Reactivity of FeVO4 towards MgMoO4 in the solid-state

A compound of the formula Fe₃Mg₂Mo₂V₃O₂₀ has been obtained as a result of a reaction between FeVO₄ and MgMoO₄ taken at a molar ratio of 3:2. This compound crystallises in the monoclinic system and its unit cell parameters are the following: a=0.6971 nm, b=0.9055 nm,c=1.2542 nm, g=102.00°, Z=2. This revised version was published online in July 2006 with corrections to the Cover Date.     

Comparative studies in subsolidus areas of ternary oxide systems PbO–V2O5–In2O3 and PbO–V2O5–Fe2O3

Thermal stability of PbO was studied. Reactivity of oxides in the systems PbO–M₂O₃ (M = In, Fe) was investigated up to 650 °C. Using the DTA and XRD methods, parts of investigated ternary oxide systems, labelled by compounds: V₂O₅, Pb₈V₂O₁₃ and M₂O₃ (M = In, Fe), have been divided into partial ternary systems. IR spectra of compounds Pb₂MV₃O₁₁ (M = In, Fe) have been compared.     

New compound Mg3In4V6O24 and its physicochemical characteristic

Journal of Thermal Analysis and Calorimetry - A new compound of the formula Mg3In4V6O24 belonging to the family M3A4V6O24 [where M?=?metal(II), A?=?metal(III)] was obtained...     

The Reaction Mechanism and Kinetics of the Zn2.5VMoO8 Phase Synthesis in the Solid State

Studies on the reaction kinetics and mechanism of the synthesis of the Zn_2.5VMoO₈ compound in the solid state have been carried out in situ in a high-temperature X-ray diffraction attachment. The apparent activation energy, 212±26 kJ mol^-1 was calculated by using the diffusion controlled Ginstling-Brounstein model. There was also determined a temperature dependence of unit cell parameters for Zn₃V₂O₈ and Zn_2.5VMoO₈. This revised version was published online in July 2006 with corrections to the Cover Date.     

Magnetic study of Cr ion in M2CrV3O11−x (MZn, Mg) compounds

Electron paramagnetic resonance (EPR) and magnetic susceptibility measurements on the recently synthesized vanadates M₂CrV₃O_11−x (M=Zn, Mg) have been analyzed. Two absorption lines with g≈2.0 (type I) and g≈1.98 (type II) were recorded in the EPR spectra, which can be attributed to V⁴⁺ ions and Cr³⁺ ion clusters (pairs), respectively. The exchange constant J between Cr³⁺ ions has been calculated, using both EPR and magnetic susceptibility data. Fitting of the EPR and magnetic susceptibility data has been carried out. The sign of J is a negative one for all samples and indicates antiferromagnetic interactions. Some difference in the J constant value among samples has been obtained. Volumetric titration confirms distinctly the presence of vanadium V⁴⁺ ions in the investigated compounds.     

DTA-TG and XRD study on the reaction between ZrOCl2·8H2O and (NH4)2HPO4 for synthesis of ZrP2O7

In this paper, we report results of thermoanalytical investigation on the reaction between ZrOCl₂·8H₂O and (NH₄)₂HPO₄ in molar ratio 1:2. Differential thermal-thermogravimetric and X-ray diffraction analyses were performed in order to reveal the chemical transformations, which took place during heating of the individual compounds ZrOCl₂·8H₂O, (NH₄)₂HPO₄ and the mixture ZrOCl₂·8H₂O:2(NH₄)₂HPO₄. It was shown that the transformations in the mixture below 160 °C were connected with dehydration of ZrOCl₂·8H₂O and interaction between the components of the mixture, which resulted in the formation of NH₄Cl, NH₄H₂PO₄ and a mainly amorphous zirconium phase, most likely t-ZrO₂. The zirconium component subsequently reacted with ammonium dihydrophosphate (below 200 °C) or with dehydrated phosphate derivatives (above 200 °C), which in both cases yielded an amorphous product. The interaction between the components of the mixture resulting in the formation of ZrP₂O₇ was completed by its crystallisation at 610 °C. Our study indicates an alternative low-temperature approach for the synthesis of the technologically important ZrP₂O₇ material.     

Physicochemical and Adsorption Characteristics of Divinylbenzene-co-Triethoxyvinylsilane Microspheres as Materials for the Removal of Organic Compounds

In this work, organic-inorganic materials with spherical shape consisting of divinylbenzene (DVB) and triethoxyvinylsilane (TEVS) were synthesized and investigated by different complementary techniques. The obtained microspheres may be applied as sorbent systems for the purification of organic compounds from water. The hybrid microspheres combine the properties of the constituents depending on the morphologies and interfacial bonding. In this work, the influence of the molar ratio composition of crosslinked monomer (DVB) and silane coupling agent (TEVS) (DVB:TEVS molar ratios: 1:2, 1:1 and 2:1) on the morphology and quality of organic-inorganic materials have been examined. The materials were analysed using small angle X-ray scattering (SAXS) analysis, low-temperature nitrogen sorption, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) to provide information on their structural and surface properties. Moreover, thermal analysis was performed to characterize the thermal stability of the studied materials and the adsorbent-adsorbate interactions, while adsorption kinetic studies proved the utility of the synthesized adsorbents for water and wastewater treatment.     

EPR study of defect centers in Zn2InV3O11

A multicomponent vanadate compound Zn₂InV₃O₁₁ has been synthesized and investigated using the electron paramagnetic resonance (EPR) technique. The Zn₂InV₃O₁₁ compound is isostructural with a previously studied magnetic system M₂FeV₃O₁₁ (M = Mg, Zn, Co, Ni). According to the nominal stoichiometry of the Zn₂InV₃O₁₁ compound all ions are non-magnetic, but the registered EPR spectra in the 4–300 K temperature range have revealed the presence of a rich variety of paramagnetic centers involving predominantly monomeric and dimeric units, as well as clusters of V⁴⁺ ions. The most intense EPR component, attributed to the VO²⁺ vanadyl ion in an axial symmetry, has displayed a well resolved hyperfine structure. The presence of a complicated spectrum at low magnetic field (g  4.4) and a broad line at g  2 has confirmed the existence of vanadium dimers. A spectral feature attributed to vanadyl spin clusters has been observed at temperatures above 80 K in the 270–310 mT magnetic field range. The role of oxygen deficiency in the appearance of the observed magnetic centers has been discussed. Comparison with the previously studied Mg₂InV₃O_11?δ compound has been made and the influence of specific cations on magnetic defect centers has been considered.     

Study on Phase Relations in Zn3V2O8–ZnMoO4 System

The phase equlibria established in the Zn₃V₂O₈–ZnMoO₄ system over the whole component concentration range up to 1000°C have been investigated. A phase diagram has been constructed using the results of DTA and XRD methods. This revised version was published online in July 2006 with corrections to the Cover Date.