Research of the mineral additives influence on aggregative stability of foam concrete mixture

An effective method for increasing the aggregate stability of non-autoclave heat-insulating foam concrete is proposed. This material is prepared using a two-stage technology on a turbulent-type installation. An increase in the stability of the foam in the mortar mixture by 9.5-23% has been established. An increase in the viscosity of the foam concrete mixture by 13.5% was revealed. Wollastonite and diopside are actively involved in the formation of a stable structure of foam concrete and are structurally modifying centers. The introduction of mineral additives contributes to the formation of a homogeneous stable structure of non-autoclave foam concrete. Thus, an increase in the stability of the cellular system in the technology of non-autoclave cement-ash foam concrete is possible due to the control of the processes of structure formation when using dispersed mineral additives of wollastonite and diopside. Due to the structural-modifying effect of additives as crystallization centers for neoplasms, a more complete hydration of the cement and a strong contact of the additives with the cement stone should be ensured

INFLUENCE OF SYNTHESIS CONDITIONS ON AGGREGATIVE STABILITY OF Ag ALCOSOLS

Впервые в работе представлены результаты исследования влияния типа спиртовой среды на свойства высококонцентрированных золей наночастиц серебра. С помощью спектрофотометрии установлено наличие селективной полосы поглощения, обусловленной поверхностным плазмонным резонансом наночастиц серебра. Измерение дзета-потенциала показало, что вне зависимости от типа среды поверхность наночастиц серебра заряжена отрицательно. Обнаружено, что наиболее агрегативно устойчивые частицы, сохраняющие стабильность в концентрированных растворах хлорида натрия, получены в среде изопропилового спирта и характеризуются дзета-потенциалом, равным -99,8 мВ. For the first time, the paper presents the results of investigation the effect of the type of alcoholic medium on the properties of highly concentrated sols of silver nanoparticles. Spectrophotometry revealed the presence of a selective absorption band corresponding to the surface plasmon resonance of silver nanoparticles. Measurement of the zetta potential showed that, regardless of the type of medium, the surface of silver nanoparticles is negatively charged. It was found that the most aggregatively stable particles that retain stability even in concentrated sodium chloride solutions were obtained in isopropyl alcohol and are characterized by the zetta potential equal to -99,8 mV. Keywords: silver nanoparticles, optical properties, electroacoustic spectroscopy, zeta potential, nanoparticle stability.

