脉冲偏压下电弧离子镀等离子体负载的等效电路模型及其定量表征

为了解决电弧离子镀(AIP)工艺中脉冲偏压电源与AIP等离子体负载间的匹配问题,结合脉冲偏压下AIP工艺实验,运用等离子体鞘层理论、电路理论和仿真模拟技术,得到AIP等离子体负载本质上是由鞘层引起的容性负载,在电路中可以等效为电容和电阻相并联的单元;根据AIP等离子体鞘层演化的特性,将AIP等离子体负载的等效电容表征为与时间无关而只与脉冲偏压幅度和等离子体相关参数有关的量,AIP等离子体负载的等效电阻,可以在直流偏压下通过测量与脉冲偏压幅值对应的AIP等离子体负载电流来确定.经验证,本文建立的AIP等离子体负载的等效电路模型及其定量表征是有效性的.     

脉冲偏压下电弧离子镀等离子体负载的等效电路模型及其定量表征

为了解决电弧离子镀（AIP）工艺中脉冲偏压电源与AIP等离子体负载间的匹配问题，结合脉冲偏压下AIP工艺实验，运用等离子体鞘层理论、电路理论和仿真模拟技术，得到AIP等离子体负载本质上是由鞘层引起的容性负载，在电路中可以等效为电容和电阻相并联的单元；根据AIP等离子体鞘层演化的特性，将AIP等离子体负载的等效电容表征为与时间无关而只与脉冲偏压幅度和等离子体相关参数有关的量，AIP等离子体负载的等效电阻，可以在直流偏压下通过测量与脉冲偏压幅值对应的AIP等离子体负载电流来确定。经验证，本文建立的AIP等离子体负载的等效电路模型及其定量表征是有效的。     

Characterization of an inductively coupled plasma with xylene solutions introduced as monodisperse aerosols

The optimum operating parameters of the inductively coupled plasma (ICP) with organic solvents are different from those with aqueous solutions. With organic solvents, the ICP is operated at higher power to overcome plasma cooling due to the organic solvent, and aerosol desolvation is necessary in order to reduce solvent load into the plasma. The monodisperse dried microparticulate injector (MDMI) offers the possibility of controlling solvent load by controlling the frequency with which droplets are introduced into the plasma. A test solution that contained 0.5 mg/L Ba in xylene was used to study the influence of MDMI operating parameters on the behavior of the ICP with an organic solvent. The spatial and temporal distribution of the solvent in the ICP was determined for different droplet production frequencies and MDMI oven temperatures, and the optimum operating conditions were established. The best detection limit for Ba in xylene was 1.5 ng/mL, or 0.16 pg (in 200 droplets).     

Preparation and characterization of bioactive monolayer and functionally graded coatings

Hydroxyapatite powders were made by reacting orthophosphoric acid with calcium hydroxide and dense bioactive coatings were subsequently produced by the plasma spray technique. Three types of hydroxyapatite (flame spheroidized) monolayer coatings and three types of functionally graded coatings were manufactured. It was found that average microhardness values of monolayer coatings decreased as the indentation load increased. The relationship between indentation load and indent diagonal length observed Meyer's law. Microhardness and fracture toughness of coatings were affected by characteristics of feedstock powders for plasma spraying. The indentation fracture toughness of coatings could be significantly increased by incorporating a toughening phase. ©1999 Kluwer Academic Publishers     

Thermal loads of plasma focus chambers

The passage of current through the electrodes of a plasma focus chamber is analyzed taking into account the skin effect; the thermal load on the elliptical shaped electrodes is studied in the interaction with the current-plasma sheath, calculated within the two-dimensional ideal magnetohydrodynamic model. The heating of the anode of the plasma focus chamber by the discharge current is assessed under the limit modes of operation. Signs of the thermal action of plasma particles on the electrode surface are demonstrated.     

