Browsing by Author "Ryu, Jong Eun"
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Item Au nanoparticle assembly on cnts using flash induced solid-state dewetting(2015-04-28) Kulkarni, Ameya; Ryu, Jong Eun; Agarwal, Mangilal; Xie, Jian; Cheng, RuihuaCarbon Nanotubes (CNTs) are used extensively in various applications where substrate are required to be possessing higher surface area, porosity and electrical and thermal conductivity. Such properties can be enhanced to target a particular gas and biochemical for efficient detection when CNT matrix is functionalized with Nanoparticles (NPs). Conventional functionalization involves harsh oxidation repeated washing, filtration and sonication, which induce defects. The defects lead to hindered mobility of carriers, unwanted doping and also fragmentation of the CNTs in some cases. In this document we demonstrate functionalization of CNT with Au nanoparticles on a macro scale under dry and ambient condition using Xenon ash induced solid-state dewetting. A sputtered thin film was transformed into nanoparticles which were confirmed to be in a state of thermodynamic equilibrium. We worked on 3 nm, 6 nm, 9 nm, 15 nm, 30 nm initial thickness of thin films. Xenon ash parameters of energy, number of pulse, duration of pulse, duration of gap between consecutive pulses were optimized to achieve complete dewetting of Au thin films. 3 nm deposition was in the form of irregular nano-islands which were transformed into stable nanoparticles with a single shot of 10 J/cm2 of 2 ms duration. 6 nm and 9 nm deposition was in form of continues film which was also dewetted into stable nanoparticles with a single pulse but with an increased energy density of 20 J/cm2 and 35 J/cm2 respectively. In case of 15 nm and 30 nm deposition the thin film couldn't be dewetted with a maximum energy density of 50 J/cm2, it was observed that 3 and 4 pulses of 2 ms pulse duration and 2 ms gap duration with an energy density of 50 J/cm2 were required to completely dewet the thicker films. However irregularity was induced in the sizes of the NPs due to Ostwald ripening phenomenon which causes smaller particle within a critical difiusion length to combine and form a larger particle during or after dewetting process. For comparison, the Au thin films were also dewetted by a conventional process involving annealing of samples until the thin film was fully transformed into NPs and the size of NPs seized to grow. Scanning electron microscope (SEM) was used to characterize the samples. Thermodynamic stability of the particles was confirmed with statistical analyses of size distribution after every additional pulse.Item Characterization of tensile, creep, and fatigue properties of 3D printed Acrylonitrile Butadiene Styrene(2016-08) Zhang, Hanyin; Zhang, Jing; Ryu, Jong Eun; Jones, Alan S.; Anwar, SohelAcrylonitrile Butadiene Styrene (ABS) is the most widely used thermoplastics in 3D printing for making models, prototypes, patterns, tools and end-use parts. However, there is a lack of systematic understanding of the mechanical properties of 3D printed ABS components, including orientation-dependent tensile strength, creep, and fatigue properties. These mechanical properties are critically needed for design and application of 3D printed components. The main objective of this research is to systematically characterize key mechanical properties of 3D printed ABS components, including tensile, creep, and fatigue properties. Additionally, the eff ects of printing orientation on the mechanical prop- erties are investigated. There are two research approaches employed in the thesis: rst, experimental investigation of the tensile, creep, and fatigue properties of the 3D printed ABS components; second, laminate based finite-element modeling of tensile test to understand the stress distributions in different printing layers. The major conclusions of the thesis work are summarized as follows. The tensile test experiments show that the 0 printing orientation has the highest Young's modulus, 1.81 GPa, and ultimate strength, 224 MPa. The tensile test simulation shows a similar Young's modulus as the experiment in elastic region, indicating the robustness of laminate based finite element model. In the creep test, the 90 printing orientation has the lowest k value of 0.2 in the plastics creep model, suggesting the 90 is the most creep resistant among 0 , 45 , and 90 printing orientations. In the fatigue test, the average cycle number under load of 30 N is 3796 revolutions. The average cycle number decreases to 128 revolutions when the load is below 60N. Using the Paris Law, with the crack size of 0.75 mm long and stress intensity factor is varied from 352 to 700 MN -m^3/2 , the predicted fatigue crack growth rate is 0.0341 mm/cycle.Item A Combined Modeling and Experimental Study of Tensile Properties of Additively Manufactured Polymeric Composite Materials(Springer, 2020) Meng, Lingbin; Yang, Xuehui; Salcedo, Eduardo; Baek, Dong-Cheon; Ryu, Jong Eun; Lu, Zhe; Zhang, Jing; Mechanical