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141.
Zeolite synthesis in contemporary chemical industries is predominantly conducted using organic structure-directing agents (OSDAs), which are chronically hazardous to humans and the environment. It is a growing trend to develop an eco-friendly and nuisanceless OSDA for zeolite synthesis. Herein, choline is employed as a non-toxic and green OSDA to synthesize high silica Y zeolite with SiO2/Al2O3 ratios of 6.5–6.8. The prepared Y zeolite samples exhibited outstanding (hydro)thermal stability at ultrahigh temperature owing to the higher SiO2/Al2O3 ratio. The XRF, SEM, 29Si-NMR and 13Na+ results suggested that choline plays a structure-directing role in the synthesis of Y zeolite, while the feed molar fraction of Na+ is a crucial determinant for the framework SiO2/Al2O3 ratio and the crystal morphology. 相似文献
142.
iPP/sPP, iPP/rPP, iPP/PVDF and iPP/PA-6 blends, and their β-nucleated forms were prepared in the present study. The components of iPP/sPP and iPP/rPP blends are compatible in the molten state. The phase structure of the melt of iPP/PVDF and iPP/PA-6 blends is heterogeneous. The melting and crystallisation characteristics as well as the structure and polymorphic composition of these blends were studied by polarised light microscopy (PLM) and differential scanning calorimetry (DSC). When semicrystalline polymers are added to iPP, the most important factor of the formation a blend with β-crystalline phase is the α-nucleation effect of the second polymer. In the case of polymers with an α-nucleating effect, the temperature range of their crystallisation should be lower than that of β-iPP. β-nucleated iPP/PVDF and iPP/PA-6 blends are extreme examples showing that completely β-iPP matrix can not form even in the presence of a highly effective β-nucleant, because of the strong α-nucleating ability and higher crystallisation temperature range of PVDF and PA-6. We found that the β-crystallisation tendency of random propylene copolymers can be enhanced by adding an iPP homopolymer. 相似文献
143.
The reversed-phase high-performance liquid Chromatographic (RP-HPLC) behaviour of the binary chelates of V(V) and V(IV) with 4-(2-pyridylazo) resorcinol (PAR) and ternary chelates of vanadium with PAR and auxiliary ligands: hydrogen peroxide, hydroxylamine, tartrate and citrate were studied using a C18 column. The complex double-peak chromatograms of V(IV)/V(V)-PAR systems were studied and the origin of each peak was proved. Vanadium in ternary systems with PAR and hydrogen peroxide was found exclusively in V(V)-H2O2-PAR complex (single peak on the chromatogram) despite its initial oxidation state. The double role of hydroxylamine (complex agent and reductor) in vanadium systems with PAR was confirmed: in the V(V) system three species were identified (V(V)-PAR, V(V)-NH2OH-PAR and V(IV)-PAR), but in the V(IV) system only two: V(IV)-PAR and V(V)-NH2OH-PAR. Citrate and tartrate giving single peak were found as auxiliary ligands in ternary V(V) systems of analytical importance. Due to its masking potential towards iron (III) ions, citrate was chosen as the most suitable third component of a ternary vanadium system with PAR, to form the basis of an RP-HPLC method for direct determination of V in steel. 相似文献
144.
C. Marhag H. Said P. Satre C. Favotto J. Rogez 《Journal of Thermal Analysis and Calorimetry》2003,74(1):275-285
Study of solid-liquid phase diagram of LiPO3-Pb(PO3)2 binary system, in certain calcination conditions, shows the existence of several metastable phasis. When heated at a temperature
of 723 K the binary mixtures lead uncompletely to a defined compound Pb2Li(PO3). On heating these ternary solid mixtures, three eutectic reactions have been observed: LiPO3+Pb(PO3)2→Liquid at a temperature of 793 K(1) LiPO3+Pb2Li(PO3)5→Liquid at a temperature of 843 K (2) Pb2Li(PO3)5+Pb(PO3)2→Liquid at a temperature of 891 K (3) The metastable liquid phase appears in the system at temperature of 793 K. DTA experiments
performed on the binary LiPO3-Pb(PO3)2 mixtures, show a superposition of two diagrams. The first one is metastable and the second represents the stable equilibrium
phase diagram. Measurements of liquid enthalpy of binary LiPO3-Pb(PO3)2 system at temperature of 979.65 K were reported. The corresponding values were very small and so the binary system can be
considered as athermal. Assuming an ideal behaviour, the liquidus curves in the metastable diagram were calculated and the
eutectic reaction (LiPO3-Pb(PO3)2→Liquid) was confirmed at 793 K.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
145.
