News & EventsDepartment Events
Events
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May13
EVENT DETAILS
lessTBA
TIME Monday, May 13, 2024 at 11:00 AM - 12:00 PM
LOCATION 1101, Pancoe-NSUHS Life Sciences Pavilion map it
CONTACT Andrew Liguori andrew.liguori@northwestern.edu EMAIL
CALENDAR McCormick - Civil and Environmental Engineering (CEE)
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May15
EVENT DETAILS
lessAbstract: Grain boundaries have a central importance for functional properties of materials. They can critically control thermal and elactrical transport, determining the performance of energy and electronic materials. In thermoelectric materials – promising for refrigerant-free cooling and waste heat energy harvesting – grain boundaries can be leveraged to suppress the thermal conductivity, but can also detrimentally suppress the carrier mobility. Grain boundaries are not all equal: they are associated to several degrees of freedom, and can come in multiple orientations, symmetries, and chemistries. Recent evidence suggests that some types of grain boundaries could be more beneficial than others for the thermoelectric performance. Despite the importance, we lack a clear understanding of how grain boundaries modify the microscale transport owing to the scarcity of local investigations. Usually the role of grain boundaries is inferred from bulk, effective measurements. However, understanding how grain boundaries impact transport locally is a crucial perspective to enable grain-boundary engineering for the next generation of high-performance thermoelectrics.
In this seminar, I will introduce our recent work on thermal conductivity imaging of grain boundaries via spatially-resolved frequency-domain thermoreflectance. Measurements with microscale resolution reveal a suppression in thermal conductivity at grain boundaries both in thermoelectric SnTe and photovoltaic multicrystalline silicon. In contrast to conventional thermal modeling, which assumes that all boundaries are perfect scatterers and lead to uniformly suppressed thermal conductivity, we observe a non-uniform suppression localized within a few microns of a boundary. Furthermore, not all grain boundaries behave the same: misorientation angle, symmetry, as well as interface roughness and morphology are found to strongly correlate with the effective thermal boundary resistance. Extracting transport properties from microscale imaging can provide comprehensive understanding of how individual microstructural components work. In particular, it can advance the study of grain boundary phases - i.e. two-dimensional phases stabilized at the boundary and that can be controlled via thermodynamics - by correlating how thier local chemistry and structure impact functional properties. This development can improve our understanding of carrier-defect interactions, enabling the rational engineering of interfaces and materials microstructures for superior performance in energy and electronics.
Bio: Eleonora Isotta is currently a Postdoctoral scholar in the Department of Materials Science and Engineering at Northwestern University. She joined in fall 2022 and has been working on thermal transport in semiconductors, developing methods to perform thermal imaging of defects, with a focus on grain boundaries, together with Prof. G. J. Snyder and Prof. O. Balogun. She received her B.S. in Environmental Engineering in 2015 and M.S. in Energy Engineering in 2017 from University of Trento. In 2021, she received a Ph.D. in Materials Science from University of Trento, with a dissertation on the interplay between crystal structure and transport properties in thermoelectric materials. She then pursued a Postdoc at Michigan State University working on thermal transport and elasticity in thermoelectric materials. Her current research interests involve thermal transport, microstructure engineering, and materials for thermoelectrics and electronics.
TIME Wednesday, May 15, 2024 at 11:00 AM - 12:00 PM
LOCATION A236, Technological Institute map it
CONTACT Andrew Liguori andrew.liguori@northwestern.edu EMAIL
CALENDAR McCormick - Civil and Environmental Engineering (CEE)
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May17
EVENT DETAILS
lessTBA
TIME Friday, May 17, 2024 at 2:00 PM - 3:00 PM
LOCATION A236, Technological Institute map it
CONTACT Andrew Liguori andrew.liguori@northwestern.edu EMAIL
CALENDAR McCormick - Civil and Environmental Engineering (CEE)
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May20
EVENT DETAILS
lessTBA
TIME Monday, May 20, 2024 at 11:00 AM - 12:00 PM
LOCATION 1101, Pancoe-NSUHS Life Sciences Pavilion map it
CONTACT Andrew Liguori andrew.liguori@northwestern.edu EMAIL
CALENDAR McCormick - Civil and Environmental Engineering (CEE)
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May22
EVENT DETAILS
lessTitle: Mechanism-based multi-scale models for damage and failure in heterogeneous materials
Abstract: A large variety of modern engineering materials such as polymers and their composites (unidirectional, textile, nanocomposites) have a heterogeneous microstructure. As a result, their failure behavior under multi-axial stresses is highly complex, consisting of multiple simultaneous meso-scale damage mechanisms. Moreover, the heterogeneous microstructure also makes the fracturing distinct quasi-brittle character (neither fully brittle nor fully ductile). This has important implications on structural behavior, especially in terms of size effects in strength and fracture toughness. Since structural designs often rely on numerical modeling, an accurate prediction of load-bearing capacities and energy dissipation during these failures is essential. This talk will focus on the class of semi-multiscale constitutive models called the microplane models (pioneered at Northwestern), which effectively address this challenge. These models have a dual-scale architecture, and can reproduce complex macro-scale behaviors via simple, intuitive formulation of meso-scale damage mechanisms. They also provide a physically sound basis to homogenize the meso-scale damage to predict the macro-scale failure growth and structural size effects. They are thus an effective strategy for multi-mechanism failures in heterogeneous materials. First, we will introduce the quintessential spherical microplane model, first developed for concrete, and applicable in general to isotropic materials. We will present its application to the failure of brittle-plastic polymers and demonstrate its abilities to capture complex aspects such as tension-compression asymmetry and pressure sensitivity. Next, we will introduce the cylindrical microplane model, which applies to unidirectionally reinforced polymer composites, which are transversely isotropic. We will present a successful application of this model to compression induced kink band failures. Following that we will introduce the microplane triad model, which applies to textile composites, which are orthotropic and have additional complexities due to yarn undulations. We will demonstrate its successful application to prediction of ballistic impact of woven composite lamina. Lastly, we will discuss the challenges of applying these models to real world applications and directions for future work.
