Kumoh Institute team makes silica nanofiber mat that captures 98.6% of 2–4 µm particles

Researchers at Kumoh National Institute of Technology have established conditions for making silica nanofibers that withstand heat and chemical exposure, according to shinailbo.co.kr. The team of professors Eun Jong-hyun and Seol In-hwan (Materials Design Engineering) reported that fibers made under optimal conditions captured 98.6% of particles 2–4 µm in size in a filter test shinailbo.co.krshinailbo.co.krshinailbo.co.krOpen source ↗. The results were published online on October 24 in the Journal of Membrane Science shinailbo.co.krshinailbo.co.krshinailbo.co.krOpen source ↗.

Process conditions for silica nanofibers

Silica nanofibers resist heat and chemicals, so they are considered for high-temperature, corrosive environments where ordinary polymer filters are hard to use. The authors name hot exhaust gas filtration at steelworks, power plants and incinerators, and removal of fine particles in chemical processes, as possible uses shinailbo.co.krshinailbo.co.krshinailbo.co.krOpen source ↗. A stable fiber structure requires precise control of the ratio between the silica precursor TEOS and the polymer PVP shinailbo.co.krshinailbo.co.krshinailbo.co.krOpen source ↗.

The team varied TEOS concentration from 8 to 24 wt%, changed the amount of PVP and the aging time of the spinning solution, and analyzed how the fiber structure changed. Uniform nanofibers without structural defects formed at 18 wt% TEOS and 2.4 g PVP shinailbo.co.krshinailbo.co.krshinailbo.co.krOpen source ↗. The paper, titled "Balancing reaction kinetics and chain entanglement for structurally stable electrospun silica nanofibers in TEOS/PVP systems," describes control of reaction rate and polymer chain entanglement in electrospun fibers shinailbo.co.krshinailbo.co.krshinailbo.co.krOpen source ↗.

Heat treatment at 300 °C kept the fiber form and raised tensile strength from about 0.14 MPa to 0.30 MPa, an increase of 114.3% shinailbo.co.krshinailbo.co.krshinailbo.co.krOpen source ↗.

Shaping the mat into 3D filter forms

In a forming experiment, the team placed a nanofiber mat of the optimal composition between upper and lower molds made on a 3D printer and applied pressure. The mat took a three-dimensional shape without tearing or holes shinailbo.co.krshinailbo.co.krshinailbo.co.krOpen source ↗. According to the researchers, silica-based nanofibers have previously been difficult to shape, and the result points to filters made to fit equipment geometry, such as cylindrical cartridges shinailbo.co.krshinailbo.co.krshinailbo.co.krOpen source ↗.

The team also suggests possible use in industrial dust collection and in cleanroom and exhaust filters for semiconductor, display and secondary-battery production shinailbo.co.krshinailbo.co.krshinailbo.co.krOpen source ↗. These applications have not been demonstrated in the reported experiments.

Master's student Lee Seon-bin is the first author; Seol In-hwan and Eun Jong-hyun are co-corresponding authors shinailbo.co.krshinailbo.co.krshinailbo.co.krOpen source ↗. Eun said the work gives design guidelines for inorganic nanofibers for filters that require thermal stability, by finding a balance between reaction rate and chain entanglement shinailbo.co.krshinailbo.co.krshinailbo.co.krOpen source ↗.