Search results for "thermal [Radiation mechanisms]"
showing 10 items of 2571 documents
Electrical and thermomechanical properties of CVI- Si3N4 porous rice husk ash infiltrated by Al-Mg-Si alloys
2017
Abstract The effect of following processing parameters on the electrical and thermomechanical properties of Al/Si3N4 deposited silica composites was investigated using the Taguchi method and analysis of variance (ANOVA): infiltration temperature and time, atmosphere, effect of Si3N4 coating, porosity content in the preforms, and magnesium content in the alloy. The contributions of each of the parameters to modulus of elasticity, electrical resistivity, coefficient of thermal expansion (CTE), and thermal diffusivity of the resulting composites were determined. The maximum modulus of elasticity and electrical resistivity of obtained composites were 265 GPa, and 1.37 × 10−3 Ω m, respectively. …
Properties of Nanosized Ferrite Powders and Sintered Materials Prepared by the Co-Precipitation Technology, Combined with the Spray-Drying Method
2016
Cobalt and nickel ferrites powders are synthesized by the co-precipitation technology, combined with the spray-drying method. The crystallite size, specific surface area (SSA), magnetic properties of synthesized products are investigated. All the synthesized ferrites are nanocrystalline single phase materials with crystallite size of 5-6 nm, the SSA of 80-85 m2/g and the calculated particle size of 13-15 nm. After spray-drying granules of the size up to 10 μm are obtained. After thermal treatment at 550 and 950 °C SSA decreases to 40-50 m2/g and 20-22 m2/g, respectively. The saturation magnetization at these temperatures increase from 17 to 40 emu/g for NiFe2O4 and from 51 to 77 emu/g for C…
Microstructure and electric properties of low-pressure plasma sprayed β-FeSi 2 based coatings
2017
Abstract Thermoelectric material β-FeSi 2 based coating was fabricated by the technique low-pressure plasma spray (LPPS) on the Al 2 O 3 substrate from different alloy powders. During the process LPPS, the phase transformation had occurred through the peritectoid, eutectoid reaction and their inverse reaction. The grain size of the as-sprayed β-FeSi 2 doped Co coatings was reduced comparing with the original feedstock powders, which implied the thermal conductivity could effectively decreased by the LPPS process. The room temperature electrical conductivity showed metal and semiconductor properties on the as-sprayed and annealed coatings. This method and the results could solve the problems…
Long-term moisture absorption and durability of FRP pultruded rebars
2021
Abstract Up to 15-years long moisture diffusion into carbon, glass, and aramid fiber reinforced plastic (FRP) rebars is studied. To eliminate uncertainties in identification of the radial and axial diffusivities, a successive methodology for determination of the diffusion coefficients is proposed. The concept of apparent diffusivity taking into account anisotropy and edge effects is extended to cylindrical samples. The ratio of the axial and radial diffusivities is the lowest for carbon (3) and the highest for glass (81) FRP rebars. Durability performance of the rebars is estimated by monitoring their interlaminar shear strength (ILSS). Long-term exposure of FRP rebars in a humid environmen…
Deposition of hollow sphere In2O3 coatings by liquid flame spray
2019
Hollow sphere In(OH)3 coatings were deposited by a simple liquid flame spray with hollow sphere In(OH)3 suspension, which was synthesized by improved soft template methods. The morphology of the In...
Optimization of a laser ion source for $^{163}$Ho isotope separation
2019
To measure the mass of the electron neutrino, the “Electron Capture in Holmium-163” (ECHo) collaboration aims at calorimetrically measuring the spectrum following electron capture in 163Ho. The success of the ECHo experiment depends critically on the radiochemical purity of the 163Ho sample, which is ion-implanted into the calorimeters. For this, a 30 kV high transmission magnetic mass separator equipped with a resonance ionization laser ion source is used. To meet the ECHo requirements, the ion source unit was optimized with respect to its thermal characteristics and material composition by means of the finite element method thermal-electric calculations and chemical equilibrium simulation…
Continuous hydrothermal synthesis in supercritical conditions as a novel process for the elaboration of Y-doped BaZrO3
2021
Abstract The present work describes a novel process for the elaboration of a ceramic material. Y-doped barium zirconate, an electrolyte material for Protonic Ceramic Fuel cell, was synthesized by a continuous hydrothermal process in supercritical conditions (410 °C/30.0 MPa) using nitrate precursors and NaOH reactants. The use of supercritical water allowed the formation of particles of about 50 nm in diameter with a narrow size distribution. X-Ray Diffraction examination revealed that a major perovskite phase with few BaCO3 and YO(OH) impurities was obtained. BaCO3 is assumed to form due to faster kinetics than Y-doped BaZrO3 resulting in a Ba-deficient perovskite phase. The Ba-deficiency …
Effect of process parameters and crystal orientation on 3D anisotropic stress during CZ and FZ growth of silicon
2017
Abstract Simulations of 3D anisotropic stress are carried out in and oriented Si crystals grown by FZ and CZ processes for different diameters, growth rates and process stages. Temperature dependent elastic constants and thermal expansion coefficients are used in the FE simulations. The von Mises stress at the triple point line is ~5–11% higher in crystals compared to crystals. The process parameters have a larger effect on the von Mises stress than the crystal orientation. Generally, the crystal has a higher azimuthal variation of stress along the triple point line (~8%) than the crystal (~2%). The presence of a crystal ridge increases the stress beside the ridge and decreases it on the ri…
Thermal stability of magnetic characteristics of Co/Ag/Fe and Co/Ag/Fe20Ni80 spin-valve structures
2017
Abstract We investigated the thermal stability of magnetic characteristics of Co/Ag/Fe and Co/Ag/Fe 20 Ni 80 spin-valve structures. Thin film systems were obtained with the help of sputtering method. For the first type of systems two particular thicknesses ( d ML = 3 and 20 nm) and different disposition of magnetic layers (ML) were used. For the second type different thickness of Ag ( d NML ) spacer layer was used. The research of the crystal structure was performed with the transmission electron microscope. The results demonstrate that every investigated as-deposited sample does not include solid solutions, intermetallic compounds or impurities. It has been found that among the spin-valve…
Gel combustion synthesis and magnetic properties of CoFe2O4, ZnFe2O4, and MgFe2O4 using 6-aminohexanoic acid as a new fuel
2020
Abstract For the first time, 6-aminohexanoic acid is used as an alternative fuel in the synthesis of the spinel ferrites with compositions CoFe2O4, ZnFe2O4 and MgFe2O4 using gel combustion synthesis with different oxidizer-to-fuel (O/F) ratios. The gel precursors were studied by differential thermal analysis and thermogravimetry (DTA/TG), which showed that the ignition temperature depends on the gel precursor, being around 230 °C, 130 °C and 275 °C for CoFe2O4, ZnFe2O4, and MgFe2O4, respectively. These results showed than the 6-aminohexanoic acid has an ignition temperature lower than the urea and the citric acid when were used in the synthesis of the spinel ferrites by gel combustion. More…