摘要:

The intercalation of a cubical octamer derived from the controlled hydrolysis of 3-aminopropyltriethoxysilane with smectite clays has been examined. The organosilicon cubanes are adsorbed in an amount that exceeds the cation exchange capacity of the mineral. The excess quantity is incorporated in the form of physically adsorbed ion pairs. The results suggest that the physically adsorbed ionpaired cubic units, participate in alkylation reactions affording the corresponding tetraalkylammonium derivatives under triphase conditions. The alkylated products were studied by chemical analysis, X-ray diffraction and FT-infrared spectroscopy.

ISSN:1058-725X    

DOI:10.1080/10587259808042409

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A dissolution-reprecipitation process from a mixed solution of NH4VO3and In(NO3)3is described for the low-temperature preparation of amorphous InVO4·2.3H2O. Crystallized phases were obtained depending on the annealing temperature of amorphous InVO4·2.3H2O. An electrochemical investigation has shown that these compounds, depending on their amorphous/crystallized nature, can react with large amounts of Li, leading to reversible capacities as large as 900 mA-h/g. Both electrochemical and in-situ X-ray diffraction studies suggest that a mechanism of Li uptake/removal, different from the usual Li insertion/deinsertion process, is occurring in these vanadates.

ISSN:1058-725X    

DOI:10.1080/10587259808042410

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Two new oxidation processes are described : the electrochemical oxidation in alkaline solution uses the electrical potential as the driving force for intercalating oxygen, at room temperature, into oxide networks such as perovskites or Ln2MO4(M ˭Ni, Cu) compounds. The second one is based on thein situdestruction of ammonium ions in oxide lattices by interaction with NO2gas, at moderate temperatures. Pictures of the reaction mechanisms are also proposed.

ISSN:1058-725X    

DOI:10.1080/10587259808042411

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

WS2/PEO (poly-ethylene oxide, -CH2CH2O-) nanocomposites were prepared by direct flocculation when single layer WS2in suspension in water was mixed with a PEO aqueous solution. As with earlier work on similar systems using MoS2, the resultant composite material is a remarkably well-ordered polymer-intercalated tungsten disulfide. The powder x-ray diffraction patterns contain (hk0) peaks of the two-dimensional type and (00I) peaks of the three-dimensional type. No mixed (hkl) peaks are observed. The diffraction clearly shows that the system is turbostratically restacked with the WS2layers parallel to each other with an expanded interlayer spacing due to the insertion of PEO, but random in translation along the layers and in rotation about the normal to the layers. The host WS2layers have a strongly distorted octahedral structure with a 2a0superlattice and an expanded a-spacing.

ISSN:1058-725X    

DOI:10.1080/10587259808042412

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Restacking of exfoliated MoS2in the presence of cationic metal complexes (M ˭Fe, Co, Ni, Ru) or metallic cations (M ˭Mn, Fe Co, Ni) leads to nanocomposite materials consisting of alternating layers of molybdenum disulfide and metal complex compounds or metal hydroxide clusters respectively.

ISSN:1058-725X    

DOI:10.1080/10587259808042413

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Recently, we have successfully synthesized new type of high-Tcsuperconductors of (HgX2)0.5Bi2Sr2Cam-1CumOy(X˭Br, I, and m = 1, 2) by means of intercalation technique. From the X-ray diffraction(XRD) and X-ray absorption spectroscopy(XAS) analyses, we found that the intercalated mercuric halides are stabilized as the isolated gaseous molecules in the interlayer space of superconducting lattice, leading to an increase of basal spacing. A small amount of charge transfer between guest molecule and host lattice could be observed upon intercalation with a slight depression ofTc. For the extension of metal halide intercalation into high-Tc, superconductor, we have developed new type of hybridized superconducting nanohybrid with periodic stacking of organic and superconducting layer by stepwise synthetic approach, where organic compounds are stabilized in the form of organic-inorganic complex salt in-between Bi-O double layers of Bi-based high-Tccuprates. The synthetic strategy proposed here can be applicable to many other layered systems

ISSN:1058-725X    

DOI:10.1080/10587259808042414

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Dynamic high-resolution transmission electron microscopy (DHRTEM) has been used to follow the early events in ammonia/2H-TaS2intercalation. This molecular intercalation process is characterized by two intriguing transient partial gallery expansions of 0.6 and 1.4 Å, prior to and during intercalation, respectively. These expansions do not persist throughout the intercalation process, eventually yielding to full gallery expansions of 3.0 Å. The former partial expansion was observed prior to intercalation during preintercalation ammonia adsorption on the basal planes and can be associated with a charge-transfer-induced host-layer “loosening” of the outermost guest gallery via octahedral-to-trigonal prismatic restacking of the adjacent host layers. The latter expansion is associated with the formation of a near planar ammonia species, which reduces the elastic strain energy for molecular intercalation.

ISSN:1058-725X    

DOI:10.1080/10587259808042415

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We applied X-ray Absorption Spectroscopy, in combination with electronic band structure calculations, to probe the electronic structure before and after lithium intercalation into TiS2, TiSe2and 2H-NbSe2. We are then able to precisely determine the nature of the charge transfer from intercalated lithium to the host It is shown that lithium is not fully ionized and that chalcogen atoms are deeply involved in the charge transfer process.

ISSN:1058-725X    

DOI:10.1080/10587259808042416

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Using high resolution x-ray diffraction data, we show that the composition dependence of the normalized basal-spacing,dN(x), of the bi-layer alkali perovskites, CsxRb1-x[LaNb2O7], measured over the range 0≤x≤1, can be quantitatively accounted for with the anharmonic Lennard-Jones (aLJ) model which incorporates deformations ofboththe host layers and the guest ions. With the same independently determined value of the Rb/Cs stiffness constant ratio, 1.73, used in previous studies of CsxRb1-x[Ca2Nb3O10], the tri-layer perovskites, the aLJ model yields a very good one-parameter fit todN(x) for the bi-layer perovskites. The single fitting parameter, β = [d(0)-t]/[d(1) -t] wheretis the host layer thickness, yields atvalue of 7.73Å in very good (3%) agreement with the value 7.97Å deduced from structural studies.

ISSN:1058-725X    

DOI:10.1080/10587259808042417

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper reports the formation of monomolecular lamellar arrays of thionine (TH) and methylene blue (MB) by self-assembly in the interlayer of metal phosphates formulated as M(IV)(HPO4)2• H2O, with M ˭Sn and Zr (α-SnP and α-ZrP). We apply the molecular exciton model to the interpretation of the electronic reflectance spectra of the intercalation compounds and find that metachromatia upon sorption and intercalation is understandable with exciton theory. We describe how delaminated α-SnP and α-ZrP are useful as template layers for self-assembly of amphiphilic dyes in well-ordered monolayers. Starting with well-characterized template layers, it is possible to quantify the self-assembly steps and infer how the order of the active sites in the template layers extends to the molecular aggregates. We find that the dye layers achieve a high orientational order and that the organization of active sites in the template layers is an essential factor. The agreement between observed and calculated exciton displacement terms proves the possibility of deducing ultra-structure characteristics of nano-composite materials by simple absorption measurements.

ISSN:1058-725X    

DOI:10.1080/10587259808042418

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor