Composition And Structural Optimization Of Yttrium/Lanthanum Lithium Aluminosilicate Glass With Mechanical Function Orientation

Lithium aluminosilicate glass is a high-strength glass with a high network density structure,high elastic modulus,and suitable for chemical strengthening.It can be used as a cover plate for electronic equipment,transparent components for aviation,and windows for vehicles and ships.With the continuous expansion of application fields and the continuous improvement of usage requirements,there is an urgent need for lithium aluminosilicate glass products with higher strength and more complete performance.In order to further improve the mechanical properties of lithium aluminosilicate glass,this article studies the composition and structure of glass through a combination of theoretical research,experimental exploration,and performance testing.Firstly,the influence of different glass components on strength was investigated and analyzed.The types of oxides that are beneficial for improving the mechanical properties of glass were summarized from the aspects of dissociation energy,ion field strength,and electrostatic attraction energy of glass composition oxides,choosing to introduce Y₂O₃and La₂O₃into the lithium aluminosilicate glass component to improve mechanical properties.Based on the study of the effects of different components on the structure and properties of glass,this article explores the effects of different Y₂O₃and La₂O₃contents on the structure of lithium aluminosilicate glass.The structural changes of[Si O₄]and[Al O₄]in the glass network were characterized.The introduction of Y₂O₃and La₂O₃disrupted the Si-O network structure in the glass,increasing the number of non bridging oxygen,while the proportion of[Al O₄]structures that have the function of repairing the glass network structure gradually increased;In addition,Y³⁺and La³⁺with high field strength can improve the aggregation degree of glass network structure and increase the atom packing density of glass;The mechanical properties of lithium aluminosilicate glass containing Y₂O₃and La₂O₃were tested.When the content of Y₂O₃and La₂O₃was 4 mol%and 2 mol%respectively（LAS-42 glass）,its Vickers hardness,elastic modulus and bending strength could reach 712.8 H_V,99.72 GPa and140.47 MPa,respectively,which increased by 13.1%,14.9%and 59.9%compared with the strength of parent glass.In order to improve the melting process of lithium aluminosilicate glass and clarify the relationship between glass properties and temperature,this article studied the effects of Y₂O₃and La₂O₃on the thermal properties of lithium aluminosilicate glass.As the content of Y₂O₃and La₂O₃increases,the viscosity of the glass first decreases and then increases,and the slope of the viscosity temperature curve increases.The viscous activation energy of glass at different temperature stages was calculated.After introducing 4 mol%Y₂O₃or La₂O₃,the viscous activation energy at low temperature stage increased from 210.5 KJ/mol to 779.2 KJ/mol and 599.2 KJ/mol,respectively.Reducing the melting temperature from 1550℃to 1370℃;The temperature range of micro-crystalline phase precipitation in lithium aluminosilicate glass has been clarified,and a method has been proposed to reduce micro-crystalline phase precipitation by accelerating the cooling rate of lithium aluminosilicate glass at low temperature.The two-step chemical strengthening process was used to enhance the strength of lithium aluminosilicate glass containing Y₂O₃and La₂O₃.The effects of molten salt ratio,ion exchange time,and temperature during the two-step chemical strengthening process on the compressive stress（CS）and depth of stress layer（DOL）on the surface of 5 mm lithium aluminosilicate glass were investigated,The two-step chemical strengthening process suitable for 5 mm lithium aluminosilicate glass is 430℃/80wt%Na NO₃,20 wt%KNO₃/12 h+420℃/pure KNO₃/12 h.After two-step chemical strengthening,the mechanical properties of the glass are significantly improved,with LAS-42 glass having the best mechanical properties,CS being 906.50 MPa and DOL being 380.17μm.The Vickers hardness and bending strength of the glass are 750.95H_Vand 812.74 MPa,respectively,which are 9.6%and 18.7%higher than those of the toughened parent glass,and the preparation of high-strength lithium aluminosilicate glass is realized.