PhD, University of Cincinnati, 2024, Arts and Sciences: Chemistry

Carbon nanotubes (CNTs) hold immense promise in various technological applications, yet their efficacy has been hindered by challenges in establishing robust connections with metal surfaces. This study explores novel methods to address this limitation and enhance the electrical conductivity of CNT-metal interfaces. The resultant CNT-metal hybrid consists of strong bonding in between CNTs, and metal has been investigated in various applications such as sensors and energy storage devices. Covalent bond formation between open-ended CNTs and Cu surfaces is explored experimentally and theoretically. Vertical orientation of CNTs relative to the substrate, coupled with carboxylic functional groups on CNTs reacting with aminophenyl linkers on metal surfaces, facilitates amide bond formation at low temperatures. Theoretical analysis reveals bridge-like bond formations between carbon and adjacent Cu atoms, supporting the observed electrical conductivity enhancement. The robustness of covalent bonding is demonstrated through sonication tests. Due to the appealing nature of carbon nanotubes (CNT) in applications, the investigation extended on CNT films bonded to metal surfaces. Utilizing aligned CNT films, chemically covalent bonds are established between CNTs and various metal surfaces, including Cu, stainless steel, Au, indium tin oxide, and Al. Characterization techniques confirm the formation of robust bonds, with scanning electron microscopy validating their stability post-ultrasonication. Enhanced electrode performance suggests potential applications in sensor technology. Further, CNT bonded to metal electrodes were investigated in energy storage applications. Innovative fabrication of CNT-metal electrodes is achieved by forming chemical bonds between vertically aligned carbon nanotubes (VACNTs) and Au metal surfaces using linker molecules. Covalent bonds between CNTs and diazonium-based linker molecules on the Au surface result in highly conductive interfa (open full item for complete abstract)

Committee: Noe Alvarez Ph.D. (Committee Chair); Jianbing Jiang Ph.D. (Committee Member); Hairong Guan Ph.D. (Committee Member) Subjects: Chemistry

Doctor of Philosophy (Ph.D.), University of Dayton, 2017, Materials Engineering

The purpose of this research was to develop novel nanoparticle-enabled material shields and conductors for use in electrical coaxial cables, and to create appropriate methods to characterize their response to high frequency electromagnetic fields. In addition, techniques to distinguish the effects of mechanical degradation on electrical properties were developed. Traditional electrical measurements methods are ineffectual to such characterization due to limitations with frequency range, sample geometry, field impingement, and false assumptions of field coupling to non-metal center conductors. In this study, a reverberation chamber was used to develop a novel measurement method using conduction characterizations from a network analyzer. Samples were fatigued to identify the effects of heavy use and mechanical degradation on shielding effectiveness and system characterization, including impedance, voltage standing wave ratio, return loss, and insertion loss. The novel measurement of shielding effectiveness as well as system characterizations was used to determine the effect of material properties on cabling functionality, both electrical and mechanical and their inter-relationship. The results showed that the combination of carbon nanotube yarn center conductors and carbon nanotube tape shields led to more signal attenuation and therefore much higher characteristic impedance. Utilizing the novel method to measure the shielding effectiveness allowed for the incorporation of these differences in power transmission while simultaneously analyzing the immunity of the three-dimensional shield within a high frequency field. The carbon nanotube tape shields provided lightweight and efficient shielding at higher frequencies (towards 5 GHz) due to a decreasing skin depth at higher frequencies. A braid architecture, that which was incorporated in the silver coated copper clad steel shield, proved to withstand mechanical fatigue better, while the carbon nanotube helical tap (open full item for complete abstract)

Committee: Donald Klosterman Ph.D. (Advisor) Subjects: Electromagnetics; Engineering; Materials Science

MS, University of Cincinnati, 2013, Engineering and Applied Science: Mechanical Engineering

