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Thermal conductivity prediction of MgAl2O4:a non-equilibrium molecular dynamics calculation

Journal of Iron and Steel Research(International) 2020年第5期27卷 500-505页

作者： Cheng-ming Ni Hua-wei Fan Xu-dong Wang Man Yao School of Materials Science and Engineering Dalian University of TechnologyDalian 116000LiaoningChina

Magnesium aluminate spinel(MgAl2O4)is widely used in steel metallurgy industry.Thermal conductivity at high temperature signifcantly infuences the cooling process of blast furnace and the heat preservation of steel converter.The efect of external(temperature)and internal(antisite defect and grain boundary)factors on the thermal conductivity of MgAl2O4 was studied with non-equilibrium molecular dynamics.The main factors afecting the thermal conductivity of MgAl2O4 were summarized.In the temperature range of 100-2000 K,the results showed that the thermal conductivity of MgAl2O4 changed from 11.54 to 4.95 W/(m K)with the increase in temperature and was relatively stable at the temperature above 1000 K.The thermal conductivity of MgAl2O4 declined frst and then rose with the increase in the antisite defects,and the minimum value was 6.95 W/(m K)at the inversion parameter i=0.35.In addition,grain boundaries reduced the thermal conductivity of MgAl2O4 by 20%-30%at temperature below 1000 K comparing with the non-grain boundary system.The grain boundary rotation angle at temperature above 1000 K had less efect on the thermal conductivity than that below 1000 K.Present simulation scheme for thermal conductivity of MgAl2O4 can also be applied to the study of other nonmetallic ceramics.

关键词： non-equilibrium molecular dynamics Thermal conductivity Magnesium aluminate spinel Antisite defect Grain boundary

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单晶铝中微喷射的分子动力学研究

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Acta Mechanica Sinica 2023年第3期39卷 7-25页

作者：杨鑫赵晗高学军雷刚陈臻林 College of Environment and Civil Engineering Chengdu University of TechnologyChengdu 610059China School of Intlligent Manufacturing Chengdu Technological UniversiyChengdu 611730China Faculty of Quality Management and Inspection Yibin UniversityYibin 644000China

采用非平衡分子动力学模拟方法,研究了方形冲击波在含有圆锥和正弦缺陷的单晶铝中一维和二维的微射流演化.利用正向和反向粒子追踪技术获得了微射流的粒子源,发现微射流不同部位的粒子源结构与缺陷类型密切相关,微射流的形成是从缺陷表... 详细信息

采用非平衡分子动力学模拟方法,研究了方形冲击波在含有圆锥和正弦缺陷的单晶铝中一维和二维的微射流演化.利用正向和反向粒子追踪技术获得了微射流的粒子源,发现微射流不同部位的粒子源结构与缺陷类型密切相关,微射流的形成是从缺陷表层到内层的分层聚集过程.锥形情况下的射流头部速度最初急剧增加,然后快速下降至恒定速度;锥形和正弦情况下的喷射体积先经历非线性增加,后保持不变.通过进一步对喷射粒子数量、密度、速度和温度之间的关系分析,发现在圆锥和正弦情况下,当冲击速度为6 km/s时喷射物速度在冲击方向上基本呈线性变化,且射流最大速度位于射流头部;但在正弦情况下,当冲击速度为2 km/s时喷射物速度在冲击方向上波动变化,射流头部速度低于为头部后侧的速度.更重要的是,本文揭示了两种机制,即一维射流的颈缩与二维射流的孔洞增长和贯穿,它们主导了射流的破碎.实际上,速度、温度和压力的扰动都有助于射流破碎,其中速度扰动对其破碎具有最重要影响.此外,速度梯度会引起孔洞边界变厚,从而导致射流头部密度增加.

关键词： non-equilibrium molecular dynamics Single crystal Al Micro jet Ejecta source Breakup mechanism

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molecular Simulations of Water Transport Resistance in Polyamide RO Membranes: Interfacial and Interior Contributions

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Engineering 2020年第5期6卷 577-584页

作者： Yang Song Mingjie Wei Fang Xu Yong Wang State Key Laboratory of Materials-Oriented Chemical Engineering College of Chemical EngineeringNanjing Tech UniversityNanjing 211816China

Understanding the transport resistance of water molecules in polyamide(PA)reverse osmosis(RO)membranes at the molecular level is of great importance in guiding the design,preparation,and applications of these membranes.In this work,we use molecular simulation to calculate the total transport resistance by dividing it into two contributions:the interior part and the interfacial part.The interior resistance is dependent on the thickness of the PA layer,while the interfacial resistance is not.Simulation based on the 5 nm PA layer reveals that interfacial resistance is the dominating contribution(>62%)to the total resistance.However,for real-world RO membranes with a 200 nm PA layer,interfacial resistance plays a minor role,with a contribution below 10%.This implies that there is a risk of inaccuracy when using the typical method to estimate the transport resistance of RO membranes,as this method involves simply multiplying the total transport resistance of the simulated value based on a membrane with a 5 nm PA layer.Furthermore,both the interfacial resistance and the interior resistance are dependent on the chemistry of the PA layer.Our simulation reveals that decreasing the number of residual carboxyl groups in the PA layer leads to decreased interior resistance;therefore,the water permeability can be improved at no cost of ion rejection,which is in excellent agreement with the experimental results.

关键词： Transport resistance Reverse osmosis non-equilibrium molecular dynamics Water molecule affinity Modeling

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