and Energy Engineering, School of Engineering and TechnologyIn this study, the mechanical properties, in terms of stress–strain curves, of additively manufactured polymeric composite materials, Tango black plus (TB+), vero white plus (VW ), and their intermediate materials with different mixing ratios, are reported. The ultimate tensile strength and elongation at break are experimentally measured using ASTM standard tensile test. As the content of VM+ increases, the strength of the polymeric materials increases and elongation decreases. Additionally, the Shore A hardness of the materials increases with reduced TB+ concentration. In parallel to the experiment, hyperelastic models are employed to fit the experimental stress–strain curves. The shear modulus of the materials is obtained from the Arruda–Boyce model, and it increases with reduced concentration of TB+. Due to the good quality of the fitted data, it is suggested that the Arruda–Boyce model is the best model for modeling the additively manufactured polymeric materials. With the well characterized and modeled mechanical properties of these hyperelastic materials, designers can conduct computational study for application in flexible electronics field.Item Controlled short time large scale synthesis of magnetic cobalt nanoparticles on carbon nanotubes by flash annealing(AIP, 2020) Mosey, Aaron; Yue, Lanping; Gaire, Babu; Ryu, Jong Eun; Cheng, Ruihua; Physics, School of ScienceNanopatterned arrays of discrete cobalt nanostructures showing characteristic parameter-dependent sizes are formed from continuous thin films on a carbon nanotube substrate using millisecond pulsed intense UV light. The nanoparticles exhibit ferromagnetic behavior with magnetic remanence and coercivity depending on the particle size. The end-state particle size is shown to be a function of initial thin film thickness and excitation energy and is therefore tunable. The evolutionary process from continuous thin films to a discrete morphology is thermodynamically driven by the large surface energy difference between metastable thin films and the underlying carbon nanotube substrate. Evidence of the Danielson model of the dewetting process is observed. These arrays can find applications as platforms for the self-assembly of magnetically susceptible materials, such as iron or nickel nanostructures, into a conduction matrix for applications in energy extraction from a latent heat storage device.Item Fabry-Perot cavity resonance enabling highly polarization-sensitive double-layer gold grating(Springer Nature, 2018-10-03) Hwang, Jehwan; Oh, Boram; Kim, Yeongho; Silva, Sinhara; Kim, Jun Oh; Czaplewski, David A.; Ryu, Jong Eun; Kim, Eun Kyu; Urbas, Augustine; Zhou, Jiangfeng; Ku, Zahyun; Lee, Sang Jun; Mechanical and Energy Engineering, School of Engineering and TechnologyWe present experimental and theoretical investigations on the polarization properties of a single- and a double-layer gold (Au) grating, serving as a wire grid polarizer. Two layers of Au gratings form a cavity that effectively modulates the transmission and reflection of linearly polarized light. Theoretical calculations based on a transfer matrix method reveals that the double-layer Au grating structure creates an optical cavity exhibiting Fabry-Perot (FP) resonance modes. As compared to a single-layer grating, the FP cavity resonance modes of the double-layer grating significantly enhance the transmission of the transverse magnetic (TM) mode, while suppressing the transmission of the transverse electric (TE) mode. As a result, the extinction ratio of TM to TE transmission for the double-layer grating structure is improved by a factor of approximately 8 in the mid-wave infrared region of 3.4-6 μm. Furthermore, excellent infrared imagery is obtained with over a 600% increase in the ratio of the TM-output voltage (Vθ = 0°) to TE-output voltage (Vθ = 90°). This double-layer Au grating structure has great potential for use in polarimetric imaging applications due to its superior ability to resolve linear polarization signatures.Item High Extinction Ratio Subwavelength 1D Infrared Polarizer by Nanoimprint Lithography(2016) Kim, Jeonghwan; Ryu, Jong Eun; Zhu, Likun; Agarwal, Mangilal; Anwar, SohelInfrared (IR) polarizers have been widely used in military and commercial applications. Controlling the polarization of incident light is one of major issues in the detector systems. However, conventional polarimetric IR detectors require series of polarizers and optical components, which increase the volume and weight of the system. In this research, stacked 1-dimensional (1-D) subwavelength grating structures were studied to develop compact size IR polarimetric detector by using surface plasmonic polariton. Experimental parameters were optimized by Finite Difference Time Domain (FDTD) simulation. Effects of gold (Au) grating size, numbers of stacked gratings, and dielectric space height were tested in the FDTD study. The fabrication of grating layers was conducted by using