Effect of Reaction Products on the Kinetics of Copper Dipivaloylmethanate Reduction to Copper

The effects of 2,2-dimethyl-1-propanol, acetone, carbon monoxide, and water vapors on the kinetics and mechanism of copper deposition from Cu(dpm)₂ vapor are studied in the range 200–350°C. The results demonstrate that 2,2-dimethyl-1-propanol has no effect of the deposition process, while acetone inhibits Cu deposition and impairs the quality of the resulting film. Carbon monoxide reduces the deposition rate and raises the activation energy of the process to 46 ± 8 kJ/mol. The introduction of water vapor accelerates film growth and reduces the activation energy to 10 ± 7 kJ/mol.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 7, 2005, pp. 792–798.Original Russian Text Copyright © 2005 by Bakovets, Levashova, Dolgovesova, Danilovich.     

Chemical Vapor Deposition of Copper Films from Copper Dipivaloylmethanate in Hydrogen Atmosphere

Data are presented on the kinetics and mechanism of copper deposition from Cu(dpm)₂ vapor in a hydrogen atmosphere at normal pressure. From kinetic analysis of the deposition rate as a function of substrate temperature (200–390°C) and Cu(dpm)₂ vapor pressure (7.8 Pa), the main parameters of kinetically limited deposition were determined: activation energy of 27 ± 7 kJ/mol, preexponential factor of (2.9 ± 1.8) × 10² cm/s, and reaction order of unity. Under diffusion-control conditions, the diffusion rate constant is 4.8 cm/s, and the thickness of the diffusion layer is 8 × 10^–2 cm. The films grow by a mixed (island–layer) mechanism, and their electrical resistivity is close to that of bulk copper.     

Thermal transformations of the Cu(dpm)<Subscript>2</Subscript> complex in inert and reducing atmospheres

The transformation kinetics of the Cu(dpm)₂ complex have been studied by thermal analysis under steady-state conditions. The results indicate that, in noncatalytic systems, the dominant process in the temperature range 150–300°C is vaporization of the complex, with an enthalpy of 62 ± 12 kJ/mol. In hydrogen atmosphere on nickel and copper surfaces, responsible for the formation of adsorbed atomic hydrogen, the dominant process is copper reduction. Weight loss data obtained in thermoanalytical runs between 185 and 220°C were used to separate the contribution of the chemical process and to evaluate the apparent activation energies for the hydrogen reduction of copper on nickel and copper surfaces: 32 ± 6 and 48 ± 9 kJ/mol, respectively.     

Interfacial reactions and intermetallic compound growth between indium and copper

The growth kinetics of intermetallic compound layers formed between pure indium solder and bare Cu substrate by solid-state isothermal aging were examined at temperatures between 343 and 393 K for 0–4×10⁶ s. A quantitative analysis of the intermetallic compound layer thickness as a function of time and temperature was performed. Experimental results showed that the Cu₁₁In₉ intermetallic compound was observed for bare copper substrate. Additionally, the thickness of the Cu₁₁In₉ intermetallic compound was increased with the aging temperature and time. The layer growth of the intermetallic compound in the couple of the In/Cu system followed a parabolic law over the given temperature range. As a whole, because the values of time exponent (n) were approximately 0.5, the layer growth of the intermetallic compound was mainly controlled by a diffusion mechanism over the temperature range studied. The apparent activation energy of Cu₁₁In₉ intermetallic compound in the couple of the In/Cu was 34.16 kJ mol^–1.     

Electrodeposition of adherent copper film on unmodified tungsten

Adherent Cu films were electrodeposited onto polycrystalline W foils from purged solutions of 0.05 M CuSO₄ in H₂SO₄ supporting electrolyte and 0.025 M CuCO₃Cu(OH)₂ in 0.32 M H₃BO₃ and corresponding HBF₄ supporting electrolyte, both at pH 1. Films were deposited under constant potential conditions at voltages between −0.6 V and −0.2 V vs. Ag/AgCl. All films produced by pulses of 10 s duration were visible to the eye; copper colored, and survived the Scotch tape test. Characterization by scanning electron microscopy (SEM)/energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS) confirmed the presence of metallic Cu, with apparent dendritic growth. No sulfur impurity was observable by XPS or EDX. Kinetics measurements indicate that the Cu nucleation process in the sulfuric bath is slower than in the borate bath. In both baths, nucleation kinetics does not correspond to either instantaneous or progressive nucleation. Films deposited from 0.05 M CuSO₄/H₂SO₄ solution at pH>1 at −0.2 V exhibited poor adhesion and decreased Cu reduction current. In both borate and sulfate baths, small Cu nuclei are observable by SEM upon deposition at higher negative overpotentials, while only large nuclei (approx. 1 μm or larger) are observed upon deposition at less negative potentials.     

