+publisher:"Georgia Tech" +contributor:("Dr. Peter J. Hesketh")

1. Wang, Xiaojia. Study of the radiative properties of aligned carbon nanotubes and silver nanorods.

Degree: PhD, Mechanical Engineering, 2011, Georgia Tech

► Arrays of nanotubes/rods made of appropriate materials can yield unique radiative properties, such as large absorption and optical anisotropy, with broad applications from high-efficiency emitters… (more)

▼ Arrays of nanotubes/rods made of appropriate materials can yield unique radiative properties, such as large absorption and optical anisotropy, with broad applications from high-efficiency emitters and absorbers for energy conversion to the polarization conversion via anisotropic responses. The objective of this dissertation is to investigate the radiative properties of arrays formed by aligned carbon nanotubes (CNTs) and silver nanorods (AgNRs). The CNT arrays used in the present study consist of multi-walled CNTs synthesized vertically on silicon substrates using thermal chemical vapor deposition. Their close-to-unity absorptance is demonstrated by measuring the directional-hemispherical reflectance in the visible and near-infrared spectral ranges using an integrating sphere. The bidirectional reflectance distribution function and angle-resolved reflectance were measured at the 635-nm wavelength. The results demonstrate that high-absorptance CNT arrays may be diffusely or specularly reflecting and have important applications in radiometry. Theoretical modeling based on the effective medium theory (EMT) and reflectivity of an anisotropic medium are developed to explain the high absorption and polarization dependence. The effective optical constants of the CNT array for both ordinary and extraordinary polarizations are quantitatively determined by fitting the angle-resolved reflectance. The AgNR arrays used in the present study were fabricated using oblique angle deposition, which results in inclined Ag nanorods that can be modeled as an effective homogenous and optically anisotropic thin film. The spectral and directional radiative properties of AgNRs grown on different substrates, including a glass slab with a silver film, and compact disc gratings, were characterized at the 635-nm and 977-nm wavelengths for different polarizations. The results are analyzed based on the EMT, rigorous coupled-wave analysis, and anisotropic thin-film optics. The results of this dissertation help gain a better understanding of radiative properties of anisotropic nanostructures for potential applications in high-efficiency energy conversion, radiometric devices, and optical systems. Advisors/Committee Members: Dr. Zhuomin Zhang (Committee Chair), Dr. Baratunde A. Cola (Committee Member), Dr. Peter J. Hesketh (Committee Member), Dr. Thomas K. Gaylord (Committee Member), Dr. Yiping Zhao (Committee Member).

Subjects/Keywords: Thermal radiation; Nanoarray; Effective medium; Anisotropic wave propagation; BRDF; Scattering; Nanotubes; Nanostructured materials; Carbon; Radiative transfer; Silver

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APA (6^th Edition):

Wang, X. (2011). Study of the radiative properties of aligned carbon nanotubes and silver nanorods. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/42871

Chicago Manual of Style (16^th Edition):

Wang, Xiaojia. “Study of the radiative properties of aligned carbon nanotubes and silver nanorods.” 2011. Doctoral Dissertation, Georgia Tech. Accessed April 13, 2021. http://hdl.handle.net/1853/42871.

MLA Handbook (7^th Edition):

Wang, Xiaojia. “Study of the radiative properties of aligned carbon nanotubes and silver nanorods.” 2011. Web. 13 Apr 2021.

Vancouver:

Wang X. Study of the radiative properties of aligned carbon nanotubes and silver nanorods. [Internet] [Doctoral dissertation]. Georgia Tech; 2011. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/1853/42871.

