Search results for "Thermal"
showing 10 items of 3576 documents
Steady state and transient thermal-hydraulic characterization of full-scale ITER divertor plasma facing components
2008
Abstract In the frame of the activities related to ITER divertor R&D, ENEA CR Brasimone was in charge by EFDA (European Fusion Development Agreement) to investigate the thermal-hydraulic behaviour of the full-scale divertor plasma facing components, i.e. the outer vertical target, the inner vertical target and the dome-liner, both in steady state and during draining and drying transient. The investigation was performed by means of both experimental test campaigns performed at ENEA CR Brasimone and theoretical simulation developed in RELAP5 Mod.3.3 environment at the Department of Nuclear Engineering of the University of Palermo (DIN). This paper presents the achieved experimental results fo…
On the theoretical–numerical study of the ITER Upper Port Plug structure hydraulic behaviour under steady state and draining and drying transient con…
2011
Abstract The ITER diagnostic Upper Port Plug (UPP) is a water-cooled stainless steel structure aimed to integrate within vacuum vessel the plasma diagnostic systems, shielding them from neutron and photon irradiation. Due to the very intense heat loads expected, a proper cooling circuit has been designed to ensure an adequate UPP cooling with an acceptable thermal rise and an unduly high pumping power and to perform its draining and drying procedure by injection of pressurized nitrogen. A theoretical research activity has been launched at the Department of Nuclear Engineering of the University of Palermo aiming to investigate the hydraulic behaviour of the UPP Trapezoid Section cooling circ…
Strain-dependent electrical resistance of epoxy/MWCNT composite after hydrothermal aging
2015
Abstract The electrical resistance of epoxy/multi-wall carbon nanotube (MWCNT) composites was studied under the effect of hygro- and hydrothermal aging. Tensile tests were conducted and the responses in the electrical resistance were measured during the tests for samples with different prehistory of environmental exposure. The overall pattern of the electrical resistance change versus strain for the samples tested consists of linear and nonlinear regions with a broad peak that precedes the ultimate strength of the sample and occurs at the onset of evident plastic deformation in the stress–strain curve. The composite with lower content of MWCNTs exhibits a more pronounced nonlinear behavior …
Thermodiffusion of sodium polystyrene sulfonate in a supporting electrolyte
2019
Thermodiffusion, or the Soret phenomenon, is well understood in simple systems, but in multicomponent and polyvalent electrolyte systems the process becomes more complicated due to the coupling of fluxes. We experimentally investigate the time evolution of a concentration gradient generated by thermodiffusion of a polyelectrolyte (poly(sodium 4-styrene sulfonate), NaPSS) in a 1:1 supporting electrolyte. We also derive and solve the transport equations that are used to extract the Soret coefficient from the experimental observations. It is shown that NaPSS thermodiffusion in NaCl is strongly dependent on concentration, with almost 100% thermal separation in concentrations below 15 nmol L−1. …
Low temperature synthesis of monodisperse nanoscaled ZrO2with a large specific surface area
2012
Thermal decomposition of Zr(C(2)O(4))(2)·4H(2)O within an autoclave or in a conventional tube furnace at temperatures below 380 °C resulted in nano- and micron-sized ZrO(2), respectively. Reactions under autogenic pressure yielded monodisperse monoclinic (m) and tetragonal (t) ZrO(2) nanoparticles with an average diameter of ~8 nm and interconnected t-ZrO(2) nanoparticles with diameters of ~4 nm, depending on the synthesis temperature. Samples were characterised by X-ray diffraction (XRD), small angle X-ray scattering (SAXS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) associated with energy dispersive X-ray spectroscopy (EDS), Raman microspectroscopy and phot…
Morphological Control of Hydrothermal Ni(OH)2 in the Presence of Polymers and Surfactants: Nanocrystals, Mesocrystals, and Superstructures
2008
International audience; Polymers with different hydrophilic groups [polyvinylpyrrolidone (PVP), ammonium polyacrylate (APA), and hydroxypropylmethyl cellulose (HPMC)] and surfactants [cetyltrimethylammonium bromide (CTAB) and sodium dodecylbenzensulfonate (SDBS)] were used as additives to modify the crystallization of β-Ni(OH)2 in hydrothermal conditions. Marked morphological changes in the β-Ni(OH)2 particles were observed depending on the additive concentration and on the duration of the hydrothermal treatment. The final morphology is the result of a complex, time-dependent self-assembly and growth process. Well-defined particles with sizes from submicrometer range to a few micrometers co…
Room temperature vacuum-deposition of CsPbI2Br perovskite films from multiple-sources and mixed halide precursors
2020
Fully inorganic cesium lead halide perovskites, such as CsPbI2Br, show enhanced thermal stability compared to hybrid ones and are being widely investigated as wide bandgap absorbers for tandem applications. Despite their simple stoichiometry, the preparation of highly crystalline and stable cesium lead halide thin films is not trivial. In general, high-efficiency solar cells based on solution-processed CsPbI2Br thin films are prepared by hightemperature annealing or the use of chemical additives. In this work, we use solvent-free synthesis to investigate the formation of CsPbI2Br in bulk or in thin films via mechanochemical synthesis and multiple-source vacuum deposition, respectively. We d…
Highly Efficient Thermally Co-evaporated Perovskite Solar Cells and Mini-modules
2020
The rapid improvement in the power conversion efficiency (PCE) of perovskite solar cells (PSCs) has prompted interest in bringing the technology toward commercialization. Capitalizing on existing industrial processes facilitates the transition from laboratory to production lines. In this work, we prove the scalability of thermally co-evaporated MAPbI3 layers in PSCs and mini-modules. With a combined strategy of active layer engineering, interfacial optimization, surface treatments, and light management, we demonstrate PSCs (0.16 cm2 active area) and mini-modules (21 cm2 active area) achieving record PCEs of 20.28% and 18.13%, respectively. Un-encapsulated PSCs retained ∼90% of their initial…
FORMATION OF FRACTAL MICRO- AND NANO-STRUCTURES IN CERAMIC TANTALUM PENTOXIDE UNDER CONCENTRATED FLUX OF LIGHT AND THEIR EFFECT ON THERMAL EXPANSION
2009
ABSTRACT Oxides of weak thermal expansion are the basis for stable ceramics and artefacts resistant to sharp cyclic variations of temperature. For technical applications is a wide interest in high-temperature materials of low or negative thermal expansion and, particularly, in studies of the micromechanisms in Ta2O5. Thermal expansion of ceramic pentoxides of tantalum is affected by conditions under which they are formed. After treatment by concentrated light flows anomalous segments of zero and even negative thermal expansion appear in ceramics of Ta2O5. The effect of treatment by concentrated light flux on formation of fractal nano-structures and thermal expansion of ceramic tantalum pent…
Unstable behaviour of normally-off GaN E-HEMT under short-circuit
2018
The short-circuit capability of power switching devices plays an important role in fault detection and the protection of power circuits. In this work, an experimental study on the short-circuit (SC) capability of commercial 600 V Gallium Nitride enhancement-mode high-electron-mobility transistors (E-HEMT) is presented. A different failure mechanism has been identified for commercial p-doped GaN gate (p-GaN) HEMT and metal-insulator-semiconductor (MIS) HEMT. In addition to the well known thermal breakdown, a premature breakdown is shown on both GaN HEMTs, triggered by hot electron trapping at the surface, which demonstrates that current commercial GaN HEMTs has requirements for improving the…