Special Issue "Metallurgy of Non-ferrous, Rare and Precious Metals"

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Manufacturing Processes and Systems".

Deadline for manuscript submissions: 1 September 2020.

Special Issue Editor

Prof. Dr. Alexander A. Gromov
Website
Guest Editor
National University of Science & Technology (MISIS), Moscow, Russian Federation
Interests: additive manufacturing; metals; oxidation; combustion; powders
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Special Issue Information

Dear Colleagues,

Modern metallurgy of non-ferrous, rare, and precious metals in 21st century has progressed significantly from the end of 19th century, when the metallurgical processes of, say, aluminum production were so expensive that French Emperor Napoleon III ate off of aluminum plates, while the gold and silver ones were served for his guests. However, a lot of energy is still required for the metallurgy of non-ferrous, rare, and precious metals. The trend of energy saving for this field is of primary importance. Another important problem is implification of the new fast and energy saving methods and high-tech devises made of non-ferrous metals production: additive manufacturing for the complex-shape articles, micron-sized and nanometal powders production, characterization, application and modern powder metallurgy, new sintering and processing methods like spark plasma sintering (SPS), self-propagated high-temperature synthesis (SHS), mechanical alloying and mechanosynthesis etc. The above mentioned processes of innovative metallurgy will be covered in this Special Issue. The problems of secondary non-ferrous metal raw materials treatment will be are also of interest. The amount of accumulated non-ferrous metallic wastes on our planet are billion tons recently. Thus, the ecological aspects of their utilization and re-use requires special attention and will be one of the topic for this Special Issue.

Prof. Alexander Alexandrovich Gromov
Guest Editor

Manuscript Submission Information

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Keywords

  • non-ferrous
  • rare and precious metals
  • powder metallurgy
  • metal wastes
  • SPS, SHS
  • metallic wastes

Published Papers (5 papers)

