November 2018 - Msepostdoc-list

Seminar Notice for Kyle Starkey's Preliminary Exam. Seminar Monday, Dec. 3, at 9:00 a.m.
by Son, Rosemary E 30 Nov '18

30 Nov '18

Please consider attending the following: MATERIALS ENGINEERING SEMINAR "Status of Continuum Dislocation Dynamics Modeling of Metal Deformation" By Kyle R. Starkey Purdue MSE Ph.D. Preliminary Exam Advisor: Professor Anter El-Azab ABSTRACT Dislocation are known to be the carriers of plasticity in metals. It is therefore imperative to develop accurate models that describe their collective behavior during metal deformation. In this context, the discrete dislocation dynamics simulation method proved to be a valuable tool for studying systems of dislocations and investigating their collective mechanisms. Due to the computational cost of discrete simulations, however, the study of dislocation systems at large scales becomes infeasible and, consequently, continuum dislocation dynamics models must be introduced. This presentation will cover the modern approaches to describing dislocation systems at the mesoscale from a continuum perspective. First, an introduction is given as to how the continuum representation of dislocations was introduced to connect dislocation densities to the incompatibilities arising in the displacement field in deforming crystals. Following that, statistical models are introduced with a special focus on the statistical mechanical derivation of continuum dislocation dynamics equations in 2D. Next, 3D formalisms of continuum dislocation dynamics are introduced. The latter include the Field Dislocation Mechanics theory and other mesoscale formalisms representing dislocations by density vectors and combination of scalar and geometrically-necessary dislocation fields. PURDUE MSE [cid:image002.png@01D48891.F4728B90] Date: Monday, December 3, 2018 Time: 9:00 A.M. Place: ARMS B061

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Seminar Notice for Baishakhi Bose's Preliminary Exam. Seminar, Monday Dec. 3, in ARMS 1028, at 2:30 p.m. Review, Tuesday, Dec. 4, in WANG 4062, Exam, Tuesday, Dec. 4, in WANG 4062
by Son, Rosemary E 30 Nov '18

30 Nov '18

Please consider attending the following: MATERIALS ENGINEERING SEMINAR "Structure-Property Relationship of Shrinkage Reducing Admixtures in Cementitious Composites and their Interactions with Superabsorbent Polymers" By Baishakhi Bose Purdue MSE Ph.D. Preliminary Exam Advisor: Professor Kendra A. Erk ABSTRACT With the advents of technology, the use of high-performance concrete (HPC) has ensured greater durability and strength of concrete infrastructures. However, HPC is susceptible to autogenous shrinkage which can lead to cracking and eventual collapse. Shrinkage reducing admixtures (SRA) and superabsorbent polymers (SAP) have both been used in the past to mitigate shrinkage. However, dosing the concrete with these admixtures introduces issues related to mechanical and durability-related properties of the concrete. This proposal aims to understand the effect changing the hydrophobic or hydrophilic characteristics of surfactants on their performance as SRAs. The effect of altering the molecular structure of the surfactants on the cement hydration and durability characteristics will be studied. Also, a methodological investigation of synthesized poly (acrylic acid-acrylamide) hydrogels' interaction with the surfactants in the cementitious systems is proposed in this study. The outcomes of this study will aid in identifying the structure property relationship of model SRAs and their synergistic interactions with SAP in cementitious composites. Keywords: shrinkage reducing admixtures, superabsorbent polymers, surfactants Date: Monday, December 3, 2018 Time: 2:30 P.M.

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Seminar Reminder for Eduardo Barocio's Ph.D. Final Exam. Today, November 29, at 2:00 p.m., in IMI 130
by Son, Rosemary E 29 Nov '18

29 Nov '18

Please consider attending the following: MATERIALS ENGINEERING SEMINAR "Fusion Bonding of Fiber Reinforced Semi-Crystalline Polymers in Extrusion Deposition Additive Manufacturing" By Eduardo Barocio Purdue MSE Ph.D. Final Exam Advisor: Professor R. Byron Pipes ABSTRACT Extrusion Deposition Additive Manufacturing (EDAM) is a large-scale Additive Manufacturing (AM) technology able to fabricate parts from the desktop scale to the size of a full vehicle. Fiber reinforced polymers have been the primary enabler for this steep transition by reducing the thermal expansion and increasing the stiffness of printing materials. The EDAM process consists of depositing beads of molten material in a layer-by-layer manner, thus large temperature gradients develop during part manufacturing. Further, shear flow introduced during material extrusion and deposition orients fibers dominantly along the print direction. In the absence of fibers reinforcing the interface between adjacent layers, the bond developed by the polymer matrix is the primary mechanism governing the interlayer mechanical properties. The combination of residual stresses due to anisotropy and temperature gradients with weak interlayer bonding can lead to delamination of parts during manufacturing. Hence, there is a need for predictive simulation tools to mitigate the empirical process of determining printing strategies that lead to crack free parts. Significant contributions were made towards this objective by developing simulation tools for predicting the evolution of temperature and interlayer strength during part manufacturing. The continuous deposition of material is replicated virtually utilizing a framework developed previously for EDAM process simulation. A suite of user-defined subroutines in Abaqus(c) was utilized for implementing different mechanisms of heat transfer as well as a model for fusion bonding. Methods for characterizing not only the properties of printing materials for EDAM process simulations but also the processing conditions used in the EDAM process are presented. Additionally, the Composites Additive Manufacturing Research Instrument (CAMRI) was developed to investigate the physical phenomena dominating the EDAM process. Printed composite tooling for high-temperature autoclave and compression molding composites manufacturing has been the primary demonstrator for this technology. Date: Thursday, November 29, 2018 Time: 2:00 P.M. Place: IMI 130

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FW: “Theoretical Chemistry’s Role in Providing Sustainable Energy” - Chemistry Mueller Lecture by Dr. Emily Carter; Thur Nov 29 4:30PM
by Coar, Stacey L 28 Nov '18

28 Nov '18

[cid:image001.png@01D48732.A8B7CF40] The Mueller Lecture Thursday, November 29, 2018 4:30PM in WTHR 104 Reception 4:00PM in BRWN 4102

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Seminar Reminder for Sami El Awad Azrak's Preliminary Exam. Friday, Nov. 30, at 1:30 p.m., in ARMS 1028
by Son, Rosemary E 28 Nov '18

28 Nov '18

Please consider attending the following: MATERIALS ENGINEERING SEMINAR "Large Scale Processing of Mechanically Fibrillated Cellulose Nanofiber (CNF) Films" By Sami M. El Awad Azrak Purdue MSE Ph.D. Preliminary Exam Advisor: Professor Jeffrey P. Youngblood ABSTRACT Driven by the invention of the first semi- and fully- synthetic polymers by John Wesley (1869) and Leo Baekeland (1907), and the need to preserve precious natural resources during World War II (1935), man-made polymer products have become vital components of our daily lives. Out of the many possible end products; polymeric films, sheets, and porous fabrics have seen large use in the packaging industry ($198 billion globally) and textile industry ($17 billion in the USA). In order to meet the current demand for synthetic polymer products (335 million metric tons of raw polymers produced in 2016) innovative large scale processing techniques have been developed. Some of the popular techniques used to process common engineering polymers (PE, PP, PET, etc.) into films and sheets include; extrusion, film blowing, melt/sheet casting, and calendaring. All of which take advantage of the formability and flowability of these polymers when heated above their glass and melting temperatures as well as the shear thickening or thinning behavior of the melt. Other techniques like carding, spunbonding, and the papermaking process are used to create bonded porous fabrics, also known as nonwovens, from man-made polymer fibers (Tencel, PP, PE, PET, PTT, Nylon 6,6) or naturally made fibers like cellulose. Yet, with an ever increasing need to replace and reduce the dependency on oil sourced polymers, degradable and sustainable polymers will need to be processed into similar useable forms. Additionally, these bio-friendly products will need to perform equally well or outperform common engineering polymers. Fibrillated cellulose, also known as microfibrillated cellulose (MFC) or cellulose nanofibers (CNF), is a perfect candidate to be processed into films due to its abundancy and sustainability. Furthermore, it has been shown that films produced from differently treated versions of MFC material have exceptional mechanical and optical properties which rival and surpass those found in common engineering polymers and even some metals like steel when considering its low density (~1.6 g/cm). Though extremely promising, the processing of CNF into films has lagged behind other polymers in industry. Techniques found in literature that can directly process this material remain largely semiautomatic and have very long lead times (from an hour to a couple of weeks). In order to further the efforts and help elucidate the processing of this novel material, common polymer processing techniques will be reviewed, as well as those used for nonwoven fabrics and the papermaking process. A comparison will be made between these techniques and those used to process pure CNF films. The challenges of processing CNF with current industrial techniques will be brought up and possible solutions will be proposed. Pilot scale plants that have successfully produced self-standing films will also be mentioned. Additionally, important parameters that affect the overall mechanical performance of CNF films will be discussed. Date: Friday, Nov. 30, 2018 Time: 1:30 P.M. Place: ARMS 1028

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Seminar Reminder for Eduardo Barocio's Ph.D. Final Exam. Thursday, November 29, at 2:00 p.m., in IMI 130
by Son, Rosemary E 28 Nov '18

28 Nov '18

Please consider attending the following: MATERIALS ENGINEERING SEMINAR "Fusion Bonding of Fiber Reinforced Semi-Crystalline Polymers in Extrusion Deposition Additive Manufacturing" By Eduardo Barocio Purdue MSE Ph.D. Final Exam Advisor: Professor R. Byron Pipes ABSTRACT Extrusion Deposition Additive Manufacturing (EDAM) is a large-scale Additive Manufacturing (AM) technology able to fabricate parts from the desktop scale to the size of a full vehicle. Fiber reinforced polymers have been the primary enabler for this steep transition by reducing the thermal expansion and increasing the stiffness of printing materials. The EDAM process consists of depositing beads of molten material in a layer-by-layer manner, thus large temperature gradients develop during part manufacturing. Further, shear flow introduced during material extrusion and deposition orients fibers dominantly along the print direction. In the absence of fibers reinforcing the interface between adjacent layers, the bond developed by the polymer matrix is the primary mechanism governing the interlayer mechanical properties. The combination of residual stresses due to anisotropy and temperature gradients with weak interlayer bonding can lead to delamination of parts during manufacturing. Hence, there is a need for predictive simulation tools to mitigate the empirical process of determining printing strategies that lead to crack free parts. Significant contributions were made towards this objective by developing simulation tools for predicting the evolution of temperature and interlayer strength during part manufacturing. The continuous deposition of material is replicated virtually utilizing a framework developed previously for EDAM process simulation. A suite of user-defined subroutines in Abaqus(c) was utilized for implementing different mechanisms of heat transfer as well as a model for fusion bonding. Methods for characterizing not only the properties of printing materials for EDAM process simulations but also the processing conditions used in the EDAM process are presented. Additionally, the Composites Additive Manufacturing Research Instrument (CAMRI) was developed to investigate the physical phenomena dominating the EDAM process. Printed composite tooling for high-temperature autoclave and compression molding composites manufacturing has been the primary demonstrator for this technology. Date: Thursday, November 29, 2018 Time: 2:00 P.M. Place: IMI 130

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Seminar Reminder for David Lowing's Ph.D. Final Exam Today, Wednesday, Nov. 28, in ARMS 1028
by Son, Rosemary E 28 Nov '18

28 Nov '18

Please consider attending the following: MATERIALS ENGINEERING SEMINAR “Microstructural Evolution in NiO-MgO: Linking Equilibrium Crystal Shape and Grain Growth” By David A. Lowing Purdue MSE Ph.D. Final Exam Advisor: Professor John Blendell ABSTRACT Ceramic materials are natural or synthetic, inorganic, non-metallic materials incorporating ionic and covalent bonding. Most ceramics in use are polycrystalline materials where grains are connected by a network of solid-solid interfaces called grain boundaries. The structure of the grain boundaries and their arrangement play a key role in determining materials properties. Developing a fundamental understanding of the formation, structure, migration and methods of control grain boundaries have drawn the interest of scientists for over a century. While grain boundaries were initially treated as isotropic, advances in materials science has expanded to include energetically anisotropic boundaries. The orientation and structure of a grain boundary, determined by this anisotropy, controls the mobility of a grain boundary. The mobility is the controlling factor during grain growth impacting the microstructural evolution of a material. This thesis covers fundamental research to model how a materials’ equilibrium crystal shape can be used as a grain growth control mechanism. First an overview of ceramic processing and microstructural development is presented with a focus on the role of grain boundaries in determining the properties of a material. The role of anisotropy and related recent work is highlighted setting the foundation for the link between the equilibrium crystal shape and grain growth. A discussion on the selection of the NiO-MgO system for all experimental work is included. A novel production and processing route for NiO-MgO was developed. Mechanical alloying and milling resulted in significant impurity contamination therefore a chemical production route was used. A modified amorphous citrate process was developed where metal salts containing Ni and Mg were mixed with a polyfunctional organic acid. Rapid dehydration and calcination at 500°C resulted in chemically homogeneous powders. The amorphous citrate production route produced powder with crystallites ranging from 244-393 nm and agglomerates ranging from 20-300 μm with plate-like morphology. NiO-MgO powders produced via the amorphous citrate method were sintered using various techniques. Conventional sintering was unable to produce fully dense samples peaking with relative densities from 95-96%. The introduction of pressure through spark plasma sintering and hot pressing improved the relative sample density to 97-100%. It was discovered that exposure to the vacuum required for spark plasma sintering and hot pressing resulted in the reduction of NiO. Spark plasma sintering created oxygen depleted regions and hot pressing further reduced NiO to pure nickel metal which precipitated out at the grain boundaries. Due to the poor sintering behavior of NiO-MgO grain growth experiments were carried out on the large agglomerates formed during the amorphous citrate process. Agglomerates with more than 50 grains with a thickness of at least 1 μm were selected. Grain growth was measured across five compositions with Ni:Mg ratios of 100:0, 75:25, 50:50, 25:75, 0:100. The average grain size and growth rate increased with increasing nickel content with a significant jump between 50% and 75%. Increasing nickel content was also observed to correspond with a higher number of grains exhibiting surface faceting. The NiO-MgO equilibrium crystal shape as a function of composition was measured previously. To make the equilibrium crystal shape a more viable control for grain growth a quantitative microstructural characterization technique was developed to measure a materials equilibrium crystal shape. Topographic surface information (surface facets measured by atomic force microscopy, AFM) and grain crystallographic orientation (measured by electron back-scattered diffraction, EBSD) were combined to produce the crystallographic topography of a sample surface. Surface crystallographic topography was used to identify the faceting behavior of grains with a range of orientations. Using the combined data, facet stability maps (n‑diagrams) for NiO-MgO were developed. Controlling grain growth via the equilibrium crystal shape offers the potential to produce microstructures with a high frequency of desirable grain boundaries (grain boundary engineering) and therefore properties. The combination of using AFM and EBSD to create crystallographic topographical surface data and n-diagrams has been demonstrated. N-diagrams for most materials do not exist, but the technique used here can be applied to a wide range of materials and will expand the ability to control microstructures of ceramic materials. Date: Wednesday, November 28, 2018 Time: 12:30 P.M. Place: ARMS 1028

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Seminar Reminder for Greg Scofield's Preliminary Exam. Today, Wednesday, November 28, at 2:00, in HAMP 1252
by Son, Rosemary E 28 Nov '18

