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In this paper, polyimide-graphite (PG) composite was prepared and used as a solid lubricant at elevated temperatures. PG composite was characterized by X-ray diffraction, and its thermal stability was evaluated based on thermogravimetric/differential thermal analysis and Fourier transform infrared spectrometry analysis. The results show that in PG composite, there was some interaction between the graphite (GR) and the polyimide (PI) matrix. Consequently, the PG composite exhibited better thermal stability than PI. The friction behavior of the PG composite sliding against steel at elevated temperatures (300–600°C at an interval of 100°C) was evaluated with a ring-on-ring tribometer. It was found that the PG composite exhibited excellent friction-reducing ability and good load-carrying capacity in the temperature range of 300–600°C and applied loads of 300–700 N. Moreover, this excellent lubricating performance of the PG composite might be attributed to its good thermal stability as a result of the interaction between the GR and the PI matrix. Therefore, PG composite could be used as an excellent solid lubricant under the high-temperature conditions.

The effects of pre‐exposure and surface notch on the tensile properties of T91 steel in oxygen saturation lead–bismuth eutectic (LBE) have been investigated by slow strain rate tensile tests at 350°C with a strain rate of 1 × 10−5 s−1, and the reference tests were performed in Ar gas. The pre‐exposure was conducted in liquid LBE at 500°C with an oxygen concentration of 10−8 wt% for 500 h. It is shown that the tensile properties of the nonpre‐exposed specimens whether with or without a notch were not affected by LBE, but obvious liquid metal embrittlement (LME) was observed on the pre‐exposure specimens. After being pre‐exposed, the notched one was more prone to liquid LBE embrittlement compared to the unnotched specimen. Morphology similar to fatigue striations was observed on the fracture surface of the notched specimen with pre‐exposure, which was probably attributed to the rapid growth of the crack. The results revealed that pre‐exposure had a critical effect on LME, and surface notch intensified this phenomenon when pre‐exposure was present. [ABSTRACT FROM AUTHOR]

China prioritizes clean energy for power generation in response to climate change and air pollution. By the end of 2021, the installed capacity of wind power has reached 328.48 GW, accounting for 13.8% of China's total installed capacity of 2376.92 GW. However, wind power is inherently unstable and its output depends on resources, which poses challenges for the national grid. Wind curtailment is often encountered when electricity production is plentiful. The main objective of this work is to develop a clean energy generation system for on-demand power supply to improve the utilization of wind resources. The LBE reactor is also a clean energy source with flexible power regulation that helps mitigate the impact of wind variability. Therefore, a hybrid wind-nuclear power system (HWNPS) is proposed. This paper demonstrates the technical feasibility of the LBE reactor and conducts a preliminary analysis of the economics of the HWNPS. The additional cost of HWNPS due to power regulation is about $ 9.04/MWh, which has potential for research and development. [ABSTRACT FROM AUTHOR]

Corrosion tests of T91 were carried out in the stagnant lead–bismuth eutectic (LBE) containing 10−6, 10−7, and 10−8 wt% oxygen at 500°C for up to 2000 h, respectively. The dependence of corrosion characteristics on oxygen concentrations in LBE was obtained. The results show that the oxide‐scale structure changes from a three‐layer magnetite/spinel/internal oxidation zone (IOZ) scale under the oxygen concentration of 10−6 wt%, to the formation of a two‐layer spinel/IOZ scale under the oxygen concentrations of 10−7 and 10−8 wt%. In addition, with the decrease of the oxygen concentration, the Cr/Fe ratio in the Fe–Cr spinel slightly increases in a linear rule while the thicknesses of the oxide layers gradually decrease. [ABSTRACT FROM AUTHOR]

Nano zero-valent iron (NZVI) particles were prone to forming aggregates owing to their intrinsic magnetism and van der Waals force. In this work, a composite material containing mesoporous silica MCM-41 and NZVI was prepared to avoid the problem of NZVI aggregation. The structures and morphologies of the as-prepared composite were confirmed using X-ray diffraction, Fourier transform infrared spectrometry, transmission electron microscopy, N2adsorption–desorption, and X-ray photoelectron spectroscopy techniques. It was found that NZVI particles were well dispersed in the composite, although the size of NZVI particle was larger than that of bare NZVI. Moreover, the composite was used as adsorbent for removing Pb(II) from aqueous solution at room temperature. The effects of contact time, initial solution pH, and adsorbent dosage on the removal efficiency of Pb(II) were studied using batch adsorption experiments. The results indicated the composite exhibited enhanced adsorption properties, with the maximum adsorption capacity of 416.17 mg/g for Pb(II) removal from aqueous solution. In addition, the adsorption isotherms and adsorption kinetics were also investigated systematically, it was found that the isothermal data were well fitted to Langmuir model, and the kinetic data were well suitable to pseudo-second-order kinetics model. [ABSTRACT FROM PUBLISHER]

