The thermodynamic driving force in

The thermodynamic driving force in cold sintering is enabled through an interface-driven mechanism known as pressure solution creep.6–9 The presence of a transient phase along with an appliedstress led to the dissolution of solids at grain contacts, the diffusion through grain boundaries, and the precipitation at pore walls.35,36 As shown in Fig. 1, these three steps of pressure solution creeps are induced by the existence of chemical potential differences between the solid stressed at grain contacts and the solid at pore surfaces.Earlier work in our group highlighted anisothermal heating rate studies, isothermal grain growth studies, and using tracers (isotopesand solid solution additives) to determine the epitaxial reprecipitation on grain surfaces to establish evidence through the formation of a core–shell.37–39 The energetics of the processes have been determined to be significantly lower than the equivalent activation energies under the cold sintering process relative to the conventional sintering process. There are no methods to experimentally and thoroughly investigate chemical reactions at interfaces in cold sintering process (CSP) conditions, nor in molten hydroxides. However, promising developments to monitor in situ changes in materials during CSP have been highlighted by Allen et al., using small angle scattering techniques.40 ReaxFF molecular dynamics simulations have pointed to complex and dynamic oxide/solvent chemical reactions that drive diffusion rates by orders of magnitude in grain boundaries.41 Recent investigations highlighted chemical reactions dynamics in the BT/NaOH–KOH system.42 Although there might be several mechanistic similarities, a thorough discussion of chemical reactions in the BT/Ba(OH)2⋅8H2O system is beyond the scope of this paper.