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...
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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 combined effects of defect planes and surface scattering on phonon transport and thermoelectric properties of defect-engineered InAs nanowires. A microfabricated device is employed to measure the thermal conductivity and thermopower of individual suspended indium arsenide nanowires grown by metal organic vapor phase epitaxy. The four-probe measurement device consists of platinum resistance thermometers and electrodes patterned on two adjacent SiNx membranes. A nanowire was suspended between the two membranes, and electrical contact between the nanowire and the platinum electrodes was made with the evaporation of a Ni/Pd film through a shadow mask. The exposed back side of the device substrate allows for characterization of the crystal structure of the suspended nanowire with transmission electron microscopy (TEM) following measurement. The 100-200 nm diameter zincblende (ZB) InAs nanowire samples were grown with randomly spaced twin defects, stacking faults, or phases boundaries perpendicular to the nanowire growth direction, as revealed by transmission electron microscopy (TEM) analysis. Compared to single-crystal ZB InAs nanowires with a similar lateral dimension, the thermal conductivity of the defect-engineered nanowires is reduced by fifty percent at room temperature.
Considerable efforts have been devoted to the design and synthesis of low-dimensional, nanostructured materials due to their morphology-dependent performances. In particular, one-dimensional (1-D) TiO2 nanostructures,...
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ISBN:
(纸本)9780857296375
Considerable efforts have been devoted to the design and synthesis of low-dimensional, nanostructured materials due to their morphology-dependent performances. In particular, one-dimensional (1-D) TiO2 nanostructures, including nanorods (NRs), nanowires (NWs), and nanotubes (NTs), have attracted considerable interest due to their unique characteristics. In dye-sensitized solar cell (DSSC) operation, 1-D nanostructure-based photoanodes can contribute to rapid electron transport, ensuring efficient charge collection by the conducting substrate in competition with recombination. Relying on the ordering of 1-D TiO2 nanomaterial, the conversion efficiency of DSSCs was affected because electron collection is determined by trapping/detrapping events at the site of the electron traps, such as defects, surface states, grain boundaries, and self-trapping. This point has promoted research on self-ordered, 1-D photoanodes stretched on a substrate with enhanced electron transport properties due to their desirable features: highly decreased intercrystalline contacts and a structure with a specified directionality. In this literature review, the preparation of various 1-D nanomaterials from disordered to ordered states and their electron dynamics in the application of DSSCs are reviewed.
The effects of various synthesis conditions on the structure and composition of ferrisilicate analogs of zeolite ZSM-5 were considered. Scanning electron microscopy (SEM) was used to determine the particles size distr...
The effects of various synthesis conditions on the structure and composition of ferrisilicate analogs of zeolite ZSM-5 were considered. Scanning electron microscopy (SEM) was used to determine the particles size distributions and morphologies. Particle sizes vary from tenths of a micron to several microns, depending on degree of agitation during crystal growth, while morphology is additionally dependent on the concentration of iron in the gel during crystallization. X-ray emissive spectroscopy (XES) performed in the transmission electron microscope (TEM) was used to determine their composition variation. The distribution of iron amongst the crystals is more homogeneous if the gel is stirred and it does not depend on particle size.
Carbon-fiber microelectrodes(CFMEs) have been a useful tool for micro devices because of their small size,strength,and good electrochemical *** this study,a conventional carbon fiber was developed microelectrodes,whic...
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Carbon-fiber microelectrodes(CFMEs) have been a useful tool for micro devices because of their small size,strength,and good electrochemical *** this study,a conventional carbon fiber was developed microelectrodes,which was fabricated through surface exfoliation of carbon fiber using microwave irradiation without multiple and extremely high temperature *** surface exfoliation,carbon fiber and intercalant such as nitric acid and potassium permanganate were mixed by a glass bar at a weight ratio of 1:1:2 in a porcelain dish at room ***,the porcelain dish was placed in a domestic microwave oven and irradiated for 60 *** surface of carbon fiber was successfully exfoliated which was investigated by scanning electron *** electrical properties of surface exfoliated carbon fiber were investigated though fabricated micro *** surface exfoliated carbon fiber had good electrical conductivity and well interconnection at cross point in micro circuit without any external soldering or *** research in this field will likely concentrate on fabricating smaller electrodes,high electrical conductivity,and electrode arrays.
A noval waterborne polyurethane dye EBT-PU and a reference BDO-PU were synthesized using toluene diisocyanate, polyoxypropylene glycol, 2, 2-dimethylol propionic acid and eriochrome black T (EBT) or 1, 4-butanediol (B...
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A noval waterborne polyurethane dye EBT-PU and a reference BDO-PU were synthesized using toluene diisocyanate, polyoxypropylene glycol, 2, 2-dimethylol propionic acid and eriochrome black T (EBT) or 1, 4-butanediol (BDO) by self-emulsification method. The structure of EBT-PU and BDO-PU was confirmed by Fourier transform infrared spectroscopy. It was found that the maximum absorption of 528 nm in UV-Visible spectrum appeared a bathochromic shift of 44 nm because of the disappearance of auxochrome -OH and the change of conjugate system for EBT during the reaction between EBT and -NCO group. Although the soft and hard segments in chains of EBT-PU and BDO-PU are incompatible, the conjugate structure of EBT has a big effect on the incompatibility comparing to the aliphatic chain of BDO. The experimental result shows that EBT-PU is an amorphous polymer, and the conjugate structure of EBT can introduce a distinct improve for the thermal stability of EBT-PU.
An extremely simple approach is described here to synthesize bulk quantities of conducting polymer microspirals assembled from nanofibers by in situ chemical oxidative polymerization in the presence of a conventional ...
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An extremely simple approach is described here to synthesize bulk quantities of conducting polymer microspirals assembled from nanofibers by in situ chemical oxidative polymerization in the presence of a conventional surfactant. It is worth noting that the surfactant used in our approach is in crystalline state, which is quite different from micellar state in emulsional polymerization reported previously. The growth mechanism of the conducting polymer is proposed.
We conducted community-based participatory research with a cross-sectional repeated measures design in Visalia, Tulare County, California. We report on a novel modification of both an existing field dust wipe method a...
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ISBN:
(纸本)9781627482721
We conducted community-based participatory research with a cross-sectional repeated measures design in Visalia, Tulare County, California. We report on a novel modification of both an existing field dust wipe method and laboratory analysis procedure for extracting then quantifying phthalates from pre-wetted wipes. Twelve individuals- of 34 at baseline from convenience sample meeting selection criteria recruited in spring 2009- agreed to comprehensive home visits;nine completed first visits July, 2009 (Shendell et al, 2010). We confirmed each participant at baseline had 13 physician-diagnosed respiratory diseases, e.g., asthma. Four of five targeted phthalates [DEHP (diethylhexyl phthalate), DBP (dibutyl phthalate), DEP (diethyl phthalate) and BBzP (butylbenzyl phthalate), not DINP (diisononyl phthalate)] were measured above study analytic detection limits in most study homes. Measured levels of phthalates varied between kitchen floors compared to front hallways/entry areas (FH) and TV rooms/dens for DBP and DEHP;for DnBP and BBzP, levels were consistently higher in FH.
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