辐照法制备纳米银粉的研究

研究了~(60)Coγ射线辐照硝酸银水溶液体系制备纳米银粉。利用XRD、TEM、DSC、LSPSDA分别表征了材料的物相、粒径、形貌、以及熔点。结果表明,表面活性剂(PCM)在0.6-2.2g/100mL范围内,反应得到的纳米银粒子的粒径随浓度的增加而减小,纳米银粒子的熔点随着粒径的减小而减小。表面活性剂浓度为2.2g/100mL时,粒径最小可达到19.9nm,相应熔点为126.18℃。不同PH值的辐照溶液所得产物均为单质银颗粒,银盐溶液的酸碱性对其辐照产物基本不产生影响。     

电子束辐照制备纳米银

在水溶液中,常温常压下不加入任何催化剂,用电子加速器辐照作为一种新的方法可以成功制备出纳米银。我们利用XRD、TEM、UV、DSC来分别表征材料的结构、形貌、大小、光学特性以及材料的熔点。TEM图像证明颗粒大小为30nm,这与XRD实验通过Scherer理论公式计算的结果相一致。     

电子束辐照制备的纳米硫化镉研究

在常温常压下，采用电子束辐照法在水溶液体系中合成了纳米硫化镉粒子。X射线衍射分析表明该产物为面心立方结构晶体的纳米硫化镉；透射电子显微镜分析表明该纳米粒子形貌呈球状颗粒，平均粒径为15nm；其光学性能研究表明，其紫外吸收光谱的吸收边波长为487nm；激发波长为350nm时，纳米粒子的荧光发射波长的峰值为476nm，主要为由带边发射引起的发光。用激光粒度仪研究了表面活性剂聚乙烯醇浓度对辐射制备纳米硫化镉粒径的影响，在一定范围内随着聚乙烯醇浓度的增大，纳米粒子的粒径相应减小。     

Plating of archaeological metallic objects - studies by differential PIXE

The differential PIXE method using an external proton beam up to 3 MeV energy was applied to examine plated layers of tin, silver and gold on bronze, brass, iron and silver objects from Roman and Early Medieval period. The concentration profiles were deduced from the measurements by the method of virtual slicing the target into layers, and minimizing the differences between the measured and calculated X-ray yields. The tinned layers were usually thin (about 1 μm), but the thickness of silver and gold layers was in several cases thicker and exceeded the proton range. The plating techniques were identified as application of the molten metal for tinning, and as fire gilding for the gilded objects.     

Preparation and characterization of Ag-coated cenospheres by magnetron sputtering method

In this paper, we show the feasibility of the magnetron sputtering deposition technique to grow 10-100-nm thick, uniform, continuous and well adhesive silver films on cenosphere particles so that the properties of the core particles can be suitably modified. Experiments were conducted with a magnetron sputtering deposition system in which a newly designed sample stage equipped with an ultrasonic vibration generator was used for the tumbling of cenosphere particles. The cenosphere particles are characterized by X-ray diffraction (XRD) analysis, field emission scanning electron microscope (FE-SEM) and inductively coupled plasma-atom emission spectrometer (ICP-AES) before and after the coating process. All results show the metal film has been successfully coated onto cenosphere particles. Under the given conditions, up to 3.0 wt.% silver was deposited on cenosphere particles measured by ICP-AES. The FE-SEM results indicate that at the micro-scale the relatively uniform, compact and well adhesive silver films with about 51 nm thickness were successfully deposited on cenosphere particles. The XRD analytic result indicates that the nanometer metal film has a face-centered cubic structure.     

Preparation of copper nano-particle powder by γ-irradiation

Copper nano-particles were prepared by 100 kGy room temperature γ-ray irradiation of CuSO4 aqueous solution added with surfactant and inactive agent.Effects of the surfactants and pH value on particle size and morphology of the Cu powder,and the storage stability,were investigated.Structure,morphology,particle size and melting point of the copper nano-particles were characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM),laser particle size analyzer and differential scanning calorimetry(DSC),respectively.The results show that the Cu nano-particles prepared with PCM as surfactant and N,N-bis-hydroxyethyl dodecyl amide as inactive agent,in pH=4.0-6.5 of the aqueous solution,can be stored in air for 140 days.     

Effects of proton irradiation on electronic structure of NdFeB permanent magnets

Effects of proton irradiation on electronic structure and atomic local structure of N35EH-type NdFeB permanent magnet were investigated by soft X-ray absorption spectrometry and Mössbauer spectrometry. The local coordination environment of Fe atoms changes after proton irradiation, and the average hyperfine field H_in of the magnets decreases from 288.4 to 286.9 kOe. The effects of irradiation on Fe atoms local environment at different lattice sites are different. The near edge structure of Fe L₃ edge is changed, indicating the density of unoccupied state of Fe 3d electrons increases after proton irradiation.     

