Inorganic Materials (v.47, #1)
Graphene: A novel carbon nanomaterial by S. V. Tkachev; E. Yu. Buslaeva; S. P. Gubin (1-10).
This review analyzes what the term graphene means today, and examines graphene preparation and identification methods and its chemical properties. The applications of this novel carbon nanomaterial are briefly discussed.
Critical parameters of the vapor-liquid-solid growth of silicon whiskers by V. A. Nebol’sin; A. I. Dunaev; A. A. Dolgachev; M. A. Zavalishin; G. A. Sladkikh; V. V. Korneeva; A. Yu. Eframeev (11-15).
We have determined critical parameters that restrict the vapor-liquid-solid growth of silicon whiskers. We demonstrate that there are maximum and minimum critical radii for whisker growth and identify boundary conditions that lead to solvent droplet breakdown and crystal branching.
Thermal conductivity of Sn1 − x Nd x S single crystals by Kh. A. Adigezelova; M. I. Murguzov; Sh. S. Ismailov; O. M. Gasanov (16-17).
The thermal conductivity of Sn1 − x Nd x S (x = 0, 0.001, 0.002) single crystals has been measured in the temperature range 80–840 K. The results have been used to evaluate the electronic and lattice components of the thermal conductivity. Both the electronic and lattice components are shown to decrease with increasing temperature and to increase with neodymium content.
Growth and properties of nanostructured layers based on Pb1 − x Cd x Se (x = 0−0.20) solid solutions by V. A. Moshnikov; A. E. Gamarts; D. B. Chesnokova; E. V. Maraeva (18-22).
We have produced nanostructured layers based on supersaturated Pb1−x Cd x Se (x = 0−0.20) solid solutions with an efficient room-temperature photoluminescence in the range 3–5 μm and studied the effect of growth conditions on their chemical and phase compositions and properties. Their photoluminescence spectra have been measured, and the main radiative recombination mechanisms in activated solid-solution layers have been identified. The role of iodine in the formation of the emitting nanostructures has been discussed.
Synthesis, morphology, and optical properties of colloidal CdTe/CdSe and CdTe/CdS nanoheterostructures based on CdTe tetrapods by D. N. Dirin; R. B. Vasiliev; M. S. Sokolikova; A. M. Gaskov (23-28).
We report the synthesis of colloidal CdTe/CdSe and CdTe/CdS nanoheterostructures based on CdTe tetrapods with a CdSe or CdS shell. The shell growth takes place on the lateral faces of the tetrapod legs, whereas the leg length remains essentially unchanged. Both the CdSe and CdS shell growth shifts the luminescence of the nanoheterostructures to the near-IR range, up to 850 nm, with a quantum yield of up to 20%. Analysis of the kinetics of the shift of the excitonic absorption band during nanoheterostructure growth suggests that the growth rate of CdS exceeds that of CdSe. The variation of the luminescence wavelength with shell thickness is compared to numerical modeling results.
Deposition of superconducting niobium coatings on titanium from molten salts by A. A. Shevyrev; V. N. Kolosov (29-35).
Superconducting niobium coatings have been electrodeposited from molten salts onto titanium substrates with a copper, nickel, or molybdenum protective layer, and their structure and magnetic properties have been studied. The coatings are shown to be suitable as a starting material for the superconducting layer of the rotor of cryogenic gyroscopes.
Preparation of nickel nanoparticles for catalytic applications by Yu. G. Morozov; O. V. Belousova; M. V. Kuznetsov (36-40).
Spherical oxidized nickel particles 15 to 200 nm in average size have been produced by a crucibleless aerosol method involving metal vapor condensation in an inert gas flow and oxidation processes. The particles have been characterized by scanning electron microscopy, X-ray microanalysis, X-ray diffraction, BET surface area measurements, and vibrating-sample magnetometry. The process parameters have been optimized for the preparation of particles with tailored size, specific surface area, and saturation magnetization. A dc electric field applied to the condensation zone during the oxidation process reduces the size and increases the extent of oxidation of the particles. We have studied low-temperature oxidation of carbon monoxide and propane on nickel nanopowders differing in particle size and extent of oxidation. The nanoparticles with optimized characteristics have been shown to have a marked catalytic effect on these processes.
