Coaxial Plasma Accelerator Research Articles

Quadruple Langmuir probe characterization of different fuel gases in a plasma deflagration accelerator

Astrophysical flows may be studied by reproducing similar conditions using a coaxial plasma accelerator operating in the deflagration regime (or plasma deflagration accelerator). This allows for the recreation and investigation of dynamics present in complex highly coupled plasma systems at the laboratory scale. We report on measurements of the plasma density, temperature, plasma potential and velocity found using a quadruple Langmuir probe (QLP) on such a deflagration accelerator in the form of the Stanford Coaxial High ENerGy (CHENG) device operating with multiple gases – specifically argon, nitrogen and hydrogen. Experiments show a general decrease in bulk plasma velocity with gas atomic mass from upwards of $120\ {\rm km}\ {\rm s}^{-1}$ with hydrogen to less than $30\ {\rm km}\ {\rm s}^{-1}$ with argon. There was an accompanying increase in peak plasma density with increasing atomic mass from ${\sim }3\times 10^{20}\ {\rm m}^{-3}$ with hydrogen to ${\sim }1.5 \times 10^{21}\ {\rm m}^{-3}$ with argon. It was found that the momentum flux and internal energy density also generally increase with atomic mass while the particle flux is constant between shots. Further investigation is needed to understand these correlations and the underlying physics. Lastly, comparisons with scaling laws show that while the CHENG device may be operated in such a way as to simulate the effects of bulk solar wind movement, it may not properly capture the thermal effects.

INFLUENCE OF CONFIGURATION OF THE ELECTRODE SYSTEM OF A COAXIAL MAGNETO PLASMA ACCELERATOR ON ARC DISCHARGE FORMATION AND DEVELOPMENT

Link for citation: Tsimmerman A.I., Shanenkov I.I., Nassyrbayev A.R., Nikitin D.S., Sivkov A.A. Influence of configuration of the electrode system of a coaxial magneto plasma accelerator on arc discharge formation and development. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 8, рр. 39-50. In Rus. The relevance of the research is explained by a wide range of practical areas, where various plasma generators can be used, including analytical devices, technological installations, tokamaks, ion and plasma engines, satellites, laser technology, as well as by the possibility of applying them for both producing coatings on various surfaces and synthesizing fine and nanopowders. The main aim of the research is to determine the best way to initiate an arc discharge in the acceleration channel of the coaxial magnetoplasma accelerator, to estimate the effect of the plasma formation zone configuration on the electrodynamic loads of the accelerator, and to calculate the efficiency of conversion of stored energy to supplied one. Objects: coaxial magnetoplasma accelerator, arc discharge initiation, central electrode, electrode-barrel, plasma formation zone. Methods: experiment, plasma dynamic synthesis, measurement and registration of pulsed currents and voltages, electrical erosion measurement by means of weighing the eroding electrode-bore, high-speed photoregistration of the plasma jet. Results. Two methods of arc discharge initiation using metal wires and graphitization were considered. It is established that they do not affect the energy parameters of the plasma dynamic synthesis, but the graphitization looks preferable due to the greater processability of the procedure that provides easy accelerator preparation and reliability of its operation. The possibility of reducing the arc discharge current amplitude by 29 % with increasing the plasma formation zone length from 5,5 to 11,5 mm was established that results in reducing electrodynamic loads on all system nodes. The optimal plasma formation zone length of 9,5 mm was determined to provide obtaining a high efficiency of conversion of stored energy into supplied energy and reliability of the system operation.

Simplified Plasmadynamics Model of a Coaxial Self-Field Plasma Accelerator

A simplified plasmadynamics model is presented that examines radial and axial dependence of the current sheet structure of a coaxial quasi-steady self-field plasma accelerator, dominated by electromagnetic forces. Two radial electric field distributions are considered as limiting cases. In the first case, constant current flows between constant-radius electrodes; in the second case, constant current flows between electrodes and also extends downstream of the electrodes. Calculations for Teflon () plasma show the distribution of plasma parameters inside the current sheet, as well as terminal values for kinetic efficiency, voltage, and impedance for both distributions. Evaluation of the validity of simplifying assumptions is presented, as is the behavior of previously developed accelerators as interpreted by the model.

