KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Search Results

Now showing 1 - 10 of 15

Some of the metrics are blocked by your
consent settings
The roles of CO2 and water vapour on the high temperature corrosion of a type 430 stainless steel as an interconnect of bio-gas fuel intermediate temperature SOFCs
(2025-12-01)
Thublaor, Thammaporn
;
Srihathai, Padungaut
;
Tengprasert, Watcharapon
;
Suparapinyopapkul, Grid
;
Yan, Jiayi
A Type 430 stainless steel was exposed to Ar-20 %CO<inf>2</inf> without and with water vapour at 800 °C up to 96 h. Increasing water vapour content from 5 % to 40 % helped reduce mass gain, enhance volatilisation, and improve scale adhesion with fewer pores at scale/steel interface. Mechanisms for Cr and Mn volatilisations including the direct reactions between Cr-containing oxide and CO<inf>2</inf> were suggested with the aid of the XPS results. Mathematical relations that express the role of water vapour on concentrations of defects responsible for scale growth were proposed to help explain the reduced oxidation rate.
Some of the metrics are blocked by your
consent settings
Effects of temperature and water vapour on Cr-species volatilisation, oxidation and scale adhesion of a Type 409L stainless steel for application as interconnect of low temperature solid oxide fuel cells
(2024-06-01)
Homjabok, Wanna
;
Tengprasert, Watcharapon
;
Thublaor, Thammaporn
;
Wiman, Panya
;
Nilsonthi, Thanasak
Though the classical transport theory does not mathematically express the Arrhenius-like relation between Cr-loss flux due to volatilisation and absolute temperature, such relation was experimentally observed for 409L stainless steel exposed at 600–750 °C. Volatilisation calculation in the present cases can be estimated giving such relation because of the nearly linear relation between mass transfer coefficient and temperature. Cr-loss fluxes in O<inf>2</inf> with 20 and 40 % H<inf>2</inf>O are close to or coincided with the fluxes calculated from MnCr<inf>2</inf>O<inf>4</inf> evaporation. Increasing water vapour could enhance volatilisation contributed from the raised CrO<inf>2</inf>(OH)<inf>2</inf> pressure, reduce oxidation rate, and worsen scale adhesion.
Some of the metrics are blocked by your
consent settings
Oxidation and Scale Adhesion of a Type 430 Stainless Steel in Ar–CO2 Gas Mixtures at 800 °C
(2023-04-01)
Wiman, Panya
;
Muengjai, Angkana
;
Srihathai, Padungaut
;
Thublaor, Thammaporn
;
Siripongsakul, Thamrongsin
Biogas is an alternative source of fuel potentially used to run solid oxide fuel cells (SOFCs). It mainly consists of CH<inf>4</inf> and CO<inf>2</inf> which can degrade the SOFC interconnect, which is typically made of stainless steel. To investigate the effect of each gas constituent, we focussed here on the effect of CO<inf>2</inf> on high-temperature oxidation behavior of and scale adhesion on the stainless steel interconnect, Type 430 stainless steel. The samples studied were oxidised in CO<inf>2</inf> at contents of 5–100% at 800 °C. The oxidation kinetics were found to be parabolic with the rate constant increasing when the CO<inf>2</inf> content increased. The scale adhesion was assessed using a tensile-test method. The scale formed in the atmosphere containing higher CO<inf>2</inf> content exhibited poorer scale adhesion, as indicated by a lower strain initiating the first spallation and a larger spallation percentage after the first spallation took place. The worsened scale adhesion relates to pores formed at the scale/steel interface. The adhesion energies were further quantified giving the values of about 40–100 J m–2. Oxidation mechanisms were suggested based on the dependence of the parabolic rate constant on the oxygen partial pressure and the inward diffusion of carbon-bearing species.
Some of the metrics are blocked by your
consent settings
Oxidative stability of Iresine herbstii extract-containing coconut oil during storage
(2023-01-01)
Sai-Ut, S.
;
Senphan, T.
;
Pongsetkul, J.
;
Kaewthong, P.
;
Tuntivisoottikul, K.
Virgin coconut oil was used as green solvent for the extraction of total phenolics from I. herbstii (I. herbstii: coconut oil, 1:10 (w/w)). I. herbstii extract-containing coconut oil (ECC) had dark red in color. Acid value (AV), peroxide value (PV), thiobarbituric acid-reactive substances (TBARS), ρ-anisidine value and volatile compounds were taken as parameters for evaluation of oxidative stability of EEC sample. All parameters of EEC sample were lowered, in comparison with the control sample during storage for 7 weeks. ECC sample produced less TBARS value than the control (p<0.05). Abundance of volatile compounds in all samples correlated well with the TBARS value. Results revealed the use of coconut oil as green solvent for extraction of bioactive compounds and natural red pigment from I. herbstii, where I. herbstii as antioxidant to prevent lipid oxidation in vegetable oil.
Some of the metrics are blocked by your
consent settings
Treatment of Lignin Wastewater Using Peroxydisulfate Combined with Manganese Oxide-Loaded Biochar
(2022-09-01)
Suwannarat, Glinsukol
;
Sontabam, Kemason
;
Sawangying, Soraya
;
Chaiyaraksa, Chompoonut
