Catalytic properties of sodium zirconium molybdate phosphates in methanol transformations

Molybdate phosphates Na_1?y Zr₂(MoO₄) _y (PO₄)_{3 ? y} (y = 0, 0.25, 0.5) having the NaZr₂(PO₄)₃ structure were prepared by the sol-gel method. The catalytic properties of the molybdate phosphates in dehydration and dehydrogenation of methanol in inert and oxidizing atmospheres were studied.     

Cationic mobility in Li3?2xNbxFe2?x(PO4)3 complex phosphates

Synthesis and ionic conductivity of Li_3−2x Nb _x Fe_2−x (PO₄)₃ complex phosphates were studied by X-ray powder diffraction and impedance spectroscopy. These phosphates are formed only at 900–1000°C. Variations in their thermal expansivity and unit cell parameters induced by aliovalent doping were characterized. The conductivity of these materials increases monotonically in the series Li_0.5Nb_1.25Fe_0.75(PO₄)₃-LiNbFe(PO₄)₃ and Li_1.2Nb_0.9Fe_1.1(PO₄)₃-Li₃Fe₂(PO₄)₃, which is explained by consecutive occupation of the Li(1) and Li(2) positions in their structures. Original Russian Text ? A.R. Shaikhlislamova, I.A. Stenina, A.B. Yaroslavtsev, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 12, pp. 1957–1962.     

Synthesis and thermolysis of substitutional solid solutions (Cu1?yMy)2(OH)PO4·xH2O (x = 0.1?0.2; M = Zn, Co, Ni)

Substitutional solid solutions (Cu_1−y Zn _y )₂(OH)PO₄·xH₂O (0 ≤ y ⩽ 0.26, x = 0.1−0.2), (Cu_1−y Co _y )₂(OH)PO₄·xH₂O (0 ≤ y ≤ 0.10, x = 0.1−0.2), and (Cu_1−y Ni _y )₂(OH)PO₄·xH₂O (0 ≤ y ≤ 0.08, x = 0.1−0.2) were synthesized. The unit cell parameters of the resulting phosphates were determined, and their IR absorption spectra were measured. The reactants were H3PO4 and mixtures of hydrous carbonates of the appropriate metals. Thermolysis of the solid solutions was examined with (Cu_1−y Co _y )₂(OH)PO₄·xH₂O (0 ≤ y ≤ 0.10, x = 0.1−0.2) as an example.     

Interactions in the subsolidus region of the Na2MoO4-NiMoO4-Fe2(MoO4)3 system

Phase relations have been investigated in the subsolidus region of the Na₂MoO₄-NiMoO₄-Fe₂(MoO₄)₃ system by X-ray diffraction, differential thermal analysis, and vibrational spectroscopy. The phase of variable composition Na_1−x Ni_1−x Fe_1+x (MoO₄)₃(0≤x≤0.5) with the NASICON structure (space group R c) and the NaNi₃Fe(MoO₄)₅ ternary molybdate crystallizing in the triclinic crystal system (space group P ) have been obtained. A high conductivity was found in Na_1−x Ni_1−x Fe_1+x (MoO₄)₃, which allows one to consider this phase of variable composition as a promising solid electrolyte with sodium ion conduction. Original Russian Text ? N.M. Kozhevnikova, A.V. Imekhenova, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 4, pp. 695–700.     

Solid-phase chemical transformations in molybdate systems

The ternary salt systems M₂MoO₄−AMoO₄−Zr(MoO₄)₂ (M=K, Tl; A=Mg, Mn, Ni, Co, Cu, Zn, Cd) in a sub-solidus region were studied. New ternary molybdates with the M₅A_0.5Zr_1.5(MoO₄)₆ and MA_0.5Zr_0.5(MoO₄)₂ compositions were synthesized by solid-phase reactions in these systems. The crystallographic and thermal characteristics of the compounds were found. The electrical properties of potassium—manganese—zirconium molybdates were studied. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1036–1039, June, 1999.     

