Though not very often, there are some cases in the literature where discrepancies exist in the temperature dependence of elastic constants of materials. A particular example of this case is the behavior of C12 coeffic...
详细信息
Though not very often, there are some cases in the literature where discrepancies exist in the temperature dependence of elastic constants of materials. A particular example of this case is the behavior of C12 coefficient of a simple metal, aluminum. In this paper we attempt to provide insight into various contributions to temperature dependence in elastic properties by investigating the thermoelastic properties of fcc aluminum as a function of temperature through the use of two computational techniques and experiments. First, ab initio calculations based on density functional theory (DFT) are used in combination with quasiharmonic theory to calculate the elastic constants at finite temperatures through a strain-free energy approach. Molecular dynamics (MD) calculations using tight-binding potentials are then used to extract the elastic constants through a fluctuation-based formalism. Through this dynamic approach, the different contributions (Born, kinetic, and stress fluctuations) to the elastic constants are isolated and the underlying physical basis for the observed thermally induced softening is elucidated. The two approaches are then used to shed light on the relatively large discrepancies in the reported temperature dependence of the elastic constants of fcc aluminum. Finally, the polycrystalline elastic constants (and their temperature dependence) of fcc aluminum are determined using resonant ultrasound spectroscopy (RUS) and compared to previously published data as well as the atomistic calculations performed in this work.
Here we report a nano-size catalyst-enhanced enzymatic bioanode for glucose biofuel cells. The bioanode was constructed by coating a crosslinked mixture of glucose oxidase (GOx), 2,5-dihydroxybenzaldehyde (DHB), bovin...
详细信息
Here we report a nano-size catalyst-enhanced enzymatic bioanode for glucose biofuel cells. The bioanode was constructed by coating a crosslinked mixture of glucose oxidase (GOx), 2,5-dihydroxybenzaldehyde (DHB), bovine serum albumin (BSA) and glutaraldehyde on a MWCNT-modified screen printed carbon electrode (SPCE). By presenting Ru-supported CMK-3 (Ru-CMK-3) in the bioanode, the biofuel cell's power output was significantly enhanced and could reach 60 W·cm -2 at 25°C. And we found that the enhancement was attributed to CMK-3 or Ru-CMK-3-catalyzed oxidation of gluconic acid. Therefore, Ru-CMK-3 can work synergistically with GOx and achieve more complete oxidation of glucose in a biofuel cell.
Carbon-Electrode Dielectrophoresis (CarbonDEP) is a novel variation of the conventional electrode-based DEP. The use of carbon, instead of metal, offers advantages like a wider electrochemical stability window, excell...
详细信息
ISBN:
(纸本)9780816910700
Carbon-Electrode Dielectrophoresis (CarbonDEP) is a novel variation of the conventional electrode-based DEP. The use of carbon, instead of metal, offers advantages like a wider electrochemical stability window, excellent biocompatibility, and great mechanical properties. In order to optimize the performance of electrokinetic experiments, such as separation and concentration of microparticles, it is necessary to know the dielectric properties of the particle of interest a priori. For the extraction of dielectric properties using DEP, it is required that other electrokinetic phenomena, such as electroosmotic flow (EOF) and electrophoresis (EP), are not present on the experiment. Presented in this work is the implementation of a dielectric properties characterization platform based on CarbonDEP. A microdevice containing planar carbon electrodes was employed to manipulate carboxylated polystyrene particles with diameters of 1 μm and 2.28 μm. Particle responses were obtained by varying the magnitude and frequency of the applied AC potential. Velocity induced on the particles was measured experimentally and electric parameters of the microchannel were obtained through simulations in COMSOL Multiphysics. With this information, a system of non linear equations was built, from which the dielectric properties can be extracted. Potential applications of this work include, but are not limited to, environmental screening for water contamination, food safety, clinical analyses, and improvement of clean energy production methods. The results of this work have great potential to be used as guidelines for the further design and operation of CarbonDEP based systems.
