N. V. Bulina

Effect of strontium and barium doping on the magnetic state and electrical conductivity of GdCoO3

A coordinated investigation of the magnetic and electrical properties of polycrystalline cobalt oxide compounds CdCoO3, Gd0.9Ba0.1CoO3, and Gd0.9Sr0.1CoO3 is carried out. Undoped GdCoO3 reveals a low conductivity; a magnetic moment of 7.4 μB per molecule, which is less than the theoretical value for the Gd3+ ion; and an asymptotic Curie temperature of −6 K. Doping GdCoO3 with barium and strontium to substitution of 10 at. % Gd brings about an increase in the conductivity and magnetic transitions at T = 300 K for Gd0.9Ba0.1CoO3 and T = 170 K for Gd0.9Sr0.1CoO3. The magnetization anomalies imply the formation of magnetic clusters. The behavior of the electrical conductivity at high temperatures suggests a variable activation energy. At low temperatures, Mott hopping conduction sets in.

Hybrid material polyvinyl alcohol-copper oxide and its electrical properties

The hybrid material polyvinyl alcohol-copper oxide was produced by the thermal decomposition of polyvinyl alcohol-copper hydroxide complex compound. It was analyzed by means of XRD, UV-VIS, IR, and Raman spectroscopy. It was concluded that the most part of copper oxide has an amorphous structure and consists of -(Cu-O)n- chains. The electrical properties of this material were investigated at direct and alternating current in 80–375 K temperature range.

Complexes of polyvinyl alcohol with insoluble inorganic compounds

Hybrid materials of polyvinyl alcohol-hydroxides/oxides of Be, Mg, Zn, Cd, B, Al, Cr, and Fe have been obtained. The studies have been carried out by the methods of optical spectroscopy, X-ray diffraction, and synchronous thermal analysis. Interpretation of experimental data is presented, presuming that, in systems with zinc, boron, aluminum, chromium, and iron hydroxides/oxides, interpolymeric complexes of polyvinyl alcohol with corresponding polymeric inorganic compounds are formed. They belong to a new class of materials with unusual structure containing chains of inorganic polymers isolated in the organic matrix.

Polymeric sulfides CdS, CuS, and NiS in polyvinyl alcohol matrix

Cadmium, copper, and nickel sulfides have been synthesized in a polyvinyl alcohol matrix. The specimens have been investigated by means of vibration spectroscopy and X-ray diffraction analysis. The obtained data have confirmed the formation of cadmium sulfide with a polymeric chain structure in polyvinyl alcohol. The possibility of producing similar materials based on copper and nickel sulfides has been discussed.

Solid-state NMR and computational insights into the crystal structure of silicocarnotite-based bioceramic materials synthesized mechanochemically

In this work, we report the results of a detailed structural study of a promising bioceramic material silicocarnotite Ca5(PO4)2SiO4 (SC) synthesized from mechanochemically treated nanosized silicon-substituted hydroxyapatite by annealing at 1000°C. This novel synthetic approach represents an attractive and efficient route towards large-scale manufacturing of the silicocarnotite-based bioceramics. A combination of solid-state nuclear magnetic resonance (NMR), powder X-ray crystallography and density function theory (DFT) calculations has been implemented to characterize the phase composition of the prepared composite materials and to gain insight into the crystal structure of silicocarnotite. The phase composition analysis based on the multinuclear solid-state NMR has been found in agreement with X-ray powder diffraction indicating the minority phases of CaO (5-6wt%) and residual silicon-apatite (7-8wt%), while the rest of the material being a fairly crystalline silicocarnotite phase (86-88wt%). A combination of computational (CASTEP) and experimental methods was used to address the anionic site disorder in the silicocarnotite crystal structure. Distorted [OPO3] pyramids have appeared as an important structural motif in the SC crystal structure. The ratio between regular [PO4] and distorted [OPO3] tetrahedra is found between 2:1 and 3:1 based on XRD experiments and CASTEP calculations. The natural abundance 43Ca magic angle spinning NMR spectra of silicocarnotite are reported for the first time.

Hybrid material polyvinyl alcohol-stannic acid/stannic oxide

Hybrid materials polyvinyl alcohol (PVA)-stannic acid and PVA-SnO2 were produced in the form of transparent films. Their investigations by means of optical spectroscopy, X-ray analysis, thermo-gravimetry, and mass-spectrometry were carried out as well as electrical measurements. The model is discussed where the polymeric chains of inorganic constituent are linked by coordinative bonds with carbon polymeric chains. Photoconductivity of PVA-SnO2 was discovered.

Synthesis and study of manganese-containing endohedral fullerenes

Fullerenes containing manganese and iron atoms are synthesized in a high-frequency carbonhelium plasma at atmospheric pressure. The electron paramagnetic resonance (EPR) spectrum of the synthesized compound contains not only lines attributed to iron atoms but also the lines of a manganese ion pair with an additional hyperfine structure. The latter lines are assigned to the endohedral complex Mn2@Cn (n > 70). The possible existence of these structures is evaluated from quantum-chemical calculations of the optimum geometry of the endothedral fullerene Mn2@C84 with C2v symmetry. It is found that the manganese atoms are spaced ∼2.72 Å apart at the center of the molecule.

Synthesis and investigation of iron fullerene clusters

Iron fullerene clusters are prepared by plasma chemical synthesis and investigated using electron magnetic resonance. It is shown that these clusters can be prepared both by plasma chemical synthesis of fullerenes with iron and by mixing of a fullerene solution with a powder of iron nanoparticles coated with carbon shells. A liquid chromatographic technique is proposed for separating iron fullerence clusters.

Mechanochemical Synthesis of Sr-Substituted Hydroxyapatite

We demonstrate that a nanoparticulate Sr-substituted carbonate hydroxyapatite can be prepared by fast mechanochemical synthesis, without further annealing of the material. The synthesis process takes 30 min and yields single-phase products. We have obtained a series of Ca10–xSrx(PO4)6(OH)2 samples with x = 0–2.

Effect of the Reaction Medium on the Mechanochemical Synthesis of LiAlO2

An unactivated mixture of aluminum hydroxide (gibbsite) and lithium carbonate and a mixture mechanically activated in an AGO-2 planetary mill were heat-treated in air and under vacuum (0.05 Pa) at temperatures of up to 800–850°C, and the phase composition of the heat treatment products was determined by in situ X-ray diffraction. The results demonstrate that, in the case of the unactivated mixture or after mechanical activation for 1 min, heat treatments in air and under vacuum lead to the formation of α-LiAlO2 and γ-LiAlO2, respectively. After mechanical activation for 5 or 10 min, heat treatment both in air and under vacuum leads to γ-LiAlO2 formation. A possible mechanism behind the effect of the reaction medium on the phase composition of LiAlO2 is analyzed.