- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Microstructure Influence of SACX0307-TiO2 Composite Solder Joints on Thermal Properties of Power LED Assemblies
摘要： The effect of the microstructure of solder joints on the thermal properties of power LEDs is investigated. Solder joints were prepared with different solder pastes, namely 99Sn0.3Ag0.7Cu (as reference solder) and reinforced 99Sn0.3Ag0.7Cu–TiO2 (composite solder). TiO2 ceramic was used at 1 wt.% and with two different primary particle sizes, which were 20 nm (nano) and 200 nm (submicron). The thermal resistance, the electric thermal resistance, and the luminous efficiency of the power LED assemblies were measured. Furthermore, the microstructure of the different solder joints was analyzed on the basis of cross-sections using scanning electron and optical microscopy. It was found that the addition of submicron TiO2 decreased the thermal and electric thermal resistances of the light sources by 20% and 16%, respectively, and it slightly increased the luminous efficiency. Microstructural evaluations showed that the TiO2 particles were incorporated at the Sn grain boundaries and at the interface of the intermetallic layer and the solder bulk. This caused considerable refinement of the Sn grain structure. The precipitated TiO2 particles at the bottom of the solder joint changed the thermodynamics of Cu6Sn5 formation and enhanced the spalling of intermetallic grain to solder bulk, which resulted in a general decrease in the thickness of the intermetallic layer. These phenomena improved the heat paths in the composite solder joints, and resulted in better thermal and electrical properties of power LED assemblies. However, the TiO2 nanoparticles could also cause considerable local IMC (Intermetallic Compounds) growth, which could inhibit thermal and electrical improvements.
关键词： power LED,SAC composite alloy,TiO2 ceramic,luminous efficiency,thermal resistance,microstructure characterization
更新于2025-09-23 15:19:57
-
Laser Patterning a Graphene Layer on a Ceramic Substrate for Sensor Applications
摘要： This paper describes a method for patterning the graphene layer and gold electrodes on a ceramic substrate using a Nd:YAG nanosecond fiber laser. The technique enables the processing of both layers and trimming of the sensor parameters. The main aim was to develop a technique for the effective and efficient shaping of both the sensory layer and the metallic electrodes. The laser shaping method is characterized by high speed and very good shape mapping, regardless of the complexity of the processing. Importantly, the technique enables the simultaneous shaping of both the graphene layer and Au electrodes in a direct process that does not require a complex and expensive masking process, and without damaging the ceramic substrate. Our results confirmed the effectiveness of the developed laser technology for shaping a graphene layer and Au electrodes. The ceramic substrate can be used in the construction of various types of sensors operating in a wide temperature range, especially the cryogenic range.
关键词： cryogenic,ceramic substrate,laser patterning,graphene
更新于2025-09-23 15:19:57
-
Laser-assisted glass-based sealing of polished porcelain stoneware tile surface to increase stain resistance
摘要： This study aims to develop a new approach for the permanent sealing of surface pores on polished porcelain stoneware tiles, using ceramic frits for the filling pores, followed by laser-sealing to ensure the fixation of the applied material. The laser-sealing parameters compatible with the ceramic substrate were focus height (z) of 105 mm, scan speed (v) of 2640 mm.min-1, and power values of 750, 800, and 850 W. In order to define the working parameters, three ceramic frits with 30, 50, and 70 wt.% solid contents were tested by sealing at the mentioned powers. High stain resistant polished stoneware tiles were obtained using frit 1 and frit 3 with 50 and 70 wt.% solid contents, respectively, and the proposed procedure. High ease of cleaning is obtained related to the current treatment, demonstrating its suitability for improving the stain resistance for meeting the ISO 13006:2012 requirements.
关键词： Ceramic frits. Laser Processing. Porcelain Tile. Porosity. Stain Resistance.