Effect of external longitudinal magnetic field on the dynamics of pulsed plasma stream

A spectroscopic study is carried out to investigate pulsed plasma stream produced in a coaxial plasma accelerator under the influence of an external longitudinal magnetic field. The dynamics of Argon plasma stream that includes the excitations and emissions of plasma species and its different parameter variations on the application of an external longitudinal magnetic field are reported in this work. The behavior of the ionized and neutral species of argon plasma is studied from their intensity distribution profiles which indicate the occurrence of faster recombination as compared to the field-free case. The variation of pressure reveals a significant influence on the recombination and diffusion process of the plasma species. Moreover, the variation of cathode voltage leads to variation in input energy to the system which influences the ionization and excitation processes of the plasma species. A plasma density (Ne) jump is achieved from 1021–1022 m−3 at a relatively higher pressure ∼8 bar plenum pressure in presence of the magnetic field. Saturation of the emissions and excitations of plasma species are revealed from the intensity profile and electron excitation temperature (Texc) profile which occur at different pressure and voltage both for field and field-free cases. The electron temperature (Te) is estimated using the FLYCHK code by comparing the simulated charge state distributions with the experimental findings. Using known parameters in the code, the different estimated Te shows a linear and an exponential decrement respectively in the absence and presence of the magnetic field. Maximum Te of 2.2 eV is reported which decreases to 1.51 eV at a significant increase of plasma density of 1022 m−3.

Investigation of dust formation during changes in the structural and surface properties of plasma-irradiated materials

• The contribution of surface defects (cracks, craters, bubbles) and structural changes (recrystallization) exposed by the plasma beam candidate materials to dust formation is studied. • The scanning electron microscopy (SEM), and elemental and X-ray diffraction (XRD) analysis were used to study the surface morphology, chemical composition, and crystal structure of plasma beam irradiated materials. • On the surface of tungsten target the well-developed micro-cracks are formed, and defects such as melting and flaking of the surface layer, drop-shaped structures formation are also observed. The increasing of the pulse dose led to an increase in the width and depth of these microcracks. • Tungsten target erosion (mass loss) occurs due to the ejection of particles from the tungsten surfaces, both as droplets and as solid dust during crack development. • The measured peak shift in carbon was 0.03 degrees after x5 plasma load. Thereby, carbon is generally more resistant to plasma beam impact than tungsten. This paper presents the results of studying the impact of a plasma beam during the interaction of divertor candidate materials in a coaxial plasma accelerator, where graphite and tungsten plates were used as candidate materials. The authors consider the contribution of surface defects (cracks, craters, bubbles) and structural changes (recrystallization) in candidate materials to dust formation under the action of a plasma beam. The other aspect studied in the paper is the erosion of copper substrates (nearby components) under the action of a hot target dust cloud with account for the kinetic influence of hot dust particles on nearby components. It should be noted that these particles are formed by the erosion of the material by the plasma beam. Scanning electron microscopy (SEM), elemental and X-ray diffraction analysis (XRD) were used to study the material surface morphology, chemical composition, and crystal structure. The authors also consider some undesirable effects revealed after irradiation of divertor candidate materials. The obtained experimental results will be useful for evaluating the prospects for further application of these materials in existing and future fusion reactors (e.g., in the international fusion reactor ITER).

Pulsed plasma flow diagnostics

This paper presents the results of optical and probe diagnostics of hydrogen plasma flow in a coaxial plasma accelerator. The triple probe and the Optosky ATP2000P linear spectrometer with a spectral range of 200-1100 nm were used for measuring the electron current and obtaining the hydrogen plasma emission spectrum. The individual spectral lines were observed using an M833 monochromator spectrometer with a spectral resolution of 0.024 nm. From the measured electron currents and emission spectrums, the electron densities in the flux of a hydrogen pulsed plasma were calculated. We used the Stark method of Hβ hydrogen line broadening for calculations of electron densities. The obtained experimental results from the probe and spectroscopic measurements of electron density correspond well. In this work, we also obtained the dependence of the electron density on the voltages applied to the capacitor bank. The electron density increases with increasing voltage, because of the increased energy applied to the discharge. The average electron densities in the plasma flux showed  1.13 ∙ 1021 m-3,  4.14 ∙ 1021 m-3, and  5.57 ∙ 1021 m-3 at three values of voltages of 3 kV, 4 kV, and 5 kV, respectively.

