Bulletin of the American Physical Society
83rd Annual Meeting of the APS Southeastern Section
Volume 61, Number 19
Thursday–Saturday, November 10–12, 2016; Charlottesville, Virginia
Session C4: Applied Physics |
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Chair: Michel Pleimling, Virginia Tech University Room: Preston Room |
Thursday, November 10, 2016 1:30PM - 1:42PM |
C4.00001: Atomistic Investigation of the Effect of Crystallographic Orientation on Laser-Induced Generation of Crystal Defects in Metals Maxim Shugaev, Chengping Wu, Leonid Zhigilei The results of the recent electron backscatter diffraction measurements [Sedao \textit{et al.}, Appl. Phys. Lett. 104, 171605, 2014] are suggesting a strong effect of the crystallographic orientation of grains in polycrystalline metal targets on the generation and accumulation of crystal defects in the surface region of the irradiated targets. In order to explain the experimental observations and to reveal the physical origin of the sensitivity of the laser-induced surface modification to the crystallographic orientation of irradiated surface, a series of large-scale atomistic simulations of femtosecond laser irradiation of Ni targets with (001), (011), and (111) surface orientations is performed. The results of the simulations do confirm the significant influence of the crystal orientation on the formation of sub-surface defects and provide detailed information on the defect configurations generated in each target. Overall, the results of this investigation clarify the mechanisms responsible for the laser-induced generation of crystal defects, including generation of growth twins and dislocation during rapid resolidification, and explain the sensitivity of the structural modification of metal surfaces to the crystallographic orientation of irradiated targets. [Preview Abstract] |
Thursday, November 10, 2016 1:42PM - 1:54PM |
C4.00002: Graphene quantum dot synthesis using nanosecond laser pulses Khomidkhodzha Kholikov, Dovletgeldi Seyitliyev, Dana Biechele-Speziale, zachary thomas, skyler smith, selahaddin gumus, Benjamin Kash, Ali Er A biocompatible photodynamic therapy agent that generates a high amount of singlet oxygen with high water dispersibility and excellent photostability is desirable. In this work, a graphene based biomaterial which is a promising alternative to a standard photosensitizers was produced. Methylene blue was used as a reference photosensitizer. Bacteria deactivation by methylene blue was shown to be inhibited inside human blood due to protein binding. Graphene quantum dots (GQD) were synthesized by irradiating benzene and nickel oxide mixture using nanosecond laser pulses. High resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, and nuclear magnetic resonance (NMR) were used for characterization of GQDs. Initial results show graphene quantum dots whose size less than 10 nm were successfully obtained. UV-VIS spectra shows absorption peak around 310 nm. The results of these studies can potentially be used to develop therapies for the eradication of pathogens in open wounds, burns, or skin cancers. New therapies for these conditions are particularly needed when antibiotic-resistant infections are present. [Preview Abstract] |
Thursday, November 10, 2016 1:54PM - 2:06PM |
C4.00003: Laser Induced Hydrogen Generation from Coal in Water Dovletgeldi Seyitliyev, Dana Biechele-speziale, Byron Grant, Khomidkhodzha Kholikov, Ali Er We report an alternative way of obtaining hydrogen using nanosecond laser pulses and various ranks of coal and coke. SEM-EDS analysis shows the atomic concentrations of elements on each of the powders which also is in good agreement with calorimeter analysis. Coal and coke powders were irradiated with 1064nm IR and 532 nm green Nd:YAG pulsed laser beam for 45 minutes. The volume of the total gas generated after irradiation of each rank was measured using the water displacement method. The amount of gas generated increased when using 532 nm compared to 1064 nm. Post-irradiation SEM images show structural differences with samples before irradiation. The amount of gas generation with respect to laser energy density shows nonlinear correlation. Generated gas concentrations were then analyzed using gas chromatography (GC). Hydrogen and carbon monoxide were the two most highly generated gases, and the efficiency of each rank of coal was determined by analyzing the hydrogen to carbon monoxide ratio. The highest efficiency rank was anthracite, with hydrogen to carbon monoxide ratio of 1.4. GC analysis also showed that the maximum hydrogen generation occurs at 100 mJ/pulse laser energy. The efficiency of each rank of coal was observed to correlate with carbon content. [Preview Abstract] |
Thursday, November 10, 2016 2:06PM - 2:18PM |
C4.00004: Computational Modeling and Advanced Synthesis Techniques for the Improved Design of ZSM-5 Zeolite Catalysts Arian Ghorbanpour, Jeffrey Rimer, Lars Grabow Zeolites are the most widely used catalysts in industry. Active sites in zeolites are created by Al substitution of framework Si atoms in crystallographically different positions on the exterior or in the porous interior of zeolite crystals. This leads to heterogeneous chemical/kinetic behavior of various active sites, which can be employed to tune the properties of zeolites in catalytic processes. On the experimental side of this project, the shape selectivity of ZSM-5, an important zeolite catalyst in the petrochemical industry, is enhanced by manipulating its active site distribution. An advanced synthesis method was designed to passivate the external surface of ZSM-5 particles and suppress the reaction of bulky reactants over the exterior of the catalyst particles. The investigation of the impact of heterogeneous distribution of H-ZSM-5 active sites is continued through density functional theory (DFT) simulation, which reveals a large variation in the characteristics of 12 distinct active sites. The modeling of a test reaction indicates that pore confinement effects vary among different H-ZSM-5 active site locations, resulting in non-identical kinetic behavior through different extents of transition state stabilization. This heterogeneous performance not only causes different rates of reaction, but also impacts the dominant reaction mechanism at typical reaction conditions. [Preview Abstract] |
Thursday, November 10, 2016 2:18PM - 2:30PM |
C4.00005: Evaluation of Bond Strength with Opto-Acoustic Method Takumi Kamimura, Tomohiro Sasaki, Sanichiro Yioshida An attempt has been made to evaluate the bond strength of ultrasonically welded joints with an opto-acoustic method. One end of the specimen (1 cm x 10 cm rectangle with 1 mm thick where the middle of the 10 cm length is lap-welded) is oscillated with an acoustic transducer (1 -- 20 kHz), and the harmonic response of the specimen is detected with a Michelson interferometer. One of the 1-cm ends of the specimen is driven by the acoustic transducer (input end) and the other surface on the other 1-cm end (output end) is configured as one of the end-mirrors of the interferometer. A regular mirror is used for the other end mirror. A photodiode is placed behind the beam splitter to detect the change in the relative optical-path length of the interferometric arms due to the acoustic oscillation. The signal from the photodiode is analyzed in the frequency domain to evaluate the input-end to output-end displacement transfer function. It is expected that the bond strength can be differentiated in resonant behavior of the specimen; a weaker bond shows a lower resonant frequency than the stronger bond in the applied frequency range. Our preliminary study with the use of a capacitive displacement sensor, in place of the optical interferometer, indicates the feasibility of this method. [Preview Abstract] |
Thursday, November 10, 2016 2:30PM - 2:42PM |
C4.00006: Acoustic Investigation of Buried Objects William Grismore, Eli Owens Granular materials are ubiquitous. However, sound propagates through these materials in a nonlinear, poorly understood fashion. Acoustic waves may provide a non-invasive means of investigating granular materials. This project uses acoustic waves to investigate objects buried in a granular material composed of sand, with either a concrete or lead brick buried in the middle. Piezoelectric sensors are placed throughout the granular material; these output a voltage directly proportional to the sound amplitude. The frequency response of the system, with and without the buried object, is studied. We find that the lead and concrete interfaces suggest acoustic reflection, with the lead interface exhibiting more reflection than the concrete interface. We also found that at frequencies below approximately 2000 Hz the sand systems attenuates the acoustic waves better than the concrete or lead systems do, although this is not the case at frequencies higher than 2000 Hz. At these higher frequencies, sound penetrates lead less so than concrete, and concrete less so than sand alone. We find that the power spectrum qualitatively scales with the interface density at these higher frequencies, but does not scale with the interface modulus or sound speed. [Preview Abstract] |
Thursday, November 10, 2016 2:42PM - 2:54PM |
C4.00007: Experiments on Levitation with the Electrodynamic Wheel Angel Gutarra-leon, Vincent Cordrey, Walerian Majewski Our Experiments explored inductive magnetic levitation (MagLev) and the possibility of using simple permanent magnets and conductive tracks instead of coils for MagLev applications. Our investigations used a circular Halbach array with the strong variable magnetic field on the outer rim of the ring. Such a system is usually called an Electrodynamic Wheel (EDW). Rotating this wheel around a horizontal axis above a flat conducting surface should induce eddy currents in said surface through the variable magnetic flux. The eddy currents produce, in turn, their own magnetic fields which interact with the magnets of the EDW. We constructed a four inch diameter Electrodynamic Wheel using twelve Neodymium permanent magnets and demonstrated that the magnetic interactions produce both lift and drag forces on the EDW which can be used for levitation propulsion of the EDW. The focus of our experiments is the direct measurement of lift and drag forces to compare with theoretical models to demonstrate magnetic levitation without the need for coils and complex control circuitry. [Preview Abstract] |
Thursday, November 10, 2016 2:54PM - 3:06PM |
C4.00008: Refinement of Production Grade Biodiesel. Ken McGill, Zachary Huffman, Campbell Axt, Christopher Barrett, Elizabeth Cronan, JaMichael Williams, Tyler Wilhoit, Annaleigh Jackson, Sydney Ninneman The modified Burton method for the thermal hydrogen-cracking of peanut oil has been investigated in McGill Research Group since 2009. The successful and reliable production of biodiesel has been achieved since 2014. A hydrocarbon with viscosity similar to Production Grade Diesel will work in modern diesel engines. The current product has a viscosity significantly lower than production grade diesel. The starting material has a viscosity significantly higher than Production Grade Diesel. Current research is investigating methodologies to mix starting material and product to achieve target viscosity. [Preview Abstract] |
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