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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 ...
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 ...
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 ...
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 ...
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 ...
Relation between optical and microscopic properties of hydrogenated silicon thin films with integrated germanium and tin nanoparticles
Stuchlík, Jiří; Stuchlíková, The-Ha; Čermák, Jan; Kupčík, Jaroslav; Fajgar, Radek; Remeš, Zdeněk
2019 - English
The hydrogenated amorphous silicon layers (a-Si:H) were deposited by PECVD method on quartz substrates. During interruption of PECVD process the vacuum chamber was pumped up to 10-5 Pa and 1 nm thin films of Germanium or Tin were evaporated on the surface. The materials form isolated nanoparticles (NPs) on the a-Si:H surface. Then the deposited NPs were covered and stabilized by a-Si:H layer by PECVD. Those two deposition processes were alternated 5 times. The a-Si:H thin films with integrated Ge or Sn NPs were characterized optically by PDS and CPM methods, and microscopically by SEM and AFM microscopies. Optical and microscopic properties of the structures are correlated and discussed considering their application in photovoltaics.\n
Keywords:
thin films; a-Si:H; nanoparticles; germanium; tin
Available in digital repository of the ASCR
Relation between optical and microscopic properties of hydrogenated silicon thin films with integrated germanium and tin nanoparticles
The hydrogenated amorphous silicon layers (a-Si:H) were deposited by PECVD method on quartz substrates. During interruption of PECVD process the vacuum chamber was pumped up to 10-5 Pa and 1 nm thin ...
Inactivation of aspergillus niger on paints containing ZnO
Rácová, Z.; Baudys, M.; Krýsa, J.; Tichá, P.; Demo, Pavel
2019 - English
Antifungal capability of ZnO against bacteriae A. niger (including its photocatalytic activity) was analyzed. The optimal conditions for mould mycelium growth was estimated from evolution growth models. It was shown that prepared protective coating exhibits antifugal effect.
Keywords:
self-cleaning; ZnO; photocatalysis; niger
Available at various institutes of the ASCR
Inactivation of aspergillus niger on paints containing ZnO
Antifungal capability of ZnO against bacteriae A. niger (including its photocatalytic activity) was analyzed. The optimal conditions for mould mycelium growth was estimated from evolution growth ...
MOVPE GaN/AlGaN HEMT nano-structures
Hulicius, Eduard; Kuldová, Karla; Hospodková, Alice; Pangrác, Jiří; Dominec, Filip; Humlíček, J.; Pelant, Ivan; Cibulka, Ondřej; Herynková, Kateřina
2019 - English
GaN/AlGaN-based high electron mobility transistors (HEMTs) attain better performance than their state-of-the-art full silicon-based counterparts do, offering higher power, higher frequency as well as higher temperature of operation and stability, although their voltage and current limits are somewhat lower than for the SiC-based HEMTs. GaN/AlGaN-based HEMTs are a potential choice for electric-powered vehicles, for which they are approved not only for their power parameters, but also for their good temperature stability, lifetime and reliability. It is important to optimize HEMT structures and their growth parameters to reach the optimum function for the real-world applications. HEMT structures were grown by MOVPE technology in AIXTRON apparatus on (111)-oriented single-surface polished Si substrates. Structural, optical and transport properties of the structures were measured by X-ray diffraction, optical reflectivity, time-resolved photoluminescence and micro-Raman spectroscopy.\n
Keywords:
GaN; MOVPE; HEMT
Available at various institutes of the ASCR
MOVPE GaN/AlGaN HEMT nano-structures
GaN/AlGaN-based high electron mobility transistors (HEMTs) attain better performance than their state-of-the-art full silicon-based counterparts do, offering higher power, higher frequency as well as ...
New binary refractory metal-Fe intermetallic compounds for hard magnet applications
Tchaplianka, Maxim; Shick, Alexander
2019 - English
We investigate theoretically the electronic and magnetic structure of Fe2Hf. The density functional theory is used to calculate the magnetic moments on individual atoms, the total and projected densities of states, and the magnetic anisotropy energy. The Fe2Hf is found to be metallic and ferrimagnetic, with the magnetic moments of Fe and Hf atoms pointing in the opposite directions. The negative magnetic anisotropy, and the “in-plane” preferential direction of the magnetization are found as a result of theoretical calculations. Our study suggests that the chemical control of the magnetic anisotropy has to be investigated in order to evaluate the potential of Fe2Hf for the permanent magnet applications.\n
Keywords:
electronic structure; magnetic anisotropy; permanent magnets
Available at various institutes of the ASCR
New binary refractory metal-Fe intermetallic compounds for hard magnet applications
We investigate theoretically the electronic and magnetic structure of Fe2Hf. The density functional theory is used to calculate the magnetic moments on individual atoms, the total and projected ...
Microstructure and mechanical properties of the potentially biodegradable ternary system Zn-Mg0. 8-Ca0.2
Pinc, Jan; Čapek, Jaroslav; Kubásek, J.; Veřtát, Petr; Hosová, K.
2019 - English
Zinc and zinc alloys exhibit suitable corrosion properties for biodegradable implants. Insufficient mechanical properties (for some applications) or low biocompatible Zn2+ concentrations can be modified by the alloying by essential elements like magnesium, calcium or strontium. The alloying elements also enhance the biocompatibility of zinc due to a decrease of Zn2+ release which could be toxic in a concentration exceeding 100 µM. In this study, the microstructure and hardness of a potentially biodegradable alloy ZnMg0.8Ca0.2 were observed in relation to different cooling rates. It was found that zinc dendrites, Mg2Zn11 (MgZn2) and CaZn13 phases occur in the material structure. The micro-hardness measurements revealed constant hardness of the particular phases, however, the macro-harness slightly decreased with the decreasing cooling rate due to changes in phase sizes and distribution.
Keywords:
biodegradable materia; zinc; microstructure; hardness; ternary system
Available at various institutes of the ASCR
Microstructure and mechanical properties of the potentially biodegradable ternary system Zn-Mg0. 8-Ca0.2
Zinc and zinc alloys exhibit suitable corrosion properties for biodegradable implants. Insufficient mechanical properties (for some applications) or low biocompatible Zn2+ concentrations can be ...
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