Grain Size Of Cu Research Articles

Effect of Mo nanoparticles on microstructure and mechanical properties of Cu alloys by self-propagating and spark plasma sintering

Cu alloys strengthened with Mo nanoparticle, with Mo contents of 2 at.%, 4 at.%, 6 at.%, 8 at.%, and 10 at.%, were fabricated by self-propagating high-temperature synthesis, followed by two-step hydrogen reduction and spark plasma sintering. The microstructures, mechanical properties, and thermal conductivity of these Cu-Mo alloys were investigated. The results reveal that two-step hydrogen reduction effectively reduces the average Mo particle size to 13.8 nm compared to one-step reduction. With increasing Mo content, the average grain size of Cu initially decreases but then increases due to the segregation of Mo particles. Notably, the Cu-6 at.% Mo alloy exhibits the smallest average grain size of 0.46 μm, with dispersed nanoscale Mo particles of 25.6 nm. The Cu-6 at.% Mo alloy demonstrates superior mechanical properties, with a tensile strength of 405.0 MPa and an elongation of 24.9 %. Furthermore, the Cu-6 at.% Mo alloy has a high thermal conductivity of 320.0 Wm−1K−1 even at 400 °C and a high electrical conductivity of 82.3 % IACS at room temperature. This work offers valuable insights for the design of advanced Cu composites suitable for heat sink applications.

Effect of annealing temperature on interface diffusion behavior of ultra-thin Cu/Al composite sheet by secondary micro-rolling

In this paper, the effect of different annealing temperatures on the interface diffusion behavior of ultra-thin Cu/Al composite sheets was studied. The ultra-thin Cu/Al composite sheet of 0.04 mm was successfully prepared by micro-rolling. The results show that with the increase of annealing temperature, the thickness of diffusion layer increases and the grain size of Cu and Al increases, the interface diffusion of Cu/Al becomes more sufficient. Comparison of diffusion layer thickness between secondary micro-rolling ultra-thin Cu/Al composite sheet and primary micro-rolling ultra-thin Cu/Al composite sheet at the same annealing temperature, the thickness of the interface diffusion layer decreases at the annealing temperature of 360℃ and 400℃, but increases at the annealing temperature of 440℃. The intermetallic compounds CuAl2, Cu4Al and Cu9Al4 are formed at the annealing temperature of 360, 400 and 440℃ after primary micro-rolling ultra-thin Cu/Al composite sheet. Intermetallic compounds CuAl2, Cu4Al and Cu9Al4 were formed at the annealing temperature of 360℃, and intermetallic compounds CuAl2, Cu4Al, Cu9Al4 and CuAl were formed at at the annealing temperature of 400℃ and 440℃ after secondary micro-rolling of ultra-thin Cu/Al composite sheet.

Effect of Trace Elements on the Thermal Stability and Electrical Conductivity of Pure Copper

Abstract: The impact of introducing trace transition elements on the thermal stability and conductivity of pure copper was examined through metallographic microscopy (OM), transmission electron microscopy (TEM), and electrical conductivity measurements; the interaction between trace transition element and trace impurity element S in the matrix was analyzed. The results show that the addition of trace Ti and trace Cr, Ni, and Ag elements significantly enhances the thermal stability of the pure copper grain size. After high-temperature treatment at 900 °C/30 min, the grain sizes of Cu, Cu-Ti-S, and Cu-Cr-Ni-Ag-S were measured and found to be 200.24 μm, 83.83 μm, and 31.08 μm, respectively, thus establishing a thermal stability ranking of Cu-Cr-Ni-Ag-S > Cu-Ti-S > Cu. Furthermore, the conductivities of pure copper remain high even after the addition of trace transition elements, with recorded values for Cu, Cu-Ti-S, and Cu-Cr-Ni-Ag-S of 100.7% IACS, 100.2% IACS, and 98.5% IACS, respectively. The enhancement of thermal stability is primarily attributed to the pinning effect of the TiS and CrS phases, as well as the solid solution dragging of Ni and Ag elements. Trace Ti and Cr elements can react with S impurities to form a hexagonal-structure TiS phase and monoclinic-structure CrS phase, which are non-coherent with the matrix. Notably, the CrS phase is smaller than the TiS phase. In addition, the precipitation of these compounds also reduces the scattering of free electrons by solute atoms, thereby minimizing their impact on the alloy’s conductivity.

