Glass - Back to the Future!

Presenting Author:
Rikiya Kado

article posted 6 April 2016

Rikiya Kado has a masters degree from Tokyo Institute of Technology and is currently there as a PhD candidate.

Structural Alteration of Sodium-Aluminosilicate Glass Batch Using High-Temperature Raman Spectroscopy

Rikiya Kado*(1), Tetsuo Kishi(1), Tetsuji Yano(1), Koichi Shiraki(2),
Yukihito Nagashima(2), Chihiro Sakai(2) & Koichi Sakaguchi(2)
(1) Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8550 Japan
(2) Nippon Sheet Glass Co., Ltd. Itami, Hyogo 664-8520 Japan

In glass melting process, homogeneous glass melt is formed from the batch via various chemical and physical processes; dehydration, solid-state reactions between raw material particles, forming melt phases, atomic diffusion and mass flow etc. This study pursues the alternation of materials from glass batch to molten glass in atomic level using Raman spectroscopy. The target composition is sodium-aluminosilicate glass system shown by 33Na2OxAl2O3(67-x)SiO2 in mol%, where x=0, 4, 8, 12 and 16, and the sample glasses are labeled as NAS00x.
High-temperature Raman spectra are collected from the batch composed of Na2CO3, Al2O3 (alpha-alumina), SiO2(quartz sand) in a platinum crucible on heating from room temperature to 1400C at a rate of 5 K/min. Nanosecond Q-switched SHG Nd:YAG laser (lamda=532 nm) is used as an excitation source.

Figure 1. High-temperature Raman spectra of NAS004 from room temperature to 1400C.

Figure 1 shows some examples of the Raman spectra collected from NAS004 sample on heating up to 1400C. Respective spectral intensities are normalized by the maximum peak in each spectrum. From low frequency side, SiOSi and CO stretching vibration bands in silica sand and sodium carbonate are found at 470 and 1080 cm, respectively, at T<800C. When T>800C, structural alternations are clearly found as shown in Figure 2; SiO stretching in Na2SiO3 appears at 970 cm-1 accompanying with the increasing band around 600 cm-1, meaning the chemical reaction between quartz and Na2CO3 starts to proceed at around 875C. All carbonates decompose below 900C, and another SiO band of Na2Si2O5 liquid phase appears at around 1050 cm-1.

Figure 2. Detail of Raman spectra of NAS004 in the reaction temperature zone from 800 to 1000C.

Quantitative XRD analysis reveals that 17% and 87% of initial quartz and alumina still remain in batch, respectively, and the glass melt with the apparent composition of 34Na2O14Al2O352SiO2 (in mol%) is generated at 1200C. Even when the temperature reaches 1400C without any trace of quartz and alumina, the spectrum does not agree with that of homogeneously melted glass at the same temperature. Further reaction time is necessary to attain equilibrium structure at 1400C. The effect of Al2O3 on the structural alternation of batch is discussed from the analysis of the collected Raman spectra.