**2.4.2.3 Concentration of SnCl2 solution**

By observing brightness and reflectance versus concentration of SnCl2 solution, based on Taguchi method and the use of Winrobust software it can be observed that the maximum of brightness and reflectance is related to concentration of about level 3 (figure 2.8). It can be seen that with the increase in the concentration of SnCl2 solution, to a level higher than 3 causes the lightness and reflectance of the pigment to decrease.

The relationship between the intensities of reflected light, transmitted light, scattered light, absorbed light and the intensity of incident light is I = S+T+D+A [2.16], where S, T, D and A represent the strength of reflecting light, transmitting light, scattering light and absorbing light respectively. These are function of tin chloride concentration. When I is fixed, the thicker the membrane layer, the larger the value of A, while the smaller the value of S and T. As T decreasing, there is less incident light traveling through the coating layer and arriving at the surface of the mica substrate. Thus, the intensity of reflecting light generated at the surface decreases, the reflection and interference action becomes weaker, and the lightness decreases.

Figure 2.9 shows SEM images of a great thickness of SnO2 layer at a great concentration of SnCl2 solution. This figure is related to the SEM photo of sample of 2.7 in that the lightness and reflectance are small, because the thickness of SnO2 layer is so high.

Fig. 2.8. Effect of concentration parameter on the a) lightness and b) reflection , at different levels

Also increasing temperature causes the weakening of hydrogen bonding between SnO2

By observing brightness and reflectance versus concentration of SnCl2 solution, based on Taguchi method and the use of Winrobust software it can be observed that the maximum of brightness and reflectance is related to concentration of about level 3 (figure 2.8). It can be seen that with the increase in the concentration of SnCl2 solution, to a level higher than 3

The relationship between the intensities of reflected light, transmitted light, scattered light, absorbed light and the intensity of incident light is I = S+T+D+A [2.16], where S, T, D and A represent the strength of reflecting light, transmitting light, scattering light and absorbing light respectively. These are function of tin chloride concentration. When I is fixed, the thicker the membrane layer, the larger the value of A, while the smaller the value of S and T. As T decreasing, there is less incident light traveling through the coating layer and arriving at the surface of the mica substrate. Thus, the intensity of reflecting light generated at the surface decreases, the reflection and interference action becomes weaker, and the lightness

Figure 2.9 shows SEM images of a great thickness of SnO2 layer at a great concentration of SnCl2 solution. This figure is related to the SEM photo of sample of 2.7 in that the lightness

(a) (b)

Fig. 2.8. Effect of concentration parameter on the a) lightness and b) reflection , at different

and reflectance are small, because the thickness of SnO2 layer is so high.

particles and mica flakes [2.13].

decreases.

levels

**2.4.2.3 Concentration of SnCl2 solution** 

causes the lightness and reflectance of the pigment to decrease.

Fig. 2.9. SEM image of pigment synthesized at great concentration
