Applications of molten salt and progress of molten salt electrolysis in secondary metal resource recovery

Molten salt is an excellent medium for chemical reaction,energy transfer,and storage.Molten salt innovative technologies should be developed to recover metals from secondary resources and reserve metals from primary natural sources.Among these technologies,molten salt electrolysis is an economic and environment-friendly method to extract metals from waste materials.From the perspective of molten salt characteristics,the application of molten salts in chemistry,electrochemistry,energy,and thermal storage should be comprehensively elaborated.This review discusses further directions for the research and development of molten salt electrolysis and their use for metal recovery from various metal wastes,such as magnet scrap,nuclear waste,and cemented carbide scrap.Attention is placed on the development of various electrolysis methods for different metal containing wastes,overcoming some problems in electrolytes,electrodes,and electrolytic cells.Special focus is given to future development directions for current associated processing obstacles.

Unveiling the planar deformation mechanisms for improved formability in pre-twinned AZ31 Mg alloy sheet at warm temperature

To investigate the role of pre-twins in Mg alloy sheets during warm planar deformation, the stretch forming is conducted at 200 ℃. Results suggest the formability of the pre-twinned AZ31 Mg alloy sheet is enhanced to 11.30 mm. The mechanisms for the improved formability and the deformation behaviors during the planar stretch forming are systematically investigated based on the planar stress states. The Schmid factor for deformation mechanisms are calculated, the results reveal that planar stress states extremely affect the Schmid factor for {10-12}twinning. The detwinning is activated and the prismatic slip is enhanced in the pre-twinned sheet, especially under the planar extension stress state in the outer region. Consequently, the thickness-direction strain is accommodated better. The dynamic recrystallization(DRX) type is continuous DRX(CDRX) regardless of the planar stress state. However, the CDRX degree is greater under the planar extension stress state.Some twin lattices deviate from the perfect {10-12} twinning relation due to the planar compression stress state and the CDRX. The basal texture is weakened when the planar stress state tends to change the texture components.

Improvement in oxidation resistance of Cantor alloy through microstructure tailoring

A method of improving the oxidation resistance of Cantor alloy through microstructure tailoring was revealed.Samples with distinctive microstructures were achieved by different annealing treatments on the cold-rolled Cantor alloy.Oxidation test was then carried out on the various annealed samples at 800°C for 24 h in air.The oxidation behavior was evaluated in terms of oxidation rate,surface and cross-section microstructure characterization.Although stratified oxide layers including outer Mn_(2)O_(3) and inner Cr_(2)O_(3) were observed in all the annealed samples,the thickness of Mn_(2)O_(3) and Cr_(2)O_(3) layers was different.Also,the samples exhibited different oxidation rates.The results indicate that the oxidation resistance of various annealed samples is closely related with grain size as well as twin density.

Comprehensive recovery of W,V,and Ti from spent selective reduction catalysts

In this study,spent WO_(3)/V_(2)O_(5)-TiO_(2) catalysts used for selective catalytic reduction were treated by a hydrometallurgical process to comprehensively recover valuable metallic elements,such as W,V,and Ti.Al and Si impurities were preferentially removed by selective micro wave-assisted alkali leaching.W and V were leached by enhanced high-pressure leaching with efficiencies estimated at 95% and 81%.The leaching of W and V followed the nuclear shrinkage model controlled by the combination of product layer diffusion and interfacial chemical reaction.A synergistic extraction was applied to separate W and V using an extractant mixture of di-(2-ethylhexyl)phosphoric acid P204 and the primary amine N1923.The extraction efficiencies of V and W reached 86.5% and 6.3%,respectively,with a separation coefficient(V/W) of 95.30.The product was precipitated after extraction to yield ammonium paratung state(APT) and NH_(4)VO_(3).The TiO_(2)catalyst carrier residue meets commercial specifications for reuse.This comprehensive recovery process with the characteristics of high-pressure leaching and synergistic extraction realizes the resourceful utilization of the spent catalysts.

Efect of Pre‑stretch Strain at High Temperatures on the Formability of AZ31 Magnesium Alloy Sheets

High-temperature pre-stretching experiments were carried out on the AZ31 Mg alloy at 723 K with strain levels of 2.54%,6.48%,10.92%,and 19.2%to alter the microstructure and texture for improving room-temperature formability.The results showed that the strain-hardening coefcient increased,while the Lankford value decreased.In addition,the Erichsen values of all pre-stretch sheets were enhanced compared with that of the as-received sheet.The maximum Erichsen value increased from 2.38 mm for the as-received sample to 4.03 mm for the 10.92%-stretched sample,corresponding to an improvement of 69.32%.This improvement was mainly attributed to the gradual increase in grain size,and the(0001)basal texture was weakened due to the activated non-basal slip as the high-temperature pre-stretching strain levels increased.The visco-plastic self-consistent analysis was performed on the as-received and high-temperature pre-stretched samples.Results confrmed the higher activity of the prismatic slip in 10.92%-stretched sample,leading to divergence and weakening of basal texture components.This results in an augmentation of the Schmid factor under diferent slip systems.Therefore,it can be concluded that high-temperature pre-stretching technology provided an efective method to enhance the formability of Mg alloy sheets.

Regulation of morphology and visible light-driven photocatalysis of WO_(3)nanostructures by changing pH

The controlled preparation of hexagonal tungsten trioxide(h-WO_(3))nanostructures was achieved by adjusting the pH of the precursor solution.The effect of the pH on the morphology,elemental composition,and photocatalytic performance of the samples was characterized via X-ray diffraction(XRD),scanning electron microscopy,energy dispersive X-ray spectroscopy,and Raman spectroscopy.Ultraviolet-visible(UV-Vis)spectra were used to evaluate the absorbance and the photocatalytic performance of methylene blue.Photoluminescence(PL),electrochemical impedance spectroscopy,photocurrent response and Brunauer-Emmett-Teller(BET)were used to study the optical properties,electrical performance,and specific surface area of the WO_(3)-nanostructures,respectively.The results indicate that the WO_(3) nanorods prepared at pH=1.0 exhibit the highest photocatalytic performance(87.4%in 1 h),whereas the WO_(3) nanoblocks prepared at p H=3.0 show the lowest.The photocatalytic performance of the one dimensional(1 D)-nanorods can be attributed to their high specific surface area and charge transfer ability.The h-WO_(3) nanostructures were synthesized via a simple method and without a capping agent.They show an excellent photocatalytic performance,which is promising for their application in environment purification.