13 research outputs found
Luminescence from europium, europium-chromium, erbium, samarium and terbium-activated powder, ceramic and polycrystalline cubic boron nitride
No full textA wide range of luminescent materials has been produced based on cubic boron nitride and studied by photoluminescence spectroscopy at room temperature and 7 K. These materials were in the form of micropowders, ceramic compacts and polycrystalline aggregates. The luminescence was excited by 325 nm or 488 nm excitation of Eu, Eu-Cr, Er, Sm and Tb additions to the various preparations. Eu-Cr pair emission has been discovered for the first time with its main line at 686 nm in Eu and Cr codoped polycrystalline cBN. The emitted light, which was quite intense in some cases, spanned a wide range of the visible spectrum. It was often highly structured and could be related to the well-known emission characteristics of the 3+ charge states of the relevant ions. The materials have potential applications as phosphors that are required to operate in extreme environmental conditions.A wide range of luminescent materials has been produced based on cubic boron nitride and studied by photoluminescence spectroscopy at room temperature and 7 K. These materials were in the form of micropowders, ceramic compacts and polycrystalline aggregates. The luminescence was excited by 325 nm or 488 nm excitation of Eu, Eu-Cr, Er, Sm and Tb additions to the various preparations. Eu-Cr pair emission has been discovered for the first time with its main line at 686 nm in Eu and Cr codoped polycrystalline cBN. The emitted light, which was quite intense in some cases, spanned a wide range of the visible spectrum. It was often highly structured and could be related to the well-known emission characteristics of the 3+ charge states of the relevant ions. The materials have potential applications as phosphors that are required to operate in extreme environmental conditions
Influence of Al additions and thermobaric treatment on the UV emission from ceramic and polycrystalline Gd‐activated cubic boron nitride
No full textPhotoluminescence Investigations of Cubic Boron Nitride Doped with Neodymium during High-Pressure Synthesis
No full textInternational audienceMicropowders of cubic boron nitride doped with neodymium are prepared under high-pressure and high-temperature conditions. The phase composition of the micropowders is studied using X-ray diffractometry and X-ray fluorescence analysis. The photoluminescence, photoluminescence excitation spectra, and the life-time of the 4F3/2 excited state of Nd ions introduced into cubic boron nitride are investigated. In photoluminescence spectra of the micropowders, structured bands are recorded in the range of the 4F3/2→4I9/2 and 4F3/2 4I11/2 electronic transitions. A higher intensity of the first structured band indicates that the corresponding photoluminescence in cubic boron nitride doped with neodymium is excited by the “three-level scheme.” It is demonstrated that an increase in the concentration of the neodymium compound in the growth batch leads to the formation of two luminescence centers Nd1 and Nd2 formed by neodymium ions located in different low-symmetry crystal fields in the micropowders. This is confirmed by X-ray diffraction investigations and the study of the photoluminescence decay curves. The 4F3/2 short-lived state is assigned to the Nd ions forming the Nd1 centers, and the long-lived state is attributed to the Nd ions forming the Nd2 centers
Paramagnetic, mechanical properties and structural characteristics of polyethylene terephthalate films implanted by ions antimony with energy 60 keV / V. B. Odzaev, A. N. Oleshkevich, N. M. Lapchuk, Т. М. Lapchuk, S. V. Leonchik, A. V. Neverovskaya
