Search results for "ELECTRICITY"
showing 10 items of 1225 documents
Nonlinear Disorder Mapping via Three Wave Mixing in Poled Lithium Tantalate
2010
We introduce and test a simple approach for the characterization of domain distribution in bulk quadratic ferroelectric crystals, such as periodically poled Lithium Tantalate with random mark-to space ratio.
Influence of Electromechanical Fields on Dielectric Properties of PLZT−x/65/35 Ceramics (x = 6 and 7)
2011
High density and transparent PLZT−x/65/35 (x = 6 and 7) ceramics with the average grain size of 5–7 μm was obtained by two−stage hot−pressing technology. The measurements of temperature/frequency dependence of the permittivities of these ceramics under uniaxial pressure (0–100 MPa) applied parallel to the ac electric field have been carried out. It was found that uniaxial pressure significantly influences dielectric properties of these ceramics. With the increase of pressure the maximum intensity in ϵ(T) curve decreases, becomes more diffuse and shifts towards higher temperature, dielectric dispersion decreases and classical ferroelectric seems to change to relaxor one. It was concluded, th…
The Ba2LnFeNb4O15 “tetragonal tungsten bronze”: Towards RT composite multiferroics
2009
Several Niobium oxides of formula Ba2LnFeNb4O15 (Ln = La, Pr, Nd, Sm, Eu, Gd) with the Tetragonal Tungsten Bronze (TTB) structure have been synthesised by conventional solid-state methods. The Neodymium, Samarium and Europium compounds are ferroelectric with Curie temperature ranging from 320 to 440K. The Praseodymium and Gadolinium compounds behave as relaxors below 170 and 300 K respectively. The Praseodymium, Neodymium, Samarium, Europium and Gadolinium compounds exhibit magnetic hysteresis loops at room temperature originating from traces of a barium ferrite secondary phase. The presence of both ferroelectric and magnetic hysteresis loops at room temperature allows considering these mat…
Point Defects, Dielectric Relaxation and Conductivity in Ferroelectric Perovskites
2000
In all ferroelectric perovskites, intentionally introduced or “unwanted” point defects do play a role in the dielectric spectra and in the conductivity.
High-performance of PbO2 nanowire electrodes for lead-acid battery
2014
Abstract PbO2 nanowires were obtained by template electrodeposition in polycarbonate membranes and tested as positive electrode for lead-acid battery. Nanowires were grown on the same material acting as current collector that was electrodeposited too. The nanostructured electrodes were assembled in a zero-gap configuration using commercial negative plate and separator. Cell performance was tested by galvanostatic charge/discharge cycles in a 5 M H2SO4 aqueous electrolyte. PbO2 nanostructured electrodes were able to deliver at 1C rate an almost constant capacity of about 190 mAh g−1 (85% of active material utilization), close to the theoretical value (224 mAh g−1). The nanowire array provide…
SYNTHESIS AND CHARACTERIZATION OF SB-SUBSTITUTED (K0.5Na0.5)NbO3 PIEZOELECTRIC CERAMICS
2008
ABSTRACT Lead-free piezoelectric ceramics (K0.5Na0.5)(Nb1-xSbx)O3+0.5 mol.%MnO2, where x = 0 ÷ 0.10, with single phase structure and rhombohedral symmetry at room temperature were prepared by conventional ceramic technology. The optimal sintering temperatures of compositions were within 1100°–1140°C. MnO2 functions as a sintering aid and effectively improves the densification. The samples reached density from 4.26 g/cm3 for undoped (K0.5Na0.5)NbO3 to 4.40 g/cm3 for Mn/Sb5+ co-doped ceramics. The co-effects of MnO2 doping and Sb5+ substitution lead to significant improvement in dielectric and piezoelectric properties: e at the Tc increased from 6000 (KNN) to 12400 (x = 0.04), d33 = 92 ÷ 192 …
SINTERING OF LEAD-FREE (K0.5Na0.5)NbO3 BASED SOLID SOLUTION
2009
ABSTRACT In this study lead-free solid solution (K0.5Na0.5)NbO3 was prepared, structure, dielectric parameters of ceramics were investigated. The doping of sintering aids did not affect the crystallographic structure of the ceramics significantly; all ceramic samples had a single-phase perovskite structure. Added elements CdO, ZnO, MnO2, V2O5 effectively decreased the sintering temperature of KNN by 50°–80°C. All sintering aids influenced sinterability, microstructure and dielectric properties of ceramics. Dielectric constant for doped samples increased from 6000 up to 8000; Pr = 15 μC/cm2, Ec = 9 kV/cm, d33 = 110 pC/N, kp = 0.38 and Qm = 190 for MnO2 doped samples.
Thermoeletric Heusler Compounds
2015
Thermoelectric converters for power generation aim at reducing CO\(_2\) emission via the conversion of a part of the low-grade waste heat generated by engines, industrial furnaces, gas pipes, etc. to electricity. The recovery of waste heat from the exhaust of an automotive engine, in particular, is an attractive, albeit not very efficient way for reduction of fuel consumption. Thermoelectric converters with high overall efficiency convert heat directly into electricity without moving parts and, thus, not only decrease our reliance on fossil fuels but also actively counteract global warming. State-of-the-art converters are simply too inefficient to be economic, partly due to expensive elemen…
Reduction of oxygen to H2O2 at carbon felt cathode in undivided cells. Effect of the ratio between the anode and the cathode surfaces and of other op…
2019
Abstract In the last years, the electrochemical conversion of oxygen to hydrogen peroxide at carbon felt has been largely studied in order to define a new route for the production of H2O2 and to optimize the electro-Fenton process, which is based on the cathodic generation of H2O2. In particular, many studies regarding electro-Fenton process were carried out in undivided cells in order to avoid the costs of the separator and to reduce the cell potentials. Hence, in order to optimize the cathodic conversion of oxygen to H2O2 in undivided cells, the effect of many parameters linked to the anodic process were here evaluated. In particular, it was demonstrated that the performances of the proce…
Performance Enhancement of Alkaline Water Electrolyzer Using Nanostructured Electrodes Synthetized by Template Electrosynthesis
2018
The increase of power generation by renewable sources is causing problems in the management of the electricity grid. In order to favor the transition from the current energy production towards renewable energy sources, it is necessary to plan strategy to develop suitable energy storage systems. Certainly, the electrochemical hydrogen production can be considered as one of the most promising storage technologies. In this work, an innovative alkaline electrolyzer is presented from its design based on the use of nanostructured electrodes up to its implementation suggested by the results of tests simulating real operation. The nanostructured electrodes were fabricated by template electrosynthes…