Study on effects of swift heavy ion irradiation on the crystal structure in CeO2 doped with Gd2O3

To simulate the effects of Gd₂O₃-doping and high-energy fission products in UO₂, Gd₂O₃-doped CeO₂ pellets were irradiated with 200-MeV Xe¹⁴⁺ ions. Doping and irradiation effects were analyzed using X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS). The lattice constant of CeO₂ decreases and the local structure is disordered with increased doping levels. However, the irradiation induces an expansion of the lattice and a disordering of atomic arrangement near the Gd atoms. The effects of the irradiation become more pronounced with increasing Gd₂O₃-dopant levels. Our results are compared with those of a study involving Er₂O₃-doped CeO₂.     

Effects of swift heavy ion irradiation on the structure of Er2O3-doped CeO2

In order to simulate the effects of burnable poison doping on the fission fragment damage of UO₂ nuclear fuels, Er₂O₃-doped CeO₂ pellets were irradiated with 200 MeV Xe¹⁴⁺ ions. The irradiation effect was measured by means of X-ray diffraction (XRD). The expansion of lattice and the disordering of atomic arrangement due to the irradiation become more remarkable with increasing the concentration of the Er₂O₃ dopant.     

烧绿石(La1-yNdy)2Zr2O7模拟固化241Am的晶体结构稳定性研究

为研究²⁴¹Am在La₂Zr₂O₇烧绿石中的固化行为及其对烧绿石晶体结构稳定性的影响,实验选用Nd作为²⁴¹Am的模拟物,采用Sol-喷雾热解法合成了(La_1-yNd_y)₂Zr₂O₇（0.0≤y≤1.0）系列样品,并借助X射线衍射和振动光谱手段对样品的晶体结构稳定性进行了研究。实验结果表明：随着Nd掺杂量的增加,O48f位置参数x_48f和I₍₁₁₁₎ /I₍₂₂₂₎均呈规律性增大,Raman谱逐渐展宽,IR谱发生蓝移,所有结果均证实用Nd不断替换La将导致烧绿石晶体结构有序化程度逐渐降低。另外,实验发现掺杂量y≈0.8是烧绿石晶体结构发生几何相变的逾渗阈值,超过该阈值有序的烧绿石结构将发生突变进而加速向无序萤石结构转变,该实验结果可为(La_1-yAm_y)2Zr2O7固溶体的结构稳定性研究提供参考。     

γ辐照联合H_2O_2处理污泥滤液的研究

采用60 Coγ射线辐照处理污泥滤液,通过对比处理前后化学需氧量(COD)、紫外可见吸光度和浑浊度的变化,研究了辐照处理中初始pH、初始H2O2浓度和吸收剂量对污泥滤液处理效果的影响。结果表明:在相同吸收剂量和初始H2O2浓度条件下,酸性条件更利于CODCr的降低;γ辐照联合H2O2处理存在显著协同效应,吸收剂量为18.75kGy、初始H2O2浓度为2mmol/L时,污泥滤液CODcr去除率达70.4%,浑浊度下降94.9%。     

Application of combined neutron diffraction and impedance spectroscopy for in-situ structure and conductivity studies of La2Mo2O9

In-situ neutron diffraction combined with AC impedance spectroscopy was applied successfully to investigate the correlation between crystal structure and electrical properties of the La₂Mo₂O₉ oxide ion conducting electrolyte material. Neutron diffraction patterns were collected as a function of temperature while the AC impedance spectra were recorded simultaneously using a modified sample environment to monitor the conductivity change of the sample. A close relationship between unit cell parameters and the bulk conductivity was observed, confirming that the oxygen transport is dependent on the lattice structure. With the transition from the low temperature alpha to the high temperature beta phase, expansion of the crystal structure makes more space available for oxygen transport, leading to a dramatic increase of the ionic conductivity. The successful application of this technique provides a new method to simultaneously investigate crystal structure and electrical properties in electro-ceramics in the future.     

Thermodynamics of the Li2O fusion reactor breeder

Lithium oxide is one of the candidate tritium breeders for a fusion reactor. A computational survey, using experimentally measured activity coefficients for LiOH in Li₂O, was made of the thermodynamic behavior of Li₂O as a fusion reactor breeder blanket material. All significant species involved in establishing an equilibrium state, including those generated from the effects of H-T exchange, are included in the analysis. Oxygen activity, particularly at values less than approximately 10^?15, is a variable that was found to strongly influence the balance of the molar quantities and activities of various species. These relationships are important in assessing the HT-HTO balance in the gas phase, the enhancement of tritium release by protium purging, the vaporization of LiOH/LiOT and Li, and the effects of elemental lithium and LiT in the condensed phase.     

