Dissertations / Theses on the topic 'Mechanical and optical properties'
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Hartschuh, Ryan D. "Optical Spectroscopy of Nanostructured Materials." University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1195016254.
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Conley, Jill Anne. "Hygro-thermo-mechanical behavior of fiber optic apparatus." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/17308.
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Johnson, Jeremy A. (Jeremy Andrew). "Optical characterization of complex mechanical and thermal transport properties." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68543.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2011.Page 176 blank. Cataloged from PDF version of thesis.
Includes bibliographical references (p. 163-175).
Time-resolved impulsive stimulated light scattering (ISS), also known as transient grating spectroscopy, was used to investigate phonon mediated thermal transport in semiconductors and mechanical degrees of freedom linked to structural relaxation in supercooled liquids. In ISS measurements, short optical pulses are crossed to produce a periodic excitation profile in or at the surface of the sample. Light from a probe beam that diffracts off the periodic material response is monitored to observe the dynamics of interest. A number of improvements were put into practice including the ability to separate so-called amplitude and phase grating signal contributions using heterodyne detection. This allowed the measurement of thermal transport in lead telluride and gallium arsenide-aluminum arsenide superlattices, and also provided the first direct observation of the initial crossover from diffusive to ballistic thermal transport in single crystal silicon and gallium arsenide at room temperature. Recent first-principles calculations of the thermal conductivity accumulation as a function of phonon mean free path allowed direct comparison to our measured results. In an effort to test theoretical predictions of the prevailing first principles theory of the glass transition, the mode coupling theory (MCT), photoacoustic measurements throughout much of the MHz acoustic frequency range were conducted in supercooled liquids. Longitudinal and shear acoustic waves were generated and monitored in supercooled liquid triphenyl phosphite in order to compare the dynamics. An additional interferometric technique analogous to ISS was developed to probe longitudinal acoustic waves at lower frequencies than was typically accessible with ISS. Lower frequency acoustic data were collected in supercooled tetramethyl tetraphenyl trisiloxane in conjunction with piezotransducer, ISS, and picosecond ultrasonics measurements to produce the first truly broadband mechanical spectra of a viscoelastic material covering frequencies continuously from mHz to hundreds of GHz. This allowed direct testing of the MCT predicted connection between fast and slow relaxation in supercooled liquids. Measurements of the quasi-longitudinal speed of sound in the energetic material cyclotrimethylene trinitramine (RDX) were also performed with ISS and picosecond ultrasonics from 0.5 to 15 GHz in order to resolve discrepancies in published low and high frequency elastic constants.
by Jeremy A. Johnson.
Ph.D.
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Wagner, Christian Friedemann. "Mechanical, Electronic and Optical Properties of Strained Carbon Nanotubes." Doctoral thesis, Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-226260.
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This dissertation deals with the calculation of the mechanical properties, electronic structure, electronic transport, and optical properties of strained carbon nanotubes (CNTs). CNTs are discussed for straintronics as their electronic bands show a strong strain-sensitivity. Further, CNTs are stiff, possess a large rupture strain and they are chemically inert, which make them a suitable material in terms of reliability and functionality for straintronic devices. Therefore, this work aims to explore the potential of strain-dependent CNT devices with regard to their mechanical, electronic, and optical properties from a first-principles point of view. There is no work so far that systematically compares these strain-dependent, physical properties from ab initio calculations, which are suitable for small CNTs only, to tight-binding calculations, which are suitable to model large CNTs. First, the structural and mechanical properties of CNTs are investigated: Structural properties are obtained by geometry optimization of many CNTs using density functional theory (DFT). The mechanical properties of CNTs are calculated in the same way. The resulting stress-strain relations are investigated and their key parameters are systematically displayed with respect to the CNT chirality and radius. The ground state electronic properties are calculated using tight-binding models and DFT. Both methods are compared systematically and it is explored where the tight-binding approximation can be applied in order to obtain meaningful results. On top of the electronic structure, a transport model is used to calculate the current through strained CNTs. The model includes the effect of ballistic conductance, parametrized electron-phonon scattering and the influence of an applied gate voltage. Finally, a computationally efficient model is described, which is able to predict the current through strained CNT transistors and enables to find optimal operation regimes for single-chirality devices and devices containing CNT mixtures. Optical properties of strained CNTs are explored by calculating quasiparticle excitations by the means of the GW approximation and the solution of the Bethe-Salpeter equation for CNT excitons. Due to the numerical effort of these approaches, the data for just one CNT is obtained. Still, it is explored how the above-mentioned many-body properties can be related to the ground state results for this CNT. This finally leads to empirical approaches that approximately describe the many-body results from the ground state properties. It is elucidated how such a model can be generalized to other CNTs in order to describe the strain dependence of their optical transitionsDiese Dissertation befasst sich mit der Berechnung der mechanischen Eigenschaften, der elektronischen Struktur, der Transport- und der optischen Eigenschaften von verspannten Kohlenstoffnanoröhrchen (engl. carbon nanotubes, CNTs). CNTs werden für die Straintronik diskutiert, da ihre elektronischen Bänder eine starke Dehnungsempfindlichkeit aufweisen. Weiterhin sind CNTs steif, besitzen eine hohe Zugfestigkeit und sind chemisch inert, weshalb sie in Bezug auf Zuverlässigkeit und Funktionalität ein geeignetes Material für straintronische Bauelemente sind. Ziel dieser Arbeit ist es daher, das Potenzial von dehnungsabhängigen CNT-Bauteilen hinsichtlich ihrer mechanischen, elektronischen und optischen Eigenschaften aus der Perspektive von first principles-Methoden zu untersuchen. Es gibt bisher keine Arbeit, in der die Ergebnisse verschiedener Methoden – ab initio-basierte Berechnungen für kleine CNTs und tight-binding Berechnungen, die näherungsweise die elektronische Struktur großer CNTs beschreiben – miteinander systematisch vergleicht. Einführend werden die strukturellen und mechanischen Eigenschaften von CNTs untersucht: Strukturelle Eigenschaften ergeben sich durch Geometrieoptimierung vieler CNTs mittels Dichtefunktionaltheorie (DFT). Die mechanischen Eigenschaften von CNTs werden in gleicher Weise berechnet. Die daraus resultierenden Spannungs-Dehnungs-Beziehungen werden untersucht und deren relevante Parameter systematisch in Abhängigkeit von CNT-Chiralität und CNT-Radius dargestellt. Die Eigenschaften des CNT-Grundzustands werden unter Verwendung von tight-binding-Modellen und DFT berechnet. Beide Methoden werden systematisch verglichen und es wird untersucht, wo die tight-binding-Näherung angewendet werden kann, um aussagekräftige Ergebnisse zu erzielen. Basierend auf der elektronischen Struktur der CNTs wird ein Transportmodell aufgesetzt, durch das der Strom durch verspannte CNTs berechnet werden kann. Dieses Modell beinhaltet den Einfluss der ballistischen Leitfähigkeit, Elektron-Phonon-Streuung in parametrisierter Form und den Einfluss eines Gates. Damit wird ein numerisch effizientes Modell beschrieben, das in der Lage ist, den Strom durch verspannte CNT-Transistoren vorherzusagen. Auf dessen Basis wird es möglich, optimale Arbeitsbereiche für reine CNT-Bauelemente und Bauelemente mit CNT-Mischungen zu berechnen. Die optischen Eigenschaften verspannter CNTs werden durch die Berechnung von Quasiteilchenanregungen mittels der GW-Approximation und der Lösung der Bethe-Salpeter-Gleichung für CNT-Exzitonen untersucht. Aufgrund des numerischen Aufwandes dieser Ansätze werden diese Daten für nur ein CNT erhalten. Daran wird der Zusammenhang zwischen den oben genannten Vielteilchen-Eigenschaften und den Grundzustandseigenschaften für dieses CNT demonstriert. Daraus ergeben sich empirische Ansätze, die es gestatten, die Vielteilchen-Ergebnisse näherungsweise auf die elektronischen Grundzustandseigenschaften zurückzuführen. Es wird dargestellt, wie ein solches Modell für andere CNTs verallgemeinert werden kann, um die Verspannungsabhängigkeit ihrer optischen Übergänge zu beschreiben
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Franze, Kristian. "Mechanical and optical properties of nervous tissue and cells." Leipzig Leipziger Univ.-Verl, 2007. http://d-nb.info/99874204X/04.
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Cheng, Yi. "Detecting tissue optical and mechanical properties with an ultrasound-modulated optical imaging system." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/24845.
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Tissue optical and mechanical properties are related to tissue pathological changes. The ability to measure both tissue elasticity and its optical properties using the same hardware offers a significant advantage over existing techniques in, e.g. imaging of cancer. Therefore this thesis aims to develop a dual mode imaging system capable of noninvasively sensing local optical and mechanical properties at centimetre depths in samples. The proposed method is based on the detection of photons modulated by ultrasound and shear waves with a modified acoustic radiation force assisted ultrasound modulated optical tomography (ARF-UOT) system. Firstly the detection of the shear wave and ultrasound modulation with UOT was demonstrated at the surface of tissue mimicking phantoms. The ultrasound field or shear wave wavefront could be imaged by a single CCD exposure and analysis of local laser speckle contrast. Secondly, within tissue mimicking phantoms, while the shear waves cannot be imaged directly due to optical scattering, the propagation of a transient shear wave was tracked with global laser speckle contrast analysis. A differential method was developed to measure the local shear wave speed and quantify the elasticity of the tissue mimicking phantoms at ~cm depths. The method (SW-LASCA) was based on a modified ARF-UOT system. By generating continuous shear waves at different frequencies, the dispersion of shear wave speed was also investigated. The feasibility of the viscosity measurement was demonstrated by fitting the measured attenuation dispersion using the Voigt model. Finally, the dual mode system was explored by combining the SW-LASCA and ARF-UOT. The system was demonstrated in an optical reflection detection geometry and the scanning results of heterogeneous phantoms demonstrated the potential of the system to distinguish optical contrast, mechanical contrast and optical/mechanical contrast in a reflection detection geometry.
