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Analytical electron microscopy of lead-free nanopowder solders
Buršík, Jiří ; Sopoušek, J. ; Zálešák, Jakub ; Buršíková, V.
During the last decade, the EU legislative regulations enforced lead-free solders and hence initiated an extensive search for the best replacement of lead-containing solders. Parallel to new binary and ternary bulk solders, metal nanoparticles are also considered as potential candidates for solder materials. It is known that physical, electric and thermodynamic properties of nanoobjects are significantly different from those of the bulk materials. The oxidation, high reactivity of the surfaces and aggregation are frequent problems of nanotechnology applications. The nanoparticles of pure metals and alloys exhibit the depression of the melting point compared to bulk material, hence they are able to aggregate and to form firm interlayer joints at low temperatures. Exploiting this effect can save energy, work and materials.
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ZnO NANOPARTICLES AND THEIR APPLICATIONS – NEW ACHIEVMENTS
Nohavica, Dušan ; Gladkov, Petar
The advantages of ZnO are a low price, good gas sensing properties, photocatalytic activity, antibacterial activity, possibility to prepare structures with interesting optical properties, like photonic crystals, catalytic materials etc. In our laboratory the special research type of MOCVD apparatus has been developed. In the study we have investigated the influence of the growth rate on the morphology of ZnO deposited on Si (100), GaP (111) as well as nanoporous GaP. The same apparatus has been used for ZnO nanoparticles preparation with the diameter of individual nanoparticles of about 25 nm.
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Multi-wall carbon nanotube networks prepared from pure MWCNT and their oxidised forms effect of compressive strain on electric resistence
Olejník, R. ; Slobodian, P. ; Říha, Pavel ; Kimmer, D. ; Sáha, P.
Multi-wall carbon nanotube networks were prepared by filtration of CNT aqueous dispersions. CNT dispersions were prepared with the help of surfactant system (sodium dodecyl sulfate with amylalcohol) by ultrasonication. Three types of MWCNT tubes were used. The first were pure CNT delivered by supplier. The others were oxidized CNT oxidized (1. acid solution of KMnO4; 2. the mixture of acids H2SO4 + HNO3). It was found that oxidization significantly changes properties of prepared carbon nanotube networks. There were observed differences in porous structures networks analyzed by SEM microscopy. Moreover, the apparent density of prepared MWCNT networks also changes according to the used CNT. The network electrical resistance is also affected by process of MWCNT oxidation as well as by compressive strain. It was found that the network resistance is sensitive to compressive strain both in the course of strain growth and when loading/unloading cycles are imposed.
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Fluorescent nanodiamonds: The new platform for construction of chemo- and biosensors
Cígler, Petr ; Ledvina, Miroslav ; Tvrdoňová, Monika ; Řezáčová, V. ; Nesládek, M. ; Kratochvílová, Irena ; Fendrych, František ; Štursa, Jan ; Kučka, Jan ; Ráliš, Jan
Over the past few years, fluorescent nanodiamonds (FNDs) have been recognized as potential fluorophores for use in bioimaging, owing to their unique and attractive chemical and particularly spectral properties. The source material for their preparation, synthetic nanodiamond (ND), is non-expensive and commercially available. Notably, NDs have the highest biocompatibility of all carbon nanomaterials and their surface can be chemically modified by various techniques. FNDs are capable of fluorescing with almost quantitative quantum yields from point defects of crystall lattice - nitrogen-vacancy (NV) centers. In particular, the long-wavelength emission, high brightness, no photobleaching, no photoblinking, and an exceptional resistance to chemical degradation make them almost ideal core for development of fluorescent bioimaging probes.
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