Growth of 1D TiO2nanostructures on Ti substrates incorporated with residual stress through humid oxidation and their characterizations

M M Arafat; B Dinan; A S M A Haseeb; S A Akbar; B M A Rahman; S Rozali; S Naher

doi:10.1088/1361-6528/ac1d77

Growth of 1D TiO₂nanostructures on Ti substrates incorporated with residual stress through humid oxidation and their characterizations

Nanotechnology. 2021 Sep 1;32(47). doi: 10.1088/1361-6528/ac1d77.

Authors

M M Arafat¹, B Dinan², A S M A Haseeb³, S A Akbar², B M A Rahman⁴, S Rozali³, S Naher¹

Affiliations

¹ Department of Mechanical Engineering and Aeronautics, School of Mathematics, Computer Science and Engineering, City, University of London, Northampton Square, London EC1V 0HB, United Kingdom.
² Department of Materials Science and Engineering, Ohio State University, 2041 College Road, Columbus, OH 43210, United States of America.
³ Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia.
⁴ Department of Electrical and Electronic Engineering, School of Mathematics, Computer Science and Engineering, City, University of London, Northampton Square, London EC1V 0HB, United Kingdom.

PMID: 34388742
DOI: 10.1088/1361-6528/ac1d77

Abstract

Different Ti substrates, such as particles (as-received and ball milled), plate and TEM grid were oxidized for the growth of one dimensional (1D) TiO₂nanostructures. The Ti substrates were oxidized for 4 h at temperatures of 700 °C-750 °C in humid and dry Ar containing 5 ppm of O₂. The effects of residual stress on the growth of 1D TiO₂nanostructures were investigated. The residual stress inside the Ti particles was measured by XRD-sin²ψtechnique. The oxidized Ti substrates were characterized using field emission scanning electron microscope equipped with energy dispersive x-ray spectroscope, transmission electron microscope, x-ray diffractometer and x-ray photoelectron spectroscope. Results revealed that humid environment enhances the growth of 1D TiO₂nanostructures. Four different types of 1D morphologies obtained during humid oxidation, e.g. stacked, ribbon, plateau and lamp-post shaped nanostructures. The presence of residual stress significantly enhances the density and coverage of 1D nanostructures. The as-grown TiO₂nanostructures possess tetragonal rutile structure having length up to 10μm along the 〈1 0 1〉 directions. During initial stage of oxidation, a TiO₂layer is formed on Ti substrate. Lower valence oxides (Ti₃O₅, Ti₂O₃and TiO) then form underneath the TiO₂layer and induce stress at the interface of oxide layers. The induced stress plays significant role on the growth of 1D TiO₂nanostructures. The induced stress is relaxed by creating new surfaces in the form of 1D TiO₂nanostructures. A diffusion based model is proposed to explain the mechanism of 1D TiO₂growth during humid oxidation of Ti. The 1D TiO₂nanostructures and TiO₂layer is formed by the interstitial diffusion of Ti⁴⁺ions to the surface and reacts with the surface adsorbed hydroxide ions (OH^-). Lower valence oxides are formed at the metal-oxide interface by the reaction between diffused oxygen ions and Ti ions.

Keywords: 1D nanostructures; Ti substrates; TiO2 nanostructures; humid oxidation; rutile; thermal oxidation.