Synthesis of 6H-SiC single-crystal nanowires in a flow of carbon-silicon high-frequency arc plasma

Silicon carbide 6H-SiC nanoparticles and nanowires were obtained in carbon-silicon high-frequency arc plasma plasma in a helium atmosphere at a pressure of 0.1–0.6 MPa. It was shown that 6H-SiC nanowires grow from the arc plasma, as well as from the vapor, according to the known mechanism of vapor-solid condensation on a cold surface covered with single-crystal silicon carbide nuclei. The content of silicon carbide nanowires in the condensate reached 60 wt %. The obtained single-crystal silicon 6H-SiC nanowires had the diameter of 15–18 nm and length of 200–600 nm.     

Highly diastereoselective 1,3-dipolar cycloaddition of nonstabilized azomethine ylides to 3-nitro-2-trihalomethyl-2H-chromenes: synthesis of 1-benzopyrano[3,4-c]pyrrolidines

Reactions of 3-nitro-2-trifluoro(trichloro)methyl-2H-chromenes, including 2-unsubstituted derivatives, with N-alkyl-α-amino acids (sarcosine, proline) and paraformaldehyde proceed diastereoselectively to give 1-benzopyrano[3,4-c]pyrrolidines in good yields as a result of a 1,3-dipolar cycloaddition of the intermediate nonstabilized azomethine ylide at the Δ³-bond of the chromene system.     

Synthesis of new 5-aza-isosteres of guanine—5-aminosubstituted 1,2,4-triazolo[1,5-a]-1,3,5-triazin-7-ones

The reaction of 4-amino-substituted 6-hydrazinyl-1,3,5-triazin-2(1H)-ones with orthoformate proceeds via the Dimroth-type rearrangement to give 5-amino-substituted 1,2,4-triazolo[1,5-a]-1,3,5-triazine-7-ones. IR, NMR and X-ray studies have shown that the only product of the reaction was the [1,5-a]-isomer as prototropic 3H- and 6H-tautomers.     

Synthesis of chromeno[3,4-c][1,2]oxazine-N-oxides via formal [4+2] cycloaddition of 3-nitro-2-trihalomethyl-2H-chromenes with cyclohexanone and pinacolone enamines

3-Nitro-2-trichloro(trifluoro)methyl-2H-chromenes undergo a formal [4+2] cycloaddition reaction to cyclohexanone and pinacolone enamines, producing chromeno[3,4-c][1,2]benzoxazin-6-oxides with high diastereoselectivity and in good yields. In addition, some novel 2,3,4-trisubstituted chromanes were obtained. The stereochemistry of the products was established based on a 2D NOESY experiment and an X-ray diffraction study.     

Product of three Airy beams

A two-dimensional field that is a product of three Airy beams is proposed and investigated. It is shown that the Fourier image of this field has a cubic phase and a radially symmetric intensity with a super-Gaussian decrease. Propagation of the product of three Airy beams in a Fresnel zone is investigated numerically.     

LiVPO4F/Li3V2(PO4)3 nanostructured composite cathode materials prepared via mechanochemical way

Single-phase LiVPO₄F and LiVPO₄F/Li₃V₂(PO₄)₃ nanostructured composite cathode materials were prepared by heating of the VPO₄?+?LiF mechanochemically activated mixture to 700 °C and subsequent quick or slow cooling to room temperature, respectively. The formation of the composites was proved by a combination of different physico-chemical methods, including XRD, FTIR, ⁶Li and ³¹P NMR, SEM, TEM, and HRTEM. It has been shown that in the composites LiVPO₄F and Li₃V₂(PO₄)₃ nanocrystals well inset into each other resulting in the nanodomain composite formation. Charge–discharge curves of the composites have a sloping profile both in the high-voltage (3.0–4.5 V) and in the low-voltage (1.3–2.5 V) ranges, noticeably different from plateaus for a phase-pure LiVPO₄F, thus indicating a probable change of a two-phase regime of lithium intercalation for a single-phase one. Enhanced rate capability of the LiVPO₄F/Li₃V₂(PO₄)₃ composites is associated with their microstructure and high ionic conductivity of Li₃V₂(PO₄)₃.     

Proton magnetic resonance spectra of homoannular ferrocenes

The proton magnetic resonance spectra of homannular isomeric diethyl- and diacetyl-ferrocenes were studied. Chemical shifts were determined, and the results are discussed in terms of inductive and hyperconjugative effects of the substituent groups.