Heterophase metal-oxide structures formed in a range of low-temperature activation of iron. 1. 3D-video-microprobing reflectometry

Investigation of the morphology and composition of a nonuniform layer formed on the iron surface upon an hour of oxidation at an oxygen pressure of 0.001 to 10 mmHg and a temperature of 300°C is carried out. Computer digital optical images of a small probed surface site upon digital processing enable us to introduce and estimate parameters of the morphological heterogeneity of the surface thermo-oxide layer, which affect its functional characteristics. By the data of morphological investigations (3D probe), the oxide layer has a heterogeneous multilayer structure and consists of a magnetite phase layer adjacent to the metal and an external hematite microcrystalline layer. At an increase in the oxygen pressure from 0.1 to 10 mmHg, α-Fe₂O₃ plates grow on the magnetite surface and gradually cover the whole surface forming a closely packed structure. In this case, the external oxide layer is composed of thin hematite microplates separated with clearly seen nano-size intergranular domains characterized by a high superficial micro-order and nano-heterogeneity in the oxide depth, which may explain pronounced functional, semiconducting, catalytic, and sensor properties, as well as the heightened reactivity of iron and its alloy oxidized in the range of a low-temperature activation. Original Russian Text ? V.A. Kotenev, A.Yu. Tsivadze, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 5, pp. 488–498.     

Octa- and tetra-(benzo-15-crown-5)phthalocyanines in surfactant-containing solutions

The behavior of octa-(benzo-15-crown-5)phthalocyanine (H₂cr₈Pc), as well as cobalt octa- and tetra-(benzo-15-crown-5)phthalocyaninates (Cocr₈Pc and Cocr₄Pc), in aqueous solutions containing cationic or anionic surfactants, such as cetyl trimethylammonium bromide (CTAB), sodium carboxymethyl cellulose (Na-CMC), and sodium dodecyl sulfate (SDS), is studied using electronic spectroscopy. The presence of eight benzo-15-crown-5 ether fragments on the periphery of the phthalocyanine ring is shown to facilitate the dissolution of Pc in an aqueous environment. The interactions between CTAB and crown-containing Pc promotes the dissolution of H₂cr₈Pc; Cocr₈Pc; and, to a lesser degree, Cocr₄Pc, which is accompanied by the appearance of molecular aggregates, including heteronuclear cofacial dimers. The presence of a metal in the ring is not the necessary condition of the process. In microscopically heterogeneous medium, such as an aqueous SDS-containing solution, H₂cr₈Pc is present in monomeric form at SDS concentrations close to C _cr and in dimeric form at SDS content below C _cr. Under similar conditions (environment, surfactant), Cocr₄Pc can exist in monomeric form at SDS concentrations much high than C _cr. The effect of the size of cation on the form of the crown-containing Pc in an aqueous solution is illustrated by an example of H₂cr₈Pc. Na-CMC promotes the dissolution of Pc and enables one to produce K⁺/Mcr₈Pc-modified films from aqueous solutions.     

Alternating-current electrocontact oxidation of Kh18N10T steel

Properties of surface oxide layers formed on extended Kh18N10T steel specimens upon oxidation at residual pressure P = 10^?4–10¹ mmHg under typical heating in a furnace and alternating-current (50 Hz) electrocontact heating (300°C) are studied. A strong activating effect of alternating-current heating on the oxidation of steel at P = 0.01 mmHg is noticed. Compared to typical heating in a furnace, electrocontact heating promotes saturation of the surface oxide with chromium and homogenization of the chromium distribution in the depth of the oxide and the resulting formation of iron chromite.     