Enhanced thermal expansion with nanocrystalline Cu in SiO2 vias for hybrid bonding

The thermal expansion of copper pads within dielectric vias plays a crucial role during hybrid bonding. In this paper, we tailored the thermal expansion of Cu pads by modifying the grain size of Cu, and adopted in-situ heating atomic force microscopy (AFM) to measure their surface profiles at room temperature, 100, 150, and 200 °C. Results showed that by reducing the grain size from 2.5 μm to 0.15 μm, the expansion (8.4 nm) of nanocrystalline Cu pads at 200 ℃ increased to more than twice that of coarse-grained Cu counterparts (3.7 nm). This significant enhancement in Cu expansion is critical for enlarging the process window of hybrid bonding in 3D IC fabrication. Microstructural differences and significant plastic deformation in the nanocrystalline Cu pads further indicate the dominance of Coble creep, resulting in the discrepancy in total expansion. Additionally, the thermal expansion of nanocrystalline Cu pads with (111)-preferred orientation was investigated. Their higher-than-expected expansion offers the potential for high-quality hybrid bonding.

Characterization of residual-resistance-ratio of Cu stabilizer in commercial REBCO tapes

Residual-resistance-ratio (RRR) of Cu stabilizer in REBCO coated conductor is an important design parameter for REBCO magnets. Cu stabilizer with high RRR is especially beneficial for quench protections of REBCO magnets. In this work, we study RRR of electroplated Cu stabilizer in commercial REBCO tapes. We present RRR of over 180 samples measured for the quality assurance programs of REBCO magnet projects at the National High Magnetic Field Laboratory, USA (NHMFL). To investigate the factors that influence RRR, several samples were analyzed extensively by using scanning electron microscopy, secondary ion mass spectroscopy, and inductively coupled plasma mass spectroscopy. We found that RRR is strongly correlated with the grain size of Cu, which suggests that resistivity at low temperatures is dominated by grain boundary resistivity. In addition, low RRR corresponds to high concentration of chlorine impurity. This is explained by that higher chlorine impurity hindered the grain growth in the self-annealing process at room temperature which resulted in smaller grain size and low RRR. Annealing at 300C significantly enlarged the grain size and enhanced RRR. Due to the concern of critical current degradation, however, annealing is not recommended as a practical method to improve RRR of Cu in REBCO tapes.

Effect of Heat Treatment on the Interfacial Structure and Microstructure of Al/Al/Cu Composites Prepared by Different Accumulative Roll Bonding Passes

The effects of heat treatment ((300–500 °C) × 30 min) on the interfacial structure, microstructure, and tensile properties of Al4343/Al3003/Cu composites prepared by different accumulative roll bonding (ARB) passes are studied by scanning electron microscopy, energy dispersion spectrometry, electron backscattered diffraction, and tensile tests at room temperature. The results show that the total thickness of the diffusion layer at the Al3003/Cu interface in the same ARB pass Al/Al/Cu composite increases with the increase in temperature. At the same temperature, the total thickness of the diffusion layer at the Al3003/Cu interface increases from ARB0 to ARB3 passes and decreases at ARB5 passes. In the same ARB pass Al/Al/Cu composites, the grains of Al4343 grow with the increase of temperature; the grain of Al3003 increases slightly from 300 to 400 °C, and grows along the interface direction after 500 °C. After 400 and 500 °C, the final average grain size of Cu decreases from ARB0 to ARB3 passes and increases slightly at ARB5 passes. The tensile properties of the composites are affected by recovery and recrystallization at lower temperatures and ARB passes, and by the total thickness and volume fraction of the diffusion layer at higher temperatures and ARB passes.

Influences of solution treatments on the microstructure and mechanical properties of TiCx-Cu (x = 0.5, 0.6, 0.7) cermets prepared by infiltration method

In this study, TiCx-Cu (x = 0.5, 0.6, 0.7) cermets were prepared combined with subsequent solution treatment, and the influences of solution treatment on the microstructures and mechanical properties were analyzed. The fracture mechanisms of cermets before and after solution treatment were mainly observed and analyzed. The results show that solution treatment can significantly improve the comprehensive mechanical properties of TiCx-Cu cermets. The fracture toughness KIC of TiC0.5-Cu and TiC0.7-Cu cermets increased by 28% and 11%, respectively. The improvements of the comprehensive properties of TiCx-Cu cermets were benefited by the reduction of the content of hard brittle intermetallic compound Cu4Ti and the refinements of the grain size of Cu.

