Influence of Vanadium Microalloying on Deformation-Induced Pearlite Transformation of Eutectoid Steel

A theoretical analysis of the vibrational modes of ammonium metavanadate

Vanadium(v) is an extremely rare and precious metal, mainly used in aerospace equipment and new energy construction. However, an efficient, simple, and environmentally friendly method for separating V from its compounds is still lacking. In this study, we used first-principles density functional theory to analyse the vibrational phonon density of states of ammonium metavanadate and simulated its infrared absorption and Raman scattering spectra. By analysing the normal modes, we found that the V-related vibration has a strong infrared absorption peak at 711 cm^-1, while other significant peaks above 2800 cm^-1 are from N-H stretching vibrations. Therefore, we propose that providing high-power terahertz laser radiation at 711 cm^-1 may facilitate the separation of V from its compounds through phonon-photon resonance absorption. With the continuous progress of terahertz laser technology, this technique is expected to be developed in the future, and it may offer new technological possibilities.

Bioleaching of vanadium by Acidithiobacillus ferrooxidans from vanadium-bearing resources: Performance and mechanisms

Bioleaching is promising to meet the demand of strategic vanadium both economically and environmentally. Whereas the combination of bioleaching with traditional techniques is of great interest, little is known on bioleaching of vanadium from abundant vanadium-bearing resources utilized/produced in existing processes. This study investigated the bioleaching of vanadium from vanadium-titanium magnetite, steel slag, and clinker, which are common raw mineral and intermediates used in conventional vanadium extraction process. Clinker had greater leachability by Acidithiobacillus ferrooxidans, compared to vanadium-titanium magnetite and steel slag. Pulp density, inoculum volume, initial pH and initial Fe²⁺ concentration had influencing effects on this bioleaching process. Under optimal condition with 3% pulp density, 10% inoculum volume, initial pH at 1.8, and 3 g/L initial Fe²⁺ concentration, the bioleaching of clinker achieved the maximum vanadium leaching efficiency of 59.0%. Both X-ray fluorescence and energy dispersive spectroscopy analysis confirmed the reduction of vanadium content in the solid residues after leaching. The results of Community Bureau of Reference sequential extraction suggested that vanadium in acid-soluble and oxidizable phase was more easily leachable. This study is helpful to develop sustainable and practical techniques for vanadium extraction from abundant raw materials and step forward in combining bioleaching with traditional process.

Reduction and Nitridation of Iron/Vanadium Oxides by Ammonia Gas: Mechanism and Preparation of FeV45N Alloy

The steel micro-alloyed with ferrovanadium nitride has extremely superior properties that make it widely utilized in structural components, construction and aircraft. The conventional methods for synthesizing ferrovanadium nitride include nitridation of pure ferrovanadium alloy or carbothermal nitridation of metallic oxides, using nitrogen or ammonia gas as nitrogen sources. In this study, ferrovanadium nitride (FeV45N) was prepared by direct reduction and nitridation of the corresponding metal oxides with ammonia as the reductant and nitrogen source. This method avoids the introduction of other impurity elements, except the negligible trace elements accompanied with the raw materials. The thermodynamics of the reduction and nitridation process were initially analyzed. During the subsequent ammonia reduction process, the FeV45N powders were successfully obtained at 1273 K for 6 h. The obtained powders were pressed into cylindrical briquettes by hot pressing (HP) at 1473 K for 1 h in vacuum. In the investigation, the X-ray diffraction and morphological analysis of the products was also carried out, and the reaction mechanisms were discussed in detail. The nitrogen content of the final product can reach 11.85 wt. %, and the residual oxygen content can be reduced to 0.25 wt. %. By sintering, the density of the alloy can reach 5.92 g/cm3.