Scratch resistance and electrochemical corrosion behavior of hydroxyapatite coatings on Ti6Al4V in simulated physiological media

Using an electrochemical process, needle-like hydroxyapatite crystals with Ca/P ratio of 1.67 were synthesized on Ti₆Al₄V without the formation of any precursor. In vitro dissolution/precipitation process was investigated by immersion of the coated substrate into Hank??s solution up to 14?days. Physical and chemical characterizations were performed by scanning electron microscope coupled with energy dispersive X-ray spectroscopy and by X-ray diffraction. In particular, through a sequence of reactions including dissolution, precipitation, and ions exchange during immersion tests, a precipitated bone-like apatite coating homogenous and less porous was formed. Further, the corrosion behavior of the untreated and HA-coated specimens in simulated body fluid was evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy. The results showed that the corrosion rates of the samples with HA layer before and after immersion tests were 72 and 80?% lower than that of the bare titanium alloy. At last, the adhesion of the HA layer was determined through the use of scratch tests. A particular tribological behavior and a strong link to the substrate were revealed.     

Hydroxyapatite coating on titanium surface with titania nanotube layer and its bond strength to substrate

A vertically aligned titania nanotube layer on titanium surface was prepared by electrochemical anodic oxidation in an F⁻-containing electrolyte, followed by annealing at 450 °C. Bioactive hydroxyapatite (HA) coatings on as anodized titania nanotube layer were obtained by a biomimetic method without other surface treatment. The morphology, crystal structure, and components of the titania nanotube layer and bioactive coatings were examined by scanning electron microscopy, thin film X-ray diffraction, and Fourier transform infrared spectroscopy. The bond strength between the HA coatings and substrates was tested using a mechanical tester. The diameter of the titania nanotubes was about 100 nm, the wall thickness about 19 nm and the height about 1 μm. HA rapidly deposited on the as anodized nanotube surface after immersion in a biomineral solution only for 1 day. The HA coatings were carbonated apatite and composed of a number of column-like crystals with nanometer size. Tensile test shows that the bond strength between the HA coating and the nanotube layer was larger than 15.3 MPa.     

Failure Surface Analysis of Polyimide/Titanium Notched Coating Adhesion Specimens

Adhesively-bonded joints of LaRC^TM PETI-5, a phenylethynyl-terminated polyimide, with chromic acid anodized titanium were fabricated and debonded interfacially. The adhesive-substrate failure surfaces were investigated using several surface analysis techniques. From Auger spectroscopy, field emission scanning electron microscopy, and atomic force microscopy studies, polymer appears to be penetrating the pores of the anodized substrate to a depth of approximately 100 nm. From X-ray photoelectron spectroscopy data, the polymer penetrating the pores appears to be in electrical contact with the titanium oxide, leading to differential charging. These analyses confirm that the polymer is becoming mechanically interlocked within the substrate surface.     

Boron doped titaniumdioxide nanotube arrays: production,characterization and photocatalytic properties

In numerous studies, regularly oriented anatase titanium dioxide nanotube arrays (TNTAs), obtained through electrochemical anodization, have been employed as catalyst surfaces for photocatalytical applications. However, in many practical applications the phocatalytical activities are restricted due to their wide band gaps. This work shows that photocatalytical activity of TNTAs can be improved by a novel approach which provides boron incorporation into TiO₂ structure during anodization process without any further treatment. Anodization was performed in an aqueous solution containing hydrofluoric acid, oxalic acid and sodium fluoroborate (NaBF₄) at room temperature on titanium (Gr2) substrates. The anodized samples were annealed at 480?°C for 2 h in air in order to obtain anatase transformation and intended crystalline structure. As-prepared B-doped TNT structure was characterized by field emission scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction, atomic force microscopy and ultraviolet–visible light diffuse absorbance spectroscopy. The photocatalytic kinetics of B-doped TNTAs for the degradation of methylene blue (MB) under visible light irradiation were evaluated in details.     