Synthesis of copper and copper(I) oxide nanoparticles by thermal decomposition of a new precursor

The present investigation reports, the novel synthesis of nanoparticles Cu and Cu₂O using thermal decomposition and its physicochemical characterization. The nanoparticles copper powder have been prepared using [Bis(salicylidiminato)copper(II)], [Cu(sal)₂], as precursor. Cu nanoparticles are initially formed and subsequently oxidized to form Cu₂O. Transmission electron microscopy (TEM) analysis demonstrated nanoparticles Cu₂O with an average diameter of about 10 nm. As-prepared copper nano-particles were characterized by X-ray diffraction measurements (XRD), scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDAX), and Fourier transform infra-red spectroscopy (FTIR). XRD analysis revealed broad pattern for fcc crystal structure of copper metal and cubic cuprite structure for Cu₂O. Optical absorption measured by UV–visible spectroscopy was used to monitor oxidation course of Cu → Cu₂O and to determine the band-gap energy about 2.4 eV for Cu₂O nanoshells.     

Solid state intermetallic compound layer growth between Sn-8Zn-3Bi solder and bare copper substrate

The growth kinetics of the intermetallic compound layer formed between Sn-8Zn-3Bi solder and a bare Cu substrate by solid-state isothermal aging were examined at temperatures between 343 and 423 K for periods ranging from 0 to 100 days. A quantitative analysis was performed of the intermetallic compound layer thickness as a function of the aging time and aging temperature. For the identification of the intermetallic compounds, both Energy Dispersive X-ray and X-Ray Diffraction were employed.The experimental results showed that the γ -Cu₅Zn₈ intermetallic compound was observed at the interface between the solder and the bare copper substrate. Additionally, the thickness of the γ -Cu₅Zn₈ intermetallic compound increased with increasing aging temperature and aging time. The layer growth of the intermetallic compound in the Cu/Zn couple follow a parabolic law within a given temperature range. As a whole, because the value of the time exponent (n) is approximately equal to 0.5, the layer growth of the intermetallic compound was mainly controlled by the diffusion mechanism in the temperature range studied. The apparent activation energy of the γ -Cu₅Zn₈ intermetallic compound was 61.19 kJmol.     

Electrodeposition and morphology analysis of Bi-Te thermoelectric alloy nanoparticles on copper substrate

Nanoscale Bi-Te particles with thermoelectric properties on copper substrate were investigated. The substrate was prepared by electroplating copper layer on a copper zinc alloy plate in a copper sulfate solution. Electrodeposition of the Bi-Te alloy particles was then performed in a nitrate bath. The electrolyte is composed of 0.05 M bismuth nitrate and 0.01 M tellurium dioxide dissolved in 2.0 M HNO₃. Cyclic voltammetry and quartz microbalance tests associated with the electrodeposition process were conducted to show the mechanism and kinetics of the deposition. The morphology and compositional analysis of Bi-Te was obtained using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) respectively. The morphology analysis suggested that nanoscale Bi-Te particles were obtained and the EDS results indicated that the surface of the copper substrate contained Cu₂O. The atomic ratio 1:1 for Bi:Te in the alloy, which is equivalent to the weight percentage of Bi:Te = 62%:38% was confirmed from the data obtained.     

