一种无铼二代镍基单晶高温合金蠕变机制研究

利用层层静电自组装技术将聚乙烯亚胺(PEI-Ag+)、PdCl42-交替沉积在基底上,然后用硼氢化钠还原,构筑了含银/钯复合纳米粒子的PEI-Ag/Pd纳米复合薄膜.通过扫描电子显微镜(FESEM),X射线光电子能谱(XPS)和循环伏安(CV)等手段对复合膜的成分、微结构和性质进行了测试分析.膜上生成了不规则和立方体状的银/钯纳米复合物,导致膜表面有一定的粗糙度.结果表明,双金属{PEI-Ag/Pd}n复合膜比单金属{PEI/Pd}n或{PEI-Ag/PSS}n膜对多巴胺的氧化有更好的电催化活性.     

Polyaniline-related ion-barrier anticorrosion coatings: I. Ionic permeability of polyaniline,cationic, and bipolar films

Ionic permeabilities of coating films were studied with a variety of experimental methods including measurements of membrane potential, salt diffusion, and electron spectroscopy for chemical analysis (ESCA). The results show that polyaniline (PAn) allows diffusion of anions (if PAn is dispersed in a cationic polymer matrix, the resulting film may have cationic defects that allow the passage of cations), a cationic film is permeable to cations, and the combination of a PAn containing primer with the cationic topcoat is an ion-barrier which delays penetration of both anions and cations.     

Conductive potassium feldspar/polyaniline composites prepared by in situ chemical polymerization

Conductive potassium feldspar/polyaniline (K-feldspar/PAn) composites were prepared by the chemical polymerization of aniline in the presence of K-feldspar particles using potassium dichromate in an acidic aqueous medium. The effects of K-feldspar particle size, aniline concentration and temperature upon the PAn amount in the composite and the electrical surface resistance of the composites were examined. Electrical conductivity was higher in the composites prepared by the smaller K-feldspar particles in which the PAn yield is low. The microhardness values of K-feldspar/PAn composites increased to a certain PAn content and then decreased. The microhardness of the composites containing PAn in the range of 1–6%, which were prepared by K-feldspar having particle size smaller than 0.125–0.250 nm, was higher that of pure K-feldspar and PAn (0.843 kPa). Scanning electron microscopy (SEM) showed that PAn covered the surface of K-feldspar particles with an unsmooth PAn layer. The characterization of composites was also made by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA).     

Actuation behaviour of layered composites of polyaniline,carbon nanotubes and polypyrrole

Layered composites of polyaniline (PAn), single-walled carbon nanotubes (CNTs) and polypyrrole (PPy) were produced by coating PAn or PAn/CNT on a PPy hollow fibre containing a platinum (Pt) helix. The actuation behaviour of PAn/PPy and PAn/CNT/PPy composites was compared with that of neat PPy. The Pt helix reduces the IR drop along the fibre, thus enhancing the actuation strain. Components of the composite with low actuation strain such as PAn and/or CNT restrict the actuation displacement of the PPy substrate causing a reduced strain in the composite. In particular, a minimal quantity of CNT (1.3 wt.%) in the composite leads to a discernible decrease in actuation strain but also increases the Young's modulus and tensile strength of the composite. Sodium nitrate (1 M) aqueous solution used as an electrolyte gives good actuation stability where the actuation strain is almost independent of applied stress (5–12 MPa). This can be explained by the unchanged Young's modulus at the reduced (contracted) and oxidized (expanded) states during the actuation process. The polyaniline/polypyrrole composite produced the highest work-per-cycle reported to date under isotonic conditions.     

Nanocomposites of polyaniline,its derivatives and platinum prepared using aqueous Pt sol

Polyaniline (PANI), poly(o-methoxyaniline) (POMA) and poly(o-toluidine) (POT) have been used as matrices for incorporation of Pt nanoparticles from the previously prepared aqueous Pt sol. Polymer–Pt nanocomposites thus obtained have been characterized by X-ray diffraction, transmission electron microscopy and IR spectroscopy. It has been revealed that metal nanoparticles (predominantly of sizes in the range between 2 and 4 nm) have been present in all the composites. It can be postulated that the polymers prevent Pt nanoparticles from agglomeration, i.e. act as their stabilizers. As has been found, charge transfer interactions between polymer chains and Pt nanoparticles are responsible for this stabilization. Among the polymers studied, POT shows the weakest stabilizing effect.Catalytic isopropyl alcohol conversion has shown that PANI–Pt nanocomposite obtained using aqueous Pt sol exhibits strong redox properties. Its overall catalytic activity is ca. three times higher than that of PANI–Pt composite containing larger Pt particles. This is connected with better dispersion of Pt particles in the composite prepared using aqueous Pt sol.     

