## 5 Applications
### Energy Storage
The authors prepared several composites of Se:P:C by P-milling carried out in presence of the 7 mm amplitude and 16 Hz frequency of milling cylinder vibrations. A discharge frequency of 60 kHz with 15 kV voltage and 1.5 A of current was applied. Among the other composites, anode material prepared by the amorphous Se:2P/C@30h composite exhibited better electrochemical performance for Potassium-ion batteries (PIBs) with 634 mA h g\({}^{-1}\) of reversible capacity at 0.05 A g\({}^{-1}\) current density and 248.6 mA h g\({}^{-1}\) of rate capability at 1 A g\({}^{-1}\) of current density. The resultant composite material has lower particle size and reduced the diffusion distance of potassium ion. It also enhanced the conductivity of the active material by preventing the formation of polyselenide in the charging and discharging process. The practical performance of the electrode was lower than the theoretical one due to the new incomplete phases due to potassiation. Fabrication of 0.925(K\({}_{0.5}\)Na\({}_{0.5}\))NbO\({}_{3}\).0075 Bi(Zn\({}_{2/3}\)(Ta\({}_{0.5}\)Nb\({}_{0.5}\))\({}_{1/3}\))O\({}_{3}\) (KNN-BZTN) relaxor ferroelectric ceramic material by [PERSON] et al. [125] via high energy ball milling route showed different morphologies. The effect of high sintering temperature and short relaxation time operated on material in two steps resulted a reduction in the grain size and large number of grain boundaries, effectively enhancing the energy storage performance. The electric breakdown effect was increased from 222 to 317 kV cm\({}^{-1}\) due to large band gap and lower charge carrier concentration properties. The resulting material showed improved energy storage characteristics such as 4.02 J.cm\({}^{3}\) of energy density and 87.4% of energy efficiency. Besides the electrochemical storage, materials have also been employed for energy storage by other means. The thermal energy storage (TES) capacity of the solid-state Lithium sulfate (LS)-Sodium sulfate (NS) composite, LS/NS composite material synthesized by the ball milled method was investigated by [PERSON] et al. [128] composite material was used for TES storage at 450-550 \({}^{\circ}\)C temperature. The authors used the Calphad method to study the performance of the TES by analyzing the various theoretical parameters such as heat capacity, free energy, volume expansion, transition temperature, and enthalpies of reactions. The LS/NS composite with 79:21 and 50:50 stoichiometric ratio exhibited 270 J g\({}^{-1}\) and 318 J g\({}^{-1}\) of theoretical enthalpy transformation values respectively and enthalpy value of 185 J g\({}^{-1}\) and 160 J g\({}^{-1}\) respectively. This material could be useful in latent heat storage applications to store heat without loss of temperature. Further, the perovskite material La\({}_{0.6}\)Sr\({}_{0.4}\)CoO\({}_{3-\delta}\) (LSC) synthesized by the Pechini method and further calcined at 1000 \({}^{\circ}\)C and ball milled at different milling time was studied for the structural and electrochemical performances by [PERSON] et al. [125]. The result showed that as the milling time increased (up to 36 h), the particle size was reduced with increasing the surface area; after a certain milling time (48 h), particles started to aggregate and resulting in increased the particle size. The authors also concluded that the performance of ball milled LSC exhibited superior electrocatalytic activity for oxygen reduction and oxygen evolution reaction (ORR and OER) than the non- ball milled LSC sample. The resulting ball milled sample also showed satisfactory performance for lithium air battery for ORR and OER with high rate of capacity and reversibility. Plasma milling or P-milling is yet another technique that provides opportunities to synthesize materials with better physical and/or chemical properties. During the P-milling process, electrons and ions of the plasma collide with the reactive precursors with very high speed and transfer their energy to the latter resulting in an increase in the material temperature.