Vol 4, No 1 (2020)


6-12 334

244Cm is a very important nuclide due to the high specific heat release and it may become reasonable to recycle the spent nuclear fuel to extract this isotope. In this work, the dynamics of 244Cm isotope production for the fuel assembly of the WWER-1200 reactor with an enrichment of 4.95% and burnup up to 70 MW · day/kg was calculated using Serpent Monte Carlo code. A similar calculations was performed for MOX-based fuel assembly with the same irradiation characteristics. It has been shown that production of 244Cm in high burnup uranium dioxide fuel, and especially in MOX fuel, reaches a high value, which can cause problems during spent fuel management. The main problems associated with the curium relates to the residual heat and neutron activity.

13-18 331

Specific mode of the collinear cluster tri-partition of the252Cf nucleus is discussed. The structure manifests itself as a rhombic-spiral structure in the fission fragments correlation mass distribution.

19-28 416

Neutron transfer and nuclear breakup processes in reaction with weakly bound nucleus 11Li at energies near the Coulomb barrier are investigated in the framework of the time-dependent Schrödinger equation. The evolution of probability density of outer weakly bound neutrons of 11Li in the collision with 208Pb was studied. The probabilities and cross sections of outer neutrons removal (breakup processes and transfer to target nucleus) were calculated. Theoretical predictions of the two-neutron removal probability values were obtained for angles from 140◦ to 180◦ . The theoretical results have close similarity with experimental data for the two-neutron removal in reaction 208Pb(11Li,9 Li).

29-37 398

The results of seasonal Al and Mn activity on the surface of the atmosphere above the city of Nur-Sultan are shown from October 2016 to January 2017. The technique of sampling aerosols in various fractions and further analysis of the data are described. Together with scientists from the University of Hiroshima (Hiroshima, Japan) and the University of Tsukuba (Tsukuba, Japan), the composition of aerosols in the air of Astana was monitored. The aim of the project was to develop a methodology for sampling aerosols in various fractions and conduct measurements on an ongoing basis. The studies were carried out using a high-volume air sampler and a cascade of impactors that measure the size distribution and the respirable mass fraction of airborne particles of the environment. Fiberglass filters, which are a commonly used material for sample collection, were also used. The data obtained in the study of aerosol samples using a cascade of impactors allowing the selection of aerosols with sizes up to 0.49 µm showed the content of aluminum isotope in the atmosphere of the city. The smaller the clearance gap, the more particles are trapped. On average, aerosols were taken from more than 200 thousand cubic meters of air.

38-49 360

High-density polyethylene (HDPE) composite films with di erent amounts of SiO 2 nanoparticles ( 1 - 20 % vol.) were prepared by melt blending using a high-pressure thermal pressing technique. The morphological characterization, surface topology and distribution of nanoparticles in polymer matrix of nanocomposites were investigated by using Scanning electron microscopy (SEM) and atomic force microscopy (AFM). The thermal characterization of the nanocomposites were investigated by di erential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). SEM and AFM results revealed that silica nanoparticles aggregates were distributed mainly homogeneously. The nano-fillers change supramolecular structure and surface morphology of HDPE strongly. DSC results showed addition of nano-SiO 2 particles slightly decrease the melting temperature by 3-4 degree but strongly decrease the crystallization temperature by 7-8 degree. And crystallinity degree of the HDPE decrease. The thermal stability of the composite films was measured using Thermo Gravimetric analysis (TGA). Polymer nanocomposite showed higher thermal stability as compared with pure HDPE. Composites with 20% vol. of nano-SiO 2 have maximum thermal degradation temperature of 498.4 ◦ C.

50-60 350

The formation of nanosized films of silicides on the surface of Si (111) and Si (100) was studied by the method of low-energy ion implantation. The optimal technological modes of ion implantation and subsequent annealing for the formation of thin nanoscale films of silicides were determined. It is shown that the appearance of new surface superstructures is additional confirmation of the formation of thin silicide films with a single crystal structure.

