Evaluation of Gas Permeability in Microfluidic Device by Confocal Micro-PIV Combined With LIF Technique

2011 ◽  
Author(s):  
Mitsuhisa Ichiyanagi ◽  
Keita Sakai ◽  
Shinya Kidani ◽  
Yasuhiro Kakinuma ◽  
Yohei Sato ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Surface Area ◽  
Liquid Flow ◽  
Gas Permeability ◽  
Gas Permeation ◽  
Membrane Thickness ◽  
Micro Machining ◽  
Dissolved Gas ◽  
Gas Concentration ◽  
Elastomeric Material

Microfluidic devices with the gas permeability through polymer membranes were developed for further high-efficiency of gas-liquid chemical reactions and high-accuracy of environmental diagnosis. The devices were composed of a cover glass and a polydimethylsiloxane (PDMS) chip which has the ability to permeate various gases, because PDMS is made of the elastomeric material. In the chip, microchannels with a width ranging from a few micrometers to a few hundred micrometers were manufactured by using the cryogenic micro machining. The gas permeation phenomena in microchannels are dominated by several factors, such as the gas and liquid flow rates, the membrane thickness between gas and liquid flow, and the surface area of membranes. The advantage of the present work is to realize the simple control of the gas permeability by changing the surface roughness of PDMS, because the cryogenic micro machining enables to control the surface roughness of microchannels and the increase in its roughness yields that in the surface area of membranes. For the evaluation of the gas permeability, the velocity and dissolved gas concentration distribution in the liquid flow field were measured by utilizing micron-resolution particle image velocimetry combined with laser induced fluorescence, and the measurement system was based on the confocal microscope to improve the depth resolution drastically. The experiments were performed under the several conditions with a change in the gas flow rate, the PDMS membrane thickness and the surface roughness, which affect the gas permeation phenomena. The results indicate that the velocity-vector distributions in the liquid flow have a similar pattern and the magnitudes of the velocity are approximately the same values under all conditions, while the dissolved gas concentration distributions have different patterns. It was quantitatively clear that the gas permeability through PDMS membranes was increased with an increase in the surface roughness and has the linearity to the surface area of membranes. The important conclusion is that the proposed device achieves to control the gas permeability by using the elastomeric material and changing the surface roughness.

PEMFC Development at Asahi Glass Co., Ltd.

1999 ◽  
Vol 575 ◽  
Author(s):  
M. Yoshitake ◽  
E. Yanagisawa ◽  
T. Naganuma ◽  
Y. Kunisa
Keyword(s):  
Ion Exchange ◽  
Mechanical Strength ◽  
Water Content ◽  
Hydrogen Permeation ◽  
Specific Resistance ◽  
Gas Permeability ◽  
Cell Voltage ◽  
Free Cell ◽  
Gas Permeation ◽  
Membrane Thickness

ABSTRACTPerfluorinated ion exchange membranes were studied and the membrane technology for PEMFC has been developed. Thermal stability, mechanical strength, water content, AC specific resistance and gas permeability were measured. The influence of membrane thickness on gas permeability and the influence of incorporation of cations on water content and AC specific resistance of Flemion® and Nafion® 117 were estimated. Gas permeation rates of the membranes decreased in inverse proportion to the increase of the membrane thickness and gas permeability coefficients were nearly constant and independent of the thickness. Hydrogen permeation rates of Flemion®S at 70°C were converted to 2.1 mA/cm2 as cunent density. Flemion®R-electrode assembly showed to maintain stable perfonnance for over 3,500hr. Furthermore, it was found that usage of thinner membranes or one with higher ion-exchange capacity gave not only lower intemal cell voltage but also higher iR-free cell voltage. PTFE-yam embedded type membrane (Flemion®Mc and Sc) and PTFE-flbril dispersed type (Flemion®R12) was examined to afford improvement in mechanical strength at moist and high temperature atmosphere. Flemion®Sc (80!am) was examined to give high cell performance of 0.67V at 0.5A/cm2, 80°C, I ata. Flemior®Mc-electrode assembly was examined to keep stable performance during the life test of over 1,500hr.

scholarly journals Synthesis and Gas-Permeation Characterization of a Novel High-Surface Area Polyamide Derived from 1,3,6,8-Tetramethyl-2,7-diaminotriptycene: Towards Polyamides of Intrinsic Microporosity (PIM-PAs)

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 361 ◽  
Author(s):  
Giuseppe Genduso ◽  
Bader Ghanem ◽  
Yingge Wang ◽  
Ingo Pinnau
Keyword(s):  
Surface Area ◽  
Gas Permeability ◽  
High Surface ◽  
High Surface Area ◽  
Gas Permeation ◽  
Bet Surface Area ◽  
Mixed Gas ◽  
Fractional Free Volume ◽  
Intrinsic Microporosity

