Behaviour of implanted helium in boron carbide in the temperature range 750 to 1720°C

Helium behaviour in implanted boron carbide

“…The results we obtained here were coherent with previous ones [10][11][12][13][14][15]. However, implanting helium in a thin slab led to different behaviours as compared to those observed in homogeneously implanted or neutron irradiated materials.…”

“…Two methods can be used: either by recording a diffraction pattern then indexing it, or performing high resolution observations by measuring the distance between atomic planes then deducing their Miller indexes. Both methods led to the same result: the bubbles were oriented along the (111) rhombohedral plane (or (0003) hexagonal plane), as was already reported in literature [10][11][12][13]. Fig.…”

“…It was difficult to orientate those flat bubbles with respect to the crystal structure, because they need to be on the edge for the observation (which is not exactly the case here), and the sample could not be correctly oriented because the sample was too far from a zone axis. We can notice the presence of strain fields around the clusters as a pattern of "butterfly's wings", which was a consequence of the high pressure of the gas inside the cluster [13].…”

“…Helium accumulates in flat, high pressure and parallel bubbles (mainly parallel to the (111) planes [10][11][12][13] and also to the (100) and (110) planes [12][13][14][15] of the rhombohedral structure). In fast neutron reactors, the combination of heat release and helium production induces strong radial thermal gradients and extensive cracking of the absorber pellets [4,16,17] as shown in Figure 4.…”

In Situ EELS and TEM Observation of Boron Carbide (B4C) During Hydrogen- and Helium-Ion Bombardments

“…The B4C also attracts a lot of attention for the use as the first-wall material in a fusion device because of its favorable nuclear properties to suppress plasma impurities [1,2]. From these viewpoints, many kinds of studies have been carried out on the irradiation effects of neutron- [3,4], hydrogen- [5], electron- [6], and helium-ion irradiations [7] on this material. There are few data, however, with electron energyloss spectroscopy (EELS) on B4C, the information from which is expected to help us understand the chemical aspect of the structural change of particle-bombarded B4C.…”