共查询到20条相似文献,搜索用时 31 毫秒
1.
Masahiko Numakura Yoshihiro Okamoto Hideaki Shiwaku Atsushi Nezu Yasuaki Shimohara Olivier Pauvert Pierre Chamelot 《Journal of fluorine chemistry》2010,131(10):1039-1043
X-ray absorption fine structure (XAFS) measurements on terbium fluoride in molten lithium fluoride and in molten lithium-calcium fluoride mixtures, (e.g. 0.20TbF3-0.80LiF, 0.20TbF3-0.62LiF-0.18CaF2, 0.20TbF3-0.48LiF-0.32CaF2, 0.50TbF3-0.50LiF, and 0.50TbF3-0.38LiF-0.12CaF2), have been carried out. In the solid state, coordination number of terbium (Ni) and inter ionic distances between terbium and fluorine in the first neighbor (ri) are nearly constant in all mixtures. In 0.20TbF3-0.80LiF, 0.20TbF3-0.62LiF-0.18CaF2 and 0.50TbF3-0.50LiF mixtures, Ni's decrease from ca. 8 to 6 and ri's also decrease from ca. 2.29 to 2.26 Å on melting. On the other hands, in molten 0.20TbF3-0.48LiF-0.32CaF2 and 0.50TbF3-0.38LiF-0.12CaF2 mixtures, Ni's are slightly larger than 6 and ri's do not change. These facts correspond to the amount of F− supplied by solvent melts, i.e. the effect of CaF2 becomes predominant at bCaF2 > 0.32 in ternary 0.20TbF3-aLiF-bCaF2 mixtures and at bCaF2 > 0.12 in ternary 0.50TbF3-aLiF-bCaF2 mixtures. 相似文献
2.
Hexakis (organoamino) cyclotriphosphazenes (RNH)6P3N3 {R = i-Bu (1), R = i-Pr (2)} react with ortho-, meta- and para-derivatives of α,α′-dibromo xylene in 2:1 ratio to form salts of compositions [{(RNH)6P3N3}2xyl]Br2, {R = i-Bu, o-xyl (3); R = i-Pr, m-xyl (4); R = i-Pr, p-xyl (5)}. These contain dications consisting of two phosphazene rings, which are tethered together via ring N centres by a xylylene unit. X-ray structure analyses show that the substitution pattern at the xylylene bridge controls the orientation and distance between the two tethered phosphazene rings. The solid state structures exhibit dense networks of hydrogen bonds linking dications and anions. Direct N-H?N bonds between dications are observed in the crystal structure of 3. 相似文献
3.
Eugene L. Kolychev Viacheslav V. Shuntikov Mikhail S. Nechaev 《Journal of organometallic chemistry》2009,694(15):2454-13583
Reactions of neat 1,3- and 1,4-dibromides with N,N′-diarylformamidines in the presence of diisopropylethylamine (DIPEA) afford corresponding amidinium salts in high yields (>80%). Six- and seven-membered ring amidinium salts bearing bulky Mes (2,4,6-Me3C6H2) and Dipp (2,6-iPr2C6H3) aryl groups were prepared using this method. Free six-membered ring carbene 6-Dipp was generated from amidinium salt using LiHMDS as a base. NHC-Ag(I) complexes were obtained by the reactions of amidinium salts with Ag2O. NHC complexes of Pd and Rh are not accessible by deprotonation of amidinium salts, nor by transmetallation of Ag(I) complexes. However NHC-Cu(I) complexes were obtained by transmetallation of NHC-Ag(I). Thus, transmetallation of six- and seven-membered NHC-Ag(I) complexes was documented for the first time. 相似文献
4.
Phase equilibria, crystal structure, and transport properties in the (100−x) La0.95Ni0.6Fe0.4O3-xCeO2 (LNFCx) system (x=2-75 mol%) were studied in air. Evolution of phase compositions and crystal structure of components was observed. The LNFCx (2≤x≤10) are three-phase and comprise the perovskite phase with rhombohedral symmetry (R3?c), the modified ceria with fluorite structure (Fm3?m), and NiO as a secondary phase. These multiphase compositions exhibit metallic-like conductivity above 300 °C. Their conductivity gradually decreases from 395.6 to 260.6 S/cm, whereas the activation energy remains the same (Ea=0.04-0.05 eV), implying the decrease in the concentration of charge carriers. Phase compositions in the LNFCx (25≤x≤75) are more complicated. A change from semiconducting to metallic-like conductivity behavior was observed in LNFC25 at about 550 °C. The conductivity of LNFCx (25≤x≤75) could be explained in terms of a modified simple mixture model. 相似文献
5.
