Interfacial microstructure and hardness of nickel (Ni) nanoparticle-doped tin–silver–copper (Sn–Ag–Cu) solders on immersion silver (Ag)-plated copper (Cu) substrates

Sn–Ag–Cu composite solder has been prepared by adding Ni nanoparticles. Interfacial reactions, the morphology of the intermetallic compounds (IMC) that were formed, the hardness between the solder joints and the plain Cu/immersion Ag-plated Cu pads depending on the number of the reflow cycles and the aging time have all been investigated. A scallop-shaped Cu₆Sn₅ IMC layer that adhered to the substrate surface was formed at the interfaces of the plain Sn–Ag–Cu solder joints during the early reflow cycles. A very thin Cu₃Sn IMC layer was found between the Cu₆Sn₅ IMC layer and the substrates after a lengthy reflow cycle and solid-state aging process. However, after adding Ni nanoparticles, a scallop-shaped (Cu, Ni)–Sn IMC layer was clearly observed at both of the substrate surfaces, without any Cu₃Sn IMC layer formation. Needle-shaped Ag₃Sn and sphere-shaped Cu₆Sn₅ IMC particles were clearly observed in the β-Sn matrix in the solder-ball region of the plain Sn–Ag–Cu solder joints. Additional fine (Cu, Ni)-Sn IMC particles were found to be homogeneously distributed in the β-Sn matrix of the solder joints containing the Ni nanoparticles. The Sn–Ag–Cu–0.5Ni composite solder joints consistently displayed higher hardness values than the plain Sn–Ag–Cu solder joints for any specific number of reflow cycles–on both substrates–due to their well-controlled, fine network-type microstructures and the homogeneous distribution of fine (Cu, Ni)–Sn IMC particles, which acted as second-phase strengthening mechanisms. The hardness values of Sn–Ag–Cu and Sn–Ag–Cu–0.5Ni on the Cu substrates after one reflow cycle were about 15.1 and 16.6 Hv, respectively–and about 12.2 and 14.4 Hv after sixteen reflow cycles, respectively. However, the hardness values of the plain Sn–Ag–Cu solder joint and solder joint containing 0.5 wt% Ni nanoparticles after one reflow cycle on the immersion Ag plated Cu substrates were about 17.7 and 18.7 Hv, respectively, and about 13.2 and 15.3 Hv after sixteen reflow cycles, respectively.     

Long-term and controlled release of chlorhexidine–copper(II) from organically modified montmorillonite (OMMT) nanocomposites

Drug/metal ion complexes exhibit improved antimicrobial activity and intercalating the above complexes into the interlayer of clay endows a long-term and controlled-release behavior. In this study, chlorhexidine was first complexed with copper (II) ion and then intercalated into the interlayer of MMT to form chlorhexidine–copper (II)/montmorillonite (CHX–Cu/MMT) nanocomposites. The nanocomposites were characterized with Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). A nearly lateral-monolayer arrangement of CHX–Cu was supposed for the intercalation. Release kinetics indicated that the release process satisfied a pseudo-second-order mode. The antibacterial results showed that the CHX–Cu/MMT composites had long-term and controlled-release behavior.     

Influence of cerium oxide (CeO2) nanoparticles on the microstructure and hardness of tin–silver–copper (Sn–Ag–Cu) solders on silver (Ag) surface-finished copper (Cu) substrates

