at the edge were higher than those at the center due to the uneven shear strain.At the same conditions,the HA coating on HPT-ZEK was denser,thicker than that on ZEK sample and the crystal sizes of HA were smaller on HPT-ZEK.These were attributed to fine,uniform distributed secondary phases and lots of fine grains,twins,grain boundaries in HPT-ZEK substrates which can provide more nucleation sites for the HA crystal.In terms of the amount of Mg(OH)2 nanopowder,Mg(OH)2 nanopowder significantly influenced the microstructure and thickness of the HA coating.And at a 0.3 mg/mL content of Mg(OH)2 nanopowder,there was the densest,thickest HA coating on magnesium alloys,and the crystal size of HA was minimum.Specifically,the HA coating thickness on ZEK-03(0.3 mg/mL Mg(OH)2 nanopowder)was 1.8 times of that on ZEK-00(0 mg/mL Mg(OH)2 nanopowder),while the HA coating thickness on HPT-03 was 2.6 times of that on ZEK-00.And the adhesion strength of HA coating on HPT-03 substrate was better than that on ZEK-03.In addition,HPT technology and surface modification by HA coating simultaneously increased the corrosion resistance of ZEK100 magnesium alloy and the corrosion of HPT-ZEK samples occurred in a more uniform manner,while it was pitting on the surface of ZEK100 magnesium alloy.Therefore,there was the best corrosion resistance on HPT-03 sample,which could promote the application of magnesium alloys in biomedical fields.展开更多
The hydroxyapatite(HA) ceramic coating was successfully prepared on Ti6A14V alloy by the hydrothermal-electrochemical deposition method with constant voltage model. The phases of deposits were analyzed by X-ray diff...The hydroxyapatite(HA) ceramic coating was successfully prepared on Ti6A14V alloy by the hydrothermal-electrochemical deposition method with constant voltage model. The phases of deposits were analyzed by X-ray diffraction. The releationship between crystallinity and depositing temperature was discussed. The microstructures of hydroxyapatite coating were observed by scanning electron microscope. The experimental results showed that the phases, crystaUinity and morphologies of deposits were influenced by depositing temperature (100℃, 120℃, 140℃, 160℃, 180℃ and 200℃, respectively). The special hydrothermal environment can lower the crystallization temperature of HA. The crystallinity of HA increases firstly and then decreases with the increase of temperature. There is little hydroxyapatite deposited on the Ti6A14V surface when the depositing temperature is 100℃. The HA deposition increases with the increase of the depositing temperature. And the HA morphologies are influenced by the depositing temperature.展开更多
Magnesium is a candidate metal for biodegradable implant applications for its biodegradation tendency and excellent biocompatibility.Unfortunately,the high degradation rate of magnesium and also its localized degradat...Magnesium is a candidate metal for biodegradable implant applications for its biodegradation tendency and excellent biocompatibility.Unfortunately,the high degradation rate of magnesium and also its localized degradation in physiological conditions are the main issues for its successful implant applications.The degradation rate of magnesium has been reduced to some degree via alloying,but the localized degradation susceptibility is a great concern.For many years,hydroxyapatite(HAp),a biocompatible ceramic material,has been extensively used for bio-implant applications.Recently,a substantial amount of research has been carried out on coating HAp on magnesium-based materials for improved degradation resistance in particular and also to enhance the biocompatibility.This review article focuses on the different methods of HAp coating on magnesium-based materials and also the recent cutting-edge advancements made in the coating process for improved degradation resistance and biocompatibility.The mechanical stability of the HAp coated magnesium-based materials is also discussed.展开更多
