Morphological, microstructural and magnetic characteristics of electrodeposited Ni-Fe-WCu alloy powders

Nanostructured Ni-Fe-W-Cu alloy powders were electrodeposited from an alkaline ammonium citrate solution on a titanium cathode. Powder particles were dendrite- and cauliflower-shaped. The dendritic particles had a high density of branches made up of interconnected globules. XRD analysis showed that the powder contained an amorphous matrix and FCC nanocrystals of the solid solution of Fe, W and Cu in Ni. As the deposition current density increased, the mean nanocrystal size decreased, and the mean value of internal microstrain and the total weight percent of Fe and Ni in the alloy increased. The powders deposited at higher current densities exhibited higher magnetization. During annealing at temperatures up to 460°C, the powders underwent short-range ordering, which caused an increase in magnetization, whereas at temperatures above 460°C, the magnetization decreased due to the formation of large FCC crystalline grains

Current efficiency in the chlorate cell process

A mathematical model has been set up for current efficiency in a chlorate cell acting as an ideal electrochemical tubular reactor with a linear increase in hypochlorite concentration from the entrance to the exit. Good agreement was found between the results on current efficiency experimentally obtained under simulated industrial chlorate production conditions and the theoretical values provided by the mathematical model. © 2014 SCS. All rights reserved

Razvoj titanskih RuO2/TiO2 anoda i uređaja za in situ proizvodnju aktivnog hlora

Chlorine is used worldwide for water disinfection purposes. However, due to its toxicity the EU has imposed a set of standards that must be applied when transporting and storing chlorine. In Serbia, numerous studies have been conducted attempting to develop the technology for the generation of active chlorine disinfectant but with a non-toxic aqueous solution of sodium chloride as the raw material. This study provides an overview of the titanium anodes activated by thermally obtained solid solution of ruthenium and titanium oxide development. It also presents new findings on the effect of the temperature of thermal treatment, the composition, the thickness of an active coating on its microstructural properties, and consequently on the catalytic activity, ion selectivity, and corrosion stability during active chlorine generation through the electrolysis of dilute sodium chloride solutions at room temperature. The study also evaluates the effect of the kinetic and operational parameters of the electrochemical process of active chlorine generation on both current and energy efficiencies. The results obtained were used to determine optimal values of technological parameters of the production process. This comprehensive research resulted in the construction of different types of remote-controlled and fully automated active chlorine generating plants.U radu je dat pregled razvoja aktivnih titanskih anoda za reakciju oksidacije hloridnih jona u istraživačkim laboratorijama u Srbiji. Prikazani su i novi rezultati istraživanja efekta temperature termičke obrade, sastava i debljine aktivne RuO2/TiO2 prevlake na titanu na njena mikrostrukturna svojstva i odraz ovih svojstava na katalitičku aktivnost, jonselektivnost i korozionu stabilnost u procesu dobijanja aktivnog hlora. Ustanovljen je i efekat kinetičkih i operativnih parametara procesa elektrolize razblaženih rastvora natrijum-hlorida na iskorišćenje struje i energije po aktivnom hloru. Na osnovu ovih ispitivanja konstruisana je ćelija za elektrolizu i utvrđene su optimalne vrednosti tehnoloških parametara procesa proizvodnje aktivnog hlora. Sveobuhvatna istraživanja rezultirala su konstrukcijom različitih tipova postrojenja za in situ proizvodnju aktivnog hlora

Morphological, microstructural and magnetic characteristics of electrodeposited Ni-Fe-W-Cu alloy powders

Nanostructured Ni-Fe-W-Cu alloy powders were electrodeposited from an alkaline ammonium citrate solution on a titanium cathode. Powder particles were dendrite- and cauliflower-shaped. The dendritic particles had a high density of branches made up of interconnected globules. XRD analysis showed that the powder contained an amorphous matrix and FCC nanocrystals of the solid solution of Fe, W and Cu in Ni. As the deposition current density increased, the mean nanocrystal size decreased, and the mean value of internal microstrain and the total weight percent of Fe and Ni in the alloy increased. The powders deposited at higher current densities exhibited higher magnetization. During annealing at temperatures up to 460 °C, the powders underwent short-range ordering, which caused an increase in magnetization, whereas at temperatures above 460 °C, the magnetization decreased due to the formation of large FCC crystalline grains

The effect of the composition of the alloy of RuO2 and Pt nanocrystals on intermediate adsorption during methanol oxidation

A catalytic coating composed of a mixture of RuO2 and Pt nanocrystals was prepared by a thermal procedure on a titanium substrate and used for the electrochemical oxidation of methanol. The adsorption of the intermediate CO, formed by methanol oxidation on Pt nanocrystals, depended on potential and the coating composition. An increase in the RuO2 content decreased the rate of methanol dehydrogenation and increased the rate of oxidation of the strongly bound intermediate COad. This caused a decrease in the maximum coverage of Pt nanocrystals with COad and a shift of the rapid linear drop in COad coverage to more negative potentials

Mathematical model of electrocatalysis of methanol oxidation at the mixture of nanocrystals of platinum and ruthenium dioxide

