Xin Xin Ma

Effects of Negative Bias Pulse on Characteristics of a-C:H Films Prepared by Plasma-Based Ion Implantation

A series of a-C:H films have been prepared by plasma-based ion implantation (PBII) with acetylene on AISI 321 substrates. The effect of negative bias pulse on the characteristics of these films was investigated. The structures of the films were analyzed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The surface hardness was measured by microindentation tests. The results indicated that the characteristics of these films are strongly depended on the negative bias pulse. When the bias pulse ranges from -10kV to -40kV, the films are typical diamond like carbon (DLC) films, while the films deposited at -5kV are polymer films. The peak intensity ratio of the D-band to that of the G-band (ID/IG) of the DLC films changes with the negative bias pulse. The minimum value of ID/IG (1.02) was gotten at -10kV.

Electrodeposition of Aluminum on 316L Stainless Steel from Molten Salts Based on Chlorides

The electrodeposition of aluminum on 316L stainless steel from a molten salts based on chloride has been studied. The surface morphology of the aluminum layer has been examined through scanning electron microscope (SEM) and the structure of the aluminum layer has been analyzed by X-ray diffraction (XRD). The thickness of the deposited aluminum layer has been measured by the method of cross-section scan. It has been suggested that a white, smooth, non-porous and a high purity aluminum layer can be obtained on 316L stainless steel from the ternary chloride molten salts (AlCl3 – NaCl - KCl). And the structure of the aluminum layer was single-phase.

Synthesis of Boron Carbonitride Films by Plasma-Based Ion Implantation

BCN films were prepared with unbalanced magnetron sputtering boron carbide film followed by nitrogen plasma-based ion implantation at different voltages on Si substrate. The implantation voltages vary from 10 kV to 50 kV. The chemical states of B, C and N of the films were studied with X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The nano-hardness and elastic modulus of films were measured by Nano-Indenter. The results showed that amorphous BCN films formed in the nitrogen implanted layer. The amorphous peak becomes obvious with increasing of the implanted voltage when the voltage is under of 40 kV. The Nano-Indenter measurement showed that the B-C bond content and the disorder degree affect the hardness and modulus.

Effect of Sr-Doping Concentration on Structure and Phase-Separation between Ferromagnetic and Paramagnetic Phases in Lanthanum Manganite Oxide

The perovskite La1-xSrxMnO3 (LSMO) nanocrystalline compounds with the doping concentration x in the range of 0.2~0.5 have been synthesized by combustion method using the pair of citric acid and ethylene glycol as a burning fuel. It was found that the sintering temperatures at which the compounds began forming the single-phase of LSMO increased from 900 °C up to 1200 °C corresponding to the increasing of Sr-doping content. X-ray pattern investigations presented the crystalline sizes of all samples sintered at 1200 °C evidently reduced from 77.7 nm to 18.9 nm as the doping concentration x increases. The effects of Sr-doping levels on Mn4+/Mn3+ ratio as well as on their electrical resistivity are also studied by X-ray photoelectron spectroscopy and four-point probes method, respectively. By using a resistive approximation model, the role of the Sr-doping with respect to the phase-separation between ferromagnetic and paramagnetic phases with respect to colossal magnetoresistance effect of these compounds is discussed.

RF Magnetron Sputtered SiOx Coatings on Papers

Silicon oxide (SiOx) were deposited on many substrates such as silicon, glass, and poly (ethylene terephthalate) (PET) and widely used in industry due to their excellent impressive barrier, electrical, optical and eco-friendly properties. However, few publications that focus on paper as substrate in sputtering have been found. SiOx films were deposited on papers by radio frequency (RF) magnetron sputtering. The influences of process parameters, RF power density and deposition time on deposition rate, surface roughness, mechanical properties and humidity barrier of the films were investigated. The result from atomic force microscopy (AFM) applied to investigate the surface morphologies showed that papers being deposited SiOx (SiOx/Paper) films with the average roughness were much more homogenous and smoother than raw papers. Horizontal, vertical elastic modulus and yield strength of SiOx/Pap clearly increased. The water vapor transmission rate of SiOx/Paper films, which prepared at RF density of 2.78 W/cm2, argon (Ar) flux of 40 sccm and deposition time of 36 min decreased 15times, and the oxygen transmission rate did 10 times. Additional investigations regarding printability focusing on the color reproduction properties were also carried out.

