Brad Ruff

Polymer Coating of Carbon Nanotube Fibers for Electric Microcables

Carbon nanotubes (CNTs) are considered the most promising candidates to replace Cu and Al in a large number of electrical, mechanical and thermal applications. Although most CNT industrial applications require macro and micro size CNT fiber assemblies, several techniques to make conducting CNT fibers, threads, yarns and ropes have been reported to this day, and improvement of their electrical and mechanical conductivity continues. Some electrical applications of these CNT conducting fibers require an insulating layer for electrical insulation and protection against mechanical tearing. Ideally, a flexible insulator such as hydrogenated nitrile butadiene rubber (HNBR) on the CNT fiber can allow fabrication of CNT coils that can be assembled into lightweight, corrosion resistant electrical motors and transformers. HNBR is a largely used commercial polymer that unlike other cable-coating polymers such as polyvinyl chloride (PVC), it provides unique continuous and uniform coating on the CNT fibers. The polymer coated/insulated CNT fibers have a 26.54 μm average diameter-which is approximately four times the diameter of a red blood cell-is produced by a simple dip-coating process. Our results confirm that HNBR in solution creates a few microns uniform insulation and mechanical protection over a CNT fiber that is used as the electrically conducting core.

Development of Lightweight Sustainable Electric Motors

Abstract There are two ways to manufacture components and devices, the top-down and bottom-up processes. Each process has its advantages and disadvantages. In our group, the bottom-up process was selected to build up electromagnetic devices using nanoscale materials in a series of steps. The design of a lightweight electric motor is described based on using nanoscale materials. Development of the motor is work in progress and various processes and results are described. There are several potential applications for lightweight sustainable electric motors. One billion electric motors are produced in the world each year.

Carbon Nanotube Sheet: Processing, Characterization and Applications

Abstract Individual carbon nanotubes (CNTs) have exceptional mechanical and electrical properties. However, the transfer of these extraordinary qualities into CNT products, without compromising performance, remains a challenge. This chapter presents an overview of the manufacturing of CNT sheets and buckypaper and also describes research performed at the University of Cincinnati in this field. CNT arrays were grown using the chemical vapor deposition method. Sheets were drawn from the spinnable CNT arrays and characterized using scanning electron microscopy to show the highly unidirectional alignment of the nanotubes in the sheet. The anisotropic morphology of the sheet provides superior properties along one material axis as observed by measuring the tensile strength, electrical resistivity, optical transmittance, and electromagnetic interference shielding properties of the material. Surface modification of aligned multiwall nanotube sheets was carried out via incorporation of an atmospheric pressure plasma jet in the sheet posttreatment process. Helium/oxygen plasma was utilized to produce carboxyl (–COO−) functionality on the surface of the nanotubes. X-ray photoelectron spectroscopy confirmed the presence of the functional groups on the nanotube surface. The sheet was further characterized using Raman spectroscopy, Fourier transform infrared spectroscopy, and contact angle testing. Composite laminates made from functionalized CNT sheets showed higher strength than those made with pristine sheets. The effects of plasma power and oxygen concentration were studied in order to determine the best possible parameters for functionalization. Plasma treatment is a useful tool for fast, clean and dry functionalization of CNTs. This study demonstrates the ease of incorporating the plasma tool in the manufacturing process of sheets leading to the production of CNT/polymer composites. Macroscopic structures of nanotubes such as threads and sheets are leading to novel applications.

Carbon Nanotube Fiber Doping

Carbon nanotubes (CNTs) have been at the frontier of nanotechnology research for the past two decades. The interest in CNTs is due to their unique physical and chemical properties, which surpass those of most other materials. To put CNTs into macroscale applications, the nanotubes can be spun to form continuous fiber materials. Thus far, the properties of the fibers are far below the properties of the individual nanotubes. If the electrical and mechanical properties of the fibers could be improved, the resulting superfiber materials would change the industry and society. For example, CNT materials might replace copper wires providing lighter, stronger cables for aerospace applications. The small size of individual nanotubes, and the mixture of different diameters and chiralities, limits the electrical conductivity of CNT fiber. A simple way to improve the electrical conductivity of CNT fibers is chemically doping the CNTs within the fibers. This chapter attempts to summarize, classify and provide a basic understanding of doping at the atomic and molecular levels. Characterization of doping and current results of our doping efforts are discussed.

New Applications and Techniques for Nanotube Superfiber Development

Abstract Nanotubes are a unique class of materials because their properties depend not only on their composition but also on their geometry. The diameter, number of walls, length, chirality, van der Waals forces, and quality all affect the properties and performance of nanotubes. This dependence on geometry is what makes scaling-up nanotubes to form bulk material so challenging. Nanotubes are also unusual because they stick together to form bundles or strands. Nanotube superfiber materials are fibrous assemblages of nanotubes and strands. The hope and dream of researchers around the world is that nanotube superfiber materials will have broad applications and change engineering design. This chapter gives a perspective on nanotube superfiber development. This chapter discusses new applications—where we think we can go with the material properties and what applications will be enabled—and new techniques for developing superfiber material.

MODELING THE ELECTRICAL IMPEDANCE OF CARBON NANOTUBE RIBBON

Carbon Nanotube (CNT) ribbon is a thin layer of aligned, partially overlapping CNTs drawn from a forest of CNTs grown on a substrate. The electrical properties of the ribbon must be understood to put this material into multifunctional applications. Measurements show that CNT ribbon exhibits interesting characteristics including frequency-dependent electrical impedance. The impedance is mainly a combination of resistive and capacitive impedance. The magnitude of the impedance of ribbon increases moderately with increasing frequency then decreases significantly at higher frequency, MHz and above. An electrical model was developed to approximate the electrical impedance of the CNT ribbon. Based on this model, some important properties of the CNT ribbon can be understood. The ribbon capacitance, CNT–CNT contact resistance and resistivity can be approximated using the model. This information is useful in determining the suitability of ribbon for different applications. Methods to improve the electrical conduction of CNT ribbon are also discussed.

Chapter 25 – Tiny Medicine

Medical change is coming. Robots and tiny machines built using nanoscale materials are going to fundamentally change engineering at the microscale and medicine will be the first area to benefit. In tiny machine design, copper and iron are replaced with carbon nanotube superfiber wire and magnetic nanocomposite materials. Because of the small size of tiny machines, high magnetic fields can be generated and high-force, high-speed devices can be built. Tiny machines are still in the early stages of being built and this chapter describes their engineering design and the work underway to build them. The tiny machines will operate inside the body and detect disease at an early stage, then provide precise therapy or surgery. There will also be engineering applications for the tiny machines such as performing high-throughput manufacturing operations at the microscale. The design principles and materials processing techniques described herein will facilitate the development of nanomaterial robots and tiny machines for myriad applications ranging from miniaturized sensors, actuators, energy harvesting devices, high-performance electric motors, and energy storage devices to smart structures with built-in artificial responsive behavior.

Carbon nanotube responsive materials and applications

Carbon nanotubes (CNTs) have attracted a lot of interest in the past 20 years. Superior mechanical, …