Session JJ00: Virtual Poster Session II (1:30pm-3:00pm CST)

Trimesic Acid on Highly Ordered Pyrolytic Graphite

The formation of self-assembled monolayers of organic molecules on the conductive surfaces is of great interest. These monolayers play an important role on organic electronic devices and as the thin coating used as corrosion protection. In this project, to get self-assembled monolayers, trimesic acid was deposited on a highly ordered pyrolytic graphite (HOPG) substrate. Then the sample surface was characterized using Nanosurf NaioSTM to study structural and electronic properties. The trimesic acid modified HOPG surface was found mettalic.   

Theoretical Band Structure and X-Ray Spectroscopy Calculations for Lithium Battery Materials

X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray spectroscopy (RIXS) allow for direct measurement of an atom’s electronic environment, giving insights into the mechanisms behind lithium cyclability and ionic diffusion to improve the ionic conductivity and energy density of batteries. Advancements in lower-energy XAS and RIXS have allowed for the direct measurement of the lithium K-edge in experiments, corresponding to the 2s → 2p electron transition. However, common theoretical calculations of the lithium K-edge to produce XAS and RIXS spectra have produced inaccurate simulations of the spectra due to the low number of valence electrons in lithium affecting their response to the core hole. . Using density functional theory plus Hubbard U correction (DFT+U) calculations performed using QuantumESPRESSO and Bethe-Salpeter equation (BSE) calculations performed using OCEAN, we produce theoretical XAS spectra of common lithium compounds with increased sensitivity to core-level excitations and compare them to experimental RIXS, delineating a new protocol to model the lithium K-edge and providing important information on electronic environments of the atomic species.    

Higher Harmonic Magnetic Nanoparticle Characterization using AC Faraday Rotation

Faraday rotation (FR) is a magneto-optic phenomenon where the polarization of light traveling through a medium is rotated in an applied magnetic field parallel to the direction of light propagation. This phenomenon depends on the field's strength, path length, and material properties that the light travels through. The material properties that determine the magneto-optic response give rise to the Verdet constant, which measures the effectiveness of the Faraday Effect on the material. When investigating magnetic nanoparticles (MNPs), interpreting the Verdet constant is not straightforward.

This work used monodispersed iron oxide (Fe₃O₄) magnetic nanoparticles (MNPs) with a nominal diameter of 20nm. This diameter is consistent with MNPs' superparamagnetic response to the applied magnetic field. These were purchased commercially from Ocean Nanotech. 175µL of these MNPs were dissolved in 6mL of ultra-high purity water to conduct the experiments. We used a He-Ne laser and subjected the MNP sample to an AC magnetic field. The transmitted light intensity showed intensity oscillations resulting from oscillating polarization detected using a photodetector (Thorlabs LMR1). This allowed for a lock-in-based detection of 1^st, 2^nd, 3^rd, 4^th, and 6^th harmonics in response to the AC magnetic field. These higher harmonics provide strong evidence for aggregate formation at this concentration and particle size. We propose an explanation for the observed data based on aggregate formation. We also compare these findings with results obtained for smaller MNPs that show much more straightforward responses.   

Magnetic Nanoparticle Characterization using AC Faraday Rotation

Faraday rotation (FR) is a magneto-optic phenomenon where polarization of light traveling through a medium is rotated in an applied magnetic field, that is parallel to the direction of light propagation. This phenomenon is dependent on the strength of the field, path length, and properties of the material that the light travels through. The material properties that determine the magneto-optic response give rise to the Verdet constant, which is the measure of effectiveness of the Faraday Effect on the material. When investigating magnetic nanoparticles (MNPs), the interpretation of the Verdet constant is not straightforward.

In this work monodispersed iron oxide (Fe₃O₄) magnetic nanoparticles (MNPs), with a diameter of 10nm, were used. These were purchased commercially from Ocean Nanotech. These MNPs were dissolved in ultra-high purity water. Samples of different MNP concentration were used. In this study. The 10 nm size of MNP results in a superparamagnetic response of the nanoparticles to the applied field. We used a He-Ne laser and subjected the MNP sample to an AC magnetic field. This allowed for a lock-in based detection that resulted in the determination of a precise value of the Verdet constant of the MNPs. The transmitted light intensity showed intensity oscillations resulting from oscillating polarization that were detected using a photodetector (Thorlabs LMR1). We determined the Verdet constant of MNPs as a function of concentration. We found that the highest concentrations of MNPs departed from a straightforward dependence of Verdet constant on concentration. Our results provide a strong indication of the onset of aggregation formation in MNPs beyond a certain threshold concentration. We also discuss some recent findings of similar investigations on MNPs of larger sizes, to provide a comparison of MNP response as a function of particle size.   

Atomistic Modeling and Simulations of Thermal/Mechanical Behaviors of Glass-Ceramics

The research on a wide range of glass-ceramics has gained a great attention in the areas of nanotechnology and materials science. In particular, lithium disilicate, aluminum silicates, lithium aluminum silicate glass-ceramics have been successful in many industry applications, owing to their generally superior mechanical properties such as high flexural strength and fracture toughness. As such, it is virally important to obtain fundamental understanding of mechanical/thermal characteristics of the glass ceramic materials to be extended to other commercial applications like display glasses and heat exchangers. However, the mechanical/thermal properties of those materials still remain elusive because of the lack of computational effort to model such a complex system. Here, we perform reactive molecular dynamics (RMD) simulations to reveal mechanical behaviors of glass-ceramics under tensile conditions. We also identify thermal behaviors of the glass-ceramics to better understand materials behaviors at extreme conditions. As such, our work will make a reasonable contribution to the scalable and reliable synthesis of glass ceramics-based composites at extreme conditions.   

