Liquid phase sintering of C fiber reinforced ultra-high temperature ceramics composites (INFINITE)
Abstract
Ultra-high temperature ceramic matrix composites (UHTCMCs) are the next generation of reusable materials for application in extreme environments associated with aerospace, military and nuclear applications. Preferably, UHTCMCs are constituted of just two essential elements that are integrated appropriately e.g.: a carbon fiber fabric and an ultra-refractory matrix. The ideal composite has neither a preprocessing fiber coating nor a post processing environmental external coating. Moreover, interface between the matrix and fiber is weak enough to enable sufficient fiber pullout to enhance toughness and dense enough to hinder penetration of corrosive/oxidative gases during exposition. These UHTCMCs are meant to be reusable owing to in situ formation of a protective scale during exposition. To produce such revolutionary materials, we have developed a time saving and low-cost process consisting of powder slurry infiltration of fiber fabrics followed by sintering. Densification through sintering at high temperature is the distinctive feature of these particular CMCs, it also the most critical aspect of the process because it is needed to provide strength and environmental resistance but uncontrolled densification may also lead to embrittlement. Many factors control the performance of these composites, but the most relevant is the residual porosity and reactions at fiber/matrix interface. The matrix should be dense enough to ensure good oxidation/environmental resistance, but the interface with the matrix must be controlled to avoid fiber degradation. Thus, the type of the interface formed during sintering is of great importance. The main objective of this proposal is to study the densification behavior of UHTCMCs to maximize the performance at elevated temperatures. The hypothesis driving the present research is: Liquid phase sintering is more effective for densification of UHTCMCs with carbon fibers than solid state sintering because it allows for maintaining pristine fibers. A unidirectional carbon fiber architecture combined with a matrix consisting of mainly ZrB2 is being used as a base composition to represent this class of composites. The knowledge generated will be then easy extended to other matricies for UHTCMCs. Another important outcome of this research will be a list of guidelines useful for researchers and manufacturers for the creation of reusable advanced materials with temperature capability over 2000 ¡C for aerospace applications. The control of densification and interfaces in these composites is being pursued using experimental studies, physics-based models, and analytical characterization techniques. The INFINITE project will benefit from the combined expertise of research groups at ISTEC in UHTC densification and UHTCMC fabrication and expertise of the research group at Missouri S&T in elevated temperature mechanical behavior and environmental response. Evolution of the matrix/fiber interface during service at elevated temperature will be investigated in the unique ultra-high temperature mechanical testing facility at Missouri S&T. INFINITE responds to the need to develop new ceramic materials for applications in extreme environments. Moreover, the topic Òmaterials for extreme environmentsÓ is a highly specialized area of research and development in need of highly trained scientists and engineers to lead future research efforts. The project will directly impact this area of the ceramic field by facilitating workforce development at both institutions. Early-career researchers working on this project will develop unique global awareness of emerging research areas related to materials for extreme environments while also developing deep technical expertise in UHTCMCs.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 07, 2021
- Source ID
- W911NF2110333
Entities
People
- Luca Zoli
Organizations
- Army Contracting Command
- Institute of Science and Technology of Ceramic Materials
- United States Army