New Condensed-Phase Approaches for Soot Formation, Aging, and Burnout

这个关于燃烧产生的煤烟的项目主要关注火焰中存在的复杂碳质凝聚相，使用的概念和工具是为P.I.中的其他碳材料开发的的实验室。新的工具包括直接测量高温和短时间下的动态活性位点损失，使用分布式活化能公式来理解和模拟反应性损失（老化）和氧化，以及使用原子对势模拟来研究更高的多环芳烃（PAH）相互作用。为了解决表观幂律动力学领域长期存在的矛盾，统一高低温下的动力学数据库，新的分布点动力学模型被应用于烟尘氧化。一个关键的建模概念是将凝聚相描述为具有可变纳米结构迁移率的聚合玻璃相，而不是固体或液体相，这些迁移率控制着从聚并到团聚的转变。该项目包括一项新的实验任务，使用在P.I.合成的新的富含芳香的碳/氢纳米颗粒作为第一个火焰中年轻烟灰颗粒的物理化学模型。燃烧产生的烟尘是一种可吸入的超细颗粒物质，携带已知的致癌物和诱变剂，因此是一种主要的大气污染物。对于美国汽车制造商来说，减少柴油发动机的烟尘排放是一个特别具有挑战性的目标。减少车辆和熔炉烟尘排放的尝试集中在控制火焰化学和结构或捕获微粒和随后的低温氧化。对于这两种类型的煤烟控制措施的设计，需要更好地了解煤烟颗粒本身的结构、性质和反应性，从它们在火焰早期阶段作为可识别的凝聚有机物质首次被检测到它们最终作为完全碳化和部分氧化纳米颗粒的分形聚集体释放。本项目应用最现代的碳科学方法来理解和表征烟灰形成、演化和燃尽的各个阶段。

This project on combustion-generated soot focuses on the complex carbonaceous condensed phases present in flames using concepts and tools developed for other carbon materials in the P.I.'s laboratory. The new tools include direct measurement of dynamic active-site loss at high temperatures and short times, the use of distributed activation energy formulations to understand and model both reactivity loss (aging) and oxidation, and the use of atomic pair-potential simulations to investigate higher polycyclic aromatic hydrocarbon (PAH) interactions. New distributed-site kinetic models are being applied to soot oxidation to resolve the long-standing paradox in the field of apparent power-law kinetics and to unify the kinetic database at high and low temperatures. A key modeling concept is the description of the condensed phases not as solids or liquids, but as polymeric glassy phases with variable nanostructural mobility that governs the transition from coalescence to agglomeration. The project includes a novel experimental task employing new aromatic-rich C/H nanoparticles synthesized in the P.I.'s laboratory as the first physicochemical models for young soot particles in flames. Combustion-generated soot is a respirable, ultrafine particulate material that carries known carcinogens and mutagens and is thus a key atmospheric pollutant. The reduction of soot emissions from diesel engines is a particularly challenging goal for U.S. vehicle manufacturers. Attempts to reduce soot emission from vehicles and furnaces focus on control of the flame chemistry and structure or on capture of particulates and subsequent low-temperature oxidation. For the design of both types of soot-control measures, a better understanding is needed of the structure, properties, and reactivity of the soot particles themselves from their first detection as recognizable condensed organic matter in the early stages of flames to their final release as fractal aggregates of fully carbonized and partially oxidized nanoparticles. This project applies the most modern approaches in carbon science to the understanding and characterization of the various stages of soot formation, evolution, and burnout.