Effects of annealing temperature on interface microstructure and element diffusion of ultra-thin Cu/Al composite sheets

In this research, the ultra-thin Cu/Al metallic composite sheets of 0.06 ∼ 0.09 mm were successfully prepared by the self-designed four-high laboratory micro mill. The cold rolling reduction of single pass was up to 70%. The effect of different annealing temperatures on microstructure and element diffusion of the Cu/Al composite sheet interface was investigated at the microscale. The results show that with the increase of annealing temperature, the average grain size of Cu and Al increases gradually, the mutual diffusion of Cu/Al elements increases. Compared with the macroscale, the grain refinement of the ultra-thin Cu/Al composite sheets can promote the interdiffusion of Cu and Al elements. When the annealing temperature was 350 ∼ 450 °C, a relatively large number of micropores and microcracks appeared at the interface of Cu/Al composite sheet. When the annealing temperature was 350 °C, a diffusion layer was formed at the interface of the ultra-thin Cu/Al composite sheet, and the interface bonding method was metallurgical bonded. When the annealing temperature was 500 °C, the mutual diffusion degree of elements was the largest at the interface.

Low-Temperature (70°C) Cu-to-Cu Direct Bonding by Capping Metal Layers

Cu-Cu direct bonding at low temperature with Cr wetting layer and Au passivation has been developed, and the bonding mechanism has been investigated. A chip-level Cu-to-Cu direct bonding can be achieved under a very low thermal budget condition at 70 °C for 90 s or 150 °C for 15 s, while wafer level bonding can be achieved at 100 °C under a low vacuum environment ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-{2}}$ </tex-math></inline-formula> Torr) by deposition of capping metal layers, which can protect Cu from oxidation, as well as reduce surface roughness and grain size of Cu. During the bonding process, Cu atoms diffuse through Cr/Au layers into the bonding interface, forming a new inter-layer without voids to achieve high quality bonding. The phenomenon of recrystallization and effects of grain size have been validated by TEM analyses. This Cu-Cu bonding with capping metal layers scheme can enable bonding with ultra-low thermal budget, excellent bonding quality, good electrical performance and high reliability, showing the great feasibility for the 3D integration applications.

Morphological analysis of Cu substituted Ni\Zn in Ni-Zn ferrites

Cu substituted Ni in Ni0.5-xCuxZn0.5Fe2O4 (x = 0, 0.05, 0.1, 0.15 and 0.2) samples and Cu substituted Zn in Ni0.5Zn0.5−xCuxFe2O4 (x = 0, 0.05, 0.1, 0.15 and 0.2) is synthesized using the sol-gel auto-combustion process. Recently, we have carried out their structural analysis using XRD and FTIR and found a cubic spinel structure. In this paper, we have studied their morphological and compositional structure with the help of a Scanning Electron Microscope (SEM) attached with an Energy Dispersive Spectrometer (EDS). The comparative study shows that the grain size of Cu substituted Ni is greater than Cu substituted Zn in Ni-Zn ferrite. These smaller grain-sized ferrites are preferred for many microstructural applications. Depending on the available magnetic field, sintering temperature, and atmosphere, they can have different nucleation, and hence their application mode is different. They can have a critical concentration that can tune their properties. The EDS attached with the SEM confirmed the proper composition of samples.&#x0D; BIBECHANA 18 (2) (2020) 80-86

Facile Synthesis, Diffused Reflectance Spectroscopy & Fluorescence Studies of Ni0.5-xMg0.5CuxFe2O4 Nanoparticles.

The present study focused on the structural, morphological, optical and fluorescence properties of Ni0.5-xMg0.5CuxFe2O4 (x = 0.0, 0.1, 0.3 and 0.5) nanoparticles synthesized by using auto combustion technique. The structural formation of the ferrite nanoparticles were confirmed by FTIR spectroscopic study. From FTIR spectra of the synthesized ferrite nanoparticles, metal ions are situated in two different sub lattices i.e. tetrahedral (A-site) and octahedral (B-site) in ferrites. The surface morphology and grain size of Cu substituted Ni-Mg ferrite nanoparticles were estimated from the micrographs of atomic force microscopy (AFM); the maximum grain size 54.69 nm was obtained. Spectra of UV-Visible absorption of the synthesized ferrite nanoparticles were carried-out by using UV-Vis spectrophotometry; the maximum absorption was observed at 418 nm. The energy band gap of ferrite nanoparticles has been estimated using UV-Vis absorption spectra; the energy band gap 3.50eV was obtained. From the fluorescence emission spectraof thesynthesized ferrite nanoparticles, ferrite samples emit red colour in the region of 680 nm.

