Current Issue : July - September Volume : 2014 Issue Number : 3 Articles : 6 Articles
Carbon nanotubes have a host of properties that make them excellent candidates for electron emitters. A significant amount of\nresearch has been conducted on nanotube-based field-emitters over the past two decades, and they have been investigated for\ndevices ranging from flat-panel displays to vacuum tubes and electron microscopes. Other electron emission mechanisms from\ncarbon nanotubes, such as photoemission, secondary emission, and thermionic emission, have also been studied, although to a\nlesser degree than field-emission. This paper presents an overview of the topic, with emphasis on these less-explored mechanisms,\nalthough field-emission is also discussed. We will see that not only is electron emission from nanotubes promising for electronsource\napplications, but also its study could reveal unusual phenomena and open the door to new devices that are not directly\nrelated to electron beams....
Cross-linked polyethylene (XLPE) is commonly used in medium/high voltage insulation due to its excellent dielectric properties\nand acceptable thermomechanical properties. To improve both electrical and thermal properties to a point that would possibly\navoid the need for crosslinking, nanoclay fillers can be added to polymer matrix to form nanocomposites materials. In this paper,\nPE/clay nanocomposites were processed by mixing a commercially available premixed polyethylene/O-MMT masterbatch into a\npolyethylene blend matrix containing 80 wt% low density polyethylene LDPE and 20 wt% high density polyethylene HDPE with\nand without compatibilizer using a corotating twin-screw extruder. Various characterization techniques were employed in this\npaper, including optical microscopy, AFM, TEM, TGA, DMTA, and dielectric breakdown measurements in order to understand\nthe correlation between structure and short-term dielectric breakdown strength....
We have calculated the nucleation region (NR) location of Si nanocrystal grains prepared by pulsed laser ablation (PLA) with fluence\nof 4 J/cm2 in 10 Pa gas at room temperature, and ambient gases were He, Ne, and Ar, respectively. Results of calculation indicated\nthat NR width in Ne gas was narrowest, while it was widest in He gas.Maximum mean size of grains deposited on substrates under\nablated spot, which were placed horizontally, was the smallest in Ne gas. It would be attribute to more effective energy transfer\nduring the process of collision when atomic mass of Si and ambient gas Ne are more close to each other. In this work, an additional\ngas flow with the same element as ambient gas was introduced, which is vertical to the plume axis at different lateral positions above\nablated spot....
Attachment of PbS quantumdots (QD) to single-walled carbon nanotubes (SWNT) andmultiwalled carbon nanotubes(MWCNT)\nis described; wherein commercially obtained PbS-QD of size 2.7 nm, stabilized by oleic acid, are added to a suspension of singleormultiwalled\ncarbon nanotubes (CNT) prefunctionalized noncovalently with 1,2-benzenedimethanethiol (1,2-BDMT) in ethanol.\nThe aromatic part of 1,2-BDMTattaches to the CNT by ??-?? stacking interactions, noncovalently functionalizing the CNT.The thiol\npart of the 1,2-BDMTon the functionalizedCNTreplaces oleic acid on the surface of theQDfacilitating the noncovalent attachment\nof the QD to the CNT.The composites were characterized by TEM and FTIR spectroscopy. Quenching of NIR fluorescence of the\nPbS-QD on attachment to the carbon nanotubes (CNT) was observed, indicating FRET from the QD to the CNT....
The adhesion of long, straight, single-walled carbon nanotubes to surfaces is examined usingmultidimensional force spectroscopy.\nWe observed characteristic signatures in the deflection and frequency response of the cantilever indicative of nanotube buckling\nand slip-stickmotion as a result of compression and subsequent adhesion and peeling of the nanotube fromthe surface.The spring\nconstant and the elastic modulus of the SWNT were estimated from the frequency shifts under tension. Using elastica modeling\nfor postbuckled columns, we have determined the static coefficient of friction for the SWNT on alkanethiol-modified gold surfaces\nand showed that it varies with the identity of the monolayer terminal group....
Cobalt nanoparticles were produced by employing the liquid-phase reduction method and hydrazine. The effect of citric acid\nadditives on the formation and growthmechanism of cobalt nanoparticles was investigated using polarization methods. The cobalt\nnanoparticles produced in 0.2M cobalt sulfate and 5M hydrazine at 298 K had a spherical shape with a diameter of 400 nm. The\ndendritic nanoparticles formed with the decreasing of hydrazine concentration at 298 K. On the other hand, dendritic large particles\nare confirmed at 353K. It was confirmed that the reduction reaction progressed with the addition of citric acid, and a hexagonal\nclose-packed (??Co) phase was formed....
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