The conditions of formation and physicochemical properties of Nd1 ? xBaxMn1 ? yFeyO3 phases

The homogeneity regions of Nd_{1 − x} Ba _x MnO₃ (0.0 ≤ x ≤ 0.25) and NdMn_{1 − y} Fe _y O₃ (0.0 ≤ y ≤ 1.0) orthorhombic solid solutions in air at 1373 K were determined. The region of the existence of Nd_{1 − x} Ba _x Mn_{1 − y} Fe _y O₃ orthorhombic solid solutions in air at 1373 K was studied. A fragment of the phase diagram of the NdMnO₃-BaMnO₃-BaFeO_2.5-NdFeO₃ quasi-quaternary complex oxide system in air at 1373 K was suggested. The mechanothermal properties of Nd_0.75Ba_0.25MnO₃, Nd_0.8Ba_0.2Mn_0.9Fe_0.1O₃, Nd_0.8Ba_0.2Mn_0.7Fe_0.3O₃, and Nd_0.8Ba_0.2Mn_0.5Fe_0.5O₃ doped neodymium manganates were studied.     

Subsolidus phase relations in the Na2MoO4-CoMoO4-Cr2(MoO4)3 system

Triple molybdate NaCoCr(MoO₄)₃, a phase of variable composition Na₂MoO₄-CoMoO₄-Cr₂(MoO₄)₃ (0 ≤ x ≤ 0.5) having nasicon structure (space group R $ \bar 3 $ \bar 3 c), and triple molybdate NaCo₃Cr(MoO₄)₅ crystallizing in triclinic space group P $ \bar 1 $ \bar 1 were synthesized in the subsolidus region of the Na₂MoO₄-CoMoO₄-Cr₂(MoO₄)₃ ternary salt system. Crystal parameters were calculated for the newly synthesized molybdates and phases. The vibration spectra of Na_{1 − x} Co_{1 − x} Cr_{1 + x} (MoO₄)₃ and electrophysical properties were studied. Upon Na + Co → Cr(III) substitution, chromium cations are distributed to cobalt sites and additional vacancies are generated in the sodium sublattice.     

Synthesis of nanosized materials for lithium-ion batteries by mechanical activation. Studies of their structure and properties

This short review reports on the synthesis of nanosized electrode materials for lithium-ion batteries by mechanical activation (MA) and studies of their properties. Different structural types of compounds were considered, namely, compounds with a layered (LiNi_{1 − x − y} Co _x Mn _y O₂), spinel (LiMn₂O₄, Li₄Ti₅O₁₂), and framework (LiFePO₄, LiTi₂(PO₄)₃) structures. The compounds also differed in electronegativity, which varied from 10⁻⁴ S cm⁻¹ for LiCoO₂ to 10⁻⁹ S cm⁻¹ for LiFePO₄. The preliminary MA of mixtures of reagents in energy intensive mechanoactivators led to the formation of highly reactive precursors, and annealing of the latter formed nanosized products (the mean particle size is 50–200 nm). The local structure of the synthesized compounds and the composition of their surface were studied by spectral methods. An increase in the dispersity and defect concentration, especially in the region of the surface, improved some electrochemical characteristics. It increased the stability during cycling (LiMn₂O₄, at 3 V) and the regions of the formation of solid solutions during cycling (Li₄Ti₅O₁₂, LiFePO₄), led to growth of surface Li-ion conductivity (LiTi₂(PO₄)₃), etc. The mechanochemical approach was also used for the synthesis of core-shell type composite materials (LiFePO₄/C, LiCoO₂/MeO _x ) and materials based on two active electrode components (LiCoO₂/LiMn₂O₄).     

