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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]

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]

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]

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]

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]

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]

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]

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 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]

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]

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]

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]

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]

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]

Solid oxide fuel cells are the most promising power conversion units for fossil and biomass fuels combining ceramic and metallic components. Because of long-term high temperature operation and thermal cycling the standard materials cannot be applied for integration of active ceramic components. Different approaches are used nowadays for the integration of ceramic cells into stacks and of system components in the power plant. In this paper an overview on the application of glass and glass ceramic sealants, active and reactive air brazes as well as compressive mica sealants for solid oxide fuel cells is made. The crystallizing glasses are more favorable for cell integration in the stack for operation in a broad temperature range. Metallic brazes are mainly limited to integration of anode or metal supported cells in ferritic alloy gaskets for operation at T < 750°C and mica is a most suitable solution for system component integration in hot regions of power plants as well as for gas tight electrical isolation. In addition, this study regards aspects of degradation processes of glass ceramic and metallic sealants which allow estimations for the long-term behavior of joints. [ABSTRACT FROM AUTHOR]

Abstract: Planar solid oxide fuel cells (SOFC) are considered to be power generators with high efficiency and low emission at small power units (1–200kWel). Many prototype systems are already successfully realized. For mass production the costs have to be reduced and the long-term stability has to be enhanced. Power losses <0.5%/1000h is the target value for stacks in stationary SOFC-based power systems. To reach this goal, the factors influencing degradation have to be found and reduced. In this work the interaction between interconnect and different ceramic materials such as perovskites (La0.8Sr0.2(Mn,Co)O3, La0.65Sr0.3MnO3, La0.65Sr0.3(Mn,Co)O3) and spinels (Mn(Co,Fe)O4, (Cu,Ni)Mn2O4) was investigated on the cathode (air) side of conventional ferritic interconnect materials (CroFer22APU, ITMLC, ZMG232L). The method to determine the value of the area specific resistance between interconnect and contact layer (R #ICC) within a tolerance of 10% has been developed to provide reliable data for ASR values and their degradation. The R #ICC-value increases with annealing time. The degree of this increase depends on used materials and their combination. The spinel contact layers form a thin dense ceramic layer at the beginning of the annealing process. This layer reduces the oxidation rate of the alloy. Because of this protection layer a thinner oxide scale grows and the ASR aging rate is much lower (0.4–0.9mΩcm2/1000h). The comparison of the aging rates of different alloys with La0.8Sr0.2(Mn,Co)O3 contact layer reveals remarkable differences: 3.1mΩcm2/1000h for CroFer22APU, 10.9mΩcm2/1000h for ITMLC and 21.2mΩcm2/1000h for ZMG232L. The degradation in a stack has been determined from the R #ICC-values and geometric factors. The impact of oxidation at the cathode side of interconnect is about one third of the total stack degradation. The method opens the possibility for comparing area specific resistances of special material combinations with high accuracy. By optimized material combinations the degradation in stacks can be reduced to <0.5%/1000h. [Copyright &y& Elsevier]

The complex reaction mechanism of iron-based Fischer-Tropsch synthesis comprises of manifold primary and secondary reaction pathways. Within this work, an experimental setup for spatially-resolved measurements on promoted iron-based Fischer-Tropsch catalysts is presented, allowing for a general study of the influence of operating conditions and promotion as well as of the influence of secondary reactions on product selectivity. It was found that, depending on catalyst composition, considerable hydrogenation of 1-alcohols and olefins occurs, while no considerable influence of reinitiation of chain growth on product distribution could be found. [Display omitted] • In-situ analysis of iron-based Fischer-Tropsch synthesis at reaction conditions. • Measurement of concentration profiles for Fischer-Tropsch products. • Influence of reaction conditions and promoters on measured profiles studied. • Evidence for secondary hydrogenation of primary formed 1-alcohols and olefins. • No evidence for reinitiation of chain growth by readsorbed primary products. [ABSTRACT FROM AUTHOR]