Forming In-Situ Micro-Cavities on 316L Stainless Steel Surface by Aluminum Electrodeposition and Anodization Technology

We have studied the anodization behavior of an Al film electrodeposited on the 316L stainless steel (316L SS) substrate and demonstrated an effective approach to fabricate the micro-cavities on the conducting substrate through anodic aluminum oxide (AAO) template. The morphologies and composition of the electroplating aluminum layers and the micro-cavities were evaluated by SEM and energy dispersive X-ray analysis (EDXA) respectively. The results indicated that different shapes of cavities with size ranging from 0.6 to 2 mm were come into being directly on 316L SS substrates. The size of cavities could be controlled by adjusting the anodizing voltage and time. And the morphologies of the initial aluminum films were found to be critical factors for successfully anodizing the Al film on 316L SS surface.

The Investigation of Composition and Corrosion Resistance of PIII Nitrided M50 Steel

The evolution of composition and corrosion resistance of PIII nitrided M50 steel with various process parameters was investigated. Besides nitrogen, the oxygen also was detected in modified layer, which came from the H2O and CO2 desorbed from chamber walls at high temperature. The results show that the content and diffusion distance of oxygen and nitrogen increase with temperature firstly; while the temperature exceeds 350 , the content and diffusion distance of oxygen and nitrogen reduce dramatically, because of the external diffusion of oxygen and nitrogen in form of NOx gas. The implantation current density is beneficial to increase the content and diffusion distance of oxygen and nitrogen. The corrosion tests show that the sample with higher oxygen and nitrogen content has better corrosion resistance.

Effect of Microstructure on Transport Properties of Nano-Polycrystalline La0.7Sr0.3MnO3-D Films

The effect of microstructure on transport properties of nano-polycrystalline La0.7Sr0.3MnO3-δ films, which were prepared by DC magnetron sputtering at various working pressures and followed by air annealing at 973K for 1h, has been investigated. The result indicates that the change of working pressure can change the microstructure, metal-insulator transition temperature (TIM) and peak resistance but does not change the transport mechanism for the films. The vacancy defects have an important effect on the transport properties of the films. Higher working pressure tends to decrease the density of vacancy defects. Low vacancy defects account for the high TIM and low resistance of the films. In the region of T > TIM, the charge carriers are moving in variable range hopping mode. The behavior of resistance decreasing with the increasing of temperature at low temperature (T<23K) can be explained on the basis of thermal excitation tunneling effect. The minimum resistance results from the combined effect of the tunneling effect and intrinsic metallic transport characteristic of the films.

Tribological Behaviors at High Load of MoSX/Au Films in Vacuum

MoSx/Au films about 1μm in thickness were deposited on 9Cr18 steel substrate discs by magnetron sputtering method. The chemical composition and chemical states of the as-deposited films were determined by X-ray photoelectron spectroscopy (XPS). The effect of high loads (15~50N) on tribological behaviors of the MoSx/Au films in vacuum was studied by pin-disc wear tests. The pins were made of 2Cr13 steel. The morphologies of as-deposited films and wear track were observed by scanning electron microscopy (SEM). The results show the friction coefficient and the wear life of the films decrease with the increase of load at a sliding velocity of 1.6 m•s-1. The wear life of the films at 15N can reach 2000m. The friction process of the films can be divided into four stages based on typical variation of friction coefficient with sliding time in vacuum, e.g. running-in stage, steady stage, severe damage stage and thorough wear stage. In steady stage, the films peel in small pieces and the abrasion mechanism appears delamination wear. When the film was damaged thoroughly, the wear test carried out between 2Cr13 pin/9Cr18 disc. The adhesive wear becomes the dominant abrasion mechanism.

Effect of Micro Pits Topography on the Platelets Adhesion on 316L Stainless Steel Surface

In this paper, the micro pits were fabricated on 316L stainless steel surface, and the influence of pits topography on the platelets adhesion was investigated. For initial steel, large platelets agglomeration and long pseudopodia are observed. It is found that the pits on stainless steel surface can effectively prevent pseudopodia spreading; as a result the aggregation of platelets is fully restrained. The resistance of platelets adhesion increase with the coverage rate of pits area () on total steel surface.