Cluster and Heterometallic Alkoxide Derivatives of Rhenium and d-Elements of V–VI Groups

The paper represents a listing of results obtained by developing the original methods of controlled synthesis of cluster and mono-, bi- and trimetallic oxo-alkoxide derivatives of rhenium and d-elements of V–VI groups. The developed techniques of the synthesis of metal alkoxides include: (1) anodic dissolution of the metals in the alcohol media; (2) direct reaction of the rhenium (VII) oxide with alkoxide derivatives of the transition elements. By such techniques were obtained: Re₄O₄(OEt)₁₂, Re₄O₆(OⁱPr)₁₀; individual rhenium alkoxocomplexes: Re₄O₂(OMe)₁₆, Re₄O₆(OMe)₁₂, Re₄O_6−y(OMe)_12+y; bimetallic ReMoO₂(OMe)₇, Re_4−xMo_xO_6−y(OMe)_12+y, Re_4−xW_xO_6−y(OMe)_12+y; Nb₂(OMe)₈(ReO₄)₂, Ta₂(OMe)₈(ReO₄)₂, Nb₄O₂(OMe)₁₄(ReO₄)₂, Ta₄O₂(OMe)₁₄(ReO₄)₂, Nb₄O₂(OEt)₁₄(ReO₄)₂, Ta₄O₂(OEt)₁₄(ReO₄)₂, alkoxocomplexes: Nb_2−xTa_x(OMe)₈(ReO₄)₂, Nb_4−xTa_xO₂(OMe)₁₄(ReO₄)₂, Nb_4−xTa_xO₂(OEt)₁₄(ReO₄)₂. All compounds mentioned above are characterized with X-ray single crystal study, IR-spectroscopy, DTG. It has been shown, that thermal decomposition of alkoxide derivatives in inert or hydrogen atmosphere leads to formation nano-size powders of individual rhenium and its alloys at low temperature. Thermal decomposition in air leads to formation individual metal oxides or its solid solutions. It has been demonstrated that the alkoxide derivatives could be promising precursors for next generation catalysts manufacturing.     

Oxygen reduction in acid media by a Ru<Subscript>x</Subscript>Fe<Subscript>y</Subscript>Se<Subscript>z</Subscript>(CO)<Subscript>n</Subscript> cluster catalyst dispersed on a glassy carbon-supported Nafion film

Electrocatalytic oxygen reduction was studied on a Ru_xFe_ySe_z(CO)_n cluster catalyst with Vulcan carbon powder dispersed into a Nafion film coated on a glassy carbon electrode. The synthesis of the electrocatalyst as a mixture of crystallites and amorphous nanoparticles was carried out by refluxing the transition metal carbonyl compounds in an organic solvent. Electrocatalysis by the cluster compound is discussed, based on the results of rotating disc electrode measurements in a 0.5 M H₂SO₄. A Tafel slope of −80.00±4.72 mV dec⁻¹ and an exchange current density of 1.1±0.17×10⁻⁶ mA cm⁻² was calculated from the mass transfer-corrected curve. It was found that the electrochemical reduction reaction follows the kinetics of a multielectronic (n=4e⁻) charge transfer process producing water, i.e. O₂+4H⁺+4e⁻→2H₂O. Electronic Publication     

Thermal preparation of green-brown zircon pigments

A new multi-component mineralizer is proposed which permits the synthesis of zircon pigments Zr_1−y−zMo_yCr _z ^IV SiO₄·xCr₂O₃ in an interesting green-brown hue.

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Zusammenfassung Es wird ein neuer Mehrkomponenten-Mineralisator vorgeschlagen, der die Synthese von Zirkonpigmenten Zr_1−y−zMo_y ^IVCr_z ^IVSiO₄·xCr ₂O₃ in einem interessanten grün-braunen Farbton gestattet.

     

Synthesis and study of the variable-composition phase Na1?xCo1?xFe1+x(MoO4)3, 0 ≤ x ≤ 0.4, with nasicon structure

The synthesis conditions for variable-composition phase Na_1−x Co_1−x Fe_1+x (MoO₄)₃, 0 ≤ x ≤ 0.4, crystallizing in the nasicon structure type (R $ \bar 3 $ \bar 3 c) were examined. For this phase, the crystallographic parameters were calculated, vibrational spectra were interpreted, and temperature dependence of electrical conductivity, dielectric constant, and dielectric loss tangent were examined.     

