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Background. High-dose implantation of cobalt ions into the crystal structure of natural colourless quartz was carried out. Samples of crystal plates of rock crystal from the Svetlinskoye deposit in the South Urals plane-parallel were studied. All samples were crystallographically oriented perpendicular to the symmetry axis of the third order. Cobalt implantation into quartz was carried out using an ILU-3 ion-beam accelerator along the С axis of symmetry.Aim. To determine the ranges of thermal annealing for a controlled change in the sample colour and to establish the crystal-chemical features of the changes occurring in quartz matrix due to ionbeam modification of mineral properties.Materials and methods. Implantation modes included: room temperature, residual vacuum 10–5 torr, radiation dose from 1.0×1017 to 1.5×1017 ion/cm2 at a constant ion current density of 10 μA/cm2. Post-implantation heat treatment was carried out in three stages. The control of crystallochemical changes was carried out using a highly sensitive spectrophotometer with a wide range of wavelengths.Results. It was found that the revealed absorption bands are associated with electronic transitions in cobalt ions (Со2+ and Со 3+) coordinated in the crystal matrix of implanted and heat-treated rock crystal. The formation of an independent ultradispersed spinel phase in the irradiated quartz matrix was confirmed. The newly formed phase belongs to a partially reversed cobalt spinel.Conclusions. Taking into account the quantum-optical properties of cobalt spinel (laser shutters), the method of ion-beam modification of mineral crystal structures, quartz in particular, is highly promising in terms of creating new composite materials based on natural and artificial mineral raw materials.

For catalytic process intensification, a series of open cell foams (OCFs) made of silicon carbide (SiC) and zirconia (Zir) with pore density of 30 ppi coated with 3 wt% PdO/Co3O4 as catalyst were combined together and tested toward methane oxidation in lean conditions. In each combination, the SiC OCF was positioned in the reactor on the inlet side of the reactant gases followed by the Zir OCF. The reactor was fed at different weight hourly space velocities (WHSV, 30 and 90 NL h−1 gcat−1) and inlet methane concentrations (0.5 and 1 vol%). The best results are obtained with the combination where two supports of same length but with different thermal conductivity (higher at the inlet of the reactor, SiC, and lower at the outlet, Zir) are used in series. For all OCF combinations, mass transfer effects were evaluated using the characteristic resistances (kinetic, internal and external mass transfer). The external and internal heat transfer effects were analyzed using the Mears and Anderson criteria. Furthermore, a comparison in terms of volumetric heat transfer coefficient and heats of removal/reaction was performed.

