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1.
Organic montmorillonite (OMMT) nano‐platelets were exfoliated and well dispersed in fully bio‐based polyamide 11/Poly(vinyl alcohol) (PA11/PVA) blends. Significantly lower oxygen permeation rates (OTR) were detected for the PA1172.5PVA27.5OMMTx films than those of PA11 and PA1172.5PVA27.5 films. An extremely low OTR of 0.218 cm3/m2·day·atm was found for PA1172.5PVA27.5OMMT1 film modified with 1 PHR optimum concentration of well dispersed OMMT nano‐platelets. Similarly, the free volume characteristics evaluated for PA1172.5PVA27.5OMMTx film series reduced to a minimum as the OMMT concentration reached the optimum value. As revealed by dynamic mechanical and differential scanning calorimetric analyses of PA1172.5PVA27.5OMMTx film series, all dynamic glass transition temperature (Tg), melting temperature (Tm) and percentage crystallinity (Wc) values of PA1172.5PVA27.5OMMTx films were noticeably higher than those of PA1172.5PVA27.5 film without addition of OMMT. In fact, Tgs, Tms and Wcs evaluated for PA1172.5PVA27.5OMMTx films increased to a maximum, as their OMMT reached the optimum concentration. The considerably enhanced oxygen barrier resistance found for PA1172.5PVA27.5OMMTx films was ascribed to the considerably reduced free volume characteristics and much longer permeation path caused by impermeably OMMT nano‐platelets well dispersed in PA1172.5PVA27.5OMMTx films.  相似文献   

2.
The ease of melt‐processing, moisture‐resistance, and tensile retention properties of scCO2 and polyvinyl alcohol (PVA)–modified thermoplastic starch (scCO2TPSxPVAay) materials were explored in this investigation. These characteristics were considerably improved by PVA modification particularly with decreasing PVA degree of polymerization (DP). The intensities of O―H stretching bands of scCO2TPSxPVAay were considerably larger, and peak location of O―H stretching bands were significantly smaller than those of the corresponding TPSxPVAay and reduced gradually with the decrease in PVA's DP. The ΔH of melting and diffraction peaks of Vh‐type crystals for conditioned TPSxPVAay and scCO2TPSxPVAay were considerably smaller than those of corresponding TPS and TPSxPVAay aged for the same time period and gradually reduced in intensity with decreasing PVA's DP. Possible reasons accounting for the considerably improved melt processing, moisture resistance, tensile retention, and retrogradation of scCO2TPSxPVAay with decreasing PVA's DP are proposed.  相似文献   

3.
We describe a simple and efficient synthesis of poly(vinyl alcohol) (PVA) networks fitted with polydimethylsiloxane (PDMS) branches (PVAnetwg‐PDMS). The syntheses were achieved in two steps: (1) Grafting by urethane linking PDMS carrying ? NCO termini (PDMS‐NCO) onto PVA fitted with a few (~4) photoreactive acryl amide groups (PVAAA), followed by (2) Photocrosslinking the PVAAAg‐PDMS to PVAnetwg‐PDMS. The use of the binary N‐methyl‐2‐pyrrolidone/tetrahydrofuran (NMP/THF, 67/33) solvent system enabled the thermodynamically unfavorable mixing of hydrophobic PDMS branches with hydrophilic PVAAA backbones. The amphiphilic graft, PVAAAg‐PDMS, was characterized by 1H NMR spectroscopy, and the final graft network, PVAnetwg‐PDMS, by FTIR spectroscopy, DSC, and equilibrium swelling. The grafting of sufficient volumes of PDMS branches onto PVAAA yields cocontinuous hydrophilic/hydrophobic PVA/PDMS domains, whose existence was demonstrated by swelling in both water and hexanes. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5272–5277, 2009  相似文献   

4.
The mixed silicide‐germanides Li12Si7–xGex, Na7LiSi8–zGez, and Li3NaSi6–vGev which could serve as potential precursors for Si1–xGex materials were synthesized and characterized by X‐ray diffraction methods. The full solid solution series Li12Si7–xGex (0 ≤ x ≤ 7) is easily accessible from the elements and features preferential occupation of the more negatively charged crystallographic tetrel positions by Ge, which is the more electronegative element. In case of Na7LiSi8–zGez a broad solid solution range of 1.3 ≤ x ≤ 8 is available but the ternary silicide Na7LiSi8 could not be obtained by the tested methods of synthesis. The solubility of Ge in Li3NaSi6–vGev is highly limited to a maximum of v ≈ 0.5, and again the formally more negatively charged tetrel positions are preferred by Ge. Additionally, the two crystallographic Li positions in Li12Si7 with unusually large displacement parameters can be partially substituted by Na in Li12–yNaySi7 with 0 ≤ y ≤ 0.6. The statistical mixing of Li and Na in this solid solution contrasts the typical ordering of Li and Na in most ternary tetrelides.  相似文献   

