Atomic Imaging of Subsurface Interstitial Hydrogen and Insights into Surface Reactivity of Palladium Hydrides

Resolving interstitial hydrogen atoms at the surfaces and interfaces is crucial for understanding the mechanical and physicochemical properties of metal hydrides. Although palladium (Pd) hydrides hold important applications in hydrogen storage and electrocatalysis, the atomic position of interstitial hydrogen at Pd hydride near surfaces still remains undetermined. We report the first direct imaging of subsurface hydrogen atoms absorbed in Pd nanoparticles by using differentiated and integrated differential phase contrast within an aberration-corrected scanning transmission electron microscope. In contrast to the well-established octahedral interstitial sites for hydrogen in the bulk, subsurface hydrogen atoms are directly identified to occupy the tetrahedral interstices. DFT calculations show that the amount and the occupation type of subsurface hydrogen atoms play an indispensable role in fine-tuning the electronic structure and associated chemical reactivity of the Pd surface.     

基于SSOGI-RLSMC联合算法的加速器电源纹波抑制

重离子加速器电源系统对励磁电源输出电流的稳定度和纹波精度要求高.磁铁负载的存在产生的纹波,会对加速器通过磁场精确控制粒子运动轨迹带来影响.针对以上问题,提出一种基于SSOGI-RLSMC新型联合算法,以减小磁铁负载影响下励磁电源输出的电流纹波,提高电流稳定度.新型联合算法通过并联型二阶广义积分器(SSOGI)作为纹波检...     

FFT动态相位重建算法的滤波窗影响分析

为了优化相位重建算法,针对波面干涉图的傅里叶频谱,分析了不同滤波窗口的分布特征和频谱响应,通过计算机仿真和实验测试,确定了FFT动态相位重建算法的最佳滤波窗口类型。其中处理仿真干涉图重建的波面与原始波面的波面峰谷值残差为0.008 5λ,波面均方根值残差为0.000 1λ;处理实验干涉图获得的波面与移相干涉测量法获得的波面峰谷值残差为0.009 3λ,波面均方根值残差为0.000 5λ。结果表明:选取Hamming窗进行滤波处理并重建的相位经拟合后得到的波面较参考波面的面形残差最小,相位重建精度优于0.01λ,可进一步应用于大口径光学元件的测量中。     

微分电位溶出法测定土壤中的微量砷

用金膜电极－微分电位溶出法测定了土壤中的微量砷，讨论了最佳测定条件。     

TiB2/均相硼掺杂TiO2核/壳结构提升光催化氧化水产氧活性

光催化可实现污染物降解、分解水制氢和CO2还原等多种氧化还原反应, 因而受到了广泛关注. 光催化材料中光生电荷的数目与氧化还原能力直接影响光催化反应效率, 在许多光催化反应中, 光生空穴氧化反应被认为速控步骤. 以光催化分解水为例, 质子的还原是单电子过程, 水氧化产生氧气则涉及四个电子. 空穴的高能量不仅可赋予其高的氧化能力,还能提高其迁出表面的能力, 因此具有重要研究价值.我们组的前期工作表明, 以TiB2作为前驱体, 采用水热合成和焙烧两步法可制备出间隙硼掺杂的金红石相或锐钛矿相TiO2, 间隙硼掺杂可显著降低价带顶, 提升光催化氧化水产氧性能. 然而, 在已有的结果中, 间隙硼掺杂浓度在TiO2中均呈现从内向外逐渐增加的梯度分布, 这意味着硼掺杂浓度有限, 且表层更低的价带顶不利于体相光生空穴向表面迁移, 因此亟需实现TiO2中均相的间隙硼掺杂.本文以湿化的氩气为水解环境, 将水解过程限域在TiB2的表面以减少硼原子流失; 同时提高水解温度, 使残留的硼原子形成间隙掺杂, 避免其在二次焙烧时扩散, 从而在TiB2核的表面所形成的TiO2壳层中实现均相间隙硼掺杂, 显著提高了光催化氧化水产氧活性. 多种表征结果表明, 直径约为6-10 μm的TiB2核表面形成了厚约400 nm的TiO2壳层, 在TiO2/TiB2中TiO2壳层重量比约为30%, TiO2壳层中锐钛矿相TiO2占比为65 wt%, 金红石相TiO2占比为35 wt%. TiO2壳层中间隙硼为均相分布, 硼掺杂显著降低了价带顶位置, 提高了光生空穴的氧化能力, 从而使得TiB2/TiO2展现出比未掺杂的金红石、锐钛矿相及两者混合相的TiO2均具有更高的光催化氧化水产氧的能力.     

