S. D. Babenko

The effect of addition of functionalized graphene oxide on the dielectric properties of epoxy composite

The dependence of the complex permittivity of epoxy composite in the microwave region on the concentration of added amine-functionalized graphene fillers is studied. It is shown that the obtained composites have high values of the dielectric loss tangent at comparatively small values of ɛ′.

Anomalous behavior of dielectric permittivity of graphene-filled polymer composite

Dependences of the dielectric permittivity of a graphene-filled polymer composite and the ESR signal intensity in γ-irradiated samples of this composite on the concentration of graphene additive have been studied. Anomalous behavior of the permittivity correlates with the ESR signal intensity variation, which is indicative of the possible structural rearrangement in the epoxy resin-graphene filler system.

Kinetic analysis of photoelectrochemical hydrogen evolution over p-type silicon in acidic aqueous solutions of electrolytes

The kinetics of photoelectrochemical hydrogen evolution at p-Si single crystals in acidic aqueous solutions of electrolytes under pulse photoexcitation was studied. Despite a low stability of the silicon surface under the experimental conditions, a distinct interrelation between the characteristic time of interfacial charge transfer and stationary current was found. The determination of the characteristic transfer time does not need the detailed elaboration of generation-recombination processes in the semiconductor. The steady-state current density was shown to be determined both for the dark current and photocurrent by the surface charge density.

Transport Properties of Separating Membranes MF-4SK during Alkaline Electrolysis of Water

The transport properties of separating membranes MF-4SK are studied during electrolysis of H2O in solutions of KOH. The effective diffusion coefficients of molecules of KOH and H2O and the transfer coefficients of ions K+ and OH− and molecules of H2O are measured at KOH concentrations reaching 11 M, currents reaching 0.31 A cm−2, at ambient temperature and at 80°C. In contact with a KOH solution in the concentration interval 0.1 to 11 M, the membranes that initially swelled in H2O lose a considerable fraction of water that was present in them and the overall volume of clusters and solution-filled channels in them noticeably decreases. The coefficients of transfer by current of ions K+ out of anodic compartment into cathodic and the OH− ions in the reverse direction, respectively, happen to be equal to about 0.6 and 0.4 at ambient temperature and 0.8 and 0.2 at 80°C. The coefficients of transfer of water molecules out of the anodic volume into the cathodic volume in the process of electrolysis happen to be in the limits 1.6–1.9 at ambient temperature and in the limits 2.2–2.8 at 80°C. The effective diffusion coefficients of molecules of KOH and H2O at moderate concentrations of KOH (5.6 M) amount to ∼2.6 × 10−7 and 30 × 10−7 cm2s−1 at ambient temperature and ∼4 × 10−7 and 61 × 10−7 cm2s−1 at 80°C, respectively. At a high concentration of KOH (∼10 M) these quantities substantially diminish.

Dynamic characteristics of organic bulk-heterojunction solar cells

Transient characteristics of organic bulk-heterojunction solar cells have been studied using pulsed laser probing. An analysis of the photoresponse waveforms of a typical solar cell measured by varying load resistance within broad range at different values of the bias voltage provided detailed information on the photocell parameters that characterize electron-transport properties of active layers. It is established that the charge carrier mobility is sufficient to ensure high values of the fill factor (∼0.6) in the obtained photocells. On approaching the no-load voltage, the differential capacitance of the photocell exhibits a sixfold increase as compared to the geometric capacitance. A possible mechanism of recombination losses in the active medium is proposed.

Paramagnetic centers in a gamma-irradiated polymer composite doped with graphene

The discovery of fullerenes, carbon nanotubes,nanofibers, and graphene stirred interest in searchingfor such carbon nanostructures and their investigationand technical application [1]. According to Novoselovet al. [2], the stable carbon nanomaterails graphenes,which have a thickness of one carbon atom (on theorder of 0.1 nm), can form the basis for the nanotechnology of future.Graphene is a twodimensional atomic layer ofgraphite. It is characterized by a high mechanicalrigidity and high thermal conductivity. Ramanathan etal. [3] report that the addition of 0.05 wt % grapheneto poly(methyl methacrylate) increases the glass transition temperature of the composite by 30°C, and a0.01 wt % admixture of graphene increases the modulus of elasticity of such a nanocomposite by 33%. Theresulting material is superior to polymermatrix composite materials (PCMs) based on carbon nanotubes(CNTs) in its properties. Graphene is believed to be avery promising nanofiller [4], since it can be preparedfrom graphite, whose production cost is well belowthat of CNTs. Stankovich et al. [5] have considered ageneral approach to the formation of PCMs on thebasis of graphene. The process comprises the chemicaloxidation of graphite; its ultrasonic treatment, whichresults in exfoliation into separate oxidized graphenelayers; mixing with a polymer in a solvent; and the subsequent reduction for the removal of oxygencontaining groups.Electron paramagnetic (spin) resonance is a wellknown technique for investigation of carbon nanostructures [6–8]. Garaj et al. [6] studied the ESR spectra of a powder of carbon nanohorns at room temperature and observed two ESR signals, one signal wasbroad (0.45 mT) and the other was narrow (0.25 mT).The broad signal was attributed to graphitelike structures, and the narrow one was ascribed to graphenelike sheets. Ali et al. [7] showed that graphite oxideproduced an EPR signal with a

Influence of conditions for preparation of fullerene-containing carbon black on its microwave properties and yield of fullerenes

Conditions for preparation of the fullerene-containing carbon black with the maximum yield of fullerenes were determined. A correlation between the dielectric constant of the carbon black in the microwave range and the yield of fullerenes was found. The relation of the fullerene-containing carbon black structure to the conditions of its preparation and dielectric constant are discussed.

The transition of spontaneous polymerization of acrylamide to “explosive” regime

Experimental results related to the transition of spontaneous polymerization of acrylamide complexes with metal nitrates to the “explosive” regime at room temperature are presented. It is suggested that the “explosion” has a thermal nature.

Variation of the microwave dielectric permeability of the acrylamide-calcium nitrate system during its spontaneous polymerization

The kinetics of the variation of the complex dielectric permeability at microwave frequencies of 1.1, 1.7, 2.7, and 10 GHz during spontaneous polymerization of acrylamide in the presence of the hydrate of calcium nitrate was studied. The microwave conduction of this system has an ionic nature. It was assumed that some of the water liberated during the polymerization is both transformed into a bound state and forms microinclusions of an electrolyte solution in the bulk of the polymer.

Kinetics of the decay of nitroxyl radicals during polymerization of a complex of acrylamide with bismuth nitrate

Kinetics of the decay of nitroxyl radicals during spontaneous polymerization of complexes of acrylamide (AAm) with BiIII nitrate has been studied by ESR. From a comparison of the experimental and calculated kinetic curves, the initiation rate constant of polymerization has been determined. The approach proposed is suitable for determining the main kinetic characteristics of other polymerizable nonparamagnetic AAm complexes with metal nitrates.