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Trevett, Adrian S. "The mechanical properties of hydrogel polymers." Thesis, Aston University, 1991. http://publications.aston.ac.uk/9692/.
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Chaudhiury, Umme Salma. "Mechanical and chemical properties of rotator cuff tendons." Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.601169.
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Shoulder disease is the third most common musculoskeletal problem, and rotator cuff tendon tears account for the greatest proportion of shoulder complaints. Rotator cuff tears are estimated to affect between 5-30% of adults, with higher incidences of tearing and fa ilure to heal in elderly patients, placing a huge socioeconomic burden on an ageing British population. Serious concern arises as a large proportion of technically correct surgical repairs re-rupture. The intra-articular environment of the tendon often precludes nonnal healing and surgical repair is often necessary to improve pain and restore some function. It is feasible that there may be an inherent phys iological or biomechanical defect in the tissue that prevents complete heal ing without some further augmentation to the surgical repair. Improved understanding of the biochemical and biomechanical changes in tom rotator cuff tendons may help to reduce the high rerupture rates. This study aimed to characterise nonnal, and different sized rotator cuff tendon tears from small samples obtained intraoperatively to try to use tests that may potentially be clinica lly usefu l in the future. Tendon samples were mechanically tested using dynamic shear analysis, a fonn of rheology, to overcome gripping and slippage problems of very small specimens. It was found that tom tendons had a significandy reduced storage modulus compared to normal tendons, particularly for massive tears. Chemical analysis of tendons using Fourier transform infrared spectroscopy revealed that partial and different sized rotator cuff tendon tears are chemically distinguishable. The onset of rotator cuff tear pathology is mainly due to an alteration of the collagen structural arrangements, with associated changes in lipids and carbohydrates. Collagen structural changes in small and massive tendons were quantified us ing differential scanning calorimetry, which allows measurement of coHagen thermal properties as a reflection of their structural integrity. Small and massive tendon tears had reduced thermal properties and hence reduced collagen integrity when compared to normal tendons, although there was no difference between the two tear groups. Gene expression differences between the small, massive tears and normal tendons were studied using microarray analysis, and revealed that the different groups were biologically distinguishable.
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Root, Samuel E. "Mechanical Properties of Semiconducting Polymers." Thesis, University of California, San Diego, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10745535.
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Mechanical softness and deformability underpin most of the advantages offered by semiconducting polymers. A detailed understanding of the mechanical properties of these materials is crucial for the design and manufacturing of robust, thin-film devices such as solar cells, displays, and sensors. The mechanical behavior of polymers is a complex function of many interrelated factors that span multiple scales, ranging from molecular structure, to microstructural morphology, and device geometry. This thesis builds a comprehensive understanding of the thermomechanical properties of polymeric semiconductors through the development and experimental-validation of computational methods for mechanical simulation. A predictive computational methodology is designed and encapsulated into open-sourced software for automating molecular dynamics simulations on modern supercomputing hardware. These simulations are used to explore the role of molecular structure/weight and processing conditions on solid-state morphology and thermomechanical behavior. Experimental characterization is employed to test these predictions—including the development of simple, new techniques for rigorously characterizing thermal transitions and fracture mechanics of thin films.
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Ghorai, Suman. "Chemical, physical and mechanical properties of nanomaterials and its applications." Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/2501.
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The contribution of atmospheric aerosols towards radiative forcing has a very high uncertainty due to their short atmospheric lifetime. The aerosol effects are largely controlled by the density, elemental composition, and hygroscopic properties of the aerosol particles. Therefore, we have performed designed new methodology using Scanning Transmission X-ray Microscopy (STXM), Atomic force spectroscopy (AFM), micro-FTIR spectroscopy and Scanning Electron Microscopy (SEM) to quantify these important aerosol properties. Hygroscopic properties are quantified by plotting the mass of water on a single particle basis, calculated from STXM, as a function of relative humidity. Alternatively, micro-FTIR spectra have been used to study the effect of composition of aerosol particles on the hygroscopic properties of NaCl. Moreover, a unique combination of STXM and AFM has been utilized to quantify density and elemental composition of micrometer dimensional particles. This method has also been extended towards exploring mixing state of particles, consisting of heterogeneously mixed inorganic and organic compounds. In addition to these above mentioned properties, the fate of an atmospheric particle is often altered by chemical transformation and that in turn is influenced by the atmospheric RH. Therefore, we have studied an unusual keto-enol tautomerism in malonic acid particles at high RH, which is not observed in bulk. This observation could potentially be utilized to significantly improve the models to estimate Secondary Organic Aerosols (SOA). Using STXM and micro-FTIR technique, RH dependent equilibrium constant of the tautomerism reaction has been quantified as well.
Organic nanocrystals capable of undergoing solid state photochemical changes in a single-crystal-to-single-crystal (SCSC) manner have been particularly important in fabricating molecular switches, data storage devices etc. Mechanical properties of these nanomaterials may control its SCSC reactivity. In addition, investigation of mechanical stiffness is important to define allowable limit of stiffness towards device application. Therefore, we studied mechanical properties of series organic nano cocrystals primarily consisting of trans-1,2-bis(4-pyridyl)ethylene and substituted resorcinol using AFM nanoindentation technique. Dependence of mechanical properties and SCSC reactivity on the resorcinol structure is also investigated as well. Moreover, photolithography on the thin film of these organic cocrystals has been performed to demonstrate its applicability as a photoresist.
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Stenson, John Douglas. "Investigating the mechanical properties of yeast cells." Thesis, University of Birmingham, 2009. http://etheses.bham.ac.uk//id/eprint/304/.
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To predict cell breakage in bioprocessing it is essential to have an understanding of the cell wall mechanical properties. This project involved a study of the wall mechanical properties of individual Baker’s yeast cells (Saccharomyces cerevisiae) using compression testing by micromanipulation. An analytical model has been developed to describe the compression of a single yeast cell between flat parallel surfaces. Such cells were considered to be thin walled, liquid filled, spheres. Because yeast cells can be compressed at high deformation rates, time dependent effects such as water loss during compression and visco-elasticity of the cell wall could be and were neglected in the model. As in previously published work, a linear elastic constitutive equation was assumed for the material of the cell walls. However, yeast compression to failure requires large deformations, leading to high wall strains, and new model equations appropriate to such high strains were developed. It was shown that the preferred model, based on work-conjugate Kirchhoff stresses and Hencky strains, fitted Baker’s yeast compression data well up to cell failure. This agreement validated the modelling approach, which might also be useful in characterising the material properties of the walls of other cells and microcapsules. Using the analytical model, the effects of compression speed on the elastic modulus obtained by fitting numerical simulations to experimental compression data was investigated. It was found that above a compression speed of approximately 45 µms\(^{-1}\) the estimated elastic modulus was essentially unchanged. By using a compression speed of 68 µms\(^{-1}\) it could be assumed that water loss during compression was negligible. It was then possible to treat the initial stretch ratio and elastic modulus as adjustable parameters within the numerical simulation. In addition to this, as the numerical simulations fitted experimental data well up to the point of cell rupture, it was possible to extract cell wall failure criteria. This study has given mean cell wall properties for late stationary phase Baker’s yeast of: elastic modulus 185 ± 15 MPa, initial stretch ratio 1.039 ± 0.006, circumferential stress at failure 115 ± 5 MPa, circumferential strain at failure of 0.46 ± 0.03, and strain energy per unit volume at failure of 30 ± 3 MPa. Following this, the effect on the intrinsic material properties of treating Baker’s yeast with dithiothreitol (DTT) was investigated. DTT has the effect on Baker’s yeast cells of breaking the disulphide bonds in the cell wall releasing invertase into the suspending solution. It was found that this did not affect the intrinsic material properties or failure criteria. In addition to this, Baker’s yeast cells were mechanically perturbed by sonication and the resulting intrinsic material properties investigated. The surface modulus was found to decrease with increased sonication time while the surface strain energy at failure remained constant. However, it was not possible to determine the extent of damage to each individual cell, preventing explicit conclusions from being reached.
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Wafy, Tamer. "Characterization of chemical and mechanical properties of polymer based nanocomposites." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/characterization-of-chemical-and-mechanical-properties-of-polymer-based-nanocomposites(d04d59b3-492f-4611-8a62-e3132a995d85).html.