MOBILE MAGNETOMETER FOR RAPID TEST OF SATURATION MAGNETIZATION OF MAGNETIC NANOFLUIDS

Работа направлена на создание магнитометрического прибора для точного определения намагниченности насыщения магнитных наножидкостей и подобных по свойствам функциональных дисперсных материалов. В основе прибора лежит магнитометрический метод с холловскими преобразователями индукции, усовершенствованный с учетом особенностей физико-механических свойств жидкостей. Измерительная магнитная система прибора построена таким образом, чтобы с помощью постоянных магнитов можно было создавать однородное намагничивающее поле величиной до (2 ÷ 4)⋅10 А/м в рабочем зазоре, где установлена кювета с изучаемой магнитной наножидкостью. Под кюветой с магнитной наножидкостью в среднем ее сечении располагается преобразователь Холла, который служит для измерения напряженности намагничивающего магнитного поля. Второй преобразователь Холла, предназначенный для измерения индукции магнитного поля в веществе, установлен в канавке прямоугольного сечения и располагается по центру магнитной наножидкости в кювете. Относительная ошибка измерения намагниченности на приборе не превышала 2 % для магнитных наножидкостей с намагниченностью в диапазоне от 10 кА/м до 50 кА/м. Созданный прибор может использоваться для экспресс - измерений в лабораторных и промышленных условиях и не требует специальных профессиональных навыков. Показано, что аддитивная составляющая инструментальной погрешности измерений зависит от значений остаточного напряжения (ЭДС неэквипотенциальности), побочных гальваномагнитных эффектов и термо-ЭДС измерительного преобразователя. Мультипликативная составляющая связана с временной и температурной нестабильностью коэффициента преобразования и тока или напряжения питания. Методическая погрешность магнитометра вызвана тем, что для измерений индукции магнитного поля используется не полностью замкнутая магнитная цепь. Показано, что по своим метрологическим параметрам прибор отвечает международным стандартам на магнитные измерения магнитомягких материалов. Прибор позволил определить намагниченность коллоидных систем в магнитных полях начала парапроцессов, индивидуальную намагниченность наночастиц дисперсной фазы, агрегативную устойчивость коллоидов в магнитных и гравитационных полях, оценить размеры сольватной оболочки наночастиц. The work is aimed at creating a magnetometric device for accurate determining the saturation magnetization of magnetic nanofluids and similar properties of functional dispersed materials. The device is based on a magnetometric method with the Hall induction transducers, improved taking into account the peculiarities of the physical and mechanical properties of liquids. The measuring magnetic system of the device is designed in such a way that with the help of permanent magnets it is possible to create a uniform magnetizing field up to (2÷4)⋅10 A/m in a working gap where the cuvette with the studied magnetic nanofluid is installed. Under the cuvette with a magnetic nanofluid in its middle section is a Hall Converter, which serves to measure the strength of the magnetizing magnetic field. The second Hall Converter, designed to measure the magnetic field induction in a substance, is installed in a rectangular groove and is located in the center of the magnetic nanofluid in the cuvette. The relative error of measuring the magnetization on the device did not exceed 2% for magnetic nanofluids with a magnetization in the range from 10 kA/m to 50 kA/m. The created device can be used for Express measurements in laboratory and industrial conditions and does not require special professional skills. It is shown that the additive component of the instrumental measurement error depends on the values of the residual voltage (nonequipotential EMF), side galvanomagnetic effects and thermo - EMF of the measuring Converter. The multiplicative component is related to the time and temperature instability of the conversion coefficient and the current or voltage supply. The methodic error of the magnetometer is caused by the fact that not a fully closed magnetic circuit is used for measuring the magnetic field induction. It is shown that the device meets international standards for magnetic measurements of soft magnetic materials in terms of their metrological parameters. The device allowed us to determine the magnetization of colloidal systems in magnetic fields of a start paraprocess, individual magnetization of nanoparticles of the dispersed phase, the aggregative stability of colloids in magnetic and gravity fields to estimate the size of the solvation shell of the nanoparticles.

Colloidal Characteristics of Molybdenum Blue Nanoparticles Dispersion for Catalytic Applications

The nanosized clusters of molybdenum blues and their monodispersity make them possible to consider as promising precursors for molybdenum carbide preparation. For the synthesis of supported catalysts using sols (dispersions of nanoparticles), it is necessary to know their main colloidal-chemical properties (electro-surface characteristics, rheological properties and the conditions of aggregative stability). This paper presents the results of a study of the colloidal-chemical properties of molybdenum blue, the dispersed phase of which is represented by toroidal particles of the Mo154-x family. It was found that aggregate stable sols exist in the range of 0.8 ˂ pH ˂ 2.0. In this range, molybdenum blue particles are negatively charged, and the electrokinetic potential does not exceed 30 mV. Molybdenum blues have high aggregate stability and can be concentrated to a high concentration of the dispersed phase (20–30 wt%); at a concentration more than 30 wt.%, a transition of the sol into a gel is observed. In a wide range of concentrations, molybdenum blues are Newtonian liquids, and the viscosity mainly depends on the concentration of the dispersed phase. The results obtained can be used as a basis for the development of a sol–gel method of supported catalysts based on molybdenum blue.

Theoretical Substantiation of the Foam Concrete Strength Formation Laws

A detailed theoretical analysis of the processes occurring in foam concrete mixtures in the period between their laying in the mold and the phase transition “from viscous to solid” completion moment. The stages of the formation of inter-pore septa in foam concrete mixtures, depending on the material nature and shape of the solid dispersed particles of raw materials, are sequentially considered. It is shown that their shape affects the mass transfer rate and the density of inter-pore septa during the structure formation. The reasons for the fluctuations in the elasticity of foam films during the predominance period of viscous bonds between the components of the raw material are described. The gas inclusions factors of influence on the dispersion parameters and, as a consequence, the aggregative stability of foam mixtures, are ranked. The positive dispersed reinforcement effect on the mass transfer processes in mixtures and the hardened concrete strength is substantiated.

