Quantitative FM Spectroscopy at High Temperatures: The Detection of 1CH2 behind Shock Waves

2000 ◽  
Vol 214 (12) ◽  
Author(s):  
G. Friedrichs ◽  
H.Gg. Wagner
Keyword(s):  
High Temperature ◽  
Shock Waves ◽  
High Temperatures ◽  
Frequency Modulation ◽  
Modulation Frequency ◽  
Optical Power ◽  
Time Resolved ◽  
Signal Conversion ◽  
High Modulation ◽  
Singlet Methylene

The technique of time resolved frequency modulation (FM) spectroscopy has been shown to provide a very sensitive means to detect small radicals behind shock waves. Features of high temperature FM spectroscopy behind shock waves will be discussed and a general signal conversion procedure to carry out quantitative concentration measurements will be presented.Using a high modulation frequency, a high modulation index and high total optical power, singlet methylene radicals (α

Investigation of the Thermal Decomposition of Ketene and of the Reaction CH2 + H2 ⇔ CH3 + H

2001 ◽  
Vol 215 (12) ◽  
Author(s):  
G. Friedrichs ◽  
H.Gg. Wagner
Keyword(s):  
Thermal Decomposition ◽  
Low Temperature ◽  
Shock Waves ◽  
High Temperatures ◽  
Frequency Modulation ◽  
Decomposition Reaction ◽  
Activation Energies ◽  
Unimolecular Decomposition ◽  
First Time ◽  
Singlet Methylene

Using frequency modulation (FM) spectroscopy singlet methylene radicals have been detected for the first time behind shock waves. The thermal decomposition of ketene served as source for metylene radicals at temperatures from 1905 to 2780 K and pressures around 450 mbar. For the unimolecular decomposition reaction, (1) CHAs a first study of a methylene reaction at high temperatures by diretly tracing methylene the reaction of methylene with hydrogen, (8 + 9)log(A comparison with low temperature literature data and the systematics of activation energies of triplet methylene reactions allowed a consistent description of singlet and triplet contributions and of the forward and reverse reaction.

scholarly journals A Displacement Measuring Interferometer Based on a Frequency-Locked Laser Diode with High Modulation Frequency

2020 ◽  
Vol 10 (8) ◽  
pp. 2693
Author(s):  
Thanh Tung Vu ◽  
Hong Hai Hoang ◽  
Toan Thang Vu ◽  
Ngoc Tam Bui
Keyword(s):  
Frequency Modulation ◽  
High Speed ◽  
Modulation Frequency ◽  
Laser Source ◽  
Interference Signal ◽  
Modulation Amplitude ◽  
Hyperfine Component ◽  
Synchronous Detection ◽  
High Modulation ◽  
Uncertainty Of Measurements

Laser interferometers can achieve a nanometer-order uncertainty of measurements when their frequencies are locked to the reference frequencies of the atom or molecule transitions. There are three types of displacement-measuring interferometers: homodyne, heterodyne, and frequency modulation (FM) interferometers. Among these types of interferometer, the FM interferometer has many advantageous features. The interference signal is a series of time-dependent harmonics of modulation frequency, so the phase shift can be detected accurately using the synchronous detection method. Moreover, the FM interferometer is the most suitable for combination with a frequency-locked laser because both require frequency modulation. In previous research, low modulation frequencies at some tens of kHz have been used to lock the frequency of laser diodes (LDs). The low modulation frequency for the laser source means that the maximum measurement speed of the FM interferometers is limited. This paper proposes a novel contribution regarding the application of a high-frequency modulation for an LD to improve both the frequency stability of the laser source and the measurement speed of the FM interferometer. The frequency of the LD was locked to an I2 hyperfine component at 1 MHz modulation frequency. A high bandwidth lock-in amplifier was utilized to detect the saturated absorption signals of the I2 hyperfine structure and induce the signal to lock the frequency of the LD. The locked LD was then used for an FM displacement measuring interferometer. Moreover, a suitable modulation amplitude that affected the signal-to-noise ratio of both the I2 absorption signal and the harmonic intensity of the interference signal was determined. In order to verify the measurement resolution of the proposed interferometer, the displacement induced by a piezo electric actuator was concurrently measured by the interferometer and a capacitive sensor. The difference of the displacement results was less than 20 nm. To evaluate the measurement speed, the interferometer was used to measure the axial error of a high-speed spindle at 500 rpm. The main conclusion of this study is that a stable displacement interferometer with high accuracy and a high measurement speed can be achieved using an LD frequency locked to an I2 hyperfine transition at a high modulation frequency.

