Crystallization And Properties Of K₂O-Al₂O₃-SiO₂ Glass-ceramics

K₂O-Al₂O₃-SiO₂?KAS?system glass-ceramic has an important position in ceramic materials.The glass with the leucite as main crystal phase has the characteristics of high thermal expansion coefficient,good mechanical properties and excellent optical properties,which is an important part of dental materials.In this work,the leucite glass-ceramic was prepared by sintering method to fused with cobalt-chromium alloy matrix as dental prosthetic materials.The effects of K₂O,Al₂O₃,glass powder particle size and heat treatment on the crystal crystallization ability,crystal composition,micro structure,mechanical properties and chemical stability of glass were mainly discussed.The main work of this thesis and the results are as follows:1.With the increase of K₂O content,the crystallization temperature of glass decreased gradually,and the crystallization activation energy decreased and then increased.When the content of K₂O is 20.58%,the crystallization energy of glass is the smallest,and the crystallization effect is the best.K₂O has the influence on the crystal phase of the crystallized glass.When the content of K₂O is 15.58%,the crystal phase of the crystallized glass is garnet and potassium feldspar.With the increase of K₂O content,the feldspar feldses disappear and the crystal phase is pure leucite.When the content of K₂O is 20.58%,the comprehensive properties of glass-ceramics are better.2.The crystallization temperature of glass increases with the increase of Al₂O₃ content,and the crystallization activation energy increases with the increase of Al₂O₃.Al₂O₃ has obvious effect on the microstructure of glass-ceramics,with the increase of Al₂O₃ content,the content of crystal phase in the glass-ceramics decreases and the grain size becomes larger.3.The effects of the particle size of glass powder on the crystallization of glass and the microstructure and properties of glass-ceramics were studied.The results show that the crystallization temperature of glass-ceramics decreases from 913.9 ? to 869.9 ? when the average particle size of glass powder decreases from 38.09?m to 1.80?m.Crystallization activation energy decreased from 320.5 kJ/mol to 234.7 kJ/mol.When the the average particle size?D50?of the glass powder was 6.30?m.The glass-ceramics was homogeneous in precipitated crystals,with a density of 2.45 g-cm-3,a flexural strength of 74.93 MPa and thermal expansion coefficient of 14.32 × 10-6 K-1.4.Heat treatment parameters of the glass powder have a significant effect on the microstructure and properties of glass-ceramics.The optimum heat treatment parameters are:crystallization at 900 ? for 10 min.The comprehensive performance of the prepared glass-ceramics is the best,the coefficient of thermal expansion is 14.17×10-6K-1,the strength is 87.63 MPa and the chemical stability also meets the ISO standard.