The discovery of Carbon Nanotubes (CNTs) has sparked tremendous interest among the scientific community due to its extraordinary mechanical properties like high strength and elastic modulus and semiconductor like properties. Though spinning the CNTs into continuous yarns enabled the use of CNTs at macroscale, current spinning techniques are not able to reproduce the properties comparable to those observed at nanoscale. Motivated by this gap, a modeling approach is established to address the subject of transferability of the high strength properties from individual CNT to carbon nanotube (CNT) yarns. More specifically, a number of key factors that contribute to the reduced strength of the twisted CNT yarns are investigated. First of all, the effects of Stone-Wales defects on the strength of individual nanotubes are studied. It is found that the tensile strength of the individual CNT is not highly sensitive to the Stone-Wales defects even with relatively high ratio of defects percentage. Subsequently, molecular dynamics and mechanics simulation are performed to evaluate the load transfer mechanism and tensile strength in a bundle of CNTs. The goal is to find the most favorable twist angle for maximum tensile strength and maximum load transfer ability in between the CNTs in CNT bundles. Both small and large bundles have been studied to examine whether the results are scalable. This thesis concludes with a comparison of the simulation results with the analytical studies based on the mechanics of ropes.

Committee: Dong Qian Ph.D. (Committee Chair); Yijun Liu Ph.D. (Committee Member); Mark Schulz Ph.D. (Committee Member) Subjects: Nanotechnology

PhD, University of Cincinnati, 2022, Engineering and Applied Science: Materials Science

Floating Catalyst Chemical Vapor Deposition (FCCVD) has many unique advantages in synthesizing Carbon Nanotubes (CNTs). These advantages include the ease of continuously producing CNTs with minimal human intervention, customizable reactor design, and easy production scaling. However, FCCVD has also encountered many problems, which are usually associated with low efficiency, sensitivity to the reaction environment, as well as potential safety issues that could endanger reactor operators. This dissertation demonstrates the progress that has been made to stabilize the reactor operation, as well as adding safety features to ensure the safe operation of the reactor. This modified reactor with the enhanced safety features was then used to synthesize CNT with good electrical and mechanical properties. CNTs from the FCCVD reactor were used in four different applications in this dissertation, which are supercapacitor, heater, EMI shielding, and Zn-CO2 battery. The devices' fabrication processes are detailed in three separate chapters of this dissertation, which also include their respective characterization and performance analysis. In the first application of this dissertation, an electrochemical-based method was used to activate the CNT sheet materials to increase the surface area. Electrochemical activation delaminates the CNT sheet thereby increasing the effective surface area of the CNT strands. The increased surface area allows increasing the active materials concentration that can be integrated into the CNT sheet. A Randle-Sevcik plot was used to assess and calculate the activated surface area. Polyaniline (PANI) used as an electrochemically active material was then deposited on the activated CNTs by using a process called oxidation polymerization to create a CNT-PANI composite material for supercapacitor energy storage applications. A fully fabricated supercapacitor device with CNT-PANI electrodes was then created with excellent volumetric energy dens (open full item for complete abstract)

Committee: Mark Schulz Ph.D. (Committee Member); Vijay Vasudevan Ph.D. (Committee Member); Matthew Steiner Ph.D. (Committee Member); Vesselin Shanov Ph.D. (Committee Member) Subjects: Materials Science

Doctor of Philosophy, University of Akron, 2020, Polymer Science

Molecular dynamics is a robust research tool to investigate both bulk and interfacial phenomena. The current manuscript detailed two all-atom simulation studies. The first involves a developing work on the use of linoleic acid as a bio-oil asphalt modifier. Measurements were made on glass transition temperature, molecular mobility, viscosity, and species dispersion. Important trends were identified with potential optimality at moderate additive loading percentages. Barring the challenge in bridging the large order of magnitude difference between computationally accessible and mixing plant shear rates, a technique was detailed whereby mixing and compaction temperatures can be retrieved from construction manuals. The processing temperature reduction implications of correctly characterizing the non-Newtonian flow behaviors of modified asphalt are quantitatively and qualitatively discussed. Further, the single fatty acid species study can serve as a springboard for studies that involve diverse fatty acids with comparable compositions to those that exist in bio-oils like soybean oil and corn oil. To this effect, plausible asphaltic molecular designs were forwarded. This second part of the manuscript covers different aspects of carbon nanotube (CNT) – driven adsorption. Structurally simple yet with amphiphilic properties shared by a wide range of organic contaminants, benzoic acid was chosen as a probe adsorbate molecule. Benzoic acid attained optimal packing orientation in the adsorption region – an iv effect that propagated even outside the adsorption region when there are few or no surface oxygens. By carefully accounting for the multi-way interactions in the adsorption region peculiar mass accumulation trends were observed and explained. Carboxyl-carboxyl associations born of hydrogen bonds were proposed as providing stability to the adsorbed benzoic acid on tube exteriors. These associations were found to be secondary to the dominant aromatic-aromatic interactions (open full item for complete abstract)