Дисертація на здобуття наукового ступеня доктора філософії за спеціальністю 161 "Хімічні технології та інженерія". – Національний технічний університет "Харківський політехнічний інститут", Харків, 2020. Об'єкт дослідження – процеси фазоутворення вогнетривких барійалюмінатних цементів в системі ВаО – СоО – Al₂O₃ з комплексом заданих експлуатаційних характеристик. Предмет дослідження – закономірності й особливості синтезу в'яжучих матеріалів на основі композицій високоалюмінатної області системи ВаО – СоО – Al₂O₃, механізм процесів їх гідратації, що обумовлює формування комплексу заданих властивостей барійалюмінатних цементів. Дисертацію присвячено вирішенню науково-практичної задачі – розробка спеціальних цементів на основі композицій системи ВаО – СоО – Al₂O₃ з високою міцністю, вогнетривкістю та стійкістю до дії агресивних середовищ. У вступі обґрунтовано актуальність теми дисертаційної роботи, зазначено зв'язок роботи з науковими темами, сформульовано мету і задачі дослідження, визначено об’єкт, предмет та методи дослідження, показано наукову новизну та практичне значення отриманих результатів, наведено інформацію про практичне використання, особистий внесок здобувача, апробацію результатів дослідження та їх висвітлення у публікаціях. Приводяться відомості щодо структури та обсягу дисертаційної роботи. В першому розділі проведено аналіз основних видів неорганічних в'яжучих матеріалів та заповнювачів, що застосовуються на сучасних підприємствах для отримання тугоплавких неформованих матеріалів та шляхи підвищення їх основних експлуатаційних характеристик. Проаналізовано тенденції експлуатації неформованих вогнетривких матеріалів в сучасних теплових агрегатах. Відзначено переваги та недоліки виробництва неформованих вогнетривів на основі гідратаційних в'яжучих, в тому числі на основі глиноземних та високоглиноземних цементів. Вивчання особливостей синтезу глиноземних в'яжучих та формування основних експлуатаційних характеристик вогнетривких матеріалів на їх основі виявив низку труднощів і недоліків існуючих технологій, альтернативу яким можуть успішно скласти барійалюмінатні в'яжучі матеріали, основою яких є система ВаО – СоО – Al₂O₃. Детально вивчено і проаналізовано будову бінарних систем, що входять до даної системи. Проаналізовано базу основних сировинних матеріалів вогнетривкої галузі, що дозволило визначити перспективним – напрямок досліджень, спрямованих як на переробку відходів промисловості, так і на комплексне використання природних ресурсів – створення маловідходних та безвідходних технологій. На підставі проведеного аналізу сформульовано задачі дослідження та шляхи їх вирішення. У другому розділі наведена характеристика вихідних сировинних матеріалів, визначено вибір методик теоретичних та експериментальних досліджень, надано опис розрахункових методів, використаних у дисертаційній роботі. Теоретичні дослідження проводили із застосуванням сучасних методів аналізу згідно з положень фізичної хімії і термодинаміки силікатів. Фізико-механічні випробовування цементу проводились згідно з методикою малих зразків М. І. Стрєлкова, а оптимальні склади цементу досліджувались у відповідності до ДСТУ EN 196-1:2007 "Методи випробувань цементів. Визначення міцності", ДСТУ EN 196-3:2007 "Методи випробувань цементів. Визначення термінів тужавіння й рівномірності змін об'єму" і ДСТУ EN 196-6:2007 «Методи випробувань цементів. Визначення тонини помелу". Технічні властивості розроблених матеріалів визначались за стандартними методами: вогнетривкість – по ISO 528:1983, термостійкість – за ГОСТ 7875.2-94, температура деформації під навантаженням за температури, що зростає – за ДСТУ ISO 1893:2014, ступінь розміцнення – за величиною зменшення механічної міцності із збільшенням температури. Температури і склади евтектик в бінарних перетинах системи розраховувались за формулами Епстейна – Хоуленда, а у трикомпонентних перетинах – шляхом рішення системи нелінійних рівнянь. Математична обробка даних для будови діаграм «склад-властивість" з метою оптимізації цементних складів і фракційного складу заповнювача здійснювалась з використанням симплекс-ґратчастого методу планування експерименту. В третьому розділі представлені результати теоретичних досліджень трикомпонентної системи ВаО – СоО – Al₂O₃. Розраховані термодинамічні дані для сполук, дані яких відсутні у довідковій літературі та сформовано термодинамічну базу даних всіх сполук системи ВаО – СоО – Al₂O₃. Проведені теоретичні й експериментальні дослідження щодо можливості існування трикомпонентної сполуки Вa₃СоAl₄O₁₀ в системі ВаО – СоО – Al₂O₃, результати яких не підтвердили її утворення. Вперше проведено тріангуляцію даної системи без урахування в ній потрійних сполук та аналіз геометро-топологічних і статистичних характеристик субсолідусної будови системи. Розраховано і проаналізовано температури плавлення і склади евтектик для бінарних і потрійних перетинів системи ВаО – СоО – Al₂O₃, в результаті яких встановлено, що бінарні і потрійні перетини даної системи, які містять у своєму складі кобальтову шпінель, характеризуються температурами плавлення вище 1650 °C. Таким чином, перспективною областю з точки зору створення складів вогнетривких вʼяжучих матеріалів на основі композицій системи ВаО – СоО – Al₂O₃ є потрійний перетин ВaAl₂O₄ – ВaAl₁₂O₁₉ – CoAl₂O₄. В четвертому розділі проведено оцінку особливостей прояву в'яжучих властивостей двох- і трикомпонентними сполуками системи ВаО – СоО – Al₂O₃, в'яжучі властивості яких ще не встановлено. З метою одержання в'яжучих матеріалів, що характеризуватимуться комплексом високих експлуатаційних характеристик, а саме: міцність при стиску та вогнетривкість, на основі перерізу ВaAl₂O₄ – ВaAl₁₂O₁₉ – CoAl₂O₄ проведено оптимізацію кількісного співвідношення фаз. Визначено, що барійалюмінатні цементи на основі системи ВаО – СоО – Al₂O₃ з комплексом високих технічних характеристик мають містити, мас.%: ВaAl₂O₄ – 60 – 20; CoAl₂O₄ – 30 – 60; ВaAl₁₂O₁₉ – 10 – 20. В результаті аналізу отриманих результатів перспективним обрано бінарний перетин ВaAl₂O₄ – CoAl₂O₄ та вивчено вплив кількісного співвідношення моноалюмінату барію та кобальтової шпінелі на фізико-механічні властивості отриманих матеріалів. Раціональним для подальших досліджень визначено фазовий склад, що містить 40 мас. % ВaAl₂O₄ і 60 мас. % CoAl₂O₄, який характеризується найкращим комплексом фізико-механічних властивостей. Досліджено термомеханічні властивості барійалюмінатного цементу оптимального складу та встановлено, що отриманий матеріал є вогнетривким – вище 1750 °С, із високою термостійкістю – більше 20 теплозмін в умовах 1300 °С - повітря та характеризується низьким ступенем розміцнення в інтервалі температур 20-1300 0С - до 12 %. Проведено кінетичні дослідження процесів мінералоутворення у сумішах, що складаються з ВаСО₃, Al₂O₃ і СоO. В результаті проведених експериментальних досліджень виявлено немонотонні зміни кількості основних фаз в матеріалі зразків після випалу при різних температурах, що обумовлено особливостями утворення твердих розчинів на основі барієвої і кобальтової шпінелей. Отримані результати актуальні для прогнозування фазового складу в'яжучих матеріалів на основі системи ВаО – СоО – Al₂O₃ й регулювання їх гідратаційної активності. Визначено можливість застосування відходів хімічної промисловості як заміни імпортної мінеральної сировини у технології барійалюмінатного цементу. Проведеними дослідженнями встановлено, що відходи гідрування сірковмісних органічних сполук ПАТ "Сєвєродонецьке об'єднання Азот" та виробництва амінокапронової кислоти "Заводу хімічних реактивів" НТК "Інститут Монокристалів" можуть бути використані як сировина для виробництва барійалюмінатних цементів підвищеної вогнетривкості. Досліджено фазовий склад розроблений клінкерів, проведено дослідження їх мікроструктури. Результати фізико-механічних випробувань розроблених композицій свідчать, що вони відносяться до гідравлічних вʼяжучих повітряного тверднення, є швидкосхоплюючими: початок тверднення – 1 год. 20 хв.; кінець – 5 год. 20 хв.; високоміцними: межа міцності при стиску у 3 доби – до 50 МПа, що мають високу температуру плавлення – вище 2000 °С. Із залученням комплексу фізико-хімічних методів аналізу вивчено продукти гідратації отриманого барійалюмінатного цементу як на основі хімічно чистих оксидів оптимального складу, так і з використанням відходів промисловості. Рентгенофазовий аналіз дозволив встановити, що процес гідратації цементних композицій супроводжуються активним розчиненням основної клінкерної гідратаційно активної фази ВaAl₂O₄ за участі твердих розчинів на основі ВaAl₁₂O₁₉ з утворенням гелевих фаз, про що свідчить зменшення інтенсивностей відповідних дифракційних максимумів моноалюмінату барію та зміщення міжплощинних відстаней гексаалюмінату барію. За результатами проведеного диференційно-термічного аналізу встановлено, що видалення як хімічно зв’язаної, так і кристалізаційної води із гідратних сполук розроблених цементів відбувається у широкому діапазоні температур, що дозволяє знівелювати термічні дефекти, які виникають при нагріванні цементного каменю та конструкційних виробів на його основі. Отримані результати свідчать про те, що розроблені цементи на основі гідравлічно активних алюмінатів барію та алюмокобальтової шпінелі відносяться до швидкотверднучих, швидкотужавіючих, високоміцних в'яжучих матеріалів з високою вогнетривкістю та рекомендовані для виготовлення вогнетривких бетонів, торкрет-мас, а також мертелів для застосування їх в високотемпературних агрегатах різних галузей промисловості. У п'ятому розділі для отримання бетону високої міцності, щільності й однорідності на основі барійалюмінатного цементу обрано види заповнювачів, проведено підбір гранулометричного складу заповнювача. Встановлено оптимальне співвідношення основних компонентів вогнетривкої суміші цемент : заповнювач, а також - засобу формування виробів. Досліджено залежність термічної стійкості та ступеня розміцнення при нагріванні бетону від виду заповнювача, що застосовувався. Встановлено, що бетонні зразки на основі розробленого барійалюмінатного цементу оптимального складу із застосуванням у вигляді заповнювача як електроплавленого корунду, так і гексаалюмінату барію з раціональним співвідношенням цемент : заповнювач, виготовлені шляхом віброукладання напівжорсткої суміші з водотвердим відношення 0,08, характеризуються комплексом високих фізико-механічних властивостей, а саме: границя міцності при стиску у 28 діб тверднення – 55,8 – 60,2 МПа, уявною пористістю – 17,8 % - 21,8 %, термічною стійкістю – більше 20 циклів із збереженням більше 85 % своєї початкової міцності; ступінь розміцнення при нагріванні до 1600 °С – не перевищує 14 %; вогнетривкість складає 1700 °С; температура початку деформації під навантаженням 0,2 МПа – 1490°С - 1580 °С. За результатами дисертаційної роботи в умовах дослідного виробництва ВАТ НВП "ДОМІНАНТА" (м. Костянтинівка Донецької обл.) експериментально доведено можливість застосування і експлуатації вогнетривких деталей, що виготовлені з бетону на основі розробленого барійалюмінатного цементу і електроплавленого корунду, що відпрацювали 45 циклів у печі, робоча температура в якій склала 1400 °С -1650 °С в умовах різьких змін температур без суттєвих руйнувань. Теоретичні та практичні результати дисертаційної роботи впроваджено у практику навчального процесу кафедри технології кераміки, вогнетривів, скла та емалей НТУ "ХПІ" при підготовці студентів за спеціальністю 161 "Хімічні технології та інженерія". Thesis for obtaining the philosophy doctor scientific degree on the specialty 161 "Chemical Technology and Engineering". – National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2020. Object of research - processes of phase formation of