Methods of obtaining amorphous material

One way of obtaining amorphous material is to dry rapidly from solution. In solution, the solute is in disordered state and if dried very quickly it does not have time to recrystaUise, and so gives an amorphous product. The process of spray-drying is often used with pharmaceuticals and can therefore give an amorphous product, though some crystalKsation may occur. Resulting products need to be kept dry to prevent the 7 from being reduced by plasticisation with water or the material may recrystalKse. 

Here W is the weight of phase n and X is the mole fraction of component A in phase n. This process continues imtil the remaining mixture reaches the point E where a solid mixture of composition E (eutectic) crystallises out. Naturally, the same arguments hold if the eutectic point is approached from the opposite side where B is the crystallising component. 

Phase diagrams similar to the above, but where a pure compound crystallises out, apply to compounds such as benzene and naphthalene. However, if we consider a different system where A is assumed to be sugar and B water, an interesting observation is made. 

This can be seen to be equivalent to the Couchman-Karasz equation where k is equal to the ratio of the specific heats instead of pi Aa2/P2Aai as in the original paper [11]. P and Aa are the density and thermal expansivity respectively  

This equation can also be expressed in a hnear approximation. 

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