Synthesis and characterization of silver nanoparticles by sonoelectrodeposition

Shaped silver nanoparticles with sphere, wire and dendrite were prepared by sonoelectrochemical deposition from an aqueous solution of AgNO3 in the presence of ethylenediaminetetraacetic acid disodium salt （EDTA） and polyvinylpyrrolidone （PVP）. The diameter of spherical silver particles was about 30 nm. The diameter of the silver nanowires was also about 30 nm and the length was 200-900 nm. The dendrites were synthesized with the concentration of silver solution increasing. Silver nanoparticles were characterized by transmission electron microscope （TEM）, X-ray powder diffraction （XRD）, scanning probe microscope （SPM） and UV-vis absorption spectrum. XRD patterns revealed that silver particles were of face-centered cubic structure. UV-vis absorption spectra indicated that different morphology and size of silver particles could influence the optical properties.     

Synthesis,characterization,and thermostability of bis(2,2,6,6-tetramethyl-3,5-heptanedionato)copper(Ⅱ)

Owing to the adaptability to large scale processing,excellent composition control and film uniformity,the metal-organic chemical vapor deposition(MOCVD)technique is a promising process for high-temperature superconductor YBa2Cu3O7-δ(YBCO)preparation.In this technique,the evaporation characteristics and thermostability of adopted precursors in whole process will decide the quality and reproducible results of YBCO film.In the present report,bis(2,2,6,6-tetramethyl-3,5-heptanedionato)copper(Ⅱ)(Cu(TMHD)2)was synthesized by the interaction of copper acetate hydrate with TMHD in methanol solution,and its structure was identified by FTIR,1H NMR,and EI-MS spectroscopy.Subsequently,thermal property and the kinetics of decomposition were systematically investigated by nonisothermal thermogravimetric analysis methods(TGA)at different heating rates in streams of N2,and the average apparent activation energy of evaporation process was evaluated by the Ozawa,Kissinger,and Friedman methods.The possible conversion function was estimated through the Coats-Redfern method to characterize the evaporation patterns and followed a phase boundary reaction mechanism by the contracting area equation with average activation energy of 85.1 kJ·mol-1.     

Synthesis and characterization of Ni–P coated hexagonal boron nitride by electroless nickel deposition

Electroless plating has been receiving a steady progress over the last decade on the modification of the surface properties of ceramic materials in order to produce composite coatings with unique characteristics for critical tribological systems. In this work, an electroless nickel deposition process was used to deposit nickel-phosphorous (Ni–P) coating on hexagonal boron nitride (h-BN) particles via hypophosphitereduced acid bath solution. The substrate particles were initially subjected to series of pre-treatment operation in order to ensure that the particles are cleaned and catalytically active prior to electroless plating. The characterization of the as-received and Ni-coated powder was studied through scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and field emission scanning electron microscopy (FESEM). The result reveals that the pretreatment of h-BN powder provides substrate particle surfaces with coarse and roughened structures which are normally considered suitable for Ni–P deposition. Moreover, the result of the EDX analysis confirms the existence of nucleating agents and Ni–P coating on the surface of the treated h-BN powder. The cross-sectional microstructure of the coated powder shows that the h-BN particles were embedded in a continuous matrix layer of Ni–P deposit. The EDX mapping profiles further indicate that the deposited Ni–P alloy mass was uniformly distributed on the surface of the Ni–P codeposited h-BN particles (Ni–P–h-BN). The successful development of Ni coated h-BN powder will raise the potential of h-BN as a high-performance coating material.     

Microbially influenced corrosion and inhibition of nickel–zinc and nickel–copper coatings by Pseudomonas aeruginosa

The present study describes the effect of Pseudomonas aeruginosa on the corrosion rate of nickel–zinc and nickel–copper alloy coatings. The presence of bacteria was associated with decreases in R_ct values, suggesting that P. aeruginosa promoted the corrosion of nickel–copper alloy coatings. However, R_ct values of nickel–zinc coatings increased in response to bacterial inoculation, corresponding to a decrease in corrosion rate for nickel–zinc alloy coatings. Our results suggest that the activity of P. aeruginosa facilitated the corrosion of nickel–copper alloy, while serving a protective function for the nickel–zinc alloy.     

