二维MoSi2N4WSe2异质结的第一性原理研究

实验上新合成的MoSi2N4（MSN）由于其独特的七原子层结构和电子特性引起了人们的广泛关注。本文搭建了一种由二维MSN与二维WSe2（WS）垂直堆垛而成的二维MSN/WS异质结,其表现出直接间隙半导体和I型能带排列的特性,具有1.46 eV的带隙。在异质结界面处存在一个由电荷耗尽层MSN指向电荷积累层WS微弱的内建电场。最后,通过施加双轴应变对二维MSN/WS异质结进行调控。发现在正双轴应变的作用下,MSN/WS异质结保持了原来直接带隙半导体和I型能带排列特性;在负双轴应变作用下,MSN/WS异质结由原来的直接带隙半导体转变为间接带隙半导体,当施加的负双轴应变达到-6%与-8%时,I型能带排列转变为Ⅱ型能带排列。     

柔性微粒介电泳分离过程的多尺度模拟

介电泳分离是一种高效的微细颗粒分离技术,利用非均匀电场极化并操纵分离微流道中的颗粒. 柔性微粒在介电泳分离过程中同时受多种物理场、多相流和微粒变形等复杂因素的影响,仅用单一的计算方法对其进行模拟存在一定的难度,本文采用有限单元——格子玻尔兹曼耦合计算的方法处理这一难题.介观尺度的格子玻尔兹曼方法将流体看成由大量微小粒子组成,在离散格子上求解玻尔兹曼输运方程,易于处理多相流及大变形问题,特别适合模拟柔性颗粒在介电泳分离过程中的变形情况.另一方面,介电泳分离过程的模拟需求解流体、电场和微粒运动方程,计算量相当庞大,通过有限单元法求解介电泳力,提高计算效率.利用这种多尺度耦合计算方法,对一款现有的介电泳芯片分离过程进行了模拟.分析了微粒在电场作用下产生的介电泳力,揭示了介电泳力与电场变化率等因素之间的关系.对微粒运动轨迹及其变形的情况进行了研究,发现微粒的变形主要与流体剪切作用有关.这种多尺度耦合计算方法,为复杂微流体的计算提供了一种有效的解决方案.      

从教材到教学的研究——以“化学反应的方向”为例

通过比较3套现行高中化学教材有关“化学反应的方向”内容编排特点,进行有代表性的教学案例分析和教学论问题分析,重新设计了以能量转化观念和微粒观念建构为本的教学,并提出模块整合教学的建议.     

基于微粒作用观的“离子反应”教学研究

1 问题的提出 离子反应是中学化学中重要的核心概念之一;又是高考的重点和难点,考查方式以离子方程式的书写、判断正误和离子共存为主.一直以来,离子反应的教学均采用传统的"宏观→微观"教学法.即先让学生观察实验现象,再由化学反应分析实验现象,最后从电离的角度分析产生这些现象的微观过程.从而引出离子反应的概念和电解质在溶液中反应的实质.这种教学方法更多关注的是对宏观现象的解释,依然延续着宏观思维的方式.     

Preface

This special issue of PARTICUOLOGY is focused on the advanced topics of multiphase flow dynamics and chemical kinetics in particulate systems. The papers included represent not only the fundamental aspects of the basic parametric effects and mechanisms of such systems but also their applied nature involving such transport and reactive units as fluidized beds. risers, and downers.     

重离子碰撞中QCD物质整体极化的实验测量

高能重离子碰撞中Λ超子和φ, K^*0矢量介子的整体极化的实验数据证实了夸克物质整体极化的新现象,引起了研究人员的广泛关注,成为高能核物理前沿新的热点研究方向.本文主要从实验测量上回顾整体极化研究,着重阐述相对论重离子对撞机(RHIC)上的螺旋径迹探测器(STAR)合作组在不同对撞能量点开展的Λ超子和φ, K^*0介子的整体极化测量结果,并拓展到含有多个奇异夸克粒子Ξ,Ω的整体极化测量和Λ沿着束流方向的局域极化研究.本文也将简单点评大型强子对撞机(LHC)能区和HADES实验低能区的测量结果,并对这些实验结果给出的物理信息进行简单描述.     