Committee: Mesfin Tsige (Advisor); Yu Zhu (Committee Chair); Ali Dhinojwala (Committee Member); Hunter King (Committee Member); Jie Zheng (Committee Member) Subjects: Materials Science; Polymer Chemistry; Polymers

Master of Science in Materials Science and Engineering (MSMSE), Wright State University, 2019, Materials Science and Engineering

The primary purpose of this study is to investigate the role of surface nano-structuring in fluid separation. It is hypothesized that hierarchical carbon structures consisting of aligned carbon nanotube arrays strongly adhered to the surface of porous carbon solids such as fabric and foam, can be used for separation of polar and non-polar fluids by selective wettability of one fluid and rejection of another. The vertically-aligned carbon nanotube arrays, as synthesized, possess super hydrophobicity demonstrated by high water contact angle on their surfaces. On the other hand, they are incredibly oleophilic, showing a high affinity to adsorb oil. These properties make it possible for the carbon nanotube arrays to adsorb and reject certain liquids based on their polarity selectively. By investigating the wettability of these hierarchical structures with water and variety of model oils, initially in the presence of air, and later in the presence of each other, we demonstrate that selective capillary-based devices are thermodynamically possible under different conditions. We have measured the sorption capacity of the model oils in this study, and we have shown the increase in sorption capacity by the specific surface area. We have also shown that adsorption in multiple cycles does not decrease the sorption capacity for these structures, and therefore, they have the potential to be used multiple times without losing their efficiency. Finally, we investigated the selective wettability and separation phenomena of oil-water mixtures, with and without surfactants. These studies show the capabilities and practical limitations of these porous hierarchical structures in the separation of oil from water. We suggest that porosity control of the substrates and controlling the direction of the liquid flow could be an essential part of the future studies for making these structures more effective membranes.

Committee: Sharmila M. Mukhopadhyay Ph.D. (Advisor); Amir Farajian Ph.D. (Committee Member); H. Daniel Young Ph.D. (Committee Member); Barry Milligan Ph.D. (Other) Subjects: Materials Science; Nanotechnology

Master of Science, University of Akron, 2015, Applied Mathematics

Carbon nanotubes (CNTs) exhibit exceptional thermal, mechanical, and electronic properties and hence are of interest for potential applications in novel materials and devices. To develop these applications, researchers must achieve a better understanding of how to process and manipulate CNTs at the nanoscale. Toward this goal, here we propose a coarse-grained model to describe the mechanical response of a CNT forest compressed between two rigid substrates. We use the model to make qualitative and quantitative predictions and to conduct a set of parametric studies. The behavior of the system observed in these studies qualitatively matches the experiments on surface adhesion.

Committee: Dmitry Golovaty Dr. (Advisor); J Patrick Wilber Dr. (Advisor); Gerald Young Dr. (Committee Member) Subjects: Applied Mathematics

Master of Science (MS), Wright State University, 2007, Physics

The electromagnetic characterization of carbon nanotube films (CNT) grown by the surface decomposition of silicon carbide (SiC) has been performed. The CNT films formed on the carbon and silicon terminated face of the SiC substrate were uncapped by an annealing process at a temperature of 4000 C with dwelling time up to 60 minutes in oxygen or carbon dioxide atmosphere. X-Y scans of the quality factor were used to deduce the local conductive properties of the films measured by evanescent microwave microscopy. Real and imaginary permittivity values, as determined by these electromagnetic measurements, provided valuable information for future field emission testing on these films. A theoretical model, adapted from the literature, was used to find the real and imaginary component of the permittivity of the CNT films. The results showed improvement in the surface conductivity of the samples after the annealing treatment.