Study on cold metal transfer welding–brazing of titanium to copper

3 mm Pure titanium TA2 was joined to 3 mm pure copper T2 by Cold Metal Transfer (CMT) welding–brazing process in the form of butt joint with a 1.2 mm diameter ERCuNiAl copper wire. The welding–brazing joint between Ti and Cu base metals is composed of Cu–Cu welding joint and Cu–Ti brazing joint. Cu–Cu welding joint can be formed between the Cu weld metal and the Cu groove surface, and the Cu–Ti brazing interface can be formed between Cu weld metal and Ti groove surface. The microstructure and the intermetallic compounds distribution were observed and analyzed in details. Interfacial reaction layers of brazing joint were composed of Ti₂Cu, TiCu and AlCu₂Ti. Furthermore, crystallization behavior of welding joint and bonding mechanism of brazing interfacial reaction were also discussed. The effects of wire feed speed and groove angle on the joint features and mechanical properties of the joints were investigated. Three different fracture modes were observed: at the Cu interface, the Ti interface, and the Cu heat affected zone (HAZ). The joints fractured at the Cu HAZ had higher tensile load than the others. The lower tensile load fractured at the Cu interface or Ti interface was attributed to the weaker bonding degree at the Cu interface or Ti interface.     

Facile fabrication of ultrasmall and uniform copper nanoparticles

Ultrasmall and uniform copper nanoparticles were synthesized through a trace-level ethylenediaminetetraacetic acid (EDTA)-assisted wet chemical route in which Cu(OH)₂ colloid, KBH₄ and polyvinyl pyrrolidone (PVP) were used as the Cu source, the reducing agent, and the protective agents, respectively. The copper nanoparticles exhibit a spherical morphology with a narrow size distribution, a uniform shape, and the average diameter of ca. 4 nm. The presence of trace EDTA is indispensable for the preparation of ultrasmall and uniform copper nanoparticles. EDTA concentration directly influences the copper nanoparticle size and uniformity. As EDTA concentration decreases, the size of the copper nanoparticles decreases, whereas the uniformity increases. The possible formation mechanism of ultrasmall and uniform copper nanoparticles was determined according to experimental results.     

Strengthening effects in precipitation and dispersion hardened powder metallurgy copper alloys

The hardening of copper and copper alloy matrix using powder metallurgy (PM) techniques and different ways for dispersoids formation, as well as analysis of their single and combined effects on the strength of obtained material at room and elevated temperatures, have been presented and discussed. Gas atomized Cu–3.8 wt.%Ti and Cu–0.6 wt.%Ti–2.5 wt.%TiB₂ (Cu–Ti–TiB₂) powders and mechanically alloyed powder Cu–4 wt.%TiB₂ were used as starting materials. The powders were consolidated by hot isostatic pressing (HIP) and hot pressing (HP). Optical, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDAX), as well as transmission electron microscope (TEM) were used for microstructure characterization of the compacts. High strengthening of the Cu–Ti compacts was achieved by thermal treatment (aging) as a consequence of the development of modular structure and precipitation of metastable Cu₄Ti_(m). Hardening in the Cu–Ti–TiB₂ compacts is due to simultaneous influence of the following factors: the development of modular structure, precipitation of metastable Cu₄Ti_(m), and the presence of TiB₂ dispersoid nanoparticles. In case of Cu–TiB₂ compacts, high starting values of hardness and hardness on the elevated temperatures result from the presence of finely distributed TiB₂ particles in copper matrix obtained by mechanical alloying. Cu–Ti–TiB₂ composite yields much higher hardness values compared with the binary Cu–Ti alloys, owing to primary TiB₂ dispersions formed during atomization. Separation of metastable Cu₄Ti precipitate and the presence of significantly finer TiB₂ particles in the copper matrix are the reason for higher hardness values at peak temperatures (400–500 °C) in multiple-hardened copper alloy compared to the dispersion-hardened.     

Electromagnetic interference shielding,mechanical properties and water absorption of copper/bamboo fabric (Cu/BF) composites

Copper/bamboo fabric (Cu/BF) composites were prepared by electroless deposition via a tin-free process. The process involved 3-aminopropyltrimethoxysilane modification, noble metal (Au or Pd) activation and electroless copper planting of BF. The copper deposition rate via Pd catalytic process was 1.01 mg/cm² h, higher than that by Au catalytic process (0.85 mg/cm² h). The microstructure of Cu/BF composites was analyzed by scanning electron microscopy (SEM), and the copper coatings were composed of ball-shaped copper particles. The composition and chemical state of copper layers were measured by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) spectra, Cu⁰ was detected but copper dioxide was not found in both spectra. The electromagnetic interference, water absorption, mechanical tension, conductivity and adhesion properties of Cu/BF samples (weight ratio of Cu/BF: 0.36 ± 0.01) were measured to obtain the qualities of the composites.     

