Anna Rosa Ziefuss

Continuous-flow nanosecond microparticle laser fragmentation in liquids (ns-MP-LFL) is investigated as a scalable route for producing LaB ₆ nanoparticles from ball-milled ceramic feedstock. LaB ₆ serves as a conductive refractory ceramic to evaluate photothermal ns-fragmentation of high-melting, low-work-function materials. Optical–thermal analysis shows that, despite shallow UV absorption at 343 nm, nanosecond thermal diffusion enables substantial pulsed heating of submicrometer particles and defines the relevant feedstock size window. A fragmentation threshold of 1.8 J cm⁻² is identified for particles >100 nm. In pure water, the mass yield of particles -2 , indicating that dissipative energy-coupling losses, rather than nominal fluence, limit further yield improvement. Additive studies show that citrate and isopropyl alcohol reduce nanoparticle yield, while FeCl₃ does not enhance fragmentation, suggesting that bulk solution absorption cannot compensate for inefficient energy deposition. NaOH improves electrostatic stabilization and reduces particle size, although yield remains below that in pure water. Hofmeister-active halide salts provide additional size control: chaotropic Br⁻ and I⁻ suppress larger residual particles and narrow the distribution, with Br⁻ yielding minimum mass-weighted sizes of 45 nm. The nanoparticles show improved oxygen evolution reaction activity compared to the ball-milled reference, including a threefold current density increase to 0.45 mA cm ^-2 and a reduced Tafel slope of 110 mV dec ^-1 . However, Hofmeister-derived smaller particles do not enhance catalytic performance, suggesting halide-induced interfacial effects. Overall, ns-MP-LFL is established as a continuous process for LaB ₆ nanoparticle production, identifying fluence, feedstock size, pH, and ion-specific chemistry as key variables.

Real‐time insight into local chemistry is critical for reliable part quality in additive manufacturing, especially laser powder bed fusion (PBF‑LB/M), where rapid thermal cycles and localized evaporation can undermine part performance. Optical emission spectroscopy (OES) offers non‑intrusive, in situ plume monitoring, but detection geometry strongly affects precision. We address this through geometry‐ and physics‐based approaches and spectral measurements with angular (off‐axis) and coaxial (on‐axis) configurations, exploring how detection configurations influence signal stability, spatial consistency, and chemical precision, by varying laser power, integration time, scan position, and pattern on an Nd‐Fe‐based hard magnet alloy. By quantifying wavelength‐dependent efficiency and plume anisotropy, we establish a decision framework to choose the most suitable in situ OES setup for applications ranging from defect detection to reliable high‐precision chemical mapping. Coaxial OES offers superior detection sensitivity for low‐ionization‐energy elements like Nd, due to the forward‐peaked emission profile and high detection efficiency, enabling quantitative detection below ±0.2 at.% under optimized conditions. Angular OES is easier to integrate and reveals lateral plume structure and processing defects, but yields two‐fold lower compositional accuracy under identical conditions. These findings provide a foundation for selecting OES geometries in PBF‐LB/M and represent a clear step toward robust, material‐sensitive closed‐loop monitoring in industrial PBF‐LB/M.

Laser nanomanufacturing requires energy-efficient, high-throughput methods using inexpensive feedstocks and continuous operation. We demonstrate high-power ultraviolet nanosecond microparticle laser fragmentation in liquids as a controlled, high-yield, high-throughput route to ligand-free silver nanoparticles. Two synchronized 343 nm, 200 W beams enable sufficient laser fluence and single-pulse-per-volume conditions. Matching the thermal diffusion length to the microparticle diameter converts surface-confined absorption into deep photothermal heating, driving single-pulse phase explosion instead of photomechanical rupture. The productivity reaches 10 g h ⁻¹ of Ag nanoparticles <10 nm, at almost quantitative microparticle-to-nanoparticle conversion of up to 98% mass yield, achieving record throughput and mass conversion. Ionic-strength–mediated surface chemistry provides in-situ control over nanoparticle size. This establishes a scalable, green synthesis platform linking mechanistic understanding with industrial level throughput.

The shift to energy‐efficient near‐infrared (NIR) diode lasers in polymer powder bed fusion (PBF‐LB/P) challenges standard polymer powders due to insufficient NIR absorption and necessitates tailored feedstock modifications. This study explores the potential of surface modification (s‐mod) of polyamide 12 (PA12) with LaB ₆ nanoparticles (NP) as a scalable alternative to conventional volume modification (v‐mod) with carbon black (CB). Despite a tenfold lower overall NIR absorbance, s‐mod PA12 achieves comparable melting behavior with only a 1.5‐fold increase in laser energy. Combined differential scanning calorimetry (DSC) and X‐ray diffraction (XRD) analyses reveal that surface‐localized absorption enables partial retention of α ‐domains at intermediate energy densities, consistent with a heterogeneous, surface‐dominated melting mechanism. At higher energies, s‐mod and v‐mod converge to fully γ ‐phase materials with comparable crystallinity. Mechanical testing demonstrates that intermediate s‐mod parts exhibit higher crystallinity, whereas fully molten s‐mod parts outperform v‐mod counterparts in tensile strength while maintaining ductility. Our findings indicate that s‐mod PA12 not only matches the processability of industrial v‐mod powders but also introduces new degrees of freedom for tailoring mechanical properties via controlled melting. Decoupling energy absorption from volumetric filler loading expands the material design space for NIR‐based additive manufacturing and paving the way for next‐generation, high‐performance polymer components.

Lasers in production are becoming increasingly powerful and brilliant; however, the mate-rials currently available often fall far short of meeting modern manufacturing demands. In additive manufacturing (AM), metal powders originally developed over 60 years ago for thermal spraying—a fundamentally different process—are still widely used. When applied in today’s laser-based AM processes, these powders lead to process instabilities, porosity, and defects in the final parts. For polymer powders, the lack of a broad material and per-formance portfolio further limits technological advancement. To fully leverage laser-based additive manufacturing—which will remain essential in the future due to its high throughput and precision—a paradigm shift in feedstock design is required. This calls for a fundamental research approach that begins at the very start of the process chain: the powder material itself. Driven by the need for deeper mechanistic in-sight and novel material concepts for laser-based additive manufacturing, leading re-searchers across Germany established the Priority Programme SPP 2122 “MATframe”, supported by the German Research Foundation (DFG). Since 2018, more than 25 re-search groups and international Mercator Fellows have been collaborating in interdiscipli-nary tandem projects, linking material development with laser processing research. The programme addresses cross-material scientific questions focused on photon-driven, pow-der-based AM and has executed the first large-scale interlaboratory study (ILS) on pow-der bed fusion with integrated research data management. This article introduces the inter-disciplinary research approach and selected outcomes of MATframe, addressing the im-portance of systematic material development for the future of AM.