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ABSTRACT: The biologic/cytotoxic effects of dispersed nano graphene platelets (NGPs) to human osteosarcoma cells (MG63 cell line) were firstly studied by examining cell viability, cycle, apoptosis, the change of morphology, lactate dehydrogenase (LDH) release, alkaline phosphatase (ALP) activity and inflammation. The results shown that the cell cytotoxicity of the dispersed NGPs exhibited dose-dependent characters, which had no obvious cytotoxic effects to MG63 cells at the concentration less than 10 μg/mL, whereas could postpone cell cycle, promote cell apoptosis, damage cell microstructure, induce serious tumor necrosis factor-α (TNF-α) expression and greatly reduce ALP activity of MG63 cells at higher concentration of NGPs (>10 µg/ml ). Besides, NGPs had little influence on the LDH leakage. The cytotoxic mechanism of NGPs to MG63 cells was speculated to be intracellular activity with no physical damage of plasma membrane.
Journal of Biomedical Materials Research Part A 04/2013; · 2.63 Impact Factor
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ABSTRACT: The corrosion behavior of Ti–Nb dental alloy in artificial saliva with and without the addition of lactic acid and sodium fluoride was investigated by electrochemical techniques, with the commercial Titanium– molybdenum alloy (TMA) as a comparison. The chemical composition, microstructure and constitutional phase were characterized via energy dispersive spectrometry, optical microscope and X-ray diffraction, meanwhile the open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization measurements were carried out to study the corrosion resistance of experimental alloys, with the corroded surface being further characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that the corrosion behavior of Ti–Nb alloy was similar to those TMA alloy samples in both artificial and acidified saliva solutions, whereas statistical analysis of the electrochemical impedance spectroscopy and polarization parameters showed Ti–Nb alloy exhibited better corrosion resistance in fluoridated saliva and fluoridated acidified saliva. SEM observation indicated that TMA alloy corroded heavily than Ti–Nb alloy in fluoride containing saliva. XPS surface analysis suggested that Nb 2 O 5 played an important role in anti-corrosion from the attack of fluoride ion. Based on the above finding, Ti–Nb alloy is believed to be suitable for the usage in certain fluoride treated dental works with excellent corrosion resistance in fluoride-containing oral media.
02/2011;
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ABSTRACT: The present study aimed to evaluate the bioactivity of titanium surfaces sandblasted with large-grit corundum and acid etched (SLA) plus further alkali or hydrogen peroxide and heat treatment for dental implant application. Pure titanium disks were mechanically polished as control surface (Ti-control) and then sandblasted with large-grit corundum and acid etched (SLA). Further chemical modifications were conducted using alkali and heat treatment (ASLA) and hydrogen peroxide and heat treatment (HSLA) alternatively. The surface properties were characterized by scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and contact angle and roughness measurements. Further evaluation of surface bioactivity was conducted by MC3T3-E1 cell attachment, proliferation, morphology, alkaline phosphatase (ALP) activity and calcium deposition on the sample surfaces. After insertion in the beagle's mandibula for a specific period, cylindrical implant samples underwent micro-CT examination and then histological examination. It was found that ASLA and HSLA surfaces significantly increased the surface wettability and MC3T3-E1 cell attachment percentage, ALP activity and the quality of calcium deposition in comparison with simple SLA and Ti-control surfaces. Animal studies showed good osseointegration of ASLA and HSLA surfaces with host bone. In conclusion, ASLA and HSLA surfaces enhanced the bioactivity of the traditional SLA surface by integrating the advantages of surface topography, composition and wettability.
Biomedical Materials 02/2011; 6(2):025001. · 2.16 Impact Factor
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ABSTRACT: Magnesium alloys have been recently developed as biodegradable implant materials, yet there has been no study concerning their corrosion fatigue properties under cyclic loading. In this study the die-cast AZ91D (A for aluminum 9%, Z for zinc 1% and D for a fourth phase) and extruded WE43 (W for yttrium 4%, E for rare earth mischmetal 3%) alloys were chosen to evaluate their fatigue and corrosion fatigue behaviors in simulated body fluid (SBF). The die-cast AZ91D alloy indicated a fatigue limit of 50MPa at 10⁷ cycles in air compared to 20MPa at 10⁶ cycles tested in SBF at 37°C. A fatigue limit of 110MPa at 10⁷ cycles in air was observed for extruded WE43 alloy compared to 40MPa at 10⁷ cycles tested in SBF at 37°C. The fatigue cracks initiated from the micropores when tested in air and from corrosion pits when tested in SBF, respectively. The overload zone of the extruded WE43 alloy exhibited a ductile fracture mode with deep dimples, in comparison to a brittle fracture mode for the die-cast AZ91D. The corrosion rate of the two experimental alloys increased under cyclic loading compared to that in the static immersion test.
