Elektrohemijsko taloženje Nd i Pr na W iz fluoridnih rastopa

Electrodeposition of neodymium and praseodymium metal from molten NdF3+PrF3+LiF+ 0.5wt.%Pr6O11+0.5wt.%Nd2O3 electrolytes on W was investigated using voltammetry at 1050 °C. The square wave voltammetry confirmed that Nd electrodeposition is a two-step reduction process: first, involving one electron exchange (Nd(III)→Nd(II)) and second, involving two electrons exchange (Nd(II)→Nd(0)). However, praseodymium deposition proceeds as an one-step process involving exchange of three electrons (Pr(III)→Pr(0)). Nd and Pr metals were electrodeposited applying potentiostatic mode. The working electrode surface was analyzed by X-ray diffraction after Nd and Pr co-deposition.Elektrohemijsko taloženje neodijuma i prazeodijuma iz fluoridnog NdF3+PrF3+LiF+ 0.5wt.%Pr6O11+0.5wt.%Nd2O3 rastopa na W radnoj elektrodi ispitivano je pomoću voltametrijskih tehnika na 1050 °C. Voltametrija sa pravougaonim talasima (SWV, square wave voltammetry) potvrdila je da je elektrohemijsko taloženje Nd proces koji se odvija u dva koraka: prvi, uključuje razmenu od jednog elektrona (Nd(III) → Nd(II)) i drugi korak, uključuje razmenu dva elektrona (Nd(II) → Nd(0)). Međutim, taloženje prazeodijuma uključuje izmenu tri elektrona (Pr(III) → Pr(0)) u jednom koraku. Nd i Pr su elektrohemijski taloženi primenom potenciostatskog režima. Nakon elektrohemijskog taloženja Nd i Pr površina radne elektrode analizirana je rengensko-difrakcionom tehnikom.XII YuCorr International Conference, September 13-16, 2021, Tara Mountain, Serbia, http://sitzam.org.rs/YUCORR

Zn/Au alloys formation by Zn electrodeposition from a deep eutectic system

The electrochemical deposition of Zn onto Au from a choline chloride/ethylene glycol deep eutectic system containing different ZnCl2 concentrations has been investigated. The voltammetric results demonstrated that Zn electrodeposition commences in the zinc underpotential deposition (UPD) and proceeds through to the zinc overpotential deposition (OPD) region. The results of X-ray diffraction analysis revealed that the deposit prepared at a relatively low Zn overpotential of – 0.050 V vs. Zn was composed of cubic AuZn alloy. The morphology of the deposit has been characterized by means of a scanning electron microscope and displays a relatively compact and dendrite-free Zn/Au alloy deposit formed

Formation of MgO/Mg(OH)2 Nanostructures by Molten Salt Electrolysis

Thanking its unique characteristics, magnesium oxide and magnesium hydroxide nanostruclures arc of high practical significance for possible application in the next generation of solar cells, electronic devices, displays, in detection and adsorption of different environmental pollutants [ 1]. Numerous methods of synthesis including precipitation, solvothermal and hydrothermal processes, the sono-chemical technique, the sol-gel method, microwave methods, chemical vapor deposition, carbonatization and electrochemical method are widely used for synthesis of various forms magnesium oxide/magnesium hydroxide nanostructures such as whiskers, platelets, rods, needle-like, flower like etc. Electrochemical method attracts a special attention in a production of nanostructures owing to easy control of morphology of particles by the choice of regimes and parameters of electrolysis

Isothermal kinetics of exchange of water absorbed in calcium alginate hydrogel with ethanol

The isothermal kinetics of the exchange of absorbed water in calcium alginate hydrogels with ethanol was investigated. The isothermal kinetic curves were measured within the temperature range from 297 to 316 K. By the application of differential isoconversional methods, it was found that the process of exchange of water absorbed in calcium alginate hydrogel with ethanol has a unique rate determining step (a single step process). Using the model fitting method, it was determined that the kinetics of the exchange can be mathematically described with the kinetic model of the first-order chemical reaction. The values of the kinetic parameters of water exchange: the rate constants (km), energy of activation (Ea = 18.0 kJ∙mol–1), and the pre-exponential factor (ln[A/min–1] = 4.0) were calculated. By using Eyring's equation, the values of thermodynamics parameters: standard enthalpy of activation (ΔH*), standard entropy of activation (ΔS*), and Gibbs energy of activation (ΔG*) were calculated. It was found that the rate of rearrangements of the bound water around hydrophilic groups of a polymeric network has a dominant effect on the kinetics of the exchange of the absorbed water with ethanol. The mechanism of the exchange of adsorbed water with ethanol was suggested. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172015

Development of a drug release methodology for carbamazepine CR tablets based on bioequivalence evaluation

The aim of this study was to investigate the influence of experimental conditions on carbamazepine (CBZ) release from the two controlled-release (CR) tablet formulations with proven bioequivalence and to propose the universal release method which would be biorelevant, In vitro data were obtained in various release media using the USP apparatus II in order to assess their influence on CBZ release from CR tablets. An empirical correlation between in vivo plasma concentration data expressed as a fraction drug absorbed and the cumulative amount of in vitro release was established. The most complete release and highest level A correlation was observed by using the half change method (HCM) compared to other release methodologies tested. The results obtained indicate that the release test developed offers a promising in vitro tool for predicting the in vivo performance of CBZ CR tablets, ensuring batch to batch bioequivalence and verification of certain postapproval changes without the need for additional in vivo studies

