Electron Beam Heating Research Articles

Comparison study of microstructure, chemical composition and optical properties between resistive heating and electron beam evaporated LaF3 thin films

LaF3 thin films were deposited by electron beam (EB) and resistive heating (RH) evaporation, respectively. Properties such as microstructure, chemical composition, surface morphology and optical constants of the LaF3 thin films were characterized by measurements of X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy and spectrophotometer, then comparison was made between this two deposition methods. It's found that the microstructure properties of the LaF3 films deposited by these two methods were different, and slight content of oxyfluoride films was formed during deposition according to the result of chemical composition analysis. The microstructure of LaF3 bulk materials after interaction with electron beam and resistive heating was also characterized to analyze how the two deposition processes affect the formation of LaF3 thin films and their microstructure properties. When it was for the laser resistance of the films, although the EB evaporated LaF3 thin films occupied lower absorption and optical loss than those of the RH films, they showed slightly smaller laser induced damage thresholds at 355nm, which was thought to be related to their much more rougher surface and higher tensile stress.

Improved mechanical properties of Ti–15V–3Cr–3Sn–3Al alloy by electron beam welding process plus heat treatments and its microstructure evolution

Electron beam welding (EBW) and related heat treatments were carried out on Ti–15V–3Cr–3Sn–3Al (Ti-15-3) alloy plate materials. It was found that the operated parameters in the present EBW process together with suitable heat treatments significantly enhanced the mechanical properties as well as the elongations of the Ti-15-3 weldment, which may provide a promising way for further industrial application. Furthermore, the observed nano size phase of β, α, and here first reported TiCr 2 particle, may form from the solid solution matrix of the Ti-15-3 alloy. The possible mechanisms for these phase formation are discussed.

Effects of Anodic Oxidation Process on Transmittance of Porous Alumina on Glass Substrate

Aluminum films were deposited on glass substrate by electron beam heat evaporation, and porous alumina films with high transmittance were prepared by means of anodic oxidation under different anodizing conditions in oxalic acid solution or phosphoric acid solution respectively. Thus the morphology of these porous alumina films was characterized by different structural. he optical transmittance spectrum at normal incidence over the 300~1000nm spectra region were obtained by spectrophotometer, which shows, in visible and ultraviolet light region, the transmittance of porous alumina films prepared in oxalic acid solution is much better than that prepared in phosphoric acid solution. The SEM analysis results showed that the pores are circular and uniform in porous alumina prepared in oxalic acid but irregular and non-uniform in that prepared in phosphoric acid, which affected the surface roughness of alumina films.

Formation of furans upon electron-beam heating of cellulose

Similarity between cotton cellulose and sulfate and sulfite pine celluloses in degradation during electron-beam distillation has been shown. The yield of the distillate liquid slightly depends on the type of cellulose and makes up ∼60 wt %. The product liquid contains organic compounds with molecular masses of 32 to 128, of which furfural and its derivatives prevail. Electron-beam distillation can be used as an effective method for the manufacturing of furfural and other furan derivatives from cellulose (along with the traditional pentosan conversion processes). It has been shown that grinding and preheating of cellulose lead to an increase in the proportion of furfural and other furans in the condensates.

Morphology and transmittance of porous alumina on glass substrate

The porous optical film has higher threshold of laser-induced damage than densified films, for the study of mechanism of laser-induced damage of porous optical film with ordered pore structure. Porous anodic alumina (PAA) film with high transmittance on glass substrate has been prepared. Aluminum film was deposited on glass substrate by means of resistance and electron beam heat (EBH) evaporation. Porous alumina was prepared in oxalic acid solution under different anodizing conditions. At normal incidence, the optical transmittance spectrum over 300–1000nm spectra region was obtained by spectrophotometer. SEM was introduced to analysis the morphology of the porous alumina film. The pore aperture increased with the increase of anodizing voltage, which resulted in a rapid decrease of the pore concentration and the optical thickness of porous alumina film. Damage morphology of porous alumina film is found to be typically defects initiated, and the defect is the pore presented on the film.

