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The seed of Carica papaya consists of a hard shell-like testa with inhibitors in vivo causing slow, erratic and asynchronous germination. In this work, plasma-activated water prepared by microsecond-pulsed plasma jets (μPAW) was applied to treat papaya seeds. The μPAW after plasma activation of 30 min was about 40 °C. The reactive species such as NO2, NO3, and H2O2 in the μPAW activated from deionized water were measured and correlated to the seed germination rate and the seedling growth performance. The μPAW-treated papaya seed achieved a higher germination rate of 90%, which is 26% higher than the control group using deionized water. Comparing the results with a hot water (40 °C) reference group showed that the reactive species in μPAW played primary roles in germination improvement, with little effect caused by the heat shock. The μPAW also sterilized the treated seeds, reducing the germination stress. The morphological change in the seeds was observed by SEM, showing an effect of physical etching after treatment promoting seed imbibition. The biochemical mechanism of the seed germination was deduced with reference to the evolution of surface chemistry, functional groups, and ABA content. The accelerated seed metabolism observed was corresponded to the chemical modification pathway. Besides, early seedlings developed from treated seeds were observed to be healthy, grow more leaves, and have better root structures. The content of MDA in the treated papaya seedlings decreased along with increased SOD and higher ion concentration. The μPAW that can be prepared at atmospheric pressure for bulk production offers a low-risk and cost-effective seed priming technology that may significantly increase the production of agricultural crops.

In recent years, significant increases in waste processing and material engineering have been seen by using advanced oxidation processes. The treatment results and energy yields of these processes are largely determined by the generation and retention of reactive oxygen species (ROS). However, increasing the amount of ROS remains a key challenge because of the unavailability of performance- and energy-efficient techniques. In this study, plasma electrolysis, ultrasound, and plasma electrolysis combined with ultrasound were used to treat dimethyl sulfoxide (DMSO) solutions, and the results showed that the two methods can synergistically convert filament discharge into spark discharge, and the conversion of the discharge mode can significantly increase the concentration of OH radicals and effectively improve the efficiency of DMSO degradation. We verified the rationality of the results by analyzing the mass transfer path of ROS based on the reaction coefficients and found that the ⋅OH radicals in aqueous solution were mainly derived from the decomposition of hydrogen peroxide. These findings indicated that the synergistic action of plasma electrolysis and ultrasound can enhance the production of chemically reactive species, and provide new insights and guiding principles for the future translation of this combined strategy into real-life applications. Our results demonstrated that the synergistic strategy of ultrasound and plasma electrolysis is feasible in the switching mode and increasing the ROS, and may open new routes for materials engineering and pollutant degradation.

In order to modify the tribological properties of titanium alloy, Ti53–Si32–Ni15, Ti43–Si26–Ni31 and Ti30–Si18–Ni52 (at.%) elemental powders blends were designed to fabricate Ti 5 Si 3 reinforced intermetallic composite coatings on Ti–6Al–4V titanium alloy substrate by plasma transferred arc (PTA) cladding process. Microstructure of the PTA cladding coatings was characterized by SEM, XRD and EDS. The relationship between Ti/Si/Ni atomic ratios of the Ti–Si–Ni elemental powders blends and microstructure of the PTA cladding coatings was investigated in detail. The effect of volume fraction of the Ti 5 Si 3 primary phases on microhardness and room temperature dry sliding wear behavior of the PTA cladding coatings was discussed. Results show that the PTA clad intermetallic composite coatings have a non-equilibrium solidified super-fine microstructure consisting of Ti 5 Si 3 primary phases, NiTi 2 /α-Ti/Ti 5 Si 3 ternary eutectics and a small amount of NiTi 2 /Ti 5 Si 3 binary eutectics. The PTA clad composite coatings are metallurgically bonded to the Ti–6Al–4V titanium alloy substrate. The Ti/Si/Ni atomic ratios of the Ti–Si–Ni elemental powders blends have a noticeable effect on grain size, volume fraction and solidification morphologies of the Ti 5 Si 3 primary phases. With increasing the Ni content of the elemental powder blends, grain size and volume fraction of the Ti 5 Si 3 primary phases decrease significantly. Microhardness values of the PTA clad intermetallic composite coatings are remarkable influenced by the volume fraction of the Ti 5 Si 3 primary phases. The higher the volume fraction of the Ti 5 Si 3 primary phases, the higher the microhardness value of the PTA cladding coatings. Room temperature dry sliding wear properties of the PTA cladding coatings are significantly affected by both the solidification morphologies and volume fraction of the Ti 5 Si 3 primary phases.

