AbstractCeO2 has been shown as a prominent oxygen carrier for two-step solar thermochemical (STC) CO production owing to its thermal stability and rapid reaction kinetics. However, the current two-step CeO2-based STC system suffers from a large temperature swing, leading to large heat loss as well as inconsecutive operation. To better the above metrics, the isothermal continuous STC CO production based on CeO2 is researched within our tubular reactor. The produced CO concentration is found to increase gradually at the first hour and then remain about 550 ppm for more than 8 h. The obtained amount of CO is about 14.4 mL g–1h –1, much larger than those reported before. The effects of temperature, flow rate and partial pressure on CO2 conversion ratio (χCO2) and solar-to-fuel energy efficiency (ηsolar-to-fuel) are also studied, underscoring the advantage of continuous operation and importance of avoiding excessive CO2 input. In addition, with the correction of experiment temperature, our calculated ηsolar-to-fuel is about 1.85%, an evident improvement compared to previous isothermal systems. Moreover, the non-integer CO2-splitting kinetic characteristics as well as its explicit equation are revealed, providing significant references for CO production regulation and solar reactor design.

AbstractThe products of mechanically stimulated interaction of NiO with Al were studied by X-ray diffraction and IR spectroscopy. Composites Ni/α-Al2O3, NiAl/α-Al2O3, Ni2Al3/α-Al2O3 can be fabricated by varying the ratio of initial components under the selected conditions of mechanical activation. The approach under consideration, based on a mechanically stimulated reaction, makes it possible to significantly simplify the previously proposed method of mechanically activated self-propagating high-temperature synthesis and produce nanostructured composites.

AbstractThe joint effect exerted on the hydrophobic properties of two-component polyurethane coatings by SiO2–NH2 particles prepared from tetraethoxysilane and 3-aminopropyltriethoxysilane using the sol–gel procedure and by an organosilicon block copolymer was studied. The structure and size distribution of particles were determined by Fourier IR spectroscopy, differential thermal analysis, and laser light scattering. Introduction of SiO2–NH2 particles leads to an increase in the roughness and change in topography of the polyurethane coating surface, which was proved by atomic force microscopy and scanning electron microscopy. Variation of the content of the organosilicon block copolymer influences the SiO2–NH2 particle-size distribution in the composite, the surface topography, and wetting of the coatings and allows preparation of highly hydrophobic polyurethane coatings with the contact angle and hysteresis of 166.2° and 11.9°, respectively.

AbstractThe interaction of indicator vanadium-containing silica gel IVS-1 with a wet air stream containing ammonia was examined. Based on the two-stage change in the color of the sorbent and the disappearance of hysteresis on the atomic force spectroscopy curves, it is assumed that displacement adsorption of ammonia occurs on the sorbent surface.

AbstractUsing transmission electron microscopy (TEM) and electron microdiffraction with the radiolysis effect and a series of calibration images of TEM obtained for single-phase MgH2 samples at different exposure times, we studied the topological features of the microstructure of powder hydrogen-sorbing composites based on the Mg89Ni11 eutectic alloy. It was found that after several hydrogenation–dehydrogenation cycles the composite retains a highly dispersed microstructure: in the regions of composite samples with a cross-sectional area of 1 μm2 there are grains of Mg and Mg2Ni hydride-forming phases that are in direct contact, which improves the hydrogen-sorbing characteristics of the composite.

AbstractCyanuric acid is an organic intermediate widely used in organic synthesis, and the traditional production method of cyanuric acid is the pyrolysis urea method. Due to the shortcomings of uneven mass transfer, many by-products and poor environmental friendliness, the production of cyanuric acid is extremely limited. In this paper, an effective method has been developed to synthesize cyanuric acid with high yield in a short period of time through the addition-elimination reaction of dihydric alcohol and urea under alkaline conditions. The reaction time, molar ratio of reactants, reaction temperature and other influencing factors were studied. Under optimized conditions, the yield of cyanuric acid is over 90%. And further the proposed reaction mechanism is verified. The synthetic method provided in this article has the advantages of easy availability of raw materials and reusability, simple operation and short reaction time, which makes the method novel and environmentally friendly.