Preparation and electrocatalytic property of Au-Pt/SnO<Subscript>2</Subscript>/GC composite electrode

Au-Pt/SnO₂/GC composite electrode was prepared by self-assembling Au-Pt nanoparticles on SnO₂ film, which was deposited on actived glassy carbon (GC). Atomic force microscopy (AFM) and scanning electron microscopy (SEM) images revealed that dense and uniform Au-Pt particles with 25-nm diameter were dispersed on SnO₂ film. X-ray photoelectron spectroscopy (XPS) results proved that there was an interaction between Au-Pt nanoparticles and SnO₂ support. Electrochemical experiments showed that Au-Pt/SnO₂/GC composite electrode had a good electrocatalytic activity to the oxidation of methanol.     

A comparative study of molybdate/silane composite films on galvanized steel with different treatment processes

Two types of molybdate/silane composite films were obtained on the surface of hot-dip galvanized steel sheets by either directly immersing in a solution containing silane and molybdate as additive (single-step process), or firstly immersing in a molybdate solution, then in a silane solution (two-step process). The chemical compositions and microstructures of the films were examined by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and reflection absorption infrared spectroscopy (RAIR). The corrosion resistances were investigated by electrochemical measurements and neutral salt spray (NSS) test. The results showed that the molybdate/silane composite film formed in the single-step process had a similar double-layer structure as that obtained in the two-step process. The inner layer was composed mainly of the elements O, Mo, Zn, and P, similar to the single molybdate film; whereas the outer layer was composed mainly of the elements C, O and Si, similar to the single silane film. Compared with the single molybdate or silane film, the corrosion current of the composite films was reduced and the impedance of the films was increased. Accordingly, the corrosion resistance of the composite films was remarkably enhanced to a level which was comparable to or even surpassing that of the conventional chromate passivation film.     

Preparation and electrocatalytic property of Au-Pt/SnO2/GC composite electrode

Au-Pt/SnO2/GC composite electrode was prepared by self-assembling Au-Pt nanoparticles on SnO2 film, which was deposited on actived glassy carbon (GC). Atomic force microscopy (AFM) and scanning electron microscopy (SEM) images revealed that dense and uniform Au-Pt particles with 25-nm diameter were dispersed on SnO2 film. X-ray photoelectron spectroscopy (XPS) results proved that there was an interaction between Au-Pt nanoparticles and SnO2 support. Electrochemical experiments showed that Au-Pt/SnO2/GC composite electrode had a good electrocatalytic activity to the oxidation of methanol.     

Polyaniline coating on 304 stainless steel by electropolymerisation from aqueous NaOH solution for corrosion protection in NaCl medium

Abstract

Polyaniline (PAn) coating was electrochemically synthesised on 304 stainless steel using cyclic voltammetry in 0·25M NaOH solution containing 0·1M aniline. Characterisation of the adhesive and stable PAn coating was carried out by cyclic voltammetry, Fourier transform infrared spectroscopy and scanning electron microscopy. The protective properties of PAn coating on 304 stainless steel were elucidated using linear anodic potentiodynamic polarisation and Tafel test in 3·5%NaCl solution. Linear anodic potentiodynamic polarisation test results proved that the PAn coating improved the degree of protection against pitting corrosion in NaCl solutions. Tafel test results showed that the PAn coating appeared to enhance protection for 304 stainless steel in 3·5%NaCl solution.     

Electrodeposition and characterization of nano-structured Ni-SiC composite films

Ni-SiC nano-composite coating, which simultaneously composed of both nanocrystalline consecutive Ni matrix and dispersed inert SiC nano-particles, has been fabricated by ultrasonic electroplating technique from a modified Watts bath containing SiC nano-particles. The influence of mechanical stirring and ultrasonication on the surface morphology of the nanocrystalline Ni-SiC nano-composite film has also been investigated. The surface morphology, microstructure, anti-corrosion property and electrocatalytic activity for hydrogen evolution of the obtained nanocrystalline Ni-SiC nano-composite film, are characterized using scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) system, atomic force microscopy (AFM), transmission electron microscope (TEM), X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS) techniques. The results find that, mechanical stirring mainly prevents the sedimentation of the inert particles suspended in solutions, while ultrasonication mainly prevents the particles agglomeration. In the case of only mechanical stirring to disperse the SiC nano-particles, the composite surface is cauliflower alike. While in the case of both mechanical stirring and ultrasonication, the obtained Ni-SiC composite film is much smoother and composes of particles with the mean diameter of 42.9 nm, and SiC particles are uniformly dispersed into Ni matrix. Meanwhile, the results obtained by polarization curves and EIS methods show that, when compared with the traditional polycrystalline Ni film, the obtained Ni-SiC nano-composite film exhibits the enhanced corrosion resistance in NaCl solutions, possesses much higher electrocatalytic activity for hydrogen evolution in KOH solutions.     

