电化学功能化石墨烯作为铜基复合薄膜的防腐增强材料

Cu–graphene (Gr) composite thin films were prepared by electrodeposition route using in-house synthesized Gr sheets. The Gr sheets were synthesized by the electrochemical exfoliation route using 1 M HClO₄ acid as electrolyte. The Gr sheets were confirmed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The (002) plane of Gr sheets was observed at 2θ of 25.66°. The (002) plane confirmed the crystal structure of carbon peaks. The stretching vibration of C=C bond at a wavelength of 1577 cm?1 and other functional groups of carboxyl and epoxide groups were observed from FTIR. TEM confirmed the transparent structure of Gr sheets. The prepared Gr sheets were used as reinforcement at concentrations of 0.1 and 0.3 g/L with a copper matrix to synthesize the Cu–Gr composite. The prepared composite thin films were characterized by XRD, SEM, and energy-dispersion spectrometry (EDS) for morphological and analytical studies. The presence of Gr sheets in Cu–Gr composite was confirmed by EDS analysis. The prepared Cu–Gr nanocomposite thin film showed higher corrosion resistance compared with pure copper thin films in 3.5wt% NaCl, as confirmed by Tafel plots. Electrochemical impedance spectroscopy complimented the above results and showed that 0.3 g/L composite film achieved the highest film resistance.     

A novel water-soluble anionic conjugated copolymer containing poly（p-phenylene vinylene） segments： Copolymer synthesis and multilayer construction by assembling poly（diallyl dimethyl ammonium chloride）

This paper reports the synthesis of a water soluble conjugated polymer poly（p-phenylene vinyleneco-sodium methacrylate） （ws-P（PV-co-SMA）） and the multilayer of the derived copolymer assembling poly（diallyl dimethyl ammanium chloride） （PDDA）. The self-assembling process of the multilayer was monitored by UV-vis absorption spectroscopy, and the data indicated a linear increase in film thickness with a number of ws-P（PV-co-SMA）/PDDA bilayers. The alternative deposition of ws-P （PV-co-SMA） and PDDA allowed the insertion of a non-conjugated layer between the conjugated layers, thus the migration of the photogenerated polarons was effectively confined in the isolated ws-P （PV-co-SMA） chains. Consequently, the photoluminescence quantum yield reached 0.68, 30 times higher than that of pure poly（p-phenylen vinylene）. The distinct electronic interactions between conjugated segments were confirmed by comparative analyses of the excitation spectra and time-resolved photoluminescence spectra of ws-P（PV-co-SMA） solid film and the assembled multilayers. The confinement effect of the PDDA layer on the photogenerated carriers was verified by the surface photovoltage spectroscopic measurement on both ws-P（PV-co-SMA） solid film and self-assembled multilayers.     

Hybrid solar cells based on poly（3-hexylthiophene） and electrospun TiO2 nanofibers modified with CdS nanoparticles

Organic–inorganic hybrid solar cells based on poly(3-hexylthiophene) and electrospun TiO2 nano bers were fabricated by solution process.The ef ciency of the device was improved by modifying CdS nanoparticles on the surface of TiO2 by electrochemical method.The CdS layer can lead to the increase of both open circuit voltage and short circuit current of the device,which are attributed to enhanced exciton dissociation and light absorption and suppressed carrier recombination by CdS at the heterojunction.However,too thick CdS layer led to increased series resistance and decreased ef ciency of the device.Therefore,the optimum condition of the CdS deposition was obtained,which increased the power conversion ef ciency of the device for about 50%.Our results indicate that the surface modi cation on the inorganic semiconductor layer is an effect way to improve the performance of the hybrid solar cells.     