Numerical and experimental analysis of factors leading to suture dehiscence after Billroth II gastric resection

The main goal of this study was to numerically quantify risk of duodenal stump blowout after Billroth II (BII) gastric resection. Our hypothesis was that the geometry of the reconstructed tract after BII resection is one of the key factors that can lead to duodenal dehiscence. We used computational fluid dynamics (CFD) with finite element (FE) simulations of various models of BII reconstructed gastrointestinal (GI) tract, as well as non-perfused, ex vivo, porcine experimental models. As main geometrical parameters for FE postoperative models we have used duodenal stump length and inclination between gastric remnant and duodenal stump. Virtual gastric resection was performed on each of 3D FE models based on multislice Computer Tomography (CT) DICOM. According to our computer simulation the difference between maximal duodenal stump pressures for models with most and least preferable geometry of reconstructed GI tract is about 30%. We compared the resulting postoperative duodenal pressure from computer simulations with duodenal stump dehiscence pressure from the experiment. Pressure at duodenal stump after BII resection obtained by computer simulation is 4-5 times lower than the dehiscence pressure according to our experiment on isolated bowel segment. Our conclusion is that if the surgery is performed technically correct, geometry variations of the reconstructed GI tract by themselves are not sufficient to cause duodenal stump blowout. Pressure that develops in the duodenal stump after BII resection using omega loop, only in the conjunction with other risk factors can cause duodenal dehiscence. Increased duodenal pressure after BII resection is risk factor. Hence we recommend the routine use of Roux en Y anastomosis as a safer solution in terms of resulting intraluminal pressure. However, if the surgeon decides to perform BII reconstruction, results obtained with this methodology can be valuable. (C) 2014 Elsevier Ireland Ltd. All rights reserved

Aluminium deposits from AlCl3+urea solvate ionic liquid on aluminium substrate at room temperatures

Development of low temperature processes for electrochemical deposition of aluminium is highly desirable in order to overcome high energy cost, toxic emission of fluoride and chloride from high temperature molten salt electrolytes. AlCh+urea ionic mixture known as deep eutectic solvent (DES) is recognized as an economical electrolyte for alunuruum electrodeposition at room temperatures [I, 2]. Electrodeposition experiments were conducted on aluminum electrode using constant deposition current density (2 mA cm"2 ) at different bath temperatures: 25 °C, 35°C and 50°C. Using SEM and EDS techniques the deposits were studied for their morphology dependence on the experimental conditions. particularly working temperature. Electrochemical techniques used were linear sweep voltarnmetry and chronopotentiometry. The size of individual Al grains deposited under the same constant current density became larger (from nanometers to micrometers) with increasing bath temperature. The shape of deposits ranged from regular crystal grains to complicated morphology including needle-like and flake-like structures

A possible mechanism of formation of flower-like MgO/Mg(OH)2 structures by galvanostatic molten salt electrolysis: The concept of local diffusion fields

The processes of electrodeposition from magnesium nitrate hexahydrate melt by galvanostatic regime of electrolysis have been analyzed. The structure of the formed particles was examined by X-ray diffraction (XRD), which revealed formation of MgO/Mg(OH)2 mixture by molten salt electrolysis. Morphologies of the produced deposits were characterized by scanning electron microscopy (SEM)technique. The flower-like forms constructed from very thin needles with sharp tips were predominately formed by electrodeposition at various current densities and with various amounts of electricity. Aside from that, holes formed from detached hydrogen bubbles of various shapes and sizes, from dish-like holes to those resulting in honeycomb-like structures were also observed. Mechanism of formation of the flower-like forms has been elucidated applying the general theory of disperse deposits formation which is based on the concept of local (spherical and cylindrical)diffusion fields. It is shown that the growth of the needles occurs under the conditions of predominant spherical diffusion control, while the contribution of the cylindrical diffusion to the final shapes was negligible. Comparison with morphologies of deposits obtained by electrodepositions from aqueous magnesium salt electrolytes was also made and discussed. © 2019 Elsevier B.V

Formation of the honeycomb-like MgO/Mg(OH)2 structures with controlled shape and size of holes by molten salt electrolysis

Synthesis of the honeycomb-like MgO/Mg(OH)2 structures, with controlled shape and size of holes, by the electrolysis from magnesium nitrate hexahydrate melt onto glassy carbon is presented. The honeycomb-like structures were made up of holes, formed from detached hydrogen bubbles, surrounded by walls, built up of thin intertwined needles. For the first time, it was shown that the honeycomb-like structures can be obtained by molten salt electrolysis and not exclusively by electrolysis from aqueous electrolytes. Analogies with the processes of the honeycomb-like metal structures formation from aqueous electrolytes are presented and discussed. Rules established for the formation of these structures from aqueous electrolytes, such as the increase of number of holes, the decrease of holes size and coalescence of neighbouring hydrogen bubbles observed with increasing cathodic potential, appeared to be valid for the electrolysis of the molten salt used. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172046 and Grant No. 172060