Committee: Gregory Kozlowski (Advisor) Subjects: Physics, General

MS, University of Cincinnati, 2013, Engineering and Applied Science: Mechanical Engineering

This thesis investigates the use of carbon nanotube (CNT) thread for use in distributed structural health monitoring (SHM) systems, specifically as an embedded damage and strain sensor for laminated polymeric fiber composite materials. CNT thread has shown potential to be integrated into/onto composite materials to provide confident damage detection, localization, and characterization in complex geometries without complicated detection algorithms and minimal sensing channels. This thesis articulates work done with CNT thread performance as a strain sensor, an evaluation of sensor invasiveness, identification of matrix cracking (fatigue damage), a study of damaging and non-damaging impact events, potential SHM design architectures for aircraft, and the multifunctional aspect of damping. Multifunctional here implies improving the composite material besides self-sensing of damage and strain. Besides improving the material in other ways, CNT thread is low in weight, small in size, and the material is modest in cost. As a consequence of these strong sensor and material characteristics, the author believes that this could be a game changing material for high cost composite vehicles. It is envisioned that future military and commercial composite vehicles will utilize technologies such as this sensing thread to provide safety, reliability, durability, condition-based maintenance, and multifunctionality to the structure.

Committee: Mark Schulz Ph.D. (Committee Chair); Randall Allemang Ph.D. (Committee Member); Allyn Phillips Ph.D. (Committee Member); Vesselin Shanov Ph.D. (Committee Member) Subjects: Mechanics

Doctor of Philosophy (PhD), Ohio University, 2024, Physics and Astronomy (Arts and Sciences)

The primary focus of this dissertation is the study of carbon and coal, particularly its atomistic dynamics in the conversion process to graphite or carbon foams and its interactions with plastics. Given the intricate molecular structure of coal, initial research was conducted on simpler amorphous-phase carbon structures, including amorphous graphite, multi-shell fullerenes, and multi-walled carbon nanotubes, to leverage their physical properties for understanding coal chemistry. This foundational research provided insights into fundamental properties such as interatomic interactions, thermal conductivity, and mechanical characteristics. The dissertation, organized largely as a collection of published works, explores the formation, structure, and properties of layered carbons and coal. It includes practical applications, such as coal carbonization, graphitization processes, and the development of carbon-plastic composites. The comprehensive exploration of these topics offers significant contributions to both the fundamental understanding and industrial application of coal and amorphous carbon materials.

Committee: David Drabold (Advisor) Subjects: Condensed Matter Physics; Physics

Master of Science, The Ohio State University, 2019, Chemical Engineering

Most of the hydrogen is produced from natural gas steam reforming process followed by water-gas-shift (WGS) reaction for syngas purification. The produced mixed syngas, consisting of mainly H2 and CO2, needs to be separated to complete the conversion of CO and obtain high purity H2, which can act as a clean, renewable fuel gas for widely commercial uses. Mixed-matrix membrane incorporated nanofillers containing CO2 carriers is one kind of facilitated transport membrane, which shows remarkable transport performance and excellent stability operated under high pressures and high temperature. In the present work, amino-functionalized multi-walled carbon nanotubes (AF-MWNTs) were chosen as the mechanical reinforcing filler to enhance the membrane stability and as the CO2 carrier to facilitate CO2 transport. Variable amounts of AF-MWNTs were incorporated to crosslinked PVA-poly(siloxane)/amine membranes to synthesize the CO2-selective mixed-matrix membranes. The membrane containing 10 wt.% MWNTs demonstrated optimal stable CO2 permeability of 1090 Barrer and CO2/H2 selectivity of 48 for the 100-h test at 1.5 MPa and 107 °C. The primary purpose of this work was to investigate out the effect of AF-MWNTs loading in the mixed-matrix membrane under high pressure in order to obtain the optimal transport performance. Thus, this research was considered to contribute to the syngas purification of industrial interest.