refractory barium aluminate cements in the system ВаО – СоО – Al₂O₃ with a set of specified operational characteristics. Subject of research regularities and features of synthesis of binders based of compositions of high-aluminate region of ВаО – СоО – Al₂O₃ system, mechanism of processes of their hydration that causes formation of the set properties of barium aluminate cements. The dissertation is devoted to the decision of a scientific and practical problem - development of special cements based of compositions of system ВаО – СоО – Al₂O₃ with high durability, fire resistance and resistance to action of aggressive environments. The introduction substantiates the relevance of the topic of the dissertation, indicates the connection of work with scientific topics, formulates the purpose and objectives of the study, defines the object, subject and methods of research, shows the scientific novelty and practical significance of the results, provides information on practical use, personal contribution applicant, approbation of research results and their coverage in publications. Information about the structure and scope of the dissertation is given. The first section analyzes the main types of inorganic binders and aggregates used in modern enterprises to obtain refractory unformed materials and ways to improve their basic performance. Trends in the operation of unformed refractory materials in modern heating units are analyzed. The advantages and disadvantages of the production of unformed refractories based on hydration binders, including those based on alumina and high alumina cements, are noted. The study of the synthesis of alumina binders and the formation of the main performance characteristics of refractory materials based on them revealed a number of difficulties and shortcomings of existing technologies, an alternative to which can successfully make barium aluminate binders based on ВаО – СоО – Al₂O₃. The structure of binary systems that are part of this system is studied and analyzed in detail. The base of the main raw materials of the refractory industry is analyzed, which allowed to determine the perspective the direction of research aimed at both the processing of industrial waste and the integrated use of natural resources - the creation of low-waste and non-waste technologies. On the basis of the conducted analysis the tasks of research and ways of their decision are formulated. In the second section the characteristic of initial raw materials is given, the choice of methods of theoretical and experimental researches is defined, the description of the calculation methods used in the dissertation is given. Theoretical research was carried out using modern methods of analysis in accordance with the provisions of physical chemistry and thermodynamics of silicates. Physico-mechanical tests of cement were carried out according to the method of small samples of MI Strelkov, and the optimal compositions of cement were investigated in accordance with DSTU EN 196-1: 2007 "Methods of testing cements. Determination of strength", DSTU EN 196-3: 2007 Methods of testing cements. Determination of hardening time and uniformity of volume changes" and DSTU EN 196-6: 2007" Methods of testing cements. Determination of grinding tonnage". Technical properties of the developed materials were determined by standard methods: fire resistance - according to ISO 528: 1983, heat resistance - according to GOST 7875.2-94, deformation temperature under load at increasing temperature - DSTU ISO 1893: 2014, degree of hardening - by the amount of decrease in mechanical strength with increasing temperature. Temperatures and compositions of eutectics in binary sections of the system were calculated by the Epstein-Howland formulas, and in three-component sections by solving a system of nonlinear equations. Mathematical data processing for the structure of the "composition-property" diagrams in order to optimize the cement compositions and the fractional composition of the aggregate was carried out using a simplex-lattice method of planning the experiment. The third section presents the results of theoretical studies of the threecomponent system ВаО – СоО – Al₂O₃. Thermodynamic data for compounds whose data are absent in the reference literature are calculated and a thermodynamic database of all compounds of the ВаО – СоО – Al₂O₃ system is formed. Theoretical and experimental studies on the possibility of the existence of a three-component compound Вa₃СоAl₄O₁₀ in the system ВаО – СоО – Al₂O₃, the results of which did not confirm its formation. For the first time, the triangulation of this system without taking into account ternary compounds and the analysis of geometro-topological and statistical characteristics of the subsolidus structure of the system were carried out. Melting temperatures and eutectic compositions for binary and triple cross sections of the ВаО – СоО – Al₂O₃ system were calculated and analyzed, as a result of which it was found that binary and triple cross sections of this system containing cobalt spinel are characterized by melting temperatures above 1650 ° C. Thus, a promising area in terms of creating compositions of refractory binders based on the compositions of the ВаО – СоО – Al₂O₃ system is the triple cross section ВaAl₂O₄ – ВaAl₁₂O₁₉ – CoAl₂O₄. In the fourth section, the peculiarities of the manifestation of the binding properties of two- and three-component compounds of the ВаО – СоО – Al₂O₃ system, the binding properties of which have not yet been established, have been evaluated. In order to obtain binders that will be characterized by a set of high performance characteristics, namely: compressive strength and fire resistance, based on the cross section ВaAl₂O₄ – ВaAl₁₂O₁₉ – CoAl₂O₄, the quantitative phase ratio was optimized. It is determined that barium aluminate cements based on the system ВаО – СоО – Al₂O₃ with a set of high technical characteristics should contain, wt.%: ВaAl₂O₄ - 60 - 20; CoAl₂O₄ - 30 - 60; ВaAl₁₂O₁₉ - 10 - 20. As a result of the analysis of the obtained results, the binary section ВaAl₂O₄ – CoAl₂O₄ was chosen as promising and the influence of the quantitative ratio of barium monoaluminate and cobalt spinel on the physical and mechanical properties of the obtained materials was studied. Rational for further research determined the phase composition containing 40 wt. % ВaAl₂O₄ and 60 wt. % CoAl₂O₄, which is characterized by the best set of physical and mechanical properties. The thermomechanical properties of barium aluminate cement of optimal composition were investigated and it was found that the obtained material is refractory - above 1750 °С, with high heat resistance - more than 20 heat changes in 1300 °С - air and characterized by low degree of hardening in the temperature range 20-1300 °С - up to 12 %. Kinetic studies of mineral formation processes in mixtures consisting of ВаСО₃, Al₂O₃ and CoO have been carried out. As a result of the conducted experimental researches nonmonotonic changes of quantity of the basic phases in material of samples after firing at various temperatures that is caused by features of formation of firm solutions on the basis of barium and cobalt spinels are revealed. The obtained results are relevant for predicting the phase composition of binders based on the ВаО – СоО – Al₂O₃ system and regulating their hydration activity. The possibility of using waste from the chemical industry as a replacement for imported mineral raw materials in the technology of barium aluminate cement has been determined. Studies have shown that the waste of hydrogenation of sulfur-containing organic compounds of PJSC "Severodonetsk Association Nitrogen" and production of aminocaproic acid "Chemical Reagents Plant" STC "Institute of Single Crystals" can be used as raw material for the production of barium aluminates cements of high refractoriness. The phase composition of the developed clinkers was studied, their microstructure was studied. The results of physical and mechanical tests of the developed compositions show that they belong to the hydraulic binders of air hardening, are fast-setting: the beginning of hardening - 1 hour, 20 minutes; end - 5 hours, 20 minutes; high-strength: compressive strength in 3 days - up to 50 MPa, with a high melting point - above 2000 °C. With the involvement of a set of physicochemical methods of analysis, the hydration products of the obtained barium aluminate cement were studied both on the basis of chemically pure oxides of optimal composition and with the use of industrial waste. X-ray phase analysis revealed that the hydration process of cement compositions is accompanied by active dissolution of the main clinker hydration active phase of ВaAl₂O₄ with the participation of solid solutions based on ВaAl₁₂O₁₉ with the formation of gel phases, as evidenced by a decrease in the intensities of the corresponding diffraction maxima. According to the results of differential thermal analysis, it was found that the removal of both chemically bound and crystallization water from hydrated compounds of the developed cements occurs in a wide range of temperatures, which eliminates thermal defects that occur when heating cement stone and structural products based on it. The obtained results indicate that the developed cements on the basis of hydraulically active aluminates of barium and aluminate-cobalt spinel belong to fasthardening, fast-hardening, high-strength binders with high fire resistance and are recommended for production of refractory concretes, shotcrete masses, and also in their mortars. high-temperature units of various industries. In the fifth section, the types of aggregates were selected to obtain concrete of high strength, density and homogeneity on the basis of barium aluminate cement, and the particle size distribution of aggregate was selected. The optimal ratio of the main components of the refractory mixture of cement: aggregate, as well as - the means of forming products. The dependence of thermal stability and degree of hardening when heating concrete on the type of aggregate used is investigated. It is established that concrete samples on the basis of the developed barium aluminate cement of optimum structure with application in the form of a filler both electrofusioned corundum, and barium hexaaluminate with a rational ratio of cement: aggregate made by vibrolaying of semi-rigid mix with water-solid properties, namely: compressive strength at 28 days of curing - 55.8 - 60.2 MPa, apparent porosity - 17.8% - 21.8%, thermal stability - more than 20 cycles while maintaining more than 85% of its initial strength ; the degree of hardening when heated to 1600 °C - does not exceed 14%; fire resistance is 1700 °C; the temperature of the beginning of deformation under a load of 0.2 MPa - 1490 °C - 1580 °C. According to the results of the dissertation work in the conditions of experimental production of OJSC Research and Production Enterprise "DOMINANTA" (Kostiantynivka, Donetsk region) the possibility of application and operation of refractory parts made of concrete on the basis of developed barium aluminate cement and electrofused corundum, which worked 45 cycles in the furnace, was experimentally proved, operating temperature in which made 1400 °C - 1650 °C in the conditions of sharp changes of temperatures without essential destructions. Theoretical and practical results of the dissertation are introduced into the practice of the educational process of the Department of Technology of Ceramics, Refractories, Glass and Enamels of NTU "KhPI" in the preparation of students majoring in 161 "Chemical Technology and Engineering".

