Publikační činnost Katedry materiálů a technologií pro automobily / Publications of Department of Vehicle Materials and Technologies (632)

Permanent URI for this collectionhttp://hdl.handle.net/10084/65063

Kolekce obsahuje bibliografické záznamy publikační činnosti (článků) akademických pracovníků Katedry materiálů a technologií pro automobily (632) v časopisech registrovaných ve Web of Science od roku 2003 po současnost.
Do kolekce jsou zařazeny:
a) publikace, u nichž je v originálních dokumentech jako působiště autora (adresa) uvedena Vysoká škola báňská-Technická univerzita Ostrava (VŠB-TUO),
b) publikace, u nichž v originálních dokumentech není v adrese VŠB-TUO uvedena, ale autoři prokazatelně v době jejich zpracování a uveřejnění působili na VŠB-TUO.

Bibliografické záznamy byly původně vytvořeny v kolekci Publikační činnost akademických pracovníků VŠB-TUO, která sleduje publikování akademických pracovníků od roku 1990.

Od 1.1.2012 se Katedra slévárenství (632) sloučila s Katedrou metalurgie (618). Nově vzniklá Katedra materiálů a technologií pro automobily je zařazena pod číslo 632.

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Now showing 1 - 9 out of 9 results

Preparation and physical properties of quaternary Mn2FeSi0.5Al0.5 alloy powders with heusler and β-Mn structures
(MDPI, 2025) Skotnicová, Kateřina; Juřica, Jan; Životský, Ondřej; Čegan,Tomáš; Hrabovská, Kamila; Matějka, Vlastimil; Zlá, Simona; Kawuloková, Monika; Chrobák, Artur
Manganese-based alloys with the composition Mn2FeZ (Z = Si, Al) have been extensively investigated in recent years due to their potential applications in spintronics. The Mn2FeSi alloy, prepared in the form of ingots, powders, or ribbons, exhibits either a cubic full-Heusler (L21) structure, an inverse-Heusler (XA) structure, or a combination of both. In contrast, the Mn2FeAl alloy has so far been synthesized only in the form of ingots, featuring a primitive cubic (beta-Mn type) structure. This study focuses on the new quaternary Mn2FeSi0.5Al0.5 alloy synthesized from pure Mn, Fe, Si, and Al powders via mechanical alloying. The elemental powders were ball-milled for 168 h with a ball-to-powder ratio of 10:1, followed by annealing at 550 degrees C, 700 degrees C, and 950 degrees C for 8 h in an argon protective atmosphere. The results demonstrate that annealing at lower temperatures (550 degrees C) led to the formation of a Heusler structure with a lattice constant of 0.5739 nm. Annealing at 700 degrees C resulted in the coexistence of several phases, including the Heusler phase and a newly developed primitive cubic beta-Mn structure. Further increasing the annealing temperature to 950 degrees C completely suppressed the Heusler phase, with the beta-Mn structure, having a lattice constant of 0.6281 nm, becoming the dominant phase. These findings confirm the possibility of tuning the structure of Mn2FeSi0.5Al0.5 alloy powder-and thereby its physical properties-by varying the annealing temperature. The sensitivity of magnetic properties to structural changes is demonstrated through magnetization curves and zero-field-cooled/field-cooled curves in the temperature range of 5 K to 300 K.
How to determine possible interactions of silicide and aluminide in preparation of composites
(Univerzita Jana Evangelisty Purkyně v Ústí nad Labem, 2024) Novák, Pavel; Mestek, Stanislav; Michalcová, Alena; Tsepeleva, Alisa; Skotnicová, Kateřina; Szurman, Ivo
Silicide - aluminide composites could be considered as potential tool materials, because of high wear resistance and thermal stability. Recently, the alloys based on iron aluminide and silicide were tested, but they found to be very brittle due to the occurrence of brittle Fe-Al- Si ternary phases. On the other hand, in TiAl- Ti5Si3 composite, no ternary phase was formed during sintering, even though it can be expected based on thermodynamics. Therefore, this paper aims on finding the way how to test potential interaction between silicide and aluminide phase during preparation of these composites on the example of the FeSi - NiAl composite. The approach, proposed in this work, deals with the pre-sintered iron silicide, which was surrounded by aluminide powder in the sintering die and spark plasma sintered again. After that this model sample was annealed under various conditions and the FeSi - NiAl interface was observed. The experiments proved that no chemical reaction between FeSi and NiAl phase occurs during sintering and thermal exposure at 1000 degrees C. The visible interfacial layer is just a result of mutual diffusion.
