Donavon M. Delozier

Rapid, solventless, bulk preparation of metal nanoparticle-decorated carbon nanotubes.

A rapid, solventless method is described for the decoration of carbon nanotubes with metal nanoparticles. The straightforward two-step process utilizes neither reducing agents nor electric current and involves the dry mixing of a precursor metal salt (e.g., a metal acetate) with carbon nanotubes (single- or multi-walled) followed by heating in an inert atmosphere. The procedure is scalable to multigram quantities and generally applicable to various other carbon substrates (e.g., carbon nanofiber, expanded graphite, and carbon black) and many metal salts (e.g., Ag, Au, Co, Ni, and Pd acetates). As a model system, Ag nanoparticle-decorated carbon nanotube samples were prepared under various mixing techniques, metal loading levels, thermal treatment temperatures, and nanotube oxidative acid treatments. These nanohybrids were characterized by a variety of microscopic and spectroscopic techniques. For example, X-ray diffraction and scanning electron microscopy indicated that the average size of the Ag nanoparticles has little to do with the thermal treatment temperature but can be easily controlled by varying the Ag loading. Raman spectroscopy illustrated both the metal-nanotube electronic interactions and the surface enhancement effect from the Ag nanoparticle attachment. High-resolution transmission electron microscopy captured the in situ salt-to-metal conversion events on the nanotube surface. The mechanistic implications from the characterization results are discussed.

Flexible Fabrics with High Thermal Conductivity for Advanced Spacesuits

This paper describes the effort and accomplishments for developing flexible fabrics with high thermal conductivity (FFHTC) for spacesuits to improve thermal performance, lower weight and reduce complexity. Commercial and additional space exploration applications that require substantial performance enhancements in removal and transport of heat away from equipment as well as from the human body can benefit from this technology. Improvements in thermal conductivity were achieved through the use of modified polymers containing thermally conductive additives. The objective of the FFHTC effort is to significantly improve the thermal conductivity of the liquid cooled ventilation garment by improving the thermal conductivity of the subcomponents (i.e., fabric and plastic tubes). This paper presents the initial system modeling studies, including a detailed liquid cooling garment model incorporated into the Wissler human thermal regulatory model, to quantify the necessary improvements in thermal conductivity and garment geometries needed to affect system performance. In addition, preliminary results of thermal conductivity improvements of the polymer components of the liquid cooled ventilation garment are presented. By improving thermal garment performance, major technology drivers will be addressed for lightweight, high thermal conductivity, flexible materials for spacesuits that are strategic technical challenges of the Exploration