Surface porosity nanofibers

In a different way, the surface porosity of individual nanofibers is defined by the topography which can be present on the surface of each polymer filament. Depending on their nature and on the used fabrication method, surface features can extend from the nm-scale to hundreds of nm, thus possibly being... 

In a recent work, high flux UF membrane was prepared using electrospun nano-flbers of PAN, which was coated with CH solution. The nanofibrous PAN scaffold increased the surface porosity of the membrane, resulting in higher flux with the hydrophilic CH layer (Yoon et al. 2006). In the future, the use of nanofibers made up of CH may help in improving the performance of the subsequently fabricated UF and NF membranes. 

An electrospinning unit is a system for producing ultrafine fibers with a diameter of about 20-1000 nm. A nanofiber has a very high specific surface area, a small diameter, and large porosity. There are about hundred kinds of polymers that could be used as raw materials. 

Ultrafine fibers of PANl doped with CSA were blended with PEO by electrospinning. By controlling the ratio of PANl to PEO, desired conductivities were obtained. The comparison between cast films and nanofiber mats was reported. High porosity of nanofiber mats leads to lower conductivities compared to cast films but nanofiber mats have advantages like quick dedoping due to a higher surface area. 

In all cases, the polyaniline nanofibers perform better than conventional thin films [84]. Their high surface area, porosity, and small diameters enhance diffusion of molecules and dopants into the nanofibers. 

Besides CNTs, another ID carbon nanostructure is carbon nanoflbers. For example, Shen et al. [156] prepared a series of hierarchical porous carbon libers with a BET surface area of 2,231 m g and a pore volume of 1.16 cm g. In this synthesis method, the polyacrylonitrile (PAN) nanofibers (prepared by dry-wet spinning) were selected as precnrsors, and pre-oxidation and chemical activation were involved to get the developed porosities. This type of material contained a large amount of nitrogen-containing groups (N content >8.1 wt%) and consequently basic sites, resulting in a faster adsorption rate and a higher adsorption capacity for CO2 than the commercial zeolite 13X that is conventionally used to capture CO2, in the presence of H2O (Fig. 2.27). 

---