Low-temperature antiferromagnetism in quaternary Mn2FeSi0.5Al0.5 alloys
(AIP Publishing, 2024) Životský, Ondřej; Gembalová, Lucie; Skotnicová, Kateřina; Szurman, Ivo; Čegan, Tomáš; Juřica, Jan; Malina, Ondřej; Čížek, Jakub
In this work, the quaternary Mn2FeSi0.5Al0.5 alloys are prepared for the first time in the form of cylinder-shaped ingots by traditional induction melting technique followed by homogenization annealing at 773 K for 100 h. The microstructural and magnetic properties of as-cast and annealed Mn2FeSi0.5Al0.5 samples are analyzed in detail and compared to the Mn2FeSi and Mn2FeAl ternary alloys. The Mn2FeSi0.5Al0.5 ingots are two-phase both before and after annealing, and their diffractograms correspond to the primitive cubic beta-Mn structure. Obtained lattice constant of 0.6274 nm is only slightly lower than that of Mn2FeAl alloy (0.6339 nm) and different from Mn2FeSi (0.5672 nm). The existence of both phases enriched in Si at the expense of Al and Mn was confirmed by differential thermal analysis showing two endothermic and exothermic peaks at temperatures of 1363 K and 1407 K. The magnetic properties of both quaternary samples studied in wide temperature range from 5 K to 573 K indicate paramagnetic behavior at room and elevated temperatures. The annealed system has the values of Curie temperature and effective paramagnetic moment comparable to the ternary Mn2FeAl alloy. The transition to antiferromagnetic state occurring at Neel temperatures of 34 K (as-cast sample) and 37 K (annealed sample) is caused by strong geometric frustration of beta-Mn structure. The magnetic transitions observed in both samples between Neel and room temperature are discussed in terms of the existence of Griffiths phase.
Synthesis of FeSi–FeAl composites from separately prepared FeSi and FeAl Alloys and their structure and properties
(MDPI, 2023) Novák, Pavel; Duda, Jiří; Průša, Filip; Skotnicová, Kateřina; Szurman, Ivo; Smetana, Bedřich
Composites consisting of iron aluminide and iron silicide phases were studied in this work. Powders of iron aluminide and iron silicide were prepared by mechanical alloying separately. Subsequently, they were blended in three different proportions and sintered by the SPS method under various conditions. After sintering, the composites are composed of FeAl and amounts of other silicides (Fe5Si3 and Fe3Si). Ternary Fe–Al–Si phases were not determined, even though their presence was predicted by DFT calculations. This disagreement was explained by steric factors, i.e., by differences in the space lattice of the present phases. Hardness and tribological properties were measured on composites with various weight ratios of iron aluminide and iron silicide. The results show that sintered silicides with the matrix composed of iron aluminide reach comparable hardness to tool steels. The composites with higher mass ratios of iron aluminide than silicide have higher hardness and better tribological properties.
Compact automatic controlled internal combustion engine cogeneration system based on natural gas with waste heat recovery from the combustion process
(Elsevier, 2023) Pawlenka, Tomáš; Juránek, Martin; Klaus, Pavel; Beseda, Marek; Buráň, Michal; Suchánek, Miroslav; Sehnoutka, Petr; Kulhánek, Jiří
This paper is related to cogeneration, or combined heat and power systems (CHP) and its development, which is based on an already used and low-cost internal combustion engine ICE with a fuel system redesigned for the injection of natural gas. The main role of this system is heating and electricity production and is mainly designed for small or medium-sized households or family houses. Heat is recovered from the engine's cooling circuit and its exhaust system using a special exhaust heat exchanger. The entire process is automatically controlled to keep the output heat transfer fluid at the required temperature and to keep the engine temperature within the operating range. This fluid is then used for heating the building or domestic hot water DHW. As a power generation unit - PGU, a three-phase asynchronous motor with the power of 12.5 kW was used. The theoretical charging current can be around 400 A. Part of the development is the design of control loops, which are implemented in the main control system. This control system can be connected to a smart home energy management system SHEMS and is designed for fully automatic operation. The functionality of all operating states and conditions was supported by testing and measurements. The paper includes an analysis of the energy balance from testing and measurements. The maximum overall efficiency of the CHP can reach up to 87% in operation mode, with a heating power output of 15 kW and an electrical power output of 4 kW.
