Fengyi WANG,Ziwen LV,Linxiao Sun,Hongtao CHEN,Mingyu LI
Background In the field of electronic packaging, Sn-58Bi solder paste is a promising low-temperature option for step soldering. However, the tendency for the Bi-rich phase to coarsen and segregate poses a significant challenge to the long-term reliability of the solder joints. Methods The Sn coated Zn (Zn@Sn) core-shell particles were prepared through a chemical plating process and incorporated into the Sn-58Bi low-temperature solder paste to enhance its reliability. The microstructural and mechanical characteristics of the solder joints were evaluated under thermal cycling and thermomigration conditions to assess their long-term service reliability. Significant findings The addition of Zn lowers the nucleation energy and promotes the refinement of the eutectic structure, avoiding a significant reduction in shear strength after thermal cycling. In thermomigration, the heat transfer Q* of Bi is calculated to be 22.5 kJ/mol. The Zn-rich phases hardly move and are evenly distributed within the solder joints, acting like a barrier to prevent the Bi phase diffusing from the hot end to the cold end.
A photochromic long persistent luminescent polyurethane (PLPLPU) is prepared via incorporating amino-functionalized phosphors (NH2-SrAl2O4:Eu2+,Dy3+) and the red fluorescer 1-[(2-hydrocyethly)amino]anthraquinone (HAA) based on a colour conversion process. X-ray Diffraction (XRD), UV-vis absorption spectroscopy (UV), thermogravimetric analysis (TG), a fluorescence spectrophotometer and an afterglow brightness tester as well as the percentage of the migration test were utilized to characterize the structure and properties of the resultant samples. The photoluminescence emission spectrum of phosphors is overlapped with the excitation spectrum of HAA, which demonstrates that HAA can be selected as a colour conversion agent and can be excited by phosphors in the dark. PLPLPU shows red emission in daylight and yellow in the dark, exhibiting a pleasant photochromic long persistent luminescence effect. Furthermore, HAA in PLPLPU was confirmed to have a better thermal migration stability than the blend samples due to the chemical combination.
Tungsten carbides, featured by their Pt-like electronic structure, have long been advocated as potential replacements for the benchmark Pt-group catalysts in hydrogen evolution reaction. However, tungsten-carbide catalysts usually exhibit poor alkaline HER performance because of the sluggish hydrogen desorption behavior and possible corrosion problem of tungsten atoms by the produced hydroxyl intermediates. Herein, we report the synthesis of tungsten atomic clusters anchored on P-doped carbon materials via a thermal-migration strategy using tungsten single atoms as the parent material, which is evidenced to have the most favorable Pt-like electronic structure by in-situ variable-temperature near ambient pressure X-ray photoelectron spectroscopy measurements. Accordingly, tungsten atomic clusters show markedly enhanced alkaline HER activity with an ultralow overpotential of 53 mV at 10 mA/cm 2 and a Tafel slope as low as 38 mV/dec. These findings may provide a feasible route towards the rational design of atomic-cluster catalysts with high alkaline hydrogen evolution activity.
危险品化学品经营许可证（带存储）