Council of Science Editors:

Wang X. Study of the radiative properties of aligned carbon nanotubes and silver nanorods. [Doctoral Dissertation]. Georgia Tech; 2011. Available from: http://hdl.handle.net/1853/42871

2. Haldoupis, Emmanuel. Mulitscale modeling and screening of nanoporous materials and membranes for separations.

Degree: PhD, Chemical and Biomolecular Engineering, 2013, Georgia Tech

URL: http://hdl.handle.net/1853/47669

► The very large number of distinct structures that are known for metal-organic frameworks (MOFs) and zeolites presents both an opportunity and a challenge for identifying… (more)

▼ The very large number of distinct structures that are known for metal-organic frameworks (MOFs) and zeolites presents both an opportunity and a challenge for identifying materials with useful properties for targeted separations. In this thesis we propose a three-stage computational methodology for addressing this issue and comprehensively screening all available nanoporous materials. We introduce efficient pore size calculations as a way of discarding large number of materials, which are unsuitable for a specific separation. Materials identified as having desired geometric characteristics can be further analyzed for their infinite dilution adsorption and diffusion properties by calculating the Henry's constants and activation energy barriers for diffusion. This enables us to calculate membrane selectivity in an unprecedented scale and use these values to generate a small set of materials for which the membrane selectivity can be calculated in detail and at finite loading using well-established computational tools. We display the results of using these methods for >500 MOFs and >160 silica zeolites for spherical adsorbates at first and for small linear molecules such as CO₂ later on. In addition we also demonstrate the size of the group of materials this procedure can be applied to, by performing these calculations, for simple adsorbate molecules, for an existing library of >250,000 hypothetical silica zeolites. Finally, efficient methods are introduced for assessing the role of framework flexibility on molecular diffusion in MOFs that do not require defining a classical forcefield for the MOF. These methods combine ab initio MD of the MOF with classical transition state theory and molecular dynamics simulations of the diffusing molecules. The effects of flexibility are shown to be large for CH₄, but not for CO₂ and other small spherical adsorbates, in ZIF-8. Advisors/Committee Members: Dr. David S. Sholl (Committee Chair), Dr. Christopher W. Jones (Committee Member), Dr. Krista S. Walton (Committee Member), Dr. Peter J. Hesketh (Committee Member), Dr. Sankar Nair (Committee Member).

Subjects/Keywords: Molecular simulations; Separations; Zeolites; Metal-organic frameworks; Nanoporous; Nanostructured materials; Membranes (Technology); Separation (Technology)

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APA (6^th Edition):

Haldoupis, E. (2013). Mulitscale modeling and screening of nanoporous materials and membranes for separations. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/47669

Chicago Manual of Style (16^th Edition):

Haldoupis, Emmanuel. “Mulitscale modeling and screening of nanoporous materials and membranes for separations.” 2013. Doctoral Dissertation, Georgia Tech. Accessed April 13, 2021. http://hdl.handle.net/1853/47669.

MLA Handbook (7^th Edition):

Haldoupis, Emmanuel. “Mulitscale modeling and screening of nanoporous materials and membranes for separations.” 2013. Web. 13 Apr 2021.

Vancouver:

Haldoupis E. Mulitscale modeling and screening of nanoporous materials and membranes for separations. [Internet] [Doctoral dissertation]. Georgia Tech; 2013. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/1853/47669.

Council of Science Editors:

Haldoupis E. Mulitscale modeling and screening of nanoporous materials and membranes for separations. [Doctoral Dissertation]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/47669

Georgia Tech

3. Limaye, Ameya Shankar. Design and Analysis of a Mask projection Micro Stereolithography System.

Degree: MS, Mechanical Engineering, 2004, Georgia Tech

URL: http://hdl.handle.net/1853/4943

► Mask Projection Microstereolithography (MPSLA) is an additive manufacturing process capable for fabricating true three-dimensional microparts and hence, holds promise as a potential micro-fabrication process for… (more)

Subjects/Keywords: Design; Polymerization; Stereolithography; Optical aberrations; Pahl and Beitz

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APA (6^th Edition):

Limaye, A. S. (2004). Design and Analysis of a Mask projection Micro Stereolithography System. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/4943

Chicago Manual of Style (16^th Edition):

Limaye, Ameya Shankar. “Design and Analysis of a Mask projection Micro Stereolithography System.” 2004. Masters Thesis, Georgia Tech. Accessed April 13, 2021. http://hdl.handle.net/1853/4943.

MLA Handbook (7^th Edition):

Limaye, Ameya Shankar. “Design and Analysis of a Mask projection Micro Stereolithography System.” 2004. Web. 13 Apr 2021.

Vancouver:

Limaye AS. Design and Analysis of a Mask projection Micro Stereolithography System. [Internet] [Masters thesis]. Georgia Tech; 2004. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/1853/4943.

