High-intensity Electron Beam Research Articles

Effect of high intense electron beam irradiation on structural and Raman properties of boron carbide micro powder

In the presented work, a boron carbide sample with a purity of 99.9%, particle size [Formula: see text]–[Formula: see text]m and a density of [Formula: see text] was used. Boron carbide samples were irradiated with linear electrons in the energy range of 2.5 MeV at the doses of [Formula: see text], [Formula: see text] and [Formula: see text] at room temperature. XRD results show that only in the crystal structure of [Formula: see text] compound, among boron carbide samples irradiated in the dose rate from [Formula: see text] to [Formula: see text] phase transition does not occur. The observed decrease in the lattice parameter values was explained as the strengthening of the bonds as a result of the recombination of defects in the crystal by influencing electron fluence. Dynamics of Raman spectra change and analytic analysis of intensive and duplex modes in various electron fluxes in ([Formula: see text]) CBC-structure were performed and the occurring disorder in Raman active has been identified.

Electron beam-induced changes in tips of multi-walled carbon nanotubes with/without Au nanoparticles

Tips of multi-walled carbon nanotube of dissimilar shapes with/without gold nanoparticles are irradiated under electron beam. The tips become meta-stable and cause reduction in lengths of tubes under a high intense uniform electron beam by their smaller radius of curvature when the diffusion and evaporation of carbon atoms are activated. Meanwhile, normal-tube-tips and volcano-tube-tips with/without gold nanoparticles present dissimilar changes in their diameters. The gold nanoparticles with size ≥ 3 nm not only slow down length reduction process in the normal-tube-tips and increase tips diameters but also increase their size on the normal-tube-tip by the interaction and growth, while gold nanoparticles with size ≤ 1.5 nm retard the length reduction process in volcano-tube-tips without any change in the tips diameters. Furthermore, they also activate formation of carbon shells over their surface and keep their positions fixed on the volcano-tube-tip. This abnormal interaction of gold nanoparticles with the unstable tips is elucidated in terms of irradiation-induced activation of the graphitic layers, diffusion of Au atoms and bonding between adjacent large (≥ 3 nm) Au NPs, and catalytic effects of small (≤ 1.5 nm) Au NPs. The method can be employed to modify nanotubes with almost atomic precision and to create a predefined pattern of metal nanoparticles on tube tips and surface.

Impact of O16(e,e′α)C12 measurements on the C12(α,γ)O16 astrophysical reaction rate

The $^{12}$C($\alpha,\gamma$)$^{16}$O reaction, an important component of stellar helium burning, has a key role in nuclear astrophysics. It has direct impact on the evolution and final state of massive stars and also influences the elemental abundances resulting from nucleosynthesis in such stars. Providing a reliable estimate for the energy dependence of this reaction at stellar helium burning temperatures has been a longstanding and important goal. In this work, we study the role of potential new measurements of the reaction, $^{16}$O($e,e'\alpha$)$^{12}$C reaction, in reducing the overall uncertainty. A multilevel $R$-matrix analysis is used to make extrapolations of the astrophysical S factor for the $^{12}$C($\alpha,\gamma$)$^{16}$O reaction to the stellar energy of 300 keV. The statistical precision of the $S$-factor extrapolation is determined by performing multiple fits to existing $E1$ and $E2$ ground state capture data, including the impact of possible future measurements of the $^{16}$O($e,e'\alpha$)$^{12}$C reaction. In particular, we consider a proposed MIT experiment that would make use of a high-intensity low-energy electron beam that impinges on a windowless oxygen gas target as a means to determine the total $E1$ and $E2$ cross sections for this reaction.

A novel shaped-controlled fabrication of nanopore and its applications in quantum electronics

High-intensity (107–108 A m−2) electron beams can be used to fabricate nanoscale pores. This approach enables real-time observation of nanopore drilling and precise control of the diameter of the nanopore. Nevertheless, it is not suitable for tuning the nanopore’s sidewall shape. In this study, we demonstrate the use of low-intensity electron beams to fabricate nanopores on a silicon nitride (SiNx) membrane. This technique allows the precise adjustment of the nanopore dimension and the shaping of its three-dimensional (3D) nanostructure. The 3D structures of the nanopore were evaluated by electron tomography, and series of oblique images were used in reconstructing the 3D images of nanopores using a weighted back-projection method. The sidewall shape of the nanopore was observed at different electron-beam conditions, and the formation mechanism was elucidated based on these results. The nanopore fabricated with this technique can be used as a template to develop electronics at the nanoscale based on which a quantum-dot device can be prepared with a simple evaporation process. The measured results show that the device can resolve well-defined electronic states that are characteristic for the behaviors of the quantum-dot device.

