| Carbon filament is a form of carbon that was grown from the catalytic decomposition of hydrocarbons over small metal particles, such as iron, cobalt, nickel and their alloys. The diameter of the carbon filaments is about 2 to 200 nm, and the length ranges from 5 to 100 {dollar}mu{dollar}m. Because of their extremely small diameter, large aspect ratio, large surface area, good thermal and electrical conductivity, carbon filaments are becoming increasingly important in materials research and development. This work concentrated on developing the structural applications of this material.; An electroplating method of producing submicron diameter metal filaments using the carbon filaments as substrate was developed. Nickel filaments of 0.4 {dollar}mu{dollar}m diameter with a carbon core of 0.1 {dollar}mu{dollar}m diameter were produced by this method. They exhibited high electrical conductivity, and high surface area, and involve low manufacturing cost. They are shown in this work to be attractive for electrically conductive polymer-matrix composites, EMI shielding materials, microwave conductors and waveguides, high-energy-density electrochemical cells, analytical electrodes and strain sensors.; By using such submicron nickel filaments as a filler in polymer-matrix composites, EMI shielding effectiveness and microwave surface conductance comparable to or even exceeding those of solid copper at the filament loading of only 7%-13% were attained. Filler loading at such low levels had minimum negative effects on the mechanical properties of the polymer-matrix composite.; A new type of resilient composite strain sensor using the submicron nickel filaments as filler and silicone as matrix was developed; it exhibited a negative piezoresistive effect due to the alignment of filaments under loading. A carbon filament polyethersulfone composite strain sensor was also developed; it exhibited the positive piezoresistive effect, with excellent linearity and reversibility.; A solvent cleansing method was developed to improve the electrochemical properties of carbon filaments. Using the cleansed carbon filaments to replace carbon black as an additive in MnO{dollar}sb2{dollar} electrode resulted in higher energy density and longer life lithium primary cell. This replacement also made it possible for this cell to be used in applications that need end-of-life indication such as cardiac pacemakers. Moreover, the cleansed carbon filaments used as the porous carbon electrode current collector in Li/BCX primary cell resulted in a high energy density cell due to the high electron transfer rate and higher electrolyte absorption compared to the conventional carbon black porous electrode. |
