关键词: 空间电荷陷阱/
微观结构/
分子链运动/
自由体积
English Abstract
Simulations of the effects of electric field and temperature on space charge traps in polymer
Li Li-Li1,2,Zhang Xiao-Hong1,
Wang Yu-Long1,2,
Guo Jia-Hui1
1.Key Laboratory of Engineering Dielectrics and Its Application, Ministry of Education, College of Electrical and Electronic Engineering, Harbin University of Science and Technology, Harbin 150080, China;
2.College of Rongcheng, Harbin University of Science and Technology, Rongcheng 264300, China
Fund Project:Project supported by the National Natural Science Foundation of China (Grant No. 51577045).Received Date:20 October 2016
Accepted Date:01 February 2017
Published Online:05 April 2017
Abstract:The simulations of the structure and behavior of the molecule in the simulation software are an effective way to analyze the microscopic mechanism associated with performance change of space charge trap in the polymer. To achieve this, in this paper we first present the polyethylene molecular model which is developed by using the simulation software Materials Studio (MS). Then, the microstructure and property of space charge trap are analyzed by the changes with the energy and the free volume in the polyethylene due to the chain segment motion under the universal force field (UFF), respectively. Some important findings are extracted from simulation results. First, in the process of the temperature gradually increasing from 298 K to 363 K, the phenomena of slippage and diffusion of the molecule due to the enhanced thermal motion of molecules are observed. These phenomena lead to the free volume increasing and the space charge trap energy level decreasing gradually, whose maximum value is 1542.073 and the minimum value is 0.66 eV when the temperature is 363 K. Second, when an electrostatic field of 0.0007 Hartree/Bohr is applied to the polymer, molecular chain segments are oriented by the Maxwell stress that is generated by the electric effect. Molecular chain segment orientations induce the van der Waals interaction energy to increase to -360.18 kcal/mol (1 kcal/mol = 4.18 kJ/mol), the free volume to decrease by 279.77 3, and the space charge trap energy level to decrease by 0.45 eV. Third, by comparing the cases of applying the temperature field and the electric field to the polyethylene, it is found that the electric field has stronger effect on charge trap. Specifically, the space charge trap energy level of the polyethylene associated with 0.0007 Hartree/Bohr electric field is reduced by 0.17 eV compared with that associated with the temperature of 363 K. Moreover, simulation results and measured results are compared with each other and they are well consistent. Finally, it is concluded that using electric effect and molecular thermodynamic movement is an very effective way to analyze the microscopic mechanism of changes with free volume and van der Waals interaction energy. This analysis confirms that molecular motion changes the microstructure of the polyethylene and generates charge traps. In addition, it confirms that the influence of the electric field on the polyethylene generates the lower level of space charge trap than the effect of the temperature field.
Keywords: space charge traps/
microstructure/
chain segment movement/
free volume
