CNx Films Deposited by Laser Ablation of Graphite Under Low Energy Nitrogen-Ion Beam Bombardment

Deposition of CN_(x) thin films on Si(111)has been performed by laser ablation of graphite under a low-energy nitrogen ion beam bombardment.Films with a maximum N-concentration of 34%are obtained.The N species is found to be relatively constant along the depth of films.X-ray spectroscopy data confirm the existence of covalent C-N bonds.Nanocrystallites structure has been detected in the amorphous matrix of the films.Qualitative hardness tests indicate that the films are relatively hard and adhesive.

Electropolishing of NiTi for Improving Biocompatibility

A modified electrolyte （CH3COOH-HClO4-A-B） for electropolishing （EP） of NiTi was presented for improving the corrosion resistance and biocompatibility of the alloy. Using the proposed parameters, a homogeneous and uniform surface was obtained. Atomic force microscopy （AFM） revealed that the surface roughness （Ra） for EP sample （23.21 nm） was close to mechanical polishing （MP） sample （19.36 nm）. Analysis by X-ray photoelectron spectroscopy （XPS） showed that Ti/Ni ratio increased from 3.1 for MP sample to 27.6 for EP sample. Measurements using potentiodynamic polarization in Hanks＇ solution showed that no pitting occurred for EP sample even though the applied potential increased up to 1500 mV （vs SCE）, while the MP sample was broken down at 650 mV. The present study indicates that electropolishing NiTi with this modified electrolyte contributes to the improved biocompatibility of NiTi.

Influences of nitrogen flow rate on the structures and properties of Ti and N co-doped diamond-like carbon films deposited by arc ion plating

In this paper, Ti-C-N nanocomposite films are deposited under different nitrogen flow rates by pulsed bias arc ion plating using Ti and graphite targets in the Ar/N2 mixture gas. The surface morphologies, compositions, microstructures, and mechanical properties of the Ti-C-N films are investigated systematically by field emission scanning electron mi- croscopy （FE-SEM）, x-ray photoelectron spectroscopy （XPS）, grazing incident x-ray diffraction （GIXRD）, Raman spectra, and nano-indentation. The results show that the nanocrystalline Ti（C,N） phase precipitates in the film from GIXRD and XPS analysis, and Raman spectra prove the presence of diamond-like carbon, indicating the formation of nanocomposite film with microstructures comprising nanocrystalline Ti（C,N） phase embedded into a diamond-like matrix. The nitrogen flow rate has a significant effect on the composition, structure, and properties of the film. The nano-hardness and elastic modulus first increase and then decrease as nitrogen flow rate increases, reaching a maximum of 34.3 GPa and 383.2 GPa, at a nitrogen flow rate of 90 sccm, respectively.

Growth of Fluorocarbon Films by Low-Pressure Dielectric Barrier Discharge

Plasma polymerized fluorocarbon （FC） films have been deposited on silicon substrates from dielectric barrier discharge （DBD） plasma of C4Fs at room temperature under a pressure of 25～125 Pa. The effects of the discharge pressure and frequency of power supply on the films have been systematically investigated. FC films with a less cross linked structure may be formed at a relatively high pressure. Increase in the frequency of power supply leads to a significant increase in the deposition rate. Static contact angle measurements show that deposited FC films have a stable, hydrophobic surface property. All deposited films show smooth surfaces with an atomic surface roughness. The relationship between plasma parameters and the properties of the deposited FC films are discussed.

Surface properties of diamond-like carbon films prepared by CVD and PVD methods

Diamond-like carbon （DLC） films have been deposited using three different techniques： （a） electron cyclotron resonance——plasma source ion implantation, （b） low-pressure dielectric barrier discharge, （c） filtered——pulsed cathodic arc discharge, The surface and mechanical properties of these films are compared using atomic force microscopebased tests. The experimental results show that hydrogenated DLC films are covered with soft surface layers enriched with hydrogen and sp^3 hybridized carbon while the soft surface layers of tetrahedral amorphous carbon （ta-C） films have graphite-like structure, The formation of soft surface layers can be associated with the surface diffusion and growth induced by the low-energy deposition process. For typical CVD methods, the atomic hydrogen in the plasmas can contribute to the formation of hydrogen and sp^3 hybridized carbon enriched surface layers, The high-energy ion implantation causes the rearrangement of atoms beneath the surface layer and leads to an increase in film density. The ta-C films can be deposited using the medium energy carbon ions in the highly-ionized plasma.

