Santiago Corujeira Gallo

Electrostatically Confined Plasma in Segmented Hollow Cathode Geometries for Surface Engineering

A segmented hollow cathode (SHC) geometry was used for electrostatic confinement of plasma, and surface engineering treatments were conducted in this arrangement. The assessed processes included plasma nitriding, reactive deposition of sputtered material, and deposition of carbonaceous films by plasma-enhanced chemical vapor deposition with a bipolar pulsed-dc power supply on steel substrates. The treated specimens exhibited uniform surface morphology and deposition layers. Characterization techniques included optical microscopy, scanning electron microscopy with energy dispersive X-ray capability, and X-ray diffraction. The advantages and potential applications of the SHC arrangement are discussed in view of these results.

Surface functionalization of carbon fibers with active screen plasma

The active screen plasma technology was used to functionalize carbon fibers and vitreous carbon disks. The plasma treatment conditions were mapped using optical emission spectroscopy and the functionalized surfaces were analyzed using scanning electron microscopy and atomic force microscopy, x-ray photoelectron spectroscopy, and contact angle measurements. A relationship was found between the active species in the plasma and the functional groups attached to the carbon surfaces, which provides valuable information for the optimization of the active screen plasma treatment. Moreover, the surface analyses were repeated over a period of 28 days to study the aging of the functionalized surfaces in air. The hydrophobic recovery was modeled using a surface restructuring theory which revealed a mean lifetime of 3.4 days for the functional groups.

Carbon nanofibers functionalized with active screen plasma-deposited metal nanoparticles for electrical energy storage devices

Supercapacitors are energy storage devices with higher energy densities than conventional capacitors but lower than batteries or fuel cells. There is a strong interest in increasing the volumetric and gravimetric capacitance of these devices to meet the growing demands of the electrical and electronic sectors. The capacitance depends largely on the electrode material, and carbon nanofibers (CNFs) have attracted much attention because of their relatively low cost, large surface area, and good electrical conductivity as well as chemical and thermal stability. The deposition of metal nanoparticles on CNFs is a promising way to increase their surface properties and, ultimately, the capacitance of the devices. In this study, nickel and silver nanoparticles were deposited on CNFs using the active screen plasma technology. The CNFs were characterized, and their electrochemical performance was assessed in a three-electrode cell. The results show significant improvements over the untreated CNFs, particularly after functionalization with silver nanoparticles.

In Situ Synthesis of TiC-Fe Composite Overlays from Low Cost TiO 2 Precursors Using Plasma Transferred Arc Deposition

A direct conversion of TiO2 into TiC during plasma transferred arc deposition is a cheap and novel approach to produce wear resistant coatings. The present study explored the use of a low cost titanium ore as precursor for titanium carbide in metal matrix composite overlays. The deposited layers were characterized using optical microscopy, scanning electron microscopy, x-ray diffraction and microhardness testing. A carbothermic reduction of the titanium oxides took place during the deposition of the coating by plasma transferred arc. The overlays produced in this way consisted of fine titanium carbides evenly dispersed in an iron matrix. The opportunities and limitations of this approach are discussed.