Continuous Electron Research Articles

Redesigning the Jefferson Lab Hall A beam line for high precision parity experiments

The Continuous Electron Beam Accelerator Facility (CEBAF) was built with a thermionic electron source and the three original experimental hall lines reflected this. A few years after beam delivery began a parity violation experiment was approved and two polarimeters were installed in the Hall A beam line. The beam raster system was placed after the new Compton polarimeter, before one accelerator quadrupole and four quadrupoles in the new Moller polarimeter. It was very difficult to meet experimental requirements on envelope functions and raster shape with this arrangement so a sixth quadrupole was installed downstream of the Moller polarimeter to provide an additional degree of freedome. All of the parity experiments in Hall A have been run with this still-unsatisfactory configuration. The MOLLER experiment is predicated on achieving a 2% error on a 32 ppb asymmetry. Beam line changes are required to meet the systematic error budget. This paper documents the existing beam line, an interim change which can be accomplished during a annual maintenance down, and the final configuration for MOLLER and subsequent experiments.

Carbon nanotube-supported polyimide nanoarrays as sulfur host with physical/chemical polysulfide-traps for Li–S batteries

Lithium-sulfur (Li–S) batteries have been regarded as the most promising next-generation energy storage devices due to their large specific capacity and high energy density. However, their practical implementation is still subjected to the insulation of sulfur and discharge products, serious shuttle effect, and large volume expansion of sulfur during the discharge/charge processes. Herein, polyimide nanoarrays functionalized carbon nanotubes (PI@CNT) were proposed as a sulfur host with the incorporation of additional carbon nanotubes (CNTs) conductive networks. The as-preformed polyimide nanoarrays on the surface of CNTs expose sufficient adsorption sites for sulfur loading. PI@CNT chemically bind lithium polysulfides (LiPS) via the polar Li–N bonding interaction and physically confine LiPS in the network. Meanwhile, the intertwined frameworks can bear the volume expansion of sulfur and maintain the electrode integrity. The PI@CNT/CNT/S cathode exhibits the sulfur loading as high as 70 wt% and shows the cycling stability with a capacity retention of 67% after 300 cycles at 1 C. Furthermore, the additional incorporation of CNTs can form continuous electron transfer paths, thereby promoting the rate capability. This work integrated the polar polymer host and conductive networks with robust LiPS trapping and fast conversion, and would propose a new paradigm for designing high-performance sulfur cathodes.

High-performance ternary organic photovoltaics with NC70BA as the third component material enabling thickness-insensitive photoactive performance

In this work, a thinner (100 nm) and thicker (150 and 200 nm) ternary organic photovoltaic (OPV) are fabricate by D18 as donor, Y6 as acceptor and NC70BA as third component materials. The addition of the hollow 3D spherical structure of NC70BA into D18:Y6 binary films is helpful for improving phase separation and smooth surface of ternary photoactive layer, and form more continuous electron transport channels in ternary photoactive layers. It is enhance photovoltaic performance under not only thinner photoactive layer thickness but also thicker photoactive layer thickness. Our results demonstrate the feasibility of employing D18:Y6 as a binary photovoltaic layer and fullerene derivative NC70BA as a third component material and has construct high-efficiency thickness-insensitive ternary OPVs; this approach would promote the development of thicker photoactive layer ternary OPVs to fulfill the requirements of solution coating processes.

Peek Inside the Water Mixtures of Ionic Liquids at Molecular Level: Microscopic Properties Probed by EPR Spectroscopy.

Many ionic liquids (ILs) can be mixed with water, forming either true solutions or emulsions. This favors their applications in many respects, but at the same time might strongly alter their physicochemical properties. A number of methods exist for studying the macroscopic properties of such mixtures, whereas understanding their characteristics at micro/nanoscale is rather challenging. In this work we investigate microscopic properties, such as viscosity and local structuring, in binary water mixtures of IL [Bmim]BF4 in liquid and glassy states. For this sake, we use continuous wave and pulse electron paramagnetic resonance (EPR) spectroscopy with dedicated spin probes, located preferably in IL-rich domains or distributed in IL- and water-rich domains. We demonstrate that the glassy-state nanostructuring of IL-rich domains is very similar to that in neat ILs. At the same time, in liquid state the residual water makes local viscosity in IL-rich domains noticeably different compared to neat ILs, even though the overwhelming amount of water is contained in water-rich domains. These results have to be taken into account in various applications of IL-water mixtures, especially in those cases demanding the combinations of optimum micro- and macroscopic characteristics.

