Fundamental and applied aspects of low-temperature and high-temperature superconductivity.
Physics of strength and plasticity of solids.
Physics of radiation effects and radiation materials science. Radiation, ion-beam technologies. Transmutation of nuclei and other nuclear technologies.
Physics and chemistry of ion-plasma, plasma-chemical and diffusive methods of depositing coatings to increase wear resistance, high temperature strength, corrosion stability and to improve other properties of materials.
Physical materials science of pure and superpure metals and semiconductors. Development of technology for their production and analysis.
Development of constructional materials. Composite materials. Carbon and graphite materials. High-temperature and gasostatic technologies.
Development and research of nuclear fuel and absorbing materials. Design and technology of manufacturing fuel and absorbing elements, and fuel assemblies. Handling of spent nuclear fuel. Technological support of a nuclear fuel cycle of Ukraine.
Basic results of recent years
SUPERCONDUCTIVITY
The superconductor Nb3Sn has been synthesized as a long-measuring tape with an achieved ultimate critical current density corresponding to attaining the energy of electron pair unpairing by an electron condensate. On this basis and with the use of magnetic field concentrators the laboratory solenoid was made from hydrostatically extruded dysprosium, allowing the operation in fields higher than 210═kOe.
Methods of synthesizing high-temperature superconductors (HTSC) with structures of concentrators La2CuO4 (TC=40 K), Yba2Cu3O7-d(TC=92 K), Yba2Cu4O8╠d(TC=80 K), Bi2Sr2CaCu2O8╠d(TC=80 K), Bi2Sr2Ca2Cu3O10╠d(TC=107 K), Tl2Ba2Ca2Cu3O9╠d(TC= 120═K), etc. are advanced. An investigation into the effect of replacement of elements in various HTSC crystal lattice sites on the structure and fundamental physical properties of superconductors in normal and superconducting states has allowed to optimize HTSC application in high-current engineering.
New ways of producing HTSC-based materials for high-current engineering are advanced. These are the directional crystallization of nonmonophase composites (e.g., Yba2Cu3O7-d+ Y2BaCuO5), magnetic texturing of powders at T<TC, laser processing, active action on the state of intergranular boundaries, i.e. "weak couplings" of superconducting circuits, by replacement of elements and introduction of additives (Ag, Nb, Zr, etc.). Samples of the HTSC-wires and tapes with a critical current density jC>4.5 x 104 A/ci2 are obtained. Methods of production of high-current engineering materials based on thallium HTSC with OC>120 E are developed.
The effect of electronic reflection of phonons from the "normal metal-superconductor" (N-S) boundaries that occurs with the change of sign in the phonon pulse has been investigated. The effect of abrupt change in crystal lattice parameters of YBa2Cu3O7-dis disclosed at N-S-transition in a magnetic field. Revealed is also the threshold effect of a magnetic field on the behavior of HTSC resistance curves.
Influence of irradiation on the transport properties of HTSC single crystals is investigated. The effect of sign change of the radiation contribution to TC, depending on a dose of 3 MeV electrons, is found out.
New devices based on HTSC-materials and intended for control systems, e.g., switching and multifunctional logic elements with two channels of control (in the magnetic field and in the current) were designed, constructed and patented. HTSC-materials to be applied as current limiters, energy converters, etc. are created.
PHYSICS OF RADIATION EFFECTS AND TECHNOLOGIES
New physical notions of the processes of interaction of fast particles and radiations with solids, mechanisms of defect formation and defect structure evolution are originated and developed. Phase transitions in metals, steels and alloys, in semi-conductive and superconductive materials are investigated under irradiation in reactor and accelerator conditions.
The theory and methods of rapid simulation of radiation effects occurring in materials of nuclear and fusion reactor cores are developed. The efficiency of use of high-energy electrons and gamma-quanta (30 - 250 MeV) to simulate the influence of reactor irradiation on the mechanical properties of materials is substantiated and confirmed by experiments.
The methods devised for promoted (100 - 1000 times) study and prediction of the behavior of materials in fissile cores and fusion reactors through the use of ecologically safe for the environment of high-current charged particle accelerators and computer simulation allow one to quickly select materials for in-reactor high-dose tests and to reduce by factors of 3 to 5 the time allotted for research and development of new materials.
