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10:15 AM - Noon Podium Session 3 Materials Science Union Theater--BTSU 206.

10:15 - INVESTIGATING SURFACE FINISH AND BURR FORMATION IN MICRO-MILLING OF POLYCARBONATE GLASS. Craig E. Hanson Jr.,, Muhammad P. Jahan,, Miami University, Department of Mechanical and Manufacturing Engineering, Oxford OH 45056.

Polycarbonate glass is a material most commonly known for its application as optical lenses. However, in recent years, this material has had a multitude of other applications including uses in automotive and biomedical industries. Many of the microfluidic applications of polycarbonate glass require micro-channels, which are currently made through time consuming photolithography and etching processes. In this study, micro-milling has been evaluated as a better alternative process to obtain these micro-channels. The goal was to investigate the surface finish and burr formation in the micro-milling of polycarbonate glass under varying feed rates, depths of cut, and tool coatings. In terms of surface finish, it was found that a critical depth of cut range (0.3 to 0.5 mm) produces the best surface finish of polycarbonate glass. The titanium aluminum nitride (TiAlN) coated tools produce a better surface finish than titanium nitride (TiN) and uncoated carbide tools do. We found that the higher the feed rate, the better the surface finish. The surface finish was analyzed optically with a light microscope, and quantitatively with atomic force microscope (AFM). In terms of burr formation, the same critical depth of cut range of 0.3 to 0.5 mm produced the least amount of burrs at the edges of the micro-channels. The uncoated carbide tool produced the least amount of burrs. We found that increasing the feed rate decreases the burr formation. The burrs were also optically analyzed with a light microscope. In conclusion, polycarbonate glass can be produced in ductile mode machining. A careful choice of tool and machining parameters generates a better surface finish and low burr formation.

10:30 - EFFECT OF MICROSTRUCTURES ON LUMINESCENCE KINETICS IN TRANSPARENT CERAMICS. Sahil Agarwal (1,2),, Le Zhang (1,3), Petr Stepanov (1,2), Micah Haseman (2), Farida Selim (1,2), (1) Bowling Green State University, Center for Photochemical Sciences, Bowling Green OH USA 43403, (2) Bowling Green State University, Department of Physics and Astronomy, (3) Jiangsu Key Laboratory of Advanced Laser Materials and Devices, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou, Jiangsu, P.R. China 221116.

Transparent ceramics are emerging as promising candidates for laser-host materials and scintillation applications because of their high purity, uniform composition, fewer residual pores, isotropic lattice, reduced light scattering, ease in fabrication and controlled growth processes for bulk manufacturing. The luminescence properties of two differently fabricated Ce: YAG transparent ceramics and single crystal have been studied using photoluminescence (PL) and thermoluminescence (TL) and the dependence of the luminescence kinetics on microstructure has been investigated. Positron annihilation spectroscopy (PAS) measurements comprising of PALS and Doppler broadening spectroscopy shows that PL temperature difference kinetics is different between as-grown TC and commercial TC is because of defects clusters and grain boundaries and the difference in amount makes a difference in the luminescence characteristics of the transparent ceramics. This work can serve as foundation for tuning the desired PL according to grain size and microstructure of transparent ceramics.

10:45 - IN SEARCH OF EXTRATERRESTRIAL RESOURCES: TO THE EARTH'S MOON AND BEYOND. Claire L. McLeod (1),, Mark P.S. Krekeler (2),, (1) Miami University, Department of Geology and Environmental Earth Science, 203 Shideler Hall, 250 S. Patterson Ave., Oxford OH 45056, (2) Miami University Hamilton.

