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Title: Molecular dynamics simulation of single-walled carbon nanotubes.
Creator: Cornwell, Charles F., Florida Atlantic University, Wille, Luc T.
Abstract/Description: Classical trajectory molecular dynamics methods are used to investigate open ended free standing single wall carbon nanotubes ("SWT"). Total energy calculations performed using classical three-body interatomic potentials with periodic boundary conditions along the tube axis, showed that the minimum strain energy varied as 1/$R\sp2$ relative to an unstrained graphite sheet. We discuss the development of a parallel code to simulate short-ranged empirical potentials such as those of Stillinger...
Show moreClassical trajectory molecular dynamics methods are used to investigate open ended free standing single wall carbon nanotubes ("SWT"). Total energy calculations performed using classical three-body interatomic potentials with periodic boundary conditions along the tube axis, showed that the minimum strain energy varied as 1/$R\sp2$ relative to an unstrained graphite sheet. We discuss the development of a parallel code to simulate short-ranged empirical potentials such as those of Stillinger and Weber, Tersoff, and Tersoff-Brenner. We then use the Tersoff and Tersoff-Brenner potentials to examine SWT and the tube response to axial stretching and compression. Data collected are used to calculate Young's modulus for the tubes and to develop a simple formula that approximates Young's modulus over a range of tube radii. The investigation of the free standing SWT leads to a suggestion for the possible mechanism responsible for holding the tubes open during the growth process.
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Date Issued: 1996
PURL: http://purl.flvc.org/fcla/dt/15269
Subject Headings: Carbon, Nanostructured materials, Simulation methods
Format: Document (PDF)

Title: Anisotropic physical properties of SC-15 epoxy reinforced with magnetic nanofillers under uniform magnetic field.
Creator: Malkina, Olga, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: SC-15 epoxy is used in many industrial applications and it is well known that the mechanical and viscoelastic properties of epoxy can be signicantly enhanced when reinforced with nanofillers. In this work, SC-15 epoxy is reinforced by loading with magnetically-active nanofillers and cured in a modest magnetic field. Because of the signicant magnetic response of the nanofillers, this is a low cost and relatively easy technique for imposing a strong magnetic anisotropy to the system without the...
Show moreSC-15 epoxy is used in many industrial applications and it is well known that the mechanical and viscoelastic properties of epoxy can be signicantly enhanced when reinforced with nanofillers. In this work, SC-15 epoxy is reinforced by loading with magnetically-active nanofillers and cured in a modest magnetic field. Because of the signicant magnetic response of the nanofillers, this is a low cost and relatively easy technique for imposing a strong magnetic anisotropy to the system without the need of a superconducting magnet. It is also found that this method is an effective way of enhancing the mechanical properties of epoxy. Three systems were prepared and studied. The first is a dilute system of various concentrations of Fe2O3 nanoparticles in SC-15 epoxy. The second system is a combination of Fe2O3 nanoparticles and chemically-functionalized single-walled carbon nanotubes (SWCNT(COOH)s) in SC-15 epoxy. The third is a dilute system of SWCNT(COOH)s decorated with Fe3O4 particles t hrough a sonochemical oxidation process in SC-15 epoxy. Samples have an initial cure of 6 hrs in a magnetic led of 10 kOe followed by an additional 24 hours of post curing at room temperature. These are compared to the control samples that do not have initial field curing. Tensile and compressive stress-strain analysis of the prepared systems shows that mechanical properties such as tensile strength, tensile modulus and compressive strength are enhanced with the inclusion of these nanofillers. It is also found that there is an anisotropic enhancement of these properties with respect to the imposed curing field. An interesting phenomenon is observed with the increase in modulus of toughness and fracture strain with nanotube inclusion., These parameters are drastically enhanced after curing the systems in a magnetic field. While there is a modest shift in glass transition temperature during viscoelastic analysis, the thermal stability of the created systems is not compromised. Results of these mechanical enhancements will be compared with other nanoloading techniques from literature.
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Date Issued: 2011
PURL: http://purl.flvc.org/FAU/3332722
Subject Headings: Nanostructured materials, Epoxy resins, Composite materials, Design
Format: Document (PDF)

