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Tool wear and life of cutting tools are significant evaluation criteria of machining processes. However, the occurring wear mechanisms are influenced by a number of factors such as the process parameters, tool geometry and the material properties of the tool and workpiece. Previous research has shown a high potential for the use of adapted cutting edge microgeometries on cemented carbide cutting tools. The optimal cutting edge rounding is strongly dependent on the tool material properties. However, the influence and relation between the properties of the cemented carbide tool, the microgeometry and the resulting tool wear are not yet completely understood. In this study the tool wear is investigated by systematically varying the mechanical and thermophysical properties of the tool material, the tool microgeometry and cutting process parameters. Significant influencing variables of tool wear are identified and existing relationships quantified. Results show that the occurring wear mechanisms depend on the cutting edge microgeometry as well as the mechanical properties of the cemented carbide. During continuous machining the minimum required cutting edge rounding is a function of the cemented carbide's fracture toughness. This knowledge allows an adaption of the cutting edge microgeometry depending on the substrate properties to reduce the tool wear and achieve a longer tool life. [ABSTRACT FROM AUTHOR]

The present study introduces an approach to additively manufacture non‐oxidic Ceramic Matrix Composites (CMCs) by the Material Extrusion (MEX)‐based Fused Filament Fabrication. Therefore, highly SiC particle filled thermoplastic filaments were developed containing short fibers and/or long fibers to maintain shape during the thermal treatment and exhibiting flaw tolerant behavior. Polymer Infiltration and Pyrolysis (PIP) was applied to densify the microstructure. It is shown that a low content of long fibers of about 5 % can already exhibit damage tolerance comparable to steel reinforced concrete. Thus, the mechanical behavior is different to conventional fiber composites with significant higher fiber volume content. Nevertheless, these results enable new opportunities for producing advanced complex CMC components by means of Additive Manufacturing (AM). [ABSTRACT FROM AUTHOR]

A study on the influence of the silicate composition on the self-healing ability of a promising environmental barrier coating (EBC) material is reported. The EBC material consists of silicon carbide particles dispersed in a ytterbium silicate matrix. The composition of the silicate was varied from pure monosilicate to pure disilicate including a mixture of 50 vol-% of both phases. Pre-cracked specimens were mechanically tested before and after thermal annealing in air at 1400 °C accompanied by microstructural investigations. It is shown, that the self-healing mechanism is based on the application of compressive surface stresses due to graded oxidation of the SiC particles. With increasing amount of disilicate strength and self-healing ability increase. [ABSTRACT FROM AUTHOR]

Boron carbide and Tantalum boride composites were prepared by pressureless sintering of B4C with addition of TaC powder. The effect of TaC addition on the sinterability of boron carbide was studied. High densified ceramic with a relative density of 98.7% was obtained at sintering temperature of 2250°C. The composition and the microstructure of the dense composites are characterized by means of x‐ray diffraction (XRD), scanning electron microscopy (SEM), and energy‐dispersive x‐ray spectroscopy (EDX). The studies show that the composites contain boron carbide, TaB2, and carbon phases with a homogeneous structure. In addition, the correlation between the composition and the electrical conductivity was investigated. The electrical conductivity of the composite increased with increasing addition of TaC, and a change in conduction behavior from semiconducting to metallic was observed. High hardness value of 28.49 ± 1.33 GPa was obtained by the sample with 30 wt% TaC addition. [ABSTRACT FROM AUTHOR]

Highlights • New approach of notched electrodes for low-profile fibre composite transducers. • Significant improvement of actuation due to notched electrodes. • Optimal electrode depth identified by finite element modelling. • Verification by experiments and comparison with existing transducer types. Abstract The present contribution reports on a novel approach for enhanced piezoelectric patch transducers based on round piezoceramic fibres. Starting from a critical review of the well-known Active Fibre Composite (AFC) concerning electrical coupling between electrodes and ceramic fibres, a new electrode design is proposed. By introducing notches into the fibres perpendicular to their axis and filling these notches witch a conductor, a much better coupling is created. This leads to a significantly better alignment of the intrinsic dipoles over a wide volume of the fibres during poling and thus to much higher piezoelectric performance of the transducers. With the aid of a finite element analyses, design rules for optimization of notched electrodes as well as prediction of transducer behaviour have been derived. For verification of the approach, transducers with varying notch depths have been built and glued onto polystyrene beams attaining active cantilevers. The setup was used to measure free displacement and blocking force generated by the transducers in comparison to other existing patch transducers. An improvement of the piezoelectric actuation up to a factor of four is observed for free deflection and blocking force, significantly exceeding results from state-of-the-art patch transducers such as Macro Fiber Composites (MFC). [ABSTRACT FROM AUTHOR]

Zero‐excess Li metal batteries (ZELMBs), in which a Li‐anode is formed in situ during charging, have received much attention in recent years. ZELMBs bear great potential to increase energy density and facilitate battery production, thereby reducing cost as well as material and energy consumption. Practical application of ZELMBs has so far been limited by challenges related to the non‐uniform deposition behavior of Li, leading to inadequate performance and safety concerns. To address these issues, promising approaches have been developed in recent years, including modifications of the current collector, electrolyte, and cycling protocols. While these approaches improve the long‐term stability of ZELMB, they also reduce the energy density by introducing inactive materials into the cell. Herein, critical design criteria for the various optimization approaches in ZELMB research are established. Nominal volumetric and gravimetric energy densities are determined based on the degree of modification. Thresholds are determined for each of the strategies at which the energy density gain of ZELMB vanishes compared to other cell configurations. These findings are compared to literature results to provide guidance for the further development of ZELMB. [ABSTRACT FROM AUTHOR]

