Doctoral Dissertations
Abstract
"The Sulfur-Iodine thermochemical cycle has been proposed as a method for producing large quantities of hydrogen gas from water. However, the extreme operating environments involved limit the possible materials for construction.
Through proper heat treatment and composition control, the modified patented Ni₃(Si,Nb) alloy keeps high temperature strength to greater than 750⁰C and can be deformed by cold rolling more than 50% using multiple passes and intermediate anneals. The corrosion resistance is reproducible and maintains less than 5 mpy for a broad range of boiling sulfuric acid concentrations, including 70 wt%.
In the boiling 70 wt% sulfuric acid corrosion tests, kinetic analyses using log-log plot of these results were carried out for each alloy and condition. For all alloys, the data fell into three different regions indicative of multi-stages corrosion mechanism. At State I, an oxide film is formed on the surface. At State II, the greatest oxide spallation and weight loss of samples was observed. At State III, the passivation state, the amounts of oxide spallation and weight loss are extremely low. The oxide film initially formed during corrosion consists predominantly of SiO₂ and NiSO₄·(H₂O). Although the amount of NiSO₄·(H₂O) is small, it may have a critical influence on oxide spallation and the large weight loss at State II. A Si-rich area forms locally at the metal-oxide interface, after Ni ions diffused through the oxide film and dissolved into the solution. After passivation, the oxide film is composed of almost on SiO₂ and the significant Si-rich area at the interface was observed. It seems that once the Si concentration is enriched to the critical level, the formation of NiSO₄·(H₂O) ends. After this, there is almost no NiSO₄·(H₂O) in the oxide film and the sample is passivated"--Abstract, page iii.
Advisor(s)
Newkirk, Joseph William
Committee Member(s)
Van Aken, David C.
Schlesinger, Mark E.
Brow, Richard K.
Kohser, Ronald A.
Department(s)
Materials Science and Engineering
Degree Name
Ph. D. in Metallurgical Engineering
Sponsor(s)
Nuclear Energy Research Initiative (U.S.)
United States. Department of Energy
Publisher
Missouri University of Science and Technology
Publication Date
Fall 2010
Pagination
xiv, 116 pages
Note about bibliography
Includes bibliographical references (pages 112-115).
Rights
© 2010 JenHsien Hsu, All rights reserved.
Document Type
Dissertation - Open Access
File Type
text
Language
English
Subject Headings
Nickel alloys -- Mechanical propertiesNickelSilicidesSulfur dioxide
Thesis Number
T 9714
Print OCLC #
733048887
Electronic OCLC #
911056340
Recommended Citation
Hsu, Jen-Hsien, "Understanding corrosion of Ni₃(Si,Nb) alloys in hot sulfuric acid" (2010). Doctoral Dissertations. 1786.
https://scholarsmine.mst.edu/doctoral_dissertations/1786