This study aimed to examine the biocompatibility of calcium titanate(CaTiO3) coating prepared by a simplified technique in an attempt to assess the potential of CaTiO3coating as an alternative to current implant coati...This study aimed to examine the biocompatibility of calcium titanate(CaTiO3) coating prepared by a simplified technique in an attempt to assess the potential of CaTiO3coating as an alternative to current implant coating materials. CaTiO3-coated titanium screws were implanted with hydroxyapatite(HA)-coated or uncoated titanium screws into medial and lateral femoral condyles of 48 New Zealand white rabbits. Imaging, histomorphometric and biomechanical analyses were employed to evaluate the osseointegration and biocompatibility 12 weeks after the implantation. Histology and scanning electron microscopy revealed that bone tissues surrounding the screws coated with CaTiO3were fully regenerated and they were also well integrated with the screws. An interfacial fibrous membrane layer, which was found in the HA coating group, was not noticeable between the bone tissues and CaTiO3-coated screws. X-ray imaging analysis showed in the CaTiO3coating group, there was a dense and tight binding between implants and the bone tissues; no radiation translucent zone was found surrounding the implants as well as no detachment of the coating and femoral condyle fracture. In contrast, uncoated screws exhibited a fibrous membrane layer, as evidenced by the detection of a radiation translucent zone between the implants and the bone tissues. Additionally, biomechanical testing revealed that the binding strength of CaTiO3coating with bone tissues was significantly higher than that of uncoated titanium screws, and was comparable to that of HA coating. The study demonstrated that CaTiO3coating in situ to titanium screws possesses great biocompatibility and osseointegration comparable to HA coating.展开更多
A porous cerium-containing hydroxyapatite coating on commercially pure titanium was prepared by micro-arc oxidation (MAO) in an electrolytic solution containing calcium acetate, p-glycerol phosphate disodium salt pe...A porous cerium-containing hydroxyapatite coating on commercially pure titanium was prepared by micro-arc oxidation (MAO) in an electrolytic solution containing calcium acetate, p-glycerol phosphate disodium salt pentahydrate (β-GP), and cerium nitrate. The thickness, phase, composition morphology, and biocompatibility of the oxide coating were characterized by X-ray diffraction (XRD), electron probe microanalysis (EPMA), scanning electron microscopy (SEM) with energy dispersive X-ray spectrometer (EDS), and cell culture. The thickness of the MAO film is about 15-25 ~tm, and the coating is porous and uneven, without any apparent interface to the titanium substrates. The results of XRD and EDS show that the porous coating is made up of hydroxyapatite (HA) film containing Ce. The favorable osteoblast cell affinity makes the Ce-HA film have a good biocompatibility. The Ce-HA film is expected to have significant medical applications as dental implants and artificial bone joints.展开更多
Hot pressing of hydroxyapatite(HA) Ti system material and the stability of HA component were investigated to supply the foundation of optimizing sintering procedure of HA Ti functionally graded material(FGM). The resu...Hot pressing of hydroxyapatite(HA) Ti system material and the stability of HA component were investigated to supply the foundation of optimizing sintering procedure of HA Ti functionally graded material(FGM). The results show that the HA powders used have excellent thermal stability and no decomposition is observed at 1 300 ℃. The existence of Ti can promote the dehydration and decomposition of HA. However, no new compounds form between HA and Ti. By selecting sintering parameters properly, ideal HA Ti material can be acquired. The relative densities of the mixtures of HA and Ti are always lower than those of pure HA or Ti, which may be caused by the decomposition of HA in the mixtures.展开更多
Magnesium(Mg)alloys are receiving increasing attention as biodegradable implant materials in recent years.However,their low corrosion resistance and fast degradation in the physiological environment remain challenges ...Magnesium(Mg)alloys are receiving increasing attention as biodegradable implant materials in recent years.However,their low corrosion resistance and fast degradation in the physiological environment remain challenges for a widespread application.Hydroxyapatite(HA)coating on Mg alloys can enhance their corrosion resistance,biocompatibility,and bioactivity of the Mg alloy substrates since the compositions of HA are similar to those of the hard tissue of natural bone.This review analyzes the challenges of Mg alloys for biomedical applications,the fundamental requirements for biodegradable metals,and the corrosion mechanisms of Mg alloys in the physiological environment.The benefits of HA coatings on Mg alloys,the most commonly used surface coating techniques and their advantages and limitations,and the in vitro and in vivo performance of Mg alloys with and without surface coatings are comprehensively elucidated.Multistep processes such as alkali treatment and then HA coating by electrochemical deposition on Mg alloys appear to be necessary to achieve a satisfactory surface coating on Mg alloys,which has been demonstrated to have the potential to improve the degrading behavior,bioactivity and biocompatibility.Multifunctional coatings are most effective in achieving safe and bioactive Mg alloy surfaces for promising biodegradable implant applications.展开更多
