A novel dual-functional layer exhibiting exceptional protection and photocatalytic activity by organic functionalization of plasma electrolyzed layer

The formation of inorganic-organic hybrids(IOH)on the metallic substrates would play a decisive role in improving their structural and functional features.In this work,the growth of organic coating(OC)consisting of coumarin-3-carboxylic acid(3-CCA)and albumin(ALB)on the inorganic layer(IC),produced by plasma electrolysis of AZ31 Mg alloy,led to enabling organically synergistic reactions on the porous inorganic surface,forming a flake-like structure sealing the structural defects of IC.Synergistic actions between OC and IC endow the flake-like structures with chemical protection and photocatalytic performance.Upon contact with a corrosive solution,the IOH layer possesses stable morphologies that delay the corrosive degradation of the whole structure.The electrochemical stability of the sample produced by immersion IC in the organic solution for 10 h(IOH2 sample)was superior to the other samples as it had the lowest corrosion current density(1.69×10^(−10)A·cm^(−2))and the highest top layer resistance(1.2×10^(7)Ω·cm^(2)).Moreover,the IOH layer can photodegrade the organic pollutants in model wastewater,where the highest photocatalytic efficiency of 99.47%was found in the IOH2 sample.Furthermore,computational calculations were performed to assess the relative activity of different parts of the ALB and 3-CCA structures,which provide helpful information into the formation mechanism of the IOH materials.

Self-assembly of coumarin molecules on plasma electrolyzed layer for optimizing the electrochemical performance of AZ31 Mg alloy

A novel inorganic-organic layer with outstanding corrosion resistance in a 3.5wt.% NaCl solution was fabricated by taking advantage of the unique interactions between coumarin (COM) molecules and the porous layer formed on Mg alloy. To achieve this aim, the AZ31 Mg alloy coated via microarc oxidation (MAO) coating was placed in an ethanolic solution of COM for 6 and 12 h at 25 ℃. By reducing the surface area exposed to the corrosive species, the donor-acceptor complexes produced by the particular interactions between the COM and MAO surface would successfully prevent the corrosion of Mg alloy substrate. The MAO layer would provide the ideal sites for the charge-transfer-induced physical and chemical locking, leading to uneven organic layer nucleation and crystal growth with a thatch-like structure. To evaluate the formation mechanism of such hybrid composites and highlight the key bonding modes between the COM and MAO, theoretical simulations were conducted.

Application of g-C_(3)N_(4)/sol-gel nanocomposite on AM60B magnesium alloy and investigation of its properties

To protect the AM60B magnesium alloy from corrosion,a sol-gel coating containing hydroxylated g-C_(3)N_(4)nanoplates was applied.The chemical composition of the hydroxylated g-C_(3)N_(4)nanoplates was investigated using X-ray photoelectron spectroscopy(XPS).The hydroxylation process did not affect the crystal size,specific surface area,pore volume,average pore diameter,and thermal stability of the g-C_(3)N_(4)nanoplates.After incorporating pristine and hydroxylated g-C_(3)N_(4)nanoplates,dense sol-gel coatings were obtained.Transmission electron microscopy(TEM)revealed the uniform distribution of the modified g-C_(3)N_(4)in the coating.The average roughness of the coating was also reduced after adding the modified nanoplates due to the decreased aggregation tendency.Electrochemical impedance spectroscopy(EIS)examinations in simulated acid rain revealed a significant improvement in the anticorrosion properties of the sol-gel film after the addition of the modified g-C_(3)N_(4)due to the chemical bonding of the coating to the nanoplates.

羟基磷灰石与氧化锆体积比对钛基复合支架力学性能和腐蚀性能的影响

通过环保、低成本的混合法制备氧化锆(ZrO2)和羟基磷灰石(HA)增强钛基支架材料,该材料具有较低的弹性模量(E)、足够的物理、电化学和生物学性能。研究羟基磷灰石和氧化锆体积分数的变化对支架力学性能、腐蚀性能和抗菌性能的影响。采用扫描电子显微镜结合电子色散光谱和X射线衍射对支架进行表征,通过压缩试验检测材料的力学性能及其详细的断裂机制,用电化学法测试样品在37℃模拟体液中的体外腐蚀敏感性,通过比较大肠杆菌和金黄色葡萄球菌的抑菌面积进行抑菌试验。结果表明,随着HA:ZrO_(2)体积分数比例的增加,支架的力学强度降低,当其比例为6:4时,复合支架的E最低(6.61GPa)。纯钛、HA:ZrO_(2)体积分数比例为3:2和6:4的支架材料,其腐蚀电流密度(J_(corr))分别为21、337和504μA/cm^(2)。体积分数比例为6:4的支架对金黄色葡萄球菌的抑菌能力优于其他支架。

Microstructure,mechanical properties,and corrosion resistance of an explosively welded Mg-Al composite

In this study,an attempt was made to manufacture an AZ31–Al5005 laminated composite by explosive welding.A mixture of ammonium nitrate(90%),fuel oil(5%),and TNT(5%)was used as the explosive.The detonation velocity of the explosive material was approximately 3100 m•s^(−1).The microstructure and mechanical and corrosion properties of the joint were comparatively investigated.Microstructural characterisation of the joint was conducted by optical microscopy(OM),scanning electron microscopy with energy-dispersive spectroscopy(SEM-EDS),high-resolution transmission electron microscopy(HR-TEM),and X-ray diffraction(XRD).The mechanical properties were determined using micro-Vickers hardness,tensile,and Charpy impact tests.In addition,electrochemical tests were conducted on the AZ31–Al5005 laminated composite and the individual components to determine their corrosion resistance.The corrosion behaviours of the structures were determined in a 3.5%NaCl solution at room temperature using potentiodynamic scanning(PDS).The metallurgical structure and mechanical properties of the joints were within the acceptable limits.

Improving the electrochemical stability of AZ31 Mg alloy in a 3.5wt.%NaCl solution via the surface functionalization of plasma electrolytic oxidation coating

The unique interactions between hexadecanoic acid(HA)and albumin(ALB)molecules on the surface of the porous layer of AZ31 Mg alloy were exploited to fabricate a novel hybrid composite film with excellent electrochemical stability in a 3.5 wt.%Na Cl solution.Herein,the inorganic layer(IL)obtained by plasma electrolytic oxidation of AZ31 Mg alloy in an alkaline-phosphate-WO_(3)electrolyte was soaked in an organic solution composed of ALB and HA for 10 and 24 h at 60℃.Although albumin and HA may coexist on the same surface of IL,the higher reactivity of ALB molecules would prevent the formation of a thick layer of HA.The donor-acceptor complexes formed due to the unique interactions between ALB and/or HA and IL surface would reduce the area exposed to the corrosive species which in turn would efficiently protect the substrate from corrosion.The porous structure of the IL would provide preferable sites for the physical and chemical locking triggered by charge-transfer phenomena,leading to the inhomogeneous nucleation and crystal growth of a flowery flakes-like organic layer.DFT calculations were performed to reveal the primary bonding modes between the ALB,HA,and IL and to assess the mechanistic insights into the formation of such novel hybrid composites.