Search Results (7)

Ceramic materials as coatings are known to have very good corrosion resistance properties compared to metallic or organic coatings, regardless of environmental conditions. The following samples were used for the experiments: an initial steel substrate and Al₂O₃ + YSZ (12.5%; 25% and 37.5% wt) atmospheric plasma spray-coated samples. The open circuit potential showed similar average values for all samples coated with ceramic layers, which were slightly higher than the potential of the original uncoated sample. The corrosion current densities (i_corr) of all plasma jet sputter-coated systems were very similar and significantly lower than those of the original material. Corrosion rates were much lower in the coated systems due to the chemical inertness of the ceramic coatings, particularly alumina- and zirconia-based coatings. It was observed that ceramic layers improve the corrosion resistance of the metallic material, especially at higher percentages of YSZ in the plasma spray-deposited complex layer. The porosity of the sputter-deposited layers reduced their corrosion resistance due to the contact between the electrolyte solution and the metal substrate created by the interconnection of the pores. The complex equivalent electrical circuit chosen for the analysis of the values led to results in accordance with the experimental parameters. Full article

The research aimed to enhance the aqua-jet/spunlace cellulose nonwoven fabric by deposition of copper coating by magnetron sputtering technology. Plasma technology facilitated the efficient distribution of copper particles on the surface of the cellulose nonwoven fabric, while maintaining free airflow and eliminating the need for additional layers. New cellulose-copper composites exhibit potential in biomedical applications, while minimizing their impact on biological processes such as blood plasma coagulation. Consequently, they can be utilized in the production of dressings, bandages, and other medical products requiring effective protection against bacterial infections. The cellulose-copper composite material was subjected to the physiochemical and biological investigations. The physiochemical analysis included the elemental analysis of composites, their microscopic analysis and the surface properties analysis (specific surface area and total pore volume). The biological investigations consisted of biochemical-hematological tests including the evaluation of the activated partial thromboplastin time and pro-thrombin time. Biodegradable materials based on cellulose nonwoven fabrics with the addition of copper offer a promising alternative to conventional materials. Their innovative properties, coupled with environmental friendliness and minimal impact on biological processes, offer vast application possibilities in healthcare and the production of hygiene products. Full article

A novel method for the preparation of Ni-Cu oxide catalysts—deposition on stainless steel meshes using hollow cathode plasma jet sputtering—was studied. This method allows the preparation of thin oxide films. Consequently, the whole volume of the active phase is readily accessible for the reactants and can be employed in the catalytic reaction due to the negligible effect of internal diffusion. As a result, the activity of our sputtered catalyst was seven times higher in ethanol oxidation and 61 times higher in toluene oxidation than that of the corresponding granular catalyst. Moreover, due to stainless steel meshes used as a catalyst support, the pressure drop across the catalyst bed was lower. Finally, the catalytic activity of the sputtered Ni-Cu oxide catalyst with Ni:Cu molar ratio of 1:1 in ethanol oxidation was 1.7 times higher than that of the commercial EnviCat^® VOC-1544 catalyst, while the amount of the active phase in the catalyst bed was 139 times lower. The outstanding performance of the Ni_0.5Cu_0.5 catalyst was ascribed to the synergistic effect between the copper and nickel components. Full article

The present paper presents a study of the behaviour of Fe₃Al intermetallic powders particles based on 86Fe-14Al, 86Fe-14(Fe5Mg), and 60.8Fe-39.2(Ti37.5Al) compositions obtained by mechanochemical synthesis at successive stages of the plasma spraying process: during transfer in the volume of the gas stream and deformation at the moment of impact on the substrate. The effect of the change in current on the size of powder particles during their transfer through the high-temperature stream and the degree of particle deformation upon impact with the substrate was determined. It was found that during transfer through the plasma jet, there was an increase in the average size of sputtering products by two–three times compared to the initial effects of mechanochemical synthesis due to the coagulation of some particles. In this case, an increase in current from 400 to 500 A led to a growth in average particle size by 14–47% due to the partial evaporation of fine particles with an increase in their heating degree. An increase in current also led to a 5–10% growth in particle deformation degree upon impact on the substrate due to the rising temperature and velocity of the plasma jet. Based on the research, the parameters of plasma spraying of mechanically synthesized Fe₃Al intermetallic-based powders were determined, at which dense coatings with a thin-lamellar structure were formed. Full article