更新于2025-09-23 15:19:57
-
Heat transfer model of a 50 kW solar receiver-reactor for thermochemical redox cycling using cerium dioxide
摘要： This work reports on the development of a transient heat transfer model of a solar receiver-reactor designed for thermochemical redox cycling by temperature and pressure swing of pure cerium dioxide in the form of a reticulated porous ceramic (RPC). In the first, endothermal, step the cerium dioxide RPC is directly heated with concentrated solar radiation to 1500 °C while under vacuum pressure of less than 10 mbar, thereby releasing oxygen from its crystal lattice. In the subsequent, exothermic, step the reactor is re-pressurized with carbon dioxide as it cools, and at temperatures below 1000 °C the partially reduced cerium dioxide is re-oxidized with a flow of carbon dioxide. To analyze the performance of the solar reactor and to gain insight into improved design and operational conditions, a transient heat transfer model of the solar reactor for a solar radiative input power of 50 kW during the reduction step was developed and implemented in ANSYS CFX. The numerical model couples the incoming concentrated solar radiation using Monte-Carlo ray tracing, incorporates the reduction chemistry by assuming thermodynamic equilibrium, and accounts for internal radiation heat transfer inside the porous ceria by applying effective heat transfer properties. The model was experimentally validated using data acquired in a high-flux solar simulator, where temperature evolution and oxygen production results from model and experiment agreed well. The numerical results indicate the prominent influence of solar radiative input power, where increasing it substantially reduces reduction time of the cerium dioxide structure. Consequently, the model predicts a solar-to-fuel energy conversion efficiency of > 6% at a solar radiative power input of 50 kW; efficiency > 10% can be obtained provided the RPC macro porosity is substantially increased and better volumetric absorption and uniform heating is achieved. Managing the ceria surface temperature during reduction to avoid sublimation is a critical design consideration for direct absorption solar receiver-reactors.
关键词： design optimization,reactor modelling,ceria,thermochemical cycles,solar energy,reticulated porous ceramic
更新于2025-09-23 15:19:57
-
Optimization of pyroelectric conversion of thermal energy through the PZT ceramic buzzer and natural convection
摘要： The main purpose of this work is to take advantage of the pyroelectric e?ect to produce electricity. We propose the use of the PZT ceramic buzzer, which possesses pyroelectric properties, to convert thermal energy into electrical energy by pyroelectric e?ect. We take advantage of natural convection to create temperature variation from a ?xed thermal source. The amount of power harvested by this technique is su?cient to supply low-power systems. Our experiment consists in subjecting the PZT ceramic buzzer to a temperature variation insured only by natural convection created in an oil bath. In order to verify the existence of thermal ?uctuations and con?rm the e?ciency of our technique, we use thermal imaging which shows that the temperature changes as a function of time. We propose in this paper an optimization of our energy-harvesting system by studying the e?ect of the convection system geometry on the pyroelectric response: the e?ect of volume on the pyroelectric response and the e?ect of the distance between the oil surface and the pyroelectric ceramic. It appears from our study that the harvested power increases when the distance between the buzzer and the ?uid decreases but it increases slightly with the volume of liquid.
关键词： pyroelectric effect,energy harvesting,thermal energy,PZT ceramic buzzer,natural convection
更新于2025-09-23 15:19:57
-
Effects of Electrospinning Solution Properties on Formation of Beads in Tio2 Fibers with PdO Particles
摘要： TiO2 fibers with catalytic PdO particles are of interest for use as porous catalytic converters to react NOx and CO to control air pollution. The fibers are first electrospun as template polymer fibers. The template polymer fibers are calcined to form the ceramic fibers. The electrospinning solution composition significantly affects fiber morphologies (beads) which in turn affect the catalyst performance. In this work, solutions containing Polyvinylpyrrolidone (PVP), Titanium (IV) Isopropoxide (TTIP), and Palladium (II) Chloride (PdCl2) were electrospun with the goal of fabricating beadless submicron composite fibers. The fibers were calcined to produce ceramic TiO2 submicron fibers with Palladium oxide (PdO) nanoparticles. To determine the solution recipes that form smooth PdO-TiO2 fibers without beads, fibers were electrospun and evaluated from solutions with varied mass concentrations of PVP and PdCl2 salt. The solution concentrations indirectly influenced the electrospinning performance through solution viscosity, surface tension and electrical conductivity. The ceramic fibers were produced with average diameters in the range of 180-280 nm and with minimal formation of beads when the solution had viscosity in the range of 52 to 80 cP and conductivity in the range of 45-67 μs/cm. It was found that the surface tension of the solutions did not vary significantly and did not strongly affect the formation of beads.