5.
Vanadium‐containing heteropoly acid solutions of Keggin H3+xPMo12–xVxO40 and modified HaPzMoyVxOb types (P‐Mo‐V HPAs) are promising nanosized inorganic metal‐oxygen cluster compounds with the property of reversible oxidability (VV ↔ VIV). The oxidation of reduced P‐Mo‐V HPAs at a temperature of 130–170 °C and an oxygen pressure of 4 atm is a convenient method for their regeneration, but results in regeneration degree of only 75–88 %. Various materials with electron transfer or oxidative properties, such as nitrogen doped carbon nanofibers (N‐CNFs), Sibunit‐4, HNO3, and MoO2, were investigated as additives to facilitate and accelerate the regeneration of HPA solutions. Among the studied additives HNO3 was found to show the best efficiency, resulting in regeneration degree of higher 95 %. Rapid and efficient regeneration of spent HPA catalysts is an important criterion for achieving high productivity and sustainability of oxidative processes on their basis.  相似文献   

6.
Novel ultrahigh molecular weight polyethylene (UHMWPE)/cellulose nanofiber (CNF) (F100CNFy) and UHMWPE/modified cellulose nanofiber (MCNFx) (F100MCNFxy) as‐prepared nanocomposite fibers were successfully prepared by gel‐spinning F100CNFy and F100MCNFxy gel solutions, respectively. CNF nanofillers with a specific surface area at 120 m2/g and a nanofiber diameter of 20 nm were successfully prepared by proper acid hydrolysis of cotton fibers using sulfuric acid solution. MCNFx nanofillers were prepared by grafting various contents of maleic anhydride grafted polyethylene (PEg‐MAH) onto CNF nanofillers. The ultimate σf value of the best‐prepared F100MCNFxy drawn fiber reached 4.5 GPa, which is about 67% higher than that of the UHMWPE drawn fiber prepared without the addition of any nanofiller. To understand the interesting ultradrawing, orientation, and tensile properties of F100CNFy and F100MCNFxy fibers, Fourier transform infrared, transmission electron microscopic analyses of the CNF and MCNFx nanofillers, and scanning electron microscopic analyses of profile surfaces of the etched drawn fibers were performed. This is the first work in this area of research wherein very small amounts of MCNFx nanofillers prepared from cotton fibers were efficiently used as nucleating agents to enhance the ultradrawing and ultimate tensile properties of F100MCNFxy fibers. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

7.
Vanadium–silver bimetallic oxide cluster ions (VxAgyOz+; x=1–4, y=1–4, z=3–11) are produced by laser ablation and reacted with ethane in a fast‐flow reactor. A reflectron time of flight (Re‐TOF) mass spectrometer is used to detect the cluster distribution before and after the reactions. Hydrogen atom abstraction (HAA) reactions are identified over VAgO3+, V2Ag2O6+, V2Ag4O7+, V3AgO8+, V3Ag3O9+, and V4Ag2O11+ ions, in which the oxygen‐centered radicals terminally bonded on V atoms are active sites for the facile HAA reactions. DFT calculations are performed to study the structures, bonding, and reactivity. The reaction mechanisms of V2Ag2O6++C2H6 are also given. The doped Ag atoms with a valence state of +1 are highly dispersed at the periphery of the VxAgyOz+ cluster ions. The reactivity can be well‐tuned gradually by controlling the number of Ag atoms. The steric protection due to the peripherally bonded Ag atoms greatly enhances the selectivity of the V–Ag bimetallic oxide clusters with respect to the corresponding pure vanadium oxide systems.  相似文献   

8.
14N line splittings in the spectrum of nitrobenzene (neat liquid) and metadinitrobenzene (dissolved in benzene), induced by an external electric field, have been used to determine the complete 14N quadrupole coupling tensor of these substances. Assuming that both molecules are rigid and planar, and that the quadrupole coupling tensors at the 14N nuclei are identical, the principal components in a local reference frame (x′, y′, z′) are (eQ/h)Vxx′ = ±0.34 MHz (eQ/h)Vyy′= ±1.18 Hz and (eQ/h)Vzz′ = ±1.52. The z′-direction is parallel to the CN bond and the y?direction is perpendicular to the plane of the nitrogroup. With these data the asymmetry parameter η = 0.55.  相似文献   