Influence of plasma nitriding on rolling–sliding wear of Fe–Mo sintered steels

Abstract

Dry rolling-sliding tests were carried out on plasma nitrided and heat treated Fe–Mo–C sintered alloys. Whereas the heat treated alloy undergoes oxidative wear independently of the load condition and duration of the test investigated, the plasma nitrided alloys show distinct wear stages characterised by different wear rates. In particular, while the white layer is able to remain in place the wear rate is lower than that shown by the reference heat treated material. The durability of the white layer increases on decreasing the applied loads and/or submitting the materials to heat treatment before plasma nitriding, to improve the load bearing capacity of the subsurface layers. Fatigue cracks nucleate in the subsurface layers because of the stress concentrating effect of pores, but no fatigue wear was observed during the tests. After loss of the white layer due to oxidation or microcracking, the wear rate increases because both oxidation and plastic shearing control the wear behaviour.

MST/2067     

Influence of Plasma Surface Layer on Wear Resistance of AISI4140 Steel

The results presented in this paper show that the composite plasma surface layers could improve the wear resistance of AISI 4140 steel for the case when high specific load appears at the contact zone. Composite surface layers consist of plasma nitrided and subsequent plasma deposited TiN or TiAIN. The significant differences in hardness and structures of outer hard layers, compared to the base material promote high drop of internal stress. Improvement of wear resistance for composite surface layers could be explained by decreasing stress gradient and better resistance to local plastic deformation at the wear zone compared to single hard surface layer.     

Efficiency of pulse high-current generator energy transfer into plasma liner energy

The efficiency of capacitor-bank energy transfer from a high-current pulse generator into kinetic energy of a plasma liner has been analyzed. The analysis was performed using a model including the circuit equations and equations of the cylindrical shell motion. High efficiency of the energy transfer into kinetic energy of the liner is shown to be achieved only by a low-inductance generator. We considered an “ideal” liner load in which the load current is close to zero in the final of the shell compression. This load provides a high (up to 80%) efficiency of energy transfer and higher stability when compressing the liner.     

Characterization of Plasma Nitrided and PVD-TiN Duplex Treated Armco Iron and En40B Steel by Nanoindentation

The nanoindentation test has been applied to evaluate the mechanical properties such as hardness, elastic moduli and deformation behaviors of Fe₄N iron nitride layers produced on Armco iron and En40B steel by plasma nitriding, and PVD-TiN coatings deposited on En40B with or without prior plasma nitriding treatment. Results showed that the Fe₄N layer produced on En40B exhibits higher hardness than that on Armco iron. This is attributed to the effect of the alloy compositions, especially Cr element. However, similar elastic modulus values to that of bulk ferrous alloys have been found for Fe₄N layers produced on both Armco iron and En40B. Under lower loads, TiN coatings on nitrided substrate behave quite the same in hardness and elastic modulus as TiN coatings on untreated En40B. Whilst with increasing indentation load and depth, duplex treated (i.e., combined plasma nitriding and PVD-TiN coating) En40B possesses higher composite hardness, elastic modulus and load bearing capacity than TiN coated base material.     

Process-induced oscillator frequency pulling and phase noise within plasma systems

Passive radio spectroscopy is employed to examine plasma process instabilities generated by the interaction between the power source oscillator and the plasma load. A fixed frequency of 13.56 MHz and a 170-180 kHz Flyback transformer are considered. The carrier frequencies are interrogated using a resolution bandwidth that constitutes ∼1/7000-1/580 of the target oscillator frequencies with a sweep time of less than 0.06 s across the phase noise disturbance. Within these spectrum analyzer measurement parameters, oscillator phase noise (1/f^n=1-3, discrete spurs and raised noise floor) is shown to be linked to plasma load mismatch and periodic instabilities. In the case of the Flyback circuit, it is found that the oscillator frequency pulling and modulation are linked to the plasma reactance. These results indicate that oscillator phase noise can be used as a non-invasive plasma process metrology tool.     

Magnetocumulative generator as the power supply for pulsed plasma accelerator

Results are given of theoretical and experimental investigations of schemes of matching of magnetocumulative generator (MCG) and load, which include a helical MCG, storage inductance coils, solid-state switch, and explosive current breaker. Magnetocumulative generators in combination with constant and variable storage inductances are developed and investigated. The results of numerical studies are checked in experimental runs under a model load with inductance of 100 nH and under a load with variable inductance. The possibility is demonstrated of using the MCG developed as the effective power supply for a pulsed plasma accelerator (PPA).     

