Helium Release and Physical Property Change of Neutron-Irradiated .ALPHA.-SiC Containing B4C of Different 10B Concentrations

Study of helium bubble formation in SiCf/PyC/β-SiC composites by dual-beam irradiation

“…The He release studies [3,10] showed that (a) a small amount of helium have released from SiC at temperatures below 500°C, (b) a large amount of helium are released in the temperature range 800-1500°C and (c) a final helium release peak shows up and increases very rapidly in the even higher temperature region above 1700°C. Based on those results of the He release studies, possible He diffusion modes for different temperature regions are suggested and described below.…”

“…Helium can then become mobile through the vacancy motion. In many of electron spin resonance (ESR) [12] and helium release [10] studies on b-SiC, it has been reported that silicon vacancies start substantial migration at about 800°C. Therefore, for temperatures above 800°C the He diffusion in SiC grains via vacancy mechanism would be dominant.…”

Helium release and diffusion mechanism in SiC containing B4C

“…Specimens were sintered a-SiC ceramics containing B 4 C with different 10 B concentrations, the same specimens as previously reported [8]. For helium release measurement, samples were prepared containing 0.4 wt% B 4 C with different 10 B concentrations, i.e., 19.6% and 91.6% 10 B, named natural and enriched B 4 C, respectively.…”

“…The fractional release f ðtÞ is defined as the amount of helium released until time t divided by the total released helium up to 1920°C [8]. The formula is valid if p 2 Dt=a 2 is less than 1 [11,12], and according to Ref.…”

“…Temperature dependence of helium release from powder and bulk specimens was reported. The present authors examined helium release behavior and change in physical properties of neutron-irradiated SiC ceramics containing B 4 C of different 10 B concentrations [8], and investigated their microstructures by transmission electron microscopy (TEM) after annealing at several temperatures [9].…”