Initial Mixture Research Articles

Development, Synthesis and Characterization of Tannin/Bentonite-Derived Biochar for Water and Wastewater Treatment from Methylene Blue

Novel hybrid carbon–mineral materials were synthesized by the mechanochemical activation of a mixture of tannin and bentonite in a ball mill with further pyrolysis in an argon atmosphere at 800 °C. The influence of the initial mixture ingredients content on the structural, textural, and thermal characteristics of biochars has been described using X-ray diffraction, Raman and Fourier-transform infrared spectroscopy, nitrogen adsorption–desorption, and scanning electron microscopy. The influence of bentonite clay on the carbon phase characteristics due to the formation of more heat-resistant and structured nanocarbon particles in biochars has been proven. The adsorption effectiveness of the materials towards methylene blue was studied. The adsorption data were analyzed applying Langmuir and Freundlich isotherms with high determination coefficients (R2) in the range of 0.983–0.999 (Langmuir) and 0.783–0.957 (Freundlich). The maximum adsorption amount of MB was 5.78 mg/g. The adsorption efficiency of biochars with respect to phenol was also examined. It was shown that the hybrid biochars show differentiated selectivity to the adsorption of organic compounds. It was concluded that the physicochemical properties of the surface of biochars play an important role in the adsorption effectiveness, making them a good candidate for water and wastewater remediation processes.

The effect of the ratio of peat and manure on the efficiency of the fermentation process

Manure disposal is one of the main problems of livestock complexes. At the same time animal waste is a very important and valuable raw material in the production of organic fertilizers. The fermentation process was carried out for 6 days; the mesophilic regime was replaced by thermophilic, then the mesophilic period was again established. Air was supplied periodically. Various ratios of peat and manure were used - 40:60, 50:50, 60:40. In each version of the initial mixture, a favorable ratio of carbon to nitrogen was observed - C:N=20-25:1. However the determination of catalase and dehydrogenase activity made it possible to establish the optimal ratio of peat:manure=50:50, at which the value of C:N=22.7:1 and the best conditions are created for the vital activity of microorganisms and, accordingly, the activity of their enzymes. The maximum enzymatic activity contributed to the efficient transformation of organic raw materials. The same amount of manure and peat in the initial mixture contributed to a faster completion of the transformation of the fermented mixture, as evidenced by the redox coefficient in the fermentation product close to 1. With an equal ratio of the initial components, animal waste during the fermentation process is effectively processed into high-quality organic fertilizer.

Maturing out of alcohol and cannabis co-use: A test of patterns and personality predictors.

Reductions in substance involvement into adulthood are thought to represent a normative maturing out of substance use. However, patterns and predictors of maturing out of alcohol and cannabis co-use remain largely unstudied. Therefore, the current study tested developmental trajectories of alcohol and cannabis use from late adolescence into adulthood and whether late adolescent personality traits predicted trajectory class membership. Data come from a longitudinal study of family history of alcohol disorder (N=458). Age bands were created to model trajectories of drinking quantity, negative alcohol consequences, and cannabis use frequency from late adolescence (age 18-22) to young adulthood (age 23-28) and adulthood (age 29-36). Participants reported on their sensation seeking, conscientiousness, and neuroticism during late adolescence and their typical drinking quantity, negative alcohol consequences, and cannabis use frequency at each age band. Three trajectory classes were derived from an initial Parallel Process Growth Mixture Model: (1) low-risk maturing out of alcohol-only use, (2) high-risk maturing out of co-use, and (3) high-risk switchers who increased their cannabis use into adulthood. Late adolescent sensation seeking was associated with higher odds of being in both co-use trajectories, whereas a lack of conscientiousness was associated with higher odds of being a co-use switcher. We identified heterogeneity in trajectories of co-use, which suggests that a lack of maturing out of alcohol involvement may be accompanied by increased cannabis use. Moreover, late adolescent personality traits may predispose individuals toward riskier developmental trajectories of substance use into adulthood.

