Zhang Gu-Ling

Pulsed Ion Sheath Dynamics in a Cylindrical Bore for Inner Surface Grid-Enhanced Plasma Source Ion Implantation

Based on our recently proposed grid-enhanced plasma source ion implantation (GEPSII) technique for inner surface modification of materials with cylindrical geometry, we present the corresponding theoretical studies of the temporal evolution of the plasma ion sheath between the grid electrode and the target in a cylindrical bore. Typical results such as the ion sheath evolution, time-dependent ion density and time-integrated ion energy distribution at the target are calculated by solving Poissons equation coupled with fluid equations for collisionless ions and Boltzmann assumption for electrons using finite difference methods. The calculated results can further verify the feasibility and superiority of this new technique.

A Novel Atmospheric Pressure Plasma Fluidized Bed and Its Application in Mutation of Plant Seeds

An atmospheric pressure plasma fluidized bed (APPFB) is designed to generate plasma using a dielectric barrier discharge (DBD) with one liquid electrode. In the APPFB system, the physical properties of DBD discharge and its application in plant-seed mutating are studied fundamentally. The results show that the generated plasma is a typical glow discharge free from filament and arc plasma, and the macro-temperature of the plasma fluidized bed is nearly at room temperature. There are no obvious changes in the pimientos when their seeds are treated by APPFB, but great changes are found for coxcombs.

Microstructure and Wear Resistance of Plasma Jet Clad Ti5Si3/NiTi Composite Coating

A wear resistant Ti5Si3/NiTi composite coating was fabricated on a substrate of a titanium alloy by plasma jet cladding using Ni-Ti-Si elemental powder blends. The microstructure, microhardness and wear resistance of the coating were evaluated. The result shows that the plasma jet clad composite coating has a rapidly solidified microstructure consisting of blocky primary Ti5Si3 and the inter-blocky Ti5Si3/NiTi eutectics and is metallurgically bonded to the titanium substrate. The composite coating has high hardness and excellent wear resistance under the dry-sliding-wear test condition.

Microstructure and Wear Behaviour of WC Film Prepared by Pulsed High Energy Density Plasma

A super hard and wear resistant WC film is in-situ prepared on a 0.45% C steel substrate by pulsed high energy density plasma technique at ambient temperature. The microstructure and composition of the film are analysed by x-ray diffraction, x-ray photoelectron spectroscopy, Auger electron spectroscopy and scanning electron microscopy. The hardness profile and tribological behaviour of the film are determined with nano-indenter and wear tester, respectively. The results show that the microstructure of the film was dense and uniform and mainly composed of WC and a small amount of W2C. A wide mixing interface exists between the film and the 0.45% C steel substrate. The thickness of the film is about 2 mu m. The hardness and Yangs modulus of the film are very high. The film has excellent wear resistance and low friction coefficient under dry sliding wear test conditions.

Inner Surface Modification of a Tube by Magnetic Glow-Arc Plasma Source Ion Implantation

A new method named the magnetic glow-arc plasma source ion implantation (MGA-PSII) is proposed for inner surface modification of tubes. In MGA-PSII, under the control of an axial magnetic field, which is generated by an electric coil around the tube sample, glow arc plasma moves spirally into the tube from its two ends. A negative voltage applied on the tube realized its inner surface implantation. Titanium nitride (TiN) films are prepared on the inner surface of a stainless steel tube in diameter 90 mm and length 600 mm. Hardness tests show that the hardness at the tube centre is up to 20 GPa. XRD, XPS and AES analyses demonstrate that good quality of TiN films can be achieved.

Optical Properties of Plate-Shaped ZnO Nanocrystals Grown by a Facile and Environmentally Friendly Molten Salt Method

Plate-shaped ZnO nanocrystals are prepared by a facile and environmentally friendly molten salt method, in which Zn5(CO3)2(OH)6 nanorods are first synthesized via a facile one-step, solid-state reaction route at room temperature and then decomposed in NaCl flux. Photoluminescence property demonstrates that the as-prepared plate-shaped ZnO nanocrystals exhibit a strong blue emission centered at about 483 nm. Raman scattering spectrum reveals that the as-prepared plate-shaped ZnO nanocrystals have the oxygen deficiency, which can be confirmed by the appearance of oxygen-deficiency-related vibrational mode at 583 cm−1 in the Raman spectrum. The oxygen deficiency existing in the plate-shaped ZnO nanocrystals results in the formation of the oxygen vacancy, which is most likely responsible for the strong blue emission of the plate-shaped ZnO nanocrystals. These new plate-shaped ZnO nanocrystals with strong blue emission are expected to show considerable potential applications in luminescence, lasing and optoelectronic devices.

Shadow Effect and Its Revisal in Grid-Enhanced Plasma Source with Ion Implantation Method

The implanting voltage, gas pressure and the grid electrode radius are the key parameters influencing the surface grid shadow effect that has been observed in our grid-enhanced plasma source ion implantation experiment. To reduce the shadow effect and obtain a corresponding better implantation uniformity of sample surfaces, we need to use lower implanting voltage, higher gas pressure and smaller grid radius. Furthermore, we apply an axial magnetic field to increase the plasma density inside the tube and to mix the plasma outside the grid, so that the shadow effect of sample surfaces can be weakened.

Influence of ion species ratio on grid-enhanced plasma source ion implantation

Grid-enhanced plasma source ion implantation (GEPSII) is a newly proposed technique to modify the inner-surface properties of a cylindrical bore. In this paper, a two-ion fluid model describing nitrogen molecular ions N2+ and atomic ions N+ is used to investigate the ion sheath dynamics between the grid electrode and the inner surface of a cylindrical bore during the GEPSII process, which is an extension of our previous calculations in which only N2+ was considered. Calculations are concentrated on the results of ion dose and impact energy on the target for different ion species ratios in the core plasma. The calculated results show that more atomic ions N+ in the core plasma can raise the ion impact energy and reduce the ion dose on the target.

Intertwisted fibrillar diamond-like carbon films prepared by electron cyclotron resonance microwave plasma enhanced chemical vapour deposition

In this paper, the structures, optical and mechanical properties of diamond-like carbon films are studied, which are prepared by a self-fabricated electron cyclotron resonance microwave plasma chemical vapour deposition method at room temperature in the ambient gases of mixed acetylene and nitrogen. The morphology and microstructure of the processed film are characterized by the atomic force microscope image, Raman spectra and middle Fourier transform infrared transmittance spectra, which reveal that there is an intertwisted fibrillar diamond-like structure in the film and the film is mainly composed of sp3 CH, sp3 C - C, sp2 C==C, C==N and C60. The film micro-hardness and bulk modulus are measured by a nano-indenter and the refractive constant and deposition rate are also calculated.

Deposition of TiN films by novel filter cathodic arc technique

A straight magnetic filtering arc source is used to deposit thin deposits of titanium nitride. The properties of the films depend strongly on the deposition process. TiN films can be deposited directly onto heated substrates in a nitrogen atmosphere or onto unbiased substrates by considering the Ti+ ion beam in about 300eV N-2(+) nitrogen ion bombardment. In the latter case, the film stoichiometry is varied from an N:Ti ratio of 0.6-1.1 by controlling the arrival rates of Ti and nitrogen ions. Meanwhile, simple models are used to describe the evolution of compressive stress as function of the arrival ratio and the composition of the ion-assisted TiN films.