Capturing real-time data as nanofibers form …

Capturing real-time data as nanofibers form makes electrospinning more affordable and effective

Electrospinning, a nanofiber fabrication method, can produce nanometer- to micrometer-diameter ceramic, polymer, and metallic fibers of various compositions for a wide spectrum of applications: tissue engineering, filtration, fuel cells and lithium batteries. These materials have unique properties because of their high-aspect-ratio morphology and large surface area.

Yet their development has largely been by trial and error, making it difficult to reproduce reliably in industrial settings. This challenge stems from a lack of understanding of the underlying dynamics during the process, which involves more than 10 control parameters.

The U.S. Department of Energy’s (DOE) Argonne National Laboratory is taking the guesswork out of electrospinning by leveraging its unique suite of capabilities to build a database that correlates electrospinning machine parameters with nanofiber properties. The suite will allow companies to design materials optimized for specific applications at top speed, while also making possible real-time feedback and control on the manufacturing floor.

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qingzinano: Touch Spinning of Nanofibers …

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Touch Spinning of Nanofibers

A further modification is a scalable method called touch spinning (Fig. 4.12). Nano/microfibers from 40 nm to 5 mm in diameter can be made by adjusting the rotational speed and polymer concentration (Tokarev et al., 2015). A glass rod (0.3 mm to a few millimeters in diameter) is glued to a rotating stage. A polymer solution is supplied, for example, from the needle of a syringe pump that faces the glass rod. The distance between the droplet of polymer solution and the tip of the glass rod is adjusted so that the glass rod contacts the polymer droplet as it rotates. Following the initial “touch,” the polymer droplet forms a liquid bridge. As the stage rotates, the bridge stretches and fiber length increases, with the diameter decreasing owing to mass conservation. Polyethylene nanofibers can be made by this method.

Cooling wood: Engineers create strong, sustain…

Cooling wood: Engineers create strong, sustainable solution for passive cooling

What if the wood your house was made of could save your electricity bill? In the race to save energy, using a passive cooling method that requires no electricity and is built right into your house could save even chilly areas of the US some cash. Now, researchers at the University of Maryland and the University of Colorado have harnessed nature’s nanotechnology to help solve the problem of finding a passive way for buildings to dump heat that is sustainable and strong.

Wood solves the problem—it is already used as a building material, and is renewable and sustainable. Using tiny structures found in wood—cellulose nanofibers and the natural chambers that grow to pass water and nutrients up and down inside a living tree—that specially processed wood has optical properties that radiate heat away. The results of this study were published May 9 in the journal Science.

“This work has greatly extended the use of wood towards high performance energy efficient applications and provided a sustainable route to combat the energy crisis,” said Northeast Forestry University Professor Jian Li, a member of Chinese Academy of Engineering, who is not associated with the research.

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New way to beat the heat in electronics: Rice …

New way to beat the heat in electronics: Rice University lab’s flexible insulator offers high strength and superior thermal conduction

A nanocomposite invented at Rice University’s Brown School of Engineering promises to be a superior high-temperature dielectric material for flexible electronics, energy storage and electric devices. A lab video shows how quickly heat disperses from a composite of a polymer nanoscale fiber layer and boron nitride nanosheets. When exposed to light, both materials heat up, but the plain polymer nanofiber layer on the left retains the heat far longer than the composite at right.

[…]

The nanocomposite combines one-dimensional polymer nanofibers and two-dimensional boron nitride nanosheets. The nanofibers reinforce the self-assembling material while the “white graphene” nanosheets provide a thermally conductive network that allows it to withstand the heat that breaks down common dielectrics, the polarized insulators in batteries and other devices that separate positive and negative electrodes.

The discovery by the lab of Rice materials scientist Pulickel Ajayan is detailed in Advanced Functional Materials.

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qingzinano: Nano-microfiber Composites For F…

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Nano-microfiber Composites For Filtration

Nanofibers prepared by molecular self-assembly are in general not self-supporting and therefore require stabilizing scaffold structures. In fact, a lot of research in the past has been done with supramolecular self-assembly of molecules forming a network of nanofibers used as organo/hydrogelators. But efforts to use them as a self-standing membrane or as free fibers were not strong. Therefore, the self-assembly of trisamides was also tried on a substrate, i.e., other microfiber nonwovens, leading to microenanofiber composites (Fig. 4.4) used for filtration (Weiss et al., 2016).

qingzinano: Polymer/Carbon Nanotube Composit…

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Polymer/Carbon Nanotube Composite Nanofibers

