Mark Haase

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.

A Corrugated Graphene–Carbon Nanotube Composite as Electrode Material

A graphene and carbon nanotube (CNT) array composite was synthesized by chemical vapor deposition (CVD) and chemically treated after synthesis, yielding a novel corrugated structure, visually similar to a mushroom gill. This binder-free hybrid material was used to make an electrode that may find application in energy storage devices, such as supercapacitors. The electrode performance of the corrugated graphene/CNT array composite (CGCC) was compared to that of commercial glassy carbon. The results of the comparison are presented here, along with suggestions for further development of the CGCC electrode.

Rapid, in situ plasma functionalization of carbon nanotubes for improved CNT/epoxy composites

Improved CNT/epoxy composites composed of dry-drawn, aligned and functionalized CNTs were fabricated. Dry-drawn multi-walled carbon nanotube (MWNTs) were functionalized by atmospheric pressure He/O2 based plasma during the manufacturing of the CNT sheets and epoxy resin dissolved in solvent was sprayed during the manufacturing. The extent of CNT functionalization was controlled by adjusting the plasma power and flow rate of oxygen. Functionalized CNTs were characterized by Raman, X-ray Photoelectron Spectroscopy (XPS) and contact angle testing. The % wt CNT content in the composites was controlled by adjusting the concentration of epoxy in the solution used for spraying. CNTs functionalized by 100 W plasma and 63% wt CNT content produced the best composites demonstrating 43% improvement in tensile strength and 78% improvement in modulus over composites made with pristine CNTs. High % wt CNT content in the composites allow for the creation of strong, light-weight composites demonstrating specific strength as high as 918 MPa g−1 cm−3, a 55% and 50% improvement over pristine CNT sheet and CNT/epoxy composite made with pristine CNTs, respectively.

Mechanical Strength Improvements of Carbon Nanotube Threads through Epoxy Cross-Linking

Individual Carbon Nanotubes (CNTs) have a great mechanical strength that needs to be transferred into macroscopic fiber assemblies. One approach to improve the mechanical strength of the CNT assemblies is by creating covalent bonding among their individual CNT building blocks. Chemical cross-linking of multiwall CNTs (MWCNTs) within the fiber has significantly improved the strength of MWCNT thread. Results reported in this work show that the cross-linked thread had a tensile strength six times greater than the strength of its control counterpart, a pristine MWCNT thread (1192 MPa and 194 MPa, respectively). Additionally, electrical conductivity changes were observed, revealing 2123.40 S·cm−1 for cross-linked thread, and 3984.26 S·cm−1 for pristine CNT thread. Characterization suggests that the obtained high tensile strength is due to the cross-linking reaction of amine groups from ethylenediamine plasma-functionalized CNT with the epoxy groups of the cross-linking agent, 4,4-methylenebis(N,N-diglycidylaniline).

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.

Unifying the templating effects of porous anodic alumina on metallic nanoparticles for carbon nanotube synthesis

Abstract Carbon nanotubes (CNTs) are a promising material for many applications, due to their extraordinary properties. Some of these properties vary in relation to the diameter of the nanotubes; thus, precise control of CNT diameter can be critical. Porous anodic alumina (PAA) membranes have been successfully used to template electrodeposited catalyst. However, the catalysts used in CNT synthesis are frequently deposited with more precise techniques, such as electron beam deposition. We test the efficacy of PAA as a template for electron beam-deposited catalyst by studying the diameter distribution of CNTs grown catalyst of various thicknesses supported by PAA. These are then compared by ANOVA to the diameter distributions of CNTs grown on metal catalyst supported by a conventional alumina film. These results also allow a unified description of two templating effects, the more common particles-in-pores model, and the recently described particles-between-pores.

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.