Гетерофазный синтез феррита кобальта

Objectives. The study aimed to develop new methods for the synthesis of cobalt ferrite (CoFe2O4), which is a precursor for the synthesis of CoFe2O4-based functional materials, as well as to study the physicochemical properties of the obtained phases.Methods. Two methods were used for the synthesis of CoFe2O4: (1) heterophase interaction of hydrated iron oxide with cobalt(II, III) oxide and (2) heterophase interaction of hydrated iron oxide with an aqueous solution of cobalt(II) sulfate (CCo = 0.147 mol/L, solid/liquid = 1:43). In both cases, the precursor was hydrated iron oxide (Fe2O3, 84.4 wt %), which was obtained by the heterophase interaction of iron(III) chloride with a concentrated ammonia solution (6.0–9.5 mol/L). The resulting intermediate products were subjected to thermal treatment at 750 °C (synthesis 1) and at 900 °C (synthesis 2) for 10–30 h in increments of 10 h. The synthesized phases and products of their thermolysis were studied by differential thermal analysis and differential thermogravimetry (DTA–DTG), X-ray diffraction analysis (XRDA), and granulometry.Results. The hydrated iron oxide sample remained amorphous even up to the crystallization temperature of 445 °C, which corresponds to the exothermic effect on the DTA curve. Further heating led to the α-modification of iron(III) oxide of the hexagonal system (a = b = 5.037 ± 0.002 Å; c = 13.74 ± 0.01 Å), which has an average particle size of 1.1 μm. XRDA results showed that a synthesis temperature of 750 °C (synthesis 1) and a heat treatment duration of 30 h were sufficient for the formation of a single-phase cobalt ferrite (a = 8.388 ± 0.002 Å) with an average particle diameter of 1.9 μm. For synthesis 2, a higher temperature of 900 °C was used because sample weight loss (about 12.5%) was observed in the temperature range of 720–810 °C based on the DTA results, which was due to the removal of SO2 and SO3. Moreover, when synthesis temperature and duration were at 900 °C and 30 h, respectively, CoFe2O4 with a = 8.389 ± 0.002 Å was formed. The results of the granulometric analysis showed that particles of different diameters were formed. The smallest particle size (1.5 μm) of cobalt ferrite was obtained by the heterophase interaction of hydrated iron(III) oxide (Fe2O3, 84.4 wt %) with an aqueous solution of cobalt sulfate with CCo = 0.147 mol/L. Conclusions. Depending on the method used for the synthesis of cobalt ferrite, particles of different diameters are formed. The smallest particle size of cobalt ferrite was obtained from the heterophase interaction of hydrated iron(III) oxide with an aqueous solution of cobalt(II) sulfate.Цели. Разработка новых методов синтеза феррита кобальта (CoFe2O4), являющегося предшественником для синтеза функциональных материалов на его основе, а также исследование физико-химических свойств полученных фаз.Методы. Гидратированный оксид железа и феррит кобальта получали гетерофазным методом. Синтезированные фазы и продукты их термолиза изучали методами дифференциально-термического анализа и дифференциальной термогравиметрии (ДТА–ДТГ), рентгенофазового анализа (РФА) и гранулометрии.Результаты. В статье изложены результаты двух методов синтеза феррита кобальта (CoFe2O4) и исследования полученных фаз. В обоих случаях в качестве предшественника выступал гидратированный оксид железа(III) с содержанием Fe2O3 – 84.4 мас. %, полученный гетерофазным взаимодействием хлорида железа(III) с концентрированным раствором аммиака (6.0–9.5 моль/л). Первый способ заключался во взаимодействии гидратированного оксида железа(III) с оксидом кобальта(II, III), второй – во взаимодействии гидратированного оксида железа(III) с водным раствором сульфата кобальта(II) с концентрацией ССо = 0.147 моль/л (Т : Ж = 1 : 43). Получившиеся промежуточные продукты подвергали термической обработке при 750 °C (синтез 1) и 900 °C (синтез 2) в течение 10–30 ч с шагом 10 ч.Выводы. Феррит кобальта (CoFe2O4) получен двумя способами. С использованием комплекса методов (РФА, ДТА–ДТГ, гранулометрии) исследованы физико-химические свойства синтезированных образцов. Установлено, что гидратированный оксида железа(III) вплоть до температуры кристаллизации (445 °C), соответствующей экзотермическому эффекту на кривой ДТА, остается рентгеноаморфным. Дальнейшее нагревание его приводит к образованию α-модификации оксида железа(III) гексагональной сингонии (a = b = 5.037 ± 0.002 Å; c = 13.74 ± 0.01 Å), средний размер частиц которой равен 1.1 мкм. Согласно данным РФА, в синтезе 1 при 750 °C и продолжительности термообработки 30 ч образуется однофазный феррит кобальта (a = 8.388 ± 0.002 Å) со средним диаметром частиц 1.9 мкм. В интервале температур 720–810 °C в образце наблюдается убыль массы (около 12.5%), связанная с удалением SO2 и SO3. Поэтому в синтезе 2 температуру нагревания увеличивали до 900 °C. Показано, что при 900 °C и продолжительности синтеза 30 ч также образуется феррит кобальта (CoFe2O4) (a = 8.389 ± 0.002 Å). Результаты гранулометрического анализа указывают на зависимость диаметра образующихся частиц от способа получения феррита кобальта. Наименьший размер частиц (1.5 мкм) обнаружен у феррита кобальта, полученного гетерофазным взаимодействием гидратированного оксида железа(III) (Fe2O3 – 84.4 мас. %) с водным раствором сульфата кобальта с концентрацией С(Со2+) = 0.147 моль/л

