排序方式: 共有20条查询结果,搜索用时 515 毫秒
1.
J. Emery Y. Laligant J. Y. Buzar L. Smiri F. Hlel T. Ben-Chaabane 《Solid state nuclear magnetic resonance》2000,16(4)
To understand the surprising behavior between the variations of the P′–P–P″ angles and the correlated variations of the O′–P–O″ ones, two lithium cyclohexaphosphate compounds Li6P6O18·3H2O and Li6P6O18 are studied by solid state nuclear magnetic resonance (NMR) spectroscopy. The two compounds exhibit the same [P6O18]6− ring anions but with 3m or
internal symmetry, respectively. Such symmetries induce local distortions that are exhibited by NMR spectroscopy. One-dimensional (1D) NMR gives information on structural sites of 7Li and 31P ions and the crystallographic non-equivalencies are observed. Nevertheless, in the anhydrous compound, X-ray diffraction and NMR results do not completely agree and some discrepancy exists between the number of sites observed with the first technique and the number of lines exhibited in the NMR spectra either for 7Li or 31P nuclei. This problem is elucidated by using 2D double quantum NMR spectroscopy coupled with theoretical considerations. We find that the 31P chemical shift tensor is dependent on the deviations of the O–P–O angles from those in the regular tetrahedron. Within the same empirical model, we suggest that the surprising behavior between the variations of the P′–P–P″ and the ones of the O′–P–O″ is related to the overall charge on the PO4 group. We also find the positions of the isotropic lines for 7Li essentially depend on the site co-ordination of this nuclei. 相似文献
2.
Computer simulations based on Discrete Element Method have been performed in order to investigate the influence of interparticle interactions on the kinetics of self-assembly and the mechanical strength of nanoparticle aggregates.Three different systems have been considered.In the first system the interaction between particles has been simulated using the JKR (Johnson,Kendall and Roberts) contact theory,while in the second and third systems the interaction between particles has been simulated using van der Waals and electrostatic forces respectively.In order to compare the mechanical behaviour of the three systems,the magnitude of the maximum attractive force between particles has been kept the same in all cases.However,the relationship between force and separation distance differs from case to case and thus,the range of the interparticle force.The results clearly indicate that as the range of the interparticle force increases,the self-assembly process is faster and the work required to produce the mechanical failure of the assemblies increases by more than one order of magnitude. 相似文献
3.
Echabaane M. Hfaiedh S. Smiri B. Saidi F. Dridi C. 《Journal of Solid State Electrochemistry》2021,25(6):1797-1806
Journal of Solid State Electrochemistry - The fast and sensitive detection of copper ions would be essential for water monitoring. Herein, we report a novel development of an impedimetric sensor... 相似文献
4.
Dakhlaoui A Toumi M Smiri LS Bulou A 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(1-2):193-198
Chemical preparation, infrared and Raman spectra of sodium samarium fluorosilicate, NaSmSiO(4).0.25NaF are presented. The spectra are analyzed with regard to the symmetry, and the numbers of the SiO(4)(4-) internal vibrational modes observed in the Raman and infrared spectra are consistent with the predictions. 相似文献
5.
Emery J Laligant Y Buzaré JY Smiri L Hlel F Ben-Chaabane T 《Solid state nuclear magnetic resonance》2000,16(4):291-304
To understand the surprising behavior between the variations of the P'-P-P" angles and the correlated variations of the O'-P-O" ones, two lithium cyclohexaphosphate compounds Li6P6O18 x 3H2O and Li6P6O18 are studied by solid state nuclear magnetic resonance (NMR) spectroscopy. The two compounds exhibit the same [P6O18]6- ring anions but with 3m or 1 internal symmetry, respectively. Such symmetries induce local distortions that are exhibited by NMR spectroscopy. One-dimensional (1D) NMR gives information on structural sites of 7Li and 31P ions and the crystallographic non-equivalencies are observed. Nevertheless, in the anhydrous compound, X-ray diffraction and NMR results do not completely agree and some discrepancy exists between the number of sites observed with the first technique and the number of lines exhibited in the NMR spectra either for 7Li or 31P nuclei. This problem is elucidated by using 2D double quantum NMR spectroscopy coupled with theoretical considerations. We find that the 31P chemical shift tensor is dependent on the deviations of the O-P-O angles from those in the regular tetrahedron. Within the same empirical model, we suggest that the surprising behavior between the variations of the P'-P-P" and the ones of the O'-P-O" is related to the overall charge on the PO4 group. We also find the positions of the isotropic lines for 7Li essentially depend on the site co-ordination of this nuclei. 相似文献
6.