Computer-control of surface science experiments with LabVIEW

LabVIEW TM 2009-based remote and process control program for an ultra-high vacuum system and a variety of surface science experiments is presented. The apparatus consists of five individual recipients for sample preparation, surface analysis, scanning tunneling microscopy and a central chamber connecting them by means of gate-valves. All processes like electron-beam heating, ion sputtering, gas exposure, thermal and electron-beam evaporation, analysis techniques, sample manipulation can run under full automatic control; transfers are supported. A variety of useful auxiliary functions are implemented to control bake-out processes, titanium sublimation pumps, pressure regulation of leak valves but also data acquiring, automatic reporting through ftp and emails, as well as external communication and control via a TCP/IP connection with a portable PC. Important features of the software include a time- control module to operate up to five channels (repetitive heating, sputtering, gas exposure, evaporation and manipulation to evaporation positions) as well as full process control. Such tools allows us to set up automatically processed experiments that include e.g. the preparation of single-crystal surfaces, their AES (Auger electron spectroscopy) and LEED (low energy electron diffraction) analysis as well as the evaporation and various treatments of thin films.

Stabilization of the process of electrohydrodynamic dispersion of metals with electron-beam heating

The stability of the process of nanostructure formation during the electrohydrodynamic dispersion of metals with electron-beam heating has been studied. The main factors responsible for the process breakage are considered and conditions under which the passage to a stable setup operation regime does not lead to a decrease in the efficiency of nanoparticle formation are determined. It is established that the formation of nanoparticles in this regime is a quasi-stationary process, in which the particle flux appears as a constant background with pulsations of 50% amplitude.

Numerical study of the influence of the technological parameters on the composition and stressed-deformed state of a coating synthesized under electron-beam heating

A model for the synthesis of a substrate-based coating under heating by a moving energy source typical for electron-beam treatment has been suggested and analyzed. It has been taken into account that the condensed-phase chemical conversions are accompanied by volume changes and mechanical stresses and deformations in addition to those caused by high temperature gradients. It has been assumed that the correlations between the components of stress and deformation tensors satisfy the Duhamel-Neumann equation. The distributions of temperature and the element and compound concentrations, and well as the tensor components for stresses and deformations accompanying the process of synthesis, have been determined at different time moments. It has been shown that it is principally important for the determination of possible synthesis regimes and the synthesized coating composition to take into account the interlinked character of the physicochemical and mechanical processes.

Development of a Lithium Beam Probe and Measurement of Density Pedestal in JT-60U

A lithium beam probe (LiBP) has been developed for the measurement of electron density profiles with highly spatial and temporal resolutions in JT-60U. Using an electron beam heating ion source with a capability of 10 mA extraction, a 5.5 mA beam has been injected to the plasmas. It corresponds to the equivalent neutral beam current of 2 mA. A spectrum width of the beam emission has been small enough to separate Zeeman splitting. By use of the LiBP, time evolutions of pedestal density profiles during type I and grassy edge localized modes (ELMs) have been obtained for the first time. After a type I ELM crash, the drop of the line-integrated density measured by an interferometer delays by 2 ms later than that of the pedestal density. Comparing the line-integrated density to the line integration of the edge density profile measured by the LiBP, it is found that the recovery from the type I ELM crash is correlated with the reduction of core plasma density. As for grassy ELMs, grassy ELMs have smaller density crashes than that of type I ELMs, which is mainly derived from the narrower ELM affected area.

ロケット燃焼室におけるニッケル電鋳特性向上に関する基礎研究

For the regenerative cooling cycle LNG rocket engines, improvement Nickel Electroforming technology and analysis are the major problem because of high reliability and low cost at the design and fabrication. This paper describes analysis methods, results and the successful Improved Nickel Electroforming of the stress and strain level at the Electron beam heat zone.

Zigzag zinc blende ZnS nanowires: Large scale synthesis and their structure evolution induced by electron irradiation

Large scale zigzag zinc blende single crystal ZnS nanowires have been successfully synthesized during a vapor phase growth process together with a small yield of straight wurtzite single crystal ZnS nanowires. AuPd alloy nanoparticles were utilized to catalyze a vapor-solid-solid growth process of both types of ZnS nanowires, instead of the more common vapor-liquid-solid growth process. Surprisingly, the vapor-phase grown zigzag zinc blende ZnS nanowires are metastable under high-energy electron irradiation in a transmission electron microscope, with straight wurtzite nanowires being much more stable. Upon exposure to electron irradiation, a wurtzite ZnO nanoparticle layer formed on the zigzag zinc blende ZnS nanowire surface with concomitant displacement damage. Both electron inelastic scattering and surface oxidation as a result of electron-beam heating occur during this structure evolution process. When prolonged higher-voltage electron irradiation was applied, local zinc blende ZnS nanowire bodies evolved into ZnS-ZnO nanocables, and dispersed ZnS-ZnO nanoparticle networks. Random AuPd nanoparticles were observed distributed on zigzag ZnS nanowire surfaces, which might be responsible for a catalytic oxidation effect and speed up the surface oxidation-induced structure evolution.

