Showing papers in "Russian Journal of Inorganic Chemistry in 2007"

Whitlockite solid solutions Ca9−x M x R(PO4)7 (x = 1, 1.5; M = Mg, Zn, Cd; R = Ln, Y) with antiferroelectric properties

Abstract: Whitlockite solid solutions Ca9−x M x R(PO4)7 (M = Mg, Zn, Cd; R = Ln, Y) were synthesized as powders and ceramics using solid-phase synthesis. Dielectric investigations and second harmonic generation (SHG) tests showed that ferroelectric (FE) phase transitions existing in samples with x = 0 change to antiferro-electric (AFE) transitions between two centrosymmetrical phases in samples with x = 1 or 1.5. The calcium-ion solid electrolyte conductivity in Ca9−x M x R(PO4)7 at high temperatures appears either as a result of an antiferroelectric-paraelectric (AFE-PE) phase transition (for x = 1) or as a result of a separate phase transition near 1173 K (for x = 1.5). The appearance of dielectric properties in whitlockites is discussed with reference to the features of their polar and centrosymmetrical structures.

ZnO formation under hydrothermal conditions from zinc hydroxide compounds with various chemical histories

Abstract: The sequence of phase transformations of zinc hydroxide compounds with various chemical histories during hydrothermal (HT) treatment is studied by X-ray powder diffraction and thermal analysis (TG/DTA). ɛ-Zn(OH)2 (wulfingite) is the major intermediate in ZnO production by the HT process. The micromorphology and photocatalytic activity of ZnO powders are studied.

Thermal stability of Bi2O3

Abstract: Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) of an α-Bi2O3 sample revealed staged phase transitions in the range 720–800°C (at 720, 780, and 800°C) and the elimination of oxygen to the composition Bi2O2.967 during heating to 895°C in air at 16 K/min. In dynamic vacuum (p = 1.33 Pa) at 780–800°C, Bi2O3 consecutively transforms to a phase with the cubic γ-Bi2O3 structure and tetragonal Bi2O2.3−2.4. In the latter, electron diffraction in a transmission electron microscope (ED/TEM) shows a superstructure with the superstructure vector q 110 ≈ 1/9, which indicates an ordered arrangement of oxygen vacancies.

Operating Conditions for Lithium Recovery from Natural Brines

Abstract: Lithium recovery from natural brine incontestably requires the optimization of the parameters which influence such a process This process consists of trapping lithium ions by a gel of aluminum hydroxide prepared under the action of a strong base Studied parameters are molar ratio [Al]/[Li], stirring time, reaction temperature and apparent pH A systematic study was carried out varying only one parameter at a time This procedure makes it possible to fix the studied parameters in order to recover maximum Li+ This work is done first on synthetic brines, and then it was considered convenient to check the obtained result using natural brine and an equivalent synthetic brine Some differences related to lithium yield are established between the two considered brines This is due in our opinion to the impurities contained in the natural brine, especially magnesium and boron

Synthesis of nanosized ceria with controlled particle sizes and bandgap widths

Abstract: The formation dynamics of nanosized ceria in cerium nitrate(III) and hexamethylenetetramine (HMTA) solutions has been studied for the first time using UV-visible spectroscopy. The bandgap width and particle size of CeO2 are controlled by the synthesis duration, reaction temperature, and the concentrations and molar ratio of the reagents.

Hydrothermal/microwave and hydrothermal/ultrasonic synthesis of nanocrystalline titania, zirconia, and hafnia

Abstract: We compare the physical-chemical properties (X-ray diffraction (XRD), powder X-ray diffraction, TGA, TEM, and BET) of titania, zirconia, and hafnia nanopowders (d = 10–15 nm) synthesized from amorphous titanyl hydroxide TiO2 · nH2O, zirconyl hydroxide ZrO(OH)2 · nH2O, and hafnyl hydroxide HfO(OH)2 · nH2O using hydrothermal (HT), hydrothermal/microwave (HT-MW), and hydrothermal/ultrasonic (HT-US) methods at 150, 180, and 250°C with treatment lasting 0.5–24 h. Titania, zirconia, and hafnia crystallization from amorphous hydroxides is substantially enhanced, and the percentage of the thermally stable zirconia phase (m-ZrO2) in the HT-MW and HT-US processes increases compared to conventional HT synthesis. The observed similar effects have completely different causes. A common factor in both cases is likely the uniformity of heating of treated suspensions. Local overheating in the reaction mixture, which appears during both ultrasonication and microwave treatment, can also play a role in accelerating the hydrothermal processes.

