Si Cu Alloy Research Articles

Preparation of polymer-derived SiOC-Cu ceramic composites and their tribological performance

Cu-containing silicon oxycarbide (SiOC) ceramic composites have been prepared by thermal pyrolysis of polymeric precursors and subsequent spark plasma sintering at 1600 °C. The resulting composites consist of SiO2, SiC, free carbon, and Cu-Si alloys. The microstructure of the composites has been identified via optical microscope and SEM. The mechanical properties, including the Vickers hardness, nano-indentation hardness, and Young’s modulus, of the SiOC composites have been assessed via indentation methods. The effects of Cu content on the tribological properties of the composites have additionally been investigated under different sliding frequencies against Al2O3 spheres at room temperature. It is shown that the introduction of the Cu-Si alloys is effective in reducing the friction coefficient of the material system, which decreases linearly from 0.27 of monolithic SiOC to 0.15 of SiOC with 7 wt% Cu content at 1 Hz. Raman spectroscopy has highlighted the friction-driven evolution of the free carbon phase in the SiOC ceramics. Finally, a correlation between the sliding frequency, Cu-Si content, and tribological properties of SiOC is established.

Influence of alloying elements and composition on microstructure and mechanical properties of Cu-Si, Cu-Ag, Cu-Ti, and Cu-Zr alloys

This study aims to quantitatively compare the effects of alloying elements on the microstructures and mechanical properties of Cu–Si, Cu–Ag, Cu–Ti, and Cu–Zr binary alloys over an alloying content range up to 2 wt%. The alloys were produced using vacuum arc melting, followed by homogenization and cold-rolling into plates. Subsequently, the annealing response of the cold-rolled plates was examined over a temperature range of 200–700 °C. The as-cast alloys show distinct microstructural features attributable to the alloying elements. Following the homogenization and cold-rolling processes, substantial microstructural transformations were observed. The analysis of mechanical properties revealed that solid solution hardening played a dominant role in increasing strength in Cu–Si alloys. Cu–Ag alloys displayed a minor increase in strength with alloying content, implying the influence of Cu–Ag precipitates on strength. Conversely, Cu–Ti and Cu–Zr alloys demonstrated remarkable strength improvements due to the presence of intermetallic precipitates and grain size reduction. While all other alloys displayed an inverse relationship between strength and elongation with increasing alloying content, the Cu-Si alloys exhibited a simultaneous enhancement of both strength and elongation. This effect can be attributed to the twinning-induced plasticity, brought about by the reduction of stacking fault energy in Cu through the addition of Si.

Phosphorus-doped silicon copper alloy composites as high-performance anode materials for lithium-ion batteries

Silicon (Si) anodes are considered one of the most promising candidates for next-generation lithium-ion batteries, owing to their high theoretical capacity. However, Si-based anodes suffer from significant volume expansion during lithiation, leading to severe mechanical degradation and poor cycling stability. To address these challenges, We developed phosphorus (P)-doped Si-Cu alloy composites via a simple vacuum melting method. The incorporation of Cu3Si in the composites effectively suppressed the volume expansion of Si, while P doping enabled the formation of N-type Si to improve electrical conductivity. In our study, we conducted a comprehensive analysis of the electrochemical performance of the P-doped Si-Cu alloy composites. Among the samples, the P0.5% Si-Cu alloy composite exhibited the most exceptional electrochemical performance, with a capacity of 1048 mAh/g after 60 cycles at the current density of 100 mA/g. Electrochemical impedance spectroscopy (EIS) measurements revealed a lower Rct value of 73.65 Ω for the P0.5% Si-Cu alloy composite compared to 175.2 Ω for the Si-Cu alloy composite. Our theoretical calculations also demonstrated that P doping reduces the energy barrier for lithium-ion diffusion. Our study validated the potential of P-doped Si-Cu alloy composites as high-performance anode materials for lithium-ion batteries and provides new insights into the design of Si-based anodes with improved stability and cycling performance.

