Impact of the process of polymerization of polyol and toluen diisocyanate on the environoment

The aim of this study was to investigate the impact of the process of polymerization of polyiol and tolyendiisocyanate on the environoment. Toluene diisocyanates are important industryal intermediates used in conjunction with polyether and polyester polyols as coreactants polyurethane foams, paints, varnishes, elasomers and coatings. This presentation summarizes existing information on the release and behavior of the process of polymerization of polyol and toluen diisocyanate on the environment. A major reaction of TDI in the environoment is formation of solid inert polyureas from reaction with water. In use, TDI is reacted with polyols to form many different polyurethane products. Polyurethanes have been show to be stable in the environment and in disposal have no adverse impact on municipal waste handling processes, landfills or incineration.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Corrosion behavior of compocasted ZA27/SiCp composites in sodium chloride solution

The corrosion behavior of particulate ZA27/SiCp composites in an aerated sodium chloride solution was studied. The composites were synthesized via compocasting with addition of 1, 3 and 5 wt.% SiC particles in the matrix alloy. Composite samples were immersed for 30 days in the 3.5 wt.% NaCl solution open to the atmospheric air. Surface appearance and microstructure of the composites were examined by means of optical microscopy and scanning electron microscopy, while corrosion rates of the composites were determined using the weight loss method. It was revealed that SiC particles were not influenced by corrosion. General uniform corrosion occurred in the composite matrices, mainly in the region of the η phase. Local corrosion was noticed in micro-cracks and near clusters of particulate reinforcements. Results of microstructural examinations and immersion test indicate a slightly lower corrosion resistance of the ZA27/SiCp composites compared to that of the matrix alloy

The influence of corrosion on the microstructure of thermally treated ZA27/SiCp composites

The influence of corrosion on the microstructure of ZA27/SiCp composites was examined. The composites were produced by compo casting technique and then subjected to the thermal treatment (T4 regime). Microstructural examinations were performed after 30-day exposure of thermally treated composites in the sodium-chloride solution. Corrosion processes have occurred in the composite matrix. Corrosion did not affect SiC particles in the composites. The local progress of corrosion in depth of the composite matrix was noticed in micro-cracks. Corrosion resistance of ZA27/SiCp composites was evaluated based on the mass loss of composite samples during the immersion test. It was found that corrosion resistance of the composites decreased with increase in content of SiC particles. The applied thermal treatment had a negative influence on the corrosion resistance of ZA27/SiCp composites

Corrosion behavior of compocasted ZA27/SiCp composites in sodium chloride solution

The corrosion behavior of particulate ZA27/SiCp composites in an aerated sodium chloride solution was studied. The composites were synthesized via compocasting with addition of 1, 3 and 5 wt.% SiC particles in the matrix alloy. Composite samples were immersed for 30 days in the 3.5 wt.% NaCl solution open to the atmospheric air. Surface appearance and microstructure of the composites were examined by means of optical microscopy and scanning electron microscopy, while corrosion rates of the composites were determined using the weight loss method. It was revealed that SiC particles were not influenced by corrosion. General uniform corrosion occurred in the composite matrices, mainly in the region of the η phase. Local corrosion was noticed in micro-cracks and near clusters of particulate reinforcements. Results of microstructural examinations and immersion test indicate a slightly lower corrosion resistance of the ZA27/SiCp composites compared to that of the matrix alloy

Platinum Nanocatalysts at Titanium Oxide Based Supports for Low Temperature Fuel Cell Applications

A comparative study on catalytic activity of platinum nanoparticles on different titanium oxide supports for proton exchange membrane fuel cells reactions was performed. Non stoichiometric titanium oxides – Ebonex, niobium doped titanium oxide and ruthenium doped titanium oxide were applied as the supporting materials. Platinum nanocatalysts (20% Pt) on different support were synthesized by impregnation or borohydride reduction method. Synthesized supports and catalyst were characterized by BET (Brunauer, Emmett, Teller), X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). Homogenous Pt nanoparticles distribution over the niobium and ruthenium doped TiO2 support, without pronounced particle agglomeration was confirmed by HRTEM technique. The average Pt particle size was 3 nm and 5.4 nm for Pt at niobium doped TiO2 and ruthenium doped TiO2, respectively. However, it was not possible to determine accurately average Pt particle size at Ebonex support, due to the non-uniform distribution of the Pt nanoparticles. Electrochemically active Pt surface area of the catalysts was determined by integration of the cyclic voltammetry curve in the potential region of underpotential deposition of hydrogen, after double layer charge correction, taking into account the reference value of 210 μC cm-2 for full monolayer coverage. Kinetics of the oxygen reduction reaction at Pt nanocatalysts on different titanium based supports was studied by cyclic voltammetry and linear sweep voltammetry at rotating gold disc electrode. Two different Tafel slopes at Pt catalysts on niobium and ruthenium doped supports were observed: one close to 60 mV dec-1 in low current density region, and other ~120 mV dec-1 in higher current densities region. Only at Ebonex based support one single Tafel slope (~ 106 mV dec-1) was observed. The specific activities for oxygen reduction, expressed in terms of kinetic current densities per electrochemically Pt active surface area, as well as per mass of Pt loaded, at the constant potential of practical interest (0.85 V and 0.90 V vs RHE, where the mass transport contribution current can be neglected), were compared to carbon supported one, with the same Pt loading. Stability tests, by repetitive cycling from 0.03V to high anodic potentials (up to 1.4 V vs RHE) were performed. The advantages of carbon free supports application in terms of stability, durability and life time of the catalysts were discussed

A novel platinum-based nanocatalyst at a niobia-doped titania support for the hydrogen oxidation reaction

