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Search Results: 1 - 10 of 198194 matches for " Obradovi? N. "
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Synthesis of barium-zinc-titanate ceramics
ObradoviN.,Nikoli? M.V.,Nikoli? N.,Filipovi? S.
Science of Sintering , 2012, DOI: 10.2298/sos1201065o
Abstract: Mixtures of BaCO3, ZnO and TiO2 powders, with molar ratio of 1:2:4, were mechanically activated for 20, 40 and minutes in a planetary ball mill. The resulting powders were compacted into pellets and isothermally sintered at 1250°C for 2h with a heating rate of 10°C/min. X-ray diffraction analysis of obtained powders and sintered samples was performed in order to investigate changes of the phase composition. The microstructure of sintered samples was examined by scanning electron microscopy. The photoacoustic phase and amplitude spectra of sintered samples were measured as a function of the laser beam modulating frequency using a transmission detection configuration. Fitting of experimental data enabled determination of photoacoustic properties including thermal diffusivity. Based on the results obtained correlation between thermal diffusivity and experimental conditions, as well the samples microstructure characteristics, was discussed.
Reaction sintering of the 2ZnO-TiO2 system
ObradoviN.,Labus N.,Sre?kovi? T.,Stevanovi? S.
Science of Sintering , 2007, DOI: 10.2298/sos0702127o
Abstract: Sintering kinetics of the mechanically activated ZnO-TiO2 system was studied. Mixtures of ZnO and TiO2 powders were mechanically activated using a high-energy ball mill for different time intervals from 0 to 300 minutes. Formal phenomenological analyses were performed in order to describe the specimen’s behavior during isothermal sintering at 1100oC. Non-isothermal sintering was investigated by dilatometer measurements up to 1100oC with a constant heating rate. The Dorn method was applied in order to give information on the activation energy. .
Investigation of sintering kinetics of ZnO by observing reduction of the specific surface area
Stevanovi? S.,Zeljkovi? V.,ObradoviN.,Labus N.
Science of Sintering , 2007, DOI: 10.2298/sos0703259s
Abstract: Reduction of the specific surface area of porous ZnO during the sintering process was studied. ZnO powder was sintered at temperatures from 673 K to 1173 K. The decrease in the specific surface area was observed as a function of temperature and sintering time. Two different models were involved in order to define the appropriate parameters. The Arrhenius equation was used to give information on the activation energy of sintering. The LSE method was applied for determining optimum parameter values.
111 in labeled antibodies in the detection of colorectal carcinoma
Artiko Vera M.,Obradovi? V.,Davidovi? Branka M.,Petrovi? N.
Acta Chirurgica Iugoslavica , 2003, DOI: 10.2298/aci0304043a
Abstract: The aim of the study is detection of the recurrences and metastases of colorectal carcinomas using 111-In labelled antibodies B72.3 in 14 patients. With tomography, we can access better distinction of tumour in comparison to other structures and estimation of its size. Other imaging methods (CT,US) have advantage in detection of liver metastases, while immunoscintigraphy is more specific for the assessment of malignant abdominal tumours and extrahepatic metastases. The first results point out that Oncoscint CR-103 can be useful in diagnosis of recurrences and metastases of colorectal carcinoma, viability assessment after radiotherapy and in the choice of the adequate surgical treatment in dependence of the spread of the disease.
The influence of mechanical activation on sintering process of BaCO3-SrCO3-TiO2 system
Kosanovi? Darko,ObradoviN.,?ivojinovi? J.,Mari?i? A.
Science of Sintering , 2012, DOI: 10.2298/sos1203271k
Abstract: In this article the influence of mechanical activation on sintering process of bariumstrontium-titanate ceramics has been investigated. Both non-activated and mixtures treated in a planetary ball mill for 5, 10, 20, 40, 80 and 120 minutes were sintered at 1100-1400°C for 2 hours in presence of air atmosphere. The influence of mechanical activation on phase composition and crystal structure has been analyzed by XRD, while the effect of activation and sintering process on microstructure was investigated by scanning electron microscopy. It has been established that temperature of 1100°C was too low to induce final sintering stage for this system. Electrical measurements have been conducted for the densest ceramics sintered at 1400°C for 2 hours. [Projekat Ministarstva nauke Republike Srbije, br. OI172057]
Mechanical-chemical synthesis Ba0.77Sr0.23TiO3
Kosanovi? D.,ObradoviN.,?ivojinovi? J.,Filipovi? S.