Microstructure and mechanical properties of titanium nitride coatings for cemented carbide cutting tools by pulsed high energy density plasma

Hard, wear-resistant and well-adhesive titanium nitride coatings on cemented carbide cutting tools were prepared by the pulsed high energy density plasma technique at ambient temperature. The results of Auger spectra analysis indicated that the interface between the coating and substrate was more than 250 nm. Under optimized deposition conditions, the highest critical load measured by nanoscratch tester was more than 90 mN, which meant that the TiN film was well adhesive to the substrate; the highest nanohardness and Young抯 modulus according to nanoindentation tests were near to 27 and 450 GPa. The results of cutting tests evaluated by turning hardened CrWMn steel in industrial conditions indicated that the wear resistance and edge life of the cemented carbide tools were enhanced dramatically because of the deposition of titanium nitride coatings. These improvements were attributed to the three combined effects: the deposition and ion implantation of the pulsed plasma and the becoming finer of the grain sizes.     

Fabrication of metal/metal functionally graded materials with a high melting point difference

Three kinds of full compositional distribution (from 0 to 100wt%W) W/Cu FGMs (functionally graded materials) with high density is fabricated by resistance sintering under ultra-high pressure. Microstructure analysis showed that the good grading composition of all FGMs has been obtained. The sintering mechanism of W is mainly solid state sintering. Thermal shock test in air demonstrated that the grading at the interface between W and Cu is effective for the reduction of thermal stress, but obvious transverse and vertical cracks occur in the pure W layer. The oxidation of the W60Cu40 layer and the W40Cu60 layer is heavier than that of the other layers.     

Electrochemically functionalized graphene as an anti-corrosion reinforcement in Cu matrix composite thin films

Cu–graphene(Gr) composite thin films were prepared by electrodeposition route using in-house synthesized Gr sheets. The Gr sheets were synthesized by the electrochemical exfoliation route using 1 M HClO_4 acid as electrolyte. The Gr sheets were confirmed by X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), field-emission scanning electron microscopy(FESEM), and transmission electron microscopy(TEM). The(002) plane of Gr sheets was observed at 2θ of 25.66°. The(002) plane confirmed the crystal structure of carbon peaks. The stretching vibration of C=C bond at a wavelength of 1577 cm~(-1) and other functional groups of carboxyl and epoxide groups were observed from FTIR. TEM confirmed the transparent structure of Gr sheets. The prepared Gr sheets were used as reinforcement at concentrations of 0.1 and 0.3 g/L with a copper matrix to synthesize the Cu–Gr composite. The prepared composite thin films were characterized by XRD, SEM, and energy-dispersion spectrometry(EDS) for morphological and analytical studies. The presence of Gr sheets in Cu–Gr composite was confirmed by EDS analysis. The prepared Cu–Gr nanocomposite thin film showed higher corrosion resistance compared with pure copper thin films in 3.5 wt% NaCl, as confirmed by Tafel plots. Electrochemical impedance spectroscopy complimented the above results and showed that 0.3 g/L composite film achieved the highest film resistance.     

Cyclic oxidation behavior of b-NiAlDy alloys containing varying aluminum content at 1200 1C

b-NiAlDy cast alloys containing varying aluminum content were prepared by arcmelting. The microstructures and cyclic oxidation behavior of the alloys at 1200 1C were investigated. Grain refinement was achieved by increasing aluminum content in the alloy, which is beneficial to selective oxidation. The Ni–55Al–0.1Dy alloy showed excellent cyclic oxidation resistance due to the formation of a continuous, dense and slow-growing oxide scale. In contrast to this, severe internal oxidation as well as large void formation at the scale/alloy interface occurred in the Ni–45Al–0.1Dy alloy. The aluminum content dependence of the reactive element effects in b- NiAlDy was established that Dy doping strengthened the scale/alloy interface by pegging mechanism in high-aluminum alloys but accelerated internal oxidation in low-aluminum alloys during high-temperature exposure.     

