MSE PhD Seminars II

Research overviews presented by our PhD students--184 WA

All dates for this event occur in the past.

184 Watts Hall
2041 College Rd.
Columbus, OH 43210
United States

All talks will be held in 184 Watts Hall

  

9:00 a.m. Yuan Yang advised by Dr. Michael Sumption

Influence of Chemical Doping on Microstructures and Superconducting Properties of MgB2 Wires and Bulks

Abstract:

Magnesium diboride (MgB2) is a material with a superconducting transition temperature of 39 K. Discovered in 2001, the relatively large coherence length (and associated lack of weak links) together with its simple binary composition (making phase pure formation relatively easy) have made it a material of substantial interest. However, its poor in-field performance limits the high field applications. Chemical doping is the key to increase the Bc2 of MgB2. Chemical doping aiming at Mg site or B site substitution is of interest and both routes are explored in this thesis. Structure - property correlations are developed for both those dopants that do, as well as those that do not, incorporate themselves into the MgB2 matrix.

Bio:

Yuan Yang earned his BS degree in Physics at Zhejiang University, China. He received his MS degree in Materials Science and Engineering at the Ohio State University on 2012. He is currently a research associate at the Center of Superconducting and Magnetic Materials. His research is in the area of MgB2 superconducting materials with emphasis on the chemical doping and phase formation. 

10:00 a.m. Hyun Sung Kim advised by Dr. Michael Sumption

Experimental and Numerical Analysis of Hydroformed Tubular Materials for Superconducting Radio Frequency (SRF) Cavities

Abstract: 

Superconducting radio frequency (SRF) cavities represent a well-established technology benefiting from some 40 years of research and development for particle accelerators. An increasing demand for electron and positron accelerators leads to a continuing interest in improved cavity performance and fabrication techniques. Therefore, hydroforming technique has been proposed for eliminating the multitude of electron-beam welded seams that contribute to the introduction of performance-reducing defects.

This study focused on the experimental and numerical analysis of hydroformed niobium (Nb) tubes for the successful application of hydroforming technique to the seamless fabrication of multicell SRF cavities. The heat treatment, tensile testing, and bulge testing of Cu and Nb tubes has been carried out to gain experience for the subsequent hydroforming of Nb tube into seamless SRF cavities. Based on the results of experiments, the numerical analysis using finite element modeling was performed.

Bio:

Hyun Sung Kim received his B.S. in 2007 and M.S. in 2010 in Materials science and engineering from Korea University, Seoul, Korea. He began his Phd study on hydroforming of niobium tube for SRF cavities at OSU in 2010. His research interests are superconducting applications.

11:00 a.m. Xiaolei Guo advised by Dr. Rudy Buchheit

Corrosion Inhibition of AA2024-T3 via Smart Coating, Corrosion Inhibitor, and Conversion Coating Approaches

Abstract:

Aluminum alloys have been widely used in the aerospace industry due to their high strength to weight ratio. However, the heterogeneous microstructures that are intentionally designed for the high strengths also induce different electrochemical characteristics between the intermetallic compounds (IMCs) and aluminum matrix. Over the years, a number of strategies have been proposed to prevent and reduce these corrosion issues, including application of corrosion inhibitors, barrier coatings, anticorrosion pigments, and surface modifications. The present work developed multiple strategies for the corrosion inhibition of AA2024-T3, including application of smart coatings with the self-healing capability; utilization of the synergistic effect between organic and inorganic corrosion inhibitors; and development of novel "green" organic conversion coatings with strong complexation effects with the AA2024-T3 substrate. The corrosion inhibition efficacy and mechanisms of these approaches were investigated and discussed.

Bio:

Xiaolei Guo earned his BS degree in Polymer Science and Engineering at Zhejiang University, China. He received his MS degree in Materials Science and Engineering at the Ohio State University on 2012. He is currently a research associate at the Fontana Corrosion Center. His research is in the area of corrosion science and engineering with emphasis on the corrosion inhibition and surface modification. 

1:00 p.m. Jiheon Jun advised by Dr. Gerald Frankel

Localized Corrosion of Clean 304 and S13Cr Stainless Steels in H2S-free and Sour Conditions

Abstract:

Pitting corrosion susceptibility of a clean grade of 304 stainless steel (SS304), which was processed to reduce the number and size of inclusions, was compared with regular SS304. Both regular and clean had multi-oxide inclusions, but detectable MnS phase were only found in regular SS304. Mixed acid etchant initiated pitting selectively on MnS phase, indicating pitting susceptibility of regular SS304 is due to its MnS-containing inclusions. In accordance with this trend, regular SS304 had lower pitting potentials than clean SS 304.