Quasi-gradient variation of microstructures and properties of Cu–Sn alloy along the thickness direction under cold spinning

Abstract During cold spinning, the grain size, grain boundary angle and tensile strength of Cu– Sn alloy show quasi gradient changes in the thickness direction (TD) of hollow cylinder. According to a mechanical analysis, electron backscattering diffraction observations (EBSD), and a finite element simulation, the grain size of Cu–Sn alloy after spinning increases from the outer surface to the inner surface. The number of ultrafine grains was largest on the outer surface, and the original grain boundaries were retained on the inner surface. All of the grain orientations from the outer surface to the inner surface were randomly distributed. An analysis of the grain misorientation suggested that low-angle grain boundaries (LAGBs; 10°) was inversely proportional to that of LAGBs, the grain boundary energy (GBE) of the HAGBs decreased with increasing number of LAGBs, and the number of HAGBs also decreased gradually. According to tensile tests at room temperature, the outer surface exhibited the highest ultimate tensile strength and the inner surface exhibited the greatest plasticity.

Effect of annealing treatment on the dry sliding wear behavior of copper

The effect of annealing on the wear behavior of commercial grade pure copper (Cu) was evaluated by performing unlubricated pin-on-disc wear tests of as–received and annealed samples under 0.1–10 kgf normal load. It was found that annealing at 800 °C for 24 h led to an increase of grain size of Cu from ~ 6.7 to ~ 15.3 µm and a decrease in hardness. Wear rates of both samples increased while the friction coefficients decreased with increasing normal load. Subsurface microstructure evolution and wear debris were characterized by high resolution electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) after wear tests. Dynamic recrystallization and abnormal subsurface grain growth were observed in both samples under high load. Finally, the effect of annealing on the microstructure evolution and wear resistance of Cu were discussed.

Stabilizing the metastable γ phase in Ga2O3 thin films by Cu doping

The metastable cubic γ phase Ga2O3 with a defect spinel structure presents several fascinating properties, which may be a more attractive material than the stable β form. Herein, we found that the metastable γ-Ga2O3 can be stabilized by copper (Cu) doping through a simple operation and low cost method of sol-gel. The γ-Ga2O3 thin films were prepared under the annealing of 700 °C in nitrogen atmosphere for Cu doping. The β phase Ga2O3 ones were obtained at the same condition without the Cu dopant. While the Cu doped γ phase Ga2O3 will transform to β phase for a high annealing temperature above 800 °C. The grain size of Cu doped γ-Ga2O3 and undoped β-Ga2O3 thin films increases with the increase of the annealing temperature. The UV–Vis absorption spectrum of the β-Ga2O3 thin film exhibits a sharp intrinsic absorption edge at ∼250 nm, whilst Cu doped γ-Ga2O3 thin film displays an obvious red-shift. The band gap decreases from 4.90 eV to 4.38 eV for the Cu doping. The photoluminescence intensity at the ultraviolet and blue region of Cu doped γ-Ga2O3 thin films are stronger than undoped β-Ga2O3, which can be attributed to the introduction of more defects such as oxygen vacancies in γ phase by Cu doping.

Two-stage method to enhance the grain size of Cu(In,Ga)Se2 absorbers based on sputtering quaternary Cu(In,Ga)Se2 target

Preparing CIGS thin films with grain size above 1 μm based on quaternary CIGS target is difficult, which is a barrier for the further enhancement of CIGS cell efficiency. We proposed a two-stage method to overcome this problem. Cu-rich CIGS thin film was prepared from quaternary CIGS and Cu target and then converted into Cu-poor CIGS by depositing the In2Se3 layer on the Cu-rich CIGS with the subsequent annealing. CIGS absorbers with micrometer-sized crystal based on quaternary CIGS target was prepared. The influence of the In2Se3 deposition on the physical properties of the CIGS absorber and CIGS cells has been investigated. The thickness of In2Se3 layer has been optimized which can result in the highest conversion efficiency of 9.5% in Cu-rich CIGS based solar cells.

Grain Refinement and Mechanical Properties of Cu-Cr-Zr Alloys with Different Nano-Sized TiCp Addition.