Failure Surface Analysis of Polyimide/Titanium Notched Coating Adhesion Specimens

Adhesively-bonded joints of LaRC^TM PETI-5, a phenylethynyl-terminated polyimide, with chromic acid anodized titanium were fabricated and debonded interfacially. The adhesive-substrate failure surfaces were investigated using several surface analysis techniques. From Auger spectroscopy, field emission scanning electron microscopy, and atomic force microscopy studies, polymer appears to be penetrating the pores of the anodized substrate to a depth of approximately 100 nm. From X-ray photoelectron spectroscopy data, the polymer penetrating the pores appears to be in electrical contact with the titanium oxide, leading to differential charging. These analyses confirm that the polymer is becoming mechanically interlocked within the substrate surface.     

Corrosion behaviour and biocompatibility of nanoporous niobium incorporated titanium oxide coating for orthopaedic applications

This study investigates the surface characteristics, in vitro biocompatibility and electrochemical behaviour of nanoporous niobium incorporated titanium dioxide (Nb-incorporated TiO₂) coated 316L stainless steel (SS) for orthopaedic applications. The coating material was synthesized by sol-gel methodology and was deposited on 316L SS by using spin coating technique and heat treatment. The experimental conditions were optimized to obtain a coating with nanoporous morphology. The coating was characterized using attenuated total reflectance-Infrared spectroscopy (ATR-IR), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM) and transmission electron microscopy (TEM). The analysis confirmed the formation of a crystalline nanoporous Nb-incorporated TiO₂ coating with hydrophilic nature. Mechanical studies validated that the coating has excellent adhesion to the specimen and appreciable hardness value. In vitro bioactivity test confirmed that the nanoporous morphology of the coating facilitated enhanced hydroxyapatite (HAp) growth. Electrochemical studies established that the insulative nature of the coating provides excellent corrosion resistance to 316L SS.     

Fabrication of superhydrophobic titanium surfaces by anodization and surface mechanical attrition treatment

A superhydrophobic surface of titanium was fabricated by anodization in sodium chloride solution followed by immersion in perfluorodecyltriethoxysilane. The surface characteristics of the anodic film (morphology, composition, microstructure, and adhesion) were investigated by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and scratch testing. The anodic film was comprised of TiO₂ and TiCl₃ with a thickness of 50 nm. The anodized titanium surface exhibited a hierarchical structure, which consisted of a microscale horn structure with a nanoscale strip-overlay. This structure provided superhydrophobicity (water contact angle: 151.9° and sliding angle: 3°) following the immersion process. Furthermore, coverage of the hierarchical structure on the anodized titanium surface was improved by performing surface mechanical attrition treatment (SMAT) to grain-refine titanium surface which was then anodized and it enhanced a slightly increased water contact angle. The thickness (200 nm) of the anodic film on the SMAT-pretreated titanium surface was much higher than that on the titanium surface (50 nm). This resulted from a large number of grain boundaries on the surface serving as a fast diffusion path during anodization. However, the adhesion of the SMAT-and-anodized film was worse than that formed by anodization only. This is due to a large number of pores within the SMAT-and-anodized film.     

在改性模拟体液中电沉积羟基磷灰石涂层

Hydroxyapatite coatings were directly prepared on anodized titanium by electro-deposition method in a modified simulated body fluid. The configuration, structure and bioactivity of the coating were investigated with scanning electron microscopy (SEM), X-ray diffraction analyzer (XRD) and Fourier transform infrared spectroscopy (FTIR) techniques. The results demonstrated that pure and homogeneous hydroxyapatite coating can be obtained without any post-treatment. The prepared coating showed good bioactivity in simulated body fluid (SBF). The time required for a fully covered dense hydroxyapatite coatings was 4 days immersion in SBF.     

