No (983)
Yes (4)
Used filters
(2)
Number of found documents:
987
Published from
to
PROPERTIES OF NANOCRYSTALLINE FE-NI PARTICLES PREPARED BY THERMAL REDUCTION OF OXALATE PRECURSORS
Švábenská, Eva; Roupcová, Pavla; Havlíček, Lubomír; Schneeweiss, Oldřich
2024 - English
Recent technological advancements require development of cost-effective and high-performance magnets \nwhich ideally do not contain rare earth metals or noble metals. The promising candidates are Fe-Ni-based \nalloys, in particular, the Fe50Ni50 L10 phase (tetrataenite), which has a great perspective for producing hard \nmagnetic materials. Our study explores a promising method for preparing nanoparticles of Fe-Ni alloy from an \niron-nickel oxalate precursor. The coprecipitation method was employed to prepare oxalate precursors, \nfollowed by controlled thermal decomposition in a reducing hydrogen atmosphere. The morphology and \nproperties of the resulting particles were analysed using scanning electron microscopy (SEM) coupled with \nenergy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Mössbauer spectroscopy (MS), and \nmagnetic measurements.\nThe SEM analysis revealed that the particles have approximately cube-shaped unit cell morphology with a\nsize in a range of 1 - 2 μm. Upon annealing, the samples contain multiple phases with varying Fe-Ni content.\nMagnetic measurements confirmed the formation of magnetically suitable Fe-Ni phases in the samples after \nannealing. Mössbauer spectroscopy emerged as a highly effective method for characterizing individual phases \nof the Fe-Ni system.
Keywords:
Magnetic materials; thermal decomposition; Mössbauer spectroscopy
Available at various institutes of the ASCR
PROPERTIES OF NANOCRYSTALLINE FE-NI PARTICLES PREPARED BY THERMAL REDUCTION OF OXALATE PRECURSORS
Recent technological advancements require development of cost-effective and high-performance magnets \nwhich ideally do not contain rare earth metals or noble metals. The promising candidates are ...
Evaluation of sample geometry effect on creep deformation progress using acoustic emission method
Dvořák, Jiří; Sklenička, Václav; Král, Petr; Kvapilová, Marie; Svobodová, M.; Šifner, J.; Koula, V.
2023 - Czech
This work deals with the determination of the influence of the sample geometry on the development of failure during creep exposure. Creep tests were carried out at temperature of 600 °C and a stress of 180 MPa in the protective atmosphere of argon. P92 steel samples with a conventional smooth surface and samples with a V-groove notch were chosen for the test tests. The results of creep resistance and fracture behaviour were complemented by detailed microstructural characterization to assess damage initiation and development. Based on the measured results, the creep data was evaluated using neural networks that systematically search for and process the signal from the acoustic emission (AE). Acoustic emission serves here as an effective non-destructive method for early prediction of the beginning of a possible accident of components of power and chemical plants. Tato práce se zabývá stanovením vlivu geometrie tělesa na vývoj porušení v průběhu creepové expozice. Creepové testy byly provedeny při teplotě 600 °C a napětí 180 MPa v režimu ochranné atmosféry argonu. Pro zkušební testy byl zvoleny vzorky z oceli P92 s konvekčním hladkým povrchem a vzorky opatřené V-vrubem. Výsledky creepové odolnosti a lomového chování byly doplněny podrobnou mikrostrukturní charakterizací k posouzení iniciace a vývoje creepového poškození. Na základě naměřených výsledků byla creepová data vyhodnocena pomocí neuronových sítí, které systematicky vyhledávají a zpracovávají signál z akustické emise (AE). Akustická emise byla použita jako účinná nedestruktivní metoda pro včasnou predikci počátku možné havárie komponent energetických a chemických zařízení.
Keywords:
creep specimen; creep deformation; acoustic emission
Available at various institutes of the ASCR
Evaluation of sample geometry effect on creep deformation progress using acoustic emission method
This work deals with the determination of the influence of the sample geometry on the development of failure during creep exposure. Creep tests were carried out at temperature of 600 °C and a stress ...
Creep tests of zirconium fuel cladding tubes and their interpretation
Sklenička, Václav; Kuchařová, Květa; Kloc, Luboš; Dvořák, Jiří; Král, Petr; Kvapilová, Marie; Vrtílková, V.; Krejčí, J.