9.
Energy eigenvalues of double-well potentials for three-dimensional systems are calculated by means of an expansion of the potential function V(x,y,z;Z2,λ,aIJ)=-Z2[x2+y2+z2] +λ{x4+y4+z4+2aIJ[x2y2+x2z2+y2z2]} around its minimum, using the inner product technique, for various values of perturbation parameters Z2,λ and aIJ. Some of the results calculated by this technique are compared with results obtained by other methods. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

10.
The microstructure of the free volume was studied for an amorphous perfluorinated polymer (Tg = 378 K). To this aim we employed pressure–volume–temperature experiments (PVT) and positron annihilation lifetime spectroscopy (PALS). Using the Simha‐Somcynsky equation of state the hole free volume fraction h and the specific free and occupied volumes, Vf = hV and Vocc = (1 ? h)V, were determined. Their expansivities and compressibilities were calculated from fits of the Tait equation to the volume data. It was found that in the glass Vocc has a particular high compressibility, while the compressibility of Vf is rather low, although h (300 K) = 0.108 is large. In the rubbery state the free volume dominates the total compressibility. From the PALS spectra the hole size distribution, its mean, 〈vh〉, and mean dispersion, σh, were calculated. From a comparison of 〈vh〉 with Vf a constant hole density of Nh′ = 0.25 × 1021 g?1 was estimated. The volume of the smallest representative freely fluctuating subsystem, 〈VSV〉 ∝ 1/σh2, is unusually small. This was explained by an inherent topologic disorder of this polymer. 〈vh〉 and σh show an exponential‐like decrease with increasing pressure P at 298 K. The hole density, calculated from Nh′ = Vf/〈vh〉, seems to show an increase with P which is unexpected. This was explained by the compression of holes in the glass in two, rather than three, dimensions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2519–2534, 2007  相似文献   

11.
An Erratum has been published for this article in Journal of Polymer Science Part A: Polymer Chemistry (2004) 42(10) 2575‐2576 Starlike, highly branched (AxByAz) macromolecules having from a few to 100 arms and molar masses up to 105 were prepared in three stages with the one‐pot, arms‐core‐arms method (By stands for y molcules of former diepoxides introduced into the core). Oligoalcohols, at least partially converted into their alcoholate counterpart states, reacted with diepoxy compounds giving star‐shaped, highly branched macromolecules. With the properly chosen conditions, complete conversion of both starting components was achieved. In this article homostars built with the first and second generation of poly(ethylene oxide) arms (Ax and Az, respectively) are described. The number of arms (f) was determined either by direct measurements of the number‐average molcular weight (Mn) of the first and second stars (Mn of arms Ax and Az is known) or by calculating f from branching indices g and g′ determined from the radius of gyration and the limited viscosity number measured with size exclusion chromatography (SEC) triple detection with TriSEC software. For a few samples, Mn was measured with high‐speed membrane osmometry. The progress of the stars' formation was monitored by 1H NMR, SEC, and matrix‐assisted laser desorption/ionization time‐of‐flight methods. Functionalization of the ? OH end groups in the second generation of arms was observed by 1H and/or 31P NMR. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1576–1598, 2004  相似文献   

12.
A simplified model of plane Couette flow is derived by means of a cross-stream (y) Galerkin expansion in terms of trigonometric functions appropriate for idealized stress-free boundary conditions at the plates. A set of partial differential equations is obtained, governing the in-plane (xz) space-dependence of a velocity field taken in the form: u=U0(x,z,t)+[1+U1(x,z,t)]sin(πy/2), v=V1(x,z,t)cos(πy/2), w=W0(x,z,t)+W1(x,z,t)sin(πy/2). Beyond Lorenz-like Waleffe's modeling (Waleffe 1997), this Swift–Hohenberg type of approach is expected to give an access to the microscopic mechanism of spatiotemporal intermittency typical of the transition to turbulence in plane Couette flow (Pomeau 1986, Bergé et al. 1998).  相似文献   