THE MULTICHARGED ION ACCELERATOR FOR MATERIALS SCIENCE STUDIES ("ESUVI")
Based on the studies into the influence of dissolved additives and combined effects of microalloying, high-frequency treatment and radiation-induced processes of component redistribution and segregation of elements on structural-phase states, properties and radiation resistance of steels and alloys, the scientists were able:
to reveal new aspects of a physical nature of radiation-induced phenomena in materials (swelling, embrittlement, creep, surface erosion, etc.), and thus to direct the way to increase their radiation stability;
to justify the possibility for formation and existence of nonsaturated sinks for point defects in crystal and amorphous materials under irradiation, i.e., the so-called alternating-polarity point defect recombination centres;
to discover a new phenomenon of anomalous recombination of radiation defects in continuously decomposing solid solutions under irradiation;
to develop methods for calculating and constructing radiation-modified phase diagrams of alloys at different defect production rates;
to establish regularities in the evolution of a structural-phase state under irradiation to high doses in view of cascade mechanisms of dissolution and growth of new phases, and other factors.
As a result of research into changes of mechanical and corrosive properties of structural materials (austenitic and martensitic steels, nickel-, chromium-, vanadium-, zirconium-base steels) a complex approach is developed to achieve high burnup of nuclear fuel.
The technology is developed for manufacturing products from zirconium-base alloys with a strengthened quasiisotropic fine-grained structure by the use of high-speed heat treatment. Such products (tubes, rods, etc.), after irradiation up to 8 x 1026═n/m2 showed a considerable reduction in creep and no radiation-induced growth.
New concepts are elaborated with regard to structural changes in solids at condensation of particles under irradiation. They much extend the potentialities of radiation, ion-beam and vacuum-plasma technologies for creation of radically new materials, for increase of wear resistance and corrosion stability of tools and products.
Studies into the processes of interaction of electrons and photons with polymers, organic substances and biological samples in cooperation with Institute of High-energy Physics and Nuclear Physics have led to new technologies for radiation sterilization of medical equipment; new electrophysical technologies and equipment in the field of environmental protection and agricultural production are under development.
PHYSICS AND CHEMISTRY OF COATINGS
Methods of x-ray analysis, mass-spectrometry and probing diagnostics have been used to investigate physical parameters and processes occurring in a mixed gas-metal low temperature nonequilibrium plasma of different composition. It is shown that under given conditions the maximum achievable ionization of metallic vapors (up to 100%) and high plasma-energy parameters provide for a defect-free strong cohesion of coatings with base materials and result in the formation of assigned structure and properties of coatings with coating thickness reaching 10 to 100 microns.
It is found that, in conditions of slowed adatomic two-dimensional migration and in the absence of kinetic slow-down of metal-metalloid reactions in localized regions of the surface layer, the condensate forms the structures of amorphous and microcrystal types. This process is also accompanied by the formation of strongly supersaturated solid solutions and metastable phases, absent in equilibrium diagrams.
It is shown that the polyenergetic multiphase ion flow, generated by a plasma source, allows to carry out multipurpose technologies of ion implantation at significant depths in order to modify the material surfaces. It has found application to increase the corrosion resistance of materials.
As a result of researches, a number of ecologically clean technologies of coating deposition at low temperatures have been introduced into certain engineering and consumer domains (strengthening of cutting tools and machine components, anticorrosive and protective-decorative coatings, thick-coated molding-type products, high-temperature protective coatings, etc.). For realization of these technologies special installations BULAT, AIR, YANTAR, POTOK, BAZAL'T and others are designed and constructed.
ULTRAHIGH-PURITY METALS AND NEW STRUCTRAL MATERIALS
Complex physical techniques of manufacturing ultrahigh-purity metals are developed, which are based on electron-beam remelting, vacuum distillation, zone recrystallization, electrotransfer. Physical properties of these materials are investigated.
Purity
weight. %
R293K/R4,2K
Beryllium
99,995
2000-3000
Rhenium
99,9999
60000
Ruthenium
99,999
3500
Osmium
99,999
2500
Niobium
99,9996
12000
Zirconium
99,999
450
Hafnium
99,99
400
Molybdenum
99,9999
30000
Tungsten
99,99995
70000
Chromium
99,99
140
Nickel
99,9995
1000
Gallium
99,99999
90000
Magnesium
99,99
1000
Manganese
99,99
1000
Physical principles of attacking the problem of beryllium brittleness are elaborated. As a result, a superdactile metal is produced; superthin vacuum-tight beryllium foils are manufactured; small-size transformers are made from long-measuring beryllium hyperconductors with a record high electrical conductivity at 77 K.