A series of supported Co 3 O 4 /α-Al 2 O 3 catalyst synthesized by glycerol-assisted method was thoroughly characterized (X-ray micro-tomography, XRD, RS, FTIR, SEM/TEM/EDX, TG/DTA, TPR), and their reactivity was evaluated in N 2 O decomposition in 5% N 2 O/He and 1.5% N 2 O, 1% NO x , 1 vol.% H 2 O, 2.0 vol.% O 2 . Their superior catalytic activity in comparison to the benchmark Co 3 O 4 /α-Al 2 O 3 catalyst, obtained via incipient wetness impregnation with the aqueous solution, was accounted for by differences in cobalt spinel dispersion on the alumina support, spinel nanoparticle size and faceting. Whereas for the samples prepared from the aqueous solution the spinel active phase exhibits a broad bimodal size distribution (with the maxima for 10–50 nm crystallites and 300–600 nm agglomerates) in the case of glycerol-assisted synthesis a monomodal distribution is featured by isolated spinel nanocrystallites of 10–30 nm. At the same time, the presence of glycerol changes the spinel crystallites morphology from rhombicuboctahedron with abundant exposition of the less favorable (111) planes into the truncated cubic shape with the dominant more active (100) facets. It was shown that the beneficial effect of glycerol is sustained in typical gaseous residuals (H 2 O, NO x , O 2 ) present in the tail gases of nitric acid plants. The observed effect of glycerol-assisted synthesis was accounted for by complexation of cobalt by glycerol, leading to the formation of an intrapore cobalt glycerolate, which upon calcination is transformed into well dispersed Co 3 O 4 cubic nanocrystals.

