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Non-directional rafting of γ' phases in high generation nickel-based single crystal superalloys happens when the alloys are thermally exposed at high temperatures, but so far the reason remains unclear. The microstructures and internal stress fields of a 4th generation single crystal superalloy during thermal exposure at 1100 ℃ and 950 ℃ are investigated using transmission electron microscopy and finite element analysis. It is found that the non-directional rafting of γ' phases occurs after 1100 ℃/200 h and 950 ℃/500 h thermal exposures. The γ' phases are mainly rodlike shape in the space after thermal exposures and a small quantity of γ' rafts exist as well. The elastic strain energy gradient in γ matrix caused by the inhomogeneity of matrix channel width in the alloy is most likely the driving force for the non-directional rafting. Additionally, dislocations are observed only after the thermal exposure process at 1100 ℃. The effect of dislocations on non-directional rafting during thermal exposure is discussed in detail in the paper. • TEM and finite element analysis are used to study non-directional rafting of γ'. • γ' phases are mainly rodlike spatially after thermal exposure at high temperature. • It is found that dislocations are unnecessary for the non-directional rafting. • Elastic strain energy is larger in narrower γ matrix channel at high temperature. • Elastic strain energy gradient in matrix probably causes non-directional rafting. [ABSTRACT FROM AUTHOR]

Abstract This work focuses on the recovery of valuable metal from the cathode materials of spent lithium ion batteries to ensure resource recycling and environmental protection. An environmentally friendly process involving reduction roasting and stepwise leaching is proposed to recover Li and Ni, Co, and Mn from spent LiNi x Co y Mn 1-x-y O 2 materials. Suitable leaching conditions are obtained from thermodynamic analysis (Eh-pH diagram). The effects of several factors, such as acid concentration, temperature, leaching time and liquid‒solid ratio, on the leaching efficiency of valuable metals are investigated. Under optimum conditions, the leaching efficiency of Li, Ni, Co, and Mn are as high as 93.68%, 99.56%, 99.87%, and 99.9%, respectively. The kinetic aspect of the acid leaching process is analyzed by shrinking the core model, which suggests a residue layer diffusion process. The reaction activation energies of Ni, Co, and Mn are 29.35 kJ mol−1, 24.00 kJ mol−1, and 23.29 kJ mol−1, respectively. This metallurgic method contributes to environmentally friendly and economical recovery of valuable metals from spent lithium-ion batteries. Highlights • A novel metallurgical method is proposed to recycling spent LiNi x Co y Mn 1-x-y O 2. • The leaching conditions are comprehensively investigated and optimized. • The kinetics and the controlled step of acid leaching process are analyzed. • The active energies of Ni, Co and Mn reacting with H 2 SO 4 are calculated. [ABSTRACT FROM AUTHOR]

Abstract As cathode materials for Li-ion batteries (LIBs), V 2 O 5 , possessing a large-spaced and open layered crystal structure, have attracted considerable attention due to their distinct advantages of high specific capacity, abundant raw materials and low cost. Although low-dimensional nanostructured V 2 O 5 can increase the discharge capacity of LIBs, it still suffers from poor cycling and rate performance due to serious self-aggregation and pulverization. Building micro/nano-structures is a highly promising method to address the above issues. Herein, we propose a facile oxidation strategy to successfully synthesize the unique 3D hierarchical porous sponge-like V 2 O 5 micro/nano-structures (V 2 O 5 -SLMNSs) by using the structure-similar sponge-like VO 2 (B)@C micro/nano-structures as a precursor. Importantly, as-synthesized V 2 O 5 -SLMNSs possess the distinct structural advantages of a robust structure with large surface area and abundant meso/micropores, which are beneficial for achieving a better electrochemical performance. Specific capacity during the second discharge for V 2 O 5 -SLMNSs is 232 mAh/g at 100 mA/g, with 87% of the capacity being maintained after 50 cycles, which is considerably higher than the discharge capacity (190 mAh/g) in the second cycle and the value for the capacity retention (69%) of 1D V 2 O 5 nanoribbons. Thus, as-synthesized V 2 O 5 -SLMNSs are promising cathode materials for the next-generation LIBs. Graphical abstract Image 1 Highlights • Unique 3D sponge-like V 2 O 5 micro/nano-structures (V 2 O 5 -SLMNSs) are synthesized. • V 2 O 5 -SLMNSs possess robust structure, large surface area and conductive frameworks. • V 2 O 5 -SLMNSs exhibit the greatly improved electrochemical performance. [ABSTRACT FROM AUTHOR]

Cu 2 S thin films were successfully grown in situ on Cu foil by an easy hydrothermal method. The effects of surfactant and reaction time on the formation of the Cu 2 S films were studied by X-ray diffraction, field-emission scanning electron microscopy and ABIOS profilometry. Results showed that the thin films consisted of nanoparticles, and their crystallization and surface roughness depended on the structures of surfactants and reaction time. Photocatalytic studies indicated that the film obtained at 1 h by the EDTA-2Na surfactant exhibited a good methylene blue degradation rate of 83.7%, and higher values of 89.2% and 90% were obtained with increased reaction time to 3 and 4 h. Even the decomposition rate remained at high (82%) after reuse. This good catalytic performance can be attributed to the heterojunction formed between Cu and Cu 2 S, the special surface from the reaction between [Cu-EDTA] - ion and S 2− , and the further crystal orientation with prolonged reaction time. [ABSTRACT FROM AUTHOR]

A simple low-temperature solid-state reaction in the presence of the surfactant PEG400 was developed to obtain ZnO/CdS nanocomposites. The effects of synthesis temperature and reaction time on crystal structure and optical properties of the nanocomposites were investigated by several technologies. X-ray diffraction (XRD) and high resolution transmission electron microscope (HRTEM) characterizations showed that the products consisted of the nanoparticles, and the grain growth kinetics of the cubic CdS and the hexagonal ZnO phase in the nanocomposites was described. The mechanism analysis suggested that sufficient grinding and heating treatment was a key to form the ZnO/CdS nanocomposites, and the surfactant PEG400 was proved not to involve the reaction and prevent the nanoparticles from aggregating to larger in whole grinding and heat-treatment process. Ultraviolet–visible (UV–vis) spectra revealed that the band gaps of the nanocomposites could be tuned by the reaction temperature and reaction time. Photoluminescence (PL) spectra showed that the changing position and the intensity of the emission peaks resulted from the rate of electron transfer and recombination probability under the different conditions. [ABSTRACT FROM AUTHOR]

Abstract: Yttrium aluminum garnet (YAG) powders were synthesized by a solvothermal method under mild conditions with inexpensive aluminum and yttrium nitrates as the starting materials, and the ethylenediamine (EDA) solution as the solvent. Hydroxide precursors were synthesized by two different precipitating processes, in which urea or ammonium hydrogen carbonate was used as precipitant. The formation of YAG particle was investigated by means of Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The TEM results showed that spherical YAG powders were successfully synthesized when ammonium hydrogen carbonate was used as precipitant. [Copyright &y& Elsevier]