掺杂Y2O3的铁锡复合氧化物的穆斯堡尔谱学研究

采用化学共沉淀法合成α－Ｆｅ２Ｏ３－ＳｎＯ２和α－Ｆｅ２Ｏ３－ＳｎＯ２－Ｙ２Ｏ３的铁锡复合氧化物,应用Ｘ射线衍射和穆斯堡尔谱学等手段研究材料的微结构和微粒生长情况,实验结果表明,掺杂Ｙ２Ｏ３对晶粒生长有明显抑制作用,不同温度热处理可制得不同尺寸大小的纳米晶α－Ｆｅ２Ｏ３－ＳｎＯ２－Ｙ２Ｏ３材料。     

Mass-spectrometric study of the vaporization of Li2O(s) and thermochemistry of gaseous LiO,Li2O,Li3O,and Li2O2

The equilibrium vapor pressures over solid lithium oxide (Li₂O) have been measured mass-spectrometrically using platinum Knudsen cells in the temperature range 1300–1700 K. From the gaseous equilibria the heats of formation of LiO(g), Li₂O(g), Li₃O(g), and Li₂O₂(g) were determined as follows: ΔH⁰₀(LiO) = 8.3 ± 3.3 kcal/mol, ΔH⁰₀(Li₂O) = − 42.3 ± 1.1 kcal/mol, ΔH⁰₀(Li₃O) = −48.4 ± 5.6 kcal/mol, and ΔH⁰₀(Li₂O₂) = −71.5 ± 7.4 kcal/mol. The atomization energies are D⁰₀D⁰₀(LiO) = 89.2 ± 3.3 kcal/mol, D⁰₀(Li₂O) = 178.3 ± 1.1 kcal/mol, D⁰₀(Li₃O) = 222.9 ± 5.6 kcal/mol, and D⁰₀(Li₂O₂) = 266.5 ± 7.4 kcal/mol. The relation D⁰₀(LiO) = D⁰₀(Li-OLi) is derived here. The bond dissociation energy D⁰₀(Li-Li₂O) is 44.6 ± 5.5 kcal/mol.In addition, the vaporization of Li₂O has been studied by using molybdenum, tantalum and graphite Knudsen cells in the temperature range 1200–1500 K to measure the distribution of the partial pressures under these conditions. It was found, for example, that due to the reaction of Li₂O with the wall of a molybdenum cell, their partial pressure of Li₃O, which was detected as a stable molecule for the first time, was increased by about a factor of 10 compared with its pressure measured in a platinum cell.     

稀土氧化物Gd2O3、Nd2O3、Sm2O3和Dy2O3在KCl-LiCl-Li2O熔盐中的电解

采用循环伏安法和计时电位法研究了Li₂O在KCl-LiCl熔盐中的电化学行为,并利用卷积伏安法计算了923 K下O₂^-在KCl-LiCl熔盐中的扩散系数（D),得到D=0.5×10^-5 cm²/s。以Gd₂O₃、Nd₂O₃、Sm₂O₃和Dy₂O₃为阴极,在KCl-LiCl-Li₂O(w=1%)熔盐中进行电解（恒电压3.40 V、电解温度923 K、电解时间25 h）。通过X射线衍射分析(XRD),证实稀土氧化物被部分还原为金属,并分析了电解过程中可能发生的反应。同时利用PRS模型（该模型可将固态阴极内离子的极限扩散速率与固态氧化物孔隙P、金属/氧化物摩尔体积R、阴极还原后的体积收缩率S等参数关联）分析了这些稀土氧化物的电解还原模型,得到Gd₂O₃、Nd₂O₃、Sm₂O₃和Dy₂O₃的最优孔隙率分别为18.7%、24.2%、30.6%、16.7%,最短电解时间分别为133、157、143、119 h,将这些结果与电解实验结果进行对比,发现阴极的孔隙率和电解时间均不满足金属氧化物完全被还原的要求,并给出了相应的解释。     

Gd2O3-UO2芯块中添加U3O8研究

Gd2O3-UO2可燃毒物燃料是近年来核电站采用较为普遍的可燃毒物之一。传统观点认为在芯块制造过程中添加U3O8粉末会降低芯块的烧结密度．本文研究了在Gd2O3-UO2芯块基体密度-94％T．D的基础上．添加不同品比例由AUC煅烧得到的U3O8粉末，经成型，H2/H2O气氛中1750℃烧结后表明．随着U3O8加入量的增加，芯块的密度也随之增加，U3O8添加量大于40wt％时芯块的密度达到-97％T.D．,U3O8的加入相当于起到了助烧剂的作用．这一现象和传统的U3O8降低芯块密度的观点正好相反．而芯块的平均晶粒尺寸-8μm。     