13.
Interstitial molybdenum-tungsten, vanadium-tungsten and vanadium-molybdenum-tungsten oxynitrides in the solid solution series Mo1−zWz(OxNy) and V1−zWz(OxNy) (z=0, 0.2, 0.4, 0.5, 0.6, 0.8, 1), and V1−uzMouWz(OxNy) (u, z=0.2, 0.33, 0.4, 0.6; u+z<1), have been obtained by ammonolysis of precursors resulting from the freeze-drying of aqueous solutions of the metal salts (NH4VO3, (NH4)6Mo7O24·4H2O and (NH4)6W12O39·18H2O). A study of the influence of the preparative variables on the outcomes of this procedure is presented. Compounds in the Mo1−zWz(OxNy) series are prepared as single phases by ammonolysis of the respective freeze-dried precursors (during 2 h) at different temperatures between 973 and 1023 K, optimised for each composition, followed by slow cooling of the samples (except for the Mo-only containing phase, in which fast cooling has been used). Compounds in the V1−zWz(OxNy) and V1−uzMouWz(OxNy) series are prepared as single phases by ammonolysis (during 2 h) of crystalline precursors (as resulting from thermal treatment in air at 873 K, during 12 h, of the freeze-dried precursors) at 1073 K, followed by slow cooling of the samples. All the compounds in these series have the rock-salt crystal structure, in which the metal atoms are in an fcc arrangement, with non-metal atoms occupying octahedral interstitial positions. The materials have been characterized by X-ray powder diffraction, elemental analysis, scanning electron microscopy and magnetic measurements.  相似文献   

14.
Electrospray ionization mass spectrometry (ESI-MS) combined with in-source fragmentation and tandem mass spectrometry (MS/MS) experiments were used to generate a wide range of singly and multiply charged vanadium oxide cluster anions including VxOy n– and VxOyCln– ions (x = 1–14, y = 2–36, n = 1–3), protonated clusters, and ligand-bound polyoxovanadate anions. The cluster anions were produced by electrospraying a solution of tetradecavanadate, V14O36Cl(L)5 (L = Et4N+, tetraethylammonium), in acetonitrile. Under mild source conditions, ESI-MS generates a distribution of doubly and triply charged VxOyCln– and VxOyCl(L)(n–1)– clusters predominantly containing 14 vanadium atoms as well as their protonated analogs. Accurate mass measurement using a high-resolution LTQ/Orbitrap mass spectrometer (m/Δm = 60,000 at m/z 410) enabled unambiguous assignment of the elemental composition of the majority of peaks in the ESI-MS spectrum. In addition, high-sensitivity mass spectrometry allowed the charge state of the cluster ions to be assigned based on the separation of the major from the much less abundant minor isotope of vanadium. In-source fragmentation resulted in facile formation of smaller VxOyCl(1–2)– and VxOy (1–2)– anions. Collision-induced dissociation (CID) experiments enabled systematic study of the gas-phase fragmentation pathways of the cluster anions originating from solution and from in-source CID. Surprisingly simple fragmentation patterns were obtained for all singly and doubly charged VxOyCl and VxOy species generated through multiple MS/MS experiments. In contrast, cluster anions originating directly from solution produced comparatively complex CID spectra. These results are consistent with the formation of more stable structures of VxOyCl and VxOy anions through low-energy CID. Furthermore, our results demonstrate that solution-phase synthesis of one precursor cluster anion combined with gas-phase CID is an efficient approach for the top-down synthesis of a wide range of singly and multiply charged gas-phase metal oxide cluster anions for subsequent investigations of structure and reactivity using mass spectrometry and ion spectroscopy techniques.   相似文献   

15.
Enhanced lithium electrochromic performances of mixed organo-tungsten oxide (W x O y C z )/organo-molybdenum oxide (Mo x O y C z ) films by a rapid codeposition onto 40 Ω/□ flexible polyethylene terephthalate/indium tin oxide substrates at a short exposed duration of 23 s using an atmospheric pressure plasma jet (APPJ) at various mixed concentrations of hexacarbonyl precursors [W(CO)6 and Mo(CO)6] are investigated. The flexible organo-tungsten–molybdenum oxide (WMo x O y C z ) films demonstrated noteworthy electrochromic performance for 200 cycles of reversible Li+ ion intercalation and deintercalation in a 1 M LiClO4–propylene carbonate electrolyte by the switching measurements of potential sweep from ?1 to 1 V at a scan rate of 50 mV/s and the potential step at ?1 and 1 V, even after being bent 360o around a 2.5-cm diameter rod for 1,000 cycles. The optical modulation (ΔT) of 61.3 % for MoO y C z films at a wavelength of 795.6 nm was significantly improved up to 72.5 % for WMo x O y C z films cosynthesized with an APPJ.  相似文献   

