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Subject: search.filters.subject.Knudsen diffusion

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    Modification of Al2O3-Based Membranes with Carbon Black for Enhanced Hydrogen Permeation
    (2025-11-01)
    Hankoy, Montree
    ;
    Rodchom, Mana
    ;
    Vichaphund, Supawan
    ;
    Atong, Duangduen
    ;
    Zhang, Jianfeng
    This work presents the development and characterization of alumina–carbon black (ACB) composite membranes for enhanced hydrogen separation performance. A series of membranes containing 0–3.0 wt.% carbon black was fabricated via high-temperature sintering and systematically investigated with respect to their structural, morphological, mechanical, and gas separation properties. The addition of carbon black significantly influenced membrane microstructure, promoting pore network formation, increasing specific surface area, and enhancing gas transport. Gas permeation tests using H<inf>2</inf> and N<inf>2</inf> revealed that all ACB membranes exhibited higher hydrogen permeance than the pure Al<inf>2</inf>O<inf>3</inf> membrane. Notably, the ACB3.0 specimen demonstrated the highest H<inf>2</inf> permeance of 508 × 10<sup>−6</sup> mol m<sup>−2</sup> s<sup>−1</sup> Pa<sup>−1</sup> at 303 K, which is nearly four times greater than the unmodified membrane. At an elevated temperature (773 K), H<inf>2</inf>/N<inf>2</inf> selectivity improved with increasing carbon black content, with ACB3.0 achieving a maximum selectivity of 3.82, exceeding the theoretical Knudsen value, suggesting a synergistic contribution of Knudsen diffusion and surface diffusion. These results demonstrate that carbon black is a cost-effective and versatile additive for modifying ceramic membranes, offering a promising route for advancing hydrogen purification technologies in industrial applications.
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    Enhancing the hydrogen permeation of alumina composite porous membranes via graphene oxide addition
    (2023-01-12)
    Hankoy, Montree
    ;
    Phrompet, Chaiwat
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    Ruttanapun, Chesta
    ;
    Kaewpengkrow, Prangtip Rittichote
    ;
    Vichaphund, Supawan
    Graphene oxide (GO) membranes have attracted considerable interest for hydrogen (H<inf>2</inf>) purification applications. However, the addition of GO into matrix materials to enhance the efficiency of H<inf>2</inf> permeation remains a challenge. In this study, the fabrication of alumina/graphene oxide (AGO) composites containing varying contents of GO (0.5–3.0 wt.%) was investigated. The AGO composites were formed into pellets and sintered for 2 h at 1500 °C. Accordingly, the presence of GO in the membranes following sintering was confirmed by Raman spectroscopy. Additionally, the porosity of the AGO composites increased from 3.7% to 26.9% as the GO concentration increased from 0.5 wt.% to 3.0 wt.%. Furthermore, the average pore diameter of the AGO composites was in the range of 87–228 nm, and the pore size distribution was unimodal. The performance of the AGO membranes was investigated for the permeance of single gases H<inf>2</inf> and N<inf>2</inf> at 30–500 °C to evaluate their potential for H<inf>2</inf> separation applications. The AGO membranes with a GO addition of 2.5 and 3.0 wt.% exhibited a high hydrogen permeance of 232–410 × 10<sup>−6</sup> mol m<sup>−2</sup> s<sup>−1</sup> Pa<sup>−1</sup>, which was approximately 10 times greater than that of pristine Al<inf>2</inf>O<inf>3</inf> membrane. Additionally, the ideal H<inf>2</inf>/N<inf>2</inf> selectivity values ranged from 4.02 to 4.20. Furthermore, gas permeation through the AGO membrane was observed to follow the Knudsen diffusion mechanism.
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    Oxidation and volatilisation behaviour of a type 430 stainless steel coated by Mn-Co oxide by slurry method with pre-oxidation for SOFC interconnect application
    (2021-07-15)
    Chandra-ambhorn, Somrerk
    ;
    Homjabok, Wanna
    ;
    Chandra-ambhorn, Walairat
    ;
    Thublaor, Thammaporn
    ;
    Siripongsakul, Thamrongsin
    An AISI 430 stainless steel was coated by Mn-Co spinel using a slurry method. Pre-oxidation before the coating helped reduce the oxidation rate of the coated steel at 800 °C in O<inf>2</inf>-5%H<inf>2</inf>O, relating to the formation of the continuous chromia layer which inhibited the outward diffusion of iron to the coating layer. It also helped reduce the mass flux of Cr loss due to the volatilisation. The combined molecular and Knudsen diffusion of the volatile species through the coating layer was suggested to explain the reduced volatilisation rate of the coated sample with pre-oxidation.