**2. Protocol for incorporation of nanoparticles**

The flowchart showed in **Figure 2** summarizes the range of the steps to be followed in order to prepare the model anodic film and fill its pores with nanoparticles of titanium dioxide.

### **2.1. Pretreatment: electropolishing**

The electropolishing treatment was carried out in a bath already proposed by Sulka [2]. This pretreatment aims to reduce the roughness of the aluminum substrate. The results thus Improving Tribological Behavior of Porous Anodic Film by Electrophoretic Impregnation by… http://dx.doi.org/10.5772/intechopen.75782 127

**Figure 2.** Incorporation flowchart of TiO<sup>2</sup> nanoparticles in the pores of anodic layer.

obtained are illustrated in **Figure 3**. Indeed the Al5754 aluminum substrate has an initial roughness (Ra = 740 nm and Rz = 7 μm) and a roughness after electrochemical polishing (Ra = 140 nm and Rz = 1.5 μm).

#### **2.2. Two-step anodization**

**1. Introduction**

126 Electrophoresis - Life Sciences Practical Applications

1 to 100 nm.

coatings based on TiO<sup>2</sup>

and finally rigorously examine the impact of TiO<sup>2</sup>

**2. Protocol for incorporation of nanoparticles**

**2.1. Pretreatment: electropolishing**

the composite coating already developed.

Nanotechnology is based on the knowledge and mastery of the infinitely small. They constitute a multidisciplinary field of research and development involving the fabrication of new materials and devices from tools or techniques that can be used to structure matter at the atomic, molecular, or supramolecular level. The typical scales of nanotechnology range from

The nanomaterials thus derived from these nanotechnologies are materials composed or constituted for all or part of nano-objects which confer to them improved or specific properties of the nanometric dimension. In this context, we speak of nanocharged or nanoreinforced materials. These materials are developed by incorporating nano-objects in an organic or mineral matrix to provide new functionality or to modify mechanical, optical, magnetic, or thermal properties. Nanocomposites are one example. Nano-objects (**Figure 1**) that have two different forms, nanotubes (e.g., MWNT: multi wall carbon nanotubes) or spherical particles (e.g., alumina powder) are incorporated in the porous matrix by several techniques, among which and the most interesting is that of electrophoresis. In this chapter, we are interested in presenting a work whose main objectives consisted in developing a model anodizing layer on the 5754 aluminum alloy, then a stable suspension of nanometric titanium dioxide, then composite

The flowchart showed in **Figure 2** summarizes the range of the steps to be followed in order to prepare the model anodic film and fill its pores with nanoparticles of titanium dioxide.

**Figure 1.** Different shapes of nano-objects (a) multi-wall carbon nanotubes and (b) spherical nanoparticles of alumina [1].

The electropolishing treatment was carried out in a bath already proposed by Sulka [2]. This pretreatment aims to reduce the roughness of the aluminum substrate. The results thus

nanoparticles by electrophoretic impregnation of the anodizing layer,

localization on the tribological behavior of

It should be noted that the anodization consists in carrying out the anodic polarization surface conversion of the base metal, immersed in a suitable electrolyte (generally an aqueous solution of a mineral acid). **Figure 4** shows an experimental setup of anodizing and the reactions that take place on the surfaces of the anode (Al5754) and the cathode.

Different kinds of electrolytes such as sulfuric acid, phosphoric acid, and oxalic acid can be used for anodization. Although sulfuric anodizing, which is nowadays the most commonly used process [3], phosphoric acid was used in the case of this study because it produces a

**Figure 3.** SEM observations associated with 3D roughness profiles: (a) sample after mechanical polishing and (b) after mechanical and electrochemical polishing.

porous anodic layer with the largest pore diameter. The anodizing of aluminum has to be done by preference on samples with a low surface roughness then anodized according to the **two-step anodization** to obtain an ordered porous anodic film [4] with a pore diameter greater than 100 nm. **Figure 5** reveals the approach for the conduct of the two-step anodization and **Figure 6** shows the scanning electronic microscopy (SEM) images of the obtained

Improving Tribological Behavior of Porous Anodic Film by Electrophoretic Impregnation by…

nanopowder, 10 ml of ethanol (C<sup>2</sup>

the resulting sol was introduced into the autoclave (**Figure 7**) heated up to 243°C and pressurized to overcome the critical point of ethanol (T<sup>c</sup> = 243°C, P<sup>c</sup> = 63 bar). After maintaining temperature at 243°C for 1 h, the sol-gelation occurred. To evacuate the interstitial solvent, depressurization for 1 h down to room temperature was conducted with nitrogen gas. Finally,

fabrication diagram.

Fourier-transform infrared (FTIR) spectroscopy was used to identify the functional groups

COOH), 400 μL of hydrochloric acid (HCL) were used as catalysts, and 10 ml of tita-

) 2 )4

**2.3. Electrophoretic impregnation of porous anodizing layer by synthesized TiO2**

mixture was stirred for 30 min at a constant speed of 200 rpm to obtain the TiO<sup>2</sup>

nanoparticles using **electropho-**

http://dx.doi.org/10.5772/intechopen.75782

OH), 10 ml of acetic acid

sol. Then

129

H5

 *nanopowder*

nanopowder. The FTIR absorbance spectra were given

) were mixed in the indicated order. The

anodic layer that can be impregnated with 20 nm size TiO<sup>2</sup>

 *nanoparticles*

nium tetraisopropoxide precursor(Ti (OCH(CH<sup>3</sup>

*2.3.2. Structural and morphological investigations of TiO2*

**Figure 5.** The approach for the conduct of the two-step anodization.

**retic method**.

**nanoparticles**

(CH<sup>3</sup>

*2.3.1. Synthesis of TiO2*

In order to prepare the TiO<sup>2</sup>

titanium aerogel was obtained.

**Figure 8** indicates the sol-gel TiO<sup>2</sup>

presented in the as-synthesized TiO2

**Figure 4.** Experimental setup of anodizing.

porous anodic layer with the largest pore diameter. The anodizing of aluminum has to be done by preference on samples with a low surface roughness then anodized according to the **two-step anodization** to obtain an ordered porous anodic film [4] with a pore diameter greater than 100 nm. **Figure 5** reveals the approach for the conduct of the two-step anodization and **Figure 6** shows the scanning electronic microscopy (SEM) images of the obtained anodic layer that can be impregnated with 20 nm size TiO<sup>2</sup> nanoparticles using **electrophoretic method**.