GHOLAM HOSSEIN ROUNAGHI RAZYEH SANAVI KHOSHNOOD 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(3-4):309-314
A series of competitive metal ion transport experiments have been performed. Each involved transport from an aqueous source phase across an organic membrane phase into an aqueous receiving phase. The source phase contained equimolar concentrations of cobalt(II), nickel(II), cupper(II), zinc(II), cadmium(II), silver(I) and lead(II) metal cations. The membrane phase incorporated ionophore, decyl-18-crown-6. The membrane solvents include: chloroform, dichloromethane, 1,2-dichloroethane, nitrobenzene and chloroform–nitrobenzene binary solvents. A good transport efficiency and selectivity of Pb2+ transport from aqueous solutions are observed in this investigation. The selectivity order for competitive bulk liquid membrane transport of the studied transition and post transition metal cations through chloroform is: Pb2+>Co2+>Ni2+>Ag+>Cd2+, but in the case of dichloromethane, 1,2-dichloroethane and nitrobenzene as liquid membranes, the selectivity sequences were found to be: Pb2+>Co2+>Cd2+>Cu2+>Ag+>Ni2+>Zn2+, Pb2+>Co2+>Ag+>Ni2+>Zn2+ and Pb2+>Co2+>Ni2+>Zn2+>Cd2+>Ag+, respectively. The transport rate of the metal cations in chloroform–nitrobenzene binary solvents is sensitive to the solvent composition. The transport processes were studied in absence and presence of the stearic acid and the results show that the sequence of selectivities and ion transport rates change in the presence of stearic acid. 相似文献
146.
147.
Improved estimation of duality gap in binary quadratic programming using a weighted distance measure
We present in this paper an improved estimation of duality gap between binary quadratic program and its Lagrangian dual. More specifically, we obtain this improved estimation using a weighted distance measure between the binary set and certain affine subspace. We show that the optimal weights can be computed by solving a semidefinite programming problem. We further establish a necessary and sufficient condition under which the weighted distance measure gives a strictly tighter estimation of the duality gap than the existing estimations. 相似文献
148.
This study was to describe the synthesis of complexes of gadolinium diethylenetriaminepentaacetic acid conjugates of low-molecular-weight chitosan oligosaccharide Gd-DTPA-CSn (n = 6, 8, 11) as a new class of contrast agent as well as its magnetic property in a pilot magnetic resonance imaging. The efficacy of the contrast agent was assessed by measuring the longitudinal relaxivity (r1), FLASH imaging in phantoms in vitro and signal intensity in vivo of the rat abdominal axial imaging. The r1 of Gd-DTPA-CS11 was up to 11.65 mM− 1·s− 1, which was 3 times higher than that of the analogous MRI contrast agent Gd-DTPA in commercial use. In vivo MR images of rat obtained with Gd-DTPA-CS11 showed strong signal enhancement in liver and the vessels of the liver parenchyma during the extended period of time. The present study suggests that the new synthesized gadolinium complexes can be used as a new class of practical liver-specific MRI contrast agent because of its superior performance compared with Gd-DTPA. 相似文献
149.
Cangyi Chen Ping Tang Feng Qiu 《Journal of polymer science. Part A, Polymer chemistry》2014,52(24):1583-1599
Binary polymer brushes, including mixed homopolymer brushes and diblock copolymer brushes, are an attractive class of environmentally responsive nanostructured materials. Owing to microphase separation of the two chemically distinct components in the brush, multifaceted nanomaterials with functionalized and patterned surfaces can be obtained. This review summarizes recent progress on the theory and simulations related to binary polymer brushes grafted to flat, spherical, and cylindrical substrates, with a focus on patterned morphologies of multifaceted hairy nanoparticles, an intriguing class of hybrid nanostructured particles (e.g., nanospheres and nanorods). In particular, powerful field theory and particle-based simulations suitable for revealing novel structures on these patterned surfaces, including self-consistent field theory and dissipative particle dynamics simulations, are emphasized. The unsolved yet critical issues in this research field, such as dynamic response of binary polymer brushes to environmental stimuli and the hierarchical self-assembly of binary hairy nanoparticles, are briefly discussed. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1583–1599 相似文献
150.