On the basis of ultrapure initial and auxiliary materials GaAs single crystals of improved quality are grown by the principle "a crystal in the flux". Their structure and electrophysical characteristics are investigated.
Methods of hot pressing in vacuum are developed and high productivity facilities to produce materials from ceramics ((B4C, BN2, NiB, SiC, Si3N4, Al2N3) and tungsten-containing hard alloys are created. Areas of their application are:
tribology (radial bearings, end seals, etc.);
crucibles for high-purity material melting and single-crystal growth;
cutting tools;
structural elements for work at high temperature and in aggressive media;
The method of hot rolling in vacuum enables production of bimetals and layered composites which can have the most diverse combination of layers from refractory, nonferrous, rare and other metals and alloys. A high interfacial breaking strength of bimetals and layered composites allows to use various manufacture processes (e.g., heat treatment, machining, forging, pressing, etc.) to manufacture shaped products.
THERMAL-GRADIENT GAS-PHASE TECHNOLOGIES OF CARBON-BASED AND CARBON-CARBON COMPOSITE MATERIALS
Gas-phase methods and technologies are developed to produce high-quality carbon materials. The equipment for manufacturing products from them is created, ensuring the highest possible void filling with pyrocarbon, even for large-sized products with linear dimensions up to 2600 mm. The technologies and equipment are introduced into full-scale production in the former USSR for manufacturing space-engineering products, fuel elements and absorbing elements of nuclear reactors. At the moment the technologies are used to manufacture:
high-temperature heaters (up to 3000OC), thermal shields and auxiliary equipment for silicon single crystal growth═ and production of semi-conductor materials, for melting and synthesis of other high-temperature materials;
crucibles and foundry equipment for melting of ferrous, non-ferrous and noble metals;
dies and press-forms for high-temperature pressing of metals, ceramics and diamond tool;
electrodes, baskets for heat treatment, electroplating, electrolysis and other processes;
heat-exchanging fittings for operation in aggressive liquid and gaseous environments;
structural elements of nuclear reactors and fusion devices;
The gasostatic equipment ("GAUS") is designed and made on the basis of a up to 1000 MPa and a temperature up to 2000OC. The following processes are being devised to manufacture and process components and materials at high pressures:
gasostatic pressing of metal and ceramic hard alloys, casting, single crystals, light guides, magnets, ceramic and piezoelectric ceramic products, ceramic dies;
mineralization and encapsulation of radioactive materials (high-level wastes, fuel elements and assemblies) for a long-duration storage and disposal.
VACUUM CENTRIFUGAL CASTING OF STEELS AND ALLOYS
Technologies and equipment are developed which provide:
removal of nonmetallic inclusions from steels and alloys;
reduction by factors 2 to 3 of energy consumption in manufacture of round billets from stainless and heat-resistant steel;
double gain in metal utilization;
high technological plasticity of steels and alloys.
FUEL AND ABSORBING MATERIALS, FUEL ELEMENTS
The studies of physical processes, occurring in metals during phase transitions, have given rise to the methods for heat treatment of metallic uranium, making it possible to manufacture products with the given characteristics of radiation-induced swelling and growth. As a result, new high-strength and corrosion-resistant uranium alloys are obtained.
Developed are new fuel and absorbing composite materials of a dispersion-matrix type: graphite - uranium oxide; metal (chromium, zirconium, etc.) - metallic uranium, uranium oxide; metal - cadmium, etc.
New technologies of manufacturing high-temperature oxide compounds of absorbing materials such as GdAlO3, Gd2TiO5, etc. are created.
With new materials and technologies as the basis the investigators can produce:
fuel elements for high-temperature gas-cooled reactors, for heavy-water reactors with a gaseous coolant;
fuel elements with fuel of increased density for water-moderated reactors;
fuel elements for complicated conditions of work in special apparatuses (chemically aggressive coolants, long service life, high burnups, etc.).