Microstructural Texturing of Silicon Nitride for Propulsion Applications Using a Magnetic Field

Report No. ARL-TN-0964
Authors: John J Pittari III and Stephen C Bady
Date/Pages: September 2019; 25 pages
Abstract: In recent years, the interest in employing silicon nitride (Si3N4) ceramics in propulsion applications has grown immensely due to its ideal combination of high-temperature properties and tribological behavior. However, its brittle nature promotes concern when used as critical components in certain applications. The development of microstructural texturing through alignment of the c-axis of the β grains has been shown to improve the properties of the ceramic parts. Further advances in this area may further increase the utilization of Si3N4 as propulsion components. This study aims to produce Si3N4 bodies with microstructural texturing developed through alignment in a magnetic field. Proof-of-concept experiments where Si3N4 is aligned in epoxy were produced initially. Once densified, a detailed microstructural analysis was conducted along with density, hardness, and relative toughness evaluations. X-ray diffraction was used to determine the degree of orientation in the cast bodies. Final bodies were produced through slip- or gel-casting techniques. In addition, these bodies underwent tribological and thermal cycling tests. However, the strength of the magnet available for this investigation was limited to 2T, which is well below the value required to achieve large-scale alignment, which limited the results of the study. These results are presented and discussed along with the problems encountered. Recommendations for improving future efforts in this effort are presented.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2019