Macroscopic properties and microstructure changes of heavily neutron-irradiated β-Si3N4 by 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.…”

Saturation in degradation of thermal diffusivity of neutron-irradiated ceramics at 3×1026n/m2

“…Irradiation conditions for each specimen are listed in Table 1 and additional details were reported in our previous papers [9,10]. In our previous works [6][7][8], it was reported that specimens irradiated to neutron fluences of 0.4-1.4 · 10 26 n/m 2 (correspond to specimen ID T7x) showed very low thermal diffusivity. In this work, specimens irradiated to 2.8-8.0 · 10 26 n/m 2 at higher temperatures (correspond to specimen ID T5x) were measured.…”

“…In ceramic materials, heat is mainly carried by phonons unlike metals, and neutron irradiation induces many crystalline defects that influence the phonon transfer. It has been reported that thermal diffusivity and conductivity showed significant decrease after neutron irradiation [3][4][5][6][7][8].…”

“…In our previous works [6,8], a-Al 2 O 3 , AlN, bSi 3 N 4 and b-SiC specimens that were irradiated to neutron fluences of 0. 4 low thermal diffusivity.…”

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.…”