ADVANCED MATERIALS & PROCESSES | MARCH 2026 46 iTSSe TSS iTSSe TSS FEATURE congruence with the smaller size class data, showing a consistent increase in size. However, an increased size fraction can be observed for the d90 quantile, albeit to a lesser extent. It is evident that the ratio of quantiles for each batch is consistent (Batch 1 < Intermediate < Batch 2). These findings suggest that the fine particles in the suspension are prone to agglomeration, and this increases the individual quantiles. This effect is hypothesized to be the result of the poor surface-to-volume ratio characteristic of smaller particles, which aim to reduce their increased surface energy. Notably, this effect is less pronounced for the larger particles in the d90 quantile. As these particles are still prone to agglomeration, the entire suspension degraded. Particle Diagnostics. The findings from the particle diagnostics for Batch 1 and Batch 2 are illustrated in Fig. 2. No significant deviations in particle velocity and temperature were evident for the degraded suspension. From Batch 1 to Batch 2, a slight increase in particle temperature can be observed, which is however not significant as indicated by the error bars (see Fig. 2a). Moreover, such larger particles may exhibit a reduced velocity. However, as the preceding findings indicate, the higher particle mass might not be sufficient (see Fig. 2b). Coating Properties, Microstructures, and Topographies. A comparison of the microstructures of Batches 1 and 2 in Fig. 3a reveals a high degree of consistency with similar bonding to the substrate. Furthermore, vertical cracks are present due to the high energy input from plasma and particles[4]. In the To study the microstructure, the following procedure was used: sectioning the coated specimen in the middle with a wire saw HDS 25 (well Diamantdrahtsägen GmbH, Mannheim, Germany), grounding and polishing until the final step with SiO2-suspension using the ATM Saphir 550 (Struers GmbH, Germany). A Zeiss GeminiSEM450 scanning electron microscope (Zeiss, Oberkochen, Germany) was used to observe the microstructure of the polished cross-sections. Porosity was obtained by digital image analysis by evaluating seven images of the same scale using the software ImageJ[6]. RESULTS Changes of the Particle Size Distribution. Figure 1 illustrates the d10, d50, and d90 quantiles for each batch. From Batch 1 to the Intermediate State, the lowest size fraction (d10) showed a significant increase. This behavior is even more pronounced for Batch 2, where the d10 quantiles improved again. The results for the d50 quantile demonstrate Fig. 1 — d10, d50, and d90 quantiles for Batch 1 (orange), Intermediate (blue), and Batch 2 (gray). Fig. 2 — Particle temperature (a) and velocity (b) for Batch 1 (orange) and Batch 2 (gray). (a) (b)
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