Science of Sintering , 2012, DOI: 10.2298/sos1201047k
Abstract: Barium-Strontium-Titanate Ba0.77Sr0.23TiO3 was prepared from starting materials BaCO3, SrCO3 and TiO2 through solid-state reactions. Mixtures of these oxides are mechanically activated in a high-energy planetary ball mill at different time intervals from 0 to 120 minutes. In order to obtain information on phase composition, crystal structure was determent by X-ray diffraction. It was observed that after 80 minutes in process synthesis Ba0.77Sr0.23TiO3 started Thermal analyzes were performed in order to determine the characteristic temperatures of the processes that occur in the solid phase. Particle size distribution, together with electron microscopy scanning has given us very useful information about the morphology of the powder.
Synthesis and sintering of high-temperature composites based on mechanically activated fly ash
Terzi? A.,Pavlovi? Lj.,ObradoviN.,Pavlovi? V.
Science of Sintering , 2012, DOI: 10.2298/sos1202135t
Abstract: Amount of fly ash which is and yet to be generated in the coming years highlights the necessity of developing new methods of the recycling where this waste can be reused in significant quantity. A new possibility for fly ash utilization is in high-temperature application (thermal insulators or/and refractory material products). As such, fly ash has to adequately answer the mechanical and thermal stability criteria. One of the ways of achieving it is by applying mechanical activation procedure on fly ash. In present study, fly ashes from two different power plants were mechanically activated in a planetary ball mill. Mechanically treated fly ashes were cemented with two different binders: standard Portland cement and high-aluminates cement. Physico-chemical analysis and investigation of mineralogical components of composites are emphasized, due to the changes occurred in fly ash during mechanical activation and sintering of composites. Macro-performance of the composites was correlated to the microstructure of fly ash studied by means of XRD and SEM analysis. Thermal stability of crystalline phases was investigated with DTA. Highlight was placed on determination of relationship between mechanically activated fly ash and obtained composites microstructure on one side and behavior of sintered composites on the other side. [Projekat Ministarstva nauke Republike Srbije, br. 172057, 45008 and a project F-198, financed by Serbian Academy of Sciences and Arts]
Influence of mechanical activation on microstructure and crystal structure of sintered MgO-TiO2 system
Filipovi? S.,ObradoviN.,Pavlovi? V.B.,Markovi? S.
Science of Sintering , 2010, DOI: 10.2298/sos100518002f
Abstract: Mixtures of MgO-TiO2 were mechanically activated using high-energy planetary ball mill during 5, 10, 20, 40, 80 and 120 minutes. Sintering process was preformed in air at 1100o-1400oC for 2h. The decrease in powder’s particle size was noticed as the time of mechanical activation increased and confirmed by particle size analyzer. XRD analyses were performed in order to acquire the information about phase composition. Different ratio mixtures of MgTiO3 and Mg2TiO4 are present within all sintered samples. The effect of tribophysical activation on microstructure was investigated by scanning electron microscopy. The differential thermal gravimetric analysis has been performed in order to investigate thermal behaviour of the mixtures.
Analysis of isothermal sintering of zinc-titanate doped with MgO
ObradoviN.,Stevanovi? S.,Mitri? M.,Nikoli? M.V.
Science of Sintering , 2007, DOI: 10.2298/sos0703241o
Abstract: The aim of this work was analysis of isothermal sintering of zinc titanate ceramics doped with MgO obtained by mechanical activation. Mixtures of ZnO, TiO2 and MgO (0, 1.25 and 2.5%) were mechanically activated 15 minutes in a planetary ball mill. The powders obtained were pressed under different pressures and the results were fitted with a phenomenological compacting equation. Isothermal sintering was performed in air for 120 minutes at four different temperatures. Structural characterization of ZnO-TiO2-MgO system after milling was performed at room temperature using XRPD measurements. DTA measurements showed different activation energies for pure and doped ZnO-TiO2 systems. Thus addition of MgO stabilizes the crystal structure of zinc titanate.
Influence of mechanical activation on structural and electrical properties of sintered MgTiO3 ceramics
Filipovi? S.,ObradoviN.,Pavlovi? V.,Petrovi? V.
Science of Sintering , 2009, DOI: 10.2298/sos0902117f
Abstract: The aim of this work was to analyze the influence of mechanical activation on the MgCO3-TiO2 system. Mixtures of MgCO3-TiO2 were mechanically activated for 15, 30, 60 and 120 minutes in a planetary ball mill and after that sintered at 1100°C for 1h. XRD analyses were performed in order to give information about the phase composition and to determine a variety of microstructure parameters using Scherrer's method. Also, the effect of tribophysical activation and sintering process on microstructure was investigated by scanning electron microscopy. Electrical measurements were performed in order to determine electrical properties of sintered samples. Our conclusions are that the sample activated for 120 min showed the best electrical properties ( ε r=23.86, Q=233, ρ=0.38) and exhibited the best sinterability.
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