To improve the bioactivity and corrosion resistance of AZ91 D magnesium alloy,hydroxyapatite(HAp) coatings with novel microstructured morphologies were prepared successfully on AZ91 D substrates via a facile hydroth...To improve the bioactivity and corrosion resistance of AZ91 D magnesium alloy,hydroxyapatite(HAp) coatings with novel microstructured morphologies were prepared successfully on AZ91 D substrates via a facile hydrothermal method.Different chelating agents including polyaspartic acid(PASP) and ethylenediaminetetraacetic acid(EDTA) were introduced to investigate their effects on the morphology and corrosion resistance of the coated magnesium alloys.The results revealed that the coating prepared with PASP was composed of many uniform urchin-like microspheres,while the coating prepared with EDTA consisted of many flower-like particles.Moreover,the crystallinity of the coating prepared with EDTA was much higher than that of the coating prepared with PASP.Electrochemical tests revealed that the corrosion resistance of the substrate was significantly improved after being coated with each coating.Immersion test of the coated samples in simulated body fluid(SBF) demonstrated that the coatings could be biodegraded gradually and induce the formation of calcium phosphate particles.展开更多
Hydroxyapatite (HA, Ca10(PO4)6(OH)2) coating was fabricated on pure Ti (TA2) by laser cladding technology. The phase structure, microstructure, microhardness and electrochemical behavior of the laser cladded H...Hydroxyapatite (HA, Ca10(PO4)6(OH)2) coating was fabricated on pure Ti (TA2) by laser cladding technology. The phase structure, microstructure, microhardness and electrochemical behavior of the laser cladded HA coating in artificial body fluid were investigated. The results show that the HA coating is mainly composed of highly crystallized HA. A transitional layer between HA coating and Ti substrate is formed. Microhardness measurement shows the gradually increasing of microhardness from 150 HV at TA2 substrate to 600 HV at transitional layer, and followed by a decreasing to 400 HV at HA coated layer. Electrochemical corrosion tests show that the HA coating has higher open circuit potential , lower corrosion current density and corrosion rate in comparison to the TA2 substrate.展开更多
Hydroxyapatite/titania (HA/TiO2) double layers were coated onto Ti scaffolds throughout for orthopaedic applications by sol-gel method. Differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and X-ra...Hydroxyapatite/titania (HA/TiO2) double layers were coated onto Ti scaffolds throughout for orthopaedic applications by sol-gel method. Differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and X-ray diffractometry (XRD) were used for the characterisation of the phase transformations of the dried gels and coated surface structures. Scanning electron microscope (SEM) equipped with energy dispersive spectrometry (EDS) was used for the observation and evaluation of the morphology and phases of the surface layers and for the assessment of the in vitro tests. The in vitro assessments were performed by soaking the HA/TiO2 double coated samples into the simulated body fluid (SBF) for various periods. The TiO2 dipping-coating method at a speed of 12 cm/min, followed by a heat treatment at 600 ℃ for 20 min. The HA la lyaeyre wr wasa ssu cbosaetqeude bnytl ya dipping-coated on the outer surface at the same speed and then heat-treated at difference temperatures. The results indicat that the HA phase begins to crystallize after a heat treatment at 560 ℃. The crystallinity increases obviously at 760 ℃. SEM observations find no delamination or crack at the interfaces of HA/TiO2 and TiO2/Ti. The HA/TiO2 coated Ti scaffolds displays excellent bone-like apatite forming ability when it is soaked into SBF. Ti scaffolds after HA/TiO2 double coatings can be anticipated as promising implant materials for orthopaedic展开更多
