abstract

• Nano-sized titania (anatase) and sodium and potassium titanate nanotubes were studied via in situ Raman spectroscopy at hydrostatic pressures up to 6 GPa. Analysis by scanning electron microscopy shows a uniform dispersion of sodium and potassium cations in the nanotubes. The effect of the pressure was observed by significant shifts in the Raman band structure of nano-sized anatase crystals and nanotube titanate. In nano-particulate anatase, the phonon frequencies (143, 395, 517, and 639 cm−1) increase linearly with pressure. In contrast, the upward frequency shifts in the sodium titanate nanotubes (NaTNT) and potassium-modified nanotubes (NaTNT K) occur in a stepwise fashion. These stepwise changes occur in the nanotube samples between 2 and 4 GPa (ambient pressure phonon bands in NaTNT at 274, 444, 650, and 906 cm−1) and between 4.5 and 5.5 GPa, (phonons 273 cm−1 and 436 cm−1 in NaTNT K at an ambient pressure). Post-pressure high-resolution transmission electron microscopy analysis shows evidence of nanotube distortions and a 5%25 contraction in the interlaminar spacing of both NaTNT and NaTNT K. © 2017 Author(s).
• Nano-sized titania (anatase) and sodium and potassium titanate nanotubes were studied via in situ Raman spectroscopy at hydrostatic pressures up to 6 GPa. Analysis by scanning electron microscopy shows a uniform dispersion of sodium and potassium cations in the nanotubes. The effect of the pressure was observed by significant shifts in the Raman band structure of nano-sized anatase crystals and nanotube titanate. In nano-particulate anatase, the phonon frequencies (143, 395, 517, and 639 cm−1) increase linearly with pressure. In contrast, the upward frequency shifts in the sodium titanate nanotubes (NaTNT) and potassium-modified nanotubes (NaTNT%2bK) occur in a stepwise fashion. These stepwise changes occur in the nanotube samples between 2 and 4 GPa (ambient pressure phonon bands in NaTNT at 274, 444, 650, and 906 cm−1) and between 4.5 and 5.5 GPa, (phonons 273 cm−1 and 436 cm−1 in NaTNT%2bK at an ambient pressure). Post-pressure high-resolution transmission electron microscopy analysis shows evidence of nanotube distortions and a 5%25 contraction in the interlaminar spacing of both NaTNT and NaTNT%2bK. © 2017 Author(s).

authors

• Handy Vogel Brent Edward
• José-Yacamán M.
• Mendoza-Cruz R.
• Ojeda-Galván H.J.
• Rodríguez Vázquez Ángel Gabriel
• Santos-Lõpez I.A.

publication date

• 2017-01-01

funding provided via

• Consejo Nacional de Ciencia y Tecnología, CONACYT: 237099, 241045, 388337/360229, CB2014  Grant
• National Center for Research Resources, NCRR: G12RR013646-12  Grant
• National Institute on Minority Health and Health Disparities, NIMHD: G12MD007591  Grant
• National Institutes of Health, NIH  Grant
• Universidad Autónoma de San Luis Potosí, UASLP  Grant

published in

• Journal of Applied Physics  Journal

keywords

• Crystal structure; Electron microscopy; Hydrostatic pressure; Nanotubes; Phonons; Scanning electron microscopy; Titanium compounds; Titanium dioxide; Yarn; Deformation behavior; In-situ Raman spectroscopy; Nano particulates; Phonon frequencies; Potassium titanates; Sodium titanate nanotube; Titanate nanotubes; Uniform dispersions; High resolution transmission electron microscopy

Digital Object Identifier (DOI)

• 10.1063/1.4973735

start page

end page

volume

• 121

issue

• 2