Enhanced corrosion resistance of Zr coating on biomedical TiNi alloy prepared by plasma immersion ion implantation and deposition

Zirconium film was prepared on TiNi alloy by plasma immersion ion implantation and deposition (PIIID) technique to enhance its corrosion resistance and prolong its working lifetime. The atomic force microscopy (AFM) results show that the film was relatively smooth with the root mean square roughness being 9.166 nm. The X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) results indicate that the implant element of Zr was oxidation partialness. The potentiodynamic polarization measurements in the Hank's solution at 37 °C show that the corrosion resistance of the alloy was improved by the Zr coating film and the atomic absorption spectrometry (AAS) tests also indicate that Ni ion concentration released from the substrate in the Hank's solution after the polarization test was reduced greatly, in comparison to the unmodified TiNi alloy sample.     

Growth of thin Fe(0 0 1) films for terahertz emission experiments

The electrical and magnetic properties of thin iron (Fe) films have sparked significant scientific interest. Our interest, however, is in the fundamental interactions between light and matter. We have discovered a novel application for thin Fe films. These films are sources of terahertz (THz) radiation when stimulated by an incident laser pulse. After intense femtosecond pulse excitation by a Ti:sapphire laser, these films emit picosecond, broadband THz frequencies. The terahertz emission provides a direct measure of the induced ultrafast change in magnetization within the Fe film. The THz generation experiments and the growth of appropriate thin Fe films for these experiments are discussed. Several criteria are used to select the substrate and film growth conditions, including that the substrate must permit the epitaxial growth of a continuous, monocrystalline or single crystal film, yet must also be transparent to the emitted THz radiation. An Fe(0 0 1) film grown on the (0 0 1) surface of a magnesium oxide (MgO) substrate makes an ideal sample. The Fe films are grown by physical vapor deposition (PVD) in an ultrahigh vacuum (UHV) system. Low energy electron diffraction (LEED) and Auger electron spectroscopy (AES) are used to characterize the Fe(0 0 1) films. Two substrate surface preparation methods are investigated. Fe(0 0 1) films grown on MgO(0 0 1) substrates that are used as-received and films grown on MgO(0 0 1) substrates that have been UV/ozone-cleaned ex vacuo and annealed in vacuo produce the same results in the THz generation experiments. Either substrate preparation method permits the growth of samples suitable for the THz emission experiments.     

Pulsed-laser crystallization and epitaxial growth of metal-organic films of Ca-doped LaMnO3 on STO and LSAT substrates

Ca-doped LaMnO₃ (LCMO) thin films have been successfully prepared on SrTiO₃ (STO) and [(LaAlO₃)_0.3-(SrAlTaO₆)_0.7] (LSAT) substrates using the excimer laser assisted metal-organic deposition (ELAMOD) process. The crystallization and the epitaxial growth of the amorphous metal-organic LCMO thin films have been achieved using a KrF excimer laser irradiation while the substrates were kept at constant temperature of 500 °C. Epitaxial films were obtained using laser fluence in the interval of 50-120 mJ/cm². The microstructure of the LCMO films was studied using cross-section transmission electron microscopy. High quality of LCMO films having smooth surfaces and sharp interfaces were obtained on both the STO and the LSAT substrates. The effect of the laser fluence on the temperature coefficient of resistance (TCR) was investigated. The largest values of TCR of the LCMO grown on the LSAT and the STO substrates of 8.3% K⁻¹ and 7.46% K⁻¹ were obtained at different laser fluence of 80 mJ/cm² and 70 mJ/cm², respectively.     

The effect of chemical treatment on apatite-forming ability of the macroporous zirconia films formed by micro-arc oxidation

Macroporous and nano-crystalline zirconia film was prepared by micro-arc oxidation (MAO) of zirconium, and the effect of chemical treatment in H₂SO₄ or NaOH aqueous solutions on the microstructure and apatite-forming ability of the film was investigated. Compared with the MAO film, the chemically treated films do not exhibit apparent changes in phase component, morphology and grain size, however, have more abundant basic Zr-OH groups. The films treated with H₂SO₄ and NaOH solutions can induce apatite formation on their surfaces in simulated body fluids (SBF) within 1 day, whereas no apatite was detected on the untreated ZrO₂ surface by 30 days. It is believed that the enhanced apatite-forming ability of the chemically treated ZrO₂ films is related to the abundant basic Zr-OH groups on their surface.     

