**2.3 Kikuchi patterns**

*Electron Crystallography*

field of nanotechnology research.

**2. Transmission electron microscope**

**2.1 Preferred orientation and texture**

**2.2 Dislocation**

The methods for indexing simple, complicated and imperfect patterns as well as Kikuchi lines and a combination of Kikuchi lines and spots are determined.

In this research, samples of materials such as nanoparticles, nanotubes, bulk metallic, graphene, graphene oxide, and polymer nanocomposites are investigated using an EM208S (PHILIPS) transmission electron microscopy operating at an accelerating voltage of 100 kV and a digital camera. In addition, electron diffraction pattern of several materials are expounded and structure of materials is predicted with electron diffraction pattern results interpretation. On the other hand, TEM/ STEM (STEM, JEOL JEM-2100F) equipped with an energy-dispersive X-ray spectrometry (EDS) and the operating voltage of 200 kV are used to evaluate the in-situ phase characterization, microstructural observation, dislocation pile-up and chemical composition of in-situ nanocomposite fabricated by planetary ball milling of Al/BN composite powders and hot extrusion. This paper discusses the basic principle and applications of the transmission electron microscope (TEM) in the

In some samples, the preferred orientation of planes creates by several mechanical processes such as accumulative roll bonding (ARB), cyclic extrusion compression (CEC) and equal channel angular pressing (ECAP) processes, etc. TEM image and SAED pattern of nanostructured Al 2024 alloy under ECAP process were demonstrated in **Figure 1(a)** and **(b)**, respectively. The SAED pattern of preferred orientation and textured nanostructured materials was formed from many partial rings or incomplete rings. Diffraction pattern of such materials can be described as an intermediate sample between a single and polycrystalline material. The texture produced in materials can be studied by the interpretation of their SAED. The preferred orientation {110} [001] was formed in Al 2024 alloy by this process [3].

ECAP [3] and cryo-cross-rolling (CCR) process [4, 5] were carried out on Al 5083 and Al 1050 alloys, respectively. These two processes form a matrix with highly dislocation density, which changes the diffraction pattern. Besides, SAED patterns

*(a) TEM image and (b) SAED of Al 2024 alloy under ECAP process [3].*

**10**

**Figure 1.**

Kikuchi pattern consists of spots and paired parallel dark and bright lines. The spacing between a paired parallel dark and bright-line and the angle between Kikuchi lines in the pattern specify crystal structure characteristics such as the set of reflecting planes and distance of paired lines. By enhancing the thickness of the sample, the spots become more visible and the Kikuchi lines become less visible. Kikuchi patterns usually include spots and Kikuchi lines. Generally, Kikuchi patterns represent much more data rather than the spot patterns about crystal structure. The appearance of obvious Kikuchi pattern expresses a symptom of the ideal crystal. **Figure 3** displays the Kikuchi pattern of γFe with structural specifications [3].

**Figure 4(a)** illustrates TEM image of nanostructured Al 7075 alloy under thermomechanical processing. Tilting processing of the sample in TEM was applied to investigate the crystal lattice defects and orientation relationships. The SAED pattern includes the Kikuchi lines and spots of Al 7075 alloy was shown in **Figure 4(b)**.

#### **Figure 2.**

*(a) TEM images and (b) corresponding SAEDP of Al 5083 alloy under ECAP process [3], (c) TEM images and (d) corresponding SAEDP of Al 1050 alloy under CCR process [4, 5].*

**Figure 3.** *Kikuchi pattern of γFe [3].*

**Figure 4.** *(a) TEM image and (b) SAED pattern of nanostructured Al 7075 alloy [3].*

The Kikuchi lines in SAED pattern were indexed the paired Kikuchi lines. Besides, crystal structure characteristics such as interplanar spacing and planes can be specified by measuring the distance between the paired Kikuchi lines [3].

## **2.4 Twinning**

The twinning phenomenon has been known as the crystal structure defect and emerged principally as two parallel planes in TEM observations. In the twinning phenomenon, extra spots were produced surrounding the original spots of crystal structure in the pattern owing to the difference in orientation of twinning planes from the local crystal structure. TEM image and corresponding SAED pattern of twinning planes in *γFe* matrix with a f.c.c crystal lattice were indexed and shown in **Figure 5**, respectively. The main spots corresponding matrix pattern and twin spots with zone axis z = [1 ̅23] were mirror reflections across the (11 ̅1) [3, 6].