Effect of electron beam processing on structure of electroexplosion coating of ZnO-Ag system

The structure, phase composition of the composite electroexplosion coating of ZnO- Ag system subjected to the irradiation by the high intense electron beam have been studied for the first time. The combined processing including the electroexplosion spraying of the coating of ZnO-Ag system and its subsequent electron beam processing results in the formation of multilayer structure of the coating. The electron beam melts and homogenizes the surface layer of the composite electroexplosion coating of ZnO-Ag system to the depth of 35-40 μm. The effect of the electron beam leads to the formation of the nanocrystalline phases of Ag, ZnO, Cu, CuZn, Ag5Zn8, Cu2O, Ag2O, Cu0.67Zn0.33, AgZn. The dependences of changes in crystal lattice parameters and coherent scattering regions of the phases being formed depending on the processing regime by high intense electron beam have been found.

Structural-Phase State and Properties of Steel After Plasma-Electron Modification

The results of investigation of phase and elemental compositions, defect substructure states, mechanical and tribological properties of the modified surface of Steel Gr1 are presented. The process of modification consists in plasma spraying of a Ni–Cr–B–Si-based powder coating followed by its irradiation with a high-intensity pulsed electron beam. It is shown that the coating surface formed by plasma spraying contains micro- and macro-pores and is characterized by high relief. A subsequent processing of the modified surface with a highintensity pulsed electron beam of a submillisecond duration in the mode of surface layer melting is accompanied by smoothing of the coating surface, saturation of the surface layer crystal lattice with Ni, Cr, B and Si atoms, formation of submicron cells of dendritic recrystallization, precipitation of nanosized particles of the second phase, and formation of quench structure. When combined, these treatments result in the formation of a hardened layer up to 1500 μm in thickness, whose microhardness and wear resistance by 4.6–6.5 and 4 factors exceed the respective characteristics of the initial steel.

Friction and wear behavior of WC/Ni cemented carbide tool material irradiated by high-intensity pulsed electron beam

The friction and wear behavior of high-intensity pulsed electron beam (HIPEB)-irradiated YN13 cemented carbide at energy density of 34 J/cm2 and 10 pulses with pulse frequencies of 1 and 5 Hz were investigated in this work by dry sliding wear test against hardened GCr15 bearing steel at 98 N and 0.47 m/s. Surface characterization was conducted by using scanning electron microscope, surface profilometer, X-ray diffraction and Vickers microhardness tester. The dominant wear mechanisms were identified by the worn surface morphologies. The results indicated that an intense surface remelting and ablation/evaporation was induced by HIPEB irradiation with high pulsed frequency, which resulted in the surface roughening, WC phase transformation and improved tribological properties of the YN13 cemented carbide. The specific wear rate and friction coefficient decreased as pulsed frequency increased. When pulsed frequency increased to 5 Hz, they decreased to 53.5% and 70% for non-irradiated samples. The improvement in wear resistance and the significant friction reduction of irradiated samples with the increase in pulsed frequency should be ascribed to the roughening of surface, the refinement microstructure of remelting, and the decrease in irradiated defect in the remelted layer of irradiated YN13 cemented carbide. The main wear mechanism of irradiated YN13 cemented carbide/GCr15 bearing steel pairs was micro-cutting wear in the initial stage of dry sliding wear and abrasive wear with characteristics of Ni preferential removal and fallout of WC similar to the non-irradiated samples in the stable stage.

Increase in Wear Resistance of the Surface Layers of AK10M2N Silumin at Electron-Beam Treatment

It is established that the electron-beam treatment of AK10M2N silumin by a pulsed electron beam with the specific energy of 35 J/cm2 leads to the increase in the surface layer microhardness from 0.99 up to 1.18 GPa with the simultaneous decrease in the friction coefficient by 1.3 times and in the wear coefficient by 6.6 times. After irradiation, a multilayer gradient structure is formed in the surface layer of the silumin. In the surface layer, there are no inclusions of the second phase, whereas in the deeper transient layer there are primary precipitations of intermetallic phase, which are the centers of aluminum crystallization. It is found that the changes in the mechanical and tribological properties of the silumin surface layers are associated with significant structural transformations, for instance, with the dissolution of silicon and intermetallics during irradiation of material with a high-intensity pulsed electron beam.

