Investigation of anti-corrosion property of hybrid coatings fabricated by combining PEC with MAO on pure magnesium

Novel hybrid coatings on pure magnesium were prepared by combining plasma electrolytic carburizing(PEC)with micro-arc oxidation(MAO)to further enhance the anti-corrosion property in this paper.Scanning electron microscopy(SEM)was used to observe the microstructure of the coatings,meanwhile,energy dispersive spectrometry(EDS)and X-ray diffraction(XRD)were separately used to investigate the elemental as well as phase compositions of the coatings.The anti-corrosion property of the coatings was evaluated by potentiodynamic polarization curves as well as electrochemical impedance spectroscopy(EIS).The results show that PEC process is closely related with the effects of adsorption as well as diffusion of the activated carbon atoms,and it can provide a favorable pretreatment surface with predesigned chemical composition to obtain a new kind of phase,namely Si C with superior corrosion resistance and chemical stability,in the following PEC+MAO hybrid coatings.Meanwhile,PEC preprocessing also can afford an excellent micro-structure to increase the coating thickness as well as to improve the compactness of the PEC+MAO hybrid coatings.During the fabrication process of the PEC+MAO hybrid coatings,an overlapping phenomenon in regard to coating thickness can be observed instead of heaping up layer by layer.Compared with both single PEC surface modification layers as well as single MAO coatings,the PEC+MAO hybrid coatings exhibit more superior anti-corrosion property.Especially,the EIS data reveal that the PEC+MAO hybrid coatings can act as an effective protection system to provide relatively excellent long-range anti-corrosion protection.Note also that employing same MAO technique for both single MAO treatment as well as PEC+MAO combining procedure is the key to this research.

In-situ formation characteristic, tribological characterization and anti-corrosion properties of quaternary composites films

Improvements of wear and corrosion properties are essential characteristic in engineering application. A study was made on the structure, electro-oxidation and properties of fabricated Zn-Al-SnO 2-Ti O2（Zn-Al-Sn-Ti） thin films using electrodeposition technique from chloride bath. The microstructural studies were performed by scanning electron microscopy with attached energy dispersive spectrometer（SEM-EDS）, optical microscopy（OPM） and X-ray diffractogram（XRD）. The electrochemical oxidation and erosion behavior in 3.65% Na Cl medium were studied by potentiodynamic polarization technique and characterized by atomic force microscopy（AFM）. The hardness and wear behavior of the electrodeposited film were performed by high diamond dura scan microhardness tester and CERT UMT-2 reciprocating sliding machine. It was found that a successful co-deposition of composite and particle were attained. Homogeneous imbedded grain structure distribution and fine refinement of crystal with improved micromechanical behavior was achieved. The corrosion resistance, hardness and wear stability resistance of the fabricated quaternary films improved significantly in all varied process parameter.

Bio-inspired superhydrophobic magnesium alloy surfaces with active anti-corrosion and self-healing properties

Bio-inspired superhydrophobic magnesium(Mg)alloy surfaces are of increasing interest in corrosion protection due to superior barrier and shielding effects.However,superhydrophobic(SHB)anti-corrosion surfaces are susceptible to damage,which limit their extensive applications.To this end,a micro/nano structure-functional molecule SHB composite coating with self-healing and active anti-corrosion dual-function properties was designed on Mg alloys substrate.The dual-function SHB composite anti-corrosion coating based on lauric acid(La)intercalated and modified hydrotalcite(La-LDH)consisted of three-layer structure,namely La-LDH powder/polydimethylsiloxane(PDMS)/La-LDH film.The anti-corrosion performance of as-prepared coatings was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy(EIS).The results indicate that the SHB coating shows excellent active corrosion resistance.Moreover,we also examined the self-healing and anti-corrosion properties of SHB coating upon physical damage and explained the healing mechanism.After heat treatment,the damaged SHB coating regain its surface microstructure and corrosion protection property.This work expands new insights for the wide application of Mg alloys and the research in the field of metal protection.

