38 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
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
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
Microestrutura, fases cristalinas e propriedades elétricas de porcelanas aluminosas contendo diferentes concentrações de Fe2O3sinterizadas em atmosfera redutora e oxidante
Crystallinity of polyamide-6 matrix in glass fibre/polyamide-6 composites manufactured from hybrid yarns
Composites of Polypropylene with Cellulose Fibres. 1. Influence of Conditions of Extrusion and Injection Processes on the Structure of the Polypropylene Matrix
Novel High-Pressure Nanocomposites for Cathode Materials in Sodium Batteries
A new nanocomposite material was prepared by high pressure processing of starting glass of nominal composition NaFePO4. Thermal, structural, electrical and dielectric properties of the prepared samples were studied by differential thermal analysis (DTA), X-ray diffraction (XRD) and broadband dielectric spectroscopy (BDS). It was demonstrated that high-pressure–high-temperature treatment (HPHT) led to an increase in the electrical conductivity of the initial glasses by two orders of magnitude. It was also shown that the observed effect was stronger than for the lithium analogue of this material studied by us earlier. The observed enhancement of conductivity was explained by Mott’s theory of electron hopping, which is more frequent in samples after pressure treatment. The final composite consisted of nanocrystalline NASICON (sodium (Na) Super Ionic CONductor) and alluaudite phases, which are electrochemically active in potential cathode materials for Na batteries. Average dimensions of crystallites estimated from XRD studies were between 40 and 90 nm, depending on the phase. Some new aspects of local dielectric relaxations in studied materials were also discussed. It was shown that a combination of high pressures and BDS method is a powerful method to study relaxation processes and molecular movements in solids. It was also pointed out that high-pressure cathode materials may exhibit higher volumetric capacities compared with commercially used cathodes with carbon additions
Nanocrystallization of BiO based system from the glassy state under high compression
This report presents the pressure-temperature (p-T) plane of BiO-AlO-SiO ternary system in the context of nanocrystallite formation from its amorphous state. The diagram was constructed through differential thermal analysis (DTA) performed in situ under high-pressure-high-temperature (HP-HT) conditions, with nitrogen serving as the pressurizing medium. Above the glass transition temperature T, a wide ultraviscous, supercooled liquid state spanning approximately 150 K is observed. Later heating transforms this state into nanocrystallites embedded within an amorphous matrix, thereby keeping distinctive structural characteristics even after the decompression process. The p-T plane serves as a fundamental prerequisite for the design of nanocrystallites within a glass matrix, a well-established technique known as glass-ceramics. Various paths within the p-T plane, followed by annealing just below T, can be explored, potentially leading to the development of BiO-based materials with enhanced electrical, dielectric, photonic, and mechanical properties, predicated on nanocrystallites formed by high-pressure treatment