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One of the most significant issues in nanocomposite performance is improving the dispersion of carbon nanotubes (CNTs) in thermosetting or thermoplastic polymers in order to gain good mechanical properties. Several studies have investigated the fabrication of nanocomposites based on carbon nanotubes and analysed properties, but there is still insufficient data on their structure-property relationships. This thesis has investigated the central importance of stress transfer Raman studies in epoxy composites reinforced with single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs) and multiwall carbon nanotubes (MWCNTs) to elucidate the reinforcing ability of the CNTs in an epoxy matrix. This project was undertaken to synthesise and characterize MWCNTs and determine the effect of different weight fractions of untreated MWCNTs on the stress transfer efficiency at the MWCNTS / epoxy interface and on the stiffness of the thermomechanical properties of the MWCNTS / epoxy composites. It was undertaken to assess the stress transfer efficiency at the CNT / epoxy interface and at the inter-walls of the CNTs with tensile deformation and with cyclic loading.Optimized conditions of the injection chemical vapour deposition method (CVD), such as long injection times were applied to produce MWCNTs with a high yield, high aspect ratio and well-defined G' Raman peak. The morphology and size of CNTs were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) while their thermal stability was examined by Thermogravimetric analysis (TGA). Both Raman spectroscopy and mechanical testing (static and dynamic) were utilized in this study. The Raman spectroscopy research consisted of following the G'-band frequency and linewidth as well as the intensity of radial breathing modes (RBMs) during tensile deformation. The stress-induced Raman shifts in the nanocomposites have been shown to be controlled by the number of carbon nanolayers. A theory has been developed to determine and simulate the stress transfer efficiency parameter, (k_i) for MWCNTs. Tensile tests and dynamic mechanical testing were used to assess the mechanical properties of the nanocomposites.The most obvious finding to be drawn from the present study is that the reinforcement of the epoxy resin with different loadings of MWCNTs is useful, but the best reinforcement was at low loadings of MWCNTs. One of the more significant findings to emerge from this study is that (k_i) between the inner walls of the DWCNTs and MWCNTs are quite similar (~0.7), which suggest that (k_i) may be similar for all CVD MWCNTs and DWCNTs. The second major finding was that there were RBM intensity variations for the SWCNTs and DWCNTs in the hot-cured epoxy composites and that for the DWCNTs both the inner and outer nanotube walls are stressed during deformation
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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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Allen, Mark George. "Measurement of mechanical properties and adhesion of thin polyimide films." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/15052.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE.
Bibliography: leaves 113-115.
by Mark George Allen.
M.S.
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Ng, Grace Siu-Yee 1980. "Effect of chemical mechanical planarization processing conditions on polyurethane pad properties." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/43618.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2003.Includes bibliographical references (leaves 58-59).
Chemical Mechanical Planarization (CMP) is a vital process used in the semiconductor industry to isolate and connect individual transistors on a chip. However, many of the fundamental mechanisms of the process are yet to be fully understood and defined. The difficulty in analyzing the CMP process lies in the fact that many factors, such as properties of consumables, polishing speed, polishing pressure, etc, can affect the outcome of the CMP process. This paper focuses on the thermal and mechanical properties of one of the consumables - the CMP soft pad. During the CMP process, the pad is subjected to high temperatures and chemicals from the slurry. Thus, the properties of the pad can be irreversibly changed, affecting the planarity of the resultant wafer. In this study, the CMP processing conditions were simulated in the laboratory by annealing the pad at high temperatures and soaking the pad in slurry and DIW for up to two months. The properties of the CMP pad were then measured using four thermo analytical tools - dynamic mechanical analyzer (DMA), thermo-gravimetric analyzer (TGA), thermomechanical analyzer (TMA), and modulated differential scanning calorimeter (MDSC). Results suggested that both annealing at temperatures above 140 °C and soaking in slurry for up to two weeks significantly increase the storage modulus of the sample and promote pad shrinkage in the transverse dimension. Thus, it is not recommended that the soft pad be used at operating temperatures above 140 °C and for polishing times of more than two weeks (336 hrs).
by Grace Siu-Yee Ng.
S.M.
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Dionne, Jean-Philippe. "Chapman-Jouguet properties of heterogeneous explosives." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=24055.
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The role of inert additives in the detonation characteristics of nitromethane-based heterogeneous explosives is investigated. Available experimental data on the detonation velocity are compared with theoretical CJ calculations using two different detonation codes (IDeX and Cheetah). IDeX uses the Theostar equation of state (EOS) for the fluid phase and the Murnaghan EOS for the solid phase while Cheetah uses the JCZ3-EOS for the fluid species and the OLD-EOS for the solid phase.Large deviations are observed for heterogeneous explosives with a large mass fraction of inert material. This is credited to the different relaxation times of the various equilibration processes in the detonation zone, as well as the complex shock interactions between the fluid and solid phases. The equations of state used for the detonation products are found to have only a small effect on the equilibrium CJ state. A more realistic EOS for solids is proposed.
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Pai, Chia-Ling. "Morphology and mechanical properties of electrospun polymeric fibers and their nonwoven fabrics." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/65763.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2011.Cataloged from student submitted PDF version of thesis.
Includes bibliographical references.
Electrospinning is a straight forward method to produce fibers with diameter on the order of a few tens of nanometers to the size approaching commercial fibers (on the order of 10 prm or larger). Recently, the length scale effect on physical properties has attracted great attention because of the potential to produce new materials with unique behavior. In general, the behavior of commercial fibers can be investigated by traditional experiments, and that of nanofibers can be studied by molecular dynamics simulation or Monte Carlo technique. However, the transition of their properties from the bulk to the nanoscale materials is not well understood. Electrospinning provides us a bridge to understand the properties of fibers transiting from the behavior of the bulk material to that of the nanofibers. Among these areas, I am interested in the possible remarkable changes in mechanical properties that may occur in electrospun fibers due to the size effect, where the comprehensive understanding is still lacking. My research objectives are to understand mechanical properties of electrospun polymeric fibers as a function of their size, structure and morphology. The first part of my research is to study internal structures and external topographies of electrospun fibers, and to understand their effect on mechanical properties. Amorphous polystyrene (PS) and semicrystalline polyacrylonitrile (PAN) were dissolved in a high boiling point solvent, dimethylformamide (DMF), for electrospinning. When electrospun in a high-humidity environment, the interior of these fibers was found to be highly porous rather than consolidated, despite the smooth and nonporous appearance of the fiber surfaces. The formation of interior porosity is attributed to the miscibility of water, a nonsolvent for the polymers in solution, with DMF. The resulting morphology is a consequence of the relatively rapid diffusion of water into the jet, leading to a liquid-liquid phase separation that precedes solidification due to evaporation of DMF from the jet. When electrospun in a low humidity environment, the fibers exhibit a wrinkled morphology that can be explained by a buckling instability. Understanding which structures and morphology form under a given set of conditions is achieved through the comparison of three characteristic times: the drying time, the buckling time and the phase separation time. The structures and morphology have important consequences for the properties of the fibers such as their mechanical strength and stiffness.
(cont.) Secondly, we studied the size effects of single electrospun fibers on their stiffness and strength. The Young's modulus and yield strength of individual electrospun fibers of amorphous poly(trimethyl hexamethylene terephthalamide) (PA 6(3)T) have been obtained in uniaxial extension. The Young's modulus is found to exhibit values in excess of the isotropic bulk value, and to increase with decreasing fiber diameter for fibers with diameter less than roughly 500 nm. The yield stress is also found to increase with decreasing fiber diameter. These trends are shown to correlate with increasing molecular level orientation within the fibers with decreasing fiber diameter. Using Ward's aggregate model, the correlation between molecular orientation and fiber modulus can be explained, and reasonable determinations of the elastic constants of the molecular unit are obtained. Finally, we identified a relation of stiffness between single electrospun fibers and their nonwoven fabrics. This is of interest because adequate mechanical integrity of nonwoven fabrics is generally a prerequisite for their practical usage. The Young's modulus of electrospun PA 6(3)T nonwoven fabrics were investigated as a function of the diameter of fibers that constitute the fabric. Two quantitative microstructure-based models that relate the Young's modulus of these fabrics to that of the fibers are considered, one assuming straight fibers and the other allowing for sinuous fibers. This study is particularly important for meshes comprising fibers because of our recent discovery of an enhanced size effect on their Young's modulus as well as the tendency towards a curved fiber topology between fiber junctions. The governing factors that affect the mechanical properties of nonwoven mats are the fiber network, fiber curvature, intrinsic fiber properties, and fiber-fiber junctions. Especially for small fibers, both the intrinsic fiber properties and fiber curvature dominate the mechanical behavior of their nonwoven fabrics. This thesis helps us to understand the mechanism behind the enhanced mechanical behavior of small fibers, and to identify determining parameters that can be used to tailor their mechanical performance.
by Chia-Ling Pai.
Ph.D.
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Allen, Mark George. "Measurement of adhesion and mechanical properties of thin films using microfabricated structures." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14329.
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Kamani, Sandeep Kumar. "Influence of defects on thermal and mechanical properties of metals." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2901.
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Liang, Heyi. "Rational Design of Soft Materials through Chemical Architectures." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1573085345744325.
