Transmission, buildup factors, and photon shielding capacity of vanadium reinforced tellurite glasses

The ionizing radiation shielding parameters of (90-y)TeO2-yV2O3-5CaO-5Na2O (TVCN): y = 5–20 mol% semiconductor glasses were investigated. The avarage track lengths of photons with different energies (0.015- 15 MeV) in the TVCN-glasses were simulated via MCNP-5 code, then the corresponding LAC were computed. Based on LAC values, the MACs were calculated and compared with values which obtained via XCOM software. The highest LAC achieved for low energy (0.015 MeV) and reduced from 199.549 to 169.891 cm− 1, while the lowest values achieved for gamma photon with higher energies and reduced from 0.188 to 0.161 cm− 1 with replacment of TeO2 compound by V2O5. The highest (I/Io) achieved for TVCN20 glasses and decreased from 0.703 to 0.172., while the lowest (I/Io) performed for TVCN5 glasses and decreased from 0.680 to 0.145 for glasses thickness varied between 1 and 5 cm. The thinner HVL was achieved for TVCN5 and increases from 0.003 to 3.684 cm, while the thicker HVL was achieved for TVCN20 and increases from 0.004 to 4.293 cm. The highest dose rate was recorded in the presence of theTVCN20 glasses and varied between 5.680 and 23.210 µSv/hr, while the lowest dose rate recorded in the presence of the TVCN5 glasses and varied between 4.807 and 22.448 µSv/hr for glass thickness varied in range between 1–5 cm. The highest values of the Zeff was recorded for glasses TVCN5 and varied between 21.209 and 50.402, while the lowest Zeff achieved for TVCN20 and varied between 18.489 and 40.479. The calculated buildup factors (EBF and EABF) reach maximum values for glasses TVCN5 while the lowest EBF and EABF achieved for glasses TVCN20. Therefore, the glasses TVCN5 have a higher ability to attenuate the incident gamma photons. Thus, the TVCN-glasses can be applied in various radiation shielding applications in medical area.

Kinetics and mechanism of isothermal crystallization of AsSe1.5Pbx (x = 0.025; 0.13) semiconductor glasses

В статье [Школьников, 2019] исследовано влияние добавок олова на кинетические параметры ступенчатых превращений при изотермической объемной кристаллизации стекол AsSe1.5Snx (x = 0,13 и 0,20). Влияние концентрации свинца на характер и кинетические параметры реконструктивной кристаллизации стекол AsSe1.5Pbx изучено недостаточно. Методами измерения плотности, микротвердости, температурной зависимости электропроводности, рентгенофазового анализа и оптической микроскопии закаленных образцов исследованы кинетика и механизм превращений при объемной изотермической кристаллизации полупроводниковых стекол AsSe1.5Рвx (х = 0,025, 0,13) в интервале температур 210−340 °С. Анализ кинетики валовой кристаллизации стекол выполнен по данным измерения плотности с использованием уравнения Колмогорова-Аврами, обобщенного на ступенчатые и неполные изотермические превращения. Добавка 1 ат.% Pb к стеклу As2Se3 уменьшает примерно в 2 раза индукционный период выделения фазы As2Se3 и в 6-8 раз кинетический период полупревращения. Установлено, что на первой ступени изотермической ситаллизации стекол в низкотемпературном интервале 210−255 °С преобладает гомогенное зарождение и трехмерный рост нанокристаллов низкоомной фазы PbSe, инициирующей на второй ступени гетерогенное зарождение и двумерный рост кристаллов матричной высокоомной фазы As2Se3. Реконструктивная ступенчатая кристаллизация стекол AsSe1.5Pbx связана с непрерывным изменением химического состава остаточной стеклофазы и характеризуется интервалом уменьшающихся значений эффективной энергии активации. При длительной высокотемпературной термообработке стекол As2Se3 с 5 ат.% Pb в интервале 280–340 °С наблюдаются одновременно объемно-поверхностное расстекловывание фаз PbSe и As2Se3 и вторичные диффузионные процессы с понижением дисперсности, плотности, микротвердости и химической стойкости стеклокристаллов, а также с изменением носителей заряда с р-типа на n-тип. In the article [Shkolnikov, 2019] the effect of tin additives on the kinetic parameters of stepwise transformations during isothermal crystallization of AsSe1.5Snx glasses (x = 0.13 and 0.20) was investigated. The effect of lead concentration on the nature and kinetic parameters of reconstructive crystallization of AsSe1.5Pbx glasses was not studied enough. The kinetics and mechanism of transformations in volume isothermal crystallization of AsSe1.5Pbx semiconductor glasses (x = 0.025, 0.13) in the temperature range 210–340 °С were studied by measuring the density, microhardness, temperature dependence of electrical conductivity, X-ray phase analysis and optical microscopy. The analysis of the gross crystallization kinetics of glasses was performed according to the density measurement data using the Kolmogorov-Avrami equation, generalized to stepwise and incomplete isothermal transformations. The addition of 1 at.% Pb to the As2Se3 glass reduces the induction period of separation of the As2Se3 phase by about 2 times and the kinetic half-transformation period by 6-8 times. It was found that the first stage of isothermal glass sitallization in the low−temperature range 210-255 °C is dominated by homogeneous nucleation and three-dimensional growth of nanocrystals of low-resistance phase PbSe, initiating the second stage of heterogeneous nucleation and two-dimensional crystal growth of the matrix highresistance phase As2Se3.. The reconstructive stepwise crystallization of AsSe1.5Pbx glasses is associated with a continuous change in the chemical composition of the residual glass phase and is characterized by a range of decreasing values of the effective activation energy. During long-term high-temperature heat treatment of As2Se3 glasses with 5 at.% Pb in the range of 280–340 °C observed simultaneously volume-surface devitrification of the phases PbSe and As2Se3 and secondary diffusion processes with a decrease in dispersion, density, microhardness and chemical resistance of glass- crystals, as well as with the change of charge carriers from p-type to n-type