超高效液相色谱-四极杆-飞行时间质谱法快速筛查辣椒粉中27种农药残留

建立了超高效液相色谱-四极杆-飞行时间质谱（UPLC-Q-TOF/MS）快速筛查辣椒粉中27种农药残留的检测方法。样品采用乙腈提取,经Carb/NH₂固相萃取小柱净化,用乙腈-乙酸乙酯（3：1,v/v）洗脱,电喷雾正离子模式检测。在一级质谱模式下,以目标物的保留时间、精确质量数、同位素分布和同位素丰度比定性,以准分子离子峰的峰面积定量。在Targeted MS/MS模式下,通过相应碰撞能量下的离子碎片信息进一步确证。27种化合物在各自的线性范围内线性关系良好,相关系数均大于0.997。27种化合物的定量限为2.5~5.0 μg/kg,在3个添加水平下的回收率为72.3%~118.9%,相对标准偏差（RSD）为0.21%~12.7%（n=6）。该方法快速、灵敏、准确,适用于辣椒粉中多种农药残留的同时检测。     

有机锑化合物在交叉偶联反应中的应用研究进展

近年来,有机锑化合物在交叉偶联反应中的应用引起了人们的广泛关注。本文主要对有机锑化合物在交叉偶联反应中的应用作了综述,重点介绍了其在Suzuki交叉偶联反应、Heck偶联反应以及Sonogashira偶联反应中的应用,并展望了其未来的发展方向。     

Ab initio study on the mechanism of reaction HNCO+NH_2

Ab initio UMP2 and UQCISD(T) calculations, with 6-311G** basis sets, were performed for the titled reactions. The results show that the reactions have two product channels: NH2+ HNCO→NH3+NCO (1) and NH2+HNCO-N2H3+CO (2), where reaction (1) is a hydrogen abstraction reaction via an H-bonded complex (HBC), lowering the energy by 32.48 kJ/mol relative to reactants. The calculated QCISD(T)//MP2(full) energy barrier is 29.04 kJ/mol, which is in excellent accordance with the experimental value of 29.09 kJ/mol. In the range of reaction temperature 2300-2700 K, transition theory rate constant for reaction (1) is 1.68 × 1011- 3.29 × 1011 mL · mol-1· s-1, which is close to the experimental one of 5.0 ×1011 mL× mol-1· s-1 or less. However, reaction (2) is a stepwise reaction proceeding via two orientation modes, cis and trans, and the energy barriers for the rate-control step at our best calculations are 92.79 kJ/mol (for cis-mode) and 147.43 kJ/mol (for trans-mode), respectively, which is much higher than     

Boundary coupled dual-equation numerical simulation on mass transfer in the Process of laser cladding

The coupled numerical simulation on fluid flow, heat transfer, and mass transfer in the process of laser cladding is undertaken on the basis of the continuum model.In the simulation of mass transfer in the laser molten pool, the concentration distribution in the regions on different sides of the interface between cladding layer and substrate is calculated separately and coupled at the co-boundary.The non-equilibrium solute partition coefficient is obtained from equilibrium solute partition coefficient according to the Sobolev model.By using the developed software which is based on the commercial software PHOENICS 1.4, the distribution of Fe in laser molten pool in an experiment of cladding Stellite 6 on 12CrMoV is calculated.The obtained results well coincide with the experimental ones.     

一种蓝色聚合物激光材料

聚合物作为一种有机发光材料,由于在平板显示和光电子器件中的良好应用前景而受到广泛研究［１～２］．近年来,一个重要进展是在聚合物中观测到了受激发射（简称Ｐｏｌｙ－ｍｅｒ激光）现象［３～６］．Ｐｏｌｙｍｅｒ激光最早是在溶液中实现的［３～４］．作为一种新型...