Nano-sized, non-reacting, non-coarsening CeO₂ particles with a density close to that of solder alloy were incorporated into Sn–3.0 wt%Ag–0.5 wt%Cu solder paste. The interfacial microstructure and hardness of Ag surface-finished Cu substrates were investigated, as a function of reaction time, at various temperatures. After the initial reaction, an island-shaped Cu₆Sn₅ intermetallic compound (IMC) layer was clearly observed at the interfaces of the Sn–Ag–Cu based solders/immersion Ag plated Cu substrates. However, after a prolonged reaction, a very thin, firmly adhering Cu₃Sn IMC layer was observed between the Cu₆Sn₅ IMC layer and the substrates. Rod-like Ag₃Sn IMC particles were also clearly observed at the interfaces. At the interfaces of the Sn–Ag–Cu based solder-Ag/Ni metallized Cu substrates, a (Cu, Ni)–Sn IMC layer was found. Rod-like Ag₃Sn and needle-shaped Cu₆Sn₅ IMC particles were also observed on the top surface of the (Cu, Ni)–Sn IMC layer. As the temperature and reaction time increased, so did the thickness of the IMC layers. In the solder ball region of both systems, a fine microstructure of Ag₃Sn, Cu₆Sn₅ IMC particles appeared in the β-Sn matrix. However, the growth behavior of the IMC layers of composite solder doped with CeO₂ nanoparticles was inhibited, due to an accumulation of surface-active CeO₂ nanoparticles at the grain boundary or in the IMC layers. In addition, the composite solder joint doped with CeO₂ nanoparticles had a higher hardness value than the plain Sn–Ag–Cu solder joints, due to a well-controlled fine microstructure and uniformly distributed CeO₂ nanoparticles. After 5 min of reaction on immersion Ag-plated Cu substrates at 250 °C, the micro-hardness values of the plain Sn–Ag–Cu solder joint and the composite solder joints containing 1 wt% of CeO₂ nanoparticles were approximately 16.6 and 18.6 Hv, respectively. However after 30 min of reaction, the hardness values were approximately 14.4 and 16.6 Hv, while the micro-hardness values of the plain Sn–Ag–Cu solder joints and the composite solder joints on Ag/Ni metallized Cu substrates after 5 min of reaction at 250 °C were approximately 15.9 and 17.4 Hv, respectively. After 30 min of reaction, values of approximately 14.4 and 15.5 Hv were recorded.     

Manufacture of copper weapons and tools from the chalcolithic settlement of São Pedro (Portugal)

ABSTRACT

A collection of 30 copper-based artefacts recovered during archeological excavations at the São Pedro settlement (Redondo, Portugal) was characterized by optical microscopy and Vickers microhardness testing. The radiocarbon dating of bone samples and the existence of Bell Beaker ceramics establish a chronology of c. 2700–2000 BC for tools and weapons made of copper with varying arsenic contents. The manufacture included one or more cycles of forging and annealing, while final work hardening was uncommon. The collection shows a wide range of hardness (52–142 HV0.2) without any correlation with typology or arsenic content, suggesting unawareness of the hardening potential of this alloying element. Technological features of São Pedro artefacts were compared with those of coeval metallurgies from neighboring regions (Portuguese Estremadura and Southern Andalusia) revealing common and distinctive characteristics that help to understand the use of arsenical copper alloys among communities of the third millennium BC.     

Microstructure and kinetic analysis of the properties and behavior of nickel (Ni) nano-particle doped tin–zinc–bismuth (Sn–8Zn–3Bi) solders on immersion silver (Ag)-plated copper (Cu) substrates

In order to identify the effect on the properties and behavior of tin–zinc–bismuth (Sn-8 wt% Zn-3 wt% Bi or Sn-13.6 at.% Zn-1.6 at.% Bi) based solders produced by adding nickel (Ni) nano-particles, the interfacial microstructure between plain and composite solders with newly developed immersion silver (Ag) plated copper (Cu) substrates has been investigated as a function of reaction time, at various temperatures. For plain Sn–8Zn–3Bi solder joints, a scallop-shaped Cu–Zn–Ag intermetallic compound layer was found to adhere to the surface of the immersion Ag-plated Cu substrate. However, after addition of Ni nano-particles into the Sn–8Zn–3Bi solder, Cu–Zn–Ag (at the bottom) and (Cu, Ni)–Zn (at the top) intermetallic compound layers were observed at the interfaces. In addition, these intermetallic compound layer thicknesses increased substantially with increases in the temperature and reaction time. In the solder ball region, needle-shaped α-Zn rich phase and spherically-shaped Bi-particles appeared to be homogeneously distributed throughout a beta-tin (β-Sn) matrix. However, after the addition of Ni nano-particles, needle-shaped α-Zn rich phase appeared that exhibited a fine microstructure, due to the heterogeneous nucleation of the Ni nano-particles. The calculated activation energy for the Cu–Zn–Ag intermetallic compound layer for the plain Sn–8Zn–3Bi solder/immersion Ag-plated Cu system was 29.95 kJ/mol—while the activation energy for the total [Cu–Zn–Ag + (Cu, Ni)–Zn] intermetallic compound layers formed in the Sn–8Zn–3Bi–0.5Ni (Sn-13.6 at.% Zn-1.6 at.% Bi ~1 at.% Ni) composite solder/immersion Ag-plated Cu system was 27.95 kJ/mol. Addition of Ni nano-particles reduces the activation energy which enhanced the reaction rate as we know that lower the activation energy indicates faster the reaction rate.     