The microstructure and properties of Mo alloying layer after surface alloying treatment induced by continuous scanning electron beam process

Surface alloying by scanning electron beams can improve the microstructure and mechanical properties of steel. In this study. Four electron energy densities were selected during the alloying process: E1 = 1.5J/cm2, E2 = 2.9J/cm2, E3 = 4.5J/cm2 and E4 = 5.9J/cm2. The obtained results show that the sample surface is composed of alloying zone and heat-affected zone. The microstructure of the alloy zone is concealed acicular martensite and molybdenum carbide particles. The microhardness of this area is 1250HV. The sample treated with an energy density of 5.9J/cm2 has the least amount of wear. After alloying treatment, the microhardness and wear amount of the scanned samples are significantly improved.

Numerical Simulation and Microstructure and Properties of 45 Steel by Scanning Electron Beam Bevel Polishing

In order to obtain metal products with good surface quality, it is necessary to develop an efficient bevel polishing method. Therefore, this article Uses continuous scanning electron beam polishing. The surface of the material undergoes rapid melting and solidification and generates a dynamic temperature field. The polishing treatment improves the microstructure of the surface layer of the quenched and tempered 45 steel, and significantly increases the microhardness of the surface layer. The hardness after treatment can reach up to 747.6Hv, which is about 2.4 times higher than the matrix; the structure after hardening is transformed from the mixed phase of coarse acicular martensite and lath martensite to hidden acicular martensite and retained austenite a mixed phase thereof. In addition, after bevels with different inclination angles are subjected to electron beam surface polishing modification treatments with different scanning speeds, under the same parameters, as the inclination angle increases, the hardness value at the same position decreases.

Probing charged lepton flavor violation with a positron beam at CEBAF (JLAB)

The addition of a high intensity 11 GeV polarized positron beam at the Continuous Electron Beam Accelerator Facility (CEBAF) at JLAB would allow for a search of Charged Lepton Flavor Violation (CLFV) via the process $$e^+N \rightarrow \mu ^+ X$$ . The proposed Solenoidal Large Intensity Detector (SoLID) spectrometer, in the configuration with muon chambers, would be ideal for such CLFV searches. Various new physics scenarios, including the phenomenologically convenient Leptoquark (LQ) framework, predict CLFV rates that are within reach of current or planned experiments. A positron beam with instantaneous luminosity, $${{{\mathcal {L}}}}\sim 10^{38}$$ cm $$^{-2}$$ s $$^{-1}$$ , could improve on existing HERA limits by two or three orders of magnitude. The availability of positron beam polarization would also allow for distentangling CLFV effects mediated by left-handed vs. right-handed LQs.