Minimum ignition energy of hydrogen-air and methane-air mixtures at temperatures as low as 200 K

The primary objective of this study is to measure the minimum ignition energy (MIE) of methane-air and hydrogen-air mixtures at low temperatures and atmospheric pressure. Initial fuel-air mixture temperatures as low as 200 K were considered, for a constant equivalence ratio of 1.0 for methane-air and 0.16 for hydrogen-air. The ignition source was a spark, generated by a high-voltage pulse of 100 μs duration, applied on two pin electrodes of 0.1-mm diameter, separated by a gap distance of 1 mm. The experimental methodology was validated by comparing the results obtained with those from previous studies available in the literature. First, for methane-air mixtures, the MIE as a function of the equivalence ratio followed the same trend at 295 K and 255 K, i.e., its lowest value was obtained for a stoichiometric mixture. Second, when the temperature of the mixture was decreased, the MIE increased linearly for both fuels. The rate at which the MIE changed was higher for hydrogen-air (−7.9 μJ/K) than for methane-air (−3.4 μJ/K). Overall, this study provides valuable information on the MIE of methane-air and hydrogen-air mixtures at low temperatures, which can be useful for the design of cryogenic fuel storage systems.

Prospects for the Use of Fluorinated Nanodiamonds in the Synthesis of Superhard Composites

The paper considers the possibilities of the practical use of nanoscale diamonds with a fluorine-functionalized surface for the synthesis of diamond composites under high pressures and temperatures. Optimal compositions of the initial mixtures and parameters of thermobaric treatment are established. It is shown that composites obtained by sintering homogeneous mixtures of fluorinated microdiamonds and nanodiamonds with the addition of aluminum and cobalt have an increased level of heat resistance and wear resistance which significantly exceeds the level of commercial samples.

Selective Deposition of Mo2C-Containing Coatings on {100} Facets of Synthetic Diamond Crystals.

An efficient way to improve the properties of metal–diamond composites (mechanical strength, wear resistance, thermal conductivity) is the preliminary modification of the diamond surface to improve its wettability by the metal matrix. In the present work, Mo2C-containing coatings were deposited on the diamond crystals under different conditions: hot pressing (atmosphere of argon), spark plasma sintering (forevacuum), and annealing in air. The influence of the sintering parameters on the morphology and phase composition of the coatings deposited on diamond was studied. Mo2C-containing coatings were selectively deposited on the facets of synthetic diamond microcrystals by annealing of the latter with a molybdenum powder. Experiments were carried out to deposit coatings under different conditions: during hot pressing (argon atmosphere), spark plasma sintering (forevacuum), and annealing in air. The process parameters were the temperature, holding time, and concentration of molybdenum in the initial mixture. Experiments with a pre-oxidized molybdenum powder were also conducted. The coated diamond crystals were investigated by X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The deposition was enabled by the gas phase transport of molybdenum dioxide, MoO2, contained in the starting powder. The following sequence of the coating formation stages was proposed. First, MoO2 sublimes and is adsorbed mainly on the {100} facets of diamond. Then, it is reduced to metallic molybdenum by carbon of the diamond, which further reacts with carbon to form the Mo2C carbide phase. These processes occurred during treatment of the mixtures in the hot press and the spark plasma sintering facility. When the mixture was annealed in air, no selective deposition was observed. During annealing, MoO3 particles adhered to the diamond surface.

Novel Pathway for the Combustion Synthesis and Consolidation of Boron Carbide.

