Rate‐determining steps of oxygen surface exchange kinetics on Sr2Fe1.5Mo0.5O6−δ

The oxygen surface kinetics of Sr2Fe1.5Mo0.5O6−δ was determined using the 16O2/18O2 isotope exchange method with gas phase analysis at 600-800 °C. The heterogeneous exchange rates (rH) and the oxygen diffusion coefficients (D) were calculated by processing the concentration dependences of the 18O fraction using Ezin's model. The rates of oxygen dissociative adsorption (ra) and incorporation (ri) were calculated based on a model using the three exchange type rates. It has been established that the rates ra and ri were comparable in this temperature range. Assumptions were made about the effect of the chemical composition of the surface on the rate of oxygen adsorption. It was found that the oxygen exchange coefficient (k) of Sr2Fe1.5Mo0.5O6−δ is comparable to that of La0.6Sr0.4MnO3±δ oxide. High values of the oxygen diffusion coefficient were found for Sr2Fe1.5Mo0.5O6−δ. The values were comparable to those of the double cobaltite praseodymium-barium and exceed by more than an order those of lanthanum‐strontium manganite. © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).Russian Foundation for Basic Research, RFBR: 00161Government Council on Grants, Russian FederationThe study was partly financially supported by the Russian Foundation for Basic Research (17-08-00161) and the Russian Federation Government, agreement 02.A03.21.0006 (no. 211)

Cosmostructural model of the Kalgutinskiy rare-metal deposit area (Mountainous Altai)

Cosmostructures of the Kalgutinskiy rare-metal deposit area (Mountainous Altai) have been studied on the materials of multispectral space survey Landsat ETM+ and radar-tracking survey SRTM. The area is localized inside of the large ring structure of a complex construction, characterized by the long multistage (multipulse) development. Immersing of the root (focus) part of the structure from the north - northwest to the east - southeast is established. Position of the ring structure is controlled by the crossing knot of fracture zones of northwest, northeast and northeast - sublatitudinal directions. The Kalgutinskiy granite massif and the deposit itself are located in the internal belt of the structure in the ring 15,2 km in diameter. The perspective of ore-bearing ability of the southeast part of the area is highly evaluated in connection with development of small ring structures of the second typ

Разработка технологии получения биоразлагаемых композиций на основе полиэтилена, крахмала и моноглицеридов

Objectives. This work aimed to develop technology to produce biodegradable hybrid composite (BHC) films based on low-density polyethylene (LDPE) 115030-070 and thermoplastic starches (TPS) of various origins (corn, pea, and rice), with distilled monoglycerides as the plasticizer. The properties of the produced BHC films were studied and the optimal native starch : glycerol : monoglycerides ratio is proposed.Methods. TPS and BHC films based on this material were produced from different types of native starches in laboratory extruders (Brabender and MashPlast, Russia), and the extruded melts were subjected to ultrasonic vibrations. The structure and appearance of the BHC films were studied using scanning electron microscopy and rheology. Their biodegradability was assessed by immersing them in biocompost for three months. To evaluate the mechanical performance of the BHC films produced with and without ultrasound, the changes in tensile stress and elongation at break were determined during the biodegradation process.Results. The BHC films had a homogeneous structure, except small agglomerates (non-melted starch grains), which did not reduce their quality. The films with monoglycerides had high tensile strength, which was comparable with low-density polyethylene. After removing samples of the BHC films from the biocompost, their tensile strength decreased by 20%, which shows their biodegradability.Conclusions. The produced biodegradable composite films and the technology used to produce them will be applicable for the packaging industry to reduce environmental impact.Цель. Совершенствование технологии создания биологически разрушаемых гибридных композиций (БГК) на основе полиэтилена низкой плотности (ПЭНП) 11503-070 и термопластичных крахмалов различного происхождения (кукурузы, гороха, риса) с новыми пластификаторами – моноглицеридами дистиллированными. Разработка технологической схемы производства БГК. Получение и исследование свойств биологически разрушаемых композиционных пленок, пластифицированных смесью дистиллированных моноглицеридов и глицерина. Выбор оптимального соотношения нативный крахмал : глицерин : моноглицериды.Методы. Термопластичный крахмал и композиционные пленки получали на основе нативных крахмалов разных видов в лабораторных экструдерах фирм «Брабендер» и «МашПласт» (Россия), при этом экструдируемый расплав композиции подвергали воздействию ультразвуковых колебаний. Была изучена структура композитных пленок методом сканирующей электронной микроскопии, а также их реологические характеристики. Проведена оценка органолептических свойств композитных пленок. Способность к биоразложению композитных пленок оценивали при помощи погружения их на три месяца в биогумус. Для оценки эксплуатационных свойств БГК, до и после процесса биоразложения, определяли разрушающее напряжение при растяжении и относительное удлинение при разрыве, причем оценка была проведена и для пленок, которые подвергали воздействию ультразвука.Результаты. Был достигнут положительный эффект от использования нового пластификатора – дистиллированных моноглицеридов в композициях термопластичный крахмал : полиэтилен. При производстве композиции получались однородными по структуре, иногда образовывались небольшие агломераты, представляющие собой нерасплавившиеся частицы крахмала, что не ухудшало качество готовых БГК. Композиты с моноглицеридами обладали высокой прочностью на разрыв – практически на одном уровне с ПЭНП. После изъятия образцов композитных пленок из биогумуса их прочность на разрыв снижалась на 20%, что свидетельствует о протекании процесса биоразложения.Выводы. Разработанный состав и технология получения биологически разлагаемых композитных пленок могут быть использованы в дальнейшем для производства композитных пленок с высоким содержанием крахмала для применения в упаковочной отрасли, что позволит снизить негативную нагрузку на окружающую среду

