Morphology, phase and chemical composition of the nanostructures formed in the systems containing lanthanum, cerium, and silver

X-ray phase and thermogravimetric analysis, scanning electron microscopy and energy-dispersion spectroscopy were used to study the products of phase formation during the precipitation of lanthanum and cerium salts in the presence of silver nitrate and recipients of precipitators, nucleating agents and hydrolysis regulators. Thermogravimetric analysis shows the completion of the La(OH)3 lattice dehydroxylation process at a temperature of ~ 300 °С and probable destruction of sulfates at a temperature of ~ 340 °С. The phase interaction of lanthanum oxide(III) with silver ends at T ~ 400 °C. The DTG curve shows a two-stage weight loss, which characterizes the destruction of lanthanum and silver hydroxides (250 °C) and the removal of sulfates (~ 340 °C), respectively. According to the TG, the total weight loss is 21.6 %. For the cerium-containing system the only endothermic effect of dehydroxylation of cerium hydroxide at T = 250 °C with its conversion into cerium dioxide is observed. The destruction of nitrates (anionic component of solutions) takes place at the temperature of 400 °C. Weight loss takes place at T = 150 °C and is 53.9 %. Thus, on the basis of TG-DTA data, it can be assumed that the formation of composites particles based on lanthanum and cerium oxides, modified with silver, ends at the temperature of 400 °C. The X-ray diffraction data shows that at the initial stage the system undergoes the formation of cerium and lanthanum hydroxides, and during lyophilization of the precipitate (T = 160 °C) the crystal lattice of hydroxides partial dehydroxylation takes place with the formation of trigonal oxides La2O3 and Ce2O3. It has been found that the presence of silver cations in the solution can affect the phase composition of lyophilized structures and the formation of the CeO2 phase. It is shown that the hydroxylamine chloride injection into the system can initiate the silver restoration on the lanthanum oxide surface and also partially restore it to the LaO phase. Temperature treatment of the samples (T = 400 °С) promotes homogenization of the precipitate composition: formation of 30 nm cerium dioxide particles with silver clusters evenly distributed on its surface, and hexagonal lanthanum oxide plates with individual silver particles as the second phase. In three-component systems, two modifications of lanthanum oxides (trigonal and cubic), cerium dioxide and metallic silver are formed. It is found that the chemical composition of the precipitates contains the main elements – La, Ce, O, Ag and impurity – S or Cl, as the anionic component of the initial solutions, N and K in the composition of the initial suspension. It is shown that the morphology of the samples is represented by hexagonal structures of lanthanum hydroxide and oxide, spherical and pseudocubic particles of cerium dioxide and lanthanum oxide, spherical clusters of silver.

Influence of the Composition of Solid Fuel on the Equilibrium Characteristics of a Gasification Process in the Mixtures of Oxygen and Carbon Dioxide

The gasification of solid fuels of different elemental compositions in O2/N2 and O2/CO2 mixtures was studied using equilibrium thermodynamic modeling. The dependences of process characteristics (temperature and the yield of carbon residue) on the composition of gasification agent and the stoichiometric ratio were calculated. The addition of carbon dioxide, on the one hand, promoted the conversion of carbon due to an increase in the concentration of gasifying agents and, on the other hand, decreased the process temperature due to an increase in heat capacity and an endothermic effect of the gasification reaction. The efficiency of using O2/CO2 mixtures for the gasification of fuels increased with the carbon content. The highest chemical efficiency of coke and coal gasification was achieved at an initial CO2 concentration of about 40–60 vol %.

Synthesis of bulk crystals and thin films of the ferromagnetic MnSb

High-temperature ferromagnets are widely used on a practical level. Based on them, magnetic memory for computers and various types of magnetic field sensors are created. Therefore, bulk ingots and thin-film samples of ferromagnet manganese antimonide (MnSb) with a high Curie point are of great interest, both from the practical and fundamental sides. Manganese antimonide films are obtained in hybrid structures using molecular-beam epitaxy. The thickness of the films does not exceed tens of nanometers. Despite their high sensitivity to magnetic fields, their small thickness prevents them from being used as magnetic field sensors. The aim of this work was to synthesise thick bulk ingots of manganese antimonide crystalsand films with a thickness of ~ 400 nm on sitall and silicon substrates. MnSb crystals were synthesised using the vacuum-ampoule method and identified using XRD, DTA, and microstructural analysis. The results of studies of bulk samples indicated the presence of an insignificant amount of antimony in additionto the MnSb phase. According to the DTA thermogram of the MnSb alloy, a small endothermic effect was observed at 572 °C, which corresponds to the melting of the eutectic on the part of antimony in the Mn-Sb system. Such composition, according to previous studies, guaranteed the production of manganese antimonide with the maximum Curie temperature. A study of the magnetic properties showed that the synthesised MnSb crystals were a soft ferromagnet with the Curie point ~ 587 K. Thin MnSb films were obtained by an original method using separate sequential deposition in a high vacuum of the Mnand Sb metals with their subsequent annealing. To optimise the process of obtaining films with stoichiometric composition, the dependences of the thickness of metal films on the parameters of the deposition process were calculated. The temperature range of annealing at which the metals interact with the formation of ferromagnetic MnSb films was established, the films were identified, and their electrical and magnetic properties were measured

