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101.
A versatile process for the preparation of composite films consisting of magnetite (Fe3O4) nanoparticles embedded in a polyaniline (PANI) matrix is reported. Spectroscopic properties of polyaniline matrix (PANI-EB), polyaniline protonated with camphor sulfonic acid (PANI-CSA0.5) PANI-ES and PANI/Fe3O4-CSA0.5 composites were studied, both in the state of the solutions of m-cresol and in thin films processed from the same solvents. The results of these studies indicate that m-cresol can be used for PANI/Fe3O4 composite preparation. Such films show both reasonably high electrical conductivity and magnetic permeability. A controlled application of a magnetic field during the casting process resulted in the formation of the materials with an unusual combination of magnetic and transport properties. The obtained films show the behavior that can be explained by the presence of both ferromagnetic and paramagnetic phases. The superparamagnetic contribution, if any, is very small. Application of the external magnetic field during fabrication of the composites stimulates creation of the aggregates of magnetic particles which, although keeps conductivity at a relatively high level, leads to a small decrease of the conductivity value. 相似文献
102.
Ahmed M. El-Sayed Esmat M. A. Hamzawy 《Monatshefte für Chemie / Chemical Monthly》2006,137(9):1119-1125
Summary. The magnetic and microstructure properties of Fe2O3–0.4NiO–0.6ZnO–B2O3 glass system, which was subjected to heat treatment in order to induce a magnetic crystalline phase (Ni0.4Zn0.6-Fe2O4 crystals) within the glass matrix, were investigated. DSC measurement was performed to reveal the crystallization temperature
of the prepared glass sample. The obtained samples, produced by heat treatment at 765°C for various times (1, 1.5, 2, and
3 h), were characterized by X-ray diffraction, IR spectra, transmission electron microscopy, and vibrating sample magnetometer.
The results indicated the formation of spinel Ni–Zn ferrite in the glass matrix. Particles of the ferrite with sizes ranging
from 28 to 120 nm depending on the sintering time were observed. The coercivity values for different heat-treatment samples
were found to be in the range from 15.2 to 100 Oe. The combination of zinc content and sintering times leads to samples with
saturation magnetization ranging from 12.25 to 17.82 emu/g. 相似文献
103.
Yan Ouyang Wei Zhang Yue Ma Na Xu Dai-Zheng Liao Kazuyoshi Yoshimura Shi-Ping Yan 《Structural chemistry》2007,18(6):891-898
Two new tetranuclear complexes of macrocyclic oxamide [Cd(CuL)3](NO3)2·2.5H2O 1, [Mn(CuL)3(OH)2](ClO4)2·Mn(H2O)6·4.5H2O 2 (L = 1,4,8,11-tatraazacyclotradecanne-2,3-dione) have been synthesized, structurally characterized and preliminary investigated
by magnetic studies. The structures of the title complexes consist of a tetranuclear units MCu3 (M = Cd, Mn), the packing diagram shows two-dimensional and three-dimensional system through intermolecular weak interactions.
The temperature-dependent magnetic susceptibilities of complex 2 were analyzed by an approximate treatment leading to J = −33 cm−1, gCu = 2.10, gMn = 1.95 indicating antiferromagnetic exchange between Cu(II) and Mn(II) ions. 相似文献
104.
R. Demchyna J. P. F. Jemetio Yu. Prots Th. Doert L. G. Akselrud W. Schnelle Yu. Kuz'ma Yu. Grin 《无机化学与普通化学杂志》2004,630(5):635-641
Single crystals of CeAgAs2 have been obtained by chemical transport reactions starting from a pre‐reacted powder sample. The crystal structure was solved using X‐ray diffraction (space group Pmca, No. 57, a = 5.7586(4) Å, b = 5.7852(4) Å, c = 21.066(3) Å, Z = 8) and refined to a residual of R(F) = 0.029 for 46 refined parameters and 1020 reflections. The structure of CeAgAs2 represents a new distorted and ordered variant of the HfCuSi2 type. The characteristic feature of this structure are infinite cis‐trans chains of As atoms with As—As distances of 2.563(1) Å and 2.601(1) Å. CeAgAs2 is paramagnetic (μeff = 2.37 μB, θ = —10.5(2) K), with antiferromagnetic ordering at 5.5(2) K and exhibits a metamagnetic transition starting at 4.6 kOe and T = 1.8 K. 相似文献
105.
Susumu Yonezawa Shiori Nishibu Masayuki Takashima 《Journal of fluorine chemistry》2007,128(4):438-447
The preparation of the rare earth containing oxide fluoride glasses LnF3 (Ln; Y through Lu)-BaF2-AlF3-GeO2 in which the nominal content of LnF3 reached 60 mol% in maximum and their basic properties such as density, refractive index and glass transition temperature were investigated and summarized in detail. Especially, in order to discuss the local structure around the rare earth ion in the glass, the Judd-Ofelt analysis (discussion with Ω parameters) of the HoF3-BaF2-AlF3-GeO2 glasses was carried out. The unique fluorescent behavior and the magnetic properties of LnF3-BaF2-AlF3-GeO2 glasses (Ln = Tb and/or Sm) were also studied. 相似文献
106.
