Reinforced materials for radio engineering modified with carbon nanotubes

The paper presents the results of studies of the influence of carbon nanotubes (CNTs) on radio engineering (reflection coefficient), electrophysical (surface electrical resistance), thermomechanical and strength properties of fiberglass based on epoxy binder. The compositions and technological parameters of the manufacture of fiberglass samples are proposed. The change in the electrophysical and radio technical characteristics of fiberglass samples with increasing concentrations of CNTs is shown.

CuO Films Obtained by Oxidation of Cu Layers Deposited by the PVD Process - Magnetron Sputtering

The experimental research carried out and described in this paper aimed to obtain thin films from copper oxides and their characterization from the structural point of view and the optical and electrical properties. To obtain the copper films, a PVD spray deposition system was used, consisting of a vacuum chamber with a capacity of 2 liters, a planar magnetron with ferrite magnets (40x22x9) neodymium (15x8), a vacuum pump with sliding blades, a variable source of direct current of voltage 100 - 600 volts. The atmosphere used for plasma maintenance during deposition was argon rarefied in a pressure range between 3·10-2 - 8·10-3 mbar. The deposits were made on glass plates. The films thus obtained were subsequently subjected to oxidation at temperatures of 200, 300 and 450 °C. It was found that the transparency of the films increases with the oxidation temperature from 1.464 * 10-4 for 200 ºC to 0.5 for 450 ºC and the surface electrical resistance also increases from 0.984 Ώ for 200 ºC to 3882857,1428 Ώ for 450 ºC. With increasing spray power, transparency and surface strength decrease.

A Nondestructive Evaluation Method: Measuring the Fixed Strength of Spot-Welded Joint Points by Surface Electrical Resistivity

Destructive tests are generally applied to evaluate the fixed strength of spot-welding nuggets of zinc-plated steel (which is a widely used primary structural material for automobiles). These destructive tests, however, are expensive and time-consuming. This paper proposes a nondestructive method for evaluating the fixed strength of the welded joints using surface electrical resistance. A direct current nugget-tester and probes have been developed by the authors for this purpose. The proposed nondestructive method uses the relative decrease in surface electrical resistance, α. The proposed method also considers the effect of the corona bond. The nugget diameter is estimated by two factors: RQuota, which is calculated from variation of resistance, and a constant that represents the area of the corona bond. Since the maximum tensile strength is correlated with the nugget diameter, it can be inferred from the estimated nugget diameter. When appropriate measuring conditions for the surface electrical resistance are chosen, the proposed method can effectively evaluate the fixed strength of the spot-welded joints even if the steel sheet is zinc-plated.

Surface Electrical Resistances Properties of CNF/PC Nano-Composite Processing by Injection Molding

In the present work, carbon nanofibers (CNF) were dispersed into polycarbonate (PP) with an injection molding machine. The effect of the injection conditions on the electrical resistance of carbon nanofiber/polycarbonate (CNF/PC) nanocomposites was investigated. It was found that the surface resistance decreased with the increase of injection speed and injection temperature. The surface electrical resistance was affected by the particle size and dispersion of CNF, the effect of depth on surface resistance of the composites was studied, the surface electrical resistance sharply increased from the material surface to the internal at first, after that, a decreased slowly was observed. The effect of surface roughness on surface electrical resistance was also studied, the composite with a low surface resistance was greatly influenced when surface roughness changed, while there was not a same phenomenon when the composites have a high surface resistance.

Oxygen detection using yttria-stabilized zirconia thin films doped with platinum

Yttria stabilized zirconia (YSZ) thin films are obtained using both spray-pyrolysis and dip-coating. The ability of YSZ films incorporated with platinum nanospecies (Pt-YSZ) to detect oxygen is compared with that of pure YSZ thin films using a new experimental setup. With this system, the surface electrical resistance of the films as a function the oxygen content is measured at a fixed temperature. In addition, the effects of thermal annealing on the oxygen sensitivity of the films are observed. Platinum doped samples, Pt-YSZ, show different kinetics of carrier diffusion as compared to pure YSZ samples.