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 33Na2
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 Na2
(quartz sand) in a platinum crucible on heating from room temperature to 1400°C 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 1400°C.
Figure 1 shows some examples of the Raman spectra collected from NAS004 sample on heating up to 1400°C. Respective spectral intensities are normalized by the maximum peak in each spectrum. From low frequency side, Si–O–Si and C–O stretching vibration bands in silica sand and sodium carbonate are found at 470 and 1080 cm, respectively, at T<800°C. When T>800°C, structural alternations are clearly found as shown in Figure 2; Si–O 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 875°C. All carbonates decompose below 900°C, and another Si–O 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 1000°C.
Quantitative XRD analysis reveals that 1·7% and 8·7% of initial quartz and alumina still remain in batch, respectively, and the glass melt with the apparent composition of 34Na2O–14Al2O3–52SiO2 (in mol%) is generated at 1200°C. Even when the temperature reaches 1400°C 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 1400°C. The effect of Al2O3 on the structural alternation of batch is discussed from the analysis of the collected Raman spectra.