Emission statistics of X-ray induced photoelectrons and its comparison with electron- and ion-induced electron emissions

The emission statistics of secondary electrons from a gold metal surface induced by monochromatic X-rays is studied by Monte Carlo simulations. The number distributions of emitted electrons n and their mean values γ are calculated systematically for incident photon energies from 1 to 100 keV. The results are compared with recent experimental results measured at the SPring-8 X-ray beam facility (BL15XU). We found that both theoretical and experimental results of the statistical number distributions of secondary electrons can be reproduced fairly well by Polya-type functions, showing small probabilities for one-electron emission (n = 1) and broad distributions for high-n emission. In contrast, these features can never be reproduced by Poisson statistics. Furthermore, calculated emission yields γ are found to depend rather weakly on the incident X-ray energy. These results indicate clearly that fast photoelectrons produced by high-energy X-rays are responsible for high-n emission although the photoionization cross sections are considerably smaller at higher X-ray energies. Simulations are also extended to electron and ion bombardments, and a comprehensive comparison between X-rays and charged particle impacts is given for the emission statistics of electrons from a metal surface.     

Evolution of the nanostructure of VVER-1000 RPV materials under neutron irradiation and post irradiation annealing

A high nickel VVER-1000 (15Kh2NMFAA) base metal (1.34 wt% Ni, 0.47% Mn, 0.29% Si and 0.05% Cu), and a high nickel (12Kh2N2MAA) weld metal (1.77 wt% Ni, 0.74% Mn, 0.26% Si and 0.07% Cu) have been characterized by atom probe tomography to determine the changes in the microstructure during neutron irradiation to high fluences. The base metal was studied in the unirradiated condition and after neutron irradiation to fluences between 2.4 and 14.9 × 10²³ m⁻² (E > 0.5 MeV), and the weld metal was studied in the unirradiated condition and after neutron irradiation to fluences between 2.4 and 11.5 × 10²³ m⁻² (E > 0.5 MeV). High number densities of ∼2-nm-diameter Ni-, Si- and Mn-enriched nanoclusters were found in the neutron irradiated base and weld metals. No significant copper enrichment was associated with these nanoclusters and no copper-enriched precipitates were observed. The number densities of these nanoclusters correlate with the shifts in the ΔT_{41 J} ductile-to-brittle transition temperature. These nanoclusters were present after a post irradiation anneal of 2 h at 450 °C, but had dissolved into the matrix after 24 h at 450 °C. Phosphorus, nickel, silicon and to a lesser extent manganese were found to be segregated to the dislocations.     

Micro-PIXE study of Ag in digestive glands of a nano-Ag fed arthropod (Porcellio scaber, Isopoda, Crustacea)

Micro-proton induced X-ray emission (micro-PIXE) method was applied to study the micro-localization of silver (Ag) in digestive glands of a terrestrial arthropod (Porcellio scaber) after feeding on silver nanoparticles (nano-Ag) dosed food. The aim of our work was to assess whether feeding on nano-Ag results in the assimilation of silver (Ag) in digestive gland cells. To study micro-localization and elemental distribution of Ag, the animals were fed on food dosed with nanoparticles for 14 days under controlled laboratory conditions. At the end of the feeding exposure, the animals were dissected and digestive glands prepared for micro-PIXE analyses and TEM investigation. The results obtained by micro-PIXE documented high amounts of Ag inside S-cells of the digestive gland epithelium; however, TEM investigation did not show particle aggregates inside digestive gland cells. Also no adverse effect on feeding behavior was recorded what is a measure of toxic effects. We explain the presence of Ag inside the cells as a result of the assimilation of dissoluted Ag ions from ingested nano-Ag particles. Assimilation of excessive amounts of ingested metal ions in S-cells is a well known metal detoxification mechanism in isopods. We discuss the advantages of using micro-PIXE for the micro-localization of elements in biological tissue in studies of interactions between nanoparticles and biological systems.     

PVA和PEG对电子束辐照制备的Fe3O4纳米粒子的影响

常温常压下不加入任何催化剂，用两种不同的活性剂聚乙烯醇（Polyvinyl alcohol，PVA）和聚乙二醇（Polyethylene glycol，PEG），在水溶液中通过电子束辐照可以成功地制备纳米Fe3O4粒子。通过紫外可见光分光光度计（Ultraviolet-visible spectrophotometer，UV）、X射线衍射（x-ray diffraction）、透射电子显微镜（Transmission electron microscopy，TEM）对辐照后的样品的光学特性、结构、形貌、大小进行表征。发现不同的活性剂对纳米粒子的尺寸会产生影响。     

A study on bactericidal properties of Ag coated carbon nanotubes

A silver layer is coated on carbon nanotubes (CNTs) by ion beam assisted deposition (IBAD). Standard agar dilution method is used to evaluate the bactericidal rate against Gram positive S. aureus and negative E. coli. The structure and the chemical states are investigated by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The results show that Ag coated CNTs possess very high bactericidal rate. In comparison with the Ag coated pyrolytic carbon sample, the Ag coated CNTs show stronger bactericidal property.     

