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In response to the energy needs of modern society and emerging ecological concerns, the pursuit of novel, low-cost, and environmentally friendly energy conversion and storage systems has raised significant interest. Among various energy conversion and storage systems, fuel cells have become a primary research focus since they convert chemical energy directly into electrical energy with high efficiency and low pollutant emissions. For example, direct methanol fuel cells (DMFCs), which supply the electrical energy by converting methanol to energy, are an ideal fuel cell system for applications in electric vehicles and electronic portable devices due to their relatively quick start-up, rapid response to catalyst loading, and low operating temperature. However, the wide commercial use of DMFCs in advanced hybrid electric vehicles and electronic portable devices is hampered by their high cost, poor durability, and relatively low energy and power densities. In order to address these problems, their research focuses on the development of highly active electrode catalysts coupled with a suitable electrode structure for the oxidation of methanol at the anode and the reduction of oxygen at the cathode to attain high efficiency of DMFCs, and subsequently lowering the cost. In this dissertation, the fabrication of novel platinum and platinum alloy nanoparticle-loaded carbon nanofibers (CNFs) for use as electrodes in DMFCs is demonstrated through electrospinning, carbonization, and deposition. The resulting CNF-based electrodes possess the properties of high electroactive surface area, good catalytic abilities towards the oxidation of methanol and the reduction of oxygen, and great long-time stability. As a result, DMFCs using these CNFs-supported platinum and platinum alloy nanoparticles as electrodes offer many advantages, such as improved electrocatalytic abilities, long-term stability, easy fabrication, low cost, and environmental benignity. Therefore, this new technology opens up new opportunities to develop high-performance electrode materials in the future for high-performance DMFCs, which are one of the promising power sources for consumer devices and electric vehicles, and play a critical role in solving the worldwide critical energy issue.

For nearly two decades inclusion compounds (ICs) have been formed by threading polymer chains into the cyclic starches, cyclodextrins (CDs). Non-covalently bonded crystalline ICs have been formed by threading CDs, onto guest nylon-6 (N6) chains. When excess N6 is employed, non-stoichiometric (n-s)-N6-CD-ICs with partially uncovered and dangling N6 chains result. We have been studying the constrained crystallization of the N6 chains dangling from (n-s)-N6-CD-ICs in comparison with bulk N6 samples, as a function of N6 molecular weights, lengths of uncovered N6 chains, and the CD host used. While the crystalline CD lattice is stable to ~ 300° C, the uncovered and dangling, yet constrained, N6 chains may crystallize below, or be molten above ~225° C. In the IC channels formed with host α- and γ-CDs containing 6 and 8 glucose units, respectively, single and pairs of side-by-side N6 chains can be threaded and included. In the α-CD-ICs the ~ 0.5nm channels are separated by ~ 1.4nm, while in γ-CD-ICs the ~ 1nm channels are ~ 1.7 nm apart, with each γ-CD channel including two N6 chains. The constrained dangling chains in the dense (n-s)-N6-CD-IC brushes crystallize faster and to a greater extent than those in bulk N6 melts, and this behavior is enhanced as the molecular weights/chain lengths of N6 are increased. Furthermore, when added at low concentrations (n-s)-N6-CD-ICs serve as effective nucleating agents for the bulk crystallization of N6 from the melt. Because of the biodegradable/bioabsorbable nature of CDs, (n-s)-polymer-CD-ICs can provide environmentally favorable, non-toxic nucleants for enhancing the melt crystallization of polymers and improving their properties.

Tortuosity factor is often used to characterize the structure of the pore volume in fibrous porous media. This work involves the determination of tortuosity using computational fluid dynamic (CFD) simulation and particle tracking analysis. A new method has been adopted to generate 3-D geometry for modeling fibrous porous structures using ANSYS® Parametric Design Language (APDL). Computation fluid dynamics has been used to simulate permeability of modeled 3-D fiberweb structures. The simulated permeability results are in good agreement with the models proposed by other authors. The experimental results were found to be slightly higher compared to simulated results and existing models due to the layered configuration of the samples. Permeability is found to be significantly influenced by fiber diameter, and porosity as well as fiberweb thickness. The relationship between air permeability and fiberweb thickness has been used to develop an indirect method for determination of tortuosity factor. Tortuosity factor has also been determined using a more direct method involving CFD simulation and Particle Tracking analysis. Different models established using the direct and indirect methods of determination show that tortuosity is significantly influenced by porosity, fiber diameter and fiberweb thickness, whereas the models available in the literature express tortuosity as a function of porosity only.

