Thermal Conduction Measurements of Materials using Microwave Energy

1990 ◽  
Vol 189 ◽  
Author(s):  
R. E. Giedd ◽  
G. R. Giedd
Keyword(s):  
Thermal Conductivity ◽  
Low Cost ◽  
Pulse Length ◽  
Laser Flash ◽  
High Energy ◽  
Microwave Energy ◽  
Voltage Source ◽  
Microwave System ◽  
High Voltage Source ◽  
A New Technique

ABSTRACTWe have developed a new technique to measure the thermal conductivity of materials using microwave energy. A thermal wave is induced in a material of unknown thermal conductivity using a pulse of microwave energy. This energy is incident on one side of the material. The corresponding temperature rise of the opposite side of the material is measured. The thermal diffusivity of the material can then be determined in the same way as ‘laser flash’[1]. Some of the advantages of the microwave system are the relatively low cost of the magnetron compared to the high energy laser, easily variable pulse length, and accurate measurement of the reflected energy.The microwave system consists of a 2.45 GHz magnetron that is pulse modulated to energies as high as 10 J. A typical pulse lasts for 1 ms with rise and fall times of 10µs. This is achieved by a high voltage source (5 – 8 kV at 1 – 2 A), switched by a high power, rf transmitting tube connected in the filament circuit of the magnetron.

EXEELFS (Extended Electron Energy Loss Fine Structure) Study of Tin Grown by the DC Sputtering Technique.

2000 ◽  
Vol 6 (S2) ◽  
pp. 226-227
Author(s):  
Duarte-Moller A. ◽  
F. Espinosa-Maganña ◽  
R. Martínez-S´anchez ◽  
O. Contreras
Keyword(s):  
Energy Loss ◽  
Direct Current ◽  
Physical Vapor Deposition ◽  
Standard Procedure ◽  
High Energy ◽  
Structure Study ◽  
Voltage Source ◽  
Titanium Target ◽  
High Voltage Source ◽  
Mechanical Pump

Titanium nitride coatings were grown in a physical vapor deposition system assisted by a direct current reactive magnetron sputtering technique. The vacuum chamber was evacuated with a mechanical pump and cryopump to a base pressure of 10-7 Torr. The Sputtering was performed with a direct current high voltage source (0-1 Kev and 1 A) on a titanium target (99.98% purity). The titanium target was sputtered with a high purity argon -nitrogen mixture. The films were deposited on monocrystalline silicon (mc-Si) (111) substrates at different nitrogen partial pressures from 0.08 mTorr to 1.5 mTorr. Total pressure, power applied to target and substrate temperature were keep constant in all the experiments.EXEELFS analysis were done using the standard procedure [1,2]. In this case, we are find that the atomic concentration is in good agreement with the respective established stoichioinetry N/T=0.99. Figure 1 shows the window of high energy loss where appears their respective N K-edge and Ti -L23.

scholarly journals Low-Cost High Energy Density Material for Solar Thermal Heat Storage

2020 ◽  
Vol 3 (2) ◽  
pp. 46-56
Author(s):  
Rebhi Damseh
Keyword(s):  
Thermal Conductivity ◽  
Energy Storage ◽  
Energy Density ◽  
Heat Storage ◽  
Low Cost ◽  
High Energy ◽  
Solar Thermal ◽  
Energy Storage Density ◽  
Solar Thermal Energy ◽  
Storage Density

A low-cost and enhanced thermal properties composite material for sensible heat storage in solar thermal energy storage applications is introduced. The proposed material is produced primarily for small scale solar thermal applications. However, it can be utilized for large scale solar thermal plants. The material has the advantages of high thermal conductivity and large energy storage density. The introduced material is composed of a mixture of cement and cast-iron particles. To obtain an optimal mixture, different samples of the material are prepared with different ratios of the cement-iron weights. The thermal conductivity of the produced samples is measured by using the linear heat conduction method. The specific heat capacity of the produced mixtures is calculated by using the Rule of the mixture. The obtained results show that the introduced material has a significant enhancement in thermal conductivity. Where, thermal conductivity as high as ~6.0 W/m.K and energy storage density as high as ~788 Joule/cm3 are achieved. The estimated volume energy density is ~89% higher than that of water. The produced material has the advantage of high energy volume density, being unhazardous, chemically stable, eco-friendly, easy to fabricate, and integrate with solar thermal energy systems and is a low-cost material.

scholarly journals Microwave disinfection as a treatment for blackwater from dewatered sludge

2018 ◽  
Vol 2 ◽  
pp. 16
Author(s):  
Katelyn L Sellgren ◽  
Christopher W Gregory ◽  
Ethan J.D. Klem ◽  
Jeffrey R. Piascik ◽  
Brian R. Stoner
Keyword(s):  
Cost Efficiency ◽  
Low Cost ◽  
High Energy ◽  
Microwave Energy ◽  
Disposal Site ◽  
Thermal Heating ◽  
Compact Size ◽  
Fecal Sludge ◽  
Flow Through ◽  
Potential Use

