
A. I. IvanovaTver State University · Лаборатория электронной микроскопии
A. I. Ivanova
к.ф.-м.н.
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Publications (139)
Magnetic properties of Heusler alloys with the Ni54.4Mn17.6Ga26.2Si1.8 composition subjected to comprehensive isothermal forging have been investigated. It was found that comprehensive isothermal forging leads to a shift in the temperatures of structural and magnetic phase transitions toward low temperatures, a slight decrease in magnetization and...
The results of experimental studies using optical profilometry and scanning probe microscopy of the structure and surface parameters of germanium single crystals exposed to an alternating magnetic field are presented. The change in parameters of surface roughness and relief of single crystals after treatment by magnetic field was found. Using optic...
The values of microhardness of samples of single crystals of paratellurite differing from each other in growth conditions and structural quality were measured. For the plane (110), these values lie in the range — 300—470 kG/mm2. It has been determined that mechanical stresses in paratellurite can lead to significant deviations of values of microhar...
The article continues a series of studies of permanent magnets with different magnetization reversal mechanisms (nucleation, domain boundary displacement). In this work, a correlation is established between magnetic characteristics of permanent magnets (Y25 and AlNiCo) and the fractal dimension of magneto-optical images of their stray fields. Bismu...
In this study, novel anion photo-responsive supramolecular hydrogels based on cysteine–silver sol (CSS) and iodate anions (IO3−) were prepared. The peculiarities of the self-assembly process of gel formation in the dark and under visible-light exposure were studied using a complex of modern physico-chemical methods of analysis, including viscosimet...
The paper presents the results of a comprehensive study of the hysteresis characteristics of Sm1−𝑥Gd𝑥Co3Cu2 alloys (x=0.1–0.9), considering their actual microstructure. It is shown that in the as-cast state, all alloys in the series are significantly heterogeneous and contain inclusions of up to three phase components. Hightemperature annealing at...
In this study, a novel supramolecular composite, “photogels”, was synthesized by mixing of cysteine–silver sol (CSS) and methylene blue (MB). A complex of modern physico-chemical methods of analysis such as viscosimetry, UV spectroscopy, dynamic and electrophoretic light scattering, scanning electron microscopy and energy-dispersive X-ray spectrosc...
В работе с помощью методов УФ-спектроскопии, динамического светорассеяния, рН-метрии, вискозиметрических испытаний, сканирующей электронной микроскопии изучены процессы самосборки и гелеобразования в низкоконцентрированных водных растворах на основе аминокислоты L-цистеин и нитрата серебра, так называемого цистеин-серебряного раствора, низкомолекул...
Supramolecular hydrogels based on low-molecular-weight compounds are a unique class of so-called “soft” materials, formed by weak non-covalent interactions between precursors at their millimolar concentrations. Due to the variety of structures that can be formed using different low-molecular-weight gelators, they are widely used in various fields o...
Some patterns of formation of the fractal relief of nanosized molybdenum films on the mica surface are considered using the atomic force microscopy. The tools and techniques for post-processing and analyzing 2D images acquired through this specific research methodology have been thoroughly investigated. The significance of the contributions of erro...
Results are presented from a fractal analysis of images of the surface of a KC-37 permanent magnet , obtained via the polar Kerr effect using an indicator bismuth-containing ferrite-garnet film after magnetization reversal by a pulsed field of 0.1-1.5 T. The obtained dependences of the residual magnetization on the magnitude of the external pulsed...
The results of fractal analysis of images of the surface of a permanent magnet KS37, obtained by the method of the polar Kerr effect using an indicator bismuth-containing ferrite-garnet film after magnetization reversal by a pulsed field of 0.1–1.5 T, are presented. The obtained dependences of the residual magnetization on the magnitude of the exte...
Processes of self-organization and gelation in a low-concentration aqueous solution of l-cysteine and silver nitrate were studied using singly, doubly, and triply charged metal chlorides as gelation initiators. According to the results of studies by viscometry and scanning electron microscopy, the rheological and morphological characteristics of ge...
