3.2.4.2 COMPAÑÍA MINERA VOLCAN (VOLCAAC1)
MINERAS CERRO VERDE 0.02% 2.20%
When studying doped nanomaterials it is extremely difficult to discriminate between real doping and nano-decoration. Therefore, it is very important to characterise the obtained product to investigate the presence of phase segregation, which would suggest a decoration rather than a real doping.
The XRD patterns of the synthesised materials are reported in figure 8.1 compared with pure TiO2(B).
Figure 8.1 Experimental XRD pattern of pure TiO2(B) nanotubes (in black); 2 % V-doped
TiO2(B) nanotubes (in red); 6 % V-doped TiO2(B) nanotubes (in green) and TiO2(B) calculated
pattern (in magenta).
10 20 30 40 50 60 70 In te ns ity (a .u .) 2(degrees)
TiO2(B) calculated pattern TiO2(B) nanotubes
TiO2(B) nanotubes V/Ti = 2% TiO2(B) nanotubes V/Ti = 6%
As can be seen, both V-doped samples exhibit the XRD pattern consistent with the TiO2(B) nanotubes pattern and also with the TiO2(B) calculated pattern and no
additional peaks are observed. However, in order to confirm the absence of a phase segregation, the XRD patterns for the individual samples were compared with those of an equivalent sample obtained via a mechanical mixture of TiO2(B) nanotubes and
vanadium (v) oxide. The relative XRD comparison is reported in figure 8.2 for the 2 % V-doped sample, and figure 8.3 for the 6 % V-doped sample together with the V2O5calculated pattern.
10 20 30 40 50 60 70 TiO2(B) nanotubes + 6 % Vanadium
mechanical mixture of TiO2(B) nts + 2% V2O5 V2O5calculated pattern In te ns ity (a .u .) 2(degrees)
Chapter 8. Vanadium doped TiO2(B) nanotubes
Figure 8.3 Experimental XRD pattern of 6 % V-doped TiO2(B) nanotubes (in green); 6 %
mechanical mixture of TiO2(B) nanotubes and V2O5(in blue) and V2O5calculated pattern (in cyan).
Once again, no traces of the V2O5 phase are observable in both the V-doped sample
patterns, whereas they are clearly recognisable in the mechanical mixtures, in particular in the 6 % mixture.
Further to this, the V-doped samples were also investigated using Raman spectroscopy. The Raman spectra are reported in figure 8.4 together with the pure TiO2(B) nanotubes
results.
10 20 30 40 50 60 70
TiO2(B) nanotubes + 6 % Vanadium
mechanical mixture of TiO2(B) nts + 6% V2O5 V2O5calculated pattern In te ns ity (a .u .) 2 (degrees)
Figure 8.4 Raman spectrum of pure TiO2(B) nanotubes (in black); 2 % V-doped TiO2(B)
nanotubes (in red) and 6 % V-doped TiO2(B) nanotubes (in green).
Good agreement is observed between all spectra; however a few differences can be noted for the V-doped samples. On increasing the V-doping level, a shift towards higher wavenumbers is observed for the main TiO2(B) peak at 146 cm-1, which is
found at 155 cm-1for the 6 % doped sample. Moreover, a broadening of the multiplet between 400-560 cm-1 is noted together with the appearance of a new peak at 1025 cm-1. The latter additional feature in the spectra is due to the presence of the isolated O-V-O bond stretching in the V-doped samples. The individual Raman
200 400 600 800 1000 1200 In te ns ity (a .u .) Wavenumber (cm-1) TiO2(B) nanotubes
TiO2(B) nanotubes + 2 % Vanadium TiO2(B) nanotubes + 6 % Vanadium
Chapter 8. Vanadium doped TiO2(B) nanotubes
Figure 8.5 Raman spectra of 2 % V-doped TiO2(B) nanotubes (in red) and 2 % mechanical
mixture of TiO2(B) nanotubes and V2O5(in orange).
Figure 8.6 Raman spectra of 6 % V-doped TiO2(B) nanotubes (in green) and 6 % mechanical
mixture of TiO2(B) nanotubes and V2O5(in blue).
200 400 600 800 1000 1200 In te ns ity (a .u .) Wavenumber (cm-1)
TiO2(B) nanotubes + 6 % Vanadium
mechanical mixture of TiO2(B) nts + 6% V2O5
200 400 600 800 1000 1200
TiO2(B) nanotubes + 6 % Vanadium
mechanical mixture of TiO2(B) nts + 2% V2O5
In te ns ity (a .u .) Wavenumber (cm-1)
In both cases, the Raman spectra of the V of the V2O
The analysis performed with two totally independent techniques, XRD and Raman spectroscopy, sugge
samples and that the successful doping of TiO achieved.
