Response of Surface Bound Hexacyanoferrate Films to Binary and Ternary Metal Alloys
Research Advisor: Dr. Jennifer Hampton
Recently, there has been an increase in the use of intermittent renewable energy sources. By possessing a large volumetric charge density while maintaining rapid charging and discharging rates, electrochemical capacitors contribute to the diversity of energy storage materials that are needed to accommodate these new demands. In particular, hexacyanoferrate (HCF) films possess a crystal structure which remains physically unaltered during charge cycling, making it an ideal candidate for a durable pseudocapacitor. Transition metals were deposited onto a gold substrate from solution using an electrochemical cell to produce a NiCo or NiCoCu backbone for the thin films. These films are studied in a scanning electron microscope (SEM) with an energy dispersive x-ray spectroscopy (EDS) attachment to determine their structures and compositions. This particular study focuses on how the composition and processing of the metal layer affects the HCF film properties including charge storage, charge/discharge rates, and qualitative surface characteristics. Preliminary results suggest that the alloy processing contributes only slightly to variations in electrochemical properties.
This work was generously funded by the Hope College Dean for Natural & Applied Sciences Office, the Hope College Department of Physics, and the National Science Foundation under NSF-MRI Grant No. CHE-0959282+
Characterization of Cation Intercalation in Surface Bound Prussian Blue Analogues
Research Advisor: Dr. Jennifer Hampton
With the increasing popularity of handheld, rechargeable devices (such as smartphones) the demand for Lithium-ion batteries has also increased to fill this need. Alternative battery types provide an opportunity to lower costs by using more earth abundant elements. Prussian Blue Analogue (PBA) films are one alternative that have the benefit of admitting a more diverse range of ionic intercalants than lithium. This study focuses on the characterization of PBA films which are exposed to a variety of cations (Li+, Na+, K+) that differ from the initial solution in which they were created. We found that some films would exhibit enhanced features, such as, a larger charge capacity. Preliminary results demonstrate that some cation intercalants are more kinetically favorable, and out-compete each other for interstitial site occupation within the PBA lattice. Further research could look to the effect of using 2+ ions (Mg2+ and Ca2+) as the intercalant.
This material is based upon work supported by the Hope College Department of Physics, the Hope College Dean for Natural and Applied Sciences Office, and the National Science Foundation under NSF-MRI Grant No. CHE-0959282.
Crystalline Channeling of MeV Ion Beams
Research Advisor: Dr.Stephen Remillard
Thin films of strontium titanate (SrTiO3) on single crystal magnesium oxide (MgO) substrate and strontium manganate (SrMnO3) also on single crystal MgO substrate are being considered for use in engineered superlattices. These superlattice structures exhibit unique properties which make them valuable in the semiconductor industry as well as applications which require a high sheering resistance. Crystal matching of the films to the substrates, which is essential for a low defect density, is indicated by effective channeling of ion beams through the lattice. Ion beam channeling, which occurs when the beam’s incidence angle is parallel to crystal planes, can occur in well-ordered and pure crystals. With the addition of the ability to control the azimuthal angle as well as the altitudinal angle, two dimensional rastering of the incident angle is achieved. Comparison of the backscattering yields at different incident altitudinal and azimuthal angles shows a drop in yield as the channeling angle is approached. Channeling is seen in both the bulk SrTiO3 and MgO samples, although the yield suppression revealed structure around normal incidence. This structure is observed to be consistent between two MgO samples obtained from different suppliers and has different spacing in peaks than the SrTiO3 sample.
This research was supported in part by an award to Hope College from the Howard Hughes Medical Institute through the Undergraduate Science Education Program and by the Hope College Department of Physics.
Scanning of the Intermodulation of Superconductor Resonators
Research Advisor: Dr. Stephen Remillard
At the resonant frequency, superconductor resonators produce intermodulation distortions, smaller signals near the resonant frequency. By inducing external microwave signals, it is possible to analyse the patterns of intermodulation distortions (IMD) in several different types of superconductor resonators. These measurements can be used to complement the main peak values like quality factor and frequency shift in order to understand nonlinearities present in the material of the superconductor. Once spatial distributions of IMD have been identified, they can be used to interpret IMD signals from unknown superconductors and identify various defects in the crystal structure. Using a probe outputting two combined tones into the resonator, it was possible to map the whole of a two-dimensional resonator, using the IMD as the z-direction. In order to best resolve the intermodulation distortions, two superconductors were imaged, a hairpin wide-line resonator and a thin, line resonator. A contour plot of the data was then generated, which displays the IMD of the given resonator.
Funding for this project was provided by The Hope College Natural and Applied Sciences Division and Award number DMR-1505617 from the National Science Foundation.
Obtaining the Likelihood from Unbinned Data of Detected and Simulated Pulsars
Research Advisor: Dr. Peter Gonthier
This research is made possible by the generous support of the Department of Physics and the Dean for Natural and Applied Sciences Office of Hope College.