Distribution Of Macroparticles Research Articles

Hybrid Model of a Stationary Plasma Thruster

We propose a mathematical model of processes in a stationary plasma thruster (SPT). This model is based on hybrid equations of electromagnetic hydrodynamics (EMHD) of plasma that take into account ionisation of the working substance, viz. xenon. A thorough consideration is given to the 1D2V case of plane symmetry, in which an algorithm, based on the Particle-in-Cell method, is constructed for the numerical analysis of solutions of the hybrid EMHD equations. A number of key problems are solved: the calculation of average values, interpolation, the construction of the initial distribution of macroparticles, the choice of boundary conditions for the electric field, etc. The results of the calculations are given for the equations with and without the induction fields in the SPT being taken into account.

Гибридная модель стационарного плазменного двигателя

A mathematical model is proposed for studying the processes in a stationary plasma thruster (SPT) taking into account the ionization of the working substance - Xenon, based on the hybrid equations of electromagnetic hydrodynamics (EMHD) of the plasma. The 1D2V case of plane symmetry is considered in detail, for which a numerical algorithm for investigating solutions of hybrid EMHD equations is constructed, based on the method of macroparticles. The solution of a number of fundamental issues is given: the calculation of average values, interpolation, construction of the initial distribution of macroparticles, the choice of boundary conditions for the electric field, etc. The results of calculations with and without taking into account the induction fields in the SPT are presented.

The effect of duty cycle on the mechanical and electrochemical corrosion properties of multilayer CrN/CrAlN coatings produced by cathodic arc evaporation

ABSTRACT Multilayer CrN/CrAlN coatings were deposited on the 420-SS by the cathodic arc evaporation system with different duty cycles of bias-voltage. The deposited films were characterized by XRD and FESEM techniques. Mechanical, electrochemical, and surface properties of deposited films were studied by nano-indentation, electrochemical, and AFM analysis. Microstructure investigation confirmed the formation of adhesive and dense nanostructure multilayer film. Increasing the duty cycle led to the decrease in the coating grain size and promoted the hardness to 34.1 ± 4 GPa. A clear reduction of size and distribution of macroparticles was observed by using large repulsive force at a high duty cycle. By increasing the duty cycle, the coating deposition rate was increased from 1.23 to 1.38 µm/h and the surface roughness was decreased from 155 to 70 nm. The lower corrosion current density was obtained for the film applied at the 40% duty cycle (0.59 µA cm−2), which was about 10-order of magnitude less than the substrate.

Corrosion resistance of CrN and CrCN/CrN coatings deposited using cathodic arc evaporation in Ringer's and Hank's solutions

Abstract This paper presents the corrosion resistance of CrN monolayer coatings and CrCN/CrN multilayer coatings deposited by cathodic arc evaporation onto X39Cr13 stainless steel. Corrosion tests of the coating-substrate systems were conducted in Ringer's and Hank's solutions, usually used as infusion liquids. The parameters such as corrosion potential, corrosion current density and polarisation resistance were determined on the basis of the potentiodynamic polarisation curves. The corrosion properties of coatings in as-deposited state and after the polishing were compared. The results show that coated substrates are characterised by under half the corrosion potential and 10-times lower corrosion current density compared to the reference substrate (without coating). The corrosion parameters for polished coatings are slightly worse than unpolished, which is related to the method of coating deposition. The amount and distribution of macroparticles on the surface of the tested coatings are also presented.

Deposition of chromium nitride coatings using vacuum arc plasma in increased negative substrate bias voltage

The deposition methods of thin films which allow to obtain good quality coatings are still being developed. The paper presents a particular influence of the substrate bias voltage on the results of the deposition of chromium nitride coatings on HS6-5-2 steel substrates on the front and reverse side of the substrates with respect to the cathode by cathodic arc evaporation. The deposition was carried out at a fixed nitrogen pressure amounted to 3.0 Pa and the negative substrate bias voltages: 70, 150, 300 V. The difference in the deposition rate, phase and chemical composition, amount and dimensional distribution of macroparticles and surface roughness were studied and analyzed. It was found that the coatings obtained on the reverse side of the substrate were characterized by a nearly 3-times smaller amount of surface defects, more than twice the lower surface roughness and similar chemical composition as the coatings deposited on the front side of the substrate. The measurements have also shown that the hardness of the coatings obtained on both sides of the substrate is comparable, and decreases with increasing the negative substrate bias voltage.

