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

尽管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颗粒进行原位表征的方法却很少被探索。这一缺陷不仅是因为人们对这种纳米材料的光学特性知之甚少，而且还因为缺乏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，基于激光诱导白炽灯（LII）作为烟尘诊断的一种方法，进一步发展对无机材料系统硅（Si）、锗（Ge）、铁（Fe）和铜（Cu）的粒度和体积分数的诊断。在SCHU 1369/14-1项目中获得的关于Si的新见解将进一步深化其适用性，并扩展到其他材料系统，其光学性质迄今为止在相关温度范围内尚不完全清楚。纳米颗粒在30到900毫巴的压力下在微波等离子体反应器中产生并进行光学分析。首先，波长相关的吸收函数（E(m)）将通过视距吸收（LOSA）来确定，该方法研究了用于LII的加热激光脉冲存在和不存在时粒子的光学特性。光电二极管或分光仪和条纹照相机的组合将作为探测装置。还计划证明在第一个提案期间发现的Si现象的适用性：可以通过它们的吸收/发射光谱观察液固相变。其他材料系统也将进一步这样做。此外，将记录所有材料系统的影响相关白炽光谱及其时间发展（时间分辨LII），并在粒径测定的背景下分析其发射特性。在没有气体击穿的情况下，将增加通量值，使其达到完全颗粒蒸发的范围。这可以探索干扰LII信号的非热排放的起源（轫致辐射，在LII过程中的“异常冷却”）。在实际应用的背景下，将在低通量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，将使用内联粒子质谱法（PMS）从相同的探针体积内确定颗粒大小分布。此外，通过热电泳取样和非原位透射电子显微镜（TEM）和拉曼分析，将研究颗粒大小和结晶度。所有结果结合在一起将大大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。

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.