Volume 467, Nº 1 (2016)

The role of the etchant ion (HF₂)^– in the formation of pores in silicon during its etching in hydrofluoric acid solutions has been elucidated. The pore shape, size, and orientation in (100) and (111) silicon substrates have been explained by specific features of the etchant ion (HF₂)^–.

Ab initio modeling of C_n clusters comprising up to 250 atoms and having a diamond core revealed stable primary surface elements of nondiamond nature. At large local curvature of the surface, pentaatomic rings dominate. At a smaller local curvature, the fraction of six-membered rings increases, and so does the fraction of structures that resemble open fragments of fullerenes and nuclei of cross-sectional segments of nanotubes.

A macrokinetic model of pyrolysis of carbonaceous feedstock in a tubular reactor was proposed. It was shown that, under unsteady-state conditions (at oscillating temperature of feedstock heating), higher conversions can be reached in comparison with steady-state conditions, which agrees with experimental data on flash pyrolysis of biomass in a tubular reactor during heating–cooling cycles.

Quantum-chemical modeling of cationic cobalt complexes based on o-benzoquinone and a di-tert-butyl derivative of 2,11-diaza[3.3](2,6)pyridinophane was performed by the density functional theory method in the TPSSh/6-311++G(d,p) approximation. The ground states of the studied compounds are lowspin structures consisting of the divalent metal cation and a redox-active ligand in the semiquinone form. The calculations predict incomplete transition of these complexes to the high-spin state, which is consistent with the results of magnetochemical measurements.

It has been suggested to use suspensions of solid samples in viscous liquids for the determination of the elemental composition by the total reflection X-ray fluorescence (TRXF) method. Two liquids—ethylene glycol and glycerol—have been studied as a dispersion phase. It turned out that the sedimentation stability of suspensions in these liquids is higher than in water. During 5 min of sedimentation, the suspended analyte concentration changes by 10–15 rel. % in nonaqueous media and by up to 50 rel. % in aqueous media. It has been determined that the repeatability of measurements in nonaqueous suspensions is 3–5 rel. % against 10–15 rel. % for aqueous suspensions. It has been demonstrated that ethylene glycol and glycerol can be efficiently used for preparing samples for the TRXF method.

A new carbazole-containing naphthodithiophene heteroaromatic compound, 5,6-bis[9-(2-decyltetradecyl)-9H-carbazol-3-yl]naphtho[2,1-b:3,4-b’]dithiophene (M1), was synthesized to be subsequently used as the weak donor structure for the construction of narrow bandgap D–A conjugated polymers in terms of the “weak donor–strong acceptor” concept. The composition and structure of M1 were confirmed by the data of elemental analysis and IR and ¹H and ¹³C NMR spectroscopy. The optical and electrochemical characteristics of the product were measured. The compound M1 was shown to have low-lying HOMO (–5.57 eV), which is favorable for high open-circuit voltage and to be suitable as a promising weak donor moiety in the D–A conjugated polymer for photovoltaic applications.

Features of electroflotation recovery of poorly soluble lanthanum compounds from aqueous solutions containing sodium salts were experimentally determined and studied for the first time. The role was identified that anionic, cationic, and nonionic surfactants added to various supporting electrolytes (sulfate, chloride, carbonate, nitrate) play in the efficiency of electroflotation recovery of poorly soluble lanthanum compounds. The possibility of electroflotation recovery of lanthanum hydroxide with an efficiency of 95–99% was experimentally and theoretically substantiated.