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1.
In this paper, we report the hydrothermal synthesis of VO 2, poly(ethylene oxide) (PEO)/VO 2,V 3O 7· nH 2O and PEO/V 3O 7· nH 2O nanobelts by using 1,2-propylene carbonate (1,2-PC (C 4H 6O 3)) and poly(ethylene glycol) (PEG) as templates, respectively. Structure and morphology of the samples were investigated by XRD, FTIR, SEM, and TEM. The vanadium oxide (VO 2) nanobeltcomposite show the initial specific capacity 152?mA?h?g ?1, whereas PEO/VO 2 shows 182?mA?h?g ?1. The pure V 3O 7· nH 2O nanobelts shows the initial specific capacity 192?mA?h?g ?1, while PEO/V 3O 7· nH 2O nanobelts show 297?mA?h?g ?1. It was found that PEO/VO 2 and PEO/V 3O 7· nH 2O nanocomposites show better cyclic performance and high discharge stability compared to pure vanadium oxide nanomaterials. The role of the polymeric PEO component of the hybrid material seems to be the stabilization and improvement of the specific capacity due to probable homogeneous distribution between the nanobelts. The TEM images indicate that PEO works as a surfactant to decrease the dimensions of nanobelts. 相似文献
2.
A study has been made of vibrational properties in ethylene glycol (EG; H(OCH 2CH 2)OH) and EG monomethyl ether (EGmE; CH 3(OCH 2CH 2)OH) in solution together with poly(ethylene oxide) (PEO; H(OCH 2CH 2) n,OH) at different concentrations, performed by Fourier transform infrared absorbance (FT-IR) spectroscopy. The results ae compared with previous viscometry and photon correlation spectroscopy (PCS) studies, using EG dimethyl ether (EGdE; CH 3(OCH 2CH 2)OCH 3) as solvent as well. These homologous systems differ from each other in the number of OH end groups, in particular two for EG, one for EgmE and zero for EGdE. Combining analysis of the vibrational and transport properties of EG, EGmE and EGdE in solution with PEO over a wide range of concentration made it possible to check the quality (good theta or poor) of these three different solvents and the role played by the hydrogen bond in the various solute-solvent interaction mechanisms, resulting in the well known de Gennes scaling law. 相似文献
3.
Mixed-valence states of 57Fe atoms produced after EC-decay of 57Co in a series of trinuclear cobalt-iron halogenoacetate complexes, [Co IIFe 2 III O(CH 3?nX nCO 2) 6(H 2O) 3] (0≤n≤3, X=Cl, Br, and I), were studied by comparing the results obtained by emission Mössbauer spectroscopy with those observed in absorption Mössbauer spectra of analogous trinuclear iron complexes, [Fe IIFe 2 III O(CH 3?nX nCO 2) 6(H 2O) 3]. Some of the emission Mössbauer spectra show a temperature-dependent mixed-valence state as found in the absorption Mössbauer spectra. Others show a somewhat different temperature dependence compared with the absorption Mössbauer spectra. The results were interpreted in terms of after-effects of the EC-decay. 相似文献
4.
The phase diagrams of the binary systems poly(ethylene oxide) (PEO)-resorcinol and poly(ethylene oxide)- p-nitrophenol show the presence of molecular complexes with well-defined stoichiometries. The crystal structure of these two molecular complexes has been determined from wide-angle x-ray diffraction patterns of stretched films and spherulites. The morphology of the two complexes crystallized from the melt is investigated by differential scanning calorimetry and small-angle x-ray scattering. The crystallization of the PEO-resorcinol complex from the melt gives integral-folded crystals with either extended chains (EC) or n-folded chains ( n-FC). As observed for PEO oligomers, the fraction of EC crystals of the PEO-resorcinol complex increases with the crystallization temperature to give finally only EC crystals but in a larger range of crystallization temperatures than for pure PEO. On the other hand, the PEO- p-nitrophenol complex crystallizes over all the studied crystallization range as stable nonintegral-folded (NIF) crystals. Two proposals related to the crystal structure of these complexes and their mode of growth are invoked to explain these two greatly different morphologies at the lamellar level. 相似文献
5.
