Low-field magnetic resonance in granular nanostructures

A series of (CoFeB) + (SiO₂) magnetic film samples was investigated by ferromagnetic resonance. The magnetic resonance in low fields was experimentally observed. The influence on the position and width of the low-field peak of the magnetic phase concentration in nanofilms and of the registration parameters of a spectrum were established.     

Application of ferromagnetic resonance method to study of multilayer nanostructures

The ferromagnetic resonance spectra of multilayer nanostructures synthesized from magnetic layers based on amorphous Co₄₅Fe₄₅Zr₁₀ and nonmagnetic layers of the amorphous semiconductor α-Si have been experimentally studied. It is shown that the character of the spectrum depends strongly on thicknesses of magnetic and nonmagnetic layers and the structure of the boundary layer. The resonant fields are calculated within the effective-medium approximation. In some cases, the calculation results describe well the experimental data.     

Interaction of ferrocenecarbaldehyde with zinc tetrahydroborate and its derivatives

Ferrocenecarbaldehyde was reduced to methylferrocene upon interaction with zinc tetrahydroborate in THF. The reactions proceeded rapidly (5–10 min) in high yields (ca. 90%). Analogous results were obtained when a mechanically activated mixture of zinc chloride and sodium tetrahydroborate or the complex of zinc tetrahydroborate with dibenzo-18-crown-6, 2Zn(BH₄)₂·DB-18-C-6, was used in the reaction. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 214–216, January, 1999.     

Iodination of B12H11OC(O)CH2–3, B12H11OH2–, and B12H11SCN2–

Reactions of iodination of monosubstituted derivatives of B₁₂H₁₁X^2–anion (X = OC(O)CH₃, OH, SCN) were studied. The reactions were shown to proceed smoothly to give B₁₂H₁₀(OC(O)CH₃)I^2–((carboxy)(iodo)[decahydro[I _h1551-²⁰-closo]dodecaborate(2–)] anion), B₁₂H₁₀(OH)I^2–((hydroxo)(iodo)[decahydro[I _h1551-²⁰-closo]dodecaborate(2–)] anion), and B₁₂H₁₀(SCN)I^2–((thiocyanato)(iodo)[decahydro[I _h1551-²⁰-closo]dodecaborate(2–)] anion) in high yields, irrespective of the solvent used (benzene, H₂O–ROH, where R = C₂H₅, CH₂CH₂CH₃).¹     

Preparation of New Derivatives of the closo-Dodecaborate Anion [B12H10(OC(O)CH3){OC(O)(CH2)3CH3}]2–, [B12H10(OH){OC(O)(CH2)3CH3}]2–, [B12H10(SCN){OC(O)(CH2)3CH3}]2–, and [B12H10(I){OC(O)(CH2)3CH3}]2–

Nucleophilic substitution reactions of the monosubstituted anions [B₁₂H₁₁X]^2–, where X = OC(O)CH₃, OH, SCN, and I, with pentanoic acid were studied. The obtained compounds were shown to contain the [B₁₂H₁₀X{OC(O)(CH₂)₃CH₃}]^2– anions.     

Pt-containing pillared clay catalysts for CO oxidation

Platinum has been introduced into pillared clay as a complex with the organosilicon amine N’-[3-(trimethoxysilyl)propyl]diethyltriamine, as a complex with the organosilicon amine and zirconyl chloride, as an ammine complex, and by impregnation with a chloroplatinic acid solution followed by hydrogen reduction. The catalytic activity of the Pt-containing clays in CO oxidation in excess hydrogen was also studied. The last procedure yields the most active Pt-containing pillared clay. Calcium has been introduced into pillared clay by ion exchange, and it was found that the catalytic activity of the clay decreases with increasing Ca content.     

Ferromagnetic resonance, magnetic properties, and resistivity of (CoFeZr)x(Al2O3)1 ? x/Si multilayer nanostructures

Comparative investigations of static magnetic properties, magnetoresistance, and ferromagnetic resonance data of multilayer nanostructures consisting of CoFeZr-Al₂O₃ composite magnetic layers and amorphous silicon semiconductor spacers were performed in a layer thickness range below 5 nm. The influence of layer dimension parameters and chemical peculiarities of silicon on the inner structure and type of magnetic interactions in nanostructures with 35 and 46 at % magnetic phase composite layers is discussed.     

Effect of nickel oxide additive on properties of catalysts used in the reaction of selective oxidation of carbon monoxide

Effect of nickel oxide additives on the oxidation selectivity of carbon monoxide in the presence of hydrogen was studied for the widely recognized system constituted by copper and cerium oxides. It was shown that a significant positive effect is observed upon introduction of the nickel-containing additive (??0.3%) due to the electron-donor effect of nickel oxide. It was demonstrated that the catalyst of composition NiO/CuO/CeO₂/Al₂O₃ shows high selectivity in the reaction of CO oxidation.     

Selective oxidation of CO in the presence of hydrogen on CuO/CeO<Subscript>2</Subscript> catalysts modified with Fe and Ni oxides

The selective oxidation of CO in the presence of hydrogen on CuO/CeO₂ systems containing Fe and Ni oxides as promoters was studied. The catalysts containing 1–5 wt % CuO and 1–2.5 wt % Fe₂O₃ supported on CeO₂ and the CuO/CeO₂ systems containing 1–2.5 wt % NiO were synthesized, and their catalytic activity as a function of temperature was determined. It was found that the additives of Fe and Ni oxides increased the activity of the CuO/CeO₂ catalysts with a low concentration of CuO. In this case, the conversion of CO at 150°C approached 100%. At the same time, these additives had no effect on the activity of the CuO/CeO₂ systems at a CuO concentration of 5 wt % or higher, which exhibited an initially high activity in the above temperature region. The forms of CO adsorption and the amounts of active sites for CO adsorption and oxidation were studied using temperature-programmed desorption. It was found that the introduction of Fe and Ni additives in a certain preparation procedure facilitated the formation of an additional amount of active centers associated with CuO. Data on the temperature-programmed reduction of samples (the amount of absorbed hydrogen and the maximum temperature of hydrogen absorption) suggested the interaction of all catalyst components, and the magnitude of this interaction depended on the sample preparation procedure. With the use of Mössbauer spectroscopy, it was found that the procedure of iron oxide introduction into the CuO/CeO₂ system was responsible for the electron-ion interactions of catalyst components and the reaction mixture.     

Combined analysis of static and dynamic magnetic characteristics of multilayer CoFeZr/α-Si nanostructures

The combined method of static and dynamic magnetic measurements is used to study nano-dimensional multilayer amorphous CoFeZr/α -Si films. It is established that at the thickness of magnetic layers x = 5–12 nm their magnetization does not differ from that of the bulk material. It is shown that as x is lowered to 2–3 nm, the magnetization of magnetic layers decreases, which may be due to the formation of mixed layers containing nonmagnetic silicides. At a thickness of nonmagnetic interlayers of less than 1 nm the features characteristic of a weak antiferromagnetic interaction of neighboring layers are observed.