Search academic texts

Information × Registration Number 0225U002283, (0123U101802) , R & D reports Title Inner size effects in nanocomposite structures as a physical basis for dual-use technology popup.stage_title Внутрішні розмірні ефекти в нанокристалічних структурах. Head Sukhov Volodymyr М., Кандидат фізико-математичних наук Registration Date 28-02-2025 Organization V.N. Karazin Kharkiv National University popup.description1 The goal of the project is to solve urgent scientific problems in the physics of low-dimensional systems: to establish the physical essence of the inner size effects in such nanocomposite structures. One of the goals of the work is to develop new materials suitable for the development of nanotechnologies and the creation of novel instrumental structures with increased efficiency. In this work, the structure of vacuum condensates obtained under different conditions will be determined, and methods of targeted control of the nanostructural state of the films will be developed. The size effects of electrical conductivity and thermal expansion will be investigated using the author's in situ techniques. General scientific results obtained in the study of dimensional effects in metal thin films will make it possible to determine ways of creating instrumental materials with specified properties. The study of metal layers will be extended to the case of functional thermoelectric materials. It is expected that targeted management of the metal layer microstructure will significantly improve the technological properties of functional layers based on them. In particular, it is expected to improve the thermoelectric power coefficient and bending stability of the materials. The introduction of such SMART nanocomposite materials is primarily needed to provide autonomous and continuous power for wearable medical devices, but they can also find application in improving the energy efficiency of buildings and in general and dual-use detection and signaling systems. popup.description2  The electrical conductivity and thermal expansion of nanocrystalline metal films are studied . It is shown that the temperature coefficient of electrical resistance (TСR) for Cu and Ag films is several times less than the TCR of the bulk. The observed differences decrease with increasing grain size. Qualitative differences in the electrical conductivity of Cr layers start with a grain size of ~11 nm. For such samples, there is an inversion temperature, upon reaching which the sign of the TCR changes. Up to the inversion temperature, the TCR is lower than the tabulated value but is positive. Upon passing through the inversion temperature, a negative TCR is observed but it remains linear. Size effects become even more significant with decreasing grain size . The negative TCR value for V films is observed in the whole investigated temperature range. Negative TCR is also characteristic of Mo layers. We have confirmed of the relationship between TCR and grain size. This is done using condensation-stimulated diffusion, which allows us to change the grain size of refractory films effectively. The observed phenomenon is explained within the matrix model. The physical explanation of the effect is an increase in the contribution of reflection of conduction electrons from grain boundaries when the grain size is smaller than the mean free path of electrons. Size effects were observed in the context of thermal expansion. For Ag films, these effects are quantitative. A decrease in their thermal expansion is observed. The obtained values of thermal expansion are close to the expansion of Ge and Si. An inversion of the thermal expansion coefficient is observed for V. A thermodynamic interpretation of this a phenomenon is proposed. It is based on considering the increase in the effective area of the grain boundary upon heating. According to our model, this causes a decrease in the interplanar distances in the grain volume. Product Description popup.authors Bohatyrenko Serhii I. Dukarov Serhii V. Petrushenko Serhii I. Sukhov Volodymyr M. Churilov Ihor H. popup.nrat_date 2025-02-28 Close