Magnetic Films on Self-assembled Nanospheres

1 Results Nanoparticle media using arrays of monodisperse nanoparticles with high magneticanisotropy are assumed to be the ideal future magnetic recording media. However,key requirements like control of the magnetic anisotropy orientation along with magnetic domain isolation have not been achieved so far. Here, we report on a combination of a two-dimensional topographic pattern formed of self-assembled nanoparticles with sizes as small as 20 nm and magnetic multilayer film deposition[1]. The so formed nanostructures on top of a sphere are monodisperse, reveal a uniform magnetic anisotropy and are magnetically exchange isolated(see Fig.1 at page 710). This system is distinct from the classical nanostructure geometries: Neither extrinsic properties nor the intrinsic properties are uniform in space. The film is extended over a wide region of the sphere and thus shows substantial curvature. The film thickness varies and so do the intrinsic magnetic properties most notable the magneto-crystalline anisotropy, which is a key factor affecting the fundamental nature of the reversal process[2]. Co/Pd multilayers containing thin Co layers of 0.3 nm thickness result in an anisotropy direction pointing perpendicular to the particle surface. This has a drastic impact on the switching mechanism which differs remarkably from a Stoner-Wohlfarth behavior. For Co/Pt and Co/Pd multilayer film deposition, the anisotropy direction depends critically on the Co layer thickness, thus, changing the orientation from parallel to perpendicular to the particle surface below a critical thickness of about 0.8 nm. Increasing the Co thickness allows the creation of systems with a spin reorientation transition across the cap. Experimental results will be compared to micromagnetic simulations. Furthermore, the magnetic nanopattern is used to study the size-dependent scaling of exchange bias in nanostructures. [Pd/Co]-CoO and [Pt/Co]-IrMn layers with perpendicular magnetic anisotropy were deposited onto different arrays of monodisperse PS nanospheres with a diameter ranging from 58 to 320 nm[3]. Below the blocking temperature we find for both systems a strong increase of the exchange bias field compared to continuous films. Interestingly, the exchange bias field increases drastically with decreasing particle size and shows a strong dependence on the applied cooling fields accompanied by a strong training effect.     

Ohmic contact properties of p-type surface conductive layer on H-terminated diamond films prepared by DC arc jet CVD

With the advantages of high deposition rate and large deposition area, polycrystalline diamond films prepared by direct current (DC) arc jet chemical vapor deposition (CVD) are considered to be one of the most promising materials for high-frequency and high-power electronic devices. In this paper, high-quality self-standing polycrystalline diamond films with the diameter of 100 mm were prepared by DC arc jet CVD, and then, the p-type surface conductive layer with the sheet carrier density of 1011-1013 cm?2 on the H-terminated diamond film was obtained by micro-wave hydrogen plasma treatment for 40 min. Ti/Au and Au films were deposited on the H-terminated diamond surface as the ohmic contact electrode, respectively, afterwards, they were treated by rapid vacuum annealing at different temperatures. The properties of these two types of ohmic contacts were investigated by measuring the specific contact resistance using the transmission line method (TLM). Due to the formation of Ti-related carbide at high temperature, the specific contact resistance of Ti/Au contact gradually decreases to 9.95 × 10?5 Ω·cm2 as the temperature increases to 820℃. However, when the annealing temperature reaches 850℃, the ohmic contact for Ti/Au is degraded significantly due to the strong diffusion and reaction between Ti and Au. As for the as-deposited Au contact, it shows an ohmic contact. After annealing treatment at 550℃, low specific contact resistance was detected for Au contact, which is derived from the enhancement of interdiffusion between Au and diamond films.     

High plastic Zr–Cu–Fe–Al–Nb bulk metallic glasses for biomedical applications

Four Zr–Cu–Fe–Al-based bulk metallic glasses(BMGs) with Zr contents greater than 65at% and minor additions of Nb were designed and prepared. The glass forming abilities, thermal stabilities, mechanical properties, and corrosion resistance properties of the prepared BMGs were investigated. These BMGs exhibit moderate glass forming abilities along with superior fracture and yield strengths compared to previously reported Zr–Cu–Fe–Al BMGs. Specifically, the addition of Nb into this quaternary system remarkably increases the plastic strain to 27.5%, which is related to the high Poisson's ratio and low Young's and shear moduli. The Nb-bearing BMGs also exhibit a lower corrosion current density by about one order of magnitude and a wider passive region than 316 L steel in phosphate buffer solution(PBS, pH 7.4). The combination of the optimized composition with high deformation ability, low Young's modulus, and excellent corrosion resistance properties indicates that this kind of BMG is promising for biomedical applications.     

