Mark A. Atwater

Mechanical and Electrical Characterization of Entangled Networks of Carbon Nanofibers

Entangled networks of carbon nanofibers are characterized both mechanically and electrically. Results for both tensile and compressive loadings of the entangled networks are presented for various densities. Mechanically, the nanofiber ensembles follow the micromechanical model originally proposed by van Wyk nearly 70 years ago. Interpretations are given on the mechanisms occurring during loading and unloading of the carbon nanofiber components.

Controlling carbon nanofibre morphology for improved composite reinforcement

Carbon nanofibres were grown at low temperatures on a novel fibre catalyst, palladium particles, using a novel method, growth in fuel rich combustion conditions. The growth of carbon filaments by this process was found to be remarkably rapid. Preliminary analysis of how changes in operating parameters, for example gas flow rate and reactant ratio, showed that fibre diameter and other factors such as helicity are very sensitive to the precise conditions employed, suggesting simple means to impact overall properties of the fibres. The ability to control diameter, helicity, and surface roughness are discussed with possible importance to advanced composites.

Direct Synthesis of Nanofibrous Nonwoven Carbon Components: Initial Observations, Capabilities, and Challenges

Widespread adoption of carbon nanomaterials has been hindered by inefficient production and utilization. A recently developed method has shown possibility to directly synthesize bulk nanostructured nonwoven materials from catalytically deposited carbon nanofibers (CNFs). The basic manufacturing scheme involves constraining carbon nanofiber growth to create three-dimensionally featured, macroscale products. Although previously demonstrated as a proof of concept, the possibilities and pitfalls of the method at a larger scale have not yet been explored. In this work, the basic foundation for using the constrained formation of fibrous nanostructures (CoFFiN) process is established by testing feasibility in larger volumes (as much as 2000% greater than initial experiments) and by noting the macroscale carbon growth characteristics. It has been found that a variety of factors contribute to determining the basic qualities of the macroscale fiber collection (nonwoven material), and there are tunable parameters at the catalytic and constraint levels. The results of this work have established that monolithic structures of nonwoven carbon nanofibers can be created with centimeter dimensions in a variety of crosssectional shapes. The only limit to scale noted is the tendency for nanofibers to entangle with one another during growth and self-restrict outward expansion to the mold walls. This may be addressed by pregrowing carbon before placement or selective placement of the catalyst in the mold. [DOI: 10.1115/1.4034609]