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Papers by Yohanes Chekol Malede
Geoenergy Science and Engineering
Bioresource Technology Reports
European Corrosion Congress (EUROCORR 2017), 2017
Materials and Corrosion, 2019
Ni-(35-45)Cr-4Nb alloys containing different fractions of α-Cr were exposed to potassium chloride... more Ni-(35-45)Cr-4Nb alloys containing different fractions of α-Cr were exposed to potassium chloride (KCl)-induced corrosion. The corrosion exposures were carried out for 168 hr at 600°C in a 15% (vol/vol) H 2 O (g) + 5% (vol/vol) O 2 (g) + N 2 (g; balance) atmosphere using KCl-free (reference) and predeposited KCl samples. To mimic the KCl deposition in real boilers, 24 hr exposures where KCl vapor condensed continuously onto samples were also performed. The corrosion attack of the studied materials increased significantly when KCl was present compared to the KCl-free samples. For the KCl exposures, the corrosion attack drastically increased when a significant α-Cr fraction was present. α-Cr was either selectively attacked or dissolved through solid-state diffusion and a layered build-up of the outer external scale of K 2 CrO 4 and chromia could be observed. For the in situ condensed KCl exposure, severe corrosion was observed already within the 24 hr exposure, indicating a higher corrosion rate compared with when KCl was predeposited.
SSRN Electronic Journal, 2022
CORROSION, 2018
In Denmark, biomass has been implemented in the majority of power plants either by firing biomass... more In Denmark, biomass has been implemented in the majority of power plants either by firing biomass alone or cofiring of biomass and fossil fuels/additives. This has resulted in an accumulation of ex...
Extreme Mechanics Letters, Sep 1, 2017
The application of silicon (Si) as potential anode material in Li-ion batteries provides a more t... more The application of silicon (Si) as potential anode material in Li-ion batteries provides a more than nine-fold increase in gravimetric storage capacity compared to conventional graphite anodes. However, full lithiation of Si induces the volume to increase by approximately 300%. Such enormous volume expansion causes large mechanical stress, resulting in non-elastic deformation and crack formation. This ultimately leads to anode failure and strong decrease in cycle life. This problem can be resolved by making use of structured anodes with small dimensions. Particularly honeycomb-shaped microstructures turned out to be beneficial in this respect. In the present paper, finite element modeling was applied to describe the experimentally observed mechanical deformation of honeycomb-structured Si anodes upon lithiation. A close agreement between simulated and experimentally observed shape changes is observed in all cases. The predictive ability of the model was further exploited by investigating alternative geometries, such as square-based microstructure. Strikingly, dimension and pattern optimization shows that the stress levels can be reduced even below the yield strength, while maintaining the footprint-area-specific storage capacity of the microstructures. The pure elastic deformation is highly beneficial for the fatigue resistance of optimized silicon structures. The obtained results are directly applicable for other (de)lithiating materials, such as mixed ionic-electronic conductors (MIEC) widely applied in Li-ion and future Na-ion batteries.
Journal of Materials Science
Materials at High Temperatures
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Geoenergy Science and Engineering
Bioresource Technology Reports
European Corrosion Congress (EUROCORR 2017), 2017
Materials and Corrosion, 2019
Ni-(35-45)Cr-4Nb alloys containing different fractions of α-Cr were exposed to potassium chloride... more Ni-(35-45)Cr-4Nb alloys containing different fractions of α-Cr were exposed to potassium chloride (KCl)-induced corrosion. The corrosion exposures were carried out for 168 hr at 600°C in a 15% (vol/vol) H 2 O (g) + 5% (vol/vol) O 2 (g) + N 2 (g; balance) atmosphere using KCl-free (reference) and predeposited KCl samples. To mimic the KCl deposition in real boilers, 24 hr exposures where KCl vapor condensed continuously onto samples were also performed. The corrosion attack of the studied materials increased significantly when KCl was present compared to the KCl-free samples. For the KCl exposures, the corrosion attack drastically increased when a significant α-Cr fraction was present. α-Cr was either selectively attacked or dissolved through solid-state diffusion and a layered build-up of the outer external scale of K 2 CrO 4 and chromia could be observed. For the in situ condensed KCl exposure, severe corrosion was observed already within the 24 hr exposure, indicating a higher corrosion rate compared with when KCl was predeposited.
SSRN Electronic Journal, 2022
CORROSION, 2018
In Denmark, biomass has been implemented in the majority of power plants either by firing biomass... more In Denmark, biomass has been implemented in the majority of power plants either by firing biomass alone or cofiring of biomass and fossil fuels/additives. This has resulted in an accumulation of ex...
Extreme Mechanics Letters, Sep 1, 2017
The application of silicon (Si) as potential anode material in Li-ion batteries provides a more t... more The application of silicon (Si) as potential anode material in Li-ion batteries provides a more than nine-fold increase in gravimetric storage capacity compared to conventional graphite anodes. However, full lithiation of Si induces the volume to increase by approximately 300%. Such enormous volume expansion causes large mechanical stress, resulting in non-elastic deformation and crack formation. This ultimately leads to anode failure and strong decrease in cycle life. This problem can be resolved by making use of structured anodes with small dimensions. Particularly honeycomb-shaped microstructures turned out to be beneficial in this respect. In the present paper, finite element modeling was applied to describe the experimentally observed mechanical deformation of honeycomb-structured Si anodes upon lithiation. A close agreement between simulated and experimentally observed shape changes is observed in all cases. The predictive ability of the model was further exploited by investigating alternative geometries, such as square-based microstructure. Strikingly, dimension and pattern optimization shows that the stress levels can be reduced even below the yield strength, while maintaining the footprint-area-specific storage capacity of the microstructures. The pure elastic deformation is highly beneficial for the fatigue resistance of optimized silicon structures. The obtained results are directly applicable for other (de)lithiating materials, such as mixed ionic-electronic conductors (MIEC) widely applied in Li-ion and future Na-ion batteries.
Journal of Materials Science
Materials at High Temperatures
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.