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

在气相合成过程中原位表征无机纳米粒子的方法很少探索-尽管生产定义的产品质量的重要性。这种缺陷不仅是由于这种纳米材料的光学性质知之甚少，而且还因为缺少实验，使得能够直接比较光学原位测量和常规（非原位）颗粒表征。该项目的目的是，基于激光诱导白炽（LII）作为烟尘诊断的方法，进一步开发无机材料系统硅（Si），锗（Ge），铁（Fe）和铜（Cu）的粒度和体积分数的诊断。在项目SCHU 1369/14-1中获得的硅的新见解将进一步深化适用性，并扩展到其他材料系统，其光学性质在相关温度范围内迄今为止还不完全已知。纳米粒子在微波等离子体反应器中在30和900毫巴之间的压力下产生和光学分析。首先，波长依赖性吸收函数（E（m））将通过视线吸收（LOSA）来确定，该视线吸收（LOSA）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性质。光电二极管或光谱仪和扫描相机的组合将用作检测单元。还计划证明在第一个提案期内发现的Si现象的适用性：可以通过其吸收/发射光谱观察到液-固相变。这也将进一步推动其他材料系统。此外，将记录所有材料系统的能量密度相关白炽光谱及其时间发展（时间分辨LII），并在粒度测定的背景下分析其发射特性。注量值将增加到实现完全颗粒蒸发而不发生气体分解的范围内。这允许探索可能干扰LII信号的非热发射的起源（韧致辐射，LII过程中的“异常冷却”）。基于粒子的原子发射（强度，发射寿命）将在低通量LIBS（激光诱导击穿）过程中的实际适用性的背景下进行调查。通过光学测量，将使用同一探针体积内的在线粒子质谱法（PMS）确定粒度分布。此外，通过热泳取样和非原位透射电子显微镜（TEM）和拉曼分析，粒度和结晶度将进行研究。所有结果加在一起将大大增加我们在粒子光学性质和诊断方面的知识，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.