In situ probing electrified interfacial water structures at atomically flat surfaces using Raman spectroscopy

自然界中水无处不在，人们对水分子的研究已经长达一个多世纪。特别是在材料表面，从原子结构层面理解界面水所发生的各种物理和化学过程，将有利于指导能源和环境领域中开发更好的技术和器件。文献中采用振动光谱已经推知了水在金属界面的不同构型，如四配位水、三配位水、表面特性吸附水、自由水等。然而，仍然缺乏这些界面水在不同电位下清晰的构型图像。李剑锋教授课题组采用不受体相水干扰的表面增强拉曼光谱，首次在金（111）和（100）单晶电极表面上获得了界面水的拉曼信号，并且在析氢反应过程中原位观测到了界面水的两种构型转变。发现界面水随着电位的负移，由“平行”结构向“单端氢朝下”，再向“双端氢朝下”变化。程俊教授课题组采用从头算分子动力学理论方法，模拟出不同电位下，在双电层中界面水的三种构型以及相应的氢键数目，与实验数据很好地吻合，进一步揭示了双电层的原子级结构。该研究首次在实验和理论层面，将界面水的构型转变以及氢键断裂与精确的电极电势标尺进行关联，对探知双电层的三维结构具有指导性意义。 该研究工作通过厦门大学校内合作完成，化学化工学院李剑锋教授和程俊教授为通讯作者，田中群教授提供了重要指导。李超禹博士（现美国麻省理工学院博士后）和乐家波博士（现能源材料化学协同创新中心博士后）为共同第一作者，王耀辉博士生在实验上提供了帮助，物理系的陈舒博士和杨志林教授为本工作开展了电磁场增强计算【Abstract】Molecular structures of solid/liquid interfaces are of fundamental interest, and play significantly in the efficiencies of energy storage and conversion. To elucidate the structures of electric double layers at electrochemical interfaces under bias potentials, we have collaborated in situ Raman spectroscopy and ab initio molecular dynamics, and for the first time distinguished two structural transitions of interfacial water at electrified Au(111) and Au(100) single crystal electrode surfaces. Towards negative potentials, the interfacial water molecules evolve from structurally “parallel” to “one-H-down”, and further to “two-H-down”.Concurrently, the number of hydrogen bonds among the interfacial water shows an overall decrease along with the negative shift of the potential, and undergoes two transitions as well. Our findings shed light on fundamental understanding of electric double layers and electrochemical processes at the interfaces.National Natural Science Foundation of China (Grants No. 21373166, 21522508, 21775127, 21521004, 21321062 and 21621091). 该工作得到国家自然科学基金委的大力资助，也得到了固体表面物理化学国家重点实验室、谱学分析与仪器教育部重点实验室、能源材料化学协同创新中心的支持

纯锌在我国热带海洋大气环境耐蚀寿命预测模型

采用周浸加速腐蚀试验模拟纯锌在热带海洋大气环境的腐蚀行为,通过对比腐蚀形貌、腐蚀产物、腐蚀动力学等定性和定量地评价周浸试验与户外大气暴露腐蚀试验的相关性。结果表明:周浸腐蚀试验后,纯锌的腐蚀形貌、腐蚀产物组成及腐蚀动力学均与实际海洋大气环境暴露结果具有较好的相关性;通过灰色关联分析法分析发现采用2%Na Cl溶液模拟万宁大气、5%Na Cl溶液模拟西沙大气兼具模拟性和加速性;采用周浸加速腐蚀试验方法建立纯锌在万宁、西沙两种海洋大气环境下服役的耐蚀寿命预测模型,分别为Twn=95.23t 1.01、Txs=841.60t 0.16

RV减速器摆线轮齿廓修形润滑性能分析

考虑润滑脂的压黏特性及热效应，建立摆线轮齿与针齿之间的线接触脂润滑热弹流数值模型，求得该模型的完整数值解，得到了脂膜压力分布、温升分布及脂膜形状；结合摆线轮齿廓，分析了修形方式及修形量对脂膜压力、脂膜形状、脂膜温升和摩擦损失功率的影响。结果表明，随着修形齿廓与摆线轮理论齿廓径向间隙的增大，摩擦损失功率增加，最小脂膜厚度先增加后减小；在修形齿廓与摆线轮理论齿廓同一径向间隙的条件下，反弓齿廓修形方式的润滑性能最好，正等距加正移距的组合修形方式次之，负等距加负移距的组合修形方式润滑性能最差。研究结果为考虑润滑性时RV减速器摆线轮齿廓修形提供了一种新的方法

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel

JUNO sensitivity on proton decay p → ν K + searches*

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this study, the potential of searching for proton decay in the $p\to \bar{\nu} K^+$ mode with JUNO is investigated. The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar{\nu} K^+$ is 36.9% ± 4.9% with a background level of $0.2\pm 0.05({\rm syst})\pm$$0.2({\rm stat})$ events after 10 years of data collection. The estimated sensitivity based on 200 kton-years of exposure is $9.6 \times 10^{33}$ years, which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies