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Electrochemical Studies of Molten Salt Corrosion.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Electrochemical Studies of Molten Salt Corrosion.
作者:	Ghaznavi, Touraj.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, 2022
面頁冊數:	203 p.
附註:	Source: Dissertations Abstracts International, Volume: 84-05, Section: B.
附註:	Advisor: Newman, Roger.
Contained By:	Dissertations Abstracts International84-05B.
標題:	Chemical engineering.
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=29392672
ISBN:	9798357547804

Electrochemical Studies of Molten Salt Corrosion.
Ghaznavi, Touraj.

Electrochemical Studies of Molten Salt Corrosion. - Ann Arbor : ProQuest Dissertations & Theses, 2022 - 203 p.

Source: Dissertations Abstracts International, Volume: 84-05, Section: B.

Thesis (Ph.D.)--University of Toronto (Canada), 2022.

This item must not be sold to any third party vendors.

Corrosion mechanisms of Fe-Ni and Fe-22Cr-Ni model alloys with varying Ni contents and Ni-22Cr model alloy were investigated in molten chloride salts at 350-700 °C, simulating the heat transfer circuits of molten salt reactors and thermal solar plants.This study revealed that corrosion properties in molten Cl salts depends on homologous temperatures, metallic solid-solution alloying effects, critical alloy compositions, and impurities. Dealloying of electrochemically reactive element(s) (Fe and/or Fe+Cr) was the dominant form of corrosion; fundamentals and mechanisms of dealloying, and mechanistic connections with aqueous dealloying were determined.It was discovered that at certain conditions, dealloying in molten salts obeys the same rules as the aqueous dealloying. At 350 °C, the dealloying mechanism is mediated by surface diffusion of the more-noble element (Ni) at the alloy/molten salt interface. The microporous dealloying morphology resembled that seen in aqueous systems (but much coarser). The dealloyed layer was a three-dimensional structure with core-shell ligaments; a Ni-rich shell surrounding a core with minor Fe (Fe+Cr), similar to Ag-Au systems in acidic media.At 350 °C, the fundamental parting limit (55-60 at.% of the less-noble element in aqueous solutions) decreased to 44 at.% due to the high surface mobility of elemental Ni. At 350 °C, the parting limit further decreased to a value of approximately 32 at.% Fe when elemental Ni from alloy surface was close to equilibrium with Ni2+ ions that were added to the molten salts, similar to brass in aqueous solutions.Between 500 °C and 700 °C, the dealloying morphology is an interconnected pore/ligament network; however, transitional morphologies evolved, and grain boundary dealloying was common. At 600 °C, bulk diffusion resulted in one-dimensional tunnel-like corrosion morphology ahead of the dealloyed layer. The associated dealloying threshold decreased to values close to 32 at.% and 22 at.% as the temperature rose to 600 °C and 700 °C, respectively.At high homologous temperatures, there is a strong influence of lattice diffusion of alloying elements. However, dealloying of Ni-based alloys in molten salts at up to 700 °C is consistent with percolation dissolution theory; this study revealed that the parting limit remains mostly geometric in nature.

ISBN: 9798357547804Subjects--Topical Terms:

206267
Chemical engineering.
Subjects--Index Terms:

Dealloying

Electrochemical Studies of Molten Salt Corrosion.
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245 1 0 $a Electrochemical Studies of Molten Salt Corrosion.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2022
300 $a 203 p.
500 $a Source: Dissertations Abstracts International, Volume: 84-05, Section: B.
500 $a Advisor: Newman, Roger.
502 $a Thesis (Ph.D.)--University of Toronto (Canada), 2022.
506 $a This item must not be sold to any third party vendors.
520 $a Corrosion mechanisms of Fe-Ni and Fe-22Cr-Ni model alloys with varying Ni contents and Ni-22Cr model alloy were investigated in molten chloride salts at 350-700 °C, simulating the heat transfer circuits of molten salt reactors and thermal solar plants.This study revealed that corrosion properties in molten Cl salts depends on homologous temperatures, metallic solid-solution alloying effects, critical alloy compositions, and impurities. Dealloying of electrochemically reactive element(s) (Fe and/or Fe+Cr) was the dominant form of corrosion; fundamentals and mechanisms of dealloying, and mechanistic connections with aqueous dealloying were determined.It was discovered that at certain conditions, dealloying in molten salts obeys the same rules as the aqueous dealloying. At 350 °C, the dealloying mechanism is mediated by surface diffusion of the more-noble element (Ni) at the alloy/molten salt interface. The microporous dealloying morphology resembled that seen in aqueous systems (but much coarser). The dealloyed layer was a three-dimensional structure with core-shell ligaments; a Ni-rich shell surrounding a core with minor Fe (Fe+Cr), similar to Ag-Au systems in acidic media.At 350 °C, the fundamental parting limit (55-60 at.% of the less-noble element in aqueous solutions) decreased to 44 at.% due to the high surface mobility of elemental Ni. At 350 °C, the parting limit further decreased to a value of approximately 32 at.% Fe when elemental Ni from alloy surface was close to equilibrium with Ni2+ ions that were added to the molten salts, similar to brass in aqueous solutions.Between 500 °C and 700 °C, the dealloying morphology is an interconnected pore/ligament network; however, transitional morphologies evolved, and grain boundary dealloying was common. At 600 °C, bulk diffusion resulted in one-dimensional tunnel-like corrosion morphology ahead of the dealloyed layer. The associated dealloying threshold decreased to values close to 32 at.% and 22 at.% as the temperature rose to 600 °C and 700 °C, respectively.At high homologous temperatures, there is a strong influence of lattice diffusion of alloying elements. However, dealloying of Ni-based alloys in molten salts at up to 700 °C is consistent with percolation dissolution theory; this study revealed that the parting limit remains mostly geometric in nature.
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650 4 $a Chemistry. $3 188628
650 4 $a Materials science. $3 221779
653 $a Dealloying
653 $a Electrochemistry
653 $a Molten salt corrosion
653 $a Molten salts
653 $a Ni-based alloys
653 $a Parting limit
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690 $a 0794
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710 2 $a University of Toronto (Canada). $b Chemical Engineering & Applied Chemistry. $3 857358
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