| Autor: |
Pivinskii, Yu., Semikova, S., Kaplan, F., Samarina, O., Trubitsyn, M. |
| Zdroj: |
Refractories; 1989, Vol. 30 Issue 5/6, p272-278, 7p |
| Abstrakt: |
Using as an example castings of VKVS of acid and acid-amphoteric compositions we studed the main rules governing their structure formation in the process of drying. The drying process at the first stage (reduction in moisture content by 0.5-1.2%) is characterized by shrinkage (0.05-0.3%), and in the latter stages by a gradual expansion 0.017-0.08%). We established a relationship between the various factors of dispersion in the VKVS and the expansion of the castings based on them, and showed that a decisive influence on the magnitude of the expansion is exerted by the concentration in the suspension of particles measuring less than 0.1 μm. We put forward a scheme for structure formation during drying of the casting, including three stages: shrinkage of the casting on account of the removal of physical-mechanical moisture; expansion of the casting on account of the action of repulsive forces between the colloidal particles, developing with an increase in the concentration of the latter, in the intergrain spaces, during removal of moisture; and finally the strengthening of the developed contacts on account of the formation of siloxane bonds. During the making of the goods based on VKVS we should take into consideration the stresses developing on account of the nonsimuitaneous occurrence of the processes of expansion and shrinkage across the thickness of the casting, and we need to select grinding and dispersion factors for the VKVS, bearing in mind the dimensions an required technical properties of the articles. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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