Ring size distribution

As discussed above the topological differences between the Si-N networks in Ca2SisN8 and Sr2Si5Ng/Ba2Si5N8 become obvious. In the same way the ring size distribution in a- and 3-Si3N4 significantly differs. 

Table 1. Ring size distribution in S1O2 modifications and nitridosilicates.

An indication of the effect of high pressure on the structure of vitreous silica is illustrated by the distortion of the ring size distribution. Shackelford and Masaryk... 

The concept that molecular weight and polarity play a role in determining the composition of an asphaltene fraction is very realistic but does not present any indication of the nature of the polynuclear aromatic systems in the asphaltene fraction of petroleum. Thus, the purpose of this chapter is to present new data that provide indications of the ring-size distribution in petroleum asphaltenes. The evidence is accumulated by asphaltene fractionation and subsequent examination of the fractions by high-performance liquid chromatography (HPLC) using a UV detector. 

The method is subject to the limitation of the sensitivity of polynuclear aromatic systems. Furthermore, some of the asphaltene material (<2% w/w) was irreversibly adsorbed on the adsorbent. In this case, the missing material is presumably highly polar and any deviation from the ring-size distribution outlined in the foregoing discussion is not believed to be significant enough to influence the general conclusions about the nature of the polynuclear aromatic systems in petroleum asphaltenes. 

Another initiator for this polymerization is (Me3CO)3W=W(OCMe3)j, but analysis of the products by MS shows that they are macrocyclic oligomers. Their ring-size distribution, as determined by GPC, conforms to the Jacobson-Stockmayer relationship see Ch. 11. It is evident that with the tungsten catalyst... 

Qn distribution, RING SIZE DISTRIBUTION, AND VOID SIZE DISTRIBUTION... 

As Al/Li> 1.0, most of alkali ions are already assoeiated with BO, and the deerease in the binding energy with inereasing Al/Li is not signifieant. On the other hand, the ring size distribution shifts to smaller sizes, due to the formation of tri-elusters, as seen in Fig. 9. This reduces the concentration of favorable sites for Li diffusion, increasing the strain energy and... 

Cyclic poly(methyl acrylate) (PMA) with controlled ring size and narrow ring size distribution was also successfully prepared... 

Fig. 9.12 Ring size distributions for A 2.57 obtained from both liquid quenches (black and red lines) and amorphisation of the octsq crystal (green and blue lines). The black and blue lines are obtained using rapid (steepest descent) quenches whilst the red and green lines are obtained by slower cooling...

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