Achieving macroscale superlubricity with ultra-short running-in period by using polyethylene glycol-tannic acid complex green lubricant

Superlubricating materials can greatly reduce the energy consumed and economic losses by unnecessary friction.However,a long pre-running-in period is indispensable for achieving superlubricity;this leads to severe wear on the surface of friction pairs and has become one of the important factors in the wear of superlubricating materials.In this study,a polyethylene glycol-tannic acid complex green liquid lubricant(PEG10000-TA)was designed to achieve macroscale superlubricity with an ultrashort running-in period of 9 s under a contact pressure of up to 410 MPa,and the wear rate was only 1.19×10^(–8)mm^(3)·N^(−1)·m^(−1).This is the shortest running-in time required to achieve superlubricity in Si_(3)N_(4)/glass(SiO_(2)).The results show that the strong hydrogen bonds between PEG and TA molecules can significantly reduce the time required for the tribochemical reaction,allowing the lubricating material to reach the state of superlubrication rapidly.Furthermore,the strong hydrogen bond can share a large load while fixing free water molecules in the contact zone to reduce shear interaction.These findings will help advance the use of liquid superlubricity technology in industrial and biomedical.

Charge storage coating based triboelectric nanogenerator and its applications in self-powered anticorrosion and antifouling

As a novel energy-harvesting device,a triboelectric nanogenerator(TENG)can harvest almost all mechanical energy and transform it into electrical energy,but its output is low.Although the micro-nano structures of triboelectrode surfaces can improve their output efficiency,they lead to high costs and are not suitable for large-scale applications.To address this problem,we developed a novel TENG coating with charge-storage properties.In this study,we modified an acrylic resin,a friction material,with nano-BaTiO_(3) particles and gas phase fluorination.The charge-trapping ability of nanoparticles was used to improve the output of TENG.The short-circuit current and the output voltage of coating-based TENGs featuring charge storage and electrification reached 15μA and 800 V,respectively,without decay for longtime working.On this basis,self-powered anticorrosion and antifouling systems are designed to reduce the open circuit potential of A3 steel by 510 mV and reduce the adhesion rate of algae on the surface of metal materials.This study presents a high-output,stable,coating-based TENG with potential in practical applications for anticorrosion and antifouling.

CFD-DEM investigation into flow characteristics in mixed pulsed fluidized bed under electrostatic effects

Static electricity has an important effect on gas–solid fluidized bed reactor fluidization performance.In the process of fluidization,electrostatic interaction between particles will obviously accelerate particle agglomerate formation,which consequently reduces the fluidization performance.Pulsed gas flow injection is an efficient method to enhance particle mixing,thereby weakening the occurrence of particle agglomerate.In this study,the two-dimensional hybrid pulsed fluidized bed is established.The flow characteristics are studied by using the coupled CFD-DEM numerical simulation model considering electrostatic effects.Influences of different pulsed frequencies and gas flow ratios on fluidized bed fluidization performance are investigated to obtain the optimal pulsed gas flow condition.Results show that in the presence of static electricity,the bubble generation position is lower,which is conducive to the particle flow.Pulsed gas flow can increase the particle velocity and improve the diffusion ability.The bubble generation time is different at different frequencies,and the frequency of 2.5 Hz has the most obvious effect on the flow characteristics.Different gas flow ratios have significant impacts on the particle movement amplitude.When the pulse gas flow accounts for a large ratio,the particle agglomerate tends to be larger.Therefore,in order to improve the fluidization effect,the ratio of pulsed gas flow to stable gas flow should be appropriately reduced to 0.5 or less.