Recovery of neutron-irradiation-induced defects of Al2O3, Y2O3, and yttrium-aluminum garnet

SiC fiber-reinforced SiC matrix composites (SiC_f/SiC) are considered as one of the candidates for blanket materials in future fusion reactors and as an advanced fuel cladding material for next-generation fission reactors. Generally, the densification of SiC needs sintering additives and oxides such as Al₂O₃, Y₂O₃, and yttrium-aluminum garnet (YAG, Y₃Al₅O₁₂), which are frequently added to SiC. However, the effects of neutron irradiation on sintering additives are still unclear. In this study, we performed the neutron irradiation of Al₂O₃, Y₂O₃, and YAG at fluences up to 2.0–2.5 × 10²⁴ n/m² (E > 0.1 MeV) at 60–90 °C. The isochronal recovery of the macroscopic volume of Al₂O₃ against annealing temperature showed smooth and continuous shrinkage at a temperature of up to 1200 °C, and the volume slightly increased above that temperature. In contrast, the volume of Y₂O₃ showed quick shrinkage at the low temperature range, and slower and smooth recovery was observed up to ～1100 °C. In the case of YAG, the recovery of volume occurred in a step-wise manner at 600–750 °C, and continuous shrinkage occurred at temperatures lower and higher than that temperature range. The activation energies for the macroscopic volume recoveries of three oxides were obtained from the Arrhenius plots of the rate coefficients. Two-stage recovery was observed for Al₂O₃, whereas more complicated recovery processes were suggested for Y₂O₃ and YAG.     

Vapor Species over Na2O-B2O3-SiO2-Cs2O Glass

Methods for suppression and control of the axisymmetric vertical positional instability are described on the basis of conceptural design studies with the International Tokamak Reactor (INTOR). The shell effect is well known to be useful for suppression of the fast instability. Here shell structures are presented and their usefulness is assessed. Included in the assessments are required modellings of the plasma current for determination of mutual inductances between the plasma and the inductive components around it. Three kinds of models are described and their features are compared to the shell effect. Two kinds of simplified reactor structures are described and studied by comparing them with some control characteristics of the slow instability by a pair of control coils. Their structures are selected so as to result in different shell effects between them, and are consequently found to produce different capacities of power supply, too.     

Simulation of thermal stress in Er2O3 and Al2O3 tritium penetration barriers by finite-element analysis

The physical vapor deposition method is an effective way to deposit Al2O3 and Er2O3 on 316L stainless steel substrates acting as tritium permeation barriers in a fusion reactor.The distribution of residual thermal stress is calculated both in Al2O3 and Er2O3 coating systems with planar and rough substrates using finite element analysis.The parameters influencing the thermal stress in the sputter process are analyzed,such as coating and substrate properties,temperature and Young's modulus.This work shows that the thermal stress in Al2O3 and Er2O3 coating systems exhibit a linear relationship with substrate thickness,temperature and Young's modulus.However,this relationship is inversed with coating thickness.In addition,the rough substrate surface can increase the thermal stress in the process of coating deposition.The adhesive strength between the coating and the substrate is evaluated by the shear stress.Due to the higher compressive shear stress,the Al2O3 coating has a better adhesive strength with a 316L stainless steel substrate than the Er2O3 coating.Furthermore,the analysis shows that it is a useful way to improve adhesive strength with increasing interface roughness.     

Compatibility of Eu2O3 and (Eu,Gd)2O3 with Type 316 Stainless Steel

The compatibility of Eu₃O₃ and (Eu,Gd) ₂O₃ mixed oxides which contain 0, 1, 5, 10, 50 and 100 mol% of Gd₂O₃, with type 316 stainless steel was examined by out-of-pile heatings. The heating temperature ranged from 550 to 1,000°C and heating time from 500 h to up to 5,000 h. Metallographic examinations of the stainless steel indicated that chemical reaction between Eu₂O₃ and stainless steel occurred at 650°C and that grain boundary penetration extended up to 40 μ m after heating at 1,000°C for 500 h. The penetration depth Δ was expressed as a function of heating temperature T as