Synthesis and spectroscopic characterization of fluorescent solid rareearth complexes with hydroxamic acids

The complexes RE2(DHYA)3.nH2O in the title bar were synthesized through some reactions of trivalent rareearth ions.In the process of synthesis,dihydroxam,ic acids were taken as ligands while the alcohol was taken as a solvent.The ligands included adipylhydroxamic acid(ADHA),p-phthalichydroxamic acid(PPHA),oxalohydroxamic acid (OXHA),butadihydroxamic acid(BDHA),o-phthalichydroxamic acid(OPHA),benzoylhydroxamic acid(BHA),etc.Measured at 25℃,the molar conductances in various modes are 13.00-21.05 S.cm^2.mol^-1,which shows that rare-earth complexes are nonelectrolytes and the hydroxamino groups of the complexes have taken part in bonding.Infrared spectra,ultraviolet spectra,nuclear magnetic resonance(1HNMR) spectra,and fluorescence spectra were used to investigate the complexes,Experiments have proved that the complexes of Eu^3 and Tb^3 with aromatic hydroxamic acids have good fluorescent characteristics.     

Physical and numerical characterization of the near-eutectic permeability of aluminum–copper alloys

The near-eutectic permeability of aluminum–copper alloys has been determined through physical and numerical modeling. The physical models are large-scale analogues of interdendritic structures produced by a rapid prototyping technique from three-dimensional (3-D) geometries obtained by X-ray microtomography. A glycerin-based solution was passed through the physical models and the permeability was calculated from measurements of the discharge flow rate and pressure drop. Mathematical models, considering the continuity and momentum equations, were developed for the corresponding unstructured meshes of the 3-D geometries used for the physical models. The numerically determined values of permeability are in good agreement with those measured. With the aid of this 3-D characterization, it is possible to distinguish between isolated liquid regions that are prevalent at high solid fractions and those liquid channels that contribute to interdendritic flow. The work presented in this study highlights the attention that must be paid to numerical calculations of fluid flow in the mushy zone and presents an alternative technique to determine permeability compared to conventional permeameters.     

Synthesis and electromagnetic characterization of polyaniline nanorods using Schiff base through ‘seeding’ polymerization

Two kinds of Schiff base, m-phenylenediamine-glyoxal (Schiff base A) and p-phenylenediamine-glyoxal (Schiff base B), were used as ‘seed’ to induce the polymerization of aniline and hence prepare polyaniline (PANI) nanorods. The different preparation conditions including the Schiff base structure, dosage and acidity of the reaction medium, were investigated to discuss the influence of these conditions on the conductivity of the resulting samples through two-probe method at room temperature. The products were also characterized by Fourier transform infrared (FTIR), ultraviolet–visible (UV–vis), scanning electro microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) techniques. The results implied that these conditions play an important role in the formation of PANI nanorods. Moreover, the resulting PANI nanorods exhibited an unusual electromagnetic loss at the microwave frequency (f = 8.2–12.4 GHz) arose from order arrangement of polaron as charge carrier caused by a nanorods morphology and can be used for the potential application as microwave absorbing materials.     

Synthesis and characterization of nanocrystalline Ni produced by cryomilling in liquid nitrogen

NanocrystaUine Ni powders were successfully fabricated by mechanically milling at cryogenic temperature （cryomilling） with 1 wt.%Y2O3 particles. The experimental results have shown that the Ni grain size is reduced to 25 nm after 2 h of cryomilling in the presence of the Y2O3 particles. The cryomiUed Ni/Y2O3 powders can maintain their nanocrystalline structure up to 900℃, or 62% of the melting point of Ni. A bulk nanocrystalline Ni/Y2O3 material with a thermally stable grain size of approximately 100 nm was produced by cryomilling, cold isostatic pressing, followed by hot isostatic pressing. The microhardness of bulk nanocrystalline Ni/1wt.%Y2O3 is 315 DPH, which is two times as high as that of conventional Ni.     

