December 2017 - Msepostdoc-list

Seminar Reminder for Sae Matsunaga's Prelim Exam; Seminar Monday Dec. 11, at 9:30 a.m., in ARMS 3115; Exam, same day, at 1:30, in ARMS 2009. "Segregated-Assister Shearing of the G'Phase in Ni-Based Superalloys"
by Son, Rosemary E 08 Dec '17

08 Dec '17

Please consider attending the following: MATERIALS ENGINEERING SEMINAR "Segregated-Assister Shearing of the G'Phase in Ni-Based Superalloys" By Sae Matsunaga Purdue MSE Ph.D. Preliminary Exam Advisor: Professor Michael S. Titus ABSTRACT Ni-based superalloys have been developed and used for over 60 years for high temperature applications due to their superior material properties; such as, high temperature strength, resistance to creep, high thermal/mechanical fatigue strength, and excellent oxidation resistance. Much of the high temperature strength is due to the presence of a high volume fraction (~70%) of *'-(ordered fcc/L12) precipitates, which are embedded coherently in a ***fcc/A1) matrix. These materials are widely used in gas turbines for aircraft engines, land-based turbines for natural gas-operated power plants, rocket engines, and other applications where extreme environments are present. Over the decades, the high temperature deformation mechanisms of Ni-based superalloys have been studied, and it has been revealed that the deformation mechanisms of Ni-based superalloys strongly depend on certain microstructural features (*' volume fraction, size, and shape) and alloy composition. Recently, shearing of the *' precipitates by partial dislocations has been identified as the rate-limiting creep deformation mechanism at low temperature and high stresses in some Ni-based superalloys. The current understanding of *' shearing will be discussed with special focus on the planar defects in the *' phase such as superlattice intrinsic/ extrinsic stacking faults, antiphase boundaries, and microtwins. To understand the relationship between defects in *' phase and primary alloy elements, high resolution EDX would be carried out for further investigation of segregation at faults and microtwins. This would bring a more complete understanding of the deformation mechanisms and segregation behavior of essential alloying elements would bring new insight to guided alloy design and reveal the underlying mechanisms and driving forces responsible for shearing of the *' phase. Date: Monday, December 11, 2017 Time: 9:30 A.M. Place: ARMS 3115

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Seminar Reminder for Congying Wang's Preliminary Exam: Seminar, Monday, Dec. 11, at 8:30 a.m., in ARMS 3115; Exam same day at, 10:00, in ARMS 2326. " Slip Systems in Beta-Sn: to Relate Dislocations and Grain Nucleation"
by Son, Rosemary E 08 Dec '17

08 Dec '17

Please consider attending the following: MATERIALS ENGINEERING SEMINAR “Slip Systems in Beta-Sn: to Relate Dislocations and Grain Nucleation” By Congying Wang Purdue MSE Ph.D. Preliminary Exam Advisors: Professors Carol A. Handwerker and John E. Blendell ABSTRACT β-Sn coatings are widely used in the electronic industry to provide better solderability to prevent oxidation.The formation and growth of whiskers are known to be a stress relaxation response of tin films, some of which can grow up to millimeter-long and cause short circuits in electronics. Previous studies indicate that shallow grains are critical for whisker growth, acting as preferred sites for growth compared to columnar grains. Whiskers have been observed to form through recrystallization along grain boundaries (GB) during thermal cycling of as-solidified films of tin-silver-copper alloys (SAC305). In this study, changes in surface morphology were quantified in large-grained tin films during thermal cycling (-35◦C/+85◦C) from the 1st cycle, which suggested a relationship between local dislocation activity and low-angle boundary formation. In order to relate the underlying mechanism of the dislocation motion and the grain nucleation, slip behav-iors in β-Sn has been reviewed. At least 12 nonequivalent families of slip systems have been reported due to the anisotropy of β-Sn. Unlike FCC materials, the crystallography theory and dislocation energy cannot fully explain why specific slip system was activated, or predict which slip system will become active. Other factors influencing the slip behaviors are temperature, grain size, and grain boundary. Date: Monday, December 11, 2017 Time: 8:30 A.M. Place: ARMS 3115

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Seminar Reminder for Chengzi Huang's Preliminary Exam. Seminar, Friday, Dec. 8, at 12:00, in ARMS 3115; Exam, same day, at 1:30, in ARMS 2222. "MEMS Actuator Based on Dopant-Driving Thin Film Perovskite Nickelate"
by Son, Rosemary E 07 Dec '17

07 Dec '17

Please consider attending the following: MATERIALS ENGINEERING SEMINAR "MEMS Actuator Based on Dopant-Driving Thin Film Perovskite Nickelate" By Chengzi Huang Purdue MSE Ph.D. Preliminary Exam Advisors: Professors Dana Weinstein and Shriram Ramanathan ABSTRACT Rare earth nickelate exhibits a series of fantastic properties based on its abnormal metal-insulator transition (MIT) phenomenon, which has attracted huge concerns from different areas since 1970s. Except for traditional thermally driven method for phase transition materials, electron doping is found to be another effective driving mechanism which origins from the strong correlation of electrons in the [cid:image001.png@01D36A86.73247F50] orbital of Ni2+ cation. Giant changes of resistivity and lattice parameter are observed during the phase transition. In this work, the crystal structures and phase transition mechanisms of perovskite nickelates is being discussed, and based on their performance, NdNiO3 (NNO) is selected to be the core material for MicroElectroMechanical Systems (MEMS) actuators. Synthesis as well as characterization method are also introduced to further understand and utilize its unique properties in actuators. Traditional actuation materials are being discussed in details and are compared with NNO to give a better idea to estimate the performance of NNO actuator. Although there is no record of perovskite materials utilized in actuation area, NNO is a strong candidate based on its unique properties such as high induced strain, giant resistivity change, and fast phase transition speed. This study also offers us an opportunity to explore the mechanical properties of perovskite nickelates associated with the phase transition, and their application in MEMS. Date: Friday, December 8, 2017 Time: 12:00 P.M. Place: ARMS 3115

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Seminar Reminder for Gyuchul Park's Preliminary Exam. Seminar, Friday, Dec. 8, at 8:30 a.m., in ARMS 1028; Exam same day, in ARMS B197. "Evaluation of Radiation Damage in Materials Using Extended X-ray Absorption Fine Structures (EXAFS)"
by Son, Rosemary E 07 Dec '17

07 Dec '17

Please consider attending the following: MATERIALS ENGINEERING SEMINAR “Evaluation of Radiation Damage in Materials Using Extended X-ray Absorption Fine Structures (EXAFS)” By Gyuchul Park Purdue MSE Ph.D. Preliminary Exam Advisor: Professor Maria A. Okuniewski ABSTRACT With an effort to substitute low-enriched uranium (defined as less than 20% 235U) for highly enriched uranium (defined as more than 20% 235U) by Reduced Enrichment for Research and Test Reactors program launched in 1978, uranium molybdenum (U-Mo) alloy has been considered as a promising nuclear fuel material for future research reactors. U-Mo alloy fuel displays great irradiation behavior because, γ-phase uranium, stable above 771°C, can be obtained at the operating temperature of research reactors (below 250°C) by alloying molybdenum in uranium under quenching conditions. An understanding of the irradiation behavior of U-Mo alloy fuel is crucial in order to improve the fuel performance. Accordingly, Extended X-ray Absorption Fine Structure (EXAFS), which uses a synchrotron x-ray source, is a useful experimental technique to study radiation damage on the atomic level in materials because changes in local structure such as atomic distance and coordination number can be probed within 5-6 Å from an absorbing atom. In the following document, the general radiation-induced defects observed in irradiated materials are reviewed. Then, the background of EXAFS is briefly introduced and followed by a discussion of how EXAFS can be utilized to investigate radiation damage in materials. Keywords: Radiation Damage, Uranium-Molybdenum Monolithic Fuel Alloys, Extended X-ray Absorption Fine Structure (EXAFS). Date: Friday, December 8, 2017 Time: 8:30 A.M. Place: ARMS 1028

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Seminar Reminder for Chia-Hsiu (Hugh) Chang's Preliminary exam. Seminar, Today, Thursday, Dec. 7, at 12:00, in HAMP 2107; Exam is at 1:30, in ARMS 2009. "Solid-Solution Strengthening in FCC Complex, Concentrated Alloys"
by Son, Rosemary E 07 Dec '17

