Design and test of the gas-dynamic carbon dioxide laser experimental setup

An experimental gas-dynamic laser apparatus based on acetylene-in-oxygen combustion has been designed and tested. Main setup volume was designed as a modular type for flexibility. A vacuum system, electrical and measuring elements were attached to the volume. Tests of the gas supply, vacuum system, electronics and lasing have been performed. They have shown reliable functionality and durability of all units.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200

The radiological risk assesment methodology applied on sands from public beaches

The radiological risk of public exposure to terrestrial radiation in the sand beaches is assessed through the total absorbed gamma dose rate in air and annual effective dose outdoors determination according to international recommendations. Corresponding hazards due to sand use as a building material has been estimated by gamma irradiation hazard indices, based on the data of natural radionuclides contents in sands from public seaside and riverbank beaches (Ulcinj, Belgrade- Danube) obtained in this study, using spectrometry of gamma radiation.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

The effect of simulated acid rain on metal desorption from cetraria islandica

In this paper the possibility of extracting metals: K, Al, Ca, Mg, Fe, Cu, Ba, Zn, Mn and Sr, from Cetraria islandica lichen with solutions simulating acid rain (H2SO4- HNO3-(NH4)2SO4), pH 2.00 (1) and 3.28 (2) has been investigated. The results obtained suggest that the investigated elements can be classified into ones where the highest percentage was extracted with the first extraction (K, Al, Mg, Ba, Zn and Mn) and others where the extraction percentage is relatively uniform (Ca and Fe). This indicated different bonding methods in lichen that is in accordance with literature data where two cation bonding methods in lichen were shown.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Discovery of uranium mineralizations in the rhyolite-granite complex in the Jabal Eghei area of southern Libya

During investigation of the Jabal Eghei area in southern Libya and the production of geological maps at a scale of 1:250 000 (Tibesti sector, sheet Wadi Eghei NF 34-1 and NF 34-2), regional prospecting for mineral raw materials was performed. Radiometric survey of observed targets at the sites indicated two significant uranium mineralizations in rhyolites, and some smaller ones in granites that are in close contact with rhyolites. Rhyolites are located in the central part of the investigated region. They cut through granite rocks. The first mineralization is in the central part of the rhyolite region, which is mostly composed of silificated rhyolites. The second one was discovered near the granite-rhyolite contact zone, characterized by the presence of silicified breccia rocks. These findings were confirmed by laboratory measurements of more than seventy samples collected in the area, using high resolution gamma-ray spectrometry. The concentrations of uranium in these mineralizations were found to range from approx. 50 mg kg-1 to more than 600 mg kg-1. The latter value is about 240 times above the Earth’s average. Besides uranium, these measurements have also given concentrations of thorium and potassium. Additional geochemical analysis was performed on samples taken from locations where uranium anomalies were discovered using ICP-MS technique, in which concentrations of more than forty elements were determined. Uranium mineralizations are accompained by increased contents of silver (up to 17 times), arsenic (up to 8 times), molybdenum (up to 50 times), mercury (up to 9 times), and lead (up to 14 times), in regard to the Clark’s values. These results warrant a continued investigation of this region because of potential interest in the discovery of nuclear mineral raw materials

Natural radioactivity of some spring and bottled mineral waters from several central Balkan sites, as a way of their characterization

In this work, a study of the radioactive content of some spring and bottled mineral waters originating fi-om metamorphic rock areas was carried out. A high content of radium isotopes (Ra-226, Ra-228), was found by radiometric analysis in the spring waters: Studenica (Ra-226: 289 mBq/L), Cibutkovica (Ra-226: 92, 4 mBq/L, Ra-228: 610 mBq/L), and Crni Guber (Ra-226: 120 mBq/L, Ra-228: 1170 mBq/L). On the other hand, the radiochemical results showed a higher concentration of U-238 in the bottled mineral water samples (dissolved uranium concentrations were from 0.21 mBq[L, for Kopaonik to 71.5 mBq/L fo Skadarska) than in the spring water samples (dissolved uranium concentrations were very low approximate to 10 mBq/L). The concentrations of all the present naturally occuring radionuclides: U-238, U-234, Th-232, Th-230, Th-228, Ra-228 and Ra-226 were determined by alpha/gamma spectrometric analysis. The activity ratios U-234/U-238, Ra-226/Th-230 and Th-228/Th-232, Ra-228/Th-228 were calculated and are discussed as an indication of the radioactive disequilibrium in bothe the U-238 and Th-232 radioactive series. The high contents of radium isotopes with respect to the equilibrium values expected from the respective parents Th-232/(Th-232 series) and Th-230 (U-238 series) found in the spring water samples is the main evidence for the existence of significant radioactive disequilibrium in both the radioactive series

