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Mechanical and thermal properties of AlN–BN–SiC ceramics
Authors:Andrew A. Buchheit   Greg E. Hilmas   William G. Fahrenholtz   Douglas M. Deason  Hsin Wang
Affiliation:aMaterials Science and Engineering Department, Missouri University of Science and Technology, Rolla, MO 65409, United States;bU.S. Army Space & Missile Defense Command, Building 5220, Redstone Arsenal, AL 35898, United States;cOak Ridge National Laboratory, High Temperature Materials Laboratory, Oak Ridge, TN 37831, USA
Abstract:Mechanical and thermal properties were characterized for two AlN:BN:SiC composite ceramics produced from BN with different particle sizes. The ceramics were hot pressed at temperatures from 1950 to 2100 °C to not, vert, similar97% relative density. For both materials, the matrix (90:10 vol% SiC:AlN) had a grain size of not, vert, similar0.4 μm, and the BN grains (10 vol%) were crystallographically aligned. Microhardness values were between 20 and 22 GPa, while fracture toughness values were between 2.5 and 3.1 MPa m1/2. Other properties were found to be dependent on testing direction. Elastic moduli were between 260 and 300 GPa and strengths were not, vert, similar630 MPa for small particle BN additions. Thermal conductivity was calculated to be between 25 and 37 W/m K at room temperature and 17 and 25 W/m K at 900 °C. The low values compared to traditional SiC ceramics were attributed to AlN–SiC solid solution formation and sub-micron matrix grain sizes.
Keywords:Aluminum nitride   Boron nitride   Silicon carbide   Mechanical properties   Thermal properties   Hot pressing
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