Effect of impurity trappers on the distribution and removal of phosphorus from Si with Si-Cu solvent

Titanium (Ti) and calcium (Ca), as trappers, were introduced into copper-alloyed metallurgical grade silicon (MG-Si). The effects of trappers on the segregation behavior and removal efficiency of phosphorus (P) were investigated. It was found that P tended to enrich in the TiSi2 and CaCu2Si2 phases, and quenching above the eutectic temperature of Si-Cu alloy is conducive to the P removal. The corrosion process of the P-enriched phases indicated that Ca addition was in favour of P removal, while Ti addition was opposite. The results suggested that though the addition of Ti and Ca could effectively enrich P in the Si-Cu alloy, the acid sensitivity of P-enriched phases would affect the P removal.

Aging behavior of Cu-rich precipitates in Fe-3% Si-Cu alloy

Fe-3%Si-Cu alloys with different Cu content were aging treated at 500 ∼ 800 °C. In order to study the dynamic behavior of the aging precipitations, the microstructure and the aging precipitation behavior of copper-rich phase in these alloys under different aging heat treatment were tested by OM, TEM technology and Vickers hardness. The results show that the amount of the copper-rich precipitates in the two alloys are gradually increase with the aging time going after aging treated at 600 °C. Within the 103 s aging time, the size of the copper-rich precipitates of the two samples is below 20 nm. When it reaches 105.5 s, the copper-rich precipitates have obvious cluster phenomenon and the size are not more than 100 nm. After being treated with different aging temperature, the hardness of Fe-3% Si-Cu alloys with different copper component increases first and then decreases with time going, with obvious aging hardening peaks. When the aging temperature is 500 °C and the aging time is 104.5 s, the hardness of the two alloys reaches the maximum and they are 264 HV and 238 HV, respectively. The precipitation kinetics curve of the copper-bearing Fe-3% Si-Cu alloy is in the shape of ‘C’, and there is a certain precipitation incubation period. When the aging temperature is 600 ∼ 650 °C, the precipitation incubation period is the shortest. The increase of the copper content in the alloy will shorten the incubation period of the precipitation kinetic curve, increase the precipitation tendency of copper and cause the curve shifted to the left obviously.

Preparation and electrochemical properties of silicon copper alloy for high performance anode

To improve the electrochemical performance of silicon-based anode materials, herein, silicon-copper (Si-Cu) incompatible alloy anode material were prepared via facile chemical reduction and ball milling methods. Subsequently, nitrogen-doped carbon-coated Si-Cu alloy (Si-Cu/N-C) composites were prepared via in-situ polymerization with aniline in the high-temperature calcinations process. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were performed to analyze the physical characterization of these materials. Besides, the electrochemical performance of the catalysis was studied by constant current charging and discharging, cyclic voltammetry and electrochemical AC impedance spectroscopy (EIS). Electrochemical tests demonstrate that Si-Cu anode performs a high electrocatalytic activity when the ratio of Si to Cu is 1.5∶1 and the ball milling time is 7 h. The anode exhibits an initial discharge capacity of 1 018.6 mAh/g and a capacity of 499.2 mAh/g after 100 cycles. After the coating modification, TEM result shows that this composite anode material possesses a core-shell structure. When the coating mass of N-doped carbon is 0.45, the Si-Cu/N-C electrode exhibits an initial discharge capacity of 1 147.7 mAh/g and maintains a specific capacity of 857.9 mAh/g after 100 cycles. Furthermore, the capacity retention rate of Si-Cu/N-C anode increases by 10.8% as compared with that of Si-Cu. The improved electrochemical performance after modification is attributed to the unique core-shell structure of Si-Cu/N-C. On the one hand, the N-doped carbon coating layer not only improves the conductivity, but also reduces the contact resistance between the electrolyte and electrode. On the other hand, the nitrogen doping of Si-Cu/N-C composite can increase the active site of lithium storage on the surface, reduce lithium storage potential and form a stable solid electrolyte interface (SEI) film during the cycling process.

Effect of nickel addition on microstructure, tensile and corrosion properties of cold rolled silicon bronze

In this study, silicon bronze (Cu-Si) with nickel addition was fabricated using double stir casting technique. The influence of nickel addition and cold deformation on the microstructure, hardness, tensile and corrosion properties of the fabricated alloys were investigated. The microstructure of the alloy was evaluated using an optical microscope. Microhardness tester was used to determine the hardness while the tensile property was obtained from the hardness data. Potentiodynamic polarization measurement was used to study corrosion behaviour in 0.5 M H2SO4. The result show that the Ni modified Cu-Si alloys revealed the presence of Cu rich α-phase and δ-Ni2Si precipitates along the α grain boundaries. The δ-Ni2Si precipitates increased with increase in Ni content. The addition of Ni reduces the grain sizes and refine the microstructure. The hardness and tensile strength of the Ni modified Cu-Si increased with an increase in Ni addition from 0.2 to 0.8 wt%. The silicon bronze showed excellent corrosion resistance in a sulfuric acid environment with Ni addition. This is evident from the reduction in corrosion current density (Icorr) with an increase in Ni content.