Mathieu Salanne Christian Simon Pierre Turq Paul A. Madden 《Journal of fluorine chemistry》2009,130(1):38-2315
The construction of an interaction potential for mixtures of LiF, NaF, KF and ZrF4 on a purely first-principles basis is described. Many-body interactions are included via a polarization term. The predictions of the heat-transfer properties of two mixtures, LiF-NaF-KF (FLiNaK) and NaF-ZrF4, are then compared with experimental values. Values for the densities, thermal expansions, heat capacities and viscosities are compiled into figures of merits in order to compare the suitability of those molten salts to serve as primary or secondary coolants in a nuclear reactor. 相似文献
6.
采用非水解溶胶-凝胶工艺合成氧化锆干凝胶粉,然后将干凝胶粉与熔盐混合制备氧化锆纳米棒。借助DTA-TG、XRD、FE-SEM、TEM等测试手段研究了氧化锆的物相转变过程,探讨了熔盐种类与用量、氟化物的添加等工艺参数对制备氧化锆纳米棒的影响。结果表明:以NaVO3为熔盐,用量为1:1(熔盐与干凝胶的质量比),并且在添加氟化钠的条件下能够制备产率高,且沿[010] 方向择优生长的单斜氧化锆纳米棒;氟离子一方面加速了熔盐中Zr4+离子的传质,促使氧化锆干凝胶粉的溶解,另一方面吸附在氧化锆的高能晶面上抑制该晶面的生长,两者的共同作用促进了大量氧化锆纳米棒的形成。 相似文献
7.
Yizhak Marcus 《The Journal of chemical thermodynamics》2010,42(1):60-64
The cohesive energies ces of uni-univalent molten salts and the corresponding cohesive energy densities ceds and solubility parameters δ were calculated from literature data. The ceds are much larger than the internal pressures, Pi, as expected for highly structured liquids. The solubility parameters δ are too large to be significant for the solubility of the solutes, except gases, in these molten salts. 相似文献
8.
采用非水解溶胶-凝胶工艺合成氧化锆干凝胶粉,然后将干凝胶粉与熔盐混合制备氧化锆纳米棒。借助DTA-TG、XRD、FE-SEM、TEM等测试手段研究了氧化锆的物相转变过程,探讨了熔盐种类与用量、氟化物的添加等工艺参数对制备氧化锆纳米棒的影响。结果表明:以Na VO3为熔盐,用量为1∶1(熔盐与干凝胶的质量比),并且在添加氟化钠的条件下能够制备产率高,且沿[010]方向择优生长的单斜氧化锆纳米棒;氟离子一方面加速了熔盐中Zr4+离子的传质,促使氧化锆干凝胶粉的溶解,另一方面吸附在氧化锆的高能晶面上抑制该晶面的生长,两者的共同作用促进了大量氧化锆纳米棒的形成。 相似文献
9.
Three new N2S2 donor ligands 1,1′-((2-(2-(phenylthio)phenylthio)phenyl)methylene)bis(3,5-R-1H-pyrazole), R = H (LH), R = Me (LMe), R = i-Pr (Li-Pr) have been prepared and characterized. These bifunctional ligands incorporate two distinct chelate donor systems, by virtue of the presence of bispyrazole and bisthioether functions. The preferred conformation of these ligands is such that the N2 and S2 donor moieties may be oriented in opposite directions, thus favoring the formation of molecular chains when treated with AgBF4. The X-ray structures of Ag(I) complexes show that, depending on the steric hindrance present on the pyrazole rings, these ligands behave as κ4-SSNN-μ bridging tetradentate (when R = H), or κ3-SNN-μ bridging tridentate (when R = Me, i-Pr). Interestingly, [Ag(LH)]BF4 crystallizes in the chiral space group P41, with the molecular chain that is folded around the 41 screw axis. 相似文献
10.
M. Radhamma M.V. Prabhakara Rao D.H.L. Prasad 《The Journal of chemical thermodynamics》2007,39(12):1661-1666
Excess enthalpies (HE), at ambient pressure and T = 298.15 K, have been measured by using a solution calorimeter for the binary liquid mixtures of dimethyl sulphoxide (DMSO) with ketones, as a function of composition. The ketones chosen in the present investigation were methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and cyclohexanone (CH). The HE values are positive over the entire composition range for the three binary mixtures. Furthermore, the (vapour + liquid) equilibrium (VLE) was measured at 715 Torr for these mixtures, of different compositions, with the help of Swietoslawski-ebulliometer. The experimental temperature-mole fraction (t-x) data were used to compute Wilson parameters and then used to calculate the equilibrium vapour-phase compositions as well as the theoretical points for these binary mixtures. These Wilson parameters are used to calculate activity coefficients (γ) and these in turn to calculate excess Gibbs free energy (GE). The intermolecular interactions and structural effects were analyzed on the basis of the measured and derived properties. 相似文献
11.