Effect of CO2 injection into blast furnace tuyeres on the pulverized coal combustion

CO2 injection into blast furnace tuyeres is a new technology to utilize CO2, aiming at expanding the way of CO2 self-absorption in the metallurgical industry. The decisive factor of whether CO2 can be mixed into a blast-furnace hot blast and the proper mixing ratio is the effect of CO2 injection on pulverized coal burnout. To investigate the effect of CO2 injection into tuyeres on pulverized coal burnout, a three-dimensional mathematical model of pulverized coal flow and combustion in the lower part of the pulverized coal injection lance-blowpipe-tuyere-raceway was established, and the effect of CO2 injection into tuyeres on pulverized coal combustion rate and outlet temperature is analyzed. The numerical simulation results show that the delay of pulverized coal combustion in the early stage is caused by the endothermic effect of the reaction of CO2 with carbon, and the burnout of pulverized coal is increased in the later stage due to the oxidation of CO2.

Chemical composition of the renewed fire extinguishing powder and its physical characteristics

Water, foam, dry powder, carbon dioxide and liquid chemicals are used as fire extinguishers depending on the fire types. The fire classification of ABC type includes fires caused by paper, wood, dye, fuel, oil, lubricants and flammable gases. In this work, the investigation of the procedure for re-determining the composition of prepared fire extinguishers was carried out depending on the ratio of organic and inorganic substances, and their fire extinguishing activity was tested. The Sample-1 contains about 50% of ammonium dihydrophosphate (NH4H2PO4) which is taking into account the main component and the sum of ammonium sulphate (NH4)2SO4 and other inorganic and organic components by 50%. As a result of fire extinction tests, its fire extinguishing activity was higher than that of other Samples included different ratios of substances. Based on the thermogravimetric analysis of the Sample -1, the polymerization and water release process of NH4H2PO4 was detected as endothermic effect. The weight loss was occurred by 74% and 26% remained as P2O5 when temperature reached to highest degree. Some physical parameters such as moisture content, water repellence, density and particle size were analyzed according to ISO standard method and all these important parameters showed that it can meet the requirements for fire extinguishing powder standards. Гал унтраагч шинэчилсэн бэлдмэлийн найрлага, түүний физик шинж чанарын судалгаа Хураангуй: Ус, хөөс, хуурай нунтаг, нүүрс хүчлийн хий ба химийн шингэн бодис зэргийг галын төрлөөс хамааруулан гал унтраагчаар ашигладаг. Галын ABC ангилалд цаас, мод, будаг, шатахуун, тос, тосолгооны материал, шатамхай хий зэргээс үүдэлтэй гал хамаарна. Энэхүү ажлаар импортын гал унтраагч бодисын найрлагыг шинэчлэн тогтоох судалгааг органик ба органик бус химийн бодисуудын харьцаанаас хамааруулан явуулж, тэдгээрийн гал унтраах идэвхийг ABC ангиллын галд туршив. Үндсэн бүрдэл болох аммонийн дигидрофосфат (NH4H2PO4)-ыг 50%, (NH4)2SO4 ба бусад бүрэлдэхүүн бодисуудын нийлбэрийг мөн 50%-иар тооцоолон авсан. Бэлдмэл 1-ийн гал унтраах идэвх нь бусад бэлдмэлүүдийн идэвхээс өндөр байв. Бэлдмэлийн термографийн судалгаагаар NH4H2PO4-ын их хэмжээний дулаан шингээн полимержих, ус ялгаруулах процесс DTA-ийн муруйд эндо эффект хэлбэрээр илэрсэн ба температурын дээд утгад жингийн алдагдал 74%-д хүрч, 26% нь P2O5 хэлбэрээр үлдсэн. Гал унтраагч нунтгийн физик шинж чанарын гол үзүүлэлтүүд болох чийг, хувийн жин, ус үл нэвтрүүлэх чадвар, ширхэглэлийн хэмжээг тодорхойлсон ба эдгээр үзүүлэлтүүд нь стандартын шаардлагуудыг хангасан байна. Түлхүүр үг: Гал унтраагч нунтаг, идэвх, аммонийн дигидрофосфат, DTA/TG, физик үзүүлэлт

Improvement of Fire Resistance of Polymeric Materials at their Filling with Aluminosilicates

Effect of content of synthetic aluminosilicates in medium-density polyethylene on the fire hazard characteristics and mechanical properties of compositions is investigated. It has been shown that during decomposition of the filler with the release of water, its effectiveness depends not only on the endothermic effect of decomposition and the content of dehydration products, but also on the correspondence of temperature of the dehydration of the filler and the temperature of intensive decomposition of the polymer. Regardless of the type of fillers, an increase in their content in polymer composite material helps to reduce combustibility. It has been shown that compositions based on epoxy oligomers or medium-density polyethylene and synthetic zeolite have properties of self-extinguish and fairly high physical and mechanical characteristics. It is shown that epoxy polymer composite material with the content of inorganic fillers 40-70 wt.% can be used for sealing building structures and other products operating at elevated temperatures, as well as in a mode where the fire resistance and heat resistance of the sealing compound are decisive. A number of efficiency of flame-suppressing of fillers is presented. Formulations of compositions based on epoxy oligomers or medium-density polyethylene whith synthetic zeolite having an optimal ratio of fire hazard and mechanical properties and not having toxic or carcinogenic effects when heated are recommended.