AbstractIn the present study, undiluted TBP was employed to separate arsenic from a typical leach liquor of a copper industry bearing 9.08 g/L As, 46.69 g/L Cu, 23.44 g/L Ni, 1.23 g/L Fe, 0.49 g/L Zn and 0.09 g/L Co by solvent extraction technique. The effect of different parameters such as extractant concentration, H2SO4 and HCl concentration and temperature on extraction of arsenic was examined. With increasing the concentration of sulfuric and hydrochloric acid in the leach liquor, the percentage extraction of arsenic was increased. However, with increasing the temperature, the percentage extraction decreased. The McCabe–Thiele plot indicated 4 counter current stages at A : O ratio of 1 : 4 for the quantitative extraction of arsenic. The loaded organic contained 2.26 g/L As and was stripped with water. The McCabe–Thiele plot for stripping showed 2 counter-current stages at A : O = 1 : 2 and the stripping efficacy was 99.3%. The thermodynamic parameters such as ∆H°, ∆G°, and ∆S° were calculated for arsenic extraction. The enthalpy change (∆H°) value was negative indicating the extraction processes was exothermic.

AbstractThe development of noncatalytic procedures for processing hydrocarbon gases is an important way to increase the efficiency of gas-chemical processes and decrease their power consumption. The paper deals with thermodynamic and kinetic modeling of noncatalytic processes of the partial oxidation and steam and carbon dioxide conversion of methane in the temperature interval 1400–1800 K and with analysis of the process for syngas production by matrix conversion of rich methane–oxygen mixtures. Comparison of the kinetic calculations with the experimental data demonstrated the possibility of applying published models to the description of the matrix conversion of methane. The possibility of developing a highly efficient technology based on noncatalytic partial oxidation of hydrocarbons for the syngas production without СО2 emission into the environment is discussed.

AbstractIn this work, we firstly used the most common, easily available and inexpensive β-cyclodextrin (β-CD) to construct a sensitive electrochemical sensor, with the hybrid components of polyaniline (PANI) and phosphomolybdic acid (PMo12), used for the detection of ascorbic acid (AA). First, β-CD was electropolymerized on indium tin oxide (ITO) to form the modified electrode β-CD/ITO, and then PANI and PMo12 were co-polymerized on the film of β-CD to fabricate a novel electrode PMo12-PANI/β-CD/ITO. The experimental parameters for the construction of the modified electrode were studied and the optimized conditions were gained. Compared to the electrode ITO, β-CD/ITO, PANI/ITO, PMo12-PANI/ITO, the developed electrode PMo12-PANI/β-CD/ITO shows high sensitivity for the electrochemical detection of AA, giving a low detection limit of 15 nM and wide linear concentration range from 0.01 to 3000 μM. Further, the developed electrode was used to detect AA in real samples showing excellent accuracy and reproducibility, confirming good practicability, convenience and cost-effective.

AbstractA comparative evaluation of the results of an experimental study and thermodynamic analysis of the chemical equilibrium in a heterophase heterogeneous catalytic reaction of cyclohexanone hydrogenation is reported. It is shown that when calculating the thermodynamic equilibrium constant of heterophase hydrogenation reactions in gas–liquid systems it is necessary to take into account the change in the enthalpy and entropy of the initial chemical system caused by hydrogen absorption. The value of the enthalpy of hydrogen absorption not only reflects the endothermic physical process of gas dissolution, but also characterizes the state of the reagents in the exothermic chemical reaction of hydrogenation. Therefore, the thermal simulation of the apparatus, in which gas absorption and chemical reaction with its participation occur simultaneously, should be performed without taking into account the heat of gas dissolution.

AbstractNanoparticles have been utilized in a variety of biomedical applications owing to their ability to achieve systemic stability and targeted drug delivery. In the present work, a new form of nanoparticle-embedded polymeric microbeads has been developed for controlled drug delivery applications. Copper nanoparticles are synthesized using copper sulfate pentahydrate via chemical reduction method. Using gelation technique microbeads are synthesized by combining copper nanoparticles with sodium alginate/badam gum polymeric matrix. The generated microbeads were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transition electron microscopy (TEM), selected area electron diffraction (SAED), and scanning electron microscopy (SEM). Ofloxacin used as model bioactive agent and studied the release and swelling studies at pH 2.0 and 7.4 at 37°C. Upon loading OFLX in to microbeads antibacterial activity were tested against S. mutans, K. pneumonia, and B. subtilis. The release kinetics and mechanism was analyzed by fitting the release data into different kinetic models and Korsmeyer–Peppas equation.

