Nuclear Analysis最新文献

The nanostructured Er₂O₃ thin films implanted by Helium (He) were prepared by magnetron sputtering under different He partial pressure. The creep properties of the Er₂O₃ films under different temperatures ranging from ambient temperature to 450 °C were investigated systematically by nanoindentation measurements. The morphology and microstructure of the films were determined by a scanning electron microscope (SEM) and an X-ray diffractometer (XRD), respectively. The effects of He on the creep properties of the Er₂O₃ film were discussed by using a slope ($d\dot{\epsilon }/d\sigma$) of the creep rate stress curve at the steady-state creep stage. The results show that the crystallinity of the films became weak with the He partial pressure. Furthermore, the implanting He has a strong impact on the creep resistance of the Er₂O₃ thin films.

The transparency of scintillator screen has always been an important factor restricting the imaging performance. Here we present an innovative strategy, by combining the gel glass with GOS:Tb, F, we fabricated GOS:Tb, F/gel glass scintillation screen for effectively improvement of transmittance. The transmittance of the scintillator screen is ≥ 55% in the visible region. Thereafter, the relationship between the luminescence properties of the scintillator screen and the X-ray voltage and current is discussed in detail. In addition, the resolution of the scintillator screen under X-ray is 10 lp/mm, which may provide a promising application strategy in X-ray imaging.

Stability constants and enthalpies of N-methylethylenediamine-N,N′,N'-triacetic acid (MEDTA, denoted as H₃L) complexes with uranyl were measured using potentiometry and microcalorimetry, I = 1.0 mol L⁻¹ NaClO₄ solution at 25 °C. Thermodynamic analyses revealed three U(VI)/MEDTA complexes: UO₂(HL), UO₂L⁻, and UO₂(OH)L²⁻. The results showed that the complex formation of UO₂L⁻ (UO₂²⁺ ​+ ​L³⁻ = UO₂L⁻) is endothermic and driven solely by entropy. MEDTA in the UO₂L⁻ complex is a tetradentate and coordinates with U(VI) along the ethylenediamine backbone. Stability constant of mononuclear uranyl complex with MEDTA (UO₂L⁻) is lower than UO₂²⁺/EDDA complex but higher than UO₂²⁺/HEDTA complex, indicating that dangling acetate arm of MEDTA or hydroxyethyl group of HEDTA would lower the stability.

Nanosecond laser irradiation damage of optical films is one of the main factors to limit the output power when the high power solid laser system is used to drive inertial confinement nuclear fusion. In this review, taking SiO₂ and HfO₂ antireflection films as examples, the physical mechanisms of nanosecond laser irradiation damage of optical films were summarized from two aspects, i.e., numerical simulation studies and experimental investigations, including thermal melting damage, stress damage and plasma damage during irradiation. Based on the current research and difficulties in the field of irradiation damage of optical films, a brief outlook is given here, which may be helpful to improve the output power and operation stability of laser fusion devices in the future.

In a deep geological repository system, the presence of clay colloids in the geological disposal medium is considered to be a potential factor promoting nuclide migration. In this study, Gaomiaozi bentonite colloid (GMZC) was extracted using the gravity sedimentation method, and its interaction with U(VI) at neutral pH was studied. Small angle X-ray scattering (SAXS), X-ray photoelectron spectroscopy (XPS), dynamic light scattering, and other characterizations methods were used to analyze and observe the microstructure and agglomeration morphology of the bentonite colloidal particles before and after the reaction with U(VI) at the macro-meso-microscopic level. The XPS results indicate that the U(VI) reacted with the Si–O and Al–O on the GMZC particle surfaces at room temperature, and the hydrolyzed product of the U(VI) covered the colloidal surfaces in the neutral water environment, resulting in a decrease in the absolute zeta potential (from ∼31 mV to ∼19 mV). The hydrodynamic diameter of the colloidal particles did not change significantly (∼336 nm–∼360 nm), but the small-angle scattering data revealed that the fractal dimension was larger after the reaction (∼2.8–∼3.1), indicating particle agglomeration. About 14% of the GMZC particles were precipitated after reacting with the U(VI). When the temperature was increased to 55 °C and 85 °C, the precipitation did not change significantly, but the fractal dimension of the mixed system increased (from ∼3.1 to ∼3.6), and the d₀₀₁ peak was not observed in the SAXS results. When the temperature was decreased by 25 °C, the hydrodynamic diameter of the zeta potential and SAXS image both returned to the level before the temperature increase, indicating that the unstable change in the colloidal system caused by the temperature increase was reversible.

