•The sol-gel Si-Ca-P bioglass film on titanium is amorphous with a little Ca3SiO5.•HA nanocrystallites are formed by hydrothermal treatment in CaHPO4 solutions.•The formed HA nanocrystallites improve hydrophilicity of the coating samples.•The coating samples have better corrosion resistance than the polished one.Bioglass film was sol-gel coated on titanium substrate, followed by hydrothermal treatment in water, 2.5 mM and 10 mM CaHPO4 solutions, respectively. X-ray diffraction analysis reveals amorphous nature of the gel powder sintered at 610 °C, but small diffraction peaks of Ca3SiO5 are also observed. The absorption bands of Si-O-Si bonds, PO4 and OH groups are present, while those of NO3 groups are absent in Fourier transform infrared spectrum of the sintered gel powder. Scanning electron microscopy observation shows that the surface of the sintered bioglass film is porous (pore size ~ 200 nm), and nanocrystallites (width ~ 20 nm, length ~ 200 nm) are deposited on the samples hydrothermally treated in CaHPO4 solutions. Energy dispersive x-ray, x-ray photoelectron spectroscopy and x-ray diffraction analyses indicate that the nanocrystallites are composed of hydroxyapatite, which are formed through a dissolution-precipitation reaction. The formation of hydroxyapatite nanocrystallites at the film surface improves hydrophilicity of the coating samples. Potentiodynamic polarization test in the Ca-free Hank's solution demonstrates that the coating samples have better corrosion resistance than the polished one. The calcified titanium samples are expected to possess good biological properties.

NiTi alloy was subjected to one-step hydrothermal treatment in the concentrated CaHPO4 and Ca(H2PO4)2 solutions for bioactive surface modification. Results show that the treated samples are covered by films composed of fine grains (∼70 nm) and large particles (100∼250 nm). X-ray photoelectron spectroscopy analysis indicates that Ti at the surface presents as TiO2, Ni is not detectable, and Ca and P exist in the form of calcium phosphate. X-ray diffraction peaks of anatase TiO2 and hydroxyapatite are presented for the treated samples. Potentiodynamic polarization test in a Ca-free Hank's balanced solution reveals that the treated sample has a markedly improved corrosion resistance compared with the polished sample. The present work would provide a one-step bioactive surface modification method with easy-operation, relatively low processing temperature and less corrosion, and potentially suitable for biomedical porous NiTi alloy.

Pure and Ag-containing TiO2 films (Ag/Ti = 3.3 at.%) are coated on plasma nitrided 316L stainless steel by sol–gel method for biomedical applications. The addition of Ag does not cause obvious change in TG–DSC curves of the dried gels. The rough surface generated by plasma nitriding and the addition of Ag improve structural integrity of the TiO2 films. X-ray diffraction reveals N loss and oxidation of the nitride layer during calcination treatment, and peaks of Ag or its oxides are not detected. X-ray photoelectron spectroscopy analysis indicates that Ag presents as metallic state in the film. Water contact angles of the coating samples decrease with UV irradiation treatment. The potentiodynamic polarization tests in a Ca-free Hank’s balanced salt solution show that the TiO2 coated samples have decreased corrosion resistance due to N loss and oxidation of the nitride layer. The methods for crystallization of TiO2 gel layers with minimized or avoided structural changes of the nitride layer will be tried in order to improve corrosion resistance of the duplex treated 316L stainless steel.

The surface of NiTi alloy was roughened by NaOH–HCl treatment, and the Ta-containing TiO2 films were coated on the pretreated NiTi alloy by the sol–gel method. Thermal analyses indicate that the evaporation temperature of the organics decreases with the addition of tantalum ethoxide in the TiO2 sol, but the crystallization temperature of anatase increases. The NaOH–HCl pretreatment improves the film integrity, but cracks still form in the films at high Ta contents (≥20 %, molar ratio) owing to the increasing film thickness. X-ray diffraction (XRD) confirms that the addition of Ta suppresses the crystallization of anatase. X-ray photoelectron spectroscopy (XPS) reveals that Ta exists as Ta2O5 in the film. With the increase of Ta content, the hydrophilic conversion of the films under UV illumination is impeded, but their corrosion resistance in 0.9 % NaCl solution increases, tested by the potentiodynamic polarization. The coating samples have acceptable hemolysis ratios for biomaterials (<5). The introduction of Ta improves the anti-aggregating function of the TiO2 film in the platelet adhesion test.

In this study, punch test is employed to study the deformation and fracture mechanism of materials, taking metallic glasses as an example, under the multiaxial loading. On one hand, shear bands, as the type of deformation behaviors, are observed to initiate and propagate along two directions to form the grid pattern in the three-dimensional space. On the other hand, the further understanding focuses on the deformation and fracture mechanism of materials under punch loading. Finally, the intrinsic origin is explored in the physical interest.Highlights► Deformation and fracture of amorphous material is characterized under the multiaxial stress. ► Shear bands are observed in the three-dimensional space. ► Competitive process between tensile normal stress and shear stress is convinced. ► Inherent mechanism is exploited to clarify the intrinsic physical interest.

Titania film is coated on plasma nitrided 316L stainless steel by sol-gel method. Crystallization of titania as well as N loss and formation of Fe2O3 occurs during the annealing heat treatment. The titania film has short cracks within the grooves of plasma etched grain boundaries. With the increase of annealing temperature and duration, surface hardness of the samples is increased, but the toughness is decreased due to oxidization of the surface layer. The coating sample heat treated at 350 °C for 10 min and 450 °C for 10 min has better corrosion resistance than the nitrided stainless steel tested by the potentiodynamic polarization in 0.9% NaCl solution. Water contact angle of the titania film on the rough nitrided steel substrate decreases with UV irradiation treatment, reaching 17° after 3 h treatment.Highlights► Sol-gel TiO2 film is coated on plasma nitrided 316L stainless steel. ► The coating sample has better corrosion resistance than the nitrided stainless steel. ► UV irradiation treatment greatly improves hydrophilicity of the coating sample.

Deformation-induced nanocrystallization and martensite transformation were induced in the single surface of coarse-grained austenitic stainless steel sheet by severe plastic deformation, which formed the gradient, multiscale grain sizes distribution and composite microstructures of austenite and martensite. Resultant mechanical properties were optimized with improved yield strength of 1000 MPa (from the 300 MPa), large elongation to failure of 50% and good strain hardenability. Finally, observations on the deformation and fracture behavior clarify the inherent toughness mechanism.

Amorphous carbon nitride (CNx, x = 0.05) films were reactively sputtered on Si(100) substrate, and the interface structure was studied by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). In cross-sectional TEM a gray interlayer about 5 nm thick between the bulk CNx film and silicon substrate is observed, and the interface is dense. A little Si impurity (< 1 at.%) is revealed in the films deposited for short time (7 s and 17 s) by XPS measurement. The in-depth XPS analyses indicate that there exists an interlayer with Si impurity above, and a sub-surface layer with C and N below the original surface of silicon substrate. The two layers have different chemical composition and bonding state.