Research On Composition Design Of Calcium Aluminosilicate Quasi Ternary Glasses With High Hardness And Crack Resistance

Aluminosilicate glass has been widely used in production and life for its excellent mechanical properties.How to obtain high performance glass has become the focus of scholars at home and abroad.Although the widely used surface strengthening technology can improve the mechanical properties of glass to a certain extent,it does not optimize the internal structure of glass.In this paper,the binary Al₂O₃-SiO₂glass system,which is the most basic component in the aluminosilicate glass system,is used to prepare a series of glasses by laser heating aerodynamic levitation furnace technology.The analysis of mechanical and thermal properties of glass can profoundly understand the structural origin of its performance changes,and provide a theoretical basis for the development of multi-component high-performance glass.In order to improve the stability and crack resistance of binary Al₂O₃-SiO₂glass,constant Ca O was introduced into x Al₂O₃·（100-x）SiO₂glass with different R mole ratios[R=Al₂O₃/（Al₂O₃+SiO₂）]to obtain a series of ternary Ca O-Al₂O₃-SiO₂glass.The mechanical properties of glass,such as hardness and fragmentation resistance,were characterized by microhardness tester,and the structural origin of mechanical properties of glass was explored by density,DSC,SEM,Raman and infrared spectroscopy.The main conclusions are as follows:（1）The hardness of x Al₂O₃·（100-x）SiO₂glass exhibits obvious indentation size effect with increasing load.The hardness of glass increases with the increase of x,which is mainly due to the increase of atomic packing density and mean-field bond energy density.The crack resistance in the nonlinear changes,this can be attributed to the existence of phase separation of the phase interface can effectively improve the glass in glass fracture resistance,and structure characterization of found that with the increase of x,glass bridging oxygen decrease in the number and high coordination Al content increases,the glass can be through the crack resistance of shear deformation process such as glass,The coordination and competition between the two are the structural root of the nonlinear change in the fragmentation resistance of x Al₂O₃·（100-x）SiO₂glass.（2）DSC analysis of x Al₂O₃·（100-x）SiO₂glass shows that the glass transition temperature and glass stability decrease with the increase of x.According to the calculation of crystallization activation energy and the study of crystallization mode,it is found that the tendency of crystallization increases with the increase of x.This is mainly because with the increase of Al₂O₃content,the increase of[Al O₅]and[Al O₆]leads to the gradual depolymerization of angular shared tetrahedral structure[SiO₄],the polymerization degree of glass network is reduced,and the energy barrier for glass crystallization is reduced.（3）Introducing 10 mol%Ca O in binary Al₂O₃-SiO₂glass,DSC analysis of10Ca O·x Al₂O₃·（90-x）SiO₂glass with different molar ratios R=0.3～0.63[R=Al₂O₃/（Al₂O₃+SiO₂）]shows that the stability of glass is significantly improved compared with binary Al₂O₃-SiO₂glass.This is mainly attributed to the fact that the introduction of Ca²⁺makes[Al O₅]and[Al O₆]balance in Al₂O₃-SiO₂glass so that[Al O₄]continues to participate in the construction of glass network.The results showed that glass in hardness loss of less than 10%of the case of crack resistance also has different degrees of enhancement.With the increase of R,the glass crack resistance first increases and then decreases,and the maximum value is 34.6 N at R=0.35.When R=0.3,the decrease of C_Rbecause the Ca²⁺content is not enough to balance all[Al O₅]and[Al O₆]into[Al O₄],so increasing R will continue to promote the glass network depolymerization.When R continues to increase beyond 0.35,the polymerization degree of glass network gradually increases,the atomic packing density increases,and the crack resistance of glass decreases.