Bio- Prof. Kedar Kirane is an associate professor of Mechanical Engineering at Stony Brook University, New York. His research focuses on characterizing, understanding, and predicting the fracturing and scaling behavior of various conventional and advanced heterogeneous materials. These include brittle materials, fiber reinforced composites, polymers, nanocomposites, geological and cementitious materials, and soft materials. His research combines experimental, computational, and theoretical approaches. The overarching goal is to develop reliable predictive capabilities and sound scientific bases for safe designs in various engineering applications. Prof. Kirane obtained his Ph.D. in 2014 from Northwestern University and joined the Mechanical Engineering faculty at Stony Brook University in Sept 2017. He also holds an M.S. degree from the Ohio State University (2007) and a B.S from the University of Pune, India (2004), both in mechanical engineering. Prior to joining Stony Brook, Prof. Kirane worked in industry, as a finite element analyst at Goodyear Tire & Rubber Co and later as a senior research engineer at ExxonMobil Corp. His research is supported by DOD ARO, DOD ONR, NSF NRT, and ASME. He is the recipient of the 2020 Orr Early Career Award by ASME’s Materials Division, the 2019 DOD ARO Young Investigator Award, and the 2018 Haythornthwaite Research Initiation Grant by ASME’s Applied Mechanics Division.
TIME Wednesday, May 22, 2024 at 11:00 AM - 12:00 PM
LOCATION A236, Technological Institute map it
CONTACT Andrew Liguori andrew.liguori@northwestern.edu EMAIL
CALENDAR McCormick - Civil and Environmental Engineering (CEE)
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May24
EVENT DETAILS
lessTitle- PFAS Characterization
TIME Friday, May 24, 2024 at 2:00 PM - 3:00 PM
LOCATION A236, Technological Institute map it
CONTACT Andrew Liguori andrew.liguori@northwestern.edu EMAIL
CALENDAR McCormick - Civil and Environmental Engineering (CEE)
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Jun6
EVENT DETAILS
lessDepartment ceremony to recognize the graduate students completing their degree.
TIME Thursday, June 6, 2024 at 4:00 PM - 8:00 PM
LOCATION 1702 Chicago Ave
CONTACT Andrew Liguori andrew.liguori@northwestern.edu EMAIL
CALENDAR McCormick - Civil and Environmental Engineering (CEE)
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Jun7
EVENT DETAILS
lessDinner reception to celebrate the graduating seniors from CEE undergraduate program.
TIME Friday, June 7, 2024 at 6:00 PM - 9:00 PM
LOCATION 623 W Howard St
CONTACT Andrew Liguori andrew.liguori@northwestern.edu EMAIL
CALENDAR McCormick - Civil and Environmental Engineering (CEE)
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Jun10
EVENT DETAILSmore info
lessMcCormick School of Engineering PhD Hooding and Master’s Degree Recognition Ceremony
TIME Monday, June 10, 2024 at 9:00 AM - 11:00 AM
LOCATION Welsh-Ryan Arena
CONTACT Amy Pokrass amy.pokrass@northwestern.edu EMAIL
CALENDAR McCormick School of Engineering and Applied Science
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Jun10
TIME Monday, June 10, 2024 at 2:00 PM - 4:00 PM
LOCATION Welsh-Ryan Arena
CONTACT Amy Pokrass amy.pokrass@northwestern.edu EMAIL
CALENDAR McCormick School of Engineering and Applied Science