Study on the Influence of Process Parameters on the Distribution of Macro-Particles on the Surface of Films

This paper systematically studies the distribution of macro-particles on the surface of film influenced by the substrate position under conditions of the same magnetic field, different pulsed bias voltage and reaction gas partial pressure, and analyzes the mechanism of macro-particles influenced by different parameters. This study indicates that the substrate position has a better effect on decreasing macro-particles than that of the pulsed bias voltage and particles in different substrate position are very different in their forms and appearances, which easily leads to uneven deposition; under the same bias, the number of particles firstly increases and then decreases with the increasing the distance from substrate position to the center, and the number of particles with over 2μm diameter largely decreases with the increasing the distance from substrate position to the center, so surface morphologies of films are improving; under the lower intensity of magnetic field, the distribution of macro-particles has a great change with the increasing the distance from substrate position to the center, and under the higher intensity of magnetic field, the substrate position has little influence on the distribution of macro-particles on the surface of film. Under the higher intensity (30G) of magnetic field, the distribution of macro-particles on the surface of film has minor change whatever reaction gas partial pressure and substrate position increase, and most particles are small in sizes and are solid spherical in shape. The higher intensity (30G) of magnetic field enhances the uniformity of film deposition and decreases the dependency of macro-particles distribution on other parameters.

Study on the Distribution of Macro-Particles on Films Prepared by Magnetic Field Enhanced Arc Ion Plating

Removed due to author's request.

Dependence of the friction coefficient on roughness parameters during early stage fretting of (Al,Ti)N coated surfaces

Abstract Main focus was on the correlation of the coefficient of friction (COF) with the geometrical parameters of the surface during early stage of the running-in period. TiN, TiAlN and AlTiN coatings were prepared by using rotating cathode arc evaporation unit. The roughness of the WC-Co substrate R a ranged from 0.05 to 0.2 μm and the coating thickness was 2.3 ± 0.2 μm. Part of the samples were subjected to the surface modification by the drag grinding finishing. Geometrical parameters of the surface were evaluated by means of atomic force microscopy (AFM) and fretting tests were conducted with 10 mm diameter alumina ball under 2 N load, 100 μm slip distance and the frequency of 10 Hz. It was found that the distribution of macroparticles strongly influences the geometrical parameters of the surface and the number of macroparticles increases with increasing Al content in the coating. In the case of the positive skewness S sq of the coating surface, the kurtosis S ku provides a statistically significant effect on the COF, namely the COF depends inversely on the kurtosis S ku . The kurtosis value for TiN was the highest among as-deposited coatings, subsequently, the slowest increase rate in the COF was observed for the TiN coating.

Effects of axisymmetric magnetic field on the distribution of Macroparticles on TiN and (Ti, Al) N films by arc ion plating

TiN and (Ti, Al) N films were prepared by axisymmetric magnetic field (AMF) enhanced arc ion plating (AIP). The morphology, detailed size distribution, power law distribution and area ratio of Macro-particles (MPs) on the resultant TiN and (Ti, Al) N films were systematically investigated. Fewer and smaller MPs ejection was observed with an increase in the transverse component of AMF. MPs on (Ti, Al) N films was much more and larger than that on TiN films. The MPs distribution indicated a fractal characteristic, and the scattering behavior of MPs on films had more dependence on cathode material than magnetic field applied. The area ratio covered by the MPs on TiN films decreased from 15.4% to 2.9% when the TMF increased from 0 G to 30 G and that on (Ti, Al) N films decreased from 39.4% to 6.2% when the TMF increased from 0 G to 35 G.

