In this work,the structure,viscosity and ion-exchange process of Na_(2)O-MgO-Al_(2)O_(3)-SiO_(2) glasses with different Al_(2)O_(3)/SiO_(2) molar ratios were investigated.The results showed that,with increasing Al_(2)...In this work,the structure,viscosity and ion-exchange process of Na_(2)O-MgO-Al_(2)O_(3)-SiO_(2) glasses with different Al_(2)O_(3)/SiO_(2) molar ratios were investigated.The results showed that,with increasing Al_(2)O_(3)/SiO_(2) ratio,the simple structural units Q_(1) and Q_(2) transformed into highly aggregated structural units Q_(3) and Q_(4),indicating the increase of polymerization degree of glass network.Meanwhile,the coefficient of thermal expansion decreased from 9.23×10^(-6)℃^(-1) to 8.88×10^(-6)℃^(-1).The characteristic temperatures such as melting,forming,softening and glass transition temperatures increased with the increase of Al_(2)O_(3)/SiO_(2) ratio,while the glasses working temperature range became narrow.The increasing Al_(2)O_(3)/SiO_(2) ratio and prolonging ion-exchange time enhanced the surface compressive stress(CS)and depth of stress layer(DOL).However,the increase of ion exchange temperature increased the DOL and decreased the CS affected by stress relaxation.There was a good linear relationship between stress relaxation and surface compressive stress.Chemical strengthening significantly improved the hardness of glasses,which reached the maximum value of(622.1±10)MPa for sample with Al_(2)O_(3)/SiO_(2) ratio of 0.27 after heat treated at 410℃for 2 h.展开更多
The crystallization behavior of Li_(2)O-Al_(2)O_(3)-SiO_(2) glasses with various concentration of Li2O were investigated by DSC,XRD,and FE-SEM.The h/l-quartz s.s.is the main crystalline phase for all of the glass with...The crystallization behavior of Li_(2)O-Al_(2)O_(3)-SiO_(2) glasses with various concentration of Li2O were investigated by DSC,XRD,and FE-SEM.The h/l-quartz s.s.is the main crystalline phase for all of the glass with the heat treatment of 720℃/3 h+800℃/1.5 h while the crystallinity and crystal size increase with the increase of Li2O contents.Due to the negative thermal expansion coefficient of h/l-quartz s.s.,the thermal expansion coefficient of glass-ceramics decreases with the increasing of Li2O contents.When the Li2O content is 9mol%,the near-zero CTE20-700℃=-0.09×10^(-6)℃^(-1) is obtained upon the heat treatment of 720℃/3 h+800℃/1.5 h.The crystallization activation energy of the glass with 9mol%Li2O is about 351 kJ/mol,and the crystallization mechanism is volume crystallization.展开更多
基金Funded by National Natural Science Foundation of China(Nos.52172019 and 52072148)Shandong Provincial Youth Innovation Team Development Plan of Colleges and Universities(No.2022K1100)。
文摘In this work,the structure,viscosity and ion-exchange process of Na_(2)O-MgO-Al_(2)O_(3)-SiO_(2) glasses with different Al_(2)O_(3)/SiO_(2) molar ratios were investigated.The results showed that,with increasing Al_(2)O_(3)/SiO_(2) ratio,the simple structural units Q_(1) and Q_(2) transformed into highly aggregated structural units Q_(3) and Q_(4),indicating the increase of polymerization degree of glass network.Meanwhile,the coefficient of thermal expansion decreased from 9.23×10^(-6)℃^(-1) to 8.88×10^(-6)℃^(-1).The characteristic temperatures such as melting,forming,softening and glass transition temperatures increased with the increase of Al_(2)O_(3)/SiO_(2) ratio,while the glasses working temperature range became narrow.The increasing Al_(2)O_(3)/SiO_(2) ratio and prolonging ion-exchange time enhanced the surface compressive stress(CS)and depth of stress layer(DOL).However,the increase of ion exchange temperature increased the DOL and decreased the CS affected by stress relaxation.There was a good linear relationship between stress relaxation and surface compressive stress.Chemical strengthening significantly improved the hardness of glasses,which reached the maximum value of(622.1±10)MPa for sample with Al_(2)O_(3)/SiO_(2) ratio of 0.27 after heat treated at 410℃for 2 h.
基金Funded by the Opening Project of State Key Laboratory of Special Glass and the National Natural Science Foundation of China(No.52072278)。
文摘The crystallization behavior of Li_(2)O-Al_(2)O_(3)-SiO_(2) glasses with various concentration of Li2O were investigated by DSC,XRD,and FE-SEM.The h/l-quartz s.s.is the main crystalline phase for all of the glass with the heat treatment of 720℃/3 h+800℃/1.5 h while the crystallinity and crystal size increase with the increase of Li2O contents.Due to the negative thermal expansion coefficient of h/l-quartz s.s.,the thermal expansion coefficient of glass-ceramics decreases with the increasing of Li2O contents.When the Li2O content is 9mol%,the near-zero CTE20-700℃=-0.09×10^(-6)℃^(-1) is obtained upon the heat treatment of 720℃/3 h+800℃/1.5 h.The crystallization activation energy of the glass with 9mol%Li2O is about 351 kJ/mol,and the crystallization mechanism is volume crystallization.