No full textДефектно-примесная инженерия. Радиационные эффекты в полупроводникахМетодом электронного парамагнитного резонанса при комнатной температуре исследованы образцы полиэтилентерефталата (ПЭТФ), облученные ионами сурьмы с энергией 60 кэВ флюенсом 6×10 14 см −2 –1,2×10 16 см −2 . Обнаружено, что при увеличении флюенса ионов сурьмы парамагнетизм пленок исчезает. Показано, что изменение микротвердости имплантированных образцов ПЭТФ коррелирует с изменением резонансной частоты и изменением добротности резонатора. Сделан вывод об образовании малых кластеров сурьмы и переходу имплантированного слоя ПЭТФ из парамагнитного состояния в диамагнитное.Electron paramagnetic resonance at room temperature was used to study samples of polyethylene terephthalate (PET) irradiated with antimony ions with an energy of 60 keV fluence 6×10 14 cm -2 –1.2×10 16 cm -2 . It is found that as the fluence of antimony ions increases, the paramagnetism of the films disappears. It is shown that the change in the microhardness of the implanted PET samples correlates with the change in the resonant frequency and the change in the quality factor of the resonator. A conclusion is drawn on the formation of small antimony clusters and the transition of an implanted PET layer from the paramagnetic state to the diamagnetic state
Композиционные материалы системы эпоксидная смола–W для радиационной защиты от гамма-излучения
No full textСomposite materials based on the epoxy resin–W system with varying W content (0–80 %) were obtained using the method of chemical curing. Microstructural investigations of the samples showed that with increasing W content there is a more uniform distribution of grains in the epoxy resin matrix could be observed. Agglomeration of W grains is noted for samples with filler content up to 40 %. Statistical analysis of the grain size of the initial W powder revealed that the probable diameter of W grains is 475 nm. The values of effective and relative densities of the experimental samples were obtained using the Archimedes method. The effective density varied from 1.16 to 4.36 g/cm3 with W powder content rising. The relative density values received ranged from 91 to 94 %, indica ting that there were no significant defects in the samples. X-ray diffraction analysis showed the presence of vcc-W and WO2 phases, indicating the oxidation of W in the thin surface layer of the powder. Calculation in Phy-X/PSD software allowed to evaluate the gamma radiation shielding efficiency for the epoxy resin–W system composite materials in 0.8–2.5 MeV energy range. It was observed that samples with filler content of 60 and 80 % were the most suitable for radiation shielding. It was found that the addition of W powder to the epoxy matrix contributed to the reduction of half attenuation layer values by 3.5 times from 9.448 to 2.672 cm for samples with 0 and 80 % W content, respectively, for 1.25 MeV radiation energy. The obtained results demonstrate the high efficiency of the proposed composite materials for shielding gamma radiation, which makes them a perspective candidate for manufacturing radiation shields.С использованием метода химического отверждения получены композиционные материалы на основе системы эпоксидная смола–W с варьированием содержания W от 0 до 80 %. Проведенное исследование микроструктуры образцов показало, что при увеличении содержания W наблюдается более равномерное распределение зерен в матрице эпоксидной смолы. Для образцов с содержанием наполнителя до 40 % отмечена агломерация зерен W. Статистический анализ размеров зерен исходного порошка W выявил, что вероятный их диаметр составляет 475 нм. Получены значения эффективной и относительной плотностей экспериментальных образцов с помощью метода Архимеда. Эффективная плотность изменялась в пределах от 1,16 до 4,36 г/см3 с увеличением содержания порошка W. Значения относительной плотности варьировались от 91 до 94 %, что свидетельствовало об отсутствии существенных дефектов при проведении испытания. Рентгеноструктурный анализ показал наличие фаз ОЦК-W и WO2, что указывает на окисление W в тонком поверхностном слое материала. Моделирование в программном обеспечении Phy-X/PSD позволило оценить эффективность экранирования от гамма-излучения композиционных материалов при энергии излучения в диапазоне 0,8–2,5 МэВ. Образцы с содержанием наполнителя 60 и 80 % оказались наиболее подходящими для создания экранов радиационной защиты. Обнаружено, что добавление порошка W в эпоксидную матрицу способствовало уменьшению значений слоя половинного ослабления в 3,5 раза с 9,448 до 2,672 см для образцов с содержанием W 0 и 80 % соответственно при энергии излучения гамма-квантов 1,25 МэВ. Полученные результаты демонстрируют высокую эффективность предложенных композиционных материалов в экранировании гамма-излучения, что делает их достойным вариантом для создания экранов радиационной защиты
