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Title: Enhanced surface flashover strength in vacuum of polymethylmethacrylate by surface modification using atmospheric-pressure dielectric barrier discharge

Abstract

Polymer materials, such as polymethylmethacrylate (PMMA), are widely used as insulators in vacuum. The insulating performance of a high-voltage vacuum system is mainly limited by surface flashover of the insulators rather than bulk breakdown. Non-thermal plasmas are an efficient method to modify the chemical and physical properties of polymer material surfaces, and enhance the surface insulating performance. In this letter, an atmospheric-pressure dielectric barrier discharge is used to treat the PMMA surface to improve the surface flashover strength in vacuum. Experimental results indicate that the plasma treatment method using Ar and CF{sub 4} (10:1) as the working gas can etch the PMMA surface, introduce fluoride groups to the surface, and then alter the surface characteristics of the PMMA. The increase in the surface roughness can introduce physical traps that can capture free electrons, and the fluorination can enhance the charge capturing ability. The increase in the surface roughness and the introduction of the fluoride groups can enhance the PMMA hydrophobic ability, improve the charge capturing ability, decrease the secondary electron emission yield, increase the surface resistance, and improve the surface flashover voltage in vacuum.

Authors:
; ; ;  [1];  [2];  [1];  [3]
  1. Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190 (China)
  2. (China)
  3. Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, New Mexico 87131 (United States)
Publication Date:
OSTI Identifier:
22310869
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 7; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ATMOSPHERIC PRESSURE; BREAKDOWN; CAPTURE; CARBON TETRAFLUORIDE; DIELECTRIC MATERIALS; ELECTRIC DISCHARGES; ELECTRIC POTENTIAL; ELECTRON EMISSION; ELECTRONS; FLUORIDES; FLUORINATION; MODIFICATIONS; PHYSICAL PROPERTIES; PLASMA; PMMA; ROUGHNESS; SURFACES; TRAPS