A novel pathway for the magnesiothermic reduction of boron oxide and magnesium dodecaboride (MgB12) in the presence of carbon by a self-propagating high-temperature synthesis method was proposed that was aimed at the direct preparation of boron carbide nanopowder. The combined utilization of two boron sources, boron oxide and MgB12, allowed tailoring the overall caloric effect of the process, increasing the yield of the target product and lessening the laborious leaching process. In addition, it is an alternative way to utilize magnesium borides, which are inevitable side products at boron production. Multivariate thermodynamic calculations performed in the B2O3-MgB12-Mg-C system allowed estimating equilibrium compositions of the products and deducing the optimum composition of the initial mixture for obtaining B4C. For the latter, the adiabatic temperature (Tad) is 2100 °C, which is theoretically enough for the implementation of the self-propagating reaction. The combustion reaction was shown to be extremely sensitive to the initial mixture composition, external pressure, as well as sample diameter (heat losses). It proceeds in self-oscillatory mode and leads to the product of a layered macrostructure. The combustion product was then consolidated by the spark plasma sintering technique at different conditions. Vickers microhardness was measured, and the wear erosion behavior was examined. The variation in lattice parameters of boron carbide reflected the influence of synthesis, sintering and erosion conditions on the ordering/disordering of the boron carbide structure.

Mechanosynthesis of High-Nitrogen Steels Strengthened by Secondary Titanium Nitrides.

The solid-phase mechanical synthesis of high-nitrogen ferritic and austenitic steel composites in the course of mechanical activation in a ball mill is studied by the method of Mössbauer spectroscopy and electron microscopy. For mechanical alloying, mixtures of iron alloys doped with transition metals (Ni, Cr, Mn, and Ti) and nitrides with low stability to deformation (CrN and Mn2N) were used. The correlation between the phase–concentration composition of the mechanically synthesized samples and the heat of formation of transition metal nitrides, which are part of the initial metal mixtures, is investigated. It is established that the use of titanium as an alloying additive of the Fe component of the mixture accelerates the processes of dissolution of primary nitrides and allows the transference of chromium and manganese to the position of substitution in the metallic solid solution. In addition, the titanium additive entails the formation of secondary nitrides with stabilizing the nanostructure of the mechanically synthesized samples.

Ion Current Simulation Model Design for a Spark-Ignited Engine

The use of ion current signals generated during the combustion process of mixed gas as a function of initial mixture composition, temperature and pressure to detect cylinder combustion states is the most recent approach in the design, development, and optimisation of automotive engine combustion control. This paper aims to design predictive identification and computationally fast and accurate ion current models for obtaining combustion information in the engine cylinder in real time. To build a more comprehensive ion current calculation model, the effect of the flame ionisation process, the geometry of the spark plugs, and the combustion pressure and temperature are considered in the new building ion current model. The simulation ion current waveform, which has a double-peak structure, is in good agreement with the experiment values; thus, the ion current model has the potential to be used for real-time control and optimisation of engine cylinder combustion.

Effect of scleral protein shell amendment on bacterial community succession during the pig manure composting

The impact of scleral protein shell (SPS) amendment on bacterial community succession during pig manure (PM) composting were evaluated in the present work. Five treatments representing different dry weight dosage of SPS [0 % (T1), 2.5 % (T2), 5 % (T3), 7.5 % (T4), 10 % (T5) and 12 % (T6)] were applied with initial mixture of raw materials (Wheat straw along with the PM) and composted for 42 days. Results indicated that the dominant of phyla were Proteobacteria, Actinobacteria, Bacteroidetes and Firmicutes. The relative abundance (RA) of genus un-identified, Ruminofilibacter, Thermovum, Longispora and Pseudomonas were greater among the all treatments but interestingly genus Ruminofilibacter was also higher in control treatment. The network analysis was confirmed that T6 treatment with higher dosage of SPS amendment could enhance the bacterial population and rate of organic matter mineralization. Compared with T1, the T5 has greater potential impact to enhance the bacterial population and significant correlation among the pH and temperature.

Structural Formation of Soil Concretes Based on Loam and Fly Ash, Modified with a Stabilizing Polymer Additive.

