Quantitative Structure-Property Relationship Between The Structure And Elastic Modulus Of Alkali-Free Aluminoborosilicate Glass

Alkali-free aluminoborosilicate glass boasts excellent mechanical and electrical properties,low thermal expansion coefficient,and is widely used in display substrate glass and electronic glass fiber.Most domestic and foreign substrate glass and electronic glass fiber contain a significant amount of boron oxide.The boron ions in the glass primarily exist in the form of boron-oxygen triangles and boron-oxygen tetrahedrons.Different coordination forms of boron ions have a considerable influence on the structure and performance of the glass.Therefore,it is essential to investigate the effects of boron coordination on glass structure and properties.Furthermore,it is necessary to establish a structure-activity relationship between glass structure and properties to provide theoretical guidance for practical applications.To address the aforementioned issues,this study employs the method of molecular dynamics simulation to analyze the short-range and medium-range structure of the glass.In addition,the elastic modulus is chosen as the main analysis parameter.To ensure the accuracy of the simulation results,the accuracy of the elastic modulus is validated with experimental data.By analyzing the boron coordination and combining other structure description factors,we determine the short-range structure parameters and medium-range structure parameters.We then perform fitting analysis with the elastic modulus to quantify the structure-property relationship between the short-range and medium-range structures and their relation to the elastic modulus.The research results are as follows:（1）The thermal history of the glass forming process is adjusted by varying the cooling rate from 0.1 K/ps to 1000 K/ps,with 13 groups of cooling rates set to simulate the actual glass forming thermal history.By comparing the density,elastic modulus,and Poisson’s ratio obtained from simulation and experiment,it was determined that the difference between simulated and experimental values is smallest at cooling rates of 0.5 K/ps and 1 K/ps.Additionally,five cooling rate sets closest to experimental values were selected for structural analysis.It was found that as the cooling rate increased,the[BO₄]（⁴B）content decreased from72%to 63%,while the[BO₃]（³B）content increased from 28%to 37%.Furthermore,the Q⁴content in the medium-range network structure decreased from 63.1%to 56.2%,and the ratio of non-bridging oxygen to tetrahedron coordinated cations（NBO/T）gradually increased from0.44 to 0.55.These changes led to gradual depolymerization of the glass network structure,resulting in decreases in density,elastic modulus,and Poisson’s ratio.By quantitatively analyzing the structure-property relationship with the elastic modulus,it was found that the short-range structural parameter,³B content,and the medium-range structural parameter,NBO/T,show the following relationship:=110.86-0.93and=4.61-69.19,respectively,with R² values of 0.89 and 0.83.These findings suggest that the short-range structural parameters are more effective at reflecting changes in elastic modulus than the medium-range structural parameters under varying thermal histories.（2）Based on the simulation results of different thermal histories,a cooling rate of 1 K/ps was selected for subsequent calculations.The effect of alkaline earth metal oxides on B coordination was studied by changing the B₂O₃/（CaO+Mg O）ratio.The PDF analysis of the short-range structure of the glass showed that the ionic bond length remained stable,but the intensity of the first peak changed with the composition.The content of ⁴B increased from 52%to 78%,and the content of ³B decreased from 48%to 22%through peak fitting of the B-O PDF.The overall analysis of the medium-range structure indicated that the Q⁴ content first increased and then decreased,while the Q³ and Q² contents first decreased and then increased.The medium-range structure parameter NBO/T decreased from 0.72 to 0.47 and then increased to0.62.The elastic modulus showed a trend of increasing first and then decreasing,reaching a maximum value of 82.17 GPa when B₂O₃/（CaO+Mg O）=0.2.The short-range and medium-range structural parameters were linearly analyzed with the elastic modulus,and the following structure-property relationships were obtained:=89.46-0.3,=96.19-31.81,with R² values of 0.92 and 0.82,respectively.It can be concluded that,under the condition of changing the B₂O₃/（CaO+Mg O）ratio,the short-range structural parameter ³B content can better reflect the change trend of elastic modulus.（3）In this study,the B₂O₃/Al₂O₃ ratio was adjusted while ensuring（B₂O₃+Al₂O₃）/（CaO+Mg O）=1 to investigate the effect of Al³⁺ions replacing B³⁺ions on boron coordination and changes in the structure and properties.It was found that the bond length in the short-range structure remained unchanged,but the ⁴B content obtained from the B-O PDF peak fitting increased from 61%to 71%,while the ³B content decreased from 39%to 29%.The analysis of the overall polymerization degree of the medium-range structure shows that the Q⁴content increased,while the Q³ and Q² contents decreased,and the medium-range structure parameter NBO/T reduced from 0.76 to 0.32.As B₂O₃ was replaced by Al₂O₃,the B³⁺ion sites in the glass network were replaced by Al³⁺ions,which reduced[BO₃]units,decreased the two-dimensional structure,and increased the degree of polymerization of the glass network.The elastic modulus of this group increased continuously and reached the maximum value of 86.12GPa when the B₂O₃ content was zero.Linear analysis of the short-range and medium-range structural parameters with the elastic modulus yielded the following structure-property relationships:=117.63-1.13,=95.93-29.53,with R² values of 0.95 and 0.92,respectively.Based on the structure-property relationships under the three conditions,it can be concluded that the short-range structural parameter ³B content is more suitable for reflecting the change trend of elastic modulus under specific thermal history and composition.（4）In this study,all short-range and medium-range structural parameters and their corresponding elastic moduli were analyzed together using a linear regression analysis.The obtained structure-property relationships were as follows:=95.05-0.46,=96.96-32.76,with R² values of 0.66 and 0.83,respectively.After comprehensive comparison,it was found that the short-range structural parameter of ³B content has relatively large limitations,but is more suitable to reflect the change trend of elastic modulus under specific thermal history and composition.On the other hand,the medium-range structural parameter NBO/T has a wider range of applications and is less affected by specific thermal history and composition.