The kinetics of the hydrogen oxidation reaction (HOR) was studied at Pt nanoparticles supported on niobia-doped titania (Pt/N-T). The catalyst support, with the composition of 0.05NbO2.5-δ-0.995TiO2 (0<δ<1), was synthesized by a modified sol-gel procedure and characterized by the BET and X-ray diffraction (XRD) techniques. The specific surface area of the support was found to be 70 m2 g-1. The XRD analysis revealed the presence of the anatase TiO2 phase in the support powder. No peaks indicating the existence of Nb-compounds were detected. Pt/N-T nanocatalyst was synthesized by the borohydride reduction method. Transmission electron microscopy revealed a quite homogenous distribution of the Pt nanoparticles over the support, with a mean particle size of about 3 nm. The electrochemical active surface area of Pt of 42±4 m2 g-1 was determined by the cyclic voltammetry technique. The kinetics of the HOR was investigated by linear sweep voltammetry at a rotating disc electrode in 0.5 mol dm-3 HClO4 solution. The determined value of the Tafel slope of 35 mV dec-1 and an exchange current density of 0.45 mA cm-2 per real surface area of the Pt are in good accordance with those already reported in the literature for the HOR at polycrystalline Pt and Pt nanocatalysts in acid solutions. This new catalyst exhibited better activity for the HOR in comparison with Pt nanocatalyst supported on Vulcan® XC-72R high area carbon

Synthesis of Anatase Nanopowders by Sol-gel Method and Influence of Temperatures of Calcination to Their Photocatalitic Properties

The titanium dioxide (TiO2) nanopowders were produced by sol-gel technique from tetrabutyl titanate as a precursor, varying the temperature of calcination (from 500 to 550 degrees C with the step of 10 degrees C). XRPD results have shown that all synthesized nanopowders are dominantly in anatase phase. The analysis of the shift and linewidth of the most intensive anatase E-g Raman mode confirmed the XRPD results and added the presence of small amount of highly disordered brookite phase in all samples. The analysis of pore structure from nitrogen sorption experimental data described all samples as mesoporous, with mean pore diameters in the range of 1.5 and 4.5 nm. Nanopowder properties have been related to the photocatalytic activity, tested in degradation of the textile dye (C.I. Reactive Orange 16). The sample calcined at temperature of 510 degrees C showed the best photocatalytic performance

Modifikacija strukture smektita sumpornom kiselinom i karakteristike modifikovanih smektita

Bentonite samples from Petrovac and Aleksinac were treated with sulfuric acid of different molarities. Differences in structure and texture of the initial and modified bentonite were determined by chemical analysis and Xraypowder diffraction (XRPD), infra-red spectroscopy (FTIR), scanning electron microscopy (SEM) and physisorption nitrogen at -196°C. Sulfuric acid caused an exchange of Al3+, Fe3+ and Mg2+ with H+ ions which led to a modification of the smectite crystalline structure. The Mg and Fe substitution in the octahedral sheet promoted the dispersion of those layers and forming of amorphous silicon. The sequence according to which the cations left the octahedral sheets was as follows: Mg2+>Fe3+>Al3+. The sulfuric acid activated bentonites exhibiting a lower cation exchange capacity (CEC) and a change of specific surface area (SBET) from 6 to 387 for bentonite from Petrovac and from 44 to 1784 m2 g-1 for bentonite from Aleksinac, positioning them as an excellent absorber in wine technology and in the protection of soil and environment.Uzorci bentonita iz Petrovca i Aleksinca tretirani su različitim molaritetima sumporne kiseline. Promene u strukturi i teksturi polaznih i modifikovanih bentonita utvrđene su hemijskom i analizom rendgenske difrakcije praha X-zraka (XRPD), infra crvenom spektroskopijom (FTIR), skening elektronskom mikroskopijom (SEM) i fizisorpcijom azota na -196°C. Dejstvo H2SO4 kiseline izazvalo je zamenu Al3+, Fe3+ i Mg2+ sa H+ jonima što je dovelo do modifikacije kristalne strukture smektita. Supstitucija Mg i Fe u oktaedarskom listu smektita promovisala je raspuštanje tih slojeva i formiranje silikatne faze. Redosled kojim su ovi katjoni napuštali oktaedarske listove bio je sledeći: Mg2+>Fe3+>Al3+. Sumpornom kiselinom aktivirani bentoniti pokazali su niži kapacitet katjonske izmene (CEC) i promenu specifične površine (SBET), od 6 na 387 kod bentonita Petrovca i od 44 na 1784 m2 g-1 kod bentonita Aleksinca, što ih svrstava u odlične absorbente u tehnologiji vina, zaštiti zemljišta i životne sredine

Preparation and Characterization of Pt Nanocatalyst on Tungsten Based Support for Alkaline Fuel Cells Applications

Poster presented at the 13th Annual Conference of the Materials Research Society of Serbia - YUCOMAT 2011, Herceg Novi, Montenegro, September 5–9, 201

Moisture and gamma-ray irradiation effects on the mechanical properties of carbon fibre-reinforced plastics

The effects of gamma-irradiation and moisture absorption on the mechanical properties of carbon fibres-epoxy resin composites were studied. The properties dominated by the matrix and fibre-matrix interface (interlaminar and in-plane shear strength) were measured at room temperature using standard tests. These tests were carried out before and after exposures to gamma irradiation and before and after immersion in water at 80 degrees C during 21 days. The dosage of gamma irradiation was up to 11.7 MGy. The micrographs of surfaces fractured in performed tests were observed on a scanning electron microscope. They were analyzed with consulting the stated effects on mechanical properties and the measured values of the glass transition temperature of tested coupons before and after irradiation and immersion in water. The obtained results show that moisture and irradiation, if they act one after the other, have a significant influence on the degradation of matrix-dominated mechanical properties of the tested carbon-epoxy composite