Structural and optical properties of HDPE implanted with medium fluences silver ions

The implantation of high-density polyethylene (HDPE) has been conducted using Ag+ ions with energy of 60 keV, achieved fluences 1.5 and 10•1015 ions/cm2. Transmission electron microscopy (STEM) and field emission gun - scanning electron microscopy (FEG-SEM) showed the existence of nanoparticle clusters. X ray photoelectron spectroscopy (XPS) revealed the presence of silver in the sample surface region. The surface topography was studied by atomic force microscopy (AFM), while the surface composition uniformity was analyzed using phase imaging AFM. Optical characterization obtained by spectroscopic ellipsometry (SE) showed changes in refractive index, extinction coefficient and the optical band gap with the fluence of implanted ions

Vertikalna rasprostranjenost cezijuma-137 u obradivim i neobradivim zemljištima

This paper introduces the distribution BACKGROUND: and unique characteristics of 137Cs in cultivated and undisturbed areas. The samples were taken from three measuring points of the depth of 1 m. We examined all visible horizons and determined their classifications. There were four horizons in one profile. All four horizons had a different zone thickness. 137Cs is an artificial radionuclide that has been produced primarily as a result of atmospheric thermonuclear weapon tests since the 1950. Also, the great amount of 137Cs (~85 PBq) was released in the atmosphere during the Chernobyl accident. So, 137Cs has been globally distributed, with fallout rates generally related to latitude and precipitation depth. The movement of 137Cs in soil is primarily controlled by soil erosion processes, such as processes caused by water, wind, and tillage. Thus, 137Cs is a valuable tracer to study soil erosion. The specific activity of 137Cs in soil and sediment samples was determined by using the gamma-spectrometric method.U ovom radu prikazana je rasprostranjenost i jedinstvene karakteristike cezijuma-137 kako u obradivim tako i u neobradivim zemljištima. Uzorkovanje je vršeno na tri merna mesta do 1 m dubine. Ispitani su svi vidljivi horizonti i utvrđeno je postojanje 4 horizonta u jednom profilu, koji su različitih debljina. Cezijum-137 je veštački radioizotop koji je nastao kao posledica termonuklearnih reakcija ispitivanog oružja u atmosferi zemlje kao i neželjeni proizvod nuklearnih akcidenata (Černobil, 1986). Ovaj radioizotop je široko rasprostranjen u celom svetu, gde se njegova migracija u zemljištu prati pomoću intenziteta erozije potpomognutim vodom i vetrom. Stoga je cezijum-137 važan faktor pri određivanju intenziteta erozije kako u zemljištu tako i u sedimentima, te je određena njegova specifična aktivnost korišćenjem gama spektrometrije

The influence of alumino-silicate matrix composition on surface hydrophobic properties

The purpose of this investigation is to investigate the hydrophobicity of geopolymers, new alumino-silicate materials and the influence of Si/Al ratio on their surface properties. Contact angle measurement (CAM) as reliable indicator of hydrophobicity was determined for synthesized geopolymers using water and ethylene-glycol as reference liquids. Geopolymers were synthesized from various precursors: Kaolin, bentonite and diatomite. Characterization of phase structure and microstructure was performed by XRD, FTIR, SEM/EDX methods. Contact angle measurements confirmed that the geopolymers synthesized from metakaolin are the most porous, which can be explained by the smallest Si/Al ratio. The maximum value of contact angle and free surface energy (110.2 mJ/m2) has been achieved for geopolymer synthesized by diatoms (GPMD). SEM micrograph of GPMD shows a homogeneous surface with some longitudinal cavities in the gel and is significantly different from the micrographs of other two geopolymer samples, GPMB and GPMK

Alkali activation of different type of ash as a production of combustion process

Presented study deals with the final structure and radiological properties of different fly-ash based geopolymers. Lignite fly-ash (lignite Kolubara – Serbia) and wood fly ash were obtained in combustion process together with commercial fly-ash. Synthesis of the geopolymers was conducted by mixing fly-ash, sodium silicate solution, NaOH and water. The samples were strengthened 60 °C for 48 hours after staying at room temperature in covering mold for 24 hours. The X-ray diffraction, Fourier transform infrared and SAM measurements were conducted on the samples after 28 days of geopolymerization process. The X-ray diffraction measurements of lignite fly-ash samples show anhydrite as the main constituent, while wood fly-ash samples consist of calcite, albite and gypsum minerals. Besides determination of physicochemical properties, the aim of this study was radiological characterization of lignite fly-ash, wood fly-ash and the obtained geopolymer products. Activity concentration of 40K and radionuclides from the 238U and 232Th decay series, in ash samples and fly-ash based geopolymers, were determined by means of gamma-ray spectrometry, and the absorbed dose rate, D, and the annual effective dose rate, E, were calculated in accordance with the UNSCEAR 2000 report

Mechanochemical treatment and structural properties of lead adsorption on kaolinite (Rudovci, Serbia)

In the present work, remediation of lead-containing solution using raw and modified kaolinite has been presented. The micro and nanostructure of samples has been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Laser diffraction and scattering (LDS), was analyzed by particle size analyzer based on laser diffraction and particle size distribution (PSD) was done. The degree of metal adsorption was evaluated analyzing the Pb(II) contaminated samples by inductively coupled plasma atomic emission spectrometry (micro- and nanostructure on immobilization efficiency correlCP AES). The results show the impact of immobilization efficiency and ation between micro- and nanostructure. The thermodynamic data (Delta HA degrees, Delta SA degrees, Delta GA degrees) are calculated from the temperature-dependent sorption isotherms. The results suggest sorption process of Pb(II) on kaolinite as spontaneous and endothermic

