Alkali metal and ammonium fluoro(trifluoroacetato)metallates M′[M′′3(μ3-F)(CF3COO)6(CF3COOH)3], where M′ = Li, Na, K, NH4, Rb, or Cs and M′′ = Ni or Co. Synthesis and crystal structures

A series of fluoro(trifluoroacetato)metallates were synthesized by crystallization from solutions in trifluoroacetic acid containing nickel(II) or cobalt(II) nitrate hydrates and alkali metal or ammonium fluorides: Li[Ni₃(μ₃-F)(CF₃COO)₆(CF₃COOH)₃](CF₃COOH)₃ (I), M′[Ni₃(μ₃-F)(CF₃COO)₆(CF₃COOH)₃] (M′ = Na (II), NH₄ (IV), Rb (V), and Cs (VI)), NH₄[Co₃(μ₃-F) (CF₃COO)₆(CF₃COOH)₃] (III), and Cs[Ni₃(μ₃-F)(CF₃COO)₆(CF₃COOH)₃](CF₃COOH)_0.5 (VII). The crystal structures of these compounds were determined by single-crystal X-ray diffraction. All structures contain triangular trinuclear complex anions [M ₃″(μ₃-F)(CF₃COO)₆(CF₃COOH)₃]^? (M″ = Ni, Co) structurally similar to trinuclear 3d metal oxo carboxylate complexes. The three-coordinated F atom is located at the center of the triangle formed by Ni(II) or Co(II) atoms. The metal atoms are linked in pairs by six bridging trifluoroacetate groups located above and below the plane of the [M″₃ F] triangle. The oxygen atoms of the axial CF₃COOH molecules complete the coordination environment of M″ atoms to an octahedron.     

Non-ozone-depleting hydrofluorocarbons

The state-of-the-art of transition of the chemical sector producing ozone-depleting substances (ODS) in Russia to non-ozone-depleting substances (NODS) is considered. The review summarizes the studies conducted by the Russian Scientific Center Applied Chemistry (St. Petersburg) and a number of Russian Academy Institutes including substantiation for the production methods of non-ozone-depleting hydrofluorocarbons; the most probable chemical mechanisms of their synthesis; the basis for standard process flow diagrams to be used in their full-scale manufacture; and the information on actual and newly created NODS production facilities in the Russian Federation.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2364–2371, November, 2004.     

Low-temperature method of cleaning <Emphasis Type="Italic">p</Emphasis>-GaN(0001) surfaces for photoemitters with effective negative electron affinity

The changes in the chemical composition, atomic structure, and electronic properties of the p-GaN(0001) surface upon chemical treatment in an HCl-isopropanol solution and vacuum annealing are investigated by x-ray photoelectron spectroscopy, high-resolution electron energy-loss spectroscopy, and low-energy electron diffraction. It is demonstrated that a considerable part of the surface gallium oxide is removed upon chemical treatment of the GaN surface. Subsequent annealing of the surface under vacuum at temperatures of 400–450°C leads to a decrease in the residual carbon and oxygen contamination to 3–5% of the monolayer. The preparation of a clean p-GaN(0001) surface with a (1×1) structure identical to that of the bulk unit cells is confirmed by the low-energy electron diffraction data. The cesium adsorption on the clean p-GaN surface results in a decrease in the work function by ～2.5 eV and the appearance of an effective negative electron affinity on the surface. The quantum efficiency of the GaN photocathode at a wavelength of 250 nm is equal to 26%.     

Recrystallization of cold-rolled copper and the fourier analysis of the elastic anisotropy

The presence in cold-rolled electrolytic copper sheet of a texture of the type {134}, [4¯85] has been established by x-ray methods and by analysis of the elastic anisotropy. The modulus diagrams of the sheet are described by a Fourier series of the form: E = r₀ – r₂ cos2 + r₄ · cos 4.After annealing at temperatures up to 160 °, the free term in the expansion slowly increases, while the amplitudes of the second and fourth harmonics remain unchanged. Above 160 ° the second harmonic gradually disappears in the course of recrystallization, and the amplitude of the fourth harmonic increases at the same time. The modulus diagram is described by the series E = r₀ + r₄ cos 4.Fourier analysis reveals the steady development of the orientation (100) [001], even in the initial stages of recrystallization, although x-rays show no traces of the new structure up to 250 °.     