To improve the compatibility between CNTs and polymers, the surface functionalization of CNTs has been developed (Kharaziha et al., 2014; Molnar et al., 2008; Ra et al., 2005; Mazinani et al., 2009;
Yee et al., 2012; Subagia et al., 2014; Diouri et al., 2014). For instance, Kharaziha et al. established a simple strategy to prepare electrospun gelatin/CNT composite nanofibers by using carboxyl acid groupemodified CNTs, and the well-dispersed CNTs aligned along the fibrous axis could be observed (Fig. 3.15B). This work demonstrated CNTs as a component of tough and flexible scaffolds with outstanding electrical properties (Kharaziha et al., 2014). Molnar et al. (2008) synthesized PVA/CNT composite nanofibers with diverse types of CNTs and different functional groups via electrospinning. Furthermore, other synthetic methods such as electrospinning combined with electrospraying and a surface adsorption approach have been developed as well (Xuyen et al., 2009; Kim et al., 2006b; Vaisman et al., 2007; Dai et al., 2011; Rana and Cho, 2011).

qingzinano: Polymer/Fe3O4 Composite Nanofibe…

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Polymer/Fe3O4 Composite Nanofibers

Magnetic NPs have been receiving increased attention with the rapid development of nanotechnology.Among them, Fe3O4 NPs have caused widespread interest owing to their high superparamagnetism as well as facile preparation. Their easy oxidation and resulting decline in magnetic property is a problem, however, which is effectively solved by the dispersion of Fe3O4 NPs in polymer nanofibers. The simplest way to prepare polymer/Fe3O4 composite nanofibers is to disperse Fe3O4 NPs in the polymer solution and subsequently carry out the electrospinning process. Xin et al. successfully fabricated poly(p-phenylene vinylene)/Fe3O4 composite nanofibers via electrospinning of a precursor solution and subsequent thermal conversion (Fig. 3.14A). In addition, the aligned nanofibers can be obtained by employing two parallel magnets as the collector. A variety of polymer/ Fe3O4 composite nanofibers, including PAN/Fe3O4 composite nanofibers, gelatin/Fe3O4 composite nanofibers, etc., have been reported by means of a similar method, and their potential applications in various fields have been studied as well.

qingzinano: METAL NANOFIBERS Metal nanom…

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METAL NANOFIBERS

Metal nanomaterials possess unique physical and chemical properties and certain special functions compared with many other functional nanomaterials. Electrospun metal nanofibers show excellent thermal stability and conductivity and possess potential applications in photoelectricity, sensors, hightemperature filtration, and other fields (Bognitzki et al., 2006; Hsu et al., 2012; Shao et al., 2011; Zhang et al., 2016c; Wu et al., 2007; Hansen et al., 2012). In 2006, Bognitzki et al. successfully prepared Cu nanofibers through a strategy involving an electrospinning technique followed by
calcination in an air and H2 atmosphere. It was the first time that electrospun Cu nanofibers had been reported (Bognitzki et al., 2006). Later, Hsu et al. coated a passivation layer on electrospun Cu
nanofibers (Fig. 3.12A). The results showed that the treated sample possessed superior durability as well as resistance over the bare Cu nanofibers. It is anticipated that the product can be applied as stable transparent electrodes (Hsu et al., 2012).

qingzinano: TiO2 Nanofibers  TiO2, as a ty…

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TiO2 Nanofibers 

TiO2, as a typical species of semiconductor oxide, has been widely applied in photocatalysis, mesoporous membranes, solar cells, etc. Considering their large specific surface area as well as surface/ interface effects, electrospun TiO2 nanofibers possess superior performance in various fields. In 2003, Li and Xia successfully prepared electrospun TiO2 nanofibers by employing PVP/ethanol/titanium tetraisopropoxide as a precursor solution system. The diameter and the porous structure of the obtained TiO2 nanofibers can be controlled by varying diverse parameters during the electrospinning process (Fig. 3.9). Since then, various solvent systems have been used to produce TiO2 nanofibers with different kinds of structure. Furthermore, numerous works have been reported with regard to the applications of electrospun TiO2 nanofibers. For instance, Chuangchote et al. synthesized diverse TiO2 nanofibers under different annealing temperature from 300C to 700C, and employed them as photocatalysts against hydrogen evolution. The results showed that the sample calcined at 450C exhibited the optimum catalytic activity.

qingzinano: Single-Component Synthetic Polym…

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Single-Component Synthetic Polymer Nanofibers

Herein, we divide the synthetic polymers into several species. Among them, organic solvent-soluble polymers have been greatly developed, for example, electrospun polystyrene (PS) nanofibers have been prepared from different solvent systems (Fig. 3.5A). DMF, tetrahydrofuran, and their mixtures are the most commonly used solvents (Lin et al., 2010; Nitanan et al., 2012). Electrospinning of polyacrylonitrile (PAN) nanofibers also employs DMF as solvent (Fig. 3.5B), and they are a kind of excellent precursor for the fabrication of carbon nanofibers, which have been widely studied (Fennessey and Farris, 2004; Gu et al., 2005). Polymethylmethacrylate (PMMA) is another familiar synthetic polymer; electrospun PMMA nanofibers as well as blended fibers have been developed for more than 10 years (Fig. 3.5C) (Ji et al., 2008; Carrizales et al., 2008).

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