In this work a series of cobalt spinel catalysts was synthesized by different methods and doped with 1 wt% of palladium via incipient wetness impregnation or solution combustion synthesis (SCS). Both undoped and Pd-doped spinels were characterized from the structural and surface point of view (XRD, XRF, μRS, BET, FESEM) and tested toward the oxidation of methane in lean conditions, in gas mixtures containing from 0.5 to 2 vol% of CH4. These methane concentrations are typical of processes involving combustion of CH4 in lean conditions as the after-treatment of unconverted CH4 in compressed natural gas-fed vehicle exhausts, or the treatment of fugitive CH4 from leaks in coal mines. The temperature window for the catalytic activity of the undoped Co3O4 materials spread from 350 to 600 °C. The preparation method affected the catalytic activity of undoped Co3O4, with the best catalytic activity related to the spinel prepared by SCS employing urea. The addition of 1 wt% of Pd lowered the temperature window for the catalytic activity to the range of 250–500 °C, with insignificant differences for the various preparation methods. The beneficial effect of Pd-doping was assigned to the enhancement of the reduction of cobalt in the oxide structure.

[EN] The feasibility of the electrochemical technologies for wastewater treatment greatly relies on the design of efficient but inexpensive electrocatalysts. It is generally accepted that the so-called ¿non-active¿ anodes (like the boron-doped diamond (BDD) or SnO2-based anodes), producing highly oxidizing hydroxyl radicals, are the most promising candidates for pollutants abatement. In this work, the electrocatalytic performance of various cobalt oxides, pure and doped with Cu or Au, for CN¿ oxidation has been studied and compared with that of conventional graphite, BDD, SnO2-Sb and SnO2-Sb-Pt. The metal oxide electrodes were prepared by thermal decomposition of the salt precursors onto Ti. For the M-doped Co3O4 electrodes, the nominal M/Co ratios were Cu/ Co=0.07¿1.00; and Au/Co=0.05¿0.20. The electrodes were characterized by different techniques (XRD, SEM, EDX, XPS) and their electrocatalytic response was studied by cyclic voltammetry and galvanostatic electrolysis in a H-type cell in aqueous 0.1M NaOH. The obtained results show that the nature of the dopant plays a key role on the electrocatalytic behavior of cobalt spinels. Thus, while Cu catalyzes the CN¿ electro-oxidation, Au declines it. This is explained by the fact that, unlike Au (which segregates as Au-rich particles), Cu is effectively incorporated into the spinel structure by forming a solid solution (CuxCo3-xO4). In this solid solution, atomic scale Cu(spinel)-CN¿ specific interactions occur to catalyze the reaction, whereas in segregated Au particles the oxidation is hindered probably by a too-strong adsorption of cyanide and/or its inaccessibility to oxide active sites. Electrolysis runs have revealed that ¿active¿ over-saturated Cu-doped spinels (Cu/Co=1.00) exhibit higher current efficiencies than conventional graphite and ¿non-active¿ BDD and SnO2-based anodes. Hence, we hereby demonstrate that an inexpensive ¿active¿ electrocatalyst can show even higher efficiency than the most powerful BDD anode. These results highlight the significance of anode design in the application of the electrochemical technique for wastewater treatment., Financial support from the Spanish Ministerio de Economia y Competitividad and FEDER funds (MAT2016-76595-R, IJCI-2014-20012) is gratefully acknowledged

[EN] The development of electrocatalysts based on the doping of copper over cobalt spinel supported on a microporous activated carbon has been studied. Both copper-cobalt and cobalt spinel nanoparticles were synthesized using a silica-template method. Hybrid materials consisting of an activated carbon (AC), cobalt oxide (Co3O4), and copper-doped cobalt oxide (CuCo2O4) nanoparticles, were obtained by dry mixing technique and evaluated as electrocatalysts in alkaline media for hydrogen evolution reaction. Physical mixtures containing 5, 10, and 20 wt.% of Co3O4 or CuCo2O4 with a highly microporous activated carbon were prepared and characterized by XRD, TEM, XPS, physical adsorption of gases, and electrochemical techniques. The electrochemical tests revealed that the electrodes containing copper as the dopant cation result in a lower overpotential and higher current density for the hydrogen evolution reaction., This research was funded by MINECO and FEDER (MAT2016-76595-R).