Investigation of self-generated magnetic field and dynamics of a pulsed plasma flow

Due to the growing interest in studying the compression and disruption of the plasma filament in magnetic fusion devices and Z-pinches, this work may be important for new developments in the field of controlled thermonuclear fusion. Recently, on a coaxial plasma accelerator, we managed to obtain the relatively long-lived (∼300 μs) plasma filaments with its self-magnetic field. This was achieved after modification of the experimental setup by using high-capacitive and low-inductive energy storage capacitor banks, as well as electrical cables with low reactive impedance. Furthermore, we were able to avoid the reverse reflection of the plasma flux from the end of the plasma accelerator by installing a special plasma-absorbing target. Thus, these constructive changes of the experimental setup allowed us to investigate the physical properties of the plasma filament by using the comprehensive diagnostics including Rogowski coil, magnetic probes, and Faraday cup. As a result, such important plasma parameters as density of ions and temperature of electrons in plasma flux, time dependent plasma filament’s azimuthal magnetic field were measured in discharge gap and at a distance of 23.5 cm from the tip of the cathode. In addition, the current oscillograms and I–V characteristics of the plasma accelerator were obtained. In the experiments, we also observed the charge separation during the acceleration of plasma flow via oscillograms of electron and ion beam currents.

Modification and optical degradation of thin multilayers under VUV/UV radiation from compressed plasma flows

Coaxial plasma accelerators are under consideration for generation of compressed plasma flows which are suitable for emitting of powerful broadband radiation (including the VUV/UV ranges). The using of different gases in a chamber allows to control the spectrum. For inert gases the upper value of energy is limited by its first ionization potential (for neon ≈ 21.55 eV). For air the maximum energy is limited by ≈ 6 eV. Such technical systems are suitable for studying of optical properties stability for thin multilayers and the other coatings. Such tests were fulfilled for bilayers based on HfO2/SiO2 pair on silica substrates which is stable for laser radiation in the visible and IR ranges. It was found that a single exposure of the radiation (for neon and air) caused a relative decline of the radiation durability in ≈ 1.03…1.14 times. Spectral measuring demonstrated that the maximum decline of transmission (up to of ≈ 3…4%) was detected for exposures in neon in the range of 320…450 nm.

Peculiarities of the Discharge Formation in a Plasma Accelerator and Structure of a Jet Flowing into Vacuum

We report on results of investigation into the structure of a plasma jet generated by a coaxial plasma accelerator with conical insert in the discharge formation region. Using high-speed optoelectronic camera, we detected an inhomogeneous structure of glowing fractions of argon and deuterium jets. It was found that the jet radiation intensity oscillates with a characteristic frequency of 0.3–0.9 MHz. The argon plasma jet consisted of fragments diverging from the axis; plasma recombined 20 μs after the beginning of the discharge. The deuterium plasma jet resembled flakes. Its radiation intensity decreased significantly by 8 μs. The characteristic frequencies of radiation nonuniformities on the jet axis were about 0.09 cm–1 for argon and 0.3 cm–1 for deuterium. Analysis of the behavior of the discharge in the plasma accelerator revealed that a diffuse discharge was initiated at the base of the conical insert. After 0.5 μs, the discharge emerged at the outer boundary of the insert, was contracted, and occurred between central and external electrodes. The emergence of the discharge from the accelerator was observed 3 μs later and was accompanied with a glow of the end face of the central electrode. In the measurements of temperature of the lateral surface of external electrode using an infrared camera, it was found that heating is localized near the edge of conical insert and at the outlet of the accelerator. Results of investigations can be used for gas ionization, material irradiation, and simulation of interaction of plasma flows with the magnetic field in the outer space in laboratory conditions.

Characteristics of plasma stream evolution in a pulsed plasma accelerator

The time-integrated spectroscopic measurements of argon plasma are carried out to characterize the transient plasma stream produced in a coaxial pulsed plasma accelerator. Transient plasmas produced in these types of devices have a temporal change in density and temperature. The temporal evolution of the plasma stream and its characteristic variation are studied from a time of 50–300 μs in steps of 50 μs. Analysis of different spectral lines shows the existence of some metastable states of Ar+ having a long lifetime. The evolution of different Ar+ transitions to metastable and non-metastable lower levels is observed for different time frames. From the Stark broadening and Boltzmann plot method assuming the partial local thermodynamic equilibrium model, the plasma densities and excitation temperatures are estimated. The temporal evolution study shows a decrease in plasma densities from 1.96 × 1021 m−3 at 50 μs to 1.23 × 1020 m−3 at 300 μs after the initiation of plasma formation. A reduction in excitation temperature is observed from 0.86 to 0.77 eV. Based on the density profile, the estimated energy density of the plasma stream shows a time-dependent decreasing trend from 0.06 to 0.004 MJ/m2 during the observed period. The results may be useful for optimization of the plasma stream in pulsed plasma accelerators concerning its different parameters.

