Effect of twin boundary on nanoimprint process of bicrystal Al thin film studied by molecular dynamics simulation

The effects of a twin boundary(TB) on the mechanical properties of two types of bicrystal Al thin films during the nanoimprint process are investigated by using molecular dynamics simulations.The results indicate that for the TB direction parallel to the imprinting direction,the yield stress reaches the maximum for the initial dislocation nucleation when the mould directly imprints to the TB,and the yield stress first decreases with the increase of the marker interval and then increases.However,for the TB direction perpendicular to the imprinting direction,the effect of the TB location to the imprinting forces is very small,and the yield stress is greater than that with the TB direction parallel to the imprinting direction.The results also demonstrate that the direction of the slip dislocations and the deformation of the thin film caused by spring-back are different due to various positions and directions of the TB.     

电场中MgO分子吸附H_2的理论研究

研究电场中MgO分子与H_2的相互作用是探索MgO材料储氢性能的基础.在B3LYP/6-31G**水平上研究了电场中H2在MgO分子上的吸附行为.结果给出电场中单个H_2在Mg/O上的吸附能由无电场时-0.021/-0.099eV提高到场强为0.005a.u.时的-0.037/-0.139eV.H2吸附在O离子上时,电场效应更显著.电场中MgO分子最多能吸附10个H_2,相应的质量密度达33wt%.表明电场诱导MgO材料吸附H_2是一种具有潜力的储氢方法.通过电子结构分析讨论了电场中MgO分子储氢的机理.     

电场中LiF分子吸附H_2的理论研究

采用密度泛函理论方法研究了电场中H_2在LiF分子上的吸附行为.结果表明,无电场时,H_2能在Li与F原子上形成弱的物理吸附.外加电场可显著提高其吸附强度, H_2在Li/F上的吸附能由无电场时的-0.112/-0.122eV提高到场强为0.005 a. u.时的-0.122/-0.171 eV, H_2吸附在F上时更稳定.利用分子中的原子量子理论(QTAIM)方法研究了电场增强吸附的机理,表明电场促进了H_2与LiF间的电荷转移,同时使LiF及H_2极化,增强了其间的静电作用,从而提高了吸附强度.电场中LiF最多能吸附10个H_2,相应的质量密度达43.5 wt%.表明电场诱导LiF材料吸附H_2是一种具有潜力的储氢方法.     

微波辐射法合成N-苯基马来酰亚胺

用微波辐射法合成N-苯基马来酰亚胺,在总结前人对原料配比、催化剂用量对反应收率影响的基础上,本实验以顺丁烯二酸酐和苯胺为原料用醋酐作脱水剂、醋酸钠作催化剂采用微波辐射法两步合成N-苯基马来酰亚胺。探讨最佳工艺条件为第一步用微波功率80W熟化3min,第二步用微波以功率400W加热1.5min时N-苯基马来酰亚胺的收率可达75.8%。产品经晶形、熔点和红外光谱分析确定为目标产品。     

Stability of non-constant steady-state solutions for bipolar non-isentropic Euler–Maxwell equations with damping terms

In this article, we consider the periodic problem for bipolar non-isentropic Euler–Maxwell equations with damping terms in plasmas. By means of an induction argument on the order of the time-space derivatives of solutions in energy estimates, the global smooth solution with small amplitude was established close to a non-constant steady-state solution with asymptotic stability property. Furthermore, we obtain the global stability of solutions with exponential decay in time near the non-constant steady-states for bipolar non-isentropic Euler–Poisson equations. This phenomenon on the charge transport shows the essential relation and difference between the bipolar non-isentropic and the bipolar isentropic Euler–Maxwell/Poisson equations.     

Temperature overshoots for a 4-velocity unidimensional discrete Boltzmann model

We propose a 4-velocity unidimensional discrete Boltzmann model with two different speeds 2, 1 and two different masses 1, 2. With the three conservation laws of mass, momentum, and energy satisfied, we can introduce a nontrivial temperature. First, we determine the similarity shock waves satisfying physical properties: positivity, shock stability, inequalities of the subsonic and supersonic flows, increase or decrease of both mass and temperature across the shock. It results that either the speed of the shock front is higher than the speed 1 of the slow particles and the shocks are compressive or less than 1 and the shocks are rarefactive. We observe overshoots of the temperature, across the shock, with bumps higher and higher as the shock front speed increases. Second, we study the (1+1)-dimensional shock waves. They represent the superposition and collision of two compressive shocks traveling in opposite directions and we observe temperature overshoots for not too large times.     

周期性磁谐振材料本构参数的理论分析

将薄的磁谐振介质板等效为面磁流, 利用周期性边界条件, 给出了面磁流的指数形式. 通过计算无穷个面磁流在不同空间位置上产生的总电场和总磁场, 推导出了周期性磁谐振人工材料的色散关系和布洛赫阻抗, 进而获取了布洛赫本构参数的理论计算公式. 由于考虑了磁谐振人工材料中的电反谐振对布洛赫介电常数和磁导率的影响, 所以基于仿真实验的布洛赫本构参数的提取值和布洛赫本构参数理论预测值之间的误差很小, 这说明本文推导的布洛赫本构参数的理论计算公式在描述周期性磁谐振材料的电磁特性方面是十分有效的. 这些理论公式将在解释磁谐振现象、设计和优化周期性磁谐振材料等方面提供重要的理论依据. 关键词： 周期性结构 磁谐振 布洛赫本构参数 面磁流     

二氧化钛纳米粒子和纳米管的合成、表征及对硝基苯的光催化性能研究

采用水热合成法, 通过改变反应条件, 控制反应参数, 成功地合成了粒径可控的球形TiO2纳米粒子和长径比、比表面积均比较大的纳米管. 用XRD, TEM, SAED和BET等手段对产物进行了表征. 为了测试产物的光催化性能, 以高浓度的硝基苯(NB)溶液为模拟水样, 进行了一系列提高降解效率的优化实验和光催化降解的对比实验. 通过对硝基苯溶液初始浓度、TiO2加入量和降解体系pH值等条件的考察, 得出硝基苯溶液的质量浓度为300 mg/L, TiO2的加入量为0.4 g/L, 体系的pH值为6~7时, 降解效果最好; 通过对比实验发现, 由于纳米管的大比表面积, 使得其光催化性能明显优于球形纳米粒子, 3 h后的降解率达到90%以上, 3.5 h左右硝基苯几乎被完全降解.     

Ce0.67Zr0.33O2对CH4燃烧催化剂Fe2O3/Al2O3的改性作用

固定n(Ce)/n(Zr)比为0.67/0.33,用共沉淀法制得一系列CeO2-ZrO2-Al2O3固溶体.采用这些固溶体作载体,以Fe2O3为活性组分,用浸渍法制备了一系列催化剂.BET结果显示,将适量Ce0.67Zr0.33O2引入到Al2O3载体中有助于催化剂保持较高的比表面积.TPR结果显示,载体中引入适量的Ce0.67Zr0.33O2可以改善催化剂的氧化还原性能.XRD结果表明,Fe2O3在CeO2-ZrO2-Al2O3载体上呈现出良好的分散状况,老化前后催化剂的晶相结构基本无明显变化.特别是当载体中m(Ce0.67Zr0.33O2)∶m(Al2O3)的值为1∶2时,Fe2O3/CeO2-ZrO2-Al2O3催化剂在甲烷催化燃烧中显示出最佳的催化性能和抗高温老化性能.