Microstructure and properties of SAF2507 superduplex stainless steel welded joints

SAF2507 plates （ 12 mm thickness ） were welded using shield metal arc welding （SMAW） process with E2594 electrode. The microstructure, o-phase, and impact fraetograph of the welded joints were analyzed using optical microscope and scanning electron mieroseope. The results show that the fusion zone consists of ferrite, chromium nitride, and secondary aastenite precipitation when welding is performed at low heat input （0. 5 kJ/mm）. However, the increase in heat input causes precipitation of brittle o＂ phase at the y/c~ interface in weld metal and heat-affected zone, as well as a brittle fracture along the grain boundary. Heat input in the range of O. 5 kJ/mm to 1.5 kJ/mm is suitable for joining SAF2507 plates.

Nano-silver-modified polyphosphazene nanoparticles with different morphologies:Design,synthesis,and evaluation of antibacterial activity

Drug-resistant bacteria present a severe threat to public health,emphasizing the importance of developing broad-spectrum antibacterial agents that are free from drug resistance.Among silver-based antibacterial agents,nano-silver has been found to exhibit the most promising and comprehensive performance.The exploration of the antibacterial capacity and morphological changes of silver nanoparticles(AgNPs)could offer a starting point for the development of safe and efficient antibacterial agents.In this study,three types of nano-silver-modified polyphosphazene(PRV)nanoparticles with different morphologies were synthesized using precipitation polymerization.These nanoparticles were characterized using various techniques,including Fourier-transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and thermogravimetric analysis(TGA).The antibacterial activity of these nanoparticles against Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)was assessed using minimum inhibitory concentration(MiC)/minimum bactericidal concentration(MBC)tests and inverted fluorescence microscopy.Our results revealed that the antibacterial activity of silver nanoparticles can vary significantly depending on their immobilized form.Ag@PRV Strawberry-like nanoparticles(NPs)exhibited higher antibacterial activity compared to Ag@PRV Yolk-Shell NPs and Ag@PRV Cable-like nanofibers(NFs).Notably,all three types of synthesized nanoparticles demonstrated a stronger bactericidal effect on Gram-positive bacteria than Gram-negative bacteria.Live/dead bacterial staining and scanning electron microscopy demonstrated that silver can kill bacteria by altering the permeability of their cell membranes.These findings offer valuable insights for designing and practically applying new silver-based antibacterial agents in the future.

Fully Chemical Recyclable Poly(γ-butyrolactone)-based Copolymers with Tunable Structures and Properties

The emerging chemical recyclable polymers,such as poly(γ-butyrolactone)(PGBL)and poly((R)-3,4-trans six-membered ring-fused GBL)(P((R)-M)),provide a good solution to the plastic pollution.However,these homopolymers suffer from limited structures and properties.Herein,we reported a fully chemical recyclable copolymer P(GBL-co-((R)-M))through ring-opening copolymerization(ROCOP)of GBL and(R)-M.By employing organomagnesium as the catalyst and regulating the reaction conditions,the chemical structures of copolymers were wellcontrolled(GBL content=13%-78%,Mn=6560-15600 g/mol,DM=1.08-1.59).The resultant P(GBL-co-((R)-M))exhibited fully chemical recyclability,which rapidly and quantitatively depolymerized into initial GBL and(R)-M monomer through chemolysis.By varying GBL content,tunable thermal properties were achieved for P(GBL-co-((R)-M)).The onset decomposition temperatures of copolymers varied from 193°C to 234°C.A linear evolution of glass transition temperature(T_(g))of P(GBL-co-((R)-M))versus GBL content was obtained as following equation of Tg=-1.06×GBL mol%×100+39.6.We hope that the reported fully chemical recyclable copolymers with tunable structures and properties would serve as the candidate material for sustainable applications.

Enhancement of adjustable localized surface plasmon resonance in ZnO nanocrystals via a dual doping approach

Recently, the localized surface plasmon resonance （LSPR） concept was expanded from noble metals to doped semiconductor nanocrystals （NCs）. However, the strengthening of the intrinsically very weak LSPR in NCs remains a great challenge for its applications in optics, electronics and optoelectronics fields. In this work, we report on the remarkable strengthening and controllability of LSPR in ZnO through a dual-doping strategy. First, high quality In-doped ZnO （IZO） NCs with intense LSPR were synthesized by a simple single-pot method. Importantly, the LSPR can be tuned by simply adjusting the concentration of In dopant, as well as by UV light irradiation （photo-induced doping）. The pattern of electricity of an IZO NC film matches the shift of LSPR independent of dopant concentration. The UV light irradiation clearly enhanced the electrical properties of the films （350 fl/sq） due to increase carrier density explained by LSPR and confirmed by X-ray photoelectron spectroscopy, The IZO NCs can be easily dispersed in various organic solvents and serve as inks for assembling uniform films via solution processes. These IZO NC ink is promising for application in next-generation solution-based field effect transistors and other optoelec- tronic devices.