Search

Developing efficient and long-lasting cathode catalysts is crucial for preparing high-performance lithium–sulfur (Li–S) batteries. Here, we designed and synthesized hierarchical, gradient, and multi-dimensional Co@NCNN armor catalysts by pyrolyzing g-C3N4 in the presence of cobalt nitrate. The unique structure of the Co@NCNN armor catalysts combines 0D Co nanoparticles and outer carbon protective shells, which adsorb and confine LiPSs, as well as 1D carbon nanotubes and 2D carbon nanosheets, which enhance the sulfur load and block LiPS diffusion, respectively. XANES and XPS analysis showed that Co–Co bonds with different Co valence states are the main catalytic sites for LiPSs. In situ XRD experiments and Li2S deposition tests demonstrated that the Co@NCNN armor catalysts can accelerate the liquid–solid conversion process, resulting in an initial discharge capacity of 1388.9 mA h g−1 at 0.5 C, an excellent area capacity of 5.05 mA h cm−2 and a sulfur load of 6.1 mg cm−2. More importantly, the robust carbon layer protects the highly active inner cobalt nanoparticles, enabling them to perform 1000 cycles at a current density of 7 C, with a capacity decay rate of 0.048% per cycle, and maintain stability over a wide temperature range of 0 to 60 °C. [ABSTRACT FROM AUTHOR]

Nitrile Butadiene Rubber (NBR) is widely used as a sealing material due to its excellent mechanical properties and good oil resistance. However, when using NBR material, the seal structure is unable to avoid the negative effects of rubber aging. Hence, the influence of oil and thermal aging on the characteristics of NBR seals was studied by coupling the mechanical behavioral changes with the tribological behavioral changes of NBR in oil and the thermal environment. For this paper, aging testing and compression testing of NBR were carried out. Additionally, friction testing between friction pairs under different aging times was carried out. The surface morphology of the NBR working surface under different aging conditions was also observed. Finally, coefficients of different test conditions were introduced into the finite element model of NBR seals. It can be seen from the results that the elastic modulus increased with the increase in aging time in the thermal oxidative aging testing. The elastic modulus after 7 days of thermal oxidative aging increased by 135.45% compared to the unaged case, and the elastic modulus after 7 days of oil aging increased by 15.03% compared to the unaged case. The compression set rate of NBR increased significantly with the increase in aging time and temperature. The coefficient of friction (COF) between friction pairs increased first and then decreased with the increase in aging time. The maximum contact pressure decreased by 2.43% between the shaft and sealing ring and decreased by 4.01% between the O-ring and groove. The proportion of the effective sealing area decreased by 3.05% between the shaft and sealing ring and decreased by 6.11% between the O-ring and groove. Furthermore, the sealing characteristics between the O-ring and groove were better than those between the shaft and sealing ring. [ABSTRACT FROM AUTHOR]

Highlights The design of composite I‐sections in aerostructures faces a significant challenge with conventional laminates because they are prone to delamination under out‐of‐plane loads. To address this issue, this study investigates the design, manufacture, and mechanical properties of 3D woven near‐net‐shaped composite I‐sections. The study also compares their advantages with equivalent laminates and examines the influence of weave patterns on their mechanical behavior. Specimens were manufactured using the vacuum‐assisted resin transfer molding technique, and quasi‐static tensile, compressive, and bending tests were conducted to assess the properties of I‐sections with three different weave patterns. It finds that the ultimate strength and damage tolerance of the considered design of 3D woven I‐sections are better than the considered design of 2D woven laminated counterparts, and different weave patterns play a significant effect in damage mode and load‐bearing capacity. In addition, using 3D woven preforms to manufacture composite I‐sections also exhibits shortened production time in terms of layup and resin infusion. The 3D woven I‐sections show improved damage tolerance over 2D counterparts. The design of weave patterns affects the properties of I‐section composites. Using 3D preforms to manufacture I‐sections exhibits shortened production time. Design consideration is proposed for the optimal weave pattern of the I‐sections. [ABSTRACT FROM AUTHOR]

Global mobile marketers are intensifying efforts to promote mobile applications, yet little literature addresses the effectiveness of these strategies on consumer adoption. This study investigates the impact of two mobile marketing strategies—in-app coupons and group-coupons—on mobile app adoption, considering the installed user base moderation. Utilizing data from a Chinese shopping mall, this study shows that both strategies can foster adoption, with opposite moderating effects from existing adopters. Two experiments validate social influence and scarcity perception as underlying mechanisms. These findings highlight the dynamic nature of mobile marketing, urging global mobile marketers to consider this in their strategies. [ABSTRACT FROM AUTHOR]

An experimental study on the scintillating behavior of ZnO:Ga crystals was conducted using a 7-MeV electron accelerator. The ZnO:Ga crystals were grown using both hydrothermal and chemical vapor transport methods. One of the ZnO:Ga crystals grown via the hydrothermal method exhibited a 1.5-ns afterglow time when excited by an MeV electron beam. The ultra-short scintillation was captured using both an ultrafast streak camera and a framed camera. The experimental results also confirm its potential for diagnosing electron beam trains with a repetition rate of hundreds of MHz. [ABSTRACT FROM AUTHOR]