Chandraambhorn, Walairat

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Chandra-Ambhorn, Walairat

Chandra-ambhorn, Walairat

Chandra-Ambhorn, W.

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School of Engineering

walairat.ch@kmitl.ac.th

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Characterisation and pickling behaviour of thermal oxide scale on low carbon steel produced from a thin slab
(2011-01-01)
Chandra-Ambhorn, Somrerk
;
Somphakdee, Tanongsak
;
Chandra-Ambhorn, Walairat
Thin slab interested in this work was the one with the thickness of ca. 50 mm and mainly made from recycled steel. Chemical composition of the studied steel strip produced from such slab was Fe with 0.077 wt% C, 0.233 wt% Mn, 0.191 wt% Si, 0.159 wt% Cu and 0.052 wt% Ni. Scale retained on that steel after hot rolling was studied. The hot-rolled sample was pickled in 10%v/v HCl aqueous solution at 80 °C. Weight loss and relative XRD peaks of hematite-per-iron and magnetite-per-iron were measured at different pickling periods of time. It was observed that the as-received scale was crack-free. Hematite-and-iron ratio approached zero at the pickling time of 3 seconds. Magnetite-per-iron ratio gradually decreased with increased pickling time and approached zero later. These results indicated that pickling solution attacked the outermost hematite layer resulting in removing of this layer first. Sublayers of scale consisting of magnetite were completely pickled later. Pickling behaviour was not merely volumetric since scale was crack-free. Mechanical adhesion of scale on steel substrate was additionally investigated by tensile test to help characterise the oxide scale. © (2011) Trans Tech Publications.
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Optimisation of metallic interconnects for hydrogen production by high temperature water vapour electrolysis
(2012-01-01)
Ardigo, M. R.
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Parry, V.
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Popa, I.
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Chevalier, S.
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Chandra-Ambhorn, W.
For economical and environmental reasons, hydrogen is considered as a major energetic vector for the future. Hydrogen production via high temperature water vapour electrolysis (HTE) is a promising technology. A major technical difficulty related to high temperature water vapour electrolysis is the development of interconnects working efficiently for a long period. Working temperature of 800°C enables the use of metallic materials as interconnects. Chromia forming alloys are among the best candidates. The interconnect material chosen in the present study is a ferritic stainless steel with 18% chromium content. High temperature corrosion resistance and electrical conductivity of the alloy was tested in both cathode (H<inf>2</inf>/H<inf>2</inf>O) and anode (O<inf>2</inf>/H<inf>2</inf>O) atmospheres. Corrosion products were then characterized by SEM-EDX and XRD. Moreover chromium evaporation measurements were carried out under anode atmosphere. © (2012) Trans Tech Publications.
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Arsenic adsorption using the adsorbent synthesised from oyster shell
(2017-01-01)
Khownpurk, Pichnipa
;
Wongpromrat, Wichitra
;
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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Preparation and characterization of oyster shell powder-treated rice husk ash adsorbent pellet for As(III) removal
(2018-08-14)
Khownpurk, Pichnipa
;
Chandra-Ambhorn, Walairat
The adsorbent pellet for As(III) removal was prepared from ground oyster shell and rice husk ash. The effects of particle size of oyster shell powder (OS) and the ratio between the OS and Treated rice husk ash (TRHA) on the stability of the adsorbent pellet were studied. The adsorbent pellet was characterized by XRD, XRF and SEM. The solubility and As(III) adsorption tests were performed. The results showed that the adsorbent pellet prepared from OS size <106 μm with OS:TRHA ratio of 0.7:0.3 could provide As(III) maximum adsorption capacity of approximately 26.20 mg/g. Furthermore, the XRD and SEM results indicated that the adsorbent pellet could consist of two parts i.e. CaO that could adsorb As(III) in the form of Ca-As-O and the CaSiO<inf>3</inf> and C-S-H compounds which behaved as a binder to bind the precursor powders to be stable adsorbent pellet without cracking.
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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
;
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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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.

Chandraambhorn, Walairat

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