Calibration of scintillation counters of the upgraded calorimeter of the IHEP-JINR Neutrino Detector for time of flight particle identification

In this paper, specific features of operation of the calorimeter of the IHEP-JINR Neutrino Detector on the basis of liquid scintillation counters upgraded for time of flight particle identification are described. Data acquisition system, algorithms of response reconstruction, and calibration of calorimeter counters are described in detail. Estimate of time and spatial resolution of counters is obtained on tracks of vertical cosmic muons. The averaged time resolution is σ = 1.2 ns, and the coordinate resolution is σ = 13 cm.     

Flame structure of composite pseudo-propellants based on nitramines and azide polymers at high pressure

The chemical and thermal structures of flame of composite pseudo-propellants based on cyclic nitramines (HMX, RDX) and azide polymers (GAP and BAMO–AMMO copolymer) were investigated at a pressure of 1.0 MPa by molecular beam mass spectrometry and a microthermocouple technique. Eleven species H₂, H₂O, HCN, CO, CO₂, N₂, N₂O, CH₂O, NO, NO₂, and nitramine vapor (RDX_v or HMX_v), were identified, and their concentration profiles were measured in HMX/GAP and RDX/GAP pseudo-propellant flames at a pressure of 1 MPa. Two main zones of chemical reactions in the flame of nitramine/GAP pseudo-propellants were found. In the first, narrow, zone 0.1 mm wide (adjacent to the burning surface), complete consumption of nitramine vapor and NO₂ with the formation of NO, HCN, CO, H₂, and N₂ occurs. In the second, wider high-temperature zone, oxidation of HCN and CH₂O by NO and N₂O with the subsequent formation of CO, H₂, and N₂ takes place. The leading reactions in the high-temperature zone of flame of nitramine/GAP pseudo-propellants are the same as in the case of pure nitramines. In the case of nitramine/BAMO–AMMO pseudo-propellants a presence of carbonaceous particles on the burning surface did not allow us to analyze the zone adjacent to the burning surface, therefore only one flame zone was found. Temperature profiles in the combustion wave of nitramine/azide polymer pseudo-propellants were measured at 1 MPa. The data obtained can be used to develop and validate a self-sustain combustion model for pseudo-propellants based on nitramines and azide polymers.     

Porous Pd-containing polypropylene membranes for catalytic water deoxygenation

Water deoxygenation has been studied in a catalytic membrane reactor in which oxygen is reduced with hydrogen fed into the hollow fiber of a porous polypropylene membrane containing palladium metal on its outer surface. Palladized fibers obtained by different methods and the initial fibers have been characterized by dynamic desorption porosimetry, gas permeability measurements, X-ray structure determination, and light microscopy. The possibility of efficient water deoxygenation at room temperature is demonstrated.     

Trimethylsilyl ethers of amphiphilic carbosilane dendrimers of the third–fifths generations. Specific features of hydrolysis at the water-air interface

Carbosilane dendrimers from the third to fifth generation with hydroxy groups in the surface layer of the dendrimer were synthesized, as well as their analogs with latent hydroxy groups. The dendrimers differ by the density of the carbosilane core and hydrophilic shell. The amphiphilic nature of the synthesized compounds was manifested already for more hydrophobic trimethylsilyl derivatives of dendrimers. This allowed one to observe the hydrolysis of these objects during compression of their monolayers at the water surface in the Langmuir bath. The parameters of the molecular structure of the dendrimers exert a determining effect on the rate and completeness of the hydrolysis. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2125–2133, November, 2007.     

Synthesis of 6-(α-thienyl)azulene from 2-butoxy-4-(α-thienyl)-Δ5-dihydropyran

2,5-Dibutoxy-4-(α-thienyl)-Δ³-dihydropyran was obtained by bromoalkoxylation at the double bond and dehydrobromination of 2-butoxy-4-(α-thienyl)-Δ⁵-dihydropyran. Acid hydrolysis of the product in the presence of N-methylaniline hydrochloride gave a salt of 3-(α-thienyl)glutaconic dialdehyde dianil, treatment of which with cyclopentadienylsodium in alcohol gives the corresponding fulvene, which is thermally cleaved to N-methylaniline and 6-(α-thienyl)azulene.