Simulation of the inner electrode geometry effect on the rundown phase characteristics of a coaxial plasma accelerator.

A 2D computational model, incorporating the Snowplow approximation in the mass balance, is used to simulate the acceleration of an annular current sheath along two coaxial electrodes, with the inner one having either cylindrical or conical shape. The circuit, mass and momentum equations are simultaneously solved in 2D (r, z) considering initial breakdown along the insulator surface, ideal gas mass accretion by the current sheath (snowplow model) and distributed inductance along a coaxial transmission line short-circuited by the current sheath. Plasma density and electron temperature in the current sheath are estimated using standard planar shock theory. Numerical integration of the model’s equations for a given electrode geometry yields the temporal evolution of the current sheath parameters during the axial acceleration phase. In order to see the effect of the inner electrode shape on sheath parameters (i.e. transit time, kinetic energy, total mass, shape, etc.) and/or circuit properties (i.e. circuit inductance, voltage and current evolution, etc.), the portion of the inner electrode beyond the insulator was given a conical shape. By changing the cone slant in a range between ±5°, it was found that the current driven on the plasma sheath varies nonlinearly with the angle. The divergent (positive angle) electrode gives the sheath the highest kinetic energy, being twice the value corresponding to that of the straight inner electrode case, and the transit time is reduced from 1.34 to 1.20 µs. The estimates of plasma density and electron temperature indicate that the achievable ion densities are on the order of 4x1022 m-3, which corresponds to 30 % ionization, and typical temperatures at the end of the rundown phase are on the order of 8 eV. These values are comparable with those measured in experimental devices. The development of this tool will enable us to benchmark its results against an experimental installation currently close to being operational, and a future follow-up paper will be devoted to the comparison between the prediction of the rundown phase behavior and experimental results utilizing conical electrodes.

Flow Z-pinch plasma production on the FuZE experiment

The Fusion Z Pinch Experiment (FuZE) investigates sheared-flow stabilization of classic m = 0 and m = 1 instabilities in Z pinches with an embedded axial flow. FuZE consists of a 100 cm coaxial plasma accelerator, where neutral gas is ionized and accelerated in a pulsed electrical discharge, followed by a 50 cm assembly region, where pinches are formed. Maintaining the pinch requires continuous plasma injection provided by a deflagration mode in the coaxial accelerator. Two discharge modes, with and without deflagration, are investigated on FuZE. Pinch formation is observed with deflagration only. Plasma velocities in the assembly region are found to match the E × B velocity estimated in the accelerator based on a 1D circuit model, indicating that a 1D MHD approximation may offer a valid description of the plasma in the accelerator channel. The velocity of magnetic field propagation is found to agree with the snowplow model based on momentum conservation, and the lifetime of the pinch is shown to be in agreement with constraints imposed by mass conservation.

Особенности формирования разряда в ускорителе плазмы и структура струи, истекающей в вакуум

Results of investigation of jet structure created by coaxial plasma accelerator with conical insert in discharge formation region are presented. An irregular structure of the glowing argon and deuterium jet fraction was detected using a fast electron-optical camera. An irregular structure of the glowing argon and deuterium jet fractions was detected using a fast camera. Oscillations of jet radiation intensity with characteristic frequency 0.3-0.9 MHz were detected. The jet of argon plasma consisted of fragments diverging from the axis of motion, the plasma recombined 20 µs after the start of current. The deuterium plasma jet was like flakes. The intensity of its radiation significantly decreased by 8 µs. The characteristic frequencies of irregularities of radiation on jet axis for argon were ~ 0.09 cm-1, for deuterium ~ 0.3 cm-1. Studies of discharge behavior in plasma accelerator demonstrate that diffuse discharge was initiated at the bottom of conical insert. After 0.5 µs discharge exited to the outer edge of insert, counteracted and burned between central and outer electrodes. Discharge exit from accelerator was observed after 3 µs and was accompanied by glowing of end of central electrode. In the course of measuring the temperature of side surface of the external electrode using infrared camera, the localization of heating was detected near the edge of conical insert and at accelerator outlet. The research results can be used for gas ionization, in the irradiation of materials, as well as for laboratory simulation of the interaction of plasma flows with a magnetic field in space.