• NPC of syncrude derived from H 2 O and CO 2 were calculated for 2020 and 2050. • PEM- and SOEL-based PtL concepts were compared. • For 2020, the NPC of the PEM-based process is lower due to lower equipment cost. • For 2050, SOEL allows for lower NPC due to higher efficiency. Power-to-Liquid (PtL) processes are considered as a key technology for a fossil-free raw material and energy system. With multiple technical analyses being available and technical feasibility being proven by first pilot plants, pathways towards commercial market entry are of increasing interest. In this work multiple economic aspects of Power-to-Liquid plants are being investigated. First and foremost, the seamless integration of an economic analysis in the process modeling workflow will be demonstrated. This allows for an extensive investigation of the influence of operating conditions of the considered solid oxide electrolyzer (SOEL) on process economics and a subsequent optimization not only from an engineering standpoint but considering economics as well. Furthermore, the modular nature of the model allows for a comparison of SOEL to the more mature technology of low-temperature electrolysis with a focus on possible heat integration and by-product utilization. The potential of SOEL technology for high energetic efficiency and subsequently low production cost is highlighted. The conducted forecast to 2050 shows that SOEL-based Power-to-Liquid processes offer lower production cost of NPC = 0.203 € 2020 /kWh ch compared to production cost of NPC = 0.262 € 2020 /kWh ch for the PEMEL-based process. Furthermore, based on the results of the economic assessment possible governmental support mechanisms are studied, showing that projected values for governmental incentives are expected to decrease CO 2 mitigation cost from κ CO 2 = 791 € 2020 /t CO 2 to κ CO 2 = 419 € 2020 /t CO 2 for the 2050 scenario. Thus, existing measures and currently discussed measures are not sufficient to ensure economic viability. Consequently, more extensive schemes such as mandatory quotas for sustainable PtL products need to be implemented in order to facilitate the market entry. [ABSTRACT FROM AUTHOR]

By combining results of adsorption/desorption measurements on powders and electrical conductivity studies on thick and thin films, the interaction of indium tin oxide with various ambient gas species and carbon monoxide as potential target gas was studied between room temperature and 700 °C. The results show that the indium tin oxide surfaces exhibit a significant coverage of water-related and carbonaceous adsorbates even at temperatures as high as 600 °C. Specifically carbonaceous species, which are also produced under carbon monoxide exposure, show a detrimental effect on oxygen adsorption and may impair the film's sensitivity to a variety of target gases if the material is used in gas sensing applications. Consequently, the operating temperature of an ITO based chemoresistive carbon monoxide sensor should be selected within a range where the decomposition and desorption of these species proceeds rapidly, while the surface oxygen coverage is still high enough to provide ample species for target gas interaction. [ABSTRACT FROM AUTHOR]

During metal cutting, high temperatures of several hundred-degree Celsius occur locally at the cutting edge, which greatly impacts tool wear and life. Not only the cutting parameters, but also the tool material's properties influence the arising cutting temperature which in turn alters the mechanical properties of the tool. In this study, the hardness and thermal conductivity of cemented tungsten carbides were investigated in the range between room temperature and 1000 °C. The occurring temperatures close to the cutting edge were measured with two color pyrometry. The interactions between cemented carbide tool properties and cutting process parameters, including cutting edge rounding, are discussed. The results show that cemented carbides with higher thermal conductivities lead to lower temperatures during cutting. As a result, the effective hardness at the cutting edge can be strongly influenced by the thermal conductivity. The differences in hardness measured at room temperature can be equalized or evened out depending on the combination of hardness and thermal conductivity. This in turn has a direct influence on tool wear. Wear is also influenced by the softening of the workpiece, so that higher cutting temperatures can lead to less wear despite the same effective hardness. [ABSTRACT FROM AUTHOR]

Porous ceramics can be realized by different methods and are used for various applications such as cross-flow membranes or wall-flow filters, porous burners, solar receivers, structural design elements, or catalytic supports. Within this paper, three different alternative process routes are presented, which can be used to manufacture porous ceramic components with different properties or even graded porosity. The first process route is based on additive manufacturing (AM) of macro porous ceramic components. The second route is based on AM of a polymeric template, which is used to realize porous ceramic components via replica technique. The third process route is based on an AM technology, which allows the manufacturing of multimaterial or multiproperty ceramic components, like components with dense and porous volumes in one complex-shaped component. [ABSTRACT FROM AUTHOR]

With a novel Freeze Foaming method, it is possible to manufacture porous cellular components whose structure and composition also enables them for application as artificial bones, among others. To tune the foam properties to our needs, we have to understand the principles of the foaming process and how the relevant process parameters and the foam's structure are linked. Using in situ analysis methods, like X-ray microcomputed tomography (µCT), the foam structure and its development can be observed and correlated to its properties. For this purpose, a device was designed at the Institute of Lightweight Engineering and Polymer Technology (ILK). Due to varying suspension temperature and the rate of pressure decrease it was possible to analyze the foam's developmental stages for the first time. After successfully identifying the mechanism of foam creation and cell structure formation, process routes for tailored foams can be developed in future. [ABSTRACT FROM AUTHOR]