Challenges and prospects of automated disassembly of fuel cells for a circular economy

The hydrogen economy is driven by the growing share of renewable energy and electrification of the transportation sector. The essential components of a hydrogen economy are fuel cells and electrolysis systems. The scarcity of the resources to build these components and the negative environmental impact of their mining requires a circular economy. Concerning disassembly, economical, ergonomic, and safety reasons make a higher degree of automation necessary. Our work outlines the challenges and prospects on automated disassembly of fuel cell stacks. This is carried out by summarizing the state-of-the-art approaches in disassembly and conducting manual non-/destructive disassembly experiments of end-of-life fuel cell stacks. Based on that, a chemical and mechanical analysis of the fuel cell components is performed. From this, an automation potential for the disassembly processes is derived and possible disassembly process routes are modeled. Moreover, recommendations are given regarding disassembly system requirements using a morphological box

Steel Ceramic Composites resistant to long-term contact with molten aluminum alloys

The development and evaluation of novel stainless steel-based composites for direct contact with liquid aluminum alloys has been carried out. The Steel Ceramic Composite consisted of 60 vol% 316L stainless steel powder and 40 vol% of MgO or TiO2 ceramic powder. The sample were manufactured using uniaxial pressing and subsequent surface pre-oxidation at 850, 1000 °C for 24 h.The corrosion resistance of composite was investigated against molten AlSi7Mg0.3 alloy using crucible corrosion tests. The tests were carried out at 850 °C for 24 h and 168 h. The influence of pre-oxidation on the corrosion resistance of the samples was analyzed using XRD and SEM/EDS. The corrosion phases formed in the aluminum alloy were investigated using SEM/EDS/EBSD and PSEM/ASPEX/AFA and included the assessment of aluminum alloy contamination by evaluation of corrosion precipitation content, quantity and size. The sample Steel-MgO exhibited excellent corrosion resistance with negligible contamination of the aluminum alloy

Fused Filament Fabrication of Thermal-Shock-Resistant Fine-Grained Refractories for Steel-Casting Applications

Three-dimensionally printed fine-grained refractory ceramics ready for use in contact with liquid steel based on developed one-step thermal debindable ceramic filaments that do not require any chemical solvent pre-debinding are investigated. This work exhibits the most favourable debinding and sintering regimes with an excellent form stability and reproducibility of printed products ensured. The structure of the sintered products was examined with computed tomography. The designed inner geometry with micro-porosity introduced during debinding combined with pre-designed printed macro-cavities enabled the outstanding thermal-shock performance of the specimens. The functionality of the sintered refractory products in the form of casting nozzles was preliminarily tested in contact with steel melt using a hot-stage microscope. The structure of the specimen was subsequently examined with laser scanning microscopy and scanning electron microscopy. The mechanical properties of printed samples were studied via mercury intrusion porosimetry, compressive strength testing, and spatial tensile strength testing. According to the results, the cold crushing strength of the 3D-printed specimens in the printing direction was comparable to that of pressed fine-grained alumina specimens (50–60 MPa). The measured porosity was 21.5 vol% with a pore size less than 10 µm, which is suitable for applications in contact with molten steel. In order to show thermal-shock resistance of the 3D-printed casting nozzle, a 100 kg steel-melt flow test was performed in a steel-casting simulator with the nozzle surviving all related thermal shocks as well as the ferrostatic pressure of the melt. The evaluated composition and production route of the filaments can be utilized to produce one-step, thermally debindable, thermal-shock-resistant refractory parts with a complex inner structure that are applicable in an industrial environment

Corrosion-Resistant Steel–MgO Composites as Refractory Materials for Molten Aluminum Alloys

In this study, a novel metal matrix composite based on 60 vol% 316L stainless steel and 40 vol% MgO manufactured by powder metallurgy technology was developed. The corrosion resistance of the developed steel–MgO composite material against molten aluminum alloy AlSi7Mg0.3 was investigated by means of wettability tests and long-term crucible corrosion tests. The wettability tests were carried out using the sessile drop method with the capillary purification technique in a hot-stage microscope (HSM). Static corrosion tests were performed in molten aluminum alloy at 850 °C for 168 h to evaluate the impact of pre-oxidation of the composite surface on the corrosion resistance. The pre-oxidation of steel–MgO composites was carried out at 850 and 1000 °C for 24 h, based on preliminary investigations using thermogravimetry (TG) and dilatometry. The influence of the pre-oxidation on the composite structure, the corrosion resistance, and the phase formation at the interface between the steel–MgO composite and aluminum alloy was analyzed using SEM/EDS and XRD. The impact of the steel–MgO composite material on the composition of the aluminum alloy regarding the type, size, and quantity of the formed precipitations was investigated with the aid of ASPEX PSEM/AFA and SEM/EBSD. It was revealed that the pre-oxidation of the steel–MgO composite at 1000 °C induced the formation of stable MgO-FeO solid solutions on its surface, leading to a significant increase of long-term corrosion resistance against the liquid aluminum alloy