Polyaniline–poly(vinyl alcohol) conducting composite: material with easy processability and novel application potential

The present work reports an easy route for synthesis of polyaniline (PAn) in stable aqueous solution/dispersion form, using poly(vinyl alcohol) (PVA) as an efficient steric stabilizer. Resulting composite successfully combines desirable physical properties like mechanical strength, solution processibility and electrical conductivity of PVA and PAn components. The composite was subjected to versatile characterizations and its different physical properties (especially optical, thermal, mechanical and electrical) were explored. Free standing films can be obtained from the solutions, which exhibit important microwave shielding property over the X-band. This has enhanced the importance of this material to a large extent.     

Silk fibroin fibers supported with high density of gold nanoparticles: fabrication and application as catalyst

Silk fibroin (SF) fibers were modified with sulfonated polyaniline and, via an in situ redox technique, a high density of gold (Au) nanoparticles were supported directly on the surface of the fiber. The morphology, formation, and application of the as-prepared product, Au/SPANI-modified SF composite fiber, were investigated. By controlling the concentration of HAuCl₄, the density of Au nanoparticles on the composite fiber could be effectively adjusted. It is suggested that sulfonated polyaniline contributes to the generation of a high density of Au nanoparticles supported on the SF fibers. The composite fiber exhibited good activity when taking the reduction of p-nitrophenol as a model reaction.     

Sensing of silver ions by nanotubular polyaniline film deposited on quartz-crystal in a microbalance

Nanotubular polyaniline film was deposited onto the electrode of the quartz-crystal microbalance (QCM). The film in the form of emeraldine base was exposed to a solution of silver nitrate. The reduction for silver ions took place and silver nanoparticles were produced at the film surface. The deposition of silver was monitored by using the QCM and the UV–vis spectroscopy. The morphology of the film before and after the silver deposition was studied by the scanning and transmission electron microscopy. Silver nanoparticles had sizes of about 50–120 nm and globular and triangular shape. X-ray diffraction and infrared spectroscopy were used to characterize the structure of the composite. The present approach could be used for noble-metal recovery in waste waters.     

Electroless plating of palladium and copper on polypyrrole films

A novel process for the metallization of polypyrrole (PPY) film surface through consecutive electroless plating of palladium and copper in the complete absence of the SnCl₂ sensitization step was demonstrated. X-ray photoelectron spectroscopy (XPS) technique was used to characterize the polymer surface at each stage of the metallization process. It was found that only the fully reduced PPY film could reduce palladium ions to palladium metal (Pd(0)) in substantial amounts from either the Pd(NO₃)₂ or PdCl₂ acid solution. The palladium metal was necessary for catalyzing the subsequent electroless plating of copper. The reduction of Pd(II) ions in acid solution to Pd(0) on the film surface was accompanied by a simultaneous increase in intrinsic oxidation state and doping level of the film. The copper plating process after the palladium uptake step was highly dependent on the [Pd]/[N] ratio on the film. Through XPS and Auger photoeletron spectroscopy measurements, it was postulated that during the electroless copper plating process, the Cu(II) ions were first reduced to Cu(I) on the PPY film surface before complete reduction to copper metal.     

Atomic force microscopy surface morphology studies of ‘in situ’ deposited polyaniline thin films

An ‘in situ’ deposition method is presented where combination of solutions of aniline monomer and an oxidizing agent leads to the growth of uniform polyaniline (PAn) conducting thin films on submerged substrates. The PAn films can be deposited on a variety of substrates including glass and organic materials. Film thickness can be controlled by varying the duration of the substrate dipping time; about 300 Å was produced during a dipping time of 5 min. Atomic force microscopy (AFM) was used to analyze the PAn film surface morphology and roughness. AFM images of the PAn surfaces revealed very smooth surfaces having a surface roughness (mean and root mean square) of about 30 Å. Measurements on the PAn films using UV, visible and near IR were consistent with the thickness measurements obtained with AFM. The PAn film surface morphology, as determined from AFM images, was found to be characterized by particle-like features of about 50 to 100 nm in size which were packed tightly to produce a high density structure. Using a four-probe measurement approach, the conductivity of the doped PAn films was determined to be 2–6 S/cm.     

Electronic structure of polyiminovinylene as a tractable model for polyaniline

The electronic structures of polyiminovinylene (PIV) as well as polyaniline (PAn) are studied theoretically using the one-dimensional tight-binding self consistent field-crystal orbital (SCF-CO) method. PIV was employed as a tractable model for PAn to inspect the electronic process when the redox states of PAn are changed. The conduction mechanism caused by partial protonation (oxidation) is discussed and the possibility of the formation of bipolaron in the partially protonated polymer skeleton is examined.     

