Physical property change of heavily neutron-irradiated Si3N4 and SiC by thermal annealing

Relation between macroscopic length change and the crystal structure in heavily neutron-irradiated ceramics

“…The irradiation temperatures were estimated from TED temperature monitors. On the other hand, in our previous studies [7][8][9], irradiation temperature was estimated by calculations, which led to a small difference between them and the present study. The measurement of the macroscopic length change was performed by conventional flat-type micrometer at room temperature.…”

“…In this paper, measurements of macroscopic length changes were carried out for heavilyneutron-irradiated a-Al 2 O 3 , AlN, b-Si 3 N 4 and b-SiC they were irradiated under the same conditions. Some of them were reported in our previous papers [7,8], but additional data on swelling for each specimen are presented, and the data are compared for these four kinds of ceramics. The differences are arise from many factors given above, nevertheless in this paper, we discuss the swelling behavior from the viewpoint of crystal structure for each material.…”

Structures of Dislocation Loops in Some Ceramics Induced by Fast Neutron Irradiation.

“…16),17) Figure 3 is a summary of loop for mation/XRD line broadening conditions in SiC as a function of neutron uence and irradiation temperature. 18) If SiC is irradiated in the range of no dislocationforming regime, the correspondence of lattice parameter increase and macro scopic length growth is almost the same, and recovery of the macroscopic length and lattice parameter due to thermal an nealing also indicates good correspondence of these values. In this case, the induced defects are mostly in the form of point defects such as Frenkel defect or very small clusters of point defects such as diinterstitials and divacancies.…”

Thermal Diffusivity of Ceramics During Neutron Irradiation

“…This phonon-lattice scattering is decided by grain size or concentration of impurity in the case of unirradiated ceramics, but neutron irradiated material contains many lattice defects, especially vacancy scatters phonon severely. Hence, it has also been reported that neutron-irradiated specimens show severe degradation in the thermal diffusivity [5][6][7][8][9][10][11][12]. These post irradiation measurements were performed at room temperature to specimens after the irradiation.…”