Boron boride glass boron anomalies

Boron anomaly refers to the borate or borosilicate glass, with the increase in B2O3 content, some properties of the phenomenon of extreme values. This is caused by the transformation of triangular [BO3] to tetrahedral [BO4], where [BO3] is intelligent to form a layered network, while [BO4] can participate in the framework network with [SiO4] to enhance the stability of the network. The transformation process is mainly affected by two factors: ① the number of free oxygen, triangular [BO3] only obtained free oxygen can be converted into tetrahedron [BO4]; ② [SiO4] number, tetrahedron [SiO4] isolation. These two factors can cause boron anomaly, which can be measured by Na2O / B2O3 and [BO4] / [SiO4] respectively. The former corresponds to Na2O-B2O3- SiO2 glass, which corresponds to alkali-free low-borosilicate borate glass.
For Na2O-B2O3-SiO2 glass, when Na2O / B2O3> 1, there is enough free oxygen in the glass, and the added B2O3 can be changed from triangular to tetrahedron. The density and strength of the glass network at this stage will increase with B2O3 Rise. Nature is reflected in the density, refractive index and chemical stability of the rise of a coefficient of thermal expansion. However, when Na2O / B2O3≤1, part of the B2O3 has been unable to get free oxygen, only triangular [BO3] form exists in the network, which undermines the network structure, so that a solid, close unified network is relatively reduced , The above properties will change with the increase of B2O3 content in the opposite direction. The opposite direction is at Na2O / B2O3 = 1. In the case of alkali-free low-borosilicate borate glass, alkaline earth metal oxides provide sufficient free oxygen, but the SiO2 content of the isolation is insufficient. This type of glass will increase with the increase of B2O3 content, [BO4] / [SiO4] increases, and the nature of the changes in the extreme value.

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