The binding strengths of ligand 2,2ʹ-bipyridine-6-carboxylate (BiPCA) and 1,10-phenanthroline-2-carboxylate (PhenCA) with trivalent actinides (An) like Am(III) and Cm(III), and lanthanides (Ln) like Nd(III), Sm(III), and Eu(III) were investigated by solvent extraction, potentiometry, and crystallography. Both ligands exhibit good actinides selectivity over lanthanides and radius selectivity for intragroup Ln(III) or An(III). In comparison, PhenCA is more prominent than BiPCA in these capabilities. Single crystal structures of the Nd(III)/Eu(III) with BiPCA and PhenCA illustrate that BiPCA, as well as PhenCA, is tridentate and chelates with Nd(III)/Eu(III) by two aromatic N-donors and a carboxyl O-donor. PhenCA exhibits shorter coordination bonds to the central atom than BiPCA, in agreement with the fact that in solution PhenCA behaves stronger binding strength than BiPCA to the same lanthanide cation. However, for the lanthanide complexes with the same ligand, no regular trend of the coordination bonds has been observed between Nd(III) and Eu(III).

With the development of pulsed spallation sources of neutrons in recent years has come the possibility to generate intense beams of higher energy than possible at reactor sources. This has enabled neutron total scattering methods to develop significantly for studies across a wide range of application areas. In this article we will review the background theory for analysis of total scattering in terms of the pair distribution function, we will review modern facilities and instrumentation, we will describe a range of analysis methods, and finally we will present a number of examples of recent work that illustrate many of the ideas discussed here.

FENGHUANG diffractometer at CMRR, a high-intensity multi-section neutron powder diffractometer, has been constructed to in situ studies of materials under high pressure high temperature conditions. With development of anvils, high pressure high temperature cell assemblies, high pressure device and alignment system, we have been realized the angle-dispersive neutron diffraction data collect at the range of achievable pressures and temperatures of 0–30 GPa and 300–1500 K, with the sample size of millimeter scale. This paper describes the technical characteristics of diffractometer and related techniques for high pressure neutron diffraction experiments, and gives some scientific examples that have been recently performed on FENGHUANG. The experience gained experiments on FENGHUANG could help promote the development of high pressure techniques on neutron scattering facilities.

Containerless processing is able to access the deeply supercooled regime due to the absence of heterogeneous nucleation sites, for example, container walls. Therefore, it allows us to explore a possible structural transition in the supercooled state, which is usually hidden by crystallization and difficult to detect with conventional methods. CoCrFeNi high entropy alloys (HEAs) were solidified in aerodynamic levitation containerless processing in Nanoscale-ordered Materials Diffractometer (NOMAD) BL-1B instrument at Spallation Neutron Source (SNS) Oak Ridge National Lab with expectation the distinct local ordering in CoCrFeNi HEAs. The temperature dependence of local structures was investigated from room temperature to 1500 °C on NOMAD. The phase evolution of the CoCrFeNi HEA investigated using in-situ neutron diffraction shows that room temperature face-centered cubic (fcc) phase is inherited from its high-temperature (above 1400 °C) fcc cluster.

Mass spectrometry techniques, such as AMS, TIMS and ICP-MS, represent promising techniques for the analysis of artificial radionuclides in environmental samples. They are characterized by high sensitivity, low detection limit, high sample throughput, shorter measuring time compared to conventional radiometric measurements, and the capability to provide isotopic composition information. After the Fukushima Daiichi Nuclear Power Plant accident, an increasing need was recognized for the rapid analysis of accident-released artificial radionuclides (actinides and fission products) in environmental samples for radiation dose estimation and evaluation of effectiveness of radioactive contamination remediation. This review describes the recent progress on mass spectrometric analysis of artificial radionuclides in environmental samples in Japan after the nuclear accident and discusses future research prospects for mass spectrometric techniques in radionuclide analysis.