Contact flattening

Fig. 5.38 Idealized two-sphere model for densification by contact flattening. Reproduced with permission fixrm [1]. Copyright 2003, CRC Press...

Fig. 5.43 The three mechanisms of grain-shape accommodation and neck growth during solution reprecipitation controlled densification of liquid-phase sintering a contact flattening, b dissolution of small grains, and c solid-state bonding. Reproduced with permission from [73]. Copyright 2009, Springer...

Under these conditions, a compressive pressure is exerted between the two particles due to the capillary pressure and the surface tension of the liquid. (See Section 14.2.) Because of this compressive pressure at the contact area, the chemical potential of atoms at the contact area is higher than elsewhere (i.e. at the surface of the neck region). Therefore, the solid at the contact area dissolves and the dissolved material is transported to the surface of the neck. As a result of this material transport, the contact area increases and the grain shape is accommodated (contact flattening). At the same time, the pore shrinks continuously and the compact is densified. Kingery considered the pressure... 

Since the development of the classical model and theory, almost all of the phenomena and kinetics of liquid phase sintering have been explained and analysed in terms of the three-stage model and theory. In particular, the theory of the second stage, contact flattening theory, has been the standard theory of liquid phase sintering for decades, despite doubts raised by some research-ergi3,i5,i6,i05,i06 validity of the basic assumptions. Modified contact... 

The contact flattening theory contains some inherent problems. One is the continuous reduction in pore size with increasing sintering time. Therefore, in the pore size distribution, the maximum pore size and the frequency of large pores must decrease continuously as the sintering proceeds. Such a change... 

The densification curves in Figure 16.3 represent the maximum contribution of contact flattening in a compact with an idealized geometry. In real systems,... 

The fundamental difference between the pore filling model and the contact flattening model is the material transport mechanism for densification. In the former, the mechanism is liquid flow as a result of grain growth while, in the... 

Explain the densification and shrinkage processes in the pore filling model and theory of liquid phase sintering. What are the fundamental differences between this model and Kingery s contact flattening model ... 

Densification by contact flattening was described by Kingery (43). As a result of the compressive capillary force of a wetting liquid, the solubility at the... 

Figure 10.26 Idealized two-sphere model for densification by contact flattening.

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