Magnetic nanoparticles in MCM-41 type mesoporous silica

Structural phase transformations and magnetic properties of mesoporous MCM-41 template modified with iron and nickel salts were studied by nitrogen physisorption, X-ray diffraction, Mossbauer spectroscopy and transmission electron microscopy. The FeNi-oxide or the bimetallic crystal structure is formed for low and high Ni concentrations, respectively. The average size of nanoparticles is about 10 nm. About 70% of particles exist in a superparamagnetic state at room temperature

Fifth-order susceptibility unveils growth of thermodynamic amorphous order in glass-formers

Glasses are ubiquitous in daily life and technology. However the microscopic mechanisms generating this state of matter remain subject to debate: Glasses are considered either as merely hyper-viscous liquids or as resulting from a genuine thermodynamic phase transition towards a rigid state. We show that third- and fifth-order susceptibilities provide a definite answer to this longstanding controversy. Performing the corresponding high-precision nonlinear dielectric experiments for supercooled glycerol and propylene carbonate, we find strong support for theories based upon thermodynamic amorphous order. Moreover, when lowering temperature, we find that the growing transient domains are compact - that is their fractal dimension d_f = 3. The glass transition may thus represent a class of critical phenomena different from canonical second-order phase transitions for which d_f < 3.Comment: 9 pages, 3 figure

Electrophoretic deposition of layer-by-layer unsheathed carbon nanotubes - A step towards steerable surface roughness and wettability

It is well known that carbon nanotube (CNT) oxidation (usually with concentrated HNO3) is a major step before the electrophoretic deposition (EPD). However, the recent discovery of the “onion effect” proves that multiwalled carbon nanotubes are not only oxidized, but a simultaneous unsheathing process occurs. We present the first report concerning the influence of unsheathing on the properties of the thus-formed CNT surface layer. In our study we examine how the process of gradual oxidation/unsheathing of a series of multiwalled carbon nanotubes (MWCNTs) influences the morphology of the surface formed via EPD. Taking a series of well-characterized and gradually oxidized/unsheathing Nanocyl™ MWCNTs and performing EPD on a carbon fiber surface, we analyzed the morphology and wettability of the CNT surfaces. Our results show that the water contact angle could be gradually changed in a wide range (125–163°) and the major property determining its value was the diameter of aggregates formed before the deposition process in the solvent. Based on the obtained results we determined the parameters having a crucial influence on the morphology of created layers. Our results shed new light on the deposition mechanism and enable the preparation of surfaces with steerable roughness and wettability

Surface topography of precursors Cu-Zn-Sn electrochemically deposited on Mo/glass and Mo-foil

The paper discusses the possibility of constructing thin-film solar cells based on non-toxic and abundant Cu2ZnSnSe4 components (CZTSe) obtained by electrochemical deposition on Ta-foil substrates with subsequent selenization. Foil substrates open up new possibilities for application of flexible thin-film solar cells. Atomic force microscopy and scanning electron microscopy combined with energy dispersive spectrometry of secondary electrons were employed for the investigation of thin films topography. В статье обсуждается возможность создания тонкопленочных солнечных элементов на основе нетоксичных и распространенных компонентов Cu2ZnSnSe4 (CZTSe), полученных электрохимическим осаждением на подложки из Ta-фольги с последующей селенизацией. Подложки из фольги открывают новые возможности применения гибких тонкопленочных солнечных элементов. Для исследования топографии тонких пленок использовались атомно-силовая микроскопия и сканирующая электронная микроскопия в сочетании с энергодисперсионной спектрометрией вторичных электронов

Surface topography of precursors Cu-Zn-Sn electrochemically deposited on Mo/glass and Mo-foil

The paper discusses the possibility of constructing thin-film solar cells based on non-toxic and abundant Cu2ZnSnSe4 components (CZTSe) obtained by electrochemical deposition on Ta-foil substrates with subsequent selenization. Foil substrates open up new possibilities for application of flexible thin-film solar cells. Atomic force microscopy and scanning electron microscopy combined with energy dispersive spectrometry of secondary electrons were employed for the investigation of thin films topography. В статье обсуждается возможность создания тонкопленочных солнечных элементов на основе нетоксичных и распространенных компонентов Cu2ZnSnSe4 (CZTSe), полученных электрохимическим осаждением на подложки из Ta-фольги с последующей селенизацией. Подложки из фольги открывают новые возможности применения гибких тонкопленочных солнечных элементов. Для исследования топографии тонких пленок использовались атомно-силовая микроскопия и сканирующая электронная микроскопия в сочетании с энергодисперсионной спектрометрией вторичных электронов

Determination of the 3\gamma fraction from positron annihilation in mesoporous materials for symmetry violation experiment with J-PET scanner

Various mesoporous materials were investigated to choose the best material for experiments requiring high yield of long-lived positronium. We found that the fraction of 3\gamma annihilation determined using \gamma-ray energy spectra and positron annihilation lifetime spectra (PAL) changed from 20% to 25%. The 3gamma fraction and o-Ps formation probability in the polymer XAD-4 is found to be the largest. Elemental analysis performed using scanning electron microscop (SEM) equipped with energy-dispersive X-ray spectroscop EDS show high purity of the investigated materials.Comment: 12 pages, 2 figure