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Glass transition and crystallization of ZnO-B2O3-SiO2 glass doped with Y2O3
摘要： The effect of Y2O3 on the glass transition kinetics, crystallization kinetics, phase separation and crystallization behavior of 60ZnO–30B2O3–10SiO2 glass has been investigated by non-isothermal differential thermal analysis, scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The glass transition activation energies Eg calculated by using both Kissinger and Moynihan model decrease from 668 kJ/mol to 573 kJ/mol for Kissinger model, and 682 kJ/mol to 587 kJ/mol for Moynihan model with the increase of yttrium oxide doping content from 0 to 6 mol%. And the glass crystallization kinetics parameters, crystallization activation energy Ec and Avrami exponent n stands for crystal growth, are also obtained on the basis of several well developed equations. Increase of about 58 kJ/mol in Ec values obtained by different theoretical equations is caused by addition of 6 mol% yttrium oxide into 60ZnO–30B2O3–10SiO2 glass, and the Avrami exponent (n close to 2) suggests that crystal growth in 60ZnO–30B2O3–10SiO2 glass doped with or without yttrium is mainly one-dimensional growth of crystals. The results on the phase separation and crystallization behavior occurred at 893 K and 993 K respectively for base and doped glass, are well consistent with the glass transition and crystallization kinetics results. Hence, addition of yttrium oxide into 60ZnO–30B2O3–10SiO2 glass decrease the glass transition activation energy while increase the crystallization activation energy of glass, thereby the stability of glass structure is improved. Phase separation phenomenon and crystallization behavior occurred at glass surface provide some useful information for preparing glass ceramics with micro- or nano-crystals in surface.
关键词： Thermal properties,Y2O3,Electron microscopy,Glass
更新于2025-09-23 15:22:29
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Template Synthesis, Spectral, Thermal and Glucose Sensing of Pr3+ Complexes of Metformin Schiff-Bases
摘要： Schiff-bases of metformin with each of salicylaldehyde (HL1); 2,3-dihydroxybenzaldehyde (H2L2); 2,4-dihydroxybenzaldehyde (H2L3); 2,5-dihydroxybenzaldehyde (H2L4); 3,4-dihydroxybenzaldehyde (H2L5) and 2-hydroxynaphthaldehyde (HL6) and their complexes with Pr(III) were synthesized by template reaction. The complexes were characterized through elemental analysis, conductivity and magnetic moment measurements, IR, UV-Vis., fluorescence, GC-MS and XRD spectroscopy. The complexes exhibit a series of characteristic emission bands for Pr3+ ion in the 481-472 and 590-580 nm range with a 318-332 nm excitation source. The complexes have eight coordinated structure with the formulae [PrL1-4,6(NO3)2(H2O)3].nH2O where n = 1, 1?, 3, 4, 4 and [PrL5(NO3)(H2O)5].2H2O. The suggested stereochemistry was confirmed using TGA, DTG and DTA analysis and a mechanism for thermal decomposition was proposed. Coates-Redfern equation was used to calculate kinetic and thermodynamic parameters of the main decomposition step. The utility of the complexes towards the detection of glucose at physiologically relevant pH in phosphate buffer using UV-Vis and fluorescence spectroscopy as well as viscosity measurements are tried where the association constants were calculated.
关键词： Pr(III) complexes,Spectral and thermal properties,Glucose sensing,Metformin Schiff-bases
更新于2025-09-23 15:22:29
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[ASME ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems - San Francisco, California, USA (Monday 27 August 2018)] ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems - Analysis of Thermal Properties of Power Multifinger HEMT Devices
摘要： In this paper, several methods suitable for real time on-chip temperature measurements of power AlGaN/GaN based high-electron mobility transistor (HEMT) grown on SiC substrate are presented. The measurement of temperature distribution on HEMT surface using Raman spectroscopy is presented. We have deployed a temperature measurement approach utilizing electrical I-V characteristics of the neighboring Schottky diode under different dissipated power of the transistor heat source. These methods are verified by measurements with micro thermistors. The results show that these methods have a potential for HEMT analysis in thermal management. The features and limitations of the proposed methods are discussed. The thermal parameters of materials used in the device are extracted from temperature distribution in the structure with the support of 3-D device thermal simulation. The thermal analysis of the multifinger power HEMT is performed. The effects of the structure design and fabrication processes from semiconductor layers, metallization, and packaging up to cooling solutions are investigated. The analysis of thermal behavior can help during design and optimization of power HEMT.
