Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 5Citation - Scopus: 7Characterization and Separation Behavior of Multi-Layers in Aluminum-Rich Waste Pharmaceutical Blisters(Springer, 2023) Çapkın, İrem Yaren; Gökelma, MertolAl-rich waste pharmaceutical blisters (WPBs) have a multi-layer structure that contains aluminum and polymer-based fractions. Although the aluminum mass in WPBs is less than typical aluminum packaging products such as beverage cans, establishing a feasible recycling procedure is possible by separating the fractions to recover both metal and plastic. Hydrometallurgical methods are mostly preferred for the separation of aluminum and plastic in multi-layered structures. This work reports the characterization of Al-rich WPBs and the separation behavior of aluminum and plastic layers. The effects of hydrochloric acid, acetic acid, formic acid, sulfuric acid, ethanol, acetone, and organic solvent (benzene–ethanol–water) on the separation behavior of layers were studied at different temperatures. Furthermore, the recycling yield of the aluminum fraction was experimentally assessed. © 2023, The Minerals, Metals & Materials Society.Article Citation - WoS: 1Citation - Scopus: 2An Investigation on Inclusions Forming During Remelting of Aluminum and Magnesium Scraps Under a Salt Flux(Springer, 2023) Çapkın, İrem Yaren; Gökelma, MertolDue to increasing environmental and economic concerns, the recycling of metals has been increasing in the last decades. Aluminum saves up to 95% of energy when recycled, and magnesium is one of the most common alloying elements in aluminum alloys, contributing to oxidation behavior. Both aluminum and magnesium have a high oxidation tendency during remelting, which raises the necessity for salt flux usage. Salt fluxes remove oxides and other surface contaminants from the target metal. Salt fluxes allow molten metal pieces to coagulate and form the molten bath. Furthermore, it prevents further oxidation of the metal. The presence of fluorides increases the metal yield by promoting coalescence. Although metals and salts are frequently interacting in such processes, there is still a lack of knowledge of the final and intermediate products of the interaction reactions. This study aims to contribute to the literature by investigating the interaction of aluminum and magnesium scraps with salt flux. As a result of the experiments, AlF3, MgF2, Al2O3, MgO, and MgAl2O4 were observed as the main phases in the aluminum and magnesium scraps dross. The presence of CaF2 in the salt flux, which is insoluble in water, was also observed in the analysis results. In addition, fluorine-containing compounds were observed as a result of chemical interactions among the F-, K-, and oxide layers.Review Citation - WoS: 41Citation - Scopus: 42Review on the Parameters of Recycling Ndfeb Magnets Via a Hydrogenation Process(American Chemical Society, 2023) Habibzadeh, Alireza; Küçüker, Mehmet Ali; Gökelma, MertolRegarding the restrictions recently imposed by China on the export of rare-earth elements (REEs), the world may face a serious challenge in supplying some REEs such as neodymium and dysprosium soon. Recycling secondary sources is strongly recommended to mitigate the supply risk of REEs. Hydrogen processing of magnetic scrap (HPMS) as one of the best approaches for magnet-to-magnet recycling is thoroughly reviewed in this study in terms of parameters and properties. The processes of hydrogen decrepitation (HD) and hydrogenation-disproportio-nation-desorption-recombination (HDDR) are two common methods for HPMS. Employing a hydrogenation process can shorten the production route of new magnets from the discarded magnets compared to other recycling routes such as the hydrometallurgical route. However, determining the optimal pressure and temperature for the process is challenging due to the sensitivity to the initial chemical composition and the interaction of temperature and pressure. Pressure, temperature, initial chemical composition, gas flow rate, particle size distribution, grain size, and oxygen content are the effective parameters for the final magnetic properties. All these influencing parameters are discussed in detail in this review. The recovery rate of magnetic properties has been the concern of most research in this field and can be achieved up to 90% by employing a low hydrogenation temperature and pressure and using additives such as REE hydrides after hydrogenation and before sintering.Article Citation - WoS: 10Citation - Scopus: 7Assessment of Melt Cleanliness of Secondary 5000 Aluminum Alloy Via Non-Metallic Inclusions Characterization(Springer, 2023) Li, Cong; Dang, Thien; Huang, Jinxian; Huang, Chunfa; Li, Jianguo; Friedrich, Bernd; Gökelma, MertolThe extensive energy consumption of primary aluminum production stimulates increasing need of producing primary-quality alloys with secondary sources, during which process amount of non-metallic inclusions (NMIs) in the alloy must be strictly controlled. In the present study funded by AMAP Open Innovation Research Cluster, NMIs generated