Time-resolved remote Raman study of minerals under supercritical CO 2 and high temperatures relevant to Venus exploration

2010 ◽  
Vol 368 (1922) ◽  
pp. 3167-3191 ◽  
Author(s):  
Shiv K. Sharma ◽  
Anupam K. Misra ◽  
Samuel M. Clegg ◽  
James E. Barefield ◽  
Roger C. Wiens ◽  
...  
Keyword(s):  
High Temperature ◽  
Raman Spectra ◽  
High Temperatures ◽  
Ambient Pressure ◽  
Fermi Resonance ◽  
Time Resolved ◽  
Temperature Spectra ◽  
Resonance Doublet ◽  
Partial Dissociation ◽  
Surface Mineralogy

We report time-resolved (TR) remote Raman spectra of minerals under supercritical CO 2 (approx. 95 atm pressure and 423 K) and under atmospheric pressure and high temperature up to 1003 K at distances of 1.5 and 9 m, respectively. The TR Raman spectra of hydrous and anhydrous sulphates, carbonate and silicate minerals (e.g. talc, olivine, pyroxenes and feldspars) under supercritical CO 2 (approx. 95 atm pressure and 423 K) clearly show the well-defined Raman fingerprints of each mineral along with the Fermi resonance doublet of CO 2 . Besides the CO 2 doublet and the effect of the viewing window, the main differences in the Raman spectra under Venus conditions are the phase transitions, the dehydration and decarbonation of various minerals, along with a slight shift in the peak positions and an increase in line-widths. The dehydration of melanterite (FeSO 4  · 7H 2 O) at 423 K under approximately 95 atm CO 2 is detected by the presence of the Raman fingerprints of rozenite (FeSO 4  · 4H 2 O) in the spectrum. Similarly, the high-temperature Raman spectra under ambient pressure of gypsum (CaSO 4  · 2H 2 O) and talc (Mg 3 Si 4 O 10 (OH) 2 ) indicate that gypsum dehydrates at 518 K, but talc remains stable up to 1003 K. Partial dissociation of dolomite (CaMg(CO 3 ) 2 ) is observed at 973 K. The TR remote Raman spectra of olivine, α-spodumene (LiAlSi 2 O 6 ) and clino-enstatite (MgSiO 3 ) pyroxenes and of albite (NaAlSi 3 O 8 ) and microcline (KAlSi 3 O 8 ) feldspars at high temperatures also show that the Raman lines remain sharp and well defined in the high-temperature spectra. The results of this study show that TR remote Raman spectroscopy could be a potential tool for exploring the surface mineralogy of Venus during both daytime and nighttime at short and long distances.

scholarly journals Quantitative and Sensitive Mid-Infrared Frequency Modulation Detection of HCN behind Shock Waves

Fuels ◽  
2021 ◽  
Vol 2 (4) ◽  
pp. 437-447
Author(s):  
Michael Stuhr ◽  
Sebastian Hesse ◽  
Gernot Friedrichs
Keyword(s):  
High Temperature ◽  
Shock Waves ◽  
Frequency Modulation ◽  
Quantitative Detection ◽  
Stretch Vibration Band ◽  
Vibration Band ◽  
Pressure Broadening ◽  
Detection Scheme ◽  
Mid Infrared ◽  
Reflected Shock

Despite its key role for the study and modeling of nitrogen chemistry and NOx formation in combustion processes, HCN has only rarely been detected under high-temperature conditions. Here, we demonstrate quantitative detection of HCN behind incident and reflected shock waves using a novel sensitive single-tone mid-infrared frequency modulation (mid-IR-FM) detection scheme. The temperature-dependent pressure broadening of the P(26) line in the fundamental CH stretch vibration band was investigated in the temperature range 670K≤T≤1460K, yielding a pressure broadening coefficient for argon of 2γAr296K=(0.093±0.007)cm−1atm−1 and a temperature exponent of nAr=0.67±0.07. The sensitivity of the detection scheme was characterized by means of an Allan analysis, showing that HCN detection on the ppm mixing ratio level is possible at typical shock wave conditions. In order to demonstrate the capability of mid-IR-FM spectroscopy for future high-temperature reaction kinetic studies, we also report the first successful measurement of a reactive HCN decay profile induced by its reaction with oxygen atoms.

