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Author: Schäfer, Jan × DDC: 530 × DDC: 540 × Has files: Yes × Version: publishedVersion × WGL Institute: INP ×

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Now showing 1 - 3 of 3
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    HelixJet: An innovative plasma source for next-generation additive manufacturing (3D printing)
    (Hoboken, NJ : Wiley Interscience, 2020) Schäfer, Jan; Quade, Antje; Abrams, Kerry J.; Sigeneger, Florian; Becker, Markus M.; Majewski, Candice; Rodenburg, Cornelia
    A novel plasma source (HelixJet) for use in additive manufacturing (AM)/3D printing is proposed. The HelixJet is a capacitively coupled radio frequency plasma with a double-helix electrode configuration that generates a surprisingly stable and homogeneous glow plasma at low flow rates of argon and its mixtures at atmospheric pressure. The HelixJet was tested on three polyamide powders usually used to produce parts by laser sintering, a powder-based AM process, to form local deposits. The chemical composition of such plasma-printed samples is compared with thermally produced and laser-sintered samples with respect to differences in morphology that result from the different thermal cycles on several length scales. Plasma prints exhibit unique features attributable to the nonequilibrium chemistry and to the high-speed heat exchange.
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    Plasma-based VAD process for multiply doped glass powders and high-performance fiber preforms with outstanding homogeneity
    (Hoboken, NJ : Wiley Interscience, 2020) Trautvetter, Tom; Schäfer, Jan; Benzine, Omar; Methling, Ralf; Baierl, Hardy; Reichel, Volker; Dellith, Jan; Köpp, Daniel; Hempel, Frank; Stankov, Marjan; Baeva, Margarita; Foest, Rüdiger; Wondraczek, Lothar; Wondraczek, Katrin; Bartelt, Hartmut
    An innovative approach using the vapor axial deposition (VAD), for the preparation of silica-based high-power fiber laser preforms, is described in this study. The VAD uses a plasma deposition system operating at atmospheric pressure, fed by a single, chemically adapted solution containing precursors of laser-active dopants (e.g., Yb2O3), glass-modifier species (e.g., Al2O3), and the silica matrix. The approach enables simultaneous doping with multiple optically active species and overcomes some of the current technological limitations encountered with well-established fiber preform technologies in terms of dopant distribution, doping levels, and achievable active core diameter. The deposition of co-doped silica with outstanding homogeneity is proven by Raman spectroscopy and electron probe microanalysis. Yb2O3 concentrations are realized up to 0.3 mol% in SiO2, with simultaneous doping of 3 mol% of Al2O3.
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    Surface modification of the laser sintering standard powder polyamide 12 by plasma treatments
    (Weinheim : Wiley-VCH, 2018-6-7) Almansoori, Alaa; Masters, Robert; Abrams, Kerry; Schäfer, Jan; Gerling, Torsten; Majewski, Candice; Rodenburg, Cornelia
    Polyamide 12 (PA12) powder was exposed for up to 3 h to low pressure air plasma treatment (LP-PT) and several minutes by two different atmospheric pressure plasma jets (APPJ) i.e., kINPen (K-APPJ) and Hairline (H-APPJ). The chemical and physical changes resulting from LP-PT were observed by a combination of Scanning Electron Microscopy (SEM), Hot Stage Microscopy (HSM) and Fourier transform infrared spectroscopy (FTIR), which demonstrated significant changes between the plasma treated and untreated PA12 powders. PA12 exposed to LP-PT showed an increase in wettability, was relatively porous, and possessed a higher density, which resulted from the surface functionalization and materials removal during the plasma exposure. However, it showed poor melt behavior under heating conditions typical for Laser Sintering. In contrast, brief PJ treatments demonstrated similar changes in porosity, but crucially, retained the favorable melt characteristics of PA12 powder.