Title: Effect of Processing Temperature on the Properties of Nanophase Fe-substituted Hydroxypatite.
Creator: Kathriarachchi, Vindu, Leventouri, Theodora, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: The effect of processing temperature on the crystal structure properties of the Fe-substituted Hydroxyapatite (Fe-HAp) was studied by using the Rietveld refinement method of powder x-ray (XRD) and neutron diffraction (NPD) patterns. Superconducting QUantum Interference Device (SQUID) magnetometry, transmission electron microscopy (TEM) and x-ray fluorescence spectroscopy (XRF) were used to study the magnetic properties, particle morphology and chemical composition of the prepared samples. Two...
Show moreThe effect of processing temperature on the crystal structure properties of the Fe-substituted Hydroxyapatite (Fe-HAp) was studied by using the Rietveld refinement method of powder x-ray (XRD) and neutron diffraction (NPD) patterns. Superconducting QUantum Interference Device (SQUID) magnetometry, transmission electron microscopy (TEM) and x-ray fluorescence spectroscopy (XRF) were used to study the magnetic properties, particle morphology and chemical composition of the prepared samples. Two sets of samples of chemical formula Ca5-xFex(PO4)3OH were prepared with x = 0, 0.05, 0.1, 0.2 and 0.3 by using processing temperatures of 37°C and 80°C, following a two-step co-precipitation method. A single phase HAp was identified in samples with x = 0 and 0.05. Processing temperature affects the type and percentage of secondary phases: hematite was detected in samples prepared at 37°C with x ≥ 0.1, hematite and maghemite were detected in samples prepared at 80°C with x = 0.2 and 0.3. Rietveld refinements of NPD and XRD patterns showed that the a lattice constants are greater in Fe-substituted samples prepared at 37°C, whereas the c lattice constants are greater in the 80°C samples for x ≥ 0.05. Fe preferentially substitutes at the Ca2 site in the 80°C samples, whereas Ca1 is the preferred substitution site in the 37°C samples. Fe substitution results to a decrease of the lattice constants at both preparation temperatures. The ratios Fe/(Fe + Ca) of the refined atomic fractions of the samples prepared at 80°C are greater than those of the 37°C samples. Further, more secondary phases form in samples prepared at 37°C compared to 80°C samples. The magnetic measurements reveal that pure HAp is diamagnetic, whereas samples with x = 0.05 and 0.1 are paramagnetic. Samples with x = 0.3 showed superparamagnetic behavior based on ZFC and FC measurements. Similar hysteresis loops in samples x = 0.2 and 0.3 indicate that the samples with x = 0.2 may show superparamagnetic properties. For x = 0.2 and 0.3, the samples prepared at 80°C showed higher magnetization compared to the 37°C samples, because of the maghemite secondary phase. Based on the TEM images, Fe substituted HAp nanoparticles prepared at 37°C are mainly spherically shaped, and the 80°C particles are mainly elongated. Increase of the Fe concentration favors formation of elongated particles and larger spherical particles. The XRF measurements confirm the Fe for Ca substitution in the HAp structure based on the decrease of the Ca/P and the increase of the Fe/(Fe + Ca) atomic ratios with the Fe concentration.
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Date Issued: 2015
PURL: http://purl.flvc.org/fau/fd/FA00004512, http://purl.flvc.org/fau/fd/FA00004512
Subject Headings: Biomedical materials, Nanostructured materials -- Environmental aspects, Nanostructured materials -- Mechanical properties, Pharmaceutical biotechnology, Rietveld method
Format: Document (PDF)

Title: Nanotechology in concrete: review and statistical analysis.
Creator: Glenn, Jonathan., College of Engineering and Computer Science, Department of Civil, Environmental and Geomatics Engineering
Abstract/Description: This thesis investigates the use of nanotechnology in an extensive literature search in the field of cement and concrete. A summary is presented. The research was divided into two categories: (1) nanoparticles and (2) nanofibers and nanotubes. The successes and challenges of each category is documented in this thesis. The data from the literature search is taken and analyzed using statistical prediction by the use of the Monte Carlo and Bayesian methods. It shows how statistical prediction...
Show moreThis thesis investigates the use of nanotechnology in an extensive literature search in the field of cement and concrete. A summary is presented. The research was divided into two categories: (1) nanoparticles and (2) nanofibers and nanotubes. The successes and challenges of each category is documented in this thesis. The data from the literature search is taken and analyzed using statistical prediction by the use of the Monte Carlo and Bayesian methods. It shows how statistical prediction can be used to analyze patterns and trends and also discover optimal additive dosages for concrete mixes.
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Date Issued: 2013
PURL: http://purl.flvc.org/fcla/dt/3360786
Subject Headings: Nanostructured materials, Nanofibers, Cement, Additives, Concrete, Additives
Format: Document (PDF)

Title: Development of Flexible Puncture Resistant Materials System Using Silica Nanoparticles.
Creator: Clements, Floria Eve, Mahfuz, Hassan, Florida Atlantic University
Abstract/Description: Nanoscale silica particles are functionalized and ultrasonically dispersed into a mixture of polyethylene glycol and ethanol, and then reinforced with Kevlar. The stab or puncture resistance of the flexible nanophased materials system supersedes recent advances made in this area. Through SEM scans, thermal and chemical analysis, it is evident that the functionalized nanoparticles offer multiple facets of resistance to penetration of a sharp impactor. The improvement in protection is traced to...
Show moreNanoscale silica particles are functionalized and ultrasonically dispersed into a mixture of polyethylene glycol and ethanol, and then reinforced with Kevlar. The stab or puncture resistance of the flexible nanophased materials system supersedes recent advances made in this area. Through SEM scans, thermal and chemical analysis, it is evident that the functionalized nanoparticles offer multiple facets of resistance to penetration of a sharp impactor. The improvement in protection is traced to the formation of siloxane bonds during functionalization. The framework for a theoretical model is established to estimate penetration depth under low velocity impact of a sharp object through the flexible composite. For comparison ofthese novel fabric composites, a method is also introduced to evaluate penetration resistance quantitatively. The method is capable of showing subtle changes that would otherwise be missed.
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Date Issued: 2007
PURL: http://purl.flvc.org/fau/fd/FA00012513
Subject Headings: Nanostructured materials, Reinforced plastics, Fibrous composites, Nanotechnology
Format: Document (PDF)