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Gallivan, Rebecca Anne. "Investigating coordinate network based films through mechanical and optical properties." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111257.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (page 31).
Both biological and synthetic materials crosslinked via metal coordinate dynamic chemistry display interesting advanced behavior. In particular, coordinate networks have been shown to form self-healing, self-assembling, and stimuli-responsive behaviors through its tunable optical and mechanical properties as well as its ability to for dynamic networks. However, while the majority of research has focused on characterization of bulk coordinate networks, coordinate complexes have also been shown to be useful in molecular film formation [1 and 2]. This study investigates the mechanical and optical properties of tannic acid and 4 arm catechol polyethylene glycol based coordinate network films. It shows that these films can contribute to energy dissipation and undergo pH-induced optical shifts when used as coatings on soft hydrogels. It also provides evidence that the molecular architecture of the network formers may have considerable effect on the properties and behavior of coordinate network films. Ultimately this work lays the foundation for further investigation of the underlying mechanisms and engineering potential of coordinate network based films.
by Rebecca Anne Gallivan.
S.B.
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Drew, Christopher W. "Mechanical Loading for Modifying Tissue Water Content and Optical Properties." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/32714.
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The majority of the physical properties of tissue depend directly on the interstitial or intracellular concentration of water within the epidermal and dermal layers. The relationship between skin constituent concentrations, such as water and protein, and the mechanical and optical properties of human skin is important to understand its complex nature. Localized mechanical loading has been proven to alter optical properties of tissue, but the mechanisms by which it is accomplished have not been studied in depth.
In this thesis, skinâ s complex nature is investigated experimentally and computationally to give us better insight on how localized mechanical loading changes tissues water content and its optical properties. Load-based compression and subsequent increased optical power transmission through tissue is accomplished to explore a relationship between localized mechanical loading and tissue optical and mechanical properties. Using Optical Coherence Tomography (OCT), modification of optical properties, such as refractive index, are observed to deduce water concentration changes in tissue due to mechanical compression. A computational finite element model is developed to correlate applied mechanical force to tissue strain and water transport. Comprehensive understanding of the underlying physical principles governing the optical property changes within skin due to water concentration variation will enable future development of applications in the engineered tissue optics field.Master of Science
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Liao, Guangxun. "Mechanical and Electro-Optical Properties of Unconventional Liquid Crystal Systems." Kent State University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=kent1131600449.
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Gunawidjaja, Ray. "Organic/inorganic nanostructured materials towards synergistic mechanical and optical properties /." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29733.
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Thesis (Ph.D)--Industrial and Systems Engineering, Georgia Institute of Technology, 2010.Committee Chair: Tsukruk, Vladimir; Committee Member: Bucknall, David; Committee Member: Kalaitzidou, Kyriaki; Committee Member: Shofner, Meisha; Committee Member: Tannenbaum, Rina. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Liu, Yajing. "Measurement of tissue optical properties during mechanical compression using swept source optical coherence tomography." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/32395.
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Laser-based photo-thermal therapies can provide minimally-invasive treatment of cancers. Their effectiveness is limited by light penetration depth in tissue due to its highly scattering properties. The highly disordered refractive index distribution in tissue leads to multiple-scattering of incident light. It has been hypothesized that mechanical compression has a great potential to enhance the capabilities of laser therapy by inducing localized water transport, decreasing the refractive index mismatch, and decreasing the scattering coefficient of tissue. To better understand this process, we investigated the refractive index change of ex-vivo dog skin during mechanical compression using a swept-source optical coherence tomography (OCT) device built in our lab. The Lorentz-Lorenz rule of mixtures was applied to evaluate the water and protein weight fraction of tissue simultaneously. Results show that the refractive index of skin increased from 1.38 to 1.52 during compression and water content decreased about 60%-70% when the skin sample was compressed by 70%.
In addition, we conducted compression experiments on human finger, palm, back of hand, and front of forearm in vivo. OCT images of these skin sites before and after compression by 1 minute were compared. Optical thickness of epidermis and light penetration depth in the dermis were measured. The extended Huygens-Fresnel model was applied to measure the scattering coefficient μs of skin specimens. μs of skin was measured to be about 10-17 mm-1 before compression and decreased 60%-80% after compression, which increases the averaged light intensity by 2-7 dB and almost doubles light penetration depth in dermis. It is quite significant in laser therapies especially for treating epithelia cancers which originate at 1-2 mm beneath the tissue surface.
In the OCT imaging of skin dehydration experiment, we conclude that dehydration is an important mechanism of mechanical clearing.Master of Science
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Bianchi, Giulio. "Mechanical properties of cytoskeleton proteins studied in living cells by combining optical tweezers and deformability cytometry." Doctoral thesis, Università di Siena, 2021. http://hdl.handle.net/11365/1143608.
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The topic of this thesis focuses on studying the mechanical properties of the living cell plasma membrane and the mechanical associations of the plasma membrane with the underlying cytoskeleton. The mechanical properties of the cell components, cell plasma membrane and cytoskeleton, as well as membrane-cytoskeleton associations, determine the mechanical properties of the whole cell, important for cellular shape changing behavior and mechanical signal transduction in living cells. Examples of biological processes involving cellular shape changes are deformation of erythrocytes in capillaries, cell division, phagocytosis, pseudopodium and dendritic spine formation, and electromotility of the outer hair cells.
The study of cell membrane mechanics accomplished during my PhD activity is based on the use of two most advanced technological approaches to investigate both local membrane deformation by dual laser optical tweezers (DLOT, (Bianco et al., 2011)) and global cell deformation by real-time florescence deformability cytometry (RT-FDC). This dissertation is divided into two main parts.
In the first part I present my contribution to the development and application of a system able to study the mechanical properties of plasma membrane of the Human Embryonic Kidney (HEK293) cells in the adherent state. The DLOT was first applied to investigate the dynamics of the formation/retraction of membrane nanotubes (tethers). In physiological conditions, several parameters of plasma membrane and its interaction with the underlying cytoskeleton (tether formation and elongation, tether radius, Threshold force for the membrane tether elongation and its viscoelastic nature, the tether diameter, the bending modulus, the membrane-cytoskeleton adhesion energy) were determined and compared with those present in literature. The information on cell membrane mechanics was integrated with indentation measurements by using the DLOT for applying local deformations in force feedback in the range experienced by the membrane of macrophages during phagocytosis.The mean value of the elastic modulus (Young’s modulus) derived from indentation experiments was 32 ± 8 Pa (mean ± SD), significantly lower than that obtained with AFM measurements. The difference confirms data found in previous work (Coceano et al., 2016) and indicates that my approach, though limited by its intrinsic compliance to lower time resolution, is unique in resolving the load – dependent dynamics of the cytoskeletal rearrangement triggered by a force step.
In the second part I present experiments conducted during the one-year Ph-D period spent at the University of Greifswald, under the supervision of Dr. Oliver Otto. The experiments were aimed at characterizing the mechanical properties of the HEK293 cells in suspension and how they are influenced by hypoxic stress. Mechanical parameters from control experiments under physiological condition are compared to those obtained in the presence of an increased subpopulation of cells in apoptotic/necrotic state using a high-throughput system, Real-Time Deformability Cytometry (RT-DC (Otto et al., 2015)), which allows to study a high number of cells in short time (1000 cells/s). In combination with fluorescence-based flow cytometry (RT-FDC, (Rosendahl et al., 2018)), this technology permits to analyze treated fluorescent cells and discriminate between subpopulations.
The mechanical parameters considered are cell size, elastic modulus and cell deformation. Hypoxia stressed cells were studied at different incubation times and the dependence from hypoxia of the mechanical parameters were determined. After 12h of oxygen deprivation (12h-hyp) cell stiffness is increased and cell deformation is reduced. An overall increase in concentration of the main cytoskeletal proteins (ß-actin, α/-tubulin, vinculin and talin-1), determined by Western blots, was found to accompany mechanical – structural modification by hypoxia. The successful application of the protocols developed here for the definition of local and global mechanical properties of the cell membrane and the associated underlying cytoskeleton of HEK293 line, opens the possibility of new investigations on the effects on the relevant cell mechanical parameters of different physical and chemical interventions (temperature, pH and buffer ionic composition), different physiological conditions (metabolic stress as hypoxia) modification of the membrane composition, as cholesterol content, or effect of disruption or mutation of membrane-linked cytoskeleton proteins. In this respect the methodology established in this thesis represents a new powerful tool for the investigation o membrane-cytoskeleton structure-function in health and disease.
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Wang, Na 1982. "System of measuring mechanical properties of colloidal gels with optical tweezers." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101662.
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Due to the unique rheological properties of colloidal gels, gelation of colloidal suspensions has become increasingly important to fundamental investigations, as well as to technological applications. Recent experimental approaches are mainly focused on the bulk properties of colloidal gels, using methods of static and dynamic light scattering and shear rheometry. This thesis describes the development of a system for measuring the mechanical properties of colloidal gels with optical tweezers.We make colloidal gels out of polystyrene beads of two different sizes, diameters of 3.5mum or 62nm respectively. Investigation of the colloidal gels under the light microscope shows the fractal nature of the gel structure while macroscopic study confirms that the gelation process of the smaller polystyrene beads is faster than that of the bigger polystyrene beads. We were also able to generate a phase diagram of the gelation process.
We successfully assembled the main instrument, a time-sharing single beam optical tweezers, and calibrated the lateral stiffness of the optical trap. Our optical tweezers setup is used to study the polystyrene gel and it has many more applications in colloidal samples. The strong 3D optical trapping highlights the optical tweezers as a powerful technique suitable for further investigation of colloidal samples.
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Diba, Tara. "MEASURING THE MECHANICAL PROPERTIES OF PRIMARY CILIA WITH AN OPTICAL TRAP." Cleveland State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=csu1450668664.
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Mirsakiyeva, Amina. "Electronic and optical properties of conducting polymers from quantum mechanical computations." Doctoral thesis, KTH, Materialfysik, MF, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-214979.