Δ = 3.08 × 10⁴ exp(?1.72 × 10²RT)

where R is the gas constant and the activation energy is given in cal/mol. Electron probe microanalysis and X-ray diffraction analysis indicated that main reaction product is europium silicate. When Gd, which is a decay product of Eu, is mixed with Eu₂O₃, the degree of reaction between (Eu,Gd) ₂O₃ and stainless steel decreases as increase in concentration of Gd₂O₃. It was found that actually no grain boundary attack was observed even after heating at 1,000°C for 500 h when concentration of Gd₂O₃;i in (Eu,Gd) ₂O₃ exceeded 10 Discussion was made of reaction mechanism of Eu₂O₃ and (Eu,Gd) ₂O₃ with stainless steel.     

氧化铝的热释光特性

陶瓷中常含有相当数量的氧化铝成分，研究氧化铝的热释光性特征对进一步提高古物测年的精确度至关重要。实验研究结果表明，氧化铝的热释光性质较为稳定，利用氧化铝的270℃峰测定年龄是切实可行的。     

CoFe2O4磁性液体的正电子湮没谱分析

对ＣｏＦｅ２Ｏ４磁性液体进行了正电子湮没谱研究,结果显示,ＣｏＦｅ２Ｏ４磁性液的正电了湮没谱存在３种寿命成分,分别为τ１＝１５１．０ｐｓ,τ２＝１５１．０ｐｓ,τ３＝２３２５．６ｐｓ。表明在ＣｏＦｅ２Ｏ４超微粒表面存在大量空位和空位团。     

Al2O3/Y2O3/ZrO2 Ceramic Composite Properties Investigation by Plasma Focus Device

The Al₂O₃–Y₂O₃–ZrO₂ eutectic composition samples were prepared using the Al₂O₃, Y₂O₃, ZrO₂ powder treated at 900 °C for 30 min, pressed at 5 ton for 15 s and sintered at 1500 °C for 2 h. The locally made dense plasma focus (DPF) system with energy 2.8 kJ was used to surface modification of these samples. The samples, mounted at distance about 2 cm from the anode, were exposed to three shots of the DPF in Ar gas at a pressure of 0.8 mbar. The phase and elemental analysis of the untreated and plasma treated samples were conducted by the Raman and EDX spectroscopy. The Raman spectroscopy showed the formation of new phases (α-Al₂O₃ and c-ZrO₂) in the treated samples. The micro-hardness of the plasma treated samples was increased by about 280 % in comparison with the untreated sample.     

Thermal Diffusivities and Thermal Conductivities of UO2-Gd2O3

Thermal diffusivities of samples of UO₂ and UO₂ doped with 3, 5, 7 and 10 w/0 Gd₂O₃ were measured over the temperature range of 298~2,023 K by a laser flash method. Then thermal conductivities were calculated from them. The thermal conductivity decreased with increasing Gd₂O₃ content at low temperatures, while it was independent of Gd₂O₃ content at high temperatures. An expression of the thermal conductivity was proposed for (U, Gd)O₂ solid solution as a function of Gd₂O₃ content and temperature by applying Klemens' model.     

99Tc在Fe,Fe2O3和Fe3O4上的吸附行为研究

用批式法研究了大气条件下99Tc在Fe,Fe2O3和Fe3O4上的吸附行为,考察了吸附平衡后溶液中99Tc的存在价态.实验结果表明随着溶液pH值(5～12)、CO2-3浓度(1×10-8～1×10-2 mol/L)的增大,99Tc在Fe上的吸附比减小;溶液pH值、CO2-3浓度的变化基本不影响99Tc在Fe2O3和Fe3O4上的吸附;99Tc在这3种吸附材料上的吸附行为均可用Freundlich吸附等温式表示;当Fe作吸附材料时,吸附平衡后99Tc主要以Tc(Ⅳ)的形式被吸附,当Fe2O3和Fe3O4作为吸附材料时,99Tc主要以Tc(Ⅶ)的形式被吸附.     

Volume change of Al2O3 and MgAl2O4 induced by 14-MeV neutron irradiation

Volume change of Al₂O₃ and MgAl₂O₄ induced by irradiation with 14-MeV neutrons at 50°C has been measured. It is shown that the volume change of A1₂O₃ is anisotropic and is larger than that of MgAl₂O₄ about a factor of five. The result for MgAl₂O₄ is compared with that of fission neutron irradiation.