Defense of the dissertation of Kaliyekperov Malik for the degree of Doctor of Philosophy (PhD) in the educational program «8D05305 - Nuclear physics»

L.N. Gumilyov Eurasian National University, a dissertation defense for the degree of Doctor of Philosophy (PhD) by Kaliyekperov Malik Erlanovich on the topic «Study of the effectiveness of screening of electronic and gamma radiation by composite films XBi₂O₄ - spinel type» in the educational program «8D05305 - Nuclear physics».

The dissertation was carried out at the Department of «Nuclear Physics, New Materials and Technologies» of L.N. Gumilyov Eurasian National University.

The language of defense is russian.

Official reviewers:

Myasnikova Lyudmila Nikolaevna - Candidate of Technical Sciences, associate professor, Member of the Board, Vice-Rector for Academic Affairs of K. Zhubanov Aktobe Regional University (Aktobe, Republic of Kazakhstan);

Nogay Adolf Sergeevich - Doctor of Physical and Mathematical Sciences, Professor of the Department of Radio Engineering, Electronics and Telecommunications of S. Seifullin Kazakh Agrotechnical University (Astana, Republic of Kazakhstan).

Temporary members of the Dissertation Council:

Tatkeeva Galina Galimzyanovna - Doctor of Technical Sciences, Professor, Head of the Department of Electricity Supply of S. Seifullin Kazakh Agrotechnical University (Astana, Republic of Kazakhstan);

Vityuk Vladimir Anatolyevich - Candidate of Physical and Mathematical Sciences, PhD, Deputy Director General for Science of RSE NNC RK (Kurchatov, Republic of Kazakhstan);

Lesbaev Bakytzhan Tastanovich - Candidate of Chemical Sciences, Leading Researcher at the Laboratory of Synthesis of Carbon Nanomaterials in Flame of the Institute of Combustion Problems (Almaty, Republic of Kazakhstan);

Merentsov Alexander Ilyich - Candidate of Physical and Mathematical Sciences, Associate Professor, Senior Researcher at the Institute of Metal Physics of the Ural Branch of the Russian Academy of Sciences (Yekaterinburg, Russian Federation).

Scientific consultants:

Kozlovskiy Artem Leonidovich - Doctor of Philosophy (PhD) in the specialty «6D060500 - Nuclear Physics», associate professor, lecturer-researcher of the department of «Nuclear Physics, New Materials and Technologies» of L.N. Gumilyov Eurasian National University (Astana, Republic of Kazakhstan);

Kanyukov Egor Yurievich - candidate of physical and mathematical sciences, senior researcher at the State Scientific and Production Association «Scientific and Practical Center of the National Academy of Sciences of Belarus for Materials Science» (Minsk, Republic of Belarus).

The defense will take place on June 28, 2024, at 12:00 PM in the Dissertation Council for the training direction «8D053 - Physical and chemical sciences» in the educational program «8D05305 - Nuclear physics» of L.N. Gumilyov Eurasian National University. The defense meeting is planned to be held in a mixed (offline and online) format.

Link: https://clck.ru/3Anfr3

Address: Astana, K. Satpayev str., 2, Main building, room No. 302.