Finding new ways of recycling production waste to improve the characteristics of various building materials is an urgent scientific task. This article substantiates the possibility of the disposal of fly ash in the composition of soil concrete, which is used in the construction of the structural layers of road pavements, foundations of buildings and structures, as well as sites for various purposes. The scientific novelty lies in the fact that the structure formation of soil concretes based on loam and fly ash and modified with a stabilizing additive is being studied for the first time. It was found that the investigated fly ash, according to its hydraulic properties, is classified as latent active and can be introduced into the compositions of road soil concrete modified with additives of various resources. The effectiveness of the complex method of stabilization, due to changes in soil properties as a result of the use of the binding and stabilizing additives of polymer nature “Kriogelit”, is shown. It was found that the optimal content of binder and fly ash in the samples was 8 and 10 wt.%, respectively. It was established that the use of the stabilizing additive “Kriogelit” makes it possible to obtain soil concrete with the highest strength (compressive strength 2.5 MPa, flexural strength 0.5 MPa) and frost resistance of at least F15. The microstructure, the degree of dehydration and carbonization, and the phase composition of the initial raw mixtures and soil concretes stabilized with the addition of “Kriogelit” were studied by methods of scanning electron microscopy, X-ray diffraction analysis, differential scanning calorimetry, thermogravimetry, and infrared spectroscopy. It was shown that organo-mineral complexes, with the participation of polymer and montmorillonite, are formed in stabilized soil concrete. It was revealed that structure formation is accompanied by the physical adsorption of the polymer on active centers of silicate minerals, carbonization, and hydration–dehydration processes. It was found that the reason for the increase in the strength of stabilized soil concretes is the hydrophobization of the porous structure of minerals, as well as the formation of calcium oxide silicate and dicalcium hydrated silicate. By the method of performing biotests with the test objects Daphnia magna Straus and Chlorella vulgaris Beijer, it was proven that the developed road concretes modified with the stabilizing additive “Kriogelit” do not have an acute toxic effect on the test objects and are safe for the environment and human health.

Electrochemical contributions: Adolph Wilhelm Hermann Kolbe (1818–1884)

Hermann Kolbe (Figure 1) was a German scientist who greatly contributed to the development of organic chemistry, transforming it to the state as we know it now. Kolbe pioneered organic synthesis from inorganic sources and introduced the term “synthesis” in the meaning how we use it in chemistry now. His name is associated with several synthetic reactions in organic chemistry, e.g., the Kolbe-Schmitt reaction in the preparation of aspirin, the Kolbe nitrile synthesis, etc. His work is particularly remembered in connection to electrolysis of carboxylic acids resulting in the synthesis of various organic compounds, known as the Kolbe reaction. The Kolbe reaction (Figure 2), proceeding as the electrolysis, results in the oxidative decarboxylation of carboxylic acids yielding free radicals, which dimerize producing symmetrical products. For example, the Kolbe electrolysis process can proceed in an aqueous solution of sodium acetate (Figure 2). The acetate ions get decomposed and form methyl radicals. These combine with other free methyl radicals, which leads to the generation of ethane. In general, Kolbe's electrolysis method uses sodium salts of fatty acids to form the corresponding alkanes as products (D. Klüh, W. Waldmüller, M. Gaderer, Clean. Technol. 2021, 3, 1–18). A similar electrochemical synthesis can be used to produce more sophisticated products (Figure 2B). If the initial mixture includes two different acids, the reaction results in three different products from the cross-reaction of two different free radicals. The Kolbe electrolytic decarboxylation of 1,2-dicarboxylic acids results in the formation of double or triple chemical bonds (Figure 3). When carboxylic groups are located at a longer distance in a molecule, the electrolytic decarboxylation may result in the intramolecular radical cyclization of the reaction product. It should be noted that the Kolbe electrolysis reaction may result in the formation of numerous byproducts (Figure 4). The formation of side products depends on the ease of the follow-up oxidation, which leads to carbenium ions, and their subsequent rearrangements. The exact mechanism and kinetics study of the electrochemical Kolbe process have been investigated confirming the complexity of the electrochemical reaction (A.K. Vijh, B.E. Conway, Chem. Rev. 1967, 67, 6, 623-664). The author declares no conflict of interest.

