Platinum-Niobium(V) Oxide/Carbon Nanocomposites Prepared By Microwave Synthesis For Ethanol Oxidation

In the present work, Pt nanoparticles were deposited by means of microwave synthesis on the primary carbon supported Nb2O5 composite which was prepared in two different ways: (A) by dispersion of Nb2O5 and carbon with the mass ratio equal to 1:1 in a 2-propanol solution by ultrasonication for 30 min. with further desiccation of the mixture and (B) by heating the Nb2O5/C composite obtained according to the procedure (A) at 500 °C for 2 h. The transmission electron microscopy was used to determine the shape and the size of catalyst particles. X-ray diffraction and inductively coupled plasma optical emission spectroscopy were employed to characterize the structure and composition of the synthesized catalysts. The electrocatalytic activity of the synthesized catalysts towards the oxidation of ethanol in an alkaline medium was investigated by means of cyclic voltammetry

Comparative investigation of plain and silver impregnated activated carbons for the removal of cyanide from basic aqueous solutions in the batch process

Purolite AC-20 and Norit RB 0.8CC activated carbons impregnated with AgNO3 were used for the removal of CN– and Ag–CN complex from model wastewater. The formed Ag0 centers were approved by scanning electron microscopy micrographs and X-ray powder diffraction data. The degree of Ag0 participating in CN– sorption varied from 100 to 45% on AC-20/Ag and from 100 to 73% on RB 0.8CC/Ag, by varying [CN–]/[Ag] in the initial solution from 2.0 to 19.2. The Freundlich isotherm and Fleming kinetic models were consistent with the experimental data. The KF values for the CN– adsorption on AC-20/Ag and RB 0.8CC/Ag increased by a factor of 1.2 and 1.5, but they lowered for Ag–CN adsorption by a factor of 4.1 and 2.1, respectively, as compared to that of plain activated carbons. The removal of 90% cyanides is appropriate by combining two batches from activated carbon: impregnated, mainly for the removal of CN–, and plain, removing the rest of Ag–CNValstybinis mokslinių tyrimų institutas Fizinių ir technologijos mokslų centrasVytauto Didžiojo universitetasŠvietimo akademij

Seed Layer Optimisation for Ultra-Thin Sb₂Se₃ Solar Cells on TiO₂ by Vapour Transport Deposition

Antimony selenide (Sb2Se3) material has drawn considerable attention as an Earth-abundant and non-toxic photovoltaic absorber. The power conversion efficiency of Sb2Se3-based solar cells increased from less than 2% to over 10% in a decade. Different deposition methods were implemented to synthesize Sb2Se3 thin films, and various device structures were tested. In search of a more environmentally friendly device composition, the common CdS buffer layer is being replaced with oxides. It was identified that on oxide substrates such as TiO2 using vacuum-based close-space deposition methods, an intermediate deposition step was required to produce high-quality thin films. However, little or no investigation was carried out using another very successful vacuum deposition approach in Sb2Se3 technology called vapour transport deposition (VTD). In this work, we present optimized VTD process conditions to achieve compact, pinhole-free, ultra-thin (2Se3 absorber layers. Three process steps were designed to first deposit the seed layer, then anneal it and, at the final stage, deposit a complete Sb2Se3 absorber. Fabricated solar cells using absorbers as thin as 400 nm generated a short-circuit current density over 30 mA/cm2, which demonstrates both the very high absorption capabilities of Sb2Se3 material and the prospects for ultra-thin solar cell application

Sorption of heavy metals by underground water deironing residuals

Valstybinis mokslinių tyrimų institutas Fizinių ir technologijos mokslų centrasVytauto Didžiojo universitetasŠvietimo akademij

Theoretical and Experimental Study Of NON-Stoichiometric SrRuO3SrRuO_{3}: A Role of oxygen vacancies in electron correlation effects

We present a theoretical and experimental study of the electronic structure of SrRuO3 after introduction of vacancies. Theoretically, the modeling of non-stoichiometric variations of SrRuO3 was performed by removing appropriate atoms or their combinations, whereas in the experiments the annealing treatment at moderate temperatures in ultra-high vacuum was applied. At comparison of the obtained results allows us to draw an important conclusion that the formation of oxygen vacancies may be closely related to the manifestation of strong correlation effects in SrRuO3

Synthesis, wear and corrosion of novel electrospark and electrospark–electrochemical hybrid coatings based on carbon steels

The electrospark deposition (ESD) technique is a low-heat-input process that has great potential for coating applications and the restoration of damaged high-value parts. Carbon steels are commonly used as a substrate material for ESD coatings. However, we demonstrated that carbon steels could be used successfully as the electrode tool for the ESD process. Furthermore, ESD coatings commonly have a high as–deposited roughness. In view of this, in order to reduce the roughness of the ESD coatings, electrodeposition as a tool to alter surface morphology was investigated. Hence, the micro-leveling power of several electrolytes for Ni, Fe-W, Fe, and Cr electrodeposition were evaluated. The maximum leveling effect was detected for Ni electroplated from the Watts electrolyte. Thus, the novel hybrid coatings based on an ESD layer and a subsequent layer of electrodeposited Ni were obtained. ESD layers were obtained by using the following electrode tools as anodes: several types of carbon steels (St20, St30, and St45), alloys T15K6 (WC + TiC + Co), CuNiZn; and NiCr. The morphology and structure of the obtained hybrid coatings with an electrodeposited Ni top-layer was analyzed and compared to ESD coatings from the point of view of their wear and corrosion behavior. The wear rate of the novel ESD coatings based on carbon steels was comparable with coatings obtained using the NiCr electrode tool. Moreover, for all the studied cases, the corrosion resistance of the hybrid coatings was higher than for their ESD counterparts and close to electrolytic chromium

Resistance of chromated zinc coatings to the impact of microscopic fungi

Zinc coatings are used to protect metallic parts of automobiles from corrosion. Zinc protective coatings are often chromated additionally treating them in acidic solution of chromium compounds. In recent years new technologies were designed to deposit chromate films of various thickness and resistance on zinc surface from acidic solution of Cr(III) compounds. It has been noticed, that under atmospheric corrosion conditions microscopic fungi are present in the environment affect zinc coating. The aim of the presented study was to determine if zinc coatings treated with Cr(III) solution become more resistant to fungi influence or their resistance diminishes. The analysis of steel plates coated with a zinc film and treated in four different chromium solutions has shown that in all the specimens fungi of Cladosporium herbarium species were detected and their frequency of detection was quite high, sometimes up to 50 %. However, we failed to determine the regularities of distribution of some fungi on the surface of plates chromated in different solution. The comparison of changes in the surfaces of plates treated with the four solutions has shown that the plates treated in the Likonda 3Cr5 passivation solution changed least after being exposed to atmospheric conditions. Chromated plates contaminated with mixtures of different fungi and kept for 60 days at a temperature of (26 ±2) °C under humid conditions were examined by using a scanning electron microscope (EVO 5O XP Carl Zeiss STM AG, Germany) and the peculiarities of their surface damage were determined. The peculiarities of growth of some fungi species were determined on the plates chromated in the Likonda 3Cr5 and Cr(NO3)3·9H2O + malonic acid solutions. Under these conditions the fungi of Chrysosporium merdarium, Fusarium proliferatum, Paecilomyces lilacinus, Penicillium stoloniferum can either generate and promote the damage of metal surface or stabilize its corrosion processes