The pulp and paper industry wastewater discharge into public water, it will cause water pollution problems. In this research, lignin contaminated synthetic wastewater with a COD value of 2,401 mg/L, and color intensity of 5,432 ADMI was treated using 150 mM sodium peroxydisulfate in combination with MnO<inf>x</inf>-loaded biochar (MnO<inf>x</inf>-B). The MnO<inf>x</inf>-B was produced by pyrolyzing corn core at 400 °C for 4 hours without oxygen, then dipped in 40 mM manganese sulfate for 2 hours, and heated at 600°C for 30 min without oxygen. From the characterization of MnO<inf>x</inf>-B, the surface area, pore volume, pore size, and pH value at the zero-point charges of MnO<inf>x</inf>-B were 153 m2/g, 0.054 cm3/g, 1.11 nm, and 7.23, respectively. From the FTIR spectrogram, the peak assigned to Mn-O was observed. By applying 150 mM sodium peroxydisulfate and varying three parameters: MnO<inf>x</inf>-B dosage, initial wastewater pH, and reaction time, to treat lignin wastewater, the optimum experimental condition was obtained using 2 mg/L of MnO<inf>x</inf>-B, under pH of 8 for 45 min. The COD and color removal efficiencies were 73% and 90%, respectively. However, the quality of the treated wastewater did not yet pass the pulp and paper mills effluent standards of the Department of Industrial Works.
Some of the metrics are blocked by your
consent settings
A new mechanism for resonance Rayleigh scattering detection of minoxidil based on catalytic oxidation of silver nanoparticles
(2022-07-05)
Teerasong, Saowapak
;
Praditweangkum, Wiboon
;
Chompoosor, Apiwat
This work presents a new method for minoxidil detection based on silver nanoparticle (AgNP) oxidation. Minoxidil, which is a pyrimidine N-oxide, can be reduced to its corresponding pyrimidine via a redox reaction. In this system, acetate buffer serves as a proton source. AgNPs act as electron donors that contribute electrons to the reaction, producing Ag+. Consequently, the sizes and numbers of AgNPs in the system decrease, which results in a decline in their resonance Rayleigh scattering (RRS). By monitoring the RRS intensity at 409 nm, a change in intensity was linearly related to the minoxidil concentration over a concentration range of 0.5 – 5.0 mM. The detection limit was 0.35 mM. This approach is simple and rapid. It is done by directly mixing the drug and AgNPs in an acidic buffer. The reaction was completed within 2 min. This proposed method was successfully utilized for quantification of minoxidil in topical hair-growth formulations.
Some of the metrics are blocked by your
consent settings
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.
Some of the metrics are blocked by your
consent settings
Comparative study on liquefaction behaviors of xylan hemicellulose as treated by different hydrothermal methods
(2020-02-01)
Phaiboonsilpa, Natthanon
;
Champreda, Verawat
;
Laosiripojana, Navadol
Liquefaction behaviors of xylan were studied as treated by six different hydrothermal methods. As a comparative study, a xylan sample isolated from corn core was subjected to hot-compressed water, hot-compressed 0.01 and 0.1wt% H<inf>2</inf>O<inf>2</inf> solutions under pressurization of N<inf>2</inf> or CO<inf>2</inf> at 110–250 °C for 0 min in 10-ml batch-type reactor. Not only xylose and xylo-oligosaccharides, but also arabinose, glucose, and acetic acid were recovered as hydrolyzed products. In addition, decomposition compounds, i.e. furans and organic acids were found. The highest xylose yield could be attained at 210 °C in all the studied hydrothermal methods, except for only 0.1wt% H<inf>2</inf>O<inf>2</inf> solution under pressurization of CO<inf>2</inf>. By this strongly oxidative condition, where peroxy carbonic acid was formed in situ, the temperature that xylose could be highly recovered was at 190 °C. The highest xylose yield of 61.62wt% was obtained by 0.01wt% H<inf>2</inf>O<inf>2</inf> solution under pressurization of N<inf>2</inf>. Formation of furan compounds showed a preference to the treatments with pressurized CO<inf>2</inf>, while organic acids had a better recovery when N<inf>2</inf> was applied. Different results in the production of various liquefied products could be attributed to the degree of hydrolysis and oxidation reactions which altered under the different hydrothermal methods.
Some of the metrics are blocked by your
consent settings
Xps analysis of oxide formed on the surface of co-28cr-6mo-1si alloy oxidized at 550 ºc
(2020-01-01)
Tunthawiroon, Phacharaphon
;
Kitiwan, Mettaya
;
Wongpromrat, Patthranit
;
Chiba, Akihiko
This work investigated the influence of oxidation durations on the formation of oxide on the surface of wrought Co-28Cr-6Mo-1Si alloy. The iso-thermal oxidation was individually performed in air at 550ºC for 4, 12 and 24 h. For comparison, the surface of the non-oxidized Co-28Cr-6Mo-1Si alloy was concurrently examined. The chemical compositions of the non-oxidized and oxidized alloys were principally analyzed via X-ray photoelectron spectroscopy (XPS). The XPS results revealed that the surface of the non-oxidized alloy enriched in Cr-oxide. After oxidation treatment, the Co-oxide, existing as Co2+ state was observed coexisting with two Cr-oxide states, Cr3+ and Cr4+. The low concentrations of Mo6+ were also observed on the oxidized alloy surface. With the increase in oxidation durations, the Co-oxide was suppressed by Cr-oxide. The XPS depth profile analysis indicated that the thickness of the oxide film increased with increasing the oxidation duration.
Some of the metrics are blocked by your
consent settings
Advanced microstructural investigations of AISI 441 early stage oxidation in wet atmosphere
(2017-01-01)
Wongpromrat, Wichitra
;
Parry, Valérie
;
Chandra-Ambhorn, Walairat
;
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.

KMITL

Browse

Filters

Settings

Sort By

Results per page

Search Results