1H Nuclear Magnetic Relaxation Spectroscopy of Ultradispersed Diamond Hydrosols

The spin-lattice relaxation of water protons in hydrosols of ultradispersed diamonds with the volume content of the dispersed phase up to 1% is studied by the high-resolution NMR. The relaxation rate of water protons is measured as a function of the dispersed phase concentration. It is shown that hydrosols of ultradispersed diamonds can be used as model systems for studying the relaxation parameters of aqueous phases in heterogeneous media.     

Adsorption properties of ultradispersed diamonds

The adsorption capacity of ultradispersed diamonds for synthetic dyes and medicinal preparations was studied.     

Sorption of nitrogen-containing aromatic compounds on ultradispersed diamonds

Adsorption of a number of aniline and pyridine derivatives from water-acetonitrile solution on ultradispersed diamonds was investigated using dynamic sorption method. It was shown that the nature of functional substitutes and their position in molecules of nitrogen-containing compounds of pyridine and aniline have a pronounced effect on adsorption on the surface of ultradispersed diamonds. The dependence of chromatographic sorbate retention on the content of mobile phase could be described by a curve with a minimum. Such nonlinear relationship was explained by the change in the ratio of contribution of specific and non-specific interaction to the sorbate retention that was observed on varying the volume content of an organic component in mobile phase. The influence of temperature on sorption of pyridine and aniline derivatives on ultradisperesed diamonds was investigated. The changes in enthalpy and entropy factors of competitive sorption of sorbates were determined.     

Influence of Allotropic Forms of Carbon on Formation and Cross-Linking of Heat-Resistant Polymer Binders

The thermochemical reactions of polyimide binder with various allotropic forms of carbon, fullerene C₆₀ and ultradispersed artificial diamonds, were studied by thermal and spectral analyses.     

Study of the Composition and Physicochemical Properties of Diamond Hydrogels

Six fractions of ultradispersed diamonds with different aggregate sizes are separated from a hydrogel stable with respect to sedimentation by the step-by-step ultracentrifugation. Distribution of carbon phases and impurities between the fractions is studied, and the fraction densities are calculated and experimentally determined. The structure and surface chemical composition of the dispersed phase in the diamond hydrogel are shown to be nonuniform.     

Surface chemistry of ultradispersed diamonds

The type and amount of functional groups on the surface of ultradispersed diamonds were determined. The adsorption of potential-determining ions was studied in relation to various factors, and the surface charge density was evaluated. The influence exerted by thermal treatment in argon and hydrogen on the functional composition of the surface was analyzed.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 12, 2004, pp. 1956–1959.Original Russian Text Copyright © 2004 by Eremenko, Besedina, Obraztsova.     

Use of Chelate Complexes of Lead(II) in Low-Temperature Technologies of Ceramic Piezoelectric Materials

Technology is suggested for fabrication of ceramic piezoelectric materials from the lead-containing ferroelectric phase. The technology includes a low-temperature synthesis of ultradispersed lead titanate and zirconate powders and also of phases of solid solutions on their basis and the low-temperature procedure for sintering of ceramic fabricated from ultradispersed powders of ferroelectric phases. As precursors used in the suggested low-temperature synthesis serve lead glycerate and tartrate. It was found that, when interacting (at temperatures of 240–330°C) with hydroxo-peroxo-aqua complexes of titanium and(or) zirconium(IV) in the course of 30–40 min, the precursors form ultradispersed powders of these phases, which are single-phase and contain particles with average size of less than 100 nm. It was shown that using the suggested technology makes it possible not only to reduce the energy expenditure for separate procedures for synthesis of ultradispersed ferroelectric phases and for synthesis of piezoelectric materials, but also to substantially diminish the discharge of lead(II) compounds into the atmosphere of industrial premises. It was also shown that the technology enables fabrication of piezoelectric materials with prescribed values of electrical parameters.