Time-to-failure analysis of 5 nm amorphous Ru(P) as a copper diffusion barrier

Evaluation of chemical vapor deposited amorphous ruthenium-phosphorous alloy as a copper interconnect diffusion barrier is reported. Approximately 5 nm-thick Ru(P) and TaN films in Cu/Ru(P)/SiO₂/p-Si and Cu/TaN/SiO₂/p-Si stacks are subjected to bias-temperature stress at electric fields from 2.0 MV/cm to 4.0 MV/cm and temperatures from 200 °C to 300 °C. Time-to-failure measurements suggest that chemical vapor deposited Ru(P) is comparable to physical vapor deposited TaN in preventing Cu diffusion. The activation energy of failure for stacks using Ru(P) as a liner is determined to be 1.83 eV in the absence of an electric field. Multiple models of dielectric failure, including the E and Schottky-type √E models indicate that Ru(P) is acceptable for use as a diffusion barrier at conditions likely in future technology generations.     

Interfacial microstructure and strength of brazed copper/porous copper foam towards the effect of porous copper foam pore density and brazing holding time

The porous copper foam was sandwiched between two coppers plate and then brazed using copper-tin (9.7 %)-nickel (5.7 %)-phosphorus (7 %) filler foil. Brazing process was conducted to joint copper/porous copper foam by evaluating the effect of porous copper foam pore densities [pore per inch (PPI)] and brazing holding times. The brazed joint interface of copper and porous copper foam was characterised using Field emission scanning electron microscopy and Energy-dispersive x-ray spectroscopy for the microstructure and elemental composition analysis, respectively. X-ray diffraction analysis was carried out on the shear fractured surfaces of brazed copper and porous copper foam for phase determination. The results exhibited distinct phases of copper (Cu), copper phosphide (Cu₃P), nickel phosphide (Ni₃P), and copper compound with tin (6 : 5) (Cu₆Sn₅). The filler layer was formed as an island-shaped that consists of copper phosphide and nickel phosphide. Prolong brazing holding time causes a thinner filler layer in brazing seam. While the non-uniform thickness of the filler layer was observed at different pore densities of porous copper foam. The shear strength of brazed copper/porous copper foam 15 PPI with a 10 min brazing holding time yield a maximum shear strength of 2.9 MPa.     

Relationship between dealloying conditions and coarsening behaviors of nanoporous copper fabricated by dealloying Cu-Ce metallic glasses

Monolithic nanoporous copper(NPC) with tunable ligament size(107–438 nm) was synthesized by dealloying a new Cu-Ce binary glassy precursor in dilute H_2SO_4 aqueous solution. The effects of the dealloying conditions on the morphologies of NPC were evaluated comprehensively. The results show that the ligaments of NPC can significantly coarsen with the increase of acid concentration, elevation of reaction temperature or prolongation of immersion time. These coarsening behaviors can be well described by a diffusion based growth kinetic model. Moreover, the surface diffusivity and activation energy for diffusion of Cu atoms were also estimated to investigate the formation mechanism of NPC, which is mainly governed by dissolution of Ce element in the glassy precursor coupled with nucleation and growth of Cu clusters via the precursor/solution interface. In the experiment of the degradation of methyl orange(MO) dye, the NPC fabricated by Cu-Ce metallic glasses exhibits superior sono-catalytic activity.     