Title: Investigation of nanoscale reinforcement into textile polymers.
Creator: Khan, Mujibur Rahman., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: A dual inclusion strategy for textile polymers has been investigated to increase elastic energy storage capacity of fibers used in high velocity impact applications. Commercial fibers such as Spectra and Dyneema are made from ultra high molecular weight polyethylene (UHMWPE). Dynamic elastic energy of these fibers is still low therefore limiting their wholesale application without a secondary metallic or ceramic component. The idea in this investigation is to develop methodologies so that the...
Show moreA dual inclusion strategy for textile polymers has been investigated to increase elastic energy storage capacity of fibers used in high velocity impact applications. Commercial fibers such as Spectra and Dyneema are made from ultra high molecular weight polyethylene (UHMWPE). Dynamic elastic energy of these fibers is still low therefore limiting their wholesale application without a secondary metallic or ceramic component. The idea in this investigation is to develop methodologies so that the elastic energy of polyethylene based fibers can be increased by several folds. This would allow manufacturing of an all-fabric system for high impact applications. The dual inclusion consists of a polymer phase and a nanoscale inorganic phase to polyethylene. The polymer phase was nylon-6 and the inorganic phase was carbon nanotubes (CNTs). Nylon-6 was blended as a minor phase into UHMWPE and was chosen because of its large fracture strain - almost one order higher than that of UHMWPE. On the other hand, CNTs with their very high strength, modulus, and aspect ratio, contributed to sharing of load and sliding of polymer interfaces as they aligned during extrusion and strain hardening processes. A solution spinning process was developed to produce UHMWPE filaments reinforced with CNTs and nylon-6. The procedure involved dispersing of CNTs into paraffin oil through sonication followed by dissolving polymers into paraffin-CNT solution using a homogenizer. The admixture was fed into a single screw extruder for melt mixing and extrusion through an orifice. The extrudate was rinsed via a hexane bath, stabilized through a heater, and then drawn into a filament winder with controlled stretching. In the next step, the as produced filaments were strain-hardened through repeated loading unloading cycles under tension., Neat and reinforced filaments were characterized through DSC (Differential Scanning Calorimetry), XRD (X-ray Diffraction), Raman Spectroscopy, SEM (Scanning Electron Microscope), and mechanical tests. Phenomenal improvement in properties was found; modulus, strength, fracture strain, and elastic energy increased by 219%, 100%, 107% and 88%, respectively before strain hardening. Once strain hardened the strength, modulus and elastic energy increased by almost one order of magnitude. Source of these improvements were traced to increase in crystallinity and rate of crystallization, formation of microdroplets as a minor phase, sliding between minor and major phases, coating of nanotubes with polymer and alignment of nanotubes.
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Date Issued: 2010
PURL: http://purl.flvc.org/FAU/2976443
Subject Headings: Nanostructured materials, Composite materials, Textile fibers, Synthetic, Polymers, Electric properties
Format: Document (PDF)

Title: Reinforcement of syntactic foam with SiC nanoparticles.
Creator: Das, Debdutta., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: In this investigation, polymer precursor of syntactic foam has been reinforced with SiC nanoparticles to enhance mechanical and fracture properties. Derakane 8084 vinyl ester resin was first dispersed with 1.0 wt% of SiC particles using a sonic cavitation technique. In the next step, 30.0 wt% of microspheres (3M hollow glass borosilicate, S-series) were mechanically mixed with the nanophased vinyl ester resin, and cast into rectangular molds. A small amount of styrene was used as dilutant to...
Show moreIn this investigation, polymer precursor of syntactic foam has been reinforced with SiC nanoparticles to enhance mechanical and fracture properties. Derakane 8084 vinyl ester resin was first dispersed with 1.0 wt% of SiC particles using a sonic cavitation technique. In the next step, 30.0 wt% of microspheres (3M hollow glass borosilicate, S-series) were mechanically mixed with the nanophased vinyl ester resin, and cast into rectangular molds. A small amount of styrene was used as dilutant to facilitate mixing of microspheres. The size of microspheres and SiC nanoparticles were 20-30 um and 30-50 nm, respectively. Tension, compression, and flexure tests were conducted following ASTM standards and a consistent improvement in strength and modulus within 20-35% range was observed. Fracture toughness parameters such as KIC and GIC were also determined using ASTM E-399. An improvement of about 11-15% was observed. Samples were also subjected to various environmental conditions and degradation in material properties is reported.
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Date Issued: 2009
PURL: http://purl.flvc.org/FAU/359923
Subject Headings: Composite materials, Design, Polyurethanes, Mechanical properties, Epoxy resins, Nanostructured materials
Format: Document (PDF)

$Simultaneous x-ray and neutron diffraction Rietveld refinements of nanophase Fe substituted hydroxyapatite$

