In-situ laser diagnostic of nanoparticle formation and transport behavior in flame aerosol deposition

Ren, Yihua; Wei, Jili; Li, Shuiqing

doi:10.1016/j.proci.2018.06.015

Cited by 10 publications

(4 citation statements)

References 24 publications

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“…This is in contrast to conventional LIBS, where emission from the gas phase is obtained at rather high laser intensities, which results in millimeter-sized plasma and visible sparks. Most PS-LIBS investigations are based on TiO 2 nanoparticles synthesized in vapor-fed reactors (premixed or diffusion flames) and used two-photon absorption at an excitation wavelength of 532 nm (second harmonic of a Q-switched Nd:YAG laser). ,,− With this configuration, Zhang et al demonstrated two-dimensional PS-LIBS based on band-path-filtered (Ti atomic emission at 500 nm), time-averaged (100 laser shots, at 10 Hz) images obtained from a thin laser sheet and visualized the gas-to-particle conversion zone of the diffusion flame. Xiong et al measured PS-LIBS of TiO 2 nanoparticles synthesized in a premixed flame using a resonant excitation wavelength of 355 nm (third harmonic of a Q-switched Nd:YAG laser) that, when compared to emission obtained at 532 nm excitation, resulted in an additional resonance-enhanced Ti atomic emission line (497.534 nm).…”

Section: Experimental Process and Nanoparticle Diagnosticsmentioning

confidence: 99%

Synthesis of Metal Oxide Nanoparticles in Flame Sprays: Review on Process Technology, Modeling, and Diagnostics

Meierhofer

Fritsching

2021

Energy Fuels

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The gas synthesis of nanoparticles has gained major interest by different industries and research groups for the development of new materials and their subsequent implementation in numerous devices and applications. Actually, there are numerous research and application activities in flame-based nanoparticle production, mainly focusing on the process and its development, the in situ and ex situ analyses in experiments and simulations and new material and material combination developments. This review provides an overview on the flame synthesis of metal oxide nanoparticles and focuses in particular on the process design of flame spray pyrolysis (FSP). The first part of this review describes the historical background of flame-based particle production and further summarizes the emerging developments, achievements, and trends during the past 2 decades. The second part covers a general process overview of the flame aerosol-based manufacturing by explaining the key aspects of synthesis (chemical raw materials, metal precursors, solvents, and reactor configurations), in situ conditioning approaches, and powder and byproduct collection, along with additional post-processing steps (storage, handling, and modification). Applications of flame-made nanoparticles involve catalysts, gas sensors, energy storage materials, and nanotoxicity studies, among others, which will not be discussed in detail but are overviewed by listing the latest reviews of the respective field. The third part focuses on the growth mechanisms of solid particle products in liquid droplet/spray pyrolysis (liquid-to-particle and gas-to-particle conversion). The concept of characteristic process times is then exemplified for a lab-scaled FSP reactor, while afterward, particle dynamics and continuum models for reactor simulation are reviewed. The fourth part is a survey of more than 20 different diagnostic techniques that are commonly employed for characterization of reactive sprays and flame-made powders. We briefly explain the metrology basics of each method, indicate advantages and limitations, and present exemplary measurement results that have been acquired on flame reactor facilities for particle synthesis. Finally, we summarize the review and address some current challenges that might potentially shape the near future of nanoparticle synthesis in flame sprays.

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Section: Experimental Process and Nanoparticle Diagnosticsmentioning

confidence: 99%

Synthesis of Metal Oxide Nanoparticles in Flame Sprays: Review on Process Technology, Modeling, and Diagnostics

Meierhofer

Fritsching

2021

Energy Fuels

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“…The expressions of Dp, c, and β can be found in Ref. [20]. The source term Sp is related to the vapor precursor reaction at the flame front, which can be expressed as 4 4…”

Section: Particle-phase Analysismentioning

confidence: 99%

Theoretical Single-Droplet Model for Particle Formation in Flame Spray Pyrolysis

2021

Self Cite

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In the current work, we develop a single droplet model to describe particle formation in multicomponentliquid droplet combustion. Both the gas-to-particle conversion and droplet-to-particle conversion routes of different solution properties are investigated, together with the population balance model and the droplet drying model. For multi-component droplets without precursors, the droplet combustion is limited by the species diffusion in the liquid phase. The model can well predict the droplet shrinkage history observed by previous PDA measurements. For the precursor with a low boiling point than its thermal decomposition temperature, the precursor in the droplet can then transform into nanoparticles through the gas-to-particle conversion route. The population balance model reveals that the generated nanoparticle size relies on both the precursor mass fraction and the residence time, which is consistent with the vaporfed aerosol flame synthesis. For the precursor that tends to decompose or precipitate in the liquid, it then undergoes the droplet-to-particle conversion route. The droplet behavior can be classified by the ratio of droplet evaporation time and precursor reaction or precipitation time. For small droplets with short evaporation time, the nanoparticle formation obeys the one-droplet-one-particle rule. For large droplets with long evaporation time, the competition among precipitation, thermal decomposition, and evaporation determines the final nanoparticle morphology. The single droplet model established in this study can potentially guide the precursor design and be coupled with the turbulent flame simulation of the whole flame spray pyrolysis burner.

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“…Techniques to investigate the nanoparticle formation in such a flame include electrical mobility sizer [52,43], mass spectrometry [16], laser diagnostics [35], electron microscopy [29,51], and X-ray diffraction [27,51,29]. Among these, electron microscopy imaging (i.e.…”

Section: Introductionmentioning

confidence: 99%

Detailed characterisation of TiO2 nano-aggregate morphology using TEM image analysis

Manuputty

Lindberg

Botero

et al. 2019

Journal of Aerosol Science

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A detailed morphological characterisation is performed on flame synthesised TiO 2 nano-aggregates (number of primaries, N < 10) using transmission electron microscopy (TEM) image analysis and mobility measurements. The sizedependent collection efficiency of the TEM sampling method is accounted for with a simple correction for particle deposition through impaction and diffusion. The TEM-derived sizes show excellent agreement with electrical mobility measurements. Primary particle size, aggregate size, and degree of aggregation distributions were obtained for two different flames and varying precursor loading. The analysis reveals some particle aggregation which is likely to occur only very late in the growth stage, leading to the similarity between the primary particle and spherical particle size distributions. The degree of aggregation is defined as the ratio of gyration to spherical equivalent sizes from the projected area analysis, allowing identification of particles with spherical and non-spherical morphologies. The size distributions are found to be strongly affected by precursor loading but not by flame mixture or maximum temperature. In all cases, approximately 60-70% particles are spherical while the rest form small aggregates. The detailed morphological information reported provides the much-needed experimental data for studying the early stage particle formation of TiO 2 from titanium tetraisopropoxide (TTIP) in a well-defined burner configuration.

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In-situ laser diagnostic of nanoparticle formation and transport behavior in flame aerosol deposition

Cited by 10 publications

References 24 publications

Synthesis of Metal Oxide Nanoparticles in Flame Sprays: Review on Process Technology, Modeling, and Diagnostics

Synthesis of Metal Oxide Nanoparticles in Flame Sprays: Review on Process Technology, Modeling, and Diagnostics

Theoretical Single-Droplet Model for Particle Formation in Flame Spray Pyrolysis

Detailed characterisation of TiO2 nano-aggregate morphology using TEM image analysis

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