16.
Structural Studies with Usovites: Ba2CaMIIV2F14 (MIII = Mn, Fe), Ba2CaMnFe2F14 and Ba2CaCuM2IIIF14 (MIII = Mn, Fe, Ga). Single crystals of six compounds Ba2CaMIIM2IIIF14 were prepared to refine their usovite type structure (space group C2/c, Z = 4) using X‐ray diffractometer data. The cell parameters of the phases studied with MIIM2III= MnV2, FeV2, CuMn2, MnFe2, CuFe2 und CuGa2 are within the range 1374≤a/pm≤1384, 534≤b/pm≤542, 1474≤c/pm≤1510, 91, 3≤ß/°≤93, 2. The atoms Ca and MII are incompletely ordered on the 8‐ and 6‐coordinated positions, 4e and 4b, respectively. In the case of Ba2CaFeV2F14 and Ba2CaCuGa2F14 there is reciprocal substitution (x≈0, 1): (Ca1‐xMxII) (4e) and (M1‐xIICax) (4b). In the case of the other usovites Ca‐enriched phases Ba2Ca(M1‐yIICay)M2IIIF14 occured (up to y≈0, 35), exhibiting partial substitution at the octahedral position (4b) only, showing a corresponding increase in MII‐F distances. The distortion of [MIIF6] and [MIIIF6] octahedra within the structure is considerably enhanced on replacement by CuII and MnIII. The results of powder magnetic susceptibility measurements of Ba2CaMnV2F14 and Ba2CaFeV2F14 (TN≈7K) are reported.  相似文献   

17.
Crystals of the chemical composition Ba7F12Cl2 were modified by adding a small amount of Ca2+ to allow the synthesis of the corresponding bromine compound Ba[Ca]7F12Br2. These samples were prepared in a NaBr flux and characterized by single crystal x‐ray diffraction. The new structure crystallizes in a disordered arrangement in the hexagonal space group P63/m (176). The calcium ion has a coordination number of 6. Solid solutions on the heavy halide position can be synthesised in a NaCl/NaBr flux to obtain the compounds Ba7?xCaxF12(ClyBr1?y)2 with x = ~0.5 and 0 < y < 1. Regardless the amount of calcium used in the preparation process, the Ca stoichiometry in the compound is always between 0.3 and 0.5. The lattice parameters differ depending on the Ca‐ and Br‐content between 1053.81(5) ? a = b ? 1058.93(3) pm and 421.21 ? c ? 426.78(3) pm.  相似文献   

18.
The reactions of IMes‐HCl with bimetallic iron‐copper clusters were investigated and it showed that interconversions among bimetallic FexCuy(CO)zn clusters were induced by IMes‐HCl. The reaction priority of IMes‐HCl with fragments in FexCuy(CO)zn was also investigated and the reaction behaviors of zero valent Fe(CO)4 and divalent Fe(CO)4 with IMes‐HCl were discussed.  相似文献   

19.
In this work Molecular layer deposition (MLD) technique used to synthesize titanium-vanadium (TiV x C y O z ) and aluminum-vanadium (AlV x C y O z ) hybrid organic-inorganic films via alternating surface reactions of titanium tetrachloride (or trimethylaluminum), vanadium oxochloride, and ethylene glycol. Using in situ monitoring it was found that the surface reactions were self-limiting at temperatures of 90 and 115°C. The coating thickness per molecular layer deposition cycle (growth rate) at 115°C on a silicon substrate varied from 5.8 to 11.4 Å/cycle, and the film densities, from 1.7 to 2.0 g cm–3. An analysis of the samples obtained at 115°C revealed their amorphous structure. A thermal treatment of titanium-vanadium films at 450°C in air resulted in formation of highly structured coatings. These coatings were composed of nanowires of single-crystal vanadium oxide (V2O5) and mixed nanostructures of titanium and vanadium oxides. Increase in thermal treatment temperature to 500°C resulted in elongation of the V2O5 nanowires up to tens of micrometers and in their separation from the substrate. A thermal treatment of aluminum-vanadium films in air resulted in formation of a low-density film. Pyrolysis of the films in an inert gas yielded composite coatings containing domains of graphitized carbon. These films can be potentially useful in modern devices for energy storage, electronics, medicine and other promising fields of technology.  相似文献   

20.

Blend films of poly(vinyl alcohol) (PVA) and sodium alginate (NaAlg) were prepared by casting from aqueous solutions. This blend films were characterized by tensile strength test, Fourier transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The miscibility in the blends of PVA and NaAlg was established on the basis of the thermal analysis results. DSC showed that the blends possessed single, composition‐dependent glass transition temperatures (Tgs), indicating that the blends are miscible. FT‐IR studies indicate that there is the intermolecular hydrogen bonding interactions, i.e. –OH…?OOC– in PVA/NaAlg blends. The blend films also exhibited the higher thermal stability and their mechanical properties improved compared to those of homopolymers.  相似文献   

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