Number of found documents: 650
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Low-temperature emissivity of thin Al2O3 layers deposited on copper substrate
Frolec, Jiří; Králík, Tomáš; Nyman, L.; Pudas, M.; Kallio, E.
2021 - English
Copper is commonly used in cryogenic systems due to its high thermal and electrical conductivity along with excellent solderability. Very low emissivity values of copper surface also reduce in cryogenic systems heat load transferred by thermal radiation. These values may be, however, enhanced by a prospective coating, deposited usually in order to prevent chemical changes on highly reactive copper surface. This paper focuses on protective layers of Al2O3 with thicknesses up to 28 nm, deposited on polished copper. We measured total hemispherical emissivity at cryogenic temperatures before and after the coating process. Contribution of Al2O3 layer to original copper emissivity increased with rising temperature of the layer and with the layer thickness. However, emissivity of the coated copper stayed below 2%, allowing usage of the coated copper in systems where low heat load by thermal radiation is needed. Preliminary tests with oxygen plasma shows that deposited layers can effectively protect the copper surface against oxidation and maintain the original thermal-radiative properties. Keywords: heat transfer; thermal radiation; cryogenics; surface finish Available at various institutes of the ASCR
Low-temperature emissivity of thin Al2O3 layers deposited on copper substrate

Copper is commonly used in cryogenic systems due to its high thermal and electrical conductivity along with excellent solderability. Very low emissivity values of copper surface also reduce in ...

Frolec, Jiří; Králík, Tomáš; Nyman, L.; Pudas, M.; Kallio, E.
Ústav přístrojové techniky, 2021

Patterning of conductive nano-layers on garnet
Chlumská, Jana; Lalinský, Ondřej; Matějka, Milan; Krátký, Stanislav; Kolařík, Vladimír
2021 - English
Synthetic crystalline materials of the garnet group are used as scintillators in scanning electron microscopy. If a thick conductive layer is applied on the garnet surface, slower electrons don't have enough energy to pass through this relatively thick conductive layer on the scintillator surface. Therefore, either thinner conductive layer or appropriate patterning of the thicker layer has to be used. Within this contribution we study the patterning process of such conductive nano-layer. Resolution of the patterning process is of high interest. Two approaches are compared: direct writing electron beam lithography and mask projection UV lithography. Keywords: Electron beam lithography; nano-patterning; yttrium aluminium garnet Available at various institutes of the ASCR
Patterning of conductive nano-layers on garnet

Synthetic crystalline materials of the garnet group are used as scintillators in scanning electron microscopy. If a thick conductive layer is applied on the garnet surface, slower electrons don't have ...

Chlumská, Jana; Lalinský, Ondřej; Matějka, Milan; Krátký, Stanislav; Kolařík, Vladimír
Ústav přístrojové techniky, 2021

A sampler of diffraction and refraction optically variable image elements
Horáček, Miroslav; Krátký, Stanislav; Matějka, Milan; Chlumská, Jana; Meluzín, Petr; Pirunčík, J.; Aubrecht, I.; Kotrlý, M.; Kolařík, Vladimír
2021 - English
Diffraction and refraction optically variable image elements are basic building blocks of planar structures for advanced security of documents and valuables. A sampler formed by an array of 36 diffraction structures binary, tertiary, quaternary and blazed gratings (period range 400 nm 20,000 nm) represents a cross-section throughout technological steps mastering, galvanic replication and embossing. Electron-beam writing technology with Gaussian beam and electron energy of 100 keV, with very small forward scattering of high energy electrons and with the possibilities to create a linear grating with the minimal period of 100 nm, was used to create the master. An important advantage of high-resolution electron-beam lithography is its substantial flexibility in combining possible planar structures with significantly different parameters, such as very dense and relatively shallow structures together with deep structures (approx. 10 microns) with precise shapes (micro-lenses or Fresnel structures). For protection of documents and valuables, interesting results are induced with planar optical structures consisting of non-periodic arrangements, which are characterized by high robustness to counterfeiting and imitation. While the origination process is available for grating period down to 100 nm, the mass replication technology appears to be a bottleneck of the entire technological process. Measurement of topology and profiles of the structures by atomic forces microscope and documenting the quality of technological process of the three steps of replication of planar optically variable elements was performed for all 36 structure types of sampler. Keywords: diffraction; refraction; e-beam writer; embossing; galvanic replication; mastering; optically variable image element; security; valuables Available at various institutes of the ASCR
A sampler of diffraction and refraction optically variable image elements

Diffraction and refraction optically variable image elements are basic building blocks of planar structures for advanced security of documents and valuables. A sampler formed by an array of 36 ...

