Field Electron Emission Experiments with Cold-Sprayed Cu-SiC Composite Coatings

Marcin Winnicki,Wojciech Łapa,Zbigniew Znamirowski

doi:10.3390/coatings11020134

Marcin Winnicki, Wojciech Łapa + Show 1 more

Open Access

https://doi.org/10.3390/coatings11020134

Copy DOI

Abstract

Field electron emission of cold-sprayed copper-silicon carbide composite coating on a steel substrate was investigated. Two types of copper powders morphologies, namely dendritic and spherical, were mixed with crushed silicon carbide ceramic, and used as a feedstock. The powder mixtures were sprayed on the substrates and formed coatings with the designed surface topography—(i) flat and (ii) wavy. The microstructure of the coatings as well as the ceramic contents were analyzed. Initial tests proved that field emission from the Cu-SiC composite coatings was possible and depended mostly on the copper powder morphology. It was found out that the additional SiC layer deposited onto the composite coating significantly increased the number of electron emitters and thus improved the intensity of field emission. The Fowler–Nordheim model was used to find the threshold electric field, Eth, and coefficient of electric field amplification, β. These important properties of Cu/SiC + SiC coatings were found to be in the range of Eth = 20 to 24 V/µm and β = 340 to 410, respectively.

Highlights

Low-power, low-temperature, high-current electron emitters are crucial to the development of many instruments, especially including further applications in space exploration [1,2,3]
Electron emission occurs in conductors, semiconductors or dielectrics, submitted to the action of external factors like (i) temperature leading to thermo-emission, (ii) photon bombardment leading to photo-emission; (iii) electron bombardment resulting in secondary electron emission; and (iv) strong electric field leading to field electron emission (FEE)
The paper presents the technology of Cu-SiC composite coatings deposited onto

Summary

Introduction

Low-power, low-temperature, high-current electron emitters are crucial to the development of many instruments, especially including further applications in space exploration [1,2,3]. The exemplary application of field emitters developed for space flight missions are the ionization source for a mass spectrometer, a part of the miniature X-ray tube used in an XRD (X-ray Diffractometer)/XRF Fluorescence Spectrometer) instrument, control and measurement hazardous levels of spacecraft charging, or eventually power emitting devices for electrodynamic space-tether in long-term exploration of space. With an electrodynamic tether properly developed and applied, energy of the spacecraft would be converted to a drag force from interaction between the planet magnetic field and currents flowing in a wire, to adjust the orbit of a spacecraft [3]. Electron emission occurs in conductors, semiconductors or dielectrics, submitted to the action of external factors like (i) temperature leading to thermo-emission, (ii) photon bombardment leading to photo-emission; (iii) electron bombardment resulting in secondary electron emission; and (iv) strong electric field leading to field electron emission (FEE)

Methods

Results

Discussion

Conclusion