Abstract (English): Dissertation work of Kaliyekperov Malik Yerlanovich «Study of the effectiveness of screening of electronic and gamma radiation by composite films XBi2O4 - spinel type», submitted for the degree of Doctor of Philosophy (PhD) in the educational program «8D05305 - Nuclear physics». The aim of the dissertation research The aim of the dissertation research is to determine the application efficiency of CuBi2O4 films obtained using the electrochemical deposition method as shielding materials to reduce the ionizing radiation intensity. The research objectives 1. Development of technology for production of films using the electrochemical synthesis method, as well as study of the effect of the applied potential difference variation on the phase composition of the resulting films. 2. Determination of the effect of variation in the phase composition of films associated with the formation of impurity oxide inclusions on resistance to external influences, as well as strength characteristics (wear resistance and hardness). 3. Study of the effect of formation of impurities on resistance to degradation as a result of exposure to aggressive media, as well as thermal aging. 4. Study of gamma and electron radiation shielding efficiency using the obtained films as protective shielding materials. Determination of the effect of impurities and elemental composition of films on the shielding efficiency. Research methods As the main method for the production of films, an electrochemical synthesis method was used, the variation of the conditions of which (the difference in applied potentials, temperature and electrolyte composition) allows the production of films with a given phase composition, as well as a certain thickness. Moreover, the choice of this method for production of thin films is due to the possibility of depositing films on almost any surface or material, as well as the possibility of scaling the technology of depositing films on a semi-industrial or industrial scale. Characterization of the resulting films was performed using the methods of atomic force microscopy, X-ray diffraction and energy-dispersive analysis, the combination of which made it possible to determine the dependence of alterations in morphological and structural features, alongside changes in the elemental and phase composition of films in the case of variation in synthesis conditions (alteration in applied potential difference). Determination of the effect of the applied potential difference on the change in the strength properties of the synthesized films was conducted using methods for determining the hardness and wear resistance of films under external mechanical influences. The gamma radiation shielding efficiency was assessed using a standard method for determining the difference in radiation intensity when detected without a protective shield and with a protective shield, as well as subsequent calculation of the linear and mass attenuation coefficients of gamma radiation. Determination of the electronic radiation shielding efficiency was carried out using a meethod for determining the performance of microcircuits by measuring deviations of current-voltage characteristics (ΔU) above the threshold value ΔU=0.1 V, which is a critical parameter for determination of the performance of microelectronic devices exposed to ionizing radiation. Main provisions submitted for defense: 1. It has been established that the potential difference variation from 1.0 to 2.5 V results in the displacement of the cubic Cu2O phase and the complete dominance of the tetragonal CuBi2O4 phase, and in the case of the applied potential difference growth above 5.0, the formation of an impurity Bi2O3 phase is observed. 2. It has been established that the formation of the Bi2O3/ CuBi2O4 type composite films, obtained at potential differences above 5.0 V, leads to a rise in wear resistance by 15-20 % in comparison with single-phase CuBi2O4 films. 3. It has been found that the presence of CuBi2O4 inclusions in the structure of Bi2O3 films results in corrosion resistance growth and structural degradation rate reduction by more than 10 times compared to films containing copper oxide inclusions. 4. It has been determined that the formation of two-phase Bi2O3/CuBi2O4 films obtained at an applied potential difference of 5.5-6.0 V results in an elevation in shielding efficiency of the order of 0.75-0.77 times the shielding efficiency of lead. Description of the main results of the study It has been found that at potential differences above 5.0 V, the formation of impurity inclusions in the form of Bi2O3 is observed in the composition of CuBi2O4 films, the content of which is about 2.5-7.7 wt. % with the applied potential difference growth. During analysis of the obtained X-ray diffraction data of the studied CuBi2O4 films, it was found that the formation of impurity inclusions causes deformation distortion on the structure of the films, alongside a rise in the crystal lattice parameters as a result of high bismuth concentrations. The assessment results of the effect of changes in synthesis conditions (variations in the applied potential difference) on the strength properties of CuBi2O4 films were obtained. It was ascertained that if the films contain an impurity phase Cu2O, the hardness value is about 12.4-14.5 HV, while for films that do not contain an impurity phase the hardness value is about 18-21 HV. At the same time, the formation of impurity inclusions in the form of Bi2O3 in films results in a hardness growth by 1.3-1.4 times in comparison with films containing impurities in the form of Cu2O. This strengthening is due to the reinforcement effect due to the presence of Bi2O3 inclusions in the film structure. During corrosion tests of CuBi2O4 film samples in a model solution of 0.1 M NaCl, it was found that the least resistant to degradation are films obtained at an applied potential difference of 1.0 - 2.5 V, which contain inclusions in the form of the Cu2O oxide phase, the presence of which leads to accelerated degradation of films associated with the formation of inclusions in the form of copper oxide phases and structural disorder. Analysis of the strength characteristics of CuBi2O4 films after corrosion and thermal aging tests revealed that the presence of inclusions in the form of Bi2O3 in the film composition results in a rise in resistance to softening during long periods of exposure of the samples to aggressive environments and thermal exposure. The efficiency of gamma and electron radiation shielding was determined using CuBi2O4 films obtained using the electrochemical deposition method. A comparative analysis of the gamma radiation shielding efficiency using CuBi2O4 films demonstrated that the formation of the Bi2O3 phase in the films, and an increase