AbstractA composite explosive including HMX and NTO is prepared by precipitation procedure in acetone solvent. 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) is a powerful explosive but sensitive to external stimuli. While, nitro-1,2,4-triazol-5-one (NTO) is a relatively strong explosive with lower sensitivity in comparison to HMX. The prepared composite explosive of HMX/NTO is characterized using XRD patterns and FT-IR spectra which show a minor change in the molecular structure of precursors. Thermal stability of HMX/NTO composite is investigated by study of DSC curves at various heating rates. Activation energy (Ea) of thermal decomposition reaction of HMX, NTO and HMX/NTO are obtained, 414.7, 402.6 and 435.2 kJ mol–1, respectively, by iso-conversional method of KAS which indicates more stability of HMX/NTO composite against thermal decomposition. Also, the Avrami–Erofeev equations of A3/2, A3/2, and A3 describe the thermal degradation mechanism of HMX/NTO composite, raw HMX and raw NTO, respectively. The sensitivity to impact, friction and electrostatic discharge of HMX, NTO and HMX/NTO are studied in accordance to the standards of STANAG no. 4489, STANAG no. 4487, and STANAG no. 4490, respectively, using methods of Bundesamt für Materialforschung (BAM). The results of external stimuli are also showed the less sensitivity of HMX/NTO composite in comparison to HMX and, thus, it is a candidate for insensitive munitions (IM).

AbstractThe most commonly used fast-burning composites of various compositions are reviewed. The review is based on fast-burning systems, which mainly include the compositions for retardant and special pyrautomatic devices and initiation lines, as well as nanothermites. The problem of developing gas-free (low-gas) fast-burning pyrotechnic compositions on a nanothermite basis is considered.

AbstractThe processing of ash/slag wastes were studied, while a complete analysis of the bottom ash of the Luchegorsk thermal power plant in the Primorsky Territory was carried out, and a study was performed on the separation of rare earth elements by various methods. The ash was previously cleaned from unburned coal (underburnt) and iron oxides, the resulting product was processed with various methods. Isolation and separation of products was carried out in several stages. The acidity of the medium was determined, which corresponds to the quantitative precipitation of iron and aluminum matrix ions depending on the initial concentrations of the solutions. Silicon oxide of 97% purity with a high specific surface area was obtained, as well as a solid product with a content of rare earth elements more than 100 times higher than in the original ash samples. The content of rare earth elements in the final product is 74.5% of the content of these elements in the original material, and the product is also enriched with other trace elements such as zirconium, hafnium, and tungsten. When the ash is processed, solid waste remains, which can be further utilized to fabricate ceramic materials and membranes with high technical performance.

AbstractAromatic amino acid or primary aliphatic acid available on prunus armeniaca seed coat (PASC) powder is modified (MPASC) using thioglycolic acid and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) in the form of N-substituted 2-sulfanylacetamide derivative. Infrared (FTIR), scanning electron microscopy, EDX, and XRD techniques are used for characterization of PASC and MPASC. Synthesized material is identified by the change in peak position and deformation of N–H bending vibration of primary amines peak. Peak at 1601 cm−1 due to N–H bending vibration is deformed at1656 cm–1 due to change of the primary amine into amide by thioglycolic acid. Both PASC and MPASC are then utilized for removal of As(III) form water. Adsorption experiments were conducted at different values of adsorbent dose, contact time and pH values in order to study their influence on the uptake of arsenic by the PASC and MPASC adsorbents. The Langmuir maximum adsorption capacity for PASC and MPASC were found to be 125 and 142.85 mg/g, respectively. Sulfhydryl groups on MPASC indicate high affinity for As(III) ions.