Effect of metal ion location in reaction medium on formation process and structure of PtCu–CuO nanoparticles supported on carbon and γ-Fe2O3

The process of nanoparticle formation by radiochemical synthesis in a heterogeneous system has been investigated considering the effects of the metal ion location in the reaction medium. PtCu nanoparticles supported on carbon and γ-Fe₂O₃ were synthesized using a high-energy electron beam. The metal ions in the precursor were categorized as those dissolved in solution, adsorbed on support, and precipitated. The ratio of metal ions in the solution was varied prior to the electron beam irradiation and its effects on the synthesized particle structures were examined. The nanoparticles were characterized by inductively coupled plasma-atomic emission spectrometry, transmission electron microscopy, X-ray diffraction, and X-ray absorption spectroscopy. A PtCu alloy and CuO were immobilized on the support in all the samples. The PtCu alloy nanoparticle composition depended on the Cu ion content in the solution. The nanoparticle formation mechanism could be explained using the obtained results. Metal ions present in the solution resulted in formation of the alloy. The adsorbed ions also contributed to the alloy formation by desorbing from the support when irradiated. On the other hand, alloy formation with Pt from the precipitated Cu ions was found to be difficult.     

Analysis of the monoclinic-tetragonal phase transition of zirconia under irradiation

Zirconia produced by the oxidation of zirconium alloys in nuclear reactors exhibits a phase transition under ionic irradiation, simulating a neutron irradiation. To understand the mechanism responsible for this irradiation driven phase transition, different kinds of projectiles were used to irradiate pure monoclinic zirconia samples. The evolution of these irradiated samples as a function of dpa has been studied using grazing X-ray diffraction. The Rietveld method has been applied on collected X-ray diffraction diagrams to study the phase produced under irradiation and the kinetics of its formation. Even at high dpa values, only the monoclinic and tetragonal phases were used to simulate X-ray diffraction diagrams. No amorphisation of zirconia was observed. The evolution of unit cells and short range strains in both phases under irradiation leads us to think that the irradiation driven transition is martensitic. Supposing that the inelastic stopping power in sub-cascades is responsible for the irradiation driven phase transition, we propose a model based on the Landau-Ginzburg effective hamiltonian to explain both the m→t transition observed under irradiation and the t→m transition measured during isochronal annealing after irradiation.     

Neutron radiation effects on metal oxide semiconductor (MOS) devices

The main purpose of this study is to provide the knowledge and data on Deuterium-Tritium (D-T) fusion neutron induced damage in MOS devices. Silicon metal oxide semiconductor (MOS) devices are currently the cornerstone of the modern microelectronics industry. However, when a MOS device is exposed to a flux of energetic radiation or particles, the resulting effects from this radiation can cause several degradation of the device performance and of its operating life. The part of MOS structure (metal oxide semiconductor) most sensitive to neutron radiation is the oxide insulating layer (SiO₂). When ionizing radiation passes through the oxide, the energy deposited creates electron-hole pairs. These electron-hole pairs have been seriously hazardous to the performance of these electronic components. The degradation of the current gain of the dual n-channel depletion mode MOS caused by neutron displacement defects, was measured using in situ method during neutron irradiation. The average degradation of the gain of the current is about 35 mA, and the change in channel current gain increased proportionally with neutron fluence. The total fusion neutron displacement damage was found to be 4.8 × 10⁻²¹ dpa per n/cm², while the average fraction of damage in the crystal of silicon was found to be 1.24 × 10⁻¹². All the MOS devices tested were found to be controllable after neutron irradiation and no permanent damage was caused by neutron fluence irradiation below 10¹⁰n/cm². The calculation results shows that (n,α) reaction induced soft-error cross-section about 8.7 × 10⁻¹⁴ cm², and for recoil atoms about 2.9 × 10⁻¹⁵ cm², respectively.     