To further confirm the absence of any contamination, the morphology of the 6 doped sample was also
(FESEM). The images are reported in figure 8.7. both cases, the Raman spectra of the V
O5phase, which is clearly recognisable in the mechanical mixtures.
The analysis performed with two totally independent techniques, XRD and Raman spectroscopy, suggested the total absence of phase segregation if V
samples and that the successful doping of TiO
further confirm the absence of any contamination, the morphology of the 6 doped sample was also
. The images are reported in figure 8.7. both cases, the Raman spectra of the V
phase, which is clearly recognisable in the mechanical mixtures.
The analysis performed with two totally independent techniques, XRD and Raman sted the total absence of phase segregation if V
samples and that the successful doping of TiO
further confirm the absence of any contamination, the morphology of the 6 doped sample was also investigated
. The images are reported in figure 8.7. both cases, the Raman spectra of the V-
phase, which is clearly recognisable in the mechanical mixtures.
The analysis performed with two totally independent techniques, XRD and Raman sted the total absence of phase segregation if V
samples and that the successful doping of TiO
further confirm the absence of any contamination, the morphology of the 6 vestigated using field emission scanning electron microscope . The images are reported in figure 8.7.
-doped sample
phase, which is clearly recognisable in the mechanical mixtures.
The analysis performed with two totally independent techniques, XRD and Raman sted the total absence of phase segregation if V
samples and that the successful doping of TiO2(B) nanotubes with vanadium was
further confirm the absence of any contamination, the morphology of the 6 field emission scanning electron microscope . The images are reported in figure 8.7.
doped samples do not show the fingerprint phase, which is clearly recognisable in the mechanical mixtures.
The analysis performed with two totally independent techniques, XRD and Raman sted the total absence of phase segregation if V
(B) nanotubes with vanadium was
further confirm the absence of any contamination, the morphology of the 6 field emission scanning electron microscope
do not show the fingerprint phase, which is clearly recognisable in the mechanical mixtures.
The analysis performed with two totally independent techniques, XRD and Raman sted the total absence of phase segregation if V2O5 was
(B) nanotubes with vanadium was
further confirm the absence of any contamination, the morphology of the 6 field emission scanning electron microscope
do not show the fingerprint
The analysis performed with two totally independent techniques, XRD and Raman was in the (B) nanotubes with vanadium was
further confirm the absence of any contamination, the morphology of the 6 % V- field emission scanning electron microscope
Images collected
sample, consisting mainly of tubular nano Following this
(TEM). TEM images confirmed the sampl can be seen in figure 8.8.
Moreover,
are clearly visible
confirms the successful vanadium doping of the nanotubes. Images collected at
sample, consisting mainly of tubular nano Following this, the sample was also studied
TEM images confirmed the sampl can be seen in figure 8.8.
Figure
Moreover, as can be seen are clearly visible and
confirms the successful vanadium doping of the nanotubes.
at FESEM confirmed the high morphological homogeneity of the sample, consisting mainly of tubular nano
the sample was also studied TEM images confirmed the sampl can be seen in figure 8.8.
Figure 8. 8 TEM images
can be seen in the high resolution
and no decoration on the tubes surface is observ confirms the successful vanadium doping of the nanotubes.
Chapter 8. Vanadium doped TiO
FESEM confirmed the high morphological homogeneity of the sample, consisting mainly of tubular nano-particulates.
the sample was also studied
TEM images confirmed the sample constituted mainly of nanotubes and this
TEM images of 6 % V
in the high resolution
no decoration on the tubes surface is observ confirms the successful vanadium doping of the nanotubes.
Chapter 8. Vanadium doped TiO
FESEM confirmed the high morphological homogeneity of the particulates.
the sample was also studied in the transmission electron microscope e constituted mainly of nanotubes and this
% V-doped TiO
in the high resolution images
no decoration on the tubes surface is observ confirms the successful vanadium doping of the nanotubes.
Chapter 8. Vanadium doped TiO
FESEM confirmed the high morphological homogeneity of the particulates.
the transmission electron microscope e constituted mainly of nanotubes and this
TiO2(B) nanotubes.
images, the fringes no decoration on the tubes surface is observ confirms the successful vanadium doping of the nanotubes.
Chapter 8. Vanadium doped TiO2(B) nanotubes
FESEM confirmed the high morphological homogeneity of the
the transmission electron microscope e constituted mainly of nanotubes and this
nanotubes.
the fringes of the tube no decoration on the tubes surface is observable. This
(B) nanotubes
FESEM confirmed the high morphological homogeneity of the
the transmission electron microscope e constituted mainly of nanotubes and this
of the tube walls . This again