High‐Temperature Oxidation

Sequeira, C. A. C.

doi:10.1002/9780470872864.ch20

Cited by 6 publications

(6 citation statements)

References 157 publications

(137 reference statements)

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“…The idea behind the direct annealing approach is to maximize the stress in the film by maximizing thermal stresses (σ therm ) during the synthesis process of the hematite films following the relation 31…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Stresses can be reduced by relaxation mechanisms, such as plastic deformation and/or cracks, as discussed for instance by Sequeira. 31 Chen et al 32 showed the stress relaxation in hematite through oxygen vacancies formation. This could explain the charge carrier concentration enhancement obtained by direct annealing.…”

mentioning

confidence: 99%

“…Hematite films are expected to be under compressive stresses. 31 However, further studies are required for better understanding. Furthermore, to clarify the effect of direct annealing on the photocurrent density and the charge carrier concentration, subsequent annealing was performed on the hematite photoanode directly annealed at 630 °C for 2 h (see Figure 1b).…”

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confidence: 99%

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Nanometer-Thick Hematite Films as Photoanodes for Solar Water Splitting

Chnani

Kurniawan

Bund

et al. 2022

ACS Appl. Nano Mater.

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Photoelectrochemical (PEC) water splitting is one of the most promising sustainable methods for feasible solar hydrogen production. However, this method is still impractical due to the lack of suitable photoanode materials that are efficient, stable, and cost-effective. Here, we present a surprisingly simple fabrication method for efficient, stable, and cost-effective nanometer-thick hematite films utilizing a rapid, ambient annealing approach. In the oxygen evolution reaction, the fabricated hematite films exhibit a Faradaic efficiency of 99.8% already at 1 V versus the reversible hydrogen electrode (RHE), a real photocurrent density of 2.35 mA cm–2 at 1.23 V versus RHE, and a superior photo-oxidation stability recorded for over 1000 h. Considering the active surface area, the measured photocurrent density is higher than any value achieved so far by hematite and other single-material thin-film photoanodes. Hence, we show for the first time that undoped hematite thin films can compete with doped hematite and other semiconductor materials.

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Section: ■ Results and Discussionmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Nanometer-Thick Hematite Films as Photoanodes for Solar Water Splitting

Chnani

Kurniawan

Bund

et al. 2022

ACS Appl. Nano Mater.

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“…The corrosion of various metals and alloys by molten salts at high temperatures occurs primarily due to the impurities present in the molten salts [36,37]. Since corrosion of alloys by molten salts at high temperatures is electrochemical in nature [31,38 40], for any corrosion reaction to occur, some cathodic reactions should also occur. In molten salts, the oxidants for the cathodic reaction are impurities like O 2 , OH − , H 2 O, Cl − or any other metal ion impurities.…”

Section: Resultsmentioning

confidence: 99%

High-temperature electrochemical corrosion evaluation of 2.25Cr–1Mo alloy in eutectic LiCl–KCl molten salt

Rao

Ningshen

2021

Corrosion Engineering, Science and Technology

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The Cr-Mo ferritic steels are candidate structural materials for the pyrochemical reprocessing applications due to desirable high-temperature strength, resistance to oxidation, and etc. The corrosion resistance of the alloys in molten salts depends on the moisture, impurities, oxidising nature of the electrolyte and temperature. In the present study, in order to monitor the corrosion behaviour of 2.25Cr-1Mo steel in LiCl-KCl molten salt under inert argon atmosphere at 500°C for 200 h duration, electrochemical measurements like open-circuit potential (OCP), linear polarisation resistance, and electrochemical impedance spectroscopy have been carried out. On increasing the duration of exposure to molten salt, the OCP is shifted to the noble direction, and the polarisation resistance increased. The electrochemical impedance spectra exhibited three time constants attributed to the intermittent oxide layer, which was also evident from the surface morphology. The XRD analysis did not reveal the formation of oxide films.