关键词： nanofiber,beads,Electrospinning,catalyst support,ceramic
更新于2025-09-19 17:15:36
-
Thermophysical Properties of Silicon-Carbide-Based Ceramic Composite Materials Obtained by Spark Plasma Sintering (SPS)
摘要： The factors influencing the thermal conductivity of SiC-based ceramic composite materials obtained by the spark plasma sintering technology with relative density 99% and B4C, AlN, Si3N4, Y2O3, Al2O3, and HfB2 as additives are examined. The thermophysical properties were determined in the temperature range 20 – 1300°C: specific heat, thermal diffusivity, and thermal conductivity of composites. The thermal diffusivity and specific heat were measured by the laser-spark method. The measurements of specific heat are supplemented by measurements performed with a DSC and adiabatic calorimeter. The thermal conductivity is calculated using data on the thermal diffusivity, specific heat, and density.
关键词： laser flash method,specific heat,adiabatic calorimeter,thermal conductivity,ceramic composite materials,thermal diffusivity,thermophysical properties,differential scanning calorimetry (DSC)
更新于2025-09-19 17:15:36
-
[IEEE 2018 IEEE SENSORS - New Delhi, India (2018.10.28-2018.10.31)] 2018 IEEE SENSORS - Design and Fabrication of a Piezoelectric Micromachined Ultrasonic Transducer Array Based on Ceramic PZT
摘要： This paper presents a piezoelectric micromachined ultrasonic transducer (pMUT) array fabricated using high-piezoelectric-coefficient ceramic PZT wafers. A new process for polishing ceramic PZT layers down to 5 μm has been developed and applied for manufacturing high-sensitivity pMUTs. A 2 MHz working pMUT array (8×8 elements) based on ceramic PZT has been designed, modeled, fabricated and characterized.
关键词： pMUT,piezoelectric transducers,ultrasonic,micromachined transducers,ceramic PZT
更新于2025-09-19 17:15:36
-
Al2O3-Ce:GdYAG composite ceramic phosphors for high-power white light-emitting-diode applications
摘要： In order to meet the increasing demand of high-power light-emitting-diode (LED) lighting, state-of-the-art white light-emitting diode technology needs phosphors with high thermal conductivity and high luminous efficacy as color converters. In this work, translucent Al2O3-Ce:GdYAG composite phosphors were prepared by solid-state reactive sintering. The microstructure shows that the Al2O3 particles are uniformly dispersed in the Ce:GdYAG matrix. These particles can not only improve the thermal conductivity of the ceramics, but also promote the extraction efficacy. The luminous characteristics of the Ce:GdYAG and Al2O3-Ce:GdYAG ceramics were analyzed after being packaged with blue LED. When the molar ratio of Al2O3/Ce:GdYAG is 0.8, a high luminous efficacy value of 112.6 lm/W is achieved by the Al2O3-Ce:GdYAG composite ceramic phosphor with the thickness of 0.4 mm, as well as the highest CRI valve of 71.4. The appropriate photoelectric properties of this kind of ceramic phosphor make it a promising candidate for high-power LED device.
关键词： luminous efficacy,white-LED,color coordinates,composite ceramic phosphors,Al2O3-Ce:GdYAG
更新于2025-09-19 17:15:36
-
Structure and Phase Evolution in a SiC Ceramic Surface Layer During Electron-Beam Treatment
摘要： The elemental and phase compositions and substructure changes in the surface layer of SiC ceramic irradiated by pulsed electron beams of variable intensity were investigated. The structure and phase state of the ceramic surface layer were shown to be controlled by the electron-beam parameters. The electron-beam irradiation regimes leading to nanostructure detection in the SiC-ceramic surface layer were determined.
关键词： surface layer,electron beam,polytypes,SiC ceramic
更新于2025-09-19 17:15:36