Reactions of the precursors for spray-flame of nanoparticles during partial evaporation of the spray

喷雾部分蒸发过程中纳米颗粒喷雾火焰前体的反应

• 批准号: 375856814
• 负责人: Professorin Dr. Tina Kasper
• 金额: --
• 依托单位: Lehrstuhl für Thermodynamik und Energietechnik (ThEt)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/375856814?language=en
• 关键词: Reactions; precursors; spray; flame; nanoparticles

Spray-flame synthesis is a promising option for the production of functional nanomaterials. The spray is used to introduce low-volatility precursors into the vapor phase. The thermal and chemical structure of the spray flames indicates that chemical reactions occur at substantially different reaction conditions in the different flame zones.The work in this project concentrates on the chemical transformations of the solvent and the precursor in the spray formation zone which is located in the center of the flame. In this zone, only moderate temperatures below 1000 °C are reached and the chemical matrix is dominated by oxygen, the solvent and small amounts of water and precursor. Spray formation and evaporation processes coincide with chemical transformations of the solvent and precursors. Open questions in this sub-process of spray flame synthesis are which reactions happen in the liquid phase and which reactions occur in the gas phase during spray evaporation. The reaction products of these reactions influence subsequent reaction pathways, including the formation pathways of nanoparticles. Those nanoparticles will typically be formed by two main reaction pathways, the droplet-to-particle route and the gas-to-particle route. In the second project period, three sub-processes will be investigated: Liquid phase reactions that occur during slow heating of the liquid solvent/precursor solution will be identified through a detailed chemical analysis of the composition of the solution by electrospray mass spectrometry and gas chromatography. This experiment will determine which precursors already react, i.e. hydrolyze or oxidize, in the liquid phase and are likely to react by the less favorable droplet-to-particle route. Reactions occurring during the partial evaporation of the spray will be investigated in a tubular reactor. In this simplified process, the thermal precursor reactions are separated from radical reactions in the flame by replacing the ignition of the spray and subsequent release of combustion heat by external heating of the reactor. These experiments provide information on how the precursor and solvent interact chemically during the evaporation of the spray and identify the intermediates resulting from the interactions that are present in the gas phase. Subsequent reactions of the intermediates formed from the precursors with flame gases will be investigated in a combined well-stirred and plug-flow reactor. These experiments identify the reaction patterns that lead from molecular intermediates to clusters and then nanoparticles. All experiments rely on mass spectrometric diagnostics for species identification and concentration measurements. A special sampling and transfer procedure will be used to identify charged species when sprays of salt solutions are used.The chemical insights from this project are used to formulate reaction mechanism and support the simulation of the global flame spray synthesis process within the SPP.

喷雾火焰合成是生产功能性纳米材料的一个有前途的选择。喷雾用于将低挥发性前体引入气相。喷雾火焰的热和化学结构表明，不同火焰区域中的化学反应在截然不同的反应条件下发生。该项目的工作重点是位于火焰中心的喷雾形成区域中溶剂和前体的化学转化。在此区域中，仅达到 1000 °C 以下的中等温度，化学基质主要由氧气、溶剂以及少量的水和前体组成。喷雾形成和蒸发过程与溶剂和前体的化学转变同时发生。 喷雾火焰合成的这个子过程中的悬而未决的问题是，在喷雾蒸发过程中，哪些反应发生在液相中，哪些反应发生在气相中。这些反应的反应产物影响后续反应途径，包括纳米颗粒的形成途径。这些纳米颗粒通常通过两种主要反应途径形成，即液滴到颗粒途径和气体到颗粒途径。在第二个项目期间，将研究三个子过程： 将通过电喷雾质谱和气相色谱法对溶液成分进行详细的化学分析来识别液体溶剂/前体溶液缓慢加热过程中发生的液相反应。该实验将确定哪些前体已经在液相中发生反应，即水解或氧化，并且可能通过不太有利的液滴到颗粒途径进行反应。将在管式反应器中研究喷雾部分蒸发过程中发生的反应。在这个简化的过程中，通过取代喷雾的点火以及随后通过反应器的外部加热释放燃烧热，将热前体反应与火焰中的自由基反应分开。这些实验提供了有关前体和溶剂在喷雾蒸发过程中如何发生化学相互作用的信息，并鉴定了气相中存在的相互作用产生的中间体。由前体形成的中间体与火焰气体的后续反应将在充分搅拌和活塞流组合反应器中进行研究。这些实验确定了从分子中间体到簇，然后是纳米颗粒的反应模式。所有实验都依赖于质谱诊断来进行物种鉴定和浓度测量。当使用盐溶液喷雾时，将使用特殊的采样和转移程序来识别带电物质。该项目的化学见解用于制定反应机制并支持 SPP 内全局火焰喷雾合成过程的模拟。