2023 - Czech
Time-dependent plastic deformation – creep is one of the most important degradation factors which govern the life of zirconium alloys used as fuel claddings materials in the light water reactor in nuclear power industry. This work aims to describe creep testing of Zr1%Nb (modified E110 alloy) cladding tubes used in the VVER-type reactor. In addition to a standard creep testing method under constant tensile test a nonstandard special creep testing method which has been developed to measure very small creep strains at stresses corresponding to the loading in real service. Časově závislá plastická deformace-creep je jedním z nejdůležitějších degradačních faktorů, určujících životnost zirkoniových slitin, určených k pokrytí jaderného paliva vodou chlazených reaktorů v jaderné energetice. Příspěvek je věnován creepovým zkouškám povlakových tyčí slitiny Zr1%Nb (modifikace slitiny E110) používaných v reaktorech typu VVER. Vedle standardní creepové zkoušky při konstantním tahovém napětí bude demonstrována nestandardní speciální creepová zkušební metoda umožňující měření velmi malých creepových deformací při napětích blížících se reálným podmínkám namáhání v reálné praxi.
Keywords:
creep testing; zirconium cladding alloys; degradation mechanisms
Available at various institutes of the ASCR
Creep tests of zirconium fuel cladding tubes and their interpretation
Time-dependent plastic deformation – creep is one of the most important degradation factors which govern the life of zirconium alloys used as fuel claddings materials in the light water reactor in ...
NANOCERIA PREPARED BY ELECTRON BEAM EVAPORATION
Pizúrová, Naděžda; Hlaváček, A.; Kavčiaková, Zuzana; Roupcová, Pavla; Kuběna, Ivo; Buršík, Jiří; Sokovnin, S. Y.
2022 - English
Cerium oxide nanoparticles (nanoceria) are currently one of the most investigated nanomaterials because of their attractive properties used in biomedical applications, catalysis, fuel cells, and many others. These attractive properties are connected with the Ce3+ and Ce4+ valency state ratio. In the nanoparticle form, cerium oxides contain a mixture of Ce3+ and Ce4+ on the nanoparticle surfaces. Switching between these two states requires oxygen vacancies. Therefore, nanoceria's inherent ability to act as an antioxidant in an environmentally-dependent manner and a “redox switch” to confer auto-regenerating capabilities by automatically shifting between Ce4+ and Ce3+ oxidation states is significantly affected by surface morphology. Regarding this demanded behavior, we aimed to characterize synthesized nanoparticle surface quality and its influence on the cerium oxidation states. The received results were used to evaluate the synthesis method's suitability for suggested utilization. We used nanoparticles prepared by electron beam evaporation. This unique physical method includes nanoparticle creation through the fast cooling process followed by breaking radiation damaging nanoparticle surfaces to create surface off-stoichiometry. We prepared a sample containing clusters of a mixture of ultra-small nanoparticles and approximately 100 nm particles. X-ray diffraction confirmed the CeO2 phase in both components. To extract the finest component, we used centrifugal size fractionation. We received 200 nm clusters of 2-10 nm nanoparticles. Nanoparticle shapes and facet types were analyzed using transmission electron microscopy methods. We found out most nanoparticles were formed with truncated octahedrons containing {1,1,1} and {1,0,0} facet types and truncated cuboctahedrons containing {1,1,1}, {1,0,0}, and additional {1,1,0} facets. No octahedron (without truncation) containing only {1,1,1} facets was observed. Nanoparticle shapes containing {1,1,0} and {1,0,0} are suitable for redox activity. Some amount of irregular shapes, beneficial for redox activity, was also observed. Spectroscopy methods confirmed Ce3+ content.
Keywords:
Ce3+ and Ce4+; electron beam evaporation; facet types; hrtem; Nanoceria
Available at various institutes of the ASCR
NANOCERIA PREPARED BY ELECTRON BEAM EVAPORATION
Cerium oxide nanoparticles (nanoceria) are currently one of the most investigated nanomaterials because of their attractive properties used in biomedical applications, catalysis, fuel cells, and many ...
INFLUENCE OF THE DEPOSITION PARAMETERS ON MICROSTRUCTURE AND PROPERTIES OF HVOF SPRAYED WC-CRC-NI COATING
Vražina, Tomáš; Šulák, Ivo; Poloprudský, Jakub; Zábranský, K.; Gejdoš, P.; Hadraba, Hynek; Čelko, L.
