Accession Number : ADA329890

Title :   Tough Ceramics from Fibrous Monoliths.

Descriptive Note : Final rept. 1 Apr 91-30 Mar 93,

Corporate Author : MICHIGAN UNIV ANN ARBOR DEPT OF MATERIALS SCIENCE AND ENGINEERING

Personal Author(s) : Halloran, John W.

PDF Url : ADA329890

Report Date : 25 AUG 1997

Pagination or Media Count : 66

Abstract : During this 1991-1993 grant, the University of Michigan developed "fibrous monolithic ceramics", a new class of monolithic ceramics with properties comparable to ceramic fiber reinforced ceramic matrix composites CMC's. They consist of a 250-micron "cells" of a strong polycrystalline ceramic, such as silicon carbide or silicon nitride, separated by "cell boundaries" from materials, such as boron nitride, which promote crack deflection and delamination. These materials show graceful failure in flexure, with strengths around 350 MPa and work of fracture around 2000 J/m2. Fibrous monolithic ceramics are made from conventional low-cost ceramic powder, using extrusion methods common in conventional ceramic manufacture. We have demonstrated successful fibrous monoliths with silicon carbide, silicon nitride, and alumina, using weak interfaces of graphite or boron nitride. The boron nitride systems are resistant to oxidation. Their room temperature properties are unaffected by exposure at 1400 deg C.

Descriptors :   *CERAMIC MATERIALS, CRACKING(FRACTURING), COPOLYMERS, EXTRUSION, TOUGHNESS, ROOM TEMPERATURE, IMPACT STRENGTH, ALUMINUM OXIDES, FLEXURAL PROPERTIES, SILICON CARBIDES, POWDER METALS, SILICON NITRIDES, BORON NITRIDES, MATERIAL SEPARATION.

Subject Categories : Ceramics, Refractories and Glass

Distribution Statement : APPROVED FOR PUBLIC RELEASE