Morphology of carbon/TiC composite films prepared by carbonization of polyimide/titania composites

Polyimide/titania (PI/TiO₂) composite was synthesized by in situ sol–gel polymerization, and carbon/titanium carbide (TiC) composite films were prepared by carbothermal reduction of the PI/TiO₂ composite at 1,600 °C under flowing argon. The structure and properties of the composites were studied by wide angle X-ray diffraction (WAXD), Fourier transform infrared spectrometer (FTIR), scanning electron microscopy, and energy dispersive X-ray spectroscopy. The carbon/TiC composite films exhibited metallic luster on the surface and compact structure in cross section with well dispersed TiC particles. WAXD intensity distribution revealed that TiC particles formed by tightly bonding between elemental carbon and titanium formed crystallites which as a filler provided tough films. The results indicated that heat treatment of PI/TiO₂ under argon is a promising method for preparing tough carbon composite films.     

Structure and Physical Properties of Borosilicate as Potential Bioactive Glasses

Borosilicate bioactive glasses containing titanium dioxide were prepared and investigated. The corrosion behavior of samples was examined for all samples upon immersion in phosphate solution. The erosion of the outer surface and ion exchange processes of the glass with the surrounding solution were studied by measuring the weight loss. Results were compared with samples that do not contain titanium dioxide. The final result of the reaction is the precipitation of hydroxyapatite. Characterization of the glasses was carried out by FTIR (Fourier transform infrared) absorption spectra before and after immersion in phosphate solution. The different crystalline phases and crystallographic parameters were explored using X-ray diffraction (XRD) analyzes and all indicate the precipitation of hydroxyapatite. A scanning electron microscope (SEM) is used to observe the morphological changes of the surfaces upon immersion. The atomic ratio of the final result product was obtained by the energy dispersive x-ray analysis (EDX) unit attached to the SEM. Changes in pH of the leaching solution were measured and evaluated. All measurements confirm that the studied glass has a high degree of biological activity which makes it very suitable for the field of biomaterials and other various medical applications.     

Composition,structure and mechanical properties of the titanium surface after induction heat treatment followed by modification with hydroxyapatite nanoparticles

Coatings of titania (TiO₂) and "titania–hydroxyapatite" were prepared by oxidation of commercially pure titanium VT1-00 using induction heat treatment (IHT), followed by modification with colloidal hydroxyapatite (HAp) nanoparticles. The IHT treatment was performed at temperatures within 600–1200 °C for 300 s. According to the results of scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray fluorescent analysis (EDX), nanoindentation and in vitro testing, titania coatings of high morphological heterogeneity, and high mechanical properties and biocompatibility were formed on the titanium surface after IHT. The coatings were found to consist of nano- and submicron crystals of oval, needle-like, plate and prismatic shapes. A subsequent modification with HAp nanoparticles of the coated titanium substrate leads to accelerated formation of mechanically strong oxidebioceramic composite coatings. It was established that the porous oxide coatings modified with nanoparticles of HAp that were formed at temperatures from 800 to 1000 °C and holding for at least 30 s had a high biocompatibility.     

Synthesis and electrochemical study of Pt-based nanoporous materials

In the present work, a variety of Pt-based bimetallic nanostructured materials including nanoporous Pt, Pt-Ru, Pt-Ir, Pt-Pd and Pt-Pb networks have been directly grown on titanium substrates via a facile hydrothermal method. The as-fabricated electrodes were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction and electrochemical methods. The active surface areas of these nanoporous Pt-based alloy catalysts are increased by over 68 (Pt-Pd), 69 (Pt-Ru) and 113 (Pt-Ir) fold compared to a polycrystalline Pt electrode. All these synthesized nanoporous electrodes exhibit superb electrocatalytic performance towards electrochemical oxidation of methanol and formic acid. Among the five nanoporous Pt-based electrodes, the Pt-Ir shows the highest peak current density at +0.50 V, with 68 times of enhancement compared to the polycrystalline Pt for methanol oxidation, and with 86 times of enhancement in formic acid oxidation; whereas the catalytic activity of the nanoporous Pt-Pb electrode outperforms the other materials in formic acid oxidation at the low potential regions, delivering an enhanced current density by 280-fold compared to the polycrystalline Pt at +0.15 V. The new approach described in this study is suitable for synthesizing a wide range of bi-metallic and tri-metallic nanoporous materials, desirable for electrochemical sensor design and potential application in fuel cells.     