Effect of microstructure and passive film on corrosion resistance of 2507 super duplex stainless steel prepared by different cooling methods in simulated marine environment

The effect of microstructure and passive film on the corrosion resistance of 2507 super duplex stainless steel(SDSS) in simulated marine environment was investigated by electrochemical measurements, periodic wet–dry cyclic corrosion test, scanning Kelvin probe force microscopy, atomic force microscopy, and X-ray photoelectron spectrometry. The results show that the occupation ratio of γ phase increases with the decrease in cooling rate, whereas the content of α phase reduces gradually. In addition, the σ precipitated phase only emerges in the annealed steel. The pitting sensitivity and corrosion rate of 2507 SDSS reduce first and then increase as the cooling rate decreases. The σ precipitated phase drastically reduces the protective ability of the passive film and facilitates micro-galvanic corrosion of the annealed steel. For various microstructures, the pits are preferentially distributed within the σ and γ phases. The corrosion resistance of 2507 SDSS prepared by different cooling methods is closely related to the microstructure and structure(stability and homogeneity) of the passive film. Normalized steel shows an optimal corrosion resistance, followed by the quenched and annealed steels.     

不同冷却方式制备的2507超双相不锈钢在模拟海洋环境中的微观结构和钝化膜对耐蚀性的影响

The effect of microstructure and passive film on the corrosion resistance of 2507 super duplex stainless steel (SDSS) in simulated marine environment was investigated by electrochemical measurements, periodic wet–dry cyclic corrosion test, scanning Kelvin probe force microscopy, atomic force microscopy, and X-ray photoelectron spectrometry. The results show that the occupation ratio of γ phase increases with the decrease in cooling rate, whereas the content of α phase reduces gradually. In addition, the σ precipitated phase only emerges in the annealed steel. The pitting sensitivity and corrosion rate of 2507 SDSS reduce first and then increase as the cooling rate decreases. The σ precipitated phase drastically reduces the protective ability of the passive film and facilitates micro-galvanic corrosion of the annealed steel. For various microstructures, the pits are preferentially distributed within the σ and γ phases. The corrosion resistance of 2507 SDSS prepared by different cooling methods is closely related to the microstructure and structure (stability and homogeneity) of the passive film. Normalized steel shows an optimal corrosion resistance, followed by the quenched and annealed steels.     

Silicon dots films deposited by spin-coating as a generated carrier addition layer of third generation photovoltaics

In this work, silicon ink composing of silicon powder and zinc oxide solution was formulated and spin-coated on quartz and n/p-Si substrates followed by drying the films under atmosphere at the temperature of 550°C. The results showed that this top-addition layer could be the highly promising layer for photo-generating carriers in third-generation photovoltaics to enhance blue-light absorption. X-ray diffraction and scanning electron microscopy techniques were used to study the presence of silicon and zinc oxide nano-crystallites. The thin films consisting of different energy bandgap of Si nanocrystals(～100 nm) with narrow bandgap and spherical Zn O:Bi nanocrystal(～20 nm) with wider bandgap could be obtained from the evidence of bandgap enlargement. The band gaps of the thin films were tunable by adjusting silicon dots density in Zn O:Bi film. Energy upshift of light absorption edge depended on the silicon dots density was observed in the range 1.6–3.3 eV related band gap enlargement by Tauc plot. Under illumination, a high photocurrent gain of the thin film comprised of low Si dots density coated on a quartz substrate was about 10~3 times higher compared with its dark current. This result is agreeably explained in terms of its lower superficial trap states at the interface between silicon and zinc oxide matrix. The composite layer can be applied to a third-generation solar cell with the efficiency 1.50% higher than that with a typical crystalline-Si solar cell.     

