**2.2 Synthesis of Mg2TiO4 nano-composite alloys**

In this chapter, high energy planetary ball milling techniques was used for the synthesis of Mg2TiO4 nano-composite alloys from high- purity MgO and TiO2 oxides. The starting materials were weighted according to desired stoichiometry ratios and milled for 5 – 35 hrs to reach steady state condition using planetary ball mill (Fritsch, GmBH, Germany) with the following parameters: (i) ball-to-powder ratio: 10:1; ball diameter: 8 and 16 mm; ball and vial materials: harden stainless steel; the vial rotation speed: 350 rpm. In order to avoid significant temperature rise, the milling process was stopped periodically for every 10 minutes and then resumed for 5 minutes. A brief description about the ball milling techniques is summarized below.

**Ball milling technique:** The photographic view of planetary ball mill is depicted by **Figure 1(a)** and in **Figure 1(b)** it is shown the Zirconia jars with zirconia balls. The zirconia balls are selected in order to avoid the contamination with the given sample. The vials mounted on the horizontal disc rotate in a direction opposite to that of the disc and thereby simulating a planetary-like motion (as shown in **Figure 2**). This result in large outward force acting on the balls kept inside the vial and causes the balls to collide with them and also to the wall of the vial more energetically. When the Mg2TiO4 oxide powders are kept inside the vial along with the balls, the powders undergoes repeated cold welding and fracture at the surfaces of the balls and the vial. This process leads to disintegration of the powders, resulting first in refinement of crystallite size to produce nanocrystalline alloys along with a large number of defects in the parent powders [26, 31–33]. Hence, crystallite size refinement is a natural consequence of a ball milling process. As the milling time progresses the alloy becomes amorphous. The refinement and alloying processes are estimated by the milling parameters including ball to powder weight ratio, size of the ball, speed of rotation, duration of milling etc. Moreover, the nature of the milling container (or vial), milling media and types of balls used during the milling process also played an important role in synthesizing nanocrystalline powders [34].

#### **Figure 1.**

*(a) Photographic view of planetary ball mill (b) zirconia jar with zirconia balls.*

#### **Figure 2.**

*Schematic diagram of the horizontal section of a vial depicting the movement of the balls inside the vial due to its planet like movement [26].*

*Synthesis of Nano-Composites Mg2TiO4 Powders via Mechanical Alloying Method… DOI: http://dx.doi.org/10.5772/intechopen.94275*