Cubic boron nitride (c-BN) composites produced at high pressures and temperatures are widely used as cutting tool materials. The advent of new, effective pressure-assisted densification methods, such as spark plasma sintering (SPS), has stimulated attempts to produce these composites at low pressures. Under low-pressure conditions, however, transformation of c-BN to the soft hexagonal BN (h-BN) phase can occur, with a strong deterioration in hardness and wear. In the present work, the influence of secondary phases (B2O3, Si3N4, and oxide glasses) on the transformation of c-BN was studied in the temperature range between 1100 °C and 1575 °C. The different heat treated c-BN particles and c-BN composites were analyzed by SEM, X-ray diffraction, and Raman spectroscopy. The transformation mechanism was found to be kinetically controlled solution–diffusion–precipitation. Given a sufficiently low liquid phase viscosity, the transformation could be observed at temperatures as low as 1200 °C for the c-BN–glass composites. In contrast, no transformation was found at temperatures up to 1575 °C when no liquid oxide phase is present in the composite. The results were compared with previous studies concerning the c-BN stability and the c-BN phase diagram. [ABSTRACT FROM AUTHOR]

Die filling during dry compaction shaping operations is one important process step, which influences quality and complexity of the compacts as well as the processing speed. A method for characterizing the die filling behavior under process-oriented conditions will be presented. By the use of a self-constructed filling device, the filling progress can be visualized and quantified via image processing. The density structure of the resulting bulk in the die is analyzed using computer tomography. On the basis of experiments with ceramic granules the potential of the new method is shown. [ABSTRACT FROM AUTHOR]

Freeze Foams are cellular, ceramic structures with hierarchical pore structures that are manufactured using the direct foaming process. By tailoring their morphology and strength, these foam structures are able to cover a wide range of application. Earlier works identified that pore-forming influencing factors (water and air content, suspension temperature, as well as pressure reduction rate) dictate the constitution on a macroscopic and microscopic scale. Therefore, the ability to manufacture foams whose properties align with the component requirements would be an important step in advancing towards a widespread application of these promising materials. With this goal in mind, the correlation between the pore-forming influencing factors and the resulting mechanical properties was quantified. Foams with independently adjustable porosities were produced at the micro and macro scales and evaluated according to their material failure behavior under compressive loads. As a result, foams with determined macroporosities between 38 and 62%, microporosities between 25 and 42%, and compression strengths between 1 and 7 MPa with different material failure characteristics were manufactured and systematically investigated. [ABSTRACT FROM AUTHOR]

Hardness, high mechanical strength, wear and corrosion resistance, for instance, are the most important properties of silicon nitride. Next to technical application, the material becomes more and more important for medical applications, especially for implants and the focus in research for this increase steadily. Up to now, the demands on the geometry of silicon nitride-based components could largely be met by using conventional shaping methods such as pressing and green machining or injection moulding. However, requirements in terms of complexity and function are constantly increasing. By using additive manufacturing (AM) technologies, the complexity of components can be significantly increased and additional functions such as transport channels or features like triple periodic minimal surfaces (TPMS), which seem to be advantageous for osseointegration can be integrated, for instances. High-resolution AM processes such as stereolithography enable the production of very accurate and complex ceramic components. In this work a silicon nitride suspension suitable for biomedical applications was developed and the influence of the formulation on the properties (especially flow and curing behavior) were analyzed. Afterwards, various test samples were generated by ceramic additive manufacturing via vat photopolymerization (CerAM VPP), thermally processed and the sintered parts were characterized with common ceramic methods, like mechanical tests and microstructure analyses, showing satisfying results for the described development state. [ABSTRACT FROM AUTHOR]

The blending of lithium ion insertion compounds is a novel and promising approach to design advanced electrodes for future secondary batteries. Recently, considerable improvements regarding power density and safety issues have been achieved by combining several insertion compounds. However, the understanding of basic interactions between the constituents of the blend is still ongoing. In the present theoretical study, we derive a mathematical model of the reversible heat generation rate of a blended insertion electrode based on the thermodynamic properties of its constituents. The reversible heat is found to be a function of the entropy of the lithium insertion reaction, the mass fraction, and the differential capacity of each constituent in the blend. The impact and the significance of these parameters on the reversible heat generation rate and its state of charge dependence are analyzed. The derived relations can be used to determine the reversible heat profile of a blended insertion electrode for all possible compositions if the properties of the pure constituents are known. The results suggest the opportunity of designing specific reversible heat profiles by a targeted compilation of the blend. [ABSTRACT FROM AUTHOR]

Additive Manufacturing is experiencing an upswing in many sectors of industry for a broad variety of materials. Processes are mainly developed for polymers and metals. For ceramics, hardmetals and especially cermets there are only a few additive processes suitable. The powder-based technique Binder-Jetting is one of these suitable processes with high productivity and relatively low green density. Within this study, TiCN-based cermets are printed by Binder-Jetting for the first time. The complexity of influences of the morphology and composition of cermet powders are discussed in regard to bulk density and material properties of printed and sintered parts. Studied TiCN-based cermet compositions represent different Ni and Mo2C contents. Main points of this investigation are further the adjustment of ratio of the raw materials for good sintering behaviour and their influence on the microstructures and as a function of varied sintering temperatures. [ABSTRACT FROM AUTHOR]

High-entropy carbides (HEC) are a class of promising new hard phases for a sustainable improvement of hardmetal properties. In this work, hardmetals of the HEC (Ta,Nb,Ti,V,W)C were studied with two typical binder volume fractions of 16 and 24 vol-% consisting of Co, Ni and FeNi. The sintering behaviour, microstructure, phase composition, magnetic and mechanical properties are discussed and are compared to a conventional WC-Co hardmetal. It was shown that the HEC has a high-phase stability and that dense hardmetals with promising mechanical properties were obtained. [ABSTRACT FROM AUTHOR]

