AlN Production in Co-Flow Filtration Mode at Low Pressures

In this work, the process for obtaining aluminum nitride in the combustion mode of co-flow filtration of a nitrogen–argon mixture was investigated. The combustion of granules consisting of aluminum and aluminum nitride as an inert diluent was studied under conditions of co-current filtration in a flow of nitrogen and a nitrogen–argon mixture in the range of a specific flow rate of 1.5–5.0 cm3/(s∙cm2). It was found that the specific flow rate of the gas mixture and the amount of argon in the nitrogen–argon mixture had a significant effect on the rate and the temperature of combustion. The structure and phase composition of the synthesis products were studied. The maximum achieved yield of the AlN phase was 95 wt.%. Moreover, this method is energy efficient and allows the production of metal nitrides without the use of high-pressure reactors.

Calculation of the charcteristic electronenergy for mercury

numerical study is applied to the mercury-argon mixture by solving the boltzman transport equation for different mixture percentage.

Synthesis of Electrospun TiO2 Nanofibers and Characterization of Their Antibacterial and Antibiofilm Potential against Gram-Positive and Gram-Negative Bacteria

Recently, titanium dioxide (TiO2) nanomaterials have gained increased attention because of their cost-effective, safe, stable, non-toxic, non-carcinogenic, photocatalytic, bactericidal, biomedical, industrial and waste-water treatment applications. The aim of the present work is the synthesis of electrospun TiO2 nanofibers (NFs) in the presence of different amounts of air–argon mixtures using sol-gel and electrospinning approaches. The physicochemical properties of the synthesized NFs were examined by scanning and transmission electron microscopies (SEM and TEM) coupled with energy-dispersive X-ray spectroscopy (EDX), ultraviolet-visible spectroscopy and thermogravimetric analyzer (TGA). The antibacterial and antibiofilm activity of synthesized NFs against Gram-negative Pseudomonas aeruginosa and Gram-positive methicillin-resistant Staphylococcusaureus (MRSA) was investigated by determining their minimum bacteriostatic and bactericidal values. The topological and morphological alteration caused by TiO2 NFs in bacterial cells was further analyzed by SEM. TiO2 NFs that were calcined in a 25% air-75% argon mixture showed maximum antibacterial and antibiofilm activities. The minimum inhibitory concentration (MIC)/minimum bactericidal concentration (MBC) value of TiO2 NFs against P. aeruginosa was 3 and 6 mg/mL and that for MRSA was 6 and 12 mg/mL, respectively. The MIC/MBC and SEM results show that TiO2 NFs were more active against Gram-negative P. aeruginosa cells than Gram-positive S. aureus. The inhibition of biofilm formation by TiO2 NFs was investigated quantitatively by tissue culture plate method using crystal violet assay and it was found that TiO2 NFs inhibited biofilm formation by MRSA and P. aeruginosa in a dose-dependent manner. TiO2 NFs calcined in a 25% air-75% argon mixture exhibited maximum biofilm formation inhibition of 75.2% for MRSA and 72.3% for P. aeruginosa at 2 mg/mL, respectively. The antibacterial and antibiofilm results suggest that TiO2 NFs can be used to coat various inanimate objects, in food packaging and in waste-water treatment and purification to prevent bacterial growth and biofilm formation.

Process of Obtaining Chromium Nitride in the Combustion Mode under Conditions of Co-Flow Filtration

In this work, the combustion process of chromium powder in the co-flow filtration mode was studied. The effect of nitrogen-containing gas flow rate on the nitridation of combustion products is shown. The effect of the amount of argon in the nitrogen–argon mixture on the burning rate and the burning temperature of the chromium powder is shown. It was found that an increase in the percentage of argon in the nitrogen–argon mixture can lead to the formation of an inverse combustion wave. The actual burning temperature is higher than adiabatic burning temperature in the co-flow filtration mode, thus the phenomenon of superadiabatic heating is observed. The phase composition of the obtained combustion products was studied. It was shown that the forced filtration mode allows for synthesizing non-stoichiometric Cr2N nitride.

Composite Materials Based on Plasma Treated Basalt Fibers for Heavy-Duty Concrete Products

The paper investigates the effect of plasma treatment of basalt fiber on its wettability, which is determined by the ability to absorb water. As the treatment time increases the wettability becomes higher, up to 10 minutes. The wettability-treatment power dependence passes through a maximum. The highest value is observed at a treatment power of 0.6 kW both on the day of treatment and after a 5-day rest period. A further growth in power not only does not increase this value, but in fact decreases it. The retreatment after a 5-day curing period yields lower results, but remains sufficiently high. The highest wettability is observed at a treatment power of 0.6 kW, gas flow rate of 0.04 g/s, chamber pressure of 20 Pa, air/argon mixture (1:1) as plasma support gas. The strength of concrete specimens BST V40 P2 was tested with two treatment modes: in mode 1 the treatment time was 10 minutes, the treatment power was 1.5 kW; and in mode 2 the treatment time was 5 minutes, the treatment power was 0.6 kW, with the addition of plasma treated basalt fiber (0.5 and 3 mass percent). Concrete has the highest strength when basalt fiber (3 mass percent) is subjected to plasma treatment in mode 2. In addition, the strength increases by 18 mass percent in comparison with the reference.