Horáček, Miroslav; Krátký, Stanislav; Matějka, Milan; Chlumská, Jana; Meluzín, Petr; Pirunčík, J.; Aubrecht, I.; Kotrlý, M.; Kolařík, Vladimír
Ústav přístrojové techniky, 2021

Apparatus for automatic chemical etching of metallographic samples
Ambrož, Ondřej; Čermák, Jan; Mikmeková, Šárka
2021 - English
The microstructure of steels after mechanical polishing is revealed only by the application of a suitable etchant. To achieve adequate optical or electron microscope images, the specimen surface must be free of any artifacts. Chemical etching can be defined as a controlled corrosion process. The metal of the investigated material passes as cations into the etchant solution during the chemical etching reaction. Chemical etching is usually performed manually either by immersing the sample in the etchant with simultaneous stirring or by swabbing with a lint-free cloth soaked in the etchant. It is also extremely important to debug the process of removing the sample from the bath and subsequent cleaning. It is recommended to wash the sample after removal from the etchant with water (distilled or demineralized) or alcohol (ethanol, methanol, or isopropyl alcohol) and dry it properly (depending on the etchant and the etched material). The main problem with these processes is the human factor, which significantly contributes to the already limited repeatability. All operation steps must be performed by properly trained personnel in the field of occupational safety because hazardous substances are handled. A high manual dexterity is also needed. Training a new employee is a long-term process. Moreover, keeping the exact etching time can be a challenge and one second can decide success. These problems become more serious in the case of using surface sensitive analytical method, such as a low energy scanning electron microscopy, due to the high spatial resolution and extreme surface sensitivity. We have developed an apparatus for automatic etching of metallographic samples of purpose to overcome all above-mentioned difficulties. The apparatus and results of the first experiments will be presented. Keywords: metallography; chemical etching; automation; SEM; ultrasonic bath Available at various institutes of the ASCR
Apparatus for automatic chemical etching of metallographic samples

The microstructure of steels after mechanical polishing is revealed only by the application of a suitable etchant. To achieve adequate optical or electron microscope images, the specimen surface must ...

Ambrož, Ondřej; Čermák, Jan; Mikmeková, Šárka
Ústav přístrojové techniky, 2021

Thermal stability of Ti/Ni multilayer thin films
Václavík, R.; Zábranský, L.; Souček, P.; Sťahel, P.; Buršík, Jiří; Fořt, Tomáš; Buršíková, V.
2021 - English
In this work, thermal stability and mechanical properties of Ti/Ni multilayer thin films were studied. The multilayer thin films were synthesised by alternately depositing Ti and Ni layers using magnetron sputtering. The thickness of constituent layers of Ti and Ni varied from 1.7 nm to 10 nm, and one coating was deposited by simultaneous sputtering of both targets. Single crystalline silicon was used as a substrate. The effects of thermal treatment on the mechanical properties were studied using nanoindentation and discussed in relation to microstructure evaluated by X-ray diffraction. Annealing was carried out under low-pressure conditions for 2 hours in the range of 100-800 degrees C. Keywords: Ti/Ni; multilayers; magnetron sputtering; nanoindentation; annealing Available at various institutes of the ASCR
Thermal stability of Ti/Ni multilayer thin films

In this work, thermal stability and mechanical properties of Ti/Ni multilayer thin films were studied. The multilayer thin films were synthesised by alternately depositing Ti and Ni layers using ...

Václavík, R.; Zábranský, L.; Souček, P.; Sťahel, P.; Buršík, Jiří; Fořt, Tomáš; Buršíková, V.
Ústav přístrojové techniky, 2021

Artifacts and errors in EBSD mapping of retained austenite in TRIP steel
Mikmeková, Šárka; Jozefovič, Patrik; Ambrož, Ondřej
2021 - English
The present work aims to demonstrate artifacts and errors in visualization of retained austenite phase in TRIP steel by an electron back-scattered diffraction (EBSD) technique. Retained austenite phases size and shape obtained by the EBSD are directly compared with a real image of these phases acquired by means of an atomic force microscopy (AFM). The effect of the step size parameter used for the EBSD analysis on the retained austenite phase fraction and morphology is discussed in detail and quantified. Surface roughness as a barrier for the imaging of fine features situated on a specimen surface is demonstrated. Keywords: EBSD; SEM; AFM; retained austenite; TRIP steel Available at various institutes of the ASCR
Artifacts and errors in EBSD mapping of retained austenite in TRIP steel

The present work aims to demonstrate artifacts and errors in visualization of retained austenite phase in TRIP steel by an electron back-scattered diffraction (EBSD) technique. Retained austenite ...

Mikmeková, Šárka; Jozefovič, Patrik; Ambrož, Ondřej
Ústav přístrojové techniky, 2021

Adhesion of PVD Coatings on Surface of Small Arm
Joska, Z.; Rak, L.; Daniel, Josef; Horníček, J.; Tříska, V.; Nguyen, C.H.
2020 - English
This work deals with the possibility of increasing the utility properties of the functional part of the weapon by deposition of PVD coating. These coatings are widely known for their high hardness and abrasion resistance without affecting the anticorrosion properties. The experimental part evaluates the created duplex coating on the piston of the assault rifle Sa vz. 58. Duplex coating adhesion, surface morphology and coating thickness was evaluated on opto digital microscope Olympus DSX 500. The impact resistance of the coating was evaluated by dynamic impact test. The durability tests of the coatings were carried out during the training of students in the military training. The results showed the application of PVD coating significantly reduced piston head wear and increased user comfort in the form of shortening time of the cleaning and maintenance process after firing. Keywords: adhesion of PVD Coatings Available at various institutes of the ASCR
Adhesion of PVD Coatings on Surface of Small Arm

This work deals with the possibility of increasing the utility properties of the functional part of the weapon by deposition of PVD coating. These coatings are widely known for their high hardness and ...