Acta biomaterialia 12/2010; 6(12):4605-13. · 3.98 Impact Factor
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ABSTRACT: Rapidly solidified (RS) Mg-3Ca alloy ribbons were prepared by the melt-spinning technique at different wheel rotating speeds (15 m s(-1), 30 m s(-1) and 45 m s(-1)) with the as-cast Mg-3Ca alloy ingot as a raw material. The RS45 Mg-3Ca alloy ribbon showed a much more fine grain size feature (approximately 200-500 nm) in comparison to the coarse grain size (50-100 microm) of the original as-cast Mg-3Ca alloy ingot. The corrosion electrochemical tests in simulated body fluid indicated that the corrosion rate of the as-cast Mg-3Ca alloy was strongly reduced by the RS procedure and tended to be further decreased with increasing wheel rotating speeds (1.43 mm yr(-1) for RS15, 0.94 mm yr(-1) for RS30 and 0.36 mm yr(-1) for RS45). The RS Mg-3Ca alloy ribbons showed more uniform corrosion morphology compared with the as-cast Mg-3Ca alloy after polarization. The cytotoxicity evaluation revealed that the three experimental as-spun Mg-3Ca alloy ribbon extracts did not induce toxicity to the L-929 cells, whereas the as-cast Mg-3Ca alloy ingot extract did. The L-929 cells showed more improved adhesion on the surfaces of the three as-spun Mg-3Ca alloy ribbons than that of the as-cast Mg-3Ca alloy ingot.
Biomedical Materials 05/2010; 5(3):035013. · 2.16 Impact Factor
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ABSTRACT: Ni50.2Ti49.8 alloy Nanocrystalline Amorphous Metals and alloys Corrosion and ion release Cytotoxicity Bulk nanocrystalline and amorphous Ni50.2Ti49.8 alloy samples were successfully prepared from commercial microcrystalline Ni50.2Ti49.8 alloy discs by high pressure torsion (HPT) technique. Then their corrosion resistance, surface wettability and cytotoxicity were further studied from the viewpoint of biomaterials. In both Hank's solution and artificial saliva, bulk nanocrystalline and amorphous Ni50.2Ti49.8 alloys showed significantly higher pitting corrosion potentials than that of microcrystalline Ni50.2Ti49.8 alloy. Meanwhile, the amount of Ni ion release after immersion in Hank's solution was minor, far below the threatening threshold of daily diet. Murine fibroblast and osteoblast cell lines were indirectly co-cultured with experimental sample extracts, indicating no cytotoxicity. Amongst all samples, the nanocrystalline Ni50.2Ti49.8 shows promising as best biomaterial candidate for its good combination of mechanical property, corrosion resistance and cytocompatibility.
03/2010;
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ABSTRACT: To reduce the biocorrosion rate by surface modification, Mg-Ca alloy (1.4wt.% Ca content) was soaked in three alkaline solutions (Na(2)HPO(4), Na(2)CO(3) and NaHCO(3)) for 24h, respectively, and subsequently heat treated at 773K for 12h. Scanning electron microscopy and energy-dispersive spectroscopy results revealed that magnesium oxide layers with the thickness of about 13, 9 and 26microm were formed on the surfaces of Mg-Ca alloy after the above different alkaline heat treatments. Atomic force microscopy showed that the surfaces of Mg-Ca alloy samples became rough after three alkaline heat treatments. The in vitro corrosion tests in simulated body fluid indicated that the corrosion rates of Mg-Ca alloy were effectively decreased after alkaline heat treatments, with the following sequence: NaHCO(3) heated<Na(2)HPO(4) heated<Na(2)CO(3) heated. The cytotoxicity evaluation revealed that none of the alkaline heat treated Mg-Ca alloy samples induced toxicity to L-929 cells during 7days culture.
Acta biomaterialia 02/2009; 5(7):2790-9. · 3.98 Impact Factor
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ABSTRACT: A hard and adherent TiN/Ti thin film of approximately 3 μm in thickness was deposited on the surface of Ti–50.6 at.% Ni alloy by the PIIID technique. The surface composition and chemical state of the coated samples were evaluated by XPS. The XPS results indicate that titanium oxide and titanium oxynitride were present on the TiN surface. The spectra of Ti 2p, N 1s, O 1s and C 1s electrons before and after the film being sputter etched were also discussed. Scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS) analyses demonstrate that an interfacial layer, containing Ti, N and Ni, was formed at the interface between the TiN and Ti coatings. Sliding wear tests show that the TiN coating significantly reduces the friction coefficient and improves wear resistance of the NiTi alloy.
