*3.3. Fullerene and Intercalation*

*3.3. Fullerene and Intercalation* A series of nanostructures were formed on the amorphous carbon nanofilm of the specimen mesh, which was suspended on a Cu grid. Electron irradiation induced the formation of an onion-like fullerene nanostructure under the Al nanoparticles by the A series of nanostructures were formed on the amorphous carbon nanofilm of the specimen mesh, which was suspended on a Cu grid. Electron irradiation induced the formation of an onion-like fullerene nanostructure under the Al nanoparticles by the catalysis effect and promoted the intercalation of Al atoms between the graphite shells.

#### catalysis effect and promoted the intercalation of Al atoms between the graphite shells. 3.3.1. Onion-Like Fullerene

and 12 [5,10].

3.3.1. Onion-Like Fullerene Giant onion-like fullerenes were induced from the amorphous carbon nanofilms under the Al nanodecahedra by electron beam irradiation, as shown in Figure 10. A catalytic reaction nucleated a graphitic flake along the edge of the Al nanoparticle, and Giant onion-like fullerenes were induced from the amorphous carbon nanofilms under the Al nanodecahedra by electron beam irradiation, as shown in Figure 10. A catalytic reaction nucleated a graphitic flake along the edge of the Al nanoparticle, and prolonged electron irradiation induced the growth of the fullerene, shrinking of the nanoparticles, and intercalation of Al atoms between the shells, as shown in Figures 11 and 12 [5,10].

prolonged electron irradiation induced the growth of the fullerene, shrinking of the nanoparticles, and intercalation of Al atoms between the shells, as shown in Figures 11 shells [10].

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**Figure 10.** Giant onion-like fullerenes induced under Al nanoparticles by electron irradiation at an intensity of 3.0 × 1019 e/cm2s for 2050 s. The Al nanoparticles are surrounded by onion-like fullerene shells [10]. **Figure 10.** Giant onion-like fullerenes induced under Al nanoparticles by electron irradiation at an intensity of 3.0 <sup>×</sup> <sup>10</sup><sup>19</sup> e/cm<sup>2</sup> s for 2050 s. The Al nanoparticles are surrounded by onion-like fullerene shells [10]. intensity of 3.0 × 1019 e/cm2s for 2050 s. The Al nanoparticles are surrounded by onion-like fullerene **Figure 10.** Giant onion-like fullerenes induced under Al nanoparticles by electron irradiation at an

**Figure 11.** Series of reactions between Al nanoparticles and the amorphous carbon nanofilm (used

Reactions proceed from the catalytic formation of (**a**) a graphitic shell and (**b**) an onion-like

fullerene under the Al nanoparticle, followed by (**c**) shrinking of the nanoparticle and (**d**) intercalation of Al atoms inside the shell [10]. **Figure 11.** Series of reactions between Al nanoparticles and the amorphous carbon nanofilm (used as a specimen holder for TEM) induced by electron irradiation with an intensity of 1020 e/cm2sec. Reactions proceed from the catalytic formation of (**a**) a graphitic shell and (**b**) an onion-like **Figure 11.** Series of reactions between Al nanoparticles and the amorphous carbon nanofilm (used as a specimen holder for TEM) induced by electron irradiation with an intensity of 10<sup>20</sup> e/cm<sup>2</sup> s. Reactions proceed from the catalytic formation of (**a**) a graphitic shell and (**b**) an onion-like fullerene under the Al nanoparticle, followed by (**c**) shrinking of the nanoparticle and (**d**) intercalation of Al atoms inside the shell [10]. as a specimen holder for TEM) induced by electron irradiation with an intensity of 1020 e/cm2sec. Reactions proceed from the catalytic formation of (**a**) a graphitic shell and (**b**) an onion-like fullerene under the Al nanoparticle, followed by (**c**) shrinking of the nanoparticle and (**d**) intercalation of Al atoms inside the shell [10].

