Mechanisms of fluorescence enhancement in rare earth sol-gel glass containing Al

Analysis of glasses containing Eu and Tb dopants yields new insights about the role of Al³⁺ co-doping in improving fluorescence yield of glasses containing rare earth (RE) dopants. Our work suggests that Al co-doping enhances fluorescence by two important mechanisms. (1) At low Al:RE ratio the site symmetry is lowered, allowing more admixture of opposite parity wavefunctions and increased transition probability. (2) At high Al:RE ratio, the highest frequency phonons are of lower energy; so nonradiative decay rates are reduced. In addition, a new technique - post-annealing immersion - is introduced, which allows the study of RE location in the sol-gel matrix. Al co-doping is observed to increase the tendency for RE ions to reside on pore surfaces.     

Antiferromagnetic order and spin glass behavior in Dy2CuIn3

The magnetic properties of the intermetallic compound Dy₂CuIn₃ have been investigated. Ac and dc-susceptibility measurements indicate an onset of antiferromagnetic ordering at T_N=19.5 K and an additional frequency dependent transition at T_ds∼9 K. Neutron diffraction studies confirm the ordered transition at 19.5±1 K. The magnetic unit cell can be described by the propagation vector k=(0.25,0.25,0) with the magnetic moment μ=2.63(4)μ_B/Dy³⁺ parallel to the c-axis. Nevertheless, neutron diffraction reveals no additional magnetic phase transition around or below 9 K, which suggests that, at lower temperatures, a spin glass state may be formed in coexistence with the antiferromagnetic mode as a result of frustration and the antagonism between ferromagnetic and antiferromagnetic exchange interactions.     

深度卷积神经网络在辐射环境下核废料检测中的应用

针对辐射环境下核废料检测准确率低的问题,提出一种基于深度卷积神经网络的辐射环境下核废料检测算法Dense-Dilated-YOLO V3。实验结果表明,Dense-Dilated-YOLO V3在不增加参数的情况下扩大了网络感受野,也有效避免图像信息的损失,同时能够在核辐射环境下提取到更多的目标细节特征,对辐射环境下目标检测的准确率可达93.29%,比原算法提高5.53%,召回率可达91.73%,提高了8.28%,有效解决了复杂辐射环境下核废料检测准确率低的问题,为辐射环境下核废料检测提供了新的途径。     

Direct observations of the leaching of a simulated nuclear waste glass in a radiation environment

The durability of the media proposed for the containment of commercial nuclear waste will be affected not only by the differences in groundwater composition that they might encounter but also by the changes that their own irradiation fields will make to these solutions. Experimental results that question the ability of current leaching experiments to predict the stability of nuclear waste composites are presented.     

Applications of high energy ion beam techniques in environmental science: Investigation associated with glass and ceramic waste forms

High energy ion beam capabilities including Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA) have been very effectively used in environmental science to investigate the ion-exchange mechanisms in glass waste forms and the effects of irradiation in glass and ceramic waste forms in the past. In this study, RBS and NRA along with SIMNRA simulations were used to monitor the Na depletion and D and ¹⁸O uptake in alumina silicate glasses, respectively, after the glass coupons were exposed to aqueous solution. These results show that the formation of a reaction layer and an establishment of a region where diffusion limited ion exchange occur in these glasses during exposure to silica-saturated solutions. Different regions including reaction and diffusion regions were identified on the basis of the depth distributions of these elements. In the case of ceramics, damage accumulation was studied as a function of ion dose at different irradiation temperatures. A sigmoidal dependence of relative disorder on the ion dose was observed. The defect-dechanneling factors were calculated for two irradiated regions in SrTiO₃ using the critical angles determined from the angular yield curves. The dependence of defect-dechanneling parameter on the incident energy was investigated and it was observed that the generated defects are mostly interstitial atoms and amorphous clusters. Thermal recovery experiments were performed to study the damage recovery processes up to a maximum temperature of 870 K.     

交换纤维柱分离ICP-AES测定高纯氧化镱中La、Nd、Eu和Gd

以强酸型离子交换纤维柱分离富集高纯Yb₂O₃中La,Nd,Eu和Gd等痕量杂质元素,并用Optima 5300 DV ICP-AES测定分离富集后的这4种元素。供试纤维对Yb的动态吸附容量为134 mg·g-1,4.0 g纤维柱的分离条件为：pH 3.00的试液以1.0 mL·min-1流速上柱后,分离柱先以流速为1.5 mL·min-1的pH 3.00 HNO₃溶液80 mL预淋洗,再以同样流速pH 5.00的0.01 mol·L-1 EDTA铵溶液淋洗。结果表明：10 mg Yb与各为0.100 μg的La,Nd,Eu和Gd能达到基线分离;分离含100 mg Yb的试液后,在杂质富集液中Yb的残留浓度仅为0.017 1 μg·mL-1。 研究显示,当待测试液中Yb₂O₃的浓度小于100 μg·mL-1(如Yb 87.8 μg·mL-1)时,它对测定La,Nd,Eu和Gd等杂质元素的基体干扰可以忽略不计。富集倍数分别为La₂O₃ 3.68×105,Nd₂O₃ 4.20×105,Eu₂O₃ 3.82×105,Gd₂O₃ 4.01×105。方法检出限分别为La₂O₃ 0.005 0 pg·mL-1,Nd₂O₃ 0.014 pg·mL-1,Eu₂O₃ 0.001 8 pg·mL-1,Gd₂O₃ 0.008 2 pg·mL-1。本方法已用于99.99% Yb₂O₃样品中4种稀土杂质的测定,标准加入的平均回收率分别为La₂O₃ 94.2%,Nd₂O₃ 107%,Eu₂O₃ 97.8%,Gd₂O₃ 102%,RSD (%, n=5)分别为La₂O₃ 6.2,Nd₂O₃ 5.9,Eu₂O₃ 7.3,Gd₂O₃ 2.5,校正曲线不需进行Yb的基体匹配,分析周期为4 h。     

Recent studies on radiation induced F-center and colloid particle formation in synthetic NaCI and natural rock salt

Radiation induced F-center and Na metal colloid formation have been studied, at temperatures between 100 and 350°C, in melt growth synthetic NaCl crystals and natural rock salt samples, using equipment for making optical measurements during 1–3 MeV electron irradiation. In both types of NaCl the damage formation kinetics are qualitatively similar. However, there are large quantitative differences which depend on irradiation temperature, dose rate, total dose, inherent strain, strain applied prior to irradiation and other factors. Natural rock salt samples from different localities exhibit markedly different radiation induced colloid formation rates. An extrapolation of the current data to the doses expected in radioactive waste depositories indicate that natural salt immediately adjacent to the planned waste canisters could develop between 0.1 and 50 percent colloidal sodium in 50 to 400 years.