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Author: search.filters.author.Wongpromrat, Wichitra

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    Morpho-chemical investigations and thermodynamic study of Nb-rich passive nodules grown on AISI 441 oxidized in wet atmosphere
    (2018-08-15)
    Parry, Valérie
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    Wongpromrat, Wichitra
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    Latu-Romain, Laurence
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    Pascal, Céline
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    Chandra-ambhorn, Walairat
    AISI 441 sheets were oxidized from 4 to 24 h at 800 °C in wet atmosphere. Micrometric oxide nodules containing Ti, Nb, Cr and Mn were observed to form on the passive scale. The internal microstructure of these objects was investigated using STEM–EDX and FIB-SEM tomography. Experimental results reveal a complex microstructure linked with the presence of Si and Nb and their competition for interfacial oxidation. Eventually, the chemical compositions of the nodule and of the oxidation affected zone in the nodule vicinity are discussed in relation with thermodynamic calculations investigating the stability of the different oxides.
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    Arsenic adsorption using the adsorbent synthesised from oyster shell
    (2017-01-01)
    Khownpurk, Pichnipa
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    Wongpromrat, Wichitra
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    Chandra-Ambhorn, Walairat
    Ground oyster shells were calcined and used as an adsorbent to remove As (III) from contaminated water. Adsorption experiment was performed by batch tests. The effect of pH on the adsorption performance was investigated. The result showed that at the initial concentration of 100 mg/L, over the pH range of 5-11, the highest efficiency was obtained at pH 11. The experimental data better correlated with pseudo-second order model. The maximum adsorption capacity (q<inf>m</inf>) of approximately 195.5 mg/g was obtained at pH 11.
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    Advanced microstructural investigations of AISI 441 early stage oxidation in wet atmosphere
    (2017-01-01)
    Wongpromrat, Wichitra
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    Parry, Valérie
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    Chandra-Ambhorn, Walairat
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    Chandra-Ambhorn, Somrerk
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    Galerie, Alain
    AISI 441 ferritic stainless steel is a good candidate for metallic interconnects in solid oxide fuel cells (SOFCs). The minor elements Ti and Nb are used to stabilize the ferritic matrix and also to reduce creep by a combination of solid solution strengthening and precipitation of intermetallic Laves phase particles along the grain boundaries. However their influence on the oxidation behavior is not well understood. This study focuses on the early stages oxidation (from 4 to 24 h) at 800°C of AISI 441 under 5% H<inf>2</inf>O in O<inf>2</inf>. A relatively smooth micro-crystallized oxide scale and Ti, Nb containing nodules are observed. The internal microstructure of these objects is studied by FIB tomography which allows computing cross sectional views in any direction of interest. FIB study reveals a complex microstructure and a development strongly linked to the presence of niobium and/or titanium in the substrate.
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    Reduction of chromium volatilisation from stainless steel interconnector of solid oxide electrochemical devices by controlled preoxidation
    (2016-05-01)
    Wongpromrat, Wichitra
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    Berthomé, Grégory
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    Parry, Valérie
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    Chandra-ambhorn, Somrerk
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    Chandra-ambhorn, Walairat
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    Chromium vaporisation from AISI 441 stainless steel oxidised in humidified oxygen
    (2013-06-01)
    Wongpromrat, Wichitra
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    Thaikan, Harit
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    Chandra-Ambhorn, Walairat
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    Chandra-Ambhorn, Somrerk
    Chromium vaporisation from chromia-forming alloys when exposed to high temperatures can deteriorate the protective property of oxide scale. This problem affects the lifetime of solid oxide fuel cells and solid oxide electrolysers using chromia-forming alloys as interconnectors. In this work, AISI 441, a commercial grade stainless steel which chromium vaporisation investigation has not been reported so far, was chosen for study. Chromium vaporisation rates of bare AISI 441 and AISI 430 and AISI 441 and AISI 430 coated with Mn-Co spinel by electroplating method were measured in an atmosphere of 5 % H<inf>2</inf>O in O<inf>2</inf> over the temperature range of 650-900 C with the linear velocity of the humidified oxygen stream varied in the range of 0.8-3.0 cm s<sup>-1</sup>. For uncoated samples, AISI 441 showed a lower chromium vaporisation rate in comparison with that of AISI 430. Mn-Co spinel coating could reduce the chromium vaporisation rate from AISI 430 surface. However, on the contrary, the Mn-Co spinel coating could not only fail to suppress the chromium vaporisation, but it also promoted the chromium vaporisation from AISI 441 surface by 2 times. © 2013 Springer Science+Business Media New York.