fullerene under the Al nanoparticle, followed by (**c**) shrinking of the nanoparticle and (**d**)

nucleus of the giant onion-like fullerene was first induced under the Al particles (**b**). Al nanoparticles were encapsulated in the giant onion-like fullerene (**c**,**d**). Al nanoparticles moved outside of the giant onion-like fullerene (**e**), which also induced a new giant onion-like fullerene (**f**). **Figure 12.** Schematic of a series of interaction behaviours between an Al nanoparticle and an amorphous carbon film under electron irradiation (**a**:initial). The following steps occurred: a nucleus of the giant onion-like fullerene was first induced under the Al particles (**b**). Al nanoparticles were encapsulated in the giant onion-like fullerene (**c**,**d**). Al nanoparticles moved outside of the giant onion-like fullerene (**e**), which also induced a new giant onion-like fullerene (**f**). **Figure 12.** Schematic of a series of interaction behaviours between an Al nanoparticle and an amorphous carbon film under electron irradiation (**a**:initial). The following steps occurred: a nucleus of the giant onion-like fullerene was first induced under the Al particles (**b**). Al nanoparticles were encapsulated in the giant onion-like fullerene (**c**,**d**). Al nanoparticles moved outside of the giant onion-like fullerene (**e**), which also induced a new giant onion-like fullerene (**f**). Finally, intercalation progressed as Al atoms migrated inside the giant onion-like fullerene shells (**e**,**f**) [10].

**Figure 12.** Schematic of a series of interaction behaviours between an Al nanoparticle and an amorphous carbon film under electron irradiation (**a**:initial). The following steps occurred: a nucleus of the giant onion-like fullerene was first induced under the Al particles (**b**). Al nanoparticles were encapsulated in the giant onion-like fullerene (**c**,**d**). Al nanoparticles moved outside of the giant onion-like fullerene (**e**), which also induced a new giant onion-like fullerene (**f**).

#### 3.3.2. Intercalation 3.3.2. Intercalation conducted on the electron irradiated specimen. Figure 13 shows the presence of Al atoms

3.3.2. Intercalation

(**e**,**f**) [10].

(**e**,**f**) [10].

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To verify Al atom intercalation into the graphitic shells, an analysis using energy dispersive spectroscopy (EDS), for which the JEM-2010 TEM was equipped, was conducted on the electron irradiated specimen. Figure 13 shows the presence of Al atoms in the circled area of 7 nm in diameter, accompanied by C and Cu in the grid. Moreover, the expansion of the graphite (002) lattice spacing confirmed the presence of Al atoms between the layers, as shown in Figure 14. However, the growth saturated below the composition of Al2C<sup>6</sup> owing to the blocking effect of the coexisting Cu atoms or the constraint of passing through multiple carbon layers. Electron energy loss spectra (EELS) also suggested the partial replacement of carbon atoms by Al or Cu atoms through σ bond, sp<sup>2</sup> , decrease, as shown in Figure 15 [10–12]. To verify Al atom intercalation into the graphitic shells, an analysis using energy dispersive spectroscopy (EDS), for which the JEM-2010 TEM was equipped, was conducted on the electron irradiated specimen. Figure 13 shows the presence of Al atoms in the circled area of 7 nm in diameter, accompanied by C and Cu in the grid. Moreover, the expansion of the graphite (002) lattice spacing confirmed the presence of Al atoms between the layers, as shown in Figure 14. However, the growth saturated below the composition of Al2C6 owing to the blocking effect of the coexisting Cu atoms or the constraint of passing through multiple carbon layers. Electron energy loss spectra (EELS) also suggested the partial replacement of carbon atoms by Al or Cu atoms through bond, sp2,decrease, as shown in Figure 15 [10–12]. in the circled area of 7 nm in diameter, accompanied by C and Cu in the grid. Moreover, the expansion of the graphite (002) lattice spacing confirmed the presence of Al atoms between the layers, as shown in Figure 14. However, the growth saturated below the composition of Al2C6 owing to the blocking effect of the coexisting Cu atoms or the constraint of passing through multiple carbon layers. Electron energy loss spectra (EELS) also suggested the partial replacement of carbon atoms by Al or Cu atoms through bond, sp2,decrease, as shown in Figure 15 [10–12].

