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- ItemSimple and efficient AlN-based piezoelectric energy harvesters(MDPI, 2020-01-28) Gablech, Imrich; Klempa, Jaroslav; Pekárek, Jan; Vyroubal, Petr; Hrabina, Jan; Holá, Miroslava; Kunz, Jan; Brodský, Jan; Neužil, PavelIn this work, we demonstrate the simple fabrication process of AlN-based piezoelectric energy harvesters (PEH), which are made of cantilevers consisting of a multilayer ion beam-assisted deposition. The preferentially (001) orientated AlN thin films possess exceptionally high piezoelectric coefficients d33 of (7.33 ± 0.08) pCN1. The fabrication of PEH was completed using just three lithography steps, conventional silicon substrate with full control of the cantilever thickness, in addition to the thickness of the proof mass. As the AlN deposition was conducted at a temperature of 330 °C, the process can be implemented into standard complementary metal oxide semiconductor (CMOS) technology, as well as the CMOS wafer post-processing. The PEH cantilever deflection and efficiency were characterized using both laser interferometry, and a vibration shaker, respectively. This technology could become a core feature for future CMOS-based energy harvesters.
- ItemThe 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, PetrThe 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).
- ItemIn-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, PetrThis 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.
- ItemStudy of Zinc Deposited in the Presence of Organic Additives for Zinc-based Secondary Batteries(Elsevier, 2018-12-03) Chladil, Ladislav; Čech, Ondřej; Smejkal, Jan; Vanýsek, PetrThis work is focused on the effect of selected organic additives on zinc deposit properties in relation to a possible utilizing the additives for a zinc based battery systems worked with alkaline electrolyte. The Zn layers were deposited on tin substrate from the KOH based electrolytes saturated by zinc oxide and with addition of different organic surfactants - CTAB, Slovasol 2520/2, Tween 20 and Lugalvan G 35 in concentration 500ppm. Depositions were held under low current densities 10mA/cm2 where the mossy porous deposit grows from pure KOH solutions. All additives were examined with emphasis on the study of zinc deposit morphology and their ability to create uniformly distributed porous structure which could exhibit fast electrode kinetic. All deposits were studied by X-ray crystallography and preferred structure orientations are reported. For the purpose of using additives directly in the battery systems we evaluated also the corrosion properties of the KOH solution with addition of the above mentioned surfactants. It has been found that the presence of CTAB and Slovasol 2520/2 lead to a pyramidal texture, Lugalvan G 35 produced micro-crystalline deposit with opened porous structure and finally presence of Tween 20 lead to nano-crystalline highly porous deposit almost without preferred orientation.
- ItemSodno-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, GünterThe 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.