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Conductive polymers are also known as "organic metals" due to their semiconducting properties. They are found in a wide range of applications in the field of organic electronics. However, the growing number of experimental works is not widely supported with theoretical calculations. Hence, the field of conductive polymers is experiencing lack of understanding of mechanisms occurring in the polymers. In this PhD thesis, the aim is to increase understanding of conductive polymers by performing theoretical calculations. The polymers poly(3,4-ethylenedioxythiophene) (PEDOT) together with its selenium (PEDOS) and tellurium (PEDOTe) derivatives, poly(p-phenylene) (PPP) and naphthobischalcogenadiazoles (NXz) were studied. Several computational methods were applied for analysis of mentioned structures, including density functional theory (DFT), tight-binding modelling (TB), and Car-Parrinello molecular dynamics (CPMD) calculations. The combination of CPMD and DFT calculations was applied to investigate the PEDOT, PEDOS and PEDOTe. The polymers were studied using four different functionals in order to investigate the full picture of structural changes, electronic and optical properties. Temperature effects were studied using molecular dynamics simulations. Wide statistics for structural and molecular orbitals analysis were collected. The TB method was employed for PPP. The formation and motion of the excitations, polarons and bipolarons, along the polymer backbone was investigated in presence of electric and magnetic fields. The influence of non-magnetic and magnetic impurities was determined. The extended π-conjugated structures of NXz were computed using B3LYP and ωB97XD functionals in combination with the 6-31+G(d) basis set. Here, the structural changes caused by polaron formation were analyzed. The combined analysis of densities of states and absorption spectra was used for understanding of the charge transition.QC 20170928
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Sandin, Olof. "Optical and Mechanical Properties of Cool Roof Paint Containing Hollow Thermoplastic Microspheres." Thesis, Uppsala universitet, Institutionen för kemi - Ångström, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-206056.
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This master thesis examines the effect of hollow thermoplastic microspheres in coolroof paints. These types of paints are characterized by their high reflectivity forwavelengths up to 2.5 micrometers and high absorptivity in the IR region. Thethermoplastic microspheres were produced by Expancel®, a unit withinAkzoNobel®. Optical properties were measured using a UV-VIS-NIRspectrophotometer and FTIR. The paint systems were kept as simple as possible, onlycontaining binder, pigment and additive, thus limiting the study to relativecomparisons. TiO2 was used as standard pigment. The additive component was variedbetween thermoplastic, glass or ceramic microspheres. The reference sample usedCaCO3 as additive. The microsphere particle size was found to have the greatestimpact on the paints reflectivity. The smallest microsphere tested in this study, with adiameter of around 10 micrometers was also the best performing. Absorptance andemittance were not found to be affected by incorporating microspheres into thepaint. Thermoplastic microspheres that where coated with TiO2, called coexpandedmicrospheres were also tested. The incorporation of coexpanded microspheresshowed no increase in reflectivity compared to other paints containing thermoplasticmicrospheres. Four different paint systems were color matched (blue) at a local paintshop in order to examine non-white paints as well. Paints containing thermoplasticmicrospheres performed better than paints using any of the other additives,regardless if the paints where white or non-white.
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Eliason, Jeffrey Kristian. "Optical transient grating measurements of micro/nanoscale thermal transport and mechanical properties." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98819.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 109-119).
The laser-based transient grating technique was used to study phonon mediated thermal transport in bulk and nanostructured semiconductors and surface wave propagation in a monolayer of micron sized spheres. In the transient grating technique two picosecond pulses are crossed to generate a spatially periodic intensity profile. The spatially periodic profile generates a material excitation with a well-defined wave vector. The time dependence of the spatially periodic material response is measured by monitoring the diffracted signal of an incident probe beam. Non-diffusive thermal transport was observed in thin Si membranes as well as bulk GaAs at relatively short (micron) transient grating periods. First-principles calculations of the phonon mean free paths in Si and GaAs were compared with experimental results and showed good agreement. Preliminary measurements on promising thermoelectric materials such as PbTe and Bi2Te3 are presented showing evidence of non-diffusive transport at short length scales. The transient grating technique was used to measure the thermal conductivity of Si membranes with thickness ranging from 15 nm to 1518 nm. Using the Fuchs-Sondheimer suppression function along with first-principles results, the thermal conductivity as a function of membrane thickness was calculated. The calculations showed excellent agreement with experimental measurements. A convex optimization algorithm was employed to reconstruct the phonon mean free path distribution from experimental measurements. This marks the first experimental determination of the mean free path distribution for a bulk material. Thermal conductivity measurements at low temperatures in a 200 nm Si membrane indicate the breakdown of the diffuse boundary scattering approximation. The transient grating technique was used to generate surface acoustic waves and measure their dispersion in a monolayer of 0.5 - 1 [mu]m diameter silica spheres. The measured dispersion curves show "avoided crossing" behavior due to the interaction between an axial contact resonance of the microspheres and the surface acoustic wave at a frequency of -200MHz for the 1 [mu]m spheres and -700 MHz for the 0.5 [m spheres. The experimental measurements were fit with an analytical model in which the contact stiffness was the only fitting parameter. Preliminary results of surface acoustic wave propagation in microsphere waveguides, transmission through a microsphere strip, and evidence of a nonlinear response in a 2D array of microspheres are presented.
by Jeffrey Kristian Eliason.
Ph. D.
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Fu, Jiawei. "Identification of corneal mechanical properties using optical tomography and digital volume correlation." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/14894.
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This work presents an effective methodology for measuring the depth-resolved 3D full-field deformation of semitransparent, light scattering soft tissues such as vertebrate eye cornea. This was obtained by performing digital volume correlation on optical coherence tomography volume reconstructions of silicone rubber phantoms and porcine cornea samples. Both the strip tensile tests and the posterior inflation tests have been studied. Prior to these tests, noise effect and strain induced speckle decorrelation were first studied using experimental and simulation methods. The interpolation bias in the strain results has also been analyzed. Two effective approaches have been introduced to reduce the interpolation bias. To extract material constitutive parameters from the 3D full-field deformation measurements, the virtual fields method has been extended into 3D. Both manually defined virtual fields and the optimized piecewise virtual fields have been developed and compared with each other. Efforts have also been made in developing a method to correct the refraction induced distortions in the optical coherence tomography reconstructions. Tilt tests of different silicone rubber phantoms have been implemented to evaluate the performance of the refraction correction method in correcting the distorted reconstructions.
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Bradley, John. "Investigation of the optical and mechanical properties of III-V semiconductor nanowires." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/17882/.
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This thesis concerns the theoretical and experimental study of three applications of III-V semiconductor nanowires. First, a detailed overview of the catalyst-free bottom-up growth of GaAs and InP nanowire arrays is presented. Control of nanowire radial and axial growth is demonstrated through tailoring of growth conditions and pre-growth fabrication methods. The limits of the catalyst-free growth technique are then investigated, leading to the establishment of an approach which allows for nanowire cross-section morphology to be precisely controlled. GaAs/InGaAs nanowire axial heterostructures are grown with elongated cross-section, resulting in the emission of strongly linearly polarised light from the nanowire top-facet. This represents the first demonstration of emission polarisation control in bottom-up semiconductor nanowires and provides a promising route for realisation of position-controlled linearly polarised single photon sources for quantum information applications. Control of nanowire morphology is also leveraged to enable investigation of the mechanical properties of catalyst-free GaAs nanowires with different cross-section aspect ratios. Bottom-up semiconductor nanowires show great promise as ultrasensitive nanomechanical resonators owing to their high structural quality and small motional mass. A slight random asymmetry in the hexagonal cross-section of regular nanowires which commonly arises as a result of small differences in the growth rates of the nanowire side facets, however, means that the direction of motion of the non-degenerate nanowire flexural modes cannot be determined \emph{a priori}. It is demonstrated that the ability to manipulate nanowire cross-section morphology allows for deterministic control of the direction of nanowire motion at the growth stage. Finally, a nanocavity design comprising an InP nanowire placed in a partially-etched GaAs photonic crystal slot waveguide is developed. Optimisation of the cavity design is performed using a combination of frequency-domain and FDTD simulations. After fabrication of photonic crystal slot waveguide devices using a top-down etching process, experimental realisation of the nanocavity design is achieved through nanomanipulation of individual nanowires deposited on the photonic crystal device substrate using an atomic force microscopy system. Such a cavity design provides potential for creation of high quality position-controlled nanowire photon sources integrated in GaAs photonic circuitry.
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Alhenaki, Aasem Mutlaq. "Comparison Of Mechanical And Optical Properties Between Three Different CAD/CAM Materials." Thesis, NSUWorks, 2015. https://nsuworks.nova.edu/hpd_cdm_stuetd/67.
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Objective. This study aims to compare several mechanical and optical properties between three different CAD/CAM materials. The properties tested are: flexural strength, modulus of elasticity, hardness, translucency and surface gloss. Background. Typically, CAD/CAM restorations are either ceramic based or resin based. A new resin-ceramic hybrid material has recently been introduced and is thought to combine the advantages of both materials. Methods. Samples were divided into three groups, leucite-reinforced porcelain (IPS Empress CAD), lithium dicilicate (IPS e.max CAD) and resin-ceramic hybrid material (Vita Enamic). Twenty-six bar-shaped specimens were fabricated for each group by cutting standard CAD/CAM blocks. 3-point bending test and Vickers diamond pyramid indenters were used to test the flexural strength and microhardness respectively. Seven veneers were fabricated for each material with a thickness of 0.5 mm using a CAD/CAM milling machine. These veneers were used to test the optical properties via spectrophotometry and gloss-meter analysis. One-way ANOVA, and the Tukey HSD post hoc test were used for statistical analysis between the groups (P
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Ahammou, Brahim. "Control of the mechanical and optical properties of SiNx-based films for optical and strain engineering applications." Electronic Thesis or Diss., Université de Rennes (2023-....), 2023. https://ged.univ-rennes1.fr/nuxeo/site/esupversions/1e39bf0e-e06f-4457-a06f-b08b11c3bef6.