Noble Metal-Added Titanate Nanosheets for PEFC Cathode

A large overpotential of oxygen reduction reaction (ORR) at a cathode in polymer electrolyte fuel cells (PEFCs) is one of the serious problems to decrease the energy conversion efficiency. Nørskov’s group reported that even Pt which is currently used as an ORR catalyst cannot reach the theoretical oxygen electrode potential of 1.23 V at 298 K [1]. On the other hand, Yamamoto et al. recently suggested that noble metal doped titanium dioxides (TiO2) can reach the theoretical potential by changing the absorption energies of the ORR intermediates according to the first-principle calculations [2]. However, the first-principle calculations did not consider the continuous electron supply to proceed the ORR. It is difficult to form the sufficient electron conduction path from supports to active sites on the TiO2 because TiO2 has low conductivity due to a large band gap. Therefore, we focused on the formation of the active sites on the TiO2 surface by doping noble metal such as Rh and Pd and the electron conduction path from carbon supports to the active sites by preparing the titanate nanosheets.Na2Ti3O7 was synthesized as precursor of anionic titanate nanosheets([Ti3O7]2- ;TiNS) according to the previous paper [3]. Na2Ti3O7 was treated through ion-exchange reaction with hydrochloric acid and tetramethylammonium aqueous solution, finally TiNS were obtained. A TEM observation revealed that the formation of very large sheet-like materials with a size of approximately upwards of ten micrometers, resulting that TiNS were completely synthesized.Next, we focused on the formation of the electron conduction path through nanosheets from supports using the electron tunneling effect. When the nanosheets were directly supported on the glassy carbon electrode, the ORR activity was the same as that of GC, and almost no ORR current flowed even low potential region. Then, vapor grown carbon fibers (VGCFs) as purchased, with immersion of mixed acid (MA; H2SO4 and HNO3) at 170 oC for 24 h and PDDA (Poly(diallyl dimethylammonium chloride)) as polycation were attempted to use as supports. The TiNS were immersed in the distilled water dispersed with the treated VGCFs to be supported by them. These catalysts were designated as TiNS/VGCF, TiNS/VGCF(MA), and TiNS/VGCF(MA-PDDA).The ORR current of TiNS/VGCF(MA-PDDA) was larger than that of TiNS/VGCF, TiNS/VGCF(MA). In addition, the ORR onset potential of the TiNS/VGCF(MA-PDDA) increased by 0.3 V compared to that of TiNS/VGCF. These results suggest that surface treatment of VGCFs was effective to form the electron conduction path from VGCF to active sites of nanosheet surface. The electrostatic interaction between VGCF surface positively charged by PDDA and anionic TiNS contributed the formation of the electron conduction path. However, according to the TEM observation, TiNS were partially contacted with VGCF and some TiNS were agglomerated. It is necessary to obtain higher ORR activity that a control of size of TiNS and contact with supports such as VGCF.On the other hand, we attempted to dope Rh and Pd to TiNS through solid-state reaction. Rh-,Pd-doped TiNS (designated as Rh-TiNS and Pd-TiNS) were synthesized the same way as previous paper [3]. XRD patterns of the precursors revealed that Rh2O3 or PdO were existed with Na2Ti3O7 above the addition of 5 atomic %. Rh-TiNS and Pd-TiNS were supported by VGCF(MA-PDDA) after Rh-TiNS and Pd-TiNS were treated TMAOH aqueous solution. The ORR activities of the samples with the addition of 5at% Rh or 10at% Pd were higher than those of the samples which Rh2O3 or PdO were not observed in XRD patterns. The ORR active sites were estimated by Rh2O3 or PdO deposited on the surface of the TiNS. This result showed that an amount of doped Rh or Pd was limited to Na2Ti3O7. The limitation of doped Rh or Pd was 5at% or 10at%, respectively. Therefore, the doped amounts of noble metals such as Rh or Pd to TiNS should be appropriately controlled.AcknowledgementThe authors thank the New Energy and Industrial Technology Development Organization (NEDO) for financial support. This work was partly supported by TOKYO CITY UNIVERSITY Interdisciplinary Research Center for Nano Science and Technology for instrumental analysis.Reference(1) A. Kulkarni et al., Chem. Rev., 118, 2302 (2018).(2) Y. Yamamoto et al., J. Phys. Chem. C., 123, 19486 (2019).(3) W. Soontornchaiyakul et al., RSC Adv., 7, 21790 (2017). Figure 1

(Keynote) Engineering Cyanobacteria for Nitrogen Reduction

Ammonia is currently the second most widely produced chemical in the world (second to sulfuric acid). Most ammonia (over 66%) is now produced through the Haber−Bosch process, consuming approximately 5% of the global natural gas production and contributes to over 3% of global carbon dioxide emissions. In an effort to develop an electrochemical alternative, we have engineered cyanobacterium to perform nitrogen fixation under ambient conditions without consuming natural gas, in stark contrast to the Haber-Bosch process that requires extreme temperatures and pressures to the same end. To realize the heterologous expression of nitrogenase, we transformed the cyanobacterium S. elongatus PCC 7942 with the minimal nitrogen fixation (nif) gene cluster. Nitrogenase can reduce N2 to NH3 at mild conditions (< 40 oC, atmospheric pressure). There are three known types of nitrogenase, in which the central composition of their active-site metalloclusters are molybdenum(Mo), vanadium (V), and iron (Fe), respectively. Most biological nitrogen fixation is catalyzed by the Mo-based nitrogenase enzyme. Biosynthesis of Mo-nitrogenase generally requires a large number of nif genes. However, the transformation and transcription of such a larger set of gene cluster into the cyanobacterium is challenging. In this work, a minimal nif cluster with reduced genetic complexity was chosen to accomplish the transformation of the cyanobacterium S. elongatus PCC 7942. The cyanobacterium S. elongatus PCC 7942 was transformed with nif genes and it was shown to be able to express active nitrogenase. The engineered S. elongatus PCC 7942 was immobilized on an electrode to accelerate the microbial conversion of nitrogen into ammonium using electrochemical driving forces. Methyl viologen (MV) was added as an electron mediator to shuttle electrons from the electrode to the enzyme active center, since MV can go through the cell membrane and deliver continuous electrons to nitrogenase.