Title: Simultaneous x-ray and neutron diffraction Rietveld refinements of nanophase Fe substituted hydroxyapatite.
Creator: Kyriacou, Andreas, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: The effect of Fe substitution on the crystal structure of hydroxyapatite (HAp) is studied by applying simultaneous Rietveld refinements of powder x-ray and neutron diffraction patterns. Fe is one of the trace elements replacing Ca in HAp, which is the major mineral phase in bones and teeth. The morphology and magnetic properties of the Fe-HAp system are also studied by transmission electron microscopy and magnetization measurements. Samples of Ca(5-x)Fex(PO4)3OH with 0
Show moreThe effect of Fe substitution on the crystal structure of hydroxyapatite (HAp) is studied by applying simultaneous Rietveld refinements of powder x-ray and neutron diffraction patterns. Fe is one of the trace elements replacing Ca in HAp, which is the major mineral phase in bones and teeth. The morphology and magnetic properties of the Fe-HAp system are also studied by transmission electron microscopy and magnetization measurements. Samples of Ca(5-x)Fex(PO4)3OH with 0< x < 0.3 were prepared. Single phase HAp was identified in x-ray diffraction patterns (XRD) of samples with x < 0.1 inferring that the solubility limits are less than 0.1. Hematite ((Sa(B-Fe2O3) is identified as a secondary phase for higher Fe content. The refined parameters show that Fe is incorporated in the HAp structure by replacing Ca in the two crystallographic sites with a preference at the Ca2 site. This preference explains the small effect of the Fe substitution on the lattice constants of HAp. The overall decrease of the lattice constants is explained by the ionic vi size difference of Ca and Fe. The increasing trend of the a-lattice constant with x in the Fe substituted samples is attributed to a lattice relaxation caused by the substitution of the 4- and 6-fold Fe at the 7- and 9-fold Ca1 and Ca2 sites. This Ca local geometry reduction is indicated by a slight increase of the Ca1-O3 and Ca2-O1 bond lengths. Above the solubility limit x = 0.05, the Fe is partitioned in and out of the HAp structure with increasing nominal Fe content x. The excess Fe is oxidized to hematite. The TEM analysis and magnetic measurements support the results of the simultaneous Rietveld refinements. The TEM images show no significant effect on the morphology and size of the HAp particles upon Fe incorporation. The particles are either spheres or short rods of dimensions 20-60 nm. Hematite particles are imaged in the samples with x exceeding the solubility limit. These particles
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Date Issued: 2012
PURL: http://purl.flvc.org/FAU/3342204
Subject Headings: X-rays, Diffraction, Rietveld method, Nanostructured materials, Biomedical materials
Format: Document (PDF)

Title: Improving the Mechanical Properties of Nano-Hydroxyapatite.
Creator: Khanal, Suraj P., Leventouri, Theodora, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: Hydroxyapatite (HAp) is an ideal bioactive material that is used in orthopedics. Chemical composition and crystal structure properties of HAp are similar to the natural bone hence it promotes bone growth. However, its mechanical properties of synthetic HAp are not sufficient for major load-bearing bone replacement. The potential of improving the mechanical properties of synthetic hydroxyapatite (HAp) by incorporating carboxyl functionalized single walled carbon nanotubes (CfSWCNT) and...
Show moreHydroxyapatite (HAp) is an ideal bioactive material that is used in orthopedics. Chemical composition and crystal structure properties of HAp are similar to the natural bone hence it promotes bone growth. However, its mechanical properties of synthetic HAp are not sufficient for major load-bearing bone replacement. The potential of improving the mechanical properties of synthetic hydroxyapatite (HAp) by incorporating carboxyl functionalized single walled carbon nanotubes (CfSWCNT) and polymerized ɛ-caprolactam (nylon) is studied. The fracture toughness, tensile strength, Young’s modulus, stiffness and fracture energy were studied for a series of HAp samples with CfSWCNT concentrations varying from 0 to 1.5 wt. % without, and with nylon addition. X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC) were used to characterize the samples. The fracture toughness and tensile test was performed under the standard protocol of ASTM D5045 and ASTM D638-02a respectively. Reproducible maximum values of (3.60 ± 0.3) MPa.m1/2 for fracture toughness and 65.38 MPa for tensile strength were measured for samples containing 1 wt. % CfSWCNT and nylon. The Young’s modulus, stiffness and fracture energy of the samples are 10.65 GPa, 1482.12 N/mm, and 644 J/m2 respectively. These values are comparable to those of the cortical bone. Further increase of the CfSWCNT content results to a decreased fracture toughness and tensile strength and formation of a secondary phase.
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Date Issued: 2016
PURL: http://purl.flvc.org/fau/fd/FA00004675, http://purl.flvc.org/fau/fd/FA00004675
Subject Headings: Biomedical engineering -- Materials, Biomedical materials -- Mechanical properties, Nanostructured materials -- Mechanical properties
Format: Document (PDF)

Title: Studies of nanoparticle reinforced polymer coatings for trace gas detection.
Creator: Davis, Charles, Mahfuz, Hassan, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: With the goal of improving chemical detection methods for buried improvised explosive devices (IED’s), the intention of this study is to show that functionalized nano-particles improve the sensing properties of a polymer applied to gas sensors. The approach was reinforcing the polymer, Nafion, with acid-functionalized carbon nanotubes (CNT’s). Ammonia was chosen as the analyte for its similarity to IED byproducts without the dangers of toxicity or explosion. Two sensor platforms were...
Show moreWith the goal of improving chemical detection methods for buried improvised explosive devices (IED’s), the intention of this study is to show that functionalized nano-particles improve the sensing properties of a polymer applied to gas sensors. The approach was reinforcing the polymer, Nafion, with acid-functionalized carbon nanotubes (CNT’s). Ammonia was chosen as the analyte for its similarity to IED byproducts without the dangers of toxicity or explosion. Two sensor platforms were investigated: Quartz crystal microbalances (QCM’s) and microcantilevers (MC’s). Preliminary evaluation of treated QCM’s, via frequency analyzer, showed improvements in sensitivity and fast reversal of adsorption; and suggested increased stability. Tests with coated MC’s also supported the findings of QCM tests. Amplitude response of MC’s was on average 4 times greater when the Nafion coating contained CNT’s. Quantitative QCM testing with gas-flow meters showed that with CNT inclusion: the average number of moles adsorbed increased by 35% (>1.2 times frequency response); sensitivity improved by 0.63 Hz/ppt on average; although the detection threshold decreased marginally; but reusability was much better after extended exposures to concentrated ammonia.
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Date Issued: 2013
PURL: http://purl.flvc.org/fau/fd/FA0004014
Subject Headings: Conducting polymers, Detectors -- Technological innovations, Explosives -- Detection, Nanocomposites (Materials), Nanostructured materials, Smart materials
Format: Document (PDF)

