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The structure and the phase composition of the diffusion saturation zone of 40Crand 12Cr2Ni4N-type steels subjected to nitriding in the plasma of a low-pressure gas discharge have been studied by the methods of optical, scanning, and diffraction electron microscopy. An essential potentialities have been revealed to nitride steel at low (∼200 °С) temperatures. The structural-phase state of the nitrided layer has been shown to depend strongly on the morphology and phase composition of the initial material.

Inner surface coating for tubular samples was realized by the grid enhanced plasma source ion implantation (GEPSII) method. In the GEPSII system, two electrodes, a central rod electrode and a coaxial grid electrode were coaxially assembled inside the tube. Plasma was generated between the electrodes by a radio-frequency (RF) oscillating power source. Plasma then diffused through the grid and realized inner surface ion implantation by a negative high voltage applied to the tube. The plasma was then divided, by the grid, into two regions, namely the source plasma region and the diffused plasma region. The plasma's self-bias between two RF power source electrodes was measured. At the same time, the electron temperature and plasma density in the GEPSII system were measured by a scattering spectrometer. Results showed that the plasma properties of the two regions were entirely different; the plasma self-bias, which might greatly affect the sputtering rate of the central titanium electrode, depended on the electrode structure, gas pressure and RF power.

A cold dielectric barrier discharge (DBD) plasma plume with one highly conductive liquid electrode has been developed to treat thermally sensitive materials, and its preliminary discharging characteristics have been studied. The averaged electron temperature and density is estimated to be 0.6eV and 1011/cm3, respectively. The length of plasma plume can reach 5 cm with helium gas (He), and the conductivity of the outer electrode affects the plume length obviously. This plasma plume could be touched by bare hand without causing any burning or painful sensation, which may provide potential application for safe aseptic skin care. Moreover, the oxidative particles (e.g., OH, O*, O3) in the downstream oxygen (O2) gas of the plume have been applied to treat the landfill leachate. The results show that the activated O2 gas can degrade the landfill leachate effectively, and the chemical oxygen demand (COD), conductivity, biochemical oxygen demand (BOD), and suspended solid (SS) can be decreased by 52%, 57%, 76% and 92%, respectively.

Ti–Si–N thin films with different silicon contents are deposited by a cathodic arc technique in an Ar+N2 +SiH4 mixture atmosphere. With the increase of silane Bow rate, the content of silicon in the Ti–Si–N films varies from 2.0 at. % to 12.2 at. %. Meanwhile, the cross-sectional morphology of these films changes from an apparent columnar microstructure to a dense fine-grained structure. The x-ray diffractometer (XRD) and x-ray photoelectron spectroscopy (XPS) results show that the Ti–Si–N film consists of TiN crystallites and SiNx amorphous phase. The corrosion resistance is improved with the increase of silane Bow rate. Growth defects in the films produced play a key role in the corrosion process, especially for the local corrosion. The porosity of the films decreases from 0.13% to 0.00032% by introducing silane at the Bow rate of 14sccm.

Under optimized operating parameters, a hard and wear resistant ( Ti,Al)N film is prepared on a normalized T8 carbon tool steel substrate by using pulsed high energy density plasma technique. Microstructure and composition of the film are analysed by x-ray diffraction, x-ray photoelectron spectroscopy, Auger electron spectroscopy and scanning electron microscopy. Hardness profile and tribological properties of the film are tested with nano-indenter and ring-on-ring wear tester, respectively. The tested results show that the microstructure of the film is dense and uniform and is mainly composed of ( Ti,Al)N and AlN hard phases. A wide transition interface exists between the film and the normalized T8 carbon tool steel substrate. Thickness of the film is about 1000 nm and mean hardness value of the film is about 26GPa. Under dry sliding wear test conditions, relative wear resistance of the ( Ti,Al)N film is approximately 9 times higher than that of the hardened T8 carbon tool steel reference sample. Meanwhile, the ( Ti,Al)N film has low and stable friction coefficient compared with the hardened T8 carbon tool steel reference sample.