Revisiting the stability of spatially heterogeneous predator-prey systems under eutrophication

We employ partial integro-differential equations to model trophic interaction in a spatially extended heterogeneous environment. Compared to classical reaction-diffusion models, this framework allows us to more realistically describe the situation where movement of individuals occurs on a faster time scale than the demographic (population) time scale, and we cannot determine population growth based on local density. However, most of the results reported so far for such systems have only been verified numerically and for a particular choice of model functions, which obviously casts doubts about these findings. In this paper, we analyse a class of integro-differential predator-prey models with a highly mobile predator in a heterogeneous environment, and we reveal the main factors stabilizing such systems. In particular, we explore an ecologically relevant case of interactions in a highly eutrophic environment, where the prey carrying capacity can be formally set to 'infinity'. We investigate two main scenarios: (i) the spatial gradient of the growth rate is due to abiotic factors only, and (ii) the local growth rate depends on the global density distribution across the environment (e.g. due to non-local self-shading). For an arbitrary spatial gradient of the prey growth rate, we analytically investigate the possibility of the predator-prey equilibrium in such systems and we explore the conditions of stability of this equilibrium. In particular, we demonstrate that for a Holling type I (linear) functional response, the predator can stabilize the system at low prey density even for an 'unlimited' carrying capacity. We conclude that the interplay between spatial heterogeneity in the prey growth and fast displacement of the predator across the habitat works as an efficient stabilizing mechanism.Comment: 2 figures; appendices available on request. To appear in the Bulletin of Mathematical Biolog

Features of the structure of addictive identity in adolescence

© Authors. The relevance of the study of this problem is due to the lack of reliable information about the psychological mechanisms, phenomenology and psychological structure of addictive behavior of a personality in adolescence, which is the main cause of insufficient effectiveness for implementation of corrective measures. In this regard, this article aims to study addictive identity structure in the chemical (alcohol and drug) addiction both at the level of structural components of identity in adolescence and that of their structural organization. The leading methods of the problem study are the empirical methods of studying the structural components of addictive identity. The experiment involved 96 young men at the age of 18-24 years old. Of them 55 people are with alcohol dependence, 41 people with drug (opioid) addiction. The study found that addictive identity of young persons with chemical dependence (alcohol and drug) at the level of structural components is characterized by simple undifferentiated cognitive constructs meaningfully related to the object of addiction; flattened motivational profile, as well as a discrepancy at the level of the valuable component of identity. Identified in the study features allow to state that at the level of structural organization an addictive identity of young persons, both at alcohol and drug dependence, is characterized by disintegrated structural organization of identity. Clinical and psychological diagnosis of addictive identity structure with alcohol and drug addiction should be viewed as prognostic basis in the process of socio-psychological rehabilitation of young men with chemical addiction. The identified structural features of addictive identity serve as predictors in determining the risk groups by the given deviant status