Seedless Synthesis and Thermal Decomposition of Single Crystalline Zinc Hydroxystannate Cubes

Single crystalline zinc hydroxystannate [ZnSn(OH)6] micro- and nanocubes have been successfully grown on pure tin substrates via a seedless hydrothermal synthesis method. Each ZnSn(OH)6 cube is enclosed by six equivalent {001} crystal planes. Cube size and aerial density were adjusted by controlling the reaction time and addition of diaminopropane (DAP) reagent. The hexamethylenetetramine- and DAP-assisted etching of the oxidized tin metal surface is found to play an important role in the nucleation and growth of the zinc hydroxystanate cubes. Synthesis at higher zinc nitrate concentrations as well as secondary growth resulted in the formation of ZnO nanorods in addition to the cubes. In situ scanning electron microscopy and transmission electron microscopy, thermal gravimetric analysis, and differential scanning calorimetry have been utilized to investigate the ZnSn(OH)6 thermal decomposition process. The appearance of endothermic peak near ∼540 K, attributed to the ZnSn(OH)6 decomposition, was correlated with morphology changes induced via resistive thermal annealing and localized electron beam heating.

Evolution of a Two-Temperature Plasma Expanding With Metal Vapor Generated by Electron-Beam Heating

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> During the electron-beam evaporation of metals, a weakly ionized plasma is formed, which consists of two different groups of electrons characterized by different energy spreads (or temperature). While this plasma expands along with the metal vapor, a thermodynamic equilibrium between these two groups of electrons is gradually established by electron–electron Coulomb collisions and electron–atom inelastic collisions. The evolution of this two-temperature plasma was experimentally observed by a Langmuir probe during an electron-beam evaporation of zirconium. Mathematical expressions for the effect of different interactions on the evolution of the electron temperatures of the plasma were derived and applied to our experimental observations. Taking the initial temperature of the plasma at the source of vapor, the total cross section for electron–atom inelastic collisions was calculated, the order of which agreed well with the reported values. Finally, the contributions of each type of interaction (electron–electron and electron–atom) on the cooling of the high-temperature group of electrons in the plasma are quantified. </para>

Preparation and electrochemical characterization of low-index rhodium single crystal electrodes in sulfuric acid

The electrochemical properties of low-index phase Rh(1 1 1), Rh(1 1 0) and Rh(1 0 0) single crystal bead electrodes, prepared by a novel technique combining electron beam heating with inductive annealing in a controlled atmosphere, have been characterized in 0.1 M H 2SO 4 by cyclic voltammetry and chronoamperometry. Hydrogen and sulfate adsorption as well as surface oxidation depend strongly on the crystallographic orientation of the surface. The potentials of zero total charge ( E pztc) of all three Rh electrodes in 0.1 M H 2SO 4 were determined by the combination of charge displacement and voltammetric experiments. The charge balance reveals unambiguousely that the (√3 × √7) adlayer on Rh(1 1 1) is composed of specifically adsorbed sulfate ions eventually coadsorbed with water molecules. Hydrogen-sulfate coadsorbed with hydronium ions could be excluded. The kinetics of sulfate ion desorption followed by the adsorption of hydrogen at less positive potentials could be represented by a nucleation and growth mechanism coupled with a parallel first order process. The electro-oxidation of irreversibly adsorbed carbon monoxide monolayers was also investigated and revealed distinct structure sensitivity. The reaction pathway on all three low-index phases of Rh proceeds according to a Langmuir–Hinshelwood mechanism and is controlled by nucleation of OH ads at steps and other defect sites followed by a complex growth process on terrace sites. The low surface mobility of CO ads leads to a slow and incomplete CO monolayer electro-oxidation on Rh(1 1 1). The high density of step sites on Rh(1 1 0) and the reversible formation of oxygenated species on Rh(1 0 0) at rather low potentials significantly enhance the electro-oxidation activity leading to the following reactivity sequence: Rh(1 1 1) ≪ Rh(1 1 0) ∼ Rh(1 0 0). The shape of the experimental transients and attempts to model them demonstrate the occurrence of at least two processes occurring in parallel. The long-term response represents clearly a process involving a slow surface-diffusion step.