Citation Formats

Shao, Tao, E-mail: st@mail.iee.ac.cn, Yang, Wenjin, Zhang, Cheng, Yan, Ping, Key Laboratory of Power Electronics and Electric Drive, Chinese Academy of Sciences, Beijing 100190, Niu, Zheng, and Schamiloglu, Edl. Enhanced surface flashover strength in vacuum of polymethylmethacrylate by surface modification using atmospheric-pressure dielectric barrier discharge. United States: N. p., 2014. Web. doi:10.1063/1.4893884.
Shao, Tao, E-mail: st@mail.iee.ac.cn, Yang, Wenjin, Zhang, Cheng, Yan, Ping, Key Laboratory of Power Electronics and Electric Drive, Chinese Academy of Sciences, Beijing 100190, Niu, Zheng, & Schamiloglu, Edl. Enhanced surface flashover strength in vacuum of polymethylmethacrylate by surface modification using atmospheric-pressure dielectric barrier discharge. United States. doi:10.1063/1.4893884.
Shao, Tao, E-mail: st@mail.iee.ac.cn, Yang, Wenjin, Zhang, Cheng, Yan, Ping, Key Laboratory of Power Electronics and Electric Drive, Chinese Academy of Sciences, Beijing 100190, Niu, Zheng, and Schamiloglu, Edl. Mon . "Enhanced surface flashover strength in vacuum of polymethylmethacrylate by surface modification using atmospheric-pressure dielectric barrier discharge". United States. doi:10.1063/1.4893884.
@article{osti_22310869,
title = {Enhanced surface flashover strength in vacuum of polymethylmethacrylate by surface modification using atmospheric-pressure dielectric barrier discharge},
author = {Shao, Tao, E-mail: st@mail.iee.ac.cn and Yang, Wenjin and Zhang, Cheng and Yan, Ping and Key Laboratory of Power Electronics and Electric Drive, Chinese Academy of Sciences, Beijing 100190 and Niu, Zheng and Schamiloglu, Edl},
abstractNote = {Polymer materials, such as polymethylmethacrylate (PMMA), are widely used as insulators in vacuum. The insulating performance of a high-voltage vacuum system is mainly limited by surface flashover of the insulators rather than bulk breakdown. Non-thermal plasmas are an efficient method to modify the chemical and physical properties of polymer material surfaces, and enhance the surface insulating performance. In this letter, an atmospheric-pressure dielectric barrier discharge is used to treat the PMMA surface to improve the surface flashover strength in vacuum. Experimental results indicate that the plasma treatment method using Ar and CF{sub 4} (10:1) as the working gas can etch the PMMA surface, introduce fluoride groups to the surface, and then alter the surface characteristics of the PMMA. The increase in the surface roughness can introduce physical traps that can capture free electrons, and the fluorination can enhance the charge capturing ability. The increase in the surface roughness and the introduction of the fluoride groups can enhance the PMMA hydrophobic ability, improve the charge capturing ability, decrease the secondary electron emission yield, increase the surface resistance, and improve the surface flashover voltage in vacuum.},
doi = {10.1063/1.4893884},
journal = {Applied Physics Letters},
number = 7,
volume = 105,
place = {United States},
year = {Mon Aug 18 00:00:00 EDT 2014},
month = {Mon Aug 18 00:00:00 EDT 2014}
}
  • A magnetic field is introduced to the dielectric-barrier discharge enhanced direct-current glow discharge for efficient plasma generation, with the discharge power of 2.7 W and total energy consumption reduced to 34% of the original. By spatially examining the emission spectra and plasma temperature, it is found that their peaks shift from edges to the center and the negative and anode glows merge into the positive column and disappear, accompanied by improvement of uniformity and chemical activity of the enlarged plasma. This lies in the enhancement of ionization in the curved and lengthened electron path and the dispersion of discharge domains.
  • A stable nonthermal laminar atmospheric-pressure plasma source equipped with dielectric-barrier discharge was developed to realize more efficient plasma generation, with the total energy consumption reduced to nearly 25% of the original. Temperature and emission spectra monitoring indicates that this plasma is uniform in the lateral direction of the jet core region. It is also found that this plasma contains not only abundant excited argon atoms but also sufficient excited N{sub 2} and OH. This is mainly resulted from the escape of abundant electrons from the exit, due to the sharp decrease of sustaining voltage and the coupling between ions andmore » electrons.« less
  • A plasma jet equipped with dielectric barrier discharge (DBD) is developed to generate diffuse air plasma with fairly large gap and cross sectional area. The diffuse air plasma has two discharge modes under different gap widths from the nozzle to the ground plate electrode. For large gap width, a diffuse plume fills the whole space between the nozzle and the plate electrode after coaxial DBD is ignited when the applied voltage reaches a certain value. Rather than diffuse plasma plume, a bright plasma column bridges the nozzle and the plate electrode with further increasing the applied voltage under small gapmore » width. By optical and electrical measurement, results show that the macroscopically diffuse discharge in air is obtained by the superimposition of radially distributed streamers that appear at different cycles of the applied voltage, and the bright plasma column belongs to atmospheric pressure glow discharge. The molecular vibrational temperature and the gas temperature are given as functions of the peak value of the applied voltage.« less
  • This study developed a large volume cold atmospheric plasma brush array, which was enhanced by a dielectric barrier discharge by integrating a pair of DC glow discharge in parallel. A platinum sheet electrode was placed in the middle of the discharge chamber, which effectively reduced the breakdown voltage and working voltage. Emission spectroscopy diagnosis indicated that many excited argon atoms were distributed almost symmetrically in the lateral direction of the plasma. The concentration variations of reactive species relative to the gas flow rate and discharge current were also examined.
  • The authors measured the band spectra (first and second positive systems) of the nitrogen molecule by optical emission spectroscopy with an aim to understand the mechanism of surface processing by medium- to high-pressure dielectric barrier discharge (DBD) plasmas. The experimentally measured and calculated spectra were compared to determine the vibrational and rotational temperatures of the N{sub 2} (C{sup 3}{Pi}{sub u}) state in the generated plasmas. The authors generated the N{sub 2} DBD plasmas at a driving frequency of 1-7 kHz and a discharge pressure of 20-10{sup 5} Pa for the surface modification of a polyethylene terephthalate (PET) sample. It wasmore » found that the vibrational temperature was greatly affected by the N{sub 2} pressure while the rotational temperature remained constant in the N{sub 2} pressure range of 20-10{sup 5} Pa. The emission intensity of N{sub 2} first positive system (B{sup 3}{Pi}{yields}A{sup 3}{Sigma}) rapidly decreased at an increasing N{sub 2} pressure due to the collisional relaxation process of the B{sup 3}{Pi} state with N{sub 2} molecules. The N{sub 2}{sup +}(B{sup 2}{Sigma}{sub u}{sup +}{yields}X{sup 2}{Sigma}{sub g}{sup +}) radiative transition was observed in the low-pressure DBD plasmas, which was attributed to the direct electron impact ionization of N{sub 2} molecules. The surface characterizations of treated PET samples by contact angle measurement and atomic force microscopy indicate that the low-pressure N{sub 2} DBD plasma is an effective method for the surface modification of polymers. Analysis indicates the plasma characteristics such as electron temperature and ion energy are mainly dependent on the N{sub 2} pressure, which turn to determine the surface properties of treated PET samples.« less