Mikrobiološki pokazatelji održivosti bijelog sira za brzu potrošnju

Djelovanjem tehnološko-tehničkih, ekonomskih i komercijalnih faktora došlo je do naglog uspona proizvodnje i potrošnje sitnog sira. Kod nas se svezi kravlji punomasni sitan sir proizvodi na području Vojvodine, gdje se konzumira ne samo neposredno, nego i u kombinacijama sa raznim povrćem, suhim grožđem, a naročito služi za pripremanje kolača

Photochemistry of p-(5-Substituted-2-furyl)-o-divinylbenzenes; Substituent Effects on the Reaction Course

Irradiation of 2-[2-(2-vinylphenyl)ethenyl]furan (la) and 5-methyl- 2-[2-(2-vinylphenyl)ethenyl]furan (lb) gave 9,10-đihydro-4,9-me- thano-4ff-benzo[4,5]cyclohepta[l,2-6]furan (2a) and 9,10-dihydro- 2-methyl-4,9-methano-4H-benzo[4,5]cyclohepta[l,2-b]furan (2b), respectively, in a very good yield in addition to traces of 5. Contrary to these results, the 5-substituted furan derivatives 1 (c: R = CN; d: R = P-C6H4CH3, e: R = OCH3) gave mainly, upon irradiation under the same conditions, isomerization about the double bond, high-molecular-weight products, small amount of phenanthrenes 5 and only traces of bicyclic structure 2

Pseudocapacitance behavior of polyaniline in aerated HC1 and H2SO4 solutions

High conducting polyaniline (PANI) nanofibres deposited onto glassy carbon support were studied in sulphuric (1mol dm-3 H2SO4) and hydrochloric (1mol dm-3 HCl) acid by both potentiodynamic and complex impedance methods. A large charge storage capacity was obtained in each of investigated acid solutions, particularly in HCl one. For instance, specific capacity amounting to 340 Fg-1 was observed potentiodynamically in 1mol dm-3 HCl at a scan rate of 10 mVs-1

Mild electrochemical oxidation of zeolite templated carbon in acidic solutions, as a way to boost its charge storage properties in alkaline solutions

Coulombic capacity of zeolite-templated carbon (ZTC) measured in alkaline solution was roughly doubled by a previous potentiodynamic treatment in sulfuric acidic solution. In order to explain the reasons of this capacity improvement, the changes in chemical composition of ZTC surface during its pretreatment in sulfuric acid either by simple immersion, or by potentiodynamic polarization, and during subsequent potentiodynamic polarization in KOH solutions, were studied by means of TG/DTA, FTIR spectroscopy and Raman spectroscopy. The results of this study open some novel insights in understanding of very peculiar carbon electrochemistry. The observed changes in surface chemistry include i) fast adsorption of H2O and formation of OH− and epoxide groups on immersion in sulfuric acid, ii) the multiplication of concentration of H2O/OH− and epoxide groups during potentiodynamic cycling in sulfuric acid and iii) the ring-opening of epoxide groups (formed during potentiodynamic cycling in acidic solution) upon its potentiodynamic cycling in alkaline solution, according to a SN2 type mechanism, which results in the formation of aromatic OH-containing diol compounds. © 2018 Elsevier Lt

Mechanically activated carbonized rayon fibers as an electrochemical supercapacitor in aqueous solutions

The activated carbon cloth (ACC), obtained by chemical/physical activation of carbonized rayon fibers, was grinded in a ball mill and studied from the aspect of double layer capacitance. The changes in pore structure, morphology and acid/basic properties caused by ball milling were studied by means of N-2 adsorption/desorption, Fourier-transformed infrared spectrometry, Boehm's titration and Scanning Electron Microscopy. Both potentiodynamic and galvanostatic cycling were used to evaluate the double layer capacitance in three alkaline, acidic and neutral aqueous solutions (KOH, H2SO4 and Na2SO4). While double layer capacitance of original ACC was found to be negligible, ball milled material (ACCm) displayed capacitance in the range of supercapacitors. In order to explain this huge capacitance improvement, we found that ball milling substantially increased the concentration of lactone, phenolic and quinone groups on the surface. We suggest that these groups, through improved hydrophilicity, enable faster ion diffusion into carbon micropores. The energy density stored by double layer was highest in neutral sodium sulphate solution. Namely, operational voltage of similar to 2 V and double layer capacitance of 220 F g(-1) at 1A g(-1), enable the energy density of ACCm/Na2SO4/ACCm capacitor of 31.7 Wh kg(-1) at 2000 W kg(-1), much higher than that of commercial EDLC carbon capacitors. According to the here presented literature survey in a tabular form, the energy density of the studied sample is also higher from that of numerous thus far published aqueous carbon capacitors.Peer-reviewed version: [http://cer.ihtm.bg.ac.rs/handle/123456789/3011

