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In recent years, the sudden rise of high entropy alloys (HEAs) has become a hot research topic in the field of metal materials. The high entropy alloy is located in the central region of phase diagram, which has broad alloy composition space and possible formation of microstructure. The synergistic regulation of composition and preparation process can obtain richer structure. Unconventional chemical structure is expected to break through the performance limit of traditional anti-wear and lubricating alloys. In this work, the classification of wear-resistant HEAs was discussed. The effects of the addition of chemically active metals, soft metals and refractory metals on the wear resistance and lubrication properties of HEAs were analyzed. The effects of non-metallic elements and ceramic phases on the tribological properties of HEAs matrix composites were summarized. The effects of heat treatment and surface engineering technology on the surface microstructure and tribological behavior of HEAs were reviewed. The design method of HEAs with anti-wear lubrication under severe working conditions was discussed. The future research and application of HEAs in the field of friction and wear were prospected. High entropy alloys have great potential to solve the bottleneck problems of traditional alloys, such as to realize stable lubrication and anti-wear under extreme working conditions and to ensure anti-wear under specific functions.

Three-dimension solid model of helical gear limited slip differential is built by using CATIA,and then the virtual prototype model is established through importing the 3D solid model into ADAMS/View. In the virtual environment,based on the kinematics dynamics simulation and analysis with two different typical work conditions,including straight-line driving on good pavement and double tire-road friction coefficients,the torque curve,the force and angular velocity curves of helical gear of limited slip differential are acquired.By comparing with theoretical calculations values,the correctness of model and the effectiveness of simulation method are verified. The study results provide the basis for the dynamic optimization and fatigue life prediction of the helical gear limited slip differential.

This project is the construction project of the academic report comprehensive building of the Central Youth League School. The main function of the project is the academic report room, including an 800-person lecture hall, a 300-person multi-function lecture hall, a 500-person multi-function lecture hall, an exhibition hall, etc., and three underground floors. There are three floors above the ground, and one floor is partially high. There are 12.8, 13.8, 15.7, 18.2, 18.6, 20.8, 27.8 meters in the sub-regions of the roof structure elevation. This article introduces the structural system, the judgment of structural out-of-limit situations, prestress design, steel truss design, suspension steel structure design, cantilevered large-span concrete beams, etc., through a variety of structural calculation and analysis methods, and find out structural weaknesses, and adopt Corresponding seismic strengthening measures, the calculation results show that the structure has good seismic performance and can meet the requirements of the code.

Ag@SnO2 nanosheets were prepared through a hydrothermal method followed by heat treatment and a liquid reduction process. Many Ag nanoparticles (Ag NPs) were dispersed uniformly over the surface of the SnO2 nanosheets. The thickness of the SnO2 nanosheets was approximately 10 nm. After decoration with Ag NPs, the Ag@SnO2 nanosheet sensors exhibited improved gas-sensing behaviors compared to the pure SnO2 nanosheet sensor. The response of cross-linked SnO2 nanosheets decorated by Ag NP sensors for 100 ppm formaldehyde vapor was up to 101.4, which was double that (45.5) of the pure SnO2 nanosheet sensor. The response and recovery times of the Ag@SnO2 sensor were 21 s and 23 s, respectively. The Ag@SnO2 nanosheet sensors showed reasonable cycling stability, as demonstrated by testing with 100 ppm formaldehyde 10 times. The superior gas-sensing behaviors of the Ag@SnO2 sensor were due to the large specific surface area, cross-linked nanostructure, and synergistic effect of the Ag NPs with huge sensitizing active sites and numerous SnO2 nanosheets. [ABSTRACT FROM AUTHOR]

A Ni60 cladding layer with addition of 6.0% CeO2 was prepared on 35CrMoV steel by laser cladding technology. The prepared sample was placed at 500 °C, 600 °C and 700 °C for 60 min to explore the effects of heat treatment on the tribological properties of the composite coating. The microstructure, phase composition, microhardness and tribological properties of the composite coating were characterized by optical microscopy and scanning electron microscopy (SEM), X-ray diffraction (XRD), micro-Vickers hardness tester and MicroXAM-800 optical surface photometer, respectively. According to the above experimental results analysis, the main components of 6.0% CeO2/Ni60 cladding layer are γ-(Fe,Ni),Cr7C3,Cr23C6,CrB, CrFeB and Cr2Ni3. By calculating the FWHM value and the left shift of the XRD diffraction peak, it is found that the coating grains are remarkably refined and the microstructure uniformity is significantly improved under the condition of heat treatment at 500 °C. The experimental results show that the Ni60 composite coating with 6.0% CeO2 has the best friction and wear performance at 500 °C. The wearing quality of the composite coating at 500 °C was reduced by 43%. [ABSTRACT FROM AUTHOR]

The effects of CeO2 addition on the macro-morphology, surface cracks, microstructure, precipitated phases and wear property of laser cladding Ni-based coatings on 35CrMoV steel were investigated by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscope (TEM), x-ray photoelectron spectroscopy (XPS) and friction and wear tester, respectively. The results indicated that the microstructure could be remarkably refined with the addition of CeO2. The width of eutectic structure is reduced from 1.74 μm to 237.5 nm with the amount of CeO2 increases from 0 to 4.0 wt.%. Meanwhile, CeO2 significantly decreases the number of the oxides and it can be obtained the minimal number of cracks when the CeO2 addition reaches 4.0 wt.%. The main phase composition of Ni60 cladding layer is Ni3Fe, Ni3V, Cr23C6 and Fe5C2. The distortional zone was observed around the eutectic of the coating. The average friction coefficient (0.438) and the wear resistance are the best when the addition of CeO2 is 4.0 wt.%. [ABSTRACT FROM AUTHOR]