Evaluation of alumina as protective coating for carbon fibers in aluminum-based composites

Carbon fiber reinforced aluminum metal matrix composites (Cf/Al-MMCs) have been considered as promising materials for lightweight applications. Especially for automotive and aerospace industry they offer outstanding mechanical properties combined with low density. Nevertheless, major obstacles in manufacturing of Cf/Al-MMCs are high reactivity and poor wettability of the carbon fibers with molten Al-alloy. Often an undesired formation of carbides (e.g. Al4C3) at the fiber-matrix interface is observed. Another issue is the sensitivity of carbon fibers to oxidation especially at temperatures of more than 400°C. In order to solve these problems alumina (Al2O3) protective coating was applied on carbon fiber-based high modulus (HM) 2D-textile preforms by means of atomic layer deposition (ALD). The influence of the coating on the carbon fibers was investigated by measurement of the tensile strength with single filaments and by determination of the oxidation behavior using TGA analysis. Alumina coated fibers show an enhancement of tensile strength of up to 700 MPa compared to uncoated fibers. An improved oxidation resistance of coated preforms was verified by TGA analysis. The Cf/Al-MMC using alumina coated HMfibers and alloy 239D as matrix material was prepared via gas pressure infiltration (GPI). In comparison to the alloy 226D the use of the alloy 239D allows an infiltration without formation of detrimental Cu2Al precipitations. SEM cross-section analysis of Cf(Al2O3)/239D-system revealed that the Al2O3 coating acts as an effective protective layer against the aggressive Al-melt. Furthermore it improves wettability with Al-melt and a dense composite structure can be obtained. Infiltration without alumina protective coating leads to many casting defects (e.g. uninfiltrated area) and carbide formation at the fiber-matrix interface. Interaction of alloying elements with alumina layer at the fiber-matrix interface is further studied by TEM analysis

Electrochemical Studies of Stainless Steel and Stainless Steel-TiO₂ Composite in Reference to Molten Aluminum Alloy Using a Solid-State BaCO₃ Electrolyte

The influence of TiO2 addition on the high-temperature electrochemical characteristics of stainless-steel-based materials was investigated by means of differential potential measurement, electrochemical polarization and impedance spectroscopy. A new three-electrode approach was utilized which incorporated a liquid aluminum alloy AlSi7Mg0.3 as the reference electrode, barium carbonate BaCO3 as the solid-state electrolyte, and stainless steel or a stainless steel-TiO2 composite as the working electrode. The potential differences between the steel-based working electrodes and the liquid-aluminum-alloy reference electrode were measured for 85 h throughout the whole experiment, including the heating and cooling period. The experiments were performed at 850 °C. The determination of the high-temperature open circuit potential (ECorr) in reference to the liquid aluminum alloy was carried out via potentiodynamic polarization. The polarization-related changes in the impedance characteristics were evaluated by the correlation of impedance responses before and after the polarization. The addition of 40 vol% TiO2 resulted in a reduction in the potential of the steel-TiO2 composite and led to the formation of a more uniform electrode–electrolyte interface. The reaction products on the surface of the working electrodes were investigated by means of SEM/EDS and XRD. They consisted of mixed oxides within the Fe-O, Ba-Fe-O and Ba-Cr-O systems

ANALYSIS OF HISTORY OF GRANTING CREDITS AND HANDLING TEST EXAMS ON THE ASK SYSTEMS E-EXAM PLATFORM AT WARSAW MEDICAL UNIVERSITY -A PRELIMINARY REPORT

Abstract Background: Until now, test exams at Warsaw Medical University were mostly carried out in the paperand-pen test form. Beginning in the academic year 2014-2015, it is possible to get a credit and pass a test exam on the ASK Systems e-exam platform

Al2O3 protective coatings on carbon fiber-based 3D-textile preforms prepared by ALD for application in metallic composite materials

Carbon fiber-reinforced aluminum matrix composites (CF/Al-MMC) offer favorable properties and high design flexibility for lightweight applications. Nevertheless, poor wettability of carbon fibers by liquid aluminum alloys and high reactivity of carbon with liquid aluminum hinder a further development and limit the industrial application. To overcome these limitations an alumina protective coating is applied by atomic layer deposition (ALD) on carbon fiber-based 3D-textile. The deposition is carried out at a substrate temperature of 220°C using the precursors trimethylaluminum (TMA) and ozone. SEM analysis revealed a conformal and uniform coating (34±3 nm) with good adhesion to the fibers. Only a slight tensile strength reduction from 3.95 GPa to 3.20 GPa was observed due to coa ting. TGA demonstrated the significant improvement of oxidation resistance of carbon fibers by an alumina coating. Alumina coated carbon fiber-based 3D-textile preforms are infiltrated with AlSiCu alloy