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.

Aerosol jet printing is a contactless direct-write technique that could be used for the deposition of a variety of materials. First, used for electric paths, the technology was explored for many applications. The substantial part of the process is the generation of aerosols. The size of the droplets and the stability of the process affect the quality of the sprayed lines. This article investigates the diameter of the sprayed droplets, allowing future comparison of the results with sprayed lines. Droplets from ultrasonic and pneumatic generators were sprayed at their outlet on the polyethylene terephthalate (PET) foil. Using a digital microscope and the built-in algorithm, the diameter of the droplets was measured, and the dataset was collected as CSV files and served as a background to the box plot. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) scans were applied to verify the results obtained. The ink parameters used in the process have an influence on the aerosol generation and droplet diameter, whereas the carrier gas pressure has an impact mostly on the droplet diameter. In this case, the aerosol was produced from three types of ink in combination with two generators. For inks with a dynamic viscosity below 6.5 m·Pa−1·s−1 a stable range of 5–10 μm droplet diameter was observed. A high-viscosity ink (7.5–10.5 m·Pa−1·s−1) produced droplets with diameter in the range of 6–25 μm. The diameter of the droplet decreased from 7–22 μm to 1–5 μm with a reduction in the dynamic viscosity from 7.5–10.5 m·Pa−1·s−1 to 4.5–5.5 m·Pa−1·s−1.