Finally, intercalation progressed as Al atoms migrated inside the giant onion-like fullerene shells

To verify Al atom intercalation into the graphitic shells, an analysis using energy dispersive spectroscopy (EDS), for which the JEM-2010 TEM was equipped, was

Finally, intercalation progressed as Al atoms migrated inside the giant onion-like fullerene shells

**Figure 13.** EDS analysis of the area inside the dotted circle in the nanostructure shown in Figure 11. The electron probe size was 7 nm in diameter. An Al peak was detected, indicating the possibility of intercalation, whereas the Cu peaks came from the Cu grid of the membrane [10]. **Figure 13.** EDS analysis of the area inside the dotted circle in the nanostructure shown in Figure 11. The electron probe size was 7 nm in diameter. An Al peak was detected, indicating the possibility of intercalation, whereas the Cu peaks came from the Cu grid of the membrane [10]. **Figure 13.** EDS analysis of the area inside the dotted circle in the nanostructure shown in Figure 11. The electron probe size was 7 nm in diameter. An Al peak was detected, indicating the possibility of intercalation, whereas the Cu peaks came from the Cu grid of the membrane [10].

**Figure 14.** Expansion of the onion-like graphite lattice spacing d(002)G due to Al intercalation, under

electron beam irradiation of 1.0 × 1020 e/cm2sec. The spacing increased with electron irradiation time and seemed to saturate at 0.425 nm, which coincides with the spacing of the compound Al2C6. The **Figure 14.** Expansion of the onion-like graphite lattice spacing d(002)G due to Al intercalation, under electron beam irradiation of 1.0 × 1020 e/cm2sec. The spacing increased with electron irradiation time and seemed to saturate at 0.425 nm, which coincides with the spacing of the compound Al2C6. The **Figure 14.** Expansion of the onion-like graphite lattice spacing d(002)G due to Al intercalation, under electron beam irradiation of 1.0 <sup>×</sup> <sup>10</sup><sup>20</sup> e/cm<sup>2</sup> s. The spacing increased with electron irradiation time and seemed to saturate at 0.425 nm, which coincides with the spacing of the compound Al2C<sup>6</sup> . The limit of lattice expansion stems either from the blocking effect due to the coexistence of Cu atoms or is constrained by multiple carbon layers [11].

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is constrained by multiple carbon layers [11].

**Figure 15.** Second derivative of the EELS of the intercalated structure formed under electron irradiation of 1.0 × 1021 e/cm2s for 1900 s. No change is observed in the -bond between layers after irradiation, whereas the -bond, sp2 in-plane, decreased, which suggests the Al and Cu intercalated **Figure 15.** Second derivative of the EELS of the intercalated structure formed under electron irradiation of 1.0 <sup>×</sup> <sup>10</sup><sup>21</sup> e/cm<sup>2</sup> s for 1900 s. No change is observed in the π-bond between layers after irradiation, whereas the σ-bond, sp<sup>2</sup> in-plane, decreased, which suggests the Al and Cu intercalated atoms partially replaced the carbon atoms [12].

#### atoms partially replaced the carbon atoms [12]. **4. Al2O<sup>3</sup> Derivatives**

**4. Al2O3 Derivatives** Continuous electron irradiation of metastable θ-Al2O3 at 2.1 × 1020 e/cm2s produced Al nanoparticles and stable α-Al2O3 particles, as shown in Figure 2. When the intensity and area of electron irradiation changed abruptly (i.e., flashing of the beam), Continuous electron irradiation of metastable <sup>θ</sup>-Al2O<sup>3</sup> at 2.1 <sup>×</sup> <sup>10</sup><sup>20</sup> e/cm<sup>2</sup> s produced Al nanoparticles and stable α-Al2O<sup>3</sup> particles, as shown in Figure 2. When the intensity and area of electron irradiation changed abruptly (i.e., flashing of the beam), other-shaped nanosized aluminium oxides were obtained. In this section, I present the oxide derivatives of Al2O<sup>3</sup> oxides with different shapes and phases.

#### other-shaped nanosized aluminium oxides were obtained. In this section, I present the *4.1. α-Al2O<sup>3</sup> Nanorods*

oxide derivatives of Al2O3 oxides with different shapes and phases. *4.1. α-Al2O3 Nanorods* Although α-Al2O3 with a polygonal shape was deposited beside θ-Al2O3 by the recombination of Al and O atoms, the α-Al2O3 nanorods shown in Figure 16 grew from Although α-Al2O<sup>3</sup> with a polygonal shape was deposited beside θ-Al2O<sup>3</sup> by the recombination of Al and O atoms, the α-Al2O<sup>3</sup> nanorods shown in Figure 16 grew from the surface of the parent α-Al2O3. The rods had a faceted structure surrounded by {100} surfaces and grew in the {110} direction. Figure 16 was obtained in situ, in which the nanorods grew without an amorphous oxide film.