07 Dec '17

Please consider attending the following: MATERIALS ENGINEERING SEMINAR "Solid-Solution Strengthening in FCC Concentrated Complex Alloys" By Chia-Hsiu Chang Purdue MSE Ph.D. Preliminary Exam Advisor: Professor Michael S. Titus ABSTRACT Concentrated complex alloys (CCAs) were recently proposed as a novel class of new alloys, and they are defined as alloys composed of four or more alloying elements without a majority concentration or "base" element, for example Co1Fe1Mn1Ni1. Oftentimes, researchers aim to synthesize CCAs exhibiting a single solid-solution phase (e.g. fcc or bcc) because of the significant solid-solution strengthening provided by the high concentration of many solute elements. Early research revealed that, in some case, these alloys exhibit comparable yield strength to precipitation-strengthened alloys over a large temperature range. However, the strengthening mechanisms of CCAs are not clear at present. Despite the significant historical effort to understand solid-solution strengthening in random alloys, conventional theory is unable to quantitatively predict yield strength as a function of temperature and strain rate in multi-solute, non-dilute solid-solution alloys. A new theory for predicting the yield strength of fcc CCAs has recently developed, and comparisons between predicted and experimental results based on the new model will be discussed. Because the model requires complete knowledge of the material properties for each alloying element, we seek to simplify the model in order to understand additions of a single solute to a given CCA composition. The study hypothesizes that CCAs could be treated as pseudo-binary alloys, in which the "solvent" is a given CCA and the solute is the final alloying element. A brief outline of the proposed research plan to validate and improve on the current model for predicting CCA strength will be presented Date: Thursday, December 7, 2017 Time: 12:00 P.M. Place: HAMP 2107

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Seminar Notice for Alexander Strayer's Preliminary Exam: Seminar Wednesday, Dec. 13, at 8:30 a.m., in ARMS 3115; Exam, same day, at 10:00, in ARMS 2237. " Physiochemical Interaction of SiC with Si-Based Melts"
by Son, Rosemary E 06 Dec '17

06 Dec '17

Please consider attending the following: MATERIALS ENGINEERING SEMINAR "Physiochemical Interaction of SiC with Si-Based Melts" By Alexander R. Strayer Purdue MSE Ph.D. Preliminary Exam Advisor: Professor Kenneth H. Sandhage ABSTRACT Silicon Carbide is an industrially important non-oxide ceramic because of its combination of chemical stability, thermal fatigue resistance, high stiffness, and low density. Additionally, SiC can be produced economically in near net-shape structures via liquid silicon melt infiltration into a silicon carbide/carbon porous preform. However, pure liquid Si and solid SiC cannot exist in equilibrium as there is a small amount of carbon solubility in liquid Si. Hence during infiltration dissolution of SiC in liquid Si is possible. In order to mitigate this problem, a better understanding of the physicochemical interaction between silicon carbide and liquid silicon melts is warranted. Here, a number of key publications are reviewed. Possible rate limiting steps for the dissolution are discussed, and major factors contributing to the kinetics such as poly-type, melt dopants, and atmosphere are explored along with current experiments and results aimed at filling the voids left in the literature on the topic. Date: Wednesday, December 13, 2017 Time: 8:30 A.M. Place: ARMS 3115

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Seminar Notice for Alyssa Yaeger's Preliminary Exam: Seminar, Wednesday, Dec. 13, at 8:30 a.m., in ARMS 1028: Exam same day, at 10:00, in ARMS 3119. " Microstructural Evolution of Solder Due to Surface Finish Thickness"
by Son, Rosemary E 06 Dec '17

06 Dec '17

Please consider attending the following: MATERIALS ENGINEERING SEMINAR "Microstructural Evolution of Solder Due to Surface Finish Thickness" By Alyssa N. Yaeger Purdue MSE Ph.D. Preliminary Exam Advisors: Professors Carol A. Handwerker and John E. Blendell ABSTRACT With the drive toward lighter, thinner, and more capable electronics, smaller electronic components are always being created and used. However, this miniaturization of components leads to a miniaturization of solder joints as well, which can cause reliability concerns. Surface finishes such as Electroless Nickel Immersion Gold (ENIG) and Electroless Nickel Electroless Palladium Immersion Gold (ENEPIG) contain elements that form brittle intermetallic compounds (IMCs) with the tin in solder. A large volume percentage of these brittle IMCs leads to an inability to deal with environmental stresses, and poor reliability. These surface finishes have standardized thicknesses that have not changed as the average solder volume has decreased, leading to a larger percentage of plating elements present in the solder joint, and a larger volume fraction of IMCs. Annealing at temperatures near the melting point allows researchers to view the microstructural evolution of the solder at an accelerated rate, and can be crucial in determining the reliability of the solder joint over time. Date: Wednesday, December 13, 2017 Time: 8:30 A.M. Place: ARMS 1028

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Seminar Notice for Keisuke Yazawa's Preliminary Exam: Seminar, Tuesday, Dec. 12, at 1:00, in ARMS 1028; Exam, same day, 2:30, in ARMS B197; "Electric Field Induced Strain and Switching Behavior in Ferroelectric Materials"
by Son, Rosemary E 05 Dec '17

05 Dec '17

Please consider attending the following: MATERIALS ENGINEERING SEMINAR "Electric Field Induced Strain and Switching Behavior in Ferroelectric Materials" By Keisuke Yazawa Purdue MSE Ph.D. Preliminary Exam Advisors: Professors Carol A. Handwerker and John E. Blendell ABSTRACT Ferroelectric materials have been used for actuator and sensor devices due to the electromechanical coupling property. The electromechanical coupling of ferroelectrics is attributed to piezoelectric lattice strain and polarization axis exchange (non-180o switching). It has been observed that non-180o switching plays a significant role in electric field induced strain. In addition, grain-grain interaction contributes to the effects in polycrystalline ferroelectrics. However, how the grain-grain interaction contribution affects non-180o switching is not fully understood yet. Recently, it has been observed that the grain-grain interaction induced a local elastic strain field due to inhomogeneous piezoelectric response throughout grains. Also, it has been confirmed that ferroelectric switching (180o switching) was hindered/facilitated by crystal distortion due to the elastic strain field. Considering the interaction mechanism, it can be expected that the elastic strain field by the grain-grain interaction can also influence non-180o switching, which contributes to electric field induced strain. Further experiments will be direct observations of non-180o switching and misorientation angle to a neighboring grain, which may affect the local elastic field. This experimental result will provide an insight for the grain-grain interaction contribution to the non-180o switching as well as a guideline for microstructure design for polycrystalline ferroelectrics to control the non-180o switching. Date: Tuesday, December 12, 2017 Time: 1:00 P.M. Place: ARMS 1028

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Thank you
by Coar, Stacey L 04 Dec '17

04 Dec '17

To all of the MSE family, Thank you again for all of your ongoing and amazing support. Working for MSE and such good people makes my job pretty easy to come to everyday. I could not ask for a more supportive group of people. I have had a lot of struggles this year with losing 3 grandparents and my grandma trying to die on me. However, I do not want to forget to mention the happy times too, my new grandbaby Oakley and building my new home. I just couldn't do it without all of you and your overwhelming support and I just want to thank you. Stacey

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Seminar Notice for Jonova Thomas's Preliminary Exam: Seminar, Monday, Dec. 11, at 11:30, in ARMS 1028; Exam same day, at 1:00, in ARMS 2222. " A Comprehensive Study on Neutron Irradiation Effects on Uranium-Zirconium Nuclear Fuel"
by Son, Rosemary E 04 Dec '17

04 Dec '17

Please consider attending the following: MATERIALS ENGINEERING SEMINAR "A Comprehensive Study on Neutron Irradiation Effects on Uranium-Zirconium Nuclear Fuel" By Jonova Thomas Purdue MSE Ph.D. Preliminary Exam Advisor: Professor Maria A. Okuniewski ABSTRACT Metallic U-10wt%Zr nuclear fuels are classified as potential fuels for fast breeder reactors as they possess a high fissile density and have increased compatibility with sodium, a frequently used reactor coolant. Despite their advantages when exposed to neutron irradiation in reactors, the fuels are subject to severe damage cascade and microstructural alterations. These microstructural alterations are also accompanied with large concentrations of point defects or defect clusters and fission products that cause severe fuel swelling. Void and bubble cavity growth can cause further swelling in fuels and facilitate the fuel to meet the cladding within which it has been enclosed. Contact between fuel and claddings at elevated temperatures and burnup cause fuel cladding chemical interactions (FCCI) to occur. FCCI is detrimental in reactor programs as they cause inter-diffusion between fuel and cladding constituents, which lead to eventual failure of the fuel. Previous studies on FCCI indicate that U-10wt%Zr fuels inhibit inter-diffusion to a certain extent by forming a Zr barrier between fuel and cladding. Although this may be true, most studies on FCCI done via isothermal diffusion studies between U-10Zr/HT9 fuel-cladding show varied observations on inter-diffusion layers formed and conflicting arguments on the process of formation of the Zr barrier that inhibits inter-diffusion. This report involves a detailed investigation on the swelling mechanism of irradiated U-10wt%Zr fuels and a discussion on the conflicting arguments of formation of the Zr barrier, and inter-diffusion layers. Finally, similarities between FCCI layers in neutron irradiated U-10wt%Zr/HT9 fuel-cladding is compared to observations made from isothermal diffusion experiments. Date: Monday, December 11, 2017 Time: 11:30 A.M. Place: ARMS 1028

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