Formation of cluster structures on thermoexfoliated graphite by electrochemical method

Nickel-plating thermoexfoliated graphite particles were prepared by cathodic polarization of three-dimensional electrodes in diluted nickel sulphate aqueous solutions. X-ray photoelectron spectroscopy and X-ray diffraction techniques were employed for analysis of the particles surface. It has been found that oxidation process of the electrodeposited nickel clusters occurs due to their high reactivity. The presence of essential amounts of bound oxygen on surface of thermoexfoliated graphite particles was demonstrated by cyclic voltammetry and X-ray photoelectron spectroscopy methods. The role of oxygen-containing groups on the surface of thermoexfoliated graphite in the processes of adsorption and subsequent reduction of nickel ions at cathodic polarization as well as the behaviour in neutral aqueous solutions of natural graphite electrodes, intercalated with sulfuric acid and thermoexfoliated, are discussed

Exciplexes of fullerene C60 with aromatic solvents

The solvent induced spectral shift method is applied to study stacking interactions between aromatic solvents molecules, such as benzene and toluene from one side, and solute fullerene C60. Ratios of high-energy transitions shifts to calculated shifts under dispersion interactions are considered. It is concluded that in contrast to aromatic molecules containing two or three rings which do not form complexes with aromatic solvents, fullerene forms exciplexes with high-energy excited states involved in more strong interactions rather than low-energy one. The higher is excited state, the stronger is interaction. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2062

Optical properties of metal-composite-based thin films

In the first part of this work we study the effect of a semi-infinite matrix dispersed system (MDS) on the external electromagnetic radiation in the electrostatic approximation. With the help of our previous technique, we obtain general expressions for the multipole expansion coefficients of the electric potential for a sphere accounting for the interaction between ambient particles and the substrate. The polarizability tensor and resonant frequencies of a single sphere show anisotropy due to the influence of a substrate. In the second part electrodynamical properties of thin percolating layers manufactured on the basis of the MDS are considered. Transition from 3-D to 2-D behavior, which is observed near the percolation threshold and shows itself as changing of some parameters (in comparison with those for 3-D percolating system) like the values of percolation threshold, critical indices of conductivity and permittivity, were studied

Defect formation in the intermediate layers of YBa₂Cu₃O₇₋δ superconductors depending on oxygen сontents

In YBa₂Cu₃O₇₋δ superconductors with 0≤δ0.3 the subthreshold defect formation in the intermediate layers is not observed. The subthreshold defect formation is related to the Coulomb ejection of atoms from the lattice sites in the field of the weakly damped low-frequency collective excitations enhanced by irradiation in YBa₂Cu₃O₇₋δ superconductors with δ≤0.3

Low-field electron emission and cathode luminescence of piezoelectric films of oxides and chalcogenides

Basic parameters of effective low-field emitters of electrons of piezoelectric films for bright flat cathode luminescent display and other activity are optimised. Specimens of electron emitters of cathode luminescent screens are based on compounds of SiO₂, ZnO, ZnS, solid solution of Zn1-xCdxS. High efficient "cold" emitters of electrons were prepared on the basis of mono- and polycrystalline films. The emission and cathode-luminescent properties of the films were investigated. It is shown that developed films are perspective like the flat displays with the brightness of 300 Cd/m²

Subthreshold defect formation in YBa₂Cu₃O₇₋δ at nonuniform heating of electron gas in electromagnetic field

In YBa₂Cu₃O₇₋δ high temperature superconductors with δ<0.3 the irradiation by super high-frequency electromagnetic field with impulse power 10⁴-10⁶ W gives rise to a decrease of the rates of annihilation and capture of positrons, a growth of resistance, residual resistance, thermopower and the block of diffusive transitions of Au atoms, which are caused by the subthreshold defect formation in the intermediate layers. The irradiation effect is enhanced with rise of the number of defects in samples and does not depend on an impulse power. The defect formation is related to the excitation of low-frequency weakly damped collective excitations under irradiation, whose propagation through the crystal is accompanied by the Coulomb ejection of atoms from the lattice sites and the transformation and transport of defects

Impact of Few-Layered Graphene Plates on Structure and Properties of an Epoxy Resin

Impact of few-layered graphene (FLG) plates on the properties of the ED-20 epoxy resin is experimentally studied by using various techniques. The average dimensions of FLG plates are estimated as about 50 nm in thickness and 5 μm in both width and length. The FLG-mass-loading, Cf, in the nanocomposites is ranged from 0.01% to 5%. On the whole, the FLG plates promote an improvement in the thermal and chemical resistivities of the nanocomposites due to the chemical binding of the epoxy macromolecular chains to the free carbon bonds located on lateral verges of the plates. On the other hand, the FLG plates worsen the tensile strength of the nanocomposites at Cf > 0.01%, whereas the dynamic elastic moduli undergo small variations.С использованием различных методик экспериментально исследовано влияние многослойных графеновых (МСГ) пластинок на свойства эпоксидной смолы ЭД-20. Средние размеры МСГ-пластинок составляли примерно 5 мкм в длину и ширину и 50 нм по толщине. Массовая нагрузка Cf МСГ-пластинок в нанокомпозитах изменялась от 0,01% до 5%. В целом, МСГ-пластинки способствуют улучшению как термической, так и химической стойкости нанокомпозитов вследствие химического связывания макромолекулярных цепочек смолы со свободными углеродными связями, локализованными на боковых гранях пластинок. С другой стороны, МСГ-пластинки ухудшают предел разрушения нанокомпозитов при наполнениях Cf > 0,01, в то время как динамические упругие модули претерпевают незначительные изменения.З використанням різних методик експериментально досліджено вплив багатошарових графенових (БШГ) платівок на властивості епоксидної смоли ЕД-20. Середні розміри БШГ-платівок складали приблизно 5 мкм у довжину та ширину і 50 нм у товщину. Масове навантаження Cf БШГ-платівок у нанокомпозитах змінювалося від 0,01% до 5%. У цілому, БШГ-платівки спричиняють поліпшення як термічної, так і хемічної стійкости нанокомпозитів внаслідок хемічного зв’язування макромолекулярних ланцюжків смоли з вільними Карбоновими зв’язками, що локалізовані на бічних гранях платівок. З іншого боку, БШГ-платівки призводять до погіршення межі міцности нанокомпозитів за наповнень Cf > 0,01%, хоча динамічні пружні модулі зазнають незначних змін

Surface Chemistry in Modern Nanotechnologies

A review of the properties of fine oxide surfaces at the nano level is given based on the author's work. It includes a scheme related to the structure of pyrogenic silica and the changes induced by dehydroxylation as studied by quantum chemical and spectroscopic methods. The application of non-linear optical methods has appeared to be useful for the investigation of disperse solid structures. Quantitative measurements of intermolecular interaction have been obtained by light scattering. Alteration of the surface activity due to gas-phase electron–donor molecule action on chemisorbed complexes or functional groups on the surface is considered. It is also shown how the physicochemical properties of a solid surface can be changed as a result of chemical modification. The investigations discussed could lead in practice to the creation of new lightweight ceramic materials, adsorbents, catalyst supports, hollow-body microspherical fillers and medicinal preparations. Some of these are useful for nano electronics and instrument design as well as for the solution of some meteorological problems