Council of Science Editors:

Limaye AS. Design and Analysis of a Mask projection Micro Stereolithography System. [Masters Thesis]. Georgia Tech; 2004. Available from: http://hdl.handle.net/1853/4943

Georgia Tech

4. Kumar, Surajit. Fluidic and dielectrophoretic manipulation of tin oxide nanobelts.

Degree: PhD, Mechanical Engineering, 2008, Georgia Tech

URL: http://hdl.handle.net/1853/34851

► Nanobelts are a new class of semiconducting metal oxide nanowires with great potential for nanoscale devices. The present research focuses on the manipulation of SnO₂… (more)

▼ Nanobelts are a new class of semiconducting metal oxide nanowires with great potential for nanoscale devices. The present research focuses on the manipulation of SnO₂ nanobelts suspended in ethanol using microfluidics and electric fields. Dielectrophoresis (DEP) was demonstrated for the first time on semiconducting metal oxide nanobelts, which also resulted in the fabrication of a multiple nanobelt device. Detailed and direct real-time observations of the wide variety of nanobelt motions induced by DEP forces were conducted using an innovative setup and an inverted optical microscope. High AC electric fields were generated on a gold microelectrode (~ 20 µm gap) array, patterned on glass substrate, and covered by a ~ 10 µm tall PDMS (polydimethylsiloxane) channel, into which the nanobelt suspension was introduced for performing the DEP experiments. Negative DEP (repulsion) of the nanobelts was observed in the low frequency range (< 100 kHz) of the applied voltage, which caused rigid body motion as well as deformation of the nanobelts. In the high frequency range (~ 1 MHz - 10 MHz), positive DEP (attraction) of the nanobelts was observed. Using a parallel plate electrode arrangement, evidence of electrophoresis was also found for DC and low frequency (Hz) voltages. The existence of negative DEP effect is unusual considering the fact that if bulk SnO₂ conductivity and permittivity values are used in combination with ethanol properties to calculate the Clausius Mossotti factor using the simple dipole approximation theory; it predicts positive DEP for most of the frequency range experimentally studied. A fluidic nanobelt alignment technique was studied and used in the fabrication of single nanobelt devices with small electrode gaps. These devices were primarily used for conducting impedance spectroscopy measurements to obtain an estimate of the nanobelt electrical conductivity. Parametric numerical studies were conducted using COMSOL Multiphysics software package to understand the different aspects of the DEP phenomenon in nanobelts. The DEP induced forces and torques were computed using the Maxwell Stress Tensor (MST) approach. The DEP force on the nanobelt was calculated for a range of nanobelt conductivity values. The simulation results indicate that the experimentally observed behavior can be explained if the nanobelt is modeled as having two components: an electrically conductive interior and a nonconductive outer layer surrounding it. This forms the basis for an explanation of the negative DEP observed in SnO₂ nanobelts suspended in ethanol. It is thought that the nonconductive layer is due to depletion of the charge carriers from the nanobelt surface regions. This is consistent with the fact that surface depletion is a commonly observed phenomenon in SnO₂ and other semiconducting metal oxide materials. The major research contribution of this work is that, since nanostructures have large surface areas, surface dominant properties are important. Considering only bulk electrical properties can predict misleading… Advisors/Committee Members: Dr. Peter J. Hesketh (Committee Chair), Dr. F. Levent Degertekin (Committee Member), Dr. Martha A. Gallivan (Committee Member), Dr. Rosario A. Gerhardt (Committee Member), Dr. Samuel Graham (Committee Member), Dr. Zhong Lin Wang (Committee Member).

Subjects/Keywords: Lab-on-a-Chip (LOC); Nanowire; Nanomanipulation; Nanobelt; Nanoassembly; Tin oxide (SnO); Dielectrophoresis (DEP); Nanomaterial; Nanotechnology; Microfluidics; Microsystems (MEMS); Nanomanufacturing; Nanowires; Microfluidics; Dielectrophoresis

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Kumar, S. (2008). Fluidic and dielectrophoretic manipulation of tin oxide nanobelts. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/34851

Chicago Manual of Style (16^th Edition):

Kumar, Surajit. “Fluidic and dielectrophoretic manipulation of tin oxide nanobelts.” 2008. Doctoral Dissertation, Georgia Tech. Accessed April 13, 2021. http://hdl.handle.net/1853/34851.

