Search Results (11)

The increasing global demand for raw materials underscores the importance of lightweight construction and sustainable material use, drawing attention to composite techniques like galvanic coating of plastics. To support recycling efforts, the development of efficient separation and material recovery processes is critical, particularly for end-of-life products containing metal-plated polymers. This study investigates the recyclability of metallized polymer foams and coated polymers through comminution, focusing on the potential for effective separation of metal and polymer components. Cu-ABS samples showed 27% of the products in the 8–10 mm fraction and 48% in the 10–16 mm fraction during primary comminution, while Cu-PUR achieved a more even distribution. Microscopic analyses revealed decoating rates of up to 95% for Cu-ABS compared to 19% for Cu-PUR. The comminution energy required for Cu-PUR was three times higher, with a fivefold lower decoating rate than solid materials. Particles larger than 200 µm exhibited interlocking, complicating the separation process. These findings highlight the need for optimized recycling processes to enable efficient raw material recovery and support a circular economy. Full article

High production rates and the constant expansion of production capacities for lithium-ion batteries will lead to large quantities of production waste in the future. The desired achievement of a circular economy presupposes that such rejects could be recovered. This paper presents a two-staged process route that allows one to recover graphite and conductive carbon black from already coated negative electrode foils in a water-based and function-preserving manner, and it makes it directly usable as a particle suspension for coating new negative electrodes. In a first step, coating residues, which accumulate in production (as offcuts or rejects for example), are decoated in an aqueous ultrasonic bath. The ultrasonic bath also serves as a pre-thickener. As a result, high mass concentrations of active material can already be achieved in the water after the first process step. Water is then removed from the negative electrode suspension in a subsequent step by applying dynamic cross-flow filtration. With this unit operation, it is possible to concentrate the slurry residue to a solid content similar to that of the new electrode slurries used for coatings. An important criterion for the direct utilization of production waste is that the particle properties are affected as little as possible so that the suspension can be used directly for coating new films. This work presents the individual recycling process steps and their influence on the particle and slurry properties. The aim is to assess whether the recyclate is suitable for a coating of new negative electrodes and thus also for manufacturing batteries from 100% recycled material. Full article

The preparation of semiconducting carbon nanotube (s-CNT) thin films by solution processing has become the mainstream approach nowadays. However, residual polymers are always inevitable during the sorting of s-CNTs in solution. These residual polymers will degrade the electrical properties of the CNTs. Although several post-treatment approaches have been reported to be effective in improving the performance of the device, there is no deep analysis and comprehensive comparison of these approaches, so there is no overall guidance on the optimum treatment of CNTs for performance improvement. In this work, we characterize CNT thin film with three post-treatment methods, including annealing (A), yttrium oxide coating and decoating (Y), and annealing combined with YOCD (A + Y), and evaluate and compare the performance of Field Effect Transistors (FETs) based on the above mentioned CNT thin film. The result shows that the CNT thin film treated by the A + Y method is the clearest and flattest; the average roughness determined from the overall AFM image is reduced by 28% (from 1.15–1.42 nm (O) to 0.826–1.03 nm (A + Y)), which is beneficial in improving the device contact quality, uniformity, and stability. The on-state current (I_on) of the FETs with CNTs treated by A, Y, and A + Y is improved by 1.2 times, 1.5 times, and 1.75 times, respectively, compared with that of FETs fabricated by untreated CNTs (O for original CNTs), indicating that the A + Y is the optimum post-treatment method for the A + Y and combines the effect of the other two methods. Accordingly, the contact and channel resistance (2R_c and R_ch) of the CNT FETs treated by different post-treatment methods including A, Y, and A + Y is reduced by 0.18/0.24 times, 0.37/0.32 times, and 0.48/0.41 times, respectively. The ratio of improvement in device performance is about 1:2 for the contact and channel sections for a transistor with a 500 nm channel length, and this ratio will go up further with the channel length scaling; together with the decay in the channel resistance optimization effect in the scaling device, it is necessary to adopt more methods to effectively reduce the contact resistance further. Full article

