Cabbage-head microstructures

Many investigations have been conducted to define the composition range of the glasses and the resulting glass-ceramics that are responsible for the 

At temperatures in the range of 790°- 1000°C, curved micas demonstrating a cabbage-head microstructure were formed. A typical example of this microstructure is shown in Fig. 3-14b. The growth of a second crystal phase in the form of a secondary phase was observed in the final stage of the formation of curved micas in different glass-ceramics of this type. This phase was located between the mica crystals (Fig. 3-15a), X-ray diffraction investigations have shown the phase to be composed of cordierite crystals. The formation of 

Rgure 3-14 SEM image of the formation of a cabbage head microstructure. Polished sample etched for 2.5 sec in 2% HR 

The fact that curved mica crystals were formed at low temperatures and straight ones at temperatures above 

1000°C in glasses with an identical composition indicated that the ion diffusion processes were significant in the formation of crystals. 

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Figure 3-14a shows that after having heat treated the glass at 790°C/3 h, the phlogopite formed a cabbage-head microstructure. It must be noted that the mica crystals formed spherical aggregates as early as in the initial stage of crystallization. There were no isolated crystals present that would become... 

This glass-ceramic (Glaskeramik 1995)> like Bioverit (see Section 4.4.1), exhibits a cabbage-head microstructure of mica crystals. The special properties of this glass-ceramic are ... 

The microstructures of the glass-ceramics resemble well-known structures and phenomena in nature, science, technology, and daily life. In some cases, the microstructures that are discussed exhibit ultrafine crystal structures reminiscent of those of nanopowders. To help describe the appearance of certain microstructures, comparisons are made to the structure of a cell, cabbage head, or a house of cards. These examples are addressed in the following sections. The special properties produced by the specific designs will also be discussed in these sections. 

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