Browsing by Author "Sun, Yinghao"

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    Dissociative Adsorption, Absorption and Permeation of Hydrogen on Steel Pipelines
    (2021-07-13) Sun, Yinghao; Cheng, Frank; Dann, Markus; Hugo, Ron; Cheng, Frank
    Hydrogen is a green, clean fuel. Development of hydrogen energy is critical to achieving the net-zero emission target. Pipelines provide a promising alternative for hydrogen transportation. However, hydrogen embrittlement becomes a major concern to the safety of the pipelines. This research investigates entrance and permeation of hydrogen by modelling and experimental methods. Dissociative adsorption on Fe (100) could happen in wide temperature/pressure ranges, but spontaneous dissociation could be neglected as an effective H-atoms source. Fe-H bonds are formed by hybridization via charge accumulation on H atoms and weakened by coverage and stress. Corrosion enhancement following mechano-electrochemical (M-E) interaction is found at heat affected zone (HAZ) of X80 weld, where substantial hydrogen trapping sites are included. Elastic stress elevates hydrogen entrance and diffusion while plastic stress slows down diffusion but further increase hydrogen uptake. Stress concentration near weldment and interactions between hydrogen permeation and stress would lift degradation susceptibility at HAZ.
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    Hydrogen dissociative adsorption on pipeline steels in high-pressure gaseous environments
    (2024-09-16) Sun, Yinghao; Cheng, Frank; Egberts, Philip; Hugo, Ronald
    Hydrogen is acknowledged as a key player in energy transition and the pursuit of achieving the net-zero target. Pipeline can serve as an ideal transportation method for H2 due to its high efficiency, large capacity, and relatively low cost. However, H2 pipelines are facing the problem of Hydrogen Embrittlement (HE), which might cause catastrophic failure. However, due to the size limitation, only atomic H can enter the pipeline steel and lead into HE. Thus, research on atomic H generation on steel surface, i.e., dissociative adsorption, is essential to H2 pipelines application. Up to date, there have been limited investigations on hydrogen dissociative adsorption at irregularities on pipeline steel. In this work, hydrogen dissociative adsorption on steel crystalline plane is studied to verify the feasibility of simulation methodology. Models of typical irregularities on pipeline steel surface, i.e., grain boundary, dislocation, non-metallic inclusion are constructed. To the authors’ best knowledge, it is the first time to develop microstructure models considering surface effect. It is found that interior high angle grain boundary, edge dislocation core and the sites under tensile strain, Fe side of Al2O3 interface, are preferential sites for hydrogen adsorption. The bonding mechanism for hydrogen adsorption is determined to be orbital hybridization. Electrons will shift to adsorbed H atoms from nearby Fe atoms and Al/O atoms. Partition function is applied to indicate that high pressure and low temperature are favorable for hydrogen dissociative adsorption. Oxygen included gas impurities can inhibit hydrogen adsorption by competitive attraction of electrons, while CH4 can also slightly inhibit hydrogen dissociative adsorption. Based on literature review and conducted investigations, perspectives on atomic H generation and HE under gaseous environment, and inhibiting effect of certain impurity gases on hydrogen dissociative adsorption are provided.