The objective of this paper is to demonstrate whether air plasma can change the seed germination characteristics, seedling emergence, as well as biochemical reactivity, in Andrographis paniculata (A. paniculata) seedlings by modifying the seed coat and finding a beneficial treatment dose. Eight treatment doses and one control were used to conduct electrical conductivity determination, a germination test, a seedling emergence test and a biochemical assay. The results showed that after being treated with air plasma excited at 5950 V for 10 s, the permeability of the seeds was improved significantly, resulting in the acceleration of seed germination and seedling emergence. In the meantime, the catalase activity and catalase isoenzyme expression were also improved, while the malondialdehyde content in the seedlings was decreased (which means greater counteraction with environmental stress). After being treated with 4250 V for 10 s and 5950 V for 20 s, the seed germination was enhanced, but without an obvious change in seedling emergence. However, after treatment with 3400 V for 20 s and 5100 V for 10 s, the permeability of the seeds was decreased, resulting in a delay in seedling emergence. These results indicate that air plasma can change the physiological and biochemical characteristics of Andrographis paniculata seeds by modifying the seed coat, combined with the effects of the active plasma species, and that different treating doses have different effects.

In high-power RF ion source, three different regions of the Hβand Hγintensities in the Balmer series of spectral lines for atomic hydrogen plasma were investigated. Three different regions of the Hβand Hγintensities were detected by the increase of input power (0-6 kW) at ICP. In hydrogen plasma spectrum, the Hβand Hγintensities showed three processes: slowly increase, quickly increase and stable saturation. The Stark effect in strong electrical field plays a crucial role in dominating the Balmer Hβand Hγemissions from high-density RF plasma.

We report on the characteristics of argon inductively coupled plasma (ICP) for the ITER neutral beam injection system. In argon ICP, it was found by using Langmuir probe that the radial distribution of electronic density (Ne) was uniform while the radial distributions of both electron temperature (kTe ) and electric potential (VP) were non-uniform. The former depend on two factors: the variation of Ne was small, and the value of Ne was very large. The latter is owing to the generation and disappearance of the negative ions in the ICP, where the additional dynamic processes produce the instability. In addition, both kTe and VP profiles were very similar at the cylinder height H=14 cm, which proves the plasma sheath theory to some extent. Finally, both kTe and VP began flatter with the reduction of the cylinder height, which is owing to the decrease of the negative ions in the ICP.

The conventional study of NOx removal is mainly concentrated on the various chemical reactions, but takes no account of the important effect of temperature increase caused by the discharge. In this paper, we present a method whereby the reactive temperature in reaction region can be easily measured without affecting the discharge. By measuring the reactive temperature, it is revealed that the temperature in reaction region is closely related and linearly enhanced with the discharge power, and that the catalysis is not the main reason for the reactive temperature increase. By the investigation on the temperatures effect on the NOx removal, it is found that the NOx removal rate increases with the rise of temperature in reaction region. Therefore, the NOx removal is tightly related with the temperature in reaction region that can be controlled by the discharge intensity under the various ambient temperatures.

Ti-Al-N hard films have been prepared by cathodic arc deposition by using an unipolar pulsed bias. In the present study, Ti-Al-N films were deposited on stainless steel and silicon wafers. The deposition rate, micrograph, preferred orientation and composition were systematically investigated by usingx-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and a scanning electron microscope (SEM). It is shown that substate bias duty cycle and frequency have a great effect on film structure. A simple explanation for the results is also presented.

This study aimed to that waste circuit boards in batches were incinerated by thermal plasma. Firstly, the working principle of plasma incinerator and the exhaust gas treatment main process were introduced, then, the experimental results was analyzed and discussed. Due to the thermal plasma processing waste incineration furnace has high temperature (1200 0C above), all the organic ingredients in waste circuit boards, including dioxin, can be decomposed completely in a few milliseconds, no showing the secondary pollution and no producing furans and other carcinogens. In addition, after main exhaust gas (CO, NO) concentration change with time was carefully tracked, it was found that a large amount of CO gas was produced and NO gas concentration was within national safety limits during experiment. Although 44.4 kg sample was incinerated, more than 1 kg of small pieces of metal like Copper was obtained from the cooling molten slag. Finally, it was obvious that the volume and weight of molten slag was far less than the ones of sample. The experimental result has important practical significance for protecting the environment, obtaining more CO gas resource and retrieving a variety of rare metals (such as Gold, Copper, Silver, Platinum, etc.).