Si/Cu3Si/Cu composite material synthesized by low cost and high efficiency method as anode materials for lithium-ion batteries

In this work, submicron silicon(Si) particles obtained from ball-milling the broken crystalline Si wafers was modified with nanosized copper(Cu) particles by electroless chemical deposition. As-deposited Si/Cu particles was further annealed by rapid thermal process to attain beneficial SiCu alloy at contact interface. The bare Si, as deposited Si/Cu and Si/Cu3Si/Cu composite particles were made into Li-half cells to measure electrochemical performance. The discharge specific capacity of Si/Cu3Si/Cu composite is up to 997 mAhg−1 at current density of 8.4 Ag−1 (2.0 C), which is over 100% higher than Si. Furthermore, the discharge specific capacity of Si/Cu3Si/Cu composite exhibits 1126 mAhg−1 after 100 cycles under current density of 0.5 C, exceeding that of Si by 216%.Owing to the better conductivity from copper, and interface alloy transitive structure enhancing the combining strength, Si/Cu3Si/Cu composite particles exhibit the excellent electrochemical performance.

Solvent extraction of phosphorus from Si-Cu refining system with calcium addition

Abstract Enhanced removal of P from Si-Cu alloy was obtained by Ca addition. The effectiveness of Ca addition on the phase reconstruction and P gettering in Si-50 wt%Cu alloy was investigated. It was shown that the introduction of Ca can achieve the phase reconstruction of Si-50 wt%Cu alloy by the formation of CaCu2Si2 and CaCu11Si5 phases, which were precipitated in the Cu3Si phase. Dense P was found to homogeneously precipitated in the CaCu2Si2 phase, indicating that the increase in the amount of the CaCu2Si2 phase would collect more P. It was found that the extraction fraction of P was proportional to Ca content in Si-50 wt% Cu alloy. The removal fraction of P was increased from 27% to 82% when the Si-Cu system was doped with 5 wt% Ca. The thermodynamic analysis of P removal was investigated, showing that the Ca addition could effectively decrease the segregation coefficient of P between solid Si and the Si-Cu melt. It was concluded that Ca could be used as an impurity trapper to facilitate the P removal in the Si-Cu alloy.

Mechanochemically Metamorphosed Composites of Homogeneous Nanoscale Silicon and Silicate Oxides with Lithium and Metal Compounds

An active anode material for Li-ion batteries was synthesized using a simple mechanochemical process to minimize the large change in Si volume observed during charge-discharge operation and to compensate for the associated irreversible loss of Li or irreversible capacity loss, which are obstacles to achieve high-performance electrochemical properties during charge-discharge. The composite was mechanochemically milled with Si, lithium oxide, and copper oxide as raw materials; the composite contains Si nanoparticles, amorphous silicon monoxide, and Si-Li or Si-Cu alloy compounds, and it exhibits improved electrochemical properties. In particular, this composite achieved a better capacity retention, higher coulombic efficiency (over 100%), and longer cycling performance than Si alone, indicating considerable optimization of the electrical and ionic conductivity in the composite. The developed method allowed for control of the Li content to compensate for the lack of Li ions in the composite, and the cycling performance was optimized using the Cu alloy, oxide, and Li compounds within the composite.

