ТЕОРЕТИЧЕСКОЕ И ЭКСПЕРИМЕНТАЛЬНОЕ ОБОСНОВАНИЕ ОБРАБОТКИ РАСПЛАВОВ НА ОСНОВЕ АЛЮМИНИЯ ИМПУЛЬСНЫМИ МАГНИТНЫМИ ПОЛЯМИ

Factors causing the solid-phase dispersion of the particles of alloying elements in the aluminum melt depending on their nature are considered. It is shown that the particles can be fragmented under the effect of uniform tensile stresses appearing due to heating the particles. The reasonability of using additional external effects (for example, magnetic-pulsed treatment of the foundry-alloy melt) in order to intensify the assimilation of silicon in liquid aluminum and provision of microcrystalline structure of the foundry alloy is substantiated theoretically and confirmed experimentally by the example of the Al–20wt%Si foundry alloy.Рассмотрены факторы, обуславливающие твердофазное диспергирование частиц легирующих элементов, в зависимости от их природы, в алюминиевом расплаве. Показано, что дробление частиц может происходить под воздействием всесторонних растягивающих напряжений, возникающих в результате прогрева частиц. Размеры вновь образующихся в результате дробления частиц определяются протяженностью микротрещин в исходных частицах. На примере лигатуры Al–20мас.%Si теоретически обоснована и экспериментально подтверждена целесообразность использования дополнительных внешних воздействий (например, магнитно-импульсной обработки лигатурного расплава) с целью интенсификации процессов усвоения кремния в жидком алюминии и обеспечения микрокристаллического строения лигатуры

N-doped carbon nanofibers from pyrolysis of free-base phthalocyanine

Heating free-base phthalocyanine (H2Pc) at around 450 °C under static vacuum results in the formation of a nonvolatile carbonaceous material through oxidative pyrolysis. We used a number of instrumental techniques to characterize its morphology and chemical composition. According to electron microscopy observations, the dominating morphology is fibrous. The estimated length of individual fibers, which appear as rather homogeneous and continuous structures, is several micrometers, with diameters of roughly 200 nm. According to elemental analysis estimates, the per cent contribution of carbon remains approximately the same as in pristine H2Pc, but about 5.4 at% of nitrogen is substituted by oxygen. Spectroscopic measurements suggest that the oxygen is incorporated into nanofiber structure in the form of different functionalities containing C]O and C–OH bonds. Raman spectroscopy revealed an approximately equal contribution due to sp3 and sp2 -hybridized carbon atoms, which would made one to expect that the thermal stability of nanofibers must be similar to that of defect-containing nanotubes, graphene oxide and nanodiamond. Nevertheless, according to thermogravimetric curves obtained, nanofibers are at least as thermally stable as graphene and defect-free nanotubes. Density functional theory calculations were employed to suggest possible initial steps of H2Pc oxidative pyrolysis leading to the formation of nanofibers.Financial support from the National Autonomous University of Mexico (grant DGAPA-IN101118, FTIR and Raman spectroscopic measurements; DGAPA-IN203219, SEM and EDS characterization) and from the National Council of Science and Technology, Mexico (CONACYT, grant 250655) is greatly appreciated. L. M. B.-P. is grateful to the Doctorate Degree Program in Chemical Sciences of UNAM and to CONACyT for PhD scholarshi

Nanocrystalline SnS2 coated onto reduced graphene oxide: demonstrating the feasibility of a non-graphitic anode with sulfide chemistry for potassium-ion batteries

An anode material incorporating a sulfide is reported. SnS2 nanoparticles anchored onto reduced graphene oxide are produced via a chemical route and demonstrate an impressive capacity of 350 mA h g-1, exceeding the capacity of graphite. These results open the door for a new class of high capacity anode materials (based on sulfide chemistry) for potassium-ion batteries

3D printing of poly(vinylidene fluoride-trifluoroethylene): a poling-free technique to manufacture flexible and transparent piezoelectric generators

Flexible piezoelectric generators (PEGs) present a unique opportunity for renewable and sustainable energy harvesting. Here, we present a low-temperature and low-energy deposition method using solvent evaporation-assisted three-dimensional printing to deposit electroactive poly(vinylidene fluoride) (PVDF)-trifluoroethylene (TrFE) up to 19 structured layers. Visible-wavelength transmittance was above 92%, while ATR-FTIR spectroscopy showed little change in the electroactive phase fraction between layer depositions. Electroactivity from the fabricated PVDF-TrFE PEGs showed that a single structured layer gave the greatest output at 289.3 mV peak-to-peak voltage. This was proposed to be due to shear-induced polarization affording the alignment of the fluoropolymer dipoles without an electric field or high temperature