Effect of micro-arc oxidation treatment on laser joint microstructures of Ti-6Al-4V alloy/CFRP

Resin-based carbon fibre reinforced composite (CFRP) with excellent properties has been widely applied in aerospace industry. In this study, polyether ether ketone enforced composite (PEEK-CFRP) and Ti-6V-4V titanium alloy had been joined by laser welding process. Micro-arc oxidation (MAO) process was conducted on the surface of titanium alloy to improve the joint property. Fractures and mechanical properties of joints were analysed. Interfacial microstructures of the joints had been investigated, and the formation mechanism of joint had been figured out. The results showed that after MAO treatment, the joint strength had been greatly improved and the shear strength reached to 42.3 MPa compared with pretreated sample. The wettability of CFRP on titanium alloy was rising with the contact angle of 68.8°. Fracture showed that cohesive failure contributed to the main fracture mode. As joints were formed by both mechanical bonding and chemical bonding, ‘anchor-shaped’ structures were found in the joint to enhance the mechanical bonding effects due to the flowing of the melted resin. (−OH) bonds were identified at the surface of MAO-treated titanium alloy that provided conditions for hydrogen bond interaction. TiO₂, TiO and Ti–V–C phase were found at interface, whereas Ti–F and Ti–O–F bonds were generated during the welding process, which made great contribution to the chemical bonds between titanium alloy and CFRP.     

Sol-Gel Derived Functionally Graded TiO2/HAP Films on Ti-6Al-4V Implants

Functionally graded TiO₂/HAP coatings were prepared on Ti6Al4V implants by sol-gel process using calcium nitrate and phosphoric acid dissolved in ethylene glycol monomethyl ether, and titanium isopropoxide chelated by acethylacetone, isopropanol and water as starting materials. TiO₂/HAP coating sols with variable HAP concentrations from 0% to 100% at 10% intervals were orderly spin coated on the substrates and pyrolyzed at 500°C in air. Well-crystallized HAP coatings between coating and substrate confirmed by X-ray diffraction and field emission-scanning electron microscopy were obtained by final annealing at 500°C in argon. In this work, bioactivities of the coating were studied by examining the variation of ion concentration of Ca and P in simulated body fluid after soaking using an inductively coupled plasma-atomic emission spectrometer. Coating surfaces after soaking in simulated body fluid indicated significant morphological changes by field emission-scanning electron microscopy.     

电化学法制备生物活性陶瓷材料研究

利用电化学方法可以在温和条件下制备生物活性陶瓷涂覆层，从而避免了高温喷涂引起的相变和脆裂，并可在形状复杂的基底上得到均匀的沉积层．因此，近年来在金属表面电沉积生物活性陶瓷涂覆层的研究方面已引起高度重视［’－‘j，然而，目前大多数文献报道所采用的恒电位方法，在沉积过程中电极表面的喊度会发生较大的变化，难以得到组分均匀的沉积层．本文报道用恒电流模式在Ti－6A14V合金表面沉积羟基磷灰石生物陶瓷涂层．1实验部分Ti－6A14V合金为电沉积基底（直径为0．65cm），辅助电极为Pt电极，参比电极采用饱和甘汞电极（SCE）．…     

Ellipsometric and mechanical characterization of nanostructured anodic oxide film formed on Ti-6Al-7Nb alloy

In this work, we grow TiO₂ nanotube layers by using the single-step direct anodization of Ti-6Al-7Nb alloy in aqueous electrolytes containing F^? ions. Nanotube layers are characterized by spectroscopic ellipsometry (SE) and field-emission gun scanning electron microscopy (FEG-SEM). We also use SE to monitor the anodization process for TiO₂ nanotube layers on biocompatible Ti-6Al-7Nb alloy. In addition, we study mechanical properties by nanoindentation.     