Committee: W.S. Winston Ho (Advisor); Andre Palmer (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, Case Western Reserve University, 2019, Macromolecular Science and Engineering

Thermoplastic polyurethanes (TPUs) are among the most versatile engineering polymers. The presence of hard and soft segments on their backbone and specific hydrogen bond interactions between the hard segments, provide TPUs with outstanding engineering properties whilst rendering them as very complex systems to study. Knowledge of morphology – property relationship is essential for TPUs since their thermal and mechanical behavior are directly dictated by their complicated morphology. Having in mind the need to improve TPU applications at high temperatures, TPU was optimized to reach its top performance. Exceeding the neat TPU performance limitations is possible through incorporation of nanofillers and formation of strong 3D networks. Nanocomposites were obtained through in-situ polymerization of TPU and carbon nanofillers with different geometries (carbon nanotubes (CNTs), carbon nanostructures (CNS) and graphene nanoplatelets (GNP)). By investigating nanocomposites with different nanofiller geometries, it became apparent that CNT and CNS are suitable for mechanical reinforcement while GNP is potentially the best candidate for tribological properties. For mechanical reinforcement, the goal is to form a strong percolated nanofiller network at the lowest possible filler content. It was found that addition of 0.3wt% straight CNTs or 0.1wt% of CNS extended TPU application window for more than 20oC and decreased creep strain up to 60 and 40% at 100 and 120oC, respectively. Due to their branched morphology, CNS proved to be more efficient in mechanical reinforcement than CNTs. The design strategy for nanocomposites tailored for tribological properties is not based on GNP percolated networks. Crosslinked polyurethane systems were also investigated. By activating tansesterification and transcarbamoylation dynamic exchange reactions, dynamic crosslinked networks (vitrimers) could undergo reprocessing, reshaping and self healing. Furthermore a microwave assisted (open full item for complete abstract)

Committee: Ica Manas-Zloczower (Advisor); David Schiraldi (Committee Member); Donald Feke (Committee Member); Gary Wnek (Committee Member) Subjects: Engineering; Nanotechnology; Polymer Chemistry; Polymers

MS, University of Cincinnati, 2018, Engineering and Applied Science: Aerospace Engineering

Carbon nanotubes (CNTs) have extraordinary mechanical, thermal and electrical properties. However, the macroscopic products of CNTs such as sheet and thread, lack these extraordinary physical properties. This reduction in properties for the macroscopic products of CNT is due to the presence of structural defects (disorder-induced symmetry-breaking effects in the sp2 hybridized carbon products), impurities, slipping apart of the short nanotubes in bundles, and random orientation of the CNT strands in sheet and thread. Transferring the physical properties of individual CNTs to the macroscopic scale is a challenging task. To use carbon nanotubes in different applications, intensive research is being performed to improve the mechanical, thermal and electrical properties of CNT sheet and thread. The goal of this work is to investigate methods to improve the mechanical and electrical properties of CNT sheet and thread. The research starts with tuning the CNT synthesis process to produce CNT sheet with fewer structural defects. Also, the effect of this synthesis optimization process on the mechanical and electrical properties of the CNT sheet is investigated. Towards the goal of improving the properties of CNT sheet, further post-processing techniques are studied to improve the orientation of the CNT strands in CNT sheet. It is observed that the mechanical and electrical properties improved due to improved alignment and packing of the CNT strands in the sheet. From the perspective of the application, the hydrophilicity of the CNT sheet is also studied for integrating CNT sheet into textiles. Acid treatment of CNT sheet promoted the hydrophilicity of the CNT sheet. For acid treatment of CNT sheet, hydrogen peroxide and a mixture of H2SO4+HNO3 in 3:1 ratio is used. After analyzing the IG/ID ratio from Raman analysis before and after acid treatment, hydrogen peroxide treated CNT sheet for 48 h showed the best result. Hydrogen peroxide treatment of CNT sheet for 48 h s (open full item for complete abstract)