Interaction features of cerium (III) and europium (III) acetate and pivalate with monoethanolamine

The composition of mixed-ligand complexes of cerium (III) and europium (III) acetates and pivalates with monoethanolamine (MEA) depends on the synthesis conditions and the nature of carboxylate ligand. We prepared solid complexes [Ln(Piv)₃(MEA) _x ], where Ln = Ce, Eu; HPiv-2,2-dimethylpropionic (pivalic) acid; x = 1, 1.5, and gel-like hydroxocomplexes [Ln(Carb) _{n − x − y} ,(NO₃) _x (OH) _y (MEA) _w (H₂O) _z ], where Ln = Ce, n = 4; Ln = Eu, n = 3; HCarb is acetic acid (HAcet) or HPiv. The values of the coefficients x, y, w, and z depend on the synthesis conditions and heat treatment. Prepared compounds were characterized by IR and ¹H NMR spectroscopies, elemental and thermal analyses, and MALDI-MS. The ESI-MS method was used to characterize the processes occurring in the solutions.     

On the existence of phases with a structure of NaZr2(PO4)3 in series of binary orthophosphates with different alkaline element to zirconium ratios

Complex phosphates M_xZr_2.25–0.25x(PO₄)₃, where M=Li, Na,K, Rb or Cs and x may be an integer or fraction from 0 to 9, have been synthesized, and their structure has been investigated. The concentration and temperature ranges of stability of the phosphate phases NaZr₂(PO₄)₃ have been found. The influence of the method for the synthesis of these phases and of the annealing temperature on their crystal properties is studied. It was found that the structure of NaZr₂(PO₄)₃ [NZP] exists in the above phosphate series when 0≤x≤5 for Na and K, 0≤x≤3 for Rb, and 0≤x≤1 for Cs. N. I. Lobachevskii Nizhnii Novgorod State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 6, pp. 1104–1113, November–December, 1996. Translated by L. Smolina     

Synthesis and X-ray diffraction study of complex oxides of the Zn2 ? x(ZraSnb)1 ? xFe2xO4 composition

A multicomponent system of complex refractory oxides of the composition Zn_{2 − x} (Zr _a Sn _b )_{1 − x} Fe_2x O₄ (a + b = 1; a: b = 1: 5, 1: 4, 1: 3, 1: 2, 1: 1, 2: 1, 3: 1, 4: 1; x = 0−1.0; Δx = 0.05) was studied by X-ray diffraction. The samples were prepared from oxides of appropriate metals by low-temperature plasma synthesis (hydrogen-oxygen flame). Two phases with wide homogeneity ranges were identified: α phase crystallized in the crystal system of inverse cubic spinel and β phase with the structure of tetragonal spinel. The phase boundaries were found. Structural data are presented for about 100 solid solutions.     

Phase Analysis and Crystallographic Properties of the Phosphate Systems MO-ZrO2-P2O5 (M=Mg,Ca, Sr or Ba)

Phase formation in the systems MO-ZrO₂-P₂O₅ (M=Mg, Ca, Sr or Ba) with various ratios of M to Zr cations and within the temperature interval from 20 to 1200°C was investigated by means of DTA, TG, XRD and IR spectroscopy. The orthophosphate phases M_0.5xZr_2.25−0.25x(PO₄)₃ with x=0−1, 3 and 7 were synthesized. Concentration and temperature limits of phase existence were found for phosphates belonging in the NaZr₂(PO₄)₃ structural family. They exist within the regions with M to Zr ratios of 0≤x≤1 (with the exception of the Mg phases) and in the temperature interval from room temperature to 900–1700°C. This revised version was published online in August 2006 with corrections to the Cover Date.     