原子层沉积技术在钛改性多孔氧化铝上的应用

采用原子层沉积技术进行Al₂O₃表面钛改性,利用N2吸附-脱附、X射线衍射、X射线荧光分析、透射电镜和热重-微分热重-差示扫描量热等表征手段对改性前后的Al₂O₃载体进行表征。结果表明,钛分散到Al₂O₃表面,Al₂O₃载体表面氧化钛为锐钛矿结构,改性后的载体具有良好的热稳定性。钛分散性与Al₂O₃表面化学环境有关,钛对多孔Al₂O₃表面改性可以通过原子层沉积技术实现。     

Influence of synthesis parameters on morphology and phase composition of porous titania layers prepared via water based chemical solution deposition

In this work, thick nanocrystalline mesoporous titania layers are synthesized via chemical solution deposition using a water based citratoperoxo-Ti(IV)-precursor solution. The aqueous citratoperoxo-Ti(IV)-precursor solution is modified by the addition of polyvinyl alcohol (PVA), which acts as a thickener and pore forming agent. Layers are tape casted onto ITO-coated glass substrates and are thermally processed. The influence of process parameters like Ti(IV)-concentration, blade thickness, crystallization temperature and time on the film's phase composition, morphology and thickness are investigated by means of X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), variable angle spectroscopic ellipsometry (VASE), atomic force microscopy (AFM) and profilometry.

It is shown that the Ti(IV)-concentration and heat treatment influence the size and shape of the grains of which the films are composed, the film morphology (porosity, surface roughness) and the layer thickness, but no influence on the phase formation is observed. In all cases phase pure anatase layers are obtained.     

Enhanced corrosion resistance of A3xx.x/SiCp composites in chloride media by La surface treatments

The influence of silicon carbide particles (SiCp) proportion and matrix composition of aluminium metal matrix composites (A3xx.x/SiCp) modified by lanthanum-based conversion or electrolysis coating was evaluated in 3.5 wt% NaCl aerated solution. The intermetallic compounds were preferentially covered by lanthanum-based conversion coatings obtained by immersion in 50 °C solution of La(III) salt, and the intermetallic compounds, SiCp and aluminium matrix were covered by lanthanum electrolysis treatment. The corrosion process was studied on the basis of gravimetric tests and electrochemical impedance spectroscopy (EIS) during immersion in 3.5 wt% NaCl aerated solution. The composition of both La coating and corrosion products was analyzed before and after accelerated testing, by scanning electron microscopy (SEM), atomic force microscopy (AFM), low-angle X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) to determine the influence of surface microstructural changes on corrosion behaviour during exposure to the corrosive environment. The corrosion process was more influenced by the concentration of alloy elements in the matrix than by the proportion of SiCp reinforcement. Both lanthanum treated surfaces presented better behaviour to chloride solution corrosion than original composite surfaces without treatment; however, electrolysis afforded a higher degree of protection than the conversion treatment because the coating was more extensive.     

Highly dispersed titanium(IV) oxide on α-cellulose surface: An XPS,SEM, and XRD study

Interaction of titanium chloride with a cellulose surface and the decurrent modifications introduced on its morphology were studied by scanning, electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The chemical analysis of the surface was carried by X-ray photoelectron spectroscopy (XPS) and changes in the crystallinity upon chemical treatment was determinded by the X-ray diffraction (XRD) technique. Interaction of titanium with cellulose occurs only at the surface and a decrease of its crystallinity was observed with the amount of metal oxide incorporated into the solid matrix. © 1995 John Wiley & Sons, Inc.     

