Studies On The Phase-separation,nucleation And Crystallization Of CMAS Float Glass-ceramics

The CaO-MgO-Al₂O₃-SiO₂ glass-ceramics is a very important system among various special plate glass,and it has been applied in building decoration,new energy vehicles,household appliances and other fields due to its special properties,such as excellent mechanical properties,good ware resistance and high chemical stability.Compared with the existing sintering method and rolling process,the float process have several advantages such as high automation degree,strong production ability,low consuming of energy,high quality of the products and etc.So the optimum processing technology for CMAS glass-ceramics is the float process.Specially,the surface quality of CMAS glass-ceramics prepared by float process increased visibly,which is vital for the application of CMAS glass-ceramics in building decoration and electronics field.Therefore,many scientific problems and technical difficulties need to be addressed before implementing the preparation of CMAS glass-ceramics by float process.But one of the most essential scientific problem is to contral the crystallization process of glass-ceramics.In this paper,CaO-MgO-Al₂O₃-SiO₂ glass-ceramics was taken as research object,the float process and crystallization of CMAS glass-ceramics had been studied and explored by using XRD,FESEM,DSC,AFM,EPMA,Raman,Viscosity test and etc.,and effect of heart-treatment conditions,SnO₂ and slight fluxes?F and P₂O₅?on microstructure and crystallization performance of CMAS glass-ceramics had also been studied and analyzed.The main results are as follows.?1?The melting and forming temperature of CMAS glass-ceramics?with3⁴wt%TiO₂?were 1476.5°C and 1275.3°C respectively.The upper limit of crystallization temperature?1130°C?of CMAS glass-ceramics was lower than the temperature of starting point at tin bath.All the above showed that the float processes can satisfy the production requirements of CMAS glass-ceramics.Furthermore,CMAS parent glasses produced by float process had a high surface flatness and low tin penetration.?2?After treated at 700°C,phase separation had been discovered in CMAS parent glass?containing 3⁴wt%TiO₂?and the phase-separation size was about 55nm.Dendritic diopside as a major crystalline phase was precipitated in CMAS glass-ceramics nucleated at 700°C for 30 min and followed by crystallized at 910°C for 30 min.?3?The crystallization temperature raised firstly and then decreased with the content of SnO₂ increased constantly,and the critical addition mass was 3wt%.When the SnO₂ content was higher than 3wt%,tinstone was precipitated from parent glass firstly during heat treatment.In this system,besides diopside,anorthite and tinstone had also precipitated and their grain size was decreased with the addition of SnO₂.?4?F and P₂O₅ acted as a kind of network modifier which could reduce the glass network aggregation degree,high-temperature viscidity and devitrification temperature of the glass-ceramics.In addition,when the F was used in tandem with P₂O₅ the effect became more obvious.Through the research of the heat treated samples,we found that the introduction of F and P₂O₅ could promoted phase separation and after crystallization the main crystalline phase of the glass-ceramics was diopside.With the introduction of F and P₂O₅,Tiny amphibole crystalloid,anorthite and calcium phosphate was precipitated in glass-ceramics respectively.When 1.5wt%F and 0.5wt%P₂O₅ were introduced,the corresponding glass-ceramics crystallized better than other samples,Furthermore,Crystal size was refined by the addition of F and P₂O₅.