| Aluminosilicate glass has high strength,high hardness and good mechanical properties.It is widely used in electronic information industry.With the development of technology,electronic products are developing towards miniaturization and lightening,which puts forward higher requirements for electronic information glass.We aim at the problems of high viscosity,high density and insufficient hardness of aluminosilicate glass,etc.On one hand,because B2O3 can reduce the viscosity of glass and form tetrahedron[BO4]into the glass network structure,B2O3 is introduced into aluminosilicate to study its effects on the structure and properties of glass;on the other hand,the mechanical properties of glass nanofibers are studied,which is helpful to understand the fracture mechanism and surface properties of glass.The effects of B2O3 on the structure and properties of aluminosilicate glasses were studied.14Na20·xB2O3·9Al2O3·(77-x)·SiO2(x=0,1,3,5,7)series glasses were prepared by melt cooling method.The structural changes were characterized by infrared spectroscopy,Raman spectroscopy and nuclear magnetic resonance.The results showed that Al2O3 almost formed tetrahedron[AlO4],basically no[5]Al and[6]Al.Some B2O3 would be converted into[BO4]tetrahedrons and entered the silicon-oxygen network structure.These[BO4]tetrahedrons existed mainly in[BO4](IB,3Si)structure.The remaining B2O3 were all[BO3]triangles,and most of them were annular.Overall,with the increase of B2O3,the damage to the glass network had been reduced.The DSC(differential scanning calorimeter)results showed that the temperature of the strain points of the series glass were above 570 ℃,and glasses had good technological properties.The relationship between the density,thermal expansion coefficient,microhardness and B2O3 content of a series of glasses was studied.The results showed that when 3mol%B2O3 was added to the aluminosilicate glass,the glass density was the smallest,the thermal expansion coefficient was moderate and the hardness was relatively high.The glass with 3 mol%B2O3 content was chemically strengthened at 360-420 ℃for 4-8h.The effects of boron oxide addition on microhardness,surface compressive stress and stress layer depth were studied with the samples without B2O3 as reference.It was found that B2O3 can significantly increase the surface compressive stress and the depth of stress layer,and ultimately increased the hardness of glass under the same strengthening conditions.In this paper,aluminum borosilicate glass fibers with diameters of tens of nanometers were also studied,and tensile tests were carried out through in situ transmission electron microscopy.With the decrease of the diameter of nanofibers,the tensile strength of nanofibers increased gradually,and reached 4.37 GPa at 18 nm.In addition,during the tensile process,the fracture sites of these nanofibers showed obvious necking phenomenon,and the elongation increased significantly with the decrease of fiber diameter,gradually showing some characteristics of ductile fracture.EDS(energy dispersive spectroscopy)scanning showed that a small number of oxygen vacancies existed in nanofibers.The tensile process made part of the original bridge oxygen become non-bridge oxygen.Due to the unique "bond conversion" mechanism,the broken bond moved within a certain range,showing fluidity.The smaller the fiber diameter was,the larger the percentage of the surface to the whole fiber mass was.The more significant the plastic flow was,that is,the elongation increased.In addition,the "bond conversion" process was equivalent to "repairing" a part of the broken bond,reducing the stress concentration in the tensile area,so the strength of the fiber can be improved. |
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