Experimental and theoretical investigations on the changes in the properties and structure of the structural and functional materials under the influence of temperature-force, radiation, magnetic and electric fields are carried out in the department for the development of new materials and technologies in nuclear power industry and other fields of technology:

– investigations on the processes of plastic deformation, structure formation, strengthening, softening and destruction of structural materials for reactor engineering and cryogenic technology under the extreme conditions of exposure (large plastic deformations, wide range of temperatures, including low ones, strong magnetic fields, irradiation and their combination) and establishment of correlation between the structural factors, physical and mechanical properties for obtaining the materials with high performance and restoring properties that degraded during operation;

– experimental and theoretical studies at the atomic level of the structure for crystal lattice defects, the processes of their interaction and evolution of structural elements under mechanical, thermal and radiation effects; field ion microscopy studies of quantum objects – atomic chains of carbon and graphene;

– search and study of new physical phenomena that are realized in pure and ultrapure metals and alloys on their basis in order to use them for the development of new technologies in nuclear power engineering and other fields of technology; investigation of the features of electrophysical and magnetic properties in superconducting, normal and magnetically ordered states of metals and alloys with nanoscale structures;

– investigation of adsorption and desorption for various gaseous substances, including gaseous fission products of nuclear fuel and hydrogen, functional and structural materials; study of the properties of coal sorbents on the market for their use in the manufacture and repair of iodine filters for the ventilation system of NPPs.

Research on the physics of strength

Nanostructured materials (austenitic steels, Zr, Ti, Nb and alloys) with high performance (exceeding those obtained with the traditional treatment) were obtained by the unique methods of severe plastic deformation at cryogenic temperatures (quasihydroextrusion (QHE), rolling and drawing). Reasonability for sequential combination of pressure treatments with different stress distributions in order to achieve a high level of hardening without disrupting the material continuity is experimentally substantiated.

Dependence of the yield strength for the VT6 alloy on the degree of deformation by quasihydroextrusion at 77 K after isothermal forging

For magnetically ordered metals, the unified nature of magnetoplastic (under the action of alternating magnetic field (MF)) and electroplastic (under the action of electric field (EF)) effects was determined theoretically and experimentally. The nature lies in metal softening due to the detachment of dislocations from stoppers due to short-wave (Debye) phonons, electrons generated as a result of electron-phonon interaction (EPI), which received energy from the electric field (induction under the MF effect) (jointly with IPENMA).

Methods of relaxation energy effects (ultrasound, non-stationary magnetic fields) were developed as applied to materials and welded joints of NPP equipment:

– as a result of ultrasonic action, the nanostructured Zr1Nb alloy obtained by the combined intense deformation at 77 and 300 K, in comparison with the recrystallized state, has higher creep resistance and strength level with the sufficient plasticity level at the operating temperature of the fuel element claddings;

– the effect of alternating magnetic field of industrial frequency in a certain mode leads to a significant decrease in the effects of radiation and strain hardening, as well as of thermal macrostresses in 15Kh2NMFA hull steel and its welded joints.

Temperature dependences of shock viscosity a_K

before magnetic treatment

after magnetic treatment

Structure of the welded joint (steel in the viscinity of the weld seam and the seam itself) for the 15Kh2NMFA steel before and after magnetic treatment

Study of the fine structure and properties for micro-, nano- and pico-sized materials using the field emission microscopy and mathematical modeling

The strength of carbon monatomic chains was determined experimentally and theoretically. By the method of high-field loading with electric field, it was found that the maximum experimental value for the strength of carbon chains at 5 K is 270 GPa, which corresponds to 90% of the theoretical value for the strength of ideal carbon chain. This value exceeds the strength of all known materials, including carbon nanotubes and graphene.

The change in the increase of resolution for the cryogenic field ion microscope at the decrease in the size of the samples in nano- and subnanometer ranges was studied experimentally and theoretically. The existence of anomalous increase in the field ion images and improvement in the resolution limits to 0.40 ± 0.05 Å was determined..

Schematic diagram for helium field ionization at the top of monoatomic carbon chain

Cohesion energy of special disproportionate grains depending on the misorientation angle

A new class of asymmetric specific grain boundaries that cannot be described by the traditional theory of coincidence site lattices (CSL) was revealed by the method of field ion microscopy and mathematical modeling. It was determined that such specific non-CSL boundaries have high cohesive strength, close to theoretical, and dominate in the spectrum of boundaries for cold-drawn highly textured tungsten. The results obtained can be used in grain boundary engineering of high-strength and radiation-resistant polycrystalline functional and structural materials for reactor engineering.

The phenomenon of long-range interaction of the surface atoms of radiation origin with their own interstitial atoms in the near-surface layers was found by the methods of low-temperature field ion microscopy. It was found that during tungsten irradiation with helium atoms, as a result of this interaction, loose-packed 2D clusters of adatoms appear, and 1D surface chains with the interatomic distance of ≈ 1 nm (marked with pink arrows) are self-consistently formed. A new collective mechanism of radiation-stimulated surface diffusion was determined, including the formation of linearly delocalized vacancies – voidions (dashed line in the diagram) in the surface layer; adatom that appered during irradiation is marked in red.