Removal of Boron from Molten Si and Si-Cu Using Ammonia Containing Gas

All the reported thermodynamics analysis implied that ammonia is a promising reagent for removing boron from silicon, but efforts to employ it in silicon refining have failed in practice. As such, there are few reports detailing this process. In this study, this process was analyzed experimentally. Various concentrations of ammonia were introduced to remove boron from silicon in the temperature range of 1200–1550 ∘C with a total pressure of 1 atm. Boron containing nitrides precipitates were detected in the furnace tube. The effect of ammonia content in the feeding gas was explored. It implied that higher ammonia partial pressures promote the boron removal. The experimental results have suggested that ammonia could remove boron from silicon in the form of volatiles, such as BHx (x = 1, 2, 3) and B3 H 6 N 3, in practice. The reaction-rate constant was limited to 10−6– 10−7 m/s in pure ammonia at 1450 ∘C. Moreover, a higher ammonia flow rate resulted in lower boron removal ratio. It was indicated that the rate determining steps of boron removal and silicon loss in this process were the chemical reaction at the surface of the melt and the transport of ammonia from gas phase to the surface, respectively. The relationship of the boron-removal rate with temperature followed a “V”-shaped curve, which implied the limit of thermodynamic factors at high temperature and the limit of kinetic factors at temperatures lower than 1300 ∘C. Based on the analysis results, temperature-programed reaction was designed to promote the boron-removal efficiency doubled. Cu was used to decrease the liquidus temperature of Si based alloy in the process. As a result, more than 80% boron in Si-Cu alloy could be removed.

Surface Morphology and Electrical Resistivity in Polycrystalline Au/Cu/Si(100) System

This work describes the analysis of morphology and electrical resistivity (ρ) obtained in the Au/Cu/Si system. The Au/Cu bilayers were deposited by thermal evaporation technique with thicknesses from 50 to 250 nm on SiOx/Si(100) substrates. The Au : Cu concentration ratio of the samples was of 25 : 75 at%. The bilayers were annealed into a vacuum oven with argon atmosphere at 660 K for one hour. The crystalline structures of AuCu and CuSi alloys were confirmed by X-ray diffraction analysis. The scanning electron microscopy (SEM), the atomic force microscopy (AFM), and the energy dispersive spectroscopy (EDS) were used to study the morphology, final thickness, and the atomic concentration of the alloys formed, respectively. The four-point probe technique was used to measure the electrical resistivity (ρ) in the prepared alloys as a function of thickness. The ρ value was measured and it was numerically compared with the Fuchs–Sondheimer (FS) and the Mayadas–Shatzkes (MS) models of resistivity. Results show values of electrical resistivity between 0.9 and 1.9 μΩ-cm. These values are four times smaller than the values of the AuCu systems reported in literature.

Cyclic thermal storage/discharge performances of a hypereutectic Cu-Si alloy under vacuum for solar thermochemical process

A copper-silicon alloy (Cu-Si alloy) was examined and evaluated as a phase-change material (PCM) for thermal energy storage applications such as load shaving and peak load shifting when coupled to a solar thermochemical reactor, reformer, or gasifier for the production of solar fuel. The Cu-Si alloy was selected as a high-temperature PCM thermal storage medium alternative to molten carbonate salts, and the compatibility of this alloy with a graphite-carbon encapsulation material was experimentally examined. The cyclic thermal storage/discharge properties of the Cu-Si alloy as a latent-heat energy storage material were studied with respect to thermal cycles. A thermal stability test was performed on Cu-20 wt% Si, Cu-25 wt% Si, and Cu-30 wt% Si alloys placed in a graphite container under vacuum. The performances of the Cu-Si alloys with increasing and decreasing temperature were measured during the thermal storage (heat-charge) and cooling (heat-discharge) modes, respectively. The elemental distribution of each Cu-Si alloy after the cyclic reaction was evaluated using an electron probe microanalyzer (EPMA). The heat storage capacities before and after the cyclic reaction were evaluated using differential scanning calorimetry (DSC) and were compared to the thermal storage properties of the molten carbonate salt.

Segregation behavior of iron in metallurgical grade silicon during Si[sbnd]Cu solvent refining

Impurity removal from metallurgical grade silicon (MG-Si) is an important issue for solar-grade silicon production, and solvent refining is used as an effective method to purify silicon. To evaluate the purification ability of solvent refining with SiCu melt at 1343–1603 K, the effective segregation ratio of the main impurity element Fe between solid Si and SiCu melt was experimentally and theoretically determined. The results demonstrated that the effective segregation ratio of Fe increased with the increasing temperature at the range of 1343–1603 K. The corresponding removal mechanism of Fe was investigated in detail. It was found that the effective segregation ratio of Fe calculated by Scheil equation presented the same tendency with experimental results, and the theoretical calculation was more consistent with experimental results when back diffusion was considered. Moreover, Fe was found to form SiFeMn and FeMnTi phases into SiCu alloy phase from MG-Si with the presence of Cu. It can be concluded that removal mechanism of Fe was not only a segregation process, but also a recombining process of impurity phase transformation.

