Synthesis of metallic copper nanoparticles using copper oxide nanoparticles as precursor and their metal–metal bonding properties

Abstract

This work proposes a method for preparing metallic Cu nanoparticles using CuO nanoparticles as a precursor, and performs metal–metal bonding by using the metallic Cu nanoparticles. Colloid solution of CuO nanoparticles with a longitudinal particle size of 13·0±3·0, a lateral particle size of 8·4±2·2 and a crystal size of 7·8 nm was prepared with salt base reaction using Cu(NO₃)₂ aqueous solution and NaOH aqueous solution. Preparation of the metallic Cu particle colloid solution was performed in water using the CuO nanoparticles, hydrazine and cetyltrimethylammonium bromide, which resulted in production of the metallic Cu nanoparticles with a particle size of 50·6 nm and a crystal size of 30·5 nm. Metallic copper discs could be bonded using the metallic Cu nanoparticles under annealing at 400°C and pressurising at 1·2 MPa for 5 min in H₂ gas. A shear strength required for separating the bonded discs was recorded as high as 39·6 MPa.     

Comparison between methods for predicting maximum solid solubility of transition metals in solvent metal

1　INTRODUCTIONThepredictionofsolidsolubilityofanalloyisasuspendingbutanimportant question .Therearemanymicrocosmictheoriesand goodreviews pub lishedelucidatingtheeffectsofelectronegativity ,atomicdiameterandelectronconcentrationonthesol idsolubility ,respectively[1,2 ] .However,theyaredifficulttopredictsolidsolubilitythoughtheycanex plainsomeexperimentalrules.DarkenandGurry[3,4 ]proposedatheoremconsideringbothatomicsizeandelectronegativity ,whichgreatlyimprovedtheHume Rothery swork (D …     

Synthesis and characterization of the core–shell Au covered LSMO manganite magnetic nanoparticles

In this work we report the synthesis and characterization of the nanomagnetic perovskite Sr manganites covered with Au shells having different thickness. La_2/3Sr_1/3MnO₃ (LSMO) manganite nanoparticles were first prepared by a sol–gel procedure. The LSMO manganite nanoparticles were chemically covered with gold to produce the core–shell samples. TEM, HRTEM and atomic emission spectroscopy techniques were used to determine the morphology and structure of the LSMO@Au nanoparticles. The bare LSMO nanoparticles have a mean diameter of around 4.4 nm while LSMO@Au nanoparticles have mean diameters between 7.15 and 4.8 nm depending on the gold quantity involved in the capping process. XRD studies show that both core and shell systems have the expected crystalline structure. The formation of the core–shell structure is sustained by the shift of the plasmon resonance wavelength maximum observed in the UV–vis absorbtion spectra of the LSMO@Au samples depending on the gold concentration. The magnetization versus applied magnetic field of the bare LSMO nanoparticles and LSMO@Au samples shows no hysteresis loop indicating the superparamagnetic behavior of these systems. The analysis of the temperature dependences of FC and ZFC magnetizations shows that for all the samples the axial anisotropy energy barriers are increased due to the magnetic dipolar interactions between neighbor nanoparticles.     

Carbo-oxidising of titanium by diffusion treatment in carbon–oxygen containing media

Abstract

The surface engineering of titanium with TiC_xO_1?x coatings through diffusion carbo-oxidising from graphite in oxygen containing media is investigated. The effect of oxygen partial pressure on phase composition of coatings during carbo-oxidising is evaluated. The interval of oxygen partial pressure allowing the carbo-oxide TiC_xO_1?x to form is defined as 10^?2–10³ Pa. The effects of process temperature and time on evolution of TiC_xO_1?x composition and morphology of surface layer have been investigated. It is determined that increases in temperature and process time favour an increase in carbon content in TiC_xO_1?x. It is revealed that at temperatures above the transformation temperature T_α?β, TiC_xO_1?x is formed not only in coating but also throughout grain boundaries of diffusion layer. The stages of carbo-oxide formation during diffusion carbo-oxidising of commercially pure titanium are explained as follows: surface saturation with oxygen; formation of TiO₂ film; oxide dissolution and formation of diffusion layer; formation of non-stoichiometric TiC_x and TiO_x and their interaction resulting in TiC_xO_1?x formation. Corrosion properties of carbo-oxide coatings tested in 80%H₂SO₄ are compared with nitride and oxide coatings. It is revealed that carbo-oxide coating demonstrates better corrosion resistance. The tribological properties of carbo-oxide, nitride and oxide coatings tested with bronze counterbody are compared, and carbo-oxide coating demonstrates better wear resistance.     