Microstructure and mechanical properties of Ti–45Al–2W–xC alloys
(Elsevier, 2022) Kamyshnykova, Kateryna; Lapin, Juraj; Pelachová, Tatiana; Čegan, Tomáš; Juřica, Jan; Volodarskaja, Anastasia
The microstructure and mechanical properties of five alloys with nominal compositions of Ti-45Al-2W-xC (in at. %), where x is ranging from 0.4 to 2.0 at.%, were studied. The alloys were prepared by vacuum induction melting in graphite crucibles, followed by centrifugal casting into a graphite mould. The as-cast alloys were subjected to hot isostatic pressing and heat treatment consisting of solution annealing, cooling at a constant rate and stabilisation annealing. The microstructure of the heat-treated alloys consists of equiaxed alpha 2(Ti3Al) + gamma(TiAl) lamellar grains surrounded by gamma grain boundaries with a small amount of beta/B2 particles. The alpha 2-alpha 2 interlamellar spacing lambda decreases with increasing carbon content until a solubility limit of carbon is achieved. The increase in carbon content above the solubility limit leads to the formation of primary Ti2AlC particles during solidification and an increase in the amount of gamma phase at grain boundaries. Vickers microhardness of lamellar grains depends on the carbon content and interlamellar spacing lambda. The studied Ti-45Al-2W-0.8C and Ti-45Al-2W-1.2C alloys show improved creep resistance at 800 degrees C compared to that of the reference carbon-free TiAl-W and carbon-containing TiAl-Nb based alloys with fully lamellar, nearly lamellar, convoluted or pseudo-duplex microstructure.
Cogeneration unit noise reduction by its case
(MM Science, 2021) Štramberský, Radek; Pavelka, Václav; Pawlenka, Tomáš; Šuránek, Pavel; Morzyński, Leszek
This paper deals with cogeneration unit noise measurement by the acoustic camera. Noise is not only measured as the final number of sound power levels, but also its original location is determined with the use of the beamforming algorithm. The properties of the used microphone array are considered and numerically calculated as every different microphone array layout will measure with another resolution. From the frequency spectrum, the possible technical source is determined. The results of noise source visualization show the cogeneration unit case noise decreasing effect while also offering the possibilities for design improvements.
Experimental modeling of weld thermal cycle of the heat affected zone (HAZ)
(Hrvatsko Metalurško Društvo, 2016) Kulhánek, Jiří; Tomčík, Petr; Trojan, Radim; Juránek, Martin; Klaus, Pavel
Contribution deals with experimental modeling of quick thermal cycles of metal specimens. In the introduction of contribution will be presented measured graphs of thermal cycle of heat affected zone (HAZ) of weld. Next will be presented experimental simulation of measured thermal cycle on the standard specimens, useable for material testing. This approach makes possible to create material structures of heat affected zone of weld, big enough for standard material testing.
Influence of electric field on stabilization of flame from poor methane-oxygen mixture
(IEEE, 2013) Tomčík, Petr; Klaus, Pavel; Kulhánek, Jiří; Trojan, Radim
This paper deals with the influence of the dc electric field on the stabilization of the flame created from a poor (lean) mixture of methane and oxygen. In our experiments, the electric field is created between two electrodes in a combustion chamber in which one of the electrodes is a part of a burner. The dc voltage from a high voltage source is applied to both electrodes. A mixture of methane and oxygen with the purity of 99.95% of both gases is used for the combustion process. The burner combustion power is set at 0.5 kW. The observations of the electric field effects on the stabilization of the flame are carried out by increasing the oxygen flow up to the flame extinction. The result of the measurement is the observed electric field influence on the stabilization of the flame that is created from a poor mixture of methane and oxygen. In the experiment, we observe the dependence between flame stabilization and supplied electrical energy.

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