Rare Earth Elements (REEs) are a group of transition metals which include the lanthanide series of the periodic table (lanthanum to lutetium) in addition to scandium (Sc) and yttrium (Y). These elements are integral components of devices used by humankind on a daily basis: smart phones, flash drives, computer monitors, and magnets for example, and are therefore considered a crucial resource to society. However, the REE budget of Earth is limited with < 2500 years of reserves left of several of these elements: lanthanum, neodymium, europium and yttrium. With an increasing human population projected to reach 8.5 billion by 2030, and a limited terrestrial REE budget, exploration of extraterrestrial REEs is inevitable with Earth's nearest neighbor in space a logical first target. The majority of Moon rocks contain minor amounts ([less than or equal to] 3%) of REE-bearing minerals: apatite ([Ca.sub.5](P[O.sub.4])(F,Cl)) merrillite (([Ca.sub.3])[(P[O.sub.4).sub.2]) and/or monazite ((Ce,La,Nd,Th)(P[O.sub.4])(Si[O.sub.4])). Yet to date there is no geological, mineralogical, or chemical evidence to support REEs being present on the Moon in concentrations that would be considered viable REE resource targets for economical exploration. Beyond the Moon, Mars and other extraterrestrial materials (chondritic meteorites for example) also contain REE-bearing minerals, including apatite and merrillite, yet these phases are again minor components of samples studied to date (< 0.6%). Therefore, extraterrestrial materials are not presently suitable REE resource targets. However, they are host to other resources that will likely be fundamental to the future of space exploration, for example metals (iron and aluminum) and water.

11:00 - ION TRANSPORT IN THIN-FILM PHOTOVOLTAICS. Anuja Parikh,, Marco Nardone, Bowling Green State University, 179 Overman Hall, Bowling Green OH 43403.

Ion migration plays a critical role in cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS) based thin film photovoltaic device performance. In this work, we review the physics of ion transport in solids (crystalline and polycrystalline), develop a general numerical simulation tool for ion drift-diffusion, and validate it against literature data and analytical expressions for the technologically important cases of phosphorous and copper in CdTe, and sodium in CIGS. Calculations are conducted by the finite element method using COMSOL Multiphysics[R] software. Our preliminary results show the regions of slow and fast diffusion of phosphorous and copper in single crystalline CdTe with the transition depth between 10 nm to 20 [micro]m from the surface. Given the fact that grain boundaries exist in thin-film device components, diffusion mechanisms require special attention. Our present focus is on incorporating diffusion through grain boundaries in polycrystalline material. After validation of this initial model, the simulation tool will be extended to predict the effects of ion migration on the performance of CdTe and CIGS devices by coupling it to a device simulator.

11:15 - PHOTOCONDUCTIVE ZNO FILMS PRINTED ON FLEXIBLE SUBSTRATES BY INKJET AND AEROSOL JET TECHNIQUES. D. J. Winarski (1),, E. Kreit (2), E. M. Heckman (2), E. Flesburg (1), M. Haseman (1), R. S. Aga (2), F. A. Selim (1), (1) Bowling Green State University, Center for Photochemical Sciences, Bowling Green OH 43402, (2) Air Force Research Laboratory Sensors Directorate, Wright-Patterson Air Force Base OH 45433.

Zinc oxide (ZnO) thin films have remarkable versatility in sensor applications. Here, we report simple ink synthesis and printing methods to deposit ZnO photodetectors on a variety of flexible and transparent substrates, including polyimide (Kapton), polyethylene terephthalate, cyclic olefin copolymer (TOPAS), and quartz. X-ray diffraction analysis revealed the dependence of the film orientation on the substrate type and sintering method, and ultraviolet-visible (UV--Vis) absorption measurements revealed a band edge near 380 nm. Van der Pauw technique was used to measure the resistivity of undoped ZnO and indium/gallium-codoped ZnO (IGZO) films. IGZO films showed lower resistivity and larger average grain size compared with undoped ZnO films due to addition of In3+ and Ga3+, which act as donors. A 365 nm light-emitting diode was used to photoirradiate the films to study their photoconductive response as a function of light intensity at 300 K. Experiments revealed that ZnO films printed by aerosol jet and inkjet techniques exhibited five orders of magnitude photoconductivity, indicating that such films are viable options for use in flexible photodetectors.

11:30 - SINGLE CaO ACCELERATED DENSIFICATION AND MICROSTRUCTURE CONTROL OF HIGHLY TRANSPARENT YAG CERAMIC. Tianyuan Zhou (1,2),, Sahil Agarwal (1),, Farida Selim (1),, Le Zhang (1,2), Hao Chen (2), (1) Bowling Green State University, Center for Photochemical Sciences, Department of Physics and Astronomy, Bowling Green OH 43403, (2) Jiangsu Key Laboratory of Advanced Laser Materials and Devices, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou, Jiangsu, P.R. China 221116.