Atmospheric-pressure plasma and TiO2 photocatalysis have been widely investigated separately for the management and reduction of microorganisms in aqueous solutions. In this paper, the two methods were combined in order to achieve a more profound understanding of their interactions in disinfection of water contaminated by Escherichia coli. Under water discharges carried out by microplasma jet arrays can result in a rapid inactivation of E. coli cells. The inactivation efficiency is largely dependent on the feed gases used, the plasma treatment time, and the discharge power. Compared to atmospheric-pressure N2, He and air microplasma arrays, O2 microplasma had the highest activity against E. coli cells in aqueous solution, and showed >99.9% bacterial inactivation efficiency within 4 min. Addition of TiO2 photocatalytic film to the plasma discharge reactor significantly enhanced the inactivation efficiency of the O2 microplasma system, decreasing the time required to achieve 99.9% killing of E. coli cells to 1 min. This may be attributed to the enhancement of ROS generation due to high catalytic activity and stability of the TiO2 photocatalyst in the combined plasma-TiO2 systems. Present work demonstrated the synergistic effect of the two agents, which can be correlated in order to maximize treatment efficiency.

In this paper, some discarded circuit boards in the plasma incinerator were incinerated by the converging - extended anode channel plasma torch, whose work principle and composition was described, and two experimental results were described, finally, the percentage of four major exhaust gas (CO, NO, SO2, O2) was reported, showing a good prospect on treating electronic waste with using the plasma torch.

State Key Program of National Natural Science of China [10735090]; National Natural Science Foundation of China [11005151]

The atmospheric pressure glow discharge burning in argon with small admixture of oxygen and hexamethyldisiloxane is used for the deposition of organosilicon and SiO x -like films on the stainless steel surface. The organosilicon film has high growth rate (85 nm/min) and extremely low surface roughness (0.8 nm), while the SiO x -like film shows relatively low growth rate (40 nm/min) and higher surface roughness (9 nm). The surface wettability, microhardness and the corrosion resistance of the deposited siloxane films are detected. The organosilicon film is hydrophobic (contact angle: 98°) and soft (microhardness: 0.68 GPa), while the SiO x -like film is hydrophilic (contact angle: 45°) and hard (microhardness: 7.85 GPa). The potentiodynamic polarization tests show that by depositing siloxane films on the surface, the corrosion resistance of the stainless steel in the Hanks solution can be largely improved. In particular, the SiO x -like film exhibits better corrosion resistance than the organosilicon film.

An dielectric barrier discharge (DBD) system in atmospheric pressure utilized for the treatment of industrial landfill leachate is reported. The discharge parameters, such as the operating frequency, gas flow rate, and treating duration, were found to affect significantly the removal of ammonia nitrogen (AN) in industrial landfill leachate. An increase in treating duration leads to an obvious increase in the removal efficiency of AN (up to 83%) and the leachate color changed from deep grey-black to transparent. Thus the dielectric barrier discharges in atmospheric pressure could degrade the landfill leachate effectively. Typical waveforms of both applied voltage and discharge current were also presented for analyzing the discharge processes under different discharge parameters. Optical emission spectra measurements indicate that oxidation species generated in oxygen DBD plasma play a crucial role in removing AN, oxidizing organic and inorganic substances and decolorizing the landfill leachate.

Plasma electrolytic oxidation (PEO) coatings were prepared on magnesium alloy AZ91D in a phosphate based electrolyte with different additives such as sodium fluoride (NaF) and sodium aluminate (NaAlO(2)). The effects of F(-) and AlO(2)(-) additives on the morphology, phase structure and corrosion resistance of PEO coatings were examined by scanning electron microscopy (SEM/EDX), X-ray diffraction (XRD) and potentiodynamic polarization. The results show that PEO coatings produced in F- additive solution grow faster than that in AlO(2)(-) additive one. However, the growth rate decreases with treatment time in F(-) additive solution while it increases in AlO(2)(-) additive one. It is also found that the corrosion resistance is greatly improved after PEO treatment, and coatings produced in F(-) additive solution show lower corrosion current density than that in AlO(2)(-) additive solution. (C) 2010 Elsevier B.V. All rights reserved.

Conference Name:7th Asian-European International Conference on Plasma Surface Engineering. Conference Address: Busan, SOUTH KOREA. Time:SEP 20-25, 2009.

Tantalum titanium nitride (Ta-Ti-N) films were deposited on silicon wafer substrates by pulsed high energy density plasma (PHEDP), under different intake gas pressures, ranging from 0.1 to 0.4 MPa. The films were investigated by X-ray photoelectron spectroscopy. Results were analyzed in detail, which reveals that the contents of the metallic elements (Ta and Ti) tend to decrease with pressure, while that of nitrogen increases as expected. With increasing pressure, the films can be denoted as TaTi(3.9)N(2.8), TaTi(4.7)N(6.0), TaTi(2.2)N(8.4) and TaTi(3.1)N1(3.5), respectively. The bonding state of tantalum, titanium, as well as nitrogen was fitted and discussed. Our results demonstrate that almost all the titanium bonded with nitrogen. The Ta-N and Ti-N bonds have equal shares under low gas intake pressure, while the Ti-N bonds prevail under high pressure. The preferential sputtering between the coaxial electrodes should be responsible for this phenomenon. Under low nitrogen pressure, the preferential sputtering is quite significant; while it could be neglected under high pressure. (C) 2010 Elsevier B.V. All rights reserved.

Wear resistant Fe2TiSi reinforced composite coating with a microstructure consisting of fine Fe2TiSi primary dendrites uniformly distributed in the super fine gamma-Fe/Ti5Si3 eutectic matrix was in situ fabricated on a substrate of 0.20%C plain low carbon steel substrate by the plasma transferred arc (PTA) cladding process using Fe-Ti-Si-Cr powders blend as the precursor material. Microstructure of the coating was characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray energy dispersive spectrometer (EDS). Microhardness along the depth direction of the PTA clad Fe2TiSi/gamma-Fe/Ti5Si3 multi-phase composite coating was measured. Room temperature dry sliding wear resistance of the coating was tested. Results showed that the PTA clad Fe2TiSi/gamma-Fe/Ti5Si3 composite coating had high and almost uniform hardness distribution along the depth direction of the coating. Under dry sliding wear conditions at an ambient temperature, the PTA clad Fe2TiSi/gamma-Fe/Ti5Si3 composite coating exhibited excellent abrasive and adhesive wear resistance. (C) 2010 Elsevier B.V. All rights reserved.

National Natural Science Foundation of China [10675165]; International Cooperation and Exchanges NSFC-KOSEF [10811140326]

Titanium carbonitride (TiCN) films were deposited on cemented carbide cutting tool substrates, by pulsed high energy density plasma (PHEDP). A nano-indentation system was employed to measure the nano-harness and Young's modulus of the films prepared under various conditions. The wear behaviors of the films were also investigated. The results show that the samples are significantly hardened, compared with the substrate. And more pulse of discharges creates harder films. On the other hand, the wear-resistance of the as-deposited samples has increased by times. These results strongly suggest that PHEDP is a promising way for fabricating films with good mechanical properties.

The interactions between plasma-generated excited particles and water play an integral role in sustainable degradation of pharmaceutical compounds, improving aerobic respiration of activated sludge, and efficient removal of microorganisms from water, and are fundamental to the intentional transfer of reactivity from plasmas to biological solutions for such medical applications as cancer treatment and wound healing. The physical and chemical mechanisms that govern this transfer of reactivity are complex, and include concomitant generation and consumption of species in the gas and liquid phases, and at the interface. As such, it is challenging to predict the quantities of biologically-active radicals and molecules in liquid phase from gas phase measurements alone. Rapid and accurate quantification of reactive species, such as OH radicals and H2O2 molecules within the liquid phase and their link to specific biological effects is therefore critical for medical applications of plasma-activated solutions. Using a simple, low-cost method for trapping and stabilization of OH radicals by means of salicylic acid, this work seeks to provide further insights into the physics and chemistry of generation of OH radicals within the liquid phase, and integrate these findings with decontamination outcomes for four commonly used processing gases.

In the present work, graphite grains of different sizes were added into the electrolyte to prepare ceramic coatings on aluminum by plasma electrolytic oxidation (PEO). Scanning electron microscopy (SEM) coupled with an energy dispersive X-ray analysis system (EDX), Raman spectroscopy and X-ray diffractometer (XRD) were used to characterize the coatings. A three-electrode system was used to evaluate the corrosion performances of the coatings in a 3.5 wt.% NaCl solution. It was found that the morphology and corrosion performance of the coatings were significantly influenced by the size of the graphite grains. Compared with bigger graphite grains, finer ones were involved in the oxidation process and embedded within the ceramic coatings, which made the coatings less porous and more compact. Thus, the corrosion resistance of the coatings with embedded graphite grains was greatly improved.