during remelting a 5000 Al-Mg alloy was investigated to offer benchmarking characters of NMIs with respect to type, morphology, size, composition, and concentration. Under different remelting conditions NMIs formed in the melt ahead of solidification were concentrated using Porous Disc Filtration Apparatus (PoDFA) and characterized microstructurally and quantitatively. Investigated conditions included heating cycle, organic contaminations, and refractory materials. Results suggested oxide films and cuboid particles as typical oxides with, respectively, different compositions. The amount of formed oxides declined with the increase of heating rate. With respect to aluminum carbide (Al4C3), organic contaminations were confirmed to lead to an increased amount of its formation. The carbon-containing refractory material contributed more significantly than organic contaminations on the formation of Al4C3 at melt temperatures over 760 & DEG;C. Formulas were derived based on trial results to enable translation of NMIs PoDFA value [mm(2)/kg] into their mass fraction [ppm] in the melt.Article Citation - WoS: 10Citation - Scopus: 11Behavior of Al4c3 Particles During Flotation and Sedimentation in Aluminum Melts(Springer, 2021) Gökelma, Mertol; Storm Aarnaes, Trygve; Maier, Juergen; Renkel, Maria F.; Ekstrom, Kai Erik; Friedrich, Bernd; Tranell, GabriellaAl4C3 particles form during the primary production of aluminum via molten salt electrolysis due to the carbon solubility and direct contact between bath, metal, and carbon anodes. Additional Al4C3 may form during melt processing through direct contact between the melt and carbonaceous materials. As a result of their small size and similar density to aluminum, removal of aluminum carbide particles can be challenging. If not removed, carbides can produce inclusion defects or poor surface condition in aluminum products. The current work studies the removal and behavior of Al4C3 particles during flotation with different gas mixtures, as well as sedimentation. The interaction between carbide particles and Al2O3 films during the melt treatment processes was also studied and reported. Factsage thermochemical software was used to model the interactions at the interface of inclusions and bubbles covered by films. The highest degree of carbide removal was obtained after flotation with an H2O-containing argon gas mixture, where the carbide concentration dropped below the measured solubility limit of carbon at the corresponding temperature. Strong interaction between Al4C3 particles and Al2O3 films was observed during sedimentation which worked as an efficient removal method for the particles. Oxidation of carbides and formation of oxycarbides were suggested as the mechanisms promoting the attachment of carbides on oxide films.Article Citation - WoS: 4Citation - Scopus: 4Rewas 2022: Developing Tomorrow's Technical Cycles(Springer, 2021) Fleuriault, Camille; Gökelma, Mertol; Anderson, Alexandra; Olivetti, Elsa A.REWAS, a sustainability driven conference within The Minerals, Metals & Materials Society (TMS), has a long history of bringing together academia and industry to exchange and reflect on the latest technology developments in the process optimization and waste management fields. The first edition of REWAS (REcycling and WASte symposium) took place in 1999. The scope of the conference has since then broadened to include environmental sustainability, resource management and manufacturing efficiency, liaising these developments to the metallurgical industry in a broader societal and systemic context. The 2022 edition of REWAS which will be hosted at the TMS 2022 Annual Meeting & Exhibition in Anaheim, California, provides a resolute outlook towards Developing Tomorrow's Technical Cycles. Within the metals and materials industry, technical cycles refer to the ensemble of strategies and processes applied to the development of sustainable product loops with the intent to eliminate waste and instead rethink, reuse and upcycle products. The success of technical cycles requires strengthening our circular approach for product life cycle design by providing guidelines and implementation examples to the developers, designers, policy makers and business managers. REWAS promotes such strategies within a priority sector identified for Circular Economy enablement: raw materials supply and management. REWAS 2022 consists of six symposia, and abstract submissions are expected in summer 2021. Topics include recycling and sustainability within the aluminum industry, specifically on casting technologies, recovery of metals from complex products and systems, decarbonization of the metallurgical and manufacturing industry, sustainable production and development perspectives, as well as automatization and digitalization for advanced manufacturing. REWAS 2022 will also include an honorary symposium for Dr. Diran Apelian, whose contributions in metals processing, aluminum and battery recycling, sustainability, education in materials science and more have shaped the path for sustainable materials processing.