28 Nov '18

Please consider attending the following: MATERIALS ENGINEERING SEMINAR "Investigation into the Role of Oxidation on Static Fatigue Behavior of Siliconized Silicon Carbide" By Gregory C. Scofield Purdue MSE Ph.D. Preliminary Exam Advisors: Professor Kenneth Sandhage and Professor Michael Sangid ABSTRACT Silicon carbide based ceramics matrix composites (CMCs) seek to replace nickel superalloys in gas turbine components due to their comparatively low density and high strength at elevated temperatures, however, the introduction of these new composite materials can only be achieved after failure mechanisms are properly understood. Harsh combustion environments are known to decrease fatigue life of these composite materials, though the effect of oxidation on mechanical properties is still not fully understood, leading to unpredictable failure of components. A review of the current literature relating to static fatigue of siliconized silicon carbide is presented with emphasis given to oxidation mechanisms within the composite system. Gaps within literature are addressed and a plan for continued research into the effects of oxidation on static fatigue behavior in siliconized silicon carbide is proposed. Date: Wednesday, November 28, 2018 Time: 2:00 P.M. Place: HAMP 1252 School of Materials Engineering Purdue University Neil Armstrong Hall of Engineering 701 West Stadium Ave. Room 2200 West Lafayette, IN 47907 765-494-4105

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Seminar Reminder for Francisco Montes' Ph.D. Final Exam. Tuesday, November 27, at 1:30 p.m., in the Graduate Student Center PGSC-105AB
by Son, Rosemary E 26 Nov '18

26 Nov '18

Please consider attending the following: MATERIALS ENGINEERING SEMINAR "Effects on Rheology and Hydration of the Addition of Cellulose Nanocrystals (CNC) in Portland Cement Pastes" By Francisco J. Montes Purdue MSE Ph.D. Final Exam Advisor: Professor Jeffery P. Youngblood ABSTRACT Cellulose Nanocrystals have been used in a wide range of applications including cement composites as a strength enhancer. This work analyses the use of CNC from several sources and production methods, and their effects on rheology and hydration of pastes made using different cement types with different compositions. Cement Types I/II and V were used to prepare pastes with different water to cement ratios (w/c) and measure the changes in rheology upon CNC addition. The presence of Tricalcium Aluminate (cement chemistry denotes as C3A) played an important role in the magnitude of CNC effects. At dosages under 0.5vol% relative to dry cement, CNC reduced the yield stress up to 50% the control value. Pastes with more C3A reduced yield stress over a wider range of CNC dosages. CNC also increased yield stress of pastes with dosages above 0.5%, twice the control value for pastes with high C¡A content at 1.5% CNC and up to 20 times for pastes without C¡A at the same dosage. All the CNCs used were characterized in length, aspect ratio, zeta potential to identify a definitive factor that governs the effect in the rheology of cement pastes. However, no definitive evidence was found that any of these characteristics dominated the measured effects. The CNC dosage at which the maximum yield stress reduction occurred increased with the amount of water used in the paste preparation, which evidences the dominance of the water to cement ratio in the rheological impact of CNC. Isothermal calorimetry showed that CNC cause concerning retardation effects in cement hydration. CNC slurries were then tested for sugars and other carbohydrates that could cause the aforementioned effect, then slurries were filtered, and impurities were detected in the filtrate, these impurities were quantified and characterized, however, the retardation appeared to be unaffected by the amount of the species detected, suggesting that the crystal chemistry, consequence of the CNC processing method, is responsible of this retardation. This work explores the benefits and drawbacks of the use of CNC in cement composites by individually approaching rheology and hydration on a range of physical and chemical conditions to build a better understanding of the observed effects can be achieved. Understanding the effect of CNCs on cement paste rheology can provide insights for future work of CNCs applications in cement composites. Date: Tuesday, November 27, 2018 Time: 1:30 P.M. Place: ARMS PGSC-105AB

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Seminar Notice for David Lowing's Ph.D. Final Exam Wednesday, Nov. 28, in ARMS 1028
by Son, Rosemary E 26 Nov '18

26 Nov '18

Please consider attending the following: MATERIALS ENGINEERING SEMINAR “Microstructural Evolution in NiO-MgO: Linking Equilibrium Crystal Shape and Grain Growth” By David A. Lowing Purdue MSE Ph.D. Final Exam Advisor: Professor John Blendell ABSTRACT Ceramic materials are natural or synthetic, inorganic, non-metallic materials incorporating ionic and covalent bonding. Most ceramics in use are polycrystalline materials where grains are connected by a network of solid-solid interfaces called grain boundaries. The structure of the grain boundaries and their arrangement play a key role in determining materials properties. Developing a fundamental understanding of the formation, structure, migration and methods of control grain boundaries have drawn the interest of scientists for over a century. While grain boundaries were initially treated as isotropic, advances in materials science has expanded to include energetically anisotropic boundaries. The orientation and structure of a grain boundary, determined by this anisotropy, controls the mobility of a grain boundary. The mobility is the controlling factor during grain growth impacting the microstructural evolution of a material. This thesis covers fundamental research to model how a materials’ equilibrium crystal shape can be used as a grain growth control mechanism. First an overview of ceramic processing and microstructural development is presented with a focus on the role of grain boundaries in determining the properties of a material. The role of anisotropy and related recent work is highlighted setting the foundation for the link between the equilibrium crystal shape and grain growth. A discussion on the selection of the NiO-MgO system for all experimental work is included. A novel production and processing route for NiO-MgO was developed. Mechanical alloying and milling resulted in significant impurity contamination therefore a chemical production route was used. A modified amorphous citrate process was developed where metal salts containing Ni and Mg were mixed with a polyfunctional organic acid. Rapid dehydration and calcination at 500°C resulted in chemically homogeneous powders. The amorphous citrate production route produced powder with crystallites ranging from 244-393 nm and agglomerates ranging from 20-300 μm with plate-like morphology. NiO-MgO powders produced via the amorphous citrate method were sintered using various techniques. Conventional sintering was unable to produce fully dense samples peaking with relative densities from 95-96%. The introduction of pressure through spark plasma sintering and hot pressing improved the relative sample density to 97-100%. It was discovered that exposure to the vacuum required for spark plasma sintering and hot pressing resulted in the reduction of NiO. Spark plasma sintering created oxygen depleted regions and hot pressing further reduced NiO to pure nickel metal which precipitated out at the grain boundaries. Due to the poor sintering behavior of NiO-MgO grain growth experiments were carried out on the large agglomerates formed during the amorphous citrate process. Agglomerates with more than 50 grains with a thickness of at least 1 μm were selected. Grain growth was measured across five compositions with Ni:Mg ratios of 100:0, 75:25, 50:50, 25:75, 0:100. The average grain size and growth rate increased with increasing nickel content with a significant jump between 50% and 75%. Increasing nickel content was also observed to correspond with a higher number of grains exhibiting surface faceting. The NiO-MgO equilibrium crystal shape as a function of composition was measured previously. To make the equilibrium crystal shape a more viable control for grain growth a quantitative microstructural characterization technique was developed to measure a materials equilibrium crystal shape. Topographic surface information (surface facets measured by atomic force microscopy, AFM) and grain crystallographic orientation (measured by electron back-scattered diffraction, EBSD) were combined to produce the crystallographic topography of a sample surface. Surface crystallographic topography was used to identify the faceting behavior of grains with a range of orientations. Using the combined data, facet stability maps (n‑diagrams) for NiO-MgO were developed. Controlling grain growth via the equilibrium crystal shape offers the potential to produce microstructures with a high frequency of desirable grain boundaries (grain boundary engineering) and therefore properties. The combination of using AFM and EBSD to create crystallographic topographical surface data and n-diagrams has been demonstrated. N-diagrams for most materials do not exist, but the technique used here can be applied to a wide range of materials and will expand the ability to control microstructures of ceramic materials. Date: Wednesday, November 28, 2018 Time: 12:30 P.M. Place: ARMS 1028

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