Al单晶的结合能和晶格常数的第一性原理计算研究

基于密度泛函理论框架下平面波赝势法的VASP软件包可以根据任意给定的一个晶胞棱边长度在原胞内求解Kohn-Sham方程,并算出相应的结合能,当结合能为最小值时,整个原胞的结构最为稳定,此时原胞的长度即为晶格常数。我们采用此方法计算了Al单晶的结合能和晶格常数,计算的结果与实验吻合得很好

Preparation of PdCoIr Tetrahedron Nanocatalysts and Its Performance toward Ethanol Oxidation Reaction

钯(Pd)基催化剂是直接乙醇燃料电池研究中广泛使用的催化剂,进一步提升其性能是推动燃料电池发展的重要方向。本文用一步水热法制备出四面体结构PdCo(PdCo tetrahedron,记为PdCo-TH)和少量铱(Ir)掺杂的PdCo四面体合金纳米粒子(记为PdCoIr-TH)。经TEM、ICP、XPS及CV等表征证实,PdCoIr-TH为三元合金纳米粒子,且掺杂的Ir元素倾向分布在催化剂表层。相比于商业Pd/C催化剂,PdCo-TH/C和PdCoIr-TH/C对乙醇电氧化的催化性能显著增强。研究结果表明,Pd9Co1Ir0.1-TH/C在低电位(< -0.25 V)下具有最高的乙醇电氧化活性和稳定性。Ir掺杂不仅提高了催化剂抗CO毒化的能力还有利于乙醇起始氧化电位负移。同时,随着Ir含量的增加,所制备的纳米催化剂的乙醇电氧化C1产物选择性也随之升高。针对不同组成催化剂反应性的差异,本文认为Co与Ir位点上容易产生OHad物种,这将有利于活性Pd位点上乙醇电氧化中间反应物种的有效转化。除了以上的各位点间的协同效应,三元合金的形成,进一步调控了Pd的d带电子结构,从而促进了催化剂反应性的改变。As a new energy conversion device, direct ethanol fuel cells (DEFCs) are widely concerned because of their remarkable advantages such as high theoretical energy density and wide fuel sources. However, the rapid development of DEFCs has been severely impeded due to the sluggish kinetic process and toxic intermediates especially in their anodic reactions. Palladium (Pd)-based materials are considered to be excellent anode catalysts for DEFCs, especially under alkaline conditions. And further improving their performance is an important direction to promote the development of DEFCs. Surface structure and composition are the key factors affecting the performance of catalysts which can be improved by reasonable regulation. It is reported that high-index faceted structures and element doping are beneficial to improve the performance of catalyst. In this work, the advantages of these two strategies were used comprehensively to prepare Pd-based catalysts with high efficiency. Palladium cobalt (PdCo) and Ir-doped PdCo tetrahedron alloy nanocatalysts (denoted by PdCo-TH and PdCoIr-TH, respectively) have been successfully prepared by one-step hydrothermal method. The characterization results of TEM, ICP, XPS and CV show that the PdCo-TH binary and PdCoIr-TH ternary alloys were formed, while Ir element was mainly distributed on the PdCoIr-TH surface. Compared with the commercial Pd/C, the PdCo-TH/C and PdCoIr-TH/C exhibited the enhanced catalytic properties toward ethanol oxidation reaction in alkaline solutions. Particularly, the Pd9Co1Ir0.1-TH/C catalyst showed the best activity and stability toward EOR, especially at low potentials (< -0.25 V). And Ir sites not only resisted CO poison effectively, but also shifted the initial oxidation potential of ethanol negatively. Meanwhile, the selectivity of C1 products during the electrocatalytic oxidation of ethanol has been greatly improved with the increase of Ir content. The enhanced reactivities of PdCo-TH/C and PdCoIr-TH/C could be attributed to: (a) The coexistence of Co sites and Ir sites on the surfaces can generate OHad species which can promote the oxidation of intermediate adsorbed species on Pd sites and (b) the negative shift in electron binding energy of Pd due to the addition of Ir may make reaction intermediates desorb more difficultly, which might make the reactivity of PdCoIr-TH/C differ from that of PdCo-TH/C. This research work has demostrated a strategic approach for future development in high efficiency catalysts used for DEFCs.国家自然科学基金项目(21802112);国家自然科学基金项目(21773198)通讯作者:黄蕊,孙世刚E-mail:[email protected];[email protected]:RuiHuang,Shi-GangSunE-mail:[email protected];[email protected]厦门大学化学化工学院,固体表面物理化学国家重点实验室,福建 厦门 361005State Key Laboratory of Physical Chemistry of Solid Surfaces, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, Chin