Ceramic coatings oxidized for different time periods were prepared to characterize the plasma electrolytic oxidation (PEO) process of AZ91D magnesium alloy. The coatings were analyzed using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscope and potentiodynamic polarization measurement. The results show that the PEO coatings perform different growth behaviors at different PEO stages, and different morphologies are exhibited on α- and β-phase of Mg substrate. The corrosion resistance measurement predicates that within the first 30 min oxidation, coating oxidized for 20 min is the best corrosion resistant.

Plasma electrolytic oxidation (PEO) process was carried out on magnesium alloy with a pulsed direct current (dc) power source at high and low frequencies. The morphology and phase composition of the coatings were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The corrosion performances of the different coatings were evaluated via a three-electrode system in a 3.5-wt.% NaCl solution. It was detected that the PEO coatings were mainly composed of MgF2 and Mg3(PO3)2 phase. Coatings produced at relative high frequency had smaller pore size and looked much denser than those at low frequency. As a result, they performed better corrosion resistance in the present corrosive solution. These experimental results could be ascribed to the formation mechanism of the PEO coatings: lower frequency provided longer time for one single pulse, which induced continuous discharge.

The biofilm of allylamine polymer was deposited by using the liquid sputtering apparatus, which was achieved by the atmospheric: cold plasma plume. The surface roughness of the polymer was improved by increasing the power and He gas velocity. The average allylamine polymer deposition rate was about 30 nm/min. Rich morphologies (e.g., nanoline, microcloudlet) appearing on the biofilm revealed the important information of the growing processes that occurred in the plasma deposition. The density of the amine groups was obviously related to the plasma parameters, and the highest density of amino-labeled DNA probe was about 0.9 pM/cm(2) confirmed by the dyed oligonucleotide. (C) 2008 Elsevier B.V. All rights reserved.

Using hexamethyldisiloxane (HMDSO) monomer, the magnetic nanoparticles (NPs) of nickel oxide (NiO) were modified by using an atmospheric room-temperature plasma fluidized bed (ARPFB). The plasma gas temperature of the ARPFB was not higher than 325 K, which was favorable for organic polymerization. The plasma optical emission spectrum (OES) of the gas mixture consisting of argon (Ar) and HMDSO was recorded by a UV–visible monochromator. The as-treated NPs were characterized by means of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results show that the assembling NPs were isolated greatly after modified by the organosilicon polymer. Moreover, this treatment process changed the wettability of the NPs from super-hydrophilicity to super-hydrophobicity, and the contact angle (CA) of water on the modified NPs surface exceeded 150°. Therefore, the ARPFB is a prospective technology for the NPs surface modification according to the different requirements.

(Ti,Ta)N films were prepared by pulsed high energy density plasma (PHEDP) from a coaxial gun in N2 gas. The coaxial gun is composed of a tantalum inner electrode and a titanium outer one. Material characteristics of the (Ti,Ta)N film were investigated by x-ray photoelectron spectroscopy and x-ray diffraction. The microstructure of the film was observed by a scanning electron microscope. The elemental composition and the interface of the film/substrate were analysed using Auger electron spectrometry. Our results suggest that the binary metal nitride film, (Ti,Ta)N, can be prepared by PHEDP. It also shows that dense nanocrystalline (Ti,Ta)N film can be achieved.

Ta–N thin films were deposited on AISI 317L stainless steel (SS) substrates by cathodic arc deposition (CAD) at substrate biases of −50 and −200 V. The as-deposited films were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray analysis (EDX). The results show that stoichiometric TaN with hexagonal lattice (3 0 0) preferred orientation was achieved at the bias of −200 V. On the other hand, Ta-rich Ta–N thin film deposited at −50 V shows amorphous nature. According to the XPS result, Ta element in the films surface exist in bonded state, including the Ta–N bonds characterized by the doublet (Ta 4f7/2 = 23.7 eV and Ta 4f5/2 = 25.7 eV). Electrochemical properties of the Ta–N coated stainless steel systems were investigated using potentiodynamic polarization and electrochemical impedance spectroscope (EIS) in Hank's solution at 37 °C. For the Ta–N coated samples, the corrosion current (icorr) is two or three orders of magnitude lower than that of the uncoated ones, indicating a significantly improved corrosion resistance. Growth defects in the Ta–N thin films produced by CAD, however, play a key role in the corrosion process, especially the localised corrosion. Using the polarization fitting and the EIS modelling, we compared the polarization resistance (Rp) and the porosity (P) of the Ta–N coatings deposited at different biases. It seems that Ta–N film with comparatively lower bias (−50 V) shows better corrosion behavior in artifical physiological solution. That may be attributed to the effect of ion bombarding, which can be modulated by the substrate bias.

