The development and the study of cyanourethane laquer compositions and coatings based on them

A procedure was developed for preparing cyanourethane laquer compositions based on polyisocyanates, polyesters of various structures, and dicyanodiamide. The influence of the polyester structure and component ratio on the properties of the cured laquer coatings was examined, and the compositions allowing preparation of corrosion- and heat-resistant laquer coatings were determined.     

Optical characterization of ultrasmall Si nanoparticles prepared through electrochemical dispersion of bulk Si

Studying the properties and stability of silicon nanoparticles (Si-np) in aqueous environments may lead to novel applications in biological systems. In this work, we use absorption and photoluminescence (PL) spectroscopy to characterize ultrasmall Si-np prepared through anodic etching and ultrasonic fractionation of a crystalline Si wafer. Their behavior is studied over time in 2-propanol and during treatments with water, NaOH, HCl, and H(2)O(2). The observed population is divided into two types of material: bright species consisting of well-etched Si-np, approximately 1 nm in diameter, and dark species derived from partially etched or aggregated Si structures. The dark material is seen by its scattering in the 2-propanol and water solutions and is largely removed via precipitation with the NaOH or HCl treatment. The bright material includes three distinct species with their respective emissions in the UV-B, UV-A, and hard-blue regions of the spectrum. The hard-blue PL is shown to have a simple pH dependence with a pK(a) approximately 3, providing an important insight into its chemical origin and signaling for possible application of Si-np as environmental probes. Our results offer some potential for tailoring the PL properties of ultrasmall Si-np through control of their surface chemistry.     

Effect of alkanolamines on properties of epoxy–anhydride compounds

Hot-cured epoxy compound based on ED-20 resin and isomethyltetrahydrophthalic anhydride was modified with alkanolamines of different structures. The influence exerted by the structure of alkanolamines on the structure and operation characteristics of modified epoxy–anhydride compounds was examined. Introduction of alkanolamines decreases the gel and cure times and enhances the operation properties of cured epoxy–anhydride compounds. The best products were obtained with alkanolamines derived from ethylenediamine. Their introduction into epoxy–anhydride compounds enhances by a factor of 1.5–2 the elasticity, tensile strength at uniform extension, and impact resilience of the cured formulations.     

Precursor radical recombination and its attendant effects on the surface of solids in a dissociated carbon dioxide medium

The atomic-hydrogen-initiated ejections of materials from the surface of solids (ZnS, Ni) preliminary treated with dissociated carbon dioxide are revealed. The glow of a crystalline phosphor and the dynamic effect of the reaction are observed in the dissociated carbon dioxide medium. It is found that the observed variations in the dynamic effect of the reaction are unrelated to changes in the reaction rate. These effects are used to elucidate the mechanism of heterogeneous radical recombination on the surface of solids (Al₂O₃, ZnS, Ni) in dissociated carbon dioxide. It is revealed that, under the experimental conditions, the reaction rate is independent of the chemisorbed radical concentration, because the reaction involves radicals entrapped into the precursor state with a short lifetime at the surface.     

Spin-glass, antiferromagnetism and kondo behavior in Ce2Au1−x Co x Si3 alloys

Recently, the solid solution Ce₂Au_{1− x Co} xSi₃ has been shown to exhibit many magnetic anomalies associated with the competition between magnetic ordering and the Kondo effect. Here we report high pressure electrical resistivity of Ce₂AuSi₃, ac susceptibility (X) and magnetoresistance of various alloys of this solid solution in order to gain better knowledge of the magnetism of these alloys. High pressure resistivity behavior is consistent with the proposal that Ce₂AuSi₃ lies at the left-hand side of the maximum in Doniach’s magnetic phase diagram. The ac X data reveal that there are in fact two magnetic transitions, one at 2 K and the other at 3 K for this compound, both of which are spin-glass-like. However, as the Co concentration is increased, antiferromagnetism is stabilized for intermediate compositions before attaining non-magnetism for the Co end member.     

Microphase separated structures based on N-substituted polydiallylamines

The ionogenic polymers namely poly(N,N-diallyl-N-cetylammonium hydronitrate) (PDACA · HNO₃) and poly(N,N-diallyl-N,N-dimethylammonium chloride)-block-poly(cetyl acrylate) (PDADMACl-block-PA-16) were synthesized via activation of the terminal double bond of the PDADMACl precursor and initiation of the polymerization of the acrylic monomer in alcohol solution. The microphase separated structure of a blend of both homopolymers and of the block copolymer was proved by differential scanning calorimetry (DSC) and X-ray diffraction measurements. Side chain crystallization in PDA-CA · HNO₃ completely restricts the crystallization of the ionogenic backbones which, however, control the layered structure and the crystallization of the aliphatic chains. In PDADMACl-block-PA-16 crystalline polyacrylate blocks coexist with crystalline ionogenic blocks. The length of the polyacrylate block influences the ability of the ionogenic block to form the crystalline structure.     

The growth of a single crystal of Sr3CuIrO6 and its magnetic behavior compared to polycrystals

We have grown single crystals of the psuedo-one-dimensional compound Sr₃CuIrO₆, a K₄CdCl₆-derived monoclinic structure with Cu-Ir chains along the [101] direction. We present the ac and dc magnetization behavior of the single crystals in comparison with that of the polycrystalline form reported earlier. There is a distinct evidence for at least two magnetic transitions, at 5 K (T ₁) and 19 K (T ₂), with different relative magnitudes in the single and polycrystals. The low temperature magnetic relaxation behavior of both the forms is found to be widely different, exhibiting unexpected time dependence.     

Prospects for Using Chromatography–Mass Spectrometry for the Determination of Lipids in Clinical Cardiolipidology

Journal of Analytical Chemistry - Cardiolipidology – a new direction in cardiology – is developing intensively owing to the method of mass spectrometry. This method has acquired...     

Frost- and heat-resistant composite materials based on polyurethanes

Based on a mixture of 2,4 and 2,6-tolylene diisocyanate of a grade Desmodur T-80 and polyesters P6-BA and PDA-800. Reactive isocyanate-containing prepolymers for polyurethane composite materials were synthesized. On the basis of alkanolamine Lapromol A-294, polyesters of various structures and an aromatic diamine Curalon M curing systems for polyurethane composites were developed. The effect of a ratio of isocyanate-, hydroxyl-, and amine-containing components on the properties of the prepolymers and curing systems was investigated. Polyurethane composites were produced and their performance characteristics were studied.