测试(measurement and test)

具有试验性质的测量。一般认为，计量器具示值的检定或校准，有规范化的技术文件可依，可以通称为测量或计量，而除此以外的测量，尤其是对不属于计量器具的设备、零部件、元器件的参数或特性值的确定，其方法具有试验性质，一般就称为测试。测试(measurement and test)     

Poly(acrylonitrile-co-itaconic acid)–poly(3,4-ethylenedioxythiophene) and poly(3-methoxythiophene) nanoparticles and nanofibres

This work aimed to produce poly(acrylonitrile-co-itaconic acid) (P(AN-co-IA)) nanocomposites with poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3-methoxythiophene) (PMOT). An anionic surfactant sodium dodecyl benzene sulphonate was used in emulsion polymerization for nanocomposite production. Incorporations of PEDOT and PMOT on the nanoparticles were characterized by scanning electron microscopy (SEM), atomic force microscopy, Fourier transform infrared-attenuated total reflectance spectroscopy and ultra-violet spectroscopy. These nanoparticles were blended with PAN and the blends were electrospun to produce P(AN-co-IA)–polythiophene-derivative-based nanofibres, and the obtained nanofibres were characterized by SEM and energy dispersive spectroscopy. In addition, electrochemical impedance studies conducted on nanofibres showed that PEDOT and PMOT in matrix polymer P(AN-co-IA) exhibited capacitive behaviour comparable to that of ITO–PET. Their capacitive behaviour changed with the amount of electroactive polymer.     

The corrosion and wear resistances of magnesium alloy (LZ91) electroplated with copper and followed by 1 μm-thick chromium deposits

The Mg-Li-Zn alloy, LZ91, is a potential material for industrial application owing to its high specific strength. However, the LZ91 has so high chemical reactivity that it is easily corroded in air and an aqueous environment. In this study, an eco-friendly electrodeposition method was proposed to obtain a protective Cr/Cu coating on the LZ91 substrate. That is, the LZ91 surface electroplated a Cu undercoat in an alkaline Cu-plating bath and followed by decorative 1 μm-thick Cr electroplating in a plating bath with trivalent chromium ions. After electroplating, some of the Cr/Cu-deposited specimens were heated with a reduction flame for 0.5 s to increase the hardness of Cr-deposit. The wear resistance of as-plated and flame-hardened Cr/Cu-coated LZ91 specimens was estimated with ball-on-plate wear tester by using a steel-ball counterpart. Whereas, their corrosion resistance was evaluated in a 0.1 M H₂SO₄ solution before and after wear test. Experimental results show that a Cu deposit could be uniformly electroplated on the LZ91 surface by using our proposed electroplating method. The corrosion resistance of LZ91 was markedly improved after decorative 1 μm-thick Cr electroplating. After wear test, the steel counterpart was ground obviously with either as-plated or flame-hardened Cr/Cu-coated LZ91 specimen. According to the results of electrochemical corrosion test, some parts of the Cr deposit were peeled off from worn flame-hardened Cr/Cu LZ91 surface. This reduces its corrosion resistance significantly. On the other hand, the corrosion resistance of as-plated Cr/Cu LZ91 was not changed after wear test. That is, an as-plated Cr/Cu-coated LZ91 specimen could have good corrosion and wear resistance.     

Nanostructured copper–steel microlaminates: preparation and mechanical properties

The evolution of the mechanical properties of multilayer copper–iron composites with a number of layers of 11 to 1620 in annealing at 750°C is described. It has been established that properties of composites composed of more than 300–400 layers depend on their number and the annealing time. We have experimentally confirmed the possibility to develop microlaminates whose mechanical and technological characteristics exceed substantially those of matrix metals.     

