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1.
Magnetic Properties of Ti3?xMxO5 Phases (M = V3+, Cr3+, Nb4+) The magnetic properties of Ti3?xVxO5, Ti3?xCrxO5, and Ti3?xNbxO5 phases are reported. In the case of V3+ and Cr3+ the magnetic leaping-temperature decreases, however Nb4+ shift the phase-transition towards higher temperatures. All samples show a “memory-effect” in magnetic properties, i. e. the results of heating- and cooling-cycles are higher susceptibilities of the α-phase of Ti3O5. Endowed Ti3O5 phases show for the α- and β-Ti3?xMxO5 til the leap Curie-Weiss characteristic in 1/X vs. temperature measurements. Exception is β-Ti3?xNbxO5, its susceptibility is independend of the temperature up to x ? 0.3. 相似文献
2.
The crystal structure of the hexagonal phase KxVxMo1?xO3 (x = 0.13) has been determined by single crystal X-ray analysis. The space group is P63. The parameters are a = 10.481 Å and c = 3.701 Å. The structure is formed by triple chains of octahedra sharing corners and parallel to the Oz axis. Each triple chain shares edges with three other chains.Potassium is inserted in the large tunnels. The reliability factor is R = 0.045 on the base of 158 observed reflexions. The RbxVxMo1?xO3 and CsxVxMo1?xO3 phases (0.12 ? x ? 0.14) are isostructural with KxVxMo1?xO3. 相似文献
3.
《Physics and Chemistry of Liquids》2012,50(2):261-268
Abstract The partial enthalpies of silicon, vanadium, zirconium, niobium and molybdenum in liquid tin at 1173 K were measured at high dilution by direct reaction calorimetry (drop method) with the help of a Tian-Calvet high-temperature calorimeter. When referred to liquid metals we found h si/kj. mol?1 = 99.4–263.0 x si, hv/kj. mol?1 = 102.8–14.8x v, h zr/kJ. mol?1 = 124.2–18.1x zr,h Nb/kJ .mol?1 = 81.7 + 72.5x Nb and h Mo/kJ. mol?1 = 115.4–159.9x Mo. The limiting partial enthalpies were deduced by extrapolation at infinite dilution. 相似文献
4.
S. B. Artemkina N. G. Naumov A. V. Virovets S. G. Kozlova V. E. Fedorov 《Journal of Structural Chemistry》2011,52(2):389-394
A crystal structure of a new layered [Nb4OI8][Mo6I14]2∞ polymer containing a previously unknown niobium cluster {Nb4(μ4-O)I8}2+ with a μ4 oxygen atom is determined. The compound crystallizes in the P$\bar 1$\bar 1
triclinic space group with unit cell parameters a = 10.1842(6) ?, b = 10.1880(6) ?, c = 11.5700(6) ?, α = 78.058(2)°, β = 77.944(2)°, γ = 80.738(2)°, V = 1139.85(11) ?3, Z = 1, R
f
= 0.0414. The electronic structure of the [{Nb4(μ4-O)I8}I4]2− cluster complex is calculated. 相似文献
5.
《Solid State Sciences》2004,6(7):689-696
Two interesting neutral tetrasupporting heteropolyoxometalates: [MoVI7MoVVIV8O40(PO4)][M(phen)2(OH)]2[M(phen)2(OEt)]2·xH2O (phen=1,10-phenanthroline, EtOH=ethanol, M=Co, x=7, 1; M=Ni, x=6, 2) were hydrothermally prepared and structurally characterized. The mixed molybdenum–vanadium polyoxoanion [MoVI7MoVVIV8O40(PO4)]4− exist in both two complexes, which acts as a bridge to covalently link two pairs of transition metal complex fragments, generating neutral windmill-like trimetallic nanocluster polyoxometalates. Variable-temperature magnetic susceptibility measurements of complexes 1 and 2 reveal that antiferromagnetic exchange interaction exists in this type of trimetallic tetrasupporting heteropolyoxometalates. 相似文献
6.
Restu Kartiko Widi Sharifah Bee Abd Hamid Robert Schlogl 《Reaction Kinetics and Catalysis Letters》2009,98(2):273-286
Reaction kinetics and proposed mechanism for the oxidation of propane over diluted Mo1–V0.3–Te0.23–Nb0.125–O
x
are described. The kinetic study allowed determination of the orders of propane disappearance, propene formation, CO
x
formation, and acids formation. The results show that selective oxidation of propane to propylene over this catalyst follows
the Langmuir-Hinshelwood mechanism. Deep oxidation of propane to carbon dioxide is first order with respect to hydrocarbon,
and partial order (0.21) with respect to oxygen. The selective oxidation of propane to acrylic acid is half order with respect
to hydrocarbon and partial order (0.11) with respect to oxygen, while water does not participate directly in propane transformation.
