Limin Chang

Structure and effects of electroless Ni–Sn–P transition layer during acid electroless plating on magnesium alloys

Abstract An electroless ternary Ni–Sn–P transition layer with high corrosion resistance was applied for acid electroless nickel plating on magnesium alloys. The surface morphologies and microstructure of the traditional alkaline electroless Ni–P and novel Ni–Sn–P transition layers were compared by SEM and XRD, and the bonding strengths between the transition layers and AZ31 magnesium alloys were tested. The corrosion resistance of the samples was analyzed by porosity test, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) in acid electroless solution at pH 4.5 and immersion test in 10% HCl. The results indicate that the transition layer is essential for acid electroless plating Ni–P coatings on magnesium alloys. Under the same thin thickness (~6 μm), the electroless Ni–Sn–P transition layer possesses superior properties to the traditional Ni–P transition layer, including high amorphization, smooth and dense surface without pores, enhanced bonding strength and corrosion resistance. Most importantly, acid electroless Ni–P coatings can be successfully deposited on magnesium alloys by using Ni–Sn–P transition layer.

Fabrication and characterization of a novel PbO2 electrode with a CNT interlayer

A novel PbO2 electrode (marked as CNT–PbO2) with a carbon nanotube (CNT) interlayer was prepared by electrophoretic deposition and electro-deposition. The surface morphology, structure, electrochemical activity and stability of the CNT–PbO2 electrodes were characterized by scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ·OH production test, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), bulk electrolysis and accelerated life test. The results show that, compared with the traditional PbO2 electrode, the CNT–PbO2 electrodes electrodeposited β-PbO2 outer layer above the CNT interlayer had a higher crystallinity. The CNT–PbO2-5 min electrode had a higher active surface area and lower charge transfer resistance than traditional PbO2, CNT–PbO2-10 min, and CNT–PbO2-15 min electrodes due to a large number of exposed CNTs. However, the CNT–PbO2-10 min electrode exhibited a stronger ability of ·OH production, higher direct oxidation capacity for degradation of 4-chlorophenol (4-CP) and longer service lifetime than other electrodes, whose apparent rate constant for 4-CP degradation and service lifetime was 2.7 times and 1.7 times those of traditional PbO2 electrode, respectively. Thus, the proposed CNT–PbO2-10 min electrode in this study is a promising anode for the electrochemical oxidation of refractory toxic organic pollutants.

Corrosion behavior of CuCrNiAl alloy in HC1 solutions

Abstract The corrosion behavior of a CuCrNiAl alloy in HC1 solutions was studied by means of metallograph, XRD, SEM/EDX and TEM methods. The results show that in low concentration of HC1 solutions, Cu of CuCrNiAl alloy is more easily subject to corrsion than Cr; the dechromisation of the CuCrNiAl alloy occurs at a certain concentration of HC1 solutions, at the same time Al of CuCrNiAl alloy is subject to corrosion also. The dechromisation corrosion occurs initially at the interface between Cr phase and Cu phase, then it gradually extends Cr phase until Cr phase is dissolved completely. It is also revealed that the tendency of dechromisaion of the CuCrNiAl alloy increases with the increase in concentration and temperature of HC1 solutions.

Preparation and characterization of Cu–rare earth/Al2O3 catalysts and their application in the electrochemical removal of p-nitrophenol

Cu and rare earth composite catalysts (Cu–rare earth/Al2O3) were prepared on Al2O3 particles using an impregnation method for the electro-catalytic oxidation of p-nitrophenol in this study. The surface topography and crystal structure of the products were characterized using scanning electron microscopy and X-ray diffraction. Results show that the Cu–rare earth/Al2O3 particles have a beneficial effect on p-nitrophenol removal by improving the ˙OH radical generation rate, especially the Cu–Bi/Al2O3 catalyst. The effects of the heat treatment conditions for the Cu–Bi/Al2O3 catalyst on its electro-catalytic activity were investigated. For a temperature of 550 °C and a time of 5 h, the obtained Cu–Bi/Al2O3 catalyst exhibited the highest p-nitrophenol removal, nearly 100% after 60 min electrolysis, and this was decreased by only 4.5% after 10 cycles. In addition, the intermediates formed during degradation were identified using high-performance liquid chromatography, and the major intermediates formed during degradation were benzoquinone, hydroquinone, catechol, p-aminophenol, phenol, maleic acid, succinic acid, and oxalic acid. On the basis of the reaction products identified, a possible degradation pathway for p-nitrophenol was proposed.

