Nano-oxide fibers

Other forms ofvery fine oxide fibers exist or are being developed. Single crystal whiskers which pose health risks and also present difficulties for handling, because of their very small dimensions, have not found wide use. Nano-oxide fibers are being developed which may be fine enough for liquid crystal technology to be used so as to handle them but as yet remain a possibility for the future. 

Shukla, S., et al., 2005. Electrospinning of hydroxypropyl cellulose fibers and their application in synthesis of nano and submicron tin oxide fibers. Polymer 46 (26), 12130-12145. 

A liquid phase, as opposed to a vapor or solid phase, includes dispersions, solutions and melts. Several processes, which yield continuous inorganic fibers directly from the melt, have been discussed in Chapter 4. Only one generic process, dry spinning, is known to yield one specific amorphous oxide fiber directly from a liquid phase other than that of a melt. All other processes which start with a liquid phase (see Chapters 8-12) yield first a solid, non-functional precursor or green fiber, and then a functional, nano- or polycrystailine ceramic fiber. Such refractory ceramic fibers are therefore directly derived from a solid phase, a precursor or a green fiber, and only indirectly from a liquid phase. 

Shukla S.K., Parashar G.K., Mishra A.P., Misra P., Yadav B.C., Shukla R.K., Bali L.M., Dubey G.C., Nano-like magnesium oxide films and its significance in optical fiber humidity sensor, Sens. Actuat B 2004 98 5-11. 

Carbon nanotubes (CNTs) currently attract intense interest because of their unique properties which make them suitable for many industrial applications.28 Carbon nanotubes exhibit some of the properties implied in asbestos toxicity. Carbon nanotubes share with asbestos the fibrous habit - long fibers with a diameter of a few nanometers -and a very high biopersistence. On this basis they are suspected to be hazardous and indeed the first studies in vivo14,29,30 have shown an inflammatory response followed by some evolution towards fibrosis. When inhaled, CNTs may thus constitute a possible hazard to human health. The inflammatory and fibrotic responses elicited by CNTs is similar to that caused by other toxic particles which might be the result of oxidative stress caused by particle- and/or cell-derived free radicals. There is no direct experimental evidence of a capacity of carbon nanotubes to generate free radicals similar to silica asbestos and nano sized iron oxide particles. 

The use of gas diffusion electrodes is another way to achieve high current densities. Such electrodes are used in the fuel-cell field and are typically made with porous materials. The electrocatalyst particles are highly dispersed inside the porous carbon electrode, and the reaction takes place at the gas/liquid/solid three-phase boundary. COj reduction proceeds on the catalyst particles and the gas produced returns to the gas compartment. We have used activated carbon fibers (ACF) as supports for metal catalysts, as they possess high porosity and additionally provide extremely narrow (several nm) slit-shaped pores, in which nano-space" effects can occur. In the present work, encouraging results have been obtained with these types of electrodes. Based on the nanospace effects, electroreduction under high pressure-like conditions is expected. In the present work, we have used two types of gas diffusion electrodes. In one case, we have used metal oxide-supported Cu electrocatalysts, while in the other case, we have used activated carbon (ACF)-supported Fe and Ni electrocatalysts. In both cases, high current densities were obtained. 

FIGURE 8.7 Transmission emission microscope (TEM) image of a single polyethylene oxide nanofiber embedded with nano MgO at regular intervals. (Hussain, M.M. and Ramkumar, S.S., 2006, Functionalized nanofibers for advanced applications, Indian J. Fiber Text. Res.. 31, 41-51.)... 

NFs acted as an oxidant to oxidatively polymerize aniline. Consequently, Mn O was completely consumed while PANl/TiO -NFs were formed. Composite fiber film having a PANI nanowire-on-TiO nano/microfiber hierarchical nano/microstructure was fabricated by electrospinning, calcinations and in situ polymerization [121], The photocatalytic electrodeposition of PANI in nanotubular TiO host matrice was recently reported by Janaky ef a/. [ 108]. TiO films were initially electrosynthesized on titanium foil by anodization at different voltages in fluoride-containing aqueous media, and then the PANI was electrografted onto the entire surface of... 

Kim et at deposited nano-thin PPy films on the vapor grown carbon fibers (VGCF) by using an in situ chemical oxidative polymerization of the monomer in the presence of FeCl oxidant by means of an ultrasonic... 

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