Predicting of lead distribution and immobilization in soil of the region of lignite mining (Rudovci, Serbia)

Lead distribution and immobilization in cultivated soils in Rudovci, Serbia was investigated. Sampling was carried out by the method recommended by ICP-Forests Manual, 2006, Part III Sampling and analysis of Soil. The sampling geometry was systematically designed with a random component. The maximum sampling depth was 100 cm and lead distribution was monitored during 425 days. First sample was taken after 50 days and every single next sample was taken after 50 days except for the last sample which was taken after 25 days. Before the profile contamination, physical and chemical soil analysis has been done. The cation exchange capacity of the soil was done because media affect mobility cations (anions) in soil. The effect of immobilizations of Pb is highest in the second horizons where the depth of investigating soil is 25-50 cm

Radiological Hazards of Cs-137 in Cultivated and Undisturbed Areas

The exposure of human beings to ionizing radiation from Cs-137 is a continuing and inescapable feature of life on Earth. Artificial radio nuclides are widely distributed in various geological formations and ecosystems such as rock, soil, groundwater, and foodstuffs. In the presents study, the distribution of Cs-137 was measured in soil samples collected from different lithological units of the Rudovci, Lazarevac, Serbia. Analysis of the vertical soil profiles indicated that the activity of Cs-137 was not extremely changed with depth. The activity concentrations of the Cs-137 in measured soil samples ranged from below minimal detectable concentrations up to 38.1 Bq/kg. In order to evaluate the radiological hazards due to Cs-137 in the samples, the absorbed dose rate and the annual effective dose were calculated in accordance with recommendations given in the UNSCEAR 2000 report. The distribution of radionuclides depends upon the rock composition, chemical and physical properties of the soil. The external absorbed gamma dose rates due Cs-137 were found to vary from 0 to 1.16 nGy/h

Predicting of lead distribution and immobilization in soil of the region of lignite mining (Rudovci, Serbia)

Lead distribution and immobilization in cultivated soils in Rudovci, Serbia was investigated. Sampling was carried out by the method recommended by ICP-Forests Manual, 2006, Part III Sampling and analysis of Soil. The sampling geometry was systematically designed with a random component. The maximum sampling depth was 100 cm and lead distribution was monitored during 425 days. First sample was taken after 50 days and every single next sample was taken after 50 days except for the last sample which was taken after 25 days. Before the profile contamination, physical and chemical soil analysis has been done. The cation exchange capacity of the soil was done because media affect mobility cations (anions) in soil. The effect of immobilizations of Pb is highest in the second horizons where the depth of investigating soil is 25-50 cm

Cesium removal from aqueous solution by natural mineral clinoptilolite

The aim of this study was to investigate the Cs+ ions sorption on natural minerals clinoptilolite. The analysis of clinoptilolite and clinoptilolite with adsorbed Cs+ ion was conducted by X-ray diffraction, scanning electron microscopy, X-ray fluorescence, and gamma spectrometry. The specific activity of naturally occurring radionuclides in clinoptilolite was determined by gamma spectrometry by using the HPGe semiconductor detector. Obtained activity concentrations ranged from 49 Bq/kg to 810 Bq/kg for K-40, 5.7 Bq/kg to 10 Bq/kg for U-238, 5.8 Bq/kg to 70 Bq/kg for Th-232(Ac-228), and the presence of artificial radionuclides was not detected (Cs-137 lt 0.02 Bq/kg). The study of the thermal decomposition of raw clinoptilolite and Cs adsorbed clinoptilolite by differential thermal analysis is presented in this paper. The activation energy of the reaction phase transformation of raw clinoptilolite is 156.7 kJ/mol, while Cs adsorbed clinoptilolite is 121.7 kJ/mol. The lower value of activation energy reaction of the phase transformation Cs adsorbed clinoptilolite indicates that Cs which is adsorbed destabilizes the crystal structure of clinoptilolite and thus facilitates the transition to the amorphous state

Radioactivity measurements in soils surrounding four coal-fired power plants in Serbia by gamma-ray spectrometry and estimated dose

The study of spatial distribution of activity concentration of U-238, Ra-226, (210)pb, Th-232, K-40 and Cs-237 radionuclides in the surface soil samples (n = 42) collected in the vicinity of four coal-fired power plants in Serbia is presented. Radioactivity measurements in soils performed by gamma-ray spectrometry showed values [Bqkg(-1)] in the range: 15-117 for U-238, 21-115 for Ra-226, 33-65 for (210)pb, 20-69 for Th-232, 324-736 for K-40, and 2-59 for Cs-137. Surface soil radioactivity that could have resulted from deposition of radionuclides from airborne discharges or resuspension of ash from disposal sites showed no enhanced levels. It was found that variation of soil textural properties, pH values, and carbonate content influenced activity levels of natural radionuclides while radiocesium activities were associated with soil organic matter content. Modification of some soil properties was observed in the immediate vicinity ( lt 1 km) of power plants where the soil was more alkaline with coarser particles (0.2-0.05 mm) and carbonates accumulated. Calculated average values of the absorbed gamma dose rate and annual external effective dose originating from the terrestrial radionudides were 69.4 nGy/h and 0.085 mSv, respectively