热处理对LaNi4.25Al0.75/SiO2复合材料储氢特性的影响

采用气相二氧化硅法制备了LaNi_4.25Al_0.75/SiO₂复合材料。研究了该复合材料经不同温度（473～1 073 K）热处理后的相组成、形貌及吸放氢p-C-T曲线、吸氢动力学性能和吸放氢循环性能。结果表明,随着热处理温度的升高,LaNi_4.25Al_0.75/SiO₂复合材料吸氢量减少,平台压升高,平台斜率略有增加,而动力学性能并无显著变化。经60次吸放氢循环后,经不同温度热处理后的样品均未出现粉化现象,且与未循环样品储氢性能基本保持一致。     

Diffusion of tritium in single crystal Li2O

The release of tritium from neutron irradiated spherical samples of single crystal Li₂O was measured by isothermal annealing experiments. The release is shown to be controlled by diffusion of tritium in the solid under appropriate experimental conditions. Deviations from solely diffusion controlled release were observed when traces of water were present in the He-purge gas used in the experiments. The diffusivity of tritium in single crystal Li₂O is given by In(D/cm₂s^?1) = ? (5.93 ± 0.48) ? (81.73 ± 4.24)10³J/RTfor 850 K < T < 1200 K. (R = 8.314 JK^?1mol^?1).     

Depth profiling of Al2O3 + TiO2 nanolaminates by means of a time-of-flight energy spectrometer

Atomic layer deposition (ALD) is currently a widespread method to grow conformal thin films with a sub-nm thickness control. By using ALD for nanolaminate oxides, it is possible to fine tune the electrical, optical and mechanical properties of thin films. In this study the elemental depth profiles and surface roughnesses were determined for Al₂O₃ + TiO₂ nanolaminates with nominal single-layer thicknesses of 1, 2, 5, 10 and 20 nm and total thickness between 40 nm and 60 nm. The depth profiles were measured by means of a time-of-flight elastic recoil detection analysis (ToF-ERDA) spectrometer recently installed at the University of Jyväskylä. In TOF-E measurements ⁶³Cu, ³⁵Cl, ¹²C and ⁴He ions with energies ranging from 0.5 to 10 MeV, were used and depth profiles of the whole nanolaminate film could be analyzed down to 5 nm individual layer thickness.     

Ion guiding through capillaries in uncoated Al2O3 membranes

We made an experimental study on ion guiding through capillaries in uncoated Al₂O₃ membranes using a variety of ions such as O¹⁺, O³⁺, and O⁶⁺. The incident energy was varied within the range of 30-150 keV. The results were compared with others using coated PET and Al₂O₃ capillary membranes as well as with the so-called scaling law discovered by Stolterfoht and his co-workers. Good agreement of our results with the scaling law was found. However, our membranes showed extraordinarily strong guiding ability. The reason lies in that our membranes were uncoated. A slower charge drift speed along the insulating capillary wall and a much larger equilibrium charge Q_∞ seems to exist in our experiment.     

Vacuum plasma etching of 1 wt% La2O3 dispersed tungsten

Vacuum plasma etching of 1 wt% La₂O₃ doped tungsten alloy surfaces were carried out to refine the surface morphology for enhancing its bonding characteristics with copper for fusion reactor components. Three different gas compositions containing argon with zero, 14.3 and 25 vol% hydrogen were used to carry out the plasma etching from 30 to 120 s on the given samples. Mitutoyo surface roughness (R_a) measurement, FORM TALYSURF and scanning electron microscopy (SEM) were employed to measure the changes in the surface roughness. Plasma etching with 14.3 vol% hydrogen mixture was found to be the best in micro-roughening the alloy surface. The maximum increase of 44% in R_a value was obtained with this gas mixture, when etched for 90 s.     

Temperature distribution in Li2O pellets under neutron irradiation

The center temperature of Li₂O pellets under neutron irradiation was measured using an encapsuled pin. The surface temperatures of the pellets and the pellet/cladding heat transfer coefficients were estimated on the basis of the well-known conductivity integral.     

Ion beam analysis of partial lithium extraction of LiMn2O4 by chemical delithiation

Lithium manganese oxide, LiMn₂O₄, has been studied by many research groups. This material is a great candidate to be used as positive electrode in rechargeable lithium-ion batteries because of its low cost, abundant precursors and non-toxicity. LiMn₂O₄ has a spinel Fd-3m structure and shows a reversible extraction and insertion of lithium ions that is one of the most important characteristic of positive electrodes in rechargeable batteries.In this work, LiMn₂O₄ samples were synthesized by solid state reaction. A partial lithium removal was performed on this system by chemical delithiation using HCl aqueous solutions at different concentrations. Six partial-extracted compounds were obtained and characterized by Ion beam analysis (IBA) in order to obtain the Li concentrations. X-ray diffraction (XRD) and Rietveld analyses were also performed. A rigorous study of lithium contents is critical to analyze the structure properties of these compounds and samples production parameters. The IBA method used in this work was the analysis of energy spectra of elastic backscattered (EBS) proton from Mn, O and Li nuclei and the α-particles energy from the ⁷Li(p,α)⁴He nuclear reaction (NR).     