A New Approach of the Synthesis of SiO2 Nanowires By Using Bulk Copper Foils As Catalyst

Silica nanowires (SiO2NWs) have attracted considerable attention over the last decades due to their diverse properties and broad range of applications. Among them, it is well-known the capacity of SiO2NWs to emit strong blue light. It is also widely recognized the versatility of this material as biosensor, since it can be easily functionalized in order to respond to several targets. Other applications include their potential use as anode electrode for lithium-ion batteries, or as protective layer against corrosion by exposure to the environment. In this regard, the use of a metal substrate is of paramount relevance; therefore, an adequate contact between the substrate and the nanostructures is required. Especially numerous and varied are the procedures for the growth of SiO2NWs, being one of the most employed the so-called vapor-liquid-solid (VLS) method. By this mechanism, the nanowires grow from a metal nanoparticle when the adequate gaseous precursor is added. However, the main drawback of this mechanism resides in the need of a Si substrate for the synthesis of the SiO2NWs. Apart from the original Au-Si system, a broad variety of other metals such as Fe, Co, Ni or Cu may act as catalysts for the growth. Particularly, of special interest is the case of copper, which is present in a large majority of electronic devices. Furthermore, the Cu–Si phase diagram shows a eutectic point at 802 ⁰C (16 wt% of silicon) promoting the formation of a liquid alloy at an accessible temperature for a relatively low concentration of silicon in copper. This work presents a novel procedure for the growth of SiO2 nanowires directly from polycrystalline copper foils. The single-step synthesis procedure consists of a thermal treatment at 900 ◦C without the need for additional catalysts. As a result, nanowires with an average diameter of 100 nm are synthesized. A systematic study undertaken at different stages of the SiO2NWs growth confirmed the generation of nucleation centers on the Cu surface as well as revealed the existence of an intermediate gaseous SiO species at the synthesis temperature, which promotes the growth of the SiO2NWs via a VLS mechanism. Figure 1 shows the dark field scanning transmission electron microscopy (DF-STEM) image of the as-synthesized SiO2NWs. As can be seen there, SiO2NWs growth is generated from substrate protrusions of around 200 nm in diameter, exceling from the Cu substrate. These protuberances produced during the thermal treatment could be the evidence of the formation of Cu-Si alloys required as initial step for generating the SiO2NWs. Figure 2a shows the detail of a protrusion of the Cu substrate (in bright contrast) just under the nanowire (in dark contrast). EDX elemental maps performed on the inset area confirms the presence of Cu at the bottom of the nanowire (Fig 2b). Meanwhile, Figs 2c and 2d show a homogeneous distribution of Si and O across the whole nanowire. This process with bulk Cu foils as catalytic agent allows the growth of SiO2NWs over metallic substrates, granting an adequate interconnection between both surfaces. Figure 1

Electrochemistry of CuxSi1−x Alloys in Li Cells

The structure and electrochemistry in lithium cells of sputtered thin films and ball milled alloys in the Cu-Si system (0 ≤ x ≤ 0.60 in CuxSi1−x) were investigated. Both thin films and ball milled Cu-Si alloys showed the co-existence of amorphous Si and a nanocrystalline Cu3Si phase. The lithiation potential of Cu-Si alloys was found to be significantly shifted to potentials below that of pure Si. In addition, the Cu3Si phase was found to be involved in the electrochemical reaction of the alloys with lithium, however not all of the Si could be reacted with Li to its full theoretical extent. This suggests that a ternary Cu-Li-Si phase may be formed at full lithiation of these alloys.

Micron-Sized a-Silicon-Fe-Cu Ternary Composite Anode Material for High Energy Libs

To realize the high energy LIBs, extensive studies for silicon anodes have been widely carried out for recent years in order to succeed in commercialization through overcoming its intrinsic problems of low coulombic efficiency and severe capacity degradation upon cycling as results of large volume expansion, low conductivity and lithium diffusivity. Herein, we suggested a sophisticated structure of silicon-based ternary alloy composite with a scalable series of processes by synthesizing high density micron-sized secondary particles comprising of metal silicide and amorphous silicon primary particles (~100 nm). This silicon-based ternary alloