MSEN Seminars

Date	Speaker	Topic
2/2/07	Dr. H. Eliot Fang	Computational Materials Science: a Pillar of Engineering Science
3/26/07	Dr. Michel Barsoum	The MAX Phases and Kinking Nonlinear Elastic Solids
3/30/07	Dr. Yonggang Huang	Mechanics of Stretchable Electronics
4/11/07	Dr. Alexey T. Zayak	Theoretical View on the Physics of Heusler Alloys
4/12/07	Armen G. Khachaturyan	Transformation-induced Straing and Microstructure Evolution in Complex Systems
4/18/07	Christopher Schuh	Design of Stable Nanocrystalline Alloys for Coating Applications
	also see	Materials-related seminars in other departments

Dr. H. Eliot Fang
Sandia National Laboratories	Time: 3:00 to 4:00 p.m. Date: Friday February 2, 2007 Place: CHEN 104 Faculty host: Dr. Xinghang Zhang
Computational Materials Science: a Pillar of Engineering Science
For many years, material scientists, chemists and physicists have longed to have computer simulations that predict the behavior of materials and track the evolution of their microstructures from the atomic to the engineering scales. With the staggering advances in computer speed and the continued improvements in numerical techniques in recent years, computational materials science has become a powerful and, in many cases, a predictive tool. As the field of computational materials science develops and matures, the notion that modeling efforts should be an integral part of interdisciplinary materials research and must include experimental validation is taking hold in the community. At Sandia National Laboratories, scientists develop computational models to predict the performance and behavior of complex materials, such as metals, ceramics, and polymers, across all relevant length and time scales. Promising progresses have been made in modeling material structures at interfaces and in bulk, simulating microstructural evolution during processing, and predicting the property degradation during service and aging. However, significant challenges in theory and numerical algorithm developments still remain to be overcome. In this presentation, recent efforts of materials modeling and simulation at Sandia to support national security and industry applications will be reviewed, highlighting their successes and challenges. General issues existing in the computational modeling community will be discussed. Lessons learned from bridging physics at different length scales and coupling different simulation codes will also be shared Back to top

Dr. H. Eliot Fang

Sandia National Laboratories

Time: 3:00 to 4:00 p.m.
Date: Friday
February 2, 2007
Place: CHEN 104
Faculty host: Dr. Xinghang Zhang

Computational Materials Science: a Pillar of Engineering Science

For many years, material scientists, chemists and physicists have longed to have computer simulations that predict the behavior of materials and track the evolution of their microstructures from the atomic to the engineering scales. With the staggering advances in computer speed and the continued improvements in numerical techniques in recent years, computational materials science has become a powerful and, in many cases, a predictive tool. As the field of computational materials science develops and matures, the notion that modeling efforts should be an integral part of interdisciplinary materials research and must include experimental validation is taking hold in the community.

At Sandia National Laboratories, scientists develop computational models to predict the performance and behavior of complex materials, such as metals, ceramics, and polymers, across all relevant length and time scales. Promising progresses have been made in modeling material structures at interfaces and in bulk, simulating microstructural evolution during processing, and predicting the property degradation during service and aging. However, significant challenges in theory and numerical algorithm developments still remain to be overcome.

In this presentation, recent efforts of materials modeling and simulation at Sandia to support national security and industry applications will be reviewed, highlighting their successes and challenges. General issues existing in the computational modeling community will be discussed. Lessons learned from bridging physics at different length scales and coupling different simulation codes will also be shared
Back to top

Dr. Michel Barsoum
Distinguished Faculty, Department of Materials Science and Engineering, Drexel University	Time: 4:00 to 5:00 p.m. Date: Monday March 26, 2007 Place: ZACH 105B Faculty host: Dr. Miladin Radovic
THE MAX Phases and Kinking Nonlinear Elastic Solids: A Newly Identified Class of Solids
The layered, hexagonal ternary carbides and nitrides with the general formula: Mn+1AXn, (MAX) where n = 1 to 3, M is an early transition metal, A is an A-group (mostly IIIA and IVA) element and X is either C and/or N combine some of the best attributes of metals and ceramics. Like metals, they are electrically and thermally conductive, most readily machinable (manual hack saw will suffice) not susceptible to thermal shock, plastic at high temperatures, and exceptionally damage tolerant. Like ceramics, they are elastically rigid, lightweight, and maintain their strengths to high temperatures. The ternaries Ti3SiC2 and Ti2AlC are creep, fatigue and oxidation resistant. More recently we have also shown that the MAX phases are but a subset of solids that we termed kinking nonlinear elastic, KNE, because one of their important – and in many cases only – deformation mode is the formation of fully reversible dislocation-based kink bands, KBs. The ramifications of these results are far-reaching. First, they identify the hysteretic mesoscopic units invoked to explain the behavior of nonlinear mesoscopic elastic solids in geology – that to date had remained a mystery – as incipient KBs. Second, they elucidate, for the first time, why graphite responds to stress the way it does; a 50 + year old problem. We further claim, and present compelling evidence, that most if not all solids with c/a ratios > 1.5 - which per force are plastically anisotropic – will deform by kinking. KNE solids include most layered solids, some of which, like the layered silicates are geologically important, Mg, Ti, Zn, Co, and other hexagonal metals, AlN and h-BN, GaN, MoS2, as well as sapphire, among many others. Given the diversity and ubiquity of KNE solids it is clear that incipient KBs play a much more important role in our daily life than has hitherto been appreciated. For example, we show that damping and microyielding in hexagonal metals can both be explained by invoking the formation of incipient KBs. Based on the totality of our work it is now clear that incipient KBs are one of the last, but crucial, missing pieces in the deformation-of-solids puzzle. Interesting note: The evening of March 26 Dr. Barsoum will present a lecture on his controversial theory on the fabrication of the blocks from wihch the Great Pyramids were built. Dr. Barsoum will present evidence to support his theory that the blocks were cast and/or poured, rathern than hewn from stone (using the rather soft instruments of the Bronze Age.) In other words, Dr. Barsoum proports the Pyramids are more concrete than stone. In fact, Dr. Miladin Radovic of the MSEN faculty and a student of Dr. Barsoum's, has fabricated limestone in the lab. This lecture is presented in cooperation with the Materials Advantage student group. Links to Dr. Barsoum's research: The Pyramids: Cast, Poured, or Both?: Engineering the Pyramids Pyramids Blog Casting Stones at the Pyramids Back to top

Dr. Michel Barsoum

Distinguished Faculty, Department of Materials Science and Engineering, Drexel University

Time: 4:00 to 5:00 p.m.
Date: Monday
March 26, 2007
Place: ZACH 105B
Faculty host: Dr. Miladin Radovic

THE MAX Phases and Kinking Nonlinear Elastic Solids: A Newly Identified Class of Solids

The layered, hexagonal ternary carbides and nitrides with the general formula: Mn+1AXn, (MAX) where n = 1 to 3, M is an early transition metal, A is an A-group (mostly IIIA and IVA) element and X is either C and/or N combine some of the best attributes of metals and ceramics. Like metals, they are electrically and thermally conductive, most readily machinable (manual hack saw will suffice) not susceptible to thermal shock, plastic at high temperatures, and exceptionally damage tolerant. Like ceramics, they are elastically rigid, lightweight, and maintain their strengths to high temperatures. The ternaries Ti3SiC2 and Ti2AlC are creep, fatigue and oxidation resistant. More recently we have also shown that the MAX phases are but a subset of solids that we termed kinking nonlinear elastic, KNE, because one of their important – and in many cases only – deformation mode is the formation of fully reversible dislocation-based kink bands, KBs. The ramifications of these results are far-reaching. First, they identify the hysteretic mesoscopic units invoked to explain the behavior of nonlinear mesoscopic elastic solids in geology – that to date had remained a mystery – as incipient KBs. Second, they elucidate, for the first time, why graphite responds to stress the way it does; a 50 + year old problem. We further claim, and present compelling evidence, that most if not all solids with c/a ratios > 1.5 - which per force are plastically anisotropic – will deform by kinking. KNE solids include most layered solids, some of which, like the layered silicates are geologically important, Mg, Ti, Zn, Co, and other hexagonal metals, AlN and h-BN, GaN, MoS2, as well as sapphire, among many others. Given the diversity and ubiquity of KNE solids it is clear that incipient KBs play a much more important role in our daily life than has hitherto been appreciated. For example, we show that damping and microyielding in hexagonal metals can both be explained by invoking the formation of incipient KBs. Based on the totality of our work it is now clear that incipient KBs are one of the last, but crucial, missing pieces in the deformation-of-solids puzzle.

Interesting note: The evening of March 26 Dr. Barsoum will present a lecture on his controversial theory on the fabrication of the blocks from wihch the Great Pyramids were built. Dr. Barsoum will present evidence to support his theory that the blocks were cast and/or poured, rathern than hewn from stone (using the rather soft instruments of the Bronze Age.) In other words, Dr. Barsoum proports the Pyramids are more concrete than stone. In fact, Dr. Miladin Radovic of the MSEN faculty and a student of Dr. Barsoum's, has fabricated limestone in the lab. This lecture is presented in cooperation with the Materials Advantage student group. Links to Dr. Barsoum's research:

Dr. Yonggang Y. Huang
University of Illinois at Urbana-Champaign	Time: 4:00 to 5:00 p.m. Date: Friday 3/30/2007 Place: ZACH 105B Faculty host: Dr. Dimitris Lagoudas
Mechanics of Stretchable Electronics
Stretchable electronics is important in the development of next-generation electronics since it has many applications such as portable electronics, flexible display, small optical sensor and compact digital camera, sensors and drive electronics for artificial muscles, structural monitors wrapped around aircraft wings, and surgeon’s gloves studded with stretchable sensors that can monitor a patient’s vital signs. However, silicon is an intrinsically brittle material and is not stretchable. We have produced a stretchable form of silicon that consists of sub-micrometer single crystal elements structured into shapes with microscale periodic, wave-like geometries (Science, v. 311, pp 208-212, 2006.) (This work has been selected by MIT Technology Review as “One of Ten Technologies That Will Change the World” in 2006. It is also on the museum display in The Tech Museum of Innovation, San Jose, California, since October 1, 2006.) When supported by an elastomeric substrate, this wavy silicon can be reversibly stretched and compressed to large strains without damaging the silicon. The amplitudes and periods of the waves change to accommodate these deformations, thereby avoiding significant strains in the silicon itself. Dielectrics, patterns of dopants, electrodes and other elements directly integrated with the silicon yield fully formed, high performance wavy metal oxide semiconductor field effect transistors, pn diodes and other devices for electronic circuits that can be stretched or compressed to similarly large levels of strain. Mechanics plays an important role in the development of stretchable electronics. Back to top

Dr. Yonggang Y. Huang

University of Illinois at Urbana-Champaign

Time: 4:00 to 5:00 p.m.
Date: Friday
3/30/2007
Place: ZACH 105B
Faculty host: Dr. Dimitris Lagoudas

Mechanics of Stretchable Electronics

Stretchable electronics is important in the development of next-generation electronics since it has many applications such as portable electronics, flexible display, small optical sensor and compact digital camera, sensors and drive electronics for artificial muscles, structural monitors wrapped around aircraft wings, and surgeon’s gloves studded with stretchable sensors that can monitor a patient’s vital signs. However, silicon is an intrinsically brittle material and is not stretchable. We have produced a stretchable form of silicon that consists of sub-micrometer single crystal elements structured into shapes with microscale periodic, wave-like geometries (Science, v. 311, pp 208-212, 2006.) (This work has been selected by MIT Technology Review as “One of Ten Technologies That Will Change the World” in 2006. It is also on the museum display in The Tech Museum of Innovation, San Jose, California, since October 1, 2006.)

