1 3
Topics in Current Chemistry (2020) 378:2
cases a drawback, and for this reason, the ball milling is performed with breaks or
even with the use of a liquid phase. The latter case is referred to as wet ball milling.
In most reported cases and especially towards the formation of one dimensional TiO 2
nanostructures, ball milling was utilized as a mechanochemical pretreatment to obtain
metastable polymorphs, that can be further tuned in morphology by annealing or wet
chemistry. In this part, we collected some reports in which the application of ball milling dramatically affected the final properties of the nanomaterials. Starting with 0-D
nanomaterials and ending with 1-D materials, we tried to introduce the reported results
following a chronological order. An emphasis was given when the nanomaterials were
found to possess an elevated photocatalytic capability.
3.2 0‑D Ball‑Milling‑Derived Nanostructures
In 1994, Begin-Colin et al. studied the polymorphic transformation of TiO 2 from
an anatase phase to a rutile phase by ball-milling (BM), based on XRD and Fourier transform infrared (FTIR ) spectroscopy techniques [119]. They observed that
the phase transformation was not direct, since different transient phases appeared,
with the one of type II being predominant. However, no electron microscopy
analysis was performed. The importance of this study was the conclusion that the
anatase-to-rutile transformation is not a direct process. Based on that, the authors
emphasized that the ball-milling technique is feasible to obtain alloys with various non-equilibrium crystallographic phase materials. The intermediate crystallographic phases can further be tuned with various methods, in order to obtain
desired photocatalytic properties.
An ultimately serious drawback of the ball-milling technique, especially when
the target is a material of a high purity, is the possibility of atmospheric nitrogen
incorporation into the structure or metal (predominately iron) from the used ballmilling apparatus. For instance, it was showed by Lu et al. [120] that, depending the atmosphere and the duration of the ball milling, different doping of N
or Fe could result, even under air. More interesting, titanium oxynitrile instead
of oxide can be obtained within a closed ball-milling system and extension of
the mechanochemical process for up to 90 h. In 2007, Pang et al. [121] showed
the possibility to synthesize a composite of titanium and hydroxyapatite by a wet
ball-milling method. Hydroxyapatite (HP), Ca 5 (PO 4 ) 3 (OH), is a natural mineral,
Fig. 17 BET specific surface
area and morphology/shape of
titanate products synthesized
(from raw TiO 2 of an avg. size
of 400 nm) at reaction temperature of a 90 °C, b 120 °C,
c 150 °C, and d 180 °C without
or with US irradiation (power of
7.6 W). Reprinted with permission from [117]. Copyright
(2009) Elsevier
55
Reprinted from the journal
Topics in Current Chemistry (2020) 378:2
cases a drawback, and for this reason, the ball milling is performed with breaks or
even with the use of a liquid phase. The latter case is referred to as wet ball milling.
In most reported cases and especially towards the formation of one dimensional TiO 2
nanostructures, ball milling was utilized as a mechanochemical pretreatment to obtain
metastable polymorphs, that can be further tuned in morphology by annealing or wet
chemistry. In this part, we collected some reports in which the application of ball milling dramatically affected the final properties of the nanomaterials. Starting with 0-D
nanomaterials and ending with 1-D materials, we tried to introduce the reported results
following a chronological order. An emphasis was given when the nanomaterials were
found to possess an elevated photocatalytic capability.
3.2 0‑D Ball‑Milling‑Derived Nanostructures
In 1994, Begin-Colin et al. studied the polymorphic transformation of TiO 2 from
an anatase phase to a rutile phase by ball-milling (BM), based on XRD and Fourier transform infrared (FTIR ) spectroscopy techniques [119]. They observed that
the phase transformation was not direct, since different transient phases appeared,
with the one of type II being predominant. However, no electron microscopy
analysis was performed. The importance of this study was the conclusion that the
anatase-to-rutile transformation is not a direct process. Based on that, the authors
emphasized that the ball-milling technique is feasible to obtain alloys with various non-equilibrium crystallographic phase materials. The intermediate crystallographic phases can further be tuned with various methods, in order to obtain
desired photocatalytic properties.
An ultimately serious drawback of the ball-milling technique, especially when
the target is a material of a high purity, is the possibility of atmospheric nitrogen
incorporation into the structure or metal (predominately iron) from the used ballmilling apparatus. For instance, it was showed by Lu et al. [120] that, depending the atmosphere and the duration of the ball milling, different doping of N
or Fe could result, even under air. More interesting, titanium oxynitrile instead
of oxide can be obtained within a closed ball-milling system and extension of
the mechanochemical process for up to 90 h. In 2007, Pang et al. [121] showed
the possibility to synthesize a composite of titanium and hydroxyapatite by a wet
ball-milling method. Hydroxyapatite (HP), Ca 5 (PO 4 ) 3 (OH), is a natural mineral,
Fig. 17 BET specific surface
area and morphology/shape of
titanate products synthesized
(from raw TiO 2 of an avg. size
of 400 nm) at reaction temperature of a 90 °C, b 120 °C,
c 150 °C, and d 180 °C without
or with US irradiation (power of
7.6 W). Reprinted with permission from [117]. Copyright
(2009) Elsevier
55
Reprinted from the journal