Cellular membrane microstructures

Another type of microstructure in glass-ceramics can best be described by comparing it to the structure of an organic cell. A cell is composed of a very thin membrane that separates and protects the contents of the cell from the neighboring cells. Similarly, in a cellular membrane microstructure, a very thin membrane surrounds the contents of a cell-like entity. 

This type of cellular membrane microstructure can be developed in glass-ceramics that exhibit a very low coefficient of thermal expansion because of the precipitation of p-quartz solid-solution or P-spodumene crystals (Beall 1992). The glass matrix, which is very thin and surrounds the crystals, plays the part of the cellular membrane. As a result, the crystals are separated from each other. The membrane accounts for approximately 10 vol% of the micro-structure and can, for example, act as a diffusion barrier between the crystals. 

P-quartz solid solution grows. In the high-resolution TEM image by Maier and Muller (1989) in Fig. 

the ZrTiO nucleation phase appears as a small dot measuring a few nanometers in the middle of various P-quartz solid solution crystals. Further excess ZrTiO crystals that do not initiate P-quartz crystals are also discernible as black dots in the glass matrix cellular piembrane. 

Beall (1992) attributes a great deal of importance to the glass matrix representing the cellular membrane in the solid-state reactions of P-quartz solid solution and P-spodumene solid solution glass-ceramics, the tenacious residual 

---

Figure 3-2 shows the cellular membrane microstructure of a P-quartz solid solution glass-ceramic. The individual phases are presented in connection with their effect on the different solid-state reactions to provide a better understanding of this microstructure. As described in Section 2.2.2, the nucleation of P-quartz solid-solution crystals is heterogeneously initiated by ZrTiO nucleating agents. These ZrHO crystals represent the nucleus of the... 

Figure 3-2 Cellular membrane microstructure of a B-quartz solid-solution glass-ceramic (bar 200 nm). TEM (Maier and Muller, 1989). Residual glass with ZrTi04 precipitates is observed with cellular structure.

Tn view of the complicated microstructure of the muscle fiber one would - expect that formation of ice crystals within the very small cavities would cause some damage to various cellular elements. A point of particular interest is "What influence does freezing of muscle tissue have on the sensitive membranes associated with mitochondria, the sarcoplasmic reticulum, lysosomes, and other subcellular particles In order... 

---