Permeability of microporous carbon preforms

Datta, Sandip; Simhai, Nira; Tewari, Surendra N.; Gatica, Jorge E.; Singh, Mrityunjay

doi:10.1007/bf02595458

Cited by 10 publications

(5 citation statements)

References 6 publications

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“…The permeability of the carbon monolith used as a ow through medium was calculated $11.75 AE 1.45 Â 10 À12 m 2 and found comparable with the literature report. 49 This result suggests that this highly porous carbon and the experimental setup could be useful for ltration, catalytic reactor, electro osmotic pump and drug delivery systems.…”

Section: Characterization For the Carbon Monolith As Ow Through Elec...mentioning

confidence: 92%

“…† The good-ness of the t of linear regression (R 2 ¼ 0.943) results shows the validity of Darcy's law. 49 The Darcy's equation is given by Q ¼ À(k/m)DP/L, where Q, m, DP, L and k are the volumetric ow rate, viscosity of water, pressure difference, length of the frit, and water permeability of the monolith, respectively. Hence, the slopes of the linear water ow rate versus pressure gradient curve were used to get the permeability of the carbon monolith.…”

Section: Characterization For the Carbon Monolith As Ow Through Elec...mentioning

confidence: 99%

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One-step sol–gel synthesis of hierarchically porous, flow-through carbon/silica monoliths

2016

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Section: Characterization For the Carbon Monolith As Ow Through Elec...mentioning

confidence: 92%

Section: Characterization For the Carbon Monolith As Ow Through Elec...mentioning

confidence: 99%

One-step sol–gel synthesis of hierarchically porous, flow-through carbon/silica monoliths

2016

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“…Given that the pore diameter in graphene aerogel is approximately equal to 500 nm [27], we find that Φ ≈ 2.6 × 10 −7 . • k = 3 × 10 −14 m 2 [28] • d ≈ 1 nm in supercapacitors [25] • ϵ r ≈ 1 in supercapacitors [25] • 𝐼 ≈ $ 416,000 m 2 [29] • Diameter of the graphene aerogel electrode = 5 mm By substitution with the above parameters in Eq. ( 9), we find Δ𝑝 = 18.72 × 10 6 𝐶 2 𝑡 (10)…”

Section: B Capacitance Of the Supercapacitor As A Function Of Applied...mentioning

confidence: 99%

Ultrahigh-Sensitivity Pressure Sensor With Graphene Aerogel Electrodes

Bakhoum

2023

IEEE Open J. Instrum. Meas.

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A new pressure sensor with ultrahigh sensitivity is presented. The sensor is based on the concept of creating a variable supercapacitor that responds to pressure. The sensor consists mainly of a liquid electrolyte and two graphene aerogel electrodes. As pressure is applied to the graphene aerogel electrodes, the liquid electrolyte penetrates in the pores of the electrodes and a variable supercapacitor is obtained. The sensor is sensitive to pressures of less than 0.1 Pascal. Characteristics of the sensor such as accuracy, nonlinearity, and response time are fully analyzed.

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“…The characteristic length scale used to define the Reynolds number for consolidated porous media depends to the conformation of the internal network. The average pores' diameter is usually selected as characteristic dimension for metallic and composite foams [30][31][32] . The average fibers' diameter, or the hydraulic diameter based on the radius and on the volume fraction of the fibers, is commonly used for fibrous composite materials 21,26 .…”

Section: Basic Concepts For Permeability Measurementsmentioning

confidence: 99%

“…(1)) is the most simplified relation that describes the permeability dependence and it is valid in the case of laminar, non-inertial flow (creeping or Stokes flow) 13 The average permeability tensor (K ̿ ) [15][16][24][25] can be calculated once the driving force ( ⃗⃗⃗⃗⃗ ), the average velocity across the probed area (Darcy's velocity, U D ⃗⃗⃗⃗⃗ ), and the fluid viscosity (μ f ) are known. The formal derivation of the Darcy's law is obtained from the averaging technique of the Navier-Stokes (N-S) equations applied to a Reference Elementary Volume (REV) being statistical in terms of porosity [24][25][26][27][28][29][30] . The averaging process on the entire domain is needed since it is quite complicated to solve the N-S equations inside the fluid domain due to the complex internal geometry of porous medium and due to the difficulty of defining the boundary conditions [24][25]27 .…”

Section: Basic Concepts For Permeability Measurementsmentioning

confidence: 99%

Permeability Measurements of Complex Porous Structures for Reusable Thermal Protection Systems (Invited)

Gulli

Maddalena

McKelvey

et al. 2014

19th AIAA International Space Planes and Hypersonic Systems and Technologies Conference

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Reusable thermal protection systems are one of the key technologies that have to be improved in order to afford long-duration hypersonic flights. Transpiration cooling has been demonstrated to be one of the most promising active cooling techniques in terms of temperature decreasing and coolant mass saving. The coupling of the boundary layer with the thermal response of selected porous materials plays a crucial role in enabling the practical use of the transpiration cooling technique for reusable thermal protection systems. In this work, a novel test-rig for the non-intrusive characterization in terms of local permeability of a customized porous Carbon-Carbon nose-tip is proposed. The new concept of effective permeability, conceived as the local blowing capability of a porous structure with respect to a selected coolant fluid, is also introduced. The coolant (air) mass-fluxes blown from the porous surface of the specimen, and measured by a hot-film probe, are related to the average pressure gradient across the local material thickness by using the Darcy's law on prescribed locations. A parallel work, based on the X-Ray computed tomography scan of the prototype specimen, has been carried out with the purpose of defining the most important guidelines for the effective-permeability tests. Specifically, the calculation of the average porosity is used to define the minimum area to be probed with the hot-wire. The analysis of the statistical distribution of the void structures inside the C/C cone, coupled to the use of the theory of fluid-flow through perforated plates, is performed to determine the correct distance of the hot-wire from the wall. The results show permeability variation among the surveyed locations ranging from 6% to 172%. The effective-permeability map obtained allows classifying the prototype C/C mask as a semi-pervious structure. In particular, the higher effective permeability is located near the stagnation point region where two delaminations are located. The asymmetric blowing capability of the cone highlights the importance of characterizing the entire thermal protection system instead of defining the overall properties of the material, which can be drastically different at the full-scale level due to the geometry, the system integration and the intrinsic defectology due to the manufacturing process. Nomenclature= slope of the chart pressure gradient vs. Darcy's velocity, ( • / 2 ) = transversal distance from the wall, ( .) ℎ = channels' diameter, ( ) = diameter of the control points, ( .) = local specimen's thickness, ( .) 2 ̿ = permeability tensor, ( 2 ) = permeability for the r-direction, ( ) = length, ( ) = merging or coalescence distance, ( .) ̇ = measured flow rate, ( ) = network-mesh size, ( .) = external pressure, ( ) = internal-plenum pressure, ( ) = external-plenum pressure, ( ) 2 = coefficient of determination, (−) ℎ = Reynolds number based on the channel's diameter, (−) = time, ( ) = calibration temperature, ( ) = hot-film temperature, ( ) = measured temperature during permeability tes...

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Permeability of microporous carbon preforms

Cited by 10 publications

References 6 publications

One-step sol–gel synthesis of hierarchically porous, flow-through carbon/silica monoliths

One-step sol–gel synthesis of hierarchically porous, flow-through carbon/silica monoliths

Ultrahigh-Sensitivity Pressure Sensor With Graphene Aerogel Electrodes

Permeability Measurements of Complex Porous Structures for Reusable Thermal Protection Systems (Invited)

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