The optical characterization of poly (ethylene oxide)/zinc oxide thin films has been done by analyzing the absorption spectra in the spectral wavelength region 380–800 nm using a ultraviolet-spectrophotometer at room temperature. Thin film polymer composites made of poly (ethylene oxide) (PEO) containing zinc oxide (ZnO) filler concentrations (0%, 2%, 6%, 10%, and 14%) by weight were used in this study. The optical results obtained were analyzed in terms of the absorption formula for non-crystalline materials. The optical energy gap and other basic optical constants such as dielectric constants and optical conductivity were investigated and showed a clear dependence on the ZnO filler concentration. It was found that the optical energy gap for the composite films is less than that for the neat PEO, and that it decreases as the ZnO concentration increases. Enhancement of the optical conductivity was observed with increase in the ZnO concentration. Dispersion of refractive index was analyzed using the Wemple–DiDomenico single oscillator model. The refractive index ( n), extinction coefficient ( k), and dispersion parameters ( Eo, Ed) were calculated for the investigated films. 相似文献
6.
Grand canonical histogram-reweighting Monte Carlo simulations were used to obtain the phase behaviour of several binary mixtures. The main goal of this work was to test the predictive capabilities of recently developed intermolecular potential models that accurately reproduce the phase behaviour of pure components. These united-atom potentials utilize the exponential-6 functional form for repulsive and dispersion interactions and fixed point charges for electrostatic interactions. The mixtures studied were n-pentane—methane, ethane—CO 2, propane—CO 2, n-pentane-CO 2, H 2O-ethane, CH 3OH- n-hexane and CH 3OH-CO 2. The conventional Lorentz-Berthelot combining rules, as well as a set of combining rules due to Kong (1973, J. chem. Phys., 59, 2464) were used to obtain unlike-pair potential parameters. The Lorentz—Berthelot rules generally result in more attractive unlike-pair interactions than the Kong rules. For the n-alkane—CO 2 systems, predicted phase diagrams are in excellent agreement with experiment when the Kong combining rules are used. For mixtures with CH 3OH and H 2O, the Lorentz—Berthelot rules yield better agreement with experiment than the Kong rules, but statistically significant differences remain. Our results suggest that relatively simple intermolecular potential models can be used to predict the phase behaviour of broad classes of binary systems. For mixtures with large differences in polar character of the components, however, present models do not predict the phase behaviour in quantitative agreement with experiment. New models that include higher order interactions such as polarizability may be suitable for this purpose, a hypothesis that will need to be tested in the future. 相似文献
7.
It is found for hydrated solid solutions of Ba 2?0.5x In 2O 5?x F x · nH 2O, Ba 2In 2O 5?0.5y F y · nH 2O (0 ≤ x ≤ 0.30; 0 ≤ y ≤ 0.24) that increasing the concentration of fluorine lowers the degree of hydration. The composition of proton-containing groups and the places of their localization in the structure of hydrated oxyfluorides are determined. The presence of fluorine in the complex oxide’s structure helps increase the mobility of protons. 相似文献
8.
Poly(ethylene oxide)-poly(propylene oxide)–poly(ethylene oxide) ((EO) n–(PO) m–(EO) n) block copolymers, commercially available as Pluronics (BASF Corp.) and Poloxamers (ICI Corp.), have been widely applied in medicine, biochemistry, and other fields because of their ability to form reversible micelles and physical gels in aqueous solution. Generally, for PEO–PPO–PEO block copolymers with higher ethylene oxide concentration, the micellization and gelation in aqueous solution are easier. However, if we introduce the reverse block copolymer PPO–PEO–PPO into PEO–PPO–PEO aqueous solutions, the micellization and gelation of the system will be more complex. In this work, the reverse block copolymer PO 14–EO 24–PO 14 (17R4) was added to the Pluronics EO 20–PO 70–EO 20 (P123), EO 100–PO 65–EO 100 (F127), and EO 133–PO 50–EO 133 (F108) aqueous solutions with different molar ratios. The rheological properties of different mixtures were measured to study the additive effect on the gelation behavior. The sol–gel transition temperature of the P123, F127, and F108 solutions shifted to a higher temperature when 17R4 was added to the solutions. In addition, the existence of 17R4 greatly affected the stability of gels. These results help to better understand the gelation of Pluronic aqueous solutions. 相似文献
9.