Surface characteristics and corrosion resistance of biodegradable magnesium alloy ZK60 modifi ed by Fe ion implantati on and deposition

The ZK60 magnesium alloy has been modified by Fe ion implantation and deposition with a metal vapor vacuum arc plasma source. The surface morphology, phase constituent and elemental distribution are determined by scanning electron microscopy, transmission electron microscopy, X-ray diffractometer and Auger electron spectroscopy. The results show that Fe thin film is deposited on ZK60 alloy and the corresponding thickness increases from 2.73 μm to 6.36 μm with increasing deposition time. A transition layer mainly composed of Mg, Fe and O elements is formed between Fe thin film and ZK60 substrate. The potentiodynamic polarization tests reveal that a high corrosion potential and a low corrosion current density are detected for the Fe deposited ZK60 alloy, indicating the improvement of corrosion resistance. The tensile deformation test indicates that the Fe deposited film on the ZK60 substrate can sustain 1% tensile strain without any cracks.     

Synthesis of core–shell acrylic–polyure thane hybrid latex as binder of aqueous pigment inks for digital inkjet printing

Acrylic–polyurethane (PUA) hybrid aqueous emulsion with core–shell structure was prepared via semibatch emulsion copolymerization of the acrylate monomers (AC) in the presence of a commercial polyurethane dispersion as seeds. The core–shell structure of the emulsion was observed by TEM. The particle size and distribution of the emulsion was found to vary d rastically with the core–shell ratio. The thermal response properties of emulsion film swere measured by DSC, and the results indicated the good compatibility between PA and PU moieties in PUA hybrids. The chemical structures of emulsion films were studied by FTIR, and the surface p roperties were tested by contact angle measurement. The results supported the idea that the surface of the cast films was rich in polyurethane component. The water resistance o f the cast films became better by increasing the AC fraction. The rheological properties of the latex and its utilization as a binder for aqueous pigment inks of digital inkjet printing were thoroughly investigated , indicating that the prepared hybrid emulsion could be used safely for aqueous pigment inks of digital ink jet printing.     

Electrospun composites of PHBV/pearl powder for bone repairing

Electrospun fi ber has highly structural similarity with natural bone extracelluar matrix(ECM). Many researches about fabricating organic–inorganic composite materials have been carried out in order to mimic the natural composition of bone and enhance the biocompatibility of materials. In this work, pearl powder was added to the poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV) and the composite nano fi ber scaffold was prepared by electrospinning. Mineralization ability of the composite scaffolds can be evaluated by analyzing hydroxyapatite(HA)formation on the surface of nano fi ber scaffolds. The obtained composite nano fi ber scaffolds showed an enhanced mineralization capacity due to incorporation of pearl powder. The HA formed amount of the composite scaffolds was raised as the increase of pearl powder in composite scaffolds. Therefore, the prepared PHBV/pearl composite nano fi ber scaffolds would be a promising candidate as an osteoconductive composite material for bone repairing.     

Corrosion behavior of Ni–P/nano-TiC composite coating prepared in electroless baths containing different types of surfactant

In current research, in order to enhance the incorporation of nano-sized TiC particles into electroless Ni–P (EN) coating, different types of surfactant (cationic, anionic, and polymeric) were added to the plating bath. The effects of addition of the surfactants on surface morphology, deposition rate, TiC and P contents of the prepared coatings were investigated. The surface morphology was evaluated by scanning electron microscopy (SEM). It was demonstrated that in the presence of the anionic, polymeric and somehow cationic surfactants, TiC nano-particles were embedded in the matrix which influenced the surface morphology. The effect of surfactant types on the corrosion properties of Ni–P/TiC coated steel was also studied. Corrosion behavior of the coated steel was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) which affected by the incorporation of TiC particles into the Ni–P matrix. The level of corrosion resistance improvement depended largely on the phosphorous and TiC concentration of the applied coating.     