Influence of substrate temperature and N2/Ar flow ratio on the stoichiometry,structure and hardness of TaNx coatings deposited by DC reactive sputtering

The effect of substrate temperature and N2/Ar flow ratio on the stoichiometry, structure and hardness of TaN_x coatings prepared on (111) Si substrates by DC reactive sputtering was investigated. For the structural, chemical and morphological analysis, X‐ray diffraction (XRD), Auger electron scanning and atomic force microscopy were respectively used. Hardness values of thin films were determined using the work of indentation model from nanoindentation measurements. TaN stoichiometric coatings were obtained for samples deposited at room temperature. The stoichiometric TaN phase was not obtained by increasing the temperature up to 773 K, even when increasing the N₂/Ar flow ratio. Even when a saturation in nitrogen content was achieved, nitrogen vacancies are still present in those samples. For coatings prepared at 773 K and low N₂/Ar flow ratio, a phase mixture between TaN_x and cubic α‐Ta was observed, while a cubic structure δ‐TaN was formed by increasing the N₂/Ar flow ratio. A maximum in hardness and (38 GPa) was obtained for the sample deposited at 773 K and a N₂/Ar flow ratio of 0.2, which presented a δ‐TaN cubic crystalline structure and a roughness value of 1.6 nm. Copyright © 2015 John Wiley & Sons, Ltd.     

Ti6Al4V coating for carbon/carbon composites synthesized by magnetron sputtering: microstructure and in‐vitro biotests

In order to improve the cell compatibility of biomedical carbon/carbon composites, Ti6Al4V coatings were applied on carbon/carbon composites by magnetron sputtering technique. The microstructure and cell responses of the coatings were evaluated, and the bonding strength between the coatings and carbon/carbon composites was analyzed. The Ti6Al4V coatings modulated the surface morphology, decreased the surface roughness, improved the surface wettability and achieved a strong bonding strength to carbon/carbon composites. The cells showed larger cell extension and higher cell proliferation for the Ti6Al4V coatings than for the carbon/carbon composites. Copyright © 2012 John Wiley & Sons, Ltd.     

钇的预注入对Ti-6Al-4V合金氮等离子体浸没离子注入行为的影响

为了提高氮等离子体浸没离子注入Ｔｉ－６Ａｌ－４Ｖ合金时氮原子的峰值深度,利用钇来增加氮在基体中的注入深度和扩散深度,先用２０ｋＶ的电压进行钇等离子体浸没离子注入处理,然后用３０ｋＶ的电压进行氮等离子体浸没离子注入处理。俄歇能谱测试表明氮原子的峰值深度有明显提高,注钇时间为３０ｍｉｎ的试件,氮原子的峰值深度从５０ｎｍ上升到１００ｎｍ。摩擦性能式表明处理后试件的抗磨损能力大大提高。     

Influence of the composition of BCN films deposited by reactive magnetron sputtering on their properties

Compounds of the B--C--N system are very promising to produce superhard coatings with good tribological, chemical, and thermal properties. To investigate the influence of the composition of BCN films on their properties, films with five different compositions at nearly constant nitrogen content were deposited on silicon wafers by magnetron sputtering from hexagonal boron nitride and graphite targets operated in RF and DC mode, respectively. The compositions and binding states of the films were determined by XPS. The nitrogen content was found to be almost constant for all films at about a 40 at-%, whereas boron and carbon compositions ranged between 15-35 and 25-50 at-%, respectively. The electronic and bonding structure of the coatings were analyzed by REELS using three different electron beam energies to obtain information at different depths. An increase of the carbon content of the films resulted in a significant shift of the pi-pi* interband transition with respect to the energy loss corresponding to h-BN. The absence of the pi-pi* transition in the energy loss spectra acquired at a beam energy of 1900 eV indicates the existence of a very thin overlayer mostly sp(2) bonded and probably with a distorted hexagonal structure. The position of the bulk plasmon losses corresponded to the hexagonal phase for the overlayer and presented a shift of more than 1.5 eV to the higher energy loss direction for the spectra obtained at 1900 eV beam energy. This shift and the absence of the sp(2)-bond fingerprint induced the possibility of an underlying disordered structure with a majority of sp(3) bonds.     

