CoFe/Al2O3 composite nanoparticles were successfully prepared by hydrogen-thermally reducing cobalt aluminum ferrite. Compared with CoFe alloy nanoparticles, the permeability of CoFe/Al2O3 composite nanoparticles was remarkably enhanced and an improved impedance characteristic was achieved due to the introduction of insulated Al2O3. A multilayer absorber with CoFe/Al2O3 composite nanoparticles as the impedance matching layer and CoFe nanoflake as the dissipation layer was designed by using genetic algorithm, in which an ultrawide operation frequency bandwidth over 2.5–18 GHz was obtained. The microwave absorption performance in both normal and oblique incident case was evaluated by using electromagnetic simulator. The backward radar cross-section (RCS) was decreased at least 10 dB over a wide frequency range by covering the multilayer absorber on the surface of perfect electrical conductive plate.

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Adsorbed atoms (adatoms) and vacancies have a significant role to play in the physics of surfaces and the mechanisms of film growth on a substrate. This paper investigates the effect of applied or residual strain on the energetic interaction between pairs of adatoms and vacancies. The analysis is based on a continuum-level point-defect model, where adatoms and vacancies have strain-dependent properties. Atomistic calculations are used to evaluate the defect properties for Si(111). The result is used as input for the defect model in order to investigate the strength and character of the interaction versus strain, separation distance, and relative orientation of the defects. It is found that strain may cause the defects to align in certain direction and modulate their interaction between repulsion and attraction, providing a mechanism for controlled building of nanostructures.

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