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This paper reports about the synthesis and characterization of a novel Fe/Fe2O3/polyoxocarbosilane core shell nanocomposite as a material for gas-sensing applications. The nanocomposites (Fe-based nano cores enveloped with polymeric polyoxocarbosilane shells) were prepared by the IR laser co-pyrolysis of iron pentacarbonyl and hexamethyldisiloxane. The iron-based cores become superficially oxidized in atmosphere. The morphologies, chemical content and thermal behavior were studied by different analytical techniques. The sensing properties of the polymer-poor nanocomposite thick films were tested by measuring the variation of the electrical resistance in presence of CO and CH4, at a working temperature of 450 °C. Preliminary results indicate that for CO toxic gas, an n–p transitional character of the semiconducting iron oxide appears in humid relatively to dry air. [ABSTRACT FROM AUTHOR]

Thermochemical properties of two kinds of composite material of synthetic zeolite ZSM5 in potassium form (K-ZSM5) with AgI have been studied. The composites have been prepared by treating the silver form of synthetic zeolite ZSM5 (Ag-ZSM5) with potassium iodide solution under different experimental conditions. One of the composites was additionally sintered at temperature 500°C for 20 h. Both composites have been characterized by TG, DTG, DTA, EDS analysis, X-ray powder diffractometry and X-ray photoelectron spectroscopy. The methods of thermal analysis as well as X-ray powder diffractometry and XPS confirmed the differences between the two composites caused by sintering during the synthesis. The content of AgI in the surface layer was different. No changes of the zeolitic mineral dimensions are observed. [ABSTRACT FROM AUTHOR]

Silicon suboxide films were prepared by TEA CO2 pulsed laser ablation (PLA) of the silicon monoxide target in the Kr atmosphere. The deposits were examined by means of Fourier transformed infrared spectroscopy (FTIR), electron paramagnetic resonance spectroscopy (EPR) and X-ray photoelectron spectroscopy (XPS). The generated point defects in the films – mostly silyl ≡Si· (E’ center) and silylen =Si: – were allowed to react with the gaseous ammonia NH3, methylamine MeNH2 and dimethylamine Me2NH after the ablation. As a result, the functional groups ≡SiNHxMey (x+y=2) were formed. The reactivity of the deposits are due to silyl ≡Si· and silylen =Si: radicals as deduced by comparison of the initial concentration of the silyl radicals (5.3–9.8×1019 /g, EPR) – and the newly formed -(Si)NH bonds (3.6×1019 /g, FTIR). The observed absorption bands ν(SiH) at 2223, 2214 and 2220 cm-1 could be assigned to =(O2)Si(H)NH2, =(O2)Si(H)NHMe and =(O2)Si(H)NMe2 species. The singlet line in EPR spectrum of the native deposit before exposition is due to the silyl radical with free valence on the silicon backbonded via oxygen and another silicon atom. After exposition either to NH3 or MeNH2 the silyl concentration rapidly decreased to several % of its original value. [ABSTRACT FROM AUTHOR]

The mechanochemical reduction of lead sulphide with elemental iron in a high-energy mill was studied. X-ray photoelectron spectroscopy was used for characterization of obtained products of reduction. Elemental lead as well as its divalent forms were identified in the surface layer of products of mechanochemical reduction. The mechanochemical reduction of lead sulphide with elemental iron on the surface is a complicated reaction and the identification of compounds formed in the surface layer is not unambiguous. However, only 23% of elemental lead on the surface is produced. The degree of mechanochemical transformation in the surface layer is not very high under chosen conditions. Higher power input is needed for further progress of the reaction. [ABSTRACT FROM AUTHOR]

Abstract. Decomposition of 3-butyn-2-one induced by CO[sub 2] laser radiation in the gas phase results in the deposition of carbonaceous films composed of a graphitic and monohydrogenated carbon, in which H is dominantly bonded to sp[sup 3] sites. The films incorporate oxygen in the topmost layers. The technique is suitable for the preparation of thin C-based films at low substrate temperatures. [ABSTRACT FROM AUTHOR]

Chemical reactions induced by CO-laser radiation in mixtures of silane and hexafluoroacetone afford various gaseous silicon- and carbon-containing compounds and result in deposition of microstructures of carbon, C/F/O and Si/C/O/F materials. These products are suggested to be formed by a variety of exothermic reactions initiated through SiH-photosensitized decomposition of hexafluoroacetone. Silane is shown to be a very potent reagent for the reduction of C-F bonds. [ABSTRACT FROM AUTHOR]

A composite material made up of AgI and the potassium form of mordenite has been prepared by treating the silver form of synthetic mordenite with potassium iodide. The composite as well as the silver and potassium forms of mordenite have been characterised by X-ray powder diffractometry, X-ray photoelectron spectroscopy, EDS analyses and ac conductivity measurements. It has been inferred that, in the composite material, AgI grows at the entrance of the zeolite channels without forming a continuous conducting phase. The silver form of mordenite has been proved to be a silver ion conductor by dc conductivity measurements. [ABSTRACT FROM AUTHOR]