Effect of UV irradiation on the surface Gibbs energy of Ti6Al4V and thermally oxidized Ti6Al4V

Thermal oxidation of Ti6Al4V increases the thickness, modifies the structure, and changes the amount of alloying elements of the surface titanium dioxide layer with respect to the spontaneous passive layer of Ti6Al4V. The effects on the surface properties of Ti6Al4V and thermally oxidized Ti6Al4V after different periods of UV irradiation have been studied by measurement of water, formamide, and diiodomethane contact angles. The rate of modification of the water contact angle with the irradiation time is dependent on the surface treatment, but the water adhesion work, after an initial energetic step, follows a similar trend for both. Application of the Young equation together with the van Oss approach allowed evaluation of the surface Gibbs energy of the alloys. Similar to the water adhesion work, the surface Gibbs energy dependence on the irradiation time follows a similar trend for both samples and it is due to the change of the electron-donor parameter of the acid-base component. Also, a linear relationship common for both samples has been obtained between the cosines of the water contact angle and the formamide or diiodomethane contact angle. These facts indicate that the surface modification continuously produced by the UV irradiation is similar all along the process and similar for both samples after an energetic threshold for the thermally oxidized sample. It has been also tested that the hydrophilic-hydrophobic conversion is reversible for Ti6Al4V and Ti6Al4V thermally treated.     

N-Doped Carbon Coated TiC Nanofiber Arrays on Ti-6Al-4V for Sensitive Electrochemical Determination of Cr(VI)

A sensitive electrochemical sensor for Cr(VI) detection based on N-doped carbon coated TiC nanofiber arrays (TiC@CNx NFAs) is reported. The abundant electrocatalytic active sites contained CNx shell, highly conducting TiC core, and good electrical contact between the TiC@CNx and underlying Ti alloy endow this electrode with the excellent electrochemical sensing properties. The developed electrochemical sensor shows remarkable determination activity towards Cr(VI) with a high sensitivity of 0.88 μA μM⁻¹ cm⁻², a low detection limit of 4.0 nM (S/N=3), a wide linear range from 0.2 to 24.1 μM, good selectivity and anti-interference property.     

Electrochemically induced anatase inhibits bacterial colonization on Titanium Grade 2 and Ti6Al4V alloy for dental and orthopedic devices

Bacterial contamination of implanted devices is a common cause of their failure. The aim of the present study was to assess the capability of electrochemical procedures to: (a) promote the formation of anatase on the surface of commercially pure Grade 2 Ti and Ti Grade 5 (Ti6Al4V) alloy; (b) inhibit in vitro biofilm formation of Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus mutans and Porphyromonas gingivalis and oral plaque in vivo, (c) preserve favorable response of osteoblasts and fibroblasts to materials surfaces. Ti Grade 2 and Ti Grade 5 were respectively anodized at two different voltages: 90 and 130V for pure titanium; 100 and 120V for Ti6Al4V alloy. Surface characterization was performed by scanning electron microscopy (SEM) equipped with EDS probe, laser profilometry and X-ray diffractometry. Bacterial adhesion characterization was performed either in vitro and in vivo in patients. Osteoblast and fibroblast response was evaluated by metabolic activity assessment. The higher voltage applied in the anodization treatment of pure titanium (130V) and Ti6Al4V alloy (120V) surfaces, compared to the untreated pure titanium and Ti6Al4V and to lower voltage treatments, resulted in a greater decrease in bacterial attachment and biofilm formation in both in vitro and in vivo experiments. In contrast, the high voltage treatments were found to promote osteoblasts and fibroblasts proliferation. The observations indicated that the experimented high voltage anodization treatments may contribute to preserve the tissue integration and reduce bacteria colonization of titanium and titanium alloy for implantable applications.     

