Number of found documents: 528
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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

Studium tepelných vlastností deagregovaných detonačních nanodiamantů metodami DSC-TG-MS
Zemenová, Petra; Král, Robert; Henych, Jiří; Stehlík, Štěpán
2020 - Czech
Příspěvek se zabýval studiem tepelných procesů u různě zpracovaných a frakcionovaných vzorků deagregovaných detonačních nanodiamantů metodami termických analýz (DSC-diferenční skenovací kalorimetrie a TG-termogravimetrie) a analýzy plynných produktů (MS-hmotová spektrometrie). This contribution deals with the study of thermal processes in different samples of detonation nanodiamond by thermal analyses (DSC-differential scanning calorimetry and TG-thermogravimetry) coupled with evolved gas analysis (EGA) by mass spectroscopy (MS). Keywords: degraded detonation nanodiamonds; thermal analysis Available at various institutes of the ASCR
Studium tepelných vlastností deagregovaných detonačních nanodiamantů metodami DSC-TG-MS

Příspěvek se zabýval studiem tepelných procesů u různě zpracovaných a frakcionovaných vzorků deagregovaných detonačních nanodiamantů metodami termických analýz (DSC-diferenční skenovací kalorimetrie a ...

Zemenová, Petra; Král, Robert; Henych, Jiří; Stehlík, Štěpán
Fyzikální ústav, 2020

Benefits of use of acoustic emission in scratch testing
Václavek, L.; Tomáštík, Jan; Chmelíčková, H.; Čtvrtlík, R.
2020 - English
Scratch test is regularly used for assessment of cohesive and adhesive strength of thin films and coatings. By default, its evaluation is based on analysis of depth-load-time record and microscopic observation of residual scratch groove. The visual analysis of the residual groove provides the most detailed description of the final damage of the surface (crack patterns, extent of plastic deformation, delamination, etc.), but it may be a time demanding approach. Although the continuous recording of indenter penetration depth and applied load offers instantaneous information about the performance of the tested material, it may not provide sufficient description of the sample’s deformation behaviour. Therefore, other complementary techniques for description of the deformation response to scratch loading are desirable. Keywords: acoustic emission; laser cladding; scratch test; thin films Available at various institutes of the ASCR
Benefits of use of acoustic emission in scratch testing

Scratch test is regularly used for assessment of cohesive and adhesive strength of thin films and coatings. By default, its evaluation is based on analysis of depth-load-time record and microscopic ...

Václavek, L.; Tomáštík, Jan; Chmelíčková, H.; Čtvrtlík, R.
Fyzikální ústav, 2020

Adhesion improvement between bitumen and mineral aggregate:theoretical principles and their impact on pavement structure lifetime
Trejbal, J.; Demo, Pavel; Nežerka, V.; Sveshnikov, Alexey; Valentová, T.; Valentin, J.
2019 - English
Influence of nanomaterial-based adhesion promoters on maximizing of intermolecular interactions between bitumen and aggregate surfaces was studied. Topological and physico-chemical properties were described and it is shown that presence of promoters increases adhesion about 18%. Keywords: adhesion promoters; interface interactions Available at various institutes of the ASCR
Adhesion improvement between bitumen and mineral aggregate:theoretical principles and their impact on pavement structure lifetime

Influence of nanomaterial-based adhesion promoters on maximizing of intermolecular interactions between bitumen and aggregate surfaces was studied. Topological and physico-chemical properties were ...

Trejbal, J.; Demo, Pavel; Nežerka, V.; Sveshnikov, Alexey; Valentová, T.; Valentin, J.
Fyzikální ústav, 2019

Microscopic study of multifunctional drug molecule adhesion to electronic biosensors coated with diamond and gold nanoparticles
Finsterle, T.; Pilarčíková, I.; Bláhová, I.A.; Potocký, Štěpán; Kromka, Alexander; Ukraintsev, Egor; Nepovimová, E.; Musílek, K.; Kuča, K.; Rezek, B.
2019 - English
The easy and fast detection of drug content and concentration levels is demanded in biological research as well as in clinical practice. Here we study on microscopic level how nanodiamonds and gold nanoparticles interact with a multifunctional drug molecule directly on a biosensor surface. The sensors are made of interdigitated Au electrodes coated by 5 nm hydrogenated or oxidized nanodiamonds and further combined with Au colloidal nanoparticles (size 20 nm) providing nanoscale composite (spacing 100 nm). Atomic force microscopy is employed to measure local tip-surface adhesion forces and surface topography. AFM adhesion maps show that the drug binds to all types of nanoparticles and the adhesion is also significantly influenced by the substrates on which the nanoparticles are deposited. Role of local AFM tip interaction with nanostructured surface is also discussed.\n Keywords: alzheimer drugs; biosensors; nanodiamonds; nanoparticles Fulltext is available at external website.
Microscopic study of multifunctional drug molecule adhesion to electronic biosensors coated with diamond and gold nanoparticles

The easy and fast detection of drug content and concentration levels is demanded in biological research as well as in clinical practice. Here we study on microscopic level how nanodiamonds and gold ...

Finsterle, T.; Pilarčíková, I.; Bláhová, I.A.; Potocký, Štěpán; Kromka, Alexander; Ukraintsev, Egor; Nepovimová, E.; Musílek, K.; Kuča, K.; Rezek, B.
Fyzikální ústav, 2019

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