Doctoral Dissertations

Jen-Hsien Hsu

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 properties
Nickel
Silicides
Sulfur dioxide

Thesis Number

T 9714

Print OCLC #

733048887

Electronic OCLC #

911056340

Link to Catalog Record

Electronic access to the full-text of this document is restricted to Missouri S&T users. Otherwise, request this publication directly from Missouri S&T Library or contact your local library.

http://merlin.lib.umsystem.edu/record=b8262453~S5

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