AbstractIn this study, the Cu–Mo–B catalyst in nanostructure was successfully synthesized with the chemical reduction method of sodium borohydride (NaBH4). The categorization of the attained Cu–Mo–B nano-catalyst was examined with XRD, BET, SEM, and EDS analytical methods. As a result of the ammonium borane hydrolysis of this attained catalyst, the most convenient Mo/Co ratio, NaOH impact, the impact of different catalyst amounts, and the impact of different ammonium borane concentrations on ammonium boron hydride hydrolysis were examined. In addition, hydrolysis was examined at different temperatures, and the degree and activation energy of the reaction were determined. At 333 K with the ammonium borane (AB) hydrolysis of Cu–Mo–B nanoparticles, the maximum hydrogen production rate and activation energy were found to be 4075 mL min−1gcat−1 and 21.37 kJ mol–1, respectively. In this context, Cu–Mo–B catalyst can be used in practical fuel cells since it is obtained economically and easily.

AbstractHierarchical VAPO-5 molecular sieves were prepared with different vanadium resources in the absence/presence of fluorine and characterized by XRD, SEM, N2 adsorption-desorption, and NH3-TPD. The catalytic performances of hierarchical VAPO-5 molecular sieves were evaluated using toluene oxidation as the probe reaction and the corresponding mechanism was further proposed. The sample D-AFI-2(F) synthesized in a fluorine system with NH4VO3 as metal sources show better catalytic performance than other samples in toluene oxidation, which is ascribed to the hierarchically porous structure and more acidic sites. The optimized condition of toluene oxidation was attained at the reaction temperature of 60°C, the reaction time of 5 h, the molar ratio of H2O2 to toluene 2 : 1, the mass ratio of acetonitrile to toluene 6 : 1, and the mass ratio of catalyst to toluene 10%. In this case, the toluene conversion was 21.0%, and the selectivity of benzaldehyde, benzyl alcohol, and cresol was 43.3, 11.4, and 26.2%, respectively.

AbstractNew metalloorganosiloxanes (MOSs) were prepared by hydrosilylation of Ti(IV), Zr(IV), Hf(IV), and V(IV) acetylacetonates with α,ω-dihydrooligodimethylsiloxane. The reaction products were studied by DTGA and IR spectroscopy. The effect of the metallosiloxanes obtained on the heat resistance of composites based on low-molecular-mass polydimethylsiloxane rubber (SKTN) containing various types of reinforcing fillers was examined. Introduction of MOSs in an amount of 7 × 10–3 g/(kg blend) increases the gelation onset time of the SKTN-based compound from 5 to 54 h at 250°С. In addition, the resistance of the silicone vulcanizates to thermal oxidative degradation is enhanced, and the vulcanized rubber samples preserve satisfactory physicomechanical characteristics after prolonged heat treatment. The organosilicon liquids modified with the synthesized thermal stabilizers exhibit high levels of dielectric characteristics and heat resistance in the temperature interval from 25 to 270°С. The synthesized MOSs are soluble in polyorganosiloxanes, which allows uniform distribution of small amounts of the modifier in the polymer. The presence of metals with high coordination number in the thermal stabilizer macromolecules allows efficient inactivation of free radicals in a wide temperature interval. The filled silicone vulcanizates obtained can be used as heat-resistant cable insulation and high-temperature sealants, and MOS-modified organosilicon liquids can be used as analogs of mineral oils for power transformers.

AbstractThe paper deals with the thermal synthesis of aliphatic petroleum polymer resins by heat treatment of the С5 fraction at 240–320°С. Beginning from 280°С, the intermediate oligomerization products, piperylene dimers, start to transform into resins. An increase in the temperature to 320°С leads to the decomposition of the dimers and generation of radicals. An increase in the pressure in the reactor does not influence the reaction course. An increase in the synthesis time over 2 h does not lead to a noticeable increase in the piperylene conversion and resin yield. The thermal synthesis of aliphatic petroleum polymer resins is inefficient for commercial production of the resins.

AbstractHybrid electret materials with increased surface charge thermal stability based on polytetrafluoroethylene films treated with vanadium oxochloride vapor and water are synthesized. A model of an electret filter for air treatment to remove solid particles using a modified and initial polytetrafluoroethylene film is proposed and tested. Comparative tests of a polytetrafluoroethylene film with and without vanadium oxide structures on the surface as filter material are carried out. In the presence of vanadium oxide structures in the composition of polytetrafluoroethylene, the efficiency and dust capacity of an electret air filter based on it increase by more than 90%.