关键词： thermal properties,Raman spectroscopy,thermal management,Schottky diode,power HEMT devices
更新于2025-09-23 15:21:21
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Challenges and opportunities for nanomaterials in spectral splitting for high-performance hybrid solar photovoltaic-thermal applications: A review
摘要： Hybrid photovoltaic-thermal (PV-T) collectors, which are capable of cogenerating useful thermal energy and electricity from the same aperture area, have a significantly higher overall efficiency and ability to displace emissions compared to independent, separate photovoltaic panels, solar thermal collectors or combinations thereof. Spectral splitting has emerged as a promising route towards next-generation high-performance PV-T collectors, and nanotechnology plays an important role in meeting the optical and thermal requirements of advanced spectral splitting PV-T collector designs. This paper presents a comprehensive review of spectral splitting technologies based on nanomaterials for PV-T applications. Emerging nanomaterials (nanofluids, nanofilms and nanowires) suitable for achieving spectral splitting based on reflection, diffraction, refraction and/or absorption approaches in PV-T collectors are presented, along with the associated challenges and opportunities of these design approaches. The requirements from such materials in terms of optical properties, thermal properties, stability and cost are discussed with the aim of guiding future research and innovation, and developing this technology towards practical application. Nanofluids and nanofilms are currently the most common nanomaterials used for spectral splitting, with significant progress made in recent years in the development of these materials. Nevertheless, there still remains a considerable gap between the optical properties of currently-available filters and the desired properties of ideal filters. Aiming to instruct and guide the future development of filter materials, a simple generalized method is further proposed in this paper to identify optimal filters and efficiency limits of spectral splitting PV-T systems for different scenarios. It is found that the optimal filter of a spectral splitting PV-T system is highly sensitive to the value of thermal energy relative to that of electricity, which therefore depends strongly on the application and location. The efficiency limit of spectral splitting PV-T collectors is significantly higher than that of standalone PV panels. The stability of nanomaterial filters remains a critical challenge for their long-term employment and also for high-temperature operation in practical applications.
关键词： Nanofilms,Spectral splitting,Nanomaterials,Thermal properties,Stability,Nanofluids,Optical properties,Cost,Nanowires,Hybrid photovoltaic-thermal (PV-T) collectors
更新于2025-09-23 15:21:01
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Enhanced emission of Eu3+ in lutetium tungsten molybdenum oxide phosphors: Synthesis, optical properties, thermal behavior, and LED packaging
摘要： By adjusting molar ratios of raw materials of Lu2O3 (Eu2O3) to WO3 and MoO3 as well as WO3 to MoO3, several lutetium tungsten molybdenum oxide phosphors Lu2W0?5Mo0?5O6, Lu2WxMoyO9 (x t y ? 2), Lu2W1?5Mo1?5O12, and Lu6W0?5Mo0?5O12 were synthesized through a solid-state reaction method. The materials were characterized by X-ray diffraction (XRD) patterns, scanning electron microscope (SEM) images, energy-dispersive spectra (EDS), diffuse reflection (DR) spectra, room temperature photoluminescence (PL) excitation and emission spectra, luminescence decay curves, and temperature dependent PL spectra. Red shift excitation bands were recorded in Lu2WxMoyO9 (x t y ? 2) phosphors with the concentration of Mo6t increasing. Enhanced Eu3t excitation and emission spectra were observed in the Lu2WxMoyO9 (x t y ? 2) phosphors with the concentration of W6t increasing. Possible energy transfer processes were proposed to explain the PL excitation and emission spectra. By combining phosphors with 365 nm ultraviolet (UV) chips, the obtained light emitting diodes (LEDs) gave bright red light under forward bias current. The results suggest that the obtained Eu3t doped Lu2WMoO9 have potential applications in phosphor converted based UV LEDs.
关键词： UV LED,Thermal properties,Phosphors,Optical properties,Photoluminescence
更新于2025-09-23 15:21:01
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Enhancement of the thermal properties of heterojunction perovskite solar cells by nanostructured contacts design
摘要： A perovskite solar cell design is structured and analyzed to investigate the thermal behavior of the cell. In order to perform large scale industrial devices, it is required to understand the effect of varying light intensity, ambient temperature and other sources such as joule heating and non-radiative recombination on the module. Subsequently, the enhancement of thermal stability is accomplished by selecting layers that can contribute to the reduction of operating temperature, such as transparent front electrodes and back electrodes. COMSOL Multiphysics is used to structure and simulate a regular planar heterojunction perovskite solar cell with ITO as a transparent front contact and Au as the back contact. These conventional contacts selection resulted in a maximum temperature of 79 °C for all sources of thermalization. Moreover, nine structures combinations are investigated by using FTO, AZO, Ag, and RGO electrodes. It is found that the best thermal structure is the one that utilizes AZO as a transparent contact and RGO as a back contact. This design achieves a huge reduction in the maximum temperature to ~32 °C; with a total of 59.5% thermal reduction when compared to conventional ITO/Au contacts structure.
