Measurement of Coherent Thermal Emission Due to Magnetic Polaritons in Subwavelength Microstructures

2013 ◽  
Vol 135 (9) ◽  
Author(s):  
L. P. Wang ◽  
Z. M. Zhang
Keyword(s):  
Room Temperature ◽  
Elevated Temperatures ◽  
Thermal Emission ◽  
Coupling Effect ◽  
Infrared Region ◽  
Reflectance Measurement ◽  
Scattering Rate ◽  
Lc Circuit ◽  
Magnetic Polaritons ◽  
Rigorous Coupled Wave

Spectral and directional control of thermal emission is critically important for applications such as space cooling and energy harvesting. The effect of magnetic polaritons (MPs) on spectral modulation has been analyzed in metallic grating structures with a dielectric spacer on a metallic film. It has been predicted that the spectral emission peaks exhibit omnidirectional characteristics when MPs are excited. The present work provides an experimental demonstration of coherent thermal emission from several microfabricated grating structures in the infrared region from room temperature to elevated temperatures. The emittance at elevated temperatures is directly measured using an emissometer, while the room-temperature emittance is indirectly obtained from the reflectance measurement. The rigorous coupled-wave analysis and an LC-circuit model are employed to elucidate the mechanisms of various resonant modes and their coupling effect, taking into consideration the temperature-dependent electron scattering rate of the metals.

Measurement of Coherent Thermal Emission From Subwavelength Grating Structures by the Excitation of Magnetic Polaritons

2012 ◽  
Author(s):  
L. P. Wang ◽  
Z. M. Zhang
Keyword(s):  
Elevated Temperatures ◽  
Thermal Emission ◽  
Infrared Region ◽  
Radiative Properties ◽  
Scattering Rate ◽  
Rigorous Coupled Wave Analysis ◽  
Space Cooling ◽  
Dielectric Spacer ◽  
Magnetic Polaritons ◽  
Rigorous Coupled Wave

Tailoring radiative properties such as spectral control of thermal emission is beneficial in many applications such as space cooling and energy harvesting. The effect of magnetic polaritons (MPs) on spectral modulation has been analyzed previously and shown to exhibit omnidirectional behaviors when magnetic polaritons are excited in metallic grating structures with a dielectric spacer on a metallic film. The present work provides an experimental demonstration of coherent thermal emission from such a microstructure in the infrared region at both room and elevated temperatures. Samples with different patterns are fabricated to study the geometric effect on the MPs. The emittance at elevated temperatures is directly measured using a home-built emissometer, while the room-temperature emittance is indirectly obtained from the reflectance measurements. The rigorous coupled-wave analysis and the LC model are employed to elucidate the mechanisms, by incorporating the Drude model with a temperature-dependent scattering rate.

scholarly journals Experimental Demonstration of the Effect of Magnetic Polaritons on the Radiative Properties of Deep Aluminum Gratings

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Peiyan Yang ◽  
Hong Ye ◽  
Zhuomin M. Zhang
Keyword(s):  
Periodic Structures ◽  
Coupling Effect ◽  
Incidence Angle ◽  
Infrared Region ◽  
Radiative Properties ◽  
Future Design ◽  
Specular Reflectance ◽  
Magnetic Polaritons ◽  
Rigorous Coupled Wave ◽  
Metal Gratings

Despite the abundant theoretical studies of magnetic polaritons (MPs) in tailoring the radiative properties of nanostructures, experimental investigation of MPs in deep metal gratings is still lacking. This work experimentally demonstrates the excitation of MP from several microfabricated aluminum gratings in the mid-infrared region by measuring the specular reflectance (zeroth-order diffraction) of the specimen using a Fourier-transform infrared (FTIR) spectrometer. The rigorous coupled-wave analysis (RCWA) and an LC-circuit model are employed to elucidate the mechanism of various resonant modes and their coupling effect. The influence of incidence angle, plane of incidence, polarization, and the trench depth on the spectral reflectance is also discussed. Moreover, the MP dispersion for off-plane layout has been investigated and demonstrated for the first time. The insight gained from this work may facilitate future design and applications of subwavelength periodic structures with desired radiative properties.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

