Design and Manufacture of Ultra-High Temperature Ceramics with Oriented Strengthening and Toughening Phases

Purdue University, West Lafayette IN

Investigators

Abstract

The objective of this proposed research is to provide funding to mature a new process called CeraSGel by which complex geometries of ceramic reinforced with oriented short-fiber phases can be manufactured. The process is applicable to any powder system that can be pressurelessly sintered, but for this study we have chosen a promising ultra-high temperature material, i.e. zirconium diboride or ZrB2 with short fibers of SiC. CeraSGel involves suspending submicron ceramic powders and chopped fibers in a gel created by dissolving small amounts polymer in water to provide formability of the ceramic mixture. Fiber phases are oriented by local shear-stresses that result when a spinning male mold is inserted into the ceramic/polymer mixture . The fiber phase enhances the strength and toughness of the ceramic matrix phase and pressureless sintering affords a low-cost manufacturing approach. In this project we will: (1) Characterize the role of the polymer on the formation, binder burnout, and density of the final part. (2) Determine the interaction of the polymer with the ZrB2 and SiC phases in the wet and dry states. (3) Optimize sintering conditions for green bodies including the effect of polymer loading, fiber orientation, and sintering temperature and time on density, microstructure, and mechanical properties of SiC reinforced ZrB2. Engine cowl inlets, rocket nozzle inserts, and nose-caps in high-speed aerospace surfaces are particular applications where complex-shaped, high-temperature components are required. While materials exist that meet the demanding temperature requirements for these applications, processing and forming costs are often very high and/or the mechanical properties of components are insufficient for the intended applications. In the broadest sense, the proposed work will develop a generally applicable forming process whereby complex parts can be produced with oriented strengthening or toughening phases. The process is inexpensive, as it is amenable to modern composite fabrication techniques, and minimizes expensive material losses and machining as near net-shape components can be fabricated.