Abrasive media were examined before and after application in abrasive flow machining to evaluate the wear of media due to the machining process. Both media were tested on workpieces under the same working conditions to study the effect of abrasive media wear on the results of the machining process. With the help of rheological and granulometric characterisation methods, it has been shown that alterations of rheological behaviour and composition of the abrasive medium as well as particle shape and size are responsible for the degradation of the abrasive efficiency. The increasing viscosity of the abrasive medium and progressing rounding of the large abrasive particles as a result of the machining process are the main factors that cause a decreased material removal rate and reduced surface quality. [ABSTRACT FROM AUTHOR]

Continuous direct foaming techniques for ceramics promise economical and ecological advantages compared to other manufacturing routes. No additional template is needed to generate a foam structure, and no fugitive pore formers have to be burned out. Using only air as the pore former, much lower emissions of waste gases can be achieved during the heat treatment of the foam. The challenge of the direct foaming technique is the control of the metastable wet foam state where foam destabilization processes can change or destroy the foam structure. Complex rheological and microscopic measurements were developed to investigate the relationship between rheological parameters and foam stability. It could be shown that the storage modulus G' is the dominant factor describing the stability of the wet foam. The shear-thinning behavior and the value of the viscosity of the slurry define the possible foam porosity in dependence of the manufacturing parameters of the foaming device. Foamability and foam stability are rheological contrary to each other. The Sauter diameter D32 was used to characterize the pore size. Theoretical calculations of the Sauter diameter D32 could be verified by experimental data. Suitable parameters are shown to produce stable foams with high porosities. [ABSTRACT FROM AUTHOR]

Advanced ceramics are recognized as key enabling materials possessing combinations of properties not achievable in other material classes. They provide very high thermal, chemical and mechanical resistance and typically exhibit lower densities than metals. These properties predestine ceramics for many different applications, especially those in space. Aerospike nozzles promise an increased performance compared to classic bell nozzles but are also inherently more complex to manufacture due to their shape. Additive manufacturing (AM) drastically simplifies or even enables the fabrication of very complex structures while minimizing the number of individual parts. The applicability of ceramic AM ("CerAMfacturing") on rocket engines and especially nozzles is consequently investigated in the frame of the "MACARONIS" project, a cooperation of the Institute of Aerospace Engineering at Technische Universität Dresden and the Fraunhofer Institute for Ceramic Technologies and Systems (IKTS) in Dresden. The goal is to develop novel filigree aerospike nozzles with 2.5 N and 10 N thrust. For this purpose, CerAM VPP (ceramic AM via Vat Photopolymerization) using photoreactive and highly particle-filled suspensions was utilized. This contribution gives an overview of the component development starting from CAD modeling, suspension development based on alumina AES-11C, heat treatment and investigation of the microstructure of the sintered components. It could be shown that modifying the suspension composition significantly reduced the formation of cracks during processing, resulting in defect-free filigree aerospike nozzles for application in space. [ABSTRACT FROM AUTHOR]

The effective use of energy from sustainable sources is considered a crucial step on the way to a CO2-neutral economy. Low-grade waste heat (<100 °C) is widely and ubiquitously available, but difficult to convert into electrical energy with current technologies. Here, we demonstrate an electrochemical cell capable of directly converting ambient temperature fluctuations into electricity. Based on intercalation reactions with different entropies, any temperature change leads to a cell voltage and electrical energy can be extracted. The new cell concept features the advantages of thermo-electrochemical cells and pyroelectric-like energy harvesting, which opens a wide range of possibilities for effective and sustainable use of low-grade waste heat. [ABSTRACT FROM AUTHOR]

The development of rechargeable batteries with high‐energy density is critical for future decarbonization of transportation. Anode‐free Li‐ion batteries, using a bare current collector at the anode side without any excess of Li, provide the highest volumetric energy density (>1500 Wh L−1) among all possible cell configurations. Furthermore, elimination of the anode material coating reduces material consumption and greatly simplifies cell production, which in turn lowers costs. Although significant progress has been made recently by the application of modified current collectors, optimized cycling parameters and improved liquid electrolytes, insufficient efficiencies, and dendritic growth during lithium plating lead to poor cycle life of typically less than 100 cycles as well as safety issues. Alternatively, very recent studies have demonstrated anode‐free solid‐state batteries that combine the benefits of high energy anode‐free cell configuration and solid‐state systems with high safety, exceeding 1000 cycles. This review provides an overview of recent developments toward anode‐free solid‐state batteries and highlights the current issues and challenges in this nascent field. It is concluded that, although major challenges remain at the present, the lessons learned in the fields of liquid electrolytes and solid‐state lithium metal batteries can accelerate the development of anode‐free solid‐state batteries of practical relevance. [ABSTRACT FROM AUTHOR]

Large‐scale electrochemical energy storage is considered one of the crucial steps toward a sustainable energy economy. Science and industry worldwide are conducting intensive research into various ways to improve existing battery concepts or transferring novel concepts to application. The development of materials and electrodes is an essential step in this process. However, the evaluation of the achieved performance parameters and the comparison of the different studies at this technological level with regard to practical applications is challenging, since special electrodes and cell concepts are typically used at laboratory scale. In the present work, a straightforward computational tool (Ragone calculator) is provided to estimate performance data at the full cell level based on electrochemical measurements on electrodes. Application of the Ragone calculator simplifies the comparability of the different studies and allows an appropriate classification of the reported performance data. In addition, extrapolation of the results to the battery level can make a valuable contribution to assessing at early stages whether a development is target‐oriented or in which direction it needs to be advanced. [ABSTRACT FROM AUTHOR]

