Ba Dechun

Influence of Hysteretic Behaviour in Reactive Magnetron Sputtering on the Crystal Structure and Characteristics of Aluminium Oxide Films

The influence of the hysteretic behaviour in reactive sputtering with a pure aluminium target in the presence of argon and oxygen plasma on transmittance and surface free energy of aluminium oxide films was investigated by plasma optical emission spectroscopy technology. The evolutions of aluminium, and aluminium oxide emission lines as functions of oxygen flow rate at constant power and pressure were studied. A steep transition from the metallic sputtering to the compound sputtering was observed upon increasing the oxygen flow rate from 0.0 SCCM to above 2.0 SCCM. Then an optimal deposition zone was obtained through analyzing the hysteretic curves of aluminium and aluminium oxide emission lines. The evolution of crystal structures of samples was discerned by X-ray diffraction spectra data. Energy dispersive X-ray spectroscopy data also demonstrate the relationship between the chemical compositions of aluminium oxide films and the hysteretic behaviour. The film deposited between 1.5 SCCM and 2.0 SCCM oxygen flow rate displays an optimal and stoichiometic atomic ratio of O to Al and mass ratio of O to Al. The changes in the transmittance of samples were discovered to depend on the oxygen flow rate by UV-VIS transmittance spectra, and the changes in surface free energy were studied by contact angle measurement.

Low Temperature Nitriding of 304 Austenitic Stainless Steel Using RF-ICP Method: the Role of Ion Beam Flux Density

The significant role of ion beam flux during nitriding 304 austenitic stainless steel has been investigated by using a radio frequency inductively-coupled plasma reactor into which a sample with negative bias voltage was inserted. A milliammeter is used to detect the current of ions which collide with the sample and optical emission spectroscopy is used to discern the reactive species included in the nitrogen plasma. The nitriding efficiency is indicated by X-ray diffraction and the microhardness test. The reported data reveal that the ion beam flux density as well as the deposition pressure, bias voltage and time can strongly affect the nitriding of stainless steel via the expanded multiphase microstructure inside the nitrided layer. The increase in the density of ion flux results in an ascent in the intensity of the expanded peak and a simultaneous decline in the intensity of the γ austenite peak. The evolution trend of ion beam flux density is described as a function of the operating pressure and the bias voltage. The maximum ion flux density has been achieved at 10 Pa pressure and −500 V bias voltage. A reasonable nitriding region has been, consequently, suggested after comparing this work with previously reported results.

Frictional and Optical Properties of Diamond-Like-Carbon Coatings on Polycarbonate

In this work, diamond-like-carbon (DLC) films were deposited onto polycarbonate (PC) substrates by radio-frequency plasma-enhanced chemical vapor deposition (RF PECVD), and silicon films were prepared between DLC and PC substrates by magnetron sputtering deposition so as to improve the adhesion of the DLC films. The deposited films were investigated by means of field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Subsequently, the following frictional and optical properties of the films were measured: the friction coefficient by using a ball-on-disk tribometer, the scratch hardness by using a nano-indenter, the optical transmittance by using a UV/visible spectrometer. The effects of incident power upon the frictional and optical properties of the films were investigated. Films deposited at low incident powers showed large optical gaps, which decreased with increasing incident power. The optical properties of DLC films correlated to the sp 2 content of the coatings. High anti-scratch properties were obtained at higher values of incident power. The anti-scratch properties of DLC films correlated to the sp 3 content of the coatings.

Fabrication and Characterization of Tio2 Antireflection Thin Film Deposited on the Solar Cell

TiO2 thin film has attracted considerable attention in recent years, due to its different refractive index and transparency with amorphous and different crystals in the visible and near-infrared wavelength region, high dielectric constant, wide band gap, high wear resistance and stability, etc, for which make it being used in many fields. This paper aims to investigate the antireflection characterization of TiO2 thin film on silicon solar cell. The TiO2 thin films were prepared by DC reactive magnetron sputtering process from Ti target. The reflectivity of the films were measured by UV—3101PC, the index of refraction (n) and extinction coefficient (k) were measured by n&k Analyzer 1200,and the I–V characteristic curves of uncoated and coated solar cell were measured by I–V testing system of solar cell.

