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Kamberovic Z.,University of Belgrade | Sokic M.,Institute for Technology of Nuclear and other Raw Materials | Matkovic V.,Institute for Technology of Nuclear and other Raw Materials
Metalurgia International | Year: 2012

Catalysts based on nickel, as active component, exhibit suitable properties in various heterogeneous catalysis processes; however, they quickly deactivate due to deposits formation during exploitation and sintering at elevated temperatures. Considering that catalysts with several catalytic components possess enhanced catalytic properties, in present study the influence of temperature, time and additives (PdCl2, FeCl2 and CuCl2) on the reduction degree of nickel(II)-chloride by hydrogen have been investigated. The objectives of the study were selection of an appropriate catalytic activity modifier and development of a new synthesis method for nanocomposite catalysts production, which are characterized by enhanced properties compared to the commercial Ni/Al2O3 catalysts. Obtained experimental results clearly indicate that the best effect was achieved with addition of 0.1 wt. % PdCl2, whereby NiCl2 reduction degree was 58.16% at 653 K and Pd significantly increased the reduction rate. According to the obtained results, new technological synthesis method of nanocomposite Ni-Pd/Al2O3 catalysts was proposed, where Ni and Pd, as catalytically active components, are homogeneously dispersed in monolithic Al2O3 based ceramic foam.

Marinovic V.,Serbian Academy of Science and Arts | Marinovic S.,University of Belgrade | Jovanovic M.,University of Belgrade | Jovanovic J.,Serbian Academy of Science and Arts | And 2 more authors.
International Journal of Electrochemical Science | Year: 2013

The study of the electrochemical reduction on acetonitrile modified platinum electrode and determination of trinitrotoluene (TNT) in neutral solution by simple galvanostatic technique is presented here. The obtained potential-time responses on the applied constant cathodic current pulses showed two potential transitions before achieving the steady-states, referring to the multi-step reduction process of nitro groups in TNT molecule. The calibration curves of the dependence of the square root of the first transition time (T0.5) on the TNT concentration were linear in the ranges 4.4-303.8 μM and 0.09-4.40 μM for applied constant current of 0.1 mA. The detection limit was 0.09 μM. The method was tested in the river water. The results indicated the sensitivity of the galvanostatic method for TNT determination in the environmental samples. From the first transition on the E-t curves the characteristics important for the understanding the mechanism of the reduction process were obtained. It was found that four electrons are involved in the reduction process of the first nitro group, indicating that the reduction product in a neutral electrolyte is hydroxylamine. © 2013 by ESG.

Djordjevic N.G.,Institute for Technology of Nuclear and Other Raw Materials | Obradovic N.,Serbian Academy of Science and Arts | Filipovic S.,Serbian Academy of Science and Arts
Powder Metallurgy and Metal Ceramics | Year: 2012

Three-component oxide mixtures were prepared containing MgO, Al 2 O 3 and SiO 2 in a 2 : 2 : 5 ratio with addition of 10% Bi 2 O 3. The mixtures were mechanically activated in a range from 5 to 240 min in a mill with ceramic balls, and sintered in the range 1173-1573 K. In order to determine the structure transformations, sintered products were analyzed by the XRD method. The goal of the research was to find the possible correlation between process parameters and functional properties of the cordierite-based ceramic materials. Quantitative measures of the functional sample properties, capacity (C c ) and electrical resistance (R ρ), as well as of dielectric loss (tgδ) were used. The results obtained prove that there is a correlation between mechanical activation and properties of cordierite ceramics. © 2012 Springer Science+Business Media, Inc.

Gulisija Z.,Institute for Technology of Nuclear and Other Raw Materials | Pataric A.,Institute for Technology of Nuclear and Other Raw Materials | Mihailovic M.,Institute for Technology of Nuclear and Other Raw Materials
Metalurgija | Year: 2011

The relationships between electromagnetic frequency, microstructure and mechanical properties of continuous casting aluminum alloys were studied in this paper. EN AW 2024 and EN AW 2007 aluminum alloys ingots were produced by electromagnetic continuous casting process. The microstructure and mechanical properties of as cast ingots were examined. The results showed that electromagnetic field, especially low frequency electromagnetic field, greatly influenced the microstructure and mechanical properties of as cast ingots. The significant energy savings and product quality can be achieved by the application of a proper frequency.

Nikolic V.,University of Belgrade | Kamberovic Z.,University of Belgrade | Andic Z.,University of Belgrade | Korac M.,University of Belgrade | Sokic M.,Institute for Technology of Nuclear and other Raw Materials
Materiali in Tehnologije | Year: 2014

This paper explores the possibility of synthesising catalyst supports with improved properties. Alumina foams were produced with the polymer replication technique. Representative high- and low-temperature sintering ceramics were selected. Suitable suspension amounts, the clay addition and sintering temperature were determined. A lower sintering temperature was used for an economic enhancement of the process. The sintering was conducted at the temperatures from 1573 K to 1773 K for 60 min. A comparative analysis of the studied systems shows that the best compressive strength of 6.2 MPa was achieved with the system based on the α-Al2O3-25 clay (mass fractions, w/%), polyester foam with 10 PPI, sintered at 1673 K.

Radivojevic M.,Institute PKB Agroekonomik | Grubic G.,University of Belgrade | Samanc H.,University of Belgrade | Adamovic M.,Institute for Technology of Nuclear and Other Raw Materials | Dordevic N.,University of Belgrade
African Journal of Biotechnology | Year: 2011

The main objective of this research was to study the effect of rations containing full-fat extruded soybeans or fat-extracted heat treated soybean meal, in the nutrition of dairy cows during the period of middle lactation. The study was carried out with two groups of 15 Holstein cows. The animal's health was controlled on the basis of body condition score, results in production, general condition of animals and some of the most important biochemical parameters of blood serum. In the case of nutrition based on rations where the total amount of soybeans was extruded or where it was partially replaced with fatextracted heat treated soybean meal, the production of 4% fat corrected milk was 28.43 and 28.78 kg. Observed differences were not statistically significant (p > 0.05). The differences in the achieved average content of milk fat (3.38 and 3.45%) and protein (3.48 and 3.48%) were not statistically significant (p > 0.05). Results of this work shows that the partial replacement of full-fat extruded soybeans with soybeans based products with lower oil content gave better production results of cows during the period of middle lactation. © 2011 Academic Journals.

Obradovic N.,Serbian Institute of Technical Sciences | Terzic A.,Institute for Technology of Nuclear and Other Raw Materials | Pavlovic Lj.,Institute for Technology of Nuclear and Other Raw Materials | Filipovic S.,Serbian Institute of Technical Sciences | Pavlovic V.,Serbian Institute of Technical Sciences
Journal of Thermal Analysis and Calorimetry | Year: 2012

The base mix refractory concrete is corundum-based, containing corundum as refractory aggregate and CAC as hydraulic binder, with a spinel as an additive. The authors investigated the dehydration reactions which occur from the moment when water is added (at the beginning of components mixing), to the moment when installed refractory concrete lining is put into the service. Sintering process kinetic of low-cement content refractory concrete was investigated by means of differential thermal analysis at four different heating rates (5, 10, 20, and 30 °C/min). Thus, temperature was increased from 20 to 1100 °C. It was noticed that first dehydration step occurs at lower temperatures, indicating at a desorption of physically adsorbed and interlayer water molecules. Second dehydration step, at higher temperatures is due to dehydroxylation of the lattices and decomposition of the interlayer anions. © 2011 Akadémiai Kiadó, Budapest, Hungary.

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