The TiCp/Cu master alloy was prepared via thermal explosion reaction. Afterwards, the nano-sized TiCp/Cu master alloy was dispersed by electromagnetic stirring casting into the melting Cu–Cr–Zr alloys to fabricate the nano-sized TiCp-reinforced Cu–Cr–Zr composites. Results show that nano-sized TiCp can effectively refine the grain size of Cu–Cr–Zr alloys. The morphologies of grain in Cu–Cr–Zr composites changed from dendritic grain to equiaxed crystal because of the addition and dispersion of nano-sized TiCp. The grain size decreased from 82 to 28 μm with the nano-sized TiCp content. Compared with Cu–Cr–Zr alloys, the ultimate compressive strength (σUCS) and yield strength (σ0.2) of 4 wt% TiCp-reinforced Cu–Cr–Zr composites increased by 6.7% and 9.4%, respectively. The wear resistance of the nano-sized TiCp-reinforced Cu–Cr–Zr composites increased with the increasing nano-sized TiCp content. The wear loss of the nano-sized TiCp-reinforced Cu–Cr–Zr composites decreased with the increasing TiCp content under abrasive particles. The eletrical conductivity of Cu–Cr–Zr alloys, 2% and 4% nano-sized TiCp-reinforced Cu–Cr–Zr composites are 64.71% IACS, 56.77% IACS and 52.93% IACS, respectively.

Microstructure Evolution and Protrusion of Electroplated Cu-Filled Through-Silicon Vias Subjected to Thermal Cyclic Loading

Through-silicon vias (TSVs) have become an important technology for three-dimensional integrated circuit (3D IC) packaging. Protrusion of electroplated Cu-filled vias is a critical reliability issue for TSV technology. In this work, thermal cycling tests were carried out to identify how the microstructure affects protrusion during thermal cycling. Cu protrusion occurs when the loading temperature is higher than 149°C. During the first five thermal cycles, the grain size of Cu plays a dominant role in the protrusion behavior. Larger Cu grain size before thermal cycling results in greater Cu protrusion. With increasing thermal cycle number, the effect of the Cu grain size reduces and the microstrain begins to dominate the Cu protrusion behavior. Higher magnitude of microstrain within Cu results in greater protrusion increment during subsequent thermal cycles. When the thermal cycle number reaches 25, the protrusion rate of Cu slows down due to strain hardening. After 30 thermal cycles, the Cu protrusion stabilizes within the range of 1.92 μm to 2.09 μm.

Size Control of Copper Grains by Optimization of Additives to Achieve Flat-Top Copper Pillars through Electroplating

An acidic cupric sulfate bath containing chloride ions, bis(3-sulfopropyl) disulfide (SPS), polyethylene glycol (PEG), and Janus Green B was employed to control the brightness of Cu films and the size of Cu grains for flat-top Cu pillars during a fast plating process. The plating potential, brightness of Cu films, and size of Cu grains were dominated by SPS and slightly affected by PEG at a current density of 5 A⋅dm−2. A shiny mirror-like Cu film with small Cu grains was formed upon increasing the concentration of SPS and PEG to 9 and 600 ppm, respectively; however, larger Cu grains and nodules were formed on the electrode surface when a current density of 7.5 A⋅dm−2 was applied. Using pulse experiments, we demonstrated that the size of the larger Cu grains and nodules can be reduced if the PEG molecules have sufficient time to adsorb on the surface of the electrode. In addition, the grain size of Cu decreased with decreasing the agitation speed if DC plating was used. A flat-top Cu pillar was achieved at a current density of 7.5 A⋅dm−2 when the additives were used at an optimized concentration.

Effect of pH value and calcination temperature on synthesis and characteristics of Cu–Ni nano-alloys

Cu–Ni nano-alloys were prepared using precursors synthesized by the citrate-gel method. The effects of initial solution pH value and calcination temperature on the composition, crystalline structure, purity, morphology, homogeneity and grain size of Cu–Ni nanoparticles were investigated. Both the parameters significantly affect the crystalline structure, composition and grain size. Cu–Ni alloys prepared at pH value of 1 do not contain impurities, and their compositions are Cu0.42Ni0.58, Cu0.45Ni0.55 and Cu0.52Ni0.48 reduced at 300, 400 and 500 °C, respectively. The grain size grows with the increase of calcination temperature for the precursor prepared at pH values of 1.6 and 3. The Ni content of the alloys gradually increases with the increase of calcination temperature at pH value of 3.

Influence of temperature on the mechanical alloying of Cu–Nb powder mixtures

This study focuses on the mechanical alloying behaviour of equiatomic Cu–Nb powder mixtures subjected to ball milling at temperatures between 300 and 900K. A homogeneous amorphous phase forms at room temperature. The increase of processing temperature promotes the formation of mixtures of amorphous and nanostructured Cu and Nb phases below 650K, and of nanostructured Cu–Nb composites above 650K. The grain size of Cu and Nb phases increases with temperature according to a power-law kinetics.