Design optimization of hydraulic turbine draft tube based on CFD and DOE method

In order to improve performance of the hydraulic turbine draft tube in its design process, the optimization for draft tube is performed based on multi-disciplinary collaborative design optimization platform by combining the computation fluid dynamic (CFD) and the design of experiment (DOE) in this paper. The geometrical design variables are considered as the median section in the draft tube and the cross section in its exit diffuser and objective function is to maximize the pressure recovery factor (Cp). Sample matrixes required for the shape optimization of the draft tube are generated by optimal Latin hypercube (OLH) method of the DOE technique and their performances are evaluated through computational fluid dynamic (CFD) numerical simulation. Subsequently the main effect analysis and the sensitivity analysis of the geometrical parameters of the draft tube are accomplished. Then, the design optimization of the geometrical design variables is determined using the response surface method. The optimization result of the draft tube shows a marked performance improvement over the original.

Vibration Damping Properties of NiCrAlY Coating Deposited by Arc Ion Plating

Abstract NiCrAlY coating was deposited on 3Cr13 stainless steel substrates by an arc ion plating technique. This paper is to explore the feasibility of NiCrAlY coating for the damping application and to characterize the method that may be used in defining the vibration features of the coatings. The phases of the NiCrAlY coating were determined by X-ray diffraction (XRD) technique. The surface morphology and chemical composition of the NiCrAlY coating were analyzed by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), respectively. The damping properties were characterized by dynamic mechanical analyzer (DMA) and sine sweeps. Results show that the damping properties of the substrate are considerably improved by the NiCrAlY coating.

Microstructure and Tribological Properties of Plasma Nitrided Biomedical CoCrMo Alloys

Abstract Medical forged CoCrMo alloy was treated by DC plasma nitriding process to alter its surface characteristics and to improve mechanical and tribological properties. The phase composition, microstructures, surface microhardness, and wettability were characterized by X-ray diffraction, scanning electron microscope, micro-hardness tester, and optical dynamic/static contact angle meter. Friction and wear characteristics were investigated on ball-on-disc tribotester under dry sliding conditions. The experimental analysis confirms that the plasma nitriding process is promising in producing thicker, harder, highly hydrophilic and more wear resistance layers on CoCrMo alloy for biomedical applications. At lower nitriding temperatures and for shorter time, the nitrided layer structure is composed of σ-CoCr and CrN phases. At higher nitriding temperatures and for longer time, σ-CoCr and CrN as well as Cr2N phases appear in nitrided specimens. With the increasing of nitriding temperatures and time, case depth thickness, surface roughness, microhardness and wear resistance increase while water contact angle decreases and becomes highly hydrophilic. Compared with untreated CoCrMo alloy, all nitrided specimens show an important reduction in wear rate and wear scar width, and the nitrided specimen at 800 °C/8 h exhibits the lowest wear rate and the best dry-sliding wear resistance.

The Effect of Ion Current Density on Target Etching in Radio Frequency-Magnetron Sputtering Process

The effect of ion current density of argon plasma on target sputtering in magnetron sputtering process was investigated. Using home-made ion probe with computer-based data acquisition system, the ion current density as functions of discharge power, gas pressure and positions was measured. A double-hump shape was found in ion current density curve after the analysis of the effects of power and pressure. The data demonstrate that ion current density increases with the increase in gas pressure in spite of slightly at the double-hump site, sharply at wave-trough and side positions. Simultaneously, the ion current density increases upon increase in power. Especially, the ion current density steeply increases at the double-hump site. The highest energy of the secondary electrons arising from Larmor precession was found at the double-hump position, which results in high ion density. The target was etched seriously at the double-hump position due to the high ion density there. The data indicates that the increase in power can lead to a high sputtering speed rate.