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73.
Mayank Pandey Girish M. Joshi Kalim Deshmukh Moumita Khutia Narendra Nath Ghosh 《Ionics》2014,20(10):1427-1433
Polyvinylidene fluoride (PVDF) and polyvinyl alcohol (PVA) composites were prepared by controlled loading of Nafion (5 to 15 wt%) by solution casting using water and dimethylformamide (DMF) as a solvent. The surface morphology of composite analyzed by atomic force microscopy (AFM) reveals the presence of Nafion ionomers. The increase in interlayer spacing of modified PVDF/PVA polymer system as a function of Nafion was detected by X-ray diffraction (XRD). The major change in Fourier transform infrared (FTIR) spectroscopy confirms the chemical bond C=O stretching around 1,700 cm?1 due to Nafion. Differential scanning calorimetry (DSC) demonstrates the thermal stability of polymer composites and the decrease in melting temperature (T m). The optimized AC conductivity (σ) of the prepared composite was evaluated by using an impedance analyzer as a function of temperature (40 to 150 °C) at constant 30-MHz frequency. The highest conductivity of 1.3?×?10?2 S m?1 was observed at 80 °C for 10 wt% of Nafion and correlated with structure, morphology and thermal properties of modified PVDF/PVA/Nafion composites. The experimental results may be useful for sensors, fuel cells and battery application domains. 相似文献
74.
A feasibility study was carried out on the utilization of Alkanolamide (ALK) on silica reinforcement of natural rubber (NR) by using a semi-efficient cure system. The ALK was incorporated into the NR compound at 1.0, 3.0, 5.0, 7.0 and 9.0 phr. An investigation was carried out to examine the effect of ALK on the cure characteristics and properties of NR compounds. It was found that ALK gave shorter scorch and cure times for silica-filled NR compounds. ALK also exhibited higher torque differences, tensile modulus, tensile strength, hardness and crosslink density of up to 5.0 phr of ALK loading, and then decreased with further increases of ALK loading. The resilience increased with increased ALK loading. Scanning electron microscopy (SEM) micrographs proved that 5.0 phr of ALK in the silica-filled NR compound exhibited the greatest matrix tearing line and surface roughness due to higher reinforcement level of the silica, as well as better dispersion and cure enhancement. 相似文献
75.
The relative thermal stability of copolymers of 2-hydroxyethyl methacrylate-ethyl methacrylate (HEMA-EMA) and HEMA-n-butyl methacrylate (HEMA-BMA) was investigated by thermogravimetry in an air/nitrogen atmosphere. The effect of molecular weight on thermal degradation was evaluated by taking five fractions of HEMA-EMA and four of HEMA-BMA copolymers. The enthalpic changes associated with the endothermic transition were evaluated by differential scanning calorimetry. The structural changes taking place in these copolymers during thermal degradation in air at 200°C were investigated by IR. 相似文献
76.
Fe? W heterometallic complexes, in which an FeX2 (X=Cl, SPh) moiety is attached to monodithiolene oxotungsten through a sulfide bridge, that is, [Ph4P]2[Cl2Fe(S)2WOS2] ( 1 ), [Ph4P]2[Cl2Fe(S)2WOS2(DMED)] ( 2 , DMED=dimethylethylenedicarboxylate), [Ph4P]2[Cl2Fe(S)2WO(tdt)] ( 3 , tdt=toluenedithiolate), [Ph4P]2[(SPh)2Fe(S)2WO(tdt)] ( 4 ), and [Ph4P]2[Cl2Fe(S)2WO(edt)] ( 5 , edt=ethanedithiolate), are reported. Mössbauer and EPR spectroscopy, magnetism, electrochemistry, and electronic structural analysis based on DFT and TD‐DFT calculations show the transfer of electron from the iron center to the tungsten center, thus resulting in a ferromagnetically coupled FeIIIWV unit, along with antiferromagnetic intermolecular interactions, from the starting FeII and WVI compounds. A net spin of a S=3 ground state, which arises from ferromagnetically coupled FeIII and WV atoms, displays a rare X‐band EPR in normal mode at g≈7 in the solid state. 相似文献
77.
