离子交换色谱中硼同位素交换反应平衡常数的理论预测

外部溶液相中B(OH)₃与离子交换树脂相中B(OH)₄^-、B₃O₃(OH)₅^2-、B₃O₃(OH)₄^-之间所发生的同位素交换反应的平衡常数K是离子交换色谱法分离硼同位素研究中的基本参数之一,但难以用实验手段精确测定。本研究利用密度泛函理论（DFT）在B3LYP/6—31G理论水平上计算了气态下B(OH)₃、B(OH)₄^-等的振动频率,用计算得到的频率,基于Urey模型求得B(OH)₃、B(OH)₄^-、B₃O₃(OH)₅^2-、B₃O₃(OH)₄^-的简约配分函数比（RPFR）,进而得到同位素交换反应平衡常数。结果表明,B(OH)₃和B(OH)₄^-间的同位素效应显著,其平衡常数K在25 ℃时为1.025 7,B(OH)₃与B₃O₃(OH)₅^2-和B₃O₃(OH)₄^-反应的平衡常数较小,分别约为1.017 2和1.008 4。     

Effect of Heat Treatment in α+β Phase Field on Microstructure and Corrosion Property of Zr-Sn-Nb Alloy

Uniform corrosion tests were carried out with the specimens prepared by different heat treatments at the temperature in α+β phase field. The surface microstructure of specimens was observed by scanning electron microscope, the corrosion behavior was analyzed by autoclaves, and the oxide layer on the surface after the corrosion test was analyzed by focused ion beam (FIB) and atomic force microscope (AFM). The results show that after the heat treatment in α+β phase field, lamellar β-Zr phase appeares in the Zr matrix, and after the subsequent α phase final heat treatment, the β-Zr phase will be decomposed to α-Zr and discontinuous second phase particles. For the specimens heat treated in α+β phase field, after the α phase final heat treatment, the corrosion resistance under 360 ℃/18.6 MPa pure water condition is better than that of specimens without final heat treatment. The oxide film formed on the β-Zr protrudes on the oxide surface, on the contrary, after α phase final heat treatment, β-Zr decomposes, and the oxide layer is sunken in this area.     

Balancing thermal conductivity and strength of hot-pressed AlN ceramics via pre-sintering and annealing process

The heat dissipation requirements of the new generation of semiconductors are placing higher demands on the overall performance of aluminum nitride (AlN) ceramics. This has led to an increasing emphasis on AlN ceramics that combine thermal conductivity and strength. AlN ceramics are often strengthened by hot-press sintering, but their thermal conductivity is typically modest. In this study, pre-sintering and annealing processes are introduced to optimize the thermal conductivity of hot-pressed AlN ceramics to avoid the detrimental effects of oxygen impurities in the AlN lattice. The effect of the oxide layer on the surface of commercial AlN particles is investigated, including density, phase composition, microstructure, and fracture behavior. The effect of annealing on the improvement of thermal conductivity and flexural strength is also verified. Electron paramagnetic resonance (EPR) analysis is performed to examine the concentration of intercrystalline defects under various conditions. Finally, AlN ceramics with a thermal conductivity of 204 W m⁻¹ K⁻¹ and a flexural strength of 376 MPa are obtained.     

超高通量快中子研究堆核燃料概念设计研究

提高中子注量率是高通量研究堆的发展趋势,能够大幅加速反应堆材料研发进程。但若提高中子注量率至1016 cm?2·s?1将导致功率密度峰值相较于现有研究堆高数倍,对反应堆和核燃料设计带来许多挑战。为此,本文从中子学、传热、燃料材料堆内行为等方面半定量分析了提高中子注量率对核燃料性能的影响,并提出应对超高通量和功率密度挑战的设计措施,为发展超高通量快中子研究堆燃料设计提供指导。      

Nodular Corrosion of Zr–0.85Sn–0.16Nb–0.37Fe–0.18Cr Alloy in 500 °C Steam Caused by High-temperature Processing

Oxidation of Metals - Zr–0.85Sn–0.16Nb–0.37Fe–0.18Cr alloy samples prepared by low-temperature process (LTP) and high-temperature process (HTP) show different...     