Abstract: The performances of single cell solid oxide fuel cell (SOFC) stacks with Ni/8YSZ (8 mol% Y2O3 doped ZrO2) and Ni/10CGO (10 mol% Gd2O3 doped CeO2) anodes were compared with respect to sulfur poisoning (1–50 ppm) with H2/H2O/N2 fuel mixture at 850 °C. The mechanisms of the sulfur poisoning and regeneration of Ni/8YSZ and Ni/10CGO anodes at the triple phase boundaries are discussed. The effects of various parameters as H2S contamination cycles, H2S concentration, current density, H2O concentration and contamination durations were examined. A mechanism for the progress of the sulfur poisoning in the anode is proposed. It is shown that theoretically it is possible to calculate the nickel surface area accessible for the sulfur adsorption in the anode using H2S poisoning behavior for Ni/8YSZ anodes. The sulfur poisoning mechanisms of Ni/8YSZ and of Ni/10CGO anodes are proposed by taking into account the different oxidation mechanisms of H2 in the anodes considered in previous studies. The higher sulfur resistance of Ni/10CGO is explained with its high mixed ionic electronic conductivity as well as its ability to adsorb H2. Due to these properties CGO can continue electrochemical reactions even when nickel is covered with sulfur. [Copyright &y& Elsevier]

Dense (Hf, Ta, Nb, Ti, V)C- and (Ta, Nb, Ti, V, W)C-based high-entropy carbides (HEC) were produced by three different sintering techniques: gas pressure sintering/sinter–HIP at 1900 °C and 100 bar Ar, vacuum sintering at 2250 °C and 0.001 bar as well as SPS/FAST at 2000 °C and 60 MPa pressure. The relative density varied from 97.9 to 100%, with SPS producing 100% dense samples with both compositions. Grain size measurements showed that the substitution of Hf with W leads to an increase in the mean grain size of 5–10 times the size of the (Hf, Ta, Nb, Ti, V,)C samples. Vacuum-sintered samples showed uniform grain size distribution regardless of composition. EDS mapping revealed the formation of a solid solution with no intermetallic phases or element clustering. X-ray diffraction analysis showed the structure of mostly single-phase cubic high-entropy carbides. Hardness measurements revealed that (Hf, Ta, Nb, Ti, V)C samples possess higher hardness values than (Ta, Nb, Ti, V, W)C samples. [ABSTRACT FROM AUTHOR]

An intrinsic challenge of Li‐ion batteries is the instability of electrolytes against anode materials. For anodes with a favorably low operating potential, a solid‐electrolyte interphase (SEI) formed during initial cycles provides stability, traded off for capacity consumption. The SEI is mainly determined by the anode material, electrolyte composition, and formation conditions. Its properties are typically adjusted by changing the liquid electrolyte's composition. Artificial SEIs (Art‐SEIs) offer much more freedom to address and tune specific properties, such as chemical composition, impedance, thickness, and elasticity. Art‐SEIs for intercalation, alloying, conversion and Li metal anodes have to fulfil varying requirements. In all cases, sufficient transport properties for Li‐ions and (electro‐)chemical stability must be guaranteed. Several approaches for Art‐SEIs preparation have been reported: from simple casting and coating techniques to elaborated Phys‐Chem modifications and deposition processes. This review critically reports on the promising approaches for Art‐SEIs formation on different type of anode materials, focusing on methodological aspects. The specific requirements for each approach and material class, as well as the most effective strategies for Art‐SEI coating, are discussed and a roadmap for further developments towards next‐generation stable anodes are provided. [ABSTRACT FROM AUTHOR]

A zirconia-based potentiometric solid electrolyte gas sensor with internal solid state reference was used to study the response behavior of platinum cermet and indium tin oxide sensing electrodes. Target gases included both oxygen and carbon monoxide in nitrogen-based sample gas mixtures. It was found that with the indium tin oxide sensing electrode, the low-temperature behavior is mainly a result of incomplete equilibration due to contaminations of the electrode surface. On the other hand, some of these contaminant species have been identified as being pivotal for the higher carbon monoxide sensitivity of the indium tin oxide sensing electrode as compared to platinum cermet electrodes. [ABSTRACT FROM AUTHOR]

The critical challenge for the user acceptance of electric vehicles is the simultaneous improvement of the driving range and fast charging capabilities, which are related to the energy and power density of the storage device. Lithium‐ion batteries (LIBs) are currently the most promising candidate to push electric vehicles toward the mass market. However, they suffer from a tradeoff between energy and power density, forbidding arbitrary combinations of high storage capacity and fast charging capability. Herein, a simple electrochemical principle describing the intrinsic limits of LIBs is reported. It is deduced that the tradeoff between energy and power density originates from diffusion limitations in the electrolyte. The electrochemical approach of diffusion‐limited current density is adapted to porous Li‐ion insertion electrodes, resulting in the "diffusion‐limited C‐rate" (DLC). The theoretical considerations are in excellent agreement with experimentally observed rate limitations of a large number of electrodes with different active materials and varying design parameters. While the C‐rate drawn from an LIB cannot be higher than the DLC without significant capacity decline, parameter variations that improve the DLC reduce the nominal specific capacity. This relationship makes the DLC a fundamental quantity revealing the most expedient optimization approaches and promising directions for future battery research and development. [ABSTRACT FROM AUTHOR]

