scholarly journals An Apparatus for Spectral Emissivity Measurements of Thermal Control Materials at Low Temperatures

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1141 ◽  
Author(s):  
Jiayu Ma ◽  
Yuzhi Zhang ◽  
Lingnan Wu ◽  
Haogeng Li ◽  
Lixin Song
Keyword(s):  
Fourier Transform ◽  
Background Radiation ◽  
Thermal Control ◽  
Spectral Emissivity ◽  
Standard Uncertainty ◽  
Radiative Properties ◽  
Thermal Radiative Properties ◽  
Infrared Spectral ◽  
Mechanical Modulation ◽  
The Fourier Transform

Thermal control materials are employed to adjust the temperature of a spacecraft operating in deep space. The spectral emissivity is a crucial factor in evaluating the thermal radiative properties of such materials. An apparatus, composed of a Fourier transform infrared spectrometer (FTIR), a sample cooling chamber and a mechanical modulation system was demonstrated to measure low temperature infrared spectral emissivity under vacuum. The mechanical modulation system, which includes a chopper and a lock-in amplifier, is employed to reduce the interference of background radiation during measurements. The limitation of the Fourier transform frequency on the chopper frequency can be eliminated by setting the FTIR on step-scan mode. The apparatus is separated into two parts and evacuated by different pumps. In this study, a high quality emission spectrum of a sample is measured by the apparatus. The spectral emissivity of thermal control materials are obtained in the wavelength range of 8 to 14 μm at 173 and 213 K. The combined standard uncertainty of the apparatus is 3.30% at 213 K.

The Microstructure and Thermochromic Properties of La1-XSrXMnO3 Smart Materials

2013 ◽  
Vol 690-693 ◽  
pp. 648-653 ◽  
Author(s):  
Min Xu ◽  
Zhao Hui Fu ◽  
Lin Li ◽  
Jie Bing Wang ◽  
Chun Hua Wu ◽  
...  
Keyword(s):  
Smart Materials ◽  
Thermal Control ◽  
Solid State Reaction Method ◽  
Thermal Design ◽  
Radiative Properties ◽  
X Ray Diffraction ◽  
Conventional Solid State Reaction ◽  
Thermal Radiative Properties ◽  
Potential Applications ◽  
Thermochromic Properties

The La1-xSrxMnO3 materials have potential applications in thermal control systems of microsatellites. The microstructure of La1-xSrxMnO3 materials is very sensitive to the compound of Sr incorporated into it. In this paper, preparation process of La1-xSrxMnO3 compounds was explored. Ceramic sintering process combined with a conventional solid state reaction method was used to prepare various components of La1-xSrxMnO3。 Annealing temperature, time and doped ratio were controlled in the experiment. X-ray diffraction and Raman spectroscopy were used to analyze phase structure and crystalline. Thermal radiative properties were measured on a Calorimetric Emissometer at 175K～375K. These investigations reveal that microstructure of La1-xSrxMnO3 compounds are affected by Sr2+doping level(x).Thermal emissivity of La0.825Sr0.175MnO3 materials vary widely from 0.68 to 0.37, which can meet requirement of future space thermal design.

scholarly journals Tailoring Thin-Film/Lacquer Coatings for Space Applications

2000 ◽  
Vol 12 (1) ◽  
pp. 105-112 ◽  
Author(s):  
Wanda C Peters ◽  
George Harris ◽  
Grace Miller ◽  
John Petro
Keyword(s):  
Thin Film ◽  
Thermal Control ◽  
Radiative Properties ◽  
Space Applications ◽  
Solar Absorptance ◽  
Film Coatings ◽  
Thin Film Coatings ◽  
Thermal Radiative Properties ◽  
Wide Range ◽  
Specular Surfaces

Thin-film coatings have the capability of obtaining a wide range of thermal radiative properties, but the development of thin-film coatings can sometimes be difficult and costly when trying to achieve highly specular surfaces. Given any space mission’s thermal control requirements, there is often a need for a variation of solar absorptance (αs), emittance (∊) and/or highly specular surfaces. The utilization of thin-film coatings is one process of choice for meeting challenging thermal control requirements because of its ability to provide a wide variety of αs/∊ ratios. The radiative properties of thin-film coatings can be tailored to meet specific thermal control requirements through the use of different metals and the variation of dielectric layer thickness. Surface coatings can be spectrally selective to enhance radiative coupling and decoupling. The application of lacquer to a surface can also provide suitable specularity for thin-film application without the cost and difficulty associated with polishing.

Measurements of the Thermal Radiative Properties of Liquid Uranium

1993 ◽  
Vol 115 (4) ◽  
pp. 1013-1020 ◽  
Author(s):  
M. A. Havstad ◽  
W. McLean ◽  
S. A. Self
Keyword(s):  
Spectral Emissivity ◽  
Index Of Refraction ◽  
Radiative Properties ◽  
Optical Systems ◽  
Normal Spectral Emissivity ◽  
Complex Index ◽  
Thermal Radiative Properties ◽  
Infrared Wavelengths ◽  
Complex Index Of Refraction

Measurements of the thermal radiative properties of liquid uranium have been made using an instrument with two optical systems, one for measuring the complex index of refraction by ellipsometry, the other for measuring the normal spectral emissivity by direct comparison to an integral blackbody cavity. The measurements cover the wavelength range 0.4–10 μm with sample temperatures between 1410 and 1630 K. Two 5-KeV ion sputter guns and an Auger spectrometer produce and verify, in situ, atomically pure sample surfaces. Good agreement between the two methods is observed for the normal spectral emissivity, which varies with wavelength in a manner typical of transition metals. The two components of the complex index of refraction—the index of refraction and the extinction coefficient—increase with wavelength, from ~3 at 0.4 μm to ~20 at 9.5 μm. Both components of polarized reflectivity are shown for visible to infrared wavelengths.