A triptycene-based diamine, 1,3,6,8-tetramethyl-2,7-diamino-triptycene (TMDAT), was used for the synthesis of a novel solution-processable polyamide obtained via polycondensation reaction with 4,4′-(hexafluoroisopropylidene)bis(benzoic acid) (6FBBA). Molecular simulations confirmed that the tetrasubstitution with ortho-methyl groups in the triptycene building block reduced rotations around the C–N bond of the amide group leading to enhanced fractional free volume. Based on N2 sorption at 77 K, 6FBBA-TMDAT revealed microporosity with a Brunauer–Emmett–Teller (BET) surface area of 396 m2 g−1; to date, this is the highest value reported for a linear polyamide. The aged 6FBBA-TMDAT sample showed moderate pure-gas permeabilities (e.g., 198 barrer for H2, ~109 for CO2, and ~25 for O2) and permselectivities (e.g., αH2/CH4 of ~50) that position this polyamide close to the 2008 H2/CH4 and H2/N2 upper bounds. CO2–CH4 mixed-gas permeability experiments at 35 °C demonstrated poor plasticization resistance; mixed-gas permselectivity negatively deviated from the pure-gas values likely, due to the enhancement of CH4 diffusion induced by mixing effects.

Experimental Study on Roughness Effect for Laminar Micro-Channel Gas Flow

2001 ◽  
Author(s):  
Jih-Hsing Tu ◽  
Fangang Tseng ◽  
Ching-Chang Chieng
Keyword(s):  
Experimental Study ◽  
Surface Roughness ◽  
Friction Factor ◽  
Gas Flow ◽  
Micro Channel ◽  
Micro Machining ◽  
Roughness Effect ◽  
Relative Roughness ◽  
Smooth Channel ◽  
Micro Channels

Abstract Present study investigates the roughness effect on laminar gas flow for microchannels ranging from 40 to 600 μm with various roughness heights (40–82 nm) by systematical experiments. The micro-channels are manufactured by micro-machining technology and KOH anisotropic etching is employed to achieve various roughness patterns. Experimental results shows that higher product levels of Reynolds number (Reh) and friction factor (f) are obtained for microchannels of larger size and smaller relative roughness and friction factor f approaches to laminar flow theory value f0 for very smooth channel but the ratio of (f/f0) decreases as the surface roughness increases.

Flux of silver-carbonate membranes for post-combustion CO2 capture: The effects of membrane thickness, gas concentration and time

2014 ◽  
Vol 455 ◽  
pp. 162-167 ◽  
Author(s):  
Lingling Zhang ◽  
Yunhui Gong ◽  
Kyle S. Brinkman ◽  
Tao Wei ◽  
Siwei Wang ◽  
...  
Keyword(s):  
Co2 Capture ◽  
Membrane Thickness ◽  
Silver Carbonate ◽  
Gas Concentration

Study of surface roughness in wire electrochemical micro machining

2015 ◽  
Vol 222 ◽  
pp. 103-109 ◽  
Author(s):  
Kun Xu ◽  
Yongbin Zeng ◽  
Peng Li ◽  
Di Zhu
Keyword(s):  
Surface Roughness ◽  
Micro Machining

scholarly journals Gas Permeation Through Single-Crystal ZIF-8 Membranes

2019 ◽  
Author(s):  
Chen Chen ◽  
Aydin Ozcan ◽  
A. Ozgur Yazaydin ◽  
Bradley Ladewig
Keyword(s):  
Single Crystal ◽  
Grain Boundaries ◽  
Gas Permeability ◽  
Metal Organic Framework ◽  
Gas Permeation ◽  
Microstructural Feature ◽  
Polycrystalline Metal ◽  
Transmission Electron ◽  
Metal Organic ◽  
Separation Performances