For the first time, a detailed comprehensive study of the "dry" etching of dislocation and dislocation-free germanium samples on the {111}, {110} and {100} planes has been carried out. Etching was carried out by exposure to pulses of nanosecond UV laser radiation of subthreshold intensity (wavelength 355 nm, duration ~ 10 ns, energy density ~ 0.5–1...
С помощью методов вискозиметрии, динамического светорассеяния (ДСР), Фурье-ИК и УФ спектроскопии, а также сканирующей электронной микроскопии (СЭМ) исследованы процессы самоорганизации в низкоконцентрированных водных растворах глицина и нитрата серебра (глицин-серебряный раствор – ГСР) и поливинилового спирта (ПВС) Методом отлива из раствора получе...
Представлены результаты исследования кристаллической структуры, магнитных свойств, а также микро- и доменной структуры поверхности серии соединений TbHoFeCo (x = 0,1; 0,2; 0,3; 0,4). Показано, что с увеличением относительного содержания кобальта параметр кристаллической решетки a уменьшается от 7,310Å при x = 0,1 до 7,304Å при x = 0,4, а температур...
The paper presents the results of a study of the influence of a constant magnetic field on the dispersion of the complex permittivity of a layered composite (connectivity 2-2) based on barium titanate – barium ferrite. It is shown that in the manufacture of a magnetoelectric composite of barium titanate – barium ferrite with a connectivity of 2-2,...
В настоящей работе представлены результаты исследований влияния деформации, полученной методом всесторонней изотермической ковки, на микроструктуру и магнитные свойства сплава системы NiMnGa. Показано, что микроструктура исходного сплава в ходе деформации претерпевает изменения, уменьшается размер зерен и формируется двухкомпонентная структура. Мет...
В настоящей работе изложены результаты проведенных испытаний на микротвердость методом индентирования по Виккерсу монокристаллов германия и кремния. Показано, что в исследуемых образцах существует зависимость микротвердости от кристаллографических направлений и характера легирующей примеси. Подсчитаны коэффициенты анизотропии микротвердости: для ге...
В работе представлены результаты анализа экспериментальных данных, полученных при регистрации петель диэлектрического гистерезиса и полевых зависимостей переключаемой поляризации исходных и отожженных кристаллов триглицинсульфата, легированных медью в диапазоне концентраций (4,2-8,7)⋅10 вес.%. Экспериментально установлено, что петли диэлектрическог...
В работе представлены результаты исследования влияния паров парателлурита в процессе спекания на структуру и диэлектрические свойства многокомпонентной системы на основе керамики ниобата натрия-калия (mKNN) общей формулой (NaKLiSr)(NbTaTi)O. Установлено, что парателлурит входит в состав керамики, изменяя форму и увеличивая размер зерен на порядок....
Рассмотрены закономерности формирования фрактального рельефа наноразмерных пленок железа на поверхности слюды с использованием атомносиловой микроскопии. С целью не допустить образования оксидного слоя, пленки железа исследовались непосредственно после их получения на установке магнетронного напыления. Установлено, что магнетронное напыление позвол...
Self-assembly processes in aqueous solutions of l-cysteine and silver nitrite (AgNO2) with different concentrations and varying molar ratios of the starting components were studied using UV spectroscopy, elemental analysis, scanning and transmission electron microscopy. The concentration range of hydrogelation was determined. Gel formation was not...
The effect of soft UV radiation (365 nm) on self-assembly in an aqueous l-cysteine-silver solution (CSS) and hydrogels based on it has been studied. It was determined that CSSs based on various silver salts (silver nitrate, acetate, and nitrite) exhibit different photosensitivities, and their color can change up to dark brown under UV irradiation....
The morphology of the surfaces of single-crystal germanium, corresponding to the crystallographic planes {111}, {100}, {110}, after laser heat treatment was investigated. We used repetitively pulsed radiation of a nanosecond UV laser (wavelength is 355 nm, duration is 10 ns, energy density∼0.5 – 1.3 J/cm²) of pre-threshold intensity. It was confirm...
Experimental results of the study of magnetic bismuth-containing ferrite-garnet films grown on substrates from gadolinium-gallium garnet are analysed using specialised software. Based on the analysis of the transformation of the domain structure, the major loops of magnetic hysteresis for defective and defect-free areas of the films were obtained u...
The morphology of track membranes based on polyethylene terephthalate and polypropylene with various track diameters and their surface densities were studied by UV, IR, and Raman spectroscopy and scanning electron microscopy (SEM). The SEM method was used to plot the distribution curves of the number of tracks in relation to their average size (dia...
Hydrogels prepared from L-cysteine, silver acetate, and polyhexamethyleneguanidine hydrochloride (PHMG-HC) were used in rheological, structural, and antibacterial studies. Aqueous solutions of Lcysteine and silver acetate were found to be very miscible with aqueous solutions of PHMG-HC to form transparent hydrogels. A model for the three-dimensiona...
The morphology of track membranes based on polyethylene terephthalate and polypropylene with different track diameters and their surface densities were studied by UV, IR, Raman spectroscopy, and scanning electron microscopy (SEM). The SEM method was used to plot the distribution curves of the number of tracks depending on their average size (diamet...
The present article reports the in situ preparation of silver nanoparticles (AgNPs) homogeneously distributed in the gel matrix formed using only L-cysteine (CYS) as a bio-reducing agent. The physicochemical methods of analysis confirmed the formation of a gel-network from aggregates consisting of spherical/elliptical cystine-stabilized AgNPs (core...
Effects of irradiation with visible light on the process of self-assembly in an aqueous l-cysteine-silver solution (CSS) and hydrogels based on were investigated using a set of physico-chemical methods. It was found that the exposure to light of CSS and hydrogels based on l-cysteine and silver acetate colors them firstly into yellow and subsequentl...
We investigated the process of laser heat treatment of polished brass samples (36% zinc, containing a small amount of lead, which does not dissolve in the alloy and is in the form of inclusions, having micron and submicron size) by impacting to a series of 25 - 30 ultraviolet (UV) pulses of a Nd:YAG laser (third harmonic, wavelength λ = 355 nm, dur...
Comparative studies of the pyroelectric properties and structural features of sodium niobate and sodium-potassium niobate ceramics obtained under different technological conditions for the synthesis of sodium niobate have been carried out. X-ray phase analysis revealed the existence of an additional phase with the chemical formula NaNb 10 O 18 in s...
Comparative studies of the pyroelectric properties and structural features of sodium niobate and sodium-potassium niobate ceramics obtained under different technological conditions for the synthesis of sodium niobate have been carried out. X-ray phase analysis revealed the existence of an additional phase with the chemical formula NaNb 10 O 18 in s...
В работе получены и исследованы образцы керамики на основе ниобата бария - кальция CaBaNbO, с различным процентным соотношением бария и кальция (с x = 1; 0,9; 0,8; 0,7; 0,6; 0,5; 0,4; 0,3; 0,2; 0,1 и 0 ). Исследовано влияние температуры спекания на структуру и диэлектрические свойства керамики. Одна партия образцов спекалась при температуре 1100°С,...
В работе показано, что в результате спекания образцов композита титанат бария (80 объемных %) - феррит бария (20 объемных %) в фарфоровом тигле при температуре 1300 °С возникает эвтектика. В результате сравнения свойств образцов, полученных при различных температурах спекания, установлено, что оптимальные свойства имеют образцы, спеченные при 1250...
Методом растровой электронной микроскопии исследована морфология поверхности пленок полупроводниковых полимеров: полианилина, поли-о-толуидина, поли- α -нафтиламина. Пленки получены электрохимическим синтезом из подкисленных минеральными кислотами растворов их мономеров методом циклической вольтамперометрии. Пленки сформированы на платиновых подлож...
