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  • Author: Piotr Murawski x
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Abstract

The article presents an analysis of the energy, mechanical and chemical properties of pellets made of wood material. According to the manufacturer, wood pellets were made of hard wood shredded to fractions approx. 1 mm thick and up to 3-4 mm long, and of a waste source - sawdust. Measurements of the selected properties were carried out on pellets with a diameter of 6 and 8 mm. Mechanical durability, humidity, crumble rate, ash quantity, calorific value were determined, as well as macronutrient and heavy metals content. The calorific value of pellets, with moisture content from 7.48% to 6.76% and ash content from 0.31% to 0.55%, ranged from 17.71-19.18 MJ·kg−1, which testified to the beneficial energy use of the tested raw material. Based on the conducted research, it was found that the mechanical properties of pellets made of both sawdust and hard wood predispose them for use as boiler fuel. The tested materials met high quality standards for wood pellets used for non-industrial and industrial purposes.

Abstract

In this paper, we present experimental results of photoluminescence for series of InAs:Si heavily doped samples, with doping level varying from 1.6 × 1016 cm-3 to 2.93 × 1018 cm-3. All samples were grown using MBE system equipped with a valved arsenic cracker. The measurements were performed in the temperature range of 20 K to 100 K. Although the Mott transition in InAs appears for electron concentrations above 1014 cm-3, Burstein-Moss broadening of photoluminescence spectra presented in this article was observed only for samples with concentration higher than 2 × 1017 cm-3. For the samples with lower concentrations two peaks were observed, arising from the band gap and defect states. The intensity of the defect peak was found to be decreasing with increasing temperature as well as increasing concentration, up to the point of disappearance when the Burstein-Moss broadening was visible.

Abstract

This paper presents the set of procedures developed in Radiation Protection Measurements Laboratory at National Centre for Nuclear Research for evaluation of shielding properties of high performance concrete. The purpose of such procedure is to characterize the material behaviour against gamma and neutron radiation. The range of the densities of the concrete specimens was from 2300 to 3900 kg/m3. The shielding properties against photons were evaluated using 137Cs and 60Co sources. The neutron radiation measurements have been performed by measuring the transmitted radiation from 239PuBe source. Scattered neutron radiation has been evaluated using the shadow cone technique. A set up of ionization chambers was used during all experiments. The gamma dose was measured using C-CO2 ionization chamber. The neutron dose was evaluated with recombination chamber of REM-2 type with appropriate recombination method applied. The method to distinguish gamma and neutron absorbed dose components in mixed radiation fields using twin detector method was presented. Also, recombination microdosimetric method was applied for the obtained results. Procedures to establish consecutive half value layers and tenth value layers (HVL and TVL) for gamma and neutron radiation were presented. Measured HVL and TVL values were linked with concrete density to highlight well known dependence. Also, influence of specific admixtures to concrete on neutron attenuation properties was studied. The results confirmed the feasibility of approach for the radiation shielding investigations.