in the concentration of bismuth, leads to a growth in the efficiency of gamma radiation intensity reduction, and the shielding efficiency value itself in comparison with lead for Bi2O3/CuBi2O4 films is about 0.75-0.77. During the studies aimed at determination of the efficiency of protection from the adverse effects of electronic radiation, it was found that Bi2O3/CuBi2O4 type films are the most effective, the use of which makes it possible to reduce the effect of failures (changes in the value of ∆U above 0.1 V) of microcircuits during high-dose irradiation with electrons with energies of 1.0 and 2.5 V, and to maintain the stability of the performance of microcircuits at low radiation doses (not higher than 100 kGy) at electron energies of 5.0 MeV. Description of the novelty and importance of the results obtained Using the electrochemical deposition method, a technology has been developed for producing Cu2O/CuBi2O4/Bi2O3 films with the ability to vary the phase composition (phase ratio), as well as control the structural and strength parameters. Based on the data obtained, the dynamics of phase transformations of the synthesized films was determined depending on the difference in applied potentials. During the tribological tests, the positive effect of the presence of impurity inclusions in the form of the Bi2O3 oxide phase in the composition of CuBi2O4 films on wear resistance and strength characteristics growth was established. The rise in wear resistance for CuBi2O4 films containing the Bi2O3 impurity phase is due to the reinforcing properties of this oxide, leading to a growth in strength characteristics. The results of the influence of variations in the difference of applied potentials on changes in the phase composition, in particular the possibility of the formation of impurity inclusions in the form of oxide phases of copper and bismuth in the composition of CuBi2O4 films can be used in the future for the industrial production of protective coatings based on CuBi2O4 films. Moreover, the use of the electrochemical deposition method will make it possible to apply such protective coatings to almost any surface of various geometries, and the high shielding properties of these films can be used not only for protection against ionizing radiation, but also electromagnetic influence. During the research, it was found that the formation of inclusions in the form of Bi2O3 in the structure of films leads to an elevation in degradation resistance, as well as a decline in the rate of structural disorder and softening of films by almost an order of magnitude in comparison with films that contain copper oxide inclusions. At the same time, the obtained results of degradation resistance, as well as data on the hydrophobicity of films can be used in the future to create hydrophobic protective coatings with high wear resistance and resistance to high temperature influences. The high resistance of Bi2O3/CuBi2O4 films to wear resistance under mechanical influence showed the promise of using these films not only as shielding materials, but also as friction coatings that are highly resistant to wear under prolonged mechanical action. The established reinforcing factor for increasing the wear resistance of films due to the inclusion of Bi2O3 impurity phase in the composition can subsequently be used in the selection of coatings with high wear resistance, as well as the use of these inclusions to increase the strength characteristics of such types of films. The results of experimental work related to the study of shielding characteristics can be used in the future to select promising composite materials with high shielding performance for use as protective shielding materials in microelectronics. Compliance with areas of scientific development or government programs The dissertation research was carried out within the framework of grant funding from the Ministry of Education and Science of the Republic of Kazakhstan on the topic of the project AP14871152 «Synthesis of CuBi/CuBi2O4 films - promising materials for creating protective coatings from electromagnetic and ionizing radiation» (implementation period 2022-2024). Description of the applicant's contribution to the preparation of each publication Development of the technology for production of CuBi2O4 films using the electrochemical deposition method, as well as characterization of the obtained samples using atomic force microscopy methods to determine the morphological features of the resulting films and energy-dispersive analysis in order to establish the dependence of the change in the ratio of elements with varying synthesis conditions were carried out by the applicant personally. The study of phase transformations in CuBi2O4 films with variation in the conditions for their production was carried out by the applicant together with employees of the Laboratory of Engineering Profile of the L.N. Gumilyov Eurasian National University. Experiments on shielding gamma and electron radiation in order to determine the effectiveness of using CuBi2O4 films as protective shielding materials were carried out by the applicant together with employees of the Laboratory of Radiation Effects of the State Scientific and Practical Center of the National Academy of Sciences of Belarus for Materials Science (Minsk, Belarus) and the Laboratory of Solid State Physics of the Astana Branch of the Institute of Nuclear Physics of the Ministry of Energy of the Republic of Kazakhstan (Astana, Kazakhstan). All the main conclusions and provisions submitted for defense, based on the experimental work carried out, were agreed upon by the applicant with scientific consultants during the period of scientific research and preparation of the dissertation. The main results of the research were published in 1 article, in a highly rated scientific publication indexed in the Web of Science Core Collection and Scopus databases, 3 articles in publications recommended by CQASHE MSHE RK and 5 abstracts of reports in collections of international conferences. The results of the work were presented at the following scientific conferences in the form of reports: 21st International Conference on Radiation Effects in Insulators (REI - 21) (2023, Fukuoka, Japan), 51st International Tulin Conference on the Physics of Interaction of Charged Particles with Crystals (2022, Moscow, Russia), I International Scientific School-Conference «Atom. Science. Technologies» (2022, Almaty, Kazakhstan), X International Scientific Conference «Current Problems of Solid State Physics» (2023, Minsk, Belarus), IV International Scientific Forum «NUCLEAR SCIENCE AND TECHNOLOGY», dedicated to the 65th anniversary of the Institute of Nuclear Physics (2022, Almaty, Kazakhstan).

Dissertation

Official Reviewer's Review

Official Reviewer's Review