Interaction of nickel hydroxocarbonate,ammonium paramolybdate,and ammonium metatungstate under mechanical activation

The interaction of nickel hydroxocarbonate, ammonium paramolybdate, and ammonium metatungstate (Ni: Mo: W = 3: 1: 1) is reported. Under mechanical activation conditions, nickel hydroxocarbonate particles undergo comminution and ammonium paramolybdate and ammonium metatungstate particles soften and aggregate. It is demonstrated by DTA, X-ray diffraction, and IR spectroscopy that heat treatment of the mechanically activated mixture at 400–450°C yields the salts NiMoO₄ and NiWO₄.     

Mechanochemical synthesis of nanocrystalline nickel-molybdenum compounds,their morphology and application in catalysis: I. Effect of the Ni: Mo atomic ratio on the structure and properties of nickel-molybdenum compounds prepared under mechanochemical synthesis conditions

Mechanochemical activation in high-energy planetary activators was used for the preparation of highly dispersed nickel-molybdenum compounds. Nickel hydroxocarbonate [NiCO₃ · 2Ni(OH)₂ · nH₂O] and ammonium paramolybdate [(NH₄)₆Mo₇O₂₄ · 4H₂O] were chosen as starting compounds. The effect of the Ni: Mo atomic ratio on the composition and structure of products formed in the process of mechanochemical activation followed by calcination was studied. It was found that, at the Ni: Mo atomic ratios of 1.0 and 1.4, the mechanically activated product after calcination at 520°C contained 70–100% β-NiMoO₄, which is a stable phase at temperatures lower than 180°C.     

Synthesis, structure, and physicochemical properties of K[VO2(SeO4)(H2O)] and K[VO2(SeO4)(H2O)2] · H2O

The vanadium(V) complexes K[VO₂(SeO₄)(H₂O)] and K[VO₂(SeO₄)(H₂O)₂] · H₂O were synthesized using original procedures; their physicochemical properties were studied, and the crystal structure was determined on the basis of X-ray diffraction and neutron diffraction data. The structure of K[VO₂(SeO₄)(H₂O)₂] · H₂O is composed of VO₆ octahedra connected to form infinite chains by bridging SeO₄ tetrahedra. Each VO₆ tetrahedron has short terminal V-O bonds forming the bent dioxovanadium group VO₂⁺ The unit cell parameters of K[VO₂(SeO₄)(H₂O)₂] · H₂O are a = 6.4045(1) ?, b = 9.9721(2) ?, c = 6.6104(1) ?, β = 107.183(1)°, V = 403.34 ?³, Z = 2, monoclinic system, space group P2₁. The complex K[VO₂(SeO₄)(H₂O)] forms a two-dimensional layered structure composed of highly distorted VO₆ octahedra having two short terminal V-O bonds and SeO₄ groups coordinated simultaneously by three vanadium atoms. This compound crystallizes in the monoclinic system (space group P2₁/c): a = 7.3783(1) ?, b = 10.5550(2) ?, c = 10.3460(2) ?, β = 131.625(1)°, V = 602.894(5) ?³, Z= 4. The vibrational spectra of the studied compounds are fully consistent with their structural features.     

Electronic band structure and optical absorption of nanotubular zinc oxide doped with Iron, Cobalt, or Copper

The absorption spectra of the precursor-derived solid solutions Zn_{1 ? x} M _x O (M = Fe, Co, Cu) with a tubular morphology of aggregates have been investigated in the ultraviolet and visible regions. The maximum metal concentration x in the Zn_{1 ? x} M _x O solid solutions is 0.075 for iron, 0.2 for cobalt, and 0.1 for copper. It has been found that the optical absorption and the band gap of the Zn_{1 ? x} M _x O compounds depend on the type of dopant. The obtained experimental data have been interpreted using the results of the performed ab initio calculations of the electronic band structure and optical absorption.     

Synthesis and vibrational spectra of solid solutions based on lanthanum gallate

The synthesis conditions for single-phase solid solutions based on lanthanum gallate, LaGa_{1 ? x} Mg _x O_{3 ? δ}(x= 0–0.25, solid-phase method) and La_{1 ? y}Sr_yGa_{1 ? y}Mg_yO_{3 ? δ}(y= 0–0.2, glycine nitrate method), have been investigated. The structural parameters have been calculated using X-ray powder diffraction data. The IR and Raman spectra have been analyzed. Regularities in the changes in the structural parameters and vibrational spectra with composition are established.     

The effect of preparation method on the defect structure and luminescence properties of γ-Al2O3

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