Electronic tattoos based on large-area Mo2C grown by chemical vapor deposition for electrophysiology

Tattoo electronics has attracted intensive interest in recent years due to its comfortable wearing and imperceivable sensing,and has been broadly applied in wearable healthcare and human-machine interface.However,the tattoo electrodes are mostly composed of metal films and conductive polymers.Two-dimensional(2D)materials,which are superior in conductivity and stability,are barely studied for electronic tattoos.Herein,we reported a novel electronic tattoo based on large-area Mo_(2)C film grown by chemical vapor deposition(CVD),and applied it to accurately and imperceivably acquire on-body electrophysiological signals and interface with robotics.High-quality Mo_(2)C film was obtained via optimizing the distribution of gas flow during CVD growth.According to the finite element simulation(FES),bottom surface of Cu foil covers more stable gas flow than the top surface,thus leading to more uniform Mo_(2)C film.The resulting Mo_(2)C film was transferred onto tattoo paper,showing a total thickness of~3μm,sheet resistance of 60-150Ω/sq,and skin-electrode impedance of~5×10^(5)Ω.Such thin Mo_(2)C electronic tattoo(MCET in short)can form conformal contact with skin and accurately record electrophysiological signals,including electromyography(EMG),electrocardiogram(ECG),and electrooculogram(EOG).These body signals collected by MCET can not only reflect the health status but also be transformed to control the robotics for human-machine interface.

Decorating carbon nanofibers with Mo_2C nanoparticles towards hierarchically porous and highly catalytic cathode for high-performance Li-O_2 batteries

A facile synthesis of the hierarchically porous cathode with Mo2C nanoparticles through the electrospinning technique and heat treatment is proposed. The carbonization temperature of the precursors is the key factor for the formation of M02C nanoparticles on the carbon nanofibers （MCNFs）. Compared with the Mo2N nanoparticles embedded into N-doped carbon nanofibers film （MNNFs） and N-doped carbon nanofibers film （NFs）, the battery with MCNFs cathode is capable of operation with a high-capacity （10,509 mAhg-1 at 100 mAg-l）, a much reduced discharge-charge voltage gap, and a long-term life （124 cycles at 200 mA g-1 with a specific capacity limit of 500 mAh g -1）. These excellent performances are derived from the synergy of the following advantageous factors： （1） the hierarchically self-standing and binder-free structure of MCNFs could ensure the high diffusion flux of Li＋ and O2 as well as avoid clogging of the discharge product, bulk Li202; （2） the well dispersed M02C nanoparticles not only afford rich active sites, but also facilitate the electronic transfer for catalysis.

Effect of solution pH,Cl- concentration and temperature on electrochemical behavior of PH13-8Mo steel in acidic environments

The effect of solution pH,Cl;concentration and temperature on the electrochemical corrosion behavior of PH13-8Mo steel in acidic solution was investigated by using the electrochemical tests,scanning electron microscopy and X-ray photoelectron spectroscopy.The PH13-8Mo martensitic precipitation hardened stainless steel is in the passivity state when the pH value is above 3.0,below which the anodic polarization curves of the steel are actively dissolved.The corrosion current density gradually decreases with increasing the solution pH and decreasing Cl;concentration and solution temperature.Pits are initiated on the sample surface in the presence of the Cl;and gradually developed into uniform corrosion with increasing the Cl;concentrations.Moreover,the corrosion is more serious with an increase in solution temperature.

Corrosion Behavior of Ni–20Cr–18W–1Mo Superalloy in Supercritical Water

The corrosion behavior of Ni–20Cr–18 W–1Mo superalloy in supercritical water 500 °C/25 MPa for 200 h is investigated using gravimetry, SEM/EDS, XPS, and TEM. The oxide films show a layered structure with Ni rich in the outer layer, and Cr rich in the inner layer, consisting of an outer Ni（OH）2and NiO layer, including some Cr（OH）3, and an inner Cr2O3, Ni Cr2O4, and WO3 layer. Mo elements are not oxidized. The oxide films grow via a mixed mechanism,namely metal dissolution/oxide precipitation mechanism and solid-state growth mechanism. The effects of secondary and primary carbides on the weight-gain trend and oxide formation are discussed.