A codeposition of bioglass (BG) and hydroxyapatite (HA) on the substrate Ti6Al4V is realized in a nonaqueous solution system by inducing crystallization of HA on surface of the BG grain and electrophoresis deposition ...A codeposition of bioglass (BG) and hydroxyapatite (HA) on the substrate Ti6Al4V is realized in a nonaqueous solution system by inducing crystallization of HA on surface of the BG grain and electrophoresis deposition (EPD), and then a bioactive graded ceramic coating was obtained after sintering of the coating. This technique is a new method for making bioactive graded coating. The adhesive strength between the coating and the substrate reaches 18?MPa, and the better electrophoresis depositing parameters and optimal sintering procedure are obtained.展开更多
文摘Biodegradable implants are critical for regenerative orthopaedic procedures,but they may suffer from too fast corrosion in human-body environment.This necessitates the synthesis of a suitable coating that may improve the corrosion resistance of these implants without compromising their mechanical integrity.In this study,an AZ91 magnesium alloy,as a representative for a biodegradable Mg implant material,was modified with a thin reduced graphene oxide(RGO)-calcium carbonate(CaCO_(3))composite coating.Detailed analytical and in-vitro electrochemical characterization reveals that this coating significantly improves the corrosion resistance and mechanical integrity,and thus has the potential to greatly extend the related application field.
文摘Mg and its alloys have been introduced as promising biodegradable materials for biomedical implant applications due to their excellent biocompatibility, mechanical behavior, and biodegradability. However, their susceptibility to rapid corrosion within the body poses a significant challenge and restricts their applications. To overcome this issue, various surface modification techniques have been developed to enhance the corrosion resistance and bioactivity of Mg-based implants. PEO is a potent technique for producing an oxide film on a surface that significantly minimizes the tendency to corrode. However, the inevitable defects due to discharges and poor biological activity during the coating process remain a concern. Therefore, adding suitable particles during the coating process is a suitable solution. Hydroxyapatite(HAp)has attracted much attention in the development of biomedical applications in the scientific community. HAp shows excellent biocompatibility due to its similarity in chemical composition to the mineral portion of bone. Therefore, its combination with Mg-based implants through PEO has shown significant improvements in their corrosion resistance and bioactivity. This review paper provides a comprehensive overview of the recent advances in the preparation, characterization, corrosion behavior and bioactivity applications of HAp particles on Mg-based implants by PEO.
文摘TiO2-hydroxyapatite (HA) nanostructured coatings were produced by atmospheric plasma spray method. The effects of starting powder composition and grain size on their mechanical properties were investigated. The microstructure and morphology were characterized by X-ray diffraction and scanning electron microscopy (SEM). It is found that the coating with 10% HA has the best mechanical properties. Based on Rietveld refinement method, the mean grain size of the as-received powder (212 nm) extensively decreases to 66.4 nm after 20 h of high-energy ball milling. In spite of grain growth, the deposited coatings maintain their nanostructures with the mean grain size of 112 nm. SEM images show that there is a lower porosity in the coating with a higher HA content. Optical microscopy images show that uniform thickness is obtained for all the coatings.
文摘Air plasma spraying process was employed to fabricate various hydroxyapatite(HA)coatings on titanium substrates.The influence of processing parameters on the phase composition and the microstructure of the obtained coatings was investigated.The effect of heat treatment on as-sprayed coating in terms of the crystallinity and microstructure was also studied.The phase composition of coatings was analyzed by X-ray diffraction(XRD)and FTIR.The surface and cross-section morphologies and microstructure of coatings as well as the morphology of feedstock were evaluated using scanning electron microscope(SEM).The crystallization temperature of amorphous HA phase in as-sprayed coating was examined by using differential thermal analysis(DTA). The results suggest that phase composition and microstructure of as-sprayed HA coatings strongly depend on the spraying parameters,and heat treatment at 760 ℃for 2 h is one of effective means for increasing the crystallinity and improvement in microstructure of as-sprayed HA coatings.
