56 research outputs found
Pressure-driven relaxation processes in nanocomposite ionic glass LiFeVPO
This paper presents results for systems formed in a solid glassy state after
nanocrystallization process above the glass temperature. We analyze electric
conductivity and relaxation processes after such treatment under high
temperature (HT) and high pressure (HP-HT) as well. The latter leads to ca. 8%
increase of density, two decades (100) increase of electric conductivity as
well as qualitative changes in relaxation processes. The previtreous-type
changes of the relaxation time on cooling is analyzed by the use of
critical-like and the 'critical-activated' description. Presented results
correspond well with obtained for this material and shown in ref. [8]. The
evidence for pressure evolution of the glass and crystallization temperatures,
indicating the unique possibility of maxima and crossovers is also reported
Properties of LiMnBO3 glasses and nanostructured glass-ceramics
Polycrystalline LiMnBO3 is a promising cathode material for Li-ion batteries.
In this work, we investigated the thermal, structural and electrical properties
of glassy and nanocrystallized materials having the same chemical composition.
The original glass was obtained via a standard meltquenching method. SEM and
7Li solid-state NMR indicate that it contains a mixture of two distinct glassy
phases. The results suggest that the electrical conductivity of the glass is
dominated by the ionic one. The dc conductivity of initial glass was estimated
to be in the order of 10-18 S.cm-1 at room temperature. The thermal
nanocrystallization of the glass produces a nanostructured glass-ceramics
containing MnBO3 and LiMnBO3 phases. The electric conductivity of this
glass-ceramics is increased by 6 orders of magnitude, compared to the starting
material at room temperature. Compared to other manganese and borate containing
glasses reported in the literature, the conductivity of the nanostructured
glass ceramics is higher than that of the previously reported glassy materials.
Such improved conductivity stems from the facilitated electronic transport
along the grain boundaries
Electrical conductivity in new imidazolium salts of dicarboxylic acids
Electrical conductivities of powder samples of five new imidazolium salts of aliphatic dicarboxylic acids (imidazolium malonate (1), imidazolium glutarate (2), imidazolium adipate monohydrate (3), diimidazolium suberate (4), imidazolium sebacate (5) were measured by impedance spectroscopy as a function of temperature. It was found that conductivities increase with temperature. At high temperatures, the lowest conductivity was determined for imidazolium glutarate (10 -5 S/m) and the highest -for imidazolium sebacate (10 -1 S/m). The correlation between crystal structures of the investigated salts and their ionic conductivities is discussed
Nanocząstki srebra w izotaktycznym polipropylenie. Cz. II. Modelowanie ułożenia łańcuchów polipropylenu na powierzchni nanocząstek srebra
Molecular modelling (MM) was used to explain the mechanism of formation of polymorphic form of isotactic polypropylene (iPP) at the surface of the silver nanoparticles (nAg). Geometrical optimization of iPP chains and unit cell of Ag systems was made with the use of MM+force field in vacuum. According to the results, the arrangement of methyl groups in the (110) contact plane implies a lateral packing of helices with a periodicity α ≈ 19 Å, which is a characteristic feature of the complicated packing of helices in β iPP. Partial charges calculated on the basis of the hybrid potential BLYP revealed the possibility of electrostatic interactions between hydrogens from methyl groups and silver atoms at the edge of unit cell. Analysis of the optimized iPP/Ag system confirmed that the formation of the polymorphic β iPP can be explained by the epitaxial mechanism.W celu wyjaśnienia mechanizmu tworzenia się formy β izotaktycznego polipropylenu (iPP) na powierzchni nanocząstek srebra (nAg) wykorzystano modelowanie molekularne (MM). Wykonano optymalizacje geometryczne układów iPP z nAg przy użyciu pola siłowego MM+ w próżni. Stwierdzono, że ustawienie grup metylowych w płaszczyźnie kontaktu (110) ujawnia boczne upakowanie helis z okresowością α ≈ 19 Å. Jest to cecha charakterystyczna dla upakowania helis w formie β iPP. Wyniki obliczeń ładunków cząstkowych przy użyciu potencjału hybrydowego BLYP wskazują na możliwość występowania oddziaływań elektrostatycznych między wodorami z grup metylowych łańcuchów iPP i atomami srebra leżącymi na krawędziach komórki elementarnej. Analiza optymalizowanych układów potwierdziła, że oddziaływanie atomów srebra z makrocząsteczką iPP może się przyczyniać do tworzenia polimorficznej formy β na drodze mechanizmu epitaksjalnego
The Role of Ferric(III) Oxide in Poly-(1,4-Phenylene Sulphide) Curing. EPR and X-ray Studies
Commercially available poly-(1,4-phenylene sulfide) = PPS with trade names TEDUR and RYTON contain a great amount of Fe(III) (order of 10 Fe/gram) as shown by electron spin resonance spectra. The curing of the pure and Fe-doped (0.2% FeO) PPS polymers proves that Fe(III) can be used for improvement of the PPS strength by increasing the polymer cross-linking and a decrease in the polymer crystallinity degree as shown by X-ray diffraction
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