利用脉宽为5 ns脉冲Nd: YAG 355 nm激光在功率密度为10 11–10 12 W/cm 2条件下实现了甲醛含水团簇多光子电离, 并用飞行时间质谱对其电离产物和电离过程进行了研究. 实验中观测到了甲醛的质子化团簇系列 (CH 2O) nH +(n=1–4), 甲醛的去质子化团簇系列(CH 2O) nCHO + (n=1–3), 以及两个起源于H 2CO去质子和质子化的含水团簇系列HCO +(H 2O) n(n=1,3,5)和H 3CO +(H 2O) n(n=1,3,5), 并对其中的一些团簇结构构型进行了猜测. 研究在不同的激光功率密度下甲醛团簇质谱峰的变换情况, 当激光密度达到9.3× 10 11 W/cm 2, 开始出现CH 2O和H 2O本体及其光致碎片的信号, 但对应的各质量峰没有明显地分辨开, 而是以包络的形式出现, 这是激光电离产生高能离子释放的一种表现, 提出认等离子体动力学鞘层加速机制(模型)来解释高能离子形成的物理机制.
关键词:
甲醛
团簇
飞行时间质谱
激光电离 相似文献
10.
Maleic acid-alt-styrene (MAaS) copolymer with number-average molecular weight [Mbar] n = 2500 was used as a compatibilizer in blends of poly(ethylene oxide) (PEO) and poly(styrene) (PS). PEO with weight-average molecular weight [Mbar] w = 10 5 (PEO 100) and two PS samples with [Mbar] w = 9 × 10 4 and 4 × 10 5, respectively (PS 90 and PS 400, respectively) were used. A depression of the melting temperature T m of PEO in blends containing MAaS relative to pure PEO and PEO/PS blends was observed. The melting enthalpy Δ H m for the PEO/PS blends containing MAaS was lower than those of pure PEO and PEO/PS blends without compatibilizer. The crystallization kinetics of PEO and the blends were studied by differential scanning calorimetry (DSC) at different crystallization temperatures T c. Flory-Huggins interaction parameters χ 12 for the blends were estimated. Their values are in good agreement with those obtained for similar systems and suggest that the free energy of mixing Δ G mix should be negative. Polarized optical microscopy shows differences in the macroscopic homogeneity of the blends containing compatibilizer that could be attributed to a compatibilization process. 相似文献
11.
Study of ion transport behavior in K+-ion conducting solid polymer electrolyte (SPE) films: [(1-x) PEO: xCH3COOK] has been reported. Poly (ethylene oxide) PEO has been used as polymeric host and potassium acetate: CH3COOK as complexing salt. SPE films in varying salt concentrations have been prepared by hot-press cast method. SPE film: [95PEO: 5CH3COOK] has been identified as Optimum Conducting Composition (OCC) with room temperature conductivity (σ
rt) ~ 2.74 × 10−7 S/cm. As a consequence of salt complexation in polymeric host, σ
rt-enhancement of approximately two orders of magnitude was achieved in SPE OCC film. Ion transport property has been characterized in terms of ionic conductivity (σ), total ionic (t
ion)/cation (t
+) transference numbers using different ac/dc techniques. Temperature-dependent conductivity measurement was done to explain mechanism of ion transport and to evaluate activation energy (E
a). XRD, FTIR, and DSC techniques were used to study materials property in SPE OCC film which also confirmed the complexation of salt in the polymeric host as well as increase in degree of amorphousity. 相似文献
12.