The authors studied the effect of the temperature of sodium niobate synthesis on the state of polarization in ceramic samples of pure sodium niobate and modified with lithium. A comparative study of the structure and pyroelectric properties of the obtained samples has been carried out. It is shown that the introduction of lithium as a modifier lead...
In this work, we investigated optical transmission in the wavelength range of 2-14 µm of low-resistance germanium crystals (1-3 Ω·cm) doped with donor and acceptor impurities in the temperature range from 86K to 523K. The values of the attenuation coefficients for investigated crystals are obtained. Minimum attenuation coefficients α of 0,0015-0,02...
В работе представлены результаты исследований микро- и наноструктуры поверхности быстрозакаленных лент сплавов Гейслера (NiMnAl,NiMn AlSi, NiCoMn Al) методами сканирующей электронной и атомно-силовой микроскопии. Рассмотрено влияние химического состава на размер, геометрию границ и структуру зерен. Показано, что все исследуемые образцы обладают нан...
The morphology of the relief of nanosized platinum films on the mica surface is investigated using the scanning probe (in the atomic force mode) and tunneling microscopy. Platinum films were investigated immediately after their preparation in a magnetron sputtering facility, as well as after annealing in a muffle furnace in an air atmosphere. Annea...
The article presents the results of studies of thermally induced domain processes in chromium-containing crystals of triglycine sulfate (TGS). It is shown that a change in the temperature of TGS:Cr3+ crystals in the absence of external electric fields is accompanied by a rearrangement of the domain structure, that occurs most intensively in the reg...
В данной работе коллективом авторов путём взаимодействия водных растворов хлорида трёхвалентного церия и натриевой соли цефазолина получено и выделено в твердом виде металлокомплексное соединение. Его элементный состав установлен с помощью метода рентгеноспектрального электронно-зондового анализа, описаны термические характеристики данного соединен...
Investigation of a polished surface of germanium single crystals scanned with a focused beam of pulse-frequency modulated UV radiation of Nd:YAG laser showed evidence of laser-induced surface etching at subthreshold energy densities (E ∼ 0.5–1.15 J/cm²) in the
bsence of noticeable traces of crater formation. It is suggested that the ablation cente...
The modification of the polished {111} surface of single-crystal germanium (n-type of conductivity, resistivity 47 Ohm cm) as a result of exposure to focused frequency-pulse radiation of nanosecond ultraviolet Nd:YAG laser are studied by optical profilometry, as well as scanning electron and probe microscopy.
It is revealed that the threshold of th...
We report a novel simplest strategy for the silver molybdate functional composite microspheres synthesis based on low molecular weight gelators - the amino acid, silver salt and heptamolybdate ions. The...
A mode of laser heat treatment of the brass surface prior to conducting of diffusion bonding is proposed. We used the frequency-pulse radiation of a nanosecond ultraviolet laser at a pulse energy density W = 0.15 - 0.52 J/cm ² . The metal sample was moved relative to a stationary laser beam along a raster trajectory (“snake”) so that adjacent spots...
In this paper observed values of emissivity for germanium single crystals with various surfaces received by classical methods of processing (polishing, grinding by the powders F400, F800), and also for the raw surface after a cut. The received values will allow further thermovision researches of germanium single crystals by methods of active therma...
The paper presents the results of studies of the structure, piezoelectric and dielectric properties of lead zirconate-titanate ceramics modified with lanthanum of various concentrations (PLZT). It was found that with an increase in the La content, the grain size and the average domain size increase. The PLZT 12/40/60 samples contain both labyrinth-...
Results are presented from an analysis of the nano- and magnetic domain structures of high coercive
Sm(CoCuFe)5 alloy using fractal geometry. Fractal dimension Df of the nano- and domain structures are
determined at different stages of heat treatment. It is shown that Df ~ 2.08 corresponds to the nanostructure
of samples with a coercive force of 7...
The structures of films based on L-cysteine, AgNO3, and poly(vinyl alcohol) were studied by IR and UV spectroscopy, dynamic light scattering, scanning electron microscopy, and elemental analysis. The molecular structure from which the three-dimensional gel-network was formed was found to be retained on going from a hydrogel to a film. The synthesiz...