Joska, Z.; Rak, L.; Daniel, Josef; Horníček, J.; Tříska, V.; Nguyen, C.H.
Ústav přístrojové techniky, 2020

Trip steel specimen preparation for advanced sem and EBSD
Ambrož, Ondřej; Mikmeková, Šárka; Hegrová, J.; Aoyama, T.
2020 - English
Modern scanning electron microscopy (SEM) allows observations of specimens with high surface sensitivity. The surface sensitivity is significantly affected by the accelerating voltages. With the development of the scanning electron microscopy, the requirements for the surface quality of samples increase. Metallographic methods originally intended for light microscopy become insufficient. The problem occurs especially with multiphase materials having a fine-grained structure. The investigated TRIP steel consists of a ferritic-bainitic matrix, retained austenite and martensite phases. The sizes of the smallest phases are nanometer units. The volume of residual austenite was determined by X-ray diffraction. The basic preparation of all tested samples involved conventional metallographic grinding and very fine mechanical polishing. One sample was analysed in this state. Other samples were subsequently chemically polished, electropolished and chemical-mechanically polished. The specimens were observed in the SEM using a SE and a BSE detector at low energies immediately after the preparation. An EBSD was performed in the same areas to characterize the retained austenite. Topographical imaging by special AFM, integrated into the SEM, demonstrated that the mechanical polishing results in surface deformation and residual austenite is transformed. All other methods have their specifics and for modern sensitive SEM instruments it is necessary to optimize individual procedures. Keywords: TRIP steel; metallography; SEM; EBSD; AFM Available at various institutes of the ASCR
Trip steel specimen preparation for advanced sem and EBSD

Modern scanning electron microscopy (SEM) allows observations of specimens with high surface sensitivity. The surface sensitivity is significantly affected by the accelerating voltages. With the ...

Ambrož, Ondřej; Mikmeková, Šárka; Hegrová, J.; Aoyama, T.
Ústav přístrojové techniky, 2020

Dynamic impact wear and impact resistance of W-B-C coatings
Daniel, Josef; Grossman, Jan; Buršíková, V.; Zábranský, L.; Souček, P.; Mirzaei, S.; Vašina, P.
2020 - English
Coated components used in industry are often exposed to repetitive dynamic impact load. The dynamic impact test is a suitable method for the study of thin protective coatings under such conditions. Aim of this paper is to describe the method of dynamic impact testing and the novel concepts of evaluation of the impact test results, such as the impact resistance and the impact deformation rate. All of the presented results were obtained by testing two W-B-C coatings with different C/W ratio. Different impact test results are discussed with respect to the coatings microstructure, the chemical and phase composition, and the mechanical properties. It is shown that coating adhesion to the HSS substrate played a crucial role in the coatings. Keywords: boron carbide W-B-C; fracture resistance; impact wear; W-B-C Available at various institutes of the ASCR
Dynamic impact wear and impact resistance of W-B-C coatings

Coated components used in industry are often exposed to repetitive dynamic impact load. The dynamic impact test is a suitable method for the study of thin protective coatings under such conditions. ...

Daniel, Josef; Grossman, Jan; Buršíková, V.; Zábranský, L.; Souček, P.; Mirzaei, S.; Vašina, P.
Ústav přístrojové techniky, 2020

Study of secondary phases in trip steel by advanced sem and afm techniques
Mikmeková, Šárka; Ambrož, Ondřej; Hegrová, J.; Aoyama, T.
2020 - English
The paper aims to demonstrate a modern scanning electron microscope (SEM) as a powerful tool for visualization of the secondary phases in TRIP steel. The TRIP steel specimens prepared by various metallographic techniques were imaged by the SEM and the secondary phases presence was confirmed by an electron back-scattered diffraction (EBSD) technique. The chemical polishing by 5 % HF in H2O2 for 10 seconds results in selective etching for each individual phase, as confirmed by an atomic force microscopy (AFM) and hybrid AFM-in-SEM techniques. The phases are easily distinguishable in the SEM micrographs created by the low energy high take-off angle signal electrons. The proposed sample preparation technique together with special SEM imaging conditions enables us accurate analysis of distribution of secondary phases within the TRIP steel matrix and moreover, the retained austenite is distinguishable from the martensite phase. Keywords: TRIP steel; advanced SEM; metallography Available at various institutes of the ASCR
Study of secondary phases in trip steel by advanced sem and afm techniques

The paper aims to demonstrate a modern scanning electron microscope (SEM) as a powerful tool for visualization of the secondary phases in TRIP steel. The TRIP steel specimens prepared by various ...

Mikmeková, Šárka; Ambrož, Ondřej; Hegrová, J.; Aoyama, T.
Ústav přístrojové techniky, 2020

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