Search results for "conductivity"
showing 10 items of 1988 documents
Mechanical, thermal and electrical properties of monolayer and bilayer graded Al/SiC/rice husk ash (RHA) composite
2017
Abstract The mechanical, electrical and thermal properties as well as thermal expansion of Al/SiC/RHA (rice husk ash) monolayer and bilayer composite have been studied using the Taguchi method and analysis of variance (ANOVA). The parameter that most significantly affects the modulus of elasticity of Al/SiC/RHA bilayer composites is processing time, with contribution percentages of 68 and 27% calculated from stress-strain graphs and ultrasonic method, respectively. However, the factor which mostly affects bending strength, CTE value and electrical resistivity of composites is process temperature with contribution percentages of 32, 28, and 22%, respectively. The projected values for modulus…
Bilayer graded Al/B4C/rice husk ash composite: Wettability behavior, thermo-mechanical, and electrical properties
2018
In this study, wettability behavior of B4C substrate as well as B4C/crystalline rice husk ash and B4C/amorphous rice husk ash substrates with two aluminum alloys were studied. The electrical resistivity, thermal expansion coefficients, and thermal diffusivity of bilayer Al/B4C/rice husk ash composite fabricated by one-step pressureless infiltration were measured and the obtained data were systemically analyzed using the Taguchi method and analysis of variance. Boron carbide substrates after addition of amorphous or crystalline rice husk ash display good wettability with molten aluminum alloys. The results show that, electrical resistivity of Al/B4C/rice husk ash composites is mainly influe…
Modeling of ITER TF cooling system through 2D thermal analyses and enthalpy balance
2017
Abstract The winding pack of the ITER Toroidal Field (TF) coils is composed of 134 turns of Nb3Sn Cable in Conduit Conductor (CICCs) wound in 7 double pancakes and cooled by supercritical helium (He) at cryogenic temperature. The cooling of the Stainless Steel (SS) case supporting the winding pack is guaranteed by He circulation in 74 parallel channels. A 2D approach to compute the temperature distribution in the ITER TF winding pack is here proposed. The TF is divided in 32 poloidal segments, for each segment the corresponding 2D model is built and a thermal analysis is performed applying the corresponding nuclear heating computed with MCNP code considering the latest design updates, such …
Physicochemical processes in blanket ceramic materials
2003
Abstract Effect of external magnetic field (MF) on important physicochemical processes in ceramic blanket materials, the Li4SiO4 (FZK) and Li2TiO3 (CEA) ceramic pebbles, was studied. Stoichiometric amounts of the radiation-induced defects (RD) of the electron and hole type form at radiolysis of the ceramic materials. Colloid lithium forms only in Li4SiO4 under irradiation at the temperature 423–473 K and the dose 10–20 MGy. The magnetic field increases the radiolysis efficiency by 20–25% in both materials. The efficiency of formation of RD decreases with the increasing temperature of irradiation. Complete recombination of RD takes place at 873 K. The magnetic field retards the tritium relea…
Thermal and elastic properties of poly(vinyl chloride) (PVC) + chlorinated polyethylene (CPE) blends
2003
Eight types of PVC + CPE blends with different weight ratios (PVC/CPE = 100/0, 90/10, 80/20, 60/40, 40/60, 20/80, 10/90, and 0/100) are tested. Data on the heat conductivity, thermal diffusivity, and heat capacity of the blends investigated are reported. Primary attention is paid to the structural approach for effective elastic constants: bulk, shear, and Young's modulae. The blends are considered as random mixtures of two isotropic constituents. It is found that the elastic moduli may be well represented by the Kerner and Budiansky equations.
Measurement of the surface resistivity and electrical conductivity of carbon nanotube sheets using the resonant post-method
2016
Abstract The dielectric post-resonant measurement method is extended to characterize the conduction properties of carbon nanotube sheets in the GHz frequency range ( 3 GHz f 20 GHz ) without the need for external contacts or the necessity of carbon coating. Three low-loss reference dielectrics ( TiO 2 , BaTi 4 O 9 , Teflon) with known dielectric properties are used. Conductivity values of various metals (steel, lead, brass, aluminium, copper) of the order 106–107 S/m were measured to show the suitability of the method. The electrical conductivity of the carbon nanotube sheets could be determined to approximately 1.7·105 S/m.
Non-equilibrium melting of colloidal crystals in confinement
2009
International audience; We report on a novel and flexible experiment to investigate the non-equilibrium melting behaviour of model crystals made from charged colloidal spheres. In a slit geometry polycrystalline material formed in a low salt region is driven by hydrostatic pressure up an evolving gradient in salt concentration and melts at large salt concentration. Depending on particle and initial salt concentration, driving velocity and the local salt concentration complex morphologic evolution is observed. Crystal-melt interface positions and the melting velocity are obtained quantitatively from time resolved Bragg- and polarization microscopic measurements. A simple theoretical model pr…
Hydrothermal synthesis of nanostructured zirconia materials: Present state and future prospects
2005
Abstract Hydrothermal procedures for the synthesis of zirconia-doped nanocrystalline powders show important advantages from the thermodynamic and kinetic point of view (larger domain stability of solid species, faster kinetics crystallisation) as well as from technological point of view (one-step synthesis process at low temperatures, better control of the crystallisation and grain sizes with possibilities to obtain nanocrystalline materials, versatility, environmental friendly technology). Establishment of the conditions for obtaining ZrO2-doped with different oxides is based on thermodynamic predictions. Kinetic modelling of the hydrothermal synthesis of zirconia nanopowders is presented.…
Precursor-based synthetic pathways to nanometer NdNiO3−x particles
1993
Abstract The oxygen deficient neodymium nickel perovskite, NdNiO3−x, has been obtained by different low temperature-low oxygen pressure synthetic procedures. Besides a solid-matrix based route, both ordered and disordered chemical-precursors have been used as starting products. X-ray powder diffraction shows that the structure of this defective perovskite is orthorhombic. The study of the grain morphology of the products as resulting from the different synthetic procedures indicates that the main parameter determining the average particle size, which is in the nanometer range, is the maximum temperature achieved in the synthesis. Resistivity and DSC measurements show the existence of a meta…
Tetrathiotetracene thin film morphology and electrical properties
2015
The electrical properties of organic thin films are determined by their chemical constituents and the morphology of the films deposited. In this paper the morphology of vacuum sublimed (7?10-6 mbar) tetrathiotetracene (TTT) thin films is shown to be strongly affected by the thermal deposition temperature (222-350 K) and rate of deposition. Mostly needle-like morphologies are identified by scanning electron microscopy. Optimal TTT purity (a pre-requisite for device preparation via subsequent oxidation) is evidenced by their initially low electrical conductivity. Altering the TTT morphology, by variation of the evaporation parameters, strongly affects this base electrical conductivity. Four p…