Formation of conductive oxide scale on 33NK and 47Nd interconnector alloys for solid oxide fuel cells

Two grades of chromium-free alloys were studied in order to apply them as interconnectors for solid oxide fuel cells. The surface modification methods were proposed for each alloy with the purpose of forming of oxide scales considering the required physicochemical properties. Investigations of the structure and properties of the obtained oxide scales were performed and the efficiency of the chosen surface modification methods was approved. The samples with the surface modification exhibited higher conductivity values in comparison with the nonmodified samples. A compatibility study of samples with surface modification and glass sealant of chosen composition was accomplished. The modified samples demonstrated good adhesion during testing and electrical resistance less than 40 mOhm/cm2 at 850 ◦C in air, which allowed us to recommend these alloys with respective modified oxide scales as interconnectors for SOFC. © 2019 by the authors.Russian Foundation for Basic Research, RFBR: 17-58-10006This research was funded by the Russian Foundation of Basic Research grant number 17-58-10006. The facilities of the shared access center "Composition of Compounds" of IHTE UB RAS were used in this work

Application of promising electrode materials in contact with a thin-layer ZrO2-based supporting electrolyte for solid oxide fuel cells

The paper presents the results of an investigation into thin single- and triple-layer ZrO2-Sc2O3-based electrolytes prepared using the tape-casting technique in combination with promising electrodes based on La2NiO4+δ and Ni-Ce0.8Sm0.2O2-δ materials. It is shown that pressing and joint sintering of single electrolyte layers allows multilayer structures to be obtained that are free of defects at the layer interface. Electrical conductivity measurements of a triple-layer electrolyte carried out in longitudinal and transverse directions with both direct and alternating current showed resistance of the interface between the layers on the total resistance of the electrolyte to be minimal. Long-term tests have shown that the greatest degradation in resistance over time occurs in the case of an electrolyte with a tetragonal structure. Symmetrical electrochemical cells with electrodes fabricated using a screen-printing method were examined by means of electrochemical impedance spectroscopy. The polarization resistance of the electrodes was 0.45 and 0.16 Ohm∙cm2 at 800 °C for the fuel and oxygen electrodes, respectively. The distribution of relaxation times method was applied for impedance data analysis. During tests of a single solid oxide fuel cell comprising a supporting triple-layer electrolyte having a thickness of 300 microns, a power density of about 160 mW/cm2 at 850 °C was obtained using wet hydrogen as fuel and air as an oxidizing gas. © 2020 by the authors.Russian Foundation for Basic Research, RFBR: 17‐08‐ 01227Government Council on Grants, Russian FederationFunding: The study was partly financially supported by the Russian Foundation for Basic Research (17‐08‐ 01227), Russian Federation Government, agreement 02.A03.21.0006 (No. 211) and “InEnergy” LTD agreement of 2018