Hydrogenase-based nanomaterials as anode electrode catalyst in polymer electrolyte fuel cells

We consider hydrogenase-based nanomaterials for possible use as anode electrode catalysts in polymer electrolyte fuel cells (PEFCs). We choose Fe-only hydrogenase component of Desulfovibrio desulfuricans (DdHase) as a hydrogenase complex, and investigate its catalytic activity for H₂ dissociation using ab initio calculations based on density functional theory (DFT). We found two possible H-H bond cleavage pathways, which are heterolytic and possess low activation barriers. Moreover, the H₂ dissociation can be promoted by inducing spin polarization of the H₂ adduct. We report that hydrogenase or hydrogenase-based nanomaterials can manipulate to exhibit the catalytic activity equivalent to the well-known platinum catalyst.     

Characterization and adsorptive application of ordered mesoporous silicas

The adsorption behaviour of the n-octane/ethanol binary liquid mixture has been studied on ordered mesoporous silica materials. Adsorption excesses on SBA-15, SBA-16 and MCM-48 solids are measured and described by mathematical functions. The experimental adsorption excess isotherms are presented and discussed. The mesoporous silicas used for liquid-adsorption experiments are characterized by nitrogen adsorption before and after liquid adsorption by the powder X-ray diffraction (XRD) and by the sample controlled thermal analysis (SCTA).     

Damage zone produced by the bombardment of stainless steel using Ti nitride PVD coatings

This paper presents the damage zone and defects produced by TiN thin film deposition on stainless steel using DC magnetron sputtering to produce collisions between the TiN ions and the substrate. The PVD process used a low operative pressure, reducing the bombardment damage on the substrate, in comparison with other methods.Internal friction (IF) and elastic modulus measurements were carried out in TiN-PVD coated AISI 304 stainless steel, using a sub-resonant torsion pendulum (f ≅ 1 Hz) and a vibrant-reed instrument (f ≅ 10³ Hz). Some experiments showed several internal friction peaks, which are attributed to dislocation relaxation and to martensitic transformation from γ to α′. The characterization was carried out with X-ray, AFM and SEM. Analysis of X-ray peaks indicates a residual deformation in the order of 0.0005-0.0009 for γ-phase and 0.0006-0.00204 for α′-phase. Two methods are presented to determine the adhesion energy by IF in coated materials: for the first the enthalpy is determined by means of isochronal IF measurements, while for the second it is determined using isothermal measurements. These produce an image of damage caused by the bombardment on the substrate, especially of the residual defects.     

Improving the bioactivity of NiTi shape memory alloy by heat and alkali treatment

TiO₂ films were formed on an NiTi alloy surface by heat treatment in air at 600 °C. Heat treated NiTi shape memory alloys were subsequently alkali treated with 1 M, 3 M and 5 M NaOH solutions respectively, to improve their bioactivity. Then treated NiTi samples were soaked in 1.5SBF to evaluate their in vitro performance. The results showed that the 3 M NaOH treatment is the most appropriate method. A large amount of apatite formed within 1 day's soaking in 1.5SBF, after 7 day's soaking TiO₂/HA composite layer formed on the NiTi surface. SEM, XRD, FT-IR and TEM results showed that the morphology and microstructure are similar to the human bone apatite.     

Formation of Pt-C films by ion beam assisted deposition for the application of suppression thermo-electron emission

Platinum and carbon were deposited onto the surface of molybdenum grids simultaneously by ion beam assisted deposition. The structure of the Pt-C films was studied by XRD and Raman spectroscopy. The XRD results showed that Pt exhibited mixed strong (1 1 1) and weak (2 0 0) orientations. The Raman spectra showed that the carbon existed in the form of graphite-like phase. Electron emission characteristics from the Mo grid with and without Pt-C films were measured using analogous diode method. The results showed that electron emission from the Mo grid coated with Pt-C films was much less than that from the Mo grid without Pt-C films. The obtained results demonstrated that the Pt-C films are effective grid-coating materials for the application of suppression thermo-electron emission.     