The result also shows that the overall reaction consists of three parallel process channels. One main sequence of consecutive
reactions leads to the desired product. 相似文献
7.
P. Tabero 《Journal of Thermal Analysis and Calorimetry》2007,88(1):37-41
Solid solution phases of a formula Fe8V10W16–xMoxO85 where 0≤x≤4, have been obtained, possessing a structure
of the compound Fe8V10W16O85.
It was found on the base of XRD and DTA investigations that these solution
phases melted incongruently, with increasing the value of x, in the temperature
range from 1108 (x=0) to 1083 K (x=4) depositing Fe2WO6
and WO3. The increase of the Mo6+
ions content in the crystal lattice of Fe8V10W16O85
causes the lattice parameters a=b contraction with cbeing
almost constant. IR spectra of the Fe8V10W16–xMoxO85 solid solution phases have been recorded. 相似文献
8.
A set of oxygen-containing molybdenum oxide clusters Mo
x
O
y
(x = 1–3; y = 1–9) was obtained with the use of a combination of a Knudsen cell and an ion trap cell. The reactions of positively charged clusters with C1–C4 alcohols were studied using ion cyclotron resonance. The formation of a number of organometallic ions, the products of initial insertion of molybdenum oxide ions into the C–O and C–H bonds of alcohols, and polycondensation products of methanol and ethanol were found. The reactions of neutral molybdenum oxide clusters Mo
x
O
y
(x = 1–3; y = 1–9) with protonated C1–C4 alcohols and an ammonium ion were studied. The following limits of proton affinity (PA) were found for neutral oxygen-containing molybdenum clusters: (MoO) < 180, (Mo2O4, Mo2O5, and Mo3O8) = 188 ± 8, PA(MoO2) = 202 ± 5, PA(MoO3, Mo2O6, and Mo3O9) > 207 kcal/mol. 相似文献
9.
The solid-phase interaction in the V2O5-Nb2O5-MoO3 system has been investigated, and the formation of a solid solution bounded by the compositions MoNb2V4O18 ? δ, Mo2NbV5O21 ? δ, Mo2Nb3V3O21 ? δ, and Mo4Nb9V9O57 ? δ has been found (δ is nonstoichiometry). In the V2O5?Nb2O5 system, the formation of three compounds is verified, namely, VNbO5 (tetragonal structure), VNb9O25, and V2Nb23O62.5. The first two compounds are isostructural and form a continuous solid solution with tetragonal symmetry. A new compound of the composition Mo3NbVO14 ? δ has been synthesized. This compound is isostructural to the Mo3Nb2O14 compound described in the literature and forms a tetragonal solid solution with it. The phase equilibria in the V2O5-Nb2O5-MoO3 system in the subsolidus region have been determined. 相似文献
10.
Phases of the formula A1?xфxMO4 with the scheelite-type structure are described where ф represents a vacancy at the A cation site and M is Mo6+, W6+, and/or V5+. Many different univalent, divalent, and trivalent A cations were used in this study. The phases with no defects, i.e., x = 0, were known except for those of the type A1+.5A3+.5MO4 where A1+ is Ag or Tl and M is Mo6+ or W6+. Phases with x > 0 are generally new and were prepared for catalytic studies. An excellent correlation between catalytic properties and defect concentration has been observed. 相似文献
11.
S. B. Artemkina N. G. Naumov A. V. Virovets V. E. Fedorov 《Russian Journal of Coordination Chemistry》2013,39(1):1-5
A solid solution Mo6 ? x Nb x I11 (x = 1.1–1.5) containing cluster cores {Mo5NbI8} is obtained by the high-temperature reaction of molybdenum, niobium, and iodine (550°C, 70 h, quartz ampule). According to the X-ray diffraction data, heating at 800°C in a molybdenum container results in the decomposition of the solution to Mo6I12 and Nb6I11. According to the X-ray structure analysis data, the compounds are isostructural to the high-spin modification Nb6I11 (space group Pccn). The presence of Nb atoms in the structure changes the structural type from the layered (Mo6I12) to framework structure, noticeably increases the metalmetal distances (2.661–2.716 Å, 2.695 Å) Mo6 octahedron with the retention of the distance from the metal (M) to the μ3-“capped” I atoms, and strongly elongates the M6-I-M6 bridges almost to the value observed in Nb6I11. 相似文献
12.