61-66 303

The analysis of the experimental data shows that the processes of gas adsorption and radiation defects accumulation in metal oxides correlate with each other and most likely can be described in terms of equivalent kinetic equations. Given this circumstance, the kinetics of accumulation of radiation defects in oxides of di erent metals was analyzed. The obtained equations were used to analyze: a) the kinetics of accumulation of radiation defects in di erent oxide compounds; b) the data on the destruction of radiationinduced defects in the atmosphere of di erent gases, and on the kinetics of absorption by oxides of oxygen, hydrogen, and carbon dioxide molecules. The results of such analysis are systematized and are given in the form of a table. The following conclusions were made: 1. The quantum yield of radiation defects increases monotonically with growth of the temperature of processing, tending to a certain limit value. 2. The constant of destruction of radicals from ionizing radiation increases as well. 3. The ratio of the number of surface and bulk defects in di erent oxides can be arranged in the following series: silicon oxide> beryllium oxide> aluminum oxide. Thus, the most optimal (convenient) material for creating absorbing systems by energy intensity is silicon dioxide, and by adsorption e ciency is beryllium oxide.

67-85 410

Nanocrystalline alloys of the compositions Na 0.05 Cu 1.95 S, Na 0.075 Cu 1.925 S, Na 0.10 Cu 1.90 S, Na 0.125 Cu 1.750 S, Na 0.15 Cu 1.85 S, Na 0.17 Cu 1.80 S, Na 0.20 Cu 1.77 S were synthesized in a melt medium mixtures of hydroxides NaOH and KOH at a temperature of about 165 ◦ C. X-ray phase analysis showed that the alloys are heterophasic and consist of phases of Cu 9 S 5 digenite, CuS 2 copper disulfide, Covellite CuS, Cu 7 S 4 anilite in various combinations. The crystallite sizes range from 16 to 160 nm. The degree of crystallinity of the alloys slightly increases with an increase in the sodium content from 68% in Na 0.05 Cu 1.95 S to 81% in Na 0.20 Cu 1.77 S. A quasi-one-dimensional Na 2 Cu 4 S 3 phase was detected in the composition of the Na 0.20 Cu 1.77 S alloy. The measured values of the conductivity of the alloys are two orders of magnitude lower than in isolated pure Cu 9 S 5 , CuS 2 , CuS, Cu 7 S 4 , of which the alloys consist. An activation temperature dependence of the conductivity is observed in the region from 300 K to 360 K with an activation energy of 0.08 -0.15 eV. The reason for the low conductivity of the alloys is assumed to be the presence of weakly conducting interfacial layers and sodium doping of non-stoichiometric phases Cu 9 S 5 (Cu 1.8 S) and Cu 7 S 4 (Cu 1.75 S), leading to the compensation of holes by electrons of impurity sodium atoms. The measured values of the coe cient of thermo-emf alloys at room temperature lie in the range from 0.032 to 0.147 mV/K. Due to the low thermal conductivity of the order of 0.2 W/mK, a rather high dimensionless thermoelectric figure of merit ZT ≈ 0.28 at 570 K was obtained for the composition Na 0.15 Cu 1.85 S.

86-92 394

This article investigates the influence of thermal annealing on microhardness and wear resistance of the surface of steel U9/Y9 protected by a composite coating Ti 3 SiC 2 /TiC obtained by detonation sputtering. Thermal annealing was performed in the range of temperatures 700-900 ◦ C during 1 hour. Following annealing the formation of TiO 2 and an increase in the phase content of Ti 3 SiC 2 are observed. Higher microhardness was obtained in coatings subjected to annealing at 800 ◦ C, which can be explained by an increase in the content of carbonized titanium. As the annealing temperature rises further, the thickness of the oxide layer increases, leading to a decrease in the microhardness for the coatings annealed at 900 ◦ C. According to the results of tribological tests, formation of the oxide increases wear resistance of Ti 3 SiC 2 /TiC composite surface coatings.

ISSN 2522-9869 (Print)
ISSN 2616-8537 (Online)