Oxygen reduction on a Ru x S y (CO) n cluster electrocatalyst in 0.5 M H2SO4

A ruthenium-sulfur carbonyl cluster electrocatalyst, Ru _x S _y (CO) _n , was synthesized by pyrolysis of Ru₃(CO)₁₂ and elemental sulfur in a sealed ampoule at 300 °C. The pyrolyzed compound was characterized by DSC, FT-IR, XRD and SEM (EDX) techniques. The electrocatalytic activity and kinetic parameters for the molecular oxygen reduction were determined by a rotating ring-disk electrode (RRDE) in a 0.5 M H₂SO₄ solution at 25 °C. The cathodic polarization indicates two Tafel slopes: −0.124 ± 0.002 V dec⁻¹ at low and −0.254 ± 0.003 V dec⁻¹ at high overpotentials, and first-order kinetics with respect to O₂ concentration. From the analysis of Levich plots and RRDE results, the oxygen reduction on Ru _x S _y (CO) _n was determined to proceed mostly via a multielectron transfer path (4e⁻) to water formation ( >94%). Received: 4 March 1999 / Accepted: 26 May 1999     

Oxygen ionic transport in Bi2O3-based oxides: II. The Bi2O3–ZrO2–Y2O3 and Bi2O3–Nb2O5–Ho2O3 solid solutions

Electrical conductivity, fluorite-type cubic unit cell volume and thermal expansion of the (Bi_{1− x} Nb _x )_{1− y} Ho _y O_1.5+δ (x=0.05 and 0.08; y=0.10−0.15) and (Bi_{1− x} Zr _x )_{1− y} Y _y O_1.5+δ (x=0.05 and 0.07; y=0.15) solid solutions have been found to decrease regularly with increasing dopant content. Annealing at temperatures below 900 K leads to a phase decomposition and to a sharp decrease in conductivity of the ceramics. Oxygen ion transference numbers have been determined by the e.m.f. method and by Faradaic efficiency measurement to exceed 0.9. A new technique of studying Faradaic efficiency has been proposed and verified using (Bi_0.95Zr_0.05)_0.85Y_0.15O_1.5+δ and Zr_0.90Y_0.10O_1.95 ceramic samples. Received: 31 October 1997 / Accepted: 18 December 1997     

ZrONO3)2-H3PO4-KF(HF)-H2O system at molar ratios of PO 43? /Zr = 0.5?1.6 as the basis for phase formation

The system ZrO(NO₃)₂-H₃PO₄-KF(HF)-H₂O was studied at ∼20°C along sections at molar ratios of PO₄³⁻ = 0.5, 1.0, and 1.6; KF: Zr = 1−5; and HF: Zr = 2−6. Phases in precipitates were identified by X-ray powder diffraction; IR spectroscopy; and crystal-optical, chemical, X-ray fluorescence and thermal analyses. The following crystalline phases were isolated: potassium fluorozirconates K₃ZrF₇, K₂ZrF₆, δ-KZrF₅, and KZrF₅ · H₂O; zirconium hydrophosphate Zr(HPO₄)₂ · 0.5H₂O; and potassium fluorophosphate zirconate K₃Zr₃F₃(HPO₄)₃(PO₄)₂. The following amorphous basic oxo(hydroxo)fluorohydrophosphate nitrates were isolated: K₄Zr₄O_2.5F₈(HPO₄)₂(NO₃)₃ · 6H₂O, K₂Zr₃O₃F₂(HPO₄)₂(NO₃)₂ · H₂O, and KZr₃O_1.5F₃(HPO₄)₂(NO₃)₃ · 2H₂O. Fields of solid phases were constructed, and the roles of anions and cations in the phase formation were considered.     

Recent studies on chemistry of novel μ-CO-containing butterfly Fe/E (E=S,Se,Te) cluster salts

This article describes recent developments in chemical study on a series of butterfly-shaped μ-CO-containing Fe/E (E = S, Se, Te) cluster salts. These salts include eleven novel cluster anions, which are the single butterfly one μ-CO-containing [(μ-RE)(μ-CO)Fe2(CO)6]- (A), the double butterfly two μ-CO-containing {[(μ-CO)Fe2(CO)6]2(μ-EZE-μ)}2- (B, E = S; C, E = Se), the triple butterfly three μ-CO- containing {[(μ-CO)Fe2(CO)6]3[(μ-SCH2CH2)3N]}3- (D), {[(μ-CO)Fe2(CO)6]3[1,3,5-(μ-SCH2)3C6H3]}3- (E), {[(μ- CO)...