Design and Implementation of Digital Logic Filtration on Open-Source Field-Programmable Gate Arrays

Field-programmable gate arrays (FPGAs) serve as extremely powerful hardware tools used in data acquisition (DAQ) and digital signal processing (DSP) environments thanks to their reprogrammable nature and parallel computation. Most often, this technology utilizes a custom algorithm of many parallel algebraic computations (some of which contain parameters that can be manipulated for desired applications) in a processes called data filtration. Here I discuss the importance of DSP in physics applications and detail the development of a trapezoidal method for filtering exponentially decaying pulses on an entry-level open-source FPGA. I outline the design considerations for handling data and performing analysis, the breakdown and translation of a simple summation formula for proper implementation in digital logic, and the development and final testing of a complete project on the FPGA itself. The finalized product exhibited promising results, accomplishing nearly 98% accuracy in most tests of pulse peak detection. Likely design flaws were also quick to be discovered, leaving an opportunity for making small improvements to said accuracy. Furthermore, there was success in generating an automated script that allows end users to recreate the complete project from the ground up with minimal experience.

Additionally, I have provided open access to a development package for unfettered use and modification or application to DSP environments, with plans to incorporate new DSP projects and perform upkeep.   

Design and Characterization of Ceramic-Based Flexible Devices for Mars Regolith Mitigation Applications

Yttria Stabilized Zirconia (YSZ) ceramics have been widely used as a protective boundary for high temperature environments, flame shields, intrinsic barriers to moisture, and are often considered highly suitable materials for extreme environments. This class of materials can withstand temperatures up to 3000 °C and as low as cryogenic temperatures, far exceeding the maximum temperature of operation for most other materials including polymers. As the desire for space exploration continues to grow, the need for materials that can tolerate extreme conditions becomes more urgent. The tendency for µm-scale rock fragments, known as regolith, to electrostatically adhere to sensitive surfaces poses a major challenge for space exploration. In this work the authors study the tendency of JSC-Mars1 regolith simulant to adhere to flexible thin ceramic films and characterize the interaction as a function of temperature, particle size, and surface potential. Results suggest that these surfaces can be manipulated to reduce and possibly prevent dust accumulation and pave the way for design and adoption of novel dust mitigation techniques.   

3-Dimensional, Multi-Flavor Neutrino Spin Oscillations In the Presence of a Fast Flavor Instability

In the presence of anisotropic neutrino and antineutrino fluxes, the neutrino quantum kinetic equations acquire helicity off-diagonal terms that drive coherent oscillations in neutrino spin. These oscillations depend directly on the absolute mass scale and Majorana phase, but are usually too transient to produce important effects. In this paper we present a 3-dimensional analysis of spin oscillations, analyzing the effect on the data of the 3D neutron star merger of cite{merger_simulation}. We find an interesting directional dependence that allows for resonant { ed and significant} oscillations to occur along specific directions. The solid angle spanned by these directions is extremely narrow in general, but we propose conditions under which it could be broadened. We then analyze spin-flip in the mixed-flavor regime by characterizing how the effect's resonance and timescale change during a fast flavor instability. For this analysis, we derive a generalized resonance condition that poses a restrictive requirement for resonance to exist in any flavor channel.   

Using Mg II k Lines to Probe Stellar Chromopheres

Stellar chromospheres constitute a complex and crucial part of stellar atmospheres. Understanding stellar chromospheres could improve our understanding of solar weather, plasma, and stellar magnetic fields. Past research has used the Mg II k spectral lines (at ∼ 2796.34 [A]), to gauge upper solar chromosphere activity associated with spatially resolved solar features (e.g. sunspots, plage, etc.). This study aimed to use Mg II k spectral analysis to gauge the likely chromospheric activity of other stars. We examined the spectra of 141 stars observed by NASA's Hubble Space Telescope. The most common Mg II k spectral profile was a broad line with a central reversal, forming two peaks with a central depression. The remaining 27 Mg II k spectra consisted of symmetrical or asymmetrical single peak profiles. We used a double gaussian curve fit model to, where relevant, extract each star's Mg II k spectra characteristics: Mg II k line spectral shape, peak asymmetry, relative depression depth, peak to peak width, full width at half maximum, and full width at half maximum for each individual peak. We identified how the properties of the Mg II k spectra varied with stellar characteristics, such as temperature, metallicity, age, mass, radius, and rotational period.   

Space-time Superpositions as Fluctuating Geometries

One of the most central questions of modern physics surrounds the nature of quantum gravity, this theory is a necessity in understanding phenomena such as black holes and the big bang. Our approach seeks to utilize one of these such phenomena, black holes, to construct a quantum corrected model of blackholes in the semi-classical limit. In a previous paper, this was done through the introduction of quantum fluctuations on the classical metric components. This method produced nonlocal effects while preserving critical properties such as general covariance. In this follow up paper we are reinterpreting this model as superpositions of multiple classical black hole spacetimes of varying masses.  This expands the potential applicability of this model to other areas.