Infrasonic Nanocrystal Formation in Amorphous NiTi Film: Physical Mechanism, Reasons and Conditions

The physical mechanism, reasons and conditions of nanocrystal formation in an amorphous NiTi metal film, stimulated by infrasonic action, are formulated. Nanostructural elements of an amorphous medium (relaxation centers) containing disordered nanoregions with two-level systems are considered to be responsible for this process. When exposed to infrasound, a large number of two-level systems are excited, significantly contributing to inelastic deformation and the formation of nanocrystals. The physical mechanism of the nanocrystallization of metallic glass under mechanical action includes both local thermal fluctuations and the additional quantum tunneling of atoms stimulated by shear deformation. A crystalline nanocluster appears as a result of local atomic rearrangement growing increasingly exposed to infrasound. It is possibly unstable in the absence of infrasound. When the radius of the nanocluster reaches a critical value, a potential well appears, in which a conducting electron is localized to form a phason (stable nanocrystal). Estimated values of the phason’s radius and the depth of the nanometer potential well is about 0.5 nm and 1 eV, respectively. It forms a condition of stable phason formation. The occurrence of the instability of the amorphous state and following transformation to the nanostructured state is based on the accumulation of the potential energy of inelastic deformation to a critical value equal to the latent heat of the transformation of the amorphous state into the nanostructured state.

The nanostructured or colloidal state is the fifth aggregate state of substance

The article shows that the basis of nanotechnology is the discovery in the early 20th century of a colloidal (ultradispersed) or nanostructured state of substance, in which the dimensions of physical and/or chemical dispersed phases distributed in the dispersion medium of a substance have dimensions less than 100 nanometers, at least in one coordinate. Since any substance, regardless of its chemical composition, can be converted to a nanostructured state, this state should be considered the fifth aggregate state of substance, along with the solid, liquid, gaseous and plasma states. The transfer of substances and / or materials to the nanostructured state can be carried out by numerous different methods, which defines a wide range of nanotechnologies. And since the nanostructured state is a new aggregate state of substance, it has unique physical and chemical properties compared to the usual solid substance.