1 INTRODUCTION Halide fluxes are excellent media for growing single crystals of chalcogenides[1~5]. On our research in the Ln-Cu-Zn-Se system to find new phases and to search for potential infrared ceramic materials, two new compounds, KHo2CuSe4 and KEr2CuSe4, were synthesized from the reaction of the precursor with KCl flux[6]. In an attempt to synthesize the homologous sulfide by the same method using KBr as flux in a sealed evacuated quartz tube, single crystals of Ho4S3Si2O7 w… 相似文献
107.
Sandra Ristori Grard Gebel Giacomo Martini 《Colloids and surfaces. A, Physicochemical and engineering aspects》1993,80(2-3):113-120
The aggregation properties of ammonium perfluorooctanoate (NH4-PFO) in concentrated aqueous phases have been investigated by magnetic resonance techniques and have been compared with the aggregation properties in dilute solutions. Magnetic resonance methods indicated that NH4-PFO—water systems with surfactant concentrations below 45% (w/w) behaved as isotropic purely micellar solutions in the temperature range 285–340 K. For higher concentrations the system exhibited a rather complex structure, having both isotropic and anisotropic components. The nematic nature of the anisotropic fraction was demonstrated by 19F NMR studies. The 19F NMR and EPR of nitroxides (TempTMA+, 5- and 16-DXSA) inserted as paramagnetic probes into the concentrated NH4-PFO—water systems allowed us to establish that the lamellar phase could be mechanically oriented between quartz slides. The EPR investigation also gave details concerning the dynamics of both the oriented and non-oriented structures. 相似文献
108.
A novel conjugation-elongated bis(ethylenedithio)tetraselenafulvalene (BETS) type donor, 2,5-bis(4,5-ethylenedithio-1,3-diselenol-2-ylidene)-2,3,4,5-tetrahydrothiophene (BEDT-HBDST) and its magnetic and non-magnetic anion salts, (BEDT-HBDST)2MX4 (MX4−=FeCl4−, GaCl4−, FeBr4− and GaBr4−), were prepared. These four salts are isostructural and belong to the space group of P2/c. They showed semiconducting behavior with small activation energies (59-64 meV). The band structures of these salts are quasi one-dimensional and there is a midgap between the upper band and the lower band, since the degree of dimerization is significant in the stacking direction. The MX4− ions are located between the donor columns and near to the ethylenedithio moieties of the donor molecules. The magnetic susceptibilities of the FeCl4− and FeBr4− salts follow the Curie-Weiss law with Curie constants of 4.6 and 4.8 emu K mol−1 (sum of the spins of S=5/2 and S=1/2) and negative Weiss temperatures of θ=−1.2 and −4.9 K, respectively, revealing a weak antiferromagnetic interaction of 3d spins of the FeCl4− and FeBr4− anions. The Fe?Fe (6.66-7.60 Å), Cl?Cl (4.81-4.82 Å) and Br?Br (4.74-4.77 Å) distances in the crystal structures of these salts are significantly long. Therefore, the direct magnetic interaction between the 3d spins of the nearest neighboring Fe3+ ions appears to be not readily accessible. 相似文献
109.
Olivier Kahn 《Angewandte Chemie (International ed. in English)》1985,24(10):834-850
When two paramagnetic transition metal ions are present in the same molecular entity, the magnetic properties can be totally different from the sum of the magnetic properties of each ion surrounded by its nearest neighbors. These new properties depend on the nature and the magnitude of the interaction between the metal ions through the bridging ligands. If both ions have an unpaired electron (e.g. Cu2+ ions), then the molecular state of lowest energy is either a spin singlet or a spin triplet. In the former case, the interaction is said to be antiferromagnetic, in the latter case ferromagnetic. The nature and the order of magnitude of the interaction can be engineered by judiciously choosing the interacting metal ions and the bridging and terminal ligands, and, thus, by the symmetry and the delocalization of the orbitals centered on the metal ions and occupied by the unpaired electrons (magnetic orbitals). The first success in this “molecular engineering” of bimetallic compounds was in the synthesis of a Cu2+VO2+ heterobimetallic complex in which the interaction is purely ferro-magnetic. The same strategy could be utilized for designing molecular ferromagnets, one of the major challenges in the area of molecular materials. Another striking result is the possibility of tuning the magnitude of the interaction through a given bridging network by modifying the nature of the terminal ligands, which, in some way, play the role of “adjusting screws”. By careful selection of the bridging and terminal ligands, a very large antiferro-magnetic interaction can be achieved, even if the metal ions are far away from each other. Some sulfur-containing bridges are especially suitable in this respect. 相似文献
110.
助熔剂对Y3Al5O12:Ce荧光粉性能的影响 总被引:20,自引:2,他引:20
在还原气氛下采用高温固相反应法合成了白光LED用黄色荧光粉Y3Al5O12:Ce(YAG:Ce)研究了助熔剂对YAG:Ce荧光粉发光特性的影响,。XRD的测量结果表明加入合适的助熔剂有利于YAG:Ce荧光粉的晶化,并且不引入杂相,选择BaF2和H3BO3同时使用效果要好于单独使用一种助熔剂,助熔剂的加入可增大YAG:Ce荧光粉的激发和发射光谱强度,并能有效降低荧光粉的中心粒径(D50)控制粉体的粒径分布,适用于白光LED的制造。 相似文献