Developing single-atom catalyst-based epoxy coating with active nanocatalytic anticorrosion performance in oxygen environment

The stimuli-responsive anticorrosion coatings have drawn great attention as a prospective corrosion protection approach due to their smart self-repairing properties.In contrast to passive protection mechanism based on post-corrosion microenvironmental changes,a unique active protection strategy based on nanocatalytic oxygen depletion is proposed in this work to inhibit the occurrence of corrosion.Porous FeeNeC catalysts with outstanding oxygen reduction reaction(ORR)activity(half-wave potential of 0.89 V)is firstly synthesized through pre-coordination with organosilane precursor to obtain homogeneously distributed active sites.When this catalyst is introduced into the coating matrix,uniformly distributed FeeNeC not only compensates the defects but plays a crucial role in adsorption and consumption of diffused oxygen in the coating.Under this dual action,the penetration of corrosive medium,especially oxygen,through coating to metal substrate is greatly suppressed,resulting in effective corrosion inhibition and a significant increase in corrosion resistance of the composite coating compared to pure epoxy coating.This work provides a new perspective and the starting point for the design of high-performance smart coating with active anticorrosion properties.

Residual stress and welding distortion of Al/steel butt joint by arc-assisted laser welding-brazing

The thermo-elastic.plastic finite element method(FEM)is used to simulate the thermo-mechanical behavior of Al/steel tungsten inert gas(TIG)arc-assisted laser welding-brazing(A-LWB)butt joint.The influence of material nonlinearity,geometrical nonlinearity and work hardening on the welding process is studied,and the differences in the welding temperature field,residual stress and welding distortion by A-LWB and by single laser welding-brazing(SLWB)are analyzed.The results show that the thermal cycle,residual stress distribution and welding distortion by the numerical simulation are in good agreement with the measured data by experiments,which verifies the effectiveness of FEM.Compared with the SLWB,A-LWB can make the high-temperature distribution zone of weld in width direction wider,decrease the transverse tensile stress in the weld and reduce the distribution range of longitudinal tensile stress.And the welding deformation also decreases to some extent.

Characteristics of TIG arc-assisted laser welding–brazing joint of aluminum to galvanized steel with preset filler powder

Tungsten inert gas(TIG) arc-assisted laser welding–brazing was used for the butt joining of 5A06 aluminum alloy to the galvanized steel by preset filler powder without groove. The spreading behavior of liquid metal on the back of the galvanized steel at different assisted welding currents was also investigated. The results show that the assisted TIG arc optimizes the interface reaction temperature, enhances the wettability of liquid metal on the steel side, and forms a sound butt joint at an appropriate welding current. A non-uniform intermetallic compound is formed at the interfacial layer, which is composed of Fe2Al5 close to the steel substrate and Fe4Al13 close to the solidified aluminum. The superior tensile strength of joint is indicated when the welding current ranges from 13 to 16 A. The average tensile strength can reach 151 MPa at the welding current of 16 A, and the corresponding fracture belongs to the ductile and brittle hybrid mode.

High-resolution Sonographic Measurements of Lower Extremity Bursae in Chinese Healthy Young Men

Background： Lower extremity bursae are very vulnerable to injury during strenuous physical exercises.Understanding the imaging characteristics of normal bursae is essential for early diagnosis of morphological abnormalities.Therefore, we evaluated the normal range of lower extremity bursae in healthy young men using high-resolution ultrasound （HR-US） imaging.Methods： Bursae in the lower extremities were examined by HR-US in 290 Chinese healthy young men with a median age of 18 years （range, 18-23 years）.The bilateral suprapatellar bursa （SPB）, deep infrapatellar bursa （DIPB）, popliteal bursa （PB）, and retrocalcaneal bursa （RCB） were imaged and measured for analysis.Results： The HR-US identification rates of the SPB, DIPB, PB, and RCB were 89.0% （517/580）, 55.0% （319/580）, 29.4% （171/580）, and 49.5% （287/580）, respectively.With the assumption that the bursae were normal in 95% of the study participants, the length and width values at the maximal cross-section of the SPB, DIPB, PB, and RCB were ≤18.00 and 6.09 mm, 8.10 and 2.1 1 mm, 7.67 and 3.93 mm, and 7.82 and 2.04 mm, respectively.Conclusions： Using HR-US imaging, we were able to analyze lower extremity bursae with high detection rates in healthy young men.The normal ranges of lower extremity bursa dimensions in healthy young men measured by HR-US in this study could be used as reference values for evaluation of bursa abnormalities in the lower extremity.