Study of spectroscopic and thermal characterization of TeO2-Ga2O3 oxyfluoride (TGOF) glasses and glass-ceramics activated by Pr3+ ions. The role of phonons

Embedded metallic nanoparticles in semiconductors have recently been proven to be of great interest for thermoelectric applications. These metallic nanoparticles play the role of scattering centers for phonons and a source of doping for electrons; they reduce simultaneously the thermal conductivity and increase the thermoelectric power factor of the semiconductor. It has also shown that metal/semiconductor heterostructures can be used to break the crystal momentum symmetry for hot electrons in thermionic devices, then increasing the number of electrons participating in transport. A thermoelectric module of 200 N-P pairs of InGaAlAs with embedded ErAs metallic nanoparticles has been fabricated. Network Identification by Deconvolution (NID) technique is then applied for transient thermal characterization of this thermoelectric module. The combination of this new representation of the dynamic behavior of the packaged device with high resolution thin film temperature measurement allows us to obtain information about heat transfer within the thermoelectric module. This is used to extract the thermal resistances and heat capacitances of the module.

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Optical and Thermal Analysis of Secondary Optics in Light Emitting Diodes’ Packaging: Analysis of MR16 Lamp

Journal of Physics Conference Series ◽

10.1088/1742-6596/2116/1/012121 ◽

2021 ◽

Vol 2116 (1) ◽

pp. 012121

Author(s):

Mohammad Azarifar ◽

Ceren Cengiz ◽

Mehmet Arik

Keyword(s):

Heat Dissipation ◽

Light Emitting Diodes ◽

Thermal Characterization ◽

Thermal Control ◽

Light Extraction Efficiency ◽

Thickness Effect ◽

Package Design ◽

Light Emitting

Abstract Optical and thermal control are two main factors in package design process of lighting products, specifically light emitting diodes (LEDs). This research is aimed to study the role of secondary optics in opto-thermal characterization of LED packages. Novel thin total internal reflection (TIR) multifaceted reflector (MR) lens is modelled and optimized in Monte-Carlo ray-tracing simulations for MR16 package, regarded as one of the widely used LED lighting products. With criteria of designing an optical lens with 50% reduced thickness in comparison to commercially available lenses utilized in MR16 packages, nearly same light extraction efficiency and more uniform beam angles are achieved. Optical performance of the new lens is compared with the experimental results of the MR16 lamp with conventional lens. Only 2.3% reduction in maximum light intensity is obtained while lens size reduction was more than 25%. Based on the detailed CAD design, heat transfer simulations are performed comparing the lens thickness effect on heat dissipation of MR16 lamp. It was observed that using thinner lenses can reduce the lens and chip temperature, which can result in improved light quality and lifetime of both lens and light source.

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Thermal characterization of the active layer at the Limnopolar Lake CALM-S site on Byers Peninsula (Livingston Island), Antarctica

Solid Earth ◽

10.5194/se-5-721-2014 ◽

2014 ◽

Vol 5 (2) ◽

pp. 721-739 ◽

Cited By ~ 22

Author(s):

M. A. de Pablo ◽

M. Ramos ◽

A. Molina

Keyword(s):

Thermal Behavior ◽

Active Layer ◽

Thermal Characterization ◽

Active Layer Thickness ◽

Freezing And Thawing ◽

Thermal Amplitude ◽

Permafrost Table ◽

Different Depths

Abstract. The Limnopolar Lake site (A25), of the Circumpolar Active Layer Monitoring-South network (CALM-S), is located on Byers Peninsula, where the active layer thickness is monitored systematically (by mechanical probing during the thawing season and by temperature devices continuously since 2009). Air, surface, snow and ground temperature devices have been installed to monitor ground thermal behavior, which is presented and characterized here. We use the air and ground mean daily temperature values to define the following parameters: maximum, minimum and mean temperatures, the zero annual thermal amplitude, and the depth and position of the top of the permafrost table. The freezing and thawing seasons (defining their starting dates as well as their length) and the existence of zero curtain periods have also been established. We also derive apparent thermal diffusivity and plot thermograms to study the thermal behavior of the ground at different depths and seasons. After this complete thermal characterization of the active layer, we propose the potential existence of a permafrost table at approximately 130 cm in depth as well as a former transitional layer above it, and discuss the role of water in connection with the thermal behavior of the ground during the study period.

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The Protective Role of Poly(Borosiloxanes)-Derived Ceramics in Carbon Fiber Composites

Materials Science Forum ◽

10.4028/www.scientific.net/msf.587-588.182 ◽

2008 ◽

Vol 587-588 ◽

pp. 182-186 ◽

Cited By ~ 1

Author(s):

Renato Luiz Siqueira ◽

Luiz Claudio Pardini ◽

Inez Valéria Pagotto Yoshida ◽

Marco Antônio Schiavon

Keyword(s):

Carbon Fiber ◽

Carbon Fibers ◽

Thermal Protection ◽

Ceramic Matrix Composites ◽

Thermal Characterization ◽

Protective Role ◽

Carbon Fiber Composites ◽

Matrix Composites

This work reports the synthesis and thermal characterization of poly(borosiloxanes) (PBS) derived from methyltrietoxysilane (MTES) and vinyltriethoxysilane (VTES), aiming to use these polymers as precursors of ceramic matrices for the protection of carbon fibers in ceramic matrix composites (CMCs). The resulting materials exhibited better thermal stability than the carbon fiber, especially the Cfiber/SiBCO composite derived of the methyltriethoxysilane (MTES) system prepared with a B/Si ratio of 0.5. This study showed that poly(borosiloxanes) are promising materials for the oxidation protection of carbon fibers, and consequently for thermal protection systems.

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Synthesis and Characterization of Synthetic F-Mica Containing Glass-Ceramics in the System SiO2·Al2O3·B2O3·CaO·MgO·Li2O·(K,Na)2O·F

Journal of Materials Research ◽

10.1557/jmr.2004.0160 ◽

2004 ◽

Vol 19 (4) ◽

pp. 1234-1242 ◽

Cited By ~ 1

Author(s):

D.U. Tulyaganov ◽

S. Agathopoulos ◽

H.R. Fernandes ◽

J.M.F. Ferreira

Keyword(s):

Crystallization Temperature ◽

Crystallization Process ◽

Glass Ceramics ◽

Chemical Properties ◽

Synthesis And Characterization ◽

Na Ions ◽

Anions And Cations ◽

And Chemical Properties

Ions of Li, Na, K, and B were incorporated in Ca-mica, CaMg3Al2Si2O10F2. The crystallization process and the properties of the resulting glass-ceramics were experimentally determined, and the role of the anions and cations is discussed. According to the results, Li, K, and Na ions strongly affected the formation of the crystalline phases. Until 900 °C, pargasite and F-cannilloite amphiboles and KLi-mica were predominately crystallized. The two amphiboles are dissociated, yielding stable forsterite at 900 °C and Ca-mica and spinel at 950 °C. KLi-mica showed remarkable stability and growth within the investigated temperature range, until 1000 °C. The optimum crystallization temperature for the investigated glass-ceramics is between800 °C and 900 °C. The produced glass-ceramics exhibited capability for easy bulk crystallization, high whiteness, translucency, and mechanical and chemical properties suitable for several applications.

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Digital x-ray mapping of nanometer-size supported bimetallic catalysts

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100104716 ◽

1988 ◽

Vol 46 ◽

pp. 530-531

Author(s):

L. T. Germinario

Keyword(s):

Background Radiation ◽

Metal Cluster ◽

Single Element ◽

Beam Diameter ◽

X Rays ◽

X Ray ◽

Major Interest ◽

Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

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