Grain growth kinetics in a supercooled liquid region of Zr65Cu27.5Al7.5 and Zr65Cu35 metallic glasses

The grain growth kinetics of a Zr₂Cu crystalline phase in a supercooled liquid region of Zr₆₅Cu_27.5Al_7.5 and Zr₆₅Cu₃₅ metallic glasses was examined at different temperatures. Since no significant changes in the constitution and strain in Zr₂Cu phase were seen for the annealed samples, the grain size calculated from a half value width of the X-ray diffraction peak by Scherrer's formula was used. The grain growth is controlled by a single kinetics with a thermal activation process of Arrhenius type, which is described by

Adsorption of copper(II) onto sewage sludge-derived materials via microwave irradiation

The materials with adsorbent properties were produced from urban sewage sludge by two different procedures via microwave irradiation: (1) by one single pyrolysis stage (SC); (2) by chemical activation with ZnCl₂ (SZ). The BET, SEM and FT-IR have been used to evaluate the pore structural parameters and surface chemistry of the adsorbents, respectively. Subsequently they were used for adsorption of Cu(II) from aqueous solutions. The effects of various experimental parameters, such as pH, temperature were investigated in a batch-adsorption technique. The results showed that the adsorption of Cu(II) was maximal at pH 5.0. The kinetic study demonstrated that the adsorption process was followed the second-order kinetic equation. The experimental adsorption isotherm data were well fitted with Langmuir model and the maximum adsorption capacity of Cu(II) were found to be 3.88 and 10.56 mg/g for SC and SZ, respectively, in the solution of pH 5.0. Thermodynamic parameters such as changes in the enthalpy (ΔH⁰), entropy (ΔS⁰) and free energy (ΔG⁰) indicate that Cu(II) adsorption onto SC and SZ is an endothermic and spontaneous process in nature at 15-45 °C. These results indicate that the sewage sludge-derived material via microwave induced ZnCl₂ activation is an effective and alternative adsorbent for the removal of Cu(II) from aqueous solution.     

Study on copper precipitation during continuous heating and cooling of HSLA steels using electrical resistivity

Abstract

Electrical resistivity technique was used to study the phase transformation and copper precipitation during continuous heating and cooling of three Cu bearing high strength low alloy (HSLA) steels. Dilatation measurements were performed to compare the results with the resistivity. During heating, the dilatation plot revealed Ac₁ and Ac₃ temperature, while resistivity measurements indicated precipitation of copper in the range of 370–550°C. A method was demonstrated to estimate the amount of copper precipitation during continuous heating. During continuous cooling, the austenite transformation temperatures could be derived from resistivity, which compare well with dilatometry. A hysteresis between heating and cooling curve was noted possibly owing to formation of bainite during cooling. Non-isothermal kinetic analysis of dilatation data during continuous cooling yields an activation energy of 62 kJ mol^?1, which could be related to the formation of bainite, whereas higher activation energy of 237 kJ mol^?1 obtained from resistivity data may correspond to the diffusion of Cu in iron, associated with the copper precipitation during austenite transformation.     

Effect of mechanical activation on the reactivity of powder copper

Mechanical activation is found to enhance the reactivity of copper powder with acetic acid. The milling-induced increase in the thermal effect of the reaction between Cu and acetic acid is shown to be associated with the activation of the molecular oxygen involved in the reaction. The activation is due to the presence of lattice oxygen with increased bond energies.Translated from Neorganicheskie Materialy, Vol. 41, No. 2, 2005, pp. 151–161.Original Russian Text Copyright © 2005 by Poluboyarov, Lapin, Korotaeva, Prosvirin, Bukhtiyarov, Sirotkina, Kobotaeva.     

Tensile properties of ultrathin copper films and their temperature dependence

The molecular dynamics simulations are performed with single-crystal copper thin films under uniaxial tensile loading to investigate temperature effects on the mechanical responses. We found that with increasing sample temperatures, both the maximum stress and the Young’s modulus decrease, but the maximal potential energy increases. So, we identified the critical temperature for the transition of deformation mechanism. Then, the deformation was analyzed by examining the variation of the atomic structure of the emerging dislocation. Finally, activation volume and activation free energy of tensile deformation at the maximum stress point of thin Cu film have been calculated for the first time in a temperature range from 293 to 460 K. Thus, the mechanisms of the strange temperature dependence of tensile deformation have been explained. It is found that there exist three temperature regions, which correspond to different thermal activation mechanisms of dislocation motion. When the temperature is above 370 K, the rate-controlling mechanism is dislocation climbing; when below 370 K, the mechanism is mainly characterized by the overcoming of Peierls–Nabarro barrier and a few localized pinnings; and when about 370 K, the mechanism is pipe diffusion.