文摘Globally,vast research interest is emerging towards the development of biodegradable orthopedic implants as it overcomes the toxicity exerted by non-degradable implants when fixed in the human body for a longer period.In this context,magnesium(Mg)plays a major role in the production of biodegradable implants owing to their characteristic degradation nature under the influence of body fluids.Also,Mg is one of the essential nutrients required to perform various metabolic activities by the human cells,and therefore,the degraded Mg products will be readily absorbed by the nearby tissues.Nevertheless,the higher corrosion rate in the biological environment is the primary downside of using Mg implants that liberate H2gas resulting in the formation of cavities.Further,in certain cases,Mg undergoes complete degradation before the healing of damaged bone tissue and cannot serve the purpose of providing mechanical support.So,many studies have been focused on the development of different strategies to improve the corrosion-resistant behavior of Mg according to the requirement.In this regard,the present review focused on the limitations of using pure Mg and Mg alloys for the fabrication of medical implants and how the calcium phosphate conversion coating alters the corrosive tendency through the formation of hydroxyapatite protective films for enhanced performance in medical implant applications.
基金Project(50472031) supported by the National Natural Science Foundation of China
文摘A novel biocomposite coating of hydroxyapatite/Al2O3 was fabricated on titanium using a multi-step technique including physical vapor deposition(PVD), anodization, electrodeposition and hydrothermal treatment. Anodic Al2O3 layer with micrometric pore diameter was formed by anodization of the PVD-deposited aluminum film on titanium and subsequent removal of part barrier Al2O3 layer. Hydroxyapatite coating was then electrodeposited onto the as-synthesized anodic Al2O3 on titanium. A hydrothermal process was finally applied to the fabricated biocomposite coating on titanium in alkaline medium. Scanning electron microscopy(SEM), energy dispersive spectrometry(EDS) and X-ray diffractometry(XRD) were employed to investigate the morphologies and compositions of the pre-and post-hydrothermally treated hydroxyapatite/Al2O3 biocomposite coatings. The results show that micrometric plate-like Ca-deficient hydroxyapatite (CDHA) coatings are directly electrodeposited onto anodic Al2O3 at constant current densities ranging from 1.2 to 2.0 mA/cm2 using NaH2PO4 as the phosphorous source. After hydrothermal treatment, the micrometric plate-like CDHA coating electrodeposited at 2.0 mA/cm2 is converted into nano-network Ca-rich hydroxyapatite (CRHA) one and the adhesion strength is improved from 9.5 MPa to 21.3 MPa. A mechanism of dissolution-recrystallization was also proposed for the formation of CRHA.
基金sponsored by the National Natural Science Foundation of China ( 51571150,11572222)Tianjin Natural Science Foundation ( 14JCYBJC16900)
文摘Recently,magnesium and its alloys have attracted more and more attention as promising implant materials due to their excellent properties such as good biocompatibility,biodegradation,non-toxicity and comparable mechanical properties with natural bone.They can be gradually degraded and absorbed so as to avoid the second surgery for implants removal after the tissues are healed completely.In addition,they are also able to prevent the stress shielding effect in human body environment because of the density,elastic modulus and yield strength of magnesium closer to the bone.Unfortunately,the high corrosion rate which causes early mechanical failure of the implants in physiological environment limits the widespread use of magnesium alloys for clinical application in biology.And the high corrosion process usually causes huge hydrogen evolution and alkalinization,resulting in problems against the implants as well as the surrounding tissues.In order to enhance the corrosion resistance of magnesium alloys,in this study,the ZEK100 magnesium alloy was pre-deformed with a highpressure torsion(HPT)process and then fabricated hydroxyapatite(HA)coatings with different contents of Mg(OH)2 nanopowder via hydrothermal method.The specimens were characterized by scanning electron microscope(SEM)and X-ray diffraction(XRD).At the same time,prior and after the HPT procedure,the metallography,microhardness and tensile tests of