The reciprocal organization of constructive activity in drug addiction

© 2016 Akhmetzyanova et al.The urgency of the problem stated in the article is caused by the fact that modern scientific studies show that sustainable neuro-associative connections with the object of addiction arise at chemical addiction. The aim of this study is to examine the features of the reciprocal organization of constructive activities in drug addiction. Study of the constructive activity of patients with drug addiction in comparison with the group in norm was carried out by using the experimental method. The study found a decrease of constructive activity in drug addiction by the characteristics of performance pace and accuracy, regulated by reciprocal and auditory-motor coordination, which, in turn, are also significantly reduced. Reciprocal organization in drug addiction is characterized by impaired proprioceptive kinesthetic afferentation of motor act at safety of outer space organization of movements, lack of differentiation and low handling of movements, movement program disorders, as well as the replacement of the right movements by motor patterns and stereotypes. The obtained results are experimental psychological argument for the need to introduce neuropsychological block in the system of psychotherapeutic impact, which includes the tasks aimed at increasing reciprocal organizations to improve the general level of constructive activity in order to create alternative to the stereotyped models of mental activity and patterns of behavior

Study of social network interference of memory processes in adolescence

Memory is the fundamental basis of human learning. Conceptual assessment and study of the memory mechanisms, its formation, consolidation and preservation at different levels of the structural and functional organization of the nervous system constitutes the necessary knowledge for solving many problems of practical and fundamental psychology. This article presents the study of memory, namely the process of its transition from a short-term to a more stable long-term form in a digital environment under the influence of the interference factor of social networks. The aim of the work is to study the influence of the social network interference factor on the processes of consolidation and reconsolidation of memory in adolescence. The total sample size was 68 adolescents aged 12–17 years. The authors conducted an experiment to achieve this goal. Its results showed that adolescents have difficulty remembering information in the form of short, successive videos in the digital space. It was found that videos that are characterized not only by visual accompaniment, but also by speech production are subject to better memorization. Under the influence of the interfering factor of social networks, adolescents faced difficulties in linking individual elements of stimuli with each other – they connected elements of one video with elements of another. According to one of the provisions of the theory of interference, information storage is characterized by the “unbinding” of representations of objects, followed by their reverse linking in an arbitrary combination during further reproduction

Intercomparison of five nets used for mesozooplankton sampling

Intercomparison of nets commonly used for mesozooplankton sampling in the Black and Mediterranean seas was attempted within SESAME (Southern European Seas: Assessing and Modelling Ecosystem Changes) project. Five nets were compared: three Juday nets equipped with 150 μm, 180 μm and 200 μm mesh size, Nansen net (100 μm mesh size) and WP2 (200 μm mesh size). Replicated samples were collected at one station in the western Black Sea offshore waters in April 2009. Collected samples were analyzed at species level (except for meroplankton), stages (for copepods) and size length. A decrease of total abundance values was observed with increasing mesh size, due to the significantly higher numbers of animals smaller than 1 mm in the samples obtained by fine mesh size than with coarser nets. Few comparisons were revealed significant for the abundance of animals with 1-2 mm length, while no significance was detected for specimens larger than 2 mm. The above differences resulted in discripancies between nets regarding species and stages composition. Biomass values did not differ significantly between nets, due to the strong contribution to total biomass of the large animals fraction (Calanus euxinus). The smallest and the largest animals revealed high variability between replicates collected by Nansen, Juday- 200 μm and WP2 nets. Correction factors were calculated for the conversion of abundance values between each couple of nets. The detected differences between nets regarding the abundance and biomass, the community taxonomic composition and size structure, as well as the estimated correction factors, provide useful information for the harmonization of data obtained by the above nets in the Black Sea