Characterization of Pyrolysis and Combustion of Complex Systems Using Fourier Transform Infrared Spectroscopy

1980 ◽  
Vol 34 (2) ◽  
pp. 174-185 ◽  
Author(s):  
John O. Lephardt ◽  
Robert A. Fenner
Keyword(s):  
Fourier Transform ◽  
Complex Systems ◽  
Evolved Gas Analysis ◽  
Analytical Techniques ◽  
Fourier Transform Infrared ◽  
Gas Analysis ◽  
Before And After ◽  
Infrared Spectral ◽  
Ft Ir ◽  
The Fourier Transform

Thermal analysis plays an important role in the evaluation and development of many complex chemical systems. Often combustion data as well as pyrolytic data on these systems may be important. Analytical techniques are required which maximize the amount of useful information which can be obtained per thermal experiment. Fourier transform infrared spectral analysis of gases evolving from materials vs temperature can provide information on both pyrolysis and combustion processes, and an apparatus for performing such analysis routinely is described. While the Fourier transform infrared evolved gas analysis (FT-IR-EGA) system has numerous applications, three applications using tobacco as a sample are presented for illustration. These include comparison of different materials, comparison of materials before and after modification and examination of oxygen-induced effects relative to pyrolysis effects. The FT-IR-EGA technique should prove to be a useful tool in elucidating thermal processes in complex systems.

FR-IR Molecular Microanalysis System

1990 ◽  
Vol 48 (2) ◽  
pp. 270-271
Author(s):  
John A. Reffner ◽  
William T. Wihlborg
Keyword(s):  
Fourier Transform ◽  
Fourier Transform Infrared ◽  
Integrated System ◽  
Morphological Examination ◽  
Fully Integrated ◽  
Ir Microscopy ◽  
Normal Functions ◽  
Infrared Microspectroscopy ◽  
Infrared Spectral ◽  
Ft Ir

The IRμs™ is the first fully integrated system for Fourier transform infrared (FT-IR) microscopy. FT-IR microscopy combines light microscopy for morphological examination with infrared spectroscopy for chemical identification of microscopic samples or domains. Because the IRμs system is a new tool for molecular microanalysis, its optical, mechanical and system design are described to illustrate the state of development of molecular microanalysis. Applications of infrared microspectroscopy are reviewed by Messerschmidt and Harthcock.Infrared spectral analysis of microscopic samples is not a new idea, it dates back to 1949, with the first commercial instrument being offered by Perkin-Elmer Co. Inc. in 1953. These early efforts showed promise but failed the test of practically. It was not until the advances in computer science were applied did infrared microspectroscopy emerge as a useful technique. Microscopes designed as accessories for Fourier transform infrared spectrometers have been commercially available since 1983. These accessory microscopes provide the best means for analytical spectroscopists to analyze microscopic samples, while not interfering with the FT-IR spectrometer’s normal functions.

scholarly journals Strain Sensitivity Enhancement of Broadband Ultrasonic Signals in Plates Using Spectral Phase Filtering

2021 ◽  
Vol 11 (6) ◽  
pp. 2582
Author(s):  
Lucas M. Martinho ◽  
Alan C. Kubrusly ◽  
Nicolás Pérez ◽  
Jean Pierre von der Weid
Keyword(s):  
Fourier Transform ◽  
Guided Waves ◽  
Strain Level ◽  
Energy Concentration ◽  
Short Time Fourier Transform ◽  
Time Frequency ◽  
Frequency Representation ◽  
The Fourier Transform ◽  
Short Time ◽  
Sensitivity Gain

The focused signal obtained by the time-reversal or the cross-correlation techniques of ultrasonic guided waves in plates changes when the medium is subject to strain, which can be used to monitor the medium strain level. In this paper, the sensitivity to strain of cross-correlated signals is enhanced by a post-processing filtering procedure aiming to preserve only strain-sensitive spectrum components. Two different strategies were adopted, based on the phase of either the Fourier transform or the short-time Fourier transform. Both use prior knowledge of the system impulse response at some strain level. The technique was evaluated in an aluminum plate, effectively providing up to twice higher sensitivity to strain. The sensitivity increase depends on a phase threshold parameter used in the filtering process. Its performance was assessed based on the sensitivity gain, the loss of energy concentration capability, and the value of the foreknown strain. Signals synthesized with the time–frequency representation, through the short-time Fourier transform, provided a better tradeoff between sensitivity gain and loss of energy concentration.

Determination of starch crystallinity with the Fourier-transform terahertz spectrometer

2021 ◽  
Vol 262 ◽  
pp. 117928
Author(s):  
Shusaku Nakajima ◽  
Shuhei Horiuchi ◽  
Akifumi Ikehata ◽  
Yuichi Ogawa
Keyword(s):  
Fourier Transform ◽  
The Fourier Transform ◽  
Starch Crystallinity
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