22MnB5 hot forming steel is widely used in the automotive industry due to the increasing demand for lightweight vehicles. As surface oxidation and decarburization occur during hot stamping processes, an Al-Si coating is often precoated on surfaces. The coating tends to melt into the melt pool during the laser welding of the matrix and reduce the strength of the welded joint; therefore, it should be removed. The decoating process by sub-nanosecond and picosecond lasers and process parameter optimization were conducted in this paper. The corresponding analysis of the different decoating processes, the mechanical properties and the elemental distribution was carried out after laser welding and heat treatment. It was found that the Al element has an influence on the strength and elongation of the welded joint. The high-power picosecond laser has a better removal effect than the lower power sub-nanosecond laser. The best mechanical properties of the welded joint were obtained under the process conditions of 1064 nm center wavelength, 15 kW power, 100 kHz frequency, and 0.1 m/s speed. In addition, the content of the coating metal elements (mainly Al) melted into the welded joint is reduced with increasing coating removal width, which significantly improves the mechanical properties of the welded joints. Al in the coating rarely melts into the welding pool when the coating removal width is not less than 0.4 mm, and its mechanical properties can meet the automotive stamping requirements for the welded plate. Full article

The end of fife (EoL) of new aircraft panels made of Al-Li alloys in which the stringers and skin were joined, either by laser beam welding (LBW) or by friction stir welding (FSW), was investigated at the lab scale. Different cutting strategies, ranging from cutting only for size reduction to full separation of all materials, including the removal of the welded seam, were defined, with the objective of recycling the maximum amount of panel scrap back into high-quality aircraft Al-Li alloys. Those welded aerostructures were coated with two novel Cr-free coating systems. The effect of the coatings on the recyclability of the panels and the need to eliminate the primer and topcoats were researched. Fading/enrichment of the alloying elements during recycling was determined. The chemical compatibility of the recycled alloys with four commercial Al-Li alloys was examined. The EoL route that maximized closed-loop recycling and the conservation of the valuable alloying elements was identified. Nine out of the ten configurations were found to be compatible with joint recycling. Only the LBW structure with ER4047 filler wire required sorting into scrap fractions and removing the weld seam. Decoating by corundum blasting followed by cutting before remelting is the recommended EoL process. Full article

The rising production of lithium-ion batteries (LIBs) due to the introduction of electric mobility as well as stationary energy storage devices demands an efficient and sustainable waste management scheme for legislative, economic and ecologic reasons. One crucial part of the recycling of end-of-life (EOL) LIBs is mechanical processes, which generate material fractions for the production of new batteries or further metallurgical refining. In the context of safe and efficient processing of electric vehicles’ LIBs, crushing is usually applied as a first process step to open at least the battery cell and liberate the cell components. However, the cell opening method used requires a specific pretreatment to overcome the LIB’s hazard potentials. Therefore, the dependence on pretreatment and crushing is investigated in this contribution. For this, the specific energy input for liberation is determined and compared for different recycling strategies with respect to dismantling depth and depollution temperatures. Furthermore, the respective crushing product is analyzed regarding granulometric properties, material composition, and liberation and decoating behaviour depending on the pretreatment and grid size of the crushing equipment. As a result, finer particles and components are generated with dried cells. Pyrolysis of cells as well as high dismantling depths do not allow to draw exact conclusions and predictions. Consequently, trends for a successful separation strategy of the subsequent classifying and sorting processes are revealed, and recommendations for the liberation of LIBs are derived. Full article

In recent years, CVD diamond-coated tungsten carbide (WC-Co) tools have been widely utilized due to their benefits in the machining of non-ferrous alloys and polymer composite materials, especially carbon-fiber-reinforced plastics (CFRPs). The reconditioning of such coated tools is economically attractive due to their high cost and short tool life. The decoating of the remaining diamond film from the used tools and the subsequent surface preparation by wet chemical pretreatment are essential steps for new CVD diamond film formation. Previously, it was shown that reactive ion beam etching (RIBE) could effectively remove CVD diamond films. However, some degree of WC-Co tool substrate damage is expected due to the high ion energy in RIBE and the chemical activity in wet etching. This study addresses the effects of RIBE decoating and surface pretreatment steps on WC-Co tools with a complex shape in terms of the ion-induced surface damage, geometry alteration, and adhesion of a subsequently re-applied CVD diamond film. Moreover, the cutting performance of the tools subjected to the RIBE decoating and repeated film deposition was studied via CFRP cutting tests. It has been shown that the RIBE decoated and recoated tools had a high level of cutting performance comparable to the new tools. Full article

