Forevacuum Pressure Range Research Articles

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

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

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.

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

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

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.

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.

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.

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

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.

Формирование плазмы в атмосфере азота импульсным электронным пучком вблизи диэлектрической мишени при форвакуумных давлениях

Features of the processes of beam plasma formation near a dielectric (aluminum oxide ceramic) target being irradiated by an intense pulsed electron beam in the forevacuum pressure range (4–15 Pa) have been investigated. It has been established that the density of the beam plasma near the irradiated dielectric target is higher than in the case of "free" propagation of the electron beam. The observed increase in plasma density depends on the emission current (electron beam current), gas pressure, and accelerating voltage. The influence of the dielectric target on the beam plasma density is due to emission of electrons from the target surface and the uncompensated negative potential on the target surface, which determines the energy of emitted electrons. An increase in gas pressure leads to a smaller increase in the beam plasma density due to a decrease in the absolute value of the negative potential. Varying the electron beam current and accelerating voltage provide to control the beam plasma density.

Determination of the degree of ionization of vapors of conducting and dielectric materials during electron-beam evaporation in the forevacuum range of pressure

We describe a method that uses a condensation probe for measuring the degree of ionization of the vapor of electron-beam evaporated materials in the forevacuum pressure range. The probe design and its working principles are described. The degree of ionization of solid targets evaporated by an electron beam is shown to exceed 65%.

Focused electron beam transport through a long narrow metal tube at elevated pressures in the forevacuum range

We present here our investigations of the features of focused electron beam transport in free space at elevated pressures of a few pascals. We have explored the effect of the beam accelerating voltage, operating gas pressure, and magnetic focusing upon the trajectory of beam electrons in the crossover region, in particular on the beam convergence and divergence angles. It is shown that for the forevacuum pressure range of 2–5 Pa explored, a distinctive feature of the propagation of a focused electron beam with a current of up to 20 mA at an accelerating voltage of 10–20 kV is the difference in the angles of convergence (before the focus) and divergence (after the focus). Whereas at a low pressure of 2 Pa the divergence angle is smaller than the convergence angle, as the pressure increases the divergence angle increases and for pressures greater than 5 Pa the divergence angle is greater than the convergence angle. The results obtained were used in experiments on electron beam transport through a long narrow metal tube with a diameter of 5.8–9.2 mm and length of 10–30 cm. We show that for a 30 cm long tube of 7.5 mm diameter, the focused beam transmission can exceed 70%.

Electron-Beam Deposition of Metal and Ceramic-Based Composite Coatings in the Fore-Vacuum Pressure Range

We present the experimental results on the fabrication of metal-ceramic coatings by electron-beam evaporation of alumina ceramic and copper powder composites with different fractions of the components (with Cu powder fraction from 0.1 to 20%) pre-sintered by an electron beam. The mass-to-charge composition of the multi-component plasma, generated in the electron beam transport region, was measured, demonstrating that the fraction of target ions in plasma grows with the electron beam power density. The morphology and electrical conductivity of fabricated coatings were investigated; it was found that the increase in Cu fraction in the deposited coating from 0 to 20% decreases both the volumetric and surface resistance of the coatings in around 8 orders of magnitude, thereby being a convenient tool to control the coating properties.