Ferroelastic hybrid perovskite materials have been revealed the significance in the applications of switches,sensors,actuators,etc.However,it remains a challenge to design high-temperature ferroelastic to meet the req...Ferroelastic hybrid perovskite materials have been revealed the significance in the applications of switches,sensors,actuators,etc.However,it remains a challenge to design high-temperature ferroelastic to meet the requirements for the practical applications.Herein,we reported an one-dimensional organicinorganic hybrid perovskites(OIHP)(3-methylpyrazolium)CdCl_(3)(3-MBCC),which possesses a mmmF2/m ferroelastic phase transition at 263 K.Moreover,utilizing crystal engineering,we replace-CH_(3) with-NH_(2) and-H,which increases the intermolecular force between organic cations and inorganic frameworks.The phase transition temperature of(3-aminopyrazolium)CdCl_(3)(3-ABCC),and(pyrazolium)CdCl_(3)(BCC)increased by 73 K and 10 K,respectively.Particularly,BCC undergoes an unconventional inverse temperature symmetry breaking(ISTB)ferroelastic phase transition around 273 K.Differently,it transforms from a high symmetry low-temperature paraelastic phase(point group 2/m)to a low symmetry high-temperature ferroelastic phase(point group ī)originating from the rare mechanism of displacement of organic cations phase transition.It means that crystal BCC retains in ferroelastic phase above 273 K until melting point(446 K).Furthermore,characteristic ferroelastic domain patterns on crystal BCC are confirmed with polarized optical microscopy.Our study enriches the molecular mechanism of ferroelastics in the family of organic-inorganic hybrids and opens up a new avenue for exploring high-temperature ferroic materials.展开更多
The influence of temperature on the inverse Hall-Petch effect in nanocrystalline （NC） materials is investigated using phase field crystal simulation method. Simulated results indicate that the inverse Hall-Petch eff...The influence of temperature on the inverse Hall-Petch effect in nanocrystalline （NC） materials is investigated using phase field crystal simulation method. Simulated results indicate that the inverse Hall-Petch effect in NC materials becomes weakened at low temperature. The results also show that the change in microscopic deformation mechanism with temperature variation is the main reason for the weakening of the inverse Hall-Petch effect. At elevated temperature, grain rotation and grain boundary （GB） migration seriously reduce the yield stress so that the NC materials exhibit the inverse Hall-Petch effect. However, at low temperature, both grain rotation and GB migration occur with great difficulty, instead, the dislocations nucleated from the cusp of serrated GBs become active. The lack of grain rotation and GB migration during deformation is mainly responsible for the weakening of the inverse Hall-Petch effect. Furthermore, it is found that since small grain size is favorable for GB migration, the degree of weakening decreases with decreasing average grain size at low temperature.展开更多
利用常规地面和高空观测资料、地基GPS/MET水汽资料、NCEP再分析资料以及多普勒天气雷达和双偏振雷达资料,对2018年1月3—4日和24—28日先后发生在安徽的两次暴雪过程(以下简称"0103"过程和"0124"过程)的环流背景...利用常规地面和高空观测资料、地基GPS/MET水汽资料、NCEP再分析资料以及多普勒天气雷达和双偏振雷达资料,对2018年1月3—4日和24—28日先后发生在安徽的两次暴雪过程(以下简称"0103"过程和"0124"过程)的环流背景与动力、热力、水汽输送条件进行对比分析,探讨两次过程降水相态转变过程中大气温度变化的异同。结果表明:(1)两次过程都发生在500 h Pa高空槽东移、低层切变线东伸的环流背景下,且在700 h Pa存在西南急流和逆温层;850 h Pa温度场上可见明显温度锋区,大气斜压性强;大气可降水量峰值出现在强降雪时段;暴雪过程伴随暖平流增强,暴雪区位于低层冷平流和高层暖平流叠加区域。(2)两次过程的不同点是,"0103"过程先有暖湿气流增强北上,暖湿输送强,存在一定的不稳定层结,动力辐合区深厚,降雪的对流性特征明显,而"0124"过程先有低层冷空气南下形成冷垫,垂直运动发展厚度、暖湿气流强度均不如"0103"过程;强冷空气在华东沿海形成高压,使西风槽东移较慢,造成"0124"过程降雪持续时间长。(3)双偏振雷达整体上正确识别出了两次过程中降水粒子相态,其降水粒子分类产品对预报员开展降雪短临预报具有一定的参考价值。展开更多
基金support from the National Natural Science Foundation of China(No.22175079)support from the National Natural Science Foundation of China(No.22205087)+2 种基金the Open Project Program of Jiangxi Provincial Key Laboratory of Functional Molecular Materials Chemistry,Jiangxi University of Science and Technology(No.20212BCD42018)National Natural Science Foundation of China(No.22275075)Natural Science Foundation of Jiangxi Province(Nos.20204BCJ22015 and 20202ACBL203001).
