Solid state synthesis of Mg-Ni ferrite and characterization by XRD and XPS

Single-phase magnesium-nickel ferrites with varying amounts of nickel and magnesium were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. A plot of lattice parameter versus composition of the ferrites (Mg_xNi_(1−x)Fe₂O₄, x?1) showed an abrupt deviation of lattice parameter linearity near MgFeO₄. The deviation was explained in terms of the distribution of Mg²⁺ in the octahedral and tetrahedral sites of the oxygen lattice. In XPS spectra, a broadening of the Mg 1s peak in Ni rich Mg-Ni ferrites from that observed in pure MgFe₂O₄, was explained by changes in the distribution of Mg²⁺ ion in tetrahedral and octahedral sites. A depth distribution of Mg in Ni_0.5Mg_0.5Fe₂O₄ showed an enrichment of Mg on surface.     

利用软印刷结合扩散制作纳米颗粒样品的方法

扫描探针显微镜(SPM,Sganning Probe Microscopy)是进行纳米材料表面性质测量的有力工具.制样是进行SPM观测的关键性技术.分子间作用力较强的纳米颗粒在制样过程中常常会发生二次聚合形成团簇,给SPM观测带来困难.针对纳米颗粒制样过程中的再聚合问题,本文提出了一种软印刷转印结合扩散的方法.利用基底表面的液膜对转引形成的纳米颗粒分布进行增强的扩散,从而得到适合SPM观测的纳米颗粒样品.验证实验结果表明此方法是一种可用于SPM观测纳米颗粒的有效制样手段.     

Production and preliminary characterization of DC plasma polymerized allylamine film (PPAA) by NRA, ERD and XPS

Due to its surface properties, especially the presence of amine groups, plasma polymerized allylamine (PPAA) is involved in a large range of applications. Most of them are related to biology and biochemistry. In this work, we demonstrate a quick and simple way to produce PPAA thin films by conventional DC magnetron sputtering. To the best of our knowledge, this is the first method not involving radiofrequency (RF) or microwave discharges. In this paper, we show preliminary characterizations on the produced films (bulk analysis) carried out by ion beam techniques. The Hydrogen content in the whole layers was measured by ERD. The surface composition was probed by XPS on pentafluorobenzaldehyde (PFBA) derivatized films: the maximum concentration of amine groups is 1.6%.     

Fatigue crack propagation testing using subsized rotating bending specimens

In many industrial applications, mechanical properties characterization is needed yet sufficient amount of material for standardsized specimens is not available. Miniaturized specimen testing technique has to be employed. Currently there are a lot of effort in developing subsized specimen technique for impact, fracture toughness and tensile properties. Work on fatigue properties testing is limited and largely confined to stress/strain life tests. In the current work, evaluation of fatigue crack propagation behaviour using surface crack growth in a rotating bending rod has been attempted. Nine different rod geometries have been tested. The resulting fatigue crack propagation data is more sensitive to rod diameter than to rod length. Difference in crack growth behaviour can largely be understood when crack closure is taken into account. All in all, the crack propagation data obtained from these small sized rods agree well with those obtained from standard testing employing compact tension specimens. A more precise picture about the crack growth behaviour can be obtained if crack closure is considered. If crack closure is not monitored, rods with longer length and smaller diameter are more likely to give the conservative upper bound fatigue crack propagation behaviour.     

Precision of PIXE analysis of thin fluid-residue specimens using internal standards

Different roles for internal standards in PIXE analysis of fluid residues are discussed. The efficacy of internal standards is predicated on having homogeneous targets of uniform thickness; the use of lecithin additives to achieve this is described and data are presented to illustrate the dependence of analytical precision on the mode of specimen preparation. Determination of actual thickness via measurement of the energy loss of transmitted protons is demonstrated; this provides a means of correcting for departures from the much-quoted “thin target” criterion.     

Dynamic testing of large AISI-316L steel specimens behaviour using LDTF

The paper presents the results of a series of dynamic experiments on AISI-316L steel specimens having a cross section of 2000 mm² and a gauge length of 350 mm subject to dynamic traction up to rupture. Results for dynamic tests at a nominal strain rate up to 50 s⁻¹ are compared to quasi-static ones, showing an important increase in both yield stress and flow stress. The experimental techniques are described, with special emphasis on full-field optical strain measurements based on Moiré interferometry. A 1-D numerical analysis of the experiments is presented.     

Characterization of tensile strength and fracture toughness of nuclear graphite NBG-18 using subsize specimens

The mechanical properties of NBG-18 nuclear grade graphite were characterized using small specimen test techniques and statistical treatment on the test results. New fracture strength and toughness test techniques were developed to use subsize cylindrical specimens with glued heads and to reuse their broken halves. Three sets of subsize cylindrical specimens of different sizes were tested to obtain tensile fracture strength and fracture toughness. The mean fracture strength decreased as the specimen size increased. The fracture strength data indicate that in the given diameter range the size effect is not significant and much smaller than that predicted by the Weibull moduli estimated for individual specimen groups of the Weibull distribution. Further, no noticeable size effect existed in the fracture toughness data. The mean values of the fracture toughness datasets were in a narrow range of 1.21-1.26 MPa√m.     