Batch Recycle Purification Technological Process of18O-H2O Wate

A batch purification technological process for¹⁸O-H₂O recycled water is established. The impurities was analyzed firstly. The bacteria and endotoxin in¹⁸O-H₂O recycled water could be removed by ultraviolet sterilize rand sterile membrane, and soluble impurities removed by multiple cryogenic distillation. This process makes indicators meet the accelerator pharmaceutical production requirements, together with high target and synthesis efficiency. This process, which takes advantages of¹⁸O-H₂O recycled water produced by accelerator, reduces the cost significantly and utilizes the resources reasonably and efficiently.     

Electronic sputtering of Gd3Ga5O12 and Y3Fe5O12 garnets: Yield, stoichiometry and comparison to track formation

The results of present paper have shown that sputtering of yttrium iron garnet (Y₃Fe₅O₁₂) under swift heavy ions in the electronic energy loss regime is non-stoichiometric. Here we are presenting additional experimental results for gadolinium gallium garnet (Gd₃Ga₅O₁₂) as target. The irradiations were performed with different ions (⁵⁰Cr (589 MeV), ⁸⁶Kr (195 MeV) and ¹⁸¹Ta (400 MeV)) impinging perpendicularly to the surface. As earlier, the sputtering yield was determined by collecting the emitted gadolinium and gallium atoms on a thin aluminium foil, placed upstream above the target and analyzing the Al catcher by Rutherford backscattering. Also for Gd₃Ga₅O_12, the emission of Gd and Ga is non-stoichiometric. Sputtering appears above a critical electronic stopping power of S_th = 11.6 ± 1.5 keV/nm, which is larger than the threshold for track formation, in agreement with other amorphisable materials. In addition, the angular distribution of the sputtered species was measured for Y₃Fe₅O₁₂ and Gd₃Ga₅O₁₂ using 200 MeV Au ions impinging the surface at 20° relatively to the surface. For the two garnets the ratio of Y/Fe (and Gd/Ga) varies with the angle of emitted species and the stoichiometry seems to be preserved only for an emission perpendicular to the surface.     

LiH和LiT与H2O反应机理研究

氢材料在微量H₂O、CO₂、O₂和N₂存在下可能发生物理化学反应,使材料的物理品位下降。由于反应过程十分复杂,很难从实验上准确获取这类反应的最佳通道和具体产物信息,因此,从理论上研究氢材料分子的物理化学性质及其化学反应机制,了解化学反应过程具有十分重要的意义。本文使用Gaussian03软件包和Gaussview工具软件,在6-311G(d)全电子基函数水平上,应用二阶微扰理论优化得到了⁶LiH、⁶LiT与H₂O反应的中间体、过渡态及产物的结构,总能量,振动频率和零点能等。通过计算发现⁶LiH、⁶LiT均只有1个反应通道,⁶LiH与H₂O反应的焓变、活化能和反应速率常数分别为-156.99 kJ/mol、8.95 kJ/mol和3.75×10¹⁰(mol•dm^-3)^-1/s,⁶LiT与H₂O反应的焓变、活化能和反应速率常数分别为-159.02 kJ/mol、9.92 kJ/mol和1.72×10¹⁰ (mol•dm^-3)^-1/s。     

Growth of TiO2 surfaces following low energy (<40 eV) atom and small cluster bombardment

Low energy (10-40 eV) interaction of small Ti_xO_y clusters with a rutile (1 1 0) substrate was investigated using molecular dynamics with the aim of determining the influence of various parameters on surface growth and defect formation. Rutile growth was simulated through depositing randomly selected clusters with energies in the tens of eV range. Long time scale evolution was approximated through heating the substrate. A modified second-moment-Buckingham-QEq (SMB-Q) empirical potential was developed for the purpose. Crystal growth on amorphous and anatase TiO₂ substrates was also considered. Grown lattice layers were compared by visual inspection along with radial distribution function (RDF) plots. Bombardment at an energy of around 20 eV in an oxygen rich atmosphere with a high proportion of bombarding clusters, TiO, TiO₂, as opposed to single atoms, was found to produce rutile growth with the best crystallinity.     

Radiation effect on the photoluminescence properties of Si/SiO2 thin films

Silicon ions were implanted into SiO₂ thin films with various doses and energies. For the films implanted with various ion doses the photoluminescence (PL) intensity of 470 nm firstly increased with the increase of Si ion dose, which is similar to the variation trend of displacement per atom (DPA) number during ion radiation. Further increasing Si ion dose the PL intensity of 470 nm decreased gradually since the neutral oxygen vacancy centers were destroyed. For the samples implanted with different energy the variation trend of PL intensity for 470 nm peak is similar to the result of DPA under different radiation energy according to SRIM2006 simulation. With the increase of radiation energy a new PL peak at 550 nm appeared because of the variation of defect type. Combining with the simulation results and PL spectra the radiation effect on Si/SiO₂ thin films were proposed.