文摘Ferroelastic hybrid perovskite materials have been revealed the significance in the applications of switches,sensors,actuators,etc.However,it remains a challenge to design high-temperature ferroelastic to meet the requirements for the practical applications.Herein,we reported an one-dimensional organicinorganic hybrid perovskites(OIHP)(3-methylpyrazolium)CdCl_(3)(3-MBCC),which possesses a mmmF2/m ferroelastic phase transition at 263 K.Moreover,utilizing crystal engineering,we replace-CH_(3) with-NH_(2) and-H,which increases the intermolecular force between organic cations and inorganic frameworks.The phase transition temperature of(3-aminopyrazolium)CdCl_(3)(3-ABCC),and(pyrazolium)CdCl_(3)(BCC)increased by 73 K and 10 K,respectively.Particularly,BCC undergoes an unconventional inverse temperature symmetry breaking(ISTB)ferroelastic phase transition around 273 K.Differently,it transforms from a high symmetry low-temperature paraelastic phase(point group 2/m)to a low symmetry high-temperature ferroelastic phase(point group ī)originating from the rare mechanism of displacement of organic cations phase transition.It means that crystal BCC retains in ferroelastic phase above 273 K until melting point(446 K).Furthermore,characteristic ferroelastic domain patterns on crystal BCC are confirmed with polarized optical microscopy.Our study enriches the molecular mechanism of ferroelastics in the family of organic-inorganic hybrids and opens up a new avenue for exploring high-temperature ferroic materials.
基金financially supported by the National Natural Science Foundation of China(Nos.51174168 and 51274167)Northwestern Polytechnical University Foundation for Fundamental Research(No.NPU-FFR-JC20120222)
文摘The influence of temperature on the inverse Hall-Petch effect in nanocrystalline （NC） materials is investigated using phase field crystal simulation method. Simulated results indicate that the inverse Hall-Petch effect in NC materials becomes weakened at low temperature. The results also show that the change in microscopic deformation mechanism with temperature variation is the main reason for the weakening of the inverse Hall-Petch effect. At elevated temperature, grain rotation and grain boundary （GB） migration seriously reduce the yield stress so that the NC materials exhibit the inverse Hall-Petch effect. However, at low temperature, both grain rotation and GB migration occur with great difficulty, instead, the dislocations nucleated from the cusp of serrated GBs become active. The lack of grain rotation and GB migration during deformation is mainly responsible for the weakening of the inverse Hall-Petch effect. Furthermore, it is found that since small grain size is favorable for GB migration, the degree of weakening decreases with decreasing average grain size at low temperature.
文摘利用常规地面和高空观测资料、地基GPS/MET水汽资料、NCEP再分析资料以及多普勒天气雷达和双偏振雷达资料,对2018年1月3—4日和24—28日先后发生在安徽的两次暴雪过程(以下简称"0103"过程和"0124"过程)的环流背景与动力、热力、水汽输送条件进行对比分析,探讨两次过程降水相态转变过程中大气温度变化的异同。结果表明:(1)两次过程都发生在500 h Pa高空槽东移、低层切变线东伸的环流背景下,且在700 h Pa存在西南急流和逆温层;850 h Pa温度场上可见明显温度锋区,大气斜压性强;大气可降水量峰值出现在强降雪时段;暴雪过程伴随暖平流增强,暴雪区位于低层冷平流和高层暖平流叠加区域。(2)两次过程的不同点是,"0103"过程先有暖湿气流增强北上,暖湿输送强,存在一定的不稳定层结,动力辐合区深厚,降雪的对流性特征明显,而"0124"过程先有低层冷空气南下形成冷垫,垂直运动发展厚度、暖湿气流强度均不如"0103"过程;强冷空气在华东沿海形成高压,使西风槽东移较慢,造成"0124"过程降雪持续时间长。(3)双偏振雷达整体上正确识别出了两次过程中降水粒子相态,其降水粒子分类产品对预报员开展降雪短临预报具有一定的参考价值。