Laser reflection spot as a pattern in a diamond coating – a microscopic study

Diamond coatings were deposited by the synchronous and coupled action of a hot filament CVD method and a pulsed CO2 laser in spectro-absorbing and spectro-non-absorbing diamond precursor atmospheres. The obtained coatings were structured/patterned, i.e., they were comprised of uncovered, bare locations. An extra effect observed only in the spectro-active diamond precursor atmosphere was the creation of another laser spot in the coating – a reflection spot. In order to establish the practical usability of the latter one, extensive microscopic investigations were performed with consideration of the morphology changes in the spot of the direct laser beam. Normal incidence SEM images of this spot showed a smooth surface, without any pulse radiation damage. AFM imaging revealed the actual surface condition and gave precise data on the surface characteristics

Diamond deposition on thin cylindrical substrates

Diamond coatings were deposited onto different cylindrical substrates (Cu, SiC, W and Mo) by the hot filament chemical vapor deposition (CVD) method. Continuous, adhered and well-faceted crystalline coatings of diamond were obtained on Cu-wire using a special pretreatment with a mixture of diamond and metal powders as well as carefully controlled deposition at lower power. Diamond deposition on SiC-fiber gave continuous and uniform coatings when only the filament power was properly selected. Uniform, homogeneous, euchedral diamond coatings on W- and Mo-wires, attained at a higher filament power, confirmed once more the convenience of refractory metals as substrates for diamond deposition by the CVD technique. Characterization of the obtained coatings was realized using scanning electron microscopy (SEM). The obtained results are compared with the literature data. Differences are discussed with regard to the chemical nature of the substrates as well as their thermophysical characteristics

Energy consumption in the electrolytic evolution of hydrogen with iron-nickel electrodes

The possibilities to reduce energy consumption in the electrolytic hydrogen production using ionic activators added into an alkaline electrolyte have been investigated. Two cathode/anode systems, Fe/Ni and Ni/Fe were investigated. We have found that some activators, like tris-(ethylenediamine)Co(III) chloride complex in combination with the sodium molybdate can reduce energy needs per mass unit of hydrogen produced for more than ten percent in all investigated systems compared to those of non-activated electrolytes. Additionally, iron exhibits some special properties in this view.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200

Influence of acid rain components on radiocesium-137 desorption from Cetraria islandica (L.) Ach. lichen

Desorption of 137Cs from Cetraria islandica (L.) Ach. lichen was performed by five consecutive desorptions with five identical solution volumes. Solutions of H2SO4, HNO3 and their mixtures, with pH 4.61, 5.15 and 5.75 were used for desorption. The desorbed amount of 137Cs (average value, all solutions used) from lichen, for a given pH value was 49.2% for pH 4.61; 47.0% for pH 5.15 and 47.6% for pH 5.75. The obtained values of the desorbed amount of 137Cs from lichen are in accordance with the data obtained in earlier work, when 46.2 % 137Cs was desorbed from lichen for pH 3.75, and 47.2% was desorbed for pH 2.87. A higher percentage of 59.8%, obtained for pH 2.00 indicates increased activity of H+ ions. The amount of desorbed 137Cs from lichen using solutions corresponding to acid rain cannot be lower than the stated values as they contain other substances besides the acid solutions used in this work

The electrocatalytic effects in the electrolytic separation of hydrogen isotopes

The electrolysis has been employed as one of the first and simplest methods for the production of deuterium enriched water. The economical reasons mainly expressed through the energy consumption, however, reduced its importance and use on a large scale. Recent development in the field of the electrolysis, represented by the new electrode materials, different ionic activators for electrodes, generally in the field of the electrocatalysis, makes the electrolysis an interesting process now. A remarkable improvement of the separation factors of hydrogen isotopes during alkaline water electrolysis was achieved, in this work with addition of tris(ethylenediamine) Co(III)-chloride complex into the electrolyte. Several spectroscopic and electro chemical methods like X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron on microscopy (SEM), IR and UV-VIS spectrophotometry and cyclic voltammetry, was employed to characterise the electrodes and electrolyte in order to suggest possible mechanisms and their contributions to the achieved separation factors. The overall mechanism which lends to the separation, factor improvement in the presence of trs-Co complex includes different effects like decreases of the hydrogen overvoltage and the activation energies, with their specific contributions to the achieved factors.5th International Symposium on Advances in Electrochemical Science and Technology, Nov 24-26, 1994, Madras, Indi