Synthesis of ZnO rods by a simple chemical solution deposition method by Xiaojing Yu; Xiaoqin Xu; Dalai Jin; Sali Miao; Naiyan Wang; Kuihong Yao (41-44).
ZnO short rods with large yield have been synthesized by a simple chemical solution deposition method at a low temperature of 80°C. Polymethyl methacrylate was used as the structure-directing agent in the formation of the rod-like ZnO crystals. X-ray powder diffraction and field emission scanning electron microscopy were used to characterize the obtained product. The results showed that the as-prepared ZnO crystals were rod-like, which have fairly uniform diameter of around 0.5 ∼ 2 μm and length of 4 ∼ 6 μm. A possible formation mechanism of the ZnO rods has been considered.
Effect of mechanical activation on the morphology and structure of hydroxyapatite by I. Sh. Trakhtenberg; A. P. Rubshtein; E. G. Volkova; S. A. Petrova; A. Ya. Fishman; R. G. Zakharov; V. B. Vykhodets; T. E. Kurennykh (45-50).
We have studied the effect of grinding in planetary mills on the phase composition, morphology, and water content of hydroxyapatite powder. The results indicate that milling for even relatively short times, which reduces the average particle size by a factor of 2, causes the monetite present in the unmilled powder to disappear and reduces the crystallite size of the hydroxyapatite. The fraction of nanoparticles in the powder is then 98% and remains constant during further milling. Milling for longer times leads to hydroxyapatite amorphization. For an average size of large particles R ≥ 1 μm, the surface area of the particles per unit volume, E (cm−1), is determined only by R (E ∼ 1/R).
High-temperature fluorohydroxyapatite-titanium interaction by A. A. Egorov; V. V. Smirnov; S. V. Kutsev; S. M. Barinov (51-54).
We have studied chemical interaction between fluorine-substituted hydroxyapatite and metallic titanium in the temperature range 700–1000°C. The results indicate that the phase relations in this system differ markedly from those in the hydroxyapatite-titanium system under similar conditions. The most important result is that the apatite phase persists in the former system, whereas in the hydroxyapatite-titanium system the hydroxyapatite decomposes at 900°C to form calcium titanate. The process common to the two systems is the complete oxidation of titanium and the formation of rutile at temperatures above 800°C.
Dielectric properties and electrical conductivity of Li x Na1−x Ta0.1Nb0.9O3 ferroelectric solid solutions by M. N. Palatnikov; V. A. Sandler; V. V. Efremov; N. V. Sidorov (55-62).
We have studied the dielectric properties and electrical conductivity of Li x Na1 − x Ta0.1Nb0.9O3 (x = 0.03−0.135) ferroelectric solid solutions at temperatures from 290 to 700 K and frequencies from 25 to 106 Hz. The results demonstrate that charge transport in these materials is due to the Li+ ion and that their conductivity is dominated by volume ion transport. In the temperature range studied, the Li x Na1 − x Ta0.1Nb0.9O3 solid solutions undergo a first-order ferroelectric phase transition close to second order. Increasing the lithium content enhances features characteristic of second-order transitions.
Skyrmion lattices in the BiFeO3 multiferroic by A. N. Kalinkin; V. M. Skorikov (63-67).
This work examines conditions for skyrmion lattice stability in BiFeO3 multiferroic films possessing record high ferroelectric and antiferromagnetic transition temperatures, giant polarization, and a giant magnetoelectric effect. Using analytical and numerical calculations, we demonstrate stability of solitary spin vortices (skyrmions) and skyrmion lattices in BiFeO3 films owing to the Dzyaloshinskii-Moriya interaction. Our results confirm that BiFeO3 can be used as a matrix for chips with ultrahigh data density, up to 10 Tb/cm2.
Preparation and structural characterization of bismuth ferrite crystals of different morphological types by L. P. Kozeeva; M. Yu. Kameneva; N. V. Podberezskaya; A. I. Smolentsev; V. E. Fedorov (68-74).