Structural-phase transformations in near-surface layers of alumina-zirconium ceramics induced by low-energy high-current electron beams

The effect of low-energy high-current electron beams (LEHCEBs) at E = 15 keV on mechanical characteristics of near-surface layers of alumina-zirconium ceramics (AZC) of the 20Al₂O₃-80ZrO₂(Y) composition (in mass %) is investigated by the method of dynamic indentation. It is shown that electron-beam treatment reduces Young’s modulus and nanohardness of this ceramic material. The action of LEHCEBs on the structural-phase state of modified subsurface layers of AZC specimens is analyzed. Their elemental and phase compositions are examined using several techniques: electron-probe X-ray spectral microanalysis (EPMA), secondary-ion mass spectrometry (SIMS), and X-ray diffractometry. It is found out that irradiation of the ceramic material by LEHCEBs stimulates the transitions of an m-phase of zirconium dioxide into a tetragonal modification, and results in a considerable decrease in the alumina phase. Based on the analysis of the data obtained, a conclusion is drawn that it is the processes resulting from irradiation and giving rise to formation of a subsurface layer with a phase composition different from that of the bulk material, which are responsible for the effect of modification of the material mechanical property.     

Irradiation embrittlement characterization of the EUROFER 97 material

The paper summarizes original results of irradiation embrittlement study of EUROFER 97 material that has been proposed as one candidate of structural materials for future fusion energy systems and GEN IV.Test specimens were manufactured from base metal as well as from weld metal and tested in initial unirradiated condition and also after neutron irradiation.Irradiation embrittlement was characterized by testing of toughness properties at transition temperature region - static fracture toughness and dynamic fracture toughness properties, all in sub-size three-point bend specimens (27 × 4 × 3 mm³). Testing and evaluation was performed in accordance with ASTM and ESIS standards, fracture toughness K_JC and K_Jd data were also evaluated with the “Master curve” approach. Moreover, J-R dependencies were determined and analyzed.The paper compares unirradiated and irradiated properties as well as changes in transition temperature shifts of these material parameters. Discussion about the correlation between static and dynamic properties is also given.Results from irradiation of EUROFER 97 show that this steel - base metal as well as weld metal - is suitable as a structural material for reactor pressure vessels of innovative nuclear systems - fusion energy systems and GEN IV. Transition temperature shifts after neutron irradiation by 2.5 dpa dose show a good agreement in the case of EUROFER 97 base material for both static and dynamic fracture toughness tests. From the results it can be concluded that there is a low sensitivity of weld metal to neutron irradiation embrittlement in comparison with EUROFER 97 base metal.     

Damage creation in ion irradiated Si1−xGex/Si structures

Strained SiGe/Si structures have been proposed as substrates for fabrication of high speed metal oxide semiconductor transistors. However, influence of strain and/or presence of Ge atoms on damage creation during ion irradiation have not been explored to a significant extent. In this study, Rutherford backscattering spectrometry (RBS) was used to characterize Si_1−xGe_x/Si structures irradiated by 140 keV He⁺ ions at room temperature. When compared with pure Si, strained samples show enhanced damage accumulation as a function of He fluence. Channeling angular scans did not reveal any specific configuration of displacements. Possible mechanisms for enhanced damage in strained Si are discussed.     

Assessment of DNA damage of Lewis lung carcinoma cells irradiated by carbon ions and X-rays using alkaline comet assay

DNA damage and cell reproductive death determined by alkaline comet and clonogenic survival assays were examined in Lewis lung carcinoma cells after exposure to 89.63 MeV/u carbon ion and 6 MV X-ray irradiations, respectively. Based on the survival data, Lewis lung carcinoma cells were verified to be more radiosensitive to the carbon ion beam than to the X-ray irradiation. The relative biological effectiveness (RBE) value, which was up to 1.77 at 10% survival level, showed that the DNA damage induced by the high-LET carbon ion beam was more remarkable than that induced by the low-LET X-ray irradiation. The dose response curves of “Tail DNA (%)” (TD) and “Olive tail moment” (OTM) for the carbon ion irradiation showed saturation beyond about 8 Gy. This behavior was not found in the X-ray curves. Additionally, the carbon ion beam produced a lower survival fraction at 2 Gy (SF2) value and a higher initial Olive tail moment 2 Gy (OTM2) than those for the X-ray irradiation. These results suggest that carbon ion beams having high-LET values produced more severe cell reproductive death and DNA damage in Lewis lung carcinoma cells in comparison with X-rays and comet assay might be an effective predictive test even combining with clonogenic assay to assess cellular radiosensitivity.     

新型高剂量X射线管研究

本文介绍了一种可广泛应用于血液辐照、疫苗生产、食品加工、生物学实验辐照等领域的X射线辐照设备,其利用电子束轰击金属靶韧致辐射产生的X射线进行辐照,与同位素射线辐照装置相比,该设备更安全,辐照均匀性更好,剂量可控。同时对新研制的X射线管的性能进行了测试。结果表明,X射线管辐照均匀性较好,可满足工业应用要求。