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Les couches minces à base de nitrure de silicium (SiNx) ont été reconnus comme des diélectriques essentiels dans l'industrie microélectronique et optoélectronique en raison de leurs propriétés intéressantes. Dans cette thèse, nous décrivons comment contrôler l'indice optique et les propriétés mécaniques des couches de SiNx et d'oxynitrure de silicium (SiOyNx) en ajustant les paramètres du processus de dépôt. Nous utilisons deux types de réacteurs de dépôt chimique en phase vapeur assisté par plasma : un réacteur standard à couplage capacitif avec excitation radiofréquence et un réacteur à résonance cyclotron électronique avec excitation micro-onde. Nous discutons de la fabrication et de la caractérisation des structures multicouches comme application optique de nos couches minces. Nous focalisons sur la caractérisation et la compréhension des propriétés optiques de ces couches minces grâce à l’ellipsométrie spectroscopique. Nous étudions également expérimentalement leurs propriétés mécaniques en utilisant la technique de mesure de la courbure des substrats, la fabrication de microstructures et les mesures de nanoindentation. Enfin, nous montrons des mesures précises de la distribution des contraintes induites dans le GaAs lorsque de tels couches minces sont structurés sous forme de rubans allongées de largeur variable, en utilisant la lithographie optique et la gravure au plasma. Pour cela, nous cartographions la déformation anisotrope, en mesurant le degré de polarisation de la photoluminescence (PL) à intégration spectrale générée au sein du GaAs par excitation avec un laser rouge. La PL des semi-conducteurs cubiques massifs tels que le GaAs n'est pas polarisé, tandis que sous une contrainte anisotrope un certain degré de polarisation est produit. Ces cartographies ont été mesurées soit à partir de la surface du semi-conducteur, soit à partir de sections transversales clivées. Ils fournissent une image détaillée et complète de la déformation cristalline au voisinage de la couche contrainte structurée. Ensuite, nous avons effectué des simulations par éléments finis en essayant de reproduire les cartographies expérimentales. Nous pensons que notre schéma de simulation est utile pour la conception des composants photoniques, par exemple pour prédire les changements locaux de l'indice de réfraction dus à l'effet photoélastiqueDue to their attractive properties, silicon nitride (SiNx) based films have been recognized as essential dielectric films in the microelectronic and optoelectronic industries. In this PhD thesis, we describe how we can control the refractive index and the mechanical properties of SiNx and silicon oxynitride (SiOyNx) films by tuning the deposition process parameters. We use two different plasma-enhanced chemical vapor deposition reactors: a standard capacitively coupled reactor with radiofrequency excitation and an electron cyclotron resonance reactor with microwave excitation. We discuss the fabrication and characterization of multilayer structures as an optical application of our thin films. We focus on characterizing and understanding these thin films’ optical properties through spectroscopic ellipsometry. We also study their mechanical properties experimentally using the wafer curvature measurement technique, microstructure fabrication, and nanoindentation measurements. Finally, we show accurate measurements of the strain distribution induced within GaAs wafers when such thin films are structured in the shape of elongated stripes of variable width, using standard optical lithography and plasma etching. For this, we map the anisotropic deformation, measuring the degree of polarization of the spectrally integrated photoluminescence (PL) generated within GaAs by excitation with a red laser. PL from bulk cubic semiconductors such as GaAs is unpolarized, whereas anisotropic strain produces some degree of polarization. These maps were measured either from the semiconductor surface or from cleaved cross-sections. They provide a detailed and complete image of the crystal deformation in the vicinity of the structured stressor film. Then, we performed some finite element simulations trying to reproduce the experimental maps. We believe our simulation scheme is helpful for designing the photonic components, e.g., to predict the local changes in the refractive index due to the photoelastic effect
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Wang, Yuda. "Optical Characterization of Mechanical and Electronic Properties of Visible to Infrared Semiconductor Nanowires." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1457426470.
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Ehtemam, Haghighi Shima. "Design, microstructure and mechanical properties of new Ti-based alloys." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2016. https://ro.ecu.edu.au/theses/1926.
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In this PhD study, using the DV-Xα molecular orbital method three new series of TixFe- yTa, Ti-Fe-xNb and Ti-Nb-xFe alloys are designed for the first time. The alloys are then produced by cold crucible levitation technique. The influence of Ta, Fe and Nb contents on the phase transformation, β phase stability and microstructural evolution of the alloys are investigated. Additionally, the resulting mechanical properties of the alloys are evaluated and compared with those of the widely used biomaterials, i.e. CP-Ti and Ti-6Al-4V to ascertain their suitability for orthopaedic application.
The microstructural studies revealed that Ti-xFe-yTa (x= 8, 9, 10 wt% and y= 0, 2, 5, 8, 9, 10 wt%) alloys substantially consist of α″ and β phases. However, addition of more Fe and Ta β-stabilizers to Ti–8Fe alloy reduced the likelihood to form α″ martensite during quenching, hence decreasing the volume fraction of α″ phase and finally reaching 3% in Ti- 10Fe-10Ta alloy. It is noteworthy noting that all alloys possess higher yield strength (1008- 1560) MPa and hardness (343-468) HV5 than those of CP-Ti and Ti-6Al-4V. However, among them, Ti-10Fe-10Ta alloy with dominant β phase structure exhibits the lowest elastic modulus (92 GPa) and highest plasticity (40%).
In Ti-7Fe-xNb (x= 0, 1, 4, 6, 9, 11 wt%), it was observed that only Ti-7Fe-11Nb alloy shows single β phase microstructure, while others are comprised of β and α″ phases. Moreover, Nb addition up to 11 wt% enhances the stability and volume fraction of β phase in the microstructure, hence reducing the propensity of the alloy system to form α″ phase during quenching. Yield strength, hardness and wear rate of the alloys are (985-1847) MPa, (325- 520) HV5 and (3×10-15-1×10-13) m3/m respectively. Among the alloys, Ti-7Fe-11Nb possesses the lowest elastic modulus (84 GPa) and highest deformability (42% strain) due to sence of shear bands indicates excessive deformation as a result of strain localization ADDIN EN.CITE Haghighi2
The microstructure of Ti-11Nb-xFe (x= 0.5, 3.5, 6, 9 wt.%) alloys shows that with the exception of β-type Ti-11Nb-9Fe, all alloys are comprised of β and α/α″ phases. Moreover, Fe addition is effective in suppressing α and α″ formation, hence making β more stable. Yield strength and hardness of the alloys are (796-1137) MPa and (278-357) HV5 respectively. It is noteworthy that upon increasing Fe content, the elastic modulus of the alloys decreases, while their plastic strain and elastic energy are enhanced due to retention of more β phase. The ii lowest elastic modulus (82 GPa) and highest plastic strain (38%) are observed in full β Ti- 11Nb-9Fe alloy. Moreover, Ti-11Nb-9Fe presents higher elastic energy (7.08 MJ/m3) than that of some commercial Ti-based biomaterials.
The results suggest that among the designed alloys, Ti-10Fe-10Ta, Ti-7Fe-11Nb and Ti-11Nb-9Fe present the best combination of mechanical properties making them more desirable than the commonly used CP-Ti and Ti–6Al–4V materials for implant application. Therefore, this research demonstrates that through proper alloy design it is possible to design new Ti alloys with favourable properties better than CP-Ti and Ti-6Al-4V alloys for orthopaedic application.
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Coceano, Giovanna. "Local measurement of breast cancer cells mechanical properties." Doctoral thesis, Università degli studi di Trieste, 2015. http://hdl.handle.net/10077/10895.
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2013/2014In the last decades cell mechanics has been increasingly associated to cell health and function. Elasticity is one of the most investigated mechanical properties of cells and is now considered as a potential label free marker of cancer progression. In this Thesis I report on the characterization of cells based on their mechanical properties. Three different biophysical micromanipulation tools have been used: Optical Tweezers (OT), Atomic Force Microscopy (AFM) and Speckle Sensing Microscopy (SSM). We chose three breast cell lines selected as a model to study cancer progression: MDA-MB-231, a highly aggressive cell line belonging to the Basal cell-like phenotype; MCF-7, a less aggressive tumour cell line, belonging to the Luminal A cell-like tumour subtype; and HBL-100, a non neoplastic cell line, derived from the milk of a Caucasian woman, normal control for breast basal-myoepithelial cells. The viscoelastic properties of the three cell lines have been measured using complementary approaches, thus allowing a thorough characterization: OT membrane tether pulling, OT and AFM vertical cell indentation and speckle interferometry with SSM. With AFM and OT techniques we performed local measurements on specific parts of the cell; while with SSM we considered the cell as a whole viscoelastic body and we analyzed groups of cells at the same time. OT membrane tether pulling uses a microbead trapped by the laser beam to pull cellular membrane tethers; from the resultant Force-Elongation (FE) curve, some viscoelastic parameters of the cell itself have been extracted and compared. The experimental approach results to be inefficient and time consuming and it has been, therefore, substituted by OT vertical indentation. The new approach uses the OT in a similar way of the AFM technique, i.e. indenting the cell with a micron sized bead trapped by the laser. The elastic modulus has been therefore measured by vertical cell indentation, employing AFM and OT as two complementary techniques: with AFM we applied nN forces at high loading rates, while with OT we operated at pN forces at low loading rates. OT has been implemented in an inverted optical microscope and the elastic modulus of the three cell lines results to be: 23.4 (HBL-100), 31.2 (MCF-7) and 12.6 (MDA-MB-231) Pa. AFM indentation approach has been performed using the Bioscope Catalyst in Peak Force Quantitative Nanomechanical Mapping (PF-QNM) mode. Bioscope is able of applying nN forces by means of a nano-sized tip attached at the end of a cantilever. This new AFM mode allows mapping different mechanical properties of the cell under scan. The elastic modulus of the three cell lines has been extracted, providing more information about the mechanical alterations undergoing tumorigenesis. The mean values measured near the cell nucleus were: 91.1 (HBL-100), 81.8 (MCF-7), 57.6 (MDA-MB-231) kPa. These results show that there is an inverse correlation between cell stiffness and breast cancer cell aggressiveness, since MDA-MB-231, the most aggressive cell line, has an elastic modulus significantly lower than the other two cell lines, both with OT and AFM measurements. The difference values obtained by AFM and OT are the result of the different regimes used by these techniques: AFM applies higher forces and higher loading rates in comparison to OT. Nevertheless, the trend of the values between the cell lines was the same, showing that the aggressive cells were much softer than the other two. The combination of the two techniques is proposed for a more complete characterization of the mechanical properties of cells in different mechanical conditions. Moreover we show that the stiffness of the substrate influences the elasticity of the cells; OT vertical indentation has been applied to HBL-100 cells cultured on bare and collagen coated substrates and their elastic modulus was 26±9 for bare and 19±7 Pa for collagen. These results show that cells adapt their structures to that of the substrate and demonstrate the potential of this setup for low-force probing of cell mechanics. SSM has been originally proposed by our group in an international collaboration for fast diagnosis of malaria making available the analysis of thousand of cells per minute. It is based on the analysis of the speckles formed by light scattered by the cells when illuminated by a tilted laser beam. Speckle dynamics reflects the thermal vibration of the cell, which is linked to its stiffness. In this work SSM has been applied to MCF 7 cell line for cell mechanics characterization. The final goal of this PhD Thesis is the characterization of the mechanical properties of cancer cells, by means of an integrated method based on rigorous biophysical techniques to understand the disease progression and differentiation towards metastasis.
