Properties of thermally expandable residual graphite nitrate formed in ambient air

The formation of residual graphite nitrate on keeping in air and the properties of this material were studied in relation to the amount of nitric acid taken for the graphite treatment. The dependence of the expansion ratio on temperature and on the extent of the graphite oxidation was examined. The acidity of the final product was studied in relation to the nitric acid consumption in the final step of the graphite oxidation.     

Atomic force microscopy study of the adsorption of protein molecules on transferred Langmuir monolayer

Ordered protein films have been obtained by the adsorption of protein molecules on a Langmuir monolayer, which had previously formed on a silicon substrate, using the Langmuir-Blodgett and molecular self-organization methods. A mixture of cholesterol with dipalmitoylphosphatidylcholine (DPPC) and a polymer—cellulose acetopivalinate—were used as immobilization materials. Protein molecules (catalase and alkaline phosphatase) immobilized on solid substrates have been investigated by atomic force micros-copy. It was shown that the developed combined technique provides a deposition of homogeneous ultrathin protein films with a high degree of filling.     

Structural Parameters of Cellulose Produced by Acetobacter Xylinum and Their Variation in the Course of Drying of Gel Films

The cellulose-producing power of the VKM V-800 Acetobacter xylinum strain under conditions of static culture was studied. The culture medium was optimized with the aim to increase the cellulose yield and obtain highly crystalline cellulose I with molecular weight of about 5 × 10⁵.     

Composites based on Gluconacetobacter xylinus bacterial cellulose and calcium phosphates and their dielectric properties

Dielectric properties a Gluconacetobacter xylinus bacterial cellulose and its composites with calcium phosphates were studied and used to analyze structural changes in a matrix polymer upon its mechanical treatment and introduction of a mineral fi ller. It was found that, when composites are formed, the ratio between amorphous and crystalline regions is disturbed in the cellulose matrix.     

Specific features of preparing residual graphite hydrosulfate

The hydrolysis of graphite hydrosulfate prepared in the system aqueous solution of sodium dichromate-sulfuric acid was studied, and the composition of gases evolving from the solid phase during the hydrolysis was determined. The effects of the duration of the graphite hydrosulfate hydrolysis on the expansion factor and also on the morphology and particle size of the final product, residual graphite hydrosulfate, was studied.     

Accumulation of deuterium in radiation-damaged tungsten

Experimental studies have been performed to determine the effect of high-level radiation damage on the accumulation of deuterium and erosion of tungsten samples exposed to deuterium plasma. Tungsten samples were exposed first to fast helium ions having an energy of 3–4 MeV (providing from one to ten displacements per atom) and then to deuterium plasma up to a dose of 10²⁵ ion/m². The effects of deformation and modification of the surface microstructure have been observed. The concentrations of helium and deuterium have been measured by the methods of elastic nuclear proton backscattering and nuclear recoil detection of helium ions. A high concentration of deuterium in the damaged layer of a tungsten sample has been measured, and helium has been detected in a layer ～5 μm thick. The proposed method shows promise for determining the lifetime of materials used in fusion reactors and measuring the concentration of tritium accumulated in these materials.     

Photoluminescence and Photoconductivity of Lead Halide Perovskite Films Modified with Mixed Cellulose Esters

Technical Physics - We have investigated the photoluminescence (PL) and photoconductivity of lead halide perovskite (CH3NH3PbBr3) films modified with different mixed cellulose esters (CEs). It was...     

Atomic Force Microscopy Determination of the Direction of Dislocation Lines in Single Crystals of Bismuth and Its Alloys

Crystallography Reports - A technique for determining the directions of dislocation lines using an atomic force microscope after selective etching of a single crystal is discussed. The technique...     

Hydrodynamic, conformational, and optical properties of cellulose tridecanoate molecules in solutions

Cellulose tridecanoates of various molecular weights were synthesized, and their characteristics in chloroform and tetrachloroethane solutions were studied by methods of translational diffusion, velocity sedimentation, flow birefringence (Maxwell’s method), and viscometry. The effects of solvent and temperature on the conformational characteristics of the macromolecules under consideration were examined. The anisotropy of the monomeric unit of cellulose tridecanoates was studied, and the contribution of pendant chains to the optical anisotropy of macromolecules of cellulose esters with aliphatic substituents was analyzed.     

Study of the gel films of Acetobacter Xylinum cellulose and its modified samples by 1H NMR cryoporometry and small-angle X-ray scattering

Gel films of Acetobacter Xylinum cellulose and its modified samples have been investigated by 1H nuclear magnetic resonance (NMR) cryoporometry and small-angle X-ray scattering. The joint use of these two methods made it possible to characterize the sizes of aqueous pores in gel films and estimate the sizes of structural inhomogeneities before and after the sorption of polyvinylpyrrolidone and Se₀ nanoparticles (stabilized by polyvinylpyrrolidone) into the films. According to small-angle X-ray scattering data, the sizes of inhomogeneities in a gel film change only slightly upon the sorption of polyvinylpyrrolidone and nanoparticles. The impregnated material is sorbed into water-filled cavities that are present in the gel film. ¹H NMR cryoporometry allowed us to reveal the details of changes in the sizes of small aqueous pores during modifications.