Forevacuum Pressure Research Articles

Operating Features of Assisted Hollow Electrode Discharge During Electron-Beam Evaporation of Aluminum in Oxygen in the Fore-Vacuum Pressure Range

Operating Features of Assisted Hollow Electrode Discharge During Electron-Beam Evaporation of Aluminum in Oxygen in the Fore-Vacuum Pressure Range

Modification of ZrO2 ceramic by continuous and pulsed electron beams in the forevacuum pressure range

We describe our study of the treatment of ceramics based on zirconium dioxide (ZrO2), partially stabilized with yttrium oxide (Y2O3) (5.15 % wt.), by continuous and pulsed electron beams in the forevacuum pressure range. We find that continuous electron beam treatment at certain heating rates can lead to changes in the surface structure, with increase in roughness and change in crystalline phase composition. High heating rate leads to increase in the cubic phase of ZrO2. The results of irradiation by a pulsed electron beam depends on the pulse energy density and pulse power of the beam, with noticeable changes in the surface characteristics when the energy density reaches about 10 J/cm2; increased roughness of the ceramic surface is observed at this energy density. Further increase in pulse energy density (>10 J/cm2) and/or power can lead to increase in roughness by an order of magnitude. A change in color of the ceramic surface and formation of a layer with a columnar structure is observed when the energy density reaches 21 J/cm2 at a pulse power of 320 kW. These results show the suitability of electron beam treatment for controlled modification of zirconium dioxide ceramic materials.

Electron-Beam Synthesis of Ceramic-Based Coatings in the Forevacuum Pressure Range

Electron-Beam Synthesis of Ceramic-Based Coatings in the Forevacuum Pressure Range

ALUMINUM OXIDE FILMS FABRICATED BY REACTIVE ELECTRON-BEAM EVAPORATION IN THE FORE-VACUUM PRESSURE RANGE

We have investigated the formation features and measured the electrical and optical parameters of aluminum oxide films fabricated by electron-beam evaporation in oxygen in the range of elevated fore-vacuum pressures. On the basis of the proposed physical model and numerical estimates, a consistent explanation of experimental dependences is given.

APPLICATION OF A NON-SELF-SUSTAINED GLOW DISCHARGE INITIATED BY A FOCUSED ELECTRON BEAM IN THE FOREVACUUM PRESSURE REGION FOR NITRIDING THE INNER SURFACE OF NARROW METAL TUBES

We have explored some of the features of ion-plasma nitriding the inner surface of narrow extended metal tubes by the plasma of a non-self-sustained glow discharge initiated by a focused electron beam in the forevacuum pressure range. The influence of electron beam current on the discharge parameters was determined. We found a non-monotonic dependence of plasma density, nitrogen content in the nitrided surface layer, and layer microhardness on discharge burning voltage. The microhardness of the inner surface of the nitrided tubes reaches values of 1500 kgf/mm<sup>2</sup> for AISI 321 stainless steel and 700 kgf/mm<sup>2</sup> for alloy carbon steel AISI 5135.

ELECTRON-BEAM SYNTHESIS OF ZIRCONIA CERAMIC COATINGS IN THE FOREVACUUM PRESSURE RANGE

We report the results of our experimental investigations on the synthesis of ceramic protective coatings based on zirconium oxide stabilized with yttrium oxide (ZrO<sub>2</sub>-Y<sub>2</sub>O<sub>3</sub>) by electron-beam evaporation of a solid target in the forevacuum pressure range (5-50 Pa). The mass-to-charge composition of the beam plasma was measured in the course of target evaporation. The obtained thick coatings (over 100 μm) have a columnar structure. The article includes analysis of the factors that affect changes in morphology, hardness, and tribological properties of the obtained coatings.

Modification of zirconium dioxide surface by an electron beam in the forevacuum pressure range

Modification of zirconium dioxide surface by an electron beam in the forevacuum pressure range

Effects of the substrate rotation speed on the structure and uniformity of YSZ coatings fabricated by electron-beam synthesis in the forevacuum pressure range

Effects of the substrate rotation speed on the structure and uniformity of YSZ coatings fabricated by electron-beam synthesis in the forevacuum pressure range

Electron-beam nitriding of carbon steel alloy in the forevacuum pressure range

We have explored the ion nitriding of AISI 5135 carbon steel alloy. Nitriding was performed in the plasma formed by an electron beam at the forevacuum pressure of 5 Pa. The beam was generated using a forevacuum-pressure plasma-cathode electron source. We report the results of SEM and X-ray diffraction pattern analysis of the surface of nitrided samples, as well as results of measured micro hardness, surface wear rate, coefficient of friction, roughness, and nitrogen penetration depth. We find that the sample temperature during nitriding affects the surface morphology and phase composition of surface layers. A threefold increase in surface micro hardness was achieved. The surface micro hardness increases with increasing nitriding duration. Samples nitrided at temperatures up to 500°С for a time of no less than 2 h show the greatest abrasive wear resistance. The nitrogen penetration depth is greater than 200 μm for all experimental conditions, with maximum of 450 μm.