A Facile Self-assembly Synthesis of Hexagonal ZnO Nanosheet Films and Their Photoelectrochemical Properties

Here, large-scale and uniform hexagonal zinc oxide(ZnO) nanosheet films were deposited onto indium tin oxide(ITO)-coated transparent conducting glass substrates via a facile galvanic displacement deposition process. Compared with other commonly used solution methods, this process avoids high temperature and electric power as well as supporting agents to make it simple and cost-effective. The as-fabricated ZnO nanosheet films have uniform hexagonal wurtzite structure. The photoelectrochemical(PEC) cell based on ZnO nanosheet film/ITO photoelectrode was also fabricated and its performance was improved by optimizing the solution concentration. A higher photocurrent density of*500 l A cm^(-2)under AM 1.5 G simulated illumination of 100 m W cm^(-2)with zero bias potential(vs. Ag/AgCl electrode) was obtained, which may ascribe to the increased surface-to-volume ratio of disordered Zn O nanosheet arrays. Our developed method may be used to deposit other oxide semiconductors, and the Zn O nanosheet film/ITO PEC cell can be used to design low-cost optoelectronic and photoelectrochemical devices.

A novel anti-corrosion coating for magnesium alloy

A novel enviromental protective water based metallic coating were prepared on the surface of AZ91D magnesium alloy. The properties and structure of the coating were investigated by adhension test, hardness test, heat resisting test, neutral salt spray test and scanning electron microscopy (SEM). The results show that the coating has a stepped structure which can achieve good adhesion of first-grade, heat resistance temperature of 400℃, hardness of HV_ 0.50/30210 and anti-corrosion time of 250h in salt spray test. Meanwhile, the film forming and corrosion mechanism of the coating were also put forward based on the results of the Fourier transform infrared spectroscopy (FTIR) test and electrochemical impedance spectroscopy (EIS) test.

Structure and Properties of Self-reinforced Material Made from Ultra-high Molecular Weight Polyethylene-montmorillonite Nanocomposite

High-strength and high-modulus ultra-high molecular weight polyethylene(UHMWPE), named self-reinforced material, was obtained by the elongation of UHMWPE-montmorillonite nanocomposite at melting temperature. According to the scanning electron microscope(SEM) analysis, a great deal of fibrillar texture formed in the direction of elongation, and the tensile fractured surface was similar to that of highly oriented fiber. The transmission electron microscope(TEM) and selective area electron diffraction(SAED) analyses reveal that the reinforced phase of the self-reinforced material is an extended chain crystal and its size is about 50_200 nm wide and several microns long, and the montmorillonite layers are broken up to pieces in the size from 100 to 10 nm. The broken layers which have a huge surface area interacting strongly with macromolecules reduces the entanglement density of UHMWPE and induces the chain orientation in flow field. It is supposed that the astriction of montmorillonite layers to polyethylene chains is not only end-tethered but also side-tethered. The differential scan calorimetry(DSC) analysis shows that there are two endothermal peaks for the self-reinforced material, of which the peak at a higher temperature(136.4 ℃) is ascribed to the melting of the reinforced phase.

Self-Cleaning Properties of Vanadium Doped TiO₂Sol-Gel Derived Thin Films

In this study, vanadium doped TiO2 thin films were deposited on glass substrates using a sol-gel dip-coating process. X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and UV-Vis spectrophotometer were used to characterize the structural, chemical and the optical properties of the thin films. The photo-catalytic activities of films were investigated by methylene blue degradation. Water contact angle on the film surfaces was measured by a water contact angle analyzer. The results indicated that vanadium doping had a significant effect on the self-cleaning properties of TiO2 thin films.

6AZO-CONTAINING SELF-ASSEMBLY ULTRA-THIN FILMS AND THEIR PHOTOVOLTAIC PROPERTIES

A kind of azo-containing resin(Azo-R)was synthesized by a simple way through the coupling reaction of 2-nitro-N-methyldiphenylamine-4-diazoresin(NDR)with phenol,and a new covalentely attached multilayer film from Azo-R asH-donor and photosensitive diazoresin,diphenylamine-4-diazoresin(DR)as H-acceptor via H-bonding attraction by self-assembly technique has been fabricated.Following the decomposition of diazonium group of DR under exposure to UVlight,the H-bonds between the layers of the film convert to covalent bonds and the film becomes very stable toward polarsolvents or electrolyte aqueous solutions.Thus the UV-irradiated azo-containing films can be used to measure photocurrentin a conventional three-electrode photoelectrochemical cell using KCl as supporting electrolyte.It was confirmed that theazo-containing multilayer film is responsible for the photocurrent generation.