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Pothula, Ramanarayana Reddy. "Mechanical Properties of Particleboard Composites Made from Sugarcane Bagasse and Spirulina Algae." Thesis, University of Louisiana at Lafayette, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10243742.
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To reduce formaldehyde emissions and prevent deforestation, particle boards prepared from sodium hydroxide modified algae and sugarcane bagasse were used to study the effect of process parameters such as fine-filler ratio, algae-filler ratio, ambient storage times, and sodium hydroxide concentration on mechanical properties. P-test was conducted to test for significance of parameters on flexural modulus and flexural strength. Results showed that algae-filler ratio and ambient storage times have significant impact on mechanical properties, while fine-filler ratio showing significant impact on secant flexural modulus and sodium hydroxide concentration having impact only on tangent flexural modulus. Mechanical properties of particleboard composites made from sugarcane bagasse and spirulina algae were found to be comparable to conventional particle boards.
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Giannakopoulos, Ioannis. "The mechanical properties of polyester-based coil coatings : correlations with chemical structure." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/10011.
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The present work studies the effect of changes in the formulation of coil coatings on their mechanical properties. The paint systems investigated were generally based on polyester binders that were heat-cured with hexa(methoxymethyl)melamine (HMMM). The chemical structure of the polyester, as well as the concentrations of the materials present in the formulations, was systematically changed and the mechanical properties of free-films of the paints were studied at a variety of different temperatures. Changes in the polyester back-bone resulted in significant changes in the glass transition temperature, Tg, of the paints. For example, the substitution of phthalic acid in the polyester, with iso-phthalic acid, resulted in a decrease in Tg from 36 to 8 °C. At the same time, the respective effect on the mechanical properties was modest. On the other hand, changes in cross-link density resulted in dramatic changes in the mechanical properties of the paints. For example, the maximum strain at failure decreased from 180% to 30% when the concentration of the HMMM cross-linker in the paint was increased from about 5 wt% to about 30 wt%. The effects of temperature and loading rate on the mechanical properties of the free-films of the paints were also investigated. Multi-frequency dynamic mechanical analysis (DMA) was used to obtain the correspondence between time and temperature, at low strains, in a quantitative way. This correspondence was extended to large strains, when tensile data under a range of different temperatures and loading rates were considered. Modelling studies were also performed, where a hybrid visco-elastic/hyper-elastic model was used to predict the tensile behaviour of the paints, with good agreement between the predictions and the measured data. Finally, steel panels coated with a selection of the paint systems were tested in bending, using a T-bend test at 0T. An important finding was the increase in the amount of damage in the coating with time after bending, even though the panels were not deformed further. It was generally found that panels coated with paints which showed large values of strain to failure and toughness when tested as free-films, and also with little tendency for elastic recovery, suffered the least amount of damage when tested in bending.
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Atilhan, Selma. "Molecular dynamics simulation of montmorillonite and mechanical and thermodynamic properties calculations." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1263.
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Espert, Ana. "Srategies for improving mechanical properties of polypropylene/cellulose composites." Doctoral thesis, KTH, Fibre and Polymer Technology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-179.
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The interest for polypropylene/cellulose composites has experienced a great increase in different applications such as car interiors and construction materials. Cellulose fibres are inexpensive, renewable, biodegradable, they present lower density and their mechanical properties can be compared to those of inorganic fillers. However, several factors must be considered when designing polypropylene/cellulose composites: the poor compatibility between the hydrophilic fibres and the hydrophobic thermoplastic matrix leads to a weak interface, which has to be improved by coupling agents; the hydrophilic nature of the fibres makes them very sensitive towards water absorption, which also leads to a loss of properties and swelling with subsequent dimensional instability; the reduced thermal stability of cellulose fibres leads to degradation of the fibres at thermoplastic processing temperatures producing odours in the final material; and finally the properties of composites are greatly influenced by the structure, size and quality of the fibres.
Pulp fibres modified by different methods in order to enhance the compatibility fibre-matrix, were tested. Modified fibres led to improved mechanical properties and thermal behaviour when used in composites with recycled polypropylene.
Four different types of natural fibres were used as reinforcement in two different polypropylene types: virgin and recycled polypropylene. The mechanical properties of the composites were mostly dependent on the fibre loading and slightly dependent on the type of fibre. Moreover, water absorption kinetics was studied by the Fickian diffusion theory. After absorption, a remarkable loss of properties was observed.
Hydrolysed cellulose fibres showed a greater enhancing effect on polypropylene than non-hydrolysed cellulose fibres. This is attributed to the greater mechanical properties of reduced cellulose structures.
The effect of using cellulose fibres in PP/clay nanocomposites was also studied. The interaction between the clay particles and the cellulose fibres and the combined effect of both reinforcements were believed to be the main reasons for the enhancing properties.
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Espert, Ana. "Strategies for improving mechanical properties of polypropylene/cellulose composites." Doctoral thesis, Stockholm : Fiber- och polymerteknologi, KTH, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-179.
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Repka, Michael Andrew. "Physical-mechanical and chemical properties of topical films produced by hot-melt extrusion /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Appiah, Kwadwo Ampofo. "Microstructural and microanalytical characterization of laminated (C-SiC) matrix composites fabricated by forced-flow thermal-gradient chemical vapor infiltration (FCVI)." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/14910.
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Kock, Jeffrey Wayne. "Physical and Mechanical Properties of Chicken Feather Materials." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10555.
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Materials derived from chicken feathers could be used advantageously in composite building material applications. Such applications could potentially consume the five billion pounds of feathers produced annually as a by-product of the U.S. poultry industry. To aid the development of successful applications for chicken feather materials (CFM), the physical and mechanical properties of processed CFM have been characterized in this research. Results describing the moisture content, aspect ratio, apparent specific gravity, chemical durability, Youngs modulus, and tensile strength for processed CFM and specifically their fiber and quill components are presented herein. Processed chicken feather fiber and quill samples were found to have similar moisture contents in the range of 16 - 20%. The aspect ratio (i.e., length/diameter) of samples were found to be in the range of 30 - 50, and the fiber material was found to have a larger aspect ratio than the quill material. A comparison with values in the literature suggests that different processing regimes produce CFM with higher aspect ratios. Samples were found to have apparent specific gravities in the range of 0.7 - 1.2, with the fiber material having a higher apparent specific gravity than the quill material. A comparison with values in the literature suggests that apparent specific gravity results vary with fiber length and approach the value for keratin as fiber length decreases and internal voids become increasingly accessible. Chemical durability results showed that CFM rapidly degrade in highly alkaline (pH=12.4) environments and are, thus, likely incompatible with cement-based materials without special treatment. The Youngs modulus of processed chicken feather materials was found to be in the range of 3 - greater than 50 GPa and, thus, comparable to the Youngs moduli of other natural fibers. The tensile strength of oven-dried samples was found to be in the range of 10 - greater than 70 MPa. In agreement with results in the literature, the fiber material was found to have a greater tensile strength than the quill material. Finally, a simplified approach for comparing the effective Youngs moduli and effective tensile strengths of various processed CFM samples was introduced.
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Rohm, Kristen. "Influence of emulsion stability on poly(HIPE) morphology and mechanical properties." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1547463711081874.
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Porras-Parral, Georgina. "The effect of electrical processing on mass transfer and mechanical properties of food materials." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/1496/.
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In this research work, the effect caused by electrical processing on mass transfer in food materials was studied by designing and performing experiments that allowed the visualisation of: the effect of moderate electrical fields (MEF \(\leq\)1000V cm\(^{-1}\)) on mass transfer in cellular materials; the effect of MEF on mass transfer of solutes to polymer networks; and the effect of MEF and pulsed electrical fields (PEF) on mechanical properties of polymer networks. MEF treatment was performed with continuous alternating current (50Hz frequency) at electrical fields up to 1400V m\(^{-1}\) using a jacket system processing cell to maintain constant temperatures. PEF treatment was performed with a pulse generator at Lund University, Sweden. Extraction of betanin from beetroot was monitored online and measured by spectrophotometry. Mass transfer of rhodamine6G into gel networks (alginate, albumin and gelatine) was measured by image analysis. Effective diffusion coefficients (D\(_{eff}\)) for mass transfer of betanin and rhodamine6G were estimated, assuming Fickian diffusion was valid. Mechanical properties of alginate and gellan gum treated with MEF and PEF were studied. Compression force of gel samples was measured with texture analysis. Results showed that the application of MEF and thermal treatment had an enhancing effect on the extraction of betanin from beetroot. The orientation of the beetroot slab also appeared to have an enhancing effect on extraction when the slab was placed perpendicular to the electrical field. The application of MEF had a decreasing effect on mass transfer of rhodamine6G to gel networks set with ions. Mass transfer decreased as electrical field increased. This effect was influenced by electrical conductivities of the gel and rhodamine6G solution. No significant effect of MEF was observed on gelatin or albumin. MEF and PEF had an increasing effect on compression force of polymer networks.