Plasma electrolytic oxidation (PEO), also called micro-arc oxidation (MAO) or anode spark deposition (ASD), is a novel technique to produce hard ceramic coatings on metals, such as aluminum, titanium, magnesium (called valve metals) and their alloys. Up to now, many researchers focused on the PEO process for workpieces of regular shapes such as cube, cake or stick samples, etc. But no one paid attention to the irregular samples such as tubular materials. This research emphasized the PEO process of long tubes, especially the way to obtain uniform thickness of ceramic coatings on inner surface of tubes. Furthermore, the PEO kinetic behaviors of aluminum tubes were also investigated. The potential difference between the electrodes indicated a linear relationship with the coating thickness. A central accessory electrode was axially used to eliminate the shielding effect of electric field and was effective to obtain axially uniform coating on the inner surface of the tubes. The combination of hot-dipping aluminum and PEO process to obtain ceramic coating on 45# steel tubes was also performed in this work.

The pulsed high energy density plasma (PHEDP) is generated in the working gas due to a high-voltage high-current discharge, within a coaxial gun. In PHEDP surface modification, discharge is applied for preparing the amorphous and nanostructured high-melting materials as thin films deposited on various substrates. In this investigation, Ta(C)N films were deposited using PHEDP on stainless steel. Pure tantalum and graphite were used as the inner and outer electrodes of the PHEDP coaxial gun, respectively. Nitrogen was used as the working gas and also one of the reactants. Preliminary study on the films prepared under different conditions shows that the formation of Ta(C)N is drastically voltage dependent. At lower gun voltage, no Ta(C)N was detected in the films; when the gun voltage reaches or exceeds 3.0 kV, Ta(C)N occurred. The films are composed of densely stacked nanocrystallines with diameter less than 30 nm, and some grains are within 10 nm in diameter.

Hard films prepared by pulsed high energy density plasma (PHEDP) are characterized by high film/substrate adhesive strength, and high wear resistance. Titanium carbonitride (TiCN) films were deposited onto YG11C (ISO G20) cemented carbide cutting tool substrates by PHEDP at room temperature. XRD, XPS, SEM, AES, etc. were adopted to analyze the phases (elements) composition, microstructure and the interface of the films, respectively. The results show that, the uniform dense films are composed of grains ranging from 70 to 90 nm. According to the AES result, there is a broad transition layer between the film and the substrate, due to the ion implantation effect of the PHEDP. The transition layer is favorable for the film/substrate adhesion.

A new method for inner surface modification of steel tubes, named a combined technique of hot-dipping and plasma electrolytic oxidation (PEO) was proposed and demonstrated in this paper. In this work, metallurgically bonded ceramic coatings on inner surface of steel tubes were obtained using this method. In the combined process, aluminum coatings on steel were firstly prepared by the hot-dip process and then metallurgically bonded ceramic coatings were obtained on the aluminum coatings by PEO. The element distribution, phase composition and morphology of the aluminide layer and the ceramic coatings were characterized by SEM/EDX and XRD. The corrosion resistance of the ceramic coatings were also studied. The results show that, after hot-dip treatment, the coating layers consist of two layers, where Al, Fe x Al (1− x ) were detected from external topcoat to the aluminide/steel substrate. Then after PEO process, uniform Al 2 O 3 ceramic coatings have been deposited on inner surface of steel tubes. The ceramic coatings are mainly composed of α-Al 2 O 3 and γ-Al 2 O 3 phase. The compound coatings show favorable corrosion resistance property. The investigations indicate that the combination of hot-dipping and plasma electrolytic oxidation proves a promising technique for inner surface modification of steel tubes for protective purposes.

A novel atmospheric pressure plasma fluidized bed (APPFB) with one liquid electrode was designed, and its preliminary discharge characteristics were studied. The glow discharge in the APPFB was generated by applying a low power with helium (He) gas, and the plasma gas temperature was no higher than 320 K when the applied power was lower than 11 W. The plasma optical emission spectrum (OES) of the gas mixture consisting of He and hexamethyldisiloxane (HMDSO) was recorded by a UV-visible monochromator. The calcium carbonate powders were modified by APPFB using HMDSO in the He plasma. The powder surface energy was decreased greatly by coating an organosilicon polymer onto the powder surface. This surface modification process changed the wettability of the powder from super-hydrophilicity to super-hydrophobicity, and the contact angle of water on the modified powders surface was greater than 160°.