In this study, a series of chitosan-stabilized nano zero-valent iron (CNZVI) composites with different amounts of chitosan were prepared and characterized by Fourier transform infrared spectra, X-ray diffraction, and transmission electron microscopy. The adsorption capacity of these composites was evaluated by the removal experiment of cadmium ion (Cd2+) from aqueous solution. These results showed that the as-prepared CNZVI8composite with loose aggregate structure has the maximum adsorption capacity for Cd2+. Furthermore, batch adsorption experiments of Cd2+on CNZVI8composite were performed under various conditions, such as contact time, adsorbent dosage, initial Cd2+concentration, and the initial pH of solution. The data revealed that the maximum adsorption capacity of CNZVI8is 124.74 mg/g. The removal efficiency of Cd2+increased with the increase in solution pH value, and reaches 99.9% at pH 6. In addition, the adsorption isotherm and the adsorption kinetics of Cd2+on CNZVI8were also investigated, suggesting that the isothermal data were well fitted to the Langmuir model and the kinetic data were well suitable to the pseudo-second-order kinetic model. [ABSTRACT FROM PUBLISHER]

• Laser oscillation welding was utilized for joining of steel/copper dissimilar metals. • Microstructure evolution and component changes have been comparatively studied. • Metallurgical reaction mechanism during laser oscillation welding was ascertained. • It may be a means to enhance join quality of dissimilar materials in manufacturing. In this project, we present experimental laser welding of pure copper to stainless steel in the presence of beam oscillation. The microstructure, element distribution and mechanical properties of joints welded with and without exposure to beam oscillation were contrastively investigated employing scanning electron microscopy, energy dispersive X-ray spectrometry and other methodologies. The results showed that joint microstructure subjected to beam oscillation changed from massive and columnar structures to granular and globular structures. The driven force of circular oscillating beam on the molten pool produced a vortex flow, which promoted heat and mass transfer during laser welding. Moreover, it also led to the refinement of grains and discrete distribution of precipitated phases (rich-Fe α phase and rich-Cu ε phase), thereby reducing microstructural segregation and improving the resistance to crack in welds. The hardness gradient in joints suffered from beam oscillation was significantly reduced because of improvement in microstructural homogenization. The tensile strength and elongation of welded joints subjected to beam oscillation were 282.82 MPa and 2.68 mm respectively, 110.41% of strength and 153.14% of elongation compared to that of joints welded without exposure to beam oscillation. Joint improvement in strength and plasticity was attributive to microstructural refinement and compositional homogeneity. [ABSTRACT FROM AUTHOR]

Porphyries, closely associated with the copper deposits worldwide, are usually considered to have high oxygen fugacity and high Sr/Y ratios. However, it is still ambiguous whether the high oxygen fugacity and the enrichment of chalcophile elements are inherited from magma source or obtained by magmatic processes, and the linkage between the high Sr/Y magmas and the formation of porphyry Cu deposits remains unclear. To address these issues, we performed an integrated study of zircon geochronology and oxygen fugacity, petrography, geochemical and Sr-Nd-Hf isotopic compositions for the Shanyang porphyry groups at an intra-continental setting from the South Qinling Orogen, Central China. The Shanyang porphyries can be divided into six groups in terms of their spatial distribution with the crystallization ages ranging from ca. 152 to 140 Ma. They are characterized by high Sr and Ba contents, consistent with the geochemical features of high Ba-Sr granitoids. They show a continuous evolution trend from mafic to felsic samples and mafic samples have high Mg#, Cr, and Ni contents, indicating that they were evolved from mantle-derived basaltic magmas. Most samples display homogeneous I Sr (0.704 to 0.706), ε Nd (t) (−6 to −1.5) and zircon ε Hf (t) (−4 to +2) values, suggesting that they were derived from an enriched lithospheric mantle with minor crustal contamination. Geochemical results suggest that they were generated by low degree melting of a heterogeneous lithospheric mantle at spinel facies that had been modified by previous slab-derived fluids. These porphyry bodies were derived from multiple magma reservoirs within their distinct plumbing systems and had undergone polybaric differentiation. With magma differentiation, the Shanyang porphyry magmas changed from an oxidized state (ΔFMQ +1 to +2) to a reduced state (ΔFMQ +1 to −0.5). The high (Dy/Yb) N ratios indicate crystallization of garnet had cryptically occurred in the deep crust, which induced sulfide saturation at an earlier stage. This process could result in the deficiency of chalcophile elements and elevate the oxygen fugacity in the residual melts from a relatively reduced parental mafic magma. Degassing in the shallow crust would lead to a decrease in the ƒO 2 of the felsic magmas. Thus, some other processes, such as, re-melting of early formed sulfide and gas-brine reactions, are required to concentrate chalcophile elements in the felsic magmas. Our study implies that intra-crustal processes could play a more important role in the enrichment of chalcophile elements and that the oxygen fugacity of the magma system can change during magma evolution. The observations of the Shanyang porphyry groups are very helpful for understanding similar porphyry systems globally. We propose that porphyries worldwide formed in the thickened crust with long-lived magmatic hydrothermal systems in the shallower magma reservoirs are more prone to form porphyry Cu deposits. • The late Mesozoic Shanyang porphyry groups are high Ba-Sr granitoids. • Multiple magma reservoirs co-exist feeding the Shangyang porphyry groups. • Remelting of sulfides and gas-brine reactions could enrich Cu in the felsic magma. • The long-lived magma-hydrothermal system plays a key role in the formation of PCDs. [ABSTRACT FROM AUTHOR]