11/2006;
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ABSTRACT: TiC/Ti coatings were deposited on the surface of Ti–50.6 at.% Ni alloy by plasma immersion ion implantation and deposition (PIIID) technique. The microstructure, mechanical properties and hemocompatibility of the samples were investigated by means of XRD, AFM, nanoindentation, and scratch and platelet adhesion tests. The result of XRD analysis shows that the crystalline TiC coating has a preferential orientation of (111) in the normal direction. The surface presents a very smooth and dense microstructure with 1.517 nm root mean square roughness (RMS). The average hardness and modulus values of the TiC coating are much higher than those of the NiTi substrate. In the initial stage of scratching, some obvious transversal cracks and worm-like cracks spreading into the film from both side of the scratch track were observed. At higher normal loads for the scratching test, the film delaminated from the substrate at the margins of the substrate. Platelet adhesion tests demonstrate that the hemocompatibility of the coated sample is improved.
11/2006;
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ABSTRACT: The advanced plasma immersion ion implantation and deposition (PIII&D) method has been used to deposit TiN, TiC and TiCN films on the surface of Ti–50.6 at.% Ni alloys. Smooth surface with root mean square (RMS) roughness of values 2.672 nm for the TiN, 1.517 nm for the TiCN film and 5.339 nm for the TiC film have been obtained. The XPS Ti 2p, C 1s and N 1s peaks and the valence band spectrum show that the nitrogen, carbon, carbon combined with nitrogen is fully bonded to titanium as nitride, carbide and carbonitride, respectively. Based on the electrochemical measurement and ion releasing tests, we can conclude that the treated samples exhibit better corrosion resistance and depress Ni ion release from the NiTi alloys in the Hank's solution at 37 °C.The suppression of Ni ion by the films is a beneficial phenomenon for the future application of NiTi alloys in the biomedical field.
Nq. 09/2006; 81.
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ABSTRACT: Diamond-like carbon (DLC) films have been successfully deposited on Ti-50.8 at.%Ni using plasma based ion implantation (PBII)
technique. The influences of the pulsed negative bias voltage applied to the substrate from 12kV to 40kV on the structure,
nano-indentation hardness and Young’s modulus are investigated by the X-ray photoelectron spectroscopy (XPS) and nano-indentation
technique. The results show that C 1s peak depends heavily on the bias voltage. With the increase of bias voltage, the ratio
of sp2/sp3 first decreases, reaching a minimum value at 20kV, and then increases. The DLC coating deposited at 20kV shows the highest
hardness and elastic modulus values as a result of lower sp2/sp3 ratio. The corrosion resistance of specimen deposited under 20kV is superior to uncoated NiTi alloy and slightly better
than those of the other samples deposited at 12kV, 30kV and 40kV.
Journal of Materials Science 06/2006; 41(13):4179-4183. · 2.02 Impact Factor
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ABSTRACT: An investigation has been carried out to study the effect of pulse negative bias voltage on the morphology, microstructure, mechanical, adhesive and tribological properties of TiN coatings deposited on NiTi substrate by plasma immersion ion implantation and deposition. The surface morphologies were relatively smooth and uniform with lower root mean square values for the samples deposited at 15 kV and 20 kV negative bias voltages. X-ray diffraction results demonstrated that the pulse negative bias voltage can significantly change the microstructure of TiN coatings. The intensity of TiN(220) peak increased with the increase of negative bias voltage in the range of 5–20 kV. When the negative bias voltage increased to 30 kV, the preferred orientation was TiN(200). Nanoindentation test indicates that hardness and elastic modulus increased with the increase of the negative bias voltage (5 kV, 15 kV and 20 kV), and then dropped sharply at 30 kV. The adhesion between the TiN and NiTi alloy and tribological properties of TiN coated NiTi alloy depend strongly on the bias voltage parameter; the sample deposited at 20 kV possesses good adhesion strength and excellent tribological property.