Background: Fast and efficient on-site treatment of blackwater, rejected from the dewatering process, can decrease the costs associated with disposal of fecal sludge removed from pit latrines by reducing the volume of sludge transported to the disposal site.Methods: In this study, we examine the potential use of low cost consumer microwave units for disinfecting pathogen-rich blackwater. Domestic bench top microwave units were modified to allow flow through and re-circulation of blackwater. Energy, throughput, and disinfection characteristics related to microwaves are studied and compared to conventional thermal heating. A custom flow through stack of 5 microwaves was designed and used to examine the feasibility of single pass, high throughput application.Results and Conclusions: The results show microwave energy does not play a role in the disinfection of blackwater. The benefits of a microwave disinfection system are shown to be high energy efficiency, compact size, and cost efficiency.

scholarly journals Enhanced Thermal Conductivity of Silicone Composites Filled with Few-Layered Hexagonal Boron Nitride

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2072
Author(s):  
Wei-Cheng Cheng ◽  
Yi-Ting Hsieh ◽  
Wei-Ren Liu
Keyword(s):  
Thermal Conductivity ◽  
Boron Nitride ◽  
Heat Dissipation ◽  
Hexagonal Boron Nitride ◽  
Low Cost ◽  
Laser Flash ◽  
Force Microscopy ◽  
Surface Areas ◽  
Laser Flash Analysis ◽  
Surface Morphologies

In this study, we demonstrate the use of silicone/few-layered hexagonal boron nitride (FL-hBN) composites for heat dissipation applications. FL-hBN is synthesized via a green, facile, low-cost and scalable liquid exfoliation method using a jet cavitation process. The crystal structures, surface morphologies and specific surface areas of pristine h-BN and FL-hBN were characterized by XRD, SEM, TEM and AFM (atomic force microscopy). The results confirmed that FL-hBN with a thickness of ~4 nm was successfully obtained from the exfoliation process. In addition, we introduced both pristine h-BN and FL-hBN into silicone with different ratios to study their thermal properties. The results of the laser flash analysis indicate that the silicon/FL-hBN composite exhibited a higher thermal conductivity than that of the silicone/h-BN composite. With the optimal loading content of 30 wt.% FL-hBN content, the thermal conductivity of the composite could be enhanced to 230%, which is higher than that of silicone/h-BN (189%). These results indicate that jet cavitation is an effective and swift way to obtain few-layered hexagonal boron nitride that could effectively enhance the thermal conductivity of silicone composites.

Techniques for assessing the performance of circuit materials at microwave and millimetre-wave frequencies

2003 ◽  
Vol 783 ◽  
Author(s):  
Charles E Free
Keyword(s):  
Loss Tangent ◽  
Good Accuracy ◽  
Low Cost ◽  
Resonant Cavity ◽  
New Technique ◽  
Millimetre Wave ◽  
A New Technique

This paper discusses the techniques that are available for characterising circuit materials at microwave and millimetre wave frequencies. In particular, the paper focuses on a new technique for measuring the loss tangent of substrates at mm-wave frequencies using a circular resonant cavity. The benefits of the new technique are that it is simple, low cost, capable of good accuracy and has the potential to work at high mm-wave frequencies.

Janus – A New Approach to Air Combat Pilot Training

2019 ◽  
Vol 2019 (4) ◽  
pp. 7-22
Author(s):  
Georges Bridel ◽  
Zdobyslaw Goraj ◽  
Lukasz Kiszkowiak ◽  
Jean-Georges Brévot ◽  
Jean-Pierre Devaux ◽  
...  
Keyword(s):  
Low Cost ◽  
Cost Effective ◽  
High Energy ◽  
Training System ◽  
Embedded Sensors ◽  
Pilot Training ◽  
New Approach ◽  
Combat Aircraft ◽  
Air Combat ◽  
The Cost

Abstract Advanced jet training still relies on old concepts and solutions that are no longer efficient when considering the current and forthcoming changes in air combat. The cost of those old solutions to develop and maintain combat pilot skills are important, adding even more constraints to the training limitations. The requirement of having a trainer aircraft able to perform also light combat aircraft operational mission is adding unnecessary complexity and cost without any real operational advantages to air combat mission training. Thanks to emerging technologies, the JANUS project will study the feasibility of a brand-new concept of agile manoeuvrable training aircraft and an integrated training system, able to provide a live, virtual and constructive environment. The JANUS concept is based on a lightweight, low-cost, high energy aircraft associated to a ground based Integrated Training System providing simulated and emulated signals, simulated and real opponents, combined with real-time feedback on pilot’s physiological characteristics: traditionally embedded sensors are replaced with emulated signals, simulated opponents are proposed to the pilot, enabling out of sight engagement. JANUS is also providing new cost effective and more realistic solutions for “Red air aircraft” missions, organised in so-called “Aggressor Squadrons”.