In the present work, four processes were carried out to produce ceramic coatings on aluminum substrate in two kinds of electrolytes (silicate and phosphate solution systems) using plasma electrolytic oxidation (PEO) technology. The voltage–time responses were recorded during different PEO processes. SEM/EDX and XRD were adopted to investigate the microstructure, elements distribution and phase composition of the coatings prepared in the two electrolyte systems. It is found that coatings produced in the silicate electrolyte have a more homogeneous morphology than those produced in the phosphate system. EDX analysis shows that silicon element tends to present primarily in the outer region of the coatings while phosphorus distributes uniformly throughout the coating thickness. According to the conventional anodic oxidation mechanism, a model is set up to explain the different characteristics of ceramic coatings fabricated in different electrolytes which is helpful to understand the growth mechanism of PEO coatings.

A wear-resistant (Cr,Fe)(7)C-3 carbide reinforced composite coating was fabricated on substrate of a 0.45% C carbon steel by plasma transferred arc (PTA) weld-surfacing process using Fe-Cr-C-Ni powder blends. The microstructure, microhardness and dry-sliding wear behavior of the composite coating were investigated using optical micrograph (OM), X-ray diffraction (XRD), scanning electron micrograph (SEM), energy dispersive X-ray analysis (EDS), microhardness tester and ring-on-ring wear tester. Results show that the composite coating consists of primary (Cr,Fe)(7)C-3 as the reinforcing phase and interdendritic (CrFe)(7)C-3/gamma-Fe eutectics as the matrix. The composite coating is metallurgically bonded to the 0.45% C carbon steel substrate. The (Cr,Fe)(7)C-3 carbide reinforced composite coating has high hardness and excellent wear resistance under dry sliding wear test conditions. (c) 2006 Elsevier B.V. All rights reserved.

A wear resistant (Cr, Fe)(7)C-3/gamma-Fe ceramal composite coating was fabricated on substrate of a 0.45%C carbon steel by plasma transferred arc (PTA) cladding process using the Fe-Cr-C elemental powder blends. The microstructure, microhardness and dry-sliding wear resistance of the coating were evaluated. Results shown that the plasma transferred arc clad ceramal composite coating has a rapidly solidified microstructure consisting of blocky primary (Cr, Fe)(7)C-3 and the inter-blocky (Cr, Fe)(7)C-3/gamma-Fe eutectics and is metallurgically bonded to the 0.45%C carbon steel substrate. The ceramal composite coating has high hardness and excellent wear resistance under dry sliding wear test condition. (c) 2005 Elsevier B.V. All rights reserved.

An atmospheric pressure glow discharge plume (APGD-p) using a dielectric barrier discharge reactor with one conductive liquid electrode was designed in our study. The preliminary characteristics of the plume and application in the degradation of a dye, methyl violet 5BN (MV-5BN), were presented in this paper. The APGD reactor produced a cold plasma plume with temperature not higher than 320 K at power 5 - 50 W. The MV- 5BN solution as a probe for dye wastewater was treated by the downstream gases of the plasma plume. The results indicated that the active argon (Ar) and nitrogen (N-2) gases had little effect on the MV- 5BN degradation, but the air and oxygen (O-2) gas depleted the organic molecules effectively. In particular, the downstream O-2 gas degraded the dye molecules entirely.

Plasma electrolytic oxidation (PEO) is a cost-effective technique that can be used to prepare ceramic coatings on metals such as Ti, Al, Mg, Nb, etc., and their alloys, but this promising technique cannot be used to modify the surface properties of steels, which are the most widely used materials in engineering. In order to prepare metallurgically bonded ceramic coatings on steels, a combined technique of arc spraying and plasma electrolytic oxidation (PEO) was adopted. In this work, metallurgically bonded ceramic coatings on steels were obtained using this method. We firstly prepared aluminum coatings on steels by arc spraying, and then obtained the metallurgically bonded ceramic coatings on aluminum coatings by PEO. The characteristics of duplex coatings were analyzed by X-ray diffractometer (XRD) and scanning electron microscopy (SEM). The corrosion and wear resistance of the ceramic coatings were also studied. The results show that, duplex Al2O3/aluminum coatings have been deposited on steel substrate after the combined treatment. The ceramic coatings are mainly composed of alpha-Al2O3, gamma-Al(2)o(3), theta-Al2O3 and some amorphous phase. The duplex coatings show favorable corrosion and wear resistance properties. The investigations indicate that the combination of arc spraying and plasma electrolytic oxidation proves a promising technique for surface modification of steels for protective purposes. (c) 2005 Elsevier B.V. All rights reserved.

