Stages of Liquid-Phase Sintering

Figure 2. Schematic diagram illustrating the three stages of liquid phase sintering, with the dominant mechanisms and processes for each stage. (After Ref 1.)...

Spreading is the process in which the liquid distributes itself to cover the surfaces of the particles. It is important in the early stage of liquid phase sintering because the liquid normally forms in isolated regions of the compact. A spreading liquid has a contact angle of zero. 

Figure 5. Schematic log shrinkage - log time plot showing 3 stages of liquid phase sintering of silicon nitride ceramics according to model of Kingery [17],...

The stages of liquid phase sintering are summarized in Fig. 10.3. The extent to which each stage influences densification is dependent on the volume fraction of liquid so there are many variants in this conceptual picture. When the volume fraction of liquid is high, complete densification can be achieved by the rearrangement process alone. On the other hand, at the low liquid contents common for many systems, the solid skeleton inhibits densification, so that solution-precipitation and final stage sintering are required to achieve further densification. 

Briefly discuss whether each of the following factors is likely to promote shrinkage or swelling during the initial stage of liquid-phase sintering ... 

Derive Eq. (10.38) for the shrinkage during the solution-precipitation stage of liquid-phase sintering when the phase boundary reaction is the rate controlling mechanism. 

Similarly, the mechanisms of liquid-phase sintering can be described by dividing the process into three stages. The first stage involves the redistrihulion of the liquid... 

The classical model and theory of liquid phase sintering asserts that liquid phase sintering can be divided into three stages ... 

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 mechanisms of liquid-phase sintering processes have been described in detail by Kingery (213, 214], Petzow (215), and German [216]. The sintering process can be treated as a sequence of three stages particle rearrangement solution-reprecipitation and skeleton sintering. 

Densification during liquid-phase sintering occurs in tliree stages. Initially, liquid fonns at particle intersections and redistributes tliroughout the particulate mass under the influence of the capillary action. Shear stresses due to the... 

---