Transport properties of cellulose ester membranes for separating gas and liquid mixtures

Mass-exchange characteristics of cellulose myristate or acetomyristate membranes in separating aqueous-organic, organic, or gas mixtures, particularly, in recovering aromatic hydrocarbons from binary mixtures with aliphatic alcohols, and also ethyl acetate from a mixture of esterification products, are studied.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 11, 2004, pp. 1895–1900.Original Russian Text Copyright © 2004 by Yu. Kuznetsov, Khripunov, Kruchinina, V. Kuznetsov, Turkova, Penkova.     

Self-organization of structures on a bismuth single-crystal surface in an atmosphere of atomic hydrogen

The morphology of a cleavage surface of single-crystal bismuth has been studied by atomic force microscopy after treatment in atomic hydrogen. It has been ascertained that the surface relief changes due to the formation of micro- and nanocrystalline structures.     

Analysis of a tungsten surface irradiated by fast ions and deuterium plasma

The effects occurring on the surface of tungsten under irradiation with fast ions with an energy in the megaelectrolvolt range and with high fluxes of hydrogen (deuterium) plasma are considered. These effects are radiation damage of the surface layer of the material, its erosion and deuterium retention in it. Irradiation with helium ⁴He²⁺ (3.2–4.0 MeV) and carbon ¹²C³⁺ (10 MeV) ions is performed using a cyclotron at the National Research Center Kurchatov Institute. The thickness of the damaged layer is 3.5–6 μm. The irradiated samples are exposed to steady-state deuterium plasma using a LENTA linear plasma facility to reach a plasma ion fluence of 10²¹–10²² cm^?2. Tungsten erosion and modification of the structure of the damaged layer are analyzed at a plasma-ion energy of 250 eV. Deuterium retention in the damaged layer is studied by elastic recoil detection analysis. The deuterium concentration and its penetration depth into the material are measured. The data obtained for different kinds of fast ions used in the work are compared.     

Study of the impact of steady-state plasma on radiation-damaged tungsten

Experimental studies of tungsten (as a candidate plasma-facing material for a fusion reactor) whose properties will degrade as a result of its contact with near-wall plasma and irradiation with neutrons are performed. The effect of a high level of radiation damages (1–100 displacements per atom) on deuterium accumulation and erosion caused by tungsten irradiation with deuterium plasma was studied. Radiation damages are obtained as a result of the irradiation of tungsten samples with high-energy ions in an accelerator (He⁺², C⁺³, 4–10 MeV). Then the samples are exposed to steady-state deuterium plasma at the LENTA facility (National Research Centre Kurchatov Institute). The effects of the erosion of tungsten and accumulation of hydrogen isotopes in it are studied. Modification of the surface microstructure and radiation swelling is observed. The helium and deuterium concentrations were measured using the methods of nuclear elastic backscattering and elastic recoil detection analysis. An increased accumulation of deuterium in the damaged layer to a depth of about 5 μm is revealed.     

Conformational, optical, and electrooptical properties of cellulose pelargonates in solutions

Newly prepared cellulose pelargonate samples of various molecular weights were studied in dioxane and chloroform solutions by isothermal translation diffusion, high-speed sedimentation, flow birefringence (Maxwell effect), electric birefringence (Kerr effect), and viscometry. The conformational, hydrodynamic, optical, electrooptical, and dynamic characteristics of the polymer were determined.     

Morphology of the surface of sorbents based on a copolymer of styrene and divinylbenzene according to atomic force spectroscopy data

Studies of the surface of polymer complexing sorbents (PCSes) with an o, o′-dioxy-(1-azo-1′) functional analytic group were conducted by means of atomic force spectroscopy (AFM). The characteristic linear dimensions of surface relief objects and their fractal dimensions were determined. The PCS roughness parameters (the mean-root-square profile roughness and average arithmetic roughness) were established and the quantitative dependence between them and the scanning scale was found. The effect of temperature on the sorbents’ structural organization was demonstrated. The obtained data enable us to solve the problem of sorption process intensification through the targeted impact of the class of compounds under examination on the supramolecular structure and polymer substrate morphology in creating the optimum conditions of sorption with PCS participation.     

Phase transitions of native celluloses from evolutionarily different sources into polymorph IV

A procedure was suggested for preparing cellulose polymorph IV by dissolution of native celluloses from evolutionarily different sources in trifluoroacetic acid to molecularly dispersed state, followed by regeneration and treatment under hydrothermal conditions.     

Hydrodynamic and conformational properties of cellulose valerate molecules in dilute solution

Using the methods of molecular hydrodynamics, structural-conformational studies have been performed for a number of cellulose valerate and acetovalerate samples in the molecular-mass range M = (58.1–464.3) × 10³ and with a mean degree of substitution of 182.4 with respect to valeric acid isomers. The conformations of valerate-substituted cellulose molecules are characterized by an increased local packing density of monomer units. The molecular conformations are quantitatively described in terms of the helix formed by the succession of vectors connecting glycoside oxygens of a chain. The molecular-hydrodynamic and conformational characteristics of cellulose valerate are compared with the corresponding characteristics of cellulose myristate.     

Structure of cellulose <Emphasis Type="Italic">Acetobacter xylinum</Emphasis>

The data are presented on optimization of cellulose synthesis by Acetobacter xylinum (strain VKM V-880) and the structural characteristics of A. xylinum cellulose gel film synthesized during static cultivation. The structural changes caused by the removal of water from gel films are established and the structural organization of macromolecular chains in cellulose A. xylinum is studied.