聚集态分子排列对光电性能的影响

有机小分子材料是由许多分子构成的聚集体, 其性能既与单个分子的空间构型和电子特性有关, 更与聚集体中分子的排列方式和分子间相互作用密切相关. 在有机小分子材料中, 聚集体的性质并不是组成它的单分子行为的简单线性叠加, 而是经常呈现出聚集态的整体差异性响应特点, 即: 不同的聚集态分子排列引起截然不同的性能. 因此, 科学研究已逐渐由单分子研究迈向分子聚集态科学. 随着人们对分子聚集态科学的关注, 特别是对有机分子固态下的排列和堆积方式、分子间相互作用等方面的深入研究发现, 通过不同策略对分子聚集态行为的有效调控, 可以实现完全不同于单个分子特性的聚集态发光现象, 包括发光强度、颜色、形式以及激发过程的差异. 也可以通过分子聚集态的形貌和维度的调节, 实现不同光电器件性能的调节和优化. 本综述将分别介绍聚集态分子的排列方式对力致变色、室温磷光、力致发光和有机场效应晶体管等方面的重要影响, 进一步阐述聚集态分子行为的重要性, 同时, 为有效调控聚集态分子的排列方式, 有针对性地设计和开发优异性能的光电材料提供基础.     

Probability of rebound and eject of sand particles in wind-blown sand movement

When incident particles impact into a sand bed in wind-blown sand movement, rebound of the incident particles and eject of the sand particles by the incident particles affect directly the development of wind sand flux. In order to obtain rebound and eject lift-off probability of the sand particles, we apply the particle-bed stochastic collision model presented in our pervious works to derive analytic solutions of velocities of the incident and impacted particles in the post-collision bed. In order to describe randomness inherent in the real particle-bed collision, we take the incident angle, the impact position and the direction of resultant action of sand particles in sand bed on the impacted sand particle as random variables, and calculate the rebound and eject velocities, angles and coefficients (ratio of rebound and eject velocity to incident velocity). Numerical results are found in accordance with current experimental results. The rebound and eject lift-off probabilities versus the incident and creeping velocities are predicted. The project was supported by the National Natural Science Foundation of China (10532040, 10601022). The English text was polished by Yunming Chen.     

Thermo-responsive and antifouling PVDF nanocomposited membranes based on PNIPAAm modified TiO2 nanoparticles

A novel hydrophilic nanocomposite additive(TiO2-g-PNIPAAm) was synthesized by the surface modification of titanium dioxide(TiO2) with N-isopropylacrylamide(NIPAAm) via "graft-from" technique. And the nanocomposite membrane of poly(vinylidene fluoride)(PVDF)/TiO2-g-PNIPAAm was fabricated by wet phase inversion. The graft degree was obtained by thermo-gravimetric analysis(TGA). Fourier transform infrared attenuated reflection spectroscopy(FTIR-ATR) and X-ray photoelectronic spectroscopy(XPS) characterization results suggested that TiO2-g-PNIPAAm nanoparticles segregated on membrane surface during the phase separation process. Scanning electron microscopy(SEM) was conducted to investigate the surface and cross-section of the modified membranes. The water contact angle measurements confirmed that TiO2-g-PNIPAAm nanoparticles endowed PVDF membranes better hydrophlilicity and thermo-responsive properties compared with those of the pristine PVDF membrane. The water contact angle decreased from 92.8° of the PVDF membrane to 61.2° of the nanocompostie membrane. Bovine serum albumin(BSA) static and dynamic adsorption experiments suggested that excellent antifouling properties of membranes was acquired after adding TiO2-gPNIPAAm. The maximum BSA adsorption at 40 °C was about 3 times than that at 23 °C. The permeation experiments indicated the water flux recover ratio and BSA rejection ratio were improved at different temperatures.