specimens were characterized.Meanwhile,the corrosion behavior of the specimens was evaluated by electrochemical impedance spectroscopy(EIS)and hydrogen evolution tests.And the interface bonding strength of the HA coating on the magnesium alloy substrate was evaluated by a tape adhesion test/scratch test.Results showed that HPT processing refined the grain size and introduced a great number of twins,resulting in the enhancement of microhardness and Young’s modulus of ZEK100 magnesium alloy,but hardness values at the edge were higher than those at the center due to the uneven shear strain.At the same conditions,the HA coating on HPT-ZEK was denser,thicker than that on ZEK sample and the crystal sizes of HA were smaller on HPT-ZEK.These were attributed to fine,uniform distributed secondary phases and lots of fine grains,twins,grain boundaries in HPT-ZEK substrates which can provide more nucleation sites for the HA crystal.In terms of the amount of Mg(OH)2 nanopowder,Mg(OH)2 nanopowder significantly influenced the microstructure and thickness of the HA coating.And at a 0.3 mg/mL content of Mg(OH)2 nanopowder,there was the densest,thickest HA coating on magnesium alloys,and the crystal size of HA was minimum.Specifically,the HA coating thickness on ZEK-03(0.3 mg/mL Mg(OH)2 nanopowder)was 1.8 times of that on ZEK-00(0 mg/mL Mg(OH)2 nanopowder),while the HA coating thickness on HPT-03 was 2.6 times of that on ZEK-00.And the adhesion strength of HA coating on HPT-03 substrate was better than that on ZEK-03.In addition,HPT technology and surface modification by HA coating simultaneously increased the corrosion resistance of ZEK100 magnesium alloy and the corrosion of HPT-ZEK samples occurred in a more uniform manner,while it was pitting on the surface of ZEK100 magnesium alloy.Therefore,there was the best corrosion resistance on HPT-03 sample,which could promote the application of magnesium alloys in biomedical fields.
基金Funded in Part by the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing(Wuhan University of Technology)(2013-KF7)the Research Fund of Science and Technology Commission of Shanghai Municipality(Nos.09ZR1422100,11441900500,11441900501)
文摘The hydroxyapatite(HA) ceramic coating was successfully prepared on Ti6A14V alloy by the hydrothermal-electrochemical deposition method with constant voltage model. The phases of deposits were analyzed by X-ray diffraction. The releationship between crystallinity and depositing temperature was discussed. The microstructures of hydroxyapatite coating were observed by scanning electron microscope. The experimental results showed that the phases, crystaUinity and morphologies of deposits were influenced by depositing temperature (100℃, 120℃, 140℃, 160℃, 180℃ and 200℃, respectively). The special hydrothermal environment can lower the crystallization temperature of HA. The crystallinity of HA increases firstly and then decreases with the increase of temperature. There is little hydroxyapatite deposited on the Ti6A14V surface when the depositing temperature is 100℃. The HA deposition increases with the increase of the depositing temperature. And the HA morphologies are influenced by the depositing temperature.
基金National Natural Science Foundation of China(Grant No.52071191)Open Foundation of Hubei Key Laboratory of Advanced Technology for Automotive Components(No.XDQCKF2021006)。
文摘Magnesium is a candidate metal for biodegradable implant applications for its biodegradation tendency and excellent biocompatibility.Unfortunately,the high degradation rate of magnesium and also its localized degradation in physiological conditions are the main issues for its successful implant applications.The degradation rate of magnesium has been reduced to some degree via alloying,but the localized degradation susceptibility is a great concern.For many years,hydroxyapatite(HAp),a biocompatible ceramic material,has been extensively used for bio-implant applications.Recently,a substantial amount of research has been carried out on coating HAp on magnesium-based materials for improved degradation resistance in particular and also to enhance the biocompatibility.This review article focuses on the different methods of HAp coating on magnesium-based materials and also the recent cutting-edge advancements made in the coating process for improved degradation resistance and biocompatibility.The mechanical stability of the HAp coated magnesium-based materials is also discussed.
