SYSTEM Na2O-SiO2

 

In a fig. 51 the most full investigated part of the diagram of a condition of system Na2O-SiO2 on Ф is represented. Крачеку, since structures containing less of ~70 % (мас). Na2O. In this part of system there are following double connections: ортосиликат натрия 2Na2·SiO2, метасиликат натрия Na2O·SiO2 and дисиликат натрия Na2O·2SiO2. Ортосиликат натрия плавится инконгруэнтно at 1118ЁС, being decomposed on a liquid of structure 59,3 % (мас). Na2O and 40,7 % (мас). SiO2 and crystals Na2O, мета- and дисиликаты натрия плавятся конгруэнтно: first at 1089ЁС and second at 874ЁС. Дисиликат натрия has some polymorphic versions: on the diagram of a condition they are designated /, // and /// with temperatures of polymorphic transformations 707ЁС and 678ЁС. Except for these polymorphic transformations Ф. Крачеком the polymorphic transitions дисиликата натрия were found out also at temperatures 593, 573 and 549ЁС. Thus, on Ф. Крачеку, Na2O·2SiO2 has six polymorphic versions.

Exist and a little bit other diagrams, given concerning the specified part, of a condition of system Na2O-SiO2. In particular, some authors carry 2Na2O·SiO2 to connections, плавящимся конгруэнтно at 1083ЁС and having polymorphic transformation at 960ЁС. There are also data on existence others crystal силикатов натрия, except for given on the diagram, in particular, 3Na2O·2SiO2 with temperature конгруэнтного плавления 1122ЁС and трисиликата натрия Na2O·3SiO2 with temperature плавления 750ЁС.

Connections of system Na2O-SiО2 in comparison with the majority others силикатных of connections rather легкоплавкие. The diagram Na2O-SiO2 is a vivid example, as far as is strong

 

 

Temperature плавления of mixes can be lowered at the expense of education эвтектик. For example, temperature ликвидуса is reduced from 1728ЁС for pure(clean) SiO2 up to 790 ЁС for эвтектики between SiO2 and Na2O·2SiO2, containing 73,9 % (мас). SiO2 and 26,1 % (мас). Na2O, т. е. Almost on 1000 ЁС. It explains characteristic for this diagram sharp rise of a curve ликвидуса from эвтектики between SiO2 and Na2O·2SiO2 to temperature плавления кристобалита. It allows to receive in this system various легкоплавкие of a glass.

The system Na2O-SiO2 is private(individual) under the attitude(relation) to much поликомпонентным to systems of the large applied meaning(importance), for example, in relation to systems Na2O- MgO-SiO2 and Na2O-CaO- SiO2, important for стеклоделия, to system Na2O-Fe2O3-SiO2, important for объяс-

нения of processes магматической of differentiation and т. д. Двухком-

понентная system Na2O-SiO2 has special meaning(importance) for

Technologies of manufacturing натриевых of soluble (liquid) glasses,

Representing стеклообразные силикаты натрия of changes

ного of structure with the general(common) formula mNa20-n Si02.