Formation of glass synthesized by sol-gel technology

The process of glass synthesis by the sol-gel method is studied using analysis of EPR spectra. The gelation process and formation of xerogels are considered depending on the temperature-time parameters and the type of initial components. It is established that the glass phase starts to be formed at 800°C. __________ Translated from Steklo i Keramika, No. 8, pp. 9–13, August, 2006.     

A new type of polymer-polymer PVC systems with surface layers converted into hydroxyethylcyclam nanofilms of the type “hard coating on soft substrate”

With the aim of classifying PVC materials in which surface layers are converted into interpenetrated network cyclam nanofilms among polymer-polymer systems, comparative studies of their properties were carried out with consideration for the specific conditions for the preparation of the material. The density and structures of near-surface layers, the bulk ratio of the ordered and disordered forms, the dynamics of swelling in water, and the effective partial volume occupied by water molecules were studied for PVC plates prior to and after hydrothermal treatment. The conversion of the surface layers changes the structural self-organization of PVC: the polymer structure becomes more compact and ordered both in the area adjacent to the nanofilm and in the polymer bulk, which is characteristic of systems of the type “hard coating on soft substrate”. Original Russian Text ? A.Ya. Fridman, E.M. Morozova, A.Yu. Tsivadze, N.P. Sokolova, I.I. Bardyshev, A.M. Gorbunov, O.P. Shapokhina, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 5, pp. 498–502.     

Polymerization characteristics of a dye of anthraquinone

A technical dye of the anthraquinone type was analyzed by GPC, mass spectroscopy, and elemental analysis. Along with the polymerizable component, N-[4-amino-3-methoxyanthraquinonyl-(1)] methacrylamide (I), it contained a saturated admixture, N-[4-amino-3-methoxyanthraquinonyl-(1)]-2-chloro-2-methylpropionamide (II). The homopolymerization of I was carried out, and admixture II was isolated and characterized. The copolymerization of the dye with styrene and methyl methacrylate was verified, and the retardation effect of II on the polymerization of these monomers was evaluated.     

Effect of heat treatment on the structural transformations and properties of high-nitrogen chromium steels

Conclusions  

A study of the wear resistance of a TiC–SiC composite ceramic material prepared by spark plasma sintering

The effect of the silicon carbide content and the spark plasma sintering temperature on the porosity and wear resistance of a composite material is determined. An increase in the silicon carbide content leads to an increase in the porosity from 4 to 12%. The temperature effect on the porosity becomes apparent above 1200°C. The material consists of a matrix represented by titanium carbide grains with a size of 1–3 μm and silicon carbide grains with a size of 10–30 μm. It is found that the TiC–20%SiC compound exhibits the highest wear resistance, which is 12 times higher than that of hot-pressed silicon carbide.     

Microarc oxidation in slurry electrolytes: A review

The experience gathered from the use of plasma electrolytic methods in the context of improving the performance of valve group metals is summarized. Emphasis is placed on the formation of coatings by microarc oxidation (MAO) in slurry electrolytes containing powders with different degree of dispersion (a few nanometers to a few tens of microns) and nature (oxides, carbides, nitrides, borides, graphite, etc.). A phenomenological model of the mechanism of formation of MAO coatings in slurry electrolytes is proposed; characteristics of the electrolytes and the coatings are discussed. The results of our studies of the composition of MAO coatings carried out by nuclear backscattering (NBS) spectrum simulation are described. A significant improvement in the properties of MAO coatings formed in slurry electrolytes is registered. It is concluded that this modification can considerably extend the range of application of the MAO method not only in conventional fields of mechanical and instrument engineering but also in aerospace engineering, medicine, biology, and living systems technology.     

Solubility of oxygen in CdS single crystals and their physicochemical properties

The specific features of oxygen dissolution in CdS using the example of single crystals grown by the gas-transport method with deviations from stoichiometry at 1100°C are considered. The effect of various types of intrinsic point defects in crystals of different composition on the form in the presence of oxygen is analyzed. It is shown that the most stable composition thermodynamically is that corresponding to nonstoichiometric “self-activated cadmium sulphide” stabilized with oxygen.