Nanometer grain superhard ternary Ti(C,N) coatings with Vicker's nanohardness more than 50 GPa were deposited onto WC-Co cutting tools at ambient temperature using pulsed high-energy density plasma coaxial gun. Young's modulus of the coated tools was about 550 GPa. Because of the continuously graded interfaces between the coatings and substrates, the coatings are well adherent to the tool substrates with very high critical load up to more than 100 mN measured by nanoscratch tester. The coefficients of friction were lower than 0.1. In contrast with the uncoated tools, the coated tools could be applied in turning hardened CrWMn steel at high speed under industrial conditions without lubricants, and the cutting performances were greatly improved with rather low flank wear and long tool life.

The in-situ titanium nitride (TiN) coating with a great thickness was reactive plasma sprayed in a nitrogen-containing environment. The microhardness of the coating was measured, and the indentations were used to determine the fracture toughness of the coating. The toughening mechanism was characterized by analyzing the SEM morphologies of TiN coating's fracture surfaces. Results show that the coating possesses a high hardness and toughness. The average hardness of the coating is 1200H(V) (100) (g); and the fracture toughness (K-IC) of it is 4.51 MPa center dot m(0.5). The cross-section of the TiN coating shows an obvious phenomenon of indentation size effect (ISE). The toughening mechanisms of the coating are crack deflection and pores, etc. (c) 2004 Elsevier B.V. All rights reserved.

Nanometer grain ternary Ti(C,N) coatings of excellent mechanical properties with continuously graded surface onto Si3N4 cutting tools were deposited at room temperature via a newly developed equipment, pulsed high energy density plasma coaxial gun. The maximum critical load by nanoscratch tests of the coatings onto Si3N4 substrates is approximately 100 mN. The maximum hardness of the coatings is more than 50 GPa by nanoindentation tests. Compared with the uncoated tools, the tribological properties of the coated tools, which were evaluated by the cutting performances in turning hardened CrWMn steel under industrial conditions, were improved dramatically with the flank wear reduced by a factor of 6-8. (C) 2004 Elsevier B.V. All rights reserved.

Progress of the theoretical studies on the ion sheath dynamics in plasma source ion implantation (PSII) is reviewed in this paper. Several models for simulating the ion sheath dynamics in PSII are provided. The main problem of nonuniform ion implantation on the target in PSII is discussed by analyzing some calculated results. In addition, based on the relative researches in our laboratory, some calculated results of the ion sheath dynamics in PSII for inner surface modification of a cylindrical bore are presented. Finally, new ideas and tendency for future researches on ion sheath dynamics in PSII are proposed.

High-quality and wear-resistant titanium nitride films were deposited onto silicon nitride ceramic cutting tools by pulsed high energy density plasma technique at ambient temperature. The adhesive strength of TiN film to the ceramic substrate has been satisfactory with very high critical load up to more than 80 mN measured by nanoscratch tester. The TiN films possess very high values of nanohardness and Young's modulus, which are near to 28 and 350 GPa, respectively. The wear resistance and edge life of the ceramic tools were increased greatly because of the deposition of titanium nitride coatings. The cutting performance of the silicon nitride ceramic tools with such TiN films could be optimized by varying the deposition conditions, including the (shot) number of pulsed plasma and the discharge voltage between the inner and outer electrodes, etc.

Pulsed high-energy-density plasmas were used to process the surfaces of alumina ceramics. The morphology and composition of different parts of the surfaces of the as-processed samples were examined by scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively. The distinct morphology of the surfaces of the as-processed samples, particularly smooth areas and pits, was observed and studied. Uniform sub-micrometer particles about 250 nm in diameter were observed in the pits and proved to contain copper. No elemental copper was detected in the smooth areas. The analysis results showed that the plasmas were dusty. X-ray photoelectron spectroscopy was employed to examine the valence of the copper. An adiabatic model was used to explain the observed phenomena. A possible method for rapid finishing of advanced ceramics was proposed.