High Methoxyl Pectin and Sodium Caseinate Film Matrix Reinforced with Green Carbon Quantum Dots: Rheological and Mechanical Studies.

Nowadays, proteins and polysaccharides play a fundamental role in the manufacturing of biocompatible materials applied in food packaging. The resulting films have, however, limits associated with the resistance to mechanical stress; therefore, it is important to reinforce the initial mixture with additives that promote the development of stronger molecular links. Carbon dots (CDs) are excellent candidates for this purpose due to the presence of surface functional groups that determine the formation of numerous intramolecular bonds between the charged biopolymers. The present research aims to evaluate the effect of CDs on the mechanical properties of biopolymer films obtained from sodium caseinate (CAS), high methoxyl pectin (HMP) and glycerol used as plasticizers. Green carbon dots (gCDs) were obtained from natural organic sources by green synthesis. The effects of gCDs on the flow behavior and viscoelastic properties of mixed biopolymer dispersions and the thermophysical properties of the corresponded films were evaluated by steady and unsteady shear rheological measurements and differential scanning calorimetry (DSC) tests, respectively. The dynamic mechanical measurements were realized taking into account the parameters of temperature and relative humidity. The results indicate a significant change in the viscosity of the protein–polysaccharide dispersions and the thermomechanical properties of the corresponding film samples reinforced with higher amounts of gCDs.

Vermiremediation of allopathic pharmaceutical industry sludge amended with cattle dung employing Eisenia fetida

The present study aims to vermiremediate allopathic pharmaceutical industry sludge (AS) amended with cattle dung (CD), in different feed mixtures (AS:CD) i.e (AS0) 0:100 [Positive control], (AS25) 25:75, (AS50) 50:50, (AS75) 75:25 and (AS100) 100:0 [Negative Control] for 180 days using earthworm Eisenia fetida. The earthworms could thrive and grow well up to the AS75 feed mixture. In the final vermicompost, there were significant decreases in electrical conductivity (29.18–18.70%), total organic carbon (47.48–22.39%), total organic matter (47.47–22.36%), and C: N ratio (78.15-54.59%). While, significant increases in pH (9.06-16.47%), total Kjeldahl nitrogen (69.57–139.58%), total available phosphorus (30.30–81.56%), total potassium (8.92-22.22%), and total sodium (50.56–62.12%). The heavy metals like Cr (50–18.60%), Cd (100-75%), Pb (57.14–40%), and Ni (100-50%) were decreased, whereas Zn (8.37–53.77%), Fe (199.03-254.27%), and Cu (12.90–100%) increased significantly. The toxicity of the final vermicompost was shown to be lower in the Genotoxicity analysis, with values ranging between (76–42.33%). The germination index (GI) of Mung bean (Vigna radiata) showed a value ranging between 155.02 and 175.90%. Scanning electron microscopy (SEM) analysis showed irregularities with high porosity of texture in the final vermicompost than in initial mixtures. Fourier Transform-Infrared Spectroscopy (FT-IR) spectra of final vermicompost had low peak intensities than the initial samples. The AS50 feed mixture was the most favorable for the growth and fecundity of Eisenia fetida, emphasizing the role of cattle dung in the vermicomposting process. Thus, it can be inferred that a cost-effective and eco-friendly method (vermicomposting) with the proper amendment of cattle dung and employing Eisenia fetida could transform allopathic sludge into a nutrient-rich, detoxified, stable, and mature vermicompost for agricultural purposes and further could serve as a stepping stone in the allopathic pharmaceutical industry sludge management strategies in the future.

Impact of electronic excitation on the state-to-state vibrational-chemical CO kinetics

Dissociation of carbon monoxide in shock heated flows is studied with emphasis to the phenomenon of dissociation induction. Different kinetic schemes are implemented, both neglecting and including electronic excitation; various vibrational and electronic state-resolved models of dissociation rate coefficients are assessed. Vibrational-electronic relaxation coupled to dissociation behind the shock front is simulated in the frame of the state-to-state approach for several test cases with varying initial pressure, temperature, mixture composition and shock velocity. It is found that dissociation delay may appear regardless taking into account electronic excitation; the incubation time is mainly governed by mixture composition and initial pressure. Electronic excitation noticeably influences the overall dissociation rate. Recommendations for using specific dissociation models are given for different test cases.