Structures and properties of the polyester nonwovens coated with titanium dioxide by reactive sputtering

Nanoscale titanium dioxide (TiO₂) films were deposited on the surface of polyester nonwovens by using direct current (DC) reactive magnetron sputtering. The effect of coating thickness on the surface structures and properties of TiO₂ coated fabrics was investigated by atomic force microscope (AFM), X-ray diffraction (XRD), energy dispersive X-ray analysis system (EDX), scanning electron microscope (SEM), and antistatic test in this article. The results indicated that the grain sizes of the sputtered clusters increased and the coating layer became more compact as film thickness was increased, but the crystal structure did not have any significant change. At the same time, the film mechanical properties and antistatic performance in general depended strongly on the film thickness which could lead to the optimum thickness for a particular application.     

Microwave-Assisted Synthesis of Titania Nanocubes, Nanospheres and Nanorods for Photocatalytic Dye Degradation

TiO₂ nanostructures with fascinating morphologies like cubes, spheres, and rods were synthesized by a simple microwave irradiation technique. Tuning of different morphologies was achieved by changing the pH and the nature of the medium or the precipitating agent. As-synthesized titania nanostructures were characterized by X-ray diffraction (XRD), UV–visible spectroscopy, infrared spectroscopy (IR), BET surface area, photoluminescence (PL), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and atomic force microscopy (AFM) techniques. Photocatalytic dye degradation studies were conducted using methylene blue under ultraviolet light irradiation. Dye degradation ability for nanocubes was found to be superior to the spheres and the rods and can be attributed to the observed high surface area of nanocubes. As-synthesized titania nanostructures have shown higher photocatalytic activity than the commercial photocatalyst Degussa P25 TiO₂.     

Electrochemical impedance spectroscopic characterization of titanium during alkali treatment and apatite growth in simulated body fluid

Alkali treatment of titanium with subsequent heat treatment has been adapted as an important pre-treatment procedure for hydroxyapatite formation in orthopaedic applications. The electrochemical study during the alkali treatment process has not been explored yet. In the present work, electrochemical impedance spectroscopic (EIS) studies have been employed to analyse the electrochemical behaviour of titanium during the alkali treatment. The open circuit potential and potentiodynamic polarisation measurements were carried out in simulated body fluid (SBF) solution. Scanning electron microscopy and energy dispersive X-ray analysis were used to characterize the surface morphology and to correlate the results obtained from the electrochemical studies. An optimum growth of the passive film was found to occur at the end of 17th hour of treatment by alkali treatment. The alkali treated titanium immersed in SBF solution for various durations exhibited the formation of a duplex layer structure due to an inner barrier layer and an outer gel layer during the initial periods of immersion. However, with increase in immersion time to 10 days, a stable apatite layer was formed over the barrier layer and this was confirmed from the equivalent circuit fitted for the impedance data.     

Nano-hydroxyapatite and nano-hydroxyapatite/zinc oxide scaffold for bone tissue engineering application

This research aims to evaluate the mechanical properties, biocompatibility, and degradation behavior of scaffolds made of pure hydroxyapatite (HA) and HA-modified by ZnO for bone tissue engineering applications. HA and ZnO were developed using sol-gel and precipitation methods respectively. The scaffolds properties were characterized using X-ray diffraction (XRD), Fourier transform spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), atomic absorption (AA), and atomic force microscopy (AFM). The interaction of scaffold with cells was assessed using in vitro cell proliferation and alkaline phosphatase (ALP) assays. The obtained results indicate that the HA/ZnO scaffolds possess higher compressive strength, fracture toughness, and density—but lower hardness—when compared to the pure HA scaffolds. After immersing the scaffold in the SBF solution, more deposited apatite appeared on the HA/ZnO, which results in the rougher surface on this scaffold compared to the pure HA scaffold. Finally, the in vitro biological analysis using human osteoblast cells reveals that scaffolds are biocompatible with adequate ALP activity.