Synthesis of the dendronized poly(p-phenylenevinylene) with appendent Fréchet-type dendrons

The dendronized poly(p-phenylenevinylene)s (PPVs) with appendent Fréchet-type dendrons were successfully synthesized, and characterized by laser light scattering (LLS), thermogravimetric analysis (TGA), UV-Vis and fluorescence spectra.     

Kinetics and mechanism of the nickel electrode—II. Acid solutions containing a high concentration of sulphate and nickel ions

The kinetics of the Ni electrode in acid solutions with a high sulphate and nickel ion concentration has been investigated in the range of 25–75°C. The active dissolution and the passive regions and the active-passive transition phenomena have been studied employing different potential perturbation techniques using both still and stirred solutions.Two electrochemical processes are competing within the prepassive film potential region, namely, the active Ni dissolution to Ni(II) ions and the Ni(OH)₂ film formation. Nickel passivation is explained by reaction pathways involving successive electrochemical and chemical steps implying the occurrence of hydroxo- and oxo-species as reactions intermediates. The advanced mechanism is based upon a positively charged Ni surface structure and attributes the onset of the complete passivity to a particular surface oxide species.     

Corrosion and anodic oxidation of copper in 1-butyl-3-methylimidazolium bromide–copper(II) bromide ionic liquid

Using the gravimetric and polarization methods, the corrosion behavior of copper in 1-butyl-3-methylimidazolium bromide (BMImBr) ionic liquid in its pure state and with additions of CuBr₂ (from 0.4 to 1.2 mol kg^–1) has been investigated. It is found that the corrosion in naturally aerated BMImBr ionic liquid is accompanied by oxygen depolarization. Copper dibromide in BMImBr–CuBr₂ ionic liquid plays the role of an oxidant, and the rate of copper corrosion in this case is higher by about an order of magnitude than for the pure ionic liquid. The method of cyclic voltammetry shows that the anodic dissolution of copper in BMImBr–CuBr₂ ionic liquid proceeds via the EC mechanism. It is shown that the chemical-reaction rate of dissolving the surface layer and the rate of copper corrosion (according to gravimetric and polarization data) are comparable. Copper corrosion in the studied ionic liquid is accompanied by the effect of surface polishing, as is confirmed by the atomic force microscopy and profilography.     

The passivation of nickel in aqueous solutions—II. An in situ investigation of the passivation of nickel using optical and electrochemical techniques

The film responsible for the passive behavior of nickel and the mechanisms of film formation was studied in situ. Electrochemical polarization techniques were used in conjunction with Differential Reflectometry. It was found that the film which causes nickel to passivate in 0.15 N Na₂SO₄ (pH = 4.0–12.0) is Ni(OH)₂. It is suggested that the film forms via a precipitation mechanism in the acid solutions subsequent to active metal dissolution. At low values of pH, this precipitated film, once formed, generally does not change in thickness as the potential is made increasingly anodic. Conversely, the Ni(OH)₂ film formed in higher pH solutions (pH = 8.0 open, pH = 12.0 open and de-aerated) grows by virtue of a solid state mechanism. Both NiO and NiOOH are observed to form subsequent to Ni(OH)₂ but only at higher values of pH. Although the films formed at alkaline pH values are thinner than those in the lower pH environments, they were found to be more protective.     

