The quality of powder used in powder bed-based additive manufacturing plays a key role concerning process performance and end part properties. Even though this is a generally accepted fact, there is still a lack of a comprehensive understanding of the powder property-part property relationship. However, numerous investigations focusing on selected powder properties and their corresponding influence on process aspects or final part properties have been published in recent years. Still, generalized statements on powder requirements for a defined process performance are not available. This can be attributed to the fact that the community has not yet come to an agreement which characterization techniques are most suitable for powder characterization in the additive manufacturing context and in most cases only selected aspects have been investigated for special powder materials. The aim of this review is to assess these building blocks of knowledge and to provide an overview on the current state of the art.

This paper reports the successful application of ink-jet printing to the deposition of both continuous coatings and multi-filamentary structures of YBCO. Stable inks have been prepared using both the established TFA-MOD route and novel fluorine-free precursors with appropriate rheological properties for ink-jet printing. Continuous and well textured coatings with lengths exceeding 100 m and a thickness of 0.5 µm have been deposited by electromagnetic ink-jet printing from TFA precursors on LZO-buffered Ni–W substrates and samples have achieved a Jc around 1.5 MA cm−2 (self-field, 77 K). On single crystal substrates, continuous coatings and multi-filamentary structures have been deposited using piezoelectric ink-jet printing both from TFA- and water-based precursors, achieving Jc values up to 3 MA cm−2.

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We apply a recently developed approach for calculating the transport properties of random media to the case of disordered arrays of parallel oriented and normally illuminated cylinders. Within this effective-medium theory resonant scattering of the individual scatterer is treated exactly, and by using a coated cylinder as the basic scattering unit, multiple scattering contributions are incorporated in a mean-field sense. In the longwavelength limit we are able to calculate the effective dielectric constant analytically. We compare our findings with results for periodic systems. For both ''scalar'' and ''vector'' polarization, we reliably calculate the mean-free path, the transport velocity, and the diffusion coefficient for finite frequencies for all densities of scatterers and dielectric contrasts. Furthermore, within this effective-medium approach, we present our results for the localization parameter kl t for both two-and three-dimensional systems, thereby identifying the optimal parameters for observing localization. ͓S0163-1829͑97͒02546-0͔

Chemical solution deposition (CSD) is a promising way to realize REBa 2 Cu 3 O 7 x (REBCO; RE = rare earth (here Y, Gd))-coated conductors with high performance in applied magnetic fields. However, the preparation process contains numerous parameters which need to be tuned to achieve high-quality films. Therefore, we investigated the growth of REBCO thin films containing nanometre-scale BaHfO 3 (BHO) particles as pinning centres for magnetic flux lines, with emphasis on the influence of crystallization temperature and substrate on the microstructure and superconductivity. Conductivity, microscopy and x-ray investigations show an enhanced performance of BHO nano-composites in comparison to pristine REBCO. Further, those measurements reveal the superiority of GdBCO to YBCO e.g. by inductive critical current densities, J c , at self-field and 77 K. YBCO is outperformed by more than 1 MA cm 2 with J c values of up to 5.0 MA cm 2 for 265 nm thick layers of GdBCO(BHO) on lanthanum aluminate. Transport in-field J c measurements demonstrate high pinning force maxima of around 4 GN m 3 for YBCO(BHO) and GdBCO(BHO). However, the irreversibility fields are appreciably higher for GdBCO. The critical temperature was not significantly reduced upon BHO addition to both YBCO and GdBCO, indicating a low tendency for Hf diffusion into the REBCO matrix. Angular-dependent J c measurements show a reduction of the anisotropy in the same order of magnitude for both REBCO compounds. Theoretical models suggest that more than one sort of pinning centre is active in all CSD films.