It is a well known fact that the quality of a fabric is tied to the non-uniformity of fabric properties. Although methods have been suggested to measure certain physical properties of fabrics (mass, handle, strength, comfort, permeability), there has been no single method that is industrially accepted to characterize and quantify distribution of some of these fabric properties or non-uniformities. Therefore, the purpose of this research was to investigate and suggest a new method to fill this need. During this research, data about fabric properties were obtained either directly from images of fabric appearances or indirectly from on-line measurements of yarn diameters. The yarn diameters captured through a line-scan camera were mapped into a 2-D fabric matrix by assigning each point of the yarn to a specific location (x, y) within the 2-D fabric matrix. The gray-scale image of a 2-D fabric matrix was called a virtual fabric and provided the basic information on the uniformity of the fabric property. Variance-area curves were developed to characterize and quantify non-uniformity of actual and virtual fabrics in two dimensions. Certain irregularity features such as vertical and horizontal streaks and random cloudiness produced variance-area curves that are dependent on the shape of the unit area. Thus the difference between these curves became a new way to measure isotropy features of fabric properties. Theoretical relationships between yarns and their virtual fabrics were derived using only the internal correlation information of the given underlying yarns

Hydrogen bond forming polymers such as aliphatic polyamides and polyvinyl alcohol are important engineering plastics with good mechanical properties, high melting point and good chemical resistance. However, any further attempt at improving their mechanical properties gets thwarted due to the presence of intermolecular hydrogen bonding. Many approaches have been attempted in the past to suppress hydrogen bonding in aliphatic polyamides and have met with little or no success. These include, plasticizing the structure, dry spinning, wet spinning, gel spinning, and zone drawing/annealing. We have employed a new technique that involves the dry-jet wet spinning and drawing of GaCl3/nylon 66 complex. This new method allows traditional low draw ratios for nylon 66 to be increased by disrupting the interchain hydrogen bonded network. Fibers with a high modulus were obtained when high molecular weight nylon 66 was used. Further, we have also reviewed the concept of thermoreversible gelation and its application for gel spinning of ultra high molecular weight polyethylene fibers. We developed high strength and modulus nylon 6 and PVA fibers from the gels of these polymers in N-methyl pyrrolidinone. High molecular weight is essential for achieving more drawing of polymer chains which leads to high molecular orientation. Electrostatic spinning or electrospinning has received considerable research attention in recent years. It involves the application of an electric filed to a polymer solution or melt to facilitate production of fibers in the sub-micron down to nanometer range. We have investigated the complexation of GaCl3 with nylon 6 and developed porous nanofibers via the technique of electrospinning. Pores are generated by removal of salt from the as spun nanofibers via dipping in water. Researchers have tried in the past using a highly volatile solvent, or selective removal of one polymer from a bicomponent nanofiber for developing pores in nanofibers. However, using a metal salt proved to be a simple and fast approach for generating pores in electrospun nanofibers.

A numerical model has been developed that successfully predicts heat transfer through thermally protective clothing materials and garments exposed to intense heat. The model considers the effect of fire exposure to the thermophysical properties of materials as well as the air layers between the clothing material and skin surface. These experiments involved characterizing the flash fire surrounding the manikin by measuring the temperature of the flame above each thermal sensor in the manikin surface. An estimation method is used to calculate the heat transfer coefficient for each thermal sensor in a 4 second exposure to an average heat flux of 2.00cal/cm2sec. A parameter estimation method was used to estimate fabrics dynamic thermophysical properties. The skin-clothe air gap distribution of different garments was determined using three-dimensional body scanning technology. Multi-layer skin heat transfer and a burn prediction models are used to predict second and third degree burns. The integrated generalized model developed will validated using the "Pyroman" Thermal Protective Clothing Analysis System with Kevlar/PBI® and Nomex®?A coverall garments. A parametric study conducted using this numerical model indicated the influencing parameters on garment thermal protective performance in terms of burn damage subjected to 4 second flash fire exposure. The importance of these parameters is analyzed and distinguished. These parameters includes fabric thermophysical properties, Pyroman® chamber generated flash fire characterizes, garment shrinkage and fit factors, as well as garment initial and test ambient temperature. Different skin models are also investigated using this model.