We have studied conditions for bismuth ferrite, BiFeO3, crystallization from off-stoichiometric Bi2O3-Fe2O3 melts, obtained crystals of different morphological types (dendritic and faceted pseudocubic) up to 3 mm in size, and characterized them by a variety of techniques (X-ray diffraction, IR spectroscopy, differential thermal analysis, X-ray structure analysis, and X-ray microanalysis).
Crystal structure and magnetic properties of high-coercivity Sr1 − x Pr x Fe12 − x Zn x O19 solid solutions by D. D. Polyko; L. A. Bashkirov; S. V. Trukhanov; L. S. Lobanovskii; I. M. Sirota (75-79).
Sr1−x Pr x Fe12 − x Zn x O19 ferrites with x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5 have been prepared by solid-state reactions between praseodymium, iron, and zinc oxides and strontium carbonate in air at 1470 K. According to X-ray diffraction results, the samples with x ≤ 0.2 were single-phase and those with 0.3 ≤ x ≤ 0.5 contained, in addition to the magnetoplumbite phase, small amounts of α-Fe2O3, ZnFe2O4, and PrFeO3. The mixed-phase samples further fired twice at 1470 K for 4 and 2 h contained no impurity phases at x = 0.3 and contained only α-Fe2O3 at x = 0.4 and 0.5. In the composition range 0 ≤ x ≤ 0.3, the a and c cell parameters, unit-cell volume V, and X-ray density ρx of the magnetoplumbite phase vary linearly according to the relations a(Å) = 5.8869 − 0.0162x, c(Å) = 23.027 + 0.449 x, V(Å3)= 691.10 + 9.65x, and ρx(g/cm3) = 5.102 + 0.230 x. The highest degree of combined heterovalent substitution of Pr3+ for Sr2+ and Zn2+ for Fe3+ in the SrFe12O19 ferrite (formation of Sr1−x Pr x Fe12 − x Zn x O19 solid solutions) at 1470 K is x = 0.32−0.36. The saturation magnetization per formula unit (n s) of the x = 0.1 ferrite exceeds that of SrFe12O19 by 1.7% at 6 K and by 15.2% at 308 K. The 308-K n s and coercive force (σ H c) of the x = 0.2 ferrite exceed those of SrFe12O19 by 7.6 and 8.5%, respectively.
Interaction study between drugs and some synthetic nanoporous composites by M. Zendehdel; M. M. Pouramini; H. Alikhani (80-86).
In this work MCM-41, MCM-41/NaY and Clinoptilolite/MCM-41/NaY composites that have CTMABr (N-cethyl-N,N, and N-trimethyl Ammonium Bromide) were prepared and characterized with XRD, SEM and FT-IR. Also, incorporation of two model drugs (sulfamethoxazole and metronidazole) with these composite were considered. The drug adsorption assays showed that three composites adsorb considerable amount of drugs, in particular sulfamethoxazole which was evaluated by UV spectroscopy. The results show that we have more adsorption of sulfamethoxazole for MCM-41/NaY that there is a direct relationship exists between the amounts of surfactant per gram of composite. TGA shows that the composites are more stable thermally when the ad micelles contain sulfamethoxazole in their interior. The results of adsorption of sulfamethoxazole showed that approximately 70% of drug was released from MCM-41/NaY-sulfamethoxazole system after about 24 h.
Compositionally graded ceramics based on Ba1 − x Sr x TiO3 solid solutions by V. N. Shut; S. R. Syrtsov; V. L. Trublovsky; B. A. Strukov (87-92).
Homogeneous and compositionally graded barium strontium titanate (Ba1 − x Sr x TiO3) ceramics have been prepared in the form of thick films by slip casting. The strontium content was varied across the graded films from 0 to 30 mol %. Microstructural examination and dielectric measurements have shown that, varying the composition and thickness of the layers in graded structures and the sintering conditions, one can control the behavior of their dielectric characteristics and obtain a small temperature coefficient of capacitance in a predetermined temperature range.