MSE Department Seminar

The forthcoming era of energy systems, propulsion, space re-entry vehicles, and nuclear reactors points to structural materials that can withstand increasingly extreme thermal environments. Body- centered cubic (BCC) refractory alloys are attracting renewed attention owing to the nature of atomic bonding and internal plastic dissipation pathways, yet at ambient conditions, they tend to exhibit ceramic-like behavior characterized by low toughness and ductility.

When molecules are coupled to an optical cavity, new light-matter hybrid states, so- called polaritons, are formed due to quantum light-matter interactions. With the experimental demonstrations of modifying chemical reactivities by forming polaritons under strong light-matter interactions, theorists have been encouraged to develop new methods to simulate these systems and discover new strategies to tune and control reactions. In this talk, I will first introduce the concept of polariton and discuss its relevance in the recent molecular polariton and polariton chemistry investigations.

Gels are key materials in biological systems such as tissues and may control biocondensate formation and structure. To further understand the effects of elastic environments on biomacromolecular assembly, we have investigated phase behavior and radii of coacervate droplets in polyacrylamide (PAM) networks as a function of the gel modulus. Poly-L-lysine (PLL) and sodium hyaluronate (HA) coacervate phases were prepared in PAM gels with moduli varying from 0.035 – 9.0 kPa. The size of the coacervate droplets is reported from brightfield microscopy and confocal fluorescent microscopy.

Small-Angle Scattering (SAS), including Small-Angle X-ray and Neutron Scattering (SAXS and SANS), is a powerful characterization technique for investigating the structure of biomacromolecules and their interactions. SAXS/SANS allows us to characterize structural features across a wide range of length scales, spanning from just a few nanometers to several hundred nanometers.

Conventional rechargeable batteries are formed using slurry-cast electrodes whose random nature and porosity limits both energy density and rate performance. As a general rule, such composite electrodes, consisting of a mixture of active material, solid electrolyte, and often conductive additives exhibit power and energy limitations due to the tortuosity of the ion and electron conduction pathways and lower than ideal energy densities due to the volume and mass of the additives.

An exciting research area in condensed matter and materials physics is the response of matter to ultrafast stimuli, such that the eigenmode oscillation period is relatively long. In ferroic materials, the strongly coupled order parameters (magnetization, polarization, strain) and their highly nonlinear responses to fields (magnetic, electric, mechanical, and thermal) provide additional design flexibility for discovering new fundamental phenomena and new device applications.

Computational approaches are increasingly employed to guide and understand experiments, offering a systematic and accelerated path to materials discovery. Automated ab-initio frameworks like aflow++ have rapidly expanded the volume of materials data, enabling the use of data-science methods for the prediction of new materials. These approaches have been used to study superconductors and thermoelectrics, and have proved fruitful with the discovery of new permanent Heusler magnets, superalloys, high-entropy ceramics, and phase change memory compositions.

Density-functional-theory-based calculations using high-performance computers have made enormous strides in describing the atomic-scale properties of complex materials and structures. In parallel, aberration-corrected scanning transmission electron microscopy (STEM) has reached extraordinary levels of spatial and energy resolution, in both imaging and electron-energy-loss spectroscopy (EELS). Recently, the advent of advanced monochromators has led to very high energy resolution in EELS, enabling atomic-resolution vibrational spectroscopy.

Corrosion is a complex phenomenon involving metallic alloys and the surrounding environment. The various forms of corrosion suffered by metallic materials in aqueous environments have been extensively studied and codified. In contrast, studies of corrosion at high temperatures involving gaseous environments, liquids like molten salts, and solid deposits are more limited. There is, however, continued need for studies in this area due to their impact on a broad range of industries including those in the aerospace, power generation, chemical process, and petrochemical refining sectors.

Antiferromagnets represent a new opportunity for developing spintronics with superior speed and high device density. With zero net magnetic moment, they are immune to almost any external magnetic field disturbance. Meanwhile, the intrinsic dynamics at the Terahertz frequency makes them good candidates for high speed electronics. While a lot of useful ways have been developed for manipulating spins in ferromagnets over the past decades, people’s knowledge on detecting and controlling antiferromagnetic ordering remains very limited.