Title: Modeling and analysis of aluminum/air fuel cell.
Creator: Leon, Armando J., Zilouchian, Ali, College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
Abstract/Description: The technical and scientific challenges to provide reliable sources energy for US and global economy are enormous tasks, and especially so when combined with strategic and recent economic concerns of the last five years. It is clear that as part of the mix of energy sources necessary to deal with these challenges, fuel cells technology will play critical or even a central role. The US Department of Energy, as well as a number of the national laboratories and academic institutions have been...
Show moreThe technical and scientific challenges to provide reliable sources energy for US and global economy are enormous tasks, and especially so when combined with strategic and recent economic concerns of the last five years. It is clear that as part of the mix of energy sources necessary to deal with these challenges, fuel cells technology will play critical or even a central role. The US Department of Energy, as well as a number of the national laboratories and academic institutions have been aware of the importance such technology for some time. Recently, car manufacturers, transportation experts, and even utilities are paying attention to this vital source of energy for the future. In this thesis, a review of the main fuel cell technologies is presented with the focus on the modeling, and control of one particular and promising fuel cell technology, aluminum air fuel cells. The basic principles of this fuel cell technology are presented. A major part of the study consists of a description of the electrochemistry of the process, modeling, and simulations of aluminum air FC using Matlab Simulink™. The controller design of the proposed model is also presented. In sequel, a power management unit is designed and analyzed as an alternative source of power. Thus, the system commutes between the fuel cell output and the alternative power source in order to fulfill a changing power load demand. Finally, a cost analysis and assessment of this technology for portable devices, conclusions and future recommendations are presented.
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Date Issued: 2013
PURL: http://purl.flvc.org/fau/fd/FA0004032
Subject Headings: Biomass energy, Electrocatalysis, Electrolytic capacitors -- Materials, Fuel cells -- Materials, MATLAB, Nanostructured materials, Renewable energy sources
Format: Document (PDF)

Title: Large-scale molecular dynamics simulations of semiconductor nanostructures.
Creator: Cornwell, Charles F., Florida Atlantic University, Wille, Luc T.
Abstract/Description: Classical trajectory molecular dynamics methods are used to investigate the critical strain of single-walled carbon nanotubes ("SWT") and the strength and extent of the interactions between 3D Ge structures on the surface of Si(001). The discrete model is capable of giving some insight into the critical strain of the SWT's beyond the limits of the continuous model and allow us to investigate the effects of lattice distortion due to the placement of Ge structures on the surface of a Si...
Show moreClassical trajectory molecular dynamics methods are used to investigate the critical strain of single-walled carbon nanotubes ("SWT") and the strength and extent of the interactions between 3D Ge structures on the surface of Si(001). The discrete model is capable of giving some insight into the critical strain of the SWT's beyond the limits of the continuous model and allow us to investigate the effects of lattice distortion due to the placement of Ge structures on the surface of a Si substrate. Total energy calculations performed using classical three-body interatomic potentials with appropriate boundary conditions for each case are used to investigate the two systems. We discuss the development of a parallel code to simulate short-ranged empirical potentials such as those of Stillinger and Weber, Tersoff, and Tersoff-Brenner. We then use the Tersoff potential to model C and Si/Ge system. Data collected are used to examine the behavior of the two systems.
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Date Issued: 1999
PURL: http://purl.flvc.org/fcla/dt/12614
Subject Headings: Molecular dynamics--Computer simulation, Nanostructured materials, Semiconductors
Format: Document (PDF)

