Features of Grain Growth

Figure 6.4 The effects of grain processing on the spectral appearance of proto-planetary disks in the infrared. The 10 pm features of several young stars are shown with various degrees of grain growth and crystallization. As indicated in the upper-right panel, the broadening of the feature indicates grain growth, while the appearance of sharp resonances indicates the presence of crystalline silicates. The spectra are taken from van Boekel el al. (2005).

Before we consider the details of grain growth in dense and porous ceramics, we outline some common terms and gena-al features associated with the process. 

The electrodeposited TiAl3 described above displays crystallographic features of distinctly different length scales. The deposit grain size is on the order of 0.1 to 0.5 pm while the Ll2 domain size is on the order of 5-10 nm. The domains appear to have grown through a first order nucleation and growth process that is independent... 

The first study using a wet cell, made at high w/c ratios, showed tubular growths radiating from the cement grains, which were considered to have formed by a silicate garden mechanism (D14). Later work showed that they were rich in calcium, aluminium and sulphur, and that they did not form if CjS was substituted for cement (BlOl). They have not been observed in the more recent studies made at normal w/c ratios, and do not appear to be a significant feature of normal cement hydration. 

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