Crystals of novel heterepoly complexes (HPC) Na0.5Cs2 − x
[H0.5 − x
M
x
II
XIII(OH)6Mo6O18] · 7−8H2O (MII = Fe, Mn; XIII = Cr, Al) are synthesized. Crystal structures of the complexes Na0.5Cs2 − x
[H0.5 − x
FexCr(OH)6Mo6O18] · 7H2O (I) (x = 0.19) and Na0.5Cs2 − x
[H0.5 − x
MnxAl(OH)6Mo6O18] · 8H2O (II) (x = 0.22) are determined (space group Pbcn, Z = 8, a = 23.023(4) Å, b = 22.064(4) Å, c = 11.606(3) Å, V = 5895.66 Å3 for I and a = 22.972(9) Å, b = 22.002(8) Å, c = 11.543(5) Å, V = 5834.18 Å3 for II, respectively). The [XIII(OH)6Mo6O18]3− ligands were found to be coordinated in monodentate fashion to M atoms due to the participation of a terminal O atom of the
cis-MoO2 group in coordination with the Fe and Mn atoms, which was confirmed by IR data.
__________
Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 9, 2005, pp. 663–676.
Original Russian Text Copyright ? 2005 by Gavrilova, Molchanov. 相似文献
13.
碳纳米管促进的Co-Mo-K硫化物基催化剂用于合成气制低碳混合醇 总被引:1,自引:0,他引:1
以自行制备的多壁碳纳米管(CNT)作为添加剂,制备共沉淀型CNT促进的Co-Mo-K硫化物基催化剂. 实验发现,与未添加CNT的催化剂相比,添加少量CNT可显著提高CO的加氢转化活性和生成低碳醇的选择性. 在5.0 MPa, 623 K, V(CO)∶V(H2)∶V(N2)=45∶45∶10, GHSV=3600 ml/(g·h)的反应条件下, Co1Mo1K0.3-10%CNT催化剂上CO的转化率达21.6%, 相应的总醇(C1~4醇)时空产率为241.5 mg/(g·h), 产物中C2+醇/C1醇=1.39 (C基选择性比). 添加少量CNT并不会导致Co1Mo1K0.3硫化物基催化剂上CO加氢反应表观活化能发生明显变化,但却导致工作态催化剂表面催化活性Mo物种(Mo4+)的摩尔百分率有所提高; 另一方面, CNT促进的催化剂对H2有更强的吸附活化能力,并能在相当大程度上抑制水煤气变换副反应的发生. 这些因素有利于提高催化剂的活性和选择性. 相似文献
14.
Dong Ryul Park Heesoo Kim Ji Chul Jung Sang Hee Lee In Kyu Song 《Research on Chemical Intermediates》2008,34(8-9):845-851
Vanadium-containing H6+x P2Mo18?x V x O62 (x=0?3) Wells-Dawson heteropolyacid (HPA) catalysts were prepared. The successful formation of the Wells-Dawson HPAs was confirmed by FT-IR and ICP-AES analyses. The reduction potential of the H6+x P2Mo18?x V x O62 (x=0?3) catalysts was determined by temperature-programmed reduction measurements. The Wells-Dawson HPA catalysts were applied to the vapor-phase oxidation of methacrolein and benzyl alcohol. The reduction potential, conversion of methacrolein, and conversion of benzyl alcohol showed volcano-shaped curves with respect to vanadium substitution, and decreased in the order of H8P2Mo16V2O62>H7P2Mo17V1O62>H9P2Mo15V3O62>H6P2Mo18O62. A correlation between reduction potential and catalytic activity clearly showed that the conversion was monotonically increased with increasing reduction potential of the HPA catalyst in both oxidation reactions. 相似文献
15.
M. Hartmanova M. T. Le M. Jergel V. Šmatko F. Kundracik 《Russian Journal of Electrochemistry》2009,45(6):621-629
The investigated bismuth vanadate, BiVO4, bismuth vanadomolybdate, Bi0.85V0.55Mo0.45O4, and pure bismuth molybdate, Bi2Mo3O12, oxides prepared by novel spray drying technique having the scheelite structure were found to be monoclinic in the case of
BiVO4 and Bi2Mo3O12, whereas Bi0.85V0.55Mo0.45O4 is body-centered tetragonal. The distribution of intergranular porosity across polycrystalline samples is inhomogeneous,
being larger parallel to the flat compression of the powder samples. The high polarizability of Bi3+ cations with their lone-pair electrons influences stability of the disordered oxygen sublattice. All as-prepared systems
undergo a slight structural change of the oxygen arrangement during the sample heating in the temperature region of 340–390°C,
probably due to an order ⇆ disorder transition, resulting in a decrease of lattice oxygen ion mobility and decrease of electrical
conductivity. The total bulk electrical conductivity of both vanadate systems is essentially ionic at low temperatures and
high oxygen partial pressures. Diffusion of the lattice oxygen ions in the Bi1−x/3V1−x
Mo
x
O4 scheelite structure is indirectly related to the introduction of cation vacancies. The highest conductivity was observed
in the multicomponent oxide Bi0.85V0.55Mo0.45O4, both as-prepared and thermally treated. Above 350°C the conductivity of BiVO4 and partially also Bi0.85V0.55Mo0.45O4 oxides is affected by the n-type electron contribution.