Effects of pulsing parameters on production and distribution of macroparticles in cathodic vacuum arc deposition

The effects of pulsing parameters such as the duty cycles, frequencies, and arc currents on the production and distribution of macroparticles (MPs) were studied. A tunable pulsed arc power supply that could provide either direct current (dc) or pulsed current plus dc was used in the experiments. Copper and titanium were used as the cathodes, and glasses were used as the substrate. Optical microscopy, scanning electron microscopy, and special image processing were utilized to investigate the MPs deposited onto the substrate. Our results illustrate the general trend that the MP density increases with higher dc but decreases with increasing pulsing frequency. There is no obvious relationship between the MP density and the duty cycle at high dc but the MP density obviously increases with the duty cycle at low dc.

Influence of an electrical field on the macroparticle size distribution in a vacuum arc

The results of experimental study of macroparticle distribution in a vacuum arc presented for Cu, Ti, Zr, and Cr cathodes. We have studied the macroparticle contamination of the films deposited on the substrate having floating potential and biased up to −1000 V with respect to the anode. It has been found that the macroparticle number significantly decreases (by a factor of 3–4) with substrate biasing for all examined cathode materials. A model of macroparticle motion in the quasineutral plasma and near-substrate sheath was proposed. The model bases on analyses of the macroparticle charging and motion in the quasineutral plasma and near substrate sheath. The model can qualitatively explain the macroparticle reduction in the coating due to negatively charged macroparticle reflection in an electric field.

Interaction of foreign macrodroplets in a nematic liquid crystal and induced supermolecular structures

The behavior of a system of macroscopic particles introduced in a nematic liquid crystal is studied theoretically. The energy of the pair interparticle interaction associated with the director elastic field deformation is found. The interaction intensity and character are studied as functions of the distance, the geometric parameters of foreign macroparticles, and the value of their anchoring to the mesophase. The interparticle interaction can cause nontrivial collective behavior that results in the formation of new spatially modulated structures in the macroparticle system. The periodic arrangement of chiral particles that induces a helical structure can give rise to two incommensurable periods in the average orientation distribution of macroparticles.

Macroparticle distribution in a quarter-torus plasma duct of a filtered vacuum arc deposition system

The macroparticle (MP) flux distribution in a quarter-torus filtered vacuum arc deposition system was experimentally investigated and compared with theoretical predictions based on a previously developed model. The average MP flux was measured by collecting the MPs generated from a Ti cathode on substrates located at different radial positions on the entrance and the exit planes of the quarter-torus filter, and measuring the MP size distribution function using an automated microscopic image analysis system. The average MP flux along the torus centre line decreased by a factor of 50 from the entrance to the exit, while the average MP flux decrease near the outer wall of the torus was more moderate. The flux near the outer wall was greater by a factor of three than the centreline flux. Increasing the toroidal magnetic field from 4 to 10 mT resulted in no substantial change in the MP flux on the centreline, while near the outer wall it decreased by a factor of two. The experimental results on the MP flux in the near outer wall region are consistent with electrostatic reflection of the charged MPs by the charged wall.

Macroparticle distribution and chemical composition of laser deposited apatite coatings

We have studied the effect of pulsed laser ablation conditions on the deposition of biocompatible apatite coatings on Ti and Ti–6Al–4V alloy at room temperature. We have made detailed analyses of the spatial distribution of the macroparticles (MP) and of the Ca/P ratio in the coatings. We find that (i) two types of MP are observed, differing in size, shape, and stoichiometry, and (ii) the size distribution of the MP has a maximum depending on the laser fluence and gas pressure in the deposition chamber. Manipulation of the laser deposition conditions allows fine control over both morphology and stoichiometry of coatings. Experimental results are explained on the basis of a theoretical model which includes the analysis of cluster-type ablation mechanisms due to the high pressures of gas evolved in thermal decomposition of the target material under laser irradiation.

A study of the macroparticle distribution in cathodic-arc-evaporated TiN films

Abstract The quantity, size distribution and shape of macroparticles emitted during the arc evaporation of TiN films were studied in the range of arc currents between 45 and 120 A. The quantity of macroparticles is independent of the operating background pressure and the combination of the flow of nitrogen gas and the arc current. However, the size and shape are dependent on these last two variables. It is demonstrated that the macroparticles are emitted preferentially at an angle of 60° to the plane of the target. The frequency of the mechanical striking of the arc target does not influence the total volume of macroparticles ejected towards the growing film.