メソファース は ゼオライト の 核 と ポリモルフ の 選択 に 役割 を 果たす か
Abhinaw Kumar1, Andrew H Nguyen1, Rita Okumu2
1Department of Chemistry , The University of Utah , 315 South 1400 East , Salt Lake City , Utah 84112-0850 , United States.
Journal of the American Chemical Society
|November 1, 2018
まとめ
以前に理解されなかったメタステーブルメソファースは,ゼオライト結晶の核形成とポリモルフの選択を助けることが判明した. これらの中間構造はエネルギーバリアを低くし,材料科学における特定のゼオライト構造の形成を導く.
科学分野:
- 材料科学
- 化学工学
- コンピュータ化学
背景:
- ゼオライトとメソポラスシリカは,触媒,ガス貯蔵,分離に不可欠な多孔性物質です.
- 構造指向剤 (SDA) はゼオライト結晶形成を制御するが,その核形成とポリモルフ選択における正確な役割は完全に理解されていない.
- メソポラスシリカ形成は液晶メソフェーズによってテンプレートされ,同様の現象がゼオライト合成に影響を与える可能性があることを示唆しています.
研究 の 目的:
- 分子ダイナミクスのシミュレーションを用いて,ゼオリート結晶の核形成とポリモルフ選択におけるメソファースの役割を調査する.
- SDAとテトラコーディネート結晶を好むネットワーク元 (T) を含むモデルシステムの相行動を探求する.
主な方法:
- 自発的なゼオライト核形成のための効率的なシリカポテンシャルがないため,ネットワーク前 (水とシリコンのスティリンガー=ウェバーモデル) の単純化されたモデルで分子動力学シミュレーションを使用した.
- SDA と T ネットワークの混合の相図を調査した.
- シグマ-2 (SGT) を含む様々なゼオライト構造の核形成経路を分析した.
主要な成果:
- モデルシステムは,sIIクラスレートと少なくとも6つのゼオライトを含む複雑な相図を生成した.
- シグマ2 (SGT) の核化はメソフェーズによって促進されなかった.
- 他の5つの研究されたゼオライトの核形成は,核形成の障壁を軽減し,ポリモルフの選択を導いたメタステーブルメソフェーズによって有意に助けられました.
結論:
- メタステーブルメソファースは,特定のゼオライトの核形成とポリモルフ選択を促進する上で重要な役割を果たします.
- これらの発見は,シリケート-SDA混合物の実験的証拠によって支持され,ゼオライト合成における中間メソフェーズの重要性を強調しています.
- この研究は,SDA模型のゼオライト形成を理解するための計算的枠組みを提供します.
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