Full densification (pore-free microstructure) is the basic requirement to obtain transparent ceramics with good optical quality and tetraethyl orthosilicate (Si[(O[C.sub.2][H.sub.5])).sub.4], TEOS) is often served as a common sintering additive to promote densification of transparent yttrium aluminum garnet ([Y.sub.3][Al.sub.5][O.sub.12], YAG) ceramic. The microstructure of YAG ceramics can be tuned by many factors such as the raw materials, the content of sintering aid and the sintering strategy. Literature suggests the fast grain growth of YAG ceramics at high sintering temperature when TEOS is employed. In addition, owing to charge compensation, [Si.sup.4+] ion that decomposed from TEOS would immensely deteriorate the conversion of Cr or Yb ion into a higher valence state. Recently, we reported a YAG transparent ceramics using divalent dopants (CaO and MgO) as sintering aids and found that CaO dopant was more effective in the suppression of grain growth than MgO. In this work, a small amount of CaO single dopant was adopted to realize the densification and microstructure control of fine-grained YAG ceramic by a simple solid-state reaction and one-step vacuum sintering method and highly transparent YAG ceramics (T = 84.4% at 1064 nm) were obtained after vacuum sintering at 1820 [degrees]C for 8 h. The average grain size was determined to be 2.7 [micro]m, when the amount of CaO used was as low as 0.045 wt.%. Using scanning electron microscopy (SEM), it was found that the CaO dopant promoted both densification and grain growth of YAG ceramics when the sintering temperature was lower than 1660 [degrees]C, however it dramatically inhibited grain growth when the sintering temperature was further increased. This study provides an alternative approach of synthesizing high quality YAG transparent ceramics by the use of CaO alone as a single dopant sintering additive.

11:45 - SERENDIPITOUS DISCOVERY OF ELEMENTAL ANOMALY IN AMBER. Thomas D. Farron,, Amanda M. Hunt,, University of Cincinnati Clermont College, Dept. of Geology-Geography, 4200 Clermont College Drive, Batavia OH 45103.

Amber specimens are organic materials derived from plant and tree fluid exudates. Their chemical composition varies, depending on several factors, including the plant from which they were derived and inclusions. A specimen was tested from a collection to determine its elemental constituents using a Niton[TM] XRF T3 GOLDD+ handheld analyzer by Thermo Fisher Scientific Inc. The first sample tested indicated the presence of iridium. It was re-tested 4 more times with the same result. These results were completely unanticipated. Additional specimens were then tested yielding similar results. A literature search was conducted in order to learn about the occurrence of iridium in amber. No previously reported occurrences of iridium in amber have been found. Prior to analysis, the tool was calibrated by the manufacturer, then at regular intervals in the lab using manufacturer recommended protocol. The testing surface was cleaned, according to recommended protocol, between each test. Iridium, an anomalous element in amber, was detected in concentrations of between 10 to 15 ppm [+ or -]2[sigma], in ~25 samples, with each individual sample being analyzed a minimum of 3 times for verification. Iridium is rare on the surface of the Earth. It may be present in meteorites and associated with meteorite impact events such as the K-Pg Boundary. It may also be associated with flood basalts such as the Deccan Traps of India and some deep seated volcanic eruptions. There are no known impact craters or flood basalts that are chronologically correlative with earliest Cenomanian deposition of the amber in a pyroclastic and clay matrix. There is no known associated geographic location for impact craters or flood basalts for this occurrence of Iridium. The amber is reported as being possibly partially stream transported and deposited in pyroclastic and clay matrix. Iridium has reportedly been mined on a small scale in the area. Further study is required to ascertain possible origins for this anomalous occurrence of iridium in amber. Sample analysis of the local volcanic and clay matrix is believed to be critical to further study.
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Publication:The Ohio Journal of Science
Article Type:Abstract
Date:Apr 1, 2018
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