Optical Emission Spectroscopy Study of Plasma-Precursor Interactions in TiO2 Suspension Plasma Spray

Menneveux, Jérôme; Veilleux, Jocelyn

doi:10.1007/s11090-022-10236-4

Cited by 3 publications

(2 citation statements)

References 45 publications

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“…Over the past few decades, plasma-droplet systems are investigated mainly in the context of lightning ignition [16] and material synthesis (interactions in plasma-(micro-)droplet systems, also known as plasma sprays or misty plasmas) [17]. In 2020, Oinuma et al [18] studied the transfer of OH radicals from a diffuse RF glow discharge (in He with 0.2% H 2 O) to a micrometre-size droplet of water that contains formate.…”

Section: Introductionmentioning

confidence: 99%

Propagation of nanosecond discharge in an air gap containing a water droplet: modelling and comparison with time-resolved images

Ouali,

Sebih,

Herrmann

et al. 2024

J. Phys. D: Appl. Phys.

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The plasma-water interface is a complex medium characterized by interesting physical and chemical phenomena useful for many applications such as water processing or material synthesis. In this context, optimizing the transport of reactive species from plasma to water is crucial, and it may be achieved by increasing the surface-to-volume ratio of the processed object. Herein, we study the characteristics of a streamer produced by nanosecond discharge in air gap with a droplet of deionized water. The discharge is characterized experimentally by electrical measurements as well as by 1-ns-intergated ICCD images. To report plasma properties that are not accessible through experiment, such as the spatio-temporal evolution of electron density, electric field, and space charge density, a 2D fluid model is developed and adapted to the experimental geometry. Due to the fast propagation of the ionization front, the droplet is considered as a solid dielectric. The model solves Poisson’s equation as well as the drift-diffusion equation for electrons, positive ions, and negative ions. The utilized transport coefficients are tabulated as a function of the reduced electric field. Helmholtz equations are also included in the model to account for photoionization. The electron impact ionization source obtained from the model is compared to experimental 1-ns-integrated ICCD images, and a good agreement is observed. Finally, the model is used to investigate the influence of droplet dielectric permittivity and wetting angle (the angle between a liquid surface and a solid surface) on the properties of the discharge. Overall, the data reported herein demonstrate that the model can be used to investigate plasma properties under different conditions.

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Section: Introductionmentioning

confidence: 99%

Propagation of nanosecond discharge in an air gap containing a water droplet: modelling and comparison with time-resolved images

Ouali,

Sebih,

Herrmann

et al. 2024

J. Phys. D: Appl. Phys.

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show abstract

“…The discharge characteristics depend on the size, composition, and number of bubbles in the gap [23][24][25]. Meanwhile, the latter configuration (2) results in the generation of a plasma-spray and is typically used to deposit thin films [26], synthesize nanoparticles [27], and study the ignition of lightning [28]. In this case too, the droplet size has a significant effect on discharge ignition and propagation [29].…”

Section: Introductionmentioning

confidence: 99%

Spatial and temporal dynamics of single nanosecond discharges in air with water droplets

Hamdan

Dorval²

2023

J. Phys. D: Appl. Phys.

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Discharges generated in water or water-containing media have great potential for various technological applications. However, a fundamental understanding of plasma-liquid interactions, particularly the ignition and propagation of a discharge in a gap containing liquid droplets, is lacking. This study investigates the electrical characteristics and the spatial-temporal dynamics of nanosecond discharges in air containing one or two millimetric droplets of deionized water. Analysis of the effects of voltage amplitude (Va) and pulse width on the discharge mode shows that at low Va, the discharges are run in streamer mode; however, at high Va, a streamer-to-spark transition is observed. Although the droplet size (diameter between 2 and 4 mm) does not significantly influence the discharge dynamics, its position with respect to the gap (on- or off-axis) has a strong effect. Time-resolved imaging of three droplet configurations (one on-axis droplet, one off-axis droplet, and two on-axis droplets) was used to unveil the ignition and propagation dynamics of streamers and sparks at nanosecond time scale. The findings are of interest and contribute to a better understanding of` the plasma-droplet interactions, which is crucial for the development and optimization of plasma-based applications.

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Using optical emission spectroscopy in atmospheric conditions to track the inflight reduction of plasma sprayed TiO2−x feedstock for thermoelectric applications

Mauer,

Gildersleeve V

2024

Sci Rep

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Thermal spray deposition (specifically Atmospheric Plasma Spraying, APS) is a well-established surface coating technology with a broad scope of applications (i.e., insulative coatings, tribological coatings, anti-corrosion coatings, etc.). In addition, there is a constant drive to introduce the APS process into new and emerging fields. One such niche application for APS would be sub-stoichiometric TiO2−x coatings with enhanced thermoelectric performance (compared to the bulk material). The APS process in this context has a unique ability—given the use of hydrogen as a plasma gas—to reduce TiO2−x material during processing. However, to this point, there is neither a reliable nor self-consistent method to assess (nor control by parametric optimization) the inflight reduction of molten oxide particles during processing. This study shows that using Optical Emission Spectroscopy (OES), it can be possible—even in atmospheric conditions—to identify characteristic emission peaks associated with the inflight reduction of TiO2 during APS. Using this OES data, the input spray processing parameters and their influence on coating microstructure and the degree of inflight reduction of the material will be shown. Results suggest under equilibrium conditions only a minimal amount of hydrogen gas is needed in the plasma to fulfill the TiO2 reduction.

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Optical Emission Spectroscopy Study of Plasma-Precursor Interactions in TiO2 Suspension Plasma Spray

Cited by 3 publications

References 45 publications

Propagation of nanosecond discharge in an air gap containing a water droplet: modelling and comparison with time-resolved images

Propagation of nanosecond discharge in an air gap containing a water droplet: modelling and comparison with time-resolved images

Spatial and temporal dynamics of single nanosecond discharges in air with water droplets

Using optical emission spectroscopy in atmospheric conditions to track the inflight reduction of plasma sprayed TiO2−x feedstock for thermoelectric applications

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