淬火温度对聚硫脲介电储能特性影响的分子动力学模拟  

Molecular Dynamics Simulations on the Effect of Quenching Temperature on the Dielectric Energy Storage Characteristics of Polythiourea

作　　者：冯阳[1] 渠广昊 李盛涛[1] FENG Yang;QU Guanghao;LI Shengtao(State Key Laboratory of Electrical Insulation and Power Equipment,Xi’an Jiaotong University,Xi’an 710049,China)

机构地区：[1]西安交通大学电工材料电气绝缘全国重点实验室,西安710049

出　　处：《高电压技术》2024年第6期2363-2373,共11页High Voltage Engineering

基　　金：国家自然科学基金(52207030);电工材料电气绝缘全国重点实验室资助(EIPE22311)。

摘　　要：为了提高聚硫脲(polythiourea,PTU)的储能密度,对PTU进行了淬火处理,并采用分子动力学模拟研究了PTU中氢键动力学性质对介电储能特性的影响机理。首先,借助热波动指数(thermalfluctuationindex,TFI)和约化梯度密度(reduction gradient density,RDG)描述了氢键作用模式和强度随淬火温度升高的演变规律。其次,计算了氢键供体分别与受体和氢原子的径向分布函数、自相关函数等,提取了氢键密度和平均寿命。最后,建立了氢键特征参数与介电常数的关联,揭示了淬火提高PTU储能密度的机理。研究发现,淬火温度升高,氢键作用模式发生了由双氢键至单氢键,并最终超过氢键阈值而断裂的演变规律,这造成氢键密度减少,表现为强极性双氢键硫脲阵列数目的减少,导致介电常数减小;同时,氢键强度持续减弱,氢键寿命缩短,动态变化加快,导致硫脲阵列转向势垒降低,这有利于增大介电常数。受氢键作用模式和强度的共同影响,PTU的介电常数随淬火温度升高呈现先增大后减小的变化趋势。当淬火温度为393 K时,PTU的介电常数增大至10,储能密度高达16.3 J/cm~3。In order to improve the energy density of polythiourea(PTU),the PTU was treated by quenching.The effect of hydrogen-bonding(H-bonding)kinetic properties on dielectric energy storage characteristics of PTU was studied by molecular dynamics simulation.Firstly,the evolution of H-bonding pattern and strength with the increase of quenching temperature was described by means of thermal fluctuation index(TFI)and reduction gradient density(RDG).Secondly,the radial distribution function and autocorrelation function of H-bonds were calculated,and H-bonding density and average lifetime were then extracted.Finally,the correlation between H-bonding characteristic parameters and dielectric constant was established.Based on the results above,the mechanism of quenching to improve energy density of PTU was revealed.The results show that,with the increase of the quenching temperature,the H-bonding pattern changes from dihydrogen bonds to single H-bonds,and eventually exceeds the H-bonding threshold,which is difficult to form H-bonds.It is accompanied by decreases in the H-bonding density,resulting in decreases in strongly polar dihydrogen bonding thiourea arrays and thus the dielectric constant.Meanwhile,the H-bonding strength gradually weakens as the quenching temperature increases.Moreover,the H-bonding lifetime is shortened and the dynamic motions is accelerated,which is conductive to reducing the barrier for the orientation of thiourea arrays and increasing the dielectric constant.Owing to the changes of H-bonding patterns and strength,the dielectric constant increases first and then decreases with the increasing quenching temperature.When the quenching temperature is 393 K,the dielectric constant of PTU increases to 10 and the energy density reaches 16.3 J/cm3.

关 键 词：聚硫脲 分子动力学模拟 氢键动力学性质 介电常数 储能密度 

分 类 号：TM53[电气工程—电器] TQ317[化学工程—高聚物工业]