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Nb-Based Superconductors
Published in David A. Cardwell, David C. Larbalestier, I. Braginski Aleksander, Handbook of Superconductivity, 2023
Gianluca De Marzi, Luigi Muzzi
Niobium is a ductile refractory transition metal element with atomic number Z = 41, belonging to the group 5 of the periodic table. This element is characterized by 5 valence electrons, with electronic structure [Kr]4d45s1: four electrons occupy highly localized d-orbitals, whereas the fifth electron occupies a less localized s-orbital. Niobium crystallizes in the bcc over the whole range of temperatures and at standard pressure conditions; its lattice constant is a = 3.3063 Å at T = 295 K (Roberge, 1975), and the variation of lattice parameter from room temperature to liquid helium temperature is very small (0.143%). Table B1.1 summarizes the main physical properties of elemental niobium.
Critical raw materials
Published in Natalia Yakovleva, Edmund Nickless, Routledge Handbook of the Extractive Industries and Sustainable Development, 2022
Judith A. Kinnaird, Paul A.M. Nex
For niobium, a major use is adding to steels to increase strength and toughness and to reduce weight. Such steels are used in car and truck bodies, oil pipelines, steels, ship hulls and railways, while niobium super-alloys are used for jet engines and heat resistant equipment. All of these use create bulk materials that are easily recycled. In the primary production stage, 45% of the energy needed is used out of the 72% of total gas emissions in the niobium supply chain, whereas during recycling the secondary production of niobium requires 19% of the supply chain energy and generates 7% of gas emissions. The detailed calculations show that the recycling of niobium could save around 133–161 m GJ energy between 2010 and 2050. Recycling would also contribute to the reduction of 44–53 Mt CO2-eq in the same period (Golroudbary et al., 2019).
Leaching with Acids
Published in C. K. Gupta, T. K. Mukherjee, Hydrometallurgy in Extraction Processes, 2019
Josteen13 suggested that Norwegian niobium ore containing columbite and coppite (calcium niobite) could be treated with H2SO4 by taking advantage of the fact that coppite could be opened up by digestion at 120 to 200°C, whereas columbite dissolved at a higher temperature of 280 to 320°C and that, too, after fine grinding. The Titan Co. A/S of Norway14 claimed a process for the recovery of niobium and tantalum from columbite ore by boiling it with a mixture of concentrated H2SO4 and ammonium sulfate. The digested mass was further leached with dilute H2SO4 and reduced with zinc granules to form tetravalent niobium. The solution was subsequently boiled to precipitate niobium salts which were washed and calcined to yield a pure white mixture of Nb2O5 and Ta2O5. It is also possible to prepare high-purity niobium from pyrochlore ore by digestion with H2SO4 followed by solvent extraction and precipitation. According to this process,15 one part of the ore containing 26.5 to 48.9% Nb2O5 was first digested with 3 parts of concentrated (93%) H2SO4 at around 200°C. The decomposed ore was further leached with dilute H2SO4 at a temperature of 40°C to bring niobium into solution.
High temperature behaviour of NbSi2 coating on the Nb-1Zr-0.1C alloy
Published in Surface Engineering, 2020
M. Tyagi, S. K. Ghosh, R. Tewari
Niobium based alloys, due to high temperature strength and high liquid metal corrosion resistance, are an attractive choice for high temperature structural material applications in nuclear and aerospace engineering fields [1–6]. Among various Nb alloys, Nb-1Zr-0.1C alloy has been proposed as a structural material for compact high temperature reactors [7]. However, rapid oxidation of Nb alloys beyond 400°C severely restricts their use for high temperature applications. In order to increase the applicability of Nb based alloy several approaches have been attempted to improve the oxidation properties of Nb alloys. One such approach is by alloying them with elements like Al, Cr and Ti [5]. The alloying elements which improve oxidation properties, however, adversely affect the high temperature mechanical and thermal properties of the material [8]. Thus, another approach of providing an external protective coating to the Nb alloys has become an attractive option. Protective surface coatings to improve the oxidation resistance of Nb based alloys offer several advantages, in addition to providing oxidation resistance, it does not alter mechanical and thermal properties of the substrate.
A review on the separation of niobium and tantalum by solvent extraction
Published in Mineral Processing and Extractive Metallurgy Review, 2018
Thi Hong Nguyen, Man Seung Lee
Tantalum and niobium are necessary for the manufacture of advanced materials such as superconductors, electronics, energy, and aerospace (Yang et al. 2013b). About 60% of the annually produced tantalum is consumed to manufacture capacitor powders owing to its high melting point and good corrosion resistance (Buachuang et al. 2011; Turgis et al. 2018). Most of the niobium is used in the iron and steel industry as additives (Buachuang et al. 2011; Yang et al. 2013b). Tantalum compounds are more expensive than niobium because of the low natural abundance of tantalum compared to niobium (Deblonde, Chagnes, Weigel, et al. 2016). Generally, tantalum and niobium are usually found together in nature (Ungerer et al. 2014).
Constitutive modeling of dynamic strain aging in commercially pure bcc metals
Published in Mechanics of Advanced Materials and Structures, 2023
Niobium (Nb), a bcc metal, is commonly used to enhance the strength of carbon and alloy steels. Previous numerical models for Nb at higher strain rates were effectively developed by Nemat Nasser [36] as well as by Voyiadjis et al. [24]. However, these models lacked compatibility at lower strain rates. It was also observed that while there was no DSA at higher strain rates, DSA was activated at lower strain rates (as shown in Figure 3), which could not be captured using the original VA model (Figure 4) [24].