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Laser-based diagnostics for the in situ characterization of non-soot nanoparticles

基于激光的非烟灰纳米颗粒原位表征诊断

基本信息

批准号：
222540104
负责人：
Professor Dr. Christof Schulz
金额：
--
依托单位：
Lehrstuhl für Reaktive Fluide
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2013
资助国家：
德国
起止时间：
2012-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/222540104?language=en
关键词：
Laser based diagnostics situ characterization

项目摘要

Methods that allow an in situ characterization of inorganic nanoparticles during gas-phase synthesis are only little explored - despite the importance to produce defined product qualities. This deficiency is not only due to the poorly known optical properties of such nanomaterials but also because experiments are missing enable direct comparison of optical in situ measurements and conventional (ex situ) particle characterization. The aim of this project is, based on laser-induced incandescence (LII) as a method established for soot diagnostics, to further develop diagnostics for particle size and volume fraction of the inorganic materials systems silicon (Si), germanium (Ge), iron (Fe), and copper (Cu). New insights obtained for Si within the project SCHU 1369/14-1 will be further deepened towards applicability and extended to the other material systems whose optical properties are so far incompletely known in the relevant temperature range. The nanoparticles are generated and optically analyzed in a microwave-plasma reactor at pressures between 30 and 900 mbar. First, the wavelength-dependent absorption function (E(m)) will be determined via line-of-sight absorption (LOSA) investigating the optical properties of the particles both in the absence and the presence of a heating laser pulse that is used for LII. Photodiodes or a combination of a spectrometer and a streak camera will serve as detection units. It is also planned to demonstrate the applicability of a phenomenon that has been discovered for Si in the first proposal period: Liquid-solid phase transitions can be observed via their absorption/emission spectra. This will also be further pursued for the other materials systems. In addition, fluence-dependent incandescence spectra and their temporal development (time-resolved LII) will be recorded for all materials systems and analyzed with respect to their emission properties in the context of particle-size determination. Fluence values will be increased into the range where full particle evaporation is achieved without gas breakdown. This allows to explore the origin of non-thermal emissions that can interfere with the LII signal (Bremsstrahlung, "anomalous cooling" during the LII-process). Particle-based atomic emissions will be investigated (intensity, emission lifetimes) during low-fluence LIBS (laser-induced breakdown) processes in the context of practical applicability. With the optical measurements, particle-size distributions will be determined using inline particle mass spectrometry (PMS) from within the same probe volume. In addition, by thermophoretic sampling and ex situ transmission electron microscopy (TEM) and Raman analysis, particle size and crystallinity will be investigated. All results taken together will strongly increase our knowledge in in particle optical properties and diagnostics and provide valuable input parameters for the underlying models that are required for quantitative analysis of LII and LIBS signals.

尽管对生产确定的产品质量很重要，但在气相合成过程中对无机纳米粒子进行原位表征的方法却很少被探索。这种缺陷不仅是由于人们对此类纳米材料的光学特性知之甚少，而且还因为缺少能够直接比较光学原位测量和传统（非原位）颗粒表征的实验。该项目的目的是基于激光诱导白炽光 (LII) 作为烟灰诊断方法，进一步开发无机材料系统硅 (Si)、锗 (Ge)、铁 (Fe) 和铜 (Cu) 的粒径和体积分数的诊断方法。 SCHU 1369/14-1 项目中获得的有关硅的新见解将进一步深化其适用性，并扩展到其他材料系统，这些材料系统的光学特性迄今为止在相关温度范围内尚不完全清楚。纳米颗粒在微波等离子体反应器中在 30 至 900 毫巴的压力下生成并进行光学分析。首先，将通过视线吸收 (LOSA) 来确定与波长相关的吸收函数 (E(m))，研究在不存在和存在用于 LII 的加热激光脉冲的情况下颗粒的光学特性。光电二极管或光谱仪和条纹相机的组合将用作检测单元。还计划展示在第一个提案期间发现的硅现象的适用性：可以通过吸收/发射光谱观察液-固相变。其他材料系统也将进一步追求这一点。此外，所有材料系统的依赖注量的白炽光谱及其时间发展（时间分辨LII）都将被记录，并在颗粒尺寸测定的背景下分析其发射特性。流量值将增加到实现颗粒完全蒸发而不发生气体分解的范围。这样可以探索可能干扰 LII 信号的非热发射的起源（轫致辐射，LII 过程中的“异常冷却”）。将在实际适用性的背景下，在低通量 LIBS（激光诱导击穿）过程中研究基于粒子的原子发射（强度、发射寿命）。通过光学测量，将使用同一探针体积内的在线粒子质谱 (PMS) 确定粒度分布。此外，还将通过热泳采样、异位透射电子显微镜 (TEM) 和拉曼分析来研究颗粒尺寸和结晶度。所有结果综合起来将极大地增加我们在粒子光学特性和诊断方面的知识，并为 LII 和 LIBS 信号定量分析所需的基础模型提供有价值的输入参数。