The fabrication of tool electrodes with complex geometries remains a major technological challenge in electrical discharge machining (EDM). This critical review analyzes a hybrid strategy that combines additive manufacturing of a polymer core with subsequent electroless and electrolytic copper deposition to obtain electrically conductive tool electrodes. The principal 3D printing technologies—FDM/FFF, SLA/DLP, SLS, and PolyJet—are compared for polymer core fabrication. By the considered criteria, FDM/FFF and SLA/DLP show the greatest practical potential for polymer cores for subsequent metallization. FDM/FFF offers equipment/material availability and process flexibility; SLA/DLP provides lower surface roughness and higher dimensional accuracy. FDM parameters – layer thickness, nozzle temperature, infill density, and build orientation – are examined for effects on geometric accuracy, surface roughness, and thus metal coating adhesion and uniformity. Primary metallization methods (electroless deposition, physical vapor deposition, conductive pastes) and subsequent copper electroplating are analyzed. A synthesis of experimental data shows that in most studies that included a comparison with a solid copper tool electrode, electrodes with a printed polymer core (mainly ABS) and a copper coating provided comparable material removal rate, wear, and machined surface roughness under finishing and semi-finishing conditions; at the same time, in several studies the hybrid electrodes were inferior to solid copper in material removal rate or wore 1.1–2.8 times faster, and data on the service life of the copper shell are lacking. Optimizing FDM parameters and selecting a metallization method should be treated as interdependent stages of an integrated process chain determining hybrid tool electrode performance.
The development of high-performance air electrodes operating at reduced temperatures remains a critical challenge for solid oxide fuel cells (SOFCs). In this study a dual-engineering strategy combining modification of the synthesis procedure with nanocatalyst infiltration to enhance performance of a multicomponent perovskite air electrode is reported. La0.60Sr0.40Fe0.33Co0.33Mn0.33O3–δ (LSFCM) material with configurational entropy of 1.1R was synthesized via a novel glycine-urea-assisted combustion method. Comprehensive investigation of combustion synthesis parameters revealed that fuel composition critically governs phase purity, with oxygen availability during combustion determining the formation of LaSrFeO4 secondary phase. The glycine-urea route after calcination at 800 °C yielded LSFCM (21.19 m2/g) with minor amount of SrCO3, which was successfully eliminated during short-term sintering at 1100 °C without quenching. Electrochemical characterization in contact with Ce0.8Sm0.2O1.9 electrolyte demonstrated that electrodes fabricated from glycine-urea synthesized powder exhibited polarization resistance of 0.28/1.27 Ω cm2 at 800/700 °C. Infiltration of nanocatalysts enhanced the electrode performance at decreased temperatures. With PrOₓ activation the LSFCM electrodes demonstrated Rp in the range of 0.58–0.93 Ω cm2 at 600 °C depending on material synthesis and applied collector. Stability testing over 500 hours in ambient and wet air atmospheres confirmed exceptional durability of PrOx electrode. This study demonstrates that integrating an optimized synthesis route for multicomponent perovskites with nanocatalyst infiltration offers a promising strategy for developing high-performance, stable air electrodes for intermediate- and low-temperature SOFCs.
To obtain highly transparent materials potentially suitable for infrared optical fibers and luminescent ceramics, solid solutions in the AgBr – TlCl0.74Br0.26 system were developed. Initially, the phase diagram of this system was constructed, revealing two pairs of homogeneous and heterogeneous regions with structural types corresponding to Fm3m (or Pm3m) and Fm3m+R-3 (or Pm3m +R-3). Compositions for single-crystal growth were selected from the homogeneous regions, while two-phase ceramics were designed using compositions from the heterogeneous regions. Subsequently, optimal temperature and rate parameters for the synthesis of each compound type were established, including the hydrochemical stage of the technological process. Based on these parameters, single crystals with 3, 6, and 95 wt. % TlCl0.74Br0.26 in AgBr were grown, and ceramics containing 20, 55, 80, 85, and 90 wt. % of the same system were obtained. All samples exhibited high optical transparency across the 0.4–60.0 μm range. Notably, the ceramic samples showed pronounced luminescence in the 500–700 nm region, with intensity up to 10 times higher than that of the crystalline samples. Thus, highly transparent optical materials were successfully fabricated, which makes them promising candidates for further investigation as optical fibers and luminescent materials.
Catalytic membrane reactors (CMRs) based on oxygen-permeable mixed ionic-electronic conducting membranes offer an advantageous pathway for hydrogen and syngas production from natural gas, as they integrate air separation and methane partial oxidation (POM) in a single step. However, the practical development of stable CMRs faces a critical challenge: achieving a sustainable balance between high oxygen permeability and catalytic selectivity while maintaining structural integrity under aggressive reducing and corrosive atmospheres. To address this trade-off, this work investigates the phase stability, oxygen non-stoichiometry, and catalytic performance of doped strontium ferrite La0.4Sr0.6Fe0.95W0.05O3-δ (LSFW5), fabricated as a hollow fiber membrane reactor for POM. The experimental design includes comprehensive characterizations via X-ray diffraction and SEM with EDX, coupled with oxygen permeation and catalytic tests under both O2/CH4 and CO2/CH4 gradients. The results confirm that the material exhibits excellent phase stability after prolonged exposure to H2 and CO2 at 800 °C, while surface modification with silver significantly enhances the oxygen flux by a factor of 2.7. Nevertheless, under a conventional O2/CH4 gradient, the modified membrane shows only modest hydrogen selectivity (2–4%), indicating that high oxygen permeability alone does not guarantee selective syngas production. A major finding of this work is that switching to CO2 as a mild oxidant effectively suppresses complete combustion, enabling the LSFW5_Ag membrane to achieve a substantially higher hydrogen selectivity of up to 35% at 980 °C. A key limitation of the current design remains the moderate selectivity level and the need for high operational temperatures, which constrain its immediate energy efficiency. Despite this, the demonstrated interplay between surface chemistry and oxidant selection provides a significant new strategy for tuning the oxidative potential of membrane materials, offering a viable route for future process intensification in syngas production.
Cation modification is proposed as a strategy for stabilizing layered mixed-valence vanadium oxide cathodes for aqueous zinc-ion batteries, yet the modifier is rarely considered as a competitor for the reducing agent that generates the layered phase. Here, Co2+- and Cu2+-containing vanadium oxides are prepared from V2O5 and oxalic acid via a single hydrothermal step. XRD, FTIR, XPS, ICP-AES, and electron microscopy reveal that the difference in redox activity between the two cations dictates the final product. Cobalt, which resists reduction and is partly reoxidized to Co3+ in situ, leaves most of the oxalate available for vanadium reduction, yielding a two-phase mixture of V10O24·12H2O and residual V2O5 with cobalt homogeneously dispersed throughout the matrix. In contrast, copper is readily reduced to Cu+, consuming the reductant and suppressing the layered phase, thereby producing crystalline V2O5 with a copper-enriched surface. The unmodified hydrate achieves 281 mAh·g-1 but retains only 26% after 500 cycles; the cobalt-modified sample peaks at 183.1 mAh·g-1 but fails within 140 cycles; whereas the copper-modified sample delivers 168.9 mAh·g-1 and retains 63%, offering the best stability but at lower capacity. We propose that the redox activity of the metal cation rather than ionic radius or the identity alone is a critical but often overlooked synthesis parameter that governs both structure and, consequently, functional properties in these cathode materials.
