Synthesis of nanocrystalline titanium carbide by spark erosion
Interest in nanocrystaJline ceramic powders is due to their attractive processing and mechanical properties. The disadvantages of conventional ceramics, such as large internal flaws, negligible ductility, hightemperature processing, can possibly be eliminated or minimized by starting with finegrained powders. A previous study on the sinterability of nanocrystalline ceramic powders showed that high densities can be achieved at lower temperatures, both with and without the’ application of pressure [ 11. In addition, it is remarkable that superplastic behavior has been reported in nanocrystalline ceramics at room temperature [2]. One of the novel methods for nrenaring nanocrvstalline ceramic powders is reactive spark erosion [3-51. An important feature of this method is the-capability to synthesize new materials by reacting the eroded particles with the dielectric liguid. This technique utilizes two metal or conducting electrodes sparked in a suitable dielectric liquid that reacts with the pa&les to produce the desired ceramic powders. The high temperature provided by the spark results in vaporization of the electrodes and the surrounding dielectric liquid; the reaction products formed between the various vapor species are quenched in the liquid and produce spherical particles. The aim of the present note is to report on the titanium carbide particle formation in a carbonic dielectric liquid (pentane) with titanium electrodes and charges. The nanocrystalline titanium carbide was produced in a wide range of particle size distribution and in the form of single phase spheres.
Spark erosion as a high-throughput method for producing bimodal nanostructured 316L stainless steel powder
Abstract A high-throughput shaker-pot spark erosion process was used to synthesize a spherical polydisperse 316L stainless steel nanopowder. Capacitance and target morphology of the shaker-pot spark erosion process were evaluated to optimize powder production. Nanopowders were assessed using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission scanning electron microscopy (TSEM), dynamic light scattering (DLS), and a new multispectral advanced nanoparticle tracking analysis (MANTA) technique. It was found that the chosen spark erosion dielectric, as well as capacitance, heavily impact the submicron particle size distribution and overall production rate. The distribution of the particles obtained was shown to be a wide range bimodal distribution with a small mode near 150 nm and a large mode near 50 μm. Spark energy and time were shown to have a strong correlation with the chosen dielectric and capacitance parameters.
Measuring Sheet Resistances of Dielectrics Using Co‐Planar Hydrogel Electrochemical Cells with Practical Applications to Characterize the Protective Quality of Paints on Sculptures
Electrical properties of thin dielectric films at the solid-liquid phase boundary are an important performance characteristic of many devices, coatings and sensors. In this paper, co-polymeric hydrogels of polyacrylic acid co-sulfonic acid, swollen with a salt solution to act as the solid electrolyte, were used to assess interfaces using electrochemical impedance spectroscopy (EIS) in a co-planar geometry. Silane-modified glasses were characterized by the co-planar hydrogel EIS cell and found to be distinguishable based on their surface monolayer chemistry. EIS measurements were also made on primed and painted metal substrates, using both test panels and an outdoor sculpture, Tony Smith's Stinger. The panels were then exposed to accelerated and outdoor weathering and showed degradation on the surface paint layers, which was observable electrochemically using EIS and confirmed visually by SEM. Electrochemical spectral features were compared between data from a standard paint-test cell versus this co-planar hydrogel cell; both cell types were able to measure coating capacitance, providing useful information about the condition of the bulk coating. Yet, sheet resistance (Rs) was a spectral feature seen only by the co-planar hydrogel cell. Thus, it can be concluded that the use of such co-planar hydrogel cells can provide an earlier warning sign to coating degradation and such cells provide a new type of spectral information that is not assessable by the standard geometry.