Application of varieties of technogenic raw materials in cement technology

The possibility of manufacturing a mineral binder using large-tonnage waste from other industries has been studied. The object of the research are mixtures for the manufacture of cement clinker based on systems of chalk – clay – scope of paper production and chalk – clay – husks of rice processing. At the same time, urgent tasks of developing the raw material base for cement production and resource conservation were solved. The development of new initial mixtures was carried out taking into account the peculiarities of the chemical and mineralogical composition of varieties of technogenic raw materials. According to the chemical composition, rice alkali is characterized by a content of 15.6 wt. % SiO2 with a large quantitative ratio of SiO2:Al2O3=65.2 and a small amount of alkaline earth and alkaline oxides. Scop differs from alkali in a large amount of CaO (25.8 wt. %), a lower content of SiO2 at a quantitative ratio of SiO2:Al2O3=1.3. In this case, there are quantitative ratios of oxides CaO:SiO2=2.5, CaO:Al2O3=3.3, CaO:SiO2:Al2O3=3.3:1.4:1, which determine the probable phase transformations during firing. The main rock-forming mineral in rice husks is amorphous silica; Scope is marked by the presence of crystalline phases of calcite, quartz, and kaolinite. The analysis of the possible content of the studied wastes and the determination of the compositions of the raw mixtures were carried out using the computer program «Clinker». Analysis of computer calculations and experiments indicates the possibility of reducing by 11–16 wt. % consumption of natural raw materials in the composition of mixtures for the manufacture of clinker in comparison with the known production composition. According to X-ray phase analysis, the features of the development of crystalline phases during the firing of mixtures using varieties of technogenic raw materials at a maximum temperature of 1400 ºС were established. Based on the data of technological testing, the differences in indicators of binding properties were determined - the setting time of cement when used in the composition of raw mixtures of rice husk and paper scope.

Separation of rare earth metals in countercurrent extraction cascades using binary extractants

The use of binary extractants (BE) in schemes of countercurrent extraction cascades designed for the separation of rare earth metals (REMs) has been studied. It has been shown that the main difference between the use of BE and cation-exchange extracts (CE) is the possibility of using deionized water in the re-extraction cascades, rather than solutions of mineral acids. When optimizing the REM separation scheme, a mathematical model was used to dynamically calculate the distribution of separated metals over the stages of counterflow extraction cascades. The modeling of cascades was carried out on the basis of the physicochemical description previously obtained by the authors of the processes of extraction of REM nitrates with various BE compositions prepared on the basis of industrial cation- and anion-exchange extractants. Calculation of the balance of lanthanides during successive separation by stages of cascades was performed for the initial mixture of REM nitrates with the ratio of elements corresponding to the composition of the ore of the Chuktukonskoe rare metal deposit. A scheme of cascades is proposed for isolating in pure form the five REMs of light and light/medium groups (Pr, Nd, Sm, Eu, Gd) most demanded by the industry, concentrate of La, Ce, and concentrate of REM of medium/heavy and heavy groups. The scheme includes 10 countercurrent extraction cascades with a total number of extraction stages of 390. The scheme uses BE based on di-(2-ethylhexyl)phosphoric acid, synthetic fatty acids, tri-n-octylamine, and an industrial diluent. For the proposed scheme, mineral acid is used only at the stage of obtaining REM nitrates from the initial oxides; 1.8 kg (65%) of nitric acid is consumed per 1 kg of REM oxides. For the precipitation of REM carbonates from re-extracts, the consumption of sodium carbonate is approximately 1 kg per 1 kg of the initial REM oxides. The use of BE in comparison with CE makes it possible to significantly reduce the consumption of mineral acids and bases during the separation and production of individual REMs. The work was carried out within the framework of the state task of the Institute of Chemistry and Chemical Technology of the Siberian Branch of the Russian Academy of Sciences (project 0287-2021-0014) using the equipment of the Kranoyarsk Regional Center for Collective Use of the Federal Research Center of the KSC of the Siberian Branch of the Russian Academy of Sciences.