Five-, six-, and seven-coordinate volatile butyltin(IV) heterobimetallic derivatives, respectively of the types, [BuSn{(μ-OPri)2Al(OPri)2}Cl2] (1), [BuSn{(μ-OPri)2Al(OPri)2}2Cl] (2), and BuSn{(μ-OPri)2M(OPri)x − 2}3 (3:M = Al (x = 4); 4:M = Ga (x = 4); 5:M = Nb (x = 6)) have been synthesized by the reactions of BuSnCl3 with potassium tetraisopropoxoaluminate in 1:1, 1:2, and 1:3 molar ratios. Replacement reactions of chloride in (1) and (2) with appropriate alkoxometallate (tetraisopropoxoaluminate, tetraisopropoxogallate, or hexaisopropoxoniobate) ligands result in the formation of novel BuSn(IV) heterotri- and tetra-metallic derivatives. All of these derivatives have been characterized by elemental analyses, molecular weight measurements, and spectroscopic (IR, 1H, 27Al, and 119Sn NMR) studies. Based on these studies, plausible structures for the new derivatives involving bidentate ligation of the alkoxometallate ligands have been suggested. 相似文献
12.
The structural and magnetic properties of a new ternary Ir-Mn-Ge phase, Mn3IrGe, as well as the solid solution Mn3Ir(Si1−xGex), 0?x?1, have been investigated by means of X-ray and neutron powder diffraction, magnetization measurements and first principles calculations. The crystal structure is cubic, of the AlAu4-type (an ordered form of the β-Mn structure), Z=4, space group P213, and the unit-cell dimension varies linearly with the silicon content. For all compositions, antiferromagnetic ordering is found below a critical temperature of about 225 K. The magnetic structure is noncollinear, as a result of frustrated magnetic interactions on a triangular network of Mn atoms, on which the moments rotate 120° around the triangle axes. The magnitude of the magnetic moment at 10 K is 3.39(4) μB for Mn3IrGe. The theoretical calculations reproduce with very good accuracy the magnitudes as well as the directions of the experimentally observed magnetic moments. 相似文献
13.
Elena Mas-Marzá Eduardo Peris Beatriz Royo 《Journal of organometallic chemistry》2006,691(12):2708-2712
Compound MoO2Cl2(THF)2 reacts with two equivalents of 1,3-dialkyl substituted 4,5-dimethylimidazol-2-ylidenes to give the dioxomolybdenum(VI) complexes MoO2Cl2(LR)2 [R = Me (1), i-Pr (2)]. Treatment of MoO2Cl2(THF)2 with one equivalent of the N-heterocyclic carbenes LMe, Li-Pr and C1Ln-Bu (LMe = 1,3,4,5-tetramethylimidazol-2-ylidene, Li-Pr = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene, and C1Ln-Bu = 1,3-dibutyl-4,5-dichloroimidazol-2-ylidene) affords the monocarbene adducts MoO2Cl2(LR) [R = Me (3), i-Pr (4)] and MoO2Cl2(C1Ln-Bu) (5), respectively. Decomposition of complexes 1-5 affords a molybdenum oxychloride anion [Mo2O5Cl4]2− as an imidazolium salt. 相似文献
14.
Accurate excess molar volumes (VE), at ambient pressure and 303.15 K, have been determined in the ternary liquid mixtures of N,N-dimethylformamide (DMF) + 2-pentanone (PE) + 1-alkan-1-ols (C3-C6) and in the binary mixtures of PE + alkan-1-ols (C3-C6) as a function of composition. The alkanols include 1-propanol, 1-butanol, 1-pentanol and 1-hexanol. The intermolecular interactions and structural effects were analyzed on the basis of the measured and derived properties. Excess molar volumes increase in magnitude with increase in chain length of alcohol. Valuable information on the behavior and governing factors of the liquid structure of the strongly associated solvents studied were inferred from the parameters deduced. The VE results were correlated and fitted by the Redlich-Kister equation for binary mixtures and by the Cibulka equation for ternary mixtures, as a function of mole fraction. Several predictive empirical relations were applied to predict the excess volumes of ternary mixtures from the binary mixing data. An analysis of the data indicates a good agreement between experimental results and predicted values in all ternary systems. A discussion is presented and deviations are interpreted in terms of size, shape, the position of ketone group, the chain length of alkanol and hydrogen bond effects in the liquid mixtures studied to explain chemical and thermophysical behavior. 相似文献
15.