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Research

Open AccessArticle
Obtaining Alumina from Kaolin Clay via Aluminum Chloride
Materials 2019, 12(23), 3938; https://doi.org/10.3390/ma12233938 - 28 Nov 2019
Cited by 3
Abstract
A method of alumina production based on hydrochloric acid processing of kaolin clays from the East Siberian deposits was studied. Hydrochloric acid leaching was carried out at 160 °C. The leaching solution was subjected to a two-stage crystallization of aluminum chloride hexahydrate (ACH). [...] Read more.
A method of alumina production based on hydrochloric acid processing of kaolin clays from the East Siberian deposits was studied. Hydrochloric acid leaching was carried out at 160 °C. The leaching solution was subjected to a two-stage crystallization of aluminum chloride hexahydrate (ACH). The precipitated crystals were calcinated in air at a temperature above 800 °C to produce alumina. The main part of water and chlorine during thermal decomposition of ACH was removed at 400 °C. The influence of temperature and duration of ACH calcination on the residual chlorine content in alumina was studied. The optimal temperature of ACH calcination was 900 °C with a duration of 90 min. It was shown that the increase in calcination temperature contributed to the decrease in chlorine content in the final product. However, an increase in calcination temperature above 900 °C led to the transition of the well-soluble γ-Al2O3 phase to the insoluble α-Al2O3, which negatively affected the further electrolysis of aluminum. The size of alumina particles was not affected by the calcination mode. The rate of dissolution of the prototype Al2O3 in Na3AlF6 was higher than for the alumina obtained by the classical method. Alumina content, particle morphology, and particle size distribution for the obtained alumina were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and laser diffraction methods. The obtained alumina is suitable for aluminum production according to the studied characteristics. Full article
(This article belongs to the Special Issue Metallurgy of Non-ferrous, Rare and Precious Metals)
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Open AccessFeature PaperArticle
Possibilities of Manufacturing Products from Cermet Compositions Using Nanoscale Powders by Additive Manufacturing Methods
Materials 2019, 12(20), 3425; https://doi.org/10.3390/ma12203425 - 19 Oct 2019
Cited by 3
Abstract
Complicated wear-resistant parts made by selective laser melting (SLM) of powder material based on compositions of metal and ceramics can be widely used in mining, oil engineering, and other precision engineering industries. Ceramic–metal compositions were made using nanoscale powders by powder metallurgy methods. [...] Read more.
Complicated wear-resistant parts made by selective laser melting (SLM) of powder material based on compositions of metal and ceramics can be widely used in mining, oil engineering, and other precision engineering industries. Ceramic–metal compositions were made using nanoscale powders by powder metallurgy methods. Optimal regimes were found for the SLM method. Chemical and phase composition, fracture toughness, and wear resistance of the obtained materials were determined. The wear rate of samples from 94 wt% tungsten carbide (WC) and 6 wt% cobalt (Co) was 1.3 times lower than that of a sample from BK6 obtained by the conventional methods. The hardness of obtained samples 2500 HV was 1.6 times higher than that of a sample from BK6 obtained by the traditional method (1550 HV). Full article
(This article belongs to the Special Issue Metallurgy of Non-ferrous, Rare and Precious Metals)
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Open AccessArticle
Aluminum-Alumina Composites: Part I: Obtaining and Characterization of Powders
Materials 2019, 12(19), 3180; https://doi.org/10.3390/ma12193180 - 27 Sep 2019
Abstract
The process of advanced aluminum-alumina powders production for selective laser melting was studied. The economically effective method of obtaining aluminum-alumina powdery composites for further selective laser melting was comprehensively studied. The aluminum powders with 10–20 wt. % alumina content were obtained by oxidation [...] Read more.
The process of advanced aluminum-alumina powders production for selective laser melting was studied. The economically effective method of obtaining aluminum-alumina powdery composites for further selective laser melting was comprehensively studied. The aluminum powders with 10–20 wt. % alumina content were obtained by oxidation of aluminum in water. Aluminum oxidation was carried out at ≤200 °C. The oxidized powders were further dried at 120 °C and calcined at 600 °C. Four oxidation modes with different process temperatures (120–200 °C) and pressures (0.15–1.80 MPa) were investigated. Parameters of aluminum powders oxidation to obtain composites with 10.0, 14.5, 17.4, and 20.0 wt. % alumina have been determined. The alumina content, particle morphology, and particle size distribution for the obtained aluminum-alumina powdery composites were studied by XRD, SEM, laser diffraction, and volumetric methods. According to the obtained characteristics of aluminum-alumina powdery composites, they are suitable for the SLM process. Full article
(This article belongs to the Special Issue Metallurgy of Non-ferrous, Rare and Precious Metals)
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Open AccessArticle
Hydrometallurgical Process for Tantalum Recovery from Epoxy-Coated Solid Electrolyte Tantalum Capacitors
Materials 2019, 12(8), 1220; https://doi.org/10.3390/ma12081220 - 14 Apr 2019
Cited by 1
Abstract
Tantalum is a critical metal that is widely used in electronic products. The demand for tantalum is increasing, but the supply is limited. As tantalum waste products have increased in Taiwan in recent years, the treatment of spent tantalum capacitors has become necessary [...] Read more.
Tantalum is a critical metal that is widely used in electronic products. The demand for tantalum is increasing, but the supply is limited. As tantalum waste products have increased in Taiwan in recent years, the treatment of spent tantalum capacitors has become necessary and important. The recycling of tantalum from tantalum capacitors will not only decrease pollution from waste, but will also conserve tantalum resources. The tantalum content in epoxy-coated solid electrolyte tantalum capacitors (EcSETCs) is over 40 wt.%. Here, we designed a recycling process that includes pre-treatment, leaching, and solvent extraction to recover tantalum. In the pre-treatment process, epoxy resin and wires were removed. During hydrometallurgical process, pressure leaching by hydrofluoric acid was used to leach tantalum and manganese from solid electrolyte tantalum capacitors (SETCs). During our testing of this proposed process, the acid concentration, reaction time, temperature, and solid–liquid ratio were examined for leaching. After the leaching process, Alamine 336 was used to extract tantalum from the leaching solution. The pH value, extractant concentration, extraction time, and aqueous–organic ratio were investigated. Then, tantalum was stripped using HNO3, and the HNO3 concentration, stripping time, and organic–aqueous ratio were analyzed in detail. Under optimal conditions, the recovery efficiency of tantalum reached over 98%, and a final product of tantalum pentoxide with 99.9% purity was obtained after chemical precipitation and calcination. Full article
(This article belongs to the Special Issue Metallurgy of Non-ferrous, Rare and Precious Metals)
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Open AccessArticle
An Efficient Leaching of Palladium from Spent Catalysts through Oxidation with Fe(III)
Materials 2019, 12(8), 1205; https://doi.org/10.3390/ma12081205 - 12 Apr 2019
Cited by 5
Abstract
Reclamation of spent catalysts for the efficient recovery of palladium (Pd) is gaining growing attention due to its scarcity and high supply risk. Currently Pd extraction from spent catalysts through an efficient, economical, and green method has remained a challenge. In this study, [...] Read more.
Reclamation of spent catalysts for the efficient recovery of palladium (Pd) is gaining growing attention due to its scarcity and high supply risk. Currently Pd extraction from spent catalysts through an efficient, economical, and green method has remained a challenge. In this study, Fe3+ is utilized for leaching through oxidation of Pd in a mild condition. Before leaching, distillation was proposed to remove and recover the organics from spent catalysts. The effects of HCl concentration, Fe3+ concentration, NaCl concentration, leaching time, and temperature on the leaching efficiency of Pd were investigated to determine the optimum leaching conditions. The results show that Pd extraction and dissolution of Al2O3 increase with higher HCl concentration. The effect of NaCl on Pd leaching efficiency is significant at low acid concentration (2.0 mol/L HCl). The leaching efficiency was 99.5% for Pd under the following conditions: 2.0 mol/L HCl, 4.0 mol/L NaCl, and 0.67 mol/L Fe3+ at 80 °C for 90 min. The leaching kinetics fits best to the shrinking-core model of surface chemical reaction. The activation energy for the leaching of Pd was 47.6 kJ/mol. PdCl42− was selectively adsorbed by anion exchange resin. The filtrate containing adequate H+, Cl-, and Fe3+ was reused as leaching agent. Pd leaching efficiency was over 96% after five cycle times. This study provides an efficient process for recovery of Pd from spent catalysts. Full article
(This article belongs to the Special Issue Metallurgy of Non-ferrous, Rare and Precious Metals)
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