Calculation of fuel burnup and radionuclide inventory in the Syrian miniature neutron source reactor using the GETERA code

Calculations of the fuel burnup and radionuclide inventory in the Syrian miniature neutron source reactor (MNSR) after 10 years (the reactor core expected life) of the reactor operation time are presented in this paper using the GETERA code. The code is used to calculate the fuel group constants and the infinite multiplication factor versus the reactor operating time for 10, 20, and 30 kW operating power levels. The amounts of uranium burntup and plutonium produced in the reactor core, the concentrations and radionuclides of the most important fission products and actinide radionuclides accumulated in the reactor core, and the total radioactivity of the reactor core were calculated using the GETERA code as well. It is found that the GETERA code is better than the WIMSD4 code for the fuel burnup calculation in the MNSR reactor since it is newer, has a bigger library of isotopes, and is more accurate.     

Sizing and characterization of ultrasonic indications using imaging techniques

For discontinuity analysis more and more sophisticated methods are used in the nuclear industry. The rapid development of computer technology offers the possibility to use imaging techniques. Instead of specialized focusing transducers the more flexible synthetic focusing techniques can be used. Presupposing that the material is ultrasonically isotropic and homogeneous, imaging techniques make it possible to visualize the reflectivity of the volume to be tested.Siemens developed the high speed holographic instrument Holo 3000 in cooperation with the University of Bochum. In this paper the method of Broad Band Holography is presented in the context of other imaging techniques.Different filtering methods have been investigated in order to achieve highest resolution and best signal to noise ratio with a given dataset. Different transducers respective wave modes have been applied to austenitic welds and claddings. The reconstructed image was evaluated using image processing techniques in order to investigate the possibilities to produce results easier to be quantifed than the original reconstruction.The results presented show a reliable expert tool for analysis measurements which also can be used for flaw detection.     

Calculations of fuel burn-up and radionuclide inventory in the syrian miniature neutron source reactor using the WIMSD4 code

Calculations of the fuel burn up and radionuclide inventory in the Miniature Neutron Source Reactor after 10 years (the reactor core expected life) of the reactor operating time are presented in this paper. The WIMSD4 code is used to generate the fuel group constants and the infinite multiplication factor versus the reactor operating time for 10, 20, and 30 kW operating power levels. The amounts of uranium burnt up and plutonium produced in the reactor core, the concentrations and radioactivities of the most important fission product and actinide radionuclides accumulated in the reactor core, and the total radioactivity of the reactor core are calculated using the WIMSD4 code as well.     

XPS and optical studies of Xe-implanted and annealed YSZ single crystals

Xe⁺ ion implantation with 200 keV was completed at room temperature up to a fluence of 1 × 10¹⁷ ion/cm² in yttria-stabilized zirconia (YSZ) single crystals. Optical absorption and X-ray photoelectron spectroscopy (XPS) were used to characterize the changes of optical properties and charge state in the as-implanted and annealed crystals. A broad absorption band centered at 522 or 497 nm was observed in the optical absorption spectra of samples implanted with fluences of 1 × 10¹⁶ ion/cm² and 1 × 10¹⁷ ion/cm², respectively. These two absorption bands both disappeared due to recombination of color centers after annealing at 250 °C. XPS measurements showed two Gaussian components of O_1s spectrum assigned to Zr–O and Y–O, respectively, in YSZ single crystals. After ion implantation, these two peaks merged into a single peak with the increasing etching depth. However, this single peak split into two Gaussian components again after annealing at 250 °C. The concentration of Xe decreased drastically after annealing at 900 °C. And the XPS measurement barely detected the Xe. There was no change in the photoluminescence of YSZ single crystals with a fluence of 1 × 10¹⁷ ion/cm² after annealing up to 900 °C.     