Electron-Beam Processing of Aluminum-Containing Ceramics in the Forevacuum Pressure Range

Aluminum–ceramic materials based on Al2O3 and AlN are widely used in the electronics industry and, according to a number of electrophysical and technical and economic parameters, are among the most suitable for the production of electrical and radio engineering products. In this study, it is shown that the treatment of ceramics based on Al2O3 with an electron beam with a power of 200–1100 W and a current of 10–50 mA leads to heating of the ceramic surface to a temperature of 1700 °C. When heated to a temperature of 1500 °C and kept at this temperature for no more than 10 s, an increase in the roughness of the ceramic surface is observed by more than an order of magnitude. At the same time, for ceramic substrates based on aluminum nitride, an increase in the temperature of electron beam treatment from 1300 to 1700 °C leads to an increase in thermal conductivity from 1.5 to 2 times. The edge angle of water wetting of the AlN surface can vary from 20 to 100 degrees depending on the processing temperature, which allows one to control the transition of the material from a hydrophilic to a hydrophobic state. At the same time, electron beam exposure to Al2O3 does not change the wettability of this material so much. Electron beam processing in the forevacuum pressure region allows controlled changes in the electrophysical properties of ceramic materials based on Al2O3 and AlN.

Features of Electron Beam Processing of Mn-Zn Ferrites in the Fore-Vacuum Pressure Range in Continuous and Pulse Modes

The results of electron beam processing of Mn-Zn ferrite samples using pulsed and continuous electron beams in the fore-vacuum pressure range (10 Pa) are presented. We find that continuous electron beam processing leads to surface structuring of the ferrite, changes in elemental composition on the surface, and electrical property modification. The degree of ferrite parameter changes exhibits a threshold behavior. For surface processing temperatures below 900 °C, changes are barely noticeable, while for temperatures over 1100 °C the surface resistance decreases by more than an order of magnitude to values of less than 3 kOhm. Electron beam processing with millisecond pulse duration and pulse energy density exceeding 15 J/cm2 results in the formation of low zinc content melt islands, while the remaining surface area (outside the islands) elemental content and ferrite properties remain largely unchanged. The thickness of the modified layer depends on the processing mode and can be controlled over the range of 0.1–0.5 mm. Due to its low resistance, the modified layer can be utilized to enhance the RF-absorbing properties of the ferrite, which is important in the design of modern magnetic elements of electronic equipment.

Electron-beam synthesis of thin magneto-dielectric coatings with mixed nickel-iron and upper alumina layers

We have synthesized magneto-dielectric coatings with thicknesses 290, 550, 5460 and 6063 nm with an upper protective and electrically insulating layer of alumina ceramic and a lower magnetic iron-nickel layer. The coatings were formed in a helium atmosphere at forevacuum pressures (from 1.5 to 15 Pa) by electron-beam evaporation of a mixture of iron and nickel fragments, and of a solid alumina ceramic target placed in a separate crucible. Magnetic properties of the coatings have been studied by a ferromagnetic resonance technique with estimation of the effective saturation magnetization together with evaluation of the signal-to-noise ratio and relative broadening of the resonance lines. Owing to the layer of alumina ceramic, the values of relative dielectric permittivity (5.6) and electrical conductivity (0.78–3.00 mS/m) remain typical for thin-film dielectrics.

Implantation of tantalum ions into a dielectric coating synthesized by electron-beam evaporation of aluminum oxide ceramic in the forevacuum pressure range

We describe our investigations of the electrophysical properties, phase composition and structure of Al2O3 ceramic particles in coatings formed by electron-beam evaporation of alumina ceramic and modified by implantation of tantalum ions. The ceramic coatings were synthesized in a helium atmosphere in the forevacuum pressure range of 1–10 Pa, at characteristic temperatures of beam target and substrate about 2500 and 250 Celsius, respectively, at a deposition rate of 500 nm/min. Ion implantation was performed using a metal ion source based on a vacuum arc discharge, at pressure of order 10−4 Pa; the mean tantalum ion energy was 90 keV and the implantation doses investigated were 1 × 1016, 5 × 1016, and 1 × 1017 ion/cm2. The original and modified ceramic coating samples were studied using a transmission electron microscopy technique. Measurements of the surface resistivity showed that the treatment of coatings by high-energy tantalum ion implantation leads to increase in specific resistance and decrease in sheet resistance.