Characterization of Microstructure and Stress Corrosion Cracking Susceptibility in a Multi-pass Austenitic Stainless Steel Weld Joint by Narrow-Gap TIG

Metallurgical and Materials Transactions A - In the present study, correlation of the microstructure and stress corrosion cracking (SCC) susceptibility in the top, middle and root regions of a...     

Sn含量对N36锆合金在LiOH水溶液中耐腐蚀性能的影响

比较了N36(Zr-1Sn-1Nb-0.3Fe)及低锡N36 (Zr-0.8Sn-1Nb-0.3Fe)锆合金样品在360 ℃/18.6 MPa/0.03 mol/L LiOH 水溶液中的耐腐蚀性能,发现N36提前发生腐蚀转折,转折后腐蚀增重远高于低锡N36。观察了腐蚀转折后合金样品氧化膜形貌及物相特征,发现在氧化膜断面上形成平行于氧化膜／金属界面的裂纹,而界面氧化膜呈"菜花"状生长;与N36相比,低锡N36氧化膜形貌显示断面裂纹相对较少,界面生长的氧化膜较为平整;随腐蚀速率的增加,断面裂纹增多,界面膜呈"菜花"状凸起越严重;氧化膜中产生的裂纹与四方相的转变有关。讨论了Sn对N36合金耐腐蚀性能影响的机理,认为固溶在α-Zr中的Sn含量是引起耐腐蚀性能差别的主要原因。     

电感耦合等离子体原子发射光谱法测定铪合金中锆

使用硝酸和氢氟酸溶解样品,以Zr 327.305 nm为分析谱线,建立了电感耦合等离子体原子发射光谱法(ICP-AES)测定铪合金中锆含量的分析方法。结果表明:铪质量浓度在100 μg/mL以下时,对锆的测定结果影响不显著,不需要使用基体匹配法绘制校准曲线;由于酸度对锆的测定结果有影响,待测试液与标准溶液系列的酸度应该保持一致,酸度大约为1.0 mol/L。锆的质量浓度在0.2～5.0 μg/mL范围内与发射强度呈线性,校准曲线的线性回归方程为y=39 966 x+176,相关系数r=0.999 7。方法中锆的检出限为0.001 5 μg/mL。实验方法用于铪合金样品中锆的分析,测定结果的相对标准偏差(RSD,n=6)小于1%,回收率为99%;同时与X射线荧光光谱法的测定结果进行比对,两种方法测定结果基本一致。     

核包壳管用HT9钢的600～1000℃空气氧化行为

HT9钢在核反应堆包壳管中具有巨大的应用前景。在失水事故下,包壳管材料的温度将远高于600℃。为此,研究了HT9钢600℃以上的空气氧化行为。用增重法测定其氧化动力学曲线,利用SEM、EDS和XRD分析氧化产物的形貌、成分和结构。基于对氧化动力学与氧化产物的分析,探讨其氧化机制。结果表明:在600~1 000℃范围内随着温度的升高和时间的延长,HT9钢氧化程度增加;氧化层呈双层结构,内层为(Fe,Cr)_2O_3,外层是Fe_2O_3;不同温度的氧化动力学遵循不同的规律,氧化过程主要受铁离子和铬离子的扩散共同控制。     

锆合金氧化膜的内应力计算

锆合金氧化膜中的内应力是锆合金腐蚀动力学中的重要影响因素,目前没有统一的方法得到氧化膜中内应力的大小,且数值差异较大。在传统的实验和理论方法的基础上,建立ZrO₂/Zr合金双层氧化弯曲几何模型,计算不同腐蚀状态下氧化膜中的内应力大小,得到内应力变化规律并分析其影响因素,为锆合金氧化膜内应力研究提供了一种较为可靠的方法。