渤海海底重塑土的强度-变形性质

随着我国海洋石油开发事业的展开,海洋石油平台的设计与建造已经提到议事日程上来。在平台建筑物的地基基础设计分析中,必须认识和了解建造地区海底土的强度一变形性质,这对于建筑物的经济性和安全性来说是至关重要的

Effects of EN-1 Soil Stabilizer on Soil Anti-erodibility

在土壤中应用高分子聚合物是改良土壤性质,提高土壤抗蚀能力的主要手段之一。该文以0-30cm和30-100cm土层的塿土和黄绵土为供试土壤,研究了EN-1固化剂的施用对土壤抗蚀性能的影响。利用土壤有机质含量、大于0.25mm的水稳性团聚体含量、水稳性团聚体的平均重量直径(MWD)、几何平均直径(GMD)和分形维数等指标计算土壤抗蚀性,对施用EN-1固化剂后的土壤抗蚀性能进行了定量评价。研究结果表明,EN-1固化剂对土壤抗蚀性的影响程度与固化剂掺量、土壤类型和土壤的取土层次有关,当EN-1固化剂在土壤中的掺量为0.15%(0-100cm塿土和0-30cm黄绵土)或0.20%(30-100cm黄绵土)时,土壤的抗蚀能力最强。试验结果为固化剂在黄土高原水土保持建设中的应用提供了理论指导

创造力进化理论及其演变综述

本文对创造力进化理论及其演变进行了系统性的综述,创造力进化论用最基本的自然选择规律来诠释人类的创造力,它认为创造力的产生过程中存在着类似自然界中的变异、重组和选择,它们有利于创造力的新颖性和有用性。本文并着重对基于进化理论演变的研究现状:情绪和社会网络研究进行了概述,并对未来基于创造力进化论的研究进行了展望,呼吁对可引起"变异、选择"的其他创造力影响因素进行深入研究

高速齿轮传动可倾瓦轴承预负荷系数影响研究

可倾瓦轴承因其稳定可靠的特点被广泛应用于现代工业，相关研究也蓬勃发展起来，但目前关于可倾瓦轴承预负荷系数的研究主要集中在低转速领域。以DyRoBeS软件为研究工具，取普遍使用的5块瓦可倾瓦轴承作为研究对象，分析在20 000 r/min、40 000 r/min、60 000 r/min的高转速工况下，预负荷系数对可倾瓦轴承工作性能的影响，为高速齿轮传动中可倾瓦的设计应用提供理论依据。预负荷系数从0.1增加至0.7的过程中，对功率损失影响不大，使最大油膜压力与刚度系数增加，最小油膜厚度与阻尼系数减小。预负荷系数的混合设置会影响各瓦块压力分布，同时使最小油膜厚度以外的轴承性能参数明显增加。所得结论对高转速可倾瓦轴承的优化设计起到积极的作用

Work safety accident visual reconstruction system based on 3D digital technology

摘要：为解决生产安全事故难以可视化逼真再现难题,提升警示教育效果,综合利用三维动态渲染引擎、动态参数化建模、脚本驱动的事故再现动态仿真等3D数字技术手段,研发一种生产安全事故再现系统;通过建设典型生产安全事故三维情景库、开发事故应急三维模拟演练系统、建立30套三维事故警示教育系列培训教材,实现对生产安全事故的三维可视化再现,并应用于某集团.结果表明:该系统能够实现事故发展过程及关键细节的仿真重现,提高培训的沉浸感和实操性,有助于提升集团的安全文化及员工安全意识和能力.</p

整体式单悬臂离心压缩机用高速齿轮箱的关键技术及应用

主要介绍了整体式单悬臂离心压缩机用高速齿轮箱的特点、设计原则以及设计中的注意事项,并将这种设计方法应用于具体的产品设计,在提高设计效率和齿轮箱可靠性方面取得了良好效果

基于GA-LQR两挡DCT离合器目标转矩控制

为获得更舒适的换挡品质，针对搭载有两挡双离合变速器（DCT）的电动汽车，对其换挡过程中两组离合器目标转矩进行协调控制。以冲击度与比滑摩功作为评价指标，并以冲击度与滑摩功为二次型目标泛函，采用线性二次型最优控制（LQR）方法确定换挡过程转矩相的离合器目标转矩。采用遗传算法（GA）的全局搜索能力对LQR中的加权矩阵进行最优选取，得到换挡品质更优的离合器目标转矩。最后，对当前采用定斜率计算确定的离合器目标转矩与采用所提方法确定的离合器目标转矩进行对比，结果表明，后者在换挡过程中所用的时间较少，产生的冲击度和比滑摩功都有所减小，有效提升了两挡DCT的换挡品质