MLA Handbook (7^th Edition):

Kumar, Surajit. “Fluidic and dielectrophoretic manipulation of tin oxide nanobelts.” 2008. Web. 13 Apr 2021.

Vancouver:

Kumar S. Fluidic and dielectrophoretic manipulation of tin oxide nanobelts. [Internet] [Doctoral dissertation]. Georgia Tech; 2008. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/1853/34851.

Council of Science Editors:

Kumar S. Fluidic and dielectrophoretic manipulation of tin oxide nanobelts. [Doctoral Dissertation]. Georgia Tech; 2008. Available from: http://hdl.handle.net/1853/34851

Georgia Tech

5. English, Brian Alan. Laminated Gas Generator Actuator Arrays.

Degree: PhD, Mechanical Engineering, 2006, Georgia Tech

URL: http://hdl.handle.net/1853/14074

► Existing microactuator limitations prevent control of small-scale, spin-stabilized vehicles. These applications require actuators insensitive to shock that have forces on the order of Newtons and… (more)

▼ Existing microactuator limitations prevent control of small-scale, spin-stabilized vehicles. These applications require actuators insensitive to shock that have forces on the order of Newtons and millisecond control periods. This research presents batch-fabrication lamination approaches for the realization of large arrays of high-impulse, short-duration gas generator actuators (GGAs), and system implementation approaches to integrate these GGAs into a small-scale, spin-stabilized projectile for the purpose of generating steering forces on the projectile. Electronic packaging and MEMS processing are combined to batch-fabricate millimeter-scale GGAs insensitive to large shocks. Robust, prefabricated thermoplastic and metal films are patterned by laser machining or photolithography, and multilayer devices are assembled by adhesive lamination. The GGAs remained operational after 10,000 g shocks. Optimized design and propellant selection enables control of the force profile and actuation timing. Rapid force rise times are achieved using appropriately selected solid propellants and specially designed hot-wire igniters that create a larger combustion fronts. By reshaping the combustion profile of the solid propellant, tens of Newtons are generated within milliseconds. In addition to force control, the timing of the force application was controllable to within 1 ms for optimized GGAs. Performance results demonstrate that GGA actuator arrays actuate within appropriate timescales and with enough authority to control a 40 mm projectile with a spin rate of 60 Hz. After actuator characterization, GGAs, control electronics, and power supply are mounted into a 40 mm diameter projectile, and a full flight system was flown to demonstrate divert authority of the GGAs. Advisors/Committee Members: Dr. Mark G. Allen (Committee Chair), Dr. Ari Glezer (Committee Co-Chair), Dr. Andrei Federov (Committee Member), Dr. Jerry M. Seitzman (Committee Member), Dr. Peter J. Hesketh (Committee Member).

Subjects/Keywords: Microthruster; Robust microactuators; Laminated microactuators; Combustion duration control; Impulse control

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APA (6^th Edition):

English, B. A. (2006). Laminated Gas Generator Actuator Arrays. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/14074

Chicago Manual of Style (16^th Edition):

English, Brian Alan. “Laminated Gas Generator Actuator Arrays.” 2006. Doctoral Dissertation, Georgia Tech. Accessed April 13, 2021. http://hdl.handle.net/1853/14074.

MLA Handbook (7^th Edition):

English, Brian Alan. “Laminated Gas Generator Actuator Arrays.” 2006. Web. 13 Apr 2021.

Vancouver:

English BA. Laminated Gas Generator Actuator Arrays. [Internet] [Doctoral dissertation]. Georgia Tech; 2006. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/1853/14074.

Council of Science Editors:

English BA. Laminated Gas Generator Actuator Arrays. [Doctoral Dissertation]. Georgia Tech; 2006. Available from: http://hdl.handle.net/1853/14074

Georgia Tech

6. Chen, Yu-Bin. Rigorous Modeling of the Radiative Properties of Micro/Nanostructures and Comparisons with Measurements of Fabricated Gratings and Slit Arrays.