Multi-Pulse Operation of Coaxial Magnetic Plasma Accelerator for Dynamic Synthesis of Iron Oxide Powder

The paper considers the use of multi-pulsed synthesis facility based on coaxial magnetic plasma accelerator for plasma dynamic synthesis of iron oxide powder with a high content of e-Fe2O3 phase. It is shown that the multipulsed operation of coaxial magnetic plasma accelerator considerably lowers the discharge-current amplitudes and one-pulse power supply, thereby decreasing the dynamic load in the whole system. It is found that the formation of the increased amount of e-Fe2O3 phase up to ~70 wt.% depends on the number of sequential pulses of power supply. Optimization studies determine the most favorable operating conditions with regard to an effective performance of the proposed system and maintaining the phase composition of the product obtained.

Measurement of plasma stream velocity in a pulsed plasma accelerator

The measurement of plasma stream velocity in a coaxial pulsed plasma accelerator using two pairs of double plate probe (DPP) is reported in this article. The device produces a quasisteady type high velocity and high energy plasma stream for a duration of a few hundreds of microseconds. A simple arrangement of DPP with capacitor based biasing circuits was developed in-house which detected two different instances of plasma stream reaching the probe plates. This time interval gave the measure of plasma stream velocity using the known distance of separation between the probes. A spectroscopic study of the stream velocity was also performed to validate the findings of DPP. In this experiment, nitrogen and argon gases were considered as the operating medium. The velocities of Argon and Nitrogen were found to be (25 ± 1.5) km/s and (28.5 ± 0.5) km/s, respectively. The energy density of the plasma stream is calculated from the measured velocity, and it is found to be (0.8 ± 0.05) MJ/m2 for argon plasma and (0.3 ± 0.02) MJ/m2 for nitrogen plasma. The value of energy density is significant for studying fusion relevant plasma matter interaction.

Compression of an accelerated plasma cloud in a cone

This paper describes first results of a novel compression method for a plasma by acceleration into a glass cone. The plasma is generated by a pulsed-power-driven coaxial plasma accelerator, prefilled with 2% hydrogen in a helium mixture. The pulse forming network of the experiment has a total capacitance of 27 μF at a maximum voltage of 10 kV. The low inductance of 130 nH leads to an average frequency of about 86 kHz and high current rise rates in the 10 11 A s range. Due to the high current of up to 150 kA, the Lorentz force accelerates the plasma depending on pressure and applied voltage to velocities in the 10 4 m s order. After ejection, the plasma moves into several cone geometries, placed at the end of the electrodes. The conducted studies focus on the Stark-broadening of spectral lines to determine the electron density changes due to the compression. Because of the wide broadening at high electron densities, the well-known Hβ line broadening method is not eligible for cone compressed plasmas. Alternatively, the broadening of the Hα line and a copper line has been used. The achieved electron densities could be increased approximately two orders of magnitude from 1015 cm−3 without the cone to 1017–1018 cm−3 with cone compression.

Modeling of thermalization phenomena in coaxial plasma accelerators

Coaxial plasma accelerators are electromagnetic acceleration devices that employ a self-induced Lorentz force to produce collimated plasma jets with velocities ~50 km s−1. The accelerator operation is characterized by the formation of an ionization/thermalization zone near gas inlet of the device that continually processes the incoming neutral gas into a highly ionized thermal plasma. In this paper, we present a 1D non-equilibrium plasma model to resolve the plasma formation and the electron-heavy species thermalization phenomena that take place in the thermalization zone. The non-equilibrium model is based on a self-consistent multi-species continuum description of the plasma with finite-rate chemistry. The thermalization zone is modelled by tracking a 1D gas-bit as it convects down the device with an initial gas pressure of 1 atm. The thermalization process occurs in two stages. The first is a plasma production stage, associated with a rapid increase in the charged species number densities facilitated by cathode surface electron emission and volumetric production processes. The production stage results in the formation of a two-temperature plasma with electron energies of ~2.5 eV in a low temperature background gas of ~300 K. The second, a temperature equilibration stage, is characterized by the energy transfer between the electrons and heavy species. The characteristic length scale for thermalization is found to be comparable to axial length of the accelerator thus putting into question the equilibrium magnetohydrodynamics assumption used in modeling coaxial accelerators.