Composite Materials of Epoxy Resin–W System for Radiation Shielding Against Gamma Radiation
No full textСomposite materials based on the epoxy resin–W system with varying W content (0–80 %) were obtained using the method of chemical curing. Microstructural investigations of the samples showed that with increasing W content there is a more uniform distribution of grains in the epoxy resin matrix could be observed. Agglomeration of W grains is noted for samples with filler content up to 40 %. Statistical analysis of the grain size of the initial W powder revealed that the probable diameter of W grains is 475 nm. The values of effective and relative densities of the experimental samples were obtained using the Archimedes method. The effective density varied from 1.16 to 4.36 g/cm3 with W powder content rising. The relative density values received ranged from 91 to 94 %, indica ting that there were no significant defects in the samples. X-ray diffraction analysis showed the presence of vcc-W and WO2 phases, indicating the oxidation of W in the thin surface layer of the powder. Calculation in Phy-X/PSD software allowed to evaluate the gamma radiation shielding efficiency for the epoxy resin–W system composite materials in 0.8–2.5 MeV energy range. It was observed that samples with filler content of 60 and 80 % were the most suitable for radiation shielding. It was found that the addition of W powder to the epoxy matrix contributed to the reduction of half attenuation layer values by 3.5 times from 9.448 to 2.672 cm for samples with 0 and 80 % W content, respectively, for 1.25 MeV radiation energy. The obtained results demonstrate the high efficiency of the proposed composite materials for shielding gamma radiation, which makes them a perspective candidate for manufacturing radiation shields
Эластификация артериальной стенки под действием высокоинтенсивного низкочастотного ультразвука
No full textA significant increase in the elasticity of the femoropopliteal artery segments in vitro was found as a result of the action of cavitation generated by powerful low-frequency (24–26 kHz) ultrasound introduced into the vessel by a flexible waveguide. The vessel elasticity was evaluated both by the deflection under the action of an external force and by the degree of its expansion vasodilatation by the internal pressure created by the expanding balloon. The possibility of achieving a more than two-fold decrease in the vascular wall elasticity modulus after 30-s exposure to an ultrasound intensity of 31 W/cm2 was shown. It has been established that at the 10 μm amplitude of ultrasonic vibrations, vascular wall damage occurs in the form of small foci of detachment and rupture of the intima accompanied by delamination in the media layer, when polymorphic slit-like cavities are formed with an increase in the amplitude of oscillations above 23 μm.Установлено существенное повышение эластичности бедренно-подколенных сегментов артерий in vitro в результате действия кавитации, генерированной мощным низкочастотным (24–26 кГц) ультразвуком, вводимым внутрь кровеносного сосуда гибким волноводом. Эластичность сосуда оценивалась как по прогибу под действием внешней силы, так и по степени его вазодилатации внутренним давлением, создаваемым расширяющимся баллоном. Показана возможность достижения более чем двукратного снижения модуля упругости сосудистой стенки после 30 с ультразвукового воздействия интенсивностью 31 Вт/см2. Установлено, что при амплитуде ультразвуковых колебаний 10 мкм имеет место повреждение сосудистой стенки в виде мелких фокусов отслоения и разрыва интимы, сопровождающееся расслоениями в медии с формированием полиморфных щелевидных полостей при увеличении амплитуды колебаний свыше 23 мкм
Nonoxide Sol-Gel Synthesis of Terbium-Doped Silicon Nitride Phosphors
No full textExposure of solutions of Tb(N(SiMe3)2)3 with SiCl(NEt2)3 in tetrahydrofuran to dry ammonia results in polymeric xerogels. Heating these gels in ammonia leads to amorphous Tb:SiNx phosphors that exhibit bright green luminescence under UV irradiation. MAS-NMR and combustion analysis reveal that the phosphors are silicon nitride materials analogous to those typically produced by sol–gel routes. Photoluminescence behavior is similar to that of Tb:SiNx or Tb:SiO2 films produced by ion implantation that show good electroluminescence activity