A series of Co3O4/CeO2 catalysts with increasing cobalt spinel loading in the range of 1–20 wt.% was prepared by incipient wetness impregnation of CeO2. The obtained catalysts were thoroughly examined by XRD, XPS, XRF, RS, TEM/EDX/EELS, TPR and BET techniques. The catalytic tests in deN2O reaction revealed that the 10 wt.% of cobalt spinel in supported system is able to reproduce the activity of bare Co3O4 catalyst. However, it was found that the catalyst with the lowest content of Co3O4 equal to 1 wt.% exhibits the highest apparent reaction rate per mass of the spinel active phase. The observed activity was explained basing on the transmission electron microscopy analysis in terms of the dispersion of spinel phase over ceria support. A simple model that accounts for the observed strong dispersion effect is proposed. It consists in a two-step mechanism, where N2O is dissociated on the spinel nanograins and the resultant oxygen species are preferentially recombined at the Co3O4/CeO2 interface periphery. The authors would like to acknowledge the Polish National Centre for Research and Development funding awarded by the decision number PBS2/A5/38/2013. On the Polish part the research was partially carried out with the equipment purchased thanks to the financial support of the European Regional Development Fund in the framework of the Polish Innovation Economy Operational Program (contract no.POIG.02.01.00-12-023/08).

In this work a series of palladium doped cobalt spinel catalysts was synthesized via solution combustion synthesis plus incipient wetness impregnation and tested in lean CH 4 oxidation. The obtained catalysts were characterized from the structural and surface point of view (XRD, XRF, μRS, BET). The Pd doping level, calculated as PdO, ranged from 0.5 to 5 wt.%. The optimal palladium loading was determined on the basis of catalytic tests in gas mixtures containing from 0.5 to 2 vol.% of CH 4 . The temperature window for the catalytic activity of the Pd/Co 3 O 4 materials spread from 270 to 550 °C. The optimal Pd loading was found to be 3 wt.%, and it was rationalized in terms of favorable surface Pd dispersion, since above this critical level of 3% an appreciable amount of PdO phase was formed. The reactivity of the optimal 3 wt.% Pd/Co 3 O 4 catalyst from one-shot solution combustion synthesis was evaluated with the aim of optimizing the synthesis procedure.

Presented contribution summarizes our research dealing with cobalt mixed oxide catalysts for low temperature N2O catalytic decomposition.

A series of cobalt spinel oxides with the chemical composition: Co3O4, MgCo2O4, MgCoAlO4, CoAl2O4, Mg0.5Co0.5Al2O4 and MgAl2O4 was synthesised, characterised and studied for catalytic decomposition of N2O. Selective replacement of cobalt ions in the tetrahedral and octahedral sites was employed to probe the specific activity of both types of centres. The combined experimental XRD, UV–vis, RS, XPS, BET, TPR, Temperature Programmed Catalytic Reaction (TPCatR) methods and DFT modelling allowed to explore the mechanistic role of the coordination (tetrahedral, octahedral) and valence (+2, +3) states of cobalt ions in the Co3O4 spinel matrix. The prime active sites of deN2O reaction were definitely identified as the octahedral Co3+ ions (Ea = 15–17 kcal mol−1), whereas the tetrahedral Co2+ ions were found to be clearly much less active (Ea = 27–28 kcal mol−1).

Nanocrystalline cobalt spinel has been recognized as a very active catalytic material for N2O decomposition. Its catalytic performance can be substantially modified by proper doping with alien cations with precise control of their loading and location (spinel surface, bulk, and spinel-dopant interface). Various doping scenarios for a rational design of the optimal catalyst for low-temperature N2O decomposition are analyzed in detail and the key reactivity descriptors are identified (content and topological localization of dopants, their redox vs. non-redox nature and catalyst work function). The obtained results are discussed in the broader context of the available literature data to establish general guidelines for the rational design of the N2O decomposition catalyst based on a cobalt spinel platform.

Cobalt spinel Co3O4 catalysts promoted with different potassium precursors (K2CO3, KNO3, CH3COOK, KOH) were prepared and characterized by surface (XPS, work function, SEM) and structure (Raman, XRD, H2-TPR) sensitive techniques. The stability of potassium promoter was determined by means of Species Resolved-Thermal Alkali Desorption method (SR-TAD). The N2O decomposition mechanism on series of synthesized catalysts was studied by temperature programmed reaction and pulse experiments of isotopically labeled 15N218O. The role of the octahedral cobalt ions as catalytic active sites was revealed. The most dispersed state of alkali promoter, obtained from K2CO3 precursor, results in its highest stability and lowest work function, leading to the highest catalytic activity in N2O decomposition in the investigated K-Co3O4 series. The beneficial effect of potassium is discussed in terms of the facile activation of N2O via dissociative electron transfer (N2O +e− = N2 + O−) and promotion of the preferred fast suprafacial recombination of oxygen intermediates (revealed by the isotopic experiments). This work was sponsored by Polish National Science Centre decision number DEC-2011/03/B/ST5/01564. The research was partially carried out with the equipment purchased thanks to the financial support of the European Regional Development Fund in the framework of the Polish Innovation Economy Operational Program (contract no. POIG.02.01.00-12-023/08).

Ceramic open cell foams (OCF) are characterized by lower pressure drop, high geometric surface area, and enhanced radial convection in comparison with monolith-type supports. In this work, silicon carbide (SiC) and zirconia (Zir) OCF with different pore per inch (ppi) density were coated with 200 mg of Co3O4 by solution combustion synthesis and doped with 3 wt % of Pd via wetness impregnation. Their catalytic activity was tested toward the lean oxidation of methane at different weight hourly space velocities. Zir OCF with 30 ppi exhibits the best catalytic activity for all reacting conditions, followed by Zir 45 ppi, SiC 45 ppi, and SiC 30 ppi. The better performance of Zir OCF was rationalized considering their lower volumetric heat exchange coefficients, which favor the reaction heat removal by convection via the flue gases. A 200 h stability test on the best structured catalyst demonstrated full methane conversion at a temperature below 400 °C. These results confirm the fundamental role of thermal cond...

A series of Pd/Co 3 O 4 catalysts with increasing palladium loading in the range of 0.5–5 wt.% was prepared by incipient wetness impregnation of Co 3 O 4 . Solution combustion synthesis with urea as a fuel was used to optimize the Co 3 O 4 reactive support for palladium in the combustion of methane in lean conditions. The obtained catalysts were thoroughly examined by XRD, XPS, XRF, RS, FESEM, H 2 -TPR, TGA, and N 2 -BET techniques. The catalytic tests of CH 4 combustion were performed for 0.5, 1, and 2 vol.% CH 4 , with constant lambda value. The obtained results revealed that a sub-stoichiometric fuel-to-oxidizer ratio, 0.75, results in the most catalytically active Co 3 O 4 phase. The important differences in the catalysts’ activity were apparent for the highest CH 4 concentration, with the 3% Pd/Co 3 O 4 being the most active catalyst. The observed activity was explained considering the physicochemical, spectroscopic, and microscopic characterization of the catalysts with the PdO nanocrystals surface distribution being the determining factor for the catalysts’ reactivity. A simple model accounting for the observed dispersion effect is proposed. The model is based on a two types of the interaction of the surface PdO active phase with the Co 3 O 4 support. Firstly, cobalt oxide helps to remove hydroxyl species from the PdO surface, thus making the active sites more available for methane activation. Secondly, cobalt spinel provides lattice oxygen to the PdO phase, again helping to recreate active sites thereon.

In this work a series of mixed iron-cobalt spinel catalysts was synthesized by solution combustion synthesis and doped with 3 wt% of palladium via incipient wetness impregnation. The catalysts were synthesized with different Co:Fe ratios, characterized from the structural and surface point of view (XRD, XRF, μRS, BET, FESEM), and tested toward the oxidation of methane in lean conditions, in gas mixtures containing from 0.5 to 2 vol% of CH4. The temperature window for the catalytic activity of the undoped mixed iron–cobalt spinels spread from 350 to 650 °C. While lower iron substitution levels lead to a decrease in the spinel’s activity, the catalyst with 2/3 of the cobalt in the Co3O4 substituted with iron shows similar activity to the parent Co3O4. Although the materials were proved to be heterogeneous from the crystal phase point of view (a mixture of cobalt–iron spinels), the observed reactivity still depends on the amount of iron introduced during the synthesis. The addition of Pd lowered the temperature window for the catalytic activity to the range of 250–550 °C. The promoting effect of Pd is most evident for the pure Co3O4 catalyst. In contrast to the Pd-free catalysts, the best activity of Pd-promoted samples was observed for the catalysts with the highest iron content.

In this work, a series of Co3O4 spinels were produced by different synthesis routes (precipitation, solution combustion synthesis, and hard template method), and were used as non-noble catalysts for the oxygen evolution reaction (OER) under basic conditions. The investigated catalysts have a proportional relation between electrochemical activity, surface roughness, and specific surface area. The hard template synthesis method resulted in the most active catalyst compared in this work, which we ascribe to its highly porous structure, and concomitant Co3+/Co4+ redox couple at a lower potential, attributed to the OER. The most performant catalyst was compared with a commercial catalyst (Ni@NiO, Alfa Aesar) showing only 0.01 V overpotential difference, evaluated at 10 mA cm− 2 (overpotential 0.44 V).

Natural blue Co-bearing spinel crystals are rare and actively sought as gemstones, while synthetic blue Co-bearing spinel powders are largely used as ceramic pigments. High-quality spinel single crystals with compositions closely corresponding to the solid-solution series spinel sensu stricto (MgAl 2 O 4 )-cobalt spinel (CoAl 2 O 4 ) were produced by flux growth method, with Na 2 B 4 O 7 as flux. Low-cooling rates (2 °C/h) and linear temperature profiles were applied in the thermal interval 1200–800 °C, followed by rapid cooling. Thermal runs were performed in reducing atmosphere ( f O2 10 −8 –10 −15 bars) created by a continuous flow of a CO 2 :H 2 mix with a ratio of 100:4 (cm 3 /min). Ten experiments were successfully carried out and hundreds of inclusion-free gem-quality single crystals (up to 1 mm large) were produced in each of them, sometimes together with crusty aggregates and microcrystalline powder. Selected crystals were investigated by SEM/EDS X-ray mapping to check for compositional homogeneity and by electron-microprobe analysis to obtain the chemical formula. Crystals were found to be chemically homogeneous and entirely representing the MgAl 2 O 4 -CoAl 2 O 4 solid-solution series, with the latter component ranging from 7 to 100%. With increasing Co 2+ contents, the crystals vary in color from light blue to intensely dark blue in daylight. The unit-cell parameter a increases from 8.084 to 8.105 A along the solid-solution series, and the observed increase is determined more by the inversion degree than by the variation in Co contents. The composition of crystal products does not correspond to the composition of the starting oxide mixture, being cobalt enriched in the crystals. A tentative explanation of this behavior is suggested by considering possible ionic potential as well crystal field stabilization effects.

Structured reactors based on metallic carriers for catalysts of highly enhanced transport properties can be an interesting alternative to monolithic converters. In this study the carriers based on wire gauze have been shown to improve the efficiency of the VOC combustion simultaneously decreasing the converter length. A successful application of metallic microstructures needs proper methods of catalyst layering. This study focuses on non-equilibrium plasma (NEP) deposition technique which is referred to Langmuir–Blodgett (LB) film deposition and to wet impregnation. The cobalt oxide catalyst deposited on wire gauze and steel sheets were characterised by XPS and Raman microscopy and tested in n-hexane oxidation in tubular and gradientless (jet-stirred) reactors. The model cobalt catalysts showed sufficiently high activity in relation with Pt reference catalysts. The most important factor affecting the catalyst activity was the type of the carrier. The best performance was achieved for the catalysts deposited on wire gauzes.

