Comparison and analysis of field emission characteristics of carbon cathodes based on PAN fiber and CNT filaments

Abstract

In this paper, we experimentally compare the field emission characteristics of two different cathodes based on polyacrylonitrile fibers (PAN fibers) and carbon nanotube fibers (CNT filaments). The main purpose of the study was to compare the field emission properties of materials for the cathode unit of a cathode luminescent lamp. The current-voltage, current and watt-watt characteristics of the fabricated cathodes were measured. A comparison of the current-voltage characteristics of cathodes made of the two studied materials shows that the minimum field for the occurrence of field emission current for a cathode made of a CNT filament (accelerating voltage in the diode version of measurements is about 625 V) is approximately 3 times lower than for a cathode made of PAN fibers (accelerating voltage is about 1850 V. Accordingly, the current value of about 100 μA for a cathode based on a CNT filament is achieved at an accelerating voltage of about 1300 V, and for a cathode based on PAN fibers, about 2630 V. Structural changes in cathodes were studied using scanning electron microscopy methods. Based on the totality of the results, it was concluded that it is preferable to use a CNT filament as a cathode material. The emission current of a cathode based on a CNT filament, when a constant high voltage is applied, demonstrates an increase during the transition period and reaches a stable value of more than 75 μA, apparently due to the activation of additional emission centers when a high accelerating voltage is applied. The paper also analyzes the factors that determine the efficiency of light sources created on the basis of the materials studied in the work.