Thermal Conductivity of Sodium Silicate Glasses and Melts: Contribution of Diffusive and Propagative Vibration Modes

Sohei Sukenaga,Sakiko Kawanishi,Koji Ohara,Hiroki Yamada,Koji Inoue,Hiromichi Ohta,Toru Wakihara,Takahiko Endo,Tsuyoshi Nishi,Hiroyuki Shibata

doi:10.3389/fmats.2021.753746

Abstract

The thermal conductivity of silicate melts and glasses is an important physical property for understanding the temperature distribution in high-temperature metallurgical processes; however, the mechanism of heat conduction in these non-crystalline materials remains unclear. Two types of vibration modes must be considered to understand the mechanism of heat conduction, namely, propagative and diffusive vibration modes. In the present study, we carefully derived the thermal conductivity of pure silica and sodium disilicate glasses and melts, and estimated the contribution of the diffusive vibration mode using a recently developed model. The results indicated that the diffusive vibration mode was not dominant in the silicate non-crystalline materials, whereas the propagative vibration mode (i.e., phonons) was dominant in the heat conduction of silicate glasses and melts, which is in contrast with borate glasses.

Highlights

The thermal conductivity of silicate melts and glasses is one of the least understood properties among the physical properties of non-crystalline materials, despite its importance in the design of industrial plants and processes at elevated temperatures (Glaser and Sichen, 2013; Pilon et al, 2014; Wang and Sohn, 2020; Li et al, 2021)
The results indicated that the diffusive vibration mode was not dominant in the silicate non-crystalline materials, whereas the propagative vibration mode was dominant in the heat conduction of silicate glasses and melts, which is in contrast with borate glasses
It has been found that both propagative and diffusive modes contribute to the thermal conductivity of disordered materials (Agne et al, 2018; Sørensen et al, 2020; Sørensen et al, 2021)

Summary

Introduction

The thermal conductivity of silicate melts and glasses is one of the least understood properties among the physical properties of non-crystalline materials, despite its importance in the design of industrial plants and processes at elevated temperatures (such as glass-making and metallurgical processes) (Glaser and Sichen, 2013; Pilon et al, 2014; Wang and Sohn, 2020; Li et al, 2021). The contribution of the diffusive vibration mode has not been investigated for silicate systems over a wide temperature range from room temperature (∼300 K) to elevated temperatures higher than their liquidus. The thermal conductivity of silicate glasses and melts has been associated with the MFP of phonons for a long time, it remains unclear whether this classical concept is applicable to non-crystalline silicate materials at elevated temperatures. To carefully consider the contribution of the two types of vibration modes, the physical properties of the target sample (i.e., the density, heat capacity, and velocity of sound) are required. We carefully derived the thermal conductivity of the NS2 melt from the reported thermal effusivity, density and heat capacity. The contribution of the diffusive and propagative vibration modes to the thermal conductivity was investigated

Methods

Results

Discussion

Conclusion