Published in Russian in Elektrokhimiya, 2009, Vol. 45, No. 6, pp. 659–667.
The article is published in the original.
Published by report at IX Conference “Fundamental Problems of Solid State Ionics”, Chernogolovka, 2008. 相似文献
16.
Dong Ryul Park Heesoo Kim Ji Chul Jung Sang Hee Lee Joohyung Lee In Kyu Song 《Reaction Kinetics and Catalysis Letters》2008,93(1):43-49
Vanadium-containing H6+xP2Mo18−xVxO62 (x = 0, 1, 2 and 3) Wells-Dawson heteropolyacid (HPA) and H3+xPMo12−xVxO40 (x = 0, 1, 2 and 3) Keggin HPA catalysts were applied to the vapor-phase dehydrogenation of cyclohexanol. The catalytic oxidation
activity showed a volcano-shaped curve with respect to vanadium substitution for both families of HPA catalysts. The Wells-Dawson
HPA showed a better catalytic oxidation performance than the Keggin HPA at the same level of vanadium substitution. 相似文献
17.
18.
E. S. Buyanova O. S. Kaimieva A. N. Shatokhina M. V. Morozova Yu. V. Emel’yanova S. A. Petrova 《Russian Journal of Inorganic Chemistry》2016,61(4):470-476
Solid solutions Bi3Nb1–yWyO7 ± δ, Bi3Nb1–yVyO7 ± δ, Bi3Nb1–yFeyO7 ± δ (y = 0.1–0.5; Δy = 0.1), and Bi3–xYxNb1–yWyO7 ± δ (x = 0.05, 0.1; y = 0–0.3; Δy = 0.1) have been studied. The homogeneity ranges of the solid solutions and crystal-chemical parameters have been determined by means of X-ray powder diffraction. The electrical conductivity of sintered samples has been studied by impedance spectroscopy. The joint introduction of yttrium and tungsten into the niobium sublattice does not lead to an increase in the conductivity of solid solutions, and the change of the dopant type has no noticeable effect on this conductivity. 相似文献
19.
The vanadium-molybdenum mixed oxide bronzes of composition K0.23(V5.35Mo0.65)O15 and K0.32(V5.48Mo0.52)O15 have a monoclinic structure with s.g. C2/m, Z=2, and unit-cell dimensions a=15.436(2), b=3.6527(5), c=10.150(1) Å, β=108.604(3)° and a=15.452(2), b=3.6502(5), c=10.142(1) Å, β=109.168(3)°, respectively, as determined by single-crystal X-ray diffraction. These compounds show the β-NaxV6O15 tunnel structure, which is isostructural with bannermanite, natural sodium-potassium vanadate. Structure refinements from diffracted intensities collected in the 2-38°θ range converged to final R=5.58% and 7.48% for the two crystals, respectively. The V atoms are distributed on three different crystallographic sites. Partial substitution of V with Mo occurs in only one of these positions. Oxygen atoms involved in vanadyl groups point toward the tunnels. The K ions in the tunnels are coordinated by seven oxygen atoms. The alkali metal content in these crystals is much lower than the solubility limit found for the analogous Na containing compound. 相似文献
20.
J.M. Tarascon F.J. Disalvo D.W. Murphy G.W. Hull E.A. Rietman J.V. Waszczak 《Journal of solid state chemistry》1984,54(2):204-212
Chemical and electrochemical insertion of Li at room temperature, as well as insertion of lead and tin at moderate temperatures (500°C), into the binary phase Mo6X8 forms ternary molybdenum chalcogenides MxMo6X8 (X = S, Se). Crystallographic parameters, superconducting properties, and magnetic susceptibility are reported. The stoichiometry x for lead and tin is shown not to exceed x = 1, while for Li, x can reach approximately 4.0. For the lead and tin sulfide series, the hexagonal lattice parameters and superconducting critical temperatures (Tc) are invariant to changes in the nominal composition of 0.8 < x < 1.2, while both an increase in Tc and a small decrease in ch is observed for the selenides; a narrow homogeneity range exists near x = 1 below 500°C for both these sulfides and selenides, the single-phase region being somewhat larger in the selenides. In contrast, several single-phase regions and large unit cell changes are observed in LixMo6X8 (0 < x < 3.2). Magnetic susceptibility measurements of the lithiated compounds at x ~ 3.2 reveals a structural phase transition at 140 and 185 K for the sulfide and selenide, respectively; but neither superconducts down to 1.5 K. At lower lithium concentration near x ~ 1.0, the Tc of the sulfide is raised from that of Mo6S8 (1.8 K) to 5.2 K but the Tc of Mo6Se8 (6.5 K) is depressed to 3.9 K. 相似文献