Manufacturing Technology 2025, 25(6):788-793 | DOI: 10.21062/mft.2025.079

Formation of TiO2 Hollow Nanoparticles Studied by in Situ TEM

Nikoleta Štaffenová ORCID..., Lucia Bajtošová ORCID..., Elena Chochoľaková ORCID..., Jan Hanuš ORCID..., Miroslav Cieslar ORCID...
Charles University, Faculty of Mathematics and Physics, Ke Karlovu 3, 12116 Prague, Czech Republic

Hollow TiO₂ architectures are attractive for catalysis and sensing but typically produced by wet-chemical templating and sub-micron sizes. Here we demonstrate a dry, template-free route to nanoscale hollow shells by combining DC magnetron sputtering with in situ TEM heating. Heating to 900 °C produces sub-50 nm TiO₂ hollow shells with ~20 nm compact walls via oxidation-driven Kirkendall hollowing. The oxide evolves from amorphous at low temperature to anatase locally (~500 °C) and then to a rutile/brookite mixture by ~600 °C. The hollow architecture withstands a temperature of 900 °C without measurable sintering. Beam-off regions and ex-situ air annealing show the same hollowing and phase evolution, confirming a thermally driven, not beam-induced, transformation reproducible in air.

Keywords: Hollow TiO₂, Rutile/brookite, Magnetron sputtering, in situ TEM, Kirkendall effect
Grants and funding:

We acknowledge the funding and support from the Czech Science Foundation, grant number 22-22572S.

Received: August 29, 2025; Revised: December 7, 2025; Accepted: December 10, 2025; Prepublished online: December 15, 2025; Published: December 23, 2025  Show citation

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Štaffenová N, Bajtošová L, Chochoľaková E, Hanuš J, Cieslar M. Formation of TiO2 Hollow Nanoparticles Studied by in Situ TEM. Manufacturing Technology. 2025;25(6):788-793. doi: 10.21062/mft.2025.079.
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