Characterization of oxide layers on Ti6Al4V and titanium by streaming potential and streaming current measurements

Titanium and titanium alloys (e.g. Ti6Al4V) are increasingly used as medical implant materials in a wide variety of applications. So far, many surface properties of the passive layer considered to explain interactions with biological tissues are deduced from those of the crystalline phases of titanium dioxide (anatase, rutile, brookite), but do not necessarily correspond to those of naturally formed amorphous passive layers. We report on streaming potential and streaming current measurements on oxide layers on Ti6Al4V and Ti, carried out using a microslit electrokinetic set-up (MES) and a commercial electrokinetic analyzer (EKA, PAAR). Passive and anodic oxide layers on Ti6Al4V, as well as passive layers on titanium sputtered on glass, were investigated in this study. Isoelectric points (IEP) of ≈4.4 were found for all oxide layers. The IEP of the air-formed passive layer on Ti6Al4V did not depend on the KCl concentration. Hence, it was concluded that IEP is here identical to the point of zero charge (pzc). Controversially, the charge formation process seems to depend on the chloride ion concentration in the neutral and basic pH region.     

新表面化学处理用于Ti6A14 V合金表面仿生磷酸钙涂层的制备

报道了一种新的非腐蚀性表面化学处理用于Ti6Al4V合金表面仿生磷酸钙涂层的制备.将Ti6Al4V合金从浸入的过饱和磷酸钙溶液中拉出,在空气中挥干表面附着的过饱和润湿膜,在Ti6Al4V表面生成磷酸钙晶体,且其表面覆盖率随处理次数增加而增加,直至表面完全被覆盖.再将磷酸钙晶体覆盖的Ti6Al4V浸人过饱和溶液后,表面的磷酸钙晶体迅速生长成为均匀的磷酸钙涂层.该表面化学处理的机理可能为一个挥发表面结晶过程,其优点在于润湿膜干燥为表面成核提供驱动力,因此无需采用表面腐蚀性处理或不稳定的高过饱和溶液处理.     

新表面化学处理用于Ti6Al4V合金表面仿生磷酸钙涂层的制备

报道了一种新的非腐蚀性表面化学处理用于Ti6Al4V合金表面仿生磷酸钙涂层的制备. 将Ti6Al4V合金从浸入的过饱和磷酸钙溶液中拉出, 在空气中挥干表面附着的过饱和润湿膜, 在Ti6Al4V表面生成磷酸钙晶体, 且其表面覆盖率随处理次数增加而增加, 直至表面完全被覆盖. 再将磷酸钙晶体覆盖的Ti6Al4V浸入过饱和溶液后, 表面的磷酸钙晶体迅速生长成为均匀的磷酸钙涂层. 该表面化学处理的机理可能为一个挥发表面结晶过程, 其优点在于润湿膜干燥为表面成核提供驱动力, 因此无需采用表面腐蚀性处理或不稳定的高过饱和溶液处理.     

Effect of nitrogen on mechanical,oxidation and structural behaviour of Ti–Si–B–C–N nanocomposite hard coatings deposited by DC sputtering

Ti–Si–B–C–N film was deposited by DC magnetron sputtering at different argon and nitrogen ratios such as N₂/Ar = 1 : 5, 2 : 4, 3 : 3, 4 : 1 and 5 : 0. The formation of TiN and TiB phases was observed because of incorporation of nitrogen. The hardness, modulus, microstructure, structure and bond formation with different nitrogen contents during the deposition were studied by nanoindentation, scanning electron microscope, X‐ray diffraction and X‐ray photoelectron spectroscopy, respectively. The oxidation kinetics of Ti–Si–B–C–N was investigated. The nitrogen incorporation during deposition influences different properties of the coating. Hardness and modulus decreased, and microstructure showed very fine grain presence, and film changes to fully amorphous because of incorporation of nitrogen in the film. Copyright © 2016 John Wiley & Sons, Ltd.     