The role of water on dehydrofluorination in PVDF/K2CO3 percolative composites

Percolative composites of polyvinylidene fluoride/potassium carbonate (PKC) represent a new way of incorporating activated carbon in the polymer matrix with high dielectric constant and electrical conductivity, making it promising for flexible energy storage applications. In this paper, a series of characterization techniques were applied to investigate the role of water in the PKC mixture on PVDF dehydrofluorination and the structure of the subsequently developed activated carbon. The mechanism of the initiation of PVDF dehydrofluorination was clarified from the structural variation of the activated carbon generated under different conditions. The results revealed that the presence of a suitable amount of hydrated water or sesquicarbonate of potassium in the initial mixture could initiate the dehydrofluorination reaction at low temperatures upon thermal treatment and effectively modify the structure of activated carbon to enable performance optimization of the percolative composite.

Assembly of Ultralong Hydroxyapatite Nanowires into Enamel-like Materials

To develop dental restorative materials with enamel-like structures, ultralong hydroxyapatite (HA) nanowires were synthesized by a hydrothermal method, followed by functionalization with 3-methacryloxypropyltrimethoxysilane (KH-570). The mixture of HA nanowires, KH-570, and light initiator was stirred and centrifuged. The precipitate was vacuum filtered to remove excessive KH-570 and then pressured under cold isostatic pressing (10 MPa × 24 h). Finally, the block was polymerized by lighting. Scanning electron microscopy and transmission electron microscopy showed that HA nanowires with aspect ratios >1,000 were assembled into enamel rod–like microstructures and evenly dispersed in the polymerized KH-570 silane matrix to form enamel-like structures. Thermogravimetric analysis demonstrated that the content of HA nanowires reached 72 wt% in the composite. The enamel-like composite showed a similar hardness, frictional property, and acid-etching property to those of enamel and a comparable or even better diametral tensile strength and compressive strength than some commercial composite resins in mechanical tests in vitro. In addition, the enamel-like composite had good cytocompatibility. Such enamel-like composites may have the potential to be used in biomimetic tooth restorations in the future.

Using explosion loading to obtain coatings of chromium carbide and titanium mixtures in deposition mode

The paper presents the results of studies into the microstructure, chemical and phase composition of coatings deposited on a steel substrate using the sliding explosive loading of Cr3C2 chromium carbide and titanium powder mixtures. The equilibrium phase composition of coatings was calculated by computational thermodynamic modeling using the Thermo-Calc software package. The structure and elemental composition were studied using a FEI Versa 3D scanning electron microscope with an integrated EDAX Apollo X system for energy dispersive X-ray microprobe analysis. A Bruker D8 Advance diffractometer was used for X-ray phase analysis. It was shown that when the powder layer is loaded by a sliding detonation wave, it can be shifted along the substrate surface due to the horizontal mass velocity component of compacted material particles. This shift causes the inner layer of the compacted powder and the surface layer of the substrate to melt as a result of friction. The presence of a liquid phase prevents the compacted powder layer deceleration so that the major part of it is removed from the substrate surface. The liquid phase remaining on the surface undergoes rapid quenching due to heat removal into the substrate and forms a deposited coating containing both the components of the initial powder mixture and the components of the substrate to be coated. It was established that the deposited layer structure features by extremely high dispersion (grain size does not exceed 250 nm), and its phase composition turns out to be close to a thermodynamically equilibrium one. When using powder mixtures of chromium carbide with 40% titanium, a coating is formed consisting of titanium carbide with a metal binder based on solid solutions of iron and titanium in chromium.