Spherulite Structures in a Melt Spun Fe-Ni Austenitic Steel

1985 ◽  
Vol 43 ◽  
pp. 52-53
Author(s):  
G. M. Michal ◽  
T. K. Glasgow ◽  
T. J. Moore
Keyword(s):  
Austenitic Steel ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Large Range ◽  
Amorphous Structure ◽  
Nucleation And Growth ◽  
Ni Alloys ◽  
Melt Spun ◽  
Crystal Fibers ◽  
Rapidly Solidified

Large additions of B to Fe-Ni alloys can lead to the formation of an amorphous structure, if the alloy is rapidly cooled from the liquid state to room temperature. Isothermal aging of such structures at elevated temperatures causes crystallization to occur. Commonly such crystallization pro ceeds by the nucleation and growth of spherulites which are spherical crystalline bodies of radiating crystal fibers. Spherulite features were found in the present study in a rapidly solidified alloy that was fully crysstalline as-cast. This alloy was part of a program to develop an austenitic steel for elevated temperature applications by strengthening it with TiB2. The alloy contained a relatively large percentage of B, not to induce an amorphous structure, but only as a consequence of trying to obtain a large volume fracture of TiB2 in the completely processed alloy. The observation of spherulitic features in this alloy is described herein. Utilization of the large range of useful magnifications obtainable in a modern TEM, when a suitably thinned foil is available, was a key element in this analysis.

FANSTEEL 85 METAL

Alloy Digest ◽  
1981 ◽  
Vol 30 (6) ◽  
Keyword(s):  
High Temperature ◽  
Physical Properties ◽  
Creep Strength ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Base Alloy ◽  
Heat Treating ◽  
Good Combination ◽  
Bend Strength ◽  
Temperature Performance

Abstract FANSTEEL 85 METAL is a columbium-base alloy characterized by good fabricability at room temperature, good weldability and a good combination of creep strength and oxidation resistance at elevated temperatures. Its applications include missile and rocket components and many other high-temperature parts. This datasheet provides information on composition, physical properties, microstructure, hardness, elasticity, tensile properties, and bend strength as well as creep. It also includes information on low and high temperature performance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: Cb-7. Producer or source: Fansteel Metallurgical Corporation. Originally published December 1963, revised June 1981.

Strong Coupling: Polariton Bose Condensation

2017 ◽  
Author(s):  
Alexey V. Kavokin ◽  
Jeremy J. Baumberg ◽  
Guillaume Malpuech ◽  
Fabrice P. Laussy
Keyword(s):  
Strong Coupling ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Dissipative System ◽  
Bose Condensation ◽  
Einstein Condensation ◽  
Strong Coupling Regime ◽  
Stimulated Scattering ◽  
Exciton Polaritons ◽  
Bose Einstein

In this Chapter we address the physics of Bose-Einstein condensation and its implications to a driven-dissipative system such as the polariton laser. We discuss the dynamics of exciton-polaritons non-resonantly pumped within a microcavity in the strong coupling regime. It is shown how the stimulated scattering of exciton-polaritons leads to formation of bosonic condensates that may be stable at elevated temperatures, including room temperature.

On the use of Ozawa/Flynn/Wall method to determine aging activation energy for elastomers

2021 ◽  
pp. 009524432110203
Author(s):  
Sudhir Bafna
Keyword(s):  
Mechanical Properties ◽  
Activation Energy ◽  
Weight Loss ◽  
Oxygen Consumption ◽  
Dwell Time ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Degradation Mechanism ◽  
Kinetics Of ◽  
Wall Method