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Aljdaimi, Abtesam. "Effect of Er:YAG laser radiation on the chemical and mechanical properties of mineralised tissues." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/effect-of-eryag-laser-radiation-on-the-chemical-and-mechanical-properties-of-mineralised-tissues(f5ea4fb1-9cdb-44ca-b888-8b30bc547a4f).html.
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Mechanical preparation of teeth using a conventional handpiece has been considered the gold standard in restorative dentistry, for a long time. However, it does not meet all the criteria for the ideal restorative technique. The laser technique has been introduced in dentistry, which has the advantage of a low rise of pulp temperature compared to the traditional handpiece. However, some lasers can cause damage to the pulp particularly if water cooling is not used and inappropriate parameters, such as high energy are chosen. The aim of this research was to investigate the effect of the Er:YAG laser on chemical and mechanical properties of hard tissues. The chemistry of hard tissues following the laser radiation was examined by both Fourier transform infrared spectroscopy and energy dispersive spectroscopy. Morphological changes of the hard tissues were investigated also by both two-dimensional scanning electron microscope and three-dimensional nano-CT. In restorative dentistry, the chemical and mechanical properties of the substrate play a significant role in the bonding process. Roughness of the hard tissues after laser radiation was evaluated by profilometry using both two-dimensional (2D) and three-dimensional (3D) parameters. Nano-CT readings of roughness supported the roughness measurements of the profilometer, in which a significant increase of roughness was reported following the Er: YAG laser radiation. Restorative materials (GC Fuji IX® and Biodentinâ¢) were used to connect two irradiated sections of dentine. The lased GC Fuji IX® showed the highest force required to detach the joined fragments. Shear bond strength testing was also done and showed a significant effect of the Er:YAG laser. The GC Fuji IX® had the highest shear bond strength.
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Yang, Yuehai. "Mechanical and Electrical Properties of Single-walled Carbon Nanotubes Synthesized by Chemical Vapor Deposition." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/946.
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Despite the tremendous application potentials of carbon nanotubes (CNTs) proposed by researchers in the last two decades, efficient experimental techniques and methods are still in need for controllable production of CNTs in large scale, and for conclusive characterizations of their properties in order to apply CNTs in high accuracy engineering. In this dissertation, horizontally well-aligned high quality single-walled carbon nanotubes (SWCNTs) have been successfully synthesized on St-cut quartz substrate by chemical vapor deposition (CVD). Effective radial moduli (Eradial) of these straight SWCNTs have been measured by using well-calibrated tapping mode and contact mode atomic force microscopy (AFM). It was found that the measured Eradial decreased from 57 to 9 GPa as the diameter of the SWCNTs increased from 0.92 to 1.91 nm. The experimental results were consistent with the recently reported theoretical simulation data. The method used in this mechanical property test can be easily applied to measure the mechanical properties of other low-dimension nanostructures, such as nanowires and nanodots. The characterized sample is also an ideal platform for electrochemical tests. The electrochemical activities of redox probes Fe(CN)63-/4-, Ru(NH3)63+, Ru(bpy)32+ and protein cytochrome c have been studied on these pristine thin films by using aligned SWCNTs as working electrodes. A simple and high performance electrochemical sensor was fabricated. Flow sensing capability of the device has been tested for detecting neurotransmitter dopamine at physiological conditions with the presence of Bovine serum albumin. Good sensitivity, fast response, high stability and anti-fouling capability were observed. Therefore, the fabricated sensor showed great potential for sensing applications in complicated solution.
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Girouard, Natalie. "Cellulose nanocrystal thermoset composites: A physical and chemical route to improving dispersion and mechanical properties." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54928.
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Cellulose nanocrystals (CNCs) are crystalline nanoparticles that are extracted from renewable sources such as trees or bacteria through mechanical or chemical treatments of their source. CNCs are of interest to several research communities concerned with sustainable technologies. Specifically, CNCs have attracted great interest in the polymer composite community given their high theoretical specific strength and modulus. Two key obstacles surround the use of CNCs in polymer composites, namely their comparatively lower thermal stability and hydrophilicity render their dispersion, and therefore mechanical reinforcement, in polymer matrices challenging. This research considered a waterborne epoxy and a polyurethane elastomer for CNC/polymer composites since these composites are seldom reported in literature or often suffer from degraded mechanical properties. In the epoxy/CNC composites, samples were prepared by two methods, first an epoxy emulsion was mixed with an amine crosslinker and an aqueous based CNC suspension (1-step mixing), and second, the epoxy emulsion was premixed with the aqueous based CNCs and the amine crosslinker was added some time later (2-step mixing). Both composites were mixed by magnetic stirring, however the samples prepared by the 2-step mixing method exhibited enhanced dispersion and mechanical properties, specifically the storage modulus (E’), tensile strength, and work of fracture. Zeta potential measurements and chemical analysis by FTIR indicated that the dispersion mechanism was physical in nature, rather than chemical. In the second composite system, CNCs were chemically modified with an isophorone diisocyanate (IPDI) monomer having unequally reactive isocyanate groups. The goal of the modification step was to react only one isocyanate group with the CNC surface and have a free isocyanate group available for further modification. The chemical structure of one linked isocyanate (urethane bond) and one free isocyanate was confirmed by FTIR and 13C NMR. The particles modified by IPDI (m-CNC) and the neat particles (um-CNC) were incorporated into a polyurethane matrix based on IPDI and a triol crosslinker. Upon visual inspection of the cured composites, it was clear that the modification step produced homogeneously dispersed nanoparticles in the polyurethane while the um-CNCs were aggregated. When the mechanical properties were tested by uniaxial tensile testing, it was determined that the m-CNC composites resulted in improvements in the tensile strength and work of fracture without degradation of the elongation of break property when compared to the neat matrix. Overall the findings in this research highlight important considerations for designing CNC/thermoset composites with enhanced dispersion and mechanical performance.
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Barber, Jabulani Randall Timothy. "Mechanical compression of coiled carbon nanotubes." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28216.
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Thesis (M. S.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.Committee Chair: Lawrence Bottomley; Committee Member: Aldo Ferri; Committee Member: E. Kent Barefield; Committee Member: Levent Degertekin; Committee Member: Robert Whetten; Committee Member: Satish Kumar; Committee Member: Zhong Lin Wang.
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Drira, Zouheir. "INVESTIGATION OF THE MECHANICAL PROPERTIES OF POLY (ETHYLENE GLYCOL) DIACRYLATE BY NANOINDENTATION USING ATOMIC FORCE MICROSCOPY." VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/31.
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Poly (ethylene glycol) (PEG) hydrogel based polymers are among the most widely used synthetic materials for biomedical applications. Because of their biocompatibility, and ease of fabrication, hydrogels are highly suitable for use as constructs to engineer tissues as well as for cell transplantation. A critical parameter of importance for PEG hydrogels is their mechanical properties which are highly dependent on the environmental conditions. Properties of PEG-based hydrogels can be engineered to resemble scaffolds composed of extracellular matrix molecules, which provide structural support, adhesive sites and mechanical as well as biomechanical signals to most cells. The mechanical properties of these synthetic scaffolds can affect the migration, proliferation and differentiation of the cells. Accordingly, it is important to investigate the mechanical properties of these hydrogels and observe their effect on cell behavior as PEG-based scaffolds for example. In this research, the objective is to measure the mechanical properties such as the elastic modulus (Ec) and the stiffness (S) of polyethylene glycol diacrylate (PEGDA) hydrogel matrices at the nanoscale. The effect of varying parameters in the fabrication of PEGDA hydrogels including monomer molecular weight, initiator concentration and rates of hydration were investigated via nanoindentation using an atomic force microscope (AFM). Two different silicon nitride based cantilevers were used to study the effect of varying loading rates on the mechanical properties of these materials. Indentation parameters such as loads applied and indent depths were varied for each hydrogel sample. Different models were used to fit the experimental data to obtain the parameters of interest for the material (Ec and S). In particular, the data was best described using the model of Oliver-Pharr to analyze and fit the nanoindentation curves. Scanning electron microscope was used to image and confirm the geometry of the tip before and after the indentation experiments. Under high load and displacement modes, the indentation analysis was relatively easy and the elastic modulus and stiffness values were obtained for all dry PEGDA hydrogel sample. The variation of the initiator concentration has been analyzed as well. The mechanical properties of the hydrogel increase as the amount of the initiator increase in the precursor. The degree of hydration dramatically affects the mechanical behavior of the PEGDA. The presence of water within the hydrogel network weakens the internal as well the external mechanical properties, leading to smaller values of elastic modulus and stiffness compared with the dry condition. The mechanical properties of the indenter (cantilever tips) have significant impact on the results. It is important to study carefully the indenter properties before and after the indentation experiments. Since little work has been done on investigating the mechanical properties of PEGDA hydrogels at the nanoscale via AFM, the analysis of the mechanical behavior of this type of hydrogel using this strategy is of great importance.