Synthesis and characterization of Al2O3–TiC nano-composite by spark plasma sintering

Al₂O₃–10TiC composite was synthesized by high energy ball milling followed by spark plasma sintering (SPS) process. Microstructure of the sintered composite samples reveals homogeneous distribution of the TiC particles in Al₂O₃ matrix. Effect of sintering temperature on the microstructure and mechanical properties was studied. The sample sintered at 1500 °C shows a measured density of 99.97% of their theoretical density and hardness of 1892 Hv with very high scratch resistance. These results demonstrate that powder metallurgy combined with spark plasma sintering is a suitable method for the production of Al₂O₃–10TiC composites.     

Synthesis and characterization of amorphous Al–Mg–B prepared by various deposition temperatures

Amorphous Al–Mg–B thin films were synthesized via a combinatorial sputtering approach. The properties of Al–Mg–B films with the varying deposition temperature was investigated. The deposition temperature was found to dominate the hardness of the amorphous as-deposited film. The hardness increases with increasing deposition temperature and may even exceed that of crystalline AlMgB₁₄ material. The high hardness may be attributed to the existence of randomly distributed B₁₂ icosahedra structure. Therefore, the thin film that was deposited on cemented carbide shows well-cutting performances in turning Ti alloy bar. At the same time, an appropriate method of pretreatment is the key to ensure the coating tool with the excellent adhesion by impact fracture test.     

Synthesis,characterization and photoluminescent properties of Eu(Ⅲ) complexes with 5-hydroxy-2-hydroxymethyl-4H-4-pyranone and N,N'-donor heterocyclic coligands

In present work,five novel europium complexes[Eu(L)_3·Phen(2),Eu(L)_3·Bipy(3),Eu(L)_3·Neo(4),Eu(L)_3·Biq(5) and Eu(L)_3·Batho(6)] were synthesized,derived from [Eu(L)_3·2 H_2 O](1) complex by using ligand(HL) 5-hydroxy-2-(hydroxymethyl)-4 H-pyran-4-one and coligands 1,10-phenanthroline,bipyridine,neocuproine,2,2'-biquinoline and bathophenanthroline.In order to seek excellent photoluminescent properties,coligands were introduced in the complexes to form a rigid conjugated system,thus enhancing luminescence properties of complexes.The synthesized complexes reveal four narrow characteristic emission lines of Eu(III) consistent with~5 D_0→~7 F_J transitions,where J=0,1,2 and 3 at about580,595,614 and 650 nm,respectively.The ~5 D_0→~7 F_2 transition is responsible for strong red luminescence.Color coordinate diagram also indicates that x,y coordinates lie in deep red region.Thermal data are in favour of high thermal stability of synthesized compounds.Owing to their high thermal stability and strong red luminescence,these complexes might be used in fabrication of optoelectronic devices.     

Preparation and characterization of bis(dimolybdo-nonatungstogermanate)lanthanates of potassium

The heteropoly complexes K12[Ln(GeW9Mo2O39)2] · nH2O (Ln = La, Ce, Pr, Nd, and Sm) were prepared for the first time and characterized by chemical analysis, infrared (IR) spectrum, ultraviolet (UV) spectrum, X-ray powder diffraction, and thermal analysis. IR, UV spectra, and X-ray powder diffraction studies show that the structure of the heteropoly complexes is a square antiprism consisting of eight oxygen atoms of two GeW9Mo2O398-, heteropolyanions and a lanthanide ion. The thermostability of heteropoly complexes is lower than that of saturated Keggin structure dodecatungstogermanate.     

Synthesis and luminescence properties of rare earth ternary complexes consisting of Tb(Ⅲ),β-diketones and 1,10-phenanthroline (phen)

