Hydrothermal reactions of cadmium(II) chloride with three amino-diphosphonic acids, C6H5CH2N(CH2PO3H2)2 (H4L1), C6H5CH2CH2N(CH2PO3H2)2 (H4L2) and 4-CH3-C6H4CH2N (CH2PO3H2)2) (H4L3) resulted in three new metal amino-diphosphonates, namely, Cd(H3L1)2, 1 Cd(H3L2)2·2H2O 2 and Cd(H3L3)23. In all three complexes, the Cd(II) ion is octahedrally coordinated by six phosphonate oxygen atoms from six ligands. Complexes 1 and 3 have a similar structure in which the CdO6 octahedra are cross-linked by bridging ligands into a double chain along the c-axis, such double chains are further interlinked via hydrogen bonds between non-coordinated phosphonate oxygen atoms to form 〈100〉 and 〈200〉 layers with the phenyl groups of the ligands orientated toward the interlayer space. The structure of complex 2 features a 〈100〉 cadmium(II) diphosphonate layer. The effects of the substitute groups attached to the amine groups on the structures of the metal phosphonates are also discussed. 相似文献
The kinetics of the reaction of CH2O with a quasi-aromatic metal complex (1,1,2,8,9,9-hexamethyl-4,6-dioxa-5-hydro-3,7,10,14-tetraazacyclotetradecane-2,7,10,12-tetraene)copper(II), [Cu(PnAO)-6H]0 (AH), have been studied spectrophotometrically under neutral conditions in 1/3(v/v) MeOH–H2O. The Cu, 2N, 3C quasi-aromatic heterocyclic ring in AH is highly reactive towards CH2O at the central-aromatic-carbon atom, C(12) and the following reaction mechanism is proposed.
The compounds AH, A—CH2OH and A—CH2—A were isolated and identified by i.r spectroscopy and by elemental analysis. The kinetic data supported the proposed reaction sequence. All reactions were second order overall. The rate constants and corresponding activation parameters for every step were obtained and are discussed. 相似文献
Components of co-continuous phase can form an interpenetrating network structure, which has great potential to synergistically improve the mechanical properties of the blends, and to impart the functional blends superior electrical conductivity and permeability. In this work, the effects of shear rates (50–5000 s?1) at different temperatures on the phase morphology, phase size and lamellar crystallites of biodegradable co-continuous polybutylene terephthalate (PBAT)/polybutylene succinate (PBS) blend are quantitatively investigated. The results show that the above features of the PBAT/PBS have a strong dependence on the shear flow and thermal field. The co-continuous phase of the blend is well maintained at 130 °C. Interestingly, this phase structure transforms into a “sea-island” structure at 160 °C, which gradually recovers to a co-continuous phase when the shear rate increases from 1000 s?1 to 5000 s?1. The phase size decreases with the increase of shear rate both at 130 °C and 160 °C due to the refinement and deformation of phase structures caused by strong shear stress. Unexpectedly, a unique phenomenon is observed that the shear-induced lamellar crystallites are oriented perpendicular to shear direction in the range of 500–5000 s?1 at 130 °C, while the orientation of lamellar crystallites at 160 °C is along the shear direction within the whole range of shear rates. The degree of orientation for the PBAT/PBS blend crystals increases first and then decreases at both temperatures above. In addition, the range of shear rate has reached the level in the industrial processing. Therefore, this work has important guiding significance for the regulation of the co-continuous phase structure and the performance for the blend in the practical processing.
Achieving low friction and wear of poly(phenylene sulfide)(PPS) without using fillers or blending is a challenging task, but one of considerable practical importance. Here we describe how neat PPS with high tribological performance is achieved by manipulating processing parameters(pressure, flow and temperature). The key to achieving high tribological performance is comparatively high molecular chain orientation, realized in neat PPS, at high shear rates and low pressure. The friction coefficient and wear rate are as low as ~0.3 and~10-6 mm3·N-1·m-1, respectively, which break the record for neat PPS. These values are even better than those for PPS-based blends and comparable to PPS composites. Further studies show, for the first time, that wear rate decreases exponentially with increasing molecular chain orientation, prompting us to revise the classical Archard's law by including the effect of molecular chain orientation. These findings open the possibility of using neat PPS in highly demanding tribological applications. 相似文献
In this work, the largest heterometallic supertetrahedral clusters, [Zn6Ge16]4− and [Cd6Ge16]4−, were directly self-assembled through highly-charged [Ge4]4− units and transition metal cations, in which 3-center–2-electron σ bonding in Ge2Zn or Ge2Cd triangles plays a vital role in the stabilization of the whole structure. The cluster structures have an open framework with a large central cavity of diameter 4.6 Å for Zn and 5.0 Å for Cd, respectively. Time-dependent HRESI-MS spectra show that the larger clusters grow from smaller components with a single [Ge4]4− and ZnMes2 units. Calculations performed at the DFT level indicate a very large HOMO–LUMO energy gap in [M6Ge16]4− (2.22 eV), suggesting high kinetic stability that may offer opportunities in materials science. These observations offer a new strategy for the assembly of heterometallic clusters with high symmetry. 相似文献
The correlation between aggregates and bound rubber structures in silicone rubbers(S(phr)) with various silica fractions(ΦSi) has been investigated by contrast matching small-angle neutron scattering(SANS), swelling kinetics, and low-field nuclear magnetic resonance(NMR).Mixed solvents with deuterated cyclohexane fractions of 4.9% and 53.7% were chosen to match the scattering length densities of the matrix(SMP(phr)) and the filler(SMS(phr)), respectively. All the data consistently suggest that:(i) There is a critical threshold ΦSic between 10 and 30 phr;below ΦSic, the isolated aggregates are dominant, while beyond ΦSic, some rubber fraction is trapped among the agglomerate;(ii) ΦSiindependent thicknesses around 7.5 nm(NMR) and 8.6 nm(SANS) suggest that the bound rubber formation is determined by inherent properties of the components, and the power-law around 4.2 suggests an exponential changed gradient density of the bound rubber;(iii) SMS(80) presents a bicontinuous bound rubber with three characteristic lengths of 41, 100, and 234 nm. The expanded correlation length, a 20 nm smaller aggregate sizes suggest that such existent bicontinuous network in dry samples with less ΦSi is kind of impacted by swelling. With the obtained bound rubber models, the reinforcing mechanism of filled silicone rubber is elucidated. 相似文献
A new type of Zeeman-effect atomic-absorption spectrophotometer has been developed. It uses fast heating of a special atomizer made from a pyro-coated graphite tube lined with tungsten-tantalum alloy, for easier determination of refractory and rare-earth elements. A boxcar integrator is used, and the atomic absorption, background absorption and atomization temperature can be recorded. By means of the Zeeman effect, the instrument can correct for background absorbance up to 2.0. 相似文献