Grain crystal phase

Twist grain boundary (TGB) liquid crystal phase, 15 95... 

Lubensky TC, Renn SR (1990) Twist-grain-boundary phases near the nematic smectic-A smectic-C point in liquid crystals. Phys Rev A 41 4392-4401... 

Unlike preceding cases, the broad fine-grained two-phase zone, 2 mm thick, is formed at the interface between a 20 mass % Fe-80 mass % Ni alloy and the saturated aluminium melt (Fig. 5.16e). The same applies to a 15 mass % Fe-85 mass % Ni alloy, the thickness of the two-phase zone being 1.7 mm. The FeNiAl9 compound is dominant in the two-phase zone. Its fine crystals form a framework whose pores are filled with an aluminium solid solution. The NiAl3 inclusions are relatively seldom. 

Although these mixed metal alkoxide complexes are a means of obtaining atomic mixing of the various metals, the stoichiometric ratio of metals may or may not be that desired for the ceramic powder. A different stoichiometric ratio, n, for the same two metals is not likely to be precipitated out just because the initial solution contains a different stoichiometric ratio. Also for many electronic ceramic compositions it is desirable to have many other metals incorporated at the ppm level into the ceramic powder as sintering aids, grain growth inhibitors, and crystal phase stabilizers. Adding these otiier metals is very difficult... 

The grain boundaries do not form any barrier to the electron migration. Results on nano crystalline ceria have indicated that the grain "boundary phase" is more easily reduced than the bulk of the crystal. The activation energy of the electron hopping seems to be similar to that of the bulk material. 

Kitzerow, H.-G. Twist grain boundary phases. In C. Bahr, H. Kitzerow Eds. Chirality in liquid crystals. New York Springer Vet ag, 297 2000. ... 

Grain size and dominant crystal phase at different anneal temp. 

Fig. 19. Creep behavior of silicon nitride ceramics. The composition of this ceramic contains 7 vol % Y3A15Oi2 as a sintering aid. The specimens were hot-pressed at 1750°C under a pressure of 20 Mpa. The holding times are marked on the curve. This curve indicates that crystallization of the grain-boundary phase improves the creep resistance. Garnet crystals were observed at the grain boundaries after annealing [3/]. , Sample A60 , Sample B60 A, Sample B150, x, failure.

---