<b>Abstract</b><div>Grain boundaries are an unavoidable microstructural feature in intergrown polycrystalline metal-organic framework (MOF) membranes. They have been suspected to be less size-selective than a MOF’s micropores, resulting in suboptimal separation performances – a speculation recently confirmed by transmission electron microscopy of MOF ZIF-8. Single-crystal membranes, without grain boundaries, should confine mass transport to micropores and reflect the intrinsic selectivity of the porous material. Here, we demonstrate the feasibility of fabricating single-crystal MOF membranes and directly measuring gas permeability through such a membrane using ZIF-8 as an exemplary MOF. Our single-crystal ZIF-8 membranes achieved ideal selectivities up to 28.9, 10.0, 40.1 and 3.6 for gas pairs CO<sub>2</sub>/N<sub>2</sub>, CO<sub>2</sub>/CH<sub>4</sub>, He/CH<sub>4</sub> and CH<sub>4</sub>/N<sub>2</sub> respectively, much higher than or reversely selective to over 20 polycrystalline ZIF-8 membranes, unequivocally proving the non-selectivity of grain boundaries. The permeability trend obtained in single-crystal membranes aligned with a force field that had been validated against multiple empirical adsorption isotherms.<br></div>

scholarly journals Porous Medium Equation in Graphene Oxide Membrane: Nonlinear Dependence of Permeability on Pressure Gradient Explained

Membranes ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 665
Author(s):  
Lukáš Mrazík ◽  
Pavel Kříž
Keyword(s):  
Porous Medium ◽  
Graphene Oxide ◽  
Governing Equation ◽  
Pressure Difference ◽  
Gas Permeability ◽  
Porous Medium Equation ◽  
Gas Permeation ◽  
Nonlinear Dependence ◽  
Medium Equation ◽  
Oxide Membrane

Membrane performance in gas separation is quantified by its selectivity, determined as a ratio of measured gas permeabilities of given gases at fixed pressure difference. In this manuscript a nonlinear dependence of gas permeability on pressure difference observed in the measurements of gas permeability of graphene oxide membrane on a manometric integral permeameter is reported. We show that after reasoned assumptions and simplifications in the mathematical description of the experiment, only static properties of any proposed governing equation can be studied, in order to analyze the permeation rate for different pressure differences. Porous Medium Equation is proposed as a suitable governing equation for the gas permeation, as it manages to predict a nonlinear behavior which is consistent with the measured data. A coefficient responsible for the nonlinearity, the polytropic exponent, is determined to be gas-specific—implications on selectivity are discussed, alongside possible hints to a deeper physical interpretation of its actual value.

Scaling Analysis of a- and poly-Si Surface Roughness by Atomic Force Microscopy

1994 ◽  
Vol 367 ◽  
Author(s):  
T. Yoshinobu ◽  
A. Iwamoto ◽  
K. Sudoh ◽  
H. Iwasaki
Keyword(s):  
Surface Roughness ◽  
Atomic Force Microscopy ◽  
Surface Area ◽  
Scaling Behavior ◽  
Linear Size ◽  
Scaling Analysis ◽  
Macroscopic Scale ◽  
Force Microscopy ◽  
Atomic Force ◽  
Roughness Exponent

AbstractThe scaling behavior of the surface roughness of a-and poly-Si deposited on Si was investigated by atomic force microscopy (AFM). The interface width W(L), defined as the rms roughness as a function of the linear size of the surface area, was calculated from various sizes of AFM images. W(L) increased as a power of L with the roughness exponent ∝ on shorter length scales, and saturated at a constant value of on a macroscopic scale. The value of roughness exponent a was 0.48 and 0.90 for a-and poly-Si, respectively, and σ was 1.5 and 13.6nm for 350nm-thick a-Si and 500nm-thick poly-Si, respectively. The AFM images were compared with the surfaces generated by simulation.

Oxygen Transport Through the Zirconia Top Coat in Thermal Barrier Coating Systems

1998 ◽  
Author(s):  
A.C. Fox ◽  
T.W. Clyne
Keyword(s):  
Thermal Barrier Coating ◽  
Bond Coat ◽  
Ionic Conduction ◽  
Gas Permeability ◽  
Gas Permeation ◽  
Thermal Barrier ◽  
Barrier Coating ◽  
Oxygen Gas ◽  
Plasma Sprayed ◽  
Tbc Systems

Abstract The gas permeability of plasma sprayed yttria-stabilised zirconia coatings has been measured over a range of temperature, using hydrogen and oxygen gas. The permeability was found to be greater for coatings produced with longer stand-off distances, higher chamber pressures and lower torch powers. Porosity levels have been measured using densitometry and microstructural features have been examined using SEM. A model has been developed for prediction of the permeability from such microstructural features, based on percolation theory. Agreement between predicted and measured permeabilities is good. Ionic conduction through the coatings has also been briefly explored. It is concluded that transport of oxygen through the top coat in thermal barrier coating (TBC) systems, causing oxidation of the bond coat, occurs primarily by gas permeation rather than ionic conduction, at least up to temperatures of about 1000°C and probably up to higher temperatures. Top coat permeabilities appreciably below those measured will be required if the rate of bond coat oxidation is to be reduced by cutting the supply of oxygen to the interface.

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