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Electronic and structural properties of copper monoxide (CuO) sintered as a common ceramic and nanoceramic are studied by positron annihilation spectroscopy. A CuO nanoceramic with crystallite size ranging from 15 to 90 nm was prepared from a common one by shock-wave loading. It is found that the momentum distribution of valence electrons in CuO is shifted, as compared with metallic copper, towards higher momentum values. This result is related to the effect of the Cu 3d–O 2p hybridization in the Cu–O ionic covalent bond formation. It is found that open volumes, identified mainly as small agglomerates of oxygen vacancies, appear at the nanoceramic crystallite interfaces. The degree of the Cu–O bond covalency decreases locally at the crystallite interfaces because of an oxygen deficit. The nanocrystalline state in CuO is shown to be thermally stable up to 700 K.

The affinity-induced positron state was detected in ‘defect-free’ intermetallic particles using angular correlation of annihilation radiation. It was found that approximately 98% of the positrons annihilate within nanosized and subnanosized intermetallic particles embedded in an fcc Fe–Ni–Al alloy. These particles were created by means of thermal ageing. The ultrafine particles had a structure of the Ni3Al type with addition of Fe atoms. The nanoparticles were three-dimensional and had no open-volume defects at the interfaces, which could trap a positron. These observations suggest that this positron state promises to be a powerful tool for studies of mesoscopic systems in condensed matter.

In this paper we study the effects of intermetallic nanoparticles like Ni3Al on the evolution of vacancy defects in the fcc Fe–Ni–Al alloy under electron irradiation using positron annihilation spectroscopy. It was shown that the nanosized (∼4.5 nm) intermetallic particles homogeneously distributed in the alloy matrix caused a several-fold decrease in the accumulation of vacancies as compared to their accumulation in the quenched alloy. This effect was enhanced with the irradiation temperature. The irradiation-induced growth of intermetallic nanoparticles was also observed in the pre-quenched Fe–Ni–Al alloy under irradiation at 573 K. Thus, a quantum-dot-like positron state in ultrafine intermetallic particles, which we revealed earlier, provided the control over the evolution of coherent precipitates, along with vacancy defects, during irradiation and annealing. Possible mechanisms of the absorption of point defects by coherent nanoparticles have been discussed too.