This article reviews international and Russian experience in using polymer and composite pile structures. The historical development of various pile types, their advantages and disadvantages, as well ...as the author’s classification of polymer and composite piles, are presented.
The kinetics of oxidative dissolution of powdered U
3
O
8
(preparation temperatures 480–1200°C) in aqueous NaOH–H
2
O
2
solutions was studied. The concentration of the oxidant/complexing reagent (H
2
...O
2
) in 1.0 M NaOH solution determines the chemistry and kinetics of U
3
O
8
oxidative dissolution. The rate and completeness of U
3
O
8
dissolution also depend on the characteristics of the initial oxide powder and the dissolution temperature. The reaction rate constants for all the conditions studied were calculated. Based on the results obtained, the conditions for the quantitative dissolution of U
3
O
8
in NaOH–H
2
O
2
solutions were determined.
Plastic scintillator detectors are widely used in particle physics thanks to the very good particle identification, tracking capabilities and time resolution. However, new experimental challenges and ...the need for enhanced performance require the construction of detector geometries that are complicated using the current production techniques. In this article we propose a new production technique based on additive manufacturing that aims to 3D print polystyrene-based scintillator. The production process and the results of the scintillation light output measurement of the 3D-printed scintillator are reported.
Oxidative dissolution of powdered UO
2
and U
3
O
8
samples in Na
2
CO
3
/NaHCO
3
–H
2
O
2
solutions was studied. The U
3
O
8
samples were prepared from UO
2
at 480–1200°С. The rate and degree of the ...U
3
O
8
dissolution depend on the characteristics of the oxide powder and on the dissolution temperature. The process rate constants under the conditions of the experiments were calculated. Based on the results obtained, the conditions of complete dissolution of UO
2
and U
3
O
8
in Na
2
CO
3
/NaHCO
3
–H
2
O
2
solutions were determined.
Solvent extraction separation of U(VI), Pu(IV), Pu(VI), Np(V)/Np(VI), Am(III), Ce(IV), rare earth elements (III), Mo(VI), and Cs from carbonate solutions using methyltrioctylammonium carbonate was ...studied. The separation factors of actinides, rare earth elements, molybdenum, and cesium were calculated.
The dissolution step of uranium and mixed oxide uranium-plutonium spent nuclear fuel is a key initial step of a new alternative hydrometallurgical method—the CARBEX process. The study considers ...carbonate oxidizing systems NaHCO
3
/Na
2
CO
3
–H
2
O
2
/2Na
2
CO
3
·3H
2
O
2
/М
2
S
2
O
8
, where M = Na, K, or NH
4
+
, for dissolving actinide oxide powders. The chemical and physical factors that determine the rate of oxidative dissolution of powdered individual oxides UO
2
, U
3
O
8
, PuO
2
and NpO
2
in carbonate media were found. The results obtained are important for the development of the oxidative and sonochemical options of dissolution of highly calcined crystalline samples of uranium, plutonium and neptunium oxides, as well of spent nuclear fuel in carbonate media.
As a result of studying the regularities of interaction between sludge nanoparticles with polishing powder wear and lap nanoparticles during the polishing of polystyrene, polymethylmethacrylate, and ...polyallyl diglycol carbonate by the dispersed systems of micro- and nanopowders on the basis of ab initio calculations in compliance with the quantum scattering theory, it has been established that sludge nanoparticles are elastically scattered on wear nanoparticles. The differential scattering cross section has a maximum at scattering angles of 0° and 180° to exceed the maximum value for the other angles by 2 × 10
4
–5 × 10
4
times. It has been shown that sludge nanoparticles move in the process of polishing along the optical resonator axis between the treated surface and the lap surface to be scattered only forward and backward. It has been established that the total scattering cross section of sludge nanoparticles exponentially grows with an increase in their concentration and essentially decreases with an increase in the size and kinetic energy of nanoparticles. When the resonator Q factor is increased from 7.9 to 105.5, the total scattering cross section of sludge nanoparticles exponentially decreases from 120.8 to 0.6 Mb. It has been demonstrated that the calculated total scattering cross sections of sludge nanoparticles correlate with a high degree of accuracy with the experimentally determined rate of material removal under polishing.
The investigation revealed patterns in the formation and localization of deposits of polishing powder wear nanoparticles on the processed surface during the polishing of polymeric materials using ...disperse systems of micro- and nanopowders. The total scattering cross section of polishing powder wear nanoparticles on sludge nanoparticles increases nonlinearly with the movement of particles, extremally depends on the product of spectral separation for dielectric constant separation between the processed material, polishing powder, and the disperse system, and exponentially increases with the resonator detuning. When polystyrene is polished using cerium dioxide micropowder, deposition on the processed surface is most likely to occur, with the maximum value of the total scattering cross section of polishing powder wear nanoparticles on sludge nanoparticles being at 49.7 Mb. Experimental data indicate that the localization of deposits with polishing powder wear nanoparticles on the processed surface occurs according to the distribution function of the total scattering cross section of polishing powder wear nanoparticles on sludge nanoparticles across circular zones, which aligns well with experimental results, within 12.5%. The experimentally determined average thickness of the deposit fragments of polishing powder wear nanoparticles, forming complete or partial coverage of the component surface, ranges from 1.1 to 1.5 µm.
As a result of studying the mechanism of polishing the polymer optical materials with disperse systems composed of micro- and nanoparticles of polishing powders, it has established that the energy of ...sludge and wear particles during the resonant transfer of energy from the disperse phase particles of a polishing disperse system to a treated surface and backward is inversely proportional to the spectral separation between them. It has been shown that the energies of sludge and wear particles are decreased during the polishing of polymer materials with a disperse system of nanopowders by 5 time with an increase in the spectral separation from 27 to 78 cm
–1
and from 17 to 24 cm
–1
, respectively. When polishing is performed with the disperse system of micropowders, their energies are decreased by 2–5 times with an increase in the spectral separation from 8 to 95 cm
–1
and from 16 to 57 cm
–1
. When the spectral separation between a treated material and a polishing powder is decreased, the volumes of sludge and wear particles and, correspondingly, the polishing efficiency and grows alongside with the intensity of wear on the disperse phase particles of the disperse system. It has been found that the polishing efficiency strongly depends on the efficiency of the Forster resonant energy transfer and grows with a decrease in the product of the ratios between the vibration frequencies of molecular moieties on the surface of polishing powder particles and the treated surface and an increase in the ratio between the lifetimes of treated surface clusters and clusters of polishing powder particles in an excited state. It has been shown that the results of theoretical calculations on the performance efficiency of polishing the optical materials coincides with experimental results with a deviation of 1–8%.
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