Solubilization of Crown-Substituted Magnesium Phthalocyaninates in Solutions of Salts of Bile Acids

Crown-containing Pc Mg[(B15C5O)₈Pc], Mg[(B15C5O)₄Pc], and Mg[(15C5)₄Pc] are in the monomolecular state in solutions of synthetic anionic surfactants: sodium dodecylsulfate and sodium dodecylbenzenesulfonate. In micellar solutions of bile-acid salts, molecular organization of crown-substituted Pc with different methods of introduction of crown groups into the macrocycle and their different numbers changes their state from predominantly monomeric for Mg[(B15C5O)₈Pc] in the presence of NaCl to the aggregated one in the case of Mg[(15C₅)₄Pc)]. Magnesium phthalocyaninate with annulated (15-crown-5)-fragments, Mg[(15C₅)₄Pc], is characterized by the highest sensitivity to the structure of the micelle-forming biocompatible surfactant.     

Determination of the Life Cycle of Heat-Exchange Tubes of Vapor Condensers on the Basis of Statistical Analysis of Local Pitting Corrosion According to Data of Eddy Current Testing

Protection of Metals and Physical Chemistry of Surfaces - The possibility is shown of creating a chart of local corrosion damage in the walls of heat-exchange tubes on the basis of the data of...     

Liquid-crystalline phthalocyanine-based nanostructures

Structural peculiarities of mesogenic phthalocyanines and their derivatives are considered. Liquid-crystalline materials based on self-assembled phthalocyanine molecules are promising novel functional materials for sensors, as catalysts, optically and bioactive matrices, and semiconductor cells. Mesomorphic and electrophysical characteristics of liquid-crystalline phthalocyanine-based materials are considered, possibilities of their use are discussed, and the structure-property relations are analyzed.     

Influence of the ring size in diphosphorylated dibenzo crown ethers on extraction of metals from nitric acid solutions

Extraction of metals from 0.1–7 M HNO₃ with 0.05 M chloroform solutions of functionalized crown ethers containing (n-C₄H₉O)₂P(O)- fragments and differing in the polyether ring size (18-crown-6, 21-crown-7, 24-crown-8) was studied. An increase in the size of the macroring in diphosphorylated dibenzo crown ethers leads to an appreciable increase in the performance of the extractants toward a number of metals, due to participation of phosphoryl groups in the complexation. At the same time, the reactivity of the macroring varies insignificantly, which decreases the selectivity of the recovery of metals forming host-guest complexes. These features should be taken into account when designing new macrocyclic extractants of the lariat type.     

Relaxation behavior of latex-polymers in frost-resistant aqueous-dispersion deep-penetration ground coats modified by water-soluble dye

The effect of a water-soluble indanthrene blue dye on the relaxation structure of styrene–acryl latex polymer with the glass-transition point below 5°C is studied in a frost-resistant aqueous-dispersion coat using the method of dynamic mechanical-relaxation spectroscopy. A significant difference is found between the change in the intensity of the maximum of α-relaxation dissipative losses of a latex-polymer binder in the ground coat and in free latex polymer when they are modified by a blue dye, which is due to the ground-coat composition. Special attention is paid to relaxation effects in the negative temperature range.     

The fine structure of plasmon bands in gold nanoparticles

The correlation between the electronic configurations of Au atom in the ground and excited electronic states and the E _pl plasmon energies of gold nanoparticles is studied in the many-electron approximation, taking into account 5d, 6s, and 6p valence electrons. Relativistic effects are found to result in the E _pl splitting in the visible and ultraviolet spectral ranges, and the splitting energies are predicted. The origin of low-energy plasmons with E _pl = 1.14, 2.7, and 6.4 eV is determined by 5d ⁹6s ²(² D _5/2), 5d ⁹6s ²(² D _3/2), and 5d _5/2 ⁹ 6s _1/26p _1/2 excited electronic configurations of Au atom. The bulk plasmon energy E _pl = 25.4 eV is assigned to the mixed oxidation states of Au ions in the nanoparticle cores.     

To the mutual effect of surfaces of nanometallic systems and reagents in chemisorption layers

Transformations of the carbon-monoxide adsorption layers on metallic nanosystems including group VIII metals are studied with the use of Fourier-transform infra-red (FTIR) spectroscopy. Depending on the experimental conditions, not only the state of the chemisorption layers, but also the surface structure of the systems changes.