The effect of mechanical activation on energetics and dissolution kinetics of Indian beach sand ilmenite

Abstract

Mechanical activation is a non-equilibrium process of enhancing the internal energy of solids by mechanical processes such as high energy milling and high strain rate deformation through the accumulation of non-equilibrium defects. The activated solid is a thermodynamically and structurally unstable arrangement of the lattice components, exhibiting increased enthalpy and Gibbs free energy in comparison to the stable crystalline substance. In the mechanical activation process, the non-equilibrium energy is stored in the material as point and line defects, new surfaces and interfaces, volume defects in crystals and through structural rearrangement which can be utilized to reduce the activation energy during subsequent processing. In the present thesis, the effect of the mechanical activation through high energy milling was studied on energetics and the acid dissolution kinetics of Indian beach sand ilmenite samples. The thesis consists of seven chapters. The salient features of each chapter are described below: Chapter 1 comprises of introduction and literature survey of mechanical activation process. Various activation processes and distinguishing features of the mechanical activation process are discussed in detail. The manifestations of the stored energy during the mechanical activation process and its applications in subsequent processing are also discussed. Further, the application of the mechanical activation process as a pre-treatment for dissolution of Indian beach sand ilmenite samples is justified. The literature survey summarizes the history of mechanical activation processes, milling equipments used in mechanical activation process, thermodynamic and kinetic aspects of mechanical activation, energy stored in the material and the effect of mechanical activation on the physical, chemical, structural, thermal and magnetic properties. Further, the use of mechanical activation as pretreatment in various mineral processing techniques is discussed in detail. The literature reported on processing of ilmenite samples also discussed.