Al2O3纳米粒子环氧涂层对钢筋防护性能的电化学噪声分析

目的研究Al2O3纳米粒子环氧复合涂层对钢筋的防护性能。方法制备Al2O3纳米粒子,将其添加至环氧涂料中,并涂覆在工业钢筋表面成膜。通过XRD和SEM对Al2O3进行表征;利用电化学噪声、交流阻抗谱分析技术,对复合涂层在3.5%(质量分数)NaCl介质中对工业钢筋的防护性能进行测试分析。结果制备的氧化铝纳米粒子的粒径平均为75 nm。通过对电化学噪声测试的有效数据进行时域和频域分析,通过交流阻抗谱分析及数据拟合,认为Al2O3纳米粒子添加量为0.1%(以占环氧树脂质量的百分比计)时,涂层对钢筋的防护性能最好。结论向环氧涂层中添加适量的Al2O3纳米粒子,可以明显提升其对钢筋的防护性能。     

Structural, thermal, mechanical and bioactivity evaluation of silver-loaded bovine bone hydroxyapatite grafted poly(ε-caprolactone) nanofibers via electrospinning

We report on poly(ε-caprolactone) (PCL) containing bovine bone hydroxyapatite (HA) and hydroxyapatite-silver (HA-Ag) composite nanofibers prepared via an electrospinning process for the biomedical applications. Bioactivity test was conducted by incubation in simulated body fluid (SBF). The morphology, structure and thermal properties of the PCL, PCL/HA and PCL/HA-Ag composite nanofibers before and after immersion in SBF were characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy and thermogravimetry (TGA). SEM images revealed that the nanofibers are well-oriented and incorporated the HA-Ag nanoparticles well. The SBF incubation test confirmed that the fast formation of apatite-like materials suggests in vitro bioactive behavior of the nanofibers. Mechanical study revealed that the yield stress of PCL/HA-Ag composite nanofibers showed a higher value than that of PCL/HA composite, possibly due to the addition of metallic Ag nanoparticles. This study demonstrated that electrospun PCL/HA and PCL/HA-Ag composite nanofibers activates bioactivity and supports growth of apatite-like materials.     

Impedance analysis of polyaniline prepared on interdigitated array electrode under direct current polarization potential

A new method, ‘biased impedance analysis (BIA)’, was proposed for in situ measurements of a.c. impedance of polyaniline (PAn) film during and after deposition on an interdigitated array (IDA) electrode under d.c. bias (polarization) potential. With this BIA we designed two types of experiments: one was BIA under cyclic voltammetric (CV) sweep in 1 M HCl on PAn films polymerized via a constant current (40 μA cm⁻²) mode in properly buffered media at different pH (below 1.7) but with the same chloride ion concentration ([Cl⁻] = 1 M); the other was BIA on PAn films during and after constant potential (+ 0.75 V) mode polymerization in 1 M HCl or 1 M HClO₄ both at pH = 0.2. As to the effect of pH of the polymerization media, the PAn film obtained at high pH had narrow conductive potential range during CV scans between −0.1 and 1.0 V as compared with that obtained at low pH. The PAn film obtained in HClO₄ exhibited faster and larger impedance increase (than that polymerized in HCl), leading to a poorer performance upon potential scanning especially from the conductive-oxidation state at high potential to the insulating-reduction state at low potential.     

Using nanoparticles as direct-injection printing ink to fabricate conductive silver features on a transparent flexible PET substrate at room temperature

Conductive metallic features that are flexible could have application in integrated circuits, ranging from large-area electronics to low-end applications. This paper shows the creation of conductive silver thin film and wire on the transparent flexible polyethylene terephthalate (PET) substrate by a room-temperature chemical reduction process. One-step synthesis and spectroscopic characterizations of size-controlled silver nanoparticles are also described. Transmission electron microscopy, Fourier transform infrared spectroscopy, thermal gravimetric-mass analysis, X-ray photoelectron spectroscopy and synchrotron radiation X-ray diffraction were used to characterize the dodecanoate-protected silver nanoparticles. Silver metal film and wire were produced by soaking the dodecanoate-protected silver nanoparticle film and wire, which were prepared, respectively, by spin-coating and by directly drawing with a commercial Epson T50 inkjet printer onto the flexible PET substrate using Ag nanoparticles suspended in cyclohexane (10 wt.%) as the ink, in an aqueous solution containing 80% N₂H₄. The resistivities of the Ag films are actually lower compared with the Ag thin films prepared by other conventional chemical routes, such as using silver salts as metallo-organic precursors. It is suggested that the use of nanoparticles as a precursor may be an explanation for the lower resistivity.