Defense of the dissertation of Temir Adilet Makhambetuly 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 Temir Adilet Makhambetuly on the topic «Study of the effectiveness of shielding of electron and gamma radiation by composite ceramics Bi₂O₃ – WO₃ – TeO₂» to 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:

Mukhamedov Nurzhan Erolovich – Doctor of Philosophy, PhD, Head of the Laboratory of Reactor Fuel Testing, Branch of the Institute of Atomic Energy, National Nuclear Center of the Republic of Kazakhstan (Kurchatov, 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:

Seliverstova Evgeniya Vladimirovna – Doctor of Philosophy PhD, Associate Professor, Karaganda State University named after E.A. Buketov, Senior Researcher (Karaganda, Republic of Kazakhstan);

Sagdoldina Zhuldyz – PhD, Associate Professor, Senior Researcher, Research Center «Surface Engineering and Tribology» of East Kazakhstan University named after Sarsen Amanzholov (Ust-Kamenogorsk, 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:

Zhumadilov Kassym Shaimardanovich – Doctor of Philosophy (PhD), Professor, Department of Nuclear Physics, New Materials and Technologies, L.N. Gumilyov Eurasian National University (Astana, Republic of Kazakhstan);

Trukhanov Aleksey Valentinovich – Doctor of Physical and Mathematical Sciences, Associate Professor, Academician-Secretary of the Department of Chemistry and Earth Sciences, National Academy of Sciences of Belarus (Minsk, Republic of Belarus).

The defense will take place on September 27, 2024, at 10:00 AM 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 offline and online.

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

Address: Astana, Satpayev St. 2, room 302.

