Preparation of inorganic materials via electrospinning – a basic approach for novel materials

Vojtěch Kundrát^1, Zdeněk Moravec^1, Vít Vykoukal^1, Jiří Pinkas^1

^1 Department of Chemistry, Faculty of Science, Masaryk University, Brno, Czech Republic

The electrospinning [1] is a well-known laboratory method for producing fibers in a range of tens
of nanometers up to several micrometers thickness. Since the beginning of the 21^st-century
extensive research has been done in the field of nanofiber research. Many applicable nanofibrous
materials have been synthesized, described, and also industrially produced. Next to the broad
family of organic polymeric ultrathin fibers, various inorganic materials have been produced.
However, many exploitable and relatively basic compounds have not been produced in nanofibrous form
yet. The goal of the lecture is to present research techniques and major results of the preparation
of novel nanofibrous materials.

Uranium dioxide [2] is the most important form of uranium in nuclear industry today due to its
usage in the nuclear fuel pellets. Nanoscopic fuel forms, especially nanoparticles, are highly
desired materials in accident-tolerant fuel forms. We have enlarged the family of nanoscopic
uranium-based materials with the preparation of nanofibrous U[3]O[8 ]and UO[2]. Produced
polycrystalline UO[2] nanofibers have thickness of 91 ± 89 nm.

A similar situation as in the case of uranium oxides has been observed in the case of thorium
dioxide which has not been prepared in nanofibrous form. We have studied [3] two preparation
routes, the aqueous and organic solvent-based methods. Prepared polycrystalline nanofibers were in
the range of tens of nanometers in average diameter. The biggest surface area achieved in this work
was 52 m^2 g^-1. ThO[2 ]has potential in heterogeneous catalysis, refractory materials, and the
nuclear power industry.

Despite the fact, that tungsten metal is highly wanted material and its nanoscopic forms
(nanoparticles, single-crystalline nanowires) are well described [4], the preparation of
polycrystalline tungsten nanofibers has been performed only via low-scale methods. For the first
time, we are describing the multigram preparation of silica-doped tungsten nanofibers prepared by
needle-less electrospinning.

Tungsten disulfide is a deeply studied material with a broad application field [5]. We used an
aqueous solution of silicotungstic acid (H[4]SiW[12]O[40])[ ]and polyvinyl alcohol (PVA) as
precursors for the synthesis of composite fibers by the needle-less electrospinning technique. The
obtained green fibers (av. diam. 460 nm) were converted by calcination in air to tungsten oxide
WO[3] fibers with traces of SiO[2] and a smaller diameter (335 nm). The heat treatment of the WO[3]
fibers under flowing H[2]/H[2]S/N[2] stream led to conversion to tungsten sulfide WS[2] with
retention of fibrous morphology (av. diam. 460 nm).


References:

[1] A. Greiner, J.H. Wendorff, Electrospinning: A Fascinating Method for the Preparation of
Ultrathin Fibers, Angewandte Chemie International Edition. 46 (2007) 5670–5703.
doi:10.1002/anie.200604646.

[2] Kundrat, V.; Moravec, Z.; Pinkas, J. Preparation of Thorium Dioxide Nanofibers by
Electrospinning. Journal of Nuclear Materials 2020, 152153.
https://doi.org/10.1016/j.jnucmat.2020.152153.

[3] Kundrat, V.; Moravec, Z.; Pinkas, J. Preparation of Thorium Dioxide Nanofibers by
Electrospinning. Journal of Nuclear Materials 2020, 534, 152153.
https://doi.org/10.1016/j.jnucmat.2020.152153.

[4] You, G. F.; Thong, J. T. L. Thermal Oxidation of Polycrystalline Tungsten Nanowire. Journal of
Applied Physics 2010, 108 (9), 094312. https://doi.org/10.1063/1.3504248.

[5] Feldman, Y., Frey, G.L., Homyonfer, M., Lyakhovitskaya, V., Margulis, L., Cohen, H., Hodes, G.,
Hutchison, J.L., Tenne, R., 1996. Bulk Synthesis of Inorganic Fullerene-Like MS[2] (M=Mo, W) from
the Respective Trioxides and the Reaction Mechanism. Journal of the American Chemical Society 118,
5362–5367. https://doi.org/10.1021/ja9602408