脉冲阴极弧金属等离子体源的调试及其应用

对脉冲阴极弧金属等离子体源的工作参数进行了测量,研究了离子流与磁导管偏压以及磁场电流与离子流之间的关系,确定了其最佳工作参数.并应用该脉冲阴极弧金属等离子体源和等离子体浸没离子注入与沉积技术制备了TiC薄膜.对改性层的显微硬度、摩擦磨损性能和膜基结合力进行了测试分析.结果表明:合成TiC薄膜后,试样的显微硬度、摩擦磨损性能得到了明显的改善,并且膜层与基体之间的临界载荷为36.03 N.     

Electromagnetic Analysis of the ITER Upper VS Coil

In order to control the plasma vertical stability of ITER, a novel magnet is developed, that is the vertical stability coil. The coil is located in the vacuum vessel and its safe operation is very important for ITER’s reliable working. During the normal operation, the coil should bear the electromagnetic force caused by the external superconducting magnet and plasma current. The electromagnetic load is one of the important factors to affect the lifetime of the VS coil. Therefore, it is necessary to calculate the magnetic field and evaluate the structural reliability under the electromagnetic load. In this paper, the current at the time “end of burn” was selected to perform the electromagnetic calculation. Based on the Maxwell equation, the magnetic field on the cross section of the upper VS coil was computed and the maximum electromagnetic force corresponding to the magnetic field was also presented. In order to verify the current design model, the finite element model was created by use of ANSYS. The Tresca stress was extracted and classified based on analytical design. The peak stress was compared with the ASME criteria. The analysis has verified the physical model from the perspective of electromagnetic load, and it will offer a guidance for the future optimization.     

超高分子量聚乙烯(UHMWPE)纤维表面处理对UHMWPE/环氧树脂复合材料界面性能的影响机制

从工程化应用角度研究了常压空气等离子体改性对超高分子量聚乙烯（UHMWPE）纤维/环氧树脂复合材料界面性能的调节机制,主要分析了不同处理时间对UHMWPE纤维表面状态变化的影响,及其对UHMWPE/环氧树脂复合材料界面黏结性能的影响规律。采用SEM及纤维吸水测试研究了等离子体处理对UHMWPE纤维表面物理形貌及纤维表面浸润性能的影响,分别以拉伸和弯曲的方式,通过纤维表面脱黏力及层合板层间剪切强度对UHMWPE/环氧树脂复合材料的界面黏结性能进行表征。结果表明,仅经过4 s的空气等离子体处理之后,UHMWPE纤维表面脱黏力的提高幅度为84.0%,UHMWPE/环氧树脂复合材料层合板的层间剪切强度由未处理的7.01 MPa提高至15.81 MPa,增幅高达125.5%。研究发现,通过常压空气等离子体处理改变了UHMWPE纤维的表面状态,可以显著高效地调节UHMWPE/环氧树脂复合材料的界面性能,为扩大该材料的后续工程化应用提供了理论基础。      

微孔电极中微孔参数对电声特性的影响

为研究等离子体震源的电声特性随孔特性的变化，采用微孔电极放电，通过电压和电流探头测量负载电特性，阴影成像法和高速相机记录气泡脉动特征，水听器测量声脉冲，主要研究了不同微孔间距和数目下的电特性、气泡脉动和声特性。结果表明，随着微孔间距的增加，负载电压和能量不变，而负载电流和功率却在增加。另外，声脉冲幅值随着间距的增加出现了先上升再下降的趋势，最大可达到148.8 kPa；当孔数增加时，负载的峰值电压和电流虽然减少，但气泡声脉冲数增加，致使直达波的峰值增大。因此，增加孔数对提高微孔电极放电声脉冲的峰值是有利的。     

Microstructural and tribological characterization of air plasma sprayed nanostructured alumina–titania coatings deposited with nitrogen and argon as primary plasma gases

Air plasma sprayed nanostructured Al₂O₃–13wt%TiO₂ coatings were deposited as a function of critical plasma spray parameter (CPSP), defined as the ratio of arc power to primary gas flow rate, using nitrogen and argon as the primary plasma gases. Microstructural features including percentage of α-Al₂O₃ phase, percentage of partially melted/unmelted regions, microhardness, and wear characteristics were evaluated for the deposited coatings. Effect of CPSP on microstructural and wear characteristics of coatings deposited with nitrogen was found to be relatively small. In contrast, significant effect of CPSP on coating characteristics was found for coatings deposited with argon. In wear tests, while strong effect of normal load on weight loss was observed for coatings deposited with nitrogen, weight loss for coatings deposited with argon was nearly independent of applied normal load, at least for coatings deposited at the highest CPSP.     

