Carbon Materials Research

摘要

A basic research study in carbon materials for propulsion applications led to research in seemingly diverse areas, which include carbon- carbon composite fabrication, oxidation protection of carbon, microelectromechanical (MEMs) devices, and surface tension phenomena. Carbon- carbon composites are the material of choice in many high temperature thermostructural applications, such as rocket nozzles and exit cones, missile nosetips, and leading edges of hypersonic vehicles. Although these materials are stronger than steel, stiffer than steel, lighter than aluminum, and resistant to thermal shock, they are susceptible to oxidation above 450 degrees C. In addition, they are very costly due principally to the process of densification in which a carbon matrix is placed among the carbon fibers in a perform that has been constructed to have certain mechanical properties. This study has addressed both the problems of oxidation resistance and cost of carbon-carbon composites. In addressing the issue of cost, a completely new and innovative densification approach called In Situ densification was conceived and implemented. This process has the dual advantage of both a significant cost reduction as well as a significant reduction in the time needed to densify these composites. In addressing the oxidation protection of carbon-carbon composites, the entirely new field of microtube technology was born. This technology allows the fabrication of free-standing or imbedded microscopic tubes that can possess any cross-sectional or axial shape. Numerous devices have been conceived and fabricated utilizing this technology. Since surface tension is a dominant force at microscopic dimensions, devices employing non- wetting liquids and surface tension were conceived and fabricated. During the fabrication of some of these devices, an entirely new wetting phenomenon was discovered. That is, it is possible to make a non-wetting surface wetting and a wetting surface to be non-wetting.