Structure and Properties of Electro-Explosive TiC–Ni–Mo Coatings of Die Steel after Electron-Beam Treatment

In this paper, we studied the phase and elemental composition of the surface layer of die steel 5KhNM subjected to electro-explosive sputtering deposited composite TiC–Ni–Mo coating and subsequent pulsed irradiation with a high-intensity submillisecond electron beam. The modes of electron-beam processing providing the formation of a dense, with a mirror gloss, surface layer with a submicrocrystalline structure based on titanium carbide and intermetallic compounds based on Mo, Ni, and Ti are determined. The electron-beam processing of an electro-explosive coating in the melting mode is shown to lead to the formation of a structurally uniform and concentration-uniform surface layer. TiC–Ni–Mo coatings have a 1.26 times higher wear resistance compared to die steel 5KhNM used as a substrate. The microhardness of the formed coatings is 450–2400 HV, the nanohardness is 25.5 GPa, and the modulus of elasticity is E = 398 GPa.

Pn -type substrate dependence of CsK2Sb photocathode performance

The CsK2Sb photocathode is capable of generating a high-intensity and low-emittance electron beam with visible laser light. In this study, we examined CsK2Sb photocathode evaporation on n- and p-type Si(100), GaAs(100), and Si(111) substrates, and compared their cathode performance. We found that the quantum efficiency of the p-type substrate was superior to that of the n-type substrate for the same substrate material and surface orientation. We show that this can be qualitatively analyzed by an energy-band model for the semiconductor(metal)-semiconductor junction between CsK2Sb and the substrate. We also evaporated the Cs3Sb cathode on n- and p-type Si(100) and GaAs(100) substrates, and confirmed that the cathode performance of all substrates was consistent with the model results. This finding indicates the possibility of improving the thin-film cathode performance by revisiting the semiconductor(metal)-semiconductor junction between the cathode and the substrate, which improves the understanding of high-performance photocathodes.

Evolution of the Structure and Properties of AK10M2N Silumin under Irradiation with a High-Intensity Pulsed Electron Beam

The structure of cast AK10M2N silumin has been studied by scanning electron microscopy. The results demonstrate that the silumin is a multiphase material containing silicon and intermetallic inclusions. Irradiation of silumin with a high-intensity electron beam has been shown to be accompanied by melting of the surface layer, dissolution of the silicon and intermetallic inclusions, formation of a cellular crystallization structure, and secondary precipitation of submicron- and nanometer-sized second-phase particles. Dispersion of the structure of the surface layer is accompanied by an improvement of the mechanical properties of the silumin.

Record high-gradient SRF beam acceleration at Fermilab

Many modern and future particle accelerators employ high gradient superconducting RF (SRF) to generate beams of high energy, high intensity and high brightness for research in high energy and nuclear physics, basic energy sciences, etc. In this paper we report the record performance large-scale SRF system with average beam accelerating gradient matching the International Linear Collider (ILC) specification of 31.5 MV m−1. Design of the eight cavity 1.3 GHz SRF cryomodule, its performance without the beam and results of the system commissioning with high intensity electron beam at Fermilab Accelerator Science and Technology (FAST) facility are presented. We also briefly discuss opportunities for further beam studies and tests at FAST including those on even higher gradient and more efficient SRF acceleration, as well as exploration of the system performance with full ILC-type beam specifications.

Influence of irradiation with a high-intensity pulsed electron beam on mechanical properties and structural states of coatings formed by plasma spraying

The purpose of the present studies is to establish the formation patterns of the structure and properties of the surface layer of 060A35 steel modified using a combined method that includes plasma spraying of a powder coating and the subsequent irradiation with an intense pulsed electron beam. Plasma spraying on the surface of a steel powder of the system Ni-Cr-B-Si (PGSR-4 with a fraction of 80-100 μm) was performed on the original installation equipped with two plasma generators. The irradiation of the modified steel layer was carried out with an intense pulsed electron beam on the installation SOLO. The investigation of the phase and elemental composition, the state of the defective substructure were carried out using methods of X-ray phase analysis, optical and scanning electron microscopy. The mechanical properties of the irradiated surface were characterized by microhardness. It is shown that plasma spraying of a powder coating leads to formation of a high-relief surface containing micro- and macropores. The subsequent treatment of the modified surface with an intense pulsed electron beam of a submillisecond duration in the melting mode of the surface layer is accompanied by smoothing of the coating surface, saturation of the crystalline lattice of the surface layer with Ni, Cr, B and Si atoms, formation of dendritic crystallization cells of submicron sizes, release of nanoscale particles of the second phase, formation of a quenching structure. Together, this has allowed to increase the microhardness of the modified layer in 4.6-6.5 times.