It is often necessary to assess the effect of aging at room temperature over years/decades for hardware containing elastomeric components such as oring seals or shock isolators. In order to determine this effect, accelerated oven aging at elevated temperatures is pursued. When doing so, it is vital that the degradation mechanism still be representative of that prevalent at room temperature. This places an upper limit on the elevated oven temperature, which in turn, increases the dwell time in the oven. As a result, the oven dwell time can run into months, if not years, something that is not realistically feasible due to resource/schedule constraints in industry. Measuring activation energy (Ea) of elastomer aging by test methods such as tensile strength or elongation, compression set, modulus, oxygen consumption, etc. is expensive and time consuming. Use of kinetics of weight loss by ThermoGravimetric Analysis (TGA) using the Ozawa/Flynn/Wall method per ASTM E1641 is an attractive option (especially due to the availability of commercial instrumentation with software to make the required measurements and calculations) and is widely used. There is no fundamental scientific reason why the kinetics of weight loss at elevated temperatures should correlate to the kinetics of loss of mechanical properties over years/decades at room temperature. Ea obtained by high temperature weight loss is almost always significantly higher than that obtained by measurements of mechanical properties or oxygen consumption over extended periods at much lower temperatures. In this paper, data on five different elastomer types (butyl, nitrile, EPDM, polychloroprene and fluorocarbon) are presented to prove that point. Thus, use of Ea determined by weight loss by TGA tends to give unrealistically high values, which in turn, will lead to incorrectly high predictions of storage life at room temperature.

Effects of Elevated Temperatures on the Compressive Strength of HFCC

2011 ◽  
Vol 261-263 ◽  
pp. 416-420 ◽  
Author(s):  
Fu Ping Jia ◽  
Heng Lin Lv ◽  
Yi Bing Sun ◽  
Bu Yu Cao ◽  
Shi Ning Ding
Keyword(s):  
Compressive Strength ◽  
Elevated Temperature ◽  
Fly Ash ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Relative Strength ◽  
Ordinary Concrete ◽  
Residual Compressive Strength ◽  
Fly Ash Concrete ◽  
The Relationship

This paper presents the results of elevated temperatures on the compressive of high fly ash content concrete (HFCC). The specimens were prepared with three different replacements of cement by fly ash 30%, 40% and 50% by mass and the residual compressive strength was tested after exposure to elevated temperature 250, 450, 550 and 650°C and room temperature respectively. The results showed that the compressive strength apparently decreased with the elevated temperature increased. The presence of fly ash was effective for improvement of the relative strength, which was the ratio of residual compressive strength after exposure to elevated temperature and ordinary concrete. The relative compressive strength of fly ash concrete was higher than those of ordinary concrete. Based on the experiments results, the alternating simulation formula to determine the relationship among relative strength, elevated temperature and fly ash replacement is developed by using regression of results, which provides the theoretical basis for the evaluation and repair of HFCC after elevated temperature.

Development of 8 mΩ-cm2, 1.8 kV 4H-SiC DMOSFETs

2006 ◽  
Vol 527-529 ◽  
pp. 1261-1264 ◽  
Author(s):  
Sei Hyung Ryu ◽  
Sumi Krishnaswami ◽  
Brett A. Hull ◽  
Bradley Heath ◽  
Mrinal K. Das ◽  
...  
Keyword(s):  
Threshold Voltage ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Gate Length ◽  
Gate Bias ◽  
Low Loss ◽  
Layer Resistance ◽  
Switching Characteristics ◽  
Mos Gate ◽  
Drift Layer

8 mΩ-cm2, 1.8 kV power DMOSFETs in 4H-SiC are presented in this paper. A 0.5 μm long MOS gate length was used to minimize the MOS channel resistance. The DMOSFETs were able to block 1.8 kV with the gate shorted to the source. At room temperature, a specific onresistance of 8 mΩ-cm2 was measured with a gate bias of 15 V. At 150 oC, the specific onresistance increased to 9.6 mΩ-cm2. The increase in drift layer resistance due to a decrease in bulk electron mobility was partly cancelled out by the negative shift in MOS threshold voltage at elevated temperatures. The device demonstrated extremely fast, low loss switching characteristics. A significant improvement in converter efficiency was observed when the 4H-SiC DMOSFET was used instead of an 800 V silicon superjunction MOSFET in a simple boost converter configuration.

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