Committee: Peter Nagy Ph.D. (Committee Chair); Yao Fu (Committee Member); Mark Schulz Ph.D. (Committee Member) Subjects: Nanotechnology

Doctor of Philosophy, University of Akron, 0, Polymer Engineering

The dispersion of nanofillers in polymers has been the biggest challenge in exploiting the full use of the nanocomposites. The purpose of the present study is to investigate the effect of ultrasonically aided extrusion in improving the dispersion of various nanofillers in the polymer composites. In the study, polyetherimide (PEI)/graphite, polypropylene (PP)/carbon black (CB), PP/carbon nanotube (CNT) and PP/graphene nanoplatelet (GNP) composites were prepared using a twin screw extrusion without and with imposition of ultrasonic waves. Three different screw configurations were designed to study the efficiency of ultrasonic treatment in the extrusion. Two compounding methods were utilized in preparing the PP/CNT composites. One is the direct compounding (DC) method and the other one is the masterbatch dilution (MD) method. The efficiency of nanofiller dispersion in these two methods was compared. Four kinds of PP of different molecular weight and molecular weight distribution were used in preparation of PP/CNT composites. The mechanism of ultrasonic cavitation was also investigated. The rheological, mechanical, thermal and electrical properties and morphology of all the PP composites were systematically studied to elucidate the processing-structure-properties relationship. The simulation of the nonlinear rheological behavior of PP/CNT composites was carried out. The results showed that the ultrasonic treatment is more efficient in improving the dispersion of expanded graphite (EG), CNT and CB than GNP and original graphite in polymer matrix. Among the three screw designs, the dispersion of nanofillers in polymer was found to be more related to the presence of kneading elements than the reverse elements and residence time. At higher pressure in the ultrasonic zone, the degradation of PP was less severe than at lower pressure. The ultrasonic treatment had a more prominent effect in improving the dispersion in the MD method than in the DC method. In the MD method, t (open full item for complete abstract)

Committee: Avraam Isayev Dr. (Advisor) Subjects: Plastics; Polymers

Doctor of Philosophy, Case Western Reserve University, 2016, EMC - Mechanical Engineering

Three-dimensional (3D) nanostructures comprised of one-dimensional (1D) and/or two-dimensional (2D) nanomaterials have several advantages over their base nanomaterials. Due to their dimensionally confined structures, for example, 1D carbon nanotubes (CNTs) and 2D graphene exhibit strong direction-dependent thermal transport properties with extremely inefficient cross-plane properties. However, 3D carbon nanostructures such as pillared graphene structures (PGS) are expected to be efficient in both in-plane and cross-plane thermal transport. The aim of this thesis is providing the detailed understanding of thermal transport in 3D carbon nanostructures comprised of CNTs and graphene. Reverse non-equilibrium molecular dynamics simulations were used to show that PGS and CNT networks can have both high in-plane and high cross-plane thermal conductivities comparable to their base nanomaterials, i.e. CNTs and graphene, and also to show that their thermal properties are tunable through altering their architectures. The results indicate that thermal resistances at CNT-graphene junctions result from the combined effect of phonon scattering at the junctions with distorted carbon-carbon bonds and the change in dimensionality of the phonon transport medium as phonons propagate from CNTs (1D) to graphene (2D) and then again to CNT. Moreover, wave packet analysis on SWCNT networks revealed that SWCNT-SWCNT junctions with lager diameter transmit thermal energy more efficiently than the junctions with smaller diameter, and also revealed that SWCNT-SWCNT T-junctions are more efficient in thermal energy transmission than X-junctions. A new experimental method for thermal conductivity measurements in 2D nanosheets was developed. The new method ensures a 1D heat conduction in a 2D sample by creating a spatially uniform temperature profile on the heated side of the sample, and thus improves the accuracy of the measurement in a 2D structure. A MEMS device that can measure the thermal cond (open full item for complete abstract)

Committee: Vikas Prakash (Committee Chair) Subjects: Mechanical Engineering; Nanotechnology

