Search

A compound previously reported as HAlF4 has been shown to be [pyridinium][Al3F10]. The structure of this phase was solved and refined using a combination of synchrotron X-ray and neutron powder diffraction techniques in association with a number of other analytical techniques. The structure consists of [Al3F10]n^- sheets containing both corner-sharing (common) and edge-sharing (unusual) AlF6 octahedra. The sheets are separated by pyridinium cations oriented perpendicular to the sheets. The final crystallographic data are as follows:  monoclinic, space group C2/m, a = 8.2706(3), b = 6.1998(3), c = 10.525(1) Å, β = 103.38(1)°, V = 525.0(1) ų, and Z = 2. This compound appears to be another example of a layered “clay-like” aluminum fluoride.

Methods are described for determining the P/V ratio and average vanadium oxidation state in vanadium phosphates using X-ray photoelectron spectroscopy. The determination of P/V ratios are based on a calibration derived from five organometallic complexes containing vanadium and phosphorus. The vanadium oxidation state is shown to be related to the splitting between O(1s) and V(2p3/2) transition centroids, Vox=13.82−0.68,[O(1s)−V(2p3/2)]. A simple calculation is presented, which reveals that the layered structure of (VO)2P2O7can lead to an apparent 14% phosphorus enrichment when the surface is assumed to terminate with pyrophosphate groups. Exposure of β, γ, and δ VOPO4phases to increasing concentrations of butane in 10% O2/N2results in transformation of the phases to vanadium pyrophosphate, as evidenced by the shifts in the P(2p) photoelectron transitions. During the transformation, the X-ray photoelectron spectroscopy P/V ratio in β-VOPO4increases by ca. 40%, whereas a much smaller increase is observed for the γ and δ phases. As prepared and under oxidizing conditions, the surface of β VOPO4has P/V<1.

Abstract: During the past few years a wide variety of synthetic teainiques have been developed to prepare semiconductor clusters in the nanometer size regime. These clusters possess properties which are intermediate between the molecular and bulk limits and can be considered a new class of materials. In this paper, we review their synthesis and discuss recent developments as well as possible future directions.

This paper describes the automation and control of a 'manual'synchromesh gearbox in a form suitable for use in an electric or hybrid-electric vehicle. Such a computer controlled transmission system allows full integration and control of the drive train leading to improved vehicle performance. The automation process is described, and a full description given, of the computer control algorithms necessary to ensure smooth and reliable operation of the transmission system. It is shown that an up-change can be achieved in 1.4 seconds and a down-change in 1.2 seconds. These times are shown to represent maximum gear change times and details of how they can be reduced substantially are discussed.

CdS and PbS clusters with sizes ranging from a few angstroms to 150 Å can be synthesized in polymers. The dependence of the band gap on the cluster size deviates from the prediction of a simple particle-in-a-box model owing to the breakdown of the effective-mass approximation. Instead, the dependence can be described by a simple tight-binding cluster model. The optical nonlinearity, expressed as α_2/α_0, of 50-Å CdS clusters in Nafion film is determined to be −6.1 × 10^−7 cm^2 W^−1 at 480 nm. The nonlinearity originates from the bleaching of the excitonic absorption owing to the presence of trapped carriers on the cluster surfaces. By passivating the CdS surfaces with ammonia, we have shown that the nonlinearity can be controlled by surface chemistry. We have determined that the presence of one trapped electron–hole pair can bleach the excitonic absorption of the whole CdS cluster. This efficient bleaching can be understood by using a model that considers the shifting of the exciton resonance and weakening of its oscillator strength in the presence of a trapped electron or hole. We also discuss two new classes of material: superclusters in zeolites and surface-capped clusters. Both represent our first steps toward the systematic synthesis of clusters of controlled surfaces and sizes.

Cobalt(II) ion exchanged zeolite Y is treated with the Schiff base ligand (I) to synthesize the corresponding Co complex inside the pore structure of the zeolite itself.

Two time-independent equations are developed to assess the effectiveness of riparian zones in reducing overland flow to streams for events in which the time-scale of subsurface water redistribution exceeds that of the rainfall event. In one equation, the effectiveness of the riparian area is limited by the storage capacity of its soils, while in the other equation, the infiltration rate determines the buffer’s effectiveness. Riparian zone widths, expressed as a proportion of total hillslope length, are calculated for a number of different climate, antecedent moisture, and management scenarios for hillslopes of varying topographic convergence. A riparian zone width not exceeding 20% of total hillslope length is proposed as a practical management option in this paper. Riparian zone widths that fall within these bounds are predicted for areas where both the hillslopes and riparian areas are in good condition. Where conditions in either area are degraded, disproportionately large riparian buffer widths are predicted. The results suggest that land management initiatives need to be directed at the catchment as a whole if riparian buffers of realistic widths are to be effective. riparian zone, hydrology, infiltration, storage capacity, land management.

Small ensembles of CdSe are synthesized within the cages of zeolite Y via ion exchange with Cd(NO3)2and subsequent treatment with H2Se.

are studied by XRD, EXAFS analysis, and optical absorption spectroscopy.

Samples of CdS in zeolites X, Y, and A exhibit three different emission bands, which are all attributed to defects rather than carrier recombination.

by combining EXAFS and solid‐state NMR spectroscopy with optical absorption experiments.

Small clusters of GaP included in the crystalline, periodic environment of zeolite Y are obtained by reaction of Me3Ga with PH3within the pores of Na+/H+ exchanged zeolite Y by using various loadings of Me3Ga and different reaction temp. and times with PH3.

Experimental evidence is given that demonstrates that the optical properties of small semiconductor particles can be modified by chemical interactions with surrounding molecules (e.g.

It is demonstrated that CdS and PbS clusters encapsulated in zeolites show dramatic deviations from bulk optical properties.