CERAMIC MATRIX COMPOSITES Ceramic Matrix Composites

Ceramic matrix composites (CMCs) are space-age, three-decker sandwich materials useful in applications requiring resistance to heat and certain (moderate) structural stresses. Aerospace vehicle skins, oven walls, automotive brake shoes, and certain flues and ducts for hot gases are obvious applications. Composites are a base matrix material, usually the ceramic part; an organic or inorganic-organic fiber attached to the outside of, or impregnated within, the matrix; and--in the latest versions--an interphase, third material to protect one or both of the other two and to bind them together. The best overview of the art of fabricating these materials and researching ever-improved versions is that by Naslain (13). The brochure by AlliedSignal, Inc. (ASI, hereafter) exposes the leading edge of fabrication and achievement of superior strength, heat resistance, oxidation resistance, a

. . .
mina, 253 MPa; Zr(8Y)O2, 413 MPa; Zr(4Y)O2, 582 MPa; and mullite, 588 MPa) (8:1813). The grain sizes of the zirconium and the mullite were made roughly one-sixth to one-fifth as large as the raw alumina matrix material by the infiltration process--a clear fabrication advantage. The process used by Honeyman-Colvin and Lange (8) to make their test matrices, however, was elaborate. a-Aluminum oxide powder (0.2 µm diameter) was first made into an aqueous slurry and then pressure filtered (at 17 MPa); it was then dried at room temperature for 24 hours, following which it was heated to 100(C for another 12 hours; it was then 'strengthened' by heating to 1,000(C, raised at 2(C per minute (more than 8 additional hours). The disks (first formed in the pressure-filtering step) were then cut into bars of various lengths, but all having 0.5 x 0.3 cm cross-sections. All of this initial fabrication took place before any infiltration steps (8:1810-11). Again, the process is elaborate, which has to be a disadvantage. Strangely, a year earlier Kim et al. were claiming to have overcome some of these same fabrication disadvantages (11). Like AlliedSignal, Inc. (1), these workers were particularly impressed with BN matrix composites. At
. . .

Some common words found in the essay are:
Morgan Marshall, Honeyman-Colvin Lange, Cinibalk Hay, AlliedSignal Inc, Processing Types, Art Reviewed, Si3N4 RSBN, Santa Barbara, National Laboratory, Illinois Polli, et al, matrix composites, ceram soc, ceramic matrix, ceramic matrix composites, honeyman-colvin lange, morgan marshall, g/cu cm, thermal expansion, kim et, kim et al, honeyman-colvin lange 8, lange 8, composites ceram soc, glass-ceramic matrix composites,
Approximate Word count = 3644
Approximate Pages = 15 (250 words per page)

More Essays on CERAMIC MATRIX COMPOSITES Ceramic Matrix Composites