Degree: PhD, Mechanical Engineering, 2007, Georgia Tech

URL: http://hdl.handle.net/1853/14470

► Radiative properties of a material is the core of thermal science and optics, which play critical roles in modern technologies, including microelectronics, energy conversion, and… (more)

▼ Radiative properties of a material is the core of thermal science and optics, which play critical roles in modern technologies, including microelectronics, energy conversion, and nanotechnology. The key to modify or enhance radiative properties is employing one-, two-, and three-dimensional (1, 2, and 3D) periodic micro/nanostructures. Since their applications are not fully uncovered and very few comprehensive studies are available, the objective of this dissertation is to explore applications of periodic micro/nanostructures with modified radiative properties in modern technologies through both numerically and experimentally investigations. Theses representative applications include the thermal control in rapid thermal processing, the design of a wavelength-selective radiator for thermophotovoltaic systems, and the nanothermal manufacturing. The theoretical foundation of the study is built on the rigorous coupled-wave analysis (RCWA) for numerical calculation of the far-field radiative properties and the electromagnetic field distribution in the near-field regime. Measurements of diffraction efficiencies are conducted on fabricated 1D and 2D periodic silicon microstructures with a laser scatterometer/diffractometer with high angular resolution. The diffraction efficiency can be employed for non-contact surface profile inspection tool because it strongly depends on structure patterns. For better temperature control during rapid thermal processing, the dissertation performs a parametric study on radiation absorption of a generic CMOS device together with its simplified nanoscale structures. The applicability of approximation models, which homogenize micro/nanostructures into a film, is also evaluated. Next, a new concept of complex gratings is proposed for actively tailoring the radiative properties and serving as a thermophotovoltaic (TPV) radiator. The radiator exhibits a wide-band and angle-independent high transverse magnetic wave emittance matching the bandgap of TPV cells so that the energy conversion efficiency can be improved. Furthermore, the nanoscale metallic slit arrays show polarization-dependant enhanced transmission and highly localized electromagnetic energy density, which hold promising potentials in nanothermal manufacturing. Three submicrometer metallic slit arrays are fabricated on top of a silicon substrate. Their spectral transmittance is measured with a Fourier-transform infrared spectrometer and largely agrees with RCWA modeling results. In short, the dissertation clearly demonstrates that precise control and tuning of radiative properties using micro/nanofabrication are not only feasible but also may have numerous technological impacts. Advisors/Committee Members: Dr. Zhuomin Zhang (Committee Chair), Dr. F. Levent Degertekin (Committee Member), Dr. Gee-Kung Chang (Committee Member), Dr. Pei-feng Hsu (Committee Member), Dr. Peter J. Hesketh (Committee Member).

Subjects/Keywords: Micro/Nanostructures; Gratings

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APA (6^th Edition):

Chen, Y. (2007). Rigorous Modeling of the Radiative Properties of Micro/Nanostructures and Comparisons with Measurements of Fabricated Gratings and Slit Arrays. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/14470

Chicago Manual of Style (16^th Edition):

Chen, Yu-Bin. “Rigorous Modeling of the Radiative Properties of Micro/Nanostructures and Comparisons with Measurements of Fabricated Gratings and Slit Arrays.” 2007. Doctoral Dissertation, Georgia Tech. Accessed April 13, 2021. http://hdl.handle.net/1853/14470.

MLA Handbook (7^th Edition):

Chen, Yu-Bin. “Rigorous Modeling of the Radiative Properties of Micro/Nanostructures and Comparisons with Measurements of Fabricated Gratings and Slit Arrays.” 2007. Web. 13 Apr 2021.

Vancouver:

Chen Y. Rigorous Modeling of the Radiative Properties of Micro/Nanostructures and Comparisons with Measurements of Fabricated Gratings and Slit Arrays. [Internet] [Doctoral dissertation]. Georgia Tech; 2007. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/1853/14470.

Council of Science Editors:

Chen Y. Rigorous Modeling of the Radiative Properties of Micro/Nanostructures and Comparisons with Measurements of Fabricated Gratings and Slit Arrays. [Doctoral Dissertation]. Georgia Tech; 2007. Available from: http://hdl.handle.net/1853/14470

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