Reactive wetting of Sn–2.5Ag–0.5Cu solder on copper and silver coated copper substrates

In the present work, wetting characteristics and morphology of intermetallic compounds (IMCs) formed between Sn–2.5Ag–0.5Cu lead-free solder on copper (Cu) and silver (Ag) coated copper substrates were compared. It was found that, Ag coated Cu substrate improved the wettability of solder alloy. The average values of contact angles of solder alloy solidified on Ag coated Cu substrate were reduced to about 50 % as compared to contact angles obtained on Cu substrates. Flow restrictivity for spreading of solder on Ag coated Cu was found to be lower as compared to Cu substrate. The spreading of solder alloy on Ag coated Cu exhibited halo zone. Coarse needle shaped Cu₆Sn₅ IMCs were observed at the solder/Cu substrate interface whereas at the solder/Ag coated Cu interface Cu₆Sn₅ IMCs showed scallop morphology. The formation of Cu₃Sn IMC was observed for the spreading of solder alloy on both substrates. The solder/Ag coated Cu substrate interface exhibited more particulates of Ag₃Sn precipitates as compared to solder/Cu substrate interface. The improved wettability of solder alloy on Ag coated Cu substrate is due to the formation of scallop IMCs at the interface.     

“String and bead” model of copper modified polycarbosilane: synthesis and applications

Journal of Materials Science - The synthesis of metal modified polycarbosilanes is currently an area of significant activity. These polymers can be processed to advanced materials such as ceramic...     

Some aspects on plastic deformation of copper and copper–titanium carbide powder metallurgy composite preforms during cold upsetting

The densification, workability and strain hardening behaviour of sintered copper and Cu–7.5%TiC powder metallurgy (P/M) composite preforms during cold upsetting were investigated by the constitutive model using the experimental data. Cold upsetting of copper and Cu–7.5% TiC composite preforms having different aspect ratios were carried out and the formability behaviour of the preforms under triaxial stress state was determined. The mechanisms most likely involved in the constitutive model, namely, densification and strain hardening were studied. The effects of aspect ratio and addition of titanium carbide to copper on the formability behaviour and various constants involved in the constitutive model, namely, instantaneous density coefficient, instantaneous strain hardening index, instantaneous strain rate sensitivity and instantaneous strength coefficient were discussed in detail.     

Vapor phase deposition of copper films with a Cu(I) β-diketiminate precursor

This work demonstrates the vapor phase deposition of copper films with a volatile Cu(I) β-diketiminate precursor. X-ray photoelectron spectroscopy (XPS) depth profiles of the deposited films show only background levels of carbon and oxygen. Film thickness depends on the length of precursor pulse, but the surface roughness does not, a result that suggests a uniform deposition. XPS data for the chemisorbed copper precursor show that the copper was in both the metallic and + 1 oxidation states. Chemisorption of the Cu(I) precursor deposited a Cu(I) species. However, disproportionation of some of the chemisorbed Cu(I) precursor generated Cu(0) and a volatile Cu(II) complex, which was removed from the surface. These results are characteristic of a pulsed chemical vapor deposition.     

Eu(3+) doped gadolinium oxysulfide (Gd(2)O(2)S) nanostructures-synthesis and optical and electronic properties

One-dimensional Eu(3+) doped gadolinium oxysulfide (Gd(2)O(2)S:Eu(3+)) nanotubes/nanorods have been synthesized via precursors of Gd(OH)(3) nanostructures using a hydrothermal technique. The blue-shifts in the optical spectra for the Gd(2)O(2)S:Eu(3+) system corresponding to the fundamental absorption and Eu(3+)-X(2-) ligand (X = O/S) charge transfer bands (CTBs) are significant (～0.22-0.36?eV) with respect to the bulk counterpart. The nanotubes are good candidates for investigating the size-induced electrical and optical properties of functional oxysulfides. In order to identify the origin and nature of the electronic transitions observed in the visible region, optical and photo-induced impedance measurements have been extended to the nanotubes in this report.     