Understanding and optimizing the electrolyte wetting of lithium-ion cells provides a high potential to reduce the manufacturing costs of lithium-ion cells. However, established methods to investigate the wetting of porous materials are not easily transferable to lithium-ion cells, since they neglect major paths in the wetting process. In this study, a novel method is proposed to in situ quantify the wetting progress in lithium-ion cells with graphite-based anodes. A constant potential is applied to the cell immediately after the electrolyte wetting process has been initiated and the current response is carefully analyzed as it reflects the progress of the electrolyte wetting process accompanied by SEI film formation. By applying this procedure, the influence of different separators, cell formats and ambient temperatures on the wetting time is investigated. Furthermore, the wetting behavior of laser-structured electrodes is investigated as well as of electrodes with ceramic multilayer coating which can replace the standard separator. The results demonstrate that the interface between the separator and the electrodes plays a dominant role and mainly influences the wetting process of a lithium-ion cell. The findings point out the importance of using in situ methods to analyze the wetting process of lithium-ion cells. [ABSTRACT FROM AUTHOR]

The literature describes various beneficial effects of the pulse anodizing of aluminum related to the corrosion resistance, hardness, and electronic properties of the oxide layer, the thermal impact during the anodizing process as well as reduced energy consumption. In spite of the considerable improvements, the understanding of basic mechanisms and the specific impact of the applied pulse parameters are still under discussion. Herein, the local development of the electrolyte concentration during pulse anodizing in sulfuric acid is investigated by means of finite element computations. The impact of the thickness of the porous oxide, the applied current density, and the pulse frequency are examined systematically. The results suggest that the electrolyte concentration at the oxide/electrolyte interface can be effectively controlled by applying tailored pulse parameters. [ABSTRACT FROM AUTHOR]

Thin-walled 3D-customized ceramic components can be used, e.g. for inert and thermal resistant housings as well as special surface structured kiln furniture. For manufacturing such components, deep drawing of ceramic green tapes has been used. The technology has been almost not applied for processing of ceramic green tapes. A new approach was developed to realize a homogenous ceramic particle packing and hence uniform green density within a deep drawn green tape. After debinding and sintering, defect-free model structures with a dense microstructure (density > 99%) were achieved. Within this study, the deep drawing of ceramic green tapes by using a new approach was investigated. The developed approach brings several beneficial properties together, e.g. a reproducible form deviation and more importantly a homogeneous particle distribution allowing homogeneous and dense structures. With this results, the transformation of non-complex and cheap ceramic green tapes to 3D-customized and near-net-shape thin-walled mouldings becomes possible. [ABSTRACT FROM AUTHOR]

An approach for the preparation of homogenous SrTiO3 (STO) thin films with unprecedented compositional control is presented. Nanolaminates of SrO and TiO2 were deposited at 300 °C by atomic layer deposition on bare silicon, as well as on ruthenium electrodes using metalorganic precursors [Ti(NEtMe)4 (TEMATi),Sr(iPr3Cp)2 (AbsoluteSr)]. Care was taken that the individual sublayers were grown with a number of subcycles well in the steady-state growth regime. This enabled linear composition tuning with the Sr:Ti pulse ratio, which is beneficial for process control. Still, a substrate-specific growth behavior was observed for the individual precursors leading to different cycle ratio/composition dependence for samples grown on Si as compared to Ru substrates. This could be attributed to specific nucleation conditions, which are most pronounced for the initial cycle, but also prevail throughout the film. The as-deposited layers are well separated and the sublayers are amorphous. Subsequent furnace-annealing generated polycrystalline cubic STO films, but also caused a severe distortion of the metal electrode/STO stack, due to interdiffusion. The latter was suppressed by optimized rapid thermal crystallization anneals. [ABSTRACT FROM AUTHOR]

Abstract Additive manufacturing processes become more and more important in almost all areas, also for medical implant application. Medical implants made of ceramics are known for their excellent biological compatibility. For increasing the ingrowth of cells into an implant, a function-optimized structure with a defined porosity seems to be advantageous. Additive manufacturing is suited to realize defined and filigree structures. Lithography-based ceramic manufacturing (LCM), for example, has a high resolution, but still a limited material portfolio. Alumina toughened zirconia is a very interesting material for medical applications, but not commercially available for LCM. In this study, the development of an ATZ suspension usable in the LCM process with a bulk material density higher than 99% after sintering is presented. Furthermore, printing of lattice test structures for the evaluation of accuracy in dependence of printing dimension is demonstrated. [ABSTRACT FROM AUTHOR]

The so-called Freeze Foaming method aims at manufacturing ceramic cellular scaffolds for diverse applications. One application is dedicated to potential bone replacement material featuring open, micro and interconnected porosity. However, the main challenges of this foaming method is to achieve a homogeneous pore morphology. In a current project, the authors throw light on the bubble/pore and strut formation of this process by in situ computed tomography. This allows for evaluating varying process parameter’s effects on the growth of the ceramic foam during the foaming process. As first result and basis for CT analysis, a stable and reproducible model suspension was developed which resulted in reproducible foam structures. In dependence of selected process parameters like pressure reduction rate or air content in the ceramic suspension resulting Freeze Foams became adjustable with regard to their pore morphology. Pore size and distribution data as well as the porosity were characterized and evaluated accordingly. [ABSTRACT FROM AUTHOR]