Formation of adatom linear chains as a result of long-range interaction

Voidion movement scheme

Development of ideas on the nature of high-temperature superconductors

Using the developed original method of electronic subsystem plane-contact probing, for the first time, a large-scale hole-electron conversion of charge carriers was discovered before the transition of cuprate HTSCs to the superconducting state (a sharp drop in the electrical resistance, point 4 in the figure), which shows the electronic-topological Lifshitz transition associated with the achievement of 2D-3D crossover temperature (HTSC trimerization temperatures).

For the first time, convincing experimental evidence was obtained for the existence of positively charged local pairs (LP) in the pseudogap state of HTSCs, the concept of which comes from the Hubbard model. The existence of several stages for the pseudogap temperature evolution is established, and the decrease in HTSC thermal conductivity due to LP is shown.

Precision acoustic studies of crystalline and amorphous materials

In the temperature range of 77-300 K, the elastic, vibrational and dissipative characteristics of bulk metallic glasses (BMG) were measured: Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5, Zr_52.5Ti₅Cu_17.9Ni_14.6Al₁₀ and (Zr₅₅Al₁₀Ni₅Cu₃₀)₉₉Y₁. It is shown that the difference in the elastic moduli and the Debye temperature of BMG with Be and Al corresponds to the difference in sizes of the average ordered region in the efficient cluster packing model. The established features of ultrasound absorption are associated with the intensification of relaxation processes for the migrations of atom clusters at the intercluster boundaries as a result of the action of thermal fluctuations and alternating ultrasonic stresses.

Temperature dependence of the elastic moduli in bulk metal glasses Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5 (1) and Zr5_2.5Ti₅Cu_17.9Ni_14.6Al₁₀ (2)

Acoustic research for high-purity HCP metals (Cd -> 99.999%, Hf – zone-melted) was carried out. In Cd, a first-order isotope effect (linear dependence on the difference in isotope masses) was found for the speed of sound, which shows the influence of isotopic composition on the change in the phonon spectrum; for ultrasound attenuation, a second-order effect associated with the nonuniform distribution of isotopes and additional relaxation mechanism of phonon scattering was found. In a single Hf crystal, the independent adiabatic constants of the elasticity tensor с₁₁ and с₃₃ were determined and their increase was shown together with the decrease in the dislocation density. It was found that the resonance and relaxation features in the behavior of ultrasound absorption in hafnium were caused by the oscillations of dislocation segments in the "valley" of the Peierls potential relief and by overcoming this relief.

The universal ratio for the reduced velocity of longitudinal ultrasound versus the reduced temperature T*=T(Mⁱ_C/M²_C)^1/2 for Cd isotopes

The pumping module "SKIF-1" is used for controlled saturation of the studied sorbent layers with methyl iodide/iodine admixture along the height of the adsorber experimental model at the given temperature, humidity and concentration of impurity vapors in the air flow

Investigation of carbon sorbents for NPP air filters

The SKIF-1 module was manufactured for pumping the air flow with iodine/methyl iodide admixture through the adsorber experimental model with carbon sorbent, and the method for measuring the absorption of these impurities under the conditions simulating the operation of AU-1500 adsorbers used at Ukrainian NPPs was developed.

The adsorption, aerodynamic and mechanical properties for a number of coal sorbents produced in Ukraine, Germany and Holland were studied, which made it possible to select sorbents with optimal performance characteristics. Taking into account the results of these studies, more than 200 adsorbers were repaired and manufactured by JV “Atomenergomash” of NNEGC “Energoatom”.

– Laboratory of Fundamental and Applied Superconductivity, Electronic Properties of Metals.

Investigations on the electronic processes and electronic-phase state of new alloys, metals and superconductors depending on the composition and structural state.

– Laboratory of Physics of Strength and Plasticity.

Investigation of submicron and nanometer structure formation in structural materials for reactor and cryogenic engineering by the methods of combined severe plastic deformations, study of relaxation processes in deformed and irradiated materials, welded joints when exposed to ultrasound and non-stationary magnetic fields; establishing the connection between the structural factors, physical and mechanical properties to determine the regimes of exposure that provide high-level properties for the practical use of materials; studies of adsorption and desorption for various gaseous substances (including gaseous fission products of nuclear fuel and hydrogen) in the functional and structural materials, corresponding changes in their physical and mechanical properties.

– Laboratory of Crystal Physics.

Investigation of the atomic structure and interaction of lattice defects in solids and quantum objects (atomic chains of carbon and graphene) using high-resolution low-temperature field ion microscopy and mathematical modeling; ultrasonic studies of the temperature dependence for linear acoustic characteristics (velocity and absorption of ultrasound) of metals and alloys.