Influence of hydration on segmental chain librations and dynamical transition in lipid bilayers

Continuous wave electron paramagnetic resonance spectroscopy of chain-labeled phospholipids is used to investigate the effects of hydration on the librational oscillations and the dynamical transition of phospholipid membranes in the low-temperature range 120–270 K. Bilayers of dipalmitoylphostatidiycholine (DPPC) spin-labeled at the first acyl chain segments and at the methyl ends and prepared at full, low, and very low hydration are considered. The segmental mean-square angular amplitudes of librations, 〈α2〉, are larger in the bilayer interior than at the polar/apolar interface and larger in the fully and low hydrated than in the very low hydrated membranes. For chain segments at the beginning of the hydrocarbon region, 〈α2〉-values are markedly restricted and temperature independent in DPPC with the lowest water content, whereas they increase with temperature in the low and fully hydrated bilayers, particularly at the highest temperatures. For chain segments at the chain termini, the librational amplitudes increase progressively, first slowly and then more rapidly with temperature in bilayers at any level of hydration. From the temperature dependence of the mean-square librational amplitude, the dynamical transition is detected around 240 K at the polar/apolar interface in fully and low hydrated DPPC and at around 225 K at the inner hydrocarbon region for bilayers at any hydration condition. At the dynamical transition the bilayers cross low energy barriers of activation energy in the range 10–20 kJ/mol. The results highlight biophysical properties of DPPC bilayers at low-temperature and provide evidence of the effects of the hydration on the dynamical transition in bilayers.

Molecular-Level Release of Coumarin-3-Carboxylic Acid and Warfarin-Derivatives from BSA-Based Hydrogels.

This investigation aimed at developing BSA hydrogels as a controlled release system to study the release behavior of spin-labeled coumarin-3-carboxylic acid (SL-CCS) and warfarin (SL-WFR). The release profiles of these spin-labeled (SL-) pharmaceuticals from BSA hydrogels prepared with different procedures are compared in detail. The mechanical properties of the gels during formation and release were studied via rheology, while a nanoscopic view on the release behavior was achieved by analyzing SL-drugs–BSA interaction using continuous wave electron paramagnetic resonance (CW EPR) spectroscopy. The influence of type of drug, drug concentration, duration of gel formation, and gelation methods on release behavior were characterized by CW EPR spectroscopy, EPR imaging (EPRI), and dynamic light scattering (DLS), which provide information on the interaction of BSA with SL-drugs, the percentage of drug inside the hydrogel and the nature and size of the released structures, respectively. We found that the release rate of SL-CCS and SL-WFR from BSA hydrogels is tunable through drug ratios, hydrogel incubation time and gelation procedures. All of the results indicate that BSA hydrogels can be potentially exploited in controlled drug delivery applications.

Ultrahigh-capacity semi-solid SiOx anolytes enabled by robust nanotube conductive networks for Li-ion flow batteries

Exploring semi-solid anolytes with high volumetric capacity and low potential is of great significance for boosting the energy storage capability of Li-ion flow batteries. Generally, micro-sized SiO x shows promises in fabricating high-capacity anolytes owing to its inherent advantages in specific capacity, processability and cost. However, its poor electronic conductivity and huge volume change result in unexpected issues of loss of electrical connections, structural disintegration, and unstable solid-electrolyte interphase (SEI). Herein, these issues are addressed by constructing robust conductive networks throughout anolytes by employing single-walled carbon nanotubes (SWCNT) as conductive additives. Compared with loose networks constructed by KB, such robust networks can facilitate continuous electrons transport and improve particle integrity. SiO x anolytes with robust networks display an ultrahigh capacity, excellent rate capability, and stable cyclability in static cells. Furthermore, as-prepared anolytes can simultaneously achieve suitable viscosity and superior electronic conductivity. The assembled flow cell demonstrates high volumetric capacities of 74.7–98.0 Ah L −1 under the static test and the feasibility in long-term continuous-flow mode. Our successful demonstration of SiO x semi-solid anolytes may be helpful for the construction of high-energy-density flow batteries. • SiO x semi-solid anolytes with high capacity and suitable viscosity are developed. • Robust networks are constructed by single-walled carbon nanotubes (SWCNT). • SWCNT networks favor electrons transport and particle integrity. • SiO x -SWCNT anolytes show significantly improved rate and cycle performances.

