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The use of numerical simulation for the evaluation of special transparent glass resistance
(Elsevier, 2018-04-14) Binar, Tomáš; Švarc, Jiří; Vyroubal, Petr; Kazda, Tomáš; Rolc, Stanislav; Dvořák, Aleš; Dostál, Petr
The paper is concerned with the use of numerical simulation for the evaluation of projectile interaction with an assembly composed of multiple materials (transparent armour). For the purpose of assessing the reliability of theoretical numerical models, LS-Dyna explicit solver was employed allowing the evaluation of the projectile interaction effect on the experiment material tested. The material parameters for the numerical simulations were obtained at the temperature of 20 °C. The research objective was to evaluate the projectile interaction with an assembly composed of multiple materials at the temperatures of -32 °C and 55 °C, and to evaluate the scope of damage, the delamination of individual layers of transparent armour and the depth of projectile penetration at Protection Level 2 [PARTIAL] (7.62 mm x 39 API BZ) a Level 3 (only projectile 7.62 mm x 54R B32 API).
Sodno-iontové akumulátory - budoucnost a aktuální vývoj
(NZEE, 2019-05-15) Libich, Jiří; Sedlaříková, Marie; Vondrák, Jiří; Máca, Josef; Čech, Ondřej; Fíbek, Michal; Čudek, Pavel; Chekannikov, Andrey; Fafilek, Günter
The lithium-ion technology is widely known and spread technology. The based of this technology lies on transport of lithium ions during charging or discharging from one electrode to the other, this principle is call “rocking chair”. Nowadays, this leading battery technology finds a wide range of applications from cell phones through electric vehicles up to high capacity stationary storage systems. With growing field of the application of lithium-ion batteries, the demands arising from the individual applications brings new point of view and requirements onto lithium-ion technology. For example, the area of renewable energy along with utilization of energy produced, from them calls for large energy systems storage, because all these sources are undispatchable. Currently, the lithium-ion technology has majority share in these applications, but the technology has the limitations. Main of them is the lithium elements itself, the lithium production growing very fast in recent few year and new lithium ore sources are sought. But the production of lithium does not enough supply the growing demand that leads to increasing price of lithium metal. Each renewable energy sources need to be supported with high capacity energy storage systems, the requirements to these systems are the environment friendly as much as can be and low-price. These are some but not all essential characteristics of new generation of energy storage systems. There are few new promising systems that belong among the so-called post-lithium systems like lithium-sulphur, lithium-air, magnesium battery or sodium-ion battery. These systems are development or laboratory-basic research level due to many disadvantages which must be overcome. As one of the most promising system, seems to be sodium-ion, this system removes cost and environment risk and looks like promising candidate for renewable energy large capacity energy storage system.
The importance of observation of structural changes of lead acid battery active mass in special applications in the mining industry
(Faculty of Mining, Ecology, Process Control and Geotechnologies (FBERG), Technical University of Kosice, 2015-10-26) Zimáková, Jana; Vaculík, Sebastian; Fryda, Daniel; Bača, Petr
To be able to use lead acid batteries in particularly difficult conditions in the mining industry, it is very important to understand of the events that occurs during traction operation of mining carts, or auxiliary lighting. Failure of lead accumulators in the hazardous environments, where it is desired nonexplosive embodiment, may have fatal consequences. The paper describes the possibility of observing changes in active materials at the microscopic level. The process of charging and discharging lead-acid accumulator has been described in many publications. The aim of this article is supplement known information about a series of images and analysis that will accurately show progressive changes in the structure of the negative electrode. Negative electrodes are, at each cycle, charged and discharged under the same conditions, scanned with a scanning electron microscope, it is performed elemental analysis (EDS) and is measured size of the individual sulfate crystals. Previous measured results indicate that during the charging the conversion of PbSO4 crystals into a charged form of the active mass is not complete and there is a rapid increase in the size of lead sulfate crystals on the negative electrode. This article compares changes in electrode surface composition after two cycles. There is clear loss of lead and on the other hand visible growth of sulfur. This indicate progressive surface sulfation.
A New Method for 2D Materials Properties Modulation by Controlled Induced Mechanical Strain
(MDPI, 2018-12-07) Gablech, Imrich; Pekárek, Jan; Klempa, Jaroslav; Vyroubal, Petr; Svatoš, Vojtěch; Neužil, Pavel
This paper proposes a new method for characterization of 2D materials under the precisely specified conditions. It is achieved by integration of a 2D material as a field effect transistors structures with a piezoelectric resonator. Properties of the 2D material can be mechanically adjusted by the resonator. It results in the independent and precise control of an amplitude of induced mechanical strain, its modulating frequency, which all influence the 2D material properties. The electrical field required to measure 2D material field effect transistors will not be affected by the vibrations, thus giving us a chance to perform the precise measurement of the electrical properties of the 2D material. This approach has a great potential for measuring and monitoring cells, enzymes, nucleic acids, deoxyribonucleic acid and ribonucleic acid. It can be also used for measurement of toxic, combustive or waste gases.
In-situ XRD study of a Chromium doped LiNi0.5Mn1.5O4 cathode for Li-ion battery
(Elsevier, 2021-09-01) Chladil, Ladislav; Kunický, Daniel; Kazda, Tomáš; Vanýsek, Petr; Čech, Ondřej; Bača, Petr
This paper deals with structural (in-situ XRD) and electrochemical characterization of high-voltage lithium-ion cathode materials LiMn2O4 (LMO), LiNi0.5Mn1.5O4 (LNMO), and LiCr0.1Ni0.4Mn1.5O4 (LCNMO) prepared by solid-state synthesis. Structural in-situ X-ray diffraction spectra were measured by an affordable Rigaku diffractometer. Our synthesis route produced the samples with similar morphologies where the average particle sizes were 1.11 mu m and 1.46 mu m for LNMO and LCNMO respectively. Results of the Rietveld analysis brought detailed insight into two-phase structure transitions for LMO and three-phase transitions for LNMO and LCNMO. XRD study revealed differences in the structural behavior of LMO and LNMO prepared by solid-state synthesis compared to the results of other authors using the sol-gel synthesis route. In the case of chromium-doped LNMO, our results indicate ability of the chromium metal to effectively reduce Mn3+ content while the ordering of the structure increases. Chromium doping also promotes a larger lattice parameter in a fully delithiated state than in the case of undoped LNMO. Therefore, lowering of the volume changes was observed and faster phase II/III transition taking place, when Ni3+/Ni4+ redox pair was oxidized, was also identified. Cr doping of LNMO also promotes the reaching the lattice parameters of phases in both phase transitions and thus could reduce the internal stress of active material under high C-rate cycling. Results thus suggested that chromium doping can improve the stability of the inner structure and performance at higher charging C-rates even though the structure goes through a three-phase region during charging as undoped LNMO. The evaluation of diffusion coefficients of Cr-doped LNMO revealed increased diffusivity in a full discharge state and as the cathode underwent the cycling the differences in diffusivity seemed to be more pronounced.

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