Maximum solid solubility of transition metals in vanadium solvent

Maximum solid solubility （Cmax） of different transition metals in metal solvent can be described by a semi-empirical equation using function Zf that contains electronegativity difference, atomic diameter and electron concentration. The relation between Cmax and these parameters of transition metals in vanadium solvent was studied. It is shown that the relation of Cmax and function Zf can be expressed as In Cmax = Zf = 7. 316 5- 2. 780 5 （△X）^2- 71. 278δ^2-0. 855 56n^2/3. The factor of atomic size parameter has the largest effect on the Cmax of the V binary alloy; followed by the factor of electronegativity difference; the electrons concentration has the smallest effect among the three bond parameters. Function Zf is used for predicting the unknown Cmax of the transition metals in vanadium solvent. The results are compared with Darken-Gurry theorem, which can be deduced by the obtained function Zf in this work.     

Properties of metal–polymer coatings obtained via joint electrodeposition on a cathode of a polyelectrolyte and metals

Copper- and zinc–polymer coatings were obtained via joint electrodeposition on a cathode of a water-soluble amine-containing polymer electrolyte and metals. The process of their formation, composition, structure, morphology, and properties were examined. The obtained coatings were found to possess high hardness and strength compared to pure polymer coatings if they have good elasticity.     

Synthesis and properties of multi-walled carbon nanotubes coated with inorganic nanoparticles

Rare earth fluoride EuF3 and TbF3 were coated on the multi-walled carbon nanotubes (MWNTs) via the intermediate of noncovalent hydrophobic interactions of the MWNTs surface with sodium dodecyl sulfate (SDS).They were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). The nanoparticle sizes of metal fluorides and sulfides on MWNTs are less than 20 nm. The photo physical properties of the composites were investigated, which indicated the composites exhibited the optical transitions within the 4f shell of the rare earth ions.     

Synthesis and characterization of Ag@PPy yolk–shell nanocomposite

Ag@SiO₂@polypyrrole (PPy) nanocomposites were fabricated by a simple method. Ag@PPy yolk–shell nanocomposite was obtained after the removal of the midlayer SiO₂. TEM confirmed that the movable Ag cores were encapsulated in the interior of the hollow PPy nanoparticles. The structure of the resultant product was characterized by the Raman spectrum and X-ray diffraction technologies. Thermogravimetric analysis (TGA) revealed that the thermal stability of the nanocomposites was improved as compared with the pure PPy.     

Synthesis of potential capacitive Poly 4, 4′-diaminodiphenyl sulphone–metal nanocomposites and their characterizations

4, 4′-Diaminodiphenyl sulphone was polymerized (with lithium/cobalt/lithium–cobalt salts) by chemical oxidation method using potassium perdisulphate. The solubility of the chemically prepared polymer–metal nanocomposite was ascertained and it showed good solubility in DMF, chloroform, trichloroethylene and DMSO. The PDDS–Li/Co/Li–Co nanocomposites were characterized by UV–vis and FTIR spectral studies. Amine and imine vibrations observed at 1593 and 1503 cm^?1 were shifted to lower wave numbers when the polymer–metal composites were formed. A single absorption peak due to the N–H stretching vibration of the imino groups of polymer–metal nanocomposite is observed around 3459 cm^?1 and it suggests the participation of NH group during polymerization. The X-ray diffraction studies revealed the formation of nano sized (82 nm) crystalline polymer. The conductivity of the PDDS–Li–Co nanocomposite was determined to be 6.26 × 10^?2 S cm^?1. SEM analysis showed mixed granular nature of the polymer–metal nanocomposite. The capacitance (159.04 μF) of chemically synthesized PDDS–Li–Co nanocomposite is suggested as a potential capacitive material.     