Preparation of nanopowdered M 1−x R x F 2+x (M = Ca, Sr, Ba; R = Ce, Nd, Er, Yb) Solid Solutions

Abstract: The synthesis procedure has been worked out, and nanopowders of fluoride solid solutions (ss) Ca1−x R x F2+x (R = Er, Yb), Sr1−x Nd x F2+x , and Ba1−x Ce x F2+x have been manufactured by coprecipitation from aqueous solutions. The powders consist of rounded particles with sizes from 50 to 150 nm. The particles with sizes of about 150 nm are aggregates of adhered nanoparticles. The nanoparticles are highly reactive and sinter at low temperatures (T < 0.35T m).

Hydrothermal synthesis of nanotubular Mg-Fe hydrosilicate

Abstract: Magnesium iron hydrosilicate nanotubes with a chrysotile ((Mg,Fe)3Si2O5(OH)4) structure have been synthesized hydrothermally at t = 250–450°C and p = 30–100 MPa. In the hydrothermal synthesis of (Mg,Fe)3Si2O5(OH)4 chrysotile, part of the Fe2+ ions oxidize to Fe3+ and are incorporated into the octahedron and tetrahedron layers of the chrysotile structure. The limiting iron content of chrysotile has been determined up to which cylindrically rolled layers can form to yield nanotubes. The hydrothermal treatment of precursors richer in FeO yields platelike hydrosilicates. The iron ions present in the starting components affect the synthesis parameters, morphology, size, optical properties, and thermal stability of the nanotubes.

Physical properties and electronic structure of TaC-HfC solid solutions

Abstract: The results of investigations of the physical properties and electronic structure in the Hf x Ta1−x solid solutions have been generalized. The N 3 X-ray emission spectra Ta in hafnium and tantalum carbides have been investigated for the first time. Peak locations and intensities have been compared with the results of calculations of the electron band structure of Hf x Ta1−x C alloys with x = 0, 0.25, 0.5, and 0.75. It has been found that the inversion of peak intensities with increasing hafnium concentration is due to a nonmontonic variation in the density of Ta 5d states in the valence band of these compounds.

Extraction of mineral acids with methyltrioctylammonium dinonylnaphthalenesulfonate

Abstract: The interphase distribution of hydrogen halides (HF, HCl, HBr, and HI) and oxygen-containing acids (H2SO4 and HClO4) in a system with the binary extracting agent methyltrioctylammonium dinonylnaphthalenesulfonate was studied. It was found in the extraction of mineral acids depending on the aqueous acidity, that the distribution ratios of mineral anions B m− decreased with pH in accordance of the laws of binary extraction. The extraction isotherms of mineral acids were obtained, and the apparent constants of extraction were calculated.

Structure of bismuth oxoborate Bi4B2O9 at 20, 200, and 450°C

Abstract: Single crystals of bismuth oxoborate Bi4B2O9 have been grown by slowly cooling the melt of a stoichiometric Bi2O3 + H3BO3 mixture. The structure of the borate (monoclinic space group P21/c, a = 11.107 A, b = 6.629 A, c = 11.044 A, β = 91.04°, Z = 4) has been studied at 20, 200, and 450°C. The structure is described not only in terms of full BiO6 − and BiO7 polyhedra but also in terms of truncated BiO3 − and BiO4 − polyhedra and BO3 triangles, as well as oxo-centered OBi3 triangles and OBi4 tetrahedra. It is shown that both the B-O and Bi-O bond lengths are practically unaffected by temperature. Only the angles between polyhedra change with temperature, being responsible for the strong anisotropy of Bi4B2O6 thermal expansion, which was measured by high-temperature powder X-ray diffraction: α11 = 20, α22 = 15, α33 = 6 × 10−6 °C−1, and μ = (c, α33) = −19°.

Synthesis, spectroscopy and antimicrobial activity of vanadium(III) and vanadium(IV) complexes involving Schiff bases derived from Tranexamic acid and X-ray structure of zwitter ion of Tranexamic acid

Abstract: This paper reports the synthesis of six new vanadium complexes of a Schiff base derived from Tranexamic acid. All the complexes were characterized by elemental analysis, infrared, electronic spectra, and mass spectrometry. FTIR data reveals that the Schiff base acts as a bidentate and the complexes exhibit the hexa-coordinated geometry in solid state. These complexes were screened for their biological activity against various bacterial and fungal strains. All the ligands show higher activity after complexation. The crystal structure of the Zwitter ion of the Tranexamic acid has been determined by X-ray single crystal diffraction.