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“…EDAX analysis indicated the presence of Mo in scale of corroded uncoated T22 steel. This might be attributed to oxidation of Mo present in the substrate leading to the formation of MoO 3 inner layer at the substrate scale interface, and this liquid oxide might have broken and dissolved the protective oxide scale leading to accelerated corrosion of uncoated T22 steel (Smialek and Jacobson, 2014; Sequeira, 2011). The weak peaks of Cr 2 O 3 along with major peaks of Fe 2 O 3 in case of uncoated alloy might be because of the presence of Cr in steel, and EDAX analysis has confirmed the presence of Cr in the scale.…”

Section: Discussionmentioning

confidence: 99%

Cyclic high temperature corrosion studies of carbon nanotubes-Cr₂O₃ composite coatings on boiler steel at 900^°C in molten salt environment

Goyal

Singh²,

Bhatia³

2018

ACMM

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Purpose Molten sulphate-vanadate induced hot corrosion is the main reason of failure of boiler tubes used at high temperatures in thermal power plants. The hot corrosion can be encountered by applying thermal spray coatings on the alloy steels. In this perspective, this paper aims to attempt to investigate the effect of carbon nanotubes reinforcement on Cr2O3 composite coatings on hot corrosion behaviour of ASTM-SA213-T22 steel in a corrosive environment of Na2SO4 – 60%V2O5 at 900°C for 50 cycles. Design/methodology/approach The coatings have been deposited with high velocity oxy fuel process. The samples were exposed to hot corrosion in a Silicon tube furnace at 900°C for 50 cycles. The kinetics of corrosion behaviour were analysed by the weight gain measurements after each cycle. Corrosion products were analysed with X-ray diffraction, scanning electron microscopy, energy dispersive and cross-sectional analysis techniques. Findings During investigations, the carbon nanotubes (CNT) reinforced Cr2O3 composite coatings on T22 steel were found to provide better corrosion resistance in the molten salt environment at 900°C. The coatings showed lower weight gain along with formation of protective oxide scales during the experiment. Improvement in protection against hot corrosion was observed with increase in CNT content in the coating matrix. Research limitations/implications The addition of CNT has resulted in reduction in porosity by filling the voids in chromium oxide coating, with interlocking of particle and has blocked the penetration of corroding species to enhance the corrosion resistance of the composite coatings. The corrosion rate was found to be decreasing with increase in CNT content in coating matrix. Originality/value It must be mentioned here that high temperature corrosion behaviour of thermally sprayed CNT-Cr2O3 composite coatings has never been studied, and it is not available in the literature. Hence, present investigation can provide valuable information for application of CNT-reinforced coatings in high temperature fuel combustion environments.

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High‐Temperature Oxidation

Cited by 6 publications

References 157 publications

Nanometer-Thick Hematite Films as Photoanodes for Solar Water Splitting

Nanometer-Thick Hematite Films as Photoanodes for Solar Water Splitting

High-temperature electrochemical corrosion evaluation of 2.25Cr–1Mo alloy in eutectic LiCl–KCl molten salt

Cyclic high temperature corrosion studies of carbon nanotubes-Cr₂O₃ composite coatings on boiler steel at 900^°C in molten salt environment

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High‐Temperature Oxidation

Cited by 6 publications

References 157 publications

Nanometer-Thick Hematite Films as Photoanodes for Solar Water Splitting

Nanometer-Thick Hematite Films as Photoanodes for Solar Water Splitting

High-temperature electrochemical corrosion evaluation of 2.25Cr–1Mo alloy in eutectic LiCl–KCl molten salt

Cyclic high temperature corrosion studies of carbon nanotubes-Cr2O3 composite coatings on boiler steel at 900°C in molten salt environment

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Cyclic high temperature corrosion studies of carbon nanotubes-Cr₂O₃ composite coatings on boiler steel at 900^°C in molten salt environment