Supercritical fluid CO<Subscript>2</Subscript>-extraction regeneration of nickel–molybdenum catalyst for hydrotreatment

Results from studying the supercritical fluid СО₂-extraction regeneration of DN-3531 industrial nickel–molybdenum hydrotreatment catalyst in the temperature range of 323.15–383.15 K, at pressures of up to 30 MPa, and with modification of the basic extragent with such polar compounds as chloroform, methanol, ethanol, acetone, and dimethylsulfoxide (DMSO), are presented. The order of modifiers corresponds to the increase in the solubilizing ability of modified supercritical carbon dioxide (SC-СО₂) with respect to catalyst- deactivating deposits. With DMSO as the most efficient modifier, however, not only are deactivating compounds removed but nickel and molybdenum as well, considerably reducing the final activity of a regenerated sample. During extraction regeneration, the content of coke in the catalyst is reduced by two-thirds, while the specific surface area and the pore volume grow. The activity of the deactivated catalyst in dibenzothiophene hydrodesulfurization (HDS) and naphthalene hydrogenation grows by several hundred per cent after one-time SC-CO₂ treatment and is 2.5 times higher than for a sample regenerated using the traditional oxidative method.     

Effect of hydrocarbons of different groups on the phase stability of ethanol-containing fuels

Compositions of petroleum fuels mixed with biofuels, first and foremost, ethanol, in which the oxygen content increases the completeness of fuel combustion, are being relatively widely used. A drawback of ethanol-containing fuels is their relatively low phase stability, especially when water is present in the mixture. The present work studies the effect of hydrocarbons of different classes on the phase stability of fuels.     

Composition, structure, and dielectric properties of SiC-AlN ceramic materials

We have studied the structure, relative dielectric permittivity (?), and dielectric loss tangent (tan??) of SiC-AlN ceramic materials. The results demonstrate that both ? and tan?? are anomalously high in the composition range 30?C50 wt % AlN at low frequencies (0.1 kHz). We show that the increase in ? may be due to a barrier effect on silicon carbide and aluminum nitride grain boundaries and to migration polarization.     

Spectral shift of photoluminescence bands of the (SiC)1−x (AlN)x epitaxial films due to laser annealing

The effect of laser annealing on the photoluminescence properties of (SiC)_1?x (AlN)_x epitaxial films was studied. It was proposed that annealing causes the displacement of the Al and N atoms from their lattice sites and the formation of Al_Si-N_C donor-acceptor pairs acting as the luminescence centers. According to this model, the increase in the annealing time is accompanied by the formation of donor-acceptor pairs with the shortest interatomic distances at the expense of associations of the distant defects and by a shift of the respective photoluminescence band to the high-energy spectral region.     

Dependence of the Surface Morphology and Structure of CuIn0.95Ga0.05Se2 Films on the Selenization Temperature

Semiconductors - Depending on the choice of the technology for producing CuInxGa1&nbsp;–&nbsp;xSe2 films, a spread in the electrophysical and photoelectric parameters of...     

Protective polymer coatings based on phenol-formaldehyde oligomers modified by propargyl bromoethers

In order to enhance the protective effect, phenol-formaldehyde oligomers (PFOs) are modified by propargyl bromoethers. It is found that resulting composites exhibit high heat resistance, hardness, and adhesion strength. The presence of additional reactive functional groups in their composition favors their use as protective coatings. The effects of various factors on the degree of curing of protective coatings based on PFOs modified with propargyl bromoethers are studied. Polymer coatings made of modified PFOs are tested as the protective coatings of metal samples. It is revealed that the acid resistance of samples of steel (St.-3) coated with the polymer composite survives in chlorhydric and acetic acids.     

Thermal conductivity and the Wiedemann-Franz relation in melts of indium and gallium antimonides

The thermal and electrical conductivities of indium and gallium antimonides were studied in both solid and liquid states. It is shown that the calculated values of the Lorentz number (L) in InSb and GaSb, unlike in metals, increase with increasing temperature after melting. An anomalous increase in L is consistent with anomalous (for melts) temperature dependences of density, viscosity, and coordination number of these melts at the same temperatures.     

Structural properties of the epitaxial (SiC)1 − x (AlN) x solid solution films fabricated by magnetron sputtering of SiC-Al composite targets

Epitaxial layers of the (SiC)_{1 ? x} (AlN) _x solid solution with x ≈ 0.12 and x = 0.64 without macroscopic structural distortions were grown using a new technique. It was established that the compositional dependences of crystal lattice parameters of the epitaxial films obey the Vegard’s law with an error of ～0.03. This confirms that there is formation of isomorphic substitutional solid solutions in the SiC-AlN system.     

Production technology and optical absorption characteristics of CuIn<Subscript>0.95</Subscript>Ga<Subscript>0.05</Subscript>Se<Subscript>2</Subscript> semiconductor solid solution films

A production technology of thin CuIn_0.95Ga_0.05Se₂ films has been developed based on the method of two-stage selenization of CuIn_0.95Ga_0.05 precursor by a reactive component (selenium) in a carrier gas (nitrogen) flow. The morphology and structure of obtained films were studied by electron microscopy and X-ray diffraction techniques. The spectral dependence of the optical absorption coefficient was measured.     

Dynamic effects during thermoelastic martensitic transformations in TiNiCu alloys

Spontaneous periodic oscillations in the phase transformation rate during a system evolution toward a stationary state are observed in TiNiCu alloys. The conditions of manifestation and amplification of these oscillations are established and possible applications of this phenomenon are considered.