Defect-Rich PdIr Bimetallene Nanoribbons with Interatomic Charge Localization for Isopropanol-Assisted Seawater Splitting

Metallene with outstanding physicochemical properties is an efficient two-dimensional electrocatalysts for sustainable hydrogen (H₂) production applications. However, the controllable fabrication of extended atomically thin metallene nanoribbons remains a formidable challenge. Herein, this work proposes a controllable preparation strategy for atomically thin defect-rich PdIr bimetallene nanoribbons (PdIr BNRs) with a thickness of only 1.5 nm for the efficient and stable isopropanol-assisted seawater electrolytic H₂ production. When using PdIr BNRs as catalyst to build an isopropanol-assisted seawater electrolysis system, a voltage of only 0.38 V is required at @10 mA cm⁻² to achieve energy-saving H₂ production, while producing high value-added acetone at the anode. The aberration-corrected high-resolution transmission electron microscopy (HRTEM) clearly reveals that the PdIr BNRs possess abundant structural defects, which can additionally serve as highly catalytically active sites. Density functional theory (DFT) calculations combined with X-ray absorption spectroscopy studies reveal that the introduction of Ir atoms can induce the formation of a localized charge region and shift the d-band center of Pd down, thereby reducing the adsorption energy on the catalyst in favor of the rapid desorption of H₂. This work opens the way for the controllable design and construction of defect-rich atomically thin metallene nanoribbons for efficient electrocatalytic applications.     

Ultrathin Co-N-C Layer Modified Pt–Co Intermetallic Nanoparticles Leading to a High-Performance Electrocatalyst toward Oxygen Reduction and Methanol Oxidation

The development of low platinum-based alloy electrocatalysts is crucial to accelerate the commercialization of fuel cells, yet remains a synthetic challenge and an incompatibility between activity and stability. Herein, a facile procedure to fabricate a high-performance composite that comprises Pt–Co intermetallic nanoparticles (IMNs) and Co, N co-doped carbon (Co-N-C) electrocatalyst is proposed. It is prepared by direct annealing of homemade carbon black-supported Pt nanoparticles (Pt/KB) covered with a Co-phenanthroline complex. During this process, most of Co atoms in the complex are alloyed with Pt to form ordered Pt–Co IMNs, while some Co atoms are atomically dispersed and doped in the framework of superthin carbon layer derived from phenanthroline, which is coordinated with N to form Co–N_x moieties. Moreover, the Co-N-C film obtained from complex is observed to cover the surface of Pt–Co IMNs, which prevent the dissolution and agglomeration of nanoparticles. The composite catalyst exhibits high activity and stability toward oxygen reduction reactions (ORR) and methanol oxidation reactions (MOR), delivering outstanding mass activities of 1.96 and 2.92 A mg_Pt⁻¹ for ORR and MOR respectively, owing to the synergistic effect of Pt–Co IMNs and Co-N-C film. This study may provide a promising strategy to improve the electrocatalytic performance of Pt-based catalysts.     

烧结温度对包混/复合添加工艺制备多孔SiC陶瓷性能的影响

采用包混工艺合成了核壳结构的先驱体粉体,并引入一定量Al2O3、SiO2和Y2O3复合添加剂,通过成型、炭化和烧结工艺制备了多孔碳化硅陶瓷;分析了样品的物相、表面形貌、孔隙率、热导率、热膨胀系数、抗弯强度和抗热震性能。结果表明,在较低的烧结温度下制得了多孔碳化硅陶瓷,在1650℃烧结的多孔碳化硅陶瓷综合性能较好。     

随机Sierpinski垫与Mandelbrot渗流模型的形态相位

研究了Ｓｉｅｒｐｉｎｓｋｉ垫与Ｍａｎｄｅｌｂｒｏｔ渗流模型的形态相位问题，利用对指标集的Ｂｅｒｎｏｕｌｌｉ随机在换．得出了比文献［１］．［２］更精确的相位临界值的估计。     

镶嵌在CaF2介质中纳米Cu团簇微观结构的研究

利用磁控溅射产生金属Ｃｕ团簇，同时蒸发ＣａＦ２介质，将Ｃｕ团簇包埋在ＣａＦ２介质中，团簇大小可通过改变溅射气压控制，用ＴＥＭ研究了嵌埋团簇的结构，分析结果表明：Ｃｕ团簇呈三角状多晶结构，团簇大小为１０￣７０ｎｍ，基质ＣａＦ２晶体也为多晶结构，Ｃｕ团簇的晶格常数在包埋状态下发生了膨胀，膨胀率大约在１６％左右。     