Preparation of TiO_(x)/γ-Al_(2)O_(3) Catalyst on Powdery γ-Al_(2)O_(3) by Using Reactive Sputtering Deposition

A layer of TiO_(x) was deposited on powdery γ-Al_(2)O_(3) by using Sat-target magnetron sputtering in microwave electron cyclotron resonance plasma.A vibrator was developed to coat the γ-Al_(2)O_(3) particles evenly by TiO_(x).The conversion efficiency of methane and both the yield and the selectivity of C_(2) hydrocarbons and C_(2)H_(2) were revealed to be superior to that by conventional chemical method.The use of vibrator is effective.

Effect of heat input on microstructure and properties of welded joint in magnesium alloy AZ31B

Using the optical microscope, tensile test machine and micro hardness meter, the effect of heat input on the microstructure and mechanical properties in fusion welding joints of AZ31B wrought alloys was investigated systematically, the mechanism on joint properties losing was analyzed, and a valid method to improve joint properties of the magnesium alloy fusion welding was explored. The results show that the heat input has an obvious effect on the microstructure and properties. Under the condition of penetration, with the heat input decreasing, the crystal grain in the weld and heat affected zone (HAZ) becomes fine, the width of HAZ becomes obviously narrow, and the molding of the weld is improved, so the tensile strength and elongation are increased and the hardness of joints is improved. When the heat input reaches 60 J/mm, the high quality joints can be gained.

Structures of Diamond-Like Carbon Films

The structures of diamond-like carbon （DLC） films, including a-C：H, a-C, ta-C：H and ta-C films have been investigated as a random covalent network with a dense film structure. The results show that sp2 C in a-C：H and a-C films tends to form olefinic and aromatic groups while sp^3 C in ta-C：H and ta-C films tends to form single or multiple sixfold groups. The hydrogen atoms in hydrogenated DLC films contribute to stabilizing the carbon skeletal networks. The film structures are well related to their properties such as optical gaps, density and hardness. The results also indicate that the high density and the extreme hardness of ta-C films are attributed to the forming of large sp^3 C bonded sixfold groups.

Surface Roughness of Various Diamond-Like Carbon Films

Atomic force microscopy is used to estimate and compare the surface morphology of hydrogenated and hydrogen-free diamond-like carbon （DLC） films. The films were prepared by using DC magnetron sputtering of a graphite target, pulsed cathodic carbon arcs, electron cyclotron resonance （ECR）, plasma source ion implantation and dielectric barrier discharge （DBD）. The difference in the surface structure is presented for each method of deposition. The influences of various discharge parameters on the film surface properties are discussed based upon the experimental results. The coalescence process via the diffusion of adsorbed carbon species is responsible for the formation of hydrogen-free DLC films with rough surfaces. The films with surface roughness at an atomic level can be deposited by energetic ion impacts in a highly ionized carbon plasma. The hydrocarbon species dangling bonds created by atomic hydrogen lead to the uniform growth of at the a-C：H film surfaces of the ECR or DBD plasmas

Influence of Nitrogen Vacancy Concentration on Mechanical and Electrical Properties of Rocksalt Zirconium Nitride Films

To study the influence of the nitrogen vacancy （VN） on mechanical and electrical properties of zirconium nitride deeply, ZrNx films with different VN concentrations were synthesized on the Si （111） substrates by enhanced magnetic filtering arc ion plating. The morphologies, microstructures, residual stresses, compositions, chemical states, mechanical and electrical properties of the as-deposited films were characterized by field-emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectrometry, Nanoindenter and Hall effect measurements. The results showed that ZrNx films exhibited rocksalt single-phase structure within a VN concentration ranging from 26 to 5%. The preferred orientation, thickness, grain size and residual stress of the ZrNx films kept constant at different VN concentrations. Both the nanohardness and elastic modulus first increased and then decreased with the decrease in VN concentration, reaching the peaks around 16%. And the electric conductivity of the ZrNx films showed a similar tendency with nanohardness. The underlying atomic-scale mechanisms of VN concentration-dependent hardness and electric conductivity enhancements were discussed and attributed to the different electronic band structures, rather than conventional meso-scale factors, such as preferred orientation, grain size and residual stress.