Search results for "visual_art"
showing 10 items of 2987 documents
Electrical Transport in Lead-Free [(1−x)(Na0.5Bi0.5)-xBa]Zr1 - yTiyO3Ceramics (x = 0, 0.06, and y = 0, 0.96)
2009
Lead-free ceramics based on (Na 0.5 Bi 0.5 TiO 3 , NBT)-(Ba(Ti,Zr)O 3 , BTZ) were prepared by solid phase hot pressing sintering process and their ac (σ ac ) and dc (σ dc ) conductivity have been studied (303–753 K). Low frequency (100 Hz–100 kHz) ac conductivity obeys power law σ ac ∼ ω s characteristic for disordered materials. The frequency exponent s is a decreasing function of temperature and tends to zero at high temperatures. Dc conductivity has thermally activated character and possesses four linear parts with four different activation energies and some discontinous changes. However, σ ac (T) possesses two linear parts with two different activation energies and more discontinuous ch…
Dielectric and Ferroelectric Properties of Lead-Free NKN and NKN-Based Ceramics
2011
Lead-free ceramics of Na0.5K0.5NbO3 (NKN), Na0.5K0.5(Nb0.94Sb0.06)O3 (NKNS6) and Na0.5K0.5(Nb0.94Sb0.06)O3 + 0.5%MnO2 (NKNS6 + 0.5%MnO2) have been prepared by a solid phase hot pressing sintering process. X-ray diffraction results show that the obtained samples possess the perovskite structure. The micrograph of the fractured surface showed a dense structure in a good agreement with that of 91–94% relative density determined by the Archimedes method. An average grain size decreases with Sb and Mn doping (from about 20 μm for NKN to about 5 and 2 μm for NKNS6 and NKNS6 + 0.5%MnO2, respectively). Low frequency (100 Hz–200 kHz) investigations revealed the diffuse phase transitions. It was foun…
Modification of the sheet resistance under Ti/Al/Ni/Au Ohmic contacts on AlGaN/GaN heterostructures
2018
This paper reports on the modification of the sheet resistance under Ti/Al/Ni/Au Ohmic contacts on AlGaN/GaN heterostructures, studied by means of Transmission Line Model (TLM) structures, morphological and structural analyses, as well as computer simulations. In particular, the contacts exhibited an Ohmic behaviour after annealing at 800 degrees C, with a specific contact resistance rho(c) = (2.4 +/- 0.2) x 10(-5) Omega cm(2), which was associated to morphological and structural changes of both the metal layer and the interface. Interestingly, TLM analyses gave a value of the sheet resistance under the contact (R-SK = 26.1 +/- 5.0 Omega/rectangle) significantly lower than that measured out…
Processing and properties of nanocrystalline Pb(Sc0.5Ta0.5)O3, Pb(Sc0.5nb0.5)O3 and Pb(Mg1/3Nb2/3)O3 films produced by RF-sputtering from ceramic tar…
2000
Abstract Nanocrystalline thin films of different relaxor materials, namely Pb(Sc0.5Ta0.5)O3 (PST), Pb(Sc0.5Nb0.5)O3(PSN), Pb(Mg1/3Nb2/3)O3(PMN) have been produced by RF-sputtering to investigate whether it will affect their dielectric properties if their grain size is reduced to the dimensions known from their nanodomains. The XRD shows that the amorphous film crystallizes in pyrochlore structure at lower temperatures and short times. Annealing at higher temperatures and far longer time intervals leads to an increasing amount of perovskite phase with a grain size in the nanometer range. These results including dielectric measurements will be presented and discussed.
Zinc oxide nanocrystals as electron injecting building blocks for plastic light sources
2012
Hybrid inorganic–organic light emitting devices (HyLEDs) employing ZnO nanocrystals as one of their metal oxide contacts lead to very bright devices on plastic substrates with performances superior to those obtained from the rigid counterparts employing planar films of bulk ZnO. The superior performance is related to the increase in the bandgap of the ZnO nanocrystals caused by quantum confinement effects. We demonstrate that this effect diminishes with increasing annealing temperature of the ZnO nanocrystal layer due to a gradual decrease of the bandgap towards the bulk ZnO value. Therefore, best performances were obtained with room temperature processing of the ZnO nanocrystals.
Luminescence of Er/Yb and Tm/Yb doped FAp nanoparticles and ceramics
2015
The nanoparticles of hydroxiapatite and fluorapatite doped with Er/Yb and Tm/Yb were synthesized and characterized by FTIR, XRD, SEM and TEM methods. The results of up-conversion luminescence studies were presented for the samples as prepared, annealed at 500°C and at 900-1000 °C. At annealing above 800°C the ceramic state was formed. It is shown that fluorapatite host is more appropriate than hydroxiapatite host for rare ions luminescence and up-conversion processes. The post preparing annealing of nanarticles significantly enhanced the luminescence intensity. The Tm/Yb doped fluorapatite shows intense up-conversion luminescence in 790-800 nm spectral region and is potentially useful for b…
Photoemission study of the reactivity of barium towards SiOx thermal films
2011
Abstract Barium was deposited at room temperature on a thermal silicon oxide layer and the interfacial reaction was monitored by synchrotron induced photoemission (both core level and valence band). The first step of the growth consists of an interfacial reaction which leads to the formation of an interfacial silicate layer. The next step consists in formation of barium oxide while metallic barium occurs subsequently. The deposit can be also homogenized by annealing above 575 K. This results in the formation of several layers of silicate by consumption of silicon oxide. In the case of fractional coverage, subsequent annealing at 975 K induces the decomposition of barium silicate. However, s…
Electrochemical Studies of Nonstoichiometric TiO<sub>2-x</sub> Ceramic
2014
TiO2 ceramic was prepared using extrusion technology and thermal treatment in two stages: sintering in air and subsequent annealing under high vacuum conditions. Sample thermal treatment in high vacuum conditions causes formation of nonstoichiometric titanium oxide ceramic. As a result electrical conductivity of the material significantly increases. Such a material can be used for electrode production for electrochemical water treatment.
Tritium release from breeding blanket materials in high magnetic field
2007
Abstract Under the operating conditions of a fusion reactor, the blanket materials: ceramic and Be pebbles will be at a high temperature (up to 1123 K), under action of intense radiation (up to 10 19 n m −2 s −1 ) and magnetic field (MF) up to 7–10 T. In order to introduce action of radiation and MF in post-irradiation investigations of the tritium release from the blanket materials, a special rig for thermo-annealing of pre-irradiated samples at a high temperature up to 1120 K under irradiation with fast electrons of 5 MeV and dose rate 14 MGy/h in MF up to 1.7 T was used for this study. A delay of the tritium release in MF of 2.4 T at thermo-annealing of the lithium orthosilicate Li 4 S…
Au nanowire junction breakup through surface atom diffusion.
2018
Metallic nanowires are known to break into shorter fragments due to the Rayleigh instability mechanism. This process is strongly accelerated at elevated temperatures and can completely hinder the functioning of nanowire-based devices like e.g. transparent conductive and flexible coatings. At the same time, arranged gold nanodots have important applications in electrochemical sensors. In this paper we perform a series of annealing experiments of gold and silver nanowires and nanowire junctions at fixed temperatures 473, 673, 873 and 973 K (200 degrees C, 400 degrees C, 600 degrees C and 700 degrees C) during a time period of 10 min. We show that nanowires are especially prone to fragmentatio…