There have been reports of improvements in the thermoelectric figure of merit through the use of nanostructured materials to suppress the lattice thermal conductivity. Here, we report on a fundamental study of the com...
详细信息
In order to clarify the mechanism of space charge formation and distribution in polymeric insulating materials, further experiments on preparation and charge transport of polyimide (PI) nanocomposite films were studie...
详细信息
ISBN:
(纸本)9784886860743
In order to clarify the mechanism of space charge formation and distribution in polymeric insulating materials, further experiments on preparation and charge transport of polyimide (PI) nanocomposite films were studied. polymer nanocomposites were used in electronic and electrical engineering as a result of their excellent properties. In this paper, the TiO_2 nanoparticles modified by employing surface chemical reaction were introduced into the PI matrix by using in situ polymerization. The in situ polymerization process is helpful to drive the nanoparticles into the PI matrix homogeneously. Space charge distribution in pure PI films and the PI/TiO_2 nanocomposite films are measured using the Pulsed Electroacoustic (PEA) method. Two process of space charge measurement were investigated, namely "volts on" and "Decay". Different types and levels of nanoparticles have been studied to understand the interaction between nanoparticles and polyimide matrix. The addition of nanoparticles has a significant influence on space charge formation, transport and decay process.
By employing multi-walled carbon nanotubes (MWNT) and SiO2 as fillers and silicone as matrix, (MWNT-SiO2)/RTV composites were prepared by three roll mills mixing method and the piezoresistive and dielectric properties...
详细信息
By employing multi-walled carbon nanotubes (MWNT) and SiO2 as fillers and silicone as matrix, (MWNT-SiO2)/RTV composites were prepared by three roll mills mixing method and the piezoresistive and dielectric properties of composites were investigated. The results showed that the use of KH570 modified silica could improve the dispersion of fillers in matrix and the interface binding between fillers and RTV. After modified SiO2, the pressure sensitivity of (MWNT-SiO2)/RTV composite become stronger. When the outside pressure is 150N, the relative resistance of the (MWNT-SiO2)/RTV composite with 5% SiO2 is nearly twice as much or as that of the MWNT/RTV composite and the piezoresistive sensitivity should increase nearly double. In addition, the resistance and pressure showed a good linear relationship. With increasing the aspect ratio of MWNT, the piezoresistive sensitivity of (MWNT-SiO2)/RTV composites is weaker. Dielectric constant of (MWNT-SiO2)/RTV composites decreases with increasing frequency and it increases with the increase of silica content.
Poly(vinylidene fluoride) (PVdF) fine fiber of 200–300 nm in diameter was prepared through the electrospinning process. Dehydrofluorination of PVdF-based fibers for making infusible fiber was carried out using DBU, a...
Poly(vinylidene fluoride) (PVdF) fine fiber of 200–300 nm in diameter was prepared through the electrospinning process. Dehydrofluorination of PVdF-based fibers for making infusible fiber was carried out using DBU, and the infusible PVdF-based nanofibers were then carbonized at 900–1800°C. The structural properties and morphologies of the resulting carbon nanofibers were investigated using XRD, Raman IR, SEM, TEM, and surface area & pore analysis. The PVdF-based carbon nanofibers had rough surfaces composed of 20-to 30-nm granular carbons, indicating their high surface area in the range of 400–970 m2/g. They showed amorphous structures. In the case of the highly ehydrofluorinated PVdF fiber, the resulting carbon fiber had a smoother surface, with d002 = 0.34–0.36 nm, and a very low surface area of 16–33 m2/g. The hydrogen storage capacities of the above carbon nano-fibers were measured, using the gravimetric method, by magnetic suspension balance (MSB), at room temperature and at 100 bars. The storage data were obtained after the buoyancy correction. The PVdF-based microporous carbon nanofibers showed a hydrogen storage capacity of 0.04–0.4 wt%. The hydrogen storage capacity depended on the dehydrofluorination of the PVdF nanofiber precursor, and on the carbonization temperatures.
暂无评论