Master of Science, University of Akron, 2015, Applied Mathematics

Having already shown great potential for novel engineering applications, graphene and other carbon-based nanostructures (CNSTR) are being investigated for use in nanotechnology and Nanoelectromechanical Systems. For the design of nanoscale devices, it is important to understand the geometries and behavior of CNSTR. We study an atomistic energy-based model for graphene. We model a graphene sheet as a two-dimensional sheet of atoms in ℜ³. We derive an expression for the total internal energy of a CNSTR considering only the energy of covalently bonded atoms, the energy of the local interaction between non-bonded atoms, and the energy due to the bending of adjacent atomic bonds. The configuration of a CNSTR is initialized, and we run simulations using gradient flow dynamics to minimize total energy and determine equilibrium configurations. Predictions from our model show that the structure of the final configuration depends on the relative strengths of the forces as well as the initial configuration.

Committee: Dmitry Golovaty Dr. (Advisor); Patrick Wilber Dr. (Committee Member); Malena Espanol Dr. (Committee Member) Subjects: Materials Science; Mathematics; Nanotechnology

MS, University of Cincinnati, 2013, Engineering and Applied Science: Mechanical Engineering

Laminated composite materials have gained wide use in a vast range of high strength engineering applications due to the high specific strength and stiffness of composites. However, composites have a critical limitation which is their susceptibility to matrix micro cracking and delamination which can lead to premature failure at stress levels significantly below the tensile strength of the composite. Laminated composites also have low through-the-thickness strength and conduction properties which are important for aerospace vehicles and the military defense industry. These fundamental weaknesses in FRPC can be mitigated by the use of (CNTs) as a secondary reinforcement phase due to its excellent mechanical, electrical and thermal properties. In addition, the nano-reinforcement architecture will add significant multifunctionality to laminated composites. In this thesis, different reinforcement architecture are being investigated to improve the structural properties of laminated composite materials. The first approach investigated to improve the interlaminar and flexural strength of composites was to reinforce the laminate interlayers using a short and dense CNT array. The CNT arrays toughen the matrix rich regions. A vertically aligned carbon nanotube (VACNT) laminated composite which consists of Multiwalled Carbon Nanotube (MWCNT) arrays are transferred unto IM7/977-3 carbon fiber prepreg and plies are stacked up to create a hybrid laminated composite material. A complete wetting of the short MWCNT array by the epoxy from the prepreg was sufficient to create a new interface which yielded higher interlaminar properties. Mechanical and SEM characterization of these composite materials was performed under different loading conditions which include interlaminar and in-plane shear, bending, and in-plane tension. The second phase of reinforcement in this work was to improve the interlaminar shear properties of the laminated composite without reducing its in-plane tensile (open full item for complete abstract)

Committee: Mark Schulz Ph.D. (Committee Chair); Jude Iroh Ph.D. (Committee Member); Vesselin Shanov Ph.D. (Committee Member); David Thompson Ph.D. (Committee Member) Subjects: Mechanics

Doctor of Philosophy (PhD), Wright State University, 2011, Engineering PhD

Lithium-ion battery anodes with a nanostructure of randomly dispersed carbon nanofibers (CNFs), carbon nanotubes (CNTs), and nanoparticles of tin-oxide or silicon were fabricated and tested in order to develop high capacity, easily manufactured anodes. In these anodes, a mesh of CNTs and CNFs form a conductive network within which the nanoparticles of tin-oxide are suspended. The CNT network directs electron flow to and from the nanoparticles while accommodating their volume changes. The CNFs were intended to aid electron transport by serving as conduction channels between the CNTs and the current collector. Secondarily, the CNFs reinforce the physical structure of the anodes. The nanostructure of the anodes allows the electrolyte to freely penetrate, facilitating ionic transport. In most cases, the components of the anode were held together by Van der Waals forces. Both single-walled carbon nanotubes and multi-walled carbon nanotubes were used in this study in order to determine if there performance would be similar. The anodes take advantage of the specific capacity of tin and tin-oxide, which are 981 mAh/g and 1,491 mAh/g, respectively. Because tin is known to expand to three times its original size when it alloys with lithium, it is used in nanoparticle form for these anodes and thus avoids the tendency of tin to disintegrate. To achieve the desired nanostructure, processing methods based on buckypaper formation were explored. Sonication processes were experimented with to determine the optimum conditions for the fabrication of the anodes. Additionally, additives to aid in the binding of the tin-oxide nanoparticles to the CNTs were explored. These included the addition of polyvinylidene fluoride (PVDF) or carbonized phenolic resins. Anodes were found to exhibit the highest reversible capacity when the processing times were kept to a minimum. This was most likely due to the tendency of CNTs to shorten when sonicated. The shorter sonication times were sufficient (open full item for complete abstract)

