Devitrification temperature

Fig. 1.17.1. Phase diagram for glycerine -water. Tm, melting temperature Thn, temperature of homogeneous crystallization Tg, devitrification temperature (Fig. 3 from [1.14]).

On the basis of the model of ett decay in the vicinity of the devitrification temperature described above, it was expected that the kinetic features discovered for the reactions of trapped electrons, etr, in the presence of both long-range electron tunneling and the diffusion of reagents would also hold... 

Methylbutadiene-l,3 (MB) -I- S02. A solution of S02 in MB (1 1) was prepared at T 170 K. On freezing, such a solution vitrifies. The thermoacti-vated copolymerization in the system, containing active centers stabilized during the low-temperature radiolysis, also begins in the devitrification temperature region at 100K.17... 

Essentially different from the reactions studied is the MB + S02 system.17 Whereas in the BC + Cl2 system the degree of chemical conversion did not exceed 10-15%, in the MB + S02 copolymerization reaction the conversion was practically complete. The small degree of conversion in the BC + Cl2 system is likely to be connected with the heating up of the wave front to the devitrification temperature, which leads to the effective decay of active centers as a result of their recombination. Perhaps this reason, along with the others discussed earlier, may be called to account for the increase in the degree of conversion in the wave front on passing from the nitrogen to helium temperature. In other words, in the reactions of chlorination and hydro-... 

The dependence of heating on pressure itself may be due to a decrease, with increasing pressure, of the characteristic size of dispersion grains. There is also an alternative explanation, connected with increasing devitrification temperature of a compressed matrix this factor causes a displacement of the temperature region of the intense recombination of active centers and creates the conditions for a higher degree of conversion at the front. 

Figure 4 State diagram of the glycinebetaine-water system. L unsaturated solution GB erystalline glyeinebetaine Ty solidus T devitrification temperature dotted curves represent estimated portions of the diagram for which experimental data are still missing. Reproduced with permission from Komai and Murase ...

This chapter relates to strong, anhydrous, amorphous silica bodies and to their manufacture by molding and sintering amorphous colloidal silica powders at a temperature of at least 1000°C but below the devitrification temperature of the molded bodies. 

The molded compacts are sintered by heating them at a relatively uniform rate until the sintering temperature, in the range between 1000°C and the devitrification temperature of the silica is reached, and maintaining them at this temperature until their density is in the range of about 91% to about 100% of the theoretical density of amorphous silica. The novel character of the compacts makes it possible to sinter them to the desired density in this temperature range without devitrification. 

Obviously, this change of the dynamic module is associated with the inerease of mobility of macromolecules and individual fragments of copolymer binder at the devitrification temperatures. Growth of the values E (curves 1-4, Figure 7.5a) is observed when amounts of nanotubes increase. Most probably, observed growth of the value E caused by the amounts of nanotubes occurs due to the intercalation of... 

---