Persistent radical pairs trigger nano-gold to highly efficiently and highly selectively drive the value-added conversion of nitroaromatics

The development of advanced catalyst materials capable of efficiently capturing solar energy to drive the beneficial conversion of chemicals is a key part of the blueprint for “liquid sunlight.” Here, highly dispersed ultrafine nano-Au (B/[email protected]) was anchored in situ on B/TPTH3 formed by alternate cross-linking of closo-[B12H12]2− and protonated 2,4,6-tris(4-pyridyl)-1,3,5-triazine. B/[email protected] is an outstanding heterogeneous photocatalyst that converts low-value-added nitroaromatics into high-value-added azoaromatics. Compared with the slow kinetics of previous catalysts, the time required for the conversion of nitroaromatics to azoaromatics driven by B/[email protected] is reduced by at least 10 times. These improvements could be derived from the synergy between the carrier B/TPTH3 (as a stable radical pair) and the nano-gold, including continuous electron transport in the functional carrier B/TPTH3 and the anchoring of highly dispersed ultrafine nano-Au with a strong localized surface plasmon resonance effect.

In-situ construction of sequential heterostructured CoS/CdS/CuS for building “electron-welcome zone” to enhance solar-to-hydrogen conversion

Photocatalysis has been facing challenging problems especially the inefficient photocarriers transfer at the interfaces. Here, based on Ksp difference, we prepare the sequential heterojunction of CoS/CdS/CuS via sequential cation exchange strategy, and propose the concept of "electron-welcome zone", where the point-to-point contact can be formed at the interface, thus providing continuous electron transport channels. HAADF-STEM EDS line test indicates the formation of designed structures, and the p/n junction is confirmed by band structure and Mott-Schottky analysis. Theoretical calculation indicates that CoS reduces the Gibbs free energy of the reaction. TRPL spectra show that the existence of "electron welcome zone" greatly improves the lifetime of electrons. This sequential structure enable the optimal H2 production rate to reach 123.2 mmol g−1 h−1 with AQE of 45.6%, which is among the highest values of CdS-based photocatalysts. This work opens new way to efficient photogenerated carrier transfer channel for solar-energy conversion.

Evidence of increased radio-frequency losses in cavities from the fundamental power coupler cold window

High radio-frequency (rf) losses measured for cavities in original Continuous Electron Beam Accelerator Facility (CEBAF) cryomodules, compared to the losses measured in single-cavity tests, have been a long-standing issue related to their performance. We summarize experimental evidence of increased rf losses in CEBAF cavities arising from the fundamental power coupler cold window and waveguide, respectively. Cryogenic rf tests were done on cavities tested in vertical cryostats as well as inside cryomodules in the accelerator tunnel. The cold window metallization losses were assessed by combining numerical results with measured data obtained with an existing cryogenic waveguide resonator setup. The results showed that the cold window metallization losses can increase the cavity rf heat load at 2.07 K by up to 86%, depending on the standing-wave pattern in the fundamental power coupler waveguide, and that such losses are reduced if the distance between the waveguide and the cavity cells is increased.

Continuous electron shuttling by sulfide oxidizing bacteria as a novel strategy to produce electric current

Sulfide oxidizing bacteria (SOB) are widely applied in industry to convert toxic H2S into elemental sulfur. Haloalkaliphilic planktonic SOB can remove sulfide from solution under anaerobic conditions (SOB are ‘charged’), and release electrons at an electrode (discharge of SOB). The effect of this electron shuttling on product formation and biomass growth is not known. Here, we study and demonstrate a continuous process in which SOB remove sulfide from solution in an anaerobic ‘uptake chamber’, and shuttle these electrons to the anode of an electrochemical cell, in the absence of dissolved sulfide. Two experiments over 31 and 41 days were performed. At a sulfide loading rate of 1.1 mmolS/day, electricity was produced continuously (3 A/m2) without dissolved sulfide in the anolyte. The main end product was sulfate (56% in experiment 1% and 78% in experiment 2), and 87% and 77% of the electrons in sulfide were recovered as electricity. It was found that the current density was dependent on the sulfide loading rate and not on the anode potential. Biological growth occurred, mainly at the anode as biofilm, in which the deltaproteobacterial genus Desulfurivibrio was dominating. Our results demonstrate a novel strategy to produce electricity from sulfide in an electrochemical system.

