Number of found documents: 434
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Book of Abstracts of the 30.sup.th./sup. Joint Seminar of the Development of Materials Science in Research and Education
Kožíšek, Zdeněk; Král, Robert; Zemenová, Petra
2020 - English
Conference topics: \n- Trends in development of materials research\n- Education of materials science at the universities \n- Information about the research programmes of individual institutions \n- Information on equipment for preparation and characterisation of materials \n- Results of materials science research. Keywords: material sciences Available at various institutes of the ASCR
Book of Abstracts of the 30.sup.th./sup. Joint Seminar of the Development of Materials Science in Research and Education

Conference topics: \n- Trends in development of materials research\n- Education of materials science at the universities \n- Information about the research programmes of individual institutions \n- ...

Kožíšek, Zdeněk; Král, Robert; Zemenová, Petra
Fyzikální ústav, 2020

Compression of ecaped titanium micro-pillars for two principal orientations
Vokoun, David; Maňák, Jan; Tesař, Karel; Habr, Stanislav
2020 - English
The thermomechanical processing by equal-channel angular pressing (ECAP) is used for certain metals and alloys in order to make their structure fine and to increase material strength. In the previous study done at our institute, grade 2 titanium was successfully processed using four consecutive route A passes via a 90° ECAP die with high backpressure at room temperature. Orientation dependence of compressive and tensile loading of ECAPed titanium samples was demonstrated at macro-scale. However, scarce attention has been paid so far to the mechanical behavior of ECAPed titanium samples at micro-scale. In the present study, compression experiments on titanium micro-pillars, fabricated using focused ion beam, are carried out for two main directions in respect to preceding ECAP pressing (insert and extrusion directions). The purpose of this study is to discuss the orientation dependence of mechanical response during compression of the as-ECAPed titanium micro-pillars. Keywords: ECAP; micro-pillar; titanium Available in digital repository of the ASCR
Compression of ecaped titanium micro-pillars for two principal orientations

The thermomechanical processing by equal-channel angular pressing (ECAP) is used for certain metals and alloys in order to make their structure fine and to increase material strength. In the previous ...

Vokoun, David; Maňák, Jan; Tesař, Karel; Habr, Stanislav
Fyzikální ústav, 2020

Mass production of hydrogenated ZnO nanorods
Chang, Yu-Ying; Remeš, Zdeněk; Míčová, J.
2020 - English
We have developed an inexpensive and efficient technology of hydrothermal growth of ZnO nanorods from zinc nitrate hexahydrate (Zn(NO3)2·6H2O), as a precursor and hexamethylenetetramine (HMTA) (C6H12N4), as a surfactant followed by plasma hydrogenation in a novel inductively coupled plasma (ICP) quartz reactor and equipped with the rotary sample holder to stir powder during plasma treatment. We have optimized the photoluminescence spectroscopy for measuring optical scattering samples with the high sensitivity, precise sample positioning and very low influence of the scattered excitation light. Here we present the latest results on the enhancement of the UV photoluminescence of the ZnO nanorods after plasma hydrogenation. The exciton-related photoluminescence has been significantly enhanced whereas the deep defect related yellow photoluminescence has been significantly decreased.\n Keywords: nanomaterials; ZnO; photoluminescence; excitons; inductively coupled plasma; hydrogenation Available at various institutes of the ASCR
Mass production of hydrogenated ZnO nanorods

We have developed an inexpensive and efficient technology of hydrothermal growth of ZnO nanorods from zinc nitrate hexahydrate (Zn(NO3)2·6H2O), as a precursor and hexamethylenetetramine (HMTA) ...

Chang, Yu-Ying; Remeš, Zdeněk; Míčová, J.
Fyzikální ústav, 2020

Laser-induced surface acoustic waves for thin film characterization
Kudělka, R.; Václavek, L.; Tomáštík, Jan; Malecová, S.; Čtvrtlík, R.
2020 - English
Knowledge of mechanical properties of thin films is essential for most of their applications.However, their determination can be problematic for very thin films. LAW (Laser-induced acousticwaves) is a combined acousto-optic method capable of measuring films with thickness from fewnanometers. It utilizes ultrasound surface waves which are excited via short laser pulses and detectedby a PVDF foil. Properties such as Young’s modulus, Poisson’s ratio and density of both the film andthe substrate as well as film thickness can be explored.Results from the LAW method are successfullycompared with nanoindentation for Young’s modulus evaluation and with optical method for filmthickness evaluation and also with literature data. Application of LAW for anisotropy mapping ofmaterials with cubic crystallographic lattice is also demonstrated Keywords: anisotropy; laser-induced surface acoustic waves; nanoindentation; Young’s modulus; thin films Available at various institutes of the ASCR
Laser-induced surface acoustic waves for thin film characterization