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Izquierdo-Roman, Alondra. "Localized Mechanical Compression as a Technique for the Modification of Biological Tissue Optical Properties." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/76856.
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Tissue optical clearing aims to increase the penetration depth of near-collimated light in biological tissue to enhance optical diagnostic, therapeutic, and cosmetic procedures. Previous studies have shown the effects of chemical optical clearing on tissue optical properties. Drawbacks associated with chemical clearing include the introduction of potentially toxic exogenous chemicals into the tissue, poor site targeting, as well as slow transport of the chemicals through tissue. Thus, alternative clearing methods have been investigated. Mechanical compression is one such alternative tissue optical clearing technique. The mechanisms of action of mechanical compression may be similar to those of chemical clearing, though they have yet to be investigated systematically. This research describes the design and execution of a number of procedures useful for the quantification of the tissue optical clearing effects of localized mechanical compression. The first experimental chapter presents the effects of compression on image resolution and contrast of a target imaged through ex vivo biological tissue. It was found that mechanical optical clearing allowed recovery of smaller targets at higher contrast sensitivity when compared to chemical clearing. Also, thickness-independent tissue clearing effects were observed. In the second experimental chapter, dynamic changes in tissue optical properties, namely scattering and absorption coefficients (?s' and ?a, respectively) were monitored during a controlled compression protocol using different indentation geometries. A reduction in ?s' and ?a was evident for all indentation geometries, with greater changes occurring with smaller surface area. Results indicate that localized mechanical compression may be harnessed as a minimally-invasive tissue optical clearing technique.Master of Science
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Buzzi, Stefano. "Large-scale imprinting of silver submicrometer structures and studies of their optical and mechanical properties /." Zürich : ETH, 2009. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=18338.
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Macadangdang, Joan Karla. "Nuclear and Cytoskeletal Prestress Govern the Anisotropic Mechanical Properties of the Nucleus." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23310.
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Physical forces in the cellular microenvironment play an important role in governing cell function. Forces transmitted through the cell cause distinct deformation of the nucleus, and possibly play a role in force-mediated gene expression. The work presented in this thesis drew upon innovative strategies employing simultaneous atomic force and laser-scanning confocal microscopy, as well as parallel optical stretching experiments, to gain unique insights into the response of eukaryotic cell nuclei to external force. Non-destructive approaches confirmed the existence of a clear anisotropy in nuclear mechanical properties, and showed that the nucleus' mechanical response to extracellular forces is differentially governed by both nuclear and cytoskeletal prestress: nuclear prestress regulates shape and anisotropic deformation, whereas cytoskeletal prestress modulates the magnitude and degree of deformation. Importantly, the anisotropic mechanical response was conserved among diverse differentiated cell types from multiple species, suggesting that nuclear mechanical anisotropy plays an important role in cell function.
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Neve, de Mevergnies Nathalie. "The MicroPIVOT : an Integrated Particle Image Velocimeter and Optical Tweezers Instrument for Microscale Investigations." PDXScholar, 2010. https://pdxscholar.library.pdx.edu/open_access_etds/31.
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This dissertation describes the development of a device capable of suspending a microscale object in a controlled flow. The uPIVOT is a system integrating two laser-based techniques: micron particle image velocimetry (uPIV) and optical tweezers (OT). The OT allows the suspension and manipulation of micron-sized objects such as microspheres or biological cells. uPIV provides imaging of the suspended object and velocity measurements from which fluid induced stresses can be determined. Using this device, we measured fluid velocities around an optically suspended polystyrene microsphere (an experimental first) and studied the interaction between two particles suspended in a uniform flow. The results were consistent with theoretical low Reynolds number, Newtonian flow predictions. Additionally, we analyzed a single cell's mechanical response to a controlled and measurable multiaxial external force (fluid flow) without the cell being physically attached to a surface. The cell's mechanical response was monitored by observing its morphology and measuring its deformation. The results show significant deformations of optically suspended cells at substantially smaller stresses than previously reported and demonstrate the opportunity to optically distinguish a cell by its trapping efficiency. These initial applications of the uPIVOT demonstrate the potential of this unique device as a research tool for novel studies in the fields of fluid/particle(s) interactions, non-Newtonian fluid mechanics, and single cell biomechanics.
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Souza, de Almeida Jailton. "Designing and Tuning the Properties of Materials by Quantum Mechanical Calculations." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6923.
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Ramzan, Muhammad. "Structural, Electronic and Mechanical Properties of Advanced Functional Materials." Doctoral thesis, Uppsala universitet, Materialteori, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-205243.
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The search for alternate and renewable energy resources as well as the efficient use of energy and development of such systems that can help to save the energy consumption is needed because of exponential growth in world population, limited conventional fossil fuel resources, and to meet the increasing demand of clean and environment friendly substitutes. Hydrogen being the simplest, most abundant and clean energy carrier has the potential to fulfill some of these requirements provided the development of efficient, safe and durable systems for its production, storage and usage. Chemical hydrides, complex hydrides and nanomaterials, where the hydrogen is either chemically bonded to the metal ions or physiosorbed, are the possible means to overcome the difficulties associated with the storage and usage of hydrogen at favorable conditions. We have studied the structural and electronic properties of some of the chemical hydrides, complex hydrides and functionalized nanostructures to understand the kinetics and thermodynamics of these materials. Another active field relating to energy storage is rechargeable batteries. We have studied the detailed crystal and electronic structures of Li and Mg based cathode materials and calculated the average intercalation voltage of the corresponding batteries. We found that transition metal doped MgH2 nanocluster is a material to use efficiently not only in batteries but also in fuel-cell technologies. MAX phases can be used to develop the systems to save the energy consumption. We have chosen one compound from each of all known types of MAX phases and analyzed the structural, electronic, and mechanical properties using the hybrid functional. We suggest that the proper treatment of correlation effects is important for the correct description of Cr2AlC and Cr2GeC by the good choice of Hubbard 'U' in DFT+U method. Hydrogen is fascinating to physicists due to predicted possibility of metallization and high temperature superconductivity. On the basis of our ab initio molecular dynamics studies, we propose that the recent claim of conductive hydrogen by experiments might be explained by the diffusion of hydrogen at relevant pressure and temperature. In this thesis we also present the studies of phase change memory materials, oxides and amorphization of oxide materials, spintronics and sulfide materials.
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Cao, Ke. "Telechelic Polyetherimides with Functionalized End Groups for Enhancement of Mechanical Strength, Flame Retardancy, and Optical Properties." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/97831.
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This thesis focuses on understanding the factors that affect the properties of polyetherimide (PEI) and improving the properties. As a high-performance thermoplastic resin, the first challenge in PEI application is its high processing temperature and viscosity. Therefore, two supramolecular strategies were applied to not only solve the problem of high processing temperature or viscosity but also enhance the mechanical and flame retardancy. In addition, the yellow to amber color of PEIs limits its applications in high-tech fields such as microelectronics and optoelectronics. Thus, a fundamental study of how end group and molecular weight affect the optical properties of PEIs provides a better knowledge of the mechanism and an effective strategy for designing PEIs.
To lower the processing viscosity while maintaining or even improving the mechanical properties of PEI, the first strategy was to synthesize PEI oligomers, and incorporate self-complementary quadruple hydrogen bonding ureidopyrimidinone (UPy) units at the chain ends. Surprisingly, the UPy imparted PEI with a Mn as low as 8 kDa (8k-PEI) with great film formability. Excitingly, 8k-PEI-UPy exhibited an outstanding Young's modulus higher than those of state-of-the-art high-molecular-weight (high-MW) commercial PEIs. Therefore, the incorporation of UPy was proved to be an effective method to synthesize low-molecular-weight, high-mechanical-strength PEIs.
Although low-molecular-weight PEI-UPy had high mechanical properties, its limited thermal stability and potentially low flame retardancy, however, restricted its applications in areas such as aerospace and aircrafts. Hence in another strategy, which utilize the phosphonium ionic groups were incorporated into PEI oligomers targeting at achieving high thermal stability, flame retardancy, and mechanical properties simultaneously. Functionalization of dianhydride-terminated PEI by tetraphenylphosphonium bromide afforded the synthesis of phosphonium bromide terminated PEI (PEI-PhPPh3Br), which simultaneously exhibited excellent thermal stability up to ~400°C, outstanding flame retardancy evidenced by high char yield and extremely high limiting oxygen index, and a very high mechanical strength. The study thus provides an efficient strategy to simultaneously enhance the thermal and mechanical properties as well as flame retardancy. Furthermore, the low-molecular-weight PEI-PhPPh3Br had good processability due to its strong shear thinning.
