Number of found documents: 554
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Nanostructured layer enhancing light extraction from GaN-based scintillator using MOVPE
Vaněk, Tomáš; Hubáček, Tomáš; Hájek, František; Dominec, Filip; Pangrác, Jiří; Kuldová, Karla; Oswald, Jiří; Hospodková, Alice
2021 - English
Light extraction (LE) efficiency of GaN buffer layer was studied by angle-resolved photoluminescence. We measured enhancement of light extraction efficiency (LEE) up to 154% by introducing the SiNx layer atop the GaN buffer and subsequent GaN light extraction layer (LEL) overgrowth. Morphological properties of GaN. Keywords: MOVPE; GaN; light extraction; SiNx; scintillator Available at various institutes of the ASCR
Nanostructured layer enhancing light extraction from GaN-based scintillator using MOVPE

Light extraction (LE) efficiency of GaN buffer layer was studied by angle-resolved photoluminescence. We measured enhancement of light extraction efficiency (LEE) up to 154% by introducing the SiNx ...

Vaněk, Tomáš; Hubáček, Tomáš; Hájek, František; Dominec, Filip; Pangrác, Jiří; Kuldová, Karla; Oswald, Jiří; Hospodková, Alice
Fyzikální ústav, 2021

Nanopowders of R.sub.2./sub.Fe.sub.14./sub.B-type compounds in high magnetic fields: The effects of substitutional and interstitial atoms on inter-sublattice exchange interaction
Paukov, M.; Ivanov, L.; Tereshina, I.; Tereshina-Chitrova, Evgenia; Gorbunov, D.; Andreev, A. V.; Pyatakov, A.P.; Granovsky, S.A.; Doerr, M.; Drulis, H.
2020 - English
The fundamental magnetic characteristics of R2Fe14B intermetallics are highly sensitive to atomic substitutions and interstitial absorption of light elements. In this work, both were combined, and the influence of the substitutions in the R-sublattice and hydrogen absorption on the magnetization of (RR’) 2Fe14BHx (R is Tm or Er, and R’ is Nd) in magnetic fields up to 58 T was studied. By using direct hydrogen absorption, (R0.5Nd0.5)2Fe14BHx compounds were obtained with hydrogen content 0≤x≤5.5. Magnetic measurements were carried out on nanopowders. The strength of the inter-sublattice coupling in (R0.5Nd0.5)2Fe14B and their hydrides is estimated by analysing high-field magnetization data. It is shown that hydrogenation weakens the inter-sublattice exchange interaction up to 45 %. Keywords: rare earth; intermetallics; powder metallurgy; magnetism in solids; hydride properties Available at various institutes of the ASCR
Nanopowders of R.sub.2./sub.Fe.sub.14./sub.B-type compounds in high magnetic fields: The effects of substitutional and interstitial atoms on inter-sublattice exchange interaction

The fundamental magnetic characteristics of R2Fe14B intermetallics are highly sensitive to atomic substitutions and interstitial absorption of light elements. In this work, both were combined, and the ...

Paukov, M.; Ivanov, L.; Tereshina, I.; Tereshina-Chitrova, Evgenia; Gorbunov, D.; Andreev, A. V.; Pyatakov, A.P.; Granovsky, S.A.; Doerr, M.; Drulis, H.
Fyzikální ústav, 2020

CrystalCMP: examples of use
Rohlíček, Jan
2020 - English
The program CrystalCMP can be used for comparison of crystal structures containing separated molecular objects as it is, for instance, in molecular crystals or some metal-organic compounds. The program can be useful in many different situations. This article shows the use of the program CrystalCMP on three basic exam ples for which the program was primarily intended. Keywords: molecular packing; comparison; similarity Available at various institutes of the ASCR
CrystalCMP: examples of use

The program CrystalCMP can be used for comparison of crystal structures containing separated molecular objects as it is, for instance, in molecular crystals or some metal-organic compounds. The ...

Rohlíček, Jan
Fyzikální ústav, 2020

Nanosecond laser damage of metallic mirrors
Muresan, Mihai-George; Pilná, Kateřina; Čech, Pavel; Mydlář, Martin; Vanda, Jan; Navrátil, Petr
2020 - English
Laser surface processing is an established method to introduce surface functionalities on solid surfaces with the required throughputs for a commercial process. Fabrication of laser induced surface structures in an effective matter is done by laser interaction studies, which reveal the best processing parameters (laser wavelength, fluence, repetition, together with the processing speed and environment). Customized solutions are providing the best yields and they are being implemented faster than ever. However, the optics manufacturers are not being to keep up the pace with the new requirements, so they turn instead on older, but safer technology. In order to get a better understanding of optics capabilities, thorough testing is required. Common laser metallic mirrors, commercially available, are being rigorously tested using a nanosecond Yb:YAG laser and the results are compared with the vendor’s information.\n Keywords: laser patterning; metallic mirrors; LIDT; nanosecond laser testing Available at various institutes of the ASCR
Nanosecond laser damage of metallic mirrors

Laser surface processing is an established method to introduce surface functionalities on solid surfaces with the required throughputs for a commercial process. Fabrication of laser induced surface ...

Muresan, Mihai-George; Pilná, Kateřina; Čech, Pavel; Mydlář, Martin; Vanda, Jan; Navrátil, Petr
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

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

Studium vlivu složení ve směsi CsCl-HfCl.sub.4./sub. na její tepelné vlastnosti v uzavřeném systému pomocí DSC analýzy
Král, Robert; Zemenová, Petra; Vaněček, Vojtěch; Bystřický, Aleš
2020 - Czech
Příspěvek se zabývá studiem tepelného chování směsi CsCl-HfCl4 o různém složení (nadbytek Cs- nebo Hf-složky) v uzavřeném systému (křemenné ampuli) pomocí neizotermní DSC analýzy. Ze získaných výsledků a jejich porovnáním s fázovým diagramem CsCl-HfCl4 bylo možné získat důležité informace potřebné k optimalizaci růstu krystalů Cs2HfCl6 vertikální Bridgmanovou metodou. This contribution deals with the study of thermal behavior of CsCl-HfCl4 mixture of various composition (containing excess of Cs- or Hf-component) in enclosed system (quartz ampoule) by non-isothermal DSC analysis. Important information necessary for optimization of the Cs2HfCl6 crystal growth by the vertical Bridgman method were obtained from the comparison of the recorded results and the CsCl-HfCl4 phase diagram. Keywords: CsCl-HfCl.sub.4./sub.; thermal properties; DSC analysis in closed system Available at various institutes of the ASCR
Studium vlivu složení ve směsi CsCl-HfCl.sub.4./sub. na její tepelné vlastnosti v uzavřeném systému pomocí DSC analýzy

Příspěvek se zabývá studiem tepelného chování směsi CsCl-HfCl4 o různém složení (nadbytek Cs- nebo Hf-složky) v uzavřeném systému (křemenné ampuli) pomocí neizotermní DSC analýzy. Ze získaných ...

Král, Robert; Zemenová, Petra; Vaněček, Vojtěch; Bystřický, Aleš
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

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

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