Highly thermally conductive UHMWPE/NG composites with the segregated structure and their application for heat spreader

2020 ◽  
pp. 089270572096564
Author(s):  
Xiao Wang ◽  
Hui Lu ◽  
Jun Chen
Keyword(s):  
Thermal Conductivity ◽  
Laser Flash ◽  
Heating Process ◽  
X Ray Diffraction ◽  
Heat Spreader ◽  
Conductive Composites ◽  
Compression Direction ◽  
Thermal Analyzer ◽  
Thermally Conductive ◽  
Plane Direction

In this work, ultra-high molecular weight polyethylene (UHMWPE)/natural flake graphite (NG) polymer composites with the extraordinary high thermal conductivity were prepared by a facile mixed-heating powder method. Morphology observation and X-ray diffraction (XRD) tests revealed that the NG flakes could be more tightly coated on the surface of UHMWPE granules by mixed-heating process and align horizontally (perpendicular to the hot compression direction of composites). Laser flash thermal analyzer (LFA) demonstrated that the thermal conductivity (TC) of composites with 21.6 vol% of NG reached 19.87 W/(m·K) and 10.67 W/(m·K) in the in-plane and through-plane direction, respectively. Application experiment further demonstrated that UHMWPE/NG composites had strong capability to dissipate the heat as heat spreader. The obtained results provided a valuable basis for fabricating high thermal conductive composites which can act as advanced thermal management materials.

scholarly journals Na0.76V6O15/Activated Carbon Hybrid Cathode for High-Performance Lithium-Ion Capacitors

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 122
Author(s):  
Renwei Lu ◽  
Xiaolong Ren ◽  
Chong Wang ◽  
Changzhen Zhan ◽  
Ding Nan ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Energy Density ◽  
Power Density ◽  
Cathode Materials ◽  
Low Cost ◽  
Lithium Ion ◽  
High Energy ◽  
Cycling Stability ◽  
High Energy Density ◽  
Artificial Graphite

Lithium-ion hybrid capacitors (LICs) are regarded as one of the most promising next generation energy storage devices. Commercial activated carbon materials with low cost and excellent cycling stability are widely used as cathode materials for LICs, however, their low energy density remains a significant challenge for the practical applications of LICs. Herein, Na0.76V6O15 nanobelts (NaVO) were prepared and combined with commercial activated carbon YP50D to form hybrid cathode materials. Credit to the synergism of its capacitive effect and diffusion-controlled faradaic effect, NaVO/C hybrid cathode displays both superior cyclability and enhanced capacity. LICs were assembled with the as-prepared NaVO/C hybrid cathode and artificial graphite anode which was pre-lithiated. Furthermore, 10-NaVO/C//AG LIC delivers a high energy density of 118.9 Wh kg−1 at a power density of 220.6 W kg−1 and retains 43.7 Wh kg−1 even at a high power density of 21,793.0 W kg−1. The LIC can also maintain long-term cycling stability with capacitance retention of approximately 70% after 5000 cycles at 1 A g−1. Accordingly, hybrid cathodes composed of commercial activated carbon and a small amount of high energy battery-type materials are expected to be a candidate for low-cost advanced LICs with both high energy density and power density.

scholarly journals Optically transparent and very thin structure against electromagnetic pulse (EMP) using metal mesh and saltwater for shielding windows

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Duy Tung Phan ◽  
Chang Won Jung
Keyword(s):  
Electromagnetic Pulse ◽  
Low Cost ◽  
High Energy ◽  
Metal Plate ◽  
Optical Transparency ◽  
Shielding Effectiveness ◽  
Concrete Wall ◽  
Metal Mesh ◽  
Wide Range ◽  
Optically Transparent

AbstractAn electromagnetic pulse (EMP) with high energy can damage electronic equipment instantly within a wide range of thousands of kilometers. Generally, a metal plate placed inside a thick concrete wall is used against an EMP, but it is not suitable for an EMP shielding window, which requires not only strong shielding effectiveness (SE) but also optical transparency (OT). In this paper, we propose a very thin and optically transparent structure with excellent SE for EMP shielding window application. The proposed structure consists of a saltwater layer held between two glass substrates and two metal mesh layers on the outside of the glass, with a total thickness of less than 1.5 cm. The SE and OT of the structure are above 80 dB and 45%, respectively, which not only meet the requirement of EMP shielding for military purposes but also retain the procedure of good observation. Moreover, the OT of the structure can be significantly improved using only one metal mesh film (MMF) layer, while the SE is still maintained high to satisfy the required SE for home applicants. With the major advantages of low cost, optical transparency, strong SE, and flexible performance, the proposed structure can be considered a good solution for transparent EMP shielding windows.

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