In addition to the thermal and mechanical properties and flame retardancy, the end groups affect the optical properties, especially the yellowness, of PEIs. Understanding how end group and molecular weight affect the yellowness, of PEIs is critical for their applications in fields including optoelectronics and microelectronics. Thereby, PEIs with different Mn and various end groups including electron-withdrawing and electron-donating were prepared and characterized. Electron-withdrawing end groups reduced the yellowness and increased the transparency of PEI, regardless of the Mn. Electron-donating end groups increased the yellowness of PEIs with dependence on the Mn. The Mn affected the yellowness of PEIs by changing end group density and the probability of charge-transfer complex formation. The systematic study reveals the correlations among yellowness, end group, and molecular weight of PEIs.MS
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Afshar, Abolfazl Mozaffari. "Optical properties of semiconductors quantum microcavity structures." Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298196.
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Diao, Jie. "Development of Techniques to Quantify Chemical and Mechanical Modifications of Polymer Surfaces: Application to Chemical Mechanical Polishing." Diss., Available online, Georgia Institute of Technology, 2004, 2004. http://etd.gatech.edu/theses/available/etd-11222004-001703/.
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Thesis (Ph. D.)--Chemical Engineering, Georgia Institute of Technology, 2006.Samuels, Robert J., Committee Member ; Henderson, Clifford L., Committee Member ; Danyluk, Steven, Committee Member ; Hess, Dennis W., Committee Chair ; Bottomley, Lawrence A., Committee Member ; Morris, Jeffrey F., Committee Co-Chair. Vita. Includes bibliographical references.
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Monteiro, Kelli Nunes. "Efeito da coloração nas propriedades mecânicas e ópticas de cerâmicas odontológicas à base de zircônia." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/23/23140/tde-30092016-114756/.
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Os objetivos deste trabalho foram avaliar o efeito da aplicação de sete soluções de tingimento e de três diferentes pós de partida comerciais (TZ-3YSB-E, Zpex, TZ-3Y20AB), sobre o parâmetro de translucidez, a resistência à flexão e análise de citotoxicidade de cerâmicas policristalinas à base de zircônia. As seguintes hipóteses foram testadas: (1) não há efeito da solução de tingimento ou do pó de partida nas propriedades ópticas das cerâmicas policristalinas; (2) não há efeito da solução de tingimento, do pó de partida e do envelhecimento hidrotérmico nas propriedades mecânicas das cerâmicas policristalinas; (3) não há efeito da solução de tingimento ou do pó de partida na citotoxicidade das cerâmicas policristalinas. Material e métodos: foi realizada a análise química das soluções de tingimento (FRX), caracterização dos pós cerâmicos (MEV-FEG), estudo de compactação e sinterização e análise térmica. As pastilhas cerâmicas foram confeccionadas utilizando os três pós cerâmicos. A compactação foi feita uniaxialmente com posterior prensagem isostática a frio. Após pré-sinterização, as pastilhas foram imersas nas diferentes misturas das soluções de tingimento comerciais (de acordo com a especificação do fabricante), com posterior secagem e sinterização final. Os materiais foram testados quanto às propriedades ópticas (parâmetro de translucidez (PT) e coordenadas colorimétricas), quanto à resistência à flexão em três pontos antes e após tratamento para degradação hidrotérmica (5 horas a 134°C, sob pressão de 2 bar) e análise de citoxicidade. (Resultados: Com relação ao efeito da aplicação das soluções de tingimento e de diferentes pós de partida sobre o parâmetro de translucidez, foi possível notar que o material interfere nos parâmetros de translucidez, sendo que o Zpex (PT = 11,2 ± 5,4) foi o material mais translúcido. Para o efeito do uso das soluções de tingimento, a mistura das soluções para a obtenção das cores B1 (9,5 ± 7,0) e B3 (8,7 ± 9,7) resultaram em espécimes mais translúcidos e a cor D3 (1,9 ± 0,7) apresentou espécimes com menor translucidez. Com relação ao efeito da aplicação das soluções de tingimento, dos três pós de partida e do envelhecimento sobre a resistência à flexão, foi possível notar que o material interfere na resistência à flexão das cerâmicas policristalinas, sendo que a maior média de resistência foi obtida para o TZ-3YB-E (605,8 ± 106,4 MPa). O envelhecimento causou uma diminuição dos valores de resistência, porém ao se observar cada grupo individualmente, essa queda não foi estatisticamente significativa para nenhum deles. O uso das soluções de tingimento afetou as médias de resistência, sendo que as cores A2 (614,9 ± 120,2 MPa) e C2 (625,0 ± 97,6 MPa) resultaram em resistência maior do que aquelas medidas para as cores A3 (497,0 ± 109,1 MPa) e C3 (529,5 ± 134,9 MPa). Com relação ao efeito da aplicação das soluções de tingimento e dos três diferentes pós de partida sobre a citotoxicidade, foi possível notar que ambos os fatores afetaram os valores de viabilidade celular. Entretanto, para todos os grupos analisados, a viabilidade celular obtida ficou acima de 90% e, portanto, todos os grupos apresentaram uma excelente biocompatibilidade. Conclusão: o material e as soluções de tingimento afetaram o parâmetro de translucidez e as coordenadas colorimétricas permitindo rejeitar a primeira hipótese testada. As soluções de tingimento e os materiais influenciaram a resistência à flexão das cerâmicas policristalinas, entretanto a queda de resistência no envelhecimento não foi significativa, portanto, a hipótese de que não haveria efeito do pó de partida, solução de tingimento e envelhecimento sobre a resistência à flexão foi parcialmente rejeitada A hipótese de que não haveria efeito do pó de partida e da solução de tingimento sobre a citotoxicidade foi rejeitada, mas todos os grupos testados não se apresentaram citotóxicos.The objectives of this study were to evaluate the effect of the application of seven coloring solutions and three different starting powders (TZ 3YSB-E, Zpex, TZ-3Y20AB) on the translucency parameter, flexural strength and cytotoxicity of zirconia-based polycrystalline ceramics. The following hypotheses were tested: (1) there is no effect of the coloring solution or the starting powder on the optical properties of the ceramics tested; (2) there is no effect of the coloring solution, of the starting powder and of hydrothermal aging on the mechanical properties of the materials; (3) there is no effect of the coloring solution or the starting powder in the cytotoxicity of the ceramics tested. Material and methods: we performed a chemical analysis of the coloring solutions (FRX), characterization of ceramic powders (SEM-FEG), study of compaction, sintering and thermal analysis. The ceramic discs were made using the three ceramic powders. Compression was made uniaxiallly with subsequent cold isostactic pressure. After pre-sintering, the discs were immersed in different mixtures of commercial coloring solutions (according to manufacturer\'s specifications) with subsequent drying and final sintering. The materials were tested for optical properties (translucency parameter, TP), and biaxial flexural strength before and after hydrothermal degradation protocol (5 hours at 134°C under 2 bar pressure) and cytotoxicity analysis (evaluation cell viability). Results: With regard to the effect of applying the coloring solutions and the effect of the different starting powders on the translucency parameter, it was observed that the material interfered significantly with the light transmission parameters, and the Zpex (TP=11.2 ± 5.4) was the morst translucent material. With regards to the effect of the coloring solutions on TP, mixing the solutions to obtain the shades B1 (9.5 ± 7.0) and B3 (8.7 ± 9.7) resulted in more translucent specimens and shade D3 (1.9 ± 0.7) resulted in the lowest translucency. With respect to the effect of applying the coloring solutions, the three starting powders and aging on the flexural strength, it was observed that the material interfered with the flexural strength of polycrystalline ceramics, being the highest mean strenght obtained for the TZ-3YB-E (605.8 ± 106.4 MPa). Aging caused a decrease in resistance values, but when considering each group individually, this decrease was not statistically significant for any of them. The use of coloring solutions affected the average strength, as shades A2 (614.9 ± 120.2 MPa) and C2 (625.0 ± 97.6 MPa) resulted in greater strength than those measured for shades A3 (497.0 ± 109.1 MPa) and C3 (529.5 ± 134.9 MPa). With respect to the effect ofthe coloring solutions and the powders on the cytotoxicity, it was observed that both factors affected cell viability values. However, for all groups, the obtained cell viability was above 90% and therefore all of them showed an excellent biocompatibility. Conclusion: the material and coloring solutions affected the translucency parameter and the colorimetric coordinates allowing for rejection the first hypothesis tested. The coloring solutions and the starting powder influenced the flexural strength of polycrystalline ceramics, however, the decrease in strength after aging was not significant; therefore, the second hypothesis was partially accepted. The hypothesis that there would be no effect of the starting powder and the coloring solution on the cytotoxicity was rejected, but all tested groups were not cytotoxic.
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Yucel, Orcun. "Birefringence Gradient Development During Drying of Solution Cast Functional Films and Their Mechanical, Optical and Gas Barrier Properties." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1377699282.
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Golshani, Fariborz. "Boron doping of diamond powder by enhanced diffusion and forced diffusion : diffusion concentrations, mechanical, chemical and optical properties /." free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9842530.
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[Verfasser], Chaiyaporn Lothongkam. "Dielectric strength behaviour and mechanical properties of transparent insulation materials suitable to optical monitoring of partial discharges / Chaiyaporn Lothongkam." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2014. http://d-nb.info/1063001951/34.
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Kennemore, Charles Milton III. "The effects of ion-assisted deposition on the mechanical, physical, chemical and optical properties of magnesium fluoride thin films." Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/185917.