Characteristics of plasma surface treated composite adhesive joints at high environmental temperature

When an adhesive joint is exposed to high environmental temperature, the load transmission capability of the adhesive joint decreases because the stiffness and strength of structural adhesive decrease. The load transmission capability of adhesive joint at high environmental temperature can be improved by increasing the surface free energy of adherends with surface pretreatments.

In this paper, a capacitively coupled radio frequency plasma system was designed for the surface treatment of carbon/epoxy composites. The suitable plasma surface treatment conditions were experimentally investigated with respect to gas flow rate, vacuum pressure, power intensity, and surface treatment time through measurement of surface free energy by investigating strength of single lap composite adhesive joint. The surface free energy and adhesive joint strength were investigated with respect to the surface characteristics of the carbon/epoxy composite adherend measured with atomic force microscope. Also the failure mode of the composite adhesive joint was studied with respect to surface treatment and environmental temperature.     

Carbon films deposited by MCECR plasma sputtering

The mirror-confinement-type electron cyclotron resonance (MCECR) plasma source has high plasma density and high electron temperature, and it is quite useful in many plasma processing, and has been used for etching and thin-film deposition. In this paper, the carbon films about 50 nm thickness were deposited on Si (1 0 0) by MCECR plasma sputtering the sintered carbon target with the argon plasma, and its properties were studied. The bonding structure of the film was analyzed by using the X-ray photoelectron spectropscopy (XPS) and the nanostructure was evaluated with the high-resolution transmission electron microscopy (HRTEM). The tribological properties (friction coefficient, wear rate, and wear life) of the film was investigated by using the pin-on-disk tribometer under the conditions that the normal load is 1 N and the sliding velocity is 0.05 m/s. The nanohardness of the films was measured by using the nanoindenter under conditions that the maximum displacement is 30 nm and the maximum load is 500 μN. The optical properties were measured by using the ellipsometer. The residual stress was measured with a surface profilometer. The surface morphology was studied by using the atomic force microscope (AFM).     

Friction in near-surface regions of plasma-nitrided and post-oxidized plain steel at various hydrogen contents

We investigated the low load friction behavior of plasma post-oxidized, plasma- nitrided AISI 1045 plain steel, using unidirectional sliding tests. The hydrogen content in the post-oxidation plasma was varied between 0 and 25%. The nitrided or oxidized layer thicknesses ranged from approximately 340-380 μm or 0.7-1.1 μm, respectively. The outermost iron oxide layer decreases the friction, whereas the underneath iron nitride layer increases the mechanical strength. The incorporation of hydrogen in the oxidative plasma mixture allows to control the type of iron oxide phase. It is observed that the presence of a superficial magnetite layer leads to a decrease of the friction coefficient with respect to the non-oxidized nitrided steel. The results are interpreted on the lights of crystal chemistry and with a model to explain the in-depth effects of hydrogen in the oxidative plasma.     

Influence of Substrate Temperature and Plasma Power Density on the Properties of Plasma-Assisted Chemical Vapor Deposited Titanium Nitride

Titanium nitride films deposited onto high speed steel substrates by plasma-assisted chemical vapor deposition (PACVD) from TiCl₄, H₂, N₂, and Ar gas mixtures have been investigated. The substrate temperature was varied between 250 and 550^° C via the plasma power density or via an additional electrical heater. The influence of temperature and plasma power density on the morphology, chemical composition, hardness and adhesion of the coatings was studied. At a temperature of 500^° C different plasma power densities caused changes of the morphology of the coatings. At low plasma power densities fine grained polycrystalline layers were observed. A significant change from coarse to fine grained structures was also observed with decreasing deposition temperature. Scratch test results indicate that coatings deposited at a given substrate temperature with lower plasma power density showed increased values of the critical load.