Title: Effects of Carbon Nanotube (CNT) Dispersion and Interface Condition on Thermo-Mechanical Behavior of CNT-Reinforced Vinyl Ester.
Creator: Sabet, Seyed Morteza, Mahfuz, Hassan, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: In fabrication of nanoparticle-reinforced polymers, two critical factors need to be taken into account to control properties of the final product; nanoparticle dispersion/distribution in the matrix; and interfacial interactions between nanoparticles and their surrounding matrix. The focus of this thesis was to examine the role of these two factors through experimental methodologies and molecular-level simulations. Carbon nanotubes (CNTs) and vinyl ester (VE) resin were used as nanoparticles...
Show moreIn fabrication of nanoparticle-reinforced polymers, two critical factors need to be taken into account to control properties of the final product; nanoparticle dispersion/distribution in the matrix; and interfacial interactions between nanoparticles and their surrounding matrix. The focus of this thesis was to examine the role of these two factors through experimental methodologies and molecular-level simulations. Carbon nanotubes (CNTs) and vinyl ester (VE) resin were used as nanoparticles and matrix, respectively. In a parametric study, a series of CNT/VE nanocomposites with different CNT dispersion conditions were fabricated using the ultrasonication mixing method. Thermomechanical properties of nanocomposites and quality of CNT dispersion were evaluated. By correlation between nanocomposite behavior and CNT dispersion, a thermomechanical model was suggested; at a certain threshold level of sonication energy, CNT dispersion would be optimal and result in maximum enhancement in properties. This threshold energy level is also related to particle concentration. Sonication above this threshold level, leads to destruction of nanotubes and renders a negative effect on the properties of nanocomposites. In an attempt to examine the interface condition, a novel process was developed to modify CNT surface with polyhedral oligomeric silsesquioxane (POSS). In this process, a chemical reaction was allowed to occur between CNTs and POSS in the presence of an effective catalyst. The functionalized CNTs were characterized using TEM, SEM-EDS, AFM, TGA, FTIR and Raman spectroscopy techniques. Formation of amide bonds between POSS and nanotubes was established and verified. Surface modification of CNTs with POSS resulted in significant improvement in nanotube dispersion. In-depth SEM analysis revealed formation of a 3D network of well-dispersed CNTs with POSS connections to the polymer. In parallel, molecular dynamics simulation of CNT-POSS/VE system showed an effective load transfer from polymer chains to the CNT due to POSS linkages at the interface. The rigid and flexible network of CNTs is found to be responsible for enhancement in elastic modulus, strength, fracture toughness and glass transition temperature (Tg) of the final nanocomposites.
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Date Issued: 2016
PURL: http://purl.flvc.org/fau/fd/FA00004628, http://purl.flvc.org/fau/fd/FA00004628
Subject Headings: Carbon nanotubes., Carbon composites., Polymeric composites., Fibrous composites, Nanostructured materials., Composite materials--Mechanical properties.
Format: Document (PDF)

Title: A study of the effects of nanoparticle modification on the thermal, mechanical and hygrothermal performance of carbon/vinyl ester compounds.
Creator: Powell, Felicia M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Enhancement of mechanical, thermal and hygrothermal properties of carbon fiber/vinyl ester (CFVE) composites through nanoparticle reinforcement has been investigated. CFVE composites are becoming more and more attractive for marine applications due to two reasons : high specific strength and modulus of carbon fiber and low vulnerability of vinyl ester resin to sea water. However, the problem with this composite system is that the fiber matrix (F/M) interface is inherently weak. This leads to...
Show moreEnhancement of mechanical, thermal and hygrothermal properties of carbon fiber/vinyl ester (CFVE) composites through nanoparticle reinforcement has been investigated. CFVE composites are becoming more and more attractive for marine applications due to two reasons : high specific strength and modulus of carbon fiber and low vulnerability of vinyl ester resin to sea water. However, the problem with this composite system is that the fiber matrix (F/M) interface is inherently weak. This leads to poor mechanical properties and fast ingress of water at the interface further deteriorating the properties. This investigation attempts to address these deficiencies by inclusion of nanoparticles in CFVE composites. Three routes of nanoparticle reinforcement have been considered : nanoparticle coating of the carbon fiber, dispersion of nanoparticles in the vinyl ester matrix, and nanoparticle modification of both the fiber and the matrix. Flexural, short beam shear and tensile testing was conducted after exposure to dry and wet environments. Differential scanning calorimetry and dynamic mechanical analysis were conducted as well. Mechanical and thermal tests show that single inclusion of nanoparticles on the fiber or in the matrix increases carbon/vinyl ester composite properties by 11-35%. However, when both fiber and matrix were modified with nanoparticles, there was a loss of properties.
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Date Issued: 2012
PURL: http://purl.flvc.org/FAU/3352286
Subject Headings: Composite materials, Mechanical properties, Nanostructured materials, Testing, Carbon compounds, Testing, Fibrous composites, Testing, Surface chemistry
Format: Document (PDF)

Title: Nanoparticle Reinforced Core Materials for Sandwich Construction: Investigation of Mechanical and Fracture Behavior.
Creator: Stewart, Justin Keith, Mahfuz, Hassan, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Sandwich composites provide excellent structural integrity for a variety of applications. In this study pristine and functionalized 30 nrn Silicon Carbide nanoparticles are infused into a low density polyurethane foam used for the inner core of the sandwich structure. The mechanical properties are characterized using compressive, tensile, and flexural tests. A plane-strain fracture test and a TSD (Tilted Sandwich Debond) test characterize the fracture properties of the foam and the coreskin...
Show moreSandwich composites provide excellent structural integrity for a variety of applications. In this study pristine and functionalized 30 nrn Silicon Carbide nanoparticles are infused into a low density polyurethane foam used for the inner core of the sandwich structure. The mechanical properties are characterized using compressive, tensile, and flexural tests. A plane-strain fracture test and a TSD (Tilted Sandwich Debond) test characterize the fracture properties of the foam and the coreskin interface. Thermal characterization is carried out using Dynamic Mechanical Analysis (DMA) and Thermo-Gravimetric Analysis (TGA). FTIR spectral analysis reveals changes in molecular bonding due to pristine and functionalized nanoparticle infusion. The fracture resistance of the foam is improved and the delamination strength of the sandwich construction with nanophased cores is dramatically improved. The TSD testing indicated that the G1c value rose from 0.14 kJ/m^2 in the neat foam to 0.56 kJ/m^2 with just 0.1 wt% of SiC nanoparticle inclusion reflecting an enhancement of almost 300%.
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Date Issued: 2008
PURL: http://purl.flvc.org/fau/fd/FA00012558
Subject Headings: Composite materials--Mechanical properties, Nanostructured materials--Testing, Fracture mechanics
Format: Document (PDF)