Full textAbstract:
This dissertation investigates the results of ion assisted deposition (IAD) on various properties of magnesium fluoride thin films deposited on room temperature substrates. MgF₂ films deposited in this manner have increased abrasion resistance and increased adhesion comparable to that found in films deposited at the usual substrate temperature of approximately 300°C. IAD tends to drive the normal high tensile stress of non-IAD films to a more compressive state thereby reducing the overall stress. The IAD MgF₂ films have a higher index of refraction than non-IAD films, as high as 1.41, and the ultraviolet absorption edge in shifted to longer wavelengths beginning about 350 nm but no detectable absorption at visible wavelengths is seen in the films deposited with less than 250 eV bombardment energies. However, at higher IAD energies beginning at approximately 600 eV an absorption band is present in the red end of the visible spectrum making low energy bombardment the parameter of choice. Transmission electron microscopy and X-ray diffraction studies show that the IAD films have a more amorphous-like structure with fewer and smaller crystallites than non-IAD films deposited on either heated or unheated substrates. Rutherford backscattering spectroscopy (RBS) shows the bombarded films have fluorine depletion that roughly scales with the energy of bombardment with F:Mg ratios as low as 1.69 being found. Bombardment by fluorinated compounds, specifically C₂F₆ and SF₆, limit this depletion and in some instances super fluorinate the resulting compound. Additionally, RBS shows that IAD introduces a significant amount of oxygen throughout the film that is unaccountable as water take-up. X-ray photoelectron spectroscopy (XPS) indicates the presence of two compounds of oxygen that are attributed to MgO and Mg(OH)₂ or some oxy-fluoride complex similar to them and it is the introduction of these compounds which provide for the changes in the properties of IAD MgF₂ as compared to non-IAD films of MgF₂.
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Ullah, Anayat [Verfasser]. "Optimization of the Mechanical and Optical Properties of Tunable Optical Sensor Arrays (TOSA) for a Nanospectrometer in the Visible and Near Infrared Spectral Range / Anayat Ullah." Kassel : Universitätsbibliothek Kassel, 2014. http://d-nb.info/1065080360/34.
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Smith, Damon Allen. "Mechanical, electromechanical, and optical properties of germanium nanowires." 2009. http://hdl.handle.net/2152/7678.
Full textAbstract:
In order to completely assess the potential of semiconductor nanowires for multifunctional applications such as flexible electronics, nanoelectromechanical systems (NEMS), and composites, a full characterization of their properties must be obtained. While many of their physical properties have been well studied, explorations of mechanical, electromechanical, and optical properties of semiconductor nanowires remain relatively sparse in the literature. Two major hurdles to the elucidation of these properties are: (1) the development of experimental techniques which are capable of mechanical and electromechanical measurements coupled with detailed structural analysis, and (2) the synthesis of high quality nanowires with the high yields necessary to produce the quantities needed for composite fabrication. These issues are addressed in this dissertation by utilizing the supercritical fluid-liquid-solid (SFLS) synthesis method to produce germanium (Ge) nanowire specimens for mechanical and electromechanical measurements coupled with high-resolution transmission electron microscopy (HRTEM). In addition, excellent dispersibility and large quantities allow for optical measurements of dispersions and composites. Ge cantilever nanoelectromechanical resonators were fabricated and induced into resonance. From the frequency response, the Young's modulus of the nanowires was determined to be insensitive to diameter and on par with the literature values for bulk Ge. The mechanical quality factors of the resonators were found to decrease with decreasing diameter. The data indicate that energy dissipation from the oscillating cantilevers occurs predominantly via surface losses. The mechanical strengths of individual Ge nanowires were measured by in situ nanomanipulation in a scanning electron microscope (SEM). The nanowires were found to tolerate diameter-dependent flexural strains more than two orders of magnitude higher than bulk Ge. Corresponding bending strengths were in agreement with the ideal strength of a perfect Ge crystal, indicative of a reduced presence of extended defects. The nanowires also exhibited plastic deformation at room temperature, becoming amorphous at the point of maximum strain. The optical absorbance spectra of Ge nanowires were measured and found to exhibit spectra markedly different from bulk Ge. Simulations using a discrete dipole approximation (DDA) model suggest that the difference in light absorption results from light trapping within the nanowires.text
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Erasmus, Rudolph Marthinus. "Optical properties and mechanical stress in cubic boron nitride and diamond." Thesis, 2013. http://hdl.handle.net/10539/12572.
Full textAbstract:
A thesis submitted to the Faculty of Science, University of the Witwatersrand,
Johannesburg, in fulfilment of the requirements for the degree of Doctor of
PhilosophyRaman and photoluminescence (PL) spectroscopy techniques were used to investigate the mechanical properties of diamond and cubic boron nitride (cBN) by optical means. Both these materials have extreme mechanical properties that make them the material of choice for many industrial applications, ranging from cutting and grinding to wire-drawing dies. The results obtained on single crystal diamond, polycrystalline diamond (PCD) and cBN are summarised below. Micro-Raman and photoluminescence (PL) spectroscopy were used to map the threedimensional (3D) stress and deformation distributions surrounding a plastic impression made in a synthetic, type Ib single crystal diamond. Using data from the Raman peak position, a 3D map of the stress contours surrounding the impression was generated, while the Raman width data yielded a map of the plastic deformation volume. The stress contours compare favorably with the resolved shear stress contours calculated for diamond. PL intensity maps of the zero phonon line (ZPL) associated with the [N-V]– defect centre at 1.945eV provide images of the extent of vacancy formation and movement during the impression process. Data concerning the position and width of the ZPL correspond well with the Raman results. Polycrystalline diamond (PCD) tools commonly consist of a PCD layer sintered onto a cobalt-tungsten carbide (Co-WC) substrate. These tools are used in diverse applications and both the magnitude and distribution of the stresses in the PCD layer affect tool behavior. These stresses in sample drillbits were investigated by means of micro-Raman spectroscopy. Cyclic annealing of a sample drillbit to 600 oC shows that the tool properties are retained after 5 cycles, while similar cycling to 800 oC resulted in a permanent decrease of the average surface compressive stress. This implies a reduction in the drillbit’s ability to resist crack formation and propagation and is thus a degradation of the tool properties. The method of Raman mapping of stress and deformation in diamond was also applied to single crystals of cBN. Indentations on cubic boron nitride (cBN) crystals and polycrystalline cubic boron nitride (PcBN) composites were mapped and the shifts of the cBN Raman lines from their unstressed positions used to quantify the residual stresses in the boron nitride due to the deformation brought about by the indentation. These were found to be of the order of 1 GPa. vi These measurements illustrated for the first time the use of Raman spectroscopy to study residual stresses in boron nitride. Defects in cBN were studied using photoluminescence spectroscopy at low temperature (< 10 K) of two types of cBN irradiated at ambient temperature with 1.9 MeV electrons. All the samples were small (<1 mm diameter) single crystals of cBN. Three defect centres (with narrow lines at 2.28 eV, 2.15 eV and 1.98 eV) were introduced in both the amber-coloured and blackbrown coloured samples by the irradiation. The amber coloured sample also showed a defect centre (at 1.65 eV) that is present before and after irradiation. Line shape analysis of the zero phonon lines of all three irradiation-induced centres showed that the lines are predominantly Gaussian in character, suggesting that linetype defects such as dislocations are a prevalent characteristic of these crystals. Raman spectroscopy of cBN single crystals as a function of temperature was performed over a wide temperature range from 4 K to 1373 K. The low temperature measurements extended the data previously reported in literature, as this data ranged from room temperature upwards. It was concluded from the shift of Raman peak position with temperature that both linear expansion and anharmonic effects were required to adequately account for the observed data. This is in agreement with previously published findings. Both 3- and 4-phonon processes were required to account for the observed linewidths as a function of temperature, again in agreement with literature. The results presented here and in the associated journal publications illustrate clearly how optical spectroscopy techniques can serve as non-destructive characterisation tools for the mechanical properties of ultra-hard materials.
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Khayat, Waad. "Optical and mechanical properties of polymer-infiltrated ceramics." Thesis, 2018. https://hdl.handle.net/2144/32941.
Full textAbstract:
OBJECTIVES: To determine the effects of sintering cycle and curing technique on the translucency, refractive index and flexural strength of novel polymer-infiltrated ceramics.
MATERIALS AND METHODS: Alumina and spinel matrix specimens were fabricated by slip casting (15mm diameter × 2mm thickness). Alumina and spinel specimens were divided into 7 and 6 groups respectively (n=10/group). Alumina groups AHP1, AH1and AM1 were sintered at 1150°C, groups AHP2, AH2 and AM2 at 1200°C and group AFD was fully sintered at 1550°C. Spinel groups SHP1, SH1 and SM1 were sintered at 1500°C and groups SHP2, SH2, SM2 at 1600°C. Density was calculated for each specimen. Groups AM1, AM2, AFD, SM1 and SM2 were the control groups and received no further treatment. Other groups were silanated and dried overnight at 90°C. Then, UDMA-TEGDMA (50-50 mole) resin was prepared and infiltrated into the ceramic specimens under vacuum. Groups AHP1, AHP2, SHP1 and SHP2 were cured by heat at 90°C under pressure of 138 MPa. Groups AH1, AH2, SH1 and SH2 were cured by heat at 90°C. Specimens were polished (1.5mm thickness) and density measured. The total transmission was evaluated with a spectrophotometer (X-rite Ci7600). Refractive index was measured (Presidium Refractive Index Meter II). Biaxial flexural strength was obtained (Instron 5566A) with a crosshead speed of 0.5mm/min. The microstructure was examined using a field emission scanning electron microscope (FESEM-VP, Hitachi SU6600). Statistical analyses were performed using Excel 2016 (Microsoft Office) and JMP 13 (SAS).
RESULTS: Polymer-infiltrated alumina and spinel showed significantly lower refractive index (p< .0001), higher translucency (p< .0001) and higher flexural strength (p< .0001) than their corresponding ceramic matrix groups. Sintering temperature of the ceramic matrix had a significant influence on the flexural strength of polymer-infiltrated ceramics. The application of pressure during polymerization significantly improved the translucency but did not influence significantly the flexural strength of polymer-infiltrated ceramics. Groups AHP2 and AH2 showed high strength (comparable to fully sintered alumina). Polymer-infiltrated spinel showed better translucency but lower strength than alumina groups.