Knowledge of mechanical properties of thin films is essential for most of their applications.However, their determination can be problematic for very thin films. LAW (Laser-induced acousticwaves) is a ...

Kudělka, R.; Václavek, L.; Tomáštík, Jan; Malecová, S.; Čtvrtlík, R.
Fyzikální ústav, 2020

Characterization of titanium laser welds
Chmelíčková, H.; Hiklová, H.; Václavek, L.; Tomáštík, J.; Čtvrtlík, Radim
2020 - English
Butt welding of commercially pure titanium Grade 1 and Ti6Al4V alloy sheets using a pulsed Nd:YAG laser KLS 246 - 102 LASAG were carried out to determine optimal values of pulse energy and pulse length to create completely penetrated weld. Surface peak power density of about 3.105 W.cm−2 was found as an optimal value. Weld dimensions, both face width and penetration depth, are found to be proportional to increasing energy and decreasing pulse length. Gentle sagging and root penetration were revealed by means of contact surface profilometry. The nanohardness tests on transverse cross-sections detected approximately 50% higher hardness in the fusion zone than in the base material.\n Keywords: elasticity; laser welding; nanohardness; surface profile; titanium Available at various institutes of the ASCR
Characterization of titanium laser welds

Butt welding of commercially pure titanium Grade 1 and Ti6Al4V alloy sheets using a pulsed Nd:YAG laser KLS 246 - 102 LASAG were carried out to determine optimal values of pulse energy and pulse ...

Chmelíčková, H.; Hiklová, H.; Václavek, L.; Tomáštík, J.; Čtvrtlík, Radim
Fyzikální ústav, 2020

Fracture behavior of FeAlSi intermetallics
Čech, J.; Haušild, P.; Karlík, M.; Nová, K.; Průša, F.; Novák, P.; Kopeček, Jaromír
2020 - English
The study is devoted to the intermetallic alloy FeAl20Si20 (wt.%) with the potential applications in high temperature aggressive environments. The samples of the same chemical composition were prepared by spark plasma sintering from the different mechanically alloyed powders (pure elements and pre-alloyed powders). Keywords: FeAlSi; fracture toughness; nanoindentation; SPS Available at various institutes of the ASCR
Fracture behavior of FeAlSi intermetallics

The study is devoted to the intermetallic alloy FeAl20Si20 (wt.%) with the potential applications in high temperature aggressive environments. The samples of the same chemical composition were ...

Čech, J.; Haušild, P.; Karlík, M.; Nová, K.; Průša, F.; Novák, P.; Kopeček, Jaromír
Fyzikální ústav, 2020

Mathematical method for submolecular resolution of helicene-based macrocycles by atomic force microscopy in air
Ukraintsev, Egor; Houska, Václav; Vacek, Jaroslav; Starý, Ivo; Stará, Irena G.; Rezek, B.
2020 - English
We introduce a straightforward mathematical method for improving the AFM image resolution, applied to image analysis of helicene-based macrocycles adsorbed on HOPG. The method reveals structural details from insufficiently resolved AFM images and attributes them to internal structure and ordering of the macrocycles. Our findings are also corroborated by molecular mechanics simulations, validating that the structure provided by the method has lower potential energy compared to other tested macrocycle arrangements. Keywords: atomic force microscope; mathematical modeling; submolecular resolution; macrocycles; molecular mechanics simulations Available at various institutes of the ASCR
Mathematical method for submolecular resolution of helicene-based macrocycles by atomic force microscopy in air

We introduce a straightforward mathematical method for improving the AFM image resolution, applied to image analysis of helicene-based macrocycles adsorbed on HOPG. The method reveals structural ...

