30
S. Gupta
kinetics of Ti 3 AlC 2 . In addition, they also reported this peak disappeared at 50 °C
after 2 h, or after 15 h etching treatment at RT, respectively. Ghidiu and co-workers
[102] reported that HF derived in the solution by the reaction of LiF and HCl can
etch and delaminate Ti 3 AlC 2 (this process is referred to as clay method) and form
colloidal solution of Ti 3 C 2 T x . Shahzad and co-workers [103] reported that in 6 M HCl
solution if LiF:Ti 3 AlC 2 molar ratio is increased to 7.5:1 unlike 5:1 in clay method,
then Ti 3 AlC 2 can be delaminated to Ti 3 C 2 T x without any sonication. Please note,
currently, MXenes are produced in colloidal state hence novel innovations are needed
to produce engineered particles in dry or powder state which can be further used for
producing composites. The main objective of this case study is to demonstrate the
feasibility of engineered Ti 3 AlC 2 particles by controlled etching process.
Figure 5 shows the microstructure of the Ti 3 AlC 2 particulates. Figure 6 shows the
XRD of the corresponding powder where Ti 3 AlC 2 was the major phase and minor
amount of Al 2 O 3 and TiC were observed. By comparing the two results, we can
conclude that the Ti 3 AlC 2 particles are predominantly single phase.
Table 1 summarizes the etching chemistry used to tailor the surfaces of Ti 3 AlC 2
particles. In this study, three different LiF:Ti 3 AlC 2 molar ratio were used, namely
0.075 (HTS4-35-3), 0.75 (HTS4-35-4), and 3.74 (HTS4-35-5) in 12 M HCl, respectively. The composition HTS4-35-3 showed mild etching (Fig. 7a, b), and the
sample retained similar stoichiometry of Ti 3 AlC 2 (Table 2). On further increasing
LiF:Ti 3 AlC 2 molar ratio to 0.75 (HTS4-35-4), the Ti:Al ratio increased to 7.74 (code
5, Fig. 7c, Table 2). In addition, some Al-rich regions were also observed (codes 3 and
4, Table 2). Figure 7d, e show the microstructures of the etched surfaces. In HTS435-5 where the LiF:Ti 3 AlC 2 molar ratio was 3.74, the Ti 3 AlC 2 layers unzipped to
form individual laminates at edges but 3D grain structure was visible (Fig. 8a). The
XRD data also showed (Fig. 6) that the composition still predominantly retained
Ti 3 AlC 2 lattice structure. Energy Dispersive Spectroscopy data (sample code 7,
Table 2) showed that some Al is retained in the crystal structure. Further studies
are needed whether sonification can separate these nanolaminates.
Fig. 5 Field Emission Scanning Electron Microscope (FESEM) micrographs of as synthesized,
a Ti 3 AlC 2 powder, and b Backscattered Electron (BSE) image of the same area
S. Gupta
kinetics of Ti 3 AlC 2 . In addition, they also reported this peak disappeared at 50 °C
after 2 h, or after 15 h etching treatment at RT, respectively. Ghidiu and co-workers
[102] reported that HF derived in the solution by the reaction of LiF and HCl can
etch and delaminate Ti 3 AlC 2 (this process is referred to as clay method) and form
colloidal solution of Ti 3 C 2 T x . Shahzad and co-workers [103] reported that in 6 M HCl
solution if LiF:Ti 3 AlC 2 molar ratio is increased to 7.5:1 unlike 5:1 in clay method,
then Ti 3 AlC 2 can be delaminated to Ti 3 C 2 T x without any sonication. Please note,
currently, MXenes are produced in colloidal state hence novel innovations are needed
to produce engineered particles in dry or powder state which can be further used for
producing composites. The main objective of this case study is to demonstrate the
feasibility of engineered Ti 3 AlC 2 particles by controlled etching process.
Figure 5 shows the microstructure of the Ti 3 AlC 2 particulates. Figure 6 shows the
XRD of the corresponding powder where Ti 3 AlC 2 was the major phase and minor
amount of Al 2 O 3 and TiC were observed. By comparing the two results, we can
conclude that the Ti 3 AlC 2 particles are predominantly single phase.
Table 1 summarizes the etching chemistry used to tailor the surfaces of Ti 3 AlC 2
particles. In this study, three different LiF:Ti 3 AlC 2 molar ratio were used, namely
0.075 (HTS4-35-3), 0.75 (HTS4-35-4), and 3.74 (HTS4-35-5) in 12 M HCl, respectively. The composition HTS4-35-3 showed mild etching (Fig. 7a, b), and the
sample retained similar stoichiometry of Ti 3 AlC 2 (Table 2). On further increasing
LiF:Ti 3 AlC 2 molar ratio to 0.75 (HTS4-35-4), the Ti:Al ratio increased to 7.74 (code
5, Fig. 7c, Table 2). In addition, some Al-rich regions were also observed (codes 3 and
4, Table 2). Figure 7d, e show the microstructures of the etched surfaces. In HTS435-5 where the LiF:Ti 3 AlC 2 molar ratio was 3.74, the Ti 3 AlC 2 layers unzipped to
form individual laminates at edges but 3D grain structure was visible (Fig. 8a). The
XRD data also showed (Fig. 6) that the composition still predominantly retained
Ti 3 AlC 2 lattice structure. Energy Dispersive Spectroscopy data (sample code 7,
Table 2) showed that some Al is retained in the crystal structure. Further studies
are needed whether sonification can separate these nanolaminates.
Fig. 5 Field Emission Scanning Electron Microscope (FESEM) micrographs of as synthesized,
a Ti 3 AlC 2 powder, and b Backscattered Electron (BSE) image of the same area