Diffusion-controlled pit growth of Super 13Cr stainless steel was also studied using one-dimensional (1D) pit electrodes. N2 gas and a mixture of N2 and H2S were purged into NaCl solutions at 85°C to simulate H2S-free and sour conditions. Applied potential was controlled to grow pit depth, measure diffusion-limited current density (ilim) and salt film dissolution potential (Esfd). In H2S-free conditions, both ilim and Esfd decreased with increasing NaCl concentration, and this trend was addressed using the product of diffusion coefficient of metal ions (D) and saturation concentration of FeCl2 (Csat).

Bio:

Jiheon Jun received B.Eng. (2006) and M.Eng. (2008) in Material Science and Engineering at University of Seoul in Seoul, Korea. He is currently a PhD candidate in Material Science and Engineering at The Ohio State University. His PhD study focuses on localized corrosion of super 13Cr stainless steel in sour condition to assess corrosion reliability of tubular materials exposed to H2S during oil and gas extraction. His previous works include epoxy-based composites for nuclear application, electroplating of functional metal/nano-particles composite coatings and development of cost-saving process for electronics packaging. 

2:00 p.m. I-Wen Huang advised by Dr. Rudy Buchheit

Uniform Corrosion and General Dissolution of Aluminum Alloys 2024-T3, 6061-T6, and 7075-T6

Abstract:

High strength aluminum alloys are known particularly susceptible to localized corrosion (primarily pitting) introduced by heterogeneous intermetallics, but lacking quantitative assessment of uniform corrosion along with pitting has become a major challenge for pit growth prediction. Therefore, the ability to measure pit depths and uniform corrosion simultaneously by profiliometric methods has become a critical correction to bridge the gap between practical and ideal pit growth kinetics. In this work, pitting corrosion and uniform dissolution of aluminum alloys 2024-T3, 7075-T6 and 6061-T6 were characterized quantitatively in NaCl solutions as a function of pH, temperature and exposure time. Statistical model was also utilized assisting large data analysis.

Bio:

I-Wen (Evan) Huang is currently a PhD student advised by Dr. Buchheit. He earned his MS degree from Stony Brook University (2010) and BS from National Cheng Kung University in Taiwan (2007) both in Materials Science and Engineering. His research interests include aluminum alloys corrosion and characterization by electrochemical approaches.

3:00 p.m. Don McAllister advised by Dr. Michael Mills

Shearing Mechanisms and Complex Particle Growth in Nickel Superalloy 718

Abstract:

Ni-base superalloy 718 is a γ′′-strengthened polycrystalline alloy used in high temperature applications.  The relationship between processing and mechanical properties has become well understood in 718, yet the interaction between the γ′′ and the specific deformation mechanisms at a variety of temperatures is not known.  It has been shown that the ageing temperature applied to solutionized samples directly influences the morphology of the strengthening precipitates.  Lower isothermal ageing temperatures (below 750°C) lead to a complex composite morphology while higher temperatures (above 750°C) produce primarily monolithic γ′′.  Commercially-aged 718 undergoes a series of mechanism changes from isolated intrinsic stacking fault formation at 22°C to extensive microtwinning at 649°C.  The mechanism change is assisted by reordering within the γ′′ phase.  Characterization of these complex mechanisms is essential in informing the creation of a mechanistically accurate yield strength model.

Bio:

Don McAllister attended high school at Tri-Valley High School in Dresden, Ohio and graduated in 2007.  He then went to the Ohio State University for his undergraduate degree in materials science and engineering with a specialization in metallurgy.  Upon graduation, Don began graduate school at the Ohio State University studying under Dr. Michael Mills.  He received his M.S. degree in materials science and engineering in 2014 from OSU.

 

Format and attendance:

The Department will hold all of our SP16 PhD talks (eleven) over the course of two days, April 20 & 21. The talks will be held in 184 Watts Hall, not 264 MacQuigg.

MSE grad students will be required to attend at least two of the eleven talks presented over the course of 4/20 & 21. Attendance will be taken and if a student has attended two seminars total over the course of the two days, s/he will receive a passing grade for this part of 7895. Attendance is limited to the number of seats in the room.

In early/mid-April dates & times will be finalized, as well as titles and abstracts for the talks.