The production and evaluation of oxide-based ceramic matrix composites for very high temperature electromagnetic applications

Valenzuela-Heeger, Erin Louise (2023). The production and evaluation of oxide-based ceramic matrix composites for very high temperature electromagnetic applications. University of Birmingham. Ph.D.

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Abstract

The aim of this project was to pre-emptively design a material for future military platforms suitable for high-temperature applications. When considering speeds of Mach 2, the air friction applied to any platform can generate temperatures of up to 1500°C. This requires the assessment of materials that remain thermally, chemically and mechanically stable within this boundary, and oxide-based ceramic matrix composites (CMCs) fit within this category. Alongside the high-temperature functionality, the requirement for a multifunctional material that interfered with electromagnetic radiation was required to change the signature of the platform. The decided signature change was the attenuation of any incident electromagnetic field to reduce the signature stated. The key areas of research regarding this is the large ambiguity between the current state of the art and the proposed operation for both oxide CMCs and electromagnetic attenuators.

Through detailed exploration of the current oxide-based CMC technology and further exploration of electromagnetic attenuating materials, a solution was created to meet the thermal requirements while introducing the element of electromagnetic functionality to the oxide-based CMC through numerical modelling and processing.

Aluminium phosphate created by the dehydration method forms a hydrogel with O-H bond-based dispersion energy. The hydrogel was used in the place of a sol-gel within CMC processing to create an oxide fibre reinforced aluminium phosphate CMC. The high dispersion energy gel was used to suspend material particulates selected for their potential ability to attenuate electromagnetic waves on a molecular level. The materials were selected based on their historic use and their high-temperature functionality. It was found that the use of a single material suspended within the hydrogel, after CMC processing performed inadequately as an attenuator. However, with the use of a numerical model to formulate material combinations for tailored dielectric properties, the hydrogel was able to house the material particulates for attenuation property success.

The aluminium phosphate CMCs containing 3 successful solutions were tested for their high-temperature electromagnetic attenuation and mechanical strength properties. It was found that the CMCs were weaker than traditional oxide-based CMCs, but they were able to attenuate between 70 and 80% of the applied electromagnetic wave. High-temperature influenced both the mechanical and electromagnetic performance of the materials, however this was to be expected due to both the oxide fibre technology used and the lack of recorded high-temperature electromagnetic attenuation properties.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):