Accession Number : ADA495056


Title :   Design of Ultra-High Temperature Ceramics for Improved Performance


Descriptive Note : Final performance rept. 1 Jan 2006-31 Dec 2008


Corporate Author : MISSOURI UNIV OF SCIENCE AND TECHNOLOGY ROLLA


Personal Author(s) : Fahrenholtz, William G ; Hilmas, Greg E ; Watts, Jeremy


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a495056.pdf


Report Date : 28 Feb 2009


Pagination or Media Count : 49


Abstract : The thermal shock behavior and thermal residual stresses were investigated for zirconium diboride-based ultra-high temperature ceramics. The research employed a combined experimental and finite element modeling approach to understand the factors that affected the magnitude and spatial extent of residual stresses. Then, engineered architectures were designed and fabricated to mitigate thermal stresses. This approach led to an improvement in thermal shock behavior. Whereas the strength of conventional SiC particulate reinforced zirconium diboride ceramics decreased by more than 30% after quenching from 400 deg C, fibrous monolithic ceramics could be quenched from temperatures as high as 1400 deg C without degradation of strength. The study of residual stresses revealed that the magnitude of the tensile stresses in the zirconium diboride matrix was relatively insensitive to the size of the silicon carbide particulates, but the spacial extent of the stresses was strongly linked to particle size and shape. A combination of elevated temperature neutron diffraction and Raman spectroscopy were used to measure thermal stresses for validation of the models.


Descriptors :   *THERMAL STRESSES , *CERAMIC MATERIALS , *THERMAL SHOCK , FINITE ELEMENT ANALYSIS , ZIRCONIUM , NEUTRON DIFFRACTION , SILICON CARBIDES , RAMAN SPECTROSCOPY , HIGH TEMPERATURE , THERMAL PROPERTIES , RESIDUAL STRESS


Subject Categories : Ceramics, Refractories and Glass
      Mechanics


Distribution Statement : APPROVED FOR PUBLIC RELEASE