Series of precursors was prepared by precipitation of cobalt nitrate in aqueous solutions using various precipitation agents (NH3·H2O, NaOH, Na2CO3) and reactions conditions (OH/Co molar ratio, aging time). Powder XRD showed different phase composition of the obtained precursors, in which β-Co(OH)2, CoII–CoIII layered double hydroxide, and basic cobalt carbonate were identified. Only Co3O4 spinel-like oxide was found in products after heating at 500 °C in air but different N2O conversions were observed over the examined oxide catalysts. Especially the catalysts obtained from β-Co(OH)2 precursors showed high catalytic activity in N2O decomposition. The correlation between methods of preparation, phase composition of precursors, catalytic properties of the related oxide catalysts, and the role of the cobalt ions as catalytic active sites is discussed.

Cobalt spinel catalysts promoted with different cesium loadings from various precursors (Cs2CO3, CsNO3, CH3COOCs, and CsOH) were prepared by incipient wetness impregnation. The catalysts were characterized by XRF, XRD, SEM, XPS and Raman Spectroscopy. The work function studies were used to optimized the surface doping and monitor the retention of surface oxygen. The stability of cesium promoter was evaluated by means of species resolved – thermal alkali desorption method. The catalytic activity of N2O decomposition over the synthesized catalysts was studied by temperature programmed reaction. The role of cesium precursor was evaluated in terms of dispersion and the nature of the counterion. The results show that the most active deN2O catalysts are obtained for cesium carbonate at the narrow loading range of 2–3 atoms/nm2 (complete N2O conversion at T < 200 °C). The twofold promotional effect is discussed in terms of modification of the electronic properties of the spinel catalyst (stimulation of dissociation step: N2O + e = N2 + O–) and stability of the surface oxygen species (recombination step: O– = ½O2 + e).

Blue spinel crystals in the MgAl2O4-CoAl2O4 series: II. Cation ordering over short range and long range scales

Ferrimagnetic nanoparticles of CoFe2O4 with dimensions of 4-16 nm were synthesized by pyrolysis of a mixture of acetylacetonates of iron and cobalt. In the temperature range 300-500 K investigated field dependence of magnetization up o 18 kOe. Found a significant contribution of "surface" anisotropy to the effective anisotropy of the nanoparticles. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35365

El electrodepósito es una técnica que permite la obtención de óxidos metálicos nanoestructurados de Co3O4 y RuO2 en intercapas sobre soportes de titanio. Estos composites soportados sobre titanio presentan propiedades electrocatalíticas superiores a las de materiales obtenidos por otras técnicas clásicas como sol-gel o impregnación seguida de descomposición térmica. La actividad electrocatalítica para la generación de oxígeno es determinada mediante voltametría cíclica y el aumento de la conductividad a potenciales más anódicos mediante espectroscopía de impedancia electroquímica (EIS). Las técnicas Raman, DRX, SEM y EDX son utilizadas para la caracterización estructural de los óxidos. The electrodeposit is a technique that allows the production of nanostructured metal oxides of RuO2 and Co3O4 in interlayers on titanium supports. That titanium supported composite electrodes have better electrocatalytic properties than materials obtained by other classic techniques such sol- gel or impregnation followed by thermal decomposition. The electrocatalytic activity for oxygen evolution is determined by cyclic voltammetry and the conductivity increased to more anodic potentials by electrochemical impedance spectroscopy (EIS). Raman, XRD, SEM and EDX techniques are used for structural characterization of the oxides.

La electrólisis es una alternativa eficiente para oxidar los compuestos responsables del color de los vertidos acuosos de la industria textil, como son los compuestos del tipo azo. El material del cual está fabricado el electrodo y el pH de la disolución han sido identificados como determinantes en la obtención de la máxima eficiencia en corriente. En este estudio se realizó la oxidación electroquímica del anaranjado de metilo: 4-(4’- dimetilaminofenilazo) bencensulfonato de sodio, utilizando electrodos de espinela de cobalto, dióxido de plomo y grafito, en solución de cloruro de sodio a diferentes valores de pH. The electrolysis is an efficient alternative to oxidize the compounds responsible for the color of the textile industry waste waters, like the azo compounds. The material of which is manufactured the electrode and the pH of the solution has been identified as decisive to reach the maximum current efficiency. In this study, the electrochemical oxidation of the methyl orange: sodium 4-(4’- dimethylaminophenylazo) benzensulfonate, was carried out using cobalt spinel, lead dioxide and graphite electrodes, in a sodium chloride solution at different pH values.

Mullite, 3Al2O3*2SiO2, is attractive ceramic material for advanced applications. Variety of mullite matrix composites have been recently studied. The aim of the work was to examine in situ formation of spinell-mullite composites by sol-gel synthesis of diphasic gels doped with 1, 2 and 3 at.%, Co2+ (introduced on account of aluminium). The gels were prepared by mixing Al and Co nitrate water solutions with tetraetoxysilane, dissolved in ethanol. The structural evolution with temperature has been studied by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and Rietveld structure refinement. The microstructure and morphology has been investigated by scanning electrion microscopy (SEM) and energy dispersive X-ray spectrometry (EDX). DSC analyses provide two exothermic effects, the first attributed to the spinel crystallization around 1000C, and second caused by the mullite crystallization at higher temperatures. Shift of peaks towards lower temperatures with the increase of Co2+ content has been observed. At lower taemperaturtes XRD patterns show no distinction between Co and Al-Si spinels, while sperate diffraction lines could be spotted at 1350C. SEM micrographs of samoples thermally treateed at these temperatures revealed the presence of particles with different morphology: fewer coarser particles embedded in nano-sized mullite matrix. Using EXD analises it was determined that cobalt is concentrated in coarser particles while matrix is composed of alumosilicate phase. At 1650C samples are composed of mullite, Co-spinel and traces of alpha-alumina. The differences in the mullite lattice parameters between samples could be the consequence of cobalt entering the mullite structure, on the other hand, they could be explained by variations in Al2O3 to SiO2 ratio. Rietveld analyses of the sample with 3% Co2+ indicated that the majority of Co2+ is in spinel phase. The kinetic analysis showed certain decrease in activation energy for mullite crystallization in comparison with non-doped sample.