Bulletin of the American Physical Society
85th Annual Meeting of the APS Southeastern Section
Volume 63, Number 19
Thursday–Saturday, November 8–10, 2018; Holiday Inn at World’s Fair Park, Knoxville, Tennessee
Session B04: Applied Physics I |
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Chair: Ekaterina Paerschke Room: Holiday Inn Knoxville Downtown Parlor |
Thursday, November 8, 2018 11:00AM - 11:12AM |
B04.00001: Graphene foam as current collector in a Li-S type battery Fengjiao Case, Anthony Childress, Christopher Etteh, Ky-Mani Miller, Shailendra Chiluwal, Marlena Washington, Ramakrishna Podila, Apparao M Rao Sulfur has shown great potential as an active material for use in lithium-ion batteries. In the past decade, much research has been devoted to overcoming the problems of electrode expansion during cycling and the shuttle effect whereby sulfur deposits form on the lithium anode leading to cell failure, in addition to the dendrite growth. Electrodes are typically made by casting a slurry composed of the active material plus binding agents onto aluminum or copper foils, yielding an electrode layer with a thickness in the range of 50 μm. Cell performance can be limited by the electrode thickness due to the need for ions to diffuse through the active layer. With this in mind, we have incorporated graphene foam as a current collector which allows for high mass loading of active material while maintaining performance. Here, we compare the performance of graphene foam electrodes to a typical electrode made by the doctor blade method. The graphene foam allows for superior mass loading while also mitigating the loss of cell performance typical at high discharge rates. We also use Raman spectroscopy to observe changes in the electrode during the first discharge as the solid-electrolyte interphase is formed. |
Thursday, November 8, 2018 11:12AM - 11:24AM |
B04.00002: Development of Burst-Mode Laser based High-speed Thomson Scattering Instruments for Fusion Plasma Devices Zichen He, Cary Smith, Zhili Zhang, Naibo Jiang, Sukesh Roy Practical fusion plasma devices at various DOE and international facilities need the state-of-the-art diagnostic tools to understand, predict, and control fusion plasmas. Thomson scattering (TS), as a popular diagnostics technique, has successfully measured electron temperature and density inside the plasma system. However, the traditional TS technique operates only at 10Hz. Since the devices operate at on the order of 10- 100ms, it means only one data point can be obtained for each cycle. We develop high repetition rate Thomson scattering instruments based on high-speed pulsed burst laser system. Pulse burst laser was originally developed for supersonic or hypersonic flow diagnostics. In a typical pulse burst laser, a burst (or train) of high-energy laser pulses is generated at high repetition rates over a period of time (~20 ms). The pulse sequence can reach energies of ~100 mJ per individual pulse up to MHz rates or 1 Joule per individual pulse up to 10 kHz, while maintaining low average power. Thomson scattering system is being used to obtain electron number density and electron temperature in the plasma. |
Thursday, November 8, 2018 11:24AM - 11:36AM |
B04.00003: Scalable patterning using laser-induced shock waves Joshua B Stinson, Ali Er, Claire Ottman, Dylan Sanford, Ilhom Saidjafarzoda An advanced direct imprinting method with low cost, quick, and minimal environmental impact to create thermally controllable surface pattern using the laser pulses is reported. Patterned micro indents were generated on Ni50Ti50 shape memory alloys (SMA) using an Nd:YAG laser operating at 1064 nm combined with suitable transparent overlay, a sacrificial layer of aluminum, and copper grid. Laser pulses at different energy densities which generate pressure pulses up to a few GPa on the surface was focused through the confinement medium, ablating the copper grid to create plasma and transferring the grid pattern onto the surface. Scanning electron microscope (SEM), atomic force microscope (AFM), and optical microscope images show that various patterns were obtained on the surface with high fidelity. Optical profile analysis indicates that the depth of the patterned sample initially increase with the laser energy and later levels off. Our simulations of laser irradiation process also confirm that high temperature and high pressure could be generated when laser energy of 2 J/cm2 is used. |
Thursday, November 8, 2018 11:36AM - 11:48AM |
B04.00004: Femtosecond pulsed laser micromachining of titanium foils for producing hydrogen as an energy carrier Brian K. Canfield, Alexander Terekhov, Shule Yu, Feng-Yuan Zhang, Lloyd M. Davis Proton exchange membrane electrolyzer cells are being developed as a cost-effective, sustainable route to generating hydrogen fuel for energy storage, advanced fuel production, metal refining, fertilizer, and many other applications. Designs using custom-made thin, metallic foil meshes with ~10-µm diameter through-holes, called thin and tunable gas diffusion electrodes (GDEs), can reduce device thickness and decrease rare-element catalyst needs while increasing operating efficiency. GDEs can be fabricated through femtosecond (fs) pulsed laser micromachining of titanium (Ti) foil, where foil thickness, hole size, and fill factor can all be controlled. We present results from parametric studies of fs pulsed laser machining of thin (13 & 25 µm) Ti foils for GDE applications. Tightly focused fs laser pulses can rapidly machine small holes while significantly reducing collateral thermal damage. Direct control over surface chemistry is examined by modifying atmospheric conditions during machining to eliminate non-conductive oxidation, and heating during laser irradiation is observed with thermal micrography. Machined foil is characterized through optical and scanning electron micrographies and energy dispersive spectroscopy to determine resultant chemical species. |