The ionic conductivity of electrolytes, fluid or solid, in lithium-ion cells is essential for the high-performance application in the automotive field. In colder temperatures, the literature shows the polymer solid-state approach has a weakness connected to ionic conductivity (Grundish et al., 2021; Kamaya and et al., 2011; Manthiram et al., 2017) [1–3]. At elevated temperatures the ionic conductivity rises and becomes attractive for the automotive usage. In this work, it is investigated how large automotive pouch cells, with polymer electrolyte and lithium-metal anode, can be heated up. Different heating systems and boundary conditions, as ambient temperature and heating power are investigated. Due to the anisotropic thermal conductivity in- and through-plane of the cell, a high variance in the heating time with different heating systems occurs, with up to 13% difference. A reciprocal effect of heating time and temperature spread inside one cell is observed – the shorter the heating time, the higher the temperature spread. Also, a strong influence of the ambient temperature can be seen. With lower surrounding temperature the heating time rises strongly. In comparison between the ambient temperatures −25 °C and 10 °C the heating time can be reduced by 17%. This work shows that the thermal behavior of new cell technologies needs to be investigated more closely. [Display omitted] • Transient heating behavior of a polymer solid-state cell with lithium metal anode. • Investigation of three different heating systems for automotive applications. • Influence of the heating direction and power on heating time and temperature spread. • Variation of ambient temperature and heating power. [ABSTRACT FROM AUTHOR]

Abstract: The operation of solid oxide fuel cells requires gas tight and stable sealing materials. Glass ceramic materials have been established to seal different stack designs and can be optimized to match the requirements of components and joining conditions. It is known that glass‐based sealants are sensitive to the formation of undesired chromia species in contact with ferritic steels used as interconnects. Their formation depends on the earth alkaline type and content in the glass as well as the chromium content of the interconnect. A robust interconnect material is the chromium‐based sinter alloy CFY with >93 wt.% chromium what in turn enforces the formation of chromia phases. SOFC stacks with chromium‐based interconnects and electrolyte supported cells with 10SCSZ electrolyte are candidates for SOFC systems with high efficiency in a wide power range. This study presents results on the development of sealing glasses adapted for the CFY by optimizing the glass components BaO, CaO, SiO2, and Al2O3. Depending properties like crystallization behavior, thermal expansion, adhesion and reactivity in contact with CFY have been regarded. The glass has been tested under operating conditions of SOFC (dual atmosphere, electric potentials) in samples as well as in real stacks. It has been shown that optimized glass compositions, especially regarding a limited BaO content combine a good joining behavior and minimized BaCrO4 formation in contact with the CFY alloy. [ABSTRACT FROM AUTHOR]

In our study, we investigated the additive manufacturing (AM) of ceramic-based functionally graded materials (FGM) by the direct AM technology thermoplastic 3D printing (T3DP). Zirconia components with varying microstructures were additively manufactured by using thermoplastic suspensions with different contents of pore-forming agents (PFA), which were co-sintered defect-free. Different materials were investigated concerning their suitability as PFA for the T3DP process. Diverse zirconia-based suspensions were prepared and used for the AM of singleand multi-material test components. All of the samples were sintered defect-free and in the end, we could realize a brick wall-like component consisting of dense (<1% porosity) and porous (approx. 5% porosity) zirconia areas to combine different properties in one component. T3DP opens the door to the AM of further ceramic-based 4D components, such as multi-color, multi-material, or especially, multi-functional components. [ABSTRACT FROM AUTHOR]

Superhard silicon carbide-bonded diamond materials were synthesized by liquid silicon infiltration of diamond-containing preforms. The properties of the materials were strongly influenced by the strength of the interfaces between the diamond and the silicon carbide. Interface formation was investigated through local analysis of the microstructure in the interface regions using field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and electron backscatter diffraction (EBSD) as well as X-ray diffraction (XRD). The results of these experiments revealed a pronounced orientation relationship between SiC and diamond at their interfaces and, as a result, strong bonding of the diamond particles to the ceramic matrix. There was also an orientation relationship between the nano-sized SiC grains, which were embedded in residual silicon near the diamond interfaces, and diamond. Additionally, the different morphologies and phenomena occurring in the microstructures of the diamond-SiC composites and their dependence on the infiltration temperature were studied. [ABSTRACT FROM AUTHOR]

In this work a halogen-free electrolyte to deposit platinum nanoparticle is studied. The investigated [Pt(NO 2 ) 2 SO 4 ] 2− -complex is suitable for electrochemical deposition on halogen sensitive substrates. The mechanism and kinetic of particle deposition is investigated using a glassy carbon rotating disk electrode. Nano sized platinum particles are deposited by using pulse plating technique. The size of the smallest platinum nanoparticle is 5 nm. The shape of the particle distribution strictly depends on the plating time. The platinum deposition is usually superimposed with hydrogen evolution. A diffusion coefficient of the [Pt(NO 2 ) 2 SO 4 ] 2‐ -complex is determined to 5.4 × 10 −6 cm 2 s −1 . The current efficiency depends on the deposition parameters and amounts to 37% under the chosen pulse plating conditions. [ABSTRACT FROM AUTHOR]

The solid oxide cell is a basis for highly efficient and reversible electrochemical energy conversion. A single cell based on a planar electrolyte substrate as support (ESC) is often utilized for SOFC/SOEC stack manufacturing and fulfills necessary requirements for application in small, medium and large scale fuel cell and electrolysis systems. Thickness of the electrolyte substrate, and its ionic conductivity limits the power density of the ESC. To improve the performance of this cell type in SOFC/SOEC mode, alternative fuel electrodes, on the basis of Ni/CGO as well as electrolytes with reduced thickness, have been applied. Furthermore, different interlayers on the air side have been tested to avoid the electrode delamination and to reduce the cell degradation in electrolysis mode. Finally, the influence of the contacting layer on cell performance, especially for cells with an ultrathin electrolyte and thin electrode layers, has been investigated. It has been found that Ni/CGO outperform traditional Ni/8YSZ electrodes and the introduction of a ScSZ interlayer substantially reduces the degradation rate of ESC in electrolysis mode. Furthermore, it was demonstrated that, for thin electrodes, the application of contacting layers with good conductivity and adhesion to current collectors improves performance significantly. [ABSTRACT FROM AUTHOR]