A plasma–vacuum interface tracking algorithm for magnetohydrodynamic simulations of coaxial plasma accelerators

The resistive Magneto-hydrodynamic (MHD) model describes the behavior of a strongly ionized plasma in the presence of external electric and magnetic fields. For problems involving the plasma with an open boundary to very low pressure/vacuum regions, the continuum assumption is no longer valid in the entire domain of interest. For example, this is seen in a plasma accelerator where a dense plasma expands into a vacuum background. A common practice to deal with this issue is to assign small values of density and pressure to the vacuum regions and proceed to solve the continuum based MHD equations throughout the domain. We show that this approach fails to produce solutions consistent with the physics of the problem and can give rise to unacceptable artifacts such as spurious shocks. We develop a plasma–vacuum interface tracking approach to mitigate this problem. The plasma–vacuum interface is tracked in a physically consistent manner and the MHD equations are solved only in the regions that contain the plasma. The interface tracking is achieved using a face-flux formulation derived from the theoretical solution to a 1D free expansion problem. Coupled with a threshold based approach, the interface tracking is implemented for both explicit and implicit time stepping frameworks on generalized unstructured grids. Simulations of magnetized thermal plasma jets expanding into a vacuum background indicate plume profiles devoid of the unphysical shock obtained using the small background density approach. In the context of resistive MHD simulations, the interface tracking approach overcomes the numerical stiffness induced by specifying a large background resistivity in the vacuum regions, resulting in significant wall-clock time gains.

Computational and experimental investigation of plasma deflagration jets and detonation shocks in coaxial plasma accelerators

We present a magnetohydrodynamic (MHD) numerical simulation to study the physical mechanisms underlying plasma acceleration in a coaxial plasma gun. Coaxial plasma accelerators are known to exhibit two distinct modes of operation depending on the delay between gas loading and capacitor discharging. Shorter delays lead to a high velocity plasma deflagration jet and longer delays produce detonation shocks. During a single operational cycle that typically consists of two discharge events, the plasma acceleration exhibits a behavior characterized by a mode transition from deflagration to detonation. The first of the discharge events, a deflagration that occurs when the discharge expands into an initially evacuated domain, requires a modification of the standard MHD algorithm to account for rarefied regions of the simulation domain. The conventional approach of using a low background density gas to mimic the vacuum background results in the formation of an artificial shock, inconsistent with the physics of free expansion. To this end, we present a plasma-vacuum interface tracking framework with the objective of predicting a physically consistent free expansion, devoid of the spurious shock obtained with the low background density approach. The interface tracking formulation is integrated within the MHD framework to simulate the plasma deflagration and the second discharge event, a plasma detonation, formed due to its initiation in a background prefilled with gas remnant from the deflagration. The mode transition behavior obtained in the simulations is qualitatively compared to that observed in the experiments using high framing rate Schlieren videography. The deflagration mode is further investigated to understand the jet formation process and the axial velocities obtained are compared against experimentally obtained deflagration plasma front velocities. The simulations are also used to provide insight into the conditions responsible for the generation and sustenance of the magnetic pinch. The pinch width and number density distribution are compared to experimentally obtained data to calibrate the inlet boundary conditions used to set up the plasma acceleration problem.

The nanodimension crystallite formation in steel surface after pulsed plasma flow action

 Absract. This paper presents the analysis of structural-phase changes in samples of stainless steel AISI 321 (12Х18Н10Т) and AISI 201 (12Х15Г9НД), treated by pulsed plasma flows on coaxial plasma accelerator KPU-30. Studied the sequence of phase transitions in modified layers depending on a frequency of treatment. It is shown that after treatment with a small number of shots (n = 2) in the stainless steel samples occurs plasma etching and redistribution of crystallites. At tenfold (n = 10) processing the structure of the surface layer becomes more ordered, appear nanoscale columnar blocks evenly spaced on the surface and their tracks are located mainly at the grain boundaries. The results of SEM and AFM analysis showed the presence of surface melting; this suggests probable structural and phase changes during plasma processing. Changes in the structure of the investigated structural steels, associated with the formation of new phases and the microscopic strains in the crystal lattice, studied by XRD method.       G M T   Английский Испанский Итальянский Казахский Китайский Трад Китайский Упр Корейский Русский Турецкий Французский   Английский Испанский Итальянский Казахский Китайский Трад Китайский Упр Корейский Русский Турецкий Французский                 Звуковая функция ограничена 200 символами     Настройки : История : Обратная связь : Donate Закрыть