Optimum sol viscosity for stable electrospinning of silica nanofibres

Abstract

Silica nanofibres have, due to their excellent properties, promising characteristics for multiple applications such as filtration, composites, catalysis, etc. Silica nanofibres can be obtained by combining electrospinning and the sol-gel process. To produce silica nanofibres most of the time organic solutions are applied containing a carrying polymer, which is afterwards removed by a thermal treatment to form pure ceramic nanofibres. Although electrospinning of the pure silica precursors without carrying polymer is preferred, the parameters influencing the stability of the electrospinning process are however largely unknown. In addition this knowledge is essential for potential up-scaling of the process. In this study, the optimum viscosity to electrospin in a stable manner is determined and the way to obtain this viscosity is evaluated. Sols with a viscosity between 120 and 200 mPa.s could be electrospun in a stable way, resulting in uniform and beadless nanofibres. Furthermore, this viscosity region corresponded with nanofibres having the lowest mean nanofibre diameters. Electrospinning with diluted sols was possible as well, but electrospinning of the fresh sols was more stable. These results illustrate the importance of the viscosity and degree of crosslinking of the sol for the stable electrospinning of silica nanofibres and demonstrate that upscaling of the electrospinning process of silica nanofibres is feasible.

TiO2 functionalized nanofibrous membranes for removal of organic (micro)pollutants from water

“…SEM images are shown of 0.2 wt% and 2 wt% TiO2 loaded silica nanofibers. These samples have diameters of 346 ± 44 nm and 321 ± 165 nm, which are again largely unaltered compared to nonfunctionalized silica nanofibers (302 ± 83 nm) prepared in this work and in previous research [29,30]. At a TiO2 loading of 2 wt% beads started to become present in the resulting nanofibers.…”

Silica Nanofibrous Membranes for the Separation of Heterogeneous Azeotropes

“…Electrospinning of TEOS‐Based Nanofibers : Silica nanofibers were made using the methodology described in previous work . A solution of TEOS, ethanol, distilled water, and HCl at molar ratios of 1:2:2:0.01 was used.…”

“…To increase the chemical and thermal resistance of nanofibrous structures, ceramic variants are being developed, which widens the application potential toward harsh environments, e.g., industrial acidic waste streams . Recently, our group successfully produced ceramic silica nanofibers without the need of a sacrificing polymer . In contrast to other work, in which a well‐spinnable organic polymer is mixed with a metal oxide precursors to facilitate the electrospinning process, direct electrospinning of a sol–gel solution of a tetraethyl orthosilicate (TEOS) precursor eliminates the need for a postproduction removal of the organic polymer component .…”

Hybrid sol–gel inorganic/gelatin porous fibres via solution blow spinning

“…The viscosity increases over time, governed by acid concentration, temperature, and solvent evaporation [31,62]. Whilst the viscosity can be lowered by the addition of alcohol in TEOS-based sol-gel systems [44,45], increasing the concentration of alcohol caused precipitation of gelatin in the hybrid formulations.…”

“…Electrospinning has also been used to form neat silica and calcium containing silica sol-gel fibres [31]. Most methods utilise solvent evaporation to tune the rheological properties to reach a spinning window [31,44,45]. Increased evaporation typically leads to higher colloidal concentration, which raises the rate of network formation.…”