Examination of clinical surface preparations on titanium and Ti6Al4V by X-ray photoelectron spectroscopy and nuclear reaction analysis

Nitric acid passivation, as part of the ASTM-F86 protocol for metal implant preparation, has been studied on titanium and Ti6Al4V surfaces by x-ray photoelectron spectroscopy (XPS) and nuclear reaction analysis (NRA). The surface types studied, (including thermal annealing at 1250C in vacuum, rough grinding at 600 grit, and polishing at 1m) show varying surface oxide properties and sensitivity to nitric acid treatment. Changes in surface oxide properties in terms of thickness and constituent metal content resulting from nitric acid treatment are related to metal ion dissolution behaviour in a simulated biological fluid. Ti6Al4V in general is most sensitive to treatment in nitric acid by exhibiting a decrease in surface oxide thickness, an increase in Al concentration within the oxide, and an increase in dissolution of constituent metals into serum containing culture medium. Combined XPS and NRA analysis show surface oxide thicknesses to be more variable and non-uniform than XPS analysis alone would suggest.     

TPD study of NH3 adsorption/desorption on the surface of V/Ti, V/Al based catalysts for selective catalytic reduction of Nox by ammonia 2. TPD test of commercial V/W/Ti, V/Al, Pd/V/Al catalysts

The effect of temperature on the adsorption/desorption of ammonia from the air mixture on the surface of commercial binary V/Al and ternary Pd/V/Al, V(0.65 wt.%) /W(6.73 wt.%) /Ti and V(1.8 wt.%) /W(7.3 wt.%) /Ti de-NO_x catalysts has been investigated by temperature-programmed desorption (TPD) method. The ability of the commercial catalysts to adsorb ammonia in the most stable surface species was shown to correlate well with their suppression of the NH₃ oxidation.     

Study on the layer structure of W/C multilayers deposited by magnetron sputtering using x‐ray reflectivity

A study on the layer structure of W/C multilayers deposited by magnetron sputtering is reported. In the study, soft x‐ray resonant reflectivity and hard x‐ray grazing incidence reflectivity of the W/C multilayers were measured. The imperfections at the interface such as interdiffusion and formation of compounds were dealt with by two methods. On analyzing the experimental results, we found that the incorporation of an interlayer was a more suitable method than the traditional statistical method to describe the layer structure of a W/C system we fabricated. The optical constants of each layer at a wavelength of 4.48 nm were also obtained from the analysis. Copyright © 2008 John Wiley & Sons, Ltd.     

H2S sensing properties of nanocrystalline Sr2FeO.6NiO.4MoO6 thick film prepared by sol-gel citrate method

Nanocrystalline Sr₂FeMoO₆ (SFMO) belonging to the group of double perovskite oxides, was prepared by the sol-gel citrate method. The structural and microstructural characterization has been carried out with the help of X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. XRD of Sr₂Fe_1−xNi_xMoO₆ (SFNMO) shows the formation of solid solution with average grain size of about 40 nm. A comparative study of gas sensing behaviour of Sr₂FeMoO₆ and Sr₂Fe_1−xNi_xMoO₆ with reducing gases like hydrogen sulfide (H₂S), liquid petroleum gas (LPG), hydrogen (H₂), ethanol (C₂H₅OH) and carbon monoxide (CO) were also discussed. The sensitivity is calculated by measuring the change the resistance of the sensor material in the presence of gas. Among the different composition of x (x = 0.2, 0.3, 0.4, 0.5), Sr₂Fe_0.6Ni_0.4MoO₆ (x = 0.4) shows better response to H₂S gas at 260 °C. Incorporation of palladium (Pd) improves the gas response, selectivity, response time and reduced the operating temperature from 260 to 220 °C for H₂S gas.     

Investigation of the regeneration of the passive surface oxide layer of TiAl6V4 alloy printed by WAAM technology using different electrochemical test methods

The kinetics of oxide layer formation on surface of Ti6Al4V alloy samples is a very important property especially if their application as medical implants is planned. Damaged protective surface layer usually heals in ambient condition however; during the self-healing process toxic species can get into the surrounding living tissue. In our experiment the kinetics of the healing process proceeding at 3D printed alloy surface has been studied using electrochemical methods, among them scanning electrochemical microscopy. More than 40 min. time period was found long enough for total healing.