04/2006;
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ABSTRACT: TiN coating with a thin Ti intermediate layer was deposited on the NiTi shape memory alloy substrate using plasma immersion ion implantation and deposition technique. The effect of nitrogen to argon gas flow ratio on the surface characteristics, chemical composition and mechanical properties of the as-deposited samples were investigated. Atomic force microscopy analysis indicates that all the coatings exhibited island morphology and the average root mean square (RMS) values were determined to be 2.912, 4.152 and 4.227nm for N 2 / Ar ratios of 1 / 3, 1 / 2 and 2 / 3, respectively. The results of XPS and X-ray diffraction show that the chemical composition, phase composition and preferred orientation of the TiN coating varied significantly with the N 2 / Ar gas ratio. Nanoindentation, scratch and wear tests results demonstrated that coatings deposited with N 2 / Ar = 1 / 2 exhibited the highest hardness and elastic modulus, good adhesion strength and excellent wear resistance.
03/2006;
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ABSTRACT: TiN coatings with the characteristics of excellent corrosion and wear resistance, high hardness and good biocompatibility, have received much attention in biomedical applications. Plasma immersion ion implantation and deposition (PIIID) is a novel method that can not only ensure excellent bonding between the coating and underlying material, but also overcome the line-in-sight shortcoming. The aim of the present study is to deposit TiN coatings on the surface of Ti–50.6 at.% Ni alloy by the advanced PIIID method to improve the wear resistance and hardness of a NiTi alloy surface. Two process parameters, i.e. voltage, and flows of Ar and N 2 were varied in the present experiments. The chemical composition, mechanical and corrosion resistance properties of the samples were investigated using XPS, nanoindentation and electrochemical method. The XPS results showed that the flows of Ar and N 2 had a great influence on the composition of the TiN films. The hardness and elastic modulus of the TiN films increased with an increase of pulse bias voltage and reached a maximum value for films deposited at −20 kV when the flow rate ratio of Ar to N 2 was 2/1. The experimental results revealed that the film preparation parameters directly affected the microstructure of the TiN, and thus influenced the mechanical and corrosion properties of the NiTi alloy, open circuit potential (OCP) values of the specimens increased with the negative pulse bias voltage and reached its maximum value when the flow rate of Ar/N 2 was 2/1. Combined with the results of Tafel and anodic polarization curves, an excellent corrosion resistant TiN coating by PIIID technique could be obtained by varying the process parameters.
Materials Science and Engineering A. 01/2006; 434:99-104.
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ABSTRACT: TiN coatings were deposited on the surface of Ti–50.6 at.% Ni alloy by the advanced plasma immersion ion implantation and deposition (PIIID) technique to improve the wear and corrosion resistances. The surface characteristics and corrosion property of the samples were investigated by atomic-force microscopy (AFM) and electrochemical measurement. The AFM results showed that negative pulse bias voltage and N 2 /Ar flow rate greatly influence the surface roughness of the TiN films. Combined with the results of Tafel curves, anodic polarization curves and electrochemical impedance spectroscopy, we found that an excellent corrosion resistant TiN coating by PIIID technique could be obtained by varying the process parameters. The sample deposited at −20 kV, with 1:2 nitrogen to argon flow ratio, exhibited excellent anti-corrosion property, which had a more positive value of corrosion potential E corr , a higher value of polarization resistance R p and a low corrosion current density I corr . An appropriate equivalent circuit model was proposed to describe the corrosion process of the TiN coated samples in the present study.
Materials Science and Engineering A. 01/2006; 438440:1146-1149.
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ABSTRACT: Diamond-like carbon (DLC) films have been successfully deposited on Ti – 50.8 at.% Ni alloys using plasma based ion implantation (PBII) technique. The influence of the pulsed negative bias voltage applied to the substrate from 12 eV to 40 eV on the surface characteristics and corrosion resistant property as well as hemocompatibility has been investigated. The results show that the RMS values firstly decrease from 7.202 nm (12 kV) to 5.279 nm (20 kV), and then increase to 6.991 nm (30 kV) and 7.060 nm (40 kV). With the voltage increasing the value of I(D)/I(G) ratio firstly decreases, and reaches a minimum value at 20 kV, and then increases. Combined with the Tafel measurement and SEM observation, we found that the uncoated TiNi alloy shows severe pitting corrosion, which could be due to the presence of Cl À ions in the solution. On the contrary, the coated sample shows very little pitting corrosion and behaves with better corrosion resistant property especially for the specimens deposited at 20 kV bias voltages. The platelet adhesion test shows that the hemocompatibility of DLC coated TiNi alloy is much better than that of the bare TiNi alloy, and the hemocompatibility performance of DLC coated TiNi alloy deposited at 20 kV is superior to that of the other coated specimens. D 2005 Elsevier B.V. All rights reserved.
