Amorphous critical size factor

In both the homogeneous amorphous phase and the crystal defects, the gas diffusivity is a function of molecular size. Obviously, the smaller molecules have a greater diffusivity than the larger ones. However, the critical size factor, or selectivity, is different in the two phases. 

He also showed that the size of the gas molecule is an important factor and that the solubility coefficient S of gases in amorphous polymers can be calculated from the following expression, which relates the critical temperature Tcl and boiling point Tb ... 

Initially in this study, it was planned to critically evaluate AG data for complex clays, including chlorite, illite, and the smectites. However, there is much evidence that these clays dissolve Incongruently so that the apparent equilibria in solution are determined by secondary phases, such as gibbsite, boehmite, amorphous silica, and ferric oxyhydroxldes. The smectites are frequently the dominant clays in the colloidal size fraction in natural sediments. They have very large exchange capacities, and exhibit wide chemical variations. Usually, one or more of these factors have not been considered in the experimental solubility work. Even if appropriate corrections could be made, it is uncertain whether a AG value so obtained would have applicability to natural systems. 

A third method which recently provided considerable insight into the role of crazes in deformation and fracture of amorphous polymers is the optical interference measurement of crazes (preceding a crack). Since the pioneer work of Kambour, this method has been widely used to determine characteristic craze dimensions and critical displacements. W. Doll gives an overview on recent results and on their interpretation in terms of fracture mechanics parameters (stress intensity factor, plastic zone sizes, fracture surface morphology, fracture energy). 

Titanium silicalite (TS-1) is a porous crystalline titanium silicalite with the MFI structure, analogous to ZSM-5 [1], Catalytic centers are isolated Ti sites in a silica framework [4]. Unlike Ti02/Si02 with a similar elemental composition but an amorphous structure, TS-1 is an effective catalyst for the selective oxidation of different functional groups with dilute aqueous hydrogen peroxide [2]. The structural properties of lattice Ti sites, the hydrophobicity, and the size of the tridimensional channel system (ca 0.55 nm) are thought to be critical factors in determining the unusual catalytic properties of TS-1. 

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