Synthesis, crystal structure, and thermal properties of [Pd(NH3)4][AuCl4]2

Abstract: The double complex salt [Pd(NH3)4][AuCl4]2 was synthesized and studied by X-ray diffraction: a = 7.5234(6) A, b = 7.7909(5) A, c = 8.0247(6) A, α = 108.483(2)°, β = 106.497(2)°, γ = 99.972(3)°, V = 409.43(5) A3, space group P % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVy0df9qqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaa0aaaeaaca% aIXaaaaaaa!361B! $$\overline 1 $$ , Z = 1, ρcalod = 3.456 g/cm3, R = 0.0267. The compound was characterized by powder X-ray diffraction, thermal analysis, and IR and Raman spectroscopy. The metal products of thermolysis of the complex were studied by powder X-ray diffraction.

Synthesis of zirconium (hafnium) fluoride compounds and their X-ray luminescence properties

Abstract: Twenty-five zirconium (hafnium) fluoride compounds have been synthesized at room temperature in the systems MO2-H2SO4-M′nA(HF)-H2O (M = Zr (Hf); M′ = Na, K, Rb, Cs, NH4; A = F, SO4) and their X-ray luminescence spectra (luminescence wavelengths and relative intensities) have been measured. The X-ray luminescence of the compounds has been considered as a function of the composition (cations, anions, water content) and different structural factors (CNs, polyhedra, H-bonds). Ammonium compounds do not luminesce, and sodium fluorozirconates and heptafluorozirconates are weakly luminescing. Hexafluorozirconates M2Zr(Hf)F6 (M= K, Rb, Cs) and M5Zr4F21 · 3H2O (M = Rb, Cs), as well as oxofluorozirconate Rb2Zr3OF12, are strongly luminescing compounds.

FT-IR and Raman spectroscopic study of hydrated rubidium (cesium) borates and alkali double borates

Abstract: FT-IR and Raman spectra of five hydrated alkali borates and five hydrated alkali double borates have been recorded at room temperature in the range 400 to 4000 cm−1, and analyzed. Fundamental vibrational modes have been identified and assignments tentatively made in comparison with the work of Janda and Heller, and Li Jun.

Study of nitrosation of hexaammineruthenium(II): Crystal structure of trans -[RuNO(NH 3 ) 4 Cl]Cl 2

Abstract: The nitrosation of [Ru(NH3)6]2+ in hydrochloric acid and alkaline ammonia media has been studied; the patterns of interconversion of ruthenium complexes in reaction solutions have been proposed. In both cases, nitrogen(II) oxide acts as the nitrosation agent. The procedure for the synthesis of [Ru(NO)(NH3)5]Cl3 · H2O (yield 75–80%), the main nitrosation product of [Ru(NH3)6]2+, has been optimized. Thermolysis of [Ru(NO)(NH3)5]Cl3 · H2O in a helium atmosphere has been studied; the intermediates have been identified. One of these products is polyamidodichloronitrosoruthenium(II) whose subsequent decomposition gives an equimolar mixture of ruthenium metal and dioxide. The structure of trans-[RuNO(NH3)4Cl]Cl2, formed in the second stage of thermolysis and as a by-product in the nitrosation of [Ru(NH3)6]Cl2, has been determined by X-ray diffraction.

Synthesis of complex hydroxo salts of magnesium, nickel, cobalt, aluminum, and bismuth and oxide catalysts on their base

Abstract: Synthesis methods have been developed for the precursors of oxide catalysts that include the combination of magnesium nickel cobalt aluminum hydroxocarbonate, with a layered hydrotalcite-type structure and decavanadate and paramolybdate ions in the anion layers, and bismuth hydroxocarbonate. On the base of these precursors, multicomponent oxide catalysts have been manufactured for the oxidative dehydrogenation (OD) of light alkanes. Some of these catalysts showed high selectivities and high product yields in the conversion of ethane to ethylene.

Hydrazone as complexing agent: Synthesis, structural characterization and biological studies of some complexes

Abstract: This paper deals with the synthesis, magnetic, spectral, thermal, and biological studies of Ti(III), VO(IV), Cr(III), Mn(III), Fe(III), and Zr(IV) complexes with chelating hydrazone derived from 2-hydroxy-5-methylacetophenone and furoic acid hydrazide. The acid hydrazone synthesized is 2-hydroxy-5-methylace-tophenone-furoylhydrazone. The ligand has been characterized on the basis of IR and 1H NMR spectra. The presence of water molecules and thermal stabilities of the complexes are also reported. Solid-state electrical conductivity was measured over a 313–410-K temperature range, and the compounds show semiconducting behavior. The new complexes have been screened for their antibacterial and antifungal activity, and they show higher activity than free ligands.