Title: Toward lanthanide containing coordination polymers and nanomaterials.
Creator: Greig, Natalie E., De Lill, Daniel T., Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description: The focus of this thesis is to develop lanthanide (Ln) luminescent materials through the exploration of coordination polymers and nanomaterials. Herein, dimethyl-3,4- furanedicarboxylate acid undergoes hydrolysis under hydrothermal conditions to form coordination polymers with lanthanide ions. The resulting coordination polymers exhibited luminescent properties, with quantum yields and lifetimes for the Eu-and Tb-CP of 1.14+-0.32% and 0.387=-0.0001 mx, and 3.33=-0.82% and 0.769=-0.006 ms,...
Show moreThe focus of this thesis is to develop lanthanide (Ln) luminescent materials through the exploration of coordination polymers and nanomaterials. Herein, dimethyl-3,4- furanedicarboxylate acid undergoes hydrolysis under hydrothermal conditions to form coordination polymers with lanthanide ions. The resulting coordination polymers exhibited luminescent properties, with quantum yields and lifetimes for the Eu-and Tb-CP of 1.14+-0.32% and 0.387=-0.0001 mx, and 3.33=-0.82% and 0.769=-0.006 ms, respectively. While the incorporation of lanthanides was not achieved in this work, progress toward the production of pure phase InP in the nanoregime has been made, using a low-cost, hydrothermal method. Through SEM and PXRD conflict, it is believed that pure INP particles with a size range of 58-81 nm were successfully synthesized.
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Date Issued: 2012
PURL: http://purl.flvc.org/FAU/3358558
Subject Headings: Metallic composites, Speciation, Lanthanide shift reagents, Rare earth metals catalysts, Nanostructured materials
Format: Document (PDF)

Title: Vibration, buckling and impact of carbon nanotubes.
Creator: Pentaras, Demetris., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Natural frequencies of the double and triple-walled carbon nanotubes are determined exactly and approximately for both types. Approximate solutions are found by using Bubnov-Galerkin and Petrov-Galerkin methods. For the first time explicit expressions are obtained for the natural frequencies of double and triple-walled carbon nanotubes for different combinations of boundary conditions. Comparison of the results with recent studies shows that the above methods constitute quick and effective...
Show moreNatural frequencies of the double and triple-walled carbon nanotubes are determined exactly and approximately for both types. Approximate solutions are found by using Bubnov-Galerkin and Petrov-Galerkin methods. For the first time explicit expressions are obtained for the natural frequencies of double and triple-walled carbon nanotubes for different combinations of boundary conditions. Comparison of the results with recent studies shows that the above methods constitute quick and effective alternative techniques to exact solution for studying the vibration properties of carbon nanotubes. The natural frequencies of the clamped-clamped double-walled carbon nanotubes are obtained; exact solution is provided and compared with the solution reported in the literature. In contrast to earlier investigation, an analytical criterion is derived to establish the behavior of the roots of the characteristic equation. Approximate Bubnov-Galerkin solution is also obtained to compare natural frequencies at the lower end of the spectrum. Simplified version of the Bresse-Timoshenko theory that incorporates the shear deformation and the rotary inertia is proposed for free vibration study of double-walled carbon nanotubes. It is demonstrated that the suggested set yields extremely accurate results for the lower spectrum of double-walled carbon nanotube. The natural frequencies of double-walled carbon nanotubes based on simplified versions of Donnell shell theory are also obtained. The buckling behavior of the double-walled carbon nanotubes under various boundary conditions is studied. First, the case of the simply supported double-walled carbon nanotubes at both ends is considered which is amenable to exact solution., Then, approximate methods of Bubnov-Galerkin and Petrov-Galerkin are utilized to check the efficacy of these approximations for the simply supported double-walled carbon nanotubes. Once the extreme accuracy is demonstrated for simply supported conditions, the approximate techniques are applied to two other cases of the boundary conditions, namely to clamped-clamped and simply supported-clamped double-walled carbon nanotubes. For the first time in the literature approximate expression for the buckling loads are reported for these boundary conditions. The dynamic deflection of a single-walled carbon nanotube under impact loading is analyzed by following a recently study reported on the energy absorption capacity of carbon nanotubes under ballistic impact.
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Date Issued: 2009
PURL: http://purl.flvc.org/FAU/186764
Subject Headings: Nanostructured materials, Buckling (Mechanics), Plates (Engineering), Vibration, Mathematical models, Structural analysis
Format: Document (PDF)

