Accelerated Electron Beam Irradiation Research Articles

Effect of metallic Ag growth on the electrical resistance of 3D flower‐like Ag4V2O7 crystals

AbstractIn this communication, we report for the first time the nucleation and growth of metallic Ag nanoparticles on the surface of 3D flower‐like Ag4V2O7 crystals, induced by accelerated electron beam irradiation. The growth of metallic Ag on the surfaces of Ag4V2O7 crystals were studied by transmission electron microscopy (TEM) and energy dispersive X‐ray spectroscopy (EDXS). According to TEM images and EDXS analyses, exposure to the electron beam induces a reduction process and the growth of metallic Ag nanoparticles on the surface of Ag4V2O7 crystals. Moreover, the inductively coupled plasma optical emission spectrometry measurements indicated an excess of Ag and V vacancies at Ag4V2O7 lattice. Finally, it was observed that the electrical resistance varies considerably with the exposure time to electron beam irradiation.

Electrocatalytic Activity of Pt Nanoparticles Prepared in Biocompatible Ionic Liquids By Accelerated Electron Beam Irradiation

A number of papers on the metal nanoparticle synthesis method have been reported to date because metal nanoparticles are expected to be key materials for further development of science and technology.1 Of these, from a practical application standpoint, the accelerated electron beam irradiation method,2 which can be conducted at existing industrial plants for sterilizing medical kits, has been attracting attention. In this decade, several approaches to synthesize metal nanoparticles in ionic liquid (IL) have been proposed by several research groups, too.3 Some scientists point out that IL behaves as an excellent medium for formation and stabilization of the metal nanoparticles. Recently we have succeeded in the metal nanoparticle preparation by the approach with combination of the accelerated electron beam irradiation method and the IL, which is called ionic liquid-accelerated electron beam irradiation (IL-AEBI) method.4However the past ILs used for the method are not green and expensive price. The aim of this study is to design the biocompatible and cost-effective ILs suitable for metal nanoparticle, especially Pt nanoparticle, preparation by the IL-AEBI method. After supporting the resulting Pt nanoparticles onto untreated multi-walled carbon nanotubes (Pt-MWCNTs), oxygen reduction reaction (ORR) electrocatalytic activity of the Pt-MWCNTs was also examined. Biocompatible and cost-effective ILs were prepared by a neutralization method. Carboxylic acids, e.g., propionic acid, hexanoic acid, levulinic acid, were slowly added into a choline bicarbonate aqueous solution to avoid unexpected thermal decomposition of the carboxylic acids by heat of neutralization. The crude IL solutions were purified prior to use. Solutions of 5.0 mM platinum acetylacetonate (Pt(acac)2) in biocompatible ILs were encapsulated in perfluoroalkoxyethylene container in a dry Ar gas-filled glove box with O2 and H2O <1 ppm. Accelerated electron beam irradiation experiments were carried out at an existing common industrial plant for sterilizing medical kits (accelerated energy: 4.8 MeV; beam current: 10 mA; absorbed dose: 6 kGy; irradiation time: ca. 2 sec.). Pt-MWCNTs were prepared by reference to our previous paper.5The resulting Pt nanoparticles supported on MWCNT was rinsed by acetonitrile. Characterization of all the samples prepared in this study was conducted by TEM, EDX, ICP, electrochemical measurements, etc. Solvated electrons and radicals are readily produced in various solvents by quantum beam irradiation including gamma-ray and electron beam. The generated reactive species are directly related to preparation of metal nanoparticles.2 However, as is often the case with ILs, it is hard to produce metal nanoparticles since usual ILs show a better radiation stability than conventional aqueous and organic solvents. Many years ago we revealed that only 1,3-dialkylimidazolium cation-based ILs yield a sufficient number of metal nanoparticles by the IL-AEBI because such ILs can release a limited amount of reactive species.4 It is important to know the radiation stability of biocompatible ILs in light of the application to the IL-AEBI method. NMR measurements for the neat ILs after the accelerated electron beam irradiation suggested the production of the reactive species during the irradiation. In fact, after the accelerated electron beam irradiation to the solutions of 5.0 mM Pt(acac)2 in the biocompatible ILs, existence of monodispersed Pt nanoparticles in the ILs was identified by TEM observation. Mean particle size of the Pt nanoparticle was ca. 2 ~ 3 nm. Possibility of the Pt nanoparticles as the electrocatalysts was investigated after preparing the Pt-MWCNTs.4 Surprisingly the mean particle size remained even after the preparation process at 473 K and the Pt nanoparticles were immobilized onto a basal plane of the MWCNTs. Electrocatalytic activity was examined by typical electrochemical analyses using the Pt-MWCNTs coated on a glassy carbon rotating disk electrode.5 As given in Table I, the characteristics are strongly dependent on the ionic liquid species. Given the variation in the mass activity, it is possible that the d-band center of Pt nanoparticles is influenced by the carboxylate anions. In conclusion, our designed biocompatible and cost-effective ILs are suitable reaction media for metal nanoparticle preparation by the IL-AEBI method. Acknowledgement Part of this research was supported by the Grant-in-Aid for Scientific Research, Grant Numbers 15H03591, 15K13287, and 15H2202 from the Japanese Ministry of Education, Culture, Sports, Science and Technology. References Nanoparticles: From Theory to Application, G. Schmid, ed., Wiley-VCH, Weinheim, 2004. J. Belloni, Cat. Today, 113, 141 (2006). J. Dupont and J. D. Scholten, Chem. Soc. Rev., 39, 1780 (2010). T. Tsuda, S. Seino, and S. Kuwabata, Chem. Commun.,6792 (2009); ibid, 48, 1925 (2012). K. Yoshii, T. Tsuda, T. Arimura, A. Imanishi, T. Torimoto, and S. Kuwabata, RSC Adv., 2, 8262 (2012). Figure 1

