I. A. Domashnev

Synthesis of nanosized group IV borides in ionic melts of anhydrous sodium tetraborate

The preparation of nanosized Group IV metal diborides by reacting powdery titanium, zirconium, and hafnium with fine-grained boron in Na2B4O7 ionic melts in the temperature range 600–850°C has been studied. Nanosized titanium, zirconium, and hafnium diborides are formed at temperatures of at least 750°C.

Special features of preparation of nanosized hafnium diboride of different dispersity

X-ray diffraction analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, thermogravimetry, and elemental analysis have been applied to study the products of interaction of powder hafnium with fine-crystalline boron in the Na2B4O7 ionic melt at 600–850°C and of HfCl4 with NaBH4 at 300–700°C.

Microwave-assisted chloride process for the production of titanium dioxide

The conditions for the formation of the particle-size and phase composition of titanium dioxide upon the oxidation of titanium tetrachloride in a stream of oxygen-containing microwave discharge plasma have been studied. The possibility of controlling the particle size of the resulting powder in the range of 50–100 nm by changing various operating parameters has been shown. The conditions for obtaining a nearly single-phase powder of the anatase or rutile modification have been found.

Special features of preparation of nanosized zirconium diboride powders of various dispersity

Products of the zirconium powder reaction with amorphous boron in a Na2B4O7 ionic melt at 650–850°C and those of the ZrCl4 reaction with NaBH4 at 300–725°C have been studied by means of X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, thermogravimetry, and elemental analysis. At temperature ≥750°C, single-phase ZrB2 with the particle size of 60–80 nm is formed in a Na2B4O7 ionic melt, whereas the ZrB2 powder obtained via the reaction of ZrCl4 with NaBH4 at temperature ≥575°C consists of particles differing in the shape, some of which are close to spherical with diameter of 10–35 nm.

Formation of zirconium diboride nanoparticles as a result of reaction between zirconium tetrachloride and sodium borohydride

We have studied reaction between ZrCl4 and NaBH4 at temperatures between 300 and 725°C. The results demonstrate that single-phase zirconium diboride nanoparticles are formed starting at 575°C. According to electron microscopy data, the ZrB2 powder obtained at 575 and 725°C consists of variously shaped particles, some of which are almost spherical, ranging in diameter from ~10 to 20 and from 25 to 35 nm, respectively. These values agree with the equivalent particle diameters evaluated from the measured specific surface area of ZrB2, ~14 and ~32 nm, respectively, and with the crystallite size extracted from X-ray diffraction data: Dhkl ~ 13 and 28 nm.

Microwave plasmochemical synthesis of nanopowders in the system Pb-Zr-Ti-O

Conditions for building up the composition and structure of mixed Pb, Zr, and Ti oxides in a microwave plasma-chemical process were studied. As starting substances Pb(C2H5)4, Ti(C4H9O)4, and a 80% Zr(C4H9O)4 solution in 2-propanol were used. To avoid stratification of the components the initial temperature of the flow should not exceed 1000°C. Under these conditions the crystallization of a complex structure requires a combination of a plasma-chemical synthesis with subsequent thermal treatment of the resulting powders. After the thermal treatment an average particle size of lead zirconate-titanate nanopowder was 120 nm.

Special Features of Oxidation of Hafnium Diboride Nanoparticles of Different Dispersity

Products of oxidation of HfB2 particles with mean size 50–55 and 20–25 nm with air oxygen under polythermal and isothermal conditions have been studied by means of thermal analysis, scanning electron microscopy, X-ray energy-dispersive analysis, and elemental analysis. Rate constants of oxidation of the HfB2 nanoparticles have been determined.

Prospects for Using Photocatalytic Air Cleaning Technology to Provide Safety of Sevoflurane Application to Parturition Anesthesia in Obstetric Hospitals

The product composition of photocatalytic oxidation of vaporized sevoflurane, a next-generation fluorinated inhalation anesthetic, has been studied. It has been found that the final products of oxidation are carbon dioxide and hydrogen fluoride. The possibility of complete chemical absorption of the evolved hydrogen fluoride by a lime absorber during the course of the photocatalytic reaction has been shown. A safe scheme for using photocatalysis is recommended for purifying air to remove vapors of halogen-containing anesthetics under medical hospital conditions.

Particle size control of alumina nanopowders in microwave plasma-chemical process

The effect of operating parameters of the oxidation of aluminum powder in a stream of air microwave plasma on the particle size of the obtained Al2O3 has been studied. The possibility of improving the particle size of the powder by pretreatment the starting aluminum with chemicals activating particle combustion in a reactor has been investigated. Ways of controlling the particle size of produced aluminum oxide nanopowders in the range of 20–80 nm have been found.

Production of very fine TiN-Mo composite powders in a low-temperature plasma stream

ConclusionsIn the hydrogen reduction of TiCl4, and thermal decomposition of Mo(CO)6 in a stream of shf discharge nitrogen plasma the main reaction products are titanium nitride and molybdenum. The impurity elements in the composite (carbon and oxygen) react with the titanium nitride, forming the titanium oxycarbonitride TiNxOyCz (where x + y + z = 1, y < 0.10, and z < 0.05). The formation of nitride particles takes place before the instant of full pyrolysis of Mo(C0)6, and molybdenum therefore does not cover them, but condenses in the form of free spherical particles whose mean size is about half that of the particles forming during the pyrolysis of the carbonyl without a TiCl4 addition to the reactor. A characteristic feature of the resultant fine molybdenum-nitride composite powders is a high uniformity of distribution of Ti and Mo in them.