Several methods used in the published literature for determining the deliquescence relative humidity (DRH) of salts and the mutual deliquescence relative humidity (MDRH) of salt mixtures were reviewed. Experiments were conducted to evaluate an electrical conductivity method for determining the DRH of salts and the MDRH of salt mixtures. The electrical impedance of a conductivity cell containing Na2SO4, CaCl2 and NaCl+NaNO3+KNO3 was measured as a function of relative humidity at temperatures up to 70 ∘C. To provide a basis for interpreting the results of the impedance measurements, computer modeling of the specific electrical conductivity of single salts and salt mixtures at 25 ∘C also was performed. The results of the study demonstrated that the electrical conductivity method provides a convenient and accurate method for determining the DRH of single salts and the MDRH of salt mixtures. The derived DRH and MDRH values were in good agreement with those determined using a hygrometer method. The conductivity method, however, is a more reliable technique than the hygrometer method for determining the MDRH of salt mixtures because the conductivity method is insensitive to slight deviations of mixture composition from the eutonic value. 相似文献
16.
L.Q. Lobo I.M.A. Fonseca A.G.M. Ferreira A.M.P. Senra 《The Journal of chemical thermodynamics》2006,38(12):1532-1538
The equilibrium pressure of ternary mixtures of {x1CH3F + x2HCl + x3N2O} covering the entire composition range has been measured at temperature of 182.33 K by the static method. The system exhibits a minimum pressure for the binary {x1CH3F + x2HCl}. The molar excess Gibbs free energy has been calculated from the experimental equilibrium pressure. For the equimolar mixture . The (p, x, y) surface for the ternary system and the corresponding curves for the three constituent binary mixtures obtained from the Peng-Robinson equation of state are in agreement with the experimental data. 相似文献
17.
N-Amido imidazolium salt was employed as a ligand in the palladium-catalyzed cross-coupling reaction of aryl halides and thiols, and showed good activity in the formation of thioether. The best combination for the coupling with aryl bromides was N-amido imidazolium salt 2 and NaHMDS, and that for the coupling with aryl iodides was N-amido imidazolium salt 1 and KOtBu. The coupling reactions were conducted in the presence of Pd(OAc)2 (1 mol %) in DMSO at 80 °C for 12 h. 相似文献
18.
Y.Q. Li 《Journal of solid state chemistry》2004,177(12):4687-4694
Undoped and Eu2+ or Ce3+-doped SrYSi4N7 were synthesized by solid-state reaction method at 1400-1660 °C under nitrogen/hydrogen atmosphere. The crystal structure was refined from the X-ray powder diffraction data by the Rietveld method. SrYSi4N7 and EuYSi4N7, being isotypic with the family of compounds MYbSi4N7 (M=Sr, Eu, Ba) and BaYSi4N7, crystallize with the hexagonal symmetry: space group P63mc (No. 186), Z=2, a=6.0160 (1) Å, c=9.7894 (1) Å, V=306.83(3) Å3; and a=6.0123 (1) Å, c=9.7869 (1) Å, V=306.37(1) Å3, respectively. Photoluminescence properties have been studied for Sr1−xEuxYSi4N7 (x=0-1) and SrY1−xCexSi4N7 (x=0-0.03) at room temperature. Eu2+-doped SrYSi4N7 shows a broad yellow emission band peaking around 548-570 nm, while Ce3+-doped SrYSi4N7 exhibits a blue emission band with a maximum at about 450 nm. SrYSi4N7:Eu2+ can be very well excited by 390 nm radiation, which makes this material attractive as conversion phosphor for LED lighting applications. 相似文献
19.
20.
In this paper, a kind of aromatic carboxylic acid of sulfhydryl group (2-mercaptonicotinic acid) is modified with four silane crosslinking reagents (3-methacryloyloxypropyltrimethoxysilane (S1), 3-glycidoxypropyltrimethoxysilane (S2), 3-aminopropyltrimethoxysilane (S3), and 3-(triethoxysilyl)propylisocyanate (S4)) to achieve four new kinds of functionalized molecular bridge (Pi (i = 1-4)). Subsequently, four molecular bridges and lanthanides (europium and terbium) or zinc ions have been assembled via chemical bonds through a sol-gel (cohydrolysis and copolycondensation) process with inorganic precursor (tetraethoxysilane, TEOS), resulting in four novel series of chemically bonded hybrid materials which named as Ln (Zn)-Mi (i = 1-4). The coordinated bonding makes metal ions evenly dispersed in a stable hybrid system. The intramolecular energy transfer process between lanthanide ions and the molecular bridges take place within these molecular-based hybrids and especially the luminescent quantum efficiency of them are determined, suggesting that the hybrid material systems derived from different molecular bridges present different luminescence efficiencies. 相似文献