Accession Number : ADA329644

Title :   Synthesis of High-Temperature, Monolithic Ceramic Bodies and Ceramic-Matrix Composites by the Oxidation of Solid Metal-Bearing Precursors (SMP).

Descriptive Note : Final rept. 15 Apr 94-14 Apr 95,

Corporate Author : OHIO STATE UNIV COLUMBUS DEPT OF MATERIALS SCIENCE AND ENGINEERING

Personal Author(s) : Sandhage, Ken H. ; Fraser, Hamish L.

PDF Url : ADA329644

Report Date : 21 SEP 1995

Pagination or Media Count : 50

Abstract : This one-year project has been focused on synthesizing near net-shaped celsian and celsian composites by the oxidation of solid, alkaline-earth-metal-bearinmg precursors. Key results are: Near net-shaped bodies of celsian and celsian-zirconia composites were produced from Ba(Sr)-A1-A12O3-SiO2 and Ba-A12O3-Si-SiO2-ZrO2 precursors, respectively. Monoclinic celsian and celsian-zirconia composites were synthesized at > or =1200 deg C. Altex(TM) fiber-bearing composites were also produced at > or =1260 deg C. The reaction path to celsian from Ba-A1-Si precursors was evaluated. Barium oxidized rapidly at 300 deg C. The resulting BaO2 reacted with Si at 300-500 deg C to yield Ba2SiO4. Appreciable A1 oxidation occurred during heating from 500 to 800 deg C. Continued oxidation of Si and reaction of SiO2 with A12O3 and Ba2SiO4 at 800-1100 deg C led to other intermediate silicates and then to hexacelsian. Monoclinic celsian formed at 1200-1260 deg C. With Ba-A1-A12O3-SiO2 precursors, extensive Ba2SiO4 formation also occurred at 300 deg C. However, BaA12O4 was produced at 300-650 deg C. Between 650 and 900 deg C, hexacelsian formation commenced at the expense of barium aluminate, silica, and barium silicates. Appreciable hexacelsian formation was observed after 35 hours at 1200 deg C. Monoclinic celsian formed from hexacelsian at > or =1200 deg C. Partial Sr or Mg substitution for Ba enhanced the formation of monoclinic celsian. Mg substitution also led to the formation of barium osumilite.

Descriptors :   *METAL MATRIX COMPOSITES, *CERAMIC BODIES, SILICON DIOXIDE, PRECURSORS, HIGH TEMPERATURE, CERAMIC MATRIX COMPOSITES, SYNTHESIS(CHEMISTRY), OXIDATION, ALUMINUM OXIDES, SILICATES, EVOLUTION(DEVELOPMENT), BARIUM OXIDES.

Subject Categories : Inorganic Chemistry
      Laminates and Composite Materials
      Ceramics, Refractories and Glass

Distribution Statement : APPROVED FOR PUBLIC RELEASE