Janet B. Hurst

Materials and Structures Research for Gas Turbine Applications Within the NASA Subsonic Fixed Wing Project

In an era of both declining NASA budgets and demanding space goals, the NASA Aeronautics Research Mission Directorate has elected to address foundational research problems for aeronautics. To this end, the Subsonic Fixed Wing (SFW) Project, within the Fundamental Aeronautics Program, has selected challenging goals which anticipate an increasing emphasis on aviation’s impact upon the global issue of environmental responsibility. These SFW project goals are greatly reduced noise, reduced emissions and reduced fuel consumption. Specific goals, selected by a combination of systems analysis, experience and industry input, are generational in approach, addressing 25 to 30 years of technology development. Successful implementation of these demanding goals will require development of new materials and structural approaches within gas turbine propulsion technology. The Materials and Structures discipline, within the SFW project, comprise cross-cutting technologies ranging from basic investigations to component validation in laboratory environments. Material advances are teamed with innovative designs in a multidisciplinary approach with the resulting technology advances directed to promote the goals of reduced noise and emissions along with improved performance. For propulsion needs, these technologies have been grouped into three basic categories. The first is improved hot section materials for hotter engines with minimal cooling requirements to promote reduced NOx and fuel burn. Among the technologies of interest have been new alloy compositions and improved thermal barrier coatings systems with improved capabilities. The second category being investigated for propulsion applications is lightweight and multifunctional systems which will permit reduced fuel burn via weight reduction in the engine and its surrounding structure. An example of this technology is High Temperature Shape Memory Alloys (HTSMA) for actuation applications requiring large displacements and low frequencies such as chevrons and variable area nozzles for high bypass ratio engines. The final area under investigation is the concept of the more electric aircraft, which at this time is focused primarily on turboelectric technology as a available to make reasonable progress. Technologies from very basic fundamental research to nearer term concepts are included. Additionally, vigorous supplementation of in-house capabilities is revolutionary approach to the entire SFW design space. Major challenges to be addressed in this field include improved cryocoolers and superconducting materials. A brief overview is presented of the current materials and structures research focused upon propulsion applications within the NASA Subsonic Fixed Wing Project. As such, it does not comprise the entirety of materials and structures research for gas turbine engines at NASA. Several other projects also include research of this type to address their specific project goals.© 2010 ASME

Boron Nitride Nanotubes, Silicon Carbide Nanotubes, and Carbon Nanotubes—A Comparison of Properties and Applications

Abstract This chapter describes the development of noncarbon nanotubes and compares the features of carbon and noncarbon nanotubes. Carbon nanotubes are the most widely available nanotube material and are typically used for reinforcement of polymeric and glass materials, electronic applications, etc. Noncarbon nanotubes such as boron nitride and silicon carbide have advantages for use in aggressive environments. Possible uses of noncarbon nanotubes include reinforcement of metals, polymers, and glasses; environmental and thermal barrier coatings; electronics; and radiation shielding.

Synthesis of Boron Nitride Nanotubes for Engineering Applications

Boron nitride nanotubes (BNNT) are of significant interest to the scientific and technical communities for many of the same reasons that carbon nanotubes (CNT) have attracted wide attention. Both materials have potentially unique and important properties for structural and electronic applications. However of even more consequence than their similarities may be the complementary differences between carbon and boron nitride nanotubes. While BNNT possess a very high modulus similar to CNT, they also possess superior chemical and thermal stability. Additionally, BNNT have more uniform electronic properties, with a uniform band gap of 5.5 eV while CNT vary from semiconductive to highly conductive behavior. Boron nitride nanotubes have been synthesized both in the literature and at NASA Cilenn Research Center, by a variety of methods such as chemical vapor deposition, arc discharge and reactive milling. Consistent large scale production of a reliable product has proven to be difficult. Progress in the reproducible synthesis of 1-2 gram sized batches of boron nitride nanotubes will be discussed as well as potential uses for this unique material.