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Pešek, Jakub. "Studium vlivu metalurgických a technologických parametrů na mechanické vlastnosti slitin hliníku." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-230597.
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Sugested thesis has been made with the intent to observe and describe the length of the modifying effect of three different types of modifiers and their effect on the mechanical properties of aluminium alloy. Next step was to process and evaluate links between mechanical properties and chemical composition. Chemical analysis and mechanical properties of cast samples were obtained. For this purpose and a method of metallographic processing was applied afterwards. The grain size was evaluated before and after the heat treatment. Measurements of the secondary dendrite branches and evaluation of the eutectic morphology were made. The hardness was measured on selected samples.
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Alyaz, Serhat. "Effects Of Heat Treatment And Chemical Composition On Microstructure And Mechanical Properties Of Hadfield Steels." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/2/776526/index.pdf.
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The aim of this thesis is to investigate the effects of Mn content and alloying additions such as Cr and Mo, and various heat treatment procedures on both microstructure and mechanical properties of austenitic manganese (Hadfield) steels. For this purpose, steels with two different Mn content were considered (12-14 Mn, 16-18 Mn). First, five different heat treatment procedures were applied to the as-cast 12-14 Mn specimens to decide the procedure resulting the optimum tensile properties. Then, the specimens having various amounts of Mn, Cr and Mo were cast and heat-treated to investigate the effect of alloy modifications on austenitic manganese steels. Optical and scanning electron microscopies were used for microstructural investigation. To determine the mechanical properties, tensile tests and hardness tests were carried out. In addition to correlation between microstructure and mechanical properties, ultrasonic velocity measurements were also done. The results show that both composition and heat treatment affect the performance of hadfield steels extensively, and these changes also affect the propogation velocity of the ultrasonic waves.
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Tack, Jeremy Lee. "Thermodynamic and mechanical properties of EPON 862 with curing agent DETDA by molecular simulation." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1069.
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Hatami, Mohammad. "Multiscale Analysis of Mechanical and Transport Properties in Shale Gas Reservoirs." Ohio University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1614950615095796.
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Prasad, Ajit. "Influence of processing variables on the mechanical properties of SiC fibers prepared by chemical vapor deposition." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/19651.
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Barlet, Marina. "Evolution of mechanical properties of silicate glasses: Impact of the chemical composition and Effects of irradiation." Palaiseau, Ecole polytechnique, 2014. https://tel.archives-ouvertes.fr/tel-01093014/document.
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Cette thèse vise à caractériser et à comprendre: (1) comment la composition chimique d'un verre change sa dureté, sa résistance à rupture et son comportement en corrosion sous contrainte (SCC), et (2) comment les irradiations affectent à l'échelle structurales ses propriétés. Cette étude s'inscrit dans le contexte du stockage des déchets issus de l'industrie nucléaire, actuellement confinés dans des matrices vitreuses borosilicatés et pour lesquelles il est primordial d'assurer l'intégrité. Nous avons sélectionné ici huit verres modèles simplifiés, contenant uniquement 3 oxydes (SiO2-B2O3-Na2O (SBN) suivant des proportions modulables, et nous en avons caractérisé les duretés, ténacités et comportements en SCC avant et après irradiation. L'étude des huit verres sains SBN permet de déterminer le rôle de la composition chimique sur les propriétés structurales et mécaniques. Nous avons ainsi montré que la teneur en sodium était le paramètre de composition chimique le plus important pilotant le comportement mécanique du verre : au fur et à mesure que celle-ci augmente, la plasticité du verre augmente. Le verre « s'écoule » plus facilement sous sollicitations mécaniques, entraînant une diminution de la dureté et de la ténacité. Au niveau de la corrosion sous contrainte, la présence de sodium induit un phénomène d'écrantage à la pointe de la fissure qui provoque un décalage de la limite de fatigue statique vers des valeurs plus élevées. Quatre verres des huit compositions ont été irradiés pour étudier l'impact d'irradiation élastiques (électroniques)/inélastiques (ioniques) sur la tenue mécanique des verres. Là encore, la teneur en sodium joue un rôle clé en empêchant les évolutions des propriétés mécaniques et du processus de corrosion sous contrainte sous irradiation aux électrons. Les irradiations aux ions légers et lourds ont permis de démontrer que les évolutions structurales et mécaniques sont gouvernées par des processus élastiques qui entraînent à une diminution de la dureté. Enfin il est apparu que les modifications provoquées par les processus inélastiques lors des irradiations aux ions hélium ne sont pas équivalentes à celles engendrées par les irradiations aux électronsThis thesis examines: (1) how the chemical composition changes the hardness, toughness, and stress corrosion cracking behavior in model pristine and (2) how external irradiation impact these properties. It is to be incorporated in the context of the storage of nuclear waste in borosilicate glass matrix, the structural integrity of which should be assessed. Eight simplified borosilicate glasses made of 3 oxides with modulated proportions (SiO2-B2O3-Na2O (SBN) have been selected and their hardness, toughness, and stress corrosion cracking behavior have been characterized prior and after irradiation. The comparative study of the non-irradiated SBN glasses provides the role played by the chemical composition. The sodium content is found to be the key parameter: As it increases, the glass plasticity increases, leading to changes in the mechanical response to strain. Hardness (Hv) and toughness (Kc) decrease since the flow under indenter increases. The analysis of the stress corrosion behavior evidences a clear shift of the SCC curves linked also to the glass plasticity. Four of the 8 simplified SBN glass systems highlight the influence of electron, light and heavy ions irradiations on the mechanical properties. Once again, the sodium content is a key parameter. It is found to inhibit the glass modification: Glasses with high sodium content are more stable. Ions irradiations highlight the predominant role of nuclear interaction in changing the glass properties. Finally, electronic interaction induced by helium and electron irradiation does not lead to the same structural/mechanical glasses variations
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Mayembo, Evrard. "The influence of different chemical treatments on the mechanical properties of hemp fibre-filled polymer composites." Master's thesis, Faculty of Engineering and the Built Environment, 2021. http://hdl.handle.net/11427/33797.
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The fluctuation of engineering and general-purpose polymer prices, rapid exhaustion of fossil fuel world-wide reserves and heightened awareness about environment have led the research community to explore the use of natural biodegradable raw materials as substitutes for manmade resources. Natural fibres are considered as substitutes for synthetic fibres in reinforced polymer matrix composites. Increased interest has been shown in natural fibres from plants such as cotton, jute, hemp as replacements for aramid, glass, and carbon fibres. This is due to their biodegradability, low cost, low density, and satisfactory strength to weight ratio. However, they present certain disadvantages compared to synthetic fibres which include high moisture sorption rates, low durability, and weak fibre/matrix bonding strength. The poor adhesion between natural fibres and polymer matrices leads to poor mechanical properties for natural fibre reinforced composites. Improvement of the fibre/matrix interface is required to increase the mechanical properties of the natural fibre filled polymer composite In this study, the influence of selected chemical treatments on the mechanical properties of hemp-filled epoxy composites was investigated. The aim of this study was to enhance fibre/matrix interface and hence the mechanical properties of hemp yarn-reinforced epoxy composites by modifying the chemical nature of a high crystallinity hemp yarn through chemical treatments such as alkalization, silanization (3-aminopropyltriethoxysilane) and a maleic anhydride treatment. The effectiveness of the chemical treatments was assessed by means of XRD, FTIR and TGA. Density measurements of as-received yarns (1.42-1.45 g cm-3 ) were within the range reported in the literature. Crystallinity measurements revealed the astreated yarns as having high crystallinity indices (87% weft and 84.7 warp yarns). The surface treatments used increased the crystallinity index only slightly. A decision was taken to use warp yarns (UTS = 799 MPa) rather than warp yarns (UTS = 503 MPa). Silane treatment reduced the tensile strength of yarns slightly (753 MPa) while the treatment of the fibres with maleic anhydride (562 MPa) and alkali treatment (518 MPa) had a much more significant effect on ultimate tensile strength. By contrast the modulus of the treated yarns all increased compared to the as-received yarns. Silanization was confirmed by energy dispersive X-ray spectroscopy while maleation was confirmed by the presence of characteristic absorbances in FTIR spectra. TGA revealed that silanization improved fibre thermal stability while maleic anhydride treatment did the opposite, possibly due to decarboxylation reactions. Four type of fibre/matrix interfaces, based on the treated and non-treated fibres, were generated through the production of the hemp reinforced epoxy composite plates. The results showed insignificant variations in the mechanical and thermal properties compare with the as-received hemp-filled epoxy composites which showed the high mechanical properties and thermal stability. The silanization and alkalization slightly decreased the properties of their respective properties although this was deemed statistically insignificant. The maleic anhydride treatment worsened the mechanical properties significantly. Scanning electron microscopy revealed appreciable fibre-matrix debonding which is indicative of a weak fibre/matrix interface. This was postulated as a reason for the lack of any significant reinforcement of the epoxy composites by maleic anhydride treated fibres. The tensile properties were also predicted and no statistically significant differences were observed although the experimental strengths values appeared to be lower than the predicted strengths. In general, the lack of appreciable improvement in mechanical properties of as-received fibres was concluded to be due to the initially high crystallinity of the as-received fibres. This provided little scope for further alkalization to change the surface significantly as little further removal of hemicellulose and lignin could occur.
