Effect of oxygen impurity on defect agglomeration and hardening of neutron-irradiated niobium

A channelling study of helium-ion irradiation damage in niobium I. Effect of dissolved oxygen

“…Since i t has been assumed that for the clusters of interest here the dechannelling cross-section per defect is an increasing function of cluster size, it must be supposed that the interstitial clusters are smaller than the vacancy clusters. This is consistent with the high nucleation density and small size of interstitial clusters observed by electron microscopy in niobium electron-or neutron-irradiation at low temperature, and with the effect of oxygen in reducing the size of clusters and increasing their density (Loomis andGerber 1973, Igata, Watari andMurakami 1975).…”

“…The presence of oxygen is known to increase the nucleation density and reduce the average size of interstitial clusters (Loomis andGerber 1973, Igata et al 1975). At the irradiation temperature of 86 K, oxygen single-interstitial complexes are not stable (Faber and Schultz 1977), but the effective interstitial jump-rate is reduced by repeated trapping and detrapping a t oxygen atoms.…”

“…metals (Fromm and Jehn 1972) ; in niobium it has been found by lattice-location channelling measurements that dissolved oxygen occupies octahedral interstitial sites (Matyash, Skakun and Dikii 1974). It is also kriown that the presence of gaseous impurities considerably influences radiation damage effects in niobium (Faber and Schultz 1977, Keil, Decker and Diehl 1976, Loomis and Gerber 1973), and this could have important consequences for possible use of the metal in a reactor environment. Better R .…”

Radiation damage in vanadium doped with oxygen

“…decreased r a p i d l y as a f u n c t i o n o f dose a t fi r s t , b u t a t higher doses the decrease was l e s s rapid. ,However, Looniis and Gerber (43) reported that, p a r t i c u l a r l y f o r higher-oxygen samples, the hardening r a t e increased again for s t i 11 higher doses (above about 2 4 x 1 0 '~ n/cm ), w i t h an attendant f u r t h e r decrease i n i n t e r b a r r i e r spacing. I n vanadium, S h i r a i s h i e t a1 .…”

Dispersed barrier hardening in irradiated metals

“…It is generally accepted that the dislocation loops in bcc metals are prismatic with Burgers vector ^ = 3^/2[111] (67) where a^ is the lattice parameter and that they lie on the {111} planes (50,51). Assuming slip in bcc metals to occur primarily on the {110} planes, the loops will intersect the slip planes such that half are normal and half are inclined Table 3 and are plotted in Figure 14 as a function of the annealing temperatures.…”