Assembly of 1D coaxial nanoribbons into 2D multicolor luminescence array membrane endowed with tunable anisotropic electrical conductivity and magnetism via electrospinning

A flexible 2D color-tunable coaxial nanoribbon array membrane with anisotropic electrical conductivity and magnetism assembled by 1D coaxial nanoribbons is obtained via coaxial electrospinning technology using a specially designed coaxial spinneret. Each coaxial nanoribbon in the array is composed of an Fe3O4 nanoparticle (NPs)/polymethyl methacrylate (PMMA) magnetic core and [Eu(TTA)3(TPPO)2 + Tb(TTA)3(TPPO)2]/polyaniline (PANI)/PMMA [TTA = 2-thenoyltrifluoroacetone radical, TPPO = tris(N,N-tetramethylene)phosphoric acid triamide] conductive photoluminescent shell, and the array membrane is formed by aligned coaxial nanoribbons. Tunable colors ranging from green to red can be achieved in the coaxial nanoribbon array membrane by modulating the mass ratio of Eu(TTA)3(TPPO)2, Tb(TTA)3(TPPO)2, PANI and Fe3O4 NPs. Additionally, other functions such as magnetism and anisotropic electrical conductivity are conveniently exhibited by the coaxial nanoribbon array membrane to realize multifunctionality. The ratio of the conductivity parallel and perpendicular to the length direction of the nanoribbons is as high as five due to the unique nanostructure of the array membrane. Also, the magnetic performance, electrical conductivity and electrically conductive anisotropy of the coaxial nanoribbon array membrane can be tuned by modulating the contents of PANI and Fe3O4 NPs. The coaxial nanoribbon array membrane exhibits a much better luminescent performance and electrically conductive anisotropy than its counterpart composite nanoribbon array membrane. Furthermore, the design philosophy and synthetic method for the flexible coaxial nanoribbon array membrane provide a new and facile strategy for the preparation of color-tunable 2D nanomaterials with multifunctionality.

Preparation and Characterization of Zn1−xNixO Nanoparticles: Application as a SERS Substrate

In this paper, the study of the Zn1-xNixO (x = 0, 0.01, 0.03, 0.05) nanoparticles as SERS active substrate has been reported. The structural, morphological and optical studies are carried out by XRD, XPS, SEM, UV-vis and Raman spectroscopy. The XRD spectra indicate that the four Zn1-xNixO nanoparticles (x = 0, 0.01, 0.03, 0.05) are all single wurtzite structure. XPS study further demonstrates that Ni atoms are successfully doped into ZnO lattice. We have observed strong SERS signals when the 4-mercaptobenzoic acid used as the probe molecules. An interesting phenomenon is that an appropriate amount of the Ni atoms doping can enhance the SERS spectrum, and the maximum SERS intensity appeared when the Zn1-xNixO (x = 0.03) as the SERS active substrate, and we ascribe the SERS mechanism to the charge-transfer mechanism. The energy levels caused by the surface defects of ZnO NPs by Ni doping have influence on the charge-transfer process and have benefit for the SERS performance.

Novel flexible coaxial nanoribbons arrays to help achieve tuned and enhanced simultaneous multicolor luminescence–electricity–magnetism trifunctionality

Flexible color-tunable coaxial nanoribbons array endowed with electricity and magnetism is obtained via coaxial electrospinning. Every single coaxial nanoribbon is composed of Fe3O4 nanoparticles (NPs)/polyaniline(PANI)/polymethylmethacrylate (PMMA) conductive-magnetic bifunctional core and [Eu(TTA)3(TPPO)2+Tb(TTA)3(TPPO)2]/PMMA [TTA = 2-Thenoyltrifluoroacetone radical, TPPO = tris(N,N-tetramethylene)phosphoric acid triamide] insulative-photoluminescent shell. In the coaxial nanoribbons array, the fluorescent color is adjustable in the range of green–yellow–red via modulating the mass ratios of RE(TTA)3(TPPO)2, (RE = Eu, Tb), PANI and Fe3O4 NPs, and changing excitation wavelength. The coaxial nanoribbons array possesses more excellent luminescent performance than the counterpart composite nanoribbons array. For the core of coaxial nanoribbons, the highest electrical conductivity reaches 3.152 × 10−2 S cm−1. Magnetism and electricity of the coaxial nanoribbons array can be tuned. Design philosophy and fabrication method provide a novel and facile strategy toward other nanomaterials with multifunctionality.