DYNAMIC GROWTH BEHAVIOR IN DIRECTED LASER DEPOSITED UHTC FIBERS
Abstract
Hypersonic environments demand materials that can exhibit remarkable resiliency to large mechanical loads originating from extreme flow velocities and high heat flux. While ceramics can provide necessary high strength and good oxidation resistance in these conditions, they require fiber reinforcements to mitigate catastrophic mechanical failure. To that end, a new, high temperature fiber is required. Through directed energy deposition, an innovative class of refectory ceramic fibers will be fabricated using a laser chemical vapor deposition (LCVD) technique. This method offers a rich-processing regime of laser powers (temperatures), pressures, gas mix ratios, and growth rates to control the structure and morphology of the fibers. Using in situ Fourier Transformed Infrared Spectroscopy, the intermediate phase reactants that evolve from the initial precursors will be identified and related to the kinetic pathways that control the nucleation and growth of the fibers. This information will also be forward fed to computational fluid dynamic models of the sub-millimeter growth behavior, where convective and diffusive fluid currents evolve from the dynamic growth process. The fibers will be characterized using optical and electron microscopy methods, with the phase and structure of the fibers linked to the tensile stress at failure as well as hardness. The targeted fiber to be grown is HfC because of its extreme melting temperature, phase stability with loss of carbon, stiffness, and good oxidation resistance. This project seeks to develop an advanced new material (i.e., new fiber) with exceptional temperature capabilities, design of processing configurations over complex conditions and multiple length scales, and the use of computation and characterization methodologies to address a fundamental understanding of chemistry, thermodynamics, and reaction-based mechanisms and kinetics.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 20, 2023
- Source ID
- FA95502210313
Entities
People
- Gregory B. Thompson
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of Alabama