Tungsten carbide phase transformation under non-equilibrium solidification of high intensity pulsed ion and electron beams

The WC-13Ni cemented carbides irradiated by high-intensity pulsed ion beam (HIPIB, 300 keV, 2–6 J/cm2, 70 ns) and high-intensity pulsed electron beam (HIPEB, 127 keV, 3–34 J/cm2, 180 ns) have been investigated by using scanning electron microscopy, surface profilometer and X-ray diffraction in order to explore the mechanisms of phase transformation. It was found that in both cases beams irradiation with higher energy density resulted in obvious surface remelting and phase transformation from WC to WC1-x, expect that W2C was also found for HIPEB-irradiated samples. However, surface morphology differed greatly in the two cases, HIPIB irradiation induced significant selective ablation of nickel binder, forming a wavy surface of “hill-valley” topography, whereas HIPEB irradiation caused notable surface melting but with less selective ablation, forming a flatter surface with occurrence of apparent cracks and blow holes. The formation of WC1-x phase during the process of beams irradiation should be attributed to the reaction ablation of carbon in the WC and the eutectic reaction at ∼2995 K, while the formation of W2C phase was resulted from the eutectic reaction at ∼2925 K and WC1-x decomposition during the more longer melting process of HIPEB irradiation.

Corrosion Resistance of Additively Manufactured 625 Inconel Alloy in Seawater

Additive manufacturing (AM) of metals and metal alloys offers advantages of fast and flexible design of parts of various shapes, and low-waste operation. AM manufacturing of metals/alloys involves building materials layer-by-layer from a metal/alloy powder. The powder in each layer is melted by a high intensity laser or electron beam, and individual particles within the layer and between consecutive layers are fused together during this process. Due to peculiarities of manufacturing process, microstructure of AM manufactured alloys are significantly different from their cast or wrought counterparts [1-5]. Previous research has shown that depending on AM and post-processing parameters the difference in microstructure may be detrimental [5] or beneficial [3] for corrosion resistance of AM-manufactured alloys. For example, corrosion resistance of AlSi10Mg alloy made by selective laser melting (SLM) and subsequently heat-treated for 2 h at 300oC was found to be similar to that of the gravity cast alloy, while its corrosion fatigue endurance turned out to be superior to that of the cast alloy [3]. Here, we compare corrosion behavior of 625 Inconel alloy manufactured by SLM to its wrought counterpart in the marine environment. We find that the initial polarization curves look almost identical for 625 AM and 625 wrought specimens both in 0.6 M NaCl and ASTM seawater (Fig. 1). However, the difference in open circuit potential (OCP) and microstructure of two specimens suggest different composition of surface oxides and potentially different rates of their dissolution. In order to understand how variations in microstructure and surface composition affect alloys’ long-term corrosion resistance, we perform ex-situ surface characterization and in-situ analysis of alloy dissolution while holding electrode potential at -1, -0.5, 0.5 and 1V vs Ag/AgCl reference electrode. Electrochemical experiments were conducted in three-electrode flat electrochemical cells (PAR, Inc). Freshly polished coupons of 625 AM or 625 wrought Inconel alloys served as working electrodes (WEs), while platinum mesh and Ag/AgCl in 3 M NaCl (BioLogic, Inc) were used as a counter and reference electrodes, respectively. Initial corrosion properties of the alloy electrodes were characterized by linear polarization resistance and potentiodynamic measurements. Alloy dissolution experiments were conducted in potentiostatic conditions, and concentrations of dissolved metal species were determined by ICP-MS. X-Ray Photoelectron Spectroscopy was used to determine chemical speciation of the samples after exposure to OCP and carrying out alloy dissolution experiments.

Empirical modeling of high-intensity electron beam interaction with materials

The paper proposes an empirical modeling approach to the prediction followed by optimization of the exact shape of the cross-section of a welded seam, as obtained by electron beam welding. The approach takes into account the electron beam welding process parameters, namely, electron beam power, welding speed, and distances from the magnetic lens of the electron gun to the focus position of the beam and to the surface of the samples treated. The results are verified by comparison with experimental results for type 1H18NT stainless steel samples. The ranges considered of the beam power and the welding speed are 4.2 – 8.4 kW and 3.333 – 13.333 mm/s, respectively.

