Raman Spectroscopy Study of Ternary Glass Structure of CaO-SiO2-B2O3

CaO-SiO2-B2O3 terpolymer system is used as the basic raw material to synthesize other glass and melt. Doping Pr, Eu and other rare earth elements can get special performance glass materials with good luminous performance, CaO-SiO2-B2O3 terpolymer system is widely used in packaging substrate and dielectric materials. As an ideal substitute for fluorine, boron in borosilicate has become a new research hotspot of fluorine-free protective slag technology due to its advantages of economic cost and fluxing effect. Raman spectroscopy can be used for real-time observation and microsturcture analysis of materials, which provides a powerful means for the study of high-temperature melt and glass. In this work, CaO-SiO2-B2O3 ternary glass was prepared and Raman spectrum of glass was measured, which provided the necessary basis for the subsequent analysis of its properties, structure and the relationship between its components.


Introduction
The addition of B 2 O 3 can improve a variety of physical and chemical properties of CaO-SiO 2 glass.In addition, CaO-SiO 2 -B 2 O 3 ternary glass-ceramics have many advantages [1,2] , such as low synthesis temperature, easy preparation, excellent thermal stability, good mechanical properties, technological properties and optical properties, and low coefficient of thermal expansion.Therefore, it has a high use value and is more and more widely studied and used.CaO-SiO 2 -B 2 O 3 terpolymer system is commonly used as the basic raw material to synthesize other glass and melt, doping Pr, Eu and other rare earth elements can get special performance glass materials, such borate glass has good luminous performance, is widely used in packaging substrate and dielectric materials.
As an ideal substitute for fluorine, boron in borosilicate has become a new research hotspot of fluorine-free protective slag technology and is considered to have the most extensive application prospects.The research of borosilicate protective slag becomes very important.Yan et al. [3] studied the effects of B 2 O 3 on the heat transfer and crystallization behavior of CaO-Al 2 O 3 based protective slag after replacing CaF 2 with B 2 O 3 .They concluded that B 2 O 3 and CaF 2 had similar effects on heat transfer and crystallization capacity of protective slag, and B 2 O 3 had a stronger ability to promote heat transfer and inhibit crystallization.Guirong Li et al. [4] studied various properties of fluorine free slag containing B 2 O 3 , and designed a fluorine free slag that can meet suitable conventional steel grades and some special steel grades.The study concluded that B 2 O 3 had an obvious role in reducing the melting point of the protective slag.At the same time, it was found that the crystallization rate of the slag containing B 2 O 3 was low, which was conducive to the formation of glass phase of the slag.Yang et al. [5] studied the crystallization behavior of flux-free crystallizer flux with a mass ratio of CaO/SiO 2 of 0.9-1.2, and the results showed that the crystallinity of the solvent increased with the increase of the mass ratio of CaO/SiO 2 .It was found that the content of Ca 11 Si 4 B 2 O 22 phase increased with the increase of CaO/ SiO 2 mass ratio by XRD and SEM.According to domestic and foreign literature reports, Chen Zhang et al. [6] used B 2 O 3 instead of CaF 2 to develop corresponding fluorine-free protective slag and conducted experiments on slab continuous casting process.The experimental results showed that the fluorine-free slag can be consistent with the traditional fluorine-containing slag in melting point, viscosity and other properties.With the reduce of the crystallization capacity, it was suitable for low carbon steel with low crystallization requirements.For the application of medium carbon steel, it was also necessary to improve the crystallization property of the slag.
Raman spectroscopy can be used for real-time observation and microstructure analysis of materials, which provides a powerful means for the study of high-temperature melt and glass.In this work, CaO-SiO 2 -B 2 O 3 ternary glass was prepared and Raman spectrum of glass was measured, which provided the necessary basis for the subsequent analysis of its properties, structure and the relationship between its components.

Experiment
In this experiment, pure CaO, SiO 2 , and B 2 O 3 powder was analyzed by proportional weighing (the ratio of CaO and SiO 2 is 1: 1).Firstly, appropriate amount of alcohol was adding in the samples, and the samples were placed in the agate mortar for 2 hours to fully grind it to mix evenly.Secondly, the samples were put into the Muffle furnace to heat up to 1500℃ melting state.Thirdly, the samples had been kept warm for 30 minutes, and finally the glass samples were prepared through slow water cooling.The glass samples were ground into powder and detected by Raman spectroscopy at room temperature.The composition ratio table of each sample was shown in Table 1 below.In the experiment, the ultra-high temperature pneumatic suspension laser heating picosecond Raman spectroscopy (produced by Time-gate Company of Finland) was used as testing equipment and combined with the third-generation ICCD nanosecond Raman spectroscopy detector [7] .