The mathematical description of process of heat exchange particles of oil shale and ash the coolant in the semi-coking conditions in a rotating drum reactor installation with solid heat carrier

The article deals with the modeling of heat transfer process in a drum reactor of a semi-coking unit of oil shale with a solid coolant between ash and shale particles in the conditions of constant separation of vapor-gas products. The dominant role of the convective component of the process is revealed and the curves of heating of shale particles are obtained taking into account the endothermic effect. It is established that the smallest fraction of fuel warms up within 30-60 seconds and further serves as a source of heat for other fractions. In the interval of 400-600 seconds, the heating of the largest fraction is completed. The further stay of the shale mixture in the reactor is caused by the lagging rate of the thermal decomposition process from heat exchange, and the temperature decrease by 20-250C by the presence of the endothermic effect of the decomposition of organic matter.

Effects of Moisture Content on the Minimum Explosible Concentration of Aluminum Powder and the Related Mechanism

Aluminum powder has been widely applied to various industries. However, its high activity and high burn rate can cause serious explosion risks. Many factors affecting the explosion of aluminum powder have been determined, yet moisture content has not been included. In the present work, the minimum explosible concentrations of aluminum powders with different moisture contents were measured with a 20-liter explosion test apparatus using the explosion accident in Kunshan, China, as a study case. The experimental results suggest that the minimum explosible concentration of aluminum powder dramatically increases with the increase of its moisture content first and the increasing trend becomes slower as the moisture content further increased. The oxidation time has no significant effects on the minimum explosible concentration of aluminum power in 8 hours at room temperature. Further investigation suggests that the moisture lowers the explosion risk of aluminum powder by altering its surface oxide film, ignition, and combustion process. The low contents of moisture in the range of 0%-8% increase the minimum explosible concentration of aluminum powder by inhibiting the reaction kinetics and particle agglomeration, while high contents of moistures in the range of 8%-20% affect the minimum explosible concentration by the endothermic effect and oxygen dilution effect.

Разнолигандные комплексные соединения европия (III) с o-метоксибензойной кислотой и фосфорсодержащими нейтральными лигандами

The luminescent coordination multi-ligand compounds of europium (III) with o-methoxybenzoic acid and island-containing phosphorus-containing neutral ligands of the composition Eu (MOBA) 3 • 3Н2О and Eu (MOBA) 3 • L, where MOBA is o-methoxybenzoic acid, D is hmpa (D hexamethylphosphoric triamide), tppo (triphenylphosphine oxide), Et6pa (hexaethylphosphotriamide). The composition, structure, and thermal properties of complex multi-ligand compounds of europium (III) were studied. It was shown that during thermolysis, detachment of a neutral ligand molecule occurs in one stage with an endothermic effect, complex compounds are stable up to 280 С.Based on the data of IR spectroscopy, it was found that in the europium (III) o-methoxybenzoates, the o-methoxybenzoic acid is coordinated to the europium (III) o-methoxybenzoic ion in a bidentate manner. The low luminescence intensity of multi-ligand europium (III) compounds is explained by the inefficient transfer of electronic excitation energy from o-methoxybenzoic acid and phosphorus-containing neutral ligands to the europium ion.

Potentiometric Sensor For Analgin Determination In Pharmaceutical Formulations

Ion associates (IA) of butylrodamine C with triiodide and iod bromide have been synthesized. Their thermal behavior is investigated. Thermolysis synthesized by IA BR+I3¯ passes through a number of intermediate stages, since the C4H9 radical, which is part of the dye, has a significant effect on the process of thermolysis of the ionic associate. IA BR+I3¯ begins to decompose significantly at a temperature higher than 140 єC with an endothermic effect at 240 єC and two small exothermic effects with a maximum at 282 єC and 355 єC (corresponding to the release of 2NH3, 8C2H4, 2HI). In the range of 380–720 єC, the exothermic effect of the IA combustion occurs at a temperature of 485 єC with significant mass loss. The obtained IAs are stable under normal conditions. An I3¯ and I2Br¯ sensor containing butyrodromine C associate of butylrodamine C with triiodide and iodum bromide was developed. The working interval of the pH of the triiodide sensor is 2 - 12, and for iodum bromide, the pH is 2 - 10, respectively. The linearity interval of the electrode function is in the range 9 ∙10-6 - 1 ∙10-1 mol L-1, the slope is 65 mV/pC for the triiodide, and for the iodine bromide - 1 ∙10-5 - 1 ∙10-1 mol L-1, the slope 68 mV/pC. The technique of potentiometric determination of analgin in medicines is developed.