Electron-beam modification of a surface layer deposited on low-carbon steel by means of arc spraying

State-of-the-art means of physical materials science are used to study the structure, phase composition, defect substructure, and tribological properties of a coating formed on low-carbon Hardox 450 martensite steel via the electrocontact deposition of an Fe–C–Ni–B wire and modified through subsequent irradiation with high-intensity pulsed electron beams. It is shown that electron-beam treatment results in the formation of a modified 50-μm thick surface layer, the main phases of which are the α-phase, iron boride FeB, and boron carbide B4C. In the layer modified by electron-beam treatment, the transverse size of batch martensite crystals is reduced by a factor of 3, relative to the initial Hardox 450 steel, and ranges from 50 to 70 nm. It is established that the wear resistance of the deposited layer after electron-beam treatment grows by more than 20 times with respect to the wear resistance of Hardox 450 steel, and the friction coefficient is reduced by a factor of 3.5. The microhardness of a deposited layer ~7 mm thick is more than double that of the base metal.

Dry Sliding Wear Mechanism of WC–13Ni Hard Alloy Irradiated by High-Intensity Pulsed Electron Beam

The wear properties and wear mechanism of WC–13%Ni hard alloy irradiated by high-intensity pulsed electron beam (HIPEB) at energy density of 34 J/cm2 with pulse numbers of 1–10 were investigated by dry sliding wear tests. The phase structure, cross-sectional microstructure and microhardness-depth profiles of the irradiated WC–13Ni hard alloy were examined by using X-ray diffractometer, scanning electron microscopy and Vickers testers, respectively. It was found that HIPEB irradiation induced surface remelting and preferentially ablation of Ni binder phase, resulting in the formation of a modified layer composed of remelted top layer accompany with WC phase transformation and graphite phase precipitation, and shock hardening layer. The specific wear rate of the irradiated samples decreased with the increasing pulse number and reached a minimum value of 3.8 × 10−7 mm3/N m with 10 pulses, only for 32% of the non-irradiated samples. The wear mechanism of surface remelting top layer on the irradiated samples was a homogenous microabrasion wear, which was attributed to the surface remelting and phase transformation, and the wear of the shock hardening layer involved preferential removal of Ni binder phase and detachment of WC grains, but it was restrained by strengthening of Ni binder phase from the deep hardening of HIPEB irradiation.

Electron Beam Transformation of Glass Nanoparticles

The phenomenon of electron irradiation induced quasi-fluid flow in solid amorphous silicates is examined. High-intensity electron beam irradiation of glass nanoparticles in TEM leads to a variety of transformations including rounding, bead formation, and phase separation. Evidence for possible rise in temperature, charging fields, and enhanced diffusion is collected and compared, while the latter effect (loosening of glass network) is shown to dominate.

Surface Alloying of SUS 321 Chromium-Nickel Steel by an Electron-Plasma Process

The mechanisms of forming nanostructured, nanophase layers are revealed and analyzed in austenitic steel subjected to surface alloying using an electron-plasma process. Nanostructured, nanophase layers up to 30 μm in thickness were formed by melting of the film/substrate system with an electron beam generated by a SOLO facility (Institute of High Current Electronics, SB RAS), Tomsk), which ensured crystallization and subsequent quenching at the cooling rates within the range 105–108 K/s. The surface was modified with structural stainless steel specimens (SUS 321 steel). The film/substrate system (film thickness 0.5 μm) was formed by a plasma-assisted vacuum-arc process by evaporating a cathode made from a sintered pseudoalloy of the following composition: Zr – 6 at.% Ti – 6 at.% Cu. The film deposition was performed in a QUINTA facility equipped with a PINK hot-cathode plasma source and DI-100 arc evaporators with accelerated cooling of the process cathode, which allowed reducing the size and fraction of the droplet phase in the deposited film. It is found that melting of the film/substrate system (Zr–Ti–Cu)/(SUS 321 steel) using a high-intensity pulsed electron beam followed by the high-rate crystallization is accompanied by the formation of α-iron cellular crystallization structure and precipitation of Cr2Zr, Cr3С2 and TiC particles on the cell boundaries, which as a whole allowed increasing microhardness by a factor of 1.3, Young’s modulus – by a factor of 1.2, wear resistance – by a factor of 2.7, while achieving a three-fold reduction in the friction coefficient.