Photochemistry of p-(5-Substituted-2-furyl)-o-divinylbenzenes; Substituent Effects on the Reaction Course

Irradiation of 2-[2-(2-vinylphenyl)ethenyl]furan (la) and 5-methyl- 2-[2-(2-vinylphenyl)ethenyl]furan (lb) gave 9,10-đihydro-4,9-me- thano-4ff-benzo[4,5]cyclohepta[l,2-6]furan (2a) and 9,10-dihydro- 2-methyl-4,9-methano-4H-benzo[4,5]cyclohepta[l,2-b]furan (2b), respectively, in a very good yield in addition to traces of 5. Contrary to these results, the 5-substituted furan derivatives 1 (c: R = CN; d: R = P-C6H4CH3, e: R = OCH3) gave mainly, upon irradiation under the same conditions, isomerization about the double bond, high-molecular-weight products, small amount of phenanthrenes 5 and only traces of bicyclic structure 2

Complex investigation of charge storage behavior of microporous carbon synthesized by zeolite template

Microporous zeolite templated carbon (ZTC) was synthesized by impregnation method using zeolite Y (Na-form) as a template, and furfuryl alcohol as a carbon precursor. The characterization was carried out by X-ray diffractometry, Raman spectroscopy, scanning electron microscopy, nitrogen physisorption, elemental analysis and electrochemical methods. Physisorption measurements evidenced high micro pore volume of obtained material (similar to 0.43 cm(3) g(-1)). The charge storage ability in aqueous KOH, H2SO4 and Na2SO4 solutions was systematically studied by cyclic voltammetry, galvanostatic charging/discharging and complex impedance measurements. Specific coulombic capacitance, the hydrogen storage, H-ZTC bonding and relaxation time of adsorption were found to be dependent on the type of electrolyte. Neutral Na2SO4 aqueous solution was found to be the best for supercapacitor application, thanks to: i) the highest available voltage window ii) lowest corrosion and iii) highest capacitance amounting to 123 F g(-1) at 1 A g(-1)The peer-reviewed version: [https://cer.ihtm.bg.ac.rs/handle/123456789/4318

Complex insight into the charge storage behavior of active carbons obtained by carbonization of the plane tree seed

Activated carbon was prepared using plane tree seed as a cheap and renewable raw material. The samples were prepared by carbonization under N-2 atmosphere up to 850 degrees C, and activation in CO2 atmosphere at different both temperatures (750 and 850 degrees C) and times of activation (0.3,1 and 2 h). The influence of activation parameters on physicochemical properties was studied by XRPD, Raman spectroscopy, FTIR, N-2 physisorption, SEM and electrochemical methods. The pore structure was correlated to the specific capacitance and the amount of hydrogen stored, in alkaline, neutral and acidic electrolyte solution. The relationship of asymmetrical shape of CV curves with the porosity of samples has served to better understand some unclear issues related to the complex mechanism of charge storage. The sample activated at 850 degrees C for 2 h displayed the best behavior. At a high scan rate of 300 mV s(-1), its capacitance, amounted to similar to 26.8 mu F cm(-2) 19.69 mu F cm(-2) and 25.8 mu Fcm(-2) in KOH, Na2SO4, and H2SO4 solutions, respectively

Complex electrochemical investigation of ordered mesoporous carbon synthesized by soft-templating method: charge storage and electrocatalytical or Pt-electrocatalyst supporting behavior

Ordered mesoporous carbon (OMC) was synthesized by an evaporation induced self-assembly method; under acidic conditions, with resorcinol as the carbon precursor and Pluronic F127 triblock copolymer (EO106PO70EO106) as a structure directing agent. The obtained OMC product was characterized by N-2 sorptometry, X-ray diffractometry and Raman spectroscopy. The mean pore radius of 2 nm and specific surface area of 712 m(2) g(-1) were found. The OMC sample was subjected to a complex electrochemical testing in order to check for its applicability in various energy conversion processes. For pure OMC, the charge storage properties and kinetics of oxygen reduction reaction (ORR) in alkaline solution were measured. The OMC sample delivered specific capacitance of 232 F g(-1) at 5 mV s(-1) with 83.6% capacitance retained at 100 mV s(-1). Effective ORR electrocatalysis by OMC in alkaline media was evidenced, with onset potential amounting to -0.10 V vs. saturated calomel electrode. A part of the OMC sample was used as a support of Pt nanoparticles, and examined as electrocatalyst for hydrogen evolution reaction (HOR) and ORR in acidic media. Reversible HOR kinetics was observed, while ORR performances were found to be competitive to the ones on other carbon-supported Pt electrocatalysts reported so far. A superb electrochemical behavior was correlated to physico-chemical properties of OMC. Described OMC stands out as a highly versatile material, which can be used to replace carbon materials developed for specific purposes, allowing rationalization of carbon-based technologies aimed for energy conversion purposes. (C) 2014 Elsevier Ltd. All rights reserved