When supported by an elastomeric substrate, this wavy silicon can be reversibly stretched and compressed to large strains without damaging the silicon. The amplitudes and periods of the waves change to accommodate these deformations, thereby avoiding significant strains in the silicon itself. Dielectrics, patterns of dopants, electrodes and other elements directly integrated with the silicon yield fully formed, high performance wavy metal oxide semiconductor field effect transistors, pn diodes and other devices for electronic circuits that can be stretched or compressed to similarly large levels of strain. Mechanics plays an important role in the development of stretchable electronics.
Back to top

Dr. Alexey T. Zayak
Institute for Computational Engineering and Science The University of Texas, Austin	Time: 11:00 to 12:00 p.m. Date: Wednesday 4/11/2007 Place: Chemical Engineering 112 Faculty host: Dr. Ibrahim Karaman
Theoretical View on the Physics of the Heusler Alloys
First-principle calculations demonstrate their increasing abilities to explain and predict properties of real systems, getting insight into the atomic structures of materials on the level of quantum mechanics, with approximations which have well defined limitations of their applicability. However, some materials are so complex that even after years of studies we have very little understanding of their properties Heusler alloys belong to this category. This talk is about several aspects of the stability of the Heusler structures. It will be demonstrated that the ground state of these materials can be modulated. Phonon dispersions of several systems will show relations between characteristic features in their electron and phonon spectra, and those are sensitive to the valence-electron-to-atom ratio (composition). At the end, the role of an external magnetic field will be discussed with two examples of Ni-Mn-Ga and Ni-Mn-In. The overall picture has a potential to unify separated pieces of our knowledge about Heuslers and get a better microscopic theory of the shape memory effect. Back to top

Dr. Alexey T. Zayak

Institute for Computational Engineering and Science
The University of Texas, Austin

Time: 11:00 to 12:00 p.m.
Date: Wednesday
4/11/2007
Place: Chemical Engineering 112
Faculty host: Dr. Ibrahim Karaman

Theoretical View on the Physics of the
Heusler Alloys

First-principle calculations demonstrate their increasing abilities to explain and predict properties of real systems, getting insight into the atomic structures of materials on the level of quantum mechanics, with approximations which have well defined limitations of their applicability. However, some materials are so complex that even after years of studies we have very little understanding of their properties

Heusler alloys belong to this category.

This talk is about several aspects of the stability of the Heusler structures. It will be demonstrated that the ground state of these materials can be modulated. Phonon dispersions of several systems will show relations between characteristic features in their electron and phonon spectra, and those are sensitive to the valence-electron-to-atom ratio (composition). At the end, the role of an external magnetic field will be discussed with two examples of Ni-Mn-Ga and Ni-Mn-In.

The overall picture has a potential to unify separated pieces of our knowledge about Heuslers and get a better microscopic theory of the shape memory effect.

Dr. Armen Khachaturyan
University of Illinois at Urbana-Champaign	Time: 4:00 to 5:00 p.m. Date: Friday 4/12/2007 Place: HRBB 113 Faculty host: Dr. Yongmei Jin
Transformation-induced Strain and Microstructure Evolution in Complex System
The long-range magnetostatic, electrostatic, and strain-induced interaction in ferromagnetic, ferroelectric, and structurally inhomogeneous materials have one common feature ¾ it is the dipole-dipole like interaction. Such interaction makes the total system energy dependent on spatial domain architecture in the first two cases and on the microstructure (shape, size and mutual arrangement of the structural and compositional domains) in the third case. Forexample, the main structural characteristics of a coherent two-phase system, such as orientation relationships, shape of the new phase inclusions, their habit plane and mutual arrangement, are determined by the strain energy relaxation. Therefore, they can be predicted as minimizers of the strain and interfacial energies. Similarly, the domain structure in ferromagnetics and ferroelectrics is a minimizer of the magnetostatic/electrostatic energy and interfacial energy of the domain walls. In this talk I discuss typical cases of the microstructure formation during coherent phase transformations, viz. decomposition, ordering, and martensitic/ferroelastic transformation, emphasizing a profound conceptual analogy between martensitic systems on one side and the multi-dislocation and multi-crack systems on the other. The analysis of these systems and prediction of their evolution behavior turns out to be possible dueto the recent development of the theory, associated with the use of the Phase Field Microelasticity. Given the dipole-dipole character of interactions between finite elements of elastic, magnetic and ferroelectric systems, these interactions can be easily integrated into the same theoretical formalism. With such integration, the theory becomes applicable for characterization of magnetoelastic systems such as Magnetic Shape Memory alloys. Now the theory is developed to a degree where it is able to provide reliable predictions of the mesoscopic microstructure, thermodynamics and kinetics of the phase transformations in real systems of different types. Back to top