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Liu, David ShinRen. "Controlling the mechanical and transport properties of layer-by-layer films and electrospun mat composite membranes for fuel cell applications." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91061.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references.
There is an ever increasing need for clean, portable energy devices, such as fuel cells and high energy batteries to replace or reduce the world's dependence on fossil fuels. The continued development of thin-film solid polymer electrolytes with improved mechanical and ion transport properties is critical for the further advancement of such electrochemical energy devices. For hydrogen and methanol fuel cells, the proton exchange membrane (PEM) has to have high protonic conductivity, low fuel crossover, and be mechanically and chemically stable. In particular, for direct methanol fuel cells and for high temperature (>100 °C), low relative humidity (< 60% RH) hydrogen fuel cells, the current industrial standard PEM, Nafion®, does not have all the required attributes. Layer-by-Layer (LbL) assembly allows for the controlled deposition of alternating polyelectrolytes at the nanometer scale. This technique can be used with highly proton conductive water soluble polymers as well as doped polymers. In addition, LbL assembly can be used to coat a variety of substrates of various shapes and sizes. An LbL system composed of poly(diallyl dimethyl ammonium chloride) (PDAC) and sulfonated poly(2,6-dimethyl 1,4- phenylene oxide) (sPPO) has shown to have relatively high proton conductivity and very low methanol permeability compared to that of Nafion@, but lacking in mechanical strength when hydrated and losing significant proton conductivity at lower RH conditions. Herein this thesis work describes the selection, optimization, and utilization of multilayer systems and system composites as the PEM in hydrogen and methanol fuel cells, focusing on improving and understanding the improvements to the properties of layer-by-layer films and composite membranes for fuel cell applications by targeting two main areas: the mechanical properties and the conductive properties. In addition, characterization and film analysis work was done to correlate and explain how the changing of the LbL system and fabrication techniques impacted the membrane's mechanical and conductive properties. First, the mechanical strength and stability were greatly improved by spray-assembling the films on an electrospun fiber mat to form a composite membrane. Spray-LbL assembly was performed both with and without vacuum assistance, which had complementary effects on the film properties. By combining these techniques, composite membranes with methanol permeability twenty times lower than Nafion® and through-plane proton selectivity five times greater than Nafion@ were fabricated. In addition, the planar swelling of the composite membranes in water was significantly reduced. This large reduction in swelling is hypothesized to be due to the electrostatic interaction of the LbL system with the underlying electrospun fibers and would not occur in a typical polymer blend. Second, to improve the conductivity of the LbL films overall and specifically at lower RH conditions, two approaches were used. In the first approach, divalent salts were added to the polyanion solution to provide a stronger shielding effect than monovalent salts. The divalent salts allowed for ion bridging and increased both the number and the mobility of protons associated with sulfonic acid groups in the LbL film; thus increasing the film's conductivity. Through optimization of salt type and concentration, the protonic conductivity of PDAC/sPPO films was increased fourfold, and the humidity dependence of the conductivity was decreased. In the second approach, PDAC was replaced with a phosphoric-acid-doped polymer, poly(2- vinyl pyridine) (P2VP). The phosphoric acid concentration in the LbL film and the number of free sulfonic acid groups could be controlled post film fabrication by changing the concentration of the phosphoric acid dopant. The resulting P2VP/sPPO films exhibited greater conductivity than similarly doped P2VP films and under stronger doping conditions (0.4 M - 1.0 M phosphoric acid), the film's conductivity increases seventy-fivefold (110 mS/cm at 50% RH at room temperature), resulting in a conductivity an order of magnitude greater than Nafion®. The large increases in conductivity, particularly at low RH conditions further support a recently reported and very promising proton transport mechanism that utilizes both phosphoric and sulfonic acid groups.
by David ShinRen Liu.
Ph. D.
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MENEGAZZO, ANA P. M. "Estudo da correlacao entre a microestrutura e as propriedades finais de revestimentos ceramicos do tipo gres porcelanato." reponame:Repositório Institucional do IPEN, 2001. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10892.
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Made available in DSpace on 2014-10-09T12:45:12Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T13:56:41Z (GMT). No. of bitstreams: 1 07615.pdf: 17881305 bytes, checksum: 574c726c857d80d9656ccf2bb1707b8a (MD5)
Tese (Doutoramenro)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Sethi, J. (Jatin). "Cellulose nanopapers with improved preparation time, mechanical properties, and water resistance." Doctoral thesis, Oulun yliopisto, 2018. http://urn.fi/urn:isbn:9789526221540.
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Abstracts Cellulose nanopapers are the strongest polymeric material known to us, and in the near future, they are likely to be a backbone of numerous functional materials. Cellulose nanopapers have gained much attention due to qualities such as their environmentally friendly nature, renewable raw material source and biodegradability. Additionally, they offer an industrially adaptable, water-based processing route, which is similar to current paper production. Functionally, besides being tougher than any known plastic, cellulose nanopapers remain foldable like a paper. Despite their fascinating properties, cellulose nanopapers are still far from commercialisation – mainly due to two obstacles. Firstly, it can take up to hours to prepare a nanopaper due to poor draining of cellulosic nanofibres. Secondly, cellulose nanopapers have extremely poor water and humidity resistance, as up to 90% of their stiffness is lost in the presence of water. The purpose of this dissertation is to address both obstacles and suggest an eco-friendly yet industrially relevant solution. Two approaches are employed: increasing the hydrophobicity of cellulose nanofibres with lactic acid and ultrasonication (Paper I and II), and combining cellulose nanofibres with hydrophobic materials, such as polyurethane (Paper III) and lignin-rich entities (Paper IV). By using these methods, the preparation time was improved by 75% (Paper II) and by 70% (Paper IV) respectively. All reported nanopapers were significantly more tolerant of water and moisture than the reference nanopaper. The mechanical properties were also improved in Paper I and IV. Additionally, all reported nanopapers were thermally stable. This thesis also discusses the importance of quick draining in cellulose nanofibre-reinforced paper products. The results of this study are likely to aid the commercialisation of cellulose nanopapers in practical applications and the use of cellulose nanofibres in other materials, such as reinforcing paperboards. All methods used in this thesis are water-basedTiivistelmä Selluloosapohjaiset nanopaperit ovat lujimpia tunnettuja polymeerimateriaaleja ja lähitulevaisuudessa niiden voidaan odottaa luovan perustan useille funktionaalisille materiaaleille. Nanopaperit ovat saaneet paljon huomiota ympäristöystävällisyytensä, uusiutuvan raaka-aineensa ja biohajoavuutensa ansiosta. Lisäksi niiden valmistusprosessi on vesipohjainen ja samankaltainen kuin tavallisen paperin valmistukseen käytetty teollinen prosessi. Käyttöominaisuuksiltaan ne ovat erinomaisia, sillä vaikka niiden sitkeys on parempi kuin tunnetuilla muoveilla, ovat ne silti paperin tavoin taiteltavia. Kiehtovista ominaisuuksistaan huolimatta selluloosapohjaiset nanopaperit ovat kuitenkin vielä kaukana kaupallistamisesta ja tähän vaikuttavat pääosin kaksi tekijää. Tärkein syy on selluloosananokuitujen kuivattamisen ja näin ollen nanopaperin muodostamisen vaatima huomattavan pitkä aika. Nykyisillä menetelmillä nanopaperin valmistaminen kestää useita tunteja. Toinen syy on niiden erittäin huono veden- ja kosteudenkestävyys. Ne menettävät jopa 90 % jäykkyydestään veden vaikutuksesta, mikä rajoittaa niiden käyttöä kosteissa ja vesiroiskeille alttiissa kohteissa. Tämän väitöskirjatutkimuksen päätavoitteena on löytää ekologisesti kestävä ja teollisuudessa hyödynnettävissä oleva menetelmä molempien edellä mainittujen ongelmien ratkaisemiseksi. Työssä noudatetaan kahta eri lähestymistapaa: lisätään selluloosananokuitujen hydrofobisuutta maitohapon ja ultrasonikoinnin avulla (Artikkelit I ja II), ja yhdistetään selluloosananokuituihin hydrofobisia materiaaleja, kuten polyuretaania (PU) (Artikkeli III) ja ligniinipitoisia yhdisteitä (Artikkeli IV). Näitä menetelmiä käyttämällä valmistusaikaa saatiin lyhennettyä 75 % (Artikkeli II) ja 70 % (Artikkeli IV). Kaikki valmistetut nanopaperit olivat huomattavasti veden- ja kosteudenkestävämpiä kuin verrokkinäytteet sekä osoittivat lämpöstabiiliutta. Lisäksi mekaanisia ominaisuuksia saatiin parannettua Artikkeleissa I ja IV. Tässä työssä käsitellään myös nopean kuivattamisen tärkeyttä selluloosananokuitulujitteisten paperituotteiden valmistuksessa. Saadut tulokset todennäköisesti edistävät selluloosapohjaisten nanopaperien kaupallistamista ja selluloosananokuitujen hyödyntämistä esimerkiksi kartongin lujitemateriaalina. Kaikki työssä käytetyt menetelmät ovat vesipohjaisia
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Liu, Dongmin. "The Effects of Dietary Lipids on Bone Chemical, Mechanical and Histological Properties in Japanese Quail (Coturnix C. Japonica)." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/28149.