Phase formation of complex phosphate K 4 Ti 3 Ni(PO) 4 in K 2 O-P 2 O 5 -TiO 2 -NiO melt solutions

Abstract: The principles of complex phosphate crystallization in K2O-P2O5-TiO2-NiO solution melts are studied for the ratios K/P = 0.7−1.4, Ti/P = 0.15, and Ni/Ti = 0.1−2.0. The phase-formation field and parameters are determined for a new complex phosphate K4Ti3Ni(PO4)6, which is isostructural to langbeinite. A single-crystal X-ray diffraction experiments is carried out for this phosphate (space group P213, a = 9.8247(10) A).

Ion state of atoms and the properties of perovskite-like compound CaCu3V4O12

Abstract: The binding energies and valence state of atoms in the perovskite-like compound CaCu3V4O12 have been determined using XPS spectroscopy. The stoichiometry of this phase is formulated as Ca2+Cu2+Cu 2 + (V 2 5+ V 2 4+ O12). Under an air atmosphere, the phase interacts with water vapor and oxygen. As a result, Ca(OH)2 is formed on its surface, the Cu+ and V4+ ion concentrations decrease, and the Cu2+ and V5+ concentrations increase in association. Raman spectra show shortened cation-anion bond lengths and cation-anion-cation bond angles in CaCu3V4O12 compared to perovskite CuVO3; the two structures are alike. The electrical conductivity, magnetic susceptibility, thermal and sensor properties of CaCu3V4O12 in aqueous salt solutions have been studied.

Synthesis and characterization of bis(nicotinamide) m-hydroxybenzoate complexes of Co(II), Ni(II), Cu(II), and Zn(II)

Abstract: Mixed-ligand m-hydroxybenzoate complexes of Co(II), Ni(II), Cu(II), and Zn(II) with nicotinamide were synthesized and characterized by elemental analysis, FT-IR spectrometry, solid state UV-vis spectrometry, and magnetic susceptibility measurements The thermal behavior of the complexes was studied by simultaneous TG-DTA methods in static air atmosphere The infrared spectral characteristics of the complexes are discussed and the mass spectra data are recorded The complexes contain two water molecules, two m-hydroxybenzoato (m-hba), and two nicotinamide (na) ligands per formula unit In these complexes, the m-hydroxybenzoate and nicotinamide behave as a monodentate ligand through acidic oxygen and nitrogen of the pyridine ring The decomposition pathways and the stability of the complexes are interpreted in terms of the structural data The final decomposition products were found to be the respective metal oxides

Anion effect on the thermolysis of double complexes [Co(NH3)6][Fe(CN)6] and [Co(NH3)6]4[Fe(CN)6]3

Abstract: The thermolysis of complexes [Co(NH3)6][Fe(CN)6] and [Co(NH3 6]4[Fe(CN)6]3 under an air or hydrogen atmosphere at 200, 350, and 500°C is studied. The composition and properties of thermolysis products are determined. The oxidative thermolysis yields mixtures of oxides of the central metals; the reductive thermolysis yields intermetallic compounds CoFe. The density of the complexes and the specific surface area of the intermetallic compounds are measured. Average particle sizes are calculated. The morphology and dispersion of the powders are dictated by the shape and density of the crystals of the precursor double salts and the thermolysis temperature. The thermolysis chemism in the oxidative and reductive atmospheres is discussed in the context of the nature of the complex anion.

K2SO4-KCl-H2O phase diagram in the area of heterogenization of homogeneous supercritical fluids

Abstract: The experimental investigations of phase equilibria in the K2SO4-KCl-H2O system at temperatures to 500°C and pressures to 100 MPa were directed to elucidate the phase transformation sequence that leads to the heterogenization of the supercritical fluid whose existence field propagates from the K2SO4-H2O binary subsystem to the ternary system. We suggest that fluid heterogenization in the title ternary system is accompanied by the transformation of the metastable immiscibility field to stable equilibria at elevated temperatures (near 460°C) and unexpectedly high pressures (∼60 MPa), despite the presence of a vapor phase.