Optimization of silicon nanocrystals growth process by low pressure chemical vapor deposition for non-volatile memory application

The processes of silicon nanocrystals (Si-NCs) growth on both SiO₂ and Si₃N₄ substrates by low pressure chemical vapor deposition have been systematically investigated. A two-step process was adopted for Si-NCs growth: nucleation at a high temperature (580-600 °C) and growth at a low temperature (550 °C). By adjusting the pre-deposition waiting time and deposition time, the density, size and uniformity can be effectively controlled. Compared to the growth of Si-NCs on SiO₂, the coalescence speed of Si-NCs on Si₃N₄ is faster. Uniform Si-NCs with a high density of 1.02 × 10¹² cm^− 2 and 1.14 × 10¹² cm^− 2 have been obtained on SiO₂ and Si₃N₄, respectively. Finally, a Si-NCs-based memory structure with a 2.1 V memory window was demonstrated.     

Analysis of the S–N curves of welded joints enhanced by ultrasonic peening treatment

Contrast fatigue tests were carried out on T-shape tubular joints of 20 steel in three conditions: as welded, treated by ultrasonic peening treatment (UPT) before loading and UPT under loading. Results are: (1) Dispersity of test results measured by nominal stress is much larger than that measured by hot spot stress. After UPT before loading, fatigue strength of 20 steel tubular joints measured by hot spot stress increases by 67% and fatigue life is prolonged by 22–45 times. (2) Under low stress ratio R, UPT before loading can improve the fatigue performance of welded tubular joints significantly. (3) Under high stress ratio R, UPT under loading (static load) is recommended to improve the fatigue performance of welded tubular joints. UPT under loading not only enhances the fatigue properties at low stress level, but also at high stress level. (4) The general rule of S–N curves of welded joints treated by UPT is commonly effected by external load (static load) and self release of residual stress.     

Droplet Deformation and 2-D/3-D Marangoni Flow Phenomena in Droplets Levitated by Electric Fields

An integrated numerical model is presented for free surface phenomena and Marangoni fluid flows in electrically levitated droplets under both terrestrial and microgravity conditions. The model development is based on the boundary element solution of the Maxwell equations simplified for electrostatic levitation applications and the free surface deformation that is primarily caused from the surface Maxwell stresses resulting from the applied electric fields. The electric and free surface model is further integrated with a finite element model for the surface-tension-induced fluid flows in the levitated droplets. Both 2-D and 3-D fluid flow structures may be developed in the electrically levitated droplets depending on the applied laser heating sources. The integrated model is applied to study the electric field distribution, free surface deformation, and 2-D and 3-D internal fluid flow structures in normal and microgravity for single, symmetric two-beam, four-beam, and six-beam laser heating arrangements. Among these arrangements, the six-beam arrangement with equal heating intensity gives the smallest temperature difference and the smallest maximum velocity.     

Discussion on fatigue design of welded joints enhanced by ultrasonic peening treatment (UPT)

Large numbers of fatigue testing results of welded joints after ultrasonic peening treatment (UPT) were analyzed and summarized. Differences in fatigue design between as welded and UPT joints were discussed. Results indicate that material strength has effect, to a certain extent, on the fatigue performance of UPT welded joints. Contrast tests show that slope m values (6.3–23) of S–N curves of UPT welded joints are much bigger than 3.0 (recommended by the international institute of welding-IIW). It is not appropriate to simply use m as 3.0 to analyze the fatigue testing data of UPT joints. Furthermore, after UPT, fatigue strength is not independent of the average stress any more, so stress ratio should be taken into account for fatigue design.     

Kinetic modeling of Q-switched high-power ytterbium-doped fiber lasers

We present a kinetic model for Q-switched, cladding-pumped, high-power Yb-doped fiber lasers that are based on the rate equation, in a difference equation form, of ion population and propagation equations for both pumping and signal light. The effects of fiber-laser parameters, such as doping, length, pump power, and repetition rate on pulse characteristics are analyzed. This model is used to analyze the performance of Q-switched multicore fiber lasers and to show the output pulses with enhanced characteristics.