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Excimer Laser-Induced CVD of Carbon Encapsulated Cobalt Nanoparticles
Fajgar, Radek ; Maryško, Miroslav ; Dřínek, Vladislav ; Kupčík, Jaroslav ; Šubrt, Jan
Decomposition of acetylene / Co(CO)(3)(NO)mixtures induced by excimer ArF laser pulses is an efficient technique for preparation of amorphous cobalt nanoparticles encapsulated in carbon. Vacuum heating up to 900 degrees C leads to crystallization the metal core. The cobalt core crystallizes in a face-centered cubic (beta) form as revealed by X-ray and electron diffraction techniques and carbon affords graphite outer part. Properties of the Co(core) - carbon(shell)nanocomposites were examined by spectroscopy and microscopy techniques. Magnetization studies revealed paramagnetic behavior of the as-prepared amorphous deposit and superparamagnetic behavior of the annealed samples.
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Datování jeskynních sedimentů a rekonstrukce krasové morfologie Nízkých Tater
Kadlec, Jaroslav ; Danišík, M. ; Hercman, H. ; Pruner, Petr ; Chadima, Martin ; Schnabl, Petr ; Šlechta, Stanislav ; Grygar, Tomáš ; Granger, D.
Paleomagnetická polarita byla zjišťována u klastických a chemogenních jeskynních sedimentů v jedenácti horizontálních úrovních v rozdílných nadmořských výškách v Jánské, demänovské jeskyni a jeskyni mošica v Nízkých Tatrách. Zjištěná polarita odpovídá sedimentaci v jeskyních v průběhu epoch Brunhes, Matuyma a Gauss. Další jeskynní systém se vytvářel ve vyšších nadmořských výškách v Nízkých Tatrách. Předběžná data ukazují převážně inverzní paleomagnetickou polaritu, tudíž předpokládáme ukládání klastických sedimentů během Gilbertovy epochy.
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Preparation and properties of nanocomposites based on Zr-Fe
Roupcová, Pavla ; Schneeweiss, Oldřich ; Bezdička, Petr
The spark erosion of the pure Zr and Fe electrodes in hydrogen yielded nanocrystalline powder consisting of the mixture of Zr-rich (Zr3FeH7, ZrO2, and Zr(Fe)) and Fe-rich phases with the mean chemical composition Zr-3.2wt.%Fe. Heat treatment in hydrogen atmosphere at 973K induced phase decomposition and transitions with the final composition of bcc Fe, Zr3Fe, ZrH2 and dominating ZrO2 phases. The result indicates that formation of Fe-rich phase (bcc Fe) embedded in ZrO2 could be possible using an appropriate heat treatment of the as-prepared powder.
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Preparation and properties of MgO-Ni(Fe) nanocrystalline composite
Schneeweiss, Oldřich ; Pizúrová, Naděžda ; Jirásková, Yvonna ; Žák, Tomáš ; Bezdička, Petr ; Večerníková, Eva
We have prepared MgO-Ni(Fe) nanocrystalline composites by controlled heat treatment of compacted spark synthesized nanocrystalline powders. Besides particle sizes and their chemical compositions, influence of interaction with surrounding atmosphere and adsorbed gases on phase composition and magnetic properties were investigated. Mössbauer spectroscopy, x-ray diffraction and TEM were used for phase analysis. Thermomagnetic curves and DTA/TG measurements were applied for detection of changes in structure and phase composition during heat treatments. The simultaneous gas analysis using mass spectroscopy by heating yielded information on adsorbed and dissolved gases and their reactions with the nanoparticles.
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