Dr. Armen Khachaturyan

University of Illinois at Urbana-Champaign

Time: 4:00 to 5:00 p.m.
Date: Friday
4/12/2007
Place: HRBB 113
Faculty host: Dr. Yongmei Jin

Transformation-induced Strain and Microstructure Evolution in Complex System

The long-range magnetostatic, electrostatic, and strain-induced interaction in ferromagnetic, ferroelectric, and structurally inhomogeneous materials have one common feature ¾ it is the dipole-dipole like interaction. Such interaction makes the total system energy dependent on spatial domain architecture in the first two cases and on the microstructure (shape, size and mutual arrangement of the structural and compositional domains) in the third case. Forexample, the main structural characteristics of a coherent two-phase system, such as orientation relationships, shape of the new phase inclusions, their habit plane and mutual arrangement, are determined by the strain energy relaxation. Therefore, they can be predicted as minimizers of the strain and interfacial energies. Similarly, the domain structure in ferromagnetics and ferroelectrics is a minimizer of the magnetostatic/electrostatic energy and interfacial energy of the domain walls.

In this talk I discuss typical cases of the microstructure formation during coherent phase transformations, viz. decomposition, ordering, and martensitic/ferroelastic transformation, emphasizing a profound conceptual analogy between martensitic systems on one side and the multi-dislocation and multi-crack systems on the other.

The analysis of these systems and prediction of their evolution behavior turns out to be possible dueto the recent development of the theory, associated with the use of the Phase Field Microelasticity. Given the dipole-dipole character of interactions between finite elements of elastic, magnetic and ferroelectric systems, these interactions can be easily integrated into the same theoretical formalism. With such integration, the theory becomes applicable for characterization of magnetoelastic systems such as Magnetic Shape Memory alloys. Now the theory is developed to a degree where it is able to provide reliable predictions of the mesoscopic microstructure, thermodynamics and kinetics of the phase transformations in real systems of different types.

Dr. Christopher Schuh (joint seminar with Mechanical Engineering)
Massachusetts Institute of Technology	Time: 4:00 to 5:00 p.m. Date: Wednesday, April 18 4/18/2007 Place: 101 Richardson Faculty host: Dr. Raymundo Arroyave
Design of Stable Nanocrystalline Alloys for Coating Applications
When the grain size of a metal is refined to a scale on the order of just a few nanometers, its strength, hardness, wear resistance, and other properties improve in dramatic ways. There is therefore significant interest in designing and deploying such nanocrystalline alloys for structural applications. However, refining the grain structure is a struggle against equilibrium, and nanocrystalline materials are often quite unstable; the grains grow given time even at room temperature, and the associated property benefits decline over time in service. In this talk, our efforts to design a stable family of nanocrystalline alloys will be described. We rely on selective alloying as a method to lower the energy of grain boundaries, bringing the nanocrystalline structure closer to equilibrium. The result is a suite of coatings with highly desirable properties, easy processability, and with long-term stability against structural coarsening. The science of alloy design and characterization will be discussed, as will the commercial applications of the technology. Back to top

Dr. Christopher Schuh
(joint seminar with Mechanical Engineering)

Massachusetts Institute of Technology

Time: 4:00 to 5:00 p.m.
Date: Wednesday, April 18
4/18/2007
Place: 101 Richardson
Faculty host: Dr. Raymundo Arroyave

Design of Stable Nanocrystalline Alloys for Coating Applications

When the grain size of a metal is refined to a scale on the order of just a few nanometers, its strength, hardness, wear resistance, and other properties improve in dramatic ways. There is therefore significant interest in designing and deploying such nanocrystalline alloys for structural applications. However, refining the grain structure is a struggle against equilibrium, and nanocrystalline materials are often quite unstable; the grains grow given time even at room temperature, and the associated property benefits decline over time in service. In this talk, our efforts to design a stable family of nanocrystalline alloys will be described. We rely on selective alloying as a method to lower the energy of grain boundaries, bringing the nanocrystalline structure closer to equilibrium. The result is a suite of coatings with highly desirable properties, easy processability, and with long-term stability against structural coarsening. The science of alloy design and characterization will be discussed, as will the commercial applications of the technology.