Oxidation of bulk samples of tungsten (923 K) and zirconium (773 and 873 K) by H 2O/CO 2 supercritical fluid (molar ratio [CO 2]/[H 2O] = 0.17–0.26) at a pressure of about 300 atm is investigated. Oxidation produces monoclinic WO 3, monoclinic W 19O 55, monoclinic ZrO 2, H 2, CO, CH 4, and carbon (on the surface of tungsten oxide). Differences in oxidation mechanisms for tungsten and zirconium are revealed. CO 2 molecules take part in the oxidation of tungsten only after oxide formation in reaction with H 2O. Zirconium is oxidized fully, and oxidation of tungsten terminates in the formation of the oxide layer at the metal surface. 相似文献
13.
About 150 FIR lines are produced in CH 3I by pumping with a narrowed-line continuously tunable CO 2 laser the 2 ν3 P, Q bands at 9.6 μm. We have obtained in the 330–1560 μm wavelength range, up to 2 μJ pulsed energies by pumping some of the K-sublevels of the P (16≤ J≤46) and R (16≤ J≤60) absorption lines. 相似文献
14.
Nine sharp fractions of poly(ethylene oxide) (PEO) glycol with number-average molar masses ( M n) in the range from 0.6 × 10 3 to 20 × 10 3 (PEO-0.6 to PEO-20) were characterized by magnetic susceptibility χ measured in the temperature interval 293 K to 378 K. In contrast to the liquidlike PEO-0.6 with temperature-invariant χ, the values of χ for each of the remaining solid samples, after the initial increase, exhibited two plateaus separated by a relatively narrow temperature interval of their second increase. The jumps of χ at lower and higher temperatures were attributed to a solid-state transition of unspecific nature and to the melting of the crystal fraction, respectively. The temperature-invariant values of χ n in the melt state above T m pass through a minimum for the sample PEO-2.0 and then increase again with (M n) to a limiting value χ ∞ = ?0.622 × 10 ?6. It is concluded that a considerable contribution of the molar-mass-dependent “paramagnetism” χ P = χ ? χ d (where χ d is the diamagnetic contribution estimated by Kirkwood's equation) to the total magnetic susceptibility of PEO fractions reflects distortions of the spherical symmetry of the electron shells around chain atoms resulting from the discontinuous change of both inter- and intrachain interactions as the (M n) increases through and above the critical crossover molar mass ( Mcr ) = 2 × 10 3. 相似文献
15.
Electron impact energy loss spectra at impact energies of 100 eV and 50 eV and a scattering angle of 2 degrees are presented for alkyl derivatives of H 2O and related compounds. Spectra of H 2O, CH 3OH, CH 3OCH 3, ethylene oxide, CH 3CH 2OH, (CH 3) 2CHOH, (CH 3) 3C C 2H 5OC 2H 5 and tetrahydrofuran are tentatively assigned using derived term values and ionization potentials from photoelectron spectrosc Substituent effects on Rydberg orbital energies are discussed using Taft σ* values. 相似文献
16.
以十甲基环五硅氧烷和甲烷作为反应气体,采用电子回旋共振等离子体化学气相沉积(ECR-C VD)方法制备了k = 2.45,485℃下的热稳定性优良的SiCOH低介电常数薄膜.通过薄膜结构的 FTIR谱分析,比较了十甲基环五硅氧烷(D5)液态源和不同甲烷流量下制备的薄膜的键结构差 异,发现在沉积过程中甲烷含量的增大,一方面有利于D5源环结构的保留,另一方面有利于 薄膜中形成高密度的CH n基团.高密度碳氢大分子基团的存在降低了薄膜密度, 结合薄膜中形成的本构孔隙、低极化率Si—C键以及—OH键减少的共同作用,导致薄膜介电 常数的降低.