Functional bone tissue engineering has been necessitated by the need to treat critical size defects in bones due to birth abnormalities, trauma, and pathological conditions. Appropriate conditions for in vitro osteogenesis need to be identified to establish protocols for engineering bone tissues. The success of in vitro osteogenesis lies on the type of cell source, stimuli, and scaffold material used for engineering bone constructs. Recent investigations have established the pluripotency of mesenchymal stem cells (MSCs) and their ability to differentiate down a multitude of pathways including osteogenenic. In vivo studies have shown that MSCs are primarily responsible for bone growth and regeneration and therefore have become a major candidate for bone tissue engineering. Osteogenic differentiation of MSCs via chemical stimuli has been extensively investigated using both monolayer and three-dimensional (3D) culture conditions. These investigations provided useful information on media conditions, cell seeding densities, and differentiation capabilities of MSCs. However, chemical stimulation alone might not be sufficient to accelerate osteogenesis and impart necessary mechanical strength to the final tissue construct. Mechanical strength of the final tissue construct is vital to maintain its structural integrity when exposed to physiological stresses in vivo. Stimulation of MSCs using mechanical strain might provide another method to induce MSC osteogenesis while also obtaining desired mechanical strength of the final tissue constructs. Although in vivo studies and experimental models have indicated that cyclic tensile strain could induce MSC osteogenesis, its effect on MSC osteogenesis in 3D cultures in vitro has not been investigated. The need to maintain cell viability and be able to provide chemical or mechanical cues to cells in 3D cultures requires improvements in scaffold architecture and design. While collagen provides a natural matrix for cell adhesion and growth, its contraction during culture can greatly limit culture duration and mechanical stability of the matrix. Although fibrous scaffolds can be used as an alternative to collagen scaffolds, insufficient media diffusion to the center of these 3D scaffolds could detrimentally affect uniform cell growth throughout the scaffold; hence, scaffolds with better diffusional properties need to be developed. This study investigated the use of 3D collagen matrices as a scaffold material to determine the effects of strain and chemical stimuli on osteogenic differentiation of human MSCs (hMSCs). Major attention was given to the analyses of: cell viability, matrix contraction, nuclei morphology, expression of osteogenic markers and proinflammatory cytokines, as well as changes in mechanical properties of the final tissue construct. As an approach to develop 3D fibrous scaffolds with enhanced diffusional properties, fabrication of melt spun microporous fibers using a blend of poly (lactic acid) (PLA) and sulfopolyester that could be used in 3D nonwoven scaffolds was also investigated. The findings of this study clearly illustrated the ability of cyclic tensile strain to induce osteogenic differentiation of hMSCs when cultured in a 3D environment. Expression of proinflammatory cytokines by strained hMSCs suggested that cyclic strain might have induced modulation of bone resorption in hMSCs. The results also illustrated the effects of strain on the mechanical properties of the final tissue construct. Microporous fibers created from melt spun composite fibers using binary blends of poly (lactic acid) and sulfopolyester could enhance diffusional properties of 3D nonwoven scaffolds fabricated using these fibers. As this body of work demonstrates, use of cyclic tensile strain combined with chemical stimulation to induce osteogenic differentiation of hMSCs could greatly assist the engineering of functional bone tissues in vitro. Microporous fibers created using polymer blends could provide an effective method to improve diffusional properties of 3D polymeric scaffolds.

Yarn tension control is an important parameter for quality and efficiency in textile processes. It has a significant influence on productivity in various processes such as winding, twisting and cabling. There have been several articles based on theoretical models, which discuss the effect of various factors on yarn tension variation in direct cabling, but very few have addressed the possibility of measuring and controlling it practically while the yarn is being twisted. Quality control system manufacturers like TEMCO (Textile Machinery Components) and BTSR (Best Technologies Studies and Research) have come up with smart tension scanning systems that perform online tension monitoring in various textile machines. However, these systems cannot be installed on the direct cabling machine due to their size and cost. The fact that the supply yarn package is housed inside the rotating yarn balloon restrains any wired tension sensor from performing online measurement. As such, there is an immediate need for using a wireless sensing device to perform online yarn tension measurement and execute a control mechanism that will control yarn tension adaptively. The objective of this research is to demonstrate the possibility of applying MEMS (MicroElectroMechanical Systems) technology with radio frequency (RF) transmission to effectively carry out dynamic online measurement for the control of yarn tension. A novel technique to achieve online control using the measured real-time data has been implemented. A device that ensures uniform tension in the yarn has been designed and developed. Ways of measuring twist in the cabled yarn using optical micrometers and digital imaging systems have also been explored, because variation in tension manifests variation in twist. Using the twist values obtained from these sensors, the individual tensions in the component yarns can be adjusted, resulting in the formation of a uniform cabled yarn with equal lengths of both component yarns.