EAGER: Raman Analysis of Thermophoretically Sampled Soot Particulate

碳烟是指主要由碳组成的小颗粒，是不完全燃烧过程的结果。碳烟的形成对能量的产生既有积极的作用(热颗粒辐射是锅炉内主要的传热机制)，也有负面的作用(在同一锅炉中，碳烟可能覆盖炉壁，而碳烟颗粒撞击到商用航空发动机涡轮叶片上会导致磨损)。煤烟在环境中也很重要，因为它增加了城市地区的死亡率，并促进了气候变化。在实验室，我们对煤烟形成的了解来自这个过程开始附近(通过测量小前体分子的浓度)和接近结束时(通过火焰中的光学测量和/或收集的颗粒物的微观分析)的测量。因此，有几个基本的问题没有得到解答：从平面分子到三维粒子的转变机制是什么？最年轻的颗粒中碳键的性质是什么？这个项目的目标是通过对从几种类型的火焰中采样的颗粒的研究来回答这些问题。通过了解火焰中碳烟形成和破坏的详细化学和物理过程，我们实现了燃烧系统工程，可以增强火焰中碳烟的积极影响(热传递)，同时将有害的健康影响和环境影响降至最低。该项目的首席研究员20多年来一直是烟尘形成科学的领导者。在20世纪80年代，他提出了烟尘颗粒是由扁平的、极其稳定的分子聚集体组成的，这种分子被称为多核芳香烃(PAH)。他的计算表明，将多环芳烃簇团聚集在一起的结合能足够强，即使在火焰温度下也能存活。为了证明这一假设，在这个项目中，我们使用拉曼光谱对颗粒进行了研究，在拉曼光谱中，激光从碳颗粒中散射出来，提供了关于颗粒的光学和电子性质的信息，然后可以用这些信息来推断结构和形态。对从实验室火焰中快速提取的颗粒进行分析，这些颗粒模拟了实际燃烧设备中发现的各种条件。广泛的影响：除了上述项目的技术动机外，该奖项的另一个成果将是在广州大学化学系培养一名博士生。华盛顿大学的博士项目比大多数美国的博士化学项目都要小。然而，它的规模一直是吸引顶尖学生的一个特征，他们正在寻找那里可获得的个人关注类型。它的小规模促进了跨学科研究，将化学项目与乔治华盛顿大学、美国其他学术校园和实验室以及世界各地合作机构的共同兴趣的科学家和工程师联系起来。这一战略在确保他们的毕业生在公共和私营部门找到工作方面一直是一个成功的配方。在理工科研究生项目中，乔治华盛顿大学是美国少数几所排名靠前的大学之一。与这一事实相一致的是，化学系的研究生课程和PI的实验室以女性为主。

1142284MillerIntellectual Merit: Soot is the term given to small particles that are mostly composed of carbon, and that result from incomplete combustion processes. Soot formation plays both positive roles (radiation from hot particles is the dominant mechanism for heat transfer in boilers) and negative (in the same boilers, soot may coat furnace walls and soot particle impingement on the turbine blades of a commercial airline engine leads to wear) in energy generation. Soot is also important in the environment as it increases mortality in urban areas and contributes to climate change.In the laboratory, what we understand about soot formation comes from measurements near the beginning (through the measurements of concentrations of small precursor molecules) and near the end (through optical measurements in flames and/or microscopic analysis of collected particulate matter) of the process. As a consequence, there are several fundamental questions that have gone unanswered: What is the mechanism for the transition from flat, planar molecules to three-dimensional particles? What is the nature of the carbon bonding in the youngest particles? The goal of this project is to answer these questions through a study of particles sampled from several types of flames. By understanding the detailed chemistry and physics of soot formation and destruction in flames, we enable combustion system engineering that can enhance the positive effects of soot in flames (heat transfer) and while minimizing deleterious heath effects and environmental impacts. The project's principal investigator has been a leader in the science of soot formation for more than 20 years. In the 1980s, he proposed that soot particles are composed of aggregates of flat, and extremely stable, molecules known as polynuclear aromatic hydrocarbons (PAH). His calculations suggest that the binding energy that holds clusters of PAH together is strong enough for them to survive even at flame temperatures. To prove this hypotheses, in this project particles are studied using Raman spectroscopy, in which laser light is "scattered" from the carbon particles, providing information about the optical and electronic properties of the particles, which can then be used to infer structure and morphology. Analysis is performed on particles that are rapidly extracted from laboratory flames that mimic a wide range of conditions found in practical combustion devices.Broader Impacts: In addition to the technical motivation for the project described above, an additional outcome of this award will be the education of a doctoral student in the Chemistry Department of GWU. The GWU Ph.D. program is smaller than most US doctoral chemistry programs. However, its size has been an attribute in attracting top-quality students who are looking for the type of individual attention that is available there. Its small size has catalyzed interdisciplinary research that links the chemistry program with scientists and engineers with mutual interests at GW, at other US academic campuses and laboratories, and at partner institutions throughout the world. This strategy has been a successful recipe in insuring that their graduates find employment in both the public and private sectors. George Washington University is ranked among the top few universities in the country in the population of women in science and engineering graduate programs. In line with this fact, the chemistry department's graduate program and the PI's lab have majority female populations.