Non-crystallising Glass Sealants for SOFC: Effect of Y2O3 Addition

The joining of ceramic and metal (interconnect) parts is one of the main challenges in the development of solid oxide fuel cells (SOFC). A promising approach to solving this problem is the use of glassy sealants. In this work, we investigated the effect of yttria additions on the properties of SiO2–Al2O3–CaO–Na2O–ZrO2–Y2O3 glass sealants. An increase in the concentration of yttria is shown to reduce the tendency of the glasses under study to crystallisation. A glass containing 4 wt% of Y2O3 is found to be amorphous, even after exposure at 850 °C for 100 h. Moreover, the defectiveness of the glass microstructure, after sealing, is found to decrease along with a growth in the Y2O3 concentration. The developed non-crystallising sealant was successfully applied for joining a YSZ ceramic and an Fe–Ni–Co alloy having the phase transition of around 500 °C. The use of the non-crystallising sealant allows us to join materials with very different thermal expansion coefficients and to avoid cracking under cooling, which might occur due to a large difference in thermal expansion coefficients. © 2019 Elsevier Ltd and Techna Group S.r.l.This study was financially supported by the RFBR project no. 17-58-10006. The research was partially performed using the facilities of the Shared Access Centre “Composition of Compounds” of IHTE UB RAS . The authors are grateful to Dr. S.V. Plaksin for XRD analysis, Dr. N. I. Moskalenko for AES analysis, A. S. Farlenkov for SEM analysis, and A. A. Solodyankin and V. A. Vorotnikov for their assistance in sample preparation

Sedimentation of Ultradispersed Diamonds in the Citrate Copper-Plating Electrolyte

Abstract—The aggregation and sedimentation of ultradispersed diamonds (UDDs) in a citrate copper-plating electrolyte (CCPE) used to fabricate composite electrochemical coatings are investigated. The sedimentation and aggregation stability is investigated in order to select the UDD concentration in the CCPE. This is necessary to fabricate composite copper coatings with improved operational characteristics (increased hardness, wear resistance, and corrosion resistance), as well as impart them new properties (antifriction and catalytic). The UDD content in the electrolyte varies in limits from 0.2 to 2.0 g/L. The size distribution of the UDD particles in the electrolyte immediately after the suspension preparation and after the 10-day holding is determined using a Malvern Mastersizer 2000 laser diffraction analyzer. The aggregation and sedimentation stability of the UDD suspension in the CCPE is investigated by the gravimetric method with the continuous weighing of a quartz small cap immersed into this suspension. The quartz cap is associated with a Sartorius R200D analytical balance with the help of a quartz wire. The experimentally determined time dependence of the weight of settling UDD particles is Q = f(t). The relative size distribution of the particles is determined from this dependence. It is established that the sedimentation stability is substantially affected by the aggregation of the particles, the intensity of which increases with an increase in the UDD concentration. The results satisfying the requirements on the aggregation and sedimentation stability are found for the UDD suspension in the CCPE with a concentration of 1.0 g/L. In this case, the high content of the dispersed phase is combined with aggregation and sedimentation stability, which makes it possible to fabricate copper composite coatings with improved operational properties. © 2019, Allerton Press, Inc

Oxygen diffusion and surface exchange kinetics for the mixed-conducting oxide La0.6Sr0.4Co0.8Fe0.2O3–δ

Received: 14.11.2018. Accepted: 11.12.2018. Published: 31.12.2018.Studies of oxygen surface exchange kinetics for La0.6Sr0.4Co0.8Fe0.2O3–δ oxide were performed using the technique of isotopic exchange of molecular oxygen with analysis of gas phase isotopic composition in a static circulation system at the temperatures of 600–800 °С in the oxygen pressure range of 0.27–2.13 kPa. The values of interphase exchange rate and oxygen diffusion coefficient were determined. The effective activation energies for oxygen exchange and diffusion processes as well as the exponents in the dependence of these values versus oxygen pressure in the double logarithmic coordinates were calculated. The process of oxygen dissociative adsorption at the surface of La0.6Sr0.4Co0.8Fe0.2O3–δ oxide was found to be the rate-determining stage.This work is partly supported by the Russian Science Foundation (Project No. 17‑73‑10196) using facilities of shared access center “Composition of Compounds” of IHTE UB RAS