基金supported by the National Natural Science Foundation of China(Nos.81572150,81571939)the Natural Science Foundation of Hunan Province(No.2015JJ2187)the Wu Jie-Ping Medical Foundation of the Minister of Health of China(No.320675014118)
文摘This study aimed to examine the biocompatibility of calcium titanate(CaTiO3) coating prepared by a simplified technique in an attempt to assess the potential of CaTiO3coating as an alternative to current implant coating materials. CaTiO3-coated titanium screws were implanted with hydroxyapatite(HA)-coated or uncoated titanium screws into medial and lateral femoral condyles of 48 New Zealand white rabbits. Imaging, histomorphometric and biomechanical analyses were employed to evaluate the osseointegration and biocompatibility 12 weeks after the implantation. Histology and scanning electron microscopy revealed that bone tissues surrounding the screws coated with CaTiO3were fully regenerated and they were also well integrated with the screws. An interfacial fibrous membrane layer, which was found in the HA coating group, was not noticeable between the bone tissues and CaTiO3-coated screws. X-ray imaging analysis showed in the CaTiO3coating group, there was a dense and tight binding between implants and the bone tissues; no radiation translucent zone was found surrounding the implants as well as no detachment of the coating and femoral condyle fracture. In contrast, uncoated screws exhibited a fibrous membrane layer, as evidenced by the detection of a radiation translucent zone between the implants and the bone tissues. Additionally, biomechanical testing revealed that the binding strength of CaTiO3coating with bone tissues was significantly higher than that of uncoated titanium screws, and was comparable to that of HA coating. The study demonstrated that CaTiO3coating in situ to titanium screws possesses great biocompatibility and osseointegration comparable to HA coating.
基金This work was financially supported by the Natural Science Foundation Team Project of Guangdong,China(No.04205786)the Key Science and Technology Project of the Ministry of Education of China(No.[2005]4).
文摘A porous cerium-containing hydroxyapatite coating on commercially pure titanium was prepared by micro-arc oxidation (MAO) in an electrolytic solution containing calcium acetate, p-glycerol phosphate disodium salt pentahydrate (β-GP), and cerium nitrate. The thickness, phase, composition morphology, and biocompatibility of the oxide coating were characterized by X-ray diffraction (XRD), electron probe microanalysis (EPMA), scanning electron microscopy (SEM) with energy dispersive X-ray spectrometer (EDS), and cell culture. The thickness of the MAO film is about 15-25 ~tm, and the coating is porous and uneven, without any apparent interface to the titanium substrates. The results of XRD and EDS show that the porous coating is made up of hydroxyapatite (HA) film containing Ce. The favorable osteoblast cell affinity makes the Ce-HA film have a good biocompatibility. The Ce-HA film is expected to have significant medical applications as dental implants and artificial bone joints.
文摘Hot pressing of hydroxyapatite(HA) Ti system material and the stability of HA component were investigated to supply the foundation of optimizing sintering procedure of HA Ti functionally graded material(FGM). The results show that the HA powders used have excellent thermal stability and no decomposition is observed at 1 300 ℃. The existence of Ti can promote the dehydration and decomposition of HA. However, no new compounds form between HA and Ti. By selecting sintering parameters properly, ideal HA Ti material can be acquired. The relative densities of the mixtures of HA and Ti are always lower than those of pure HA or Ti, which may be caused by the decomposition of HA in the mixtures.
基金The authors would like to acknowledge the financial support to this research by the Australian Research Council(ARC)through the Discovery Project DP170102557Future Fellowship Project FT 160100252.
文摘Magnesium(Mg)alloys are receiving increasing attention as biodegradable implant materials in recent years.However,their low corrosion resistance and fast degradation in the physiological environment remain challenges for a widespread application.Hydroxyapatite(HA)coating on Mg alloys can enhance their corrosion resistance,biocompatibility,and bioactivity of the Mg alloy substrates since the compositions of HA are similar to those of the hard tissue of natural bone.This review analyzes the challenges of Mg alloys for biomedical applications,the fundamental requirements for biodegradable metals,and the corrosion mechanisms of Mg alloys in the physiological environment.The benefits of HA coatings on Mg alloys,the most commonly used surface coating techniques and their advantages and limitations,and the in vitro and in vivo performance of Mg alloys with and without surface coatings are comprehensively elucidated.Multistep processes such as alkali treatment and then HA coating by electrochemical deposition on Mg alloys appear to be necessary to achieve a satisfactory surface coating on Mg alloys,which has been demonstrated to have the potential to improve the degrading behavior,bioactivity and biocompatibility.Multifunctional coatings are most effective in achieving safe and bioactive Mg alloy surfaces for promising biodegradable implant applications.
