The Role of Plastic Flow in Processes of High-speed Sintering of Ceramic Materials under Pressure

Abstract

A model to describe the kinetics of the compaction of conductive nitride ceramics using electropulse technologies is developed. The relationship between density and pressure is established on the basis of three components of the geometric, plastic and stressed state, which is affects the contact area between the particles. The model takes into account the change in the relative area of the interpartial contacts under the action of two mechanisms of mass transfer-diffusion and plastic flow.It is shown that a decrease in the particle size of the powder leads to an in-crease in the diffusion contribution and a decrease in the plastic flow, at all other conditions being equal. And for the case of nano-sized particles, diffusion mass transfer is predominant.Increasing in the heating rate leads to a decrease in the contribution of dif-fusion mass transfer at equal temperatures, as well as to an increase in the temperature of the beginning of shrinkage.The processes of plasma-plasma sintering, high-voltage electro-pulsed consolidation and hot pressing control the same mechanisms, plastic flow and diffusion mass transfer, which do not require, in the first approximation, the influence of the electric current on the properties of materials.

Impedance Analysis of NCM Cathode Materials: Electronic and Ionic Partial Conductivities and the Influence of Microstructure

“…The trends observed in this plot correlate well with the expected sintering behavior of ceramic materials studied in detail by Tarasova et al 48 Up to a porosity of ∼10%, the calculated ratio remains close to 1, indicating that geometric factors are responsible for the initial drop in the conductivities, which can be attributed to the formation of closed pores in the material. For total porosities higher than 10%, the formation of open pores increases, opening the system up for reactions on the now exposed surface, which is reflected in the increasing conductivity.…”

Does Flash Sintering Alter the Deformation Mechanisms of Tungsten Carbide?

“…Although the question about the correlation between the flash event and plastic flow is still under debate within the scientific community [26], "post-flash" dislocations were observed in TiO 2 [27], Er(Mn,Ti)O 3 [28] and yttria-stabilised zirconia (YSZ) [29]. In the latter case, shear stresses over 1 GPa were estimated during flash sintering, high enough to allow dislocation pile-up.…”