Influence of current density on nano-Al_2O_3/Ni+Co bionic gradient composite coatings by electrodeposition

Metal and nano-ceramic nanocomposite coatings were prepared on the gray cast iron surface by the electrodeposition method. The Ni-Co was used as the metal matrix,and nano-Al2O3 was chosen as the second-phase particulates. To avoid poor inter-face bonding and stress distribution,the gradient structure of biology materials was found as the model and therefore the gradient composite coating was prepared. The morphology of the composite coatings was flatter and the microstructure was denser than that of pure Ni-Co coatings. The composite coatings were prepared by different current densities,and the 2-D and 3-D morphologies of the surface coatings were observed. The result indicated that the 2-D structure became rougher and the 3-D surface density of apices became less when the current density was increased. The content of nanoparticulates reached a maximum value at the current density of 40mA·cm^-2,at the same time the properties including microhardness and wear-resistance were analyzed. The microhardness reached a maximum value and the wear volume was also less at the current density of 40mA·cm^-2. The reason was that nano-Al2O3 particles caused dispersive strengthening and grain refining.

Universal synthesis of metallophthalocyanine covalent organic frameworks as ultra-sensitive multifaceted electrochemical sensor

The universal synthesis of highly stable covalent organic frameworks(COFs)for ultra-sensitive and multi-component electrochemical detection in different scenarios remains a great challenge.Herein,a series of metallophthalocyanine-based twodimensional(2D)dioxin(DXI)-linked metalophthalocyanine(MPc)-n DXI-COFs(M=Ni,Zn;n=1,2)are afforded in high yield(80%-96%)by a facile trace-quinoline assisted one-pot condensation of tetracarbonitrile precursors.Powder X-ray diffraction and electron microscopy investigations disclose their lamellar texture 2D network with AA stacking mode.Experiments and calculation results elucidate that the 2DXI-linked MPc-2DXI-COFs provide the stronger built-in electronic field and more electrostatic/hydrogen bonding adsorption sites than DXI-linked MPc-DXI-COFs,and the lower electrode reaction Gibbs free energy and stronger adsorption of analytes at Ni Pc than Zn Pc unit,which grants Ni Pc-2DXI-COF excellent sensing properties for various analytes including neurotransmitters,organic pollutants,and heavy metal ions,with high sensitivity and low detection limit of 0.53 to 25.66 nM.Especially in binary and ternary systems and even in real-world conditions,simultaneous multi-component detection could be achieved.

Large-scale fabrication of decoupling coatings with promising robustness and superhydrophobicity for antifouling,drag reduction,and organic photodegradation

It is still a challenge to achieve large-area preparation of robust superhydrophobic surfaces with strong mechanical stability.Here,a simple and low-cost method to prepare robust decoupling superhydrophobic coatings on aluminum(Al)alloys substrate has been presented.The superhydrophobicity and robustness of decoupling coatings are realized by structuring surfaces at two different length scales,with nanostructures for superhydrophobicity and microstructures for robustness.This prepared decoupling coating shows promising superhydrophobicity,with water contact angle(CA)of~158.4°and roll off angle(RA)of~3°.It also exhibits high repellency for impacting water droplets.Notably,the decoupling coating processes outstanding adhesion strength on the substrate after tape-peeling and cross-cut tests,also with promising wear resistantance after sandpaper abrasion and wear test.The friction coefficient of this decoupling coating is only~0.2.In addition,the robust decoupling superhydrophobic coating is applied to underwater buoyancy enhancement and fluid resistance reduction(drag reduction rate~30.09%).This decoupling superhydrophobic coating also displays promising self-cleaning and antifouling properties.Moreover,benefitting from the photocatalytic property of TiO2,this decoupling coating is also exploited for degrading organics to achieve seawater purification.This obtained decoupling superhydrophobic coating is expected to apply on other solids in marine fields,and the simple and eco-friendly method develops the potential practical application.

A Simple Method for Fabrication of Bionic Superhydrophobic Zinc Coating with Crater-like Structures on Steel Substrate

Surface modification with superhydrophobicity is a popular and challenging research field on metals. In this work, a simple method was used to fabricate a bionic superhydrophobic zinc coating with crater-like structures on pipeline steel surface. This method involved electrodeposition of zinc coating and chemical reaction in perfluorooctanoic acid ethanol solution. The per- fluorooctanoic acid with low surface free energy was not only used for chemical etching but also used for fluorinated modifi- cation. The contact angle of water on such superhydrophobic zinc coating was up to 154.21°, and the sliding angle was less than 5° due to the micro crater-like structures and the low surface free energy. Moreover, the prepared superhydrophobic zinc coating demonstrated excellent self-cleaning property and great stability at room temperature, and the contact angle of water on this coating remained stable after storage in air for more than 80 days. This superhydrophobic zinc coating will open much wider applications of electrodeposition metal coating, including self-cleaning property, and can be easily extended to other metals.

Spontaneous Self-healing Bio-inspired Lubricant-infused Coating on Pipeline Steel Substrate with Reinforcing Anti-corrosion,Anti-fouling,and Anti-scaling Properties

Superhydrophobic surfaces(SHS)and slippery lubricant-infused porous surfaces(SLIPS)attract great attention due to their multiple properties in both industries and our daily lives.Here,we first fabricated the SHS with micro-scale flower-like structures composed of nano-sheets on pipeline steel substrate.Then,we obtained the SLIPS by spin-coating lubricant into gaps of micro-scale flower-like structures,with the air still trapped among gaps of nano-sheets.The SLIPS shows excellent liquid repellency as the SHS.The SLIPS also shows stability after the scour of flowing water.These results of polarization curves(Tafel)and electrochemical impedance spectroscopies deduced the SLIPS with better and more stable anti-corrosion property than the SHS.Compared with the SHS,the lack of attachment and CaCO_(3) on the SLIPS indicates that the SLIPS demonstrates better anti-fouling and anti-scaling properties than the SHS.Moreover,the SLIPS shows promising wear resistance under the abrasion simulated by sandpaper compared with the SHS.Notably,the air trapped among nano-sheets is conducive to the lubricant flowing to the surface quickly,exhibiting spontaneous self-healing in atmosphere,even if part flower-like structures of the SLIPS subject to damage with the lubricant consumed after scratched.