2022 - English
This paper investigates the influence of thermal spray parameters of the high-velocity oxygen fuel (HVOF) process on the properties of cermet coatings prepared from commercially available Amperit 551 WC-CrC-Ni powder. Three different processing parameters were applied to optimize the production process with the aim to achieve preeminent mechanical properties and fully dense material without microstructural defects. The deposition was carried out by a GLC5 gun. The velocity and temperature of powder particles in the spray stream were monitored by Accuraspray Tecnar diagnostic tool. The quality of deposited coatings was analyzed by means of light microscopy, scanning electron microscopy, and X-ray diffraction. The chemical composition of the used powder and sprayed WC-CrC-Ni coating was determined by energy dispersive spectroscopy. It was found that the spray parameters have a negligible effect on the resulting microstructure and phase composition of the coating. However, the porosity and surface roughness were significantly affected by the variation in process parameters. To assess the basic mechanical properties of HVOF sprayed coating instrumented Vickers hardness measurements were utilized. The coating hardness reached mean values over 1400 HV 0.1 and the indentation modulus varied from 152-279 GPa.
Keywords:
hvof; microhardness; WC-CrC-Ni
Available at various institutes of the ASCR
INFLUENCE OF THE DEPOSITION PARAMETERS ON MICROSTRUCTURE AND PROPERTIES OF HVOF SPRAYED WC-CRC-NI COATING
This paper investigates the influence of thermal spray parameters of the high-velocity oxygen fuel (HVOF) process on the properties of cermet coatings prepared from commercially available Amperit 551 ...
Inverse-Heusler Mn2FeSi alloy prepared by powder metallurgy route
Životský, O.; Skotnicová, K.; Čegan, T.; Juřica, J.; Gembalová, L.; Zažímal, František; Jirásková, Yvonna; Szurman, I.
2022 - English
The Mn2FeSi inverse-Heusler alloy was prepared by solid-state reactions using ball milling for 168 h in n hexane. Two milling procedures varying in the ball-to-powder ratio, namely 4:1 and 10:1, were used to follow \ntheir influence on alloy formation and its physical properties. In both cases no Heusler structure was obtained \ndirectly and therefore the subsequent annealing at 1223 K for 1.5 h in pure Ar was applied. The energy dispersive X-ray analysis resulted in the chemical composition about 49.0-49.9 at% Mn, 25.3-25.6 at% Fe, and \n24.8-25.4 at% Si, in a good agreement with nominal one. X-ray diffraction of both powders confirmed inverse Heusler XA structure of lattice parameters 0.5675 nm (4:1) and 0.5677 nm (10:1), only slightly higher as \ntheoretically obtained 0.560 nm. The presence of minor oxidation phases was also observed in the particle \nstructure of powders. Magnetic properties were analysed at low and room temperatures. Both alloys exhibit \nparamagnetic behaviour at room temperature confirmed by transmission Mössbauer spectroscopy \nmeasurements. Different magnetic behaviour of alloys is observed below 65 K.
Keywords:
Heusler alloy, powder, ball milling, microstructure, magnetism; powder; ball milling; microstructure; magnetism
Available at various institutes of the ASCR
Inverse-Heusler Mn2FeSi alloy prepared by powder metallurgy route
The Mn2FeSi inverse-Heusler alloy was prepared by solid-state reactions using ball milling for 168 h in n hexane. Two milling procedures varying in the ball-to-powder ratio, namely 4:1 and 10:1, were ...
Nanoparticels from brake pads wear
Švábenská, Eva; Roupcová, Pavla; Friák, Martin; Schneeweiss, Oldřich
2022 - English
Exposure to particulate air pollution has been associated with a variety of health problems. One of the main\nsources of metal-rich airborne particulate pollution in roadside environments are brake-wear emissions. The \nscanning electron microscopy (SEM) and transmission electron microscopy (TEM), Mössbauer spectroscopy \n(MS), X-ray powder diffraction (XRD) was used to a make quantitative evaluation of wear particles in two \nsamples. Sizes, morphologies, oxidation state, and trace element compositions of wear particles were\ninvestigated using combination of several methods revealed high concentrations of Fe species and phases, \noften associated with carbonaceous material. SEM and TEM observations show that brake wear particles with \na size of tens to hundreds of nm mainly form particle agglomerates. However, ultrafine (<100 nm) particles are \nlikely to pose a health threat after inhalation and/or ingestion.
Keywords:
Wear particles; analysis; TEM; iron oxides; metallic particles
Available at various institutes of the ASCR
Nanoparticels from brake pads wear
Exposure to particulate air pollution has been associated with a variety of health problems. One of the main\nsources of metal-rich airborne particulate pollution in roadside environments are ...
Advanced statistical evaluation of fatigue data obtained during the measurement of concrete mixtures with various water-cement ratio
Seitl, Stanislav; Benešová, A.; Blasón, S.; Miarka, Petr; Klusák, Jan; Bílek, V.