Hollow cathode plasma sputtering is an advantageous method of preparing catalysts in the form of thin oxide films on supports. Such catalysts are particularly suitable for processes such as catalytic total oxidation of volatile organic compounds (VOCs), representing an economically feasible and environmentally friendly method of VOC abatement. Catalysts with Ni:Co molar ratios of 1:4, 1:1, and 4:1 were prepared on stainless-steel meshes and compared with single-component Ni and Co oxide catalysts. The properties of the catalysts were characterized by EDX, SEM, powder XRD, temperature-programmed reduction (H₂-TPR), Raman spectroscopy, and XPS. Powder XRD revealed the formation of various crystalline phases that were dependent on molar the Ni:Co ratio. NiO and Co₃O₄ were identified in the single-component Ni and Co oxide catalysts, whereas Ni-Co mixed oxides with a spinel structure, together with NiO, were found in the catalysts containing both Ni and Co. Raman spectra of the catalysts prepared at high working pressures showed a slightly lower intensity of bands, indicating the presence of smaller oxide particles. The TPR profiles confirmed the improved reducibility of the Ni-Co oxide catalysts compared to the single-component Ni and Co catalysts. Catalytic activity was investigated in the deep oxidation of ethanol and toluene, which were used as model volatile organic compounds. In ethanol oxidation, the activity of sputtered catalysts was up to 16 times higher than that of the commercial Cu-Mn oxide catalyst EnviCat^® VOC-1544. The main benefits of the sputtered catalysts are the much lower content of Ni and Co oxides and a negligible effect of internal diffusion. Moreover, the process of plasma jet sputtering can be easily implemented on a large scale. Full article

A compact hollow-anode discharge (HAD) source with a size of 60 mm in radius and 70 mm in length has been developed to stably generate plasma jets for various sputtering processes in semiconductor and display fabrications. A developed HAD plasma source has been investigated by cylindrical electric probes, and the experimental results were compared to the values of numerical calculations. A uniform density discharge model with a geometry factor was proposed to estimate the profiles of plasma parameters. Owing to the difference of absolute magnitude, even with the similar trend of spatial variation, plasma parameters such as electron temperature (T_e) and plasma density (n_e) measured at z = 3 cm have been calibrated by the values of numerical calculations at the nozzle entrance (z = 0 cm, at the throat of the jet), and the calibration factors for T_e and n₀ have been deduced by comparing the experimental values to numerical calculations. These are to be explained by the decay mechanism along the axis of the jet with elastic collisions in terms of the mean free path. The developed HAD plasma source was tested for the deposition of Cu thin films with an optimized condition as a plausible application to sputtering processes. Full article

In this paper, the prospects of iron oxide films and their sulfidation for dye-sensitized solar cells (DSSC) are reviewed. Iron oxide thin films were prepared by hollow cathode plasma jet (HCPJ) sputtering, with an admixture of oxygen in the argon working gas and with an iron nozzle as the sputtering target. The discharge was powered by a constant current source in continuous mode and by a constant voltage source in pulsed mode. Plasma composition was measured by an energy-resolved mass spectrometer. Moreover, secondary electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), absorption and Raman spectra of the films are presented. Strong correlation between the color of the iron oxide film and its phase composition was revealed. Iron oxide films were sulfided at 350 °C. A relatively clean pyrite phase was obtained from the magnetite, while the marcasite with admixture of the pyrite phase was obtained from the hematite. Low influence of sulfidation on the films’ microstructure was demonstrated. Full article