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Investigation of field emission properties of polyacrylonitrile carbon fibers

Keywords:

E.P. Sheshin – Dr.Sc. (Phys.-Math.), Professor, Moscow Institute of Physics and Technology. E-mail: sheshin@mail.mipt.ru
A.J. Kolodjazhnyj – Student, Moscow Institute of Physics and Technology. E-mail: kolodyazhnyj@gmail.com
G.M. Bolejko – Ph.D., Associate Professor, Moscow Institute of Physics and Technology. E-mail: bolhel@mail.ru


With the development of field-emission technologies new fields of their application are opening up, where the cathodoluminescence light sources (CLS) may exercise all their advantages, such as environmental friendliness, resistance to mechanical vibrations, low inertia, wide operating temperature range and range of color, high brightness, long life, lack of basking parts. Currently field emission properties of various materials are under actively research with a view to their practical use. The special place in these studies occupies carbon materials, including carbon fibers (CF). At the moment, the most common of CF are polyacrylonitrile (PAN) CF, which is explained primarily due to their affordability and high repeatability properties. PAN CF is a product of the pyrolysis process of polymeric fibers based on polyacrylonitrile and their subsequent high-temperature processing. CF has a diameter of 6…10 mm and composed of 99.9% carbon. The aim of this work is to conduct a comparative analysis of field emission properties of different types of PAN CF and conclude about the possibility of their use in field emission devices. CF based field emission cathodes were manufactured for this purpose. During this work a comparison of the investigated CF emitting surface structure SEM images at different magnifications was made. Field cathodes based diode assemblies were collected. Anode-cathode distance was ~ 5 mm. Several of these diode assemblies were placed in a vacuum chamber with a residual gas pressure ~ 10-6 Torr to obtain to obtain initial information about the field emission properties of CF. Greater part of the diode assemblies have been installed in electro-vacuum devices for long-term tests: determination of life and changes in the structure of the cathodes emitting surface during operation under high vacuum in sealed devices. According to the Fowler-Nordheim theory, such cathodes parameters as the area of the emitting surface and its form factor can be defined from the dependence of the emission current density from the electric field. Therefore, during the research, CV characteristics were periodically measured from the cathodes those help to quickly identify changes that occurred with its emitting surface.
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