Magnetic fluids stabilized by polypropylene glycol

A series of samples of magnetic fluids stabilized with low-molecular weight polypropylene glycol (PPG) of different molecular masses were synthesized. The use of PPG allowed the maximum extension of the carrier fluid range to include ethyl- and butyl-acetate, ethanol, butanol, acetone, carbon tetrachloride, toluene, kerosene and PPG itself. Magnetic and rheological properties of the samples were investigated. Based on the results of investigation it has been concluded that magnetic nanoparticles are covered by a monolayer of surfactant molecules. At low temperatures the propanol-based sample preserves fluidity up to −115 °C. Measurement of critical temperatures of other base fluids showed that alcohols are the best carrier medium. Coagulation stability of the ethanol-based ferrocolloid with respect to water and kerosene was explored. It has been found that kerosene, whose fraction by weight exceeds 22.5%, does not mix with the colloid. This effect can be used to produce magneto-controllable extractors of ethyl alcohol. Under the action of water the colloid coagulates, which allows one to substitute the carrier fluid and to separate the colloid into fractions.     

Mechanisms of nuclear reactions at interaction of cosmic rays with materials and nanostructures

The mechanism of failures of microelectronic elements, caused by ionization of atoms by recoil nuclei and secondary fragments formed at nuclear interactions of cosmic-ray protons and light ions with substance, has been analyzed. Models of nuclear physics are used to calculate the macroscopic failure cross section.     

An electromechanical nanothermometer based on thermal vibrations of carbon nanotube walls

Physics of the Solid State - A new concept is proposed for an electromechanical nanothermometer. The temperature measurements are performed by measuring the conductivity of the nanosystem, which...     

Absolute negative conductivity in graphene with the Hubbard interaction in a magnetic field

The current-voltage and current-magnetic field characteristics for a graphene with the electron Hubbard interaction at low temperatures have been calculated in terms of the average electron method. The characteristics obtained have been analyzed as a function of the frequency of the external ac electric field and the magnetic field strength. The portion with an absolute negative conductivity has been revealed.     

Hybrid composites based on organic-inorganic sol-gel systems

Hybrid organic-inorganic composites were developed on the basis of sodium silicate modified with ɛ-caprolactam or ɛ-aminocaproic acid and isocyanate-containing oligourethane with improved physicomechanical properties and water resistance.     

Evolution of the structure of near-surface ultrahigh molecular weight polyethylene nanolayers during orientational drawing

A comparative investigation of the surface structure of ultrahigh molecular weight polyethylene film filaments obtained with different draw ratios from xerogels prepared from 1.5 wt % polymer solutions in decaline and mineral oil has been performed using a SUPRA-55V scanning electron microscope and a nanoluminograph for recording thermoluminescence of ultrathin near-surface layers of solids. It has been found that, with an increase in the draw ratio, the luminescence intensity decreases, and the peaks responsible for the segmental mobility are shifted toward higher temperatures. It has been assumed that this is associated with the improvement of the structure of near-surface layers of the polymer (with a decrease in the number of microcavities and segments of molecules with a high degree of coiling). It has also been revealed that the peaks observed in glow curves of the oriented gel samples from polymer solutions in decaline are shifted more significantly than those of the gel samples from polymer solutions in mineral oil, and the extremely oriented films are characterized by a large discretization of kinetic units of motion.     

Study of multigraphene films prepared by sublimation on the sic surface

Graphene films were prepared by sublimation epitaxy of SiC under vacuum. The films were studied by Auger electron spectroscopy, reflection high-energy electron diffraction, atomic force microscopy, and Raman spectroscopy. It is concluded that the films prepared are polycrystalline and consist of graphene single crystals about 50 nm in size.     

Phonon relaxation and internal friction in heterogeneous systems based on poly(vinyl chloride)

Phonon relaxation and internal friction in kaolin-and bentonite-filled PVC composites are studied. By varying the temperature and/or content of the ultrafine mineral filler in the PVC, one can control the contribution from phonon viscosity, damping force, and the effect of viscosity into the energy dissipation of ultrasonic oscillations in the MHz frequency interval. The dynamic character of the measurements makes it possible to differentiate between relaxation phenomena in the composites and to suggest methods for their controlled changes.     

Modified fluororubbers based on SKF-26: Relaxation and mechanical properties

Samples of SKF-26 fluororubber modified by incorporating pendant methoxy groups into the macromolecular chain were studied by dielectric spectroscopy and dynamic mechanical analysis.