Solid-to-liquid and gas-to-liquid transformation of alkanes under accelerated electron beam irradiation

A zero-waste method has been suggested for radiation-thermal cracking of Fischer–Tropsch waxes. The method is realized in the circulating mode and is based on the indirect action of radiation on the wax dissolved in methane or other gaseous hydrocarbons. The duration of exposure to irradiation of the feedstock components depends on their volatility. The method is characterized by the increased fixation yield of the gas. The major fraction of the final product is gasoline rich in isoalkanes.

Preparation of gold nanoparticles using reactive species produced in room-temperature ionic liquids by accelerated electron beam irradiation

Au nanoparticles that are expected to be a key material for supporting future technologies were produced with brief accelerated electron beam irradiation to various 1-alkyl-3-methylimidazolium cation ([R1MeIm]+)-based room-temperature ionic liquids (RTILs) with aurate. The resulting Au nanoparticles were able to remain in a nearly-monodispersed state in the RTILs for several weeks at least although the surface was not covered with a stabilizing agent, which is usually employed so as to prevent aggregation behaviour. The particle size increased with increasing the irradiation dose as well as decreasing the alkyl chain length of the [R1MeIm]+ if the RTIL consisted of the same anion species. The shapes of the Au nanoparticles obviously altered with the anionic species in the RTILs used for the preparation.

Various metal nanoparticles produced by accelerated electron beam irradiation of room-temperature ionic liquid

Various metal nanoparticles including base metal were produced by a brief accelerated electron beam irradiation of 1-alkyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)amide room-temperature ionic liquid without a stabilizing agent, which is usually employed so as to prevent aggregation.

Correlation of Microstructure with Hardness and Corrosion Resistance of Surface Alloyed Materials Fabricated with Fe-Based Metamorphic Powders by Accelerated Electron Beam Irradiation Method

This study aims at correlating microstructure with hardness and corrosion resistance of surface alloyed materials fabricated with Fe-based metamorphic powders by an accelerated electron beam irradiation method. The surface alloyed materials contained 48 vol.% of hard Cr2B crystalline phases in the Cr0.19Fe0.7Ni0.11 matrix, and thus its hardness was 2.5 times greater than that of the steel substrate. The corrosion resistance of the surface alloyed materials was better than that of an STS304 stainless steel or coatings fabricated by high-velocity oxygen fuel spraying of Fe-based metamorphic powders because the Cr0.19Fe0.7Ni0.11 matrix of the surface alloyed layers and coating was selectively corroded, while Cr2B borides were retained inside pits. These findings suggested that the fabricated surface alloyed materials presented good application possibilities as excellent wear- and corrosion-resistant materials.