Committee: Tarun Goswami DSc (Advisor); Ronald Coutu, Jr. PhD (Committee Member); Hong Huang PhD (Committee Member); Bor Jang PhD (Committee Member); Sharmila Mukhopahyay PhD (Committee Member) Subjects: Engineering

Master of Science in Engineering (MSEgr), Wright State University, 2010, Materials Science and Engineering

Carbon substrates have a wide variety of applications, many of which are enabled by appropriate surface modifications. In particular, the use of carbon-based substrates for biological devices can be quite advantageous due to their relative inertness and biocompatibility. Moreover, graphitic carbon can take many forms ranging from flat sheets to foams, fibers, and nanotubes. In this project, larger carbon substrates such as microcellular foam and flat graphite have been modified with carbon nanotubes, and their potential use in two types of biological applications was tested. The first study involved an investigation of the growth and proliferation of osteoblast cells on carbon, so that such structures can be evaluated for possible use as a scaffold for in-vivo tissue regeneration. The surface modifications that were compared are a collagen coating, a silica film, and a strongly adhered carbon nanotube layer. It was seen that the attachment of carbon nanotubes led to the highest density and viability of osteoblast cells on the surface indicating their potential benefit in implant and cell scaffolding applications. In the second study, carbon nanotubes were attached on the graphite, and subsequently decorated with gold nanoparticles and a ribonucleic acid (RNA) sequence. These nano-structures show advantages in detecting the DH5α E. coli bacterial strain, indicating potential use as a biosensor. Proof-of-concept results indicate increased attachment of gold nanoparticles coated with an RNA capture element compared to uncoated particles onto the E. coli. This demonstrates the potential use of this concept in creation of a multi-array sensor for fast and sensitive detection of many types of pathogens. These results clearly show that attachment of carbon nanotubes on larger carbon substrates can provide the basis for several unique biological devices.

Committee: Sharmila Mukhopadhyay PhD (Advisor); Saber Hussain PhD (Committee Member); Allen Jackson PhD (Committee Member) Subjects: Biomedical Engineering; Engineering; Materials Science; Nanotechnology

Master of Science (MS), Wright State University, 2010, Physics

The resistance of three types of bulk carbon nanotube (CNT) materials (floating catalyst CNT yarn, forest grown CNT yarn, and super acid spun CNT fiber) was measured from room temperature to 900 C. Fitting the curves to established conduction equations for disordered materials, competing conduction mechanisms pertaining to the material could be determined. Floating catalyst CNT yarn displayed both semiconductive and metallic isotropic behavior with a resistance minimum, similar to the behavior of crystalline graphite. It was found that, at room temperature, the semiconducting contribution-most likely junctions between CNTs-accounted for 99.99% of the overall resistance. The resistance of forest grown CNT yarn and super acid solution spun CNT fiber decreased monotonically with temperature at a rate similar to amorphous carbon. The impedance of all three materials was also measured to 30 MHz. All three materials followed a series resistor inductor circuit, without any resistance decrease as others have found. Finally, the conductivity and specific conductivity of all three materials was compared to metallic benchmarks. While all three materials had a similar conductivity, the floating catalyst CNT yarn had a significantly higher specific conductivity.

Committee: Gregory Kozlowski PhD (Advisor); Jerry Clark PhD (Committee Member); Benji Maruyama PhD (Committee Member); Jason Deibel PhD (Committee Member); Andrew Hsu PhD (Other); Lok Lew Yan Voon PhD (Other) Subjects: Physics