High temperature 27Al NMR time resolved study. Application to the CaO-Al2O3 binary system

1995 ◽  
Vol 92 ◽  
pp. 1871-1876 ◽  
Author(s):  
B Touzo ◽  
D Trumeau ◽  
D Massiot ◽  
I Farnan ◽  
JP Coutures
Keyword(s):  
High Temperature ◽  
Binary System ◽  
27Al Nmr ◽  
Time Resolved ◽  
Study Application

High Temperature n- and p-type Doped Microcrystalline Silicon Layers Grown by VHF PECVD Layer-by-Layer Deposition

2003 ◽  
Vol 762 ◽  
Author(s):  
A. Gordijn ◽  
J.K. Rath ◽  
R.E.I. Schropp
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
High Temperatures ◽  
Continuous Wave ◽  
Hydrogen Plasma ◽  
Silicon Layer ◽  
Dark Conductivity ◽  
High Deposition Rate ◽  
Layer By Layer ◽  
Microcrystalline Silicon

AbstractDue to the high temperatures used for high deposition rate microcrystalline (μc-Si:H) and polycrystalline silicon, there is a need for compact and temperature-stable doped layers. In this study we report on films grown by the layer-by-layer method (LbL) using VHF PECVD. Growth of an amorphous silicon layer is alternated by a hydrogen plasma treatment. In LbL, the surface reactions are separated time-wise from the nucleation in the bulk. We observed that it is possible to incorporate dopant atoms in the layer, without disturbing the nucleation. Even at high substrate temperatures (up to 400°C) doped layers can be made microcrystalline. At these temperatures, in the continuous wave case, crystallinity is hindered, which is generally attributed to the out-diffusion of hydrogen from the surface and the presence of impurities (dopants).We observe that the parameter window for the treatment time for p-layers is smaller compared to n-layers. Moreover we observe that for high temperatures, the nucleation of p-layers is more adversely affected than for n-layers. Thin, doped layers have been structurally, optically and electrically characterized. The best n-layer made at 400°C, with a thickness of only 31 nm, had an activation energy of 0.056 eV and a dark conductivity of 2.7 S/cm, while the best p-layer made at 350°C, with a thickness of 29 nm, had an activation energy of 0.11 V and a dark conductivity of 0.1 S/cm. The suitability of these high temperature n-layers has been demonstrated in an n-i-p microcrystalline silicon solar cell with an unoptimized μc-Si:H i-layer deposited at 250°C and without buffer. The Voc of the cell is 0.48 V and the fill factor is 70 %.

NICROFER 5520 Co

Alloy Digest ◽  
1995 ◽  
Vol 44 (3) ◽  
Keyword(s):  
High Temperature ◽  
Chemical Composition ◽  
Physical Properties ◽  
Tensile Properties ◽  
High Temperatures ◽  
Heat Treating ◽  
High Temperature Corrosion ◽  
Creep Properties ◽  
Nickel Chromium ◽  
Temperature Performance

Abstract NICROFER 5520 Co is a nickel-chromium-cobalt-molybdenum alloy with excellent strength and creep properties up to high temperatures. Due to its balanced chemical composition the alloy shows outstanding resistance to high temperature corrosion in the form of oxidation and carburization. This datasheet provides information on composition, physical properties, elasticity, and tensile properties. It also includes information on high temperature performance as well as forming, heat treating, machining, and joining. Filing Code: Ni-480. Producer or source: VDM Technologies Corporation.

CARLSON ALLOY C601

Alloy Digest ◽  
1994 ◽  
Vol 43 (7) ◽  
Keyword(s):  
High Temperature ◽  
Physical Properties ◽  
Stress Corrosion ◽  
Tensile Properties ◽  
High Temperatures ◽  
Stress Corrosion Cracking ◽  
Heat Treating ◽  
Resistance To Stress ◽  
Extended Exposure ◽  
Sulfur Containing

Abstract Carlson Alloy C601 is characterized by high tensile, yield and creep-rupture strengths for high temperature service. The alloy is not embrittled by extended exposure to high temperatures and has excellent resistance to stress-corrosion cracking, to carburizing, nitriding and sulfur containing environments. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as creep. It also includes information on forming, heat treating, machining, and joining. Filing Code: Ni-458. Producer or source: G.O. Carlson Inc.

INCOTHERM TD

Alloy Digest ◽  
2005 ◽  
Vol 54 (11) ◽  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Oxidation Resistance ◽  
High Temperatures ◽  
Rare Earths ◽  
Temperature Performance

Abstract Incotherm TD is a thermocouple-sheathing alloy with elements of silicon and rare earths to enhance oxidation resistance at high temperatures. This datasheet provides information on composition, physical properties, and tensile properties as well as deformation. It also includes information on high temperature performance and corrosion resistance as well as forming. Filing Code: Ni-628. Producer or source: Special Metals Corporation.

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