     

Energy characteristics of the process of air scrubbing from hydrocarbon contaminants in a barrier-discharge reactor

The electrical and chemical characteristics of air scrubbing, using a barrier discharge, from impurities of xylene, a typical organic contaminant, have been investigated. Based on the interrelation between the electrical and chemical characteristics, an approach to the optimization of the cleaning process has been proposed that allows a severalfold reduction of the energy input.     

Synthesis and colloidochemical properties of yttrium oxohydroxyde hydrosols

Abstaract  It is shown that hydrosols of oxygen-containing compounds of yttrium may be prepared by the peptization and condensation methods. Basic characteristics of hydrosols, such as the size and shape of particles, their phase compositions, electrophoretic mobility, and the pH range of the dispersion medium where sols are stable with respect to aggregation, are determined. Coagulation thresholds of the sols are estimated in the presence of sodium nitrate and sulfate. It is found that the hydrosols coagulate reversibly. Concentration and aging of the sols give rise to the spontaneous formation of slightly structured thixotropic gels. The nature of the aggregation stability of hydrosols is suggested. Original Russian Text ? I.A. Belova, K.I. Kienskaya, A.S. Grodskii, V.V. Nazarov, 2008, published in Kolloidnyi Zhurnal, 2008, Vol. 70, No. 5, pp. 601–606.     

Polytetrafluoroethylene-based polymeric composite materials intended for triboengineering applications

The influence of ultradispersed ceramics particles on formation and wear of polytetrafluoroethylene-based polymer composites was elucidated. Factors improving the performance characteristics of the composites were identified.     

Modification of polypropylene fibrous materials with ultradispersed polytetrafluoroethylene

The effects of narrowly and widely dispersed fractions of ultradispersed polytetrafluoroethylene on the structures of melt-spun polypropylene fibrous materials and the ultimate tensile half-cycle characteristics of polypropylene filaments and nonwoven materials have been studied via X-ray diffraction analysis, optical microscopy, and differential scanning calorimetry. It has been shown that the addition of 1–2% ultradispersed polytetrafluoroethylene, which exists as an individual phase in polypropylene, allows a significant increase in the relative tensile stress of the filament and its elastic modulus.     

Synthesis and Use of Highly Dispersed Zinc Oxide

Methods for synthesis of zinc oxide hydrosols by peptization and condensation were developed. The basic colloid-chemical properties of the sols were determined: electrokinetic properties, size and phase composition of particles, and stability of hydrosols against introduction of electrolytes. The possibility of obtaining antibacterial and UV-protecting cosmetic preparations from the hydrosols obtained was demonstrated.     

Effect of method of titanium dioxide hydrogel synthesis on hydrosol properties

Effect of method of titanium dioxide hydrogel precipitation from TiCl₄ and NH₄OH solutions on the properties of 0.0025–0.44 M hydrosols prepared by exposure to ultrasound radiation was studied. The hydrosols was shown to contain primary particles united into aggregates with average size 22–120 nm irrespective of hydrogel precipitation method. The method of hydrogel precipitation affects the size and porosity of the aggregates in the hydrosols.     

Synthesis and Some Colloidal Properties of Hydrosols Prepared by the Hydrolysis of Copper(II) Nitrate

The synthesis of hydrosols of copper(II) basic salts by the hydrolysis of copper(II) nitrate in the presence of ammonia was developed. A pH range and an optimal molar ratio [Cu²⁺] : [OH^–] = 1.1 : 1.0, at which hydrosols stable with respect to sedimentation were formed, were determined. The average hydrodynamic radius of dispersed phase particles ranging from 220 to 280 nm was measured by the photon correlation spectroscopy. It was shown that the hydrosols can be stabilized by poly(vinyl alcohol), and its optimal concentration providing their aggregation stability was determined. The thresholds of fast coagulation of the initial and stabilized hydrosols in the presence of potassium chloride and ammonium sulfate were found.     

