16:15 〜 16:30
[MIS18-07] パルス電子線を利用した成長条件の周期変動による結晶成長の促進
キーワード：透過電子顕微鏡、ドロマイト
Liquid cell transmission electron microscopy is a technique in which an aqueous solution is sandwiched between membranes to allow in situ observation of phenomena occurring in the solution in nano-scale using electrons as a probe. Because the environment of the solution is changed by the radiolysis of water due to electron beam irradiation, lowering the electron dose or inducing nucleation with electron beams have been conducted for the studies. In contrast, we have applied in-situ laboratory experiments of crystallization with controlled supersaturation (growth conditions) by actively utilizing the radiolysis of water by electron beams. Here, we present the results of our application to dolomite.
Dolomite (CaMg(CO3)2) is a naturally abundant carbonate mineral. However, dolomite could not be grown experimentally near ambient temperature and pressure, and natural dolomite deposition was not understood. This has been a longstanding mystery known as the "dolomite problem."
Conventional discussions of mineral formation have been based on experimental data and simulations obtained under constant growth conditions. In contrast, Sun and his colleagues used computer simulations to periodically vary the degree of saturation level so that dolomite repeatedly undergoes growth and dissolution [1]. The results suggest that the growth rate of dolomite is accelerated by up to seven orders of magnitude. To reproduce this in laboratory experiments, the growth of dolomite in liquid was observed in situ by periodically changing the growth and dissolution conditions with pulsed electron beam irradiation using a transmission electron microscope. Dolomite crystals grew 60-170 nm after 3,840 cyclic supersaturation changes using pulsed electron beam irradiation. As a result, the growth rate of dolomite was successfully increased by several orders of magnitude. Such cyclic changes in growth conditions, which occur universally in nature due to “rainfall and clear skies” and “temperature differences between day and night”, are expected to provide new guidelines for discussions on the formation mechanisms of other minerals. In addition, periodic changes in growth conditions in the crystals formation are expected to lead to faster and more efficient material synthesis.
This work was partly supported by Grant in-Aids for Scientific Research (S) from KAKENHI 20H05657. I thank J. Kawano for providing a dolomite crystal, T. Yamazaki for solution preparation, and J. Kim and W. Sun for insights based on their theoretical work.
[1] J. Kim, Y. Kimura, B. Puchala, T. Yamazaki, U. Becker, W. Sun, Dissolution enables dolomite crystal growth near ambient conditions, Science, 382 (2023) 915-920. DOI: 10.1126/science.adi3690
Dolomite (CaMg(CO3)2) is a naturally abundant carbonate mineral. However, dolomite could not be grown experimentally near ambient temperature and pressure, and natural dolomite deposition was not understood. This has been a longstanding mystery known as the "dolomite problem."
Conventional discussions of mineral formation have been based on experimental data and simulations obtained under constant growth conditions. In contrast, Sun and his colleagues used computer simulations to periodically vary the degree of saturation level so that dolomite repeatedly undergoes growth and dissolution [1]. The results suggest that the growth rate of dolomite is accelerated by up to seven orders of magnitude. To reproduce this in laboratory experiments, the growth of dolomite in liquid was observed in situ by periodically changing the growth and dissolution conditions with pulsed electron beam irradiation using a transmission electron microscope. Dolomite crystals grew 60-170 nm after 3,840 cyclic supersaturation changes using pulsed electron beam irradiation. As a result, the growth rate of dolomite was successfully increased by several orders of magnitude. Such cyclic changes in growth conditions, which occur universally in nature due to “rainfall and clear skies” and “temperature differences between day and night”, are expected to provide new guidelines for discussions on the formation mechanisms of other minerals. In addition, periodic changes in growth conditions in the crystals formation are expected to lead to faster and more efficient material synthesis.
This work was partly supported by Grant in-Aids for Scientific Research (S) from KAKENHI 20H05657. I thank J. Kawano for providing a dolomite crystal, T. Yamazaki for solution preparation, and J. Kim and W. Sun for insights based on their theoretical work.
[1] J. Kim, Y. Kimura, B. Puchala, T. Yamazaki, U. Becker, W. Sun, Dissolution enables dolomite crystal growth near ambient conditions, Science, 382 (2023) 915-920. DOI: 10.1126/science.adi3690