چكيده به لاتين
Cu2O-Al2O3-SiO2 glass ceramic system is known as a glass ceramics with low or sometimes negative thermal expansion coefficient. CuAS glass ceramics has lower melting temperature and lower Liquidous temperature than the similar system (LAS) , and because of this , has advantages in making it easier to build . The presence of crystalline phase , beta-spodomene can be attributed to the low coefficient of thermal expansion in the samples of this system.
In this research, the purpose is to obtaining glass ceramic of the CuAS system and studying the effect of reducing the temperature of thermal treatment and adding oxides on the thermal expansion behavior of the samples of this system. For this purpose, we first developed the glass by the melting and casting method and then turned it into glass ceramic by thermal treatment. Then, the thermal expansion behavior of the samples was studied at crystallization temperatures and 100 ° C lower than that. Also, in the subsequent melting, we used the CuAS base glass system plus the addition of tin oxide and calcium oxide, and examined the thermal expansion behavior of the samples.
In order to investigate the thermal expansion behavior of the samples, XRD test was used to identify the formation of optimal phases in order to decrease the thermal expansion coefficient and SEM images to prove the presence of phases and finally to use the dilatometric test to report the coefficient of thermal expansion. The results indicated that the reduction in the temperature of the thermal treatment resulted in the improvement of the crystalline phases formed in the direction of the lower coefficient of thermal expansion, the addition of tin oxide reduced the viscosity and the melting temperature and calcium oxide had a destructive effect on the removal of the crystalline beta-spodomene phase and the formation of alpha quartz phase . The thermal expansion coefficient for the CuAS glass ceramic is 5 × 10-7 and for the CuAS + SnO2 + CaO glass ceramic system, is 16 × 10-7. Also the CTE for CuAS Glasss-Ceramic heat treated in 800 ℃ is 2/7 × 10-7 .