Self-sensitization Structure of Expanded Ammonium Nitrate and Its Effect on ANFO Detonation Properties

The expanded ammonium nitrate (EAN) samples with different states were prepared by using a vacuum crystallizing technology. The structure characters,such as porosity,pore structure,specific surface area,particle surface shape and surface defects,and detonator initiation sensitivity and explosion power,of common ammonium nitrate (AN) and EAN were tested using density measuring,N2 adsorbing,scanning electron microscope (SEM) and plate trace test methods. The tested results show that the particle surface of common AN is smoother,denser,lower porosity and specific surface area than those tested of EAN. The particle surface of EAN is irregular,which has edges,protuberance and severely distorted crystal form,and its specific surface area and porosity are larger than those of un-expanded AN. EAN has typical self-sensitization structure characters. The detonator initiation sensitivity and explosion power of ammonium nitrate-fuel oil(ANFO) made of different states of EAN are related to the self-sensitization structures of EAN,and expanded ANFO sample has higher detonator initiation sensitivity and explosion power compared with un-expanded ANFO sample. The characterization techniques can be used to reveal the self-sensitization structure of EAN.

STABILITY AND ELECTROCHEMICAL PROPERTIES OF FULL-CONJUGATED SELF-ASSEMBLED FILMS BASED ON POLYANILINE AND ITS ACID-SUBSTITUTED DERIVATES

The stability of full-conjugated self-assembled （SA） multilayer films based on partially doped polyaniline （PANI） as a polycation and poly（o-aminobenzoic acid） （PCAN）, poly（aniline-2-sulfonic acid） （PSAN） as polyanions is investigated in alkali aqueous solutions. The self-assembled PANI-PCAN films keep their stability within 24 h in 1 mol/L NaOH solution,-the PANI-PSAN films, however, maintain the stability for 20 min in the same condition because the solubility of PSAN in alkali solutions is much higher than that of PCAN. The electrochemical properties of the SA films are determined, and the film-CdS composites formed in situ are also reported.

A Novel Palladium(Ⅱ)Complex Self-assembled from Anthracene-9-carboxylic Acid:Synthesis,Crystal Structure and Spectroscopic Properties

A novel palladium（II） complex [（TMEDA）Pd（anca）2].2DMSO （1, TMEDA = N,N,N＇,N＇-tetramethylethylethylenediamine, anca = anthracene-9-carboxylic acid） was synthesized and characterized by single-crystal X-ray diffraction, 1H NMR, UV-Vis and fluorescence spectroscopy. The cell belongs to orthorhombic Aba2 space group with a = 19.698（7）, b = 21.045（7） c = 9.062（3） A, Z = 4, V= 3757（2） A3, C40H46N206PdS2, Mr = 821.31, D, = 1.452 g/cm3, F（000） = 1704, the final R = 0.0272, wR = 0.0667 and GOOF = 0.999. Complex 1 exhibits an interesting distorted clip-shaped molecular configuration which is stabilized by intramolecular C-H...O hydrogen bonds. The cells are packed into a 3D supramolecular structure based on the intermolecular C-H...zr interactions which further construct the tubular channels serving as guest molecular channels to include the DMSO solvent molecules inside. Furthermore, the spectroscopic properties of 1 were also investigated.

Molecular Dynamics Study on Mechanical Properties in the Structure of Self-Assembled Quantum Dot

Stress and strain in the structure of self-assembled quantum dots constructed in the Ge/Si(001) system is calculated by using molecular dynamics simulation. Pyramidal hut cluster composed of Ge crystal with {105} facets surfaces observed in the early growth stage are computationally modeled. We calculate atomic stress and strain in relaxed pyramidal structure. Atomic stress for triplet of atoms is approximately defined as an average value of pairwise (virial) quantity inside triplet, which is the product of vectors between each two atoms. Atomic strain by means of atomic strain measure (ASM) which is formulated on the Green’s definition of continuum strain. We find the stress (strain) relaxation in pyramidal structure and stress (strain) concentration in the edge of pyramidal structure. We discuss size dependency of stress and strain distribution in pyramidal structure. The relationship between hydrostatic stress and atomic volumetric strain is basically linear for all models, but for the surface of pyramidal structure and Ge-Si interface. This means that there is a reasonable correlation between atomic stress proposed in the present study and atomic strain measure, ASM.