Vijai Singh Indra Mani Dharmendra Kumar Chaudhary Pawan Kumar Dhar 《Applied biochemistry and biotechnology》2014,172(3):1158-1171
Metabolic engineering is an important area of research that involves editing genetic networks to overproduce a certain substance by the cells. Using a combination of genetic, metabolic, and modeling methods, useful substances have been synthesized in the past at industrial scale and in a cost-effective manner. Currently, metabolic engineering is being used to produce sufficient, economical, and eco-friendly biofuels. In the recent past, a number of efforts have been made towards engineering biosynthetic pathways for large scale and efficient production of biofuels from biomass. Given the adoption of metabolic engineering approaches by the biofuel industry, this paper reviews various approaches towards the production and enhancement of renewable biofuels such as ethanol, butanol, isopropanol, hydrogen, and biodiesel. We have also identified specific areas where more work needs to be done in the future. 相似文献
78.
Spinel oxides with the composition of AIIBIII2O4 (A and B are metal ions) represent an important class of anode material for water splitting to replace the currently used noble-metal catalysts. Although spinel electrocatalysts have widely been investigated for electrochemical water oxidation, the role of octahedral and tetrahedral sites influencing catalytic performance has been a topic of discussion for a long time and still under debate. Lately, this issue has been addressed by substituting redox-inert cation to the tetrahedral sites of cobalt spinels and comparing the electrochemical activity between them. However, rapid surface structural transformation of the catalysts under operating electrochemical conditions makes it difficult to infer the exact contribution of tetrahedral and octahedral sites for water oxidation. Herein, for the first time, we utilize the oxidant-driven water oxidation approach to reveal the responsible active sites using two spinel-type nanostructures, ZnIICo2IIIO4 and CoIICo2IIIO4 (Co3O4), synthesized by using a single-source precursor approach. Strikingly, a superior O2 production rate (0.98 mmolO2 molCo?1 s?1) following first-order reaction kinetics was achieved for ZnCo2O4 in the presence of CeIV as sacrificial electron acceptor compared to Co3O4 spinel (0.29 mmolO2 molCo?1 s?1). The structural and morphological stability of the ZnCo2O4 and Co3O4 post water oxidation catalysis confirms that the catalytic activity is strictly controlled by the geometry and electronic structure of the active site of the spinel structure. The higher performance of ZnCo2O4 over Co3O4 further indicates that the presence of CoII is not essential for catalytic water oxidation. The presence of redox inert ZnII at the tetrahedral site of ZnCo2O4 can facilitate the stabilization of a high-valent CoIV intermediate via oxidation of CoIII (situated at the octahedral site), and this intermediate can be regarded as the active species for water oxidation catalyst along with structural defects caused by surface Zn leaching. 相似文献
79.
Naveenkumar Akula Neha Sharma Apurva Lohegaonkar Satishchandra B. Ogale Moumita Majumdar 《化学:亚洲杂志》2020,15(5):585-589
The organosilicon reagent 1,4‐bis‐(trimethylsilyl)‐1,4‐diaza‐2,5‐cyclohexadiene 2 plays the binary role of the simultaneous reduction of GeCl2.dioxane 1 dissolved in oleylamine to Ge nanocrystals and the formation of graphitic sheets under hot‐injection conditions. This colloidal synthetic route to germanium nanocrystals embedded on N‐doped graphitic nanosheets Ge/NG is free of any template or catalyst and involves easy purification techniques. The Ge/NG/C obtained after carbonization has been explored for anode performance in lithium‐ion batteries. Both Ge/NG and Ge/NG/C can be obtained on a gram scale and are bottleable under argon for months. 相似文献
80.
Paul D. Manuel Mostafa I. Abd-El-Barr Indra Rajasingh Bharati Rajan 《Journal of Discrete Algorithms》2008,6(1):11-19
The most popular bounded-degree derivative network of the hypercube is the butterfly network. The Benes network consists of back-to-back butterflies. There exist a number of topological representations that are used to describe butterfly—like architectures. We identify a new topological representation of butterfly and Benes networks.The minimum metric dimension problem is to find a minimum set of vertices of a graph G(V,E) such that for every pair of vertices u and v of G, there exists a vertex w with the condition that the length of a shortest path from u to w is different from the length of a shortest path from v to w. It is NP-hard in the general sense. We show that it remains NP-hard for bipartite graphs. The algorithmic complexity status of this NP-hard problem is not known for butterfly and Benes networks, which are subclasses of bipartite graphs. By using the proposed new representations, we solve the minimum metric dimension problem for butterfly and Benes networks. The minimum metric dimension problem is important in areas such as robot navigation in space applications. 相似文献