Electrodeposition of zinc–nickel–carbon nanotubes composite coatings in a reversing mode

Composite electrochemical coatings (CECs) made of zinc–nickel–carbon nanotubes have been obtained in a reversing regime. The structure and functional properties of these CECs have been investigated. It has been established that introduction of carbon nanotubes into the deposition electrolyte of a zinc–nickel alloy results in a lowered friction coefficient and enhanced protective capability of the formed coatings.     

New analytical approach to the insulator–metal transition in conductive polyaniline

A new empirical formula describing the temperature dependence of the conductivity of polyaniline films in the metallic regime close to the insulator–metal transition at temperature below 30 K is deduced from the analysis of the temperature dependence of the reduced activation energy. Its elaboration is based on a careful study of electrical transport properties of camphorsulfonic acid-doped polyaniline (PANI(CSA)_0.5) films, containing increasing amounts of triphenyl phosphate (TPP) plasticizer. The use of this three component system (polymer, protonating agent, plasticizer) and control of the amount of adsorbed water enable precise tuning of the electrical transport properties in the solution cast films, in this manner providing the set of experimental data, covering the insulating, critical and metallic regimes, necessary for the elaboration of the proposed new empirical formula.     

Technological aspects of using a carbon–fluorine-containing addition in submerged-arc welding

The technological aspects of adding carbon–fluorine-containing additions to AN-348, AN-60 and AN-67 fluxes in welding 09G2S steel are investigated. It is shown that the addition decreases the total oxygen content of the welded joint, lowers the degree of contamination with oxide non-metallic inclusions and the level of gas saturation of the weld metal, and increases the mechanical properties and impact toughness of the welded joints. The carbon concentration of the welded joint remains similar to that of the parent metal.     

Ferroelasticity in a metal–organic framework perovskite; towards a new class of multiferroics

A metal–organic framework perovskite, [(CH₂)₃NH₂][Mn(HCOO)₃], exhibits a weakly first order ferroelastic phase transition at ～272 K, from orthorhombic Pnma to monoclinic P2₁/n, and a further transition associated with antiferromagnetic ordering at ～8.5 K. The main structural changes, through the phase transition, are orientational ordering of the azetidium groups and associated changes in hydrogen bonding. In marked contrast to conventional improper ferroelastic oxide perovskites, the driving mechanism is associated with the X-point of the cubic Brillouin zone rather than being driven by R- and M-point octahedral tilting. The total ferroelastic shear strain of up to ～5% is substantially greater than found for typical oxide perovskites, and highlights the potential of the flexible framework to undergo large relaxations in response to local structural changes. Measurements of elastic and anelastic properties by resonant ultrasound spectroscopy show some of the characteristic features of ferroelastic materials. In particular, acoustic dissipation below the transition point can be understood in terms of mobility of twin walls under the influence of external stress with relaxation times on the order of ～10^?7 s. Elastic softening as the transition is approached from above is interpreted in terms of coupling between acoustic modes and dynamic local ordering of the azetidium groups. Subsequent stiffening with further temperature reduction is interpreted in terms of classical strain–order parameter coupling at an improper ferroelastic transition which is close to being tricritical. By way of contrast, there are no overt changes in elastic or anelastic properties near 9 K, implying that any coupling of the antiferromagnetic order parameter with strain is weak or negligible.     

The effect of a counterion in a protective moisture-sensitive epoxy–polyelectrolyte/epoxy–carbon sandwich system

In this work, the effect of the ionic form of a KU 2-8 synthetic cation-exchange polyelectrolyte, which was used as a filler in the moisture-sensitive layer, on the behavior of two-layer anticorrosion systems with a low-resistivity damp-proof layer has been studied. The behavior of matrices with sodium (KU 2-8-Na⁺), magnesium (KU 2-8-Mg²⁺), nickel (KU 2-8-Ni²⁺), and zinc ions (KU 2-8-Zn²⁺) has been investigated. The remarkable effect of the nature of studied counterions on moisture-sensitive, protective properties, and behavior of coatings upon cathode polarization of surface has been demonstrated.     