С помощью методов УФ спектроскопии, динамического светорассеяния (ДСР) и сканирующей электронной микроскопии (СЭМ) в водных растворах L-цистеина и N-ацетил-L-цистеина (НАЦ) с нитритом серебра (AgNO) при концентрации от 0.001 М до 0.025 М и различных соотношениях исходных компонентов изучены процессы самоорганизации, приводящие к образованию гидроге...
The threshold of optical breakdown of the nickel alloy ChS57 (Inconel) was measured at a wavelength of 0.355 μm with a laser pulse duration of 10 ns. Heat treatment of ChS57 above pulse energy density threshold (1 - 2.5 J/cm ² ) occurred mainly in the ablative mode with almost no melting. The elemental composition of the surface layer did not chang...
In this paper, we compare the structure and dielectric properties of the samples of barium titanate ceramics that have been sintered at temperatures of 1100, 1150, 1200, 1250 and 1350 °C and dielectric characteristics of the samples of barium titanate (80 vol.%) — barium ferrite (20 vol.%). It is shown that only samples sintered at the temperature...
In this article, we study the features of the surface layer formed during mechanical treatment of the sample surface of hard and soft PZT ceramics. We have compared the properties of the surface layer induced by polishing for hard and soft ferroelectric ceramics. For both ceramics, a correlation between microhardness and domain size has been found....
When studying the scanning of the polished surface of germanium single crystals by focused pulse-frequency radiation of an ultraviolet Nd:YAG laser, it was found that at subthreshold energy densities (at E ͠͠ 0.5–1.15 J/cm2), in the absence of noticeable traces of crater formation, laser etching was observed. It is assumed that the centers of ablat...
The structure and dielectric properties of barium titanate ceramics samples sintered at 1100, 1150, 1200, 1250 and 1350 °C have been compared with the dielectric properties of 80 vol.% barium titanate + 20 vol.% barium ferrite composite samples sintered at 1150, 1200 and 1250 °C. It has been shown that polarization sufficient for existence of the p...
В работе получены и исследованы образцы керамики на основе титаната бария и титаната кальция. Проведен анализ элементного состава полученной керамики. Показано, что в твердый раствор титанат кальция-бария BaCaTiO кальций входит с x<0,3 . В образцах керамики с x≥0,3 избыток CaTiO рекристаллизуется отдельными зернами. Увеличение концентрации кальция...
Введение легирующих примесей является классическим способом модификации свойств сложных оксидов семейства перовскита с общей формулой ABO. В качестве основы для создания твердых растворов широко используется ниобат натрия NaNbO. Введение замещающих катионов проводится как по позиции A, так и по позиции B. При этом особый интерес представляет случай...
Авторами получены образцы и проведено исследование структуры и диэлектрических свойств пьезоэлектрической керамики на основе ниобатов натрия и лития (LiNa) NbO при различных технологиях синтеза материала ниобата натрия. Проведено сравнительное исследование структуры и диэлектрических свойств полученных образцов. Показана существенная зависимость зе...
Методами оптической профилометрии и сканирующей электронной микроскопии исследовано воздействие излучения наносекундного ультрафиолетового лазера (λ - 355 нм, длительность импульса 10 нс, энергия в импульсе - до 8 мДж, частота следования импульсов до 100 Гц) на монокристалл кремния. При плотности энергии ≥ 1,2 Дж/см наблюдалось образование плазменн...
В работе рассмотрено влияние объемных дефектов, связанных с локальным механическим повреждением и термическим лазерным воздействием, на доменную структуру и магнитные характеристики эпитаксиальных висмутсодержащих магнитных пленок феррит-граната (Bi :ФГ). Установлено, что одноосные пленки Bi: ФГ устойчивы к объемным дефектам, размер которых не прев...
Synthesis and study of the composite ceramic based on barium titanate and barium ferrite were care out. The results of the analysis of the microstructure and phase composition of the obtained multiferroics are presented.