ISOLATION OF EMULSION RUBBER FROM LATEX USING HYDROXYLAMINE SALTS

Currently, there is a growth of industry in various sectors, including chemical and petrochemical in Russia and abroad. However, this rise in industry is inextricably linked to the emergence of environmental problems. Therefore, when developing new technologies, production facilities and improving existing ones, special attention is paid to their environmental aspect. These industries include the production of synthetic rubbers. The production of synthetic rubber is a multi-stage technology; at some stages certain problems are observed. For example, the coagulation stage is characterized by increased contamination of wastewater with residues of coagulating, acidifying agents and components of the emulsion system. Therefore, research in the direction of improving the environmental friendliness of this stage is important and relevant. Research on the search for new promising coagulants has been carried out. A comparative assessment of the coagulating ability of ammonium salts based on hydroxylamine hydrochloric acid and sulfuric acid in comparison with ammonium chloride and sulfate and sodium chloride is carried out. The effectiveness of the coagulating action of these inorganic ammonium salts is studied on industrial rubber latex SKS-30 ark. It is found that the yield of rubber crumbs naturally increased with a growth in the consumption of the coagulating agent and a decrease in the temperature regime of the process. Positive results are achieved when nitrogen-containing salts are used to reduce the aggregative stability of disperse systems. Сaoutchouc and rubbers in their basic indicators meet the requirements.

Hybrid system «layered magnesium silicate – chlorin е6 13(1),15(2),17(3)-N,N',N''-(2-hydroxyethyl)triamide»

Matrices based on layered silicates have a set of useful properties, in particular, they are able to increase the stability and photosensitizing ability of porphyrins. Hybrid systems “layered silicate - porphyrin (metal porphyrin)” are promising as active components of systems for light collecting and artificial photosynthesis, catalysts, photocatalysts. The hybrid systems with content of 1.4∙10-6 and 4.2∙10-6 mol of the chlorin e6 13(1),15(2),17(3)-N,N',N''-(2-hydroxyethyl)triamide per 1 g of layered magnesium silicate was obtained by heat treatment method of a synthetic layered magnesium silicate of hectorite composition when treated with an aqueous-alcoholic solution of organic component. The molar ratio of the starting components is: Mg(OH)2 : SiO2 : LiF = 1 : 1.51 : 0.25 : chlorin e6 derivative = 1 : 1.51 : 0.25 : (19.93∙10-5 – 59.58∙10-5). Using dynamic light scattering and laser Doppler electrophoresis, it was shown that the introduction of chlorin e6 13(1),15(2),17 (3)-N,N',N''- (2-hydroxyethyl) triamide leads to the growth of hybrid particles (162 ± 3 nm) and a decrease in their aggregative stability (-30 ± 1 mV), compared with the initial layered magnesium silicate (133 ± 1 nm, -33 ± 1 mV). In this case, the introduction of more hydrophilic chlorin e6 13(1),15(2),17(3)-N,N',N''-(2-hydroxyethyl)triamidе, in the molecule of which there are three fragments of ethanolamine, allows to obtain smaller hybrid particles (162 ± 3 nm), compared with hybrid particles (248 ± 6 nm) formed by the action of chlorin e6 13(1),17(3)-N,N'-(2-hydroxyethyl)diamide15(2)-methyl ether, in the molecule of which there are two fragments of ethanolamine. Using the methods of X-ray phase analysis and electron spectroscopy in the UV-visible region, it was found that individual molecules of chlorin e6 13(1),15(2),17(3)-N,N',N''-(2-hydroxyethyl)triamide were sorbed on the surface of silicate particles due to the electrostatic interaction between the protonated molecules of the macrocycle and the ionized hydroxyl groups of magnesium silicate. It was shown that the higher hydrophilicity of chlorin e6 13(1),15(2),17(3)-N,N',N''-(2-hydroxyethyl)triamide, compared with chlorin e6 13(1),17(3)-N,N'-(2-hydroxyethyl)diamide15(2)-methyl ether did not contribute to the intercalation of the organic component into the interlayer space of layered magnesium silicate under the conditions of a water-alcohol medium.