nanoimprint lithography. The samples were characterized by scanning electron microscopy. IR transmissions in transverse magnetic (TM) and transverse electric (TE) modes were measured by Fourier transform infrared spectroscopy (FTIR).Item Ionic liquid-assisted synthesis of Yb3+-Tm3+ codoped Y7O6F9 petal shaped microcrystals with enhanced upconversion emission(Elsevier, 2018-07) Zhao, Jinbo; Wu, Lili; Zhang, Chuanjiang; Li, Tingxi; Jiang, Qinglong; Wang, Feng; Zhao, Ping; Ryu, Jong Eun; Guo, Zhanhu; Mechanical Engineering, School of Engineering and TechnologyPetal-like Yb3+-Tm3+ codoped Y7O6F9 microparticles were achieved via ionic liquid-assisted (IL) hydrothermal process. The emission efficiency of Y7O6F9:Yb3+/Tm3+ powders is much stronger than that of Y2O3:Yb3+/Tm3+ sample. Under excitation at 980 nm with an unfocused laser beam under weak pump density of ∼0.1 W/cm2 (pump power 10 mW), the UC emission of the sample can been seen clearly. Four emission bands at 477, 540, 647 and 692 nm are observed and correspond to the 1G4 state to 3H6 state, 1D2 state to 3H5 state, 1G4 sate to 3F4 state, and 3F3 state to 3H6 state transition of Tm3+ ions. The enhanced UC emission is related to high crystallinity and lower effective phonon energy of oxyfluorides. The ionic liquid (IL) of [BMIM][BF4] is used both as the reaction medium and the source of F−.Item Reinforcement of Cu Nanoink Film with Extended Carbon Nanofibers for Large Deformation of Printed Electronics(Office of the Vice Chancellor for Research, 2016-04-08) Kim, Jeonghwan; Shankar, Akash; Zhu, Jiahua; Choi, Daniel S.; Guo, Zhanhu; Ryu, Jong EunMetallic nanoparticle inks (nanoinks) have attracted great interest in the manufacturing of printed flexible electronics. However, micro-cracks and pores generated during the sintering process deteriorate mechanical and electrical characteristics of the sintered nanoink film. To alleviate these problems, we demonstrated the use of very long carbon nanofiber (CNF, average length 200 μm) to reinforce the sintered nanoink films. In this study, different weight fractions of CNFs are dispersed into the Cu nanoink to improve the mechanical bending characteristics. Scanning electron micrographs (SEM) shows improved dispersion of oxidized CNF in the nanoink compared to the as-received CNF. The composite nanoinks are stencil printed on polyethylene terephthalate (PET) film and sintered by intense pulsed light system using Xe-flash. The electrical measurements show 90 %, 65 %, and 66 % improved electrical conductivity in the composite nanoink film (0.7 % of oxidized CNF) compared to the pure Cu nanoink under the 75 mm, 50 mm, and 25 mm of bending radii, respectively.Item Simulation and Validation of Three Dimension Functionally Graded Materials by Material Jetting(Elsevier, 2018-08) Salcedo, Eduardo; Baek, Dongcheon; Berndt, Aaron; Ryu, Jong Eun; Mechanical Engineering, School of Engineering and TechnologyThe goal of this work is to validate the material models for parts created with a Material Jetting 3-dimensional printer through the comparison of Finite Element Analysis (FEA) simulations and physical tests. The strain maps generated by a video extensometer for multi-material samples are compared to the FEA results based on our material models. Two base materials (ABS-like and rubber-like) and their composites are co-printed in the graded tensile test samples. The graded islands are embedded in the rubber-like test specimens. The simulations were conducted utilizing previously fitted material models, a two-parameter Mooney-Rivlin model for the elastic materials (Tango Black+, DM95, and DM60) and a bilinear model for the rigid material (Vero White+). The results show that the simulation results based on our material models can predict the deformation behaviors of the multi-material samples during a uniaxial tensile test. Our simulation results are able to predict the maximum strain in the matrix material (TB+) within 5% error. Both global deformation pattern and local strain level confirm the validity of the simulated material models.Item Tunable cobalt nanoparticle synthesis by intense pulse flash annealing(AIP, 2017-01) Mosey, Aaron; Gaire, Babu; Kim, Jeongwhan; Ryu, Jong Eun; Cheng, Ruihua; Department of Physics, School of ScienceMagnetically susceptible materials can serve as a basis for the directed assembly of nanoscale network devices which can be used to extract energy from phase change materials. So far, matrix production cost has been a prohibitive factor in the realization of real world applications. Here we report a cost-effective method to synthesize magnetic nanoparticles. Samples were fabricated by sputtering magnetic thin films on carbon nanotube substrates followed by xenon intense pulsed light flash annealing. The results indicate that spatially ordered magnetic spheres can be tuned by various parameters such as initial thin film thickness, xenon lamp exposure excitation energy, local surface geometries, and the presence of an external magnetic field during annealing.