Liquid phase-sintered B 6 O materials with Al 2 O 3 /Y 2 O 3 additives were recently developed to yield higher fracture toughness and strength levels than those of pure B 6 O-materials. However, the high additive contents of hot-pressed and spark plasma-sintered (FAST/SPS) materials led to the formation of strength-limiting boride precipitates. Systematic variation of the B 2 O 3 content of the grain boundary phase and thermodynamic calculations carried out in the present work showed that it is possible to avoid boride formation by controlling the decomposition of B 2 O 3 during densification and adjusting the B 2 O 3 content of the composition through direct addition of B 2 O 3 or through reaction of added transition metal oxides such as TiO 2 with the starting composition to form B 2 O 3 . [ABSTRACT FROM AUTHOR]

A combined experimental and numerical study is conducted to investigate temperature nonhomogeneities within a Spark Plasma Sintering tooling setup. Radial thermal gradients through a powder compact are encountered, a cause of microstructural nonuniformities in sintered specimens, which tend to become more significant when increasing the setup's characteristic size. In the insulating silicon nitride powder compact employed for the experimental procedures, a double pyrometer arrangement detects a strong temperature disparity between the overheated die and the area adjacent to the tooling's axis. A previous finite-element simulations campaign had individuated a possible solution in a novel punch design, consisting in the drilling of three concentric ring-shaped holes according to a specific geometrical pattern, whose efficacy is here experimentally verified. Further punch optimization strategies are drawn, involving a refinement of the three-rings geometry by linearly varying the drilled holes characteristic dimensions along the radial direction, or the selective coating and consequent insulation of the punch cross section with a thin layer of hexagonal boron nitride. Ideal configurations are identified, consisting in a concentration of the graphite punch's mass at its center by means of a tailored holes pattern, or in the coating of a portion of the conventionally shaped punch with boron nitride. [ABSTRACT FROM AUTHOR]

A new sulfur containing hydroxy sodalite (S–SOD) of high thermal and hydrothermal stability was synthesized and characterized. XRD measurements showed some differences to normal hydroxy sodalite (H–SOD). But the S–SOD is also quite different from natural sulfur containing sodalites like ultramarine blue. IR– and RAMAN-spectroscopy measurements detected no sulfur radicals in the structure of S–SOD, which was already assumed because of the colorless powder of S–SOD. 29 Si–, 27 Al– and 23 Na–MAS–NMR measurements were conducted to determine the order of the structure and the type of incorporation of the sulfur into the sodalite structure. The sulfur is most likely coordinated statistically on every possible oxygen position in the structure. The pore size of the S–SOD was determined by positron annihilation measurements and is suitable for hydrogen separations. [ABSTRACT FROM AUTHOR]

For printing the front side metallization of solar cells using the non-contact aerosol printer different silver inks with different rheological properties and silver components were tested. Both atomization methods of the aerosol printer are introduced and the optimized printing parameters are discussed. With the most suitable inks and printing parameters it was possible to achieve high aspect ratios within 2:1 up to 4:1 with small lateral resolutions. A particle-free ink and several particle-containing inks for example diluted screen printing pastes were tested as aerosol ink to evaluate the most feasible ink. According to these results it was possible to assess the most important properties for aerosol inks, which are necessary to obtain a good printability and well defined printed structures. High aspect ratios (AR) of 2:1 were achieved by aerosol printing with the pneumatic atomizer for the front side metallization grid of solar cells and efficiencies of 14-17 % were achieved. [ABSTRACT FROM AUTHOR]

Abstract: SiC-fiber/SiCN ceramic matrix composites were manufactured by means of polymer infiltration and pyrolysis. The fiber preform was made by slurry infiltration and winding using a computer-controlled winding module. Multiple infiltration steps using a Si–C–N precursor were included to increase the density. The influence of the sintering conditions on the microstructure of the CMC was demonstrated. Pipe sections made of the CMC materials were joined using a laser-supported heating technology with an Y–Al–Si–O glass–ceramic filler. The thermal response of the CMC components was controlled by the anisotropic thermal conductivity. Fast heating by laser beam was achieved for elements rotating in the direction of the fiber winding. SEM micrographs of the joints showed the good wettability of the CMC by the glass–ceramic filler. Nearly defect-free joints were obtained using a nitrogen process atmosphere. The laser-supported technology was shown to be promising for the joining of CMC components. [Copyright &y& Elsevier]

Freeze foaming is a method to manufacture cellular ceramic scaffolds with a hierarchical porous structure. These so-called freeze foams are predestined for the use as bone replacement material because of their internal bone-like structure and biocompatibility. On the one hand, they consist of macrostructural foam cells which are formed by the expansion of gas inside the starting suspension. On the other hand, a porous microstructure inside the foam struts is formed during freezing and subsequent freeze drying of the foamed suspension. The aim of this work is to investigate for the first time the formation of macrostructure and microstructure separately depending on the composition of the suspension and the pressure reduction rate, by means of appropriate characterization methods for the different pore size ranges. Moreover, the foaming behavior itself was characterized by in-situ radiographical and computed tomography (CT) evaluation. As a result, it could be shown that it is possible to tune the macro- and microstructure separately with porosities of 49–74% related to the foam cells and 10–37% inside the struts. [ABSTRACT FROM AUTHOR]