Properties and Thermal Stress Analysis of Blended Cement Self-Compacting Concrete

Self-Compacting concrete is a concrete that is able to flow and consolidate under its own weight, completely fill the formwork even in the presence of dense reinforcement, whilst maintaining homogeneity and without the need for any additional compaction. Self-Compacting concrete is achieved by using high proportions of powder content and super?plasticizers. Due to this, pronounced thermal cracking is anticipated. Thermal cracking in concrete structures is of great concern. The objective of this research is to carry out experiments and investigate fresh and hardened properties of SCC developed using a blend of ordinary Portland cement and ground granulated blast furnace slag (GGBFS), to evaluate the applicability of Japan Concrete Institute (JCI) model?equations and?to find out any similarities and differences between Self-?Compacting concrete and normal vibrated concrete—Portland blast furnace slag concrete class B. Thermal stress analysis of the proposed Self-Compacting concrete and normal vibrated concretes were investigated by simulation using 3D FEM analysis. To carry out these objectives, concrete properties such as autogenous shrinkage, adiabatic temperature rise, drying shrinkage, modulus of elasticity, splitting tensile strength and compressive strength were determined through experiments. From experimental results, it was observed that except for the fresh properties, the hardened properties of Self-Compacting exhibit similar characteristics to those of normal vibrated concrete at almost similar water to binder ratios. It was also established that Self-Compacting concrete at W/B of 32% with a 50% replacement of ground granulated blast furnace slag has better thermal cracking resistance than SCC with 30% GGBFS replacement. It is also found that provided the relevant constants are derived from experimental data, JCI model equations can be applied successfully to evaluate hardened properties of Self-Compacting concrete.

Rheological Properties and Self-Assembled Structures of Newly Synthesized Amide Organogelators, Butane 1,2,3,4-Tetracarboxamides, in Isododecane

The objectives of this study were to develop organogelators suitable for industrial use and to probe the viscosity-increasing mechanisms of such organic compounds. Butane 1,2,3,4-tetracar-boxamides, new organogelators that each has four chemical side chains, were synthesized. Two oleyl groups, each with another two side chains that varied from C4 to C18, were introduced to control the solubility and crystallinity of the compounds, and their solubility and rheological properties in isododecane were evaluated. The rheological properties of different amide compounds, N,N’,N’’,N’’’-1,2,4,5-tetra alkyl/alkenyl pyromellitamides with the same four chemical side chains, were also obtained to consider the skeleton’s effect on self-assembled structures due to hydrogen bonding among amide groups. The viscosity-increasing mechanism of the compounds was discussed through linkage of the molecular design, rheological evaluation, and morphological observations in this paper.

纤维增强微生物混凝土抗裂性能及自修复试验

为了探究纤维对微生物混凝土抗裂性能和裂缝自修复效果的改善作用,试验优选出聚丙烯腈纤维并掺入微生物混凝土中,测试掺入纤维后微生物混凝土的力学性能、自修复养护期的裂缝透水性和裂缝残余宽度。试验结果表明,当纤维掺量为1.5 kg/m^(3)时,混凝土试件的劈裂抗拉强度恢复至未加载体试件的95.1%;修复养护28 d后,平均裂缝宽度为0.43 mm的试件透水性系数由3.35×10^(-5)m/s降至3.40×10^(-6)m/s,降幅达89.9%;能够愈合的最大裂缝宽度为0.82 mm。在微生物自修复混凝土中掺入纤维可有效提高其抗裂性能,增强裂缝自修复效果。

吸波沥青混合料的制备及微波自愈合特性

吸波材料具有良好的微波传热能力,可用于沥青路面微裂缝自修复。本研究选取了炭黑粉、羰基铁粉和镍锌铁氧体粉3种吸波材料替换部分矿粉制备了SMA-13吸波沥青混合料。通过车辙试验、低温弯曲破坏试验和冻融劈裂试验对比分析了不同吸波沥青混合料的路用性能,并采用半圆弯曲(SCB)试验研究了吸波材料类型、掺量、微波加热时间等因素对吸波沥青混合料表面温度分布和自愈合性能的影响。利用扫描电子显微镜(SEM)和X射线衍射(XRD)分析吸波材料的微观特性。结果表明,随吸波材料掺量从10%增至30%,炭黑粉沥青混合料的动稳定度和冻融劈裂强度比都呈现出逐渐上升趋势,而低温弯曲应变则表现出先增加后减小的特征;羰基铁粉沥青混合料动稳定度和低温弯曲应变均呈现先增加后减小的趋势,而冻融劈裂强度比表现出逐渐减小的特征;镍锌铁氧体粉沥青混合料动稳定度和低温弯曲应变均呈现逐渐减小趋势,而冻融劈裂强度比则与之相反。吸波沥青混合料的表面温度随着吸波材料掺量和微波加热时间的增加而逐渐上升,能够快速达到沥青混合料裂缝面的愈合温度,从而增强沥青混合料的微波自愈合性能。