A. Dakhlaoui V. Maisonneuve M. Leblanc L. S. Smiri 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2573-2586
Abstract Chemical preparations, crystal structures, thermal analyses, and IR spectroscopic studies are given for two new hydrogen phosphates templated by 4-amino-2,2,6,6-tetramethylpiperidine: (C9H22N2)2·(H2PO4)·(HPO4)·(F)·H2O (I) and (C9H22N2)·(H2PO4)2(II). The structures are determined by single crystal X-ray diffraction. Both compounds crystallize in the P21/c (N°14) monoclinic space group with the unit cell parameters: a = 14.856 (1) Å, b = 14.092 (2) Å, c = 14.7166 (9) Å, β = 118.434 (7)°, V = 2709.2 (4) Å 3, and Z = 4 for (I) and a = 9.803 (2) Å, c = 0.466 (2) Å, c = 15.640 (8) Å, β = 94.990 (4), V = 1598.68 (7) Å3, and Z = 4 for (II). The structure of I, refined to R = 0.042 and Rw = 0.067 for 6009 reflections (I ≥ 2σ (I)), exhibits infinite inorganic chains ∞((H2PO4)·(HPO4)·(F)·H2O)4? linked together through weak hydrogen bonds to form layers onto which the diprotonated [C9H22N2]2 + amine molecules are anchored. The structure of II, refined to R = 0.060 and Rw = 0.086 for 1435 reflections (I ≥ 2σ (I)), consists of ∞(H2PO4)? (100) layers between which [C9H22N2]2+ cations are inserted. A network of hydrogen bonds connects the different components. IR spectra of I and II show the characteristic bands of amine groups and phosphate anions. 相似文献
7.
Artus M Tahar LB Herbst F Smiri L Villain F Yaacoub N Grenèche JM Ammar S Fiévet F 《J Phys Condens Matter》2011,23(50):506001
Highly crystalline CoFe(2)O(4) nanoparticles with different diameters ranging from 2.4 to 6.1 nm have been synthesized by forced hydrolysis in polyol. The size can be controlled through adjusting the nominal water/metal molar ratio. X-ray diffraction, transmission electron microscopy, x-ray absorption spectroscopy and (57)Fe M?ssbauer spectrometry were employed to investigate the structure and the microstructure of the particles produced. Magnetic measurements performed on these particles show that they are superparamagnetic with a size-dependent blocking temperature. At 5 K, high saturation magnetization (~85 emu g(-1)) approaching that of the bulk was found for the larger particles, whereas a very large coercivity (14.5 kOe) is observed for the 3.5 nm sized particles. 相似文献
8.
Amel Dakhlaoui Mouna Jendoubi Leila Samia Smiri Andrei Kanaev Noureddine Jouini 《Journal of Crystal Growth》2009,311(16):3989-3996
Zinc oxide monodispersed nanoparticles were synthesized using a modified polyol process without any requirement to use a catalyst or calcination step at high temperature. The morphology and the size of the resulting oxide particles were adjusted by using several synthesis parameters (temperature, alkaline ratio, hydrolysis ratio, etc.). The increasing of the alkaline ratio results in a great change of the elaborated particles morphology that evolved from irregular and anisotropic forms (conical, nanorod-like and elliptical) to spherical one. A growth mechanism of these particles was proposed on the basis of zincite crystal structure and the morphology evolution as a function of the synthesis parameters. The photoluminescence spectra show UV-excitonic and visible emission bands. The strongest intensity of the visible emission was observed in nanorod-like particles, which implies an increased fraction of oxygen vacancies in this sample. The rod-like particles with 1 μm length show the dominant UV-emission, which evidences their improved stoichiometry. 相似文献
9.
10.
Chemical preparation, X-ray single crystal, and calorimetric studies of C14H18N6O·H2O are described. The compound crystallizes in the triclinic space group, P
with unit cell dimensions: a = 6.2640(3), b = 10.9840(4), c = 12.2220(3) Å, = 105.03(2), = 96.96(2), = 101.6(2)°, V = 712.10(5) Å3, and Z = 2. The 6-butoxy-2,6-diamino-3,3-azo-dipyridine monohydrate structure is built up from organic layers parallel to the (120) plane linked via O—H···N bond. 相似文献