Title: A new method to achieve lithic use-wear discrimination using laser scanning confocal microscopy.
Creator: Farber, Elliott, Dorothy F. Schmidt College of Arts and Letters, Department of Anthropology
Abstract/Description: My study sought to acquire quantitative data from the surface of lithic tools and use that data to discriminate tools used on different contact materials. An experimental archaeological wear production method was conceived, whereby I and several volunteers produced wear on chert, heat-treated chert, and obsidian flakes by using those flakes on several contact materials. The flakes were then analyzed using a laser scanning confocal microscope, which recorded three-dimensional surface data from...
Show moreMy study sought to acquire quantitative data from the surface of lithic tools and use that data to discriminate tools used on different contact materials. An experimental archaeological wear production method was conceived, whereby I and several volunteers produced wear on chert, heat-treated chert, and obsidian flakes by using those flakes on several contact materials. The flakes were then analyzed using a laser scanning confocal microscope, which recorded three-dimensional surface data from each tool. The data was analyzed using cluster analysis to find the ideal combination of parameters which correctly discriminated the flakes based on use-wear data. After finding acceptable parameters which grouped flakes appropriately through cluster analysis, those groups were subjected to a discriminant analysis. Each analysis returned a p-value under .05, meaning that the clustering based on the parameters Sq and Sfd produced by the cluster analysis was not random, but indicative of these variables' ability to discriminate lithic use-wear. The major advantage of the approach developed in this study is that it can quantitatively discriminate use-wear produced by different contact materials on flakes with no a priori information at all.
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Date Issued: 2013
PURL: http://purl.flvc.org/fcla/dt/3362342
Subject Headings: Archaeology, Methodology, Archaeological surveying, Laser use in, Topographical surveying, Laser use in, Nanostructured materials, Tools, Prehistoric, Analysis
Format: Document (PDF)

Title: A New Approach to Sensitized Luminescence in Trivalent Lanthanide Coordination Polymers: From Fundamental Luminescence and Crystal Engineering Toward Sensing Applications.
Creator: Einkauf, Jeffrey D., De Lill, Daniel T., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description: Luminescent lanthanide containing coordination polymers and metal-organic frameworks hold great potential in many applications due to their distinctive spectroscopic properties. While the ability to design coordination polymers for specific functions is often mentioned as a major benefit bestowed upon these compounds, the lack of a meaningful understanding of the crystal engineering and luminescence in lanthanide coordination polymers remains a significant challenge toward functional design....
Show moreLuminescent lanthanide containing coordination polymers and metal-organic frameworks hold great potential in many applications due to their distinctive spectroscopic properties. While the ability to design coordination polymers for specific functions is often mentioned as a major benefit bestowed upon these compounds, the lack of a meaningful understanding of the crystal engineering and luminescence in lanthanide coordination polymers remains a significant challenge toward functional design. Currently, the study of luminescence attributed to these compounds is based on the antenna effect as derived from molecular systems, where organic antennae are used to facilitate lanthanide-centered luminescence. This molecular based approach does not take into account the unique features of extended network solids, particularly the formation of band structure. By comparing molecular and band-based approaches, it was determined that the band structure of the organic sensitizing linker needs to be considered when evaluating the luminescence of lanthanide coordination polymers. This new model, as well as work on the crystal engineering and sensor applications of these materials will be presented.
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Date Issued: 2017
PURL: http://purl.flvc.org/fau/fd/FA00004890, http://purl.flvc.org/fau/fd/FA00004890
Subject Headings: Rare earth metals., Lanthanide shift reagents., Organic compounds--Synthesis., Inorganic compounds--Synthesis., Metallic composites--Speciation., Polymeric composites., Organorare earth metal compounds., Nanostructured materials.
Format: Document (PDF)

Title: The expression and analysis of a lysine-rich wound-response protein in tomato plants.
Creator: Kaplan, Noah, Zhang, Xing-Hai, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Biological Sciences
Abstract/Description: Understanding the genetic regulation of the response to wounding and wound healing in fruiting plants is imperative to maintaining agricultural sustainability, preserving the quality of food supplies, and ensuring the economic viability of agriculture. Many genes are known to be induced by wounding, providing both structural repair and defense. The KED gene in tobacco (Nicotiana tabacum) has been shown to be induced by wounding. We have identified its homologue gene in tomato (Solanum...
Show moreUnderstanding the genetic regulation of the response to wounding and wound healing in fruiting plants is imperative to maintaining agricultural sustainability, preserving the quality of food supplies, and ensuring the economic viability of agriculture. Many genes are known to be induced by wounding, providing both structural repair and defense. The KED gene in tobacco (Nicotiana tabacum) has been shown to be induced by wounding. We have identified its homologue gene in tomato (Solanum lycopersicum) that we named SlKED. We have analyzed gene expression pattern of SlKED through tomato growth and development and in response to wounding as well as hormonal and inhibitor treatments. We found that the plant hormone ethylene played a major role in the expression of SlKED. To further identify evidence for physiological and transductional functions of KED and SlKED, the tobacco KED gene was introduced to tomato and overexpressed by the fruit tissue-active PUN1 promoter from pepper (Capsicum annuum,). The expression of this gene was compared to the expression of the native SlKED gene and other known wound response genes in both the wild-type and transgenic tomato plants. The upregulation of the native SlKED gene by wounding was significantly muted in the tobacco KED-expressing transgenic plants. The expression of other genes known to be associated with wound response transduction pathways was also altered. Our studies implicate the KED gene in defense mechanisms for mechanical stress in tomato plants.
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Date Issued: 2016
PURL: http://purl.flvc.org/fau/fd/FA00004773, http://purl.flvc.org/fau/fd/FA00004773
Subject Headings: Wound healing., Wounds and injuries--Genetic aspects., Plant gene expression., Plant genetic regulation., Nanostructured materials--Physiological effect., Biomedical engineering.
Format: Document (PDF)

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