Improved 3-omega measurement of thermal conductivity in liquid, gases, and powders using a metal-coated optical fiber

Schiffres, Scott N.; Malen, Jonathan A.

doi:10.1063/1.3593372

Cited by 36 publications

(25 citation statements)

References 25 publications

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“…Thermal conductivity measurements were performed on the SWCNT aerogel using a modified 3 ω method developed specifically for low‐thermal conductivity materials 37. This technique, which is called metal‐coated 3 ω , is capable of measuring small samples with reduced sensitivity to conduction and radiation losses at the sample boundaries, as compared to steady‐state techniques like guarded hot‐plate 37. The measurements were performed in vessels with a 15 × 10 × 5 mm 3 cavity spanned by a suspended Au coated (100 nm thick) glass fiber (25 μm in diameter).…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Gas Diffusion, Energy Transport, and Thermal Accommodation in Single‐Walled Carbon Nanotube Aerogels

Schiffres

Kim

et al. 2012

Adv Funct Materials

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103

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The thermal conductivity of gas-permeated single-walled carbon nanotube (SWCNT) aerogel (8 kg m − 3 density, 0.0061 volume fraction) is measured experimentally and modeled using mesoscale and atomistic simulations. Despite the high thermal conductivity of isolated SWCNTs, the thermal conductivity of the evacuated aerogel is 0.025 ± 0.010 W m − 1 K − 1 at a temperature of 300 K. This very low value is a result of the high porosity and the low interface thermal conductance at the tube-tube junctions (estimated as 12 pW K − 1 ). Thermal conductivity measurements and analysis of the gas-permeated aerogel (H 2 , He, Ne, N 2 , and Ar) show that gas molecules transport energy over length scales hundreds of times larger than the diameters of the pores in the aerogel. It is hypothesized that ineffi cient energy exchange between gas molecules and SWCNTs gives the permeating molecules a memory of their prior collisions. Low gas-SWCNT accommodation coeffi cients predicted by molecular dynamics simulations support this hypothesis. Amplifi ed energy transport length scales resulting from low gas accommodation are a general feature of CNT-based nanoporous materials.

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Section: Resultsmentioning

confidence: 99%

“…The thermal conductivity of the sample was determined by fitting the temperature amplitude inferred from the 3 ω signal, as a function of the applied frequency, to an analytical heat conduction model described previously 37. Representative fits are shown in Figure a for aerogel sample 1 in H 2 at pressures of 0.10 kPa and 98 kPa.…”

Section: Resultsmentioning

confidence: 99%

Gas Diffusion, Energy Transport, and Thermal Accommodation in Single‐Walled Carbon Nanotube Aerogels

Schiffres

Kim

et al. 2012

Adv Funct Materials

Self Cite

103

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“…One unique aspect of 3-Omega is that it can operate without individual sensor calibration unlike several other gas sensors. Previously, 3-Omega was pioneered to measure the thermal conductivity of thin-films and is extensively described in the literature [14][15][16][17][18]. In general, an electrical current of (angular) frequency ω = 2πf and root-mean-square value (RMS) I ω,RMS driven through a metal heater line, causing Joule heating at a frequency 2ω.…”

Section: Principles Of 3-omegamentioning

confidence: 99%

A microbridge heater for low power gas sensing based on the 3-Omega technique

Kommandur

Mahdavifar

Hesketh

et al. 2015

Sensors and Actuators A: Physical

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The 3-Omega measurement technique was applied to a microbridge heater for the purpose of low power gas sensing. The sensor performance was evaluated for mixtures of CO 2 , Ar, He and CH 4 in N 2 in an isothermal chamber where concentrations were precisely controlled by mass flow controllers. A custom 3-Omega conditioning circuit controls the AC heating current and detection of the 3-Omega voltage signal. The amplitude and phase lag, and the in-phase and outof-phase components of the 3-Omega signal are presented for each case and are related directly to gas concentrations. Advantageously, the phase lag can determine the gas concentration without calibration of an individual gas sensor. Using this technique and our current microbridge thermal conductivity detector (TCD), it is possible to resolve gas concentrations down to 0.07%. The frequency behavior of the 3-Omega signal as it pertains to the thermal environment and sensor sensitivity is discussed. The 3-Omega technique combined with the microbridge is capable of operating with power consumptions that are < 10 % of the power consumed by conventional Wheatstone bridge measurements at room temperature.

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“…Herein, we present a gas sensing technique that overcomes not only these challenges, but offers other advantages such as ease of fabrication, near room temperature measurements while still consuming power in the order of milliWatts. The design and fabrication technique of the sensor used in this work was first developed by Schiffres et al [8]. for the measurement of thermal conductivity of liquids and gases.…”

Section: Introductionmentioning

confidence: 99%

Metal-coated glass microfiber for concentration detection in gas mixtures using the 3-Omega excitation method

Kommandur

Mahdavifar

Jin

et al. 2016

Sensors and Actuators A: Physical

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The 3-Omega measurement technique was applied to a fabricated metal-coated glass fiber for the purpose of low power gas sensing. The sensor performance was evaluated for mixtures of CO 2 , Ar, He and CH 4 in N 2 in an isothermal chamber, where mass flow controllers precisely controlled concentrations. The metal-coated fiber was fabricated by depositing a thin layer of gold (~150 nm) onto a glass fiber, using a custom designed deposition lathe installed in a standard sputtering system. A custom 3-Omega conditioning circuit controls the AC heating current and detection of the 3-Omega voltage signal. The amplitude and phase lag, and the inphase and out-of-phase components of the 3-Omega voltage signal are presented for different gas mixtures and are related directly to their concentrations. Using this gas sensing technique, we have demonstrated the uncertainty in concentration (i.e., sensitivity) to be better than 50 ppm, and as low at 10 ppm for some gases. The dependence of the different 3-Omega signals on the thermophysical properties of the system is briefly described. The low power, high sensitivity nature of the sensor is also demonstrated as the metal-coated fiber sensor consumes ~ 10% of the power consumed by conventional thermal conductivity detectors (TCDs), and unlike those, it operates at near room temperatures.

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Improved 3-omega measurement of thermal conductivity in liquid, gases, and powders using a metal-coated optical fiber

Cited by 36 publications

References 25 publications

Gas Diffusion, Energy Transport, and Thermal Accommodation in Single‐Walled Carbon Nanotube Aerogels

Gas Diffusion, Energy Transport, and Thermal Accommodation in Single‐Walled Carbon Nanotube Aerogels

A microbridge heater for low power gas sensing based on the 3-Omega technique

Metal-coated glass microfiber for concentration detection in gas mixtures using the 3-Omega excitation method

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