Zirconium oxide (ZrO2) thin films are deposited at room temperature by cathodic arc at substrate biases of 0 V, -60 V and -120 V, respectively. The crystal structure, composition, morphology, and deposition rate of the as-deposited thin films are systematically investigated by x-ray diffraction, x-ray photoelectron spectroscopy (XPS) as well as scanning electron microscopy. The results show that the crystal structure, morphology and deposition rate of the films all are dependant on substrate bias. With the increase of bias voltage from 0 V to -120 V, the zirconium oxide thin film grown on silicon wafer first exhibits monoclinic lattice and tetragonal lattice, further evolves monoclinic phase with the preferred orientation along the (-111) and (-222) directions at -60 V and finally along nearly one observed preferred (002) direction under -120 V. In addition, the variations of morphology with bias voltage are correlated to changes of the film structure. The results of XPS demonstrate that Zr elements are almost oxidized completely in the films achieved under -120 V bias.

Tantalum nitride (TaN) thin films are achieved on Si(111) and SS317L substrates by cathodic vacuum arc technique, which is rarely reported in the literature. The crystal structure, composition and surface morphology of the films are characterized by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), auger electron spectroscopy, and atomic force microscopy, respectively. The influence of substrate negative bias on crystal structure, composition, surface morphology of the TaN films is systematically studied. At the substrate bias of 0 V and -50 V, the amorphous TaN film is obtained. As the bias increases to -100 V, cubic TaN phase can be found. Stoichiometric TaN with hexagonal lattice preferred (300) orientation is prepared at a bias of -200 V. Combine the XRD and XPS results, the binding energy value of 23.6 eV of Ta 4f7/2 is contributed to hexagonal TaN. Compared to other techniques, TaN thin films fabricated by cathodic vacuum arc at various substrate biases show different microstructures.

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.

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 Yang's modulus of the film are very high. The film has excellent wear resistance and low friction coefficient under dry sliding wear test conditions.

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.

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.

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.

Nano-crystalline diamond films have been prepared on glass substrate in argon and methane environments by microwave plasma chemical vapor deposition. The suitable processing parameters are methane concentration 3% in argon; total deposition pressure 13.3 kPa; substrate temperature 500°C heated by plasma. In this film, the grain size is

Pulsed high energy density plasma has been used to deposit aluminum nitride films on the surface of the 1Cr18Ni9Ti stainless steel (∼0.1% C, ∼18% Cr, ∼9% Ni, ∼0.8% Ti). The formed films are composed of nanocrystalline-structured aluminum nitride phase, whose crystal sizes are about 10 nm. Transition areas are formed across the film to the substrate and strengthen the adhesion between them. The nanocrystalline-structured aluminum nitride films contribute to the improvement of the corrosion resistance of the modified stainless steel, whose corrosion rate has been reduced by about ten times compared with that of the unmodified stainless steel.

The hardness of the surface of 0.45%C steel is improved by about six times after the surface is modified by pulsed high-energy density plasma (PHEDP) composed of particles of titanium and nitrogen. A layer of thin film about 1 mu m thick is formed on the treated surface and the microstructure of the film is examined by transmission electron microscopy, which shows that the film comprises TIN, Ti2N(alpha), Ti2N(beta) and FeTi phases. In PHEDP surface modification, the process of ion implant combined with melting and rapid quenching contributes to the formation of the polyphase film on the surface of 0.45%C steel, especially to the formation of nanometer particles and the metastable phase of Ti2N(alpha) in the film. The structure polyphase film is the main reason for the hardness improvement of the surface of 0.45%C steel. The characteristics of Ti2N(alpha) and Ti2N(beta) phases are discussed in paper. (C) 1998 Elsevier Science B.V. All rights reserved.

A novel atmospheric pressure plasma apparatus (APPA) is designed with a liquid electrode, and its discharging characteristics are studied. Relatively uniform and intense discharge can be realized in the APPA system. An experimental study on removal of NO molecules is carried out by using the APPA, and more than 95.5% of NO is decomposed when the NO initial concentration is lower than 400 ppm. Removal of NO efficiency increases rapidly with the increasing discharge power. Compared with the absence of O2, more NO2 is generated with the increase of O2 concentration. However, most of the NO molecules are decomposed to N2 and O2 directly, when O2 concentration changes from 0 to 1.1 vol%.