In order to ensure environmentally friendly mobility, electric drives are increasingly being used. As a result, the number of used lithium-ion batteries has been rising steadily for years. To ensure a closed recycling loop, these batteries must be recycled in an energy- and raw material-efficient manner. For this purpose, hydrometallurgical processes are combined with mechanical pre-treatment, including disintegration by mills, crushers and/or shears. Alternatively, electrohydraulic fragmentation (EHF) is also of great interest, as it is considered to have a selective fragmentation effect. For a better comparison, different application scenarios of EHF with other methods of mechanical process engineering for the treatment of lithium-ion batteries are investigated in the present study. Full article

The establishment of an efficient in vitro propagation system for the conservation of the Mediterranean Mandragora autumnalis is highly desirable due to its scarcity, besides its potential medicinal and pharmacological properties. In a separate unpublished study, this species has proved to be resistant to laboratory plant regeneration from vegetative tissue cultures; therefore, an alternative decoated seed (i.e., endosperm enclosed the zygotic embryo) germination approach was conducted in this study. Pre-cold treatment of M. autumnalis seeds, removal of seed coats, and exogenous application of gibberellic acid (GA₃) promoted in vitro seed germination and seedling emergence. In two separate experiments, approximately 10–27% of the germinated decoated seeds developed healthy seedlings within two weeks, compared to the non-germinated intact seeds of the potting soil controls. After 72 days, the highest rates of healthy seedlings development (67.4 and 69.4%) achieved in the in vitro decoated seed cultures supplemented with 60 and 100 mg/L GA₃, respectively, compared to only 25% seedlings emergence rate of the in vitro cultures devoid of GA₃, and 44.2% of the soil controls. The in vitro developed plants were healthy, survived transplantation conditions, and, significantly, grew faster, formed on average more than the double number of true leaves and shoot fresh weight (p ≤ 0.05), 90% more fresh weight of root system (p ≤ 0.05), and ultimately more than the double gross fresh weight (p ≤ 0.05) than that of the in vivo developed plants of the soil controls. Such in vitro seed germination approaches would be favorable due to the higher capacity of uniform seedling establishment year-round under lab-controlled conditions, facilitating proliferation and conservation of rare and threatened species, and providing fresh and axenic plant materials required for downstream studies such as those associated with leaf-derived protoplasts and genetic transformations. Full article

The objective of this study was to develop an eco-friendly method for processing spent stripping solutions, which originate from the wet chemical decoating of metal cutting tools, to generate a product that represents a useful basis for the recovery of valuable components. These liquids contain, for example, considerable quantities of Ti, Co, and W. Hence, the treatment of these solutions, especially because of the dissolved Co, is essential. The process is based on the precipitation of an insoluble compound with the use of a Ca source. The thermal treatment of the precipitate enables its reuse in the procedure, which leads to a minimum amount of solid process waste. The suggested method, which can be readily controlled by pH adjustment, results in a reduction of hazardous substances and an enrichment of valuable compounds in the solid product. Therefore, this process represents an effective preliminary step in the recovery of concentrated metals, such as Ti. Full article

This work provides an overview of the aluminum (Al) recycling process, from the scrap upgrading to the melting process. Innovations and new trends regarding the Al recycling technologies are highlighted. Aluminum recycling offers advantages in terms of environmental and economic benefits. The presence of deleterious impurities in recycled Al alloys is increasing and this is the main drawback if compared to primary alloys. The continuous growth of undesired elements can be mitigated by different technologies, preliminary operations and treatments, and by the optimization of the melting process. Downgrading and dilution are possible solutions to reduce the rate of impurities, but they are not sustainable if the final use of Al alloy continuously increases. The main objectives in the development of the Al recycling are shown and discussed. In particular, the evolution of preliminary treatments of the scrap, as sorting, comminution and de-coating, is reported and a review of the melting technologies is also presented. However, the choice of performing preliminary operations to the melting stage, thus improving the operating conditions during the furnace running, is a trade-off between costs and process efficiency. Full article