Operation Features of a Nonself-Sustained Glow Discharge in a Tube Initiated by a Focused Electron Beam in the Forevacuum Pressure Range

Operation Features of a Nonself-Sustained Glow Discharge in a Tube Initiated by a Focused Electron Beam in the Forevacuum Pressure Range

Beam-generated plasma formation near a dielectric target irradiated by a pulsed electron beam in the forevacuum pressure range

We have investigated the formation of electron beam-generated (EBG) plasma near a dielectric (ceramic) target and an insulated metal target, and the compensation of the negative charge accumulated on the insulated metal target when the targets are irradiated by an intense pulsed electron beam in the forevacuum pressure range (4–15 Pa). It is shown that the density of the EBG plasma near the irradiated ceramic target (or the irradiated insulated metal target) is greater than the plasma density for a beam propagating freely in a vacuum chamber (or for the grounded metal target). The EBG plasma near the target is formed with a certain delay with respect to the electron beam current pulse, because of which the negative potential of the insulated target is also compensated by a delay. The delay time in the formation of the EBG plasma and in the compensation of the target negative potential decreases with increasing gas pressure. Expressions have been proposed for estimating this delay time.

Deposition of layered iron-nickel-alumina ceramic magneto-dielectric thin films using a forevacuum electron source

We present the results of our investigation of layered micrometer-thin magneto-dielectric Fe–Ni–Al2O3 coatings deposited by successive electron-beam evaporation of metal (Fe, Ni) and dielectric (alumina ceramic) targets in an inert gas atmosphere (helium) at forevacuum pressure (3.5 Pa). The low-lying alumina ceramic layer provides the dielectric properties (real parts of the permittivity of 4.34 ± 1.8 and conductivity of 0.143 ± 0.001 S/m), while the magnetic properties are provided by the nickel and iron layers. Studies of the magnetic properties using a ferromagnetic resonance technique show that the effective saturation magnetization of the coatings is 5.5 ± 1.0 kG, which is close to the known value for a fully-metallic nickel layer (6.05 kG).

Effect of thermionic emission on the current in the circuit of a metal collector irradiated by an electron beam in the forevacuum pressure range

We describe the results of our exploration of current flow in the circuit of a metal collector irradiated by an electron beam at enhanced forevacuum pressures in the range of 5–30 Pa. We find that beam heating of the collector surface to a certain critical temperature results in a sharp decrease in the current measured in the collector circuit. It is shown that this decrease is mainly due to thermionic emission from the collector surface. Depending on the collector material, the thermionic current may be as high as 50% or more of the electron beam current.

Specific features of focused electron beam transport through a narrow metal tube at negative potential in the forevacuum pressure range

We describe our investigations on the transport of a focused electron beam through a long and narrow metal tube, held at negative potential with respect to the vacuum chamber walls, in the elevated forevacuum pressure range. We have explored the effect of electron beam parameters and tube potential on beam transport. It is shown that the strength of this effect is connected to the initiation of a non-self-sustained glow discharge within the tube, as well as to the beam magnetic focusing parameters. We also show that increase in the fraction of electrons transported through the tube is conducive to uniformity of the distributions of the non-self-sustained discharge current and the discharge plasma density along the tube length.

ANALYSIS OF FORMATION AND COMPOSITION OF BORON-BASED PROTECTIVE COATINGS OBTAINED BY ELECTRON-BEAM DEPOSITION AT FORE-VACUUM PRESSURES

We have investigated the process of deposition of protective boron-based thin films by electron-beam evaporation of the solid boron target. The spatial distribution of vapor of the evaporated target, temperature during deposition, and the thickness of the deposited coating have been studied, showing that higher deposition rates, coating thicknesses, and substrate temperatures were achieved at small angles (< 20 degrees) and distances (< 7 cm) between the beam and the target. The study of mass-to-charge composition of the beam-produced plasma, morphology, and the elemental analysis of the deposited coatings have demonstrated the high ratio of boron in plasma and in the coating, which has a high degree of uniformity. These findings open up possibility to use such coatings as a hard, wear-resistant top layer in multilayer combined protective and functional coatings.

Механизм ионизации пучковой плазмы, генерируемой электронным пучком в среднем вакууме

We present the results of the measurements of the ionic composition of plasma generated by an accelerated electron beam at medium vacuum (fore-vacuum) pressures. Calculations of the contribution of plasma electrons and beam electrons to the mechanism of ionization are presented. Comparison of the calculated with the experimental data led us to the conclusion about the dominating contribution of beam electrons and to the ionization process.