Preparation and application of a stretchable, conductive and temperature-sensitive dual-network nanocomposite hydrogel

Conductive hydrogel has received extensive attention in the design and application of flexible electronic equipment, due to its flexibility, easy processing, good sensitivity and excellent electrochemical performance. In this study, we designed a stretchable conductive and temperature-sensitive dual-network nanocomposite hydrogel in a simple one-pot method. Fourier transform infrared (FTIR), scanning electron microscopy （SEM） and thermogravimetric analysis (TGA) were used to characterize the nanocomposite hydrogel. The formation of the double cross-linked network greatly improves the mechanical properties of the nanocomposite hydrogel, and continuous electron transport path formed by MWCNTs dispersed in a hydrogel network endows the nanocomposite hydrogel great conductive behavior and the hydrogel exhibited a stable relative resistance change during the tensile deformation process. The nanocomposite hydrogel displayed great application potential in wearable devices, smart robots, and flexible strain sensors.

High‐Performance Carbon Fibers Prepared by Continuous Stabilization and Carbonization of Electron Beam‐Irradiated Textile Grade Polyacrylonitrile Fibers

AbstractThe manufacturing of high‐performance carbon fibers (CFs) from low‐cost textile grade poly(acrylonitrile) (PAN) homo‐ and copolymers using continuous electron beam (EB) irradiation, stabilization, and carbonization on a kilogram scale is reported. The resulting CFs have tensile strengths of up to 3.1 ± 0.6 GPa and Young's moduli of up to 212 ± 9 GPa, exceeding standard grade CFs such as Toray T300. Additionally, the Weibull strength and modulus, the microstructure, and the morphology of these CFs are determined.

A Joint Venture of Ab Initio Molecular Dynamics, Coupled Cluster Electronic Structure Methods, and Liquid-State Theory to Compute Accurate Isotropic Hyperfine Constants of Nitroxide Probes in Water.

The isotropic hyperfine coupling constant (HFCC, Aiso) of a pH-sensitive spin probe in a solution, HMI (2,2,3,4,5,5-hexamethylimidazolidin-1-oxyl, C9H19N2O) in water, is computed using an ensemble of state-of-the-art computational techniques and is gauged against X-band continuous wave electron paramagnetic resonance (EPR) measurement spectra at room temperature. Fundamentally, the investigation aims to delineate the cutting edge of current first-principles-based calculations of EPR parameters in aqueous solutions based on using rigorous statistical mechanics combined with correlated electronic structure techniques. In particular, the impact of solvation is described by exploiting fully atomistic, RISM integral equation, and implicit solvation approaches as offered by ab initio molecular dynamics (AIMD) of the periodic bulk solution (using the spin-polarized revPBE0-D3 hybrid functional), embedded cluster reference interaction site model integral equation theory (EC-RISM), and polarizable continuum embedding (using CPCM) of microsolvated complexes, respectively. HFCCs are obtained from efficient coupled cluster calculations (using open-shell DLPNO-CCSD theory) as well as from hybrid density functional theory (using revPBE0-D3). Re-solvation of “vertically desolvated” spin probe configuration snapshots by EC-RISM embedding is shown to provide significantly improved results compared to CPCM since only the former captures the inherent structural heterogeneity of the solvent close to the spin probe. The average values of the Aiso parameter obtained based on configurational statistics using explicit water within AIMD and from EC-RISM solvation are found to be satisfactorily close. Using either such explicit or RISM solvation in conjunction with DLPNO-CCSD calculations of the HFCCs provides an average Aiso parameter for HMI in aqueous solution at 300 K and 1 bar that is in good agreement with the experimentally determined one. The developed computational strategy is general in the sense that it can be readily applied to other spin probes of similar molecular complexity, to aqueous solutions beyond ambient conditions, as well as to other solvents in the longer run.

Study on surface alloying of 38CrMoAl steel by electron beam

TiN/Ni alloying of 38CrMoAl steel surface was carried out by continuous scanning electron beam. The effect of electron beam process parameters on the surface microstructures and mechanical properties of 38CrMoAl steel was studied. The results shows that the sample surface was divided into three regions: alloying layer, heat affected zone and substrate. Alloying layer made up with equiaxed crystals and short columnar crystals, microstructure of the heat affected zone was acicular and lath martensite, microstructure of substrate was tempered sorbate. The microhardness of the sample section first increased and then decreased, at a depth of 400 μm, the microhardness reached a maximum of 817.9 HV. When the beam current reached 12 mA and the moving speed reached 5.5 mm/s, the surface microhardness of the sample reached the highest 1209HV and the abrasion loss reached the lowest 4.6 mg.