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Japanese quail were used as animal models in four experiments to evaluate the effects of supplementing diets with different lipids on bone chemical, mechanical, and histological properties. In Exp. 1, laying hens were fed a basal diet containing either 5% soybean oil (SBO), hydrogenated soybean oil (HSBO), chicken fat (CF), or menhaden fish oil (FO). The addition of SBO in the maternal diet increased the levels of total n-6 fatty acids and arachidonic acid (AA, 20:4n-6) in yolk and tibial bones of newly hatched progeny (P<0.01), whereas the maternal FO diet elevated the concentrations of total n-3 fatty acids, eicosapentaenoic acid (EPA, 22:5n-3), docosahexaenoic acid (DHA, 22:6n-3) and total saturated acid, but greatly decreased the amount of AA in both egg and progeny tibiae (P<0.01). The maternal HSBO diet resulted in the accumulation of trans-18:1 fatty acid in egg yolks and tibiae at hatch. The addition of FO or HSBO to the maternal diet significantly lowered the ex vivo PGE2 production of tibiae in newly hatched quail compared to those from hens given the SBO or CF diets (P<0.01). In Exp. 2, the addition of different lipids in the maternal diets did not affect growth, tibial length, diameter or collagen content of the progeny. However, supplementing the maternal diet with 5 % FO or HSBO increased the percent bone ash , increased bone pyridinium crosslinks of collagen, enlarged the cartilaginous proliferative and hypertrophied zones, increased diaphyseal cortical thickness of the tibiae in embryos (P<0.05), and subsequently increased tibial shear force, stiffness (P<0.05) and improved cortical thickness, density and trabecular density in early growth and development of progeny compared to those from hens consuming the SBO or CF diets (P<0.05). In Exp. 3, male quail at one month of age were fed a basal diet containing either 5% SBO, HSBO, CF or FO for seven months. Long-term supplementation in the diets of different lipids did not affect body weight, food intake, tibial length or diameter, but the FO group had the highest tibial percent ash, and both FO and HSBO increased tibial mineral content in aged quail compared to those fed the SBO or CF diets (P<0.05). At 8 months of age, quail fed FO had the highest concentrations of (n-3) fatty acids (20:5n-3, 22:5n-3, 22:6n-3) but the lowest amounts of 20:4n-6 in lipids from tibial cortical bone, whereas the SBO and CF diets greatly elevated (n-6) fatty acids and 20:4n-6 levels. The HSBO diet which contains t18:1 fatty acid resulted in t18:1 accumulation in bone. Long-term supplementation with FO or HSBO increased tibial shear force, stiffness and shear stress, as well as improved cortical thickness and density compared with the SBO or CF diets
( P<.05). In Exp. 4, the addition of SBO or CF to the diet for seven months decreased tibial mineral content compared to the FO diet (P<0.05). Quail fed SBO increased collagen concentration in the tibiae (P<0.05), but the level of collagen crosslinks was higher in quail fed FO or HSBO compared to those given the SBO or CF diets (P<0.05). The PGE2 production in bone organ culture and marrow was greatly increased in quail maintained on the SBO or CF diets (P<0.05). PGE2 production in the bone microenvironment was negatively correlated with the tibial percent ash and collagen crosslinks but had a positive correlation with tibial collagen concentration. The results of these studies demonstrate that either supplementing the maternal diets with or long-term exposure to different lipids alters the chemical composition and metabolism of skeletal tissue in both embryos and aged quail. Maternal dietary SBO or CF had an adverse effect on bone growth and development in embryos. Likewise, long-term exposure to SBO or CF diet impaired bone metabolism and remodeling. In contrast, the FO or HSBO diet had beneficial effects on bone modeling in embryos and remodeling in adult quail.Ph. D.
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Kop, Erhan. "Synthesis And Characterization Of Mechanical, Thermal And Flammability Properties Of Epoxy Based Nanocomposites." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609124/index.pdf.
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Polymer-clay nanocomposites have received a lot of attention because of outstanding improvements in properties when compared with neat polymeric materials. The aim of this study was to prepare epoxy-clay nanocomposites by mixing organically modified montmorillonite with an epoxy resin and to investigate the effects of clay content on the mechanical, thermal and flammability properties of the resultant nanocomposites. The production of the epoxy-clay nanocomposites was accomplished by in-situ polymerization. In the nanocomposite synthesis, organically modified clay content was varied from 1 wt.% to 9 wt.%. Araldite LY556 epoxy resin, Aradur 918 anhydride hardener, and DY070 imidazole type accelerator were used in the epoxy system. Closite 30B, an organoclay modified with methyl, tallow, bis-2-hydroxyethyl, quaternary ammonium chloride (MT2EtOH), was used as the clay material.
X-ray diffraction results showed that d-spacing between the platelets of organoclay increased from 1.80 nm to 4.4 nm. The microstructures of nanocomposites were investigated by scanning electron microscopy (SEM). The SEM micrographs indicated that at 1 wt.% clay loading, no clay aggregates were observed. On the other hand, beyond 1 wt.% clay loading, formation of clay agglomerations was observed. Tensile strength and tensile strain values of nanocomposites decreased with clay loading. The tensile strength value of neat epoxy resin decreased from 55 MPa to 29 MPa with 9 % clay loading. On the other hand, Young’
s modulus increased with clay content and a maximum value was obtained at 5 wt. % clay loading. At 9 % clay loading, Young&
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s modulus value was 26 % higher than that of the neat epoxy resin. Impact strength property had a minimum value at 7 wt. % clay content. Flexural strength and flexural strain at break property behaved in a similar trend. They had a minimum value at 5 % clay loading. At this clay loading, flexural strength value became approximately 43 % lower compared to the flexural strength of the neat epoxy resin. On the other hand, at 9 wt.% clay loading flexural modulus value increased approximately 48 % compared to the pure epoxy resin. Up to 7 wt.% clay ratio, initial decomposition temperature of epoxy resin was slightly improved. Also, according to TGA results, amount of char formation increased with clay loading. DSC results indicate that Tg of the cured nanocomposite resins decreased from 147 oC to 129 oC with 9 wt. % clay loading. The flammability of neat epoxy resin was not significantly affected with Cloisite 30B addition.
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Osborn, Shawn James. "Morphological and Mechanical Properties of Dispersion-Cast and Extruded Nafion Membranes Subjected to Thermal and Chemical Treatments." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/37517.
Full textAbstract:
The focus of this research project was to investigate morphological and mechanical properties of both extruded and dispersion-cast Nafion® membranes. The project can be divided into three primary objectives; obtaining a fundamental understanding of the glass transition temperature of Nafion®, determining the effect of thermal annealing treatments on the morphology and mechanical properties of dispersion-cast Nafion®, and examination of dispersion-cast Nafion® subjected to an ex-situ, Fentonâ s chemical degradation test. Nafion®, a perfluorosulfonate ionomer, is considered a commercially successful semi-crystalline ionomer with primary applications in chlor-alkali cells and proton exchange membrane fuel cells.
With the aid of dynamic mechanical analysis (DMA) and dielectric spectroscopy (DS), we were able to provide definitive evidence for a genuine glass transition in Nafion®. DMA of Nafion® samples that were partially neutralized with tetrabutylammonium counterions showed a strong compositional dependence suggesting that the β-relaxations of H+-form Nafion® and the neutralized ionomers have the same molecular origin with respect to backbone segmental motions. Building upon our previous studies of the molecular and morphological origins of the dynamic mechanical relaxations of Nafion® neutralized with a series of organic ions, the glass transition temperature of H+-form Nafion® is now confirmed to be the weak β-relaxation centered at -20 °C. Dielectric spectra also showed this transition from the perspective of dipole relaxation. The signature of cooperative long range segmental motions in dielectric spectra was seen here, as with other polymers, mainly through the excellent agreement of the β-relaxation time-temperature dependence with the Vogel-Fulcher-Tammann equation.