Si基体上双层Ti－O薄膜的XPS和AES分析研究

采用沉积－离子轰击－沉积工艺制备了双层Ｔｉ－Ｏ薄膜，并利用ＸＰＳ和ＡＥＳ对膜层进行了深度分析．结果发现：在氩离子轰击后的薄膜上再沉积同质薄膜，在膜表层一定厚度内可得到具有化学配比的ＴｉＯ２薄膜；氩离子的轰击使钛及碳氧化物内迁入Ｓｉ基体，而Ｓｉ外迁到膜内，并造成多价形式的Ｔｉ氧化物共存，ＴｉＯ２在这些Ｔｉ氧化物中所占的比例随沉积膜深度呈现先逐渐减少而后又逐渐增大的分布规律；此外，氩离子的轰击使得薄膜与基体在界面处形成较宽的、复杂的混合层．混合层主要由ＴｉＯ２、Ｔｉ２Ｏ３、ＴｉＯ、未氧化完全的ＳｉＯ２－ｘ及纯Ｓｉ组成。     

Influence of resonant Raman scattering in the elemental analysis using X-ray emission based techniques

A tabulation of characteristic X-ray energies across the periodic table are provided where those X-rays are expected to result in a significant fractional resonant Raman scattering (RRS) contribution to the X-ray attenuation from a particular shell/subshell of the same or another element. The tabulations can be considered as guideline so as to know what can be expected due to RRS in typical photon- and particle-induced X-ray emission spectrometry. The RRS contribution is not included in the available theoretical attenuation coefficients, which are generally used in estimation of the matrix corrections in routine quantitative elemental analysis based on various X-ray emission techniques. The radiative RRS peaks can also interfere with normal X-ray spectrum and influence the elemental analysis. The RRS cross-section depends upon the energy difference of the X-ray energy and the shell/subshell ionization threshold taken in the units of the shell/subshell energy width, density of available states near the Fermi level, and the band structure in case the element is in the solid form. Some aspects of the dependence of the RRS contribution on the chemical forms of the elements are also discussed.     

Monte Carlo simulation of a conceptual thermal column in the Syrian miniature neutron source reactor using MCNP-4C

Based on probabilistic approach, the MCNP-4C code has been used effectively to simulate the Syrian MNSR reactor core and all its surrounding components in three dimensions, including a preliminary conceptual design of a thermal column to be installed later. For verification and validation purposes, reactor calculations include: criticality and control rod worth. Values of these parameters are 1.00517 and 6.54 mk, respectively. The thermal column is to be installed in the water of the reactor pool. Optimal conditions for this thermal column were tested using the already developed model. Optimization focused on the most suitable position for placement of the column in the water pool, dimensions, and material. The aim was to have a thermal neutron flux of 1 × 10⁹ n cm⁻² s⁻¹ in the center of thermal column, and resonant and fast neutron fluxes to be as low as possible as well.     

Effect of hydrogen on SiC-C films with AES and XPS analyses

SiC-C films with different content of SiC were deposited with r. f. magnetron sputtering followed by argon ion bombardment. These films were then permeated by hydrogen gas under the pressure of 3.23 × 107 Pa for 3h at 500K. AES and XPS were used to analyze chemical bonding states of C and Si in the SiC-C films as well as contaminating oxygen before and after hydrogen gas permeation in order to study the effect of hydrogen on them. Related mechanism was discussed in this paper.     

γ射线辐照后木荷粉自由基的ESR和XPS分析

利用电子自旋共振波谱(ESR)和X射线光电子能谱(XPS)技术分别测量γ射线辐照后木荷粉体的自由基波谱和X射线光电子能谱.分析木荷粉体在60Coγ射线辐照下自由基的变化规律、化学组成和结构变化.结果表明:木荷自由基的光谱分裂因子g=2.0033,自由基的强度随吸收剂量按指数规律I=1-e-bD增加;经过200 kGy剂量的辐照后木荷表面O/C原子比稍有增加,C-C、CH和C-O键含量增加,C=O双键含量减少,-O-C=O含量增加为原来的2.5倍,说明木材表面生成了一些含氧官能团,或碳的氧化态增高.     

Oxidizing dissolution of spent MOX47 fuel subjected to water radiolysis: Solution chemistry and surface characterization by Raman spectroscopy

The mechanisms of oxidizing dissolution of spent MOX fuel (MIMAS TU2®) subjected to water radiolysis were investigated experimentally by leaching spent MOX47 fuel samples in pure water at 25 °C under different oxidizing conditions (with and without external gamma irradiation); the leached surfaces were characterized by Raman spectroscopy. The highly oxidizing conditions resulting from external gamma irradiation significantly increased the concentration of plutonium (Pu(V)) and uranium (U(VI)) compared with a benchmark experiment (without external irradiation). The oxidation behavior of the plutonium-enriched aggregates differed significantly from that of the UO₂ matrix after several months of leaching in water under gamma irradiation. The plutonium in the aggregates appears to limit fuel oxidation. The only secondary phases formed and identified to date by Raman spectroscopy are uranium peroxides that generally precipitate on the surface of the UO₂ grains. Concerning the behavior of plutonium, solution analysis results appear to be compatible with a conventional explanation based on an equilibrium with a Pu(OH)_4(am) phase. The fission product release - considered as a general indicator of matrix alteration - from MOX47 fuel also increases under external gamma irradiation and a change in the leaching mode is observed. Diffusive leaching was clearly identified, coinciding with the rapid onset of steady-state actinide concentrations in the bulk solution.