Neutron irradiation induced amorphization of silicon carbide

This paper provides the properties of bulk stoichiometric silicon carbide w hich has been amorphized under neutron irradiation. Both high purity single crystal hcp and high purity, highly faulted (cubic) chemically vapor depos ited (CVD) SiC were irradiated at approximately 60 degrees C to a total fas t neutron fluence of 2.6 x 10(25) n/m(2). Amorphization was seen in both ma terials as evidenced by TEM, electron diffraction and X-ray diffraction tec hniques. Physical properties for the amorphized single crystal material are reported including large changes in density (-10.8%), elastic modulus as m easured using a nanoindentation technique (-45%), hardness as measured by n anoindentation (-45%), and standard Vickers hardness (-24%). Similar proper ty changes are observed for the amorphized CVD SiC. Using measured thermal conductivity data for the CVD SiC sample, the critical temperature for amor phization at this neutron dose and flux, above which amorphization is not p ossible, is estimated to be greater than similar to 125 degrees C. (C) 1999 Published by Elsevier Science B.V. All rights reserved.