Synthesis of diamond by electron irradiation of C60 intercalated graphite

Upon electron irradiation, C60 intercalated graphite was converted to diamond at only 200 kV accelerated electron beam irradiation, without the application of high pressure and temperature in a hydrogen free environment. This process took only few minutes. Conjugation of all-three carbon allotropes was observed during the decomposition of C60 intercalated graphite in diamond films.

Combined Microwave and Accelerated Electron Beam Irradiation Facilities for Applied Physics and Chemistry

A new method based on microwave (MW) energy addition to accelerated electron beam (EB) energy for material processing was developed. In order to investigate this method, several specially designed facilities which permit separate, successive, and simultaneous MW and EB irradiation were carried out. These facilities as well as the associated MW and EB injection systems are described. In comparison with separate EB or MW irradiation, the simultaneous EB and MW irradiation of the acrylamide-acrylic acid aqueous solution leads to the highest molecular weight values simultaneously with the smallest Huggins' constant values. Also, the absorbed dose is reduced from 0.8 kGy in the separate EB irradiation case to 0.4 kGy in the simultaneous EB and MW irradiation applied to acrylamide-acrylic acid co-polymerization. Significant higher vulcanization degrees are obtained only for higher EB irradiation doses, especially in terms of the values of the 300% modulus and tensile strength. By using simultaneous EB and MW irradiation, compared to separate EB irradiation, the same maximum value of 300% modulus is obtained for EB absorbed dose and irradiation time of 2.5 times lower at 60-W MW power and five times lower at 100-W MW power. Also, the same maximum value of tensile strength is obtained for EB absorbed dose and irradiation time of four times lower at 60-W MW power and 5.33 times lower at 100-W MW power. The combined EB and MW irradiation applied to the SO/sub 2/ and NO/sub x/ removal from the simulated flue gases demonstrated that for the same removal efficiency of 98% for SO/sub 2/ and 76% for NO/sub x/ at separate EB irradiation of 40 kGy, the required absorbed dose is about two times smaller for simultaneous EB and MW irradiation.

Microstructural analysis of TiC reinforced ferrous surface composites processed by accelerated electron beam irradiation

The present study aims to analyze microstructures of TiC reinforced ferrous surface composites processed by accelerated electron beam irradiation. Two kinds of powder/flux mixtures, i.e., TiC and (Ti + C) powders with 40 wt% of CaF2 flux, were deposited evenly on an AISI 304 stainless steel substrate, which was then irradiated with electron beam. TiC agglomerates and pores were found in the surface composite specimen processed by irradiation of TiC powders because of insufficient melting of TiC powders. In the specimen processed by irradiation of Ti and C powders having lower melting points than TiC powders, a lot of large TiC carbides were precipitated in the melted region, together with a few TiC agglomerates or pores. This indicated the more effective TiC precipitation obtained from the melting of Ti and C powders, instead of TiC powders. The hardness of the surface composite layer was about two times higher than that of the AISI 304 substrate mainly due to the precipitation of TiC carbides. 2001 Elsevier Science B.V. All rights reserved.

Effects of accelerated electron beam irradiation on surface hardening and fatigue properties in an AISI 4140 steel used for automotive crankshaft

This study is concerned with the effects of high-energy accelerated electron beam irradiation on surface hardening and improvement of fatigue properties in an AISI 4140 steel currently used for automotive crankshaft. The 4140 steel specimens were irradiated in air by using a high-energy electron beam accelerator, and then microstructure, hardness, and fatigue properties were examined. Beam power was varied in the range of 5.2∼7.7 kW by changing beam current. Upon irradiation, the unirradiated microstructure containing band structure was changed to martensite and bainite in the carbon-rich zone or ferrite, bainite, and martensite in the carbon-depleted zone. This microstructural modification improved greatly surface hardness and fatigue properties due to transformation of martensite whose amount and type were determined by heat input during irradiation. Thus, high-energy electron beam irradiation can be effectively applied to the surface hardening process of automotive parts. In order to investigate the thermal cycle during electron beam irradiation of quickly rotating specimens, the thermal analysis was also carried out using an analytical computer simulation. Analytical solutions gave information about the peak temperature, heating and cooling rate, and hardened depth to correlate with the overall microstructural modification.