#### the surface of the parent α-Al2O3. The rods had a faceted structure surrounded by {100} *4.2. δ-, θ-Al2O<sup>3</sup> Nanoballs/Nanowires*

surfaces and grew in the [110] direction. Figure 16 was obtained in situ, in which the nanorods grew without an amorphous oxide film. When metastable Al2O<sup>3</sup> was irradiated by electrons with a higher density over a short time, the structure was retained, but a different nanostructure was also obtained. Kameyama and Tanaka abruptly switched between intensities of 5.5 <sup>×</sup> <sup>10</sup><sup>22</sup> and <sup>5</sup> <sup>×</sup> <sup>10</sup><sup>19</sup> e/cm<sup>2</sup> s in a so-called "flashing mode," maintaining each state for 0.1 s, which facilitated the formation of θ-, δ-Al2O<sup>3</sup> nanorods/nanoballs, as shown in Figure 17, respectively [13].

> Both θ-Al2O<sup>3</sup> nanowires and nanoballs grown using flashing-mode electron beam irradiation are shown in Figure 17. They connected and grew toward the irradiation centre from the original θ-Al2O<sup>3</sup> particle surface. The nanowire and nanoball had a (111)//(101) epitaxial relationship, as shown in Figure 18. The θ-Al2O<sup>3</sup> nanoball was a sphere of 30 nm in diameter covered with an amorphous Al-O layer, suggesting that the impact of a higher irradiance electron beam resulted in a temperature rise of approximately 400 ◦C, reaction, and rapid cooling without phase transformation. The δ-Al2O<sup>3</sup> nanowires and nanoballs shown in Figure 19 were obtained by applying the same flashing electron beam to δ-Al2O<sup>3</sup> particles. The diameter of the δ-Al2O<sup>3</sup> particles was 20 nm, which was slightly smaller than that of the θ-Al2O<sup>3</sup> particles, and no explicit epitaxy relation was observed.

**Figure 16.** α-Al2O3 rods epitaxially grown from the θ-Al2O3 surface by electron beam irradiation at 2.1 × 1020 e/cm2sec, as shown in Figure 2. The rods grew in the [110] direction and were faceted by {100} surfaces [3]. **Figure 16.** α-Al2O<sup>3</sup> rods epitaxially grown from the θ-Al2O<sup>3</sup> surface by electron beam irradiation at 2.1 <sup>×</sup> <sup>10</sup><sup>20</sup> e/cm<sup>2</sup> s, as shown in Figure 2. The rods grew in the {110} direction and were faceted by {100} surfaces [3]. *Quantum Beam Sci.* **2021**, *5*, x FOR PEER REVIEW 12 of 21 *Quantum Beam Sci.* **2021**, *5*, x FOR PEER REVIEW 12 of 21


**Figure 18.** The interface of the -Al2O3 nanowire and nanoball, shown in Figure 17, exhibits a (111)//(101) epitaxial relationship. The nanoball is covered with an amorphous Al-O layer [14]. **Figure 18.** The interface of the -Al2O3 nanowire and nanoball, shown in Figure 17, exhibits a (111)//(101) epitaxial relationship. The nanoball is covered with an amorphous Al-O layer [14]. **Figure 18.** The interface of the θ-Al2O<sup>3</sup> nanowire and nanoball, shown in Figure 17, exhibits a (111)//(101) epitaxial relationship. The nanoball is covered with an amorphous Al-O layer [14].

**Figure 19.** -Al2O3 nanowire and nanoball grown under flashing mode electron beam irradiation with intensities switching between 5.5 × 1022 and 5 × 1019 e/cm2sec. They connected and grew toward the irradiation centre from the original -Al2O3 particle surface. (**a**) -Al2O3 particles before irradiation, with X indicating the irradiation centre. (**b**) -Al2O3 nanowire and nanoball grown after

**Figure 19.** -Al2O3 nanowire and nanoball grown under flashing mode electron beam irradiation with intensities switching between 5.5 × 1022 and 5 × 1019 e/cm2sec. They connected and grew toward the irradiation centre from the original -Al2O3 particle surface. (**a**) -Al2O3 particles before irradiation, with X indicating the irradiation centre. (**b**) -Al2O3 nanowire and nanoball grown after

electron beam irradiation [13].

electron beam irradiation [13].