关键词:
低介电常数
SiCOH薄膜
碳氢掺杂 相似文献
17.
Raman spectroscopic technique has been used to characterize a Ru/TiO 2 catalyst and to follow in situ their structural changes during the CO selective methanation reaction (S‐MET). For a better comprehension of the catalytic mechanism, the in‐situ Raman study of the catalysts activation (reduction) process, the isolated CO and CO 2 methanation reactions and the effect of the composition of the reactive stream (H 2O and CO 2 presence) have been carried out. Raman spectroscopy evidences that the catalyst is composed by islands of TiO 2–RuO 2 solid solutions, constituting Ru–TiO 2 interphases in the form of Ru xTi 1 − xO 2 rutile type solid solutions. The activation procedure with H 2 at 300 °C promotes the reduction of the RuO 2–TiO 2 islands generating Ru o–Ti 3+ centers. The spectroscopic changes are in agreement with the strong increase in chemical reactivity as increasing the carbonaceous intermediates observed. The selective methanation of CO proceeds after their adsorption on these Ru o–Ti 3+ active centers and subsequent C―O dissociation throughout the formation of CH x/C nH x/C nH xO/CH x―CO species. These intermediates are transformed into CH 4 by a combination of hydrogenation reactions. The formation of carbonaceous species during the methanation of CO and CO 2 suggests that the CO presence is required to promote the CO 2 methanation. Similar carbonaceous species are detected when the selective CO methanation is carried out with water in the stream. However, the activation of the catalysts occurs at much lower temperatures, and the carbon oxidation is favored by the oxidative effect of water. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
18.
The potential energy surface profiles for the gas-phase pyrolysis of methyl azidoformate (MA, CH 3OC(O)N 3) in the absence and presence of one water molecule have been investigated by ab initio methods at CCSD(T)/6-311++G(2df,2pd)//MP2(full)/6-311++G(d,p)+0.95×ZPE levels of theory. Three types of mechanisms are discussed for the gas-phase decomposition of CH 3OC(O)N 3. Ab initio calculations show that a four-membered-ring intermediate can be formed by the stepwise routes. The resulting intermediate can undergo two competitive decomposition channels to generate the major products CO 2?+?CH 2?=?NH and HNCO?+?HC(O)H. The calculated results are in qualitative agreement with the observed experimental data. However, CH 3ONCO can be produced from the Curtius-type rearrangement route. This is an intriguing finding in this study. Moreover, the effect of one water molecule on the gas-phase pyrolysis of MA has been also explored. We find that the relative energy of the hydrated transition states is effectively lowered when water is added to the reaction. However, the estimated rate constant at 625?K for the naked reaction is about 30 times faster than the reaction with water. Thus, a single water molecule cannot play an important role in the thermal decomposition of MA. 相似文献
19.
The correlation between crystallite structural changes and polarization properties of a linear crystallized [–CH 2CH 2O–] n polyethylene oxide polymer is studied. The average spherulite radius and polarization of polyethylene oxide are inspected as functions of molecular weight of polymer and crystallization temperature from melt in a nonuniform temperature field. 相似文献
20.
The amphiphilic triblock copolymer, poly(ethylene oxide)‐ block‐poly(propylene oxide)‐ block‐poly(ethylene oxide) (PEO‐ b‐PPO‐ b‐PEO) was incorporated into novolac resin to prepare thermosetting blends. The morphology of the thermosetting blends was investigated by means of atomic force microscopy (AFM) and small‐angle x‐ray scattering (SAXS) and the nanostructures were obtained. It was identified that the reaction‐induced phase separation occurred in the blends of phenolic thermosets with the model poly(propylene oxide) (PPO), whereas poly(ethylene oxide) (PEO) was miscible with novolac resin after and before the curing reaction. In terms of miscibility and phase behavior of the subchains of the triblock copolymer with novolac resin, it was demonstrated that the formation of nanostructures in the thermosets followed a mechanism of reaction‐induced microphase separation. 相似文献
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