ДИОКСИДЫ ЦИРКОНИЯ И ГАФНИЯ, СТАБИЛИЗИРОВАННЫЕ ОКСИДАМИ РЕДКОЗЕМЕЛЬНЫХ ЭЛЕМЕНТОВ (Y, Sc, Er): НОВЫЕ МЕТОДЫ СИНТЕЗА И СВОЙСТВА

The results of elaborating a method for the synthesis of zirconia and hafnia doped by rare earths (yttrium, erbium and scandium) by using low-hydrated hydroxides of zirconium and hafnium as precursors are reported. The low-hydrated zirconium and hafnium hydroxides were prepared using the heterophase reaction. The physicochemical properties (including sorption properties) of low-hydrated zirconium and hafnium hydroxides ZrxHf1-x(OH)3÷1O0.5÷1.5·0.9÷2.9H2Owere studied. The scheme of thermal decomposition of low-hydrated hydroxides in air was determined. The sorption properties of the low-hydrated hafnium hydroxide are less pronounced owing to the lower amount of sorption centers, in this case, hydroxo and aqua groups. The sequence of stages of thermal decomposition of rare earth acetates was elucidated. Single-phase zirconia and hafnia doped by rare earths (yttrium, erbium and scandium) were obtained. The parameters of the elementary lattice were calculated for each phase. It was established that the stabilization of zirconium dioxide with yttria leads to the formation of interstitial solid solutions based on tetragonal zirconia (in the case of the composition Y2O3×4ZrO2 - cubic modification), with erbium oxide - interstitial solid solutions based on cubic zirconia; with scandium oxide - solid solutions based on tetragonal zirconia. The article presents the results of measuring electrical conductivity.В статье представлен разработанный метод синтеза диоксидов циркония и гафния, легированных редкоземельными элементами (иттрием, эрбием и скандием), с использованием в качестве предшественников индивидуальных и биметаллических маловодных гидроксидов (МВГ) циркония и/или гафния общего состава ZrxHf1-x(OH)3÷1O0.5÷1.5∙0.9÷2.9H2O, 0≤х≤1, а также ацетатов редкоземельных элементов. В свою очередь, МВГ циркония и/или гафния получали гетерофазным взаимодействием оксихлоридов металлов с концентрированным раствором аммиака. Изучены физико-химические свойства маловодных гидроксидов. Показано, что при нагревании до температуры 1200 °С в случае термолиза индивидуальных МВГ образуются моноклинные модификации соответствующих диоксидов, а при термолизе биметаллического МВГ - твердые растворы замещения состава ZrxHf1-xO2 (0≤х≤1) моноклинной модификации. Установлена последовательность стадий термического разложения ацетатов иттрия, скандия и эрбия с образованием оксидов. Получены дикосиды циркония и гафния, стабилизированные оксидами редкоземельных элементов, следующих составов: Y2O3∙4ZrO2, Y2O3∙16ZrO2, Y2O3∙20ZrO2, Y2O3∙4HfO2, Y2O3∙6HfO2, Y2O3∙9HfO2, Y2O3∙18HfO2, Er2O3∙27ZrO2, Er2O3∙35ZrO2, Sc2O3∙10ZrO2, Sc2O3∙13ZrO2. Для каждой фазы рассчитаны параметры элементарной решетки. Установлено, что при стабилизации диоксида циркония оксидом иттрия образуются твердые растворы внедрения на основе ZrO2 тетрагональной модификации (в случае состава Y2O3∙4ZrO2 - кубической модификации), оксидом эрбия - твердые растворы внедрения на основе диоксида циркония кубической модификации; оксидом скандия - твердые растворы на основе диоксида циркония тетрагональной модификации. В статье представлены результаты измерения электропроводности