A study of copper stoichiometry and phase relationships in the copper-zirconium phosphate system: CuZr2(PO4)3 – Cu0.5Zr2(PO4)3

CuZr₂(PO₄)₃ crystallises with the Nasicon-type structure and is a copper(I) ion conductor. The possibility of a solid solution between CuZr₂(PO₄)₃ and Cu_0.5Zr₂(PO₄)₃ has been a controversial issue for many years. As part of a continued study, CuZr₂(PO₄)₃ and Cu_0.5Zr₂(PO₄)₃ were prepared by solid state methods and used to investigate the copper stoichiometry and phase relationships between these two materials as a function of copper content, temperature and oxygen fugacity. The following reversible reaction: Cu_0.5Zr₂(PO₄)₃ (s) + CuO (s) ↔ CuZr₂(PO₄)₃ (s) + O₂(g) was studied by thermogravimetry in an atmosphere of PO₂ = 0.22 atm and was found to occur at 475 ± 10°C. Thus, CuZr₂(PO₄)₃ is a thermodynamically stable phase in air above ∼475°C, which places a lower temperature limit on its use as an electrolyte in air. The results of X-ray powder diffractometry on materials with various copper contents that had been annealed in argon at 750°C indicate that there is no evidence for a significant solid solution between CuZr₂(PO₄)₃ and Cu_0.5Zr₂(PO₄)₃ nor, a reductive decomposition of Cu_0.5Zr₂(PO₄)₃. The coexistence of CuZr₂(PO₄)₃ and Cu_0.5Zr₂(PO₄)₃ as discrete phases is also supported by evidence from electron spin resonance spectroscopy on these materials, which indicate the presence of copper(II) ions in CuZr₂(PO₄)₃ at a dopant and dispersed level of concentration. The results from energy dispersive X-ray analysis, as well as, the novel use of the fluorescent behaviour of CuZr₂(PO₄)₃ in ultra-violet light as an analytical tool, support the above conclusions.     

Work Functions of Pd_(83.5)Si_(16.5)and Cu_(70)Ti_(30)Glassy Alloys

The work functions before and aftercrystallization of two glassy alloys,Pd_(83.5)Si_(16.5) andCu_(70)Ti_(30) have been measured by means of the con-tact potential difference method in the secondaryelectron field at room temperature under 10~(-5) Pavacuum.The results show that the work functionsof both glassy alloys are higher than those of thecorresponding crystalline alloys.     

Thermal expansion of cross-ply and woven carbon fibre–copper matrix composites

This paper presents thermal expansion data for cross-ply and woven copper matrix–carbon fibre composites (Cu–C_f MMCs) that were prepared by diffusion bonding. Thermal expansion was measured in two perpendicular in-plane directions of plate samples. For cross-ply samples (57 vol.%fibres) the mean coefficient of thermal expansion (CTE) between −20 and 300°C changed from approximately 6.5×10⁻⁶/°C to 3.5×10⁻⁶/°C during heating/cooling. The in-plane CTE increases with decreasing fibre content. Composites with woven arrangement of carbon fibres show a slightly higher CTE at elevated temperature.     

Infinite-layer,T′-Phase,and 1-D-ladder copper oxide compounds

Results of recent research on electron-doped infinite-layer compounds (e.g., Sr_1–xLa_xCuO₂), T-phase compounds (e.g., Nd_2–xCe_xCuO₄), and spin-1/2 quasi-1-D ladder compounds (e.g., Sr₁₄Cu₂₄O₄₁) are presented, including structural and magnetic measurements. Studies of steric effects indicate that superconductivity disappears in both electron-doped systems for values of the in-plane lattice constant below a critical value, a_cr 3.92 Å. Attempts to hole dope both the infinite-layer and T phases are described. For the quasi-1-D ladder compound Sr₁₄Cu₂₄O₄₁, the anisotropic susceptibility of this system and its small gap are discussed. Collaborative studies of these systems using SR, NMR, and other spectroscopies are reviewed.This research was supported by NSF Grant DMR-9158089 and Welch Foundation Grant F-1191.     

Green synthesis of bimetallic copper–silver nanoparticles and their application in catalytic and antibacterial activities

Clean Technologies and Environmental Policy - The present research is focused on the synthesis of copper–silver bimetallic nanoparticles using the extracts from the date palm tree (Phoenix...