## **2.5 Core-shell nanoparticles**

Investigation results of the fabrication of Au/Al2O3 core-shell nanoparticles were demonstrated by one-step, and a very fast method with continuous-wave fiber laser ablation on an Aluminum (Al) plate coated gold (Au) nanolayer film

**13**

**Figure 6.**

*planes of Au/Al2O3 core-shell nanoparticles [7].*

**Figure 5.**

*Transmission Electron Microscopy of Nanomaterials DOI: http://dx.doi.org/10.5772/intechopen.92212*

immersed into ethanol. The core and shell of these nanoparticles contained complete crystalline structures. **Figure 6(a)** and **(b)** illustrates TEM images of Au/Al2O3 core-shell nanoparticles fabricated by the ablation of Al surface coated with Au a nanolayer. The shape of core-shell nanoparticles was approximately spherical and the single core-shell nanoparticle contains Au (core) and Al2O3 (shell), as shown in **Figure 6(b)**. The core and shell of the nanoparticles sometimes seemed entirely regular or non-regular. The core and shell of nanoparticles are determinable by the difference in contrast in TEM images. The structure of single core-shell nanoparticle includes completely crystalline gold (dark zone) coated by Al2O3 layer with crystalline structure (gray zone), as shown in **Figure 6(a)** and **(b)**. The Al2O3 shell of core-shell nanoparticle progressively has changed to the steady Al/Al2O3 compound by overtime. Phase characterization and crystalline planes of Au, Al, and Al2O3 were carried out by the use of the SAED technique, as shown in **Figure 6(c)** and **(d)** [7].

*(a) TEM image of twinning planes and corresponding SAED pattern of* γFe *with f.c.c crystal lattice [3, 6].*

*(a, b) TEM images, (c) corresponding SAED and (d) analysis of ring pattern to identify phase and crystal* 

### *Transmission Electron Microscopy of Nanomaterials DOI: http://dx.doi.org/10.5772/intechopen.92212*

*Electron Crystallography*

**Figure 3.**

*Kikuchi pattern of γFe [3].*

The Kikuchi lines in SAED pattern were indexed the paired Kikuchi lines. Besides, crystal structure characteristics such as interplanar spacing and planes can be speci-

The twinning phenomenon has been known as the crystal structure defect and emerged principally as two parallel planes in TEM observations. In the twinning phenomenon, extra spots were produced surrounding the original spots of crystal structure in the pattern owing to the difference in orientation of twinning planes from the local crystal structure. TEM image and corresponding SAED pattern of twinning planes in *γFe* matrix with a f.c.c crystal lattice were indexed and shown in **Figure 5**, respectively. The main spots corresponding matrix pattern and twin spots

fied by measuring the distance between the paired Kikuchi lines [3].

*(a) TEM image and (b) SAED pattern of nanostructured Al 7075 alloy [3].*

with zone axis z = [1 ̅23] were mirror reflections across the (11 ̅1) [3, 6].

Investigation results of the fabrication of Au/Al2O3 core-shell nanoparticles were demonstrated by one-step, and a very fast method with continuous-wave fiber laser ablation on an Aluminum (Al) plate coated gold (Au) nanolayer film

**12**

**2.4 Twinning**

**Figure 4.**

**2.5 Core-shell nanoparticles**

immersed into ethanol. The core and shell of these nanoparticles contained complete crystalline structures. **Figure 6(a)** and **(b)** illustrates TEM images of Au/Al2O3 core-shell nanoparticles fabricated by the ablation of Al surface coated with Au a nanolayer. The shape of core-shell nanoparticles was approximately spherical and the single core-shell nanoparticle contains Au (core) and Al2O3 (shell), as shown in **Figure 6(b)**. The core and shell of the nanoparticles sometimes seemed entirely regular or non-regular. The core and shell of nanoparticles are determinable by the difference in contrast in TEM images. The structure of single core-shell nanoparticle includes completely crystalline gold (dark zone) coated by Al2O3 layer with crystalline structure (gray zone), as shown in **Figure 6(a)** and **(b)**. The Al2O3 shell of core-shell nanoparticle progressively has changed to the steady Al/Al2O3 compound by overtime. Phase characterization and crystalline planes of Au, Al, and Al2O3 were carried out by the use of the SAED technique, as shown in **Figure 6(c)** and **(d)** [7].

**Figure 5.** *(a) TEM image of twinning planes and corresponding SAED pattern of* γFe *with f.c.c crystal lattice [3, 6].*

#### **Figure 6.**

*(a, b) TEM images, (c) corresponding SAED and (d) analysis of ring pattern to identify phase and crystal planes of Au/Al2O3 core-shell nanoparticles [7].*

By using of the EDP of individual nanoparticle, many of the crystalline structural properties can be measured such as interplanar spacing and the angles of the planes. TEM image of an individual Au/Al2O3 core-shell nanoparticle (**Figure 7(a)**) and the EDP of Au as a shell (**Figure 7(b)**) were demonstrated. In addition, the zone axis and planes of the shell were determined in accordance with standard patterns in **Figure 5(c)** and **(d)**. The spot and ring EDPs of core-shell nanoparticles corroborated of their crystalline specifications. By using of follow equation, lattice parameter of the shell was obtained. = *h*2 + *k*2 + *l* \_

$$\frac{1}{a^2} = \frac{h^2 + k^2 + l^2}{a^2} \tag{1}$$

where *a* is lattice parameter, *d* is interplanar spacing, and *hkl* are Miller indices. Lattice parameter of the core was calculated by using of Eq. (1) about a = 4.0502 Å which was near to the gold lattice parameter. Therefore, surely the core of these core-shell nanoparticles was gold [7].