Abstract (English): Dissertation work of Temir Adilet Makhambetuly “Study of the effectiveness of shielding of electron and gamma radiation by composite ceramics Bi2O3 – WO3 – TeO2”, submitted for the degree of Doctor of Philosophy (PhD) in the educational program “8D05305 – Nuclear Physics”. Aim of the dissertation research The purpose of the dissertation research is to study the prospects for using composite ceramics based on Bi2O3 – WO3 – TeO2 compounds for shielding gamma and electron radiation. Research objectives On the basis of the aim, the following objectives were formulated in the framework of the dissertation research: 1. Development of technology for the production of Bi2O3 – WO3 – TeO2 glass-like ceramics with the application of solid phase synthesis. 2. Study of phase transformation processes in Bi2O3 – WO3 – TeO2 under variation of the conditions of production (changing the temperature of annealing samples). 3. Determining the influence of varying the composition of composite Bi2O3 – WO3 – TeO2 ceramics on the efficiency of shielding gamma - and electronic radiation. Research methods The synthesis of composite glass-like ceramics was carried out using the method of mechanochemical solid-phase synthesis followed by thermal annealing at various temperatures, which in turn made it possible to determine the kinetics of phase transformations of the “crystalline structure - amorphous structure” type, as well as to determine the temperatures at which amorphization occurs. The study of the structural and morphological features of the obtained ceramics depending on changes in thermal annealing conditions, as well as in the case of variations in the concentration of components, was carried out using the methods of scanning electron microscopy, transmission electron microscopy, energy-dispersive and X- ray phase analysis. The determination of shielding characteristics was carried out using standard methods for determining changes in the intensity of gamma radiation before and after the use of shielding materials. The standard sources of gamma rays were Co57 (136 keV), Cs137 (661 keV), Na22 (1274 keV), experiments on screening electron radiation were carried out at the ELV-4 accelerator by irradiation with electrons with an energy of 1.3 MeV. Main provisions submitted for defense: 1. Using the X-ray phase analysis method, it was established that amorphization and subsequent glass transition of composite Bi2O3 – WO3 – TeO2 ceramics occurs at temperatures above 750 °C. 2. It has been determined that phase transformations in Bi2O3 – WO3 – TeO2 ceramics such as Bi2Te2W3O16 → amorphous glass, lead to an increase in the attenuation factor of gamma radiation from 1.2 to 2.7 times. 3. It was determined that an increase in the concentration of Bi2O3 from 0.1 M to 0.4 M in the composition of 0.5TeO2-(0.5-x)WO3-xBi2O3 ceramics leads to a twofold increase in the shielding efficiency of gamma rays with an energy of 660- 1270 keV, and in the case of low-energy gamma quanta to almost complete absorption. 4. It has been established that varying the concentration of Bi2O3 in the composition of 0.5TeO2-(0.5-x)WO3-xBi2O3 glass-like ceramics leads to strengthening due to changes in the density of the material and the emergence of a reinforcement effect at high concentrations of Bi2O3. Description of the main results of the study The results of a study of the influence of synthesis conditions, in particular thermal annealing, on the phase composition and optical properties of ceramics were obtained, which demonstrated good prospects for the possibility of using these ceramics as shielding protective materials. The synthesis of ceramics was carried out using methods of mechanochemical synthesis and thermal sintering in the range from 300 to 800°C. The established phase diagram of transformations in ceramics of the type WO3/Bi2Te4O11→ WO3/Bi2Te2W3O16 → Bi2Te2W3O16→ amorphous-like glass makes it possible to obtain with high accuracy ceramics of different phase compositions that have different optical and shielding characteristics. The effectiveness of shielding gamma radiation with an energy of 130 keV by Bi2O3-TeO2-WO3 ceramics has been demonstrated. In the course of studying the shielding characteristics, it was found that a change in the phase composition leads to an increase in the attenuation factor of gamma radiation from 1.2 to 2.7 times. Moreover, for ceramics 0.5 mm thick, the shielding efficiency ranges from 30 to 70% depending on the phase composition of the ceramics, which is comparable to theoretical predictions for similar structures. During tests on the effectiveness of electron radiation shielding, it was found that in the case of samples obtained at temperatures of 300-500°C, the shielding efficiency is quite low and does not exceed 50%, which is due to the low density of the ceramics. An increase in the density of ceramics, as well as a change in the phase composition due to the formation of the Bi2Te2W3O16 phase, leads to an increase in shielding efficiency by 20-30%. Moreover, for amorphous ceramics, the degree of shielding is the highest and is comparable in effectiveness to similar structures of similar compositions. The work presents the results of a study of the strength, optical and gamma radiation shielding characteristics of protective glasses of the 0.5TeO2-(0.5-x)WO3- xBi2O3 type. The mechanochemical method followed by sintering at a temperature of 1000°C was chosen as the method for producing glass. This method of producing glass makes it possible to obtain amorphous-like glasses with high strength values. Bi2O3 was chosen as the dopant component in relation to which the change in all of the above properties was considered. During the experiments, it was found that doping Bi2O3 at X above 0.15 leads to a significant increase in strength by more than 30%, which indicates an increase in the resistance of glasses to external influences. Analysis of the optical characteristics showed that the addition of Bi2O3 to the glass composition leads to a slight decrease in transmission in the visible light region, as well as an increase in the band gap from 3.32 eV to 3.78-3.81 eV. According to the obtained data on the shielding characteristics, the samples TWBO-4 and TWBO-5 have the highest shielding efficiency, for which a decrease in the intensity of gamma rays is observed, varying from 50% (for gamma rays with an energy of 1270 keV) to 75% and 96% for gamma rays with energy 660 keV and 130 keV, respectively. The screening efficiency value above 50% for samples TWBO-4 and TWBO-5 in the case of screening gamma rays with an energy of 1270 keV is due to the presence of additional electron traps and absorption bands, leading to additional absorption of the resulting electron-positron pairs. The results obtained can be used in the future to develop technology for creating protective glasses on an industrial scale. In the course of studies of comparative shielding characteristics, it was found that synthesized ceramics with a thickness of 0.3-0.4 mm have shielding efficiency comparable to lead films of similar thickness, which indicates their effectiveness in use as protective materials from ionizing radiation. Moreover, unlike lead, synthesized ceramics are not toxic to the environment. Description of the novelty and importance of the obtained results Using X-ray phase analysis, it was established that varying the annealing temperature in the range of 300 – 800°C leads to phase transformations of the type WO3/Bi2Te4O11→ WO3/Bi2Te2W3O16 → Bi2Te2W3O16→ amorphous-like glass. The results obtained can be further used in the development of technology for creating protective glasses on an industrial scale. The results on the effect of doping telluride glasses with Bi2O3 made it possible to make a significant contribution to the fundamental theory of creating radiation-protective materials. It has been established that an increase in the density of ceramics, as well as a change in the phase composition due to the formation of the Bi2Te2W3O16 phase, leads to an increase in the efficiency of electron radiation screening by 20-30%. It has been shown that variation in the concentration of components in the composition of Bi2O3-WO3-TeO2 ceramics leads not only to a change in their shielding characteristics, but also to strengthening due to the reinforcement effect associated with changes in the concentration of Bi2O3. Compliance with areas of scientific development or government programs This dissertation work was carried out as part of the implementation of grant funding tasks on the topic: AP09562301 “Study of the effectiveness of shielding of electron and gamma radiation by composite ceramics Bi2O3-WO3-TeO2” (2021) and program-targeted funding BR11765580 “Development of technologies for creating new types of structural materials for nuclear energy and protection against ionizing radiation" (2022-2023). Description of the applicant’s contribution to each publication The work related to the development of methods for producing ceramics using the method of mechanochemical solid-phase synthesis, characterization of their morphological and structural features, calculations for modeling radiation damage in ceramics in order to determine the maximum ion path lengths and the magnitude of energy losses was carried out by the applicant personally in the Laboratory of Engineering Profile of L.N. Gumilyov ENU. Irradiation of samples in order to simulate the effects of heavy ions comparable to radiation damage caused by fission fragments of uranium nuclei was carried out on the basis of the DC-60 Accelerator Complex, located in the Astana branch of the Institute of Nuclear Physics of the Ministry of Energy of the Republic of Kazakhstan. When performing work related to the analysis and interpretation of data, as well as formulating the main conclusions on the dissertation work, the applicant consulted with scientific consultants Ph.D., Professor K.Sh. Zhumadilov. and Doctor of Physical and Mathematical Sciences, Associate Professor A.V. Trukhanov (Minsk, Belarus). The results of the dissertation research were published in 3 articles in journals indexed in the Web of Science Core Collection and Scopus databases, as well as 1 article in a journal from the list of recommended by CQASE and 3 abstracts in collections of international conferences. The results of the work were presented at the following scientific conferences in the form of reports: 1. III International Scientific Forum “Nuclear Science and Technology” (2021, Almaty, Kazakhstan). 2. 50th International Tulinov Conference on the physics of charged particles interaction with crystals (2021, Moscow, Russia). 3. “GYLYM JANE BILIM – 2024”, dedicated to the 125th anniversary of the great scientist K.I. Satpayev (2024, Astana, Kazakhstan).

Dissertation

List of Scientific Works

Consultant's Review

Foreign Consultant's Review

Conclusion of the Research Ethics Committee

Official Reviewer's Review

Official Reviewer's Review