Collaborative Research: Why Does Oxidation Improve Freezing? Using Laboratory Measurements and Molecular Simulations to Investigate Heterogeneous Ice Nucleation on Carbon Surfaces

合作研究：为什么氧化可以改善冷冻？

• 批准号: 1309854
• 负责人: Sarah Brooks
• 金额: $ 22万
• 依托单位: Texas A&M University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1309854&HistoricalAwards=false
• 关键词: Collaborative; Research; Why; Does; Oxidation

The Environmental Chemical Sciences (ECS) program of the Division of Chemistry supports the collaborative research efforts of Sarah D. Brooks (Texas A&M University) and Valeria Molinero (University of Utah) to investigate the heterogeneous nucleation of ice on model organic surfaces and soot using an unprecedented combination of laboratory measurements and molecular simulations. The primary objective of this project is to evaluate which specific chemical and physical properties of carbonaceous surfaces modulate their ability to act as ice nuclei for water freezing. The second objective is to elucidate the heterogeneous mechanisms of formation of ice on these surfaces. Previous laboratory results suggest that oxidation processes representative of atmospheric aging improve the ice nucleating ability of aerosols, facilitating contact freezing at warmer temperatures. Oxidation, however, alters carbon surfaces not only by incorporation of hydrophilic groups but also through a modification of the nanostructure of the surface. Laboratory experiments will be conducted to determine the prerequisite temperature and relative humidity required for immersion and deposition freezing on hydrocarbon and oxidized hydrocarbon particles. Simulations will be used to determine the effect of nanostructure, chemical modifications, and hydrophilicity of the surface on the freezing temperatures, the heterogeneous mechanism of formation of ice, and the size and structure of the critical ice embryo. Abundant in the atmosphere due to anthropogenic and biogenic sources, carbonaceous particles display a wide range of effectiveness in promoting the nucleation of ice in clouds. This variability causes major uncertainties in predictions of the effect of aerosols on climate. The project will lead to an improved understanding of the phase of water in the atmosphere and assist in the parameterization of global climate models. A workshop to train high school teachers in the use of freely available molecular visualization software to develop classroom activities that complement and enhance the high-school curriculum will be developed at the University of Utah. The molecular visualization tools and the simulations that display the formation of ice will be incorporated into undergraduate courses taught by the PIs.

化学系的环境化学科学（ECS）计划支持Sarah D. Brooks（Texas A＆M University）和Valeria Molinero（犹他大学）的合作研究工作，以使用未经预言的实验室测量和烟雾组合进行实验室测量和烟雾组合。该项目的主要目的是评估碳质表面的哪种特异性化学和物理性质调节其充当水冷冻冰核的能力。第二个目标是阐明这些表面上冰形成的异质机制。先前的实验室结果表明，代表大气老化的氧化过程可以提高气溶胶的冰核能力，从而促进温度较高的接触冻结。然而，氧化不仅可以通过掺入亲水性基团，而且通过修饰表面的纳米结构来改变碳表面。将进行实验室实验，以确定浸入碳氢化合物和氧化的烃颗粒上所需的先决条件温度和相对湿度。模拟将用于确定纳米结构，化学修饰和表面的亲水性对冰冻温度，冰形成的异质机理以及临界冰胚胎的大小和结构的影响。由于人为和生物源，在大气中丰富，碳质颗粒在促进云中冰的成核方面具有广泛的有效性。这种可变性会导致对气溶胶对气候作用的预测的主要不确定性。该项目将导致对大气中水相的了解，并有助于全球气候模型的参数化。将在犹他大学开发一个培训高中教师的研讨会，用于使用免费的分子可视化软件来开发教室活动，以补充和增强高中课程。分子可视化工具和显示冰形成的模拟将纳入PIS教授的本科课程中。