НИОБИЙ И ТАНТАЛ: СОСТОЯНИЕ МИРОВОГО РЫНКА, ОБЛАСТИ ПРИМЕНЕНИЯ, СЫРЬЕВЫЕ ИСТОЧНИКИ. Часть 2

Niobium and tantalum are rare refractory metals having significant industrial importance. Their reserves are attributed to «critical» raw material, thus leading to the necessity of estimating the risks connected with primary and technogenic raw sources of niobium and tantalum and the effect of these factors on the proposals and demands for these metals and their compounds taking into account the traditional and new areas of application. The analysis of world’s reserves of niobium and tantalum has been made. The dynamics of changing the raw material base structure and the technological solutions realized and proposed for their processing is considered. The modern market of materials on the basis of niobium and tantalum is described; the basic players in this market are specified; the trends in fluctuation of functional material consumption structure on the basis of these metals are considered.Ниобий и тантал – редкие тугоплавкие металлы, имеющие важное промышленное значение. Их запасы относят к «критическому» сырью, что приводит к необходимости оценки рисков, связанных с наличием первичных и техногенных сырьевых источников ниобия и тантала и влиянием этих факторов на предложения и спрос на эти металлы и их соединения с учетом традиционных и новых областей применения. Выполнен анализ мировых запасов ниобия и тантала, рассмотрена динамика изменения структуры сырьевой базы и технологических решений, реализованных и предлагаемых для их переработки. Описан современный рынок материалов на основе ниобия и тантала, указаны основные игроки на этом рынке, рассмотрены тенденции в изменении структуры потребления функциональных материалов на основе этих металлов

НИОБИЙ И ТАНТАЛ: СОСТОЯНИЕ МИРОВОГО РЫНКА, ОБЛАСТИ ПРИМЕНЕНИЯ, СЫРЬЕВЫЕ ИСТОЧНИКИ.Часть 1

Niobium and tantalum are rare refractory metals of industrial significant importance. Their stores are reckoned to the «critical» raw materials that results in the necessity of estimating the risks connected to the availability of fundamental and technogenic raw sources of niobium and tantalum and the effect of these factors on the offers and demand for these metals and their compounds taking into account the traditional and new areas of their application. The article gives an analysis of the world’s reserves of niobium and tantalum; the dynamics of structural change of the raw-material base and the technological solutions realized and offered for their processing is considered. The modern market of materials based on niobium and tantalum is described; basic players in this market are determined; the tendencies in structural change in the consumption of functional materials on the basis of these metals are considered.Ниобий и тантал – редкие тугоплавкие металлы, имеющие важное промышленное значение. Их запасы относят к «критическому» сырью, что приводит к необходимости оценки рисков, связанных с наличием первичных и техногенных сырьевых источников ниобия и тантала и влиянием этих факторов на предложения и спрос на эти металлы и их соединения, с учетом традиционных и новых областей применения. В статье выполнен анализ мировых запасов ниобия и тантала, рассмотрена динамика изменения структуры сырьевой базы и технологических решений, реализованных и предлагаемых для их переработки. Описан современный рынок материалов на основе ниобия и тантала, указаны основные игроки на этом рынке, рассмотрены тенденции в изменении структуры потребления функциональных материалов на основе этих металлов

The technology of forming the students’ research competence in the process of learning a foreign language

© Canadian Center of Science and Education. The research issue appears important as today's system of professional education requires an optimal structure of the academic disciplines intended for the students’ research and creative abilities development. In this regard, the purpose of the article is to develop a technique for forming the students’ research competence in the process of learning a foreign language. The flagship approaches to the development of this technology have become the research and modular competence-based approaches. The article describes the technology of the students’ research competence formation in the process of learning a foreign language, the proposed stages of which are universal and can be also used in the formation of the students’ communicative competence, while the submitted steps are particularly aimed at the formation of the students’ research competence in the process of learning a foreign language. The materials of this article may be of value to the foreign language teachers while selecting and structuring the foreign language learning curriculum aimed at the formation of the research competence among the students of higher professional schools