Dielectric and magnetic properties of nanocomposites based on opal matrixes, phosphates and vanadates of metals
Opal matrix is a regular 3D-packing of spherical particles of amorphous SiO2, forming an
ordered system of voids. Opal matrixes with spherical particles of SiO2 diameter d ≈ 260 nm
(Δd ≈ 2 %) were synthesized. The frequency dependences of the conductivity, real and imaginary
components of the dielectric and magnetic conductivity of nanocomposites containing crystallites
16–65 nm in size of magnetic materials ‒ double phosphates (LiNiPO4, LiCoPO4) and vanadates
(GdVO4 and DyVO4) were measured. The dielectric losses of nanocomposites remain low (at a
level of ~ 0.06) in the frequency range 107–1010 Hz for nanocomposites with DyVO4 and LiCoPO4.
The dielectric loss increases both in the direction of low frequencies (< 106 Hz) and in the direction
of THz frequencies.
Opal matrixes represent the regular 3D-pack of spherical particles of amorphous SiO2, forming an ordered system of voids. Opal matrixes with spherical particles of SiO2 diameter d ≈ 260 nm (Δd ≈ 2%) were synthesized. Nanocomposites were formed by filling voids (occupying ~26% of the volume) of opal matrixes by salt solutions, low-temperature heat treatment at 625–825 K and annealing at 975–1475 K. The formation in the voids of opal matrixes, depending on synthesis conditions, of the synthesized substances, SiO2 and products of interaction synthesized substances with SiO2 are submitted. The frequency dependences of the conductivity, real and imaginary components of the dielectric and magnetic permeability of nanocomposites containing crystallites 16–65 nm in size of magnetic materials — double phosphates (LiNiPO4, LiCoPO4) and vanadates (GdVO4 and DyVO4) were measured. The dielectric losses of nanocomposites remain low (at a level of ~0.06) in the frequency range 107–1010 Hz for nanocomposites with DyVO4 and LiCoPO4. The dielectric loss increases both in the direction of low frequencies (<106 Hz) and in the direction of THz frequencies. Investigations have demonstrated that the measured parameters are influenced by the phase composition, as well as the structural and magnetic state of the synthesized substances.
We present the results of the simulation tests of samples of polymer nanocomposites based on carbon nanotubes for resistance to oxygen plasma in the Earth’s upper atmosphere. Data on the weight loss of the samples, the results of analysis of their surface structure after irradiation, and data on arrays of carbon nanotubes damaged under the effect of oxygen plasma are given. Possible mechanisms of destruction of the nanotubes are discussed.
Nanocomposites TiO2/SiO2 with photocatalytic and adsorptive properties were prepared by codispersing of η-modification and anatase (commercial Hombifine N) and SiO2 (opal, granules, ultrafine) in ethanol (or ethanol–water mixture in the presence of chlorophylls or porphyrins) with ultrasonic treatments of the mixture (method 1) and an aqueous solution of KOH with a microwave treatment (method 2), as well as the introduction of SiO2 in the reaction mixture during the synthesis of TiO2 by brief hydrolysis of sulfate titanyl (method 3). It was found that the state of titania in the sample (X-ray amorphous or nanocrystalline) and its deposition on SiO2 nanocomposites depend on the method and the conditions of obtaining. It was established that the photocatalytic activity of nanocomposite TiO2/SiO2 (granules) (method 1) photosensitized by coproporphyrin I in the visible range and the photocatalytic activity of nanocomposite TiO2/SiO2 (opal) (method 3) in the near UV range exceed activity of the commercial sample of TiSiO4 by more than 20-fold and ~7-fold, respectively. It was shown that the nanocomposite TiO2/SiO2 (opal) significantly reduces the concentration of cations (in particular, Be, Ni, Bi) in the model water systems.
Generalized error-locating codes are discussed. An algorithm for calculation of the upper bound of the probability of erroneous decoding for known code parameters and the input error probability is given. Based on this algorithm, an algorithm for selection of the code parameters for a specified design and input and output error probabilities is constructed. The lower bound of the probability of erroneous decoding is given. Examples of the dependence of the probability of erroneous decoding on the input error probability are given and the behavior of the obtained curves is explained.
The dynamics of a two-component Davydov-Scott (DS) soliton with a small mismatch of the initial location or velocity of the high-frequency (HF) component was investigated within the framework of the Zakharov-type system of two coupled equations for the HF and low-frequency (LF) fields. In this system, the HF field is described by the linear Schrödinger equation with the potential generated by the LF component varying in time and space. The LF component in this system is described by the Korteweg-de Vries equation with a term of quadratic influence of the HF field on the LF field. The frequency of the DS soliton`s component oscillation was found analytically using the balance equation. The perturbed DS soliton was shown to be stable. The analytical results were confirmed by numerical simulations.
Radiation conditions are described for various space regions, radiation-induced effects in spacecraft materials and equipment components are considered and information on theoretical, computational, and experimental methods for studying radiation effects are presented. The peculiarities of radiation effects on nanostructures and some problems related to modeling and radiation testing of such structures are considered.
This volume presents new results in the study and optimization of information transmission models in telecommunication networks using different approaches, mainly based on theiries of queueing systems and queueing networks .
The paper provides a number of proposed draft operational guidelines for technology measurement and includes a number of tentative technology definitions to be used for statistical purposes, principles for identification and classification of potentially growing technology areas, suggestions on the survey strategies and indicators. These are the key components of an internationally harmonized framework for collecting and interpreting technology data that would need to be further developed through a broader consultation process. A summary of definitions of technology already available in OECD manuals and the stocktaking results are provided in the Annex section.