二硫化钼自润滑涂层性能及制备工艺的研究进展

MoS_(2)是过渡族金属二硫化物中的一员,其涂层材料因独特的层状结构而表现出优异的摩擦学性能。MoS_(2)自润滑涂层在刀具以及空间部件材料的表面减磨和保护上发挥着重要作用,但是MoS_(2)涂层对湿度的敏感性、附着力差以及耐磨寿命有限等问题限制了其应用。国内外学者在MoS_(2)涂层的摩擦学研究上做了大量工作,目前的研究重点主要是不同温度、湿度、气体介质的多环境下的摩擦学行为分析,以及通过纳米多层体系的设计实现对晶体结构的可控。本文概述了2010年以来有关MoS_(2)自润滑涂层材料的研究进展,主要综述了MoS_(2)自润滑涂层的摩擦学性能以及不同元素掺杂对其性能和结构的影响。总结了MoS_(2)涂层的组成结构、性能、制备工艺,并对其在表面润滑领域的研究和应用前景进行了展望。本文对MoS_(2)自润滑涂层的研究和工程应用具有参考意义。

智能混凝土裂缝自监测性能试验研究

为了对建筑物的裂缝进行实时监测,掌握建筑物的裂缝扩展情况及开裂位置对加入导电相材料(钢纤维和纳米炭黑)后智能混凝土的力学性能、导电性能以及自监测性能进行研究,并改变导电相材料的掺量,分析其对抗压强度、电阻变化率等性能指标的影响。结果表明,在满足力学性能和导电性能的前提下,复掺纳米炭黑与钢纤维可以发挥钢纤维长程导电与纳米炭黑短程导电的互补优势,使材料具备良好的自监测性能,且钢纤维掺量为1.50%、纳米炭黑掺量为0.75%时,裂缝自监测性能最佳。

AlCrN系列刀具涂层的研究现状与展望

刀具涂层能够有效阻挡刀具材料与工件间的元素扩散,减少因摩擦产生的大量切削热,解决硬质合金刀具加工时面临的易磨损、寿命短等问题,近年来成为高速切削领域的研究热点,并得到快速发展.AlCrN涂层凭借优异的力学性能已被广泛应用,但在高速高载热负荷的切削环境下,涂层的抗氧化性能和耐磨性能还有待提高.因此,国内外研究者通过在AlCrN涂层中掺杂各种元素改善其服役性能.本研究分别介绍了Si和Ti掺杂对涂层微观结构、力学性能和抗氧化性能的影响,归纳了V和Mo掺杂自润滑涂层研究中的关键问题,分析了O掺杂对涂层性能的影响及其影响机理.最后,总结了兼具耐磨和抗氧化性能的高熵合金刀具涂层领域中亟待解决的关键难题以及未来的研究方向.

新型自复位钢框架-复合墙连接节点研究

内填RC复合墙钢框架结构在框架与内嵌墙之间设置开缝并安装耗能连接件能减小结构损伤,改善结构力学性能。提出在内填RC复合墙和钢框架结构之间采用新型折板型耗能连接件,并采用ABAQUS对连接件的受力性能进行分析,研究了节点的受力过程和破坏模式。将耗能连接件应用于两侧开缝的密肋复合墙-钢框架结构中实现滑移连接。结果显示:折板连接件在竖向拉压荷载和水平侧向荷载作用下的变形损伤模式存在差异,折板角和折板弯折数目对连接件受力性能影响显著。折板连接件用于结构中时,结构加载前期滞回曲线表现出残余变形小的特点,具有自复位性能,因此折板连接件是一种具有自复位能力的连接形式。