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.

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.

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.

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 Poisson's 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.

Plasma electrolytic oxidation (PEO) coatings are prepared on aluminium with graphite powders added into the electrolyte. The scanning electron microscopy (SEM) coupled with an energy dispersive x-ray analysis system (EDX) is used to characterize the surface and the cross-section morphologies of the coatings. The electrochemical impedance spectroscopy (EIS) is used not only to evaluate the corrosion resistance but also to analyse the structure of the coating. Results show that graphite powders are embedded in the PEO coating. The corrosion resistances of both the inner barrier and the outer porous layer are greatly improved, and the EIS could give some valuable detailed information about the coating structure.

Ceramic coatings are synthesized on AZ31 magnesium alloy in alkaline silicate solution by the method of plasma electrolytic oxidation. The effect of two different duty cycles (10% and 50%) on the structure and corrosive properties of the coatings is investigated. It is found that the coatings are mainly composed of MgO, Mg2SiO4 and MgF2 through XRD analysis. SEM images indicate that coatings formed at 50% duty cycle have a relatively coarse surface with larger pore size and fewer pores, and have a slower growth rate than those formed at 10% duty cycle with the same treatment time. However, the results of potentiodynamic polarization tests demonstrate that coatings formed at 50% duty cycle exhibit better corrosion resistance as a result of more compact microstructure.

Under optimized operating parameters, a wear and corrosion resistant Cr3Si/γ-Fe composite coating is fabricated on a normalized 0.45% carbon steel substrate by using the plasma transferred arc (PTA) cladding technique with Fe-Cr-Si elemental powder blend as the precursor material. Microstructure, microhardness, dry-sliding wear resistance and electrochemical corrosion characteristic of the coating are evaluated. Test results show that the composite coating is mainly composed of primary Cr3Si dendrites and the interdendritic supersaturated iron-base solid solution γ-Fe. Between the Cr3Si/γ-Fe composite coating and the normalized 0.45% carbon steel substrate, there is a narrow metallurgical bonding zone. The Cr3Si/γ-Fe composite coating exhibits high microhardness, excellent wear and corrosion resistance under test conditions.

Plasma electrolytic oxidation (PEO), also called micro-arc oxidation or anode spark deposition, is a novel technique to produce hard ceramic coatings on metals, such as aluminum, titanium, magnesium and their alloys (called by a joint name of valve metals). Up to now, almost all the researchers focused attention on the PEO process for samples of regular shapes such as cubes, discs or rods, and no one paid attention to the irregular samples such as tubes. In this work, the PEO behavior of aluminum tubes was investigated. The potential difference, which had a liner relation with the coating thickness inside the tube, was measured. A central axial accessorial electrode was used to eliminate the effect of potential decay inside tubes, which was effective for obtaining axially uniform coating on the inner surface of the tube.

In this paper, composite coating (about 400 μm thick) was prepared by SHS plasma spraying technology using micro-dimensional Fe2O3-Al composite feedstock, which was fabricated by mechanical glomeration. The composition and microstructure of the coating were analyzed by X-Ray diffraction, scanning electron microscopy and transmission electron microscopy. Meanwhile, the microhardness, fracture toughness and wear resistance were also measured. It shows that the skeleton of the coating is mainly composed of nanostructured FeAl2O4 and Al2O3, and the dispersed phase is nanosized Fe. The composite coating possesses satisfactory microhardness of about Hv870. Compared with conventional alumina coating, the fracture toughness and wear resistance of composite coating are increased by one and 1.5 times, respectively.

Metallurgically bonded Al2O3 ceramic coating was prepared on steel surface with the combined method of arc spraying and electrolytic plasma processing. The composition and microstructure of the ceramic coating were analyzed by x-ray dif fraction, scanning electron microscony and EDS. The corrosion resistance and wea r resistance of the ceramic coating were measured. The results show that the cer amic coating is compact and mainly composed of α-Al2O3, γ-Al2O3, θ-Al2O3 and a little of a morphous phase. The duplex coating shows favorable corrosion resistance and wear resistance properties.