Experiment results and analysis
In figure 1, it showed that the Raman spectra of different CaO-SiO 2 -B 2 O 3 ternary glass formed after adding different contents of B 2 O 3 to glass with a weighting ratio of CaO: SiO 2 1:1.And CS-6B, CS-8B and CS-10B represented B 2 O 3 with a mass percentage of 6,8 and 10, respectively.2.
Table 2 The assignment of the major Raman-active vibrational modes for CaO-SiO The high wave-number region of CaO-SiO 2 -B 2 O 3 ternary glass was divided into three regions.The vibration in the low wave-number region of Raman spectral displacement of 343 cm -1 is mainly attributed to Ca-O stretching vibration.The vibration peak in the middle wave-number region of 646 cm -1 was Si-O-Si symmetric bending vibratio.The high wave-number region presented an envelope line, which was mainly the non-bridged oxygen symmetric stretching vibration in silica tetrahedrons (Qi) containing different bridged oxygen numbers, including island, dimer, chain, ring and layered silicate clusters.This is basically consistent with the conclusion obtained by Gong et al. [8] .It can be seen that the vibration corresponding to the characteristic Raman peak of CaO-SiO 2 -B 2 O 3 ternary glass system is mainly the vibration of Ca-O bond, Si-O-Si and silica tetrahedron.In figure 2, it was the deconvolution of calibrated spectrum of CaO-SiO 2 -B 2 O 3 glass after the peak of 800-1160 cm -1 band in the high wave number region.With the continuous addition of B 2 O 3 , it could be observed that the positions of various Qi do not change significantly.The relative area ratios of Q 2 ' /Q 2 and Q 3 /Q 2 increased with the increase of B 2 O 3 content, indicating that the total average bridge oxygen number increases and the degree of networking of silica tetrahedron increases significantly.At the same time, the relative area ratio of Q 0 /Q 2 and Q 1 /Q 2 had little change, which was different from the related research results of melt.Therefore, the increase of B 2 O 3 was mainly due to the increase in the relative content of silica tetrahedrons (Qi) with high bridge oxygen number.In addition, it was difficult to distinguish the structural information of [BO 3 ] and [BO 4 ] from the experimental results, mainly because of the overall content small and the distribution dispersed.And it also indicated that with the increase of B 2 O 3 , the bridge oxygen linking the silicon oxygen tetrahedron would form more Si-O-B connection modes.

Result
In this paper, the Raman spectra of CaO-SiO 2 -B 2 O 3 ternary glass had been tested by ultra-high temperature pneumatic suspension laser heated picosecond Raman spectrum testing equipment and the third generation ICCD nanosecond Raman detector.The major Raman-active vibrational modes and the deconvolution of calibrated spectrum of CaO-SiO 2 -B 2 O 3 glass after the peak of 800-1160 cm -1 band in the high wave number region were studied.It was resulted that the vibration corresponding to the characteristic Raman peak of CaO-SiO 2 -B 2 O 3 ternary glass system is mainly the vibration of Ca-O bond, Si-O-Si and silica tetrahedron.With the increase of B 2 O 3 , more Si-O-B connections were formed.In this work, CaO-SiO 2 -B 2 O 3 ternary glass was prepared and Raman spectrum of glass was measured, which provided the necessary basis for the subsequent analysis of its properties, structure and the relationship between its components.

Figure 2
Figure 2 The deconvolution of calibrated spectrum of CaO-SiO 2 -B 2 O 3 glass In figure 2, it was the deconvolution of calibrated spectrum of CaO-SiO 2 -B 2 O 3 glass after the peak of 800-1160 cm -1 band in the high wave number region.With the continuous addition of B 2 O 3 , it could be observed that the positions of various Qi do not change significantly.The relative area ratios of Q 2

Table 1
The composition of glass sample of ternary glass CaO-SiO 2 -B 2 O 3