Electron beam interaction, damage and reconstruction of hydroxyapatite

Abstract Synthetic hydroxyapatite (HAP) samples were observed in the high resolution transmission electron microscope (HRTEM) using an electron beam of 400 kV and, after formation of “voids”, the reconstruction of its structure was recorded. This phenomenon is most possible due to various electron–crystal interaction mechanisms, such as ballistic knock-on damage, electron-beam heating, etc., but it is still not quite sure which of them creates these contradictory phenomena. This is the first time that a process of destruction/reconstruction in apatite crystals under electron irradiation is reported.

Oxygen Ordering and Mobility in YBaCo4O7+δ

Extraordinary oxygen ordering and mobility have been found in an oxygen-nonstoichiometric mixed-valence cobalt oxide, YBaCo(4)O(8.5). The excess oxygen atoms appear to be incorporated in an orderly way into the YBaCo(4)O(7) parent lattice with different configurations as the oxygen content varies. Intense electron-beam irradiation was used to observe recurrent oxygen migration in the lattice, causing reversible structural modulation transitions. The oxygen migration can be attributed mainly to the electron-beam heating effect. This study highlights the high degree of freedom of surplus oxygen within the investigated structure and advances our understanding of the oxygen diffusion process in related transition-metal oxide systems.

Electron-beam degradation of wood: 1. Dry distillation products

Electron-beam heating to ≥270°C initiates the process of dry (destructive) distillation of wood. Birch, aspen, alder, spruce, and pine wood is decomposed yielding liquid organic products (55–61 wt %), gas (13–18 wt %), and charcoal. The liquid largely consists of carbonyl compounds. The furan fraction makes up approximately one fifth. The liquid produced from softwood is heavier and is rich in phenolic compounds. The products of dry distillation upon wood irradiation in a stream of propane and butanes are enriched in liquid alkanes, alcohols, and ethers. The feasibility of conversion of the condensable products into regular liquid fuel is discussed.

Analysis of electrical and thermal responses of n-doped silicon to an impinging electron beam and joule heating

A detailed numerical simulation for electron-beam heating of n-doped silicon is presented. Electron-beam penetration is modeled using electron-beam transport equation (EBTE). The EBTE is solved by using a Monte Carlo (MC) method to determine the electron deposition distributions, including electron density deposition and optical phonon generation. Electron and phonon temperatures of the film are then determined using electron–phonon hydrodynamic equations (EPHDEs) coupled with the deposition distributions obtained from the MC simulation. The combined EBTE and EPHDEs results indicate that an electron beam creates a depletion region near the surface of incidence and causes non-equilibrium between electron and phonon temperatures.

Electron irradiation-induced nanocrystallization of amorphous Fe 85B 15 alloy: Evidence for athermal nature

Nanocrystallization of amorphous alloys induced by electronic energy deposition has been frequently reported in recent years. In this paper, the crystallization of amorphous Fe 85B 15 alloy was performed by electron irradiation with 2 MeV electrons up to a flux of 4.0 × 10 24 m −2 s −1. It was found that at 298 K, nanocrystalline Fe–B intermetallic phases formed prior to α-Fe phase, while at 463 K, only the α-Fe phase was observed. This phenomenon cannot be interpreted in terms of the electron-beam heating, but may be attributed to the irradiation-induced increases in the short-range order and atomic diffusivity. Theoretical analysis also showed that the maximum-temperature rise driven by beam heating is much lower than that required for thermal crystallization. Our work offers strong evidence that the irradiation-induced crystallization in amorphous alloys is not a thermal activation process.

New vacuum electron beam processing method based on temperature closed-loop control

This is a novel combination of vacuum electron beam (EB) processing and automatic control theory. The concept of full EB processing method was presented. The digital control system for temperature closed-loop control in EB processing based on scanning track control was realized. The method of controlling electron beam current and heating power by real-time adjusting grid bias voltage is feasible. EB processing methods consist of two stages: heating-up stage and temperature maintaining stage. In the former stage, a fuzzy controller was used to control the temperature rising velocity, the sensitivity of the control was evaluated; in the latter stage, an integral separation PID controller was used to keep the workpiece's temperature constant, ideal static and dynamic performances were obtained. The temperature rising velocity control and the maintaining control compose the full EB processing method, the transition of the two stages is bumpless.