摘要
介孔二氧化硅作为一种人工合成纳米孔材料,其热性能调控对于材料的推广应用十分重要。本文基于典型介孔二氧化硅SBA-15建立了双尺度复合孔道模型,并采用逆非平衡态分子动力学方法模拟研究了其内部微尺度热输运行为。研究结果表明当体系长度大于12.84 nm时,无定形二氧化硅和介孔二氧化硅的尺寸效应不再明显。介孔二氧化硅的传热性能调节主要取决于孔径和孔隙率,且在相同孔隙率下,减小孔径可进一步增强材料的绝热性能。同时介孔间的微通道体系破坏了热流传输的连续性,并扩大了材料的比表面积,从而增强热载流子界面散射和热阻。此外,振动态密度分析表明介孔和微通道限制了纳米尺度的传热,降低了热载流子的平均频率,进而导致热导率降低。
Mesoporous silica is a synthetic nanoporous material,and its thermal properties regula-tion is essential for the promotion of nanomaterials.In this paper,a double-scale channel distribution model is developed based on the typical mesoporous silica SBA-15.And the inverse non-equilibrium molecular dynamics method is adopted to study the heat carrier transport and heat transfer behav-ior inside the mesoporous silica.The results show that the thermal conductivity of amorphous and mesoporous silica is insensitive to size effects when the system length is greater than 12.84 nm.The mechanisms for tuning the heat transfer characteristics mainly depend on pore size and porosity.And reducing the pore size can further enhance the thermal insulation performance of the material at the same porosity.The microchannels between mesopores disrupt the continuity of heat carrier propagation and expand the specific surface area of the material,resulting in enhanced heat car-rier interfacial scattering and thermal resistance.Moreover,the analysis of vibrational density of states(VDOS)demonstrates that mesopores and microchannels hinder nanoscale heat transfer.The porous structure reduces the average frequency of the heat carrier and leads to a decrease in thermal conductivity.
作者
黄超
魏高升
崔柳
杜小泽
HUANG Chao;WEI Gaosheng;CUI Liu;DU Xiaoze(Key Laboratory of Power Station Energy Transfer Conversion and System of Ministry of Education,North China Electric Power University,Beijing 102206,China)
出处
《工程热物理学报》
EI
CAS
CSCD
北大核心
2024年第2期551-557,共7页
Journal of Engineering Thermophysics
基金
国家自然科学基金(No.52176069)。
关键词
介孔二氧化硅
热导率
逆非平衡态分子动力学
微通道
mesoporous silica
thermal conductivity
inverse non-equilibrium molecular dynamics
microchannels