Mathematical model representing a catalytic effect of a nanocrystal mixture of metallic platinum and ruthenium dioxide for electrooxidation of methanol is established. Dependance of a current density of the methanol electrooxidation on the chemical composition and size of nanocrystals is determined in the model. A good agreement between theoretical values and experimental results corroborates that electrooxidation of methanol is guided by a bifunctional mechanism. The model is based on the fact that the catalytic effect is proportional to the length of the contact border between nanocrystals of metallic platinum and nanocrystals of ruthenium dioxide. Ru-OH particles are formed on the Ru atoms at the border of crystal grains, at potentials more negative than on platinum. These species oxidize firmly bound intermediates COad located on the adjacent Pt atoms and thus release the Pt atoms for adsorption and dehydrogenation of subsequent molecules of methanol

Electrooxidation of 1-propanol on the mixture of nanoparticles of Pt and RuO2

The catalyst composed of a mixture of nanocrystals of metallic Pt and rutile RuO2 was prepared by a thermal procedure on a titanium substrate. An effect of the mixture composition on its microstructure, surface properties, and catalytic activity for an electrooxidation of 1-propanol in an alkaline environment was examined. The relation between the microstructure of the Pt/RuO2 catalyst and its catalytic activity was determined. It was found that the increase in the RuO2 content resulted in the increase in the catalytic activity, which reached its maximum value and then decreased. The catalytic effect was caused by the bifunctional mechanism of the catalyst Pt/RuO2. Ru-OH species were formed on Ru atoms of RuO2 nanocrystals at more negative potentials than on Pt. These oxy species oxidized firmly adsorbed intermediates propionyl, COad, C2Hyad, and CHad and, thus, released Pt atoms for the adsorption and dehydrogenation of the subsequent molecules of 1-propanol

Exploring The Motives Of Religious Travel By Applying The Ahp Method – The Case Study Of Monastery Vujan (Serbia)

Religious tourism is considered as the oldest form of people’s travel. Thousands of years ago people travelled miles led by religious motives. Even though pilgrimage is older than most of the other tourism forms, research on the major motives for religious travel still occupies scientific attention. Vujan Monastery represents one of the main riddles among religious tourism researchers in Serbia. After the mysterious healing of Serbian Patriarch Pavle in 1946 who suffered from tuberculosis, this monastery became one of the most famous sacred places for orthodox Christians. The principle aim of this paper is to propose a new way for exploring and ranking the religious motivation using the Analytical Hierarchy Process (AHP) approach. In addition, the study proposes a set of motives – both religious and secular, which can be applied for exploring the motivations for visiting any sacred site. The method was applied to discover the main motives which drive people to visit Vujan Monastery, get their rankings, as well as their preferences between different types of secular and religious motives. The results indicated a strong preference for religious motives compared to secular motives of visit of this sacred site. On balance, the research provides us with a complete ranking structure, encompassing all analyzed motives of visit which show us a clear picture of the main motivation for visits to Vujan monastery

Effect of the degree of plastic deformation on the thermal electromotive force of Cu-X5crni1810 steel thermocouple

The thermal electromotive force (TEMF) and the thermal electromotive force coefficient (TEMFC) of the thermocouple consisting of a copper wire and an (X5CrNi1810) steel wire plastically deformed under tension or bending conditions were found to increase with increasing degree of plastic deformation. The increase in the degree of deformation disturbs the microstructure of steel due to increases in the density of chaotically distributed dislocations and internal microstress, resulting in a decrease in the electron density of states near the Fermi level. Through the effect of thermal energy, annealing at elevated temperatures up to 300°C leads to microstructural ordering along with simultaneous increases in the free electron density of states, TEMF and TEMFC. Based on the temporal change of the TEMF, the kinetics of microstructural ordering was determined. During the initial time interval, the process is a kinetically controlled first-order reaction. In the second time interval, the process is controlled by the diffusion of reactant species

Amorphous-Crystalline Ni-Fe Powder Mixture: Hydrogenation and Annealing Effects on Microstructure and Electrical and Magnetic Properties

The hydrogenation of a crystalline Ni-Fe (80 wt.% Ni, 20 wt.% Fe) powder mixture leads to the formation of a mixture of Face Centered Cubic (FCC)-Ni and FCC-Fe phase nanocrystals embedded in an amorphous matrix. The magnetic susceptibility of the nanostructured powder is 2.1 times higher than that of the as-produced crystalline mixture. Heating in the temperature range 420-590 K causes structural relaxation in the hydrogenated powder, resulting in an increase of the magnetic susceptibility and a decrease of the electrical resistivity. During the heating procedure, the reorientation of magnetic domains in nickel and iron takes place in the temperature range 580-650 K and 790-850 K, respectively. In the pressed sample from the powder mixture, the crystallization of the amorphous phase of nickel and its FCC lattice crystalline grain growth occurs in the temperature range 620-873 K causing a decrease in the magnetic susceptibility of the nickel FCC phase and a sudden drop in the electrical resistivity. Prolonged heating of the mixed powders at 873K results in the formation of a Ni-Fe solid solution with higher magnetic susceptibility than the starting mixture