Crystal structures of SrLnCuS3 (Ln = Gd, Lu)

Abstract: The crystal-chemical characteristics of new complex sulfides SrLnCuS3 (Ln = Gd, Lu) are determined from the data of X-ray powder diffraction patterns. SrGdCuS3 crystallizes in the orthorhombic crystal system (space group Pnma) and belongs to the Eu2CuS3 structure type with the unit cell parameters a = 10.3282(8) A, b = 3.9624(2) A, and c = 12.9364(9) A. The structure of SrLuCuS3 is orthorhombic: the KZrCuS3 structure type, space group Cmcm, and unit cell parameters are a = 3.9105(2) A, b = 12.9419(9) A, and c = 10.0191(8) A. A substantial role of crystal-chemical contraction inside the [LnCuS3] dimeric block in the stabilization of structure types based on Eu2CuS3 and KZrCuS3 is shown.

Electronic Structure of Magnetic Semiconductors Cd 1 - x Mn x GeAs 2 and Cu 1 - x Mn x GaTe 2

Abstract: The band structures of pure semiconductors CdGeAs2 and CuGaTe2, as well as magnetic semiconductors Cd1 − x Mn x GeAs2 and Cu1 − x Mn x GaTe2 (x = 0.0625), have been calculated by the density functional theory method. In both compounds, the Mn3d orbitals form a narrow band near the Fermi level. In the case of Cd1 − x Mn x GeAs2, the Mn3d orbitals are slightly involved in chemical bonding. In the case of Cu1 − x Mn x GaTe2, the same orbitals are considerably involved in chemical bonding. The relationship of these results with the properties of the compounds and ferromagnetism models is discussed.

Raman Spectra and Molecular Structure of Silicates

Abstract: The frequencies of the strong Raman bands of silicates corresponding to the Si2O52− complex anion and the SiO2 molecule have been determined. This revealed the presence of these anions in silicates with double rings or double chains and various types of layers and the presence of SiO2 molecules in silica modifications, feldspars, zeolites, and zircon group orthosilicates. A similarity between the Raman spectra of olivine group orthosilicates and garnet and phenacite group orthosilicates was found. This similarity was attributed to the existence of distorted tetrahedra in all of these groups, having disordered orientation in the garnet and phenacite groups.

Synthesis and study of Iron(II) perrhenate complexes with 4-propyl-1,2,4-triazole exhibiting 1 A 1 ⇄ 5 T 2 spin transition

Abstract: Coordination compounds of iron(II) perrhenate with 4-propyl-1,2,4-triazole (L), [Fe3L6(ReO4)4(H2O)2](ReO4)2(I), [Fe3L6(H2O)6](ReO4)6·H2O(II), and FeL3(ReO4)2(III), were synthesized. Compounds I and III were studied by static magnetic susceptibility measurements and by IR and electronic spectroscopy. These complexes exhibit a reversible 1 A 1 ⇄ 5 T 2 spin transition and thermochromism. Compound I exhibits a spin transition without hysteresis at 185 K. The temperatures of forward and reverse transition for III are 250 and 244 K, respectively. Complex II isolated by crystallization from an acidified aqueous solution of compound I has a linear trinuclear structure of the cation (X-ray diffraction data). The structure of complex I was assumed to be similar, while compound III has a polymeric structure.

Phase equilibria in the Ag-Bi-Te system

Abstract: The Ag-Bi-Te system has been investigated over the whole concentration range using DTA, powder X-ray diffraction, microhardness measurements, and measurements of the emf of concentration cells with reference to Ag/AgCl electrodes. The vertical sections Ag5Te3-Bi2Te3, AgBiTe2-Bi(Te) and Ag-Bi2Te, an isothermal section at 400 K, and liquidus-surface projection have been designed. The fields of crystalline phases, including the ternary compound AgBiTe2, have been determined.

Thermodynamic and experimental modeling of the formation of major mineral phases of uroliths

Abstract: Solubility diagrams have been calculated for the major phases of uroliths and their binary systems with a common cation or anion at 25°C. Phase-formation laws under the conditions of healthy human urea have been experimentally studied. The adequacy of the theoretical and experimental modeling to pathogenic mineralization in humans is analyzed. The applicability limits of the thermodynamic model have been refined.

Effect of the 18-crown-6 and benzo-18-crown-6 on the solvent extraction and separation of lanthanide(III) ions with 8-hydroxyquinoline

Abstract: The synergistic solvent extraction of 13 lanthanides with mixtures of 8-hydroxyquinoline (HQ) and the crown ethers (S) 18-crown-6 (18C6) or benzo-18-crown-6 (B18C6) in 1,2-dichloroethane has been studied. The composition of the extracted species has been determined as LnQ3 · S. The values of the equilibrium constant and separation factor have been calculated. Here, the effect of the synergistic agent (18C6 or B18C6) on the extraction process is discussed.