Hydrogenated carbon thin films were fabricated on the surface of polyethylene terepthalate(PET) by radio frequency plasma enhanced chemical vapor deposition (r. f.PECVD).The film structure properties were studied by means of atomic force mic roscope(AFM), x_ray photo_electron (XPS), laser Raman spectroscopy, Fourier_tra nsform infrared spectra(FTIR),etc. The barrier property of the film was conducte d on the water vapor permeation instrument. The results show that nano_hydrogen ated carbon films have been deposited on PET surface and they are mainly compose d of sp2 and sp3 hybridized hydrogenated carbon compounds. Plasma pa rameters influence the films' growth rate and structure characteristics. The fil m reduces the water vapor permeation ratio of the PET by 7 times at a film thick ness of only 900nm.

The basic idea of the reactive plasma spray (RPS) was presented. The TiN coating was successfully deposited on Q235 steel substrate by using the gas_tunnel plasma spray gun via RPS. Micro_hardness of the TiN coating under different loads has been measured, revealing an obvious indentation size effect, and a weak work_hardening effect. XRD, TEM and HRTEM were employed to analyze the prepared coating samples. Results obtained show that nanocrystalline TiN coating has been achieved via RPS, which is composed of TiN crystals of about 57—70nm in diameter and the amorphous TiN.

Smoothing, dense and uniform nano-crystalline diamondlike carbon films are pr epared by using electron cyclotron resonance (ECR) microwave acetone plasma chemical vapor deposition (CVD) method. Atomic force microscope shows that, the surface roughness of this film is less than 10nm, the average grain size is abou t 100nm, and there are no distinct Raman shift peaks. Middle infrared spectra sh ow the existence of sp1, sp2, and sp3 mixed C—C bond, sp3 mixed CH3,CO, COOH and other oxygenic hydrocarbons in the film. The micr ohardness is about 4GPa, bulk elastic modulus is about 11 GPa tested by nano-indentation. Without absorption in closed infrared area, the refractive index is 1.576 and the calculated deposition rate is 460 nm/h for the film.

Smooth, densie and uniform nano-crystalline diamond-like-carbon (DLC) film is deposited on an optical glass substrate by pulsed high energy density plasma(PHEDP) gun charging in nitrogen atmosphore. Scanning electron microscope, Raman spectra and EMSA show that, the grain size of the DLC film is less than 20nm; there are a number of nitrogen atoms and nano-crystalline diamond in the DLC film. The sheet resistance of this film is larger than 109Ω/sq. When the change voltage is lower and charge distance is longer, the deposited film is loose. Theoretic analysis show that, at higher charge voltage, the deposited grain is larger, with longer charge distance, the collision force between deposition grain and substrate is weaker. The theoretic results are in agreement with the experimental conclusion.

An electron cyclotron resonance heating experiment has been performed by using a gyrotron system for the fundamental and second harmonic resonance heating on CT-6B tokamak. Obvious changes are observed in soft x-ray radiations, electron cyclotron emission, displacement of plasma column, impurity line radiations, and bremsstrahlung radiation when heating pulse is injected, indicating an increase of the plasma electron temperature.

As a novel inner surface processing method, grid enhanced plasma source ion implantation (GEPSII) method can realize uniform inner surface ion implantation of a metal tube and metal binary compound can be produced. In the experiment, three 0.45% carbon steel (45-steel) work pieces were axially put on the inner surface of the tube, and golden titanium nitride (TiN) films were produced on the work pieces by GPSII. Structure analysis shows that the TiN films have the preferred crystal faces (111) and (200), and the depth of the films is about 20 nm with partial embedding in the substrate. Analysis on the electrochemistry corrosion, hardness and friction of the work pieces indicates that the surface property of the 45-steel has been greatly improved by the protective TiN film, and very good axial uniformity has been obtained.