关键词： Electrodes,COMSOL,Perovskite solar cell,Thermal properties
更新于2025-09-23 15:21:01
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Thermal properties and remnant state variables of ferroelectric ceramics switched by both electric field and compressive stress at room temperature
摘要： A commercial poled ferroelectric cube specimen is subject to electric ?eld and compressive stress of various magnitudes at the reference temperature 20 °C. After reaching speci?c states of remnant polarization and remnant strains, temperature of the specimen increases under no external load, measuring changes in polarization and strains. Assuming constant values of thermal properties in the temperature range of interest, we estimated pyroelectric and thermal expansion coe?cients for all tested levels of electric and stress ?elds and plotted them versus remnant state variables at 20, 50, 80, and 110 °C. The distributions of thermal properties ?t well into quadratic curves independent of electric and stress ?elds at each of the four temperatures. One could predict successfully the quadratic ?tting curves at high temperatures by using the equations of quadratic ?tting curves at reference temperature. Remnant state variables also seem to have close correlation among themselves, independent of the levels of applied electric ?eld or stress. ? 2018 The Japan Society of Applied Physics
关键词： thermal properties,compressive stress,electric ?eld,ferroelectric ceramics,remnant state variables
更新于2025-09-23 15:21:01
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Polytetrafluoroethylenea??intercalated MXene membranes with good photothermal performance for enhanced laser ignition
摘要： Photothermal effect has been widely used in many areas such as cancer therapy, photothermal energy harvesting, and laser ignition. However, exploring reliable and efficient free-standing energy converter for enhancing the photothermal performance is still a challenge. Herein, free-standing membrane based on two-dimensional MXene (Ti3C2) nanosheets and polytetrafluoroethylene (PTFE) was fabricated and characterized by X-ray diffraction, scanning electron microscopy and differential scanning calorimetry, which demonstrated a drastic temperature rise by laser irradiation and was further used as energy converter for enhancing the photothermal performance of laser ignition. Furthermore, the initiating power of the laser initiator can be largely reduced by adding a thin layer of MXene/PTFE membrane above the B/KNO3 cylinder. This work can give great promise for MXene-based membranes as the laser energy converter for reducing the initiating energy and promote the development of laser initiators with low initiating energy.
关键词： membranes,optical properties,thermal properties,composites,optical and photovoltaic applications
更新于2025-09-23 15:19:57
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Effect of tiny amount of zinc oxide on morphological and thermal properties of nanocomposite PEBA thin films
摘要： Novel PEBA-based nanocomposite thin films were prepared with different low concentrations of ZnO and characterized by AFM, FTIR, FESEM, DSC and TGA. AFM images indicated that the surface roughness of films increased by ZnO loading. FTIR spectroscopy revealed interaction between PEBA polymer and ZnO nanoparticles: The results presence of physical showed that ZnO nanoparticle undergoes an interaction with the CAOAC groups of the PEBA soft segments. DSC analysis showed that incorporation of ZnO caused substantial influence upon the thermal transition of the polyether domain of polymer. TGA showed a significant enhancement of the film thermal properties with ZnO loading. The loading of 0.5 wt% ZnO showed much better dispersion than 1.0 wt% ZnO, while the nanoparticle agglomeration for the latter was observed.
关键词： Nanocomposite thin film,ZnO nanoparticle,Thermal properties,PEBA
更新于2025-09-19 17:15:36
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Thermo-optic and spectroscopic properties of Yb:GAGG, Nd:GAGG and Nd:GGG laser materials at cryogenic temperature
摘要： The solid-state lasers provide an attractive approach to enhance the laser performance benefitting from significant improvements in both thermo-optic and spectroscopic properties of the gain mediums under cryogenic temperature. Here, thermo-optic properties of Yb:Gd3(AlxGa1-x)5O12 (Yb:GAGG) and Nd:Gd3(AlxGa1-x)5O12 (Nd:GAGG) laser crystals, including thermal conductivity (κ), thermal expansion coefficient (α) and specific heat at constant pressure (Cp) were measured from 77 to 298 K. In addition, the thermal shock resistance parameters were also calculated. The spectroscopic properties and the fluorescence lifetimes of laser gain mediums Yb:GAGG, Nd:GAGG and Nd:Gd3Ga5O12 (Nd:GGG) were characterized at 77, 150, 298 K. The stimulated emission cross sections of these laser materials were determined by use of the Füchtbauer-Ladenburg (FL) formula at each temperature.
关键词： GGG,cryogenic cooling,GAGG,spectroscopic properties,thermal properties,Neodymium,Ytterbium
更新于2025-09-19 17:13:59