Sintering behavior and thermal conductivity of nickel-coated graphite flake/copper composites fabricated by spark plasma sintering

Nickel-coated graphite flakes/copper (GN/Cu) composites were fabricated by spark plasma sintering with the surface of graphite flakes (GFs) being modified by Ni-P electroless plating. The effects of the phase transition of the amorphous Ni-P plating and of Ni diffusion into the Cu matrix on the densification behavior, interfacial microstructure, and thermal conductivity (TC) of the GN/Cu composites were systematically investigated. The introduction of Ni-P electroless plating efficiently reduced the densification temperature of uncoated GF/Cu composites from 850 to 650℃ and slightly increased the TC of the X-Y basal plane of the GF/Cu composites with 20vol%-30vol% graphite flakes. However, when the graphite flake content was greater than 30vol%, the TC of the GF/Cu composites decreased with the introduction of Ni-P plating as a result of the combined effect of the improved heat-transfer interface with the transition layer, P generated at the interface, and the diffusion of Ni into the matrix. Given the effect of the Ni content on the TC of the Cu matrix and on the interface thermal resistance, a modified effective medium approximation model was used to predict the TC of the prepared GF/Cu composites.     

Magnetoresistance of the thin film ferromagnetic nanoconstrictions

The magnetoresistance and I-V characteristics at different temperatures of the thin film ferromagnetic nanoconstrictions of variable width (from 20 to 250 nm) and 10 nm thicknesses, fabricated by electron beam lithography and vacuum thin film deposition are compared. The magnetoresistance and resistance of the thin film ferromagnetic nanoconstrictions are not related to the width of the nanoconstrictions. Instead the resistance of the local nano-region in the middle of the thin film ferromagnetic nanoconstriction has only a minor role compared to that of the two microscale thin film ferromagnetic electrodes, which contribute the majority of the measured resistance. The magnetoresistances of the thin film ferromagnetic nanoconstrictions and a 0.2 cm × 0.8 cm thin ferromagnetic film deposited under the same conditions were also compared; the thin film ferromagnetic nanoconstrictions have higher magnetoresistances than the thin ferromagnetic film, which implies that the measured magnetoresistance of the thin film ferromagnetic nanoconstrictions comes mainly from the local nano-region in their centers. In conclusion, the measured magnetoresistance of the whole sample is similar to the anisotropic magnetoresistance, because the resistance of the two microscale thin film ferromagnetic electrodes is much higher than that of the local nano-region in the middle of the samples. Comparing the experimental results for the thin film ferromagnetic nanoconstrictions and the thin ferromagnetic film reveals that the magnetoresistance of the local nano-region in the middle of the sample is much higher than that of the two microscale thin film ferromagnetic electrodes attached to it.     

Structural and Electrical Properties of Cu Films by dc Biased Plasma-Sputter-Deposited on MgO(001)

Cu films of 30nm and 15 nm thick were deposited on MgO(001) substrates at 185℃ by dc plasma-sputtering at 1.9kV and 8 mA in pure Ar gas. A dc bias voltage V_s, of 0 V or -80 V was applied to the substrate during deposition. Structural and electrical proper-ties have been investigated by cross-sectional transmission electron microscopy (XTEM), high resolution XTEM (XHRTEM) and by measuring temperature coefficient of electrical resistance (TCR;η) in the temperature interval of -135℃ to 0 ℃. The Cu film is polycrystalline at V_s= 0 V while it epitaxially grows with Cu(00) || MgO(001) and Cu[0 10] || MgO[010] at V_s=-80 V. However, the latter has a very rough surface. The change of η with film thickness and Vs is interpreted in terms of the structure change. Misfit dislocations and lattice expansion are induced along the MgO surface to relax the strain energy due to the lattice mismatch between Cu and MgO.