Synthesis and characterization of perylene-based donor–acceptor copolymers containing triple bonds

Two donor–acceptor copolymers containing perylene diimide and oligothiophenes linked through triple bonds have been designed and synthesized by palladium catalyzed Sonogashira coupling reaction. The introduction of the triple bond spacer between the electron acceptor perylene moieties and the electron donating oligothiophene moieties produces an extended conjugation along the main chain, and produces soluble and high molecular weight copolymers.The thermal, optical and electrochemical properties of these copolymers were examined. The HOMO–LUMO energy levels of these copolymers, along with the quenching of their photoluminescence in 1:1 (w/w) blends with poly(3-hexylthiophene) (P3HT), indicate that they are suitable materials for application as electron acceptor and n-type components in bulk heterojunction solar cells with P3HT.     

Nature of insulator–metal transition and novel mechanism of charge transport in the metallic state of highly doped electronic polymers

Highly conducting polymers such as polyaniline and polypyrrole in a metallic state have unusual frequency dependent conductivity, including multiple zero crossings of the dielectric function. A low frequency electromagnetic response, when be analyzed by the Drude theory of metals, is provided by an extremely small fraction of the total number electrons ∼0.1%, but with extremely high mobility or anomalously long scattering time ∼10⁻¹² s. We show that a network of metallic grains connected by resonance quantum tunneling has a Drude type response for both the high and low frequency regimes and behaves as a dielectric at intermediate frequency in agreement with experimental observations. The metallic grains in polymers represent crystalline domains of well-packed chains with delocalized electrons embedded in the amorphous media of poor chain order. Intergrain resonance tunneling occurs through the strongly localized states in amorphous media. The small concentration of electrons participating in dc-transport is assigned to the low density of resonance states, and the long relaxation time is related to the narrow width of energy levels in resonance.     

The role of wettability in metal–ceramic joining

The effects of oxygen, applied DC voltage and surface orientation on the wettability of ceramics by liquid metals are clarified and new methods for metal–ceramic joining are proposed based on information from wetting experiments, using three examples. The strengths of Ni–Al₂O₃ joints obtained at very low oxygen potentials are higher than in high oxygen potential environments. Applying a DC voltage to the interface between metals and partially stabilized zirconia is shown to improve the strength of metal–zirconia joints. Cu and SiC can be strongly joined without using active elements such as Ti and Zr by controlling the joining conditions.     

Microstructures and phase equilibria of the transition metal corner in the Rh–Al–C and Ir–Al–C ternary systems

The isotherms of the Rh–Al–C and Ir–Al–C ternary systems were determined at 1373 K for the transition metal rich corner. It has been revealed that the three-phase field consisting of primary solid solution of a transition metal, B2 type intermetallic compound and graphite extends over a very wide compositional range in these two alloy systems. There exists no carbide in related transition metal rich regions. The phase constitution in the Rh–Al–C and Ir–Al–C ternary alloys prepared by arc melting is basically the same as that by spark plasma sintering (SPS) except the presence of Al₂O₃ particles. The reaction scheme and liquidus surface projection in the transition metal corner of the Rh–Al–C and Ir–Al–C ternary systems were estimated by deliberating on the solidification sequence, as-cast microstructures and invariant reactions on the binary edges.     

Room temperature synthesis of Ag/polypyrrole core–shell nanoparticles and hollow composite capsules

Two kinds of Ag/polypyrrole composite nanoparticles have been prepared via a one-step redox reaction between silver nitrate and pyrrole monomer at room temperature. One is Ag@polypyrrole core–shell nanoparticles that were synthesized by making use of synergic inducing effect of polyvinyl pyrrolidone and p-toluenesulfonic acid existing in aqueous solutions. The other is AgCl@Ag/polypyrrole core–shell composite nanoparticles that were synthesized in the presence of HCl using the in situ-formed AgCl particles as the template. For the latter, its core can be easily removed via a simple dissolving procedure in sodium hyposulfite or ammonium chloride aqueous solutions, obtaining the Ag/polypyrrole hollow composite capsules. Experimental results suggest that the shell thickness and core diameter of the resulting composites can be controlled expediently by adjusting reaction time and concentration of pyrrole monomer.