CONCLUSION: Sintering temperature and curing technique had a significant influence on optical and mechanical properties of polymer-infiltrated ceramics.2020-10-24
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Chen, Chien-Hung, and 陳建宏. "Some mechanical and optical properties of sputtered TiO films." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/40592898010776518440.
Full textAbstract:
碩士國立高雄海洋科技大學
輪機工程研究所
93
Abstract Nanoindentation is now the most commonly used method for studying mechanical properties of materials on the nanoscale. It can also be applied to the study of the mechanical properties of TiO (Titanium oxide) films. Among the several crystal structures of TiO , rutile has the highest density and microhardness, the highest index of refraction and the highest temperature stability. However, different types of deposition techniques create TiO films with different properties. Thus, the aim of this study is to prepare TiO films with good mechanical properties through good quality control techniques. For this study, a twin DC magnetron sputtering system was used to prepare nano-layered TiO /ITO. The TiO film thickness on all the sample was 500±30nm with an average deposition rate of ~12.5nm/min, while the ITO film thickness was 140±10nm. Since it was very difficult to obtain the mechanical properties of such thin coating materials, the use of nanoindentation tester thus became a necessity. The film morphology, i.e. microstructure and surface roughness, was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). In addition, the adhesive strength and internal force of the films were evaluated by using the scratch tester and X-ray diffraction (XRD), while the optical constants were calculated by ellipsometry. The results of our experiments showed that the nanoindentation measurements on all TiO films exhibited a comparably high hardness, Young’s modulus, adhesive strength, compressive stress, and index of refraction.
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Chen, Po-Ju, and 陳柏儒. "Optical and Mechanical Properties of Cast-Dried Polyimide Films." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/45249024775672119745.
Full textAbstract:
博士國立清華大學
化學工程學系
97
The objective of this research is to investigate some physical properties arising during the drying of polyimide film, namely birefringence and curl, both are caused by drying-induced stress. Curl is an out of plane displacement toward coated side or uncoated side at the edges of substrate. In general, coated film tends to shrink during drying and this shrinkage is inhibited by adherence to the substrate, which causes the build-up of a residual tensile stress and forces substrate to curl toward coated side. In microscopic viewpoint, this tensile stress also makes polymeric chains orientation parallel to the coating plane, which result in the difference between the refractive indices parallel and perpendicular to the coating plane, and that is the out-of-plane birefringence (OPBR). In this paper, the drying-stress induced birefringence and curl of soluble polyimide films was experimentally and theoretically investigated. The experimental results of OPBR and curl have been examined, and an operating window which is a region for stable and uniform film formation was also determined experimentally. In order to calculate the drying stress, the mass balance equation, the energy balance equation and the viscoelastic equation have to be solved, and then birefringence and curl can be evaluated by the stress-optical rule and the curling model. A one-dimensional (1D) model and a simple model have been developed to predict the drying stress. All governing equations of the mass balance, the energy balance and the viscoelastics are concluded in the 1D model. The computer aided solutions by the finite element method (FEM) were found. Three assumptions that would lead the simplification of the 1D model to reduce it to a simple model. The first assumption is that at the early stage of drying process, there is no concentration gradient inside the film. The second is that the variation of film thickness is negligible after stress built-up. The third is that after stress built-up, the coating material is a homogeneous viscoelastic material and deforms following a modified Maxwell model consisting of a spring connected to two parallel elements: a dashpot and a stick/slip. Because of the simplified governing equations, the simple model can be solved by the Excel spreadsheet. The predictions of 1D model are in reasonable agreement with experimental results especially for the substrates with high surface energy such as glass, but the model itself is rather complicated. On the other hand, although simple model does not predict the results as accurate as 1D model, it thus provides some physical insight on the formation mechanism of drying stress and is much easier to apply. One just has to be careful with two cases, i.e., rapid drying and large film thickness variation after built-up concentration. On-line experiments were also carried out and the results were compared with the theoretical models, it was found that the theoretical predictions are also reasonably accurate. An operating window which is a region for stable and uniform film formation was also determined experimentally, which also put the limit of drying-controlled OPBR and curl.
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Marcus, Matthew S. "Optical and mechanical properties of single-walled carbon nanotubes." 2004. http://catalog.hathitrust.org/api/volumes/oclc/61503183.html.
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Hu, Ting-ting, and 胡婷婷. "Optical and Mechanical Properties of Thin Film Metallic Glasses." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/03183274141283955525.
Full textAbstract:
碩士國立中山大學
材料與光電科學學系研究所
100
This study is separated into two parts. Firstly, the Ag thin film was deposited on substrates with different average roughness by sputtering to examine the effect of substrate roughness on optical reflection. The results exhibit 10 percent difference of reflectivity within several nanometer changing in average roughness, indicating the reflectivity is easily affected by surface roughness. Secondly, optical reflectivity and electrical resistivity of multi-component AgMgAl alloys, both crystalline and amorphous, were measured. The crystalline alloys exhibit high reflection in infrared region but a steeper drop in visible and ultraviolet regions. By contrast, amorphous alloys show a lower but relatively uniform reflectivity in the visible and infrared regions. In both cases, the reflectivity was observed to scale with the square root of electrical resistivity. The scaling law was explained based on classical reflection theory. The different scaling factors for crystalline and amorphous alloys could be rationalized by the difference in the mean free time of charge carriers. Moreover, the mechanical properties of crystalline and amorphous thin film alloys, including hardness and modulus, were measured by nanoindentation. The hardness of thin film metallic glasses (TFMGs) is obviously higher than crystalline metals, while the modulus of TFMGs is similar to crystalline metals.
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Walavalkar, Sameer Sudhir. "Optical, Mechanical, and Electronic Properties of Etched Silicon Nanopillars." Thesis, 2011. https://thesis.library.caltech.edu/6398/1/WALAVALKAR_S_FINAL_SUBMITTED_THESIS.pdf.
Full textAbstract:
This work focuses on the fabrication, characterization and applications of silicon nanopillars. We explain the techniques involved in creating sub 50 nm diameter pillars with aspect ratios of 60:1. Original work encompassed the use of a novel etch mask made of reactive ion sputtered aluminum oxide, 'pseudo-Bosch' inductively coupled reactive ion etching (ICP-RIE) to etch structures on the nanoscale. These methods demonstrate a unique approach to the largely 'bottom-up' technology used in nanowire fabrication.
We also explored the self-terminating oxidation behavior of convex, two-dimension silicon structures. It was found that during the oxidation process, strain built up at the moving Si-SiO2 interface eventually led to a cessation of oxidation. This was used to predictably reduce the diameter of these pillars to 2 nm, making 'nanowhiskers.' We were able to characterize the results of this oxidation non-destructively by utilizing reflection mode transmission electron microscopy (R-TEM).
Using spun-on PMMA and an electron beam to constrict it and bend the pillars, we were able to incorporate as much as 25% strain. More interestingly this deformation appeared to be elastic, as the pillars, once freed from the polymer, would snap back to their upright position.
A consequence of the creation of silicon nanowhiskers was that silicon, a normally poor light emitter due to its indirect bandgap, became photoluminescent. As we reduced the diameter we noticed that the bandgap became direct and the emission peak was blue-shifted. We were able to utilize a tight-binding model (TBM) that was modified by the oxidation induced strain. This modified model predicted the blue-shift in peak emission wavelength with decreasing pillar diameter. The strain induced in the pillar during the oxidation played a significant role in the peak emission wavelength and shape of the bandstructure. By corrugating the pillars with an oscillating etch technique we were able to turn our nanopillars into quantum dots which also proved to photoluminesce.
Finally we look at the possibilities of creating a silicon light emitting diode. By creating a double-gated structure it is possible to overcome the difficulties encountered with sub 5 nm diameter pillars. A possible fabrication process, and the current work done to implement it, is presented as well as a simulation explaining the behavior of this device in the future.
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Krasnaberski, Aliaksei. "Nonlinear optical properties of modified Bacteriorhodopsins." Doctoral thesis, 2008. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2008020119.
Full textAbstract:
Recent years have shown a dramatic growth of research activity in searching of materials that exhibit nonlinear optical (NLO) behaviours. Later investigations have shown that molecule-based organic materials and biomaterials possess advantages in NLO characteristics. This thesis is devoted to the theoretical and experimental study of the second-order nonlinear optical properties of native and modified bacteriorhodopsins. A hybrid quantum mechanical/molecular mechanical-configuration interaction (QM/MM-CI) method has been used to determine the nonlinear behaviour of modified BR. The calculated structures are the ground state and M1 state of wild type BR, several BR variants, the BR mutants W86F, W189F, W182F, W138C, Y185F, and Y83F as well as a photoreceptor NpSRII. The first hyperpolarizability of two available BR mutants W86F and D85C has been determined by means of the HRS technique. The experimentally determined first hyperpolarizability value for the mutant W86F is in good agreement with that obtained theoretically. Simultaneously with the time-resolved absorption spectroscopy measurements, the time-dependent HRS measurements were performed. Changes in the HRS signal during the photocycle were detected. The kinetics of time-resolved HRS and flash spectroscopy measurements of BR and the BR mutants T46C, R225C, R227C, D96C, and D85C were compared. The obtained kinetic constant are comparable with those determined by means of absorption spectroscopy. However, an unexpected decrease in the HRS intensity during the M to N transition was observed. The program "MultiFit" (written in the Delphi environment) as well as data acquisition software (written in the C environment) can be found online at: http://repositorium.uni-osnabrueck.de/bitstream/urn:nbn:de:gbv:700-2008020119/4/MultiFit.zip and: http://repositorium.uni-osnabrueck.de/bitstream/urn:nbn:de:gbv:700-2008020119/5/TRAS.zip
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Fang, Jin Sheng, and 方金生. "The Study on Mechanical Properties of Polymer-jacketed Optical Fibers." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/51664860387754156761.
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LIN, HONG-YI, and 林宏彝. "Mechanical and optical properties of irradiated lithium fluoride single crystals." Thesis, 1989. http://ndltd.ncl.edu.tw/handle/05363439742132098404.
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