(Author Not Attending)
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B04.00005: Impact of Space radiation on Ultra-Sensitive In-Orbit IR Telescopes William J Atkinson This paper evaluates possible design considerations in reducing disruptions of scientific data in ultra-sensitive Infrared (IR) spaced-based telescopes by charged particles in space radiation. The particles modeled are protons, alphas, and heaver ions with an atomic number as high as that of iron. Performance results of proposed designs are based on a model developed at Boeing. The components modeled are the energy spectra of the ion species in cosmic rays and solar flares, the transport of the primary ions and any secondary particles produced including neutrons, the generation electron hole pairs (EHPs) by the particles passing through the focal point array (FPA), and the spread of the charge through neighboring pixels. The results show noise levels between 100 and 10000 electrons per pixel in stressing environments. IR telescopes now have a noise level as low as 100 electrons per pixel making the analysis results significant. The analysis results indicate secondary ionization alone can exceed the noise threshold of 100 e/pixel. Measures that reduced the number of electrons per pixel below the threshold given are discussed. The model can be used in selecting or de-selecting designs that potentially reduce radiation induced charging of focal point arrays before implementation. |
Thursday, November 8, 2018 12:00PM - 12:12PM |
B04.00006: Yagi-Uda nanolithographic antennas on a metal-semiconductor-metal photodiode William Rieger, Jean Joseph Heremans, Hang Ruan, Yuhong Kang, Richard Clause Nanoscale Yagi-Uda antennas were fabricated on a metal-semiconductor-metal rectifying photodetector to enhance detector efficiency. A new approach for characterizing the nanolithographic optical antennas was developed and evaluated, using a direct electrical measurement obviating the need for an ITO coating or back contact. The approach was used to demonstrate control of directivity and wavelength selectivity in an array of 400 of the nanoantennas. A modified spectrometer allowed the sample to be illuminated with monochromatic light of varied angle of incidence, while electrical measurements were performed using lock-in detection. With incoming light nearly aligned to the center lobe of the Yagi-Udas, resonances in measured photocurrent were observed at 1110 nm and 1690 nm. These correspond to scaled effective wavelengths of 388 nm and 776 nm resp., in close agreement with plasmonic theory. Quantum efficiencies are estimated 5.1% and 3.1% at 1110 nm and 1690 nm resp., representing a fourfold increase over a device lacking the antenna array. With incoming light at an angle away from the main and side lobes no resonances were observed Reference: W. Rieger et al., Appl. Phys. Lett. 113, 023102 (2018). |
Thursday, November 8, 2018 12:12PM - 12:24PM |
B04.00007: Real-Time Mass Sensing of a Flux of Incoming Particles. Sudeep Adhikari, Kevin Stuart David Beach We present a theoretical framework for determining the mass deposited on a mechanical resonator subject to a flux of incoming particles of a single species. We consider the specific example of a vibrating nanostring and infer the history of mass deposition events from the frequency shifts in real time using a numerical optimization alogrithm that correctly compensates for the configurational entropy. Our approach is tested against simulated data and is shown to perform well. |
Thursday, November 8, 2018 12:24PM - 12:36PM |
B04.00008: Broadband saturable absorption properties of 2D Ti2C MXene and its application in ultrafast fiber laser generation Jun Yi, Lin Du, Jie Li, Sergii Chertopalov, Longyu Hu, Chujun Zhao, Shuangchun Wen, Vadym N Mochalin, Ramakrishna Podila, Apparao M Rao Two-dimension (2D) materials, such as graphene, black phosphorus (BP) and transition metal dichalcogenides, have attracted much attention in the field of ultrafast fiber lasers due to their unique nonlinear optical (NLO) properties. However, due to the limitation of their intrinsic NLO properties, there is a growing need for novel broadband nonlinear materials in the near-infrared and mid-IR regimes. In this regard, MXene is a promising material due to its outstanding nonlinear properties. Here, we investigated the broadband nonlinear optical properties of 2D Ti2CTx MXene, where Tx represents functional groups such as -OH and -F. Using open aperture Z-scan method, we explored the broadband saturable absorption properties in the range 800 - 1560 nm. The large nonlinear absorption coefficient and low saturable intensity of Ti2CTx confirmed its potential use in NLO applications. Using Ti2CTx as saturable absorbers, we also developed ultrafast mode-locked fiber lasers operating at 1565 nm and 1051 nm with a pulse width of 5.3 ps and 164 ps, respectively. Lastly, we developed Ti2CTx-based passively Q-switched lasers that operated in mid-infrared regime at 2.8 um. |
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