Synthesis of hydrosols of oxygen-containing cobalt compounds

A procedure is developed for the synthesis of hydrosols of oxygen-containing cobalt compounds. The hydrosols are stable to aggregation for several weeks in the absence of additional stabilizers. It is established that the synthesized hydrosols contain crystalline particles formed from a mixture of CoO(OH) and Co₃O₄. According to transmission electron microscopy data, the most probable diameter of the particles is about 30 nm. The hydrosols are stable to aggregation at pH 6.2?C8.0. In this pH range, the particles are positively charged and the values of their electrokinetic potential are no higher than 10 mV.     

The effect of doping of the ultradispersed nickel powder by pyrocarbon on oxygen adsorption and Oads + CO reaction

Oxygen adsorption and chemisorption and the kinetics of interaction between adsorbed oxygen and CO on nickel ultradispersed powder (average size of particles, 20 nm) are studied. The ultradispersed nickel powder was dosed by the products of pyrolysis of chemisorbed ethylene (pyrocarbon) in the amount of 0.1–1.6 of a monolayer. The spectra of ferromagnetic resonance of the ultradispersed nickel powder before and after ethylene adsorption and pyrolysis and after adsorption and chemisorption of oxygen and its reduction by hydrogen are recorded. The magnetization of ultradispersed nickel powder increases upon dosing the surface with ethylene (C₂H_4ads) and pyrocarbon in the amount of 0.5 of a monolayer. Pyrocarbon inhibits the O_ads + CO reaction. The reaction orders with respect to O_ads and CO and the experimental activation energy change. The effects of small (less than a monolayer) and large (more than a monolayer) amounts of the modifying agent are different.     

SYNTHESIS OF SOAP-FREE ACRYLIC HYDROSOLS

Poly(methyl methacrylate/ethyl acrylate/acrylic acid) hydrosols were prepared by employing soap-freepolymerization, and (acrylic acid/butyl acrylate) oligomer was used as the polymeric surfactant The effect of reactioncondition on the morphology and particle size of the hydrosols was investigated. The minimum amount of acrylic acid in thehydrosols is 2%. The maximum weight average molecular weight (M_w) of polymer that assures soap-free emulsionconversion into hydrosol is about 1.2×10~5-1.3×10~5. The particle transforming process was investigated, and an obviouschange of particle diameter and morphology was observed.     

Colloidal properties of CeO<Subscript>2</Subscript>-ZrO<Subscript>2</Subscript> hydrosols

CeO₂-ZrO₂ hydrosols are synthesized and the size, shape, phase composition, density, and electrophoretic mobility of particles are studied. The pH ranges of the stability of hydrosols and the thresholds of their fast coagulation in the presence of some electrolytes are determined. The nature of the aggregation stability of CeO₂-ZrO₂ hydrosols is discussed.     

Insecticidal effect of <Emphasis Type="Italic">Mentha pulegium</Emphasis> L. and <Emphasis Type="Italic">Mentha suaveolens</Emphasis> Ehrh. hydrosols against a pest of citrus, <Emphasis Type="Italic">Toxoptera aurantii</Emphasis> (Aphididae)

Essential oils proved their efficiency as natural insecticides to fight many pests of stored products and crops whereas the hydrosols have not been evaluated yet. The objective of this work is to assess the insecticidal effect of hydrosols extracted from Mentha suaveolens Ehrh. and Mentha pulegium L. toward an insect pest of citrus, Toxoptera aurantii (Homoptera, Aphididae). The extraction of hydrosols was carried out by hydro-distillation using Clevenger apparatus and then the chemical composition was identified by gas chromatography coupled with mass spectrometry. The chemical composition of two hydrosols revealed the abundance of hydrophilic and oxygenated compounds as piperitenone oxide and carvacrol. Different concentrations of each hydrosol were separately diluted in distilled water and applied topically to aphids. The results of this investigation have shown a high insecticidal effect, and the M. suaveolens hydrosol is more effective against citrus pests than that of M. pulegium L. Consequently, these natural compounds can be used in the management of aphids on citrus.     

Low temperature gas purification on ultradispersed oxide catalysts

Catalysts on the basis of ultradispersed powders of complex oxides of transition metals have been studied in the process of low temperature deep oxidation of organic compounds.