In order to study the luminescent properties of ternary rare earth complexes with fl-diketone ligand,three new β-diketone ligands,1-phenyl-3-(p-phenylethynylphenyl)-1,3-propanedione(HPPP), 1-(2-thienyl)-3-(p-phenylethynylphenyl)-l,3-propanedione (HTPP) and 1-(2-furyl)-3-(p-phenylethynylphenyl)-1,3-propanedione (HFPP),were synthesized by Sonogashira coupling reaction and Claisen condensation.Three new ternary rare earth complexes,TbL3phen (L = PPP,TPP,or FPP),were synthesized by the reaction of rare earth chloride TbCl3,1,10-phenanthroline (phen) with HPPP,HTPP,or HFPP respectively,in alcohol solution.The compositions were characterized by means of elernental analysis,chemical analysis,and IR spectra.Luminescent properties of the three new complexes have been studied.The results show that the ternary Tb(Ⅲ) complexes only emit the weak fluorescence of the Tb(Ⅲ) ion,which reveals the triplet state energy of the ligands does not match well with the excited state vibrating energy of Tb3+ ion.     

Investigation on the syntheses and structures of Y~(Ⅲ) complexes with ami-nopolycarboxylic acids (Ⅳ)

This paper deals with the structure of the YIII complex with aminopolycarboxylic acids, synthesis and structural determination of the complex (NH4)[YIII(edta)(H2O)3]·3H2O (edta = ethylenediaminetetraacetic acid). The crystal and molecular structures of the (NH4)[YIII(edta)(H2O)3]·3H2O complex have been determined by single-crystal X-ray structure analysis. The crystal of the complex (NH4)[YIII(edta)(H2O)3]·3H2O belongs to orthorhombic crystal system and fdd2 space group. The crystal data are as follows: a=1.944 1(9) nm, b= 3.545 9(18) nm, c = 1.219 6(6) nm, V= 8.407 (7)nm3,Z=16, Mr= 503.25, Dc= 1.590g.cm3, μ= 2.844 mm 1 and F(000) = 4 160. The final R and Ru are 0.048 6 and 0.133 2 for 3 388 (I>2σ(I)) unique reflections, respectively. The complex anion [YIII(edta)(H2O)3] has a pseudo-mono-capped square antiprismatic nine-coordinate structure in which the six coordinate atoms (two N and four O) are from an edta ligand and three water molecules coordinate to the central YIII ion directly. From the res     

Nanostructured WC–Co particles produced by carbonization of spark eroded powder: Synthesis and characterization

Particles of homogeneous elementary composition are formed by spark erosion of a WC–Co hard alloy in a special assembly. The average particle diameter is 4.0 μm, and the specific surface area is 3.33 m²/g. The powder was carbonized for 4 h in CO gas. The particles produced by carbonization consist of a WC frame, with cobalt situated in WC interlayers. The thickness of WC layers in most of the particles ranges from 10 to 200 nm. The microhardness of these particles (HV = 23.7 ± 4.2 GPa) exceeds the microhardness of the initial standard hard alloy (HV = 15.47 ± 1.71 GPa).     

Synthesis and characterization of poly[(R)-(−) and (S)-(+)-3-(1′-pyrrolyl)propyl-N-(3″,5″-dinitrobenzoyl)-α-phenylglycinate]s as chiral oligomers of pyrrole

Chiral polypyrrole oligomers were prepared from (R)-(?) (1) and (S)-(+)-3-(1′-pyrrolyl)propyl-N-(3″,5″-dinitrobenzoyl)-α-phenylglycinate (2) by oxidative polymerization in the presence of FeCl₃ as an oxidant. The new polymers were characterized by ¹H NMR, FTIR and UV–vis (λ_máx = 251 nm). TGA analyses of the corresponding polymers, poly1 and poly2, demonstrate an excellent thermal stability up to 204 °C, followed by two consecutive weight losses at higher temperatures. Relative number-average molecular weights of about 1.4 × 10³ and 2.3 × 10³, for poly1 and poly2, respectively, were measured by SEC, corresponding to oligomeric chains. Specific optical rotation measurements (c 0.1, THF) for poly1 [α]_D²⁰ = ?44 and poly2 ([α]_D²⁰ = +44) suggest that chirality is retained during the polymerization. Transversal section analysis of SEM images indicates the materials isolated right after the synthesis is highly porous.