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Bismuth and antimony affected crystallization of the tubular titanate structures ... crystalline structure at different temperatures depending on the metal content.
Synthesis, structure and stability of pristine, Bi and/or Sb decorated titanate nanotubes Andrea

1 Rónavári ,

Balázs

3 Buchholcz ,

Ákos

1,2 Kukovecz ,

Zoltán

1,3 Kónya

1Department

of Applied and Environmental Chemistry, University of Szeged, Rerrich ter 1, H-6720 Szeged, Hungary 2MTA-SZTE “Lendület” Porous Nanocomposites Research Group, Rerrich ter 1, H-6720 Szeged, Hungary 3MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, Rerrich ter 1, H-6720 Szeged, Hungary

Introduction Over the recent decades, numerous studies have been published about nanoscaled materials because of their unique thermic, chemical and physical properties, and potential applications due to their size. One-dimensional (1D) titanate nanostructures have great interest in research because they are very promising materials for nanotechnology due to their unique chemical and mechanical properties [1, 2]. The properties and the applicability of these structures could be improved by different metal ion-exchange such as bismuth or antimony. In this study the synthesis and the characterization of bismuth and/or antimony decorated titanate nanostructures and their comparison were demonstrated. Bismuth and antimony affected crystallization of the tubular titanate structures during calcination was also investigated.

Methods

Results III.

Results II. Transmission electron microscopy

1. 90-100 nm long protonated titanate nanotubes were synthesized by hydrothermal method. TiO2

As synthesized

600 °C

Raman spectroscopy

In the case of bismuth the phase transformation from trititanate to rutile via anatase occurred at lower temperature than in the case of pristine, antimony and antimony–bismuth containing samples.

The spectrum of the pristine nanotubes and the other spectra as well show bands, which are corresponding to a trititanate phase.

900 °C TiONT

10 M NaOH

anatase

X-ray diffraction

TiONT TiONT

24 h 155 oC

Bi 2. Bismuth and/or antimony decorated titanate nanotubes were synthesized by ion exchange technique followed by heat treatment. TiONT + d.H2O

Bi

BiOAc and/or SbOAc

24 h

Heat treatment 600 °C 750 °C 900 °C

Sb

Sb

3. The samples were characterized by transmission electron microscopy, energy dispersive spectroscopy, X-ray diffraction and Raman spectroscopy.

Bi/Sb Bi/Sb

Results I. Energy dispersive spectroscopy The initial tubular structure was damaged and the nanotubes were transformed into rodlike nanostructures at 600 °C. In the presence of antimony the tubular structure of the titanate nanotubes was protected. The structure of the bismuth containing samples totally collapsed and homogenously dispersed 10–20 nm sized crystalline nanoparticles were formed on the surface of titanate nanostructures. Energy dispersive spectroscopy show that the samples contain Ti, O, Sb, Bi and are free from other elements.

References 1. Milanovic´M., Stijepovic´I, Nikolic´L.M..// Process. Appl. Ceram.-2010.-4 [2], p. 69-73. 2. Li N., Zhang L.,Chen Y., Fang M., Zhang J., Wang H.// Adv. Funct. Mat. -2012.-22, p. 835–841.

The structure of all the samples collapsed entirely and TiO2 nanoparticles were formed at 900 °C.

By bismuth containing sample only rutile phase can be seen on the XRD pattern at 900 °C in contrast to the pristine and antimony containing samples which have a mix phase of rutile and anatase at this temperature.

The Raman spectra of antimony and the antimony-bismuth modified titanate nanotube composites are similar to those of the pristine samples. The bismuth containing nanotube spectra differs from the other ones. The sample which was treated at 900 °C resembles the spectrum of rutile.

Conclusion Protonated titanate nanotubes were synthesized by hydrothermal method at 155 °C and used for ion exchange experiments. The titanate nanotubes were ion exchanged with antimony, bismuth and antimony–bismuth and then all samples were calcined at different temperatures. We have shown that the applied metal ions have a strong influence on this recrystallization process; the samples started to collapse and change their crystalline structure at different temperatures depending on the metal content. While antimony protects the initial tubular structure up to 600 °C and hinders the phase transformation from trititanate to rutile, the presence of bismuth in the titanate sample promotes the structural transformation to rutile.

Correspondence: Andrea Rónavári E-mail: [email protected]

International research and practice conference NANOTECHNOLOGY and NANOMATERIALS August 29 -September 1, 2013, Bukovel, Ukraine

Acknowledgement: Support by TÁMOP-4.2.2.A-11/1/KONV-20120047 is gratefully acknowledged.