基金Funded by Shandong Provincial Natural Science Foundation,China(No.ZR2014EMM019)
文摘To improve the bioactivity and corrosion resistance of AZ91 D magnesium alloy,hydroxyapatite(HAp) coatings with novel microstructured morphologies were prepared successfully on AZ91 D substrates via a facile hydrothermal method.Different chelating agents including polyaspartic acid(PASP) and ethylenediaminetetraacetic acid(EDTA) were introduced to investigate their effects on the morphology and corrosion resistance of the coated magnesium alloys.The results revealed that the coating prepared with PASP was composed of many uniform urchin-like microspheres,while the coating prepared with EDTA consisted of many flower-like particles.Moreover,the crystallinity of the coating prepared with EDTA was much higher than that of the coating prepared with PASP.Electrochemical tests revealed that the corrosion resistance of the substrate was significantly improved after being coated with each coating.Immersion test of the coated samples in simulated body fluid(SBF) demonstrated that the coatings could be biodegraded gradually and induce the formation of calcium phosphate particles.
基金Funded by the National Natural Science Foundation of China(No. 50971102)Shannxi Province "13115" Key Science and Technology Project (No. 2010ZDKG-51)
文摘Hydroxyapatite (HA, Ca10(PO4)6(OH)2) coating was fabricated on pure Ti (TA2) by laser cladding technology. The phase structure, microstructure, microhardness and electrochemical behavior of the laser cladded HA coating in artificial body fluid were investigated. The results show that the HA coating is mainly composed of highly crystallized HA. A transitional layer between HA coating and Ti substrate is formed. Microhardness measurement shows the gradually increasing of microhardness from 150 HV at TA2 substrate to 600 HV at transitional layer, and followed by a decreasing to 400 HV at HA coated layer. Electrochemical corrosion tests show that the HA coating has higher open circuit potential , lower corrosion current density and corrosion rate in comparison to the TA2 substrate.
文摘Hydroxyapatite/titania (HA/TiO2) double layers were coated onto Ti scaffolds throughout for orthopaedic applications by sol-gel method. Differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and X-ray diffractometry (XRD) were used for the characterisation of the phase transformations of the dried gels and coated surface structures. Scanning electron microscope (SEM) equipped with energy dispersive spectrometry (EDS) was used for the observation and evaluation of the morphology and phases of the surface layers and for the assessment of the in vitro tests. The in vitro assessments were performed by soaking the HA/TiO2 double coated samples into the simulated body fluid (SBF) for various periods. The TiO2 dipping-coating method at a speed of 12 cm/min, followed by a heat treatment at 600 ℃ for 20 min. The HA la lyaeyre wr wasa ssu cbosaetqeude bnytl ya dipping-coated on the outer surface at the same speed and then heat-treated at difference temperatures. The results indicat that the HA phase begins to crystallize after a heat treatment at 560 ℃. The crystallinity increases obviously at 760 ℃. SEM observations find no delamination or crack at the interfaces of HA/TiO2 and TiO2/Ti. The HA/TiO2 coated Ti scaffolds displays excellent bone-like apatite forming ability when it is soaked into SBF. Ti scaffolds after HA/TiO2 double coatings can be anticipated as promising implant materials for orthopaedic
文摘A codeposition of bioglass (BG) and hydroxyapatite (HA) on the substrate Ti6Al4V is realized in a nonaqueous solution system by inducing crystallization of HA on surface of the BG grain and electrophoresis deposition (EPD), and then a bioactive graded ceramic coating was obtained after sintering of the coating. This technique is a new method for making bioactive graded coating. The adhesive strength between the coating and the substrate reaches 18?MPa, and the better electrophoresis depositing parameters and optimal sintering procedure are obtained.