乙 (C2D6) 在气/液态和超临界状态中的热密度波动和多态相变
Vitaliy Pipich1, Joachim Kohlbrecher2, Dietmar Schwahn3
1Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz-Zentrum (MLZ), Forschungszentrum Jülich GmbH, Garching D-85747, Germany.
The journal of physical chemistry. B
|May 15, 2024
概括
微角中子散射揭示了液体乙-d6 (C2D6) 的通用相位行为. 维多姆线以上的滴滴形成表明了多态相变,挑战了以前的动态解释.
科学领域:
- 热力学是一种热力学.
- 材料科学 材料科学 材料科学
- 物理化学 物理化学
背景情况:
- 了解临界点附近的液相行为对于基础物理和化学工程至关重要.
- 以前对二氧化碳的研究表明了普遍的液态行为,但需要对其他分子液体进行实验验证.
研究的目的:
- 为了研究液体乙-d6 (C2D6) 在其临界点以下和以上的相位行为.
- 使用小角度中子散射 (SANS) 识别和描述气液,维多姆和弗伦克尔线.
- 探索超临界状态下滴滴形成的性质及其与密度波动的关系.
主要方法:
- 采用小角度中子散射 (SANS) 来研究C2D6相位过渡.
- 实验在10-45°C的温度范围和20-126bar的压力范围进行.
- 分析了散射数据以确定热密度波动的相关长度.
主要成果:
- 确定了天然气液体和Widom线路.
- 在气液线上方和超临界区域观察到来自C2D6滴滴的额外散射,定义了Frenkel线.
- 在临界点和Widom线上的相关长度 (ξ) 发现为20-35 Å,而滴滴半径为60-80 Å.
- 滴滴形成被抑制,直到 ξ下降到10 Å以下,大约在Widom线上方10 bar.
结论:
- 观察到的C2D6的相位行为与单分子液体的普遍行为一致.
- 弗伦克尔直线被解释为多态相变的下极限,而不仅仅是动态过程极限.
- 远程密度波动在抑制临界点附近的滴滴形成方面发挥着重要作用.
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