Preparation of Ni-doped carbon nanospheres with different surface chemistry and controlled pore structure

In classic carbon supports is very difficult to control pore size, pore size distribution, and surface chemical properties at the same time. In this work microporous carbons derived from furfuryl alcohol are used as support to prepare Ni-doped carbon materials. The N₂ flow rate used during the carbonisation process of the precursor influences on the size of the nanospheres obtained but not in their textural properties. Microporous carbon nanospheres have been synthesised with a narrow pore size distribution centred in 5.5 Å. The surface chemistry of these materials can be easily modified by different treatments without detriment of the pore structure of the doped carbon nanospheres.     

Microstructure evolution and magnetic properties of Co-B coatings electrolessly plated on hollow microspheres

The composites of Co-B coatings on hollow microspheres (Co-B/HMSs) have been successfully synthesized through electroless plating in this paper. The time-dependent microstructure evolution and magnetic properties of the composites were carefully investigated by scanning electron microscope (SEM), energy dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). It was found that small Co-B clusters appeared on the surface of hollow microspheres at catalytic nuclei during the initial stage. Further growth, they converged to form continuous coatings, which were actually stacking of Co-B nuclei. Interestingly, there was an increment of B content in the coating as time wore on, this phenomenon could be interpreted by electrochemical mechanism. Besides, the composites showed magnetic properties, which might be potentially important for the novel materials as magnetic carriers.     

Preparation and antibacterial effect of plasma sprayed wollastonite coatings loading silver

In this work, the plasma sprayed wollastonite coating was soaked in 5 wt% AgNO₃ solution at room temperature to load silver for improving its antibacterial effect. The surface characteristics of the silver-loaded coating were investigated by SEM, EDS and XRD. The release rate of silver from the coating was measured by ICP-OES in deionized water. The osteotoxicity of the silver-loaded coating was evaluated by in vitro cell culturing test. The antibacterial activity against Staphylococcus aureus was examined by Zone of Inhibition test. The results showed that the loaded silver reacted with the wollastonite coating to form silver silicate, which ensured a sustained release of silver in deionized water for as long as 50 days. The antibacterial activity and cell culturing tests confirmed that the silver released from silver-loaded wollastonite coating had strong inhibition against the growth of S. aureus, while they did not exhibit any adverse effects on the osteoblasts proliferation.     

Sticking coefficient of nitrogen on solid N2 at low temperatures

The sticking coefficient of nitrogen gas on a thick solid nitrogen film on a copper cold finger was studied at low temperature. For surface temperatures of about 12 K the sticking coefficient is measured to be 99.0 ± 0.6%. Our result implies that it will be possible to make a intense and high brightness slow positron source starting from a small diameter deposit of the gaseous positron emitter ¹³N₂ produced in the reaction ¹²C(d,n)¹³N.     

Effects of peak current density on the mechanical properties of nanocrystalline Ni-Co alloys produced by pulse electrodeposition

Cobalt content, grain size, microhardness and tensile strength of nanocrystalline Ni-Co deposits produced from a solution containing saccharin and cobalt sulfate at constant electrodeposition conditions (pulse on-time T_on at 1 ms and pulse off-time T_off at 15 ms) but varying the peak current density J_p were investigated. It is found that an increase in J_p makes the deposit Co content lower, colony-like morphology more obvious, grain size smaller, and hardness and tensile strength higher. All of the facts are believed to result from the higher overpotential and nucleation rates caused by the J_p increase. But its further increase could lead to reduction in the hardness and tensile strength. Peak current densities in the range of 100-120 A dm⁻² are recommended for the preparation of nanostructured Ni-Co alloy deposits with grain sizes in the range of 15-20 nm, containing 7-8% Co, possessing hardness of 590-600 kg mm⁻² and tensile strength of 1180-1200 MPa—significantly higher than the strength of pure nickel deposit which is produced by the similar method and gets similar grain size.     