Porous perovskite (LaMnO3) fibers were prepared by means of wet phase inversion spinning. The influence of different spinning procedures, slurry and coagulation bath composition on fiber shape and pore morphology was studied. The catalytic activity of the prepared fibers was tested for carbon monoxide oxidation as a model reaction in a differential recycle reactor. The results revealed that by suitable choice of process conditions porous catalytically active fibers can be prepared. Catalytic measurements confirmed that the catalytic fibers exhibit an open structure that allows full utilization of the catalytically active surface without intraparticle diffusional limitations. [ABSTRACT FROM AUTHOR]

Highlights: [•] An overview on catalyst support structures based on fibrous material is given. [•] Mass transfer and pressure drop properties of several structures are compared. [•] Fiber based structured materials offer advantageous properties for several applications. [ABSTRACT FROM AUTHOR]

Highlights: [•] PZT-modules embedded into aluminum high pressure die castings. [•] No damage of functional element despite of harsh casting conditions. [•] Different positions of the PZT-modules in the casting can be realized. [•] Integrated actuators can reach a relative functionality of 90%. [•] Functionality decreases with increasing wall thickness. [Copyright &y& Elsevier]

Abstract: Dense boron rich boron carbides were reactive sintered by hot pressing at 2050°C using elementary boron carbon compositions with carbon contents of 9.1, 11.1, 13.3 and 18.8at.%. The following material characteristics are presented: relative density, SEM images, EDX, X-ray diffraction and corresponding lattice parameters, Seebeck coefficient, electrical conductivity and thermoelectric power factor. Significant grain growth has been obtained with increasing boron content. A deeper understanding of the boron and carbon reaction and the overall sintering process is gained by thermal and chemical analysis in combination with X-ray diffraction. Additionally a thermal experiment with boron and carbon layers illustrates the solid state diffusion behaviour. The found results of boron carbide properties of this paper correspond with results by other authors. The aim is to correlate technological aspects of sintering procedure with material properties. This should help to improve the thermoelectric efficiency of boron carbide based materials. [Copyright &y& Elsevier]

Abstract: Sintered silicon carbide materials have found widespread use due to their high corrosion stability. This corrosion stability can be affected by electrochemical processes. Electrochemical corrosion experiments conducted on a SSiC material in H2SO4 at different voltages and subsequent detailed investigation of the formed surfaces was carried out. The first time a systematic local measurement of the thickness of the oxide layers was carried out. The measurements revealed the formation of SiO2 surface layers with thickness up to 125μm. The measured values also showed a strong deviation from grain to grain. The thickness of the layers does not correlate with the crystallographic orientation of the grains or the SiC-polytypes. The data indicate that the behaviour is caused by the variation of the resistivity of the grain boundaries. The measured thicknesses as a function of the electrical charge transferred indicate that the electrochemical oxidation results in the SiO2 and carbon dioxide. [Copyright &y& Elsevier]

The transition from fossil-based primary steel production to a low-emission alternative has gained increasing attention in recent years. Various schemes including Carbon Capture and Utilization (CCU) and Carbon Direct Avoidance (CDA) via hydrogen-based as well as electrochemical routes have been proposed. With multiple technical analyses being available and technical feasibility being proven by first pilot plants, pathways towards commercial market entry are of increasing interest. While multiple publications on the economic feasibility of CCU are available, data on CDA approaches is scarce. In this work an economic model for the quantification of production cost as well as CO 2 emission mitigation cost is presented. The approach is characterized by a seamless integration with a flowsheet-based process model of a direct reduction-based crude steel production plant detailed in a previous work and allows for the investigation of multiple economic aspects. Firstly, the gradual transition from the natural gas-based state-of-the-art direct reduction towards a fossil-free hydrogen-based reduction is analyzed. Furthermore, a comparison between the more mature technology of low-temperature electrolysis and a potentially more efficient solid oxide electrolysis (SOEL) is given, highlighting the potential of SOEL technology. The conducted forecast to 2050 shows that SOEL-based CDA offers lower production cost when technological maturity is reached. Based on the results of the economic assessment possible legislative support mechanisms are studied, showing that legislative actions are necessary to allow for market entry as well as for sustainable and economically feasible operation of fossil-free direct reduction plants. [ABSTRACT FROM AUTHOR]

Abstract: Cubic gallium oxynitride was synthesized using a solvothermal processing route. Crystal structure, chemical composition, optical properties and the influence of heat treatment in either reactive or inert atmospheres have been investigated. Despite a strongly distorted lattice revealed using X-ray diffraction, the Raman active modes of a cubic gallium oxynitride structure could be observed. With diffusive reflectance UV–Vis spectroscopy a band gap at around 4.8eV has been observed. Additionally, cathodoluminescence spectroscopy exhibited observable luminescence caused by defect-related transitions within the optical gap. Cathodoluminescence and photoluminescence spectra collected after heat treatments showed significant changes in the defect structure. In particular, for annealing in ammonia the main spectral modifications were related to the substitution of oxygen by nitrogen on anion sites. [Copyright &y& Elsevier]

Abstract: Materials with enhanced wear resistance are of great interest for modern industry. The different ways of producing superhard ceramic materials are shortly reviewed. In detail, the preparation of diamond–silicon carbide composites by reactive infiltration of diamond preforms with liquid silicon at ambient pressure is investigated. In addition to homogeneous SiC/diamond materials with nearly 50vol.% of diamond layered composites were also prepared. The microstructures of the materials prepared under different infiltration conditions were analyzed using X-ray diffraction, electron microscopy, electron back-scatter diffraction (EBSD) and Raman spectroscopy. The properties of the materials depend strongly on the formation of graphite interlayers at the boundary between SiC and diamond. Hardness of 47GPa was reached for materials where the formation of the interlayer was prevented. [Copyright &y& Elsevier]