04/2005;
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ABSTRACT: An investigation has been carried out to study the effect of pulse negative bias voltage on the morphology, microstructure, mechanical, adhesive and tribological properties of TiN coatings deposited on NiTi substrate by plasma immersion ion implantation and deposition. The surface morphologies were relatively smooth and uniform with lower root mean square values for the samples deposited at 15 kV and 20 kV negative bias voltages. X-ray diffraction results demonstrated that the pulse negative bias voltage can significantly change the microstructure of TiN coatings. The intensity of TiN(220) peak increased with the increase of negative bias voltage in the range of 5–20 kV. When the negative bias voltage increased to 30 kV, the preferred orientation was TiN(200). Nanoindentation test indicates that hardness and elastic modulus increased with the increase of the negative bias voltage (5 kV, 15 kV and 20 kV), and then dropped sharply at 30 kV. The adhesion between the TiN and NiTi alloy and tribological properties of TiN coated NiTi alloy depend strongly on the bias voltage parameter; the sample deposited at 20 kV possesses good adhesion strength and excellent tribological property.
Thin Solid Films.
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ABSTRACT: Magnesium alloys have been recently developed as biodegradable implant materials, yet there has been no study concerning their corrosion fatigue properties under cyclic loading. In this study the die-cast AZ91D (A for aluminum 9%, Z for zinc 1% and D for a fourth phase) and extruded WE43 (W for yttrium 4%, E for rare earth mischmetal 3%) alloys were chosen to evaluate their fatigue and corrosion fatigue behaviors in simulated body fluid (SBF). The die-cast AZ91D alloy indicated a fatigue limit of 50 MPa at 107 cycles in air compared to 20 MPa at 106 cycles tested in SBF at 37 °C. A fatigue limit of 110 MPa at 107 cycles in air was observed for extruded WE43 alloy compared to 40 MPa at 107 cycles tested in SBF at 37 °C. The fatigue cracks initiated from the micropores when tested in air and from corrosion pits when tested in SBF, respectively. The overload zone of the extruded WE43 alloy exhibited a ductile fracture mode with deep dimples, in comparison to a brittle fracture mode for the die-cast AZ91D. The corrosion rate of the two experimental alloys increased under cyclic loading compared to that in the static immersion test.
Acta Biomaterialia.
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ABSTRACT: TiN coatings were deposited on the surface of Ti–50.6 at.% Ni alloy by the advanced plasma immersion ion implantation and deposition (PIIID) technique to improve the wear and corrosion resistances. The surface characteristics and corrosion property of the samples were investigated by atomic-force microscopy (AFM) and electrochemical measurement. The AFM results showed that negative pulse bias voltage and N2/Ar flow rate greatly influence the surface roughness of the TiN films. Combined with the results of Tafel curves, anodic polarization curves and electrochemical impedance spectroscopy, we found that an excellent corrosion resistant TiN coating by PIIID technique could be obtained by varying the process parameters. The sample deposited at −20 kV, with 1:2 nitrogen to argon flow ratio, exhibited excellent anti-corrosion property, which had a more positive value of corrosion potential Ecorr, a higher value of polarization resistance Rp and a low corrosion current density Icorr. An appropriate equivalent circuit model was proposed to describe the corrosion process of the TiN coated samples in the present study.
Materials Science and Engineering: A.
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ABSTRACT: The corrosion behavior of Ti–Nb dental alloy in artificial saliva with and without the addition of lactic acid and sodium fluoride was investigated by electrochemical techniques, with the commercial Titanium–molybdenum alloy (TMA) as a comparison. The chemical composition, microstructure and constitutional phase were characterized via energy dispersive spectrometry, optical microscope and X-ray diffraction, meanwhile the open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization measurements were carried out to study the corrosion resistance of experimental alloys, with the corroded surface being further characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that the corrosion behavior of Ti–Nb alloy was similar to those TMA alloy samples in both artificial and acidified saliva solutions, whereas statistical analysis of the electrochemical impedance spectroscopy and polarization parameters showed Ti–Nb alloy exhibited better corrosion resistance in fluoridated saliva and fluoridated acidified saliva. SEM observation indicated that TMA alloy corroded heavily than Ti–Nb alloy in fluoride containing saliva. XPS surface analysis suggested that Nb2O5 played an important role in anti-corrosion from the attack of fluoride ion. Based on the above finding, Ti–Nb alloy is believed to be suitable for the usage in certain fluoride treated dental works with excellent corrosion resistance in fluoride-containing oral media.
Materials Science and Engineering: C.