We have also discovered that new dispersion-cast H+ form Nafion® membranes are susceptible to disintegration/dissolution when subjected to boiling methanol. In this work, we have achieved significant decreases in the percent solubility of H+-form Nafion® by either thermally annealing above 175 °C or solution-processing at 180 °C using a high boiling point solvent. Small Angle X ray Scattering (SAXS) displayed a change in the morphology of H+ form membranes with increasing annealing temperature by a shift in the crystalline scattering peak (q â 0.05 à 1) to lower q values. Counterion exchange of Nafion® from H+ to Na+ form had no influence on the membraneâ s susceptibility to disintegration in boiling methanol. In order to achieve mechanical stability in boiling methanol, Na+ form membranes had to be annealed at 275 °C for at least fifteen minutes. The SAXS data of annealed Na+ form membranes showed a dramatic decrease in crystalline order with annealing temperature, ultimately leading to the disappearance of the crystalline scattering peak after fifteen minutes at 275 °C. The onset of methanol stability with the melting of Nafion® crystallites suggests that chain entanglement is an important parameter in obtaining solvent stability.
With respect to chemical stability, we performed studies aimed at examining the effects of Fentonâ s Reagent on the resistance to radical attack of new generation, dispersion-cast Nafion®. Changes in the 19F solid-state NMR spectra of dispersion-cast Nafion® before and after chemical degradation via Fentonâ s Reagent predicts a rather random attack by â ¢OH and â ¢OOH radicals. Several membranes were also thermally annealed between 100-250 °C in an attempt to correlate crystallinity with chemical degradation kinetics of Nafion® via Fentonâ s Reagent. The results indicate that the effect of counterion exchange into the Na+ form was minimal, but the degree of thermal degradation had a tremendous effect on the fluoride release rate and chemical degradation kinetics. By exchanging the membranes into the Na+ form, thermal degradation was avoided, allowing us to study the role of crystallinity as a function of fluoride release. Ultimately, Nafion® crystallinity was deemed an important factor in deterring peroxide radical attack. As the percent crystallinity decreased with annealing temperature, the fluoride concentration in the resulting Fentonâ s media increased accordingly, indicating that the amorphous regions of the polymer are more susceptible to chemical degradation via peroxide radical attack.Ph. D.
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Gong, Yiwen. "Toward Better Understandings of Unconventional Reservoirs - Rock Mechanical Properties and Hydraulic Fracture Perspectives." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1605633687308252.
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Liao, Huimin. "The impact of mechanical properties of poly(ethylene glycol) hydrogels on vocal fold fibroblasts' behavior." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1266.
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Li, Xiaoyan 1963. "Coagulation between fractal aggregates and small particles and fractal properties of marine particles." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/282174.
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This dissertation includes two parts (designated A and B) that serve two separate but related research purposes. In Part A, coagulation rates between fractal aggregates (200-1000 μm) and small (1.48 μm) particles were studied for collisions induced by differential sedimentation and turbulent fluid shear. The collision frequency functions (beta) between these aggregates and small particles were found to be lower than predicted by a rectilinear collision model but much higher than predicted by a curvilinear collision model for equivalent impermeable spheres. The collision frequencies decreased with the magnitude of aggregate fractal dimensions (D). Based on fractal geometry of aggregates and the comparisons between observed settling velocities and those calculated using Stokes' law, a semi-empirical correlation was derived to describe the permeabilities of settling fractal aggregates. A filtration model was used in conjunction with this fractal permeability correlation to predict capture rates and capture efficiencies of small particles by settling fractal aggregates. In the turbulently sheared fluid, it was demonstrated that the importance of the shear rate (G) on enhancing collision frequencies was dependent on the fractal dimension of aggregates. As D approaches 3, beta became less sensitive to G as predicted by a curvilinear model. It was argued that flow through large pores formed between clusters within fractal aggregates contributed to high aggregate permeabilities and enhanced the coagulation between the aggregates and suspended small particles. In part B, fractal properties of microscopic particles (300 μm) occurring in marine systems were investigated. A new method, called the particle concentration technique (PCT), was developed to calculate the average fractal dimension of all particles in a certain size range by the analysis of particle size distributions in terms of both solid volume and length. During a simulated algae bloom in a mesocosm, as coagulation proceeded the average fractal dimension decreased with time from D = 2.52 to D = 1.68, a value typical of larger marine snow aggregates. Investigations in three eastern Pacific coastal areas suggested that the average fractal dimension indicated the importance of coagulation in determining local particle size distributions. The magnitude of the fractal dimension is likely associated with other factors, such as transparent exopolymer particles (TEP), affecting the coagulation rate of algae during a bloom in seawater.
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Worthington, Kristan Sorenson. "Control of polymer biochemical, mechanical, and physical properties for the rational design of retinal regenerative tissue scaffolds." Diss., University of Iowa, 2014. https://ir.uiowa.edu/etd/2023.
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Although millions of individuals worldwide are affected by blinding retinal degenerative diseases, most have very few options for treatment and no hope for vision restoration. Induced pluripotent stem cell (iPSC) replacement therapies represent a promising treatment option, but their effectiveness is limited by an overall lack of physical support for injected cells. Stem cell scaffolds can be used to provide this support by serving as an attachment platform for cells before, during, and after implantation. Thus, the design of polymer scaffolds with appropriate biochemistry, mechanical properties, and morphology is a critical step toward developing feasible stem cell therapies for blinding eye diseases. In this work, we aim to design a regenerative scaffold for the retina and determine the interplay among these three key design parameters. First, the feasibility of using a synthetic scaffold to grow and differentiate iPSCs to neural progenitor cells is demonstrated. The porous and degradable poly(lactic-co-glycolic acid) scaffolds employed were able to support a greater density of differentiating iPSCS than traditional tissue culture plastic. Additionally, the power of chitosan, a naturally occurring polymer, to overcome the toxic effects of copper nanoparticles is described. For two different cell types, various doses, and several time points, chitosan coated copper nanoparticles were significantly less toxic than non-coated particles. The mechanical properties of the human retina and the effects of aging and disease were also estimated using measurements of compressive modulus in animal models. In order to reach a range similar to native tissue, polymer mechanical properties were controlled using cross-linking density and surfactant templating. The influence of morphology was studied by inducing polymer structure changes via surfactant templating. Morphology significantly influenced water uptake and compressive modulus for both cross-linked poly(ethylene glycol) (PEG) and cross-linked chitosan hydrogels. Surfactant templating did not negatively affect the biocompatibility of PEG hydrogels and slightly improved the ability of chitosan hydrogels to support the growth and differentiation of iPSCs. Overall we have demonstrated the ability to tune polymer structure, mechanical properties, and biochemistry. These results add to the growing body of research aimed to understand and control cell/material interactions for biomaterial optimization.
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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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Bajwa, Tariq Mahmood. "Experimental Characterization of the Thermal, Hydraulic and Mechanical (THM) Properties of Compost Based Landfill Covers." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/20518.
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Landfills are considered to be one of the major sources of anthropogenic methane (CH4) emissions in the environment. A landfill biocover system optimizes environmental conditions for biotic CH4 consumption that controls the fugitive and residual emissions from landfills. A compost material has more oxidation potential in comparison to any other material due to its high porosity, organic content, free flux for gases and water holding capacity. Thermal, hydraulic, bio – chemical and mechanical (THMCB) properties are important factors that can significantly affect the performance of biocover material with regards to CH4 oxidation potential as well as structural stability. Technical data on the thermal, hydraulic and mechanical (THM) properties of compost based biocover materials are quite limited. Hence, a detailed experimental program has been carried out at the University of Ottawa to study the THM properties and behaviour of compost biocover material by conducting experimental tests on small compost samples as well as by performing column experiments.
The test results indicate that lower water content (dry of optimum for compaction curve) shows more free air space (FAS) in comparison to higher water content. The compost has almost the same shear strength for various initial water contents and dry unit weights; however, it settles and swells more at higher water content than lower water content per mechanical test results. The thermal and hydraulic properties of compost are a function of the compaction degree in addition to various other parameters. It is also found that the THM properties of compost are strongly coupled and the degree of saturation greatly affects the FAS.
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Karaj, Shkelqim [Verfasser]. "Characterization of physico-chemical properties of Jatropha curcas L. and optimization of mechanical oil extraction and sedimentation / Shkelqim Karaj." Aachen : Shaker, 2014. http://d-nb.info/1049380452/34.
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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.