Ukraintsev, Egor; Houska, Václav; Vacek, Jaroslav; Starý, Ivo; Stará, Irena G.; Rezek, B.
Fyzikální ústav, 2020

Comparison of microbial interactions of zinc oxide nanomaterials in various size and shape
Rutherford, D.; Jíra, J.; Mičová, J.; Remeš, Zdeněk; Hsu, H.S.; Rezek, B.
2020 - English
Zinc oxide nanoparticles (ZnO NP) have shown great potential as a novel antibacterial material at a time when resistance towards conventional antibiotics is becoming more prevalent. We report bacteria inactivation by ZnO NP with novel hedgehog-like morphology using model gram-negative (E. coli) and gram-positive (S. aureus) bacteria. E. coli exposed to the novel ZnO hedgehog NP during growth resulted in 4 orders of magnitude reduction in viable cell concentration after 24 h, which is more than 2 orders higher reduction compared to commercially available ZnO NPs with nominal sizes from 50 nm to 20 um. There was a positive correlation between hedgehog NP concentration and bacteria cell concentration reduction within the range tested 0.1 – 1.0 mg/mL. S. aureus was less sensitive to ZnO NP exposure and inactivation effect of various ZnO NP, was comparable. The effect can be thus attributed to direct mechanical damage of the bacterial mebrane that is the most effective for the novel hedgehog ZnO NP. This conclusion was corroborated also by disk diffusion assays.\n Keywords: nanotechnology; microbiology; zinc oxide Available at various institutes of the ASCR
Comparison of microbial interactions of zinc oxide nanomaterials in various size and shape

Zinc oxide nanoparticles (ZnO NP) have shown great potential as a novel antibacterial material at a time when resistance towards conventional antibiotics is becoming more prevalent. We report bacteria ...

Rutherford, D.; Jíra, J.; Mičová, J.; Remeš, Zdeněk; Hsu, H.S.; Rezek, B.
Fyzikální ústav, 2020

Why monitor acoustic emissions during nanomechanical tests?
Čtvrtlík, Radim; Václavek, L.; Tomáštík, J.
2020 - English
Acoustic Emissions (AE) monitoring has been proved as an effective non-destructive technique at the macro scale. Nevertheless, it may also be employed at nano/micro scale during nanomechanical and nanotribological testing. Local mechanical properties of surfaces or micro object are routinely explored using nanoindentation, scratch test or dynamic impact tests that are evaluated based on analysis of depth-load-time records or microscopic observation of residual indents, scratch grooves or impact craters, respectively. Although these approaches have been proven to be sufficient in most cases for a variety of materials, there are many situations where they do not provide sufficient information for a complex understanding of the deformation response. On the other hand, analysis of AE signals generated during these tests may provide valuable complementary information and provide some insight into the dynamics of phenomena like cracking, phase transitions, plastic instabilities, etc.\n Keywords: acoustic emission; indentation; scratch test; thin films Available at various institutes of the ASCR
Why monitor acoustic emissions during nanomechanical tests?

Acoustic Emissions (AE) monitoring has been proved as an effective non-destructive technique at the macro scale. Nevertheless, it may also be employed at nano/micro scale during nanomechanical and ...

Čtvrtlík, Radim; Václavek, L.; Tomáštík, J.
Fyzikální ústav, 2020

Role of Urbach Energy in Photovoltaics
Vlk, Aleš; Abelová, Lucie; Hájková, Zdeňka; Remeš, Zdeněk; Holovský, Jakub; Ledinský, Martin
2020 - English
Organic-inorganic halide perovskites provide new opportunities for improvement of optoelectronic device performance, especially the efficiency of solar cells. To evaluate the quality of a new material many parameters has to be taken into account. Here, we discuss one of the often overlooked semiconductor’s parameters, Urbach energy, which is an easily accessible measure of material disorder. Moreover, we present its importance on the example of organic-inorganic halide perovskites. Keywords: organic-inorganic halide perovskites; photoluminescence; Urbach energy Available at various institutes of the ASCR
Role of Urbach Energy in Photovoltaics

Organic-inorganic halide perovskites provide new opportunities for improvement of optoelectronic device performance, especially the efficiency of solar cells. To evaluate the quality of a new material ...

Vlk, Aleš; Abelová, Lucie; Hájková, Zdeňka; Remeš, Zdeněk; Holovský, Jakub; Ledinský, Martin
Fyzikální ústav, 2020

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