2022 - English
The Basquin’s law is usually applied for the evaluation of fatigue properties of civil engineering \nmaterials. For materials like concrete, some researchers recommended applying the Weibull model. In this\ncontribution, Basquin’s law, Castillo-Canteli model and Kohout-Věchet model were applied for the advanced \nstatistical description of S−N curves (Wöhler curve). For the application of the models, the experimental data \nmeasured on reference concrete mixtures used for the development of self-healing concrete at the Faculty of \nCivil Engineering, TU Ostrava. Fitting data of applied models were compared and analyzed
Keywords:
Concrete, fatigue; fatigue; S-N curve; Kohout-Věchet model; Castillo-Canteli model; Basquin model
Available at various institutes of the ASCR
Advanced statistical evaluation of fatigue data obtained during the measurement of concrete mixtures with various water-cement ratio
The Basquin’s law is usually applied for the evaluation of fatigue properties of civil engineering \nmaterials. For materials like concrete, some researchers recommended applying the Weibull model. In ...
Structural and magnetic properties of Fe-oxide layers prepared by inkjet printing on Si-substrate
Zažímal, František; Svoboda, T.; Dzik, P.; Homola, T.; Jirásková, Yvonna
2021 - English
Magnetic films with two, four, six, and eight layers were prepared using 2D inkjet printing on the 333 K heated Si-substrates at ambient conditions. The microstructure, phase composition of layers, and magnetic studies were investigated using wide spectrum of experimental methods with the aim to find the optimal conditions for producing magnetic sensors by digital printing technology in the near future. As the magnetic compound, the hematite powder was chosen and its milling with Si-binder dissolved in dowanol using glass balls and vial to prevent contamination was done to prepared suspension appropriate for printing. It is shown that hematite transformed markedly into maghemite, thus the layers consisted of small amount hematite and dominant maghemite phases determining the magnetic properties. From the viewpoint of magnetic behavior, the highest saturation magnetization and the lowest coercivity was obtained at the sample with 8 layers.
Keywords:
Inkjet printing; hematite; physical properties; testing methods
Available at various institutes of the ASCR
Structural and magnetic properties of Fe-oxide layers prepared by inkjet printing on Si-substrate
Magnetic films with two, four, six, and eight layers were prepared using 2D inkjet printing on the 333 K heated Si-substrates at ambient conditions. The microstructure, phase composition of layers, ...
Influence of severe plastic deformation and subsequent annealing on creep behaviour of martensitic 9% Cr steel
Král, Petr; Dvořák, Jiří; Sklenička, Václav; Horita, Z.; Tokizawa, Y.; Tang, Y.; Kunčická, Lenka; Kuchařová, Květa; Kvapilová, Marie; Svobodová, M.
2021 - English
The objective of the study is to evaluate the effects of severe plastic deformation (SPD) and annealing on creep behaviour of advanced tungsten modified creep-resistant 9 % Cr martensitic P92 steel. The as-received P92 steel was deformed by high-pressure torsion (HTP), high-pressure sliding (HPS) and rotary swaging (RS) at room temperature prior creep testing. These SPD methods imposed significantly different equivalent plastic strain in the range from 1 up to 20. Constant load creep tests in tension were performed in an argon atmosphere at 873 K and applied stress ranging from 50 to 200 MPa. The microstructure and phase composition of P92 steel were studied using a scanning electron microscope Tescan Lyra 3 and a transmission electron microscope Jeol 2100F. The results show that under the same creep loading conditions the HPT and HPS-processed P92 steel exhibited significantly faster minimum creep rates, creep fracture strain and the decrease in the value of the stress exponent of the creep rate in comparison with as-received P92 steel. However, it was revealed that the RS-processed specimens exhibited one order of magnitude lower minimum creep rate and lower ductility compared to commercial P92 steel. The creep curves for the HPT and HPS-processed states exhibited a pronounced minimum of strain rate. The pronounced minimum of strain rate disappeared when these states were annealed at 923K/500h before application of creep loading. The microstructure changes occurring during creep and different creep behaviour between as-received and deformed states are discussed.
Keywords:
Creep-resistant 9 %Cr steels; severe plastic deformation; creep; microstructure
Available at various institutes of the ASCR
Influence of severe plastic deformation and subsequent annealing on creep behaviour of martensitic 9% Cr steel
The objective of the study is to evaluate the effects of severe plastic deformation (SPD) and annealing on creep behaviour of advanced tungsten modified creep-resistant 9 % Cr martensitic P92 steel. ...
NRGL provides central access to information on grey literature produced in the Czech Republic in the fields of science, research and education. You can find more information about grey literature and NRGL at service web
Send your suggestions and comments to nusl@techlib.cz
Provider
Other bases