Effects of seed layer on the structure and property of zinc oxide thin films electrochemically deposited on ITO-coated glass

ZnO films with different morphologies were deposited on the ITO-coated glass substrate from zinc nitrate aqueous solution at 65 °C by a seed-layer assisted electrochemical deposition route. The seed layers were pre-deposited galvanostatically at different current densities (i_sl) ranging from −1.30 to −3.0 mA/cm², and the subsequent ZnO films had been done using the potentiostatic technique at the cathode potential of −1.0 V. Densities of nucleation centers in the seed layers varied with increasing the current density, and the ZnO films on them showed variable morphologies and optical properties. The uniform and compact nanocrystalline ZnO film with (0 0 2) preferential orientation was obtained on seed layer that was deposited under the current density (i_sl) of −1.68 mA/cm², which exhibited good optical performances.     

The effect of back electrode on the formation of electrodeposited CoNiFe magnetic nanotubes and nanowires

The electrodeposition of cobalt + nickel + iron alloy nanostructures in aqueous sulfate solution has been studied using vitreous templates placed on highly ordered porous anodic alumina oxide (AAO). During the deposition process some electrochemical bath parameters such as ion content, deposition voltage, pH and temperature of solution were kept constant. The morphological properties of the nanostructures were studied by scanning electron microscopy (SEM) and the chemical composition was determined by examination of the energy dispersive X-ray (EDX) spectra. The magnetic behaviour of the arrays was determined with a vibrating sample magnetometer (VSM). Voltammetric and galvanostatic results indicate that the back electrodes placed on AAO plays the main role in obtaining nanowire or nanotube structured material.     

Investigation of evolution hydrocarbon species on a Si surface during methane plasma with and without substrate bias, using infrared spectroscopy in multiple internal reflection geometry

We investigated evolution of hydrocarbon species on a Si surface during methane plasma both with and without substrate bias, using infrared spectroscopy in multiple internal reflection geometry (MIR-IRAS). We found that the relative density of the sp³-CH or sp³-CH₂ species to the sp³-CH₃ species was low in the low exposure regions, but that the relative density of the sp³-CH or sp³-CH₂ species increased as the exposure was higher. Substrate temperatures rose as the plasma exposure was higher. The changes of ratios would be ascribed to the substrate heating effect by plasma exposure, which would enhance the etching and/or hydrogen abstraction effects. We also found the change of CH_1-2/CH₃ ratios was enhanced when the high substrate bias was applied. The enhancement of the ratio was due to ion effects.     

Surface morphology of laser tracks used for forming the non-smooth biomimetic unit of 3Cr2W8V steel under different processing parameters

Aiming to form the high quality of non-smooth biomimetic unit, the influence of laser processing parameters (pulse energy, pulse duration, frequency and scanning speed in the present work) on the surface morphology of scanned tracks was studied based on the 3Cr2W8V die steel. The evolution of the surface morphology was explained according to the degree of melting and vaporization of surface material, and the trend of mean surface roughness and maximum peak-to-valley height. Cross-section morphology revealed the significant microstructural characteristic of the laser-treated zone used for forming the functional zone on the biomimetic surface. Results showed that the combination of pulse energy and pulse duration plays a major role in determining the local height difference on the irradiated surface and the occurrence of melting or vaporization. While frequency and scanning speed have a minor effect on the change of the surface morphology, acting mainly by the different overlapping amount and overlapping mode. The mechanisms behind these influences were discussed, and schematic drawings were introduced to describe the mechanisms.     

Light induced adsorption of Si nano-composites in LiF crystals at 157 nm

Si nano-composites were precipitated on LiF crystals following ablation from Si targets with laser light at 157 nm. The LiF/Si interface was analyzed with scanning electron microscopy, atomic force microscopy and energy dispersive X-ray microanalysis. It was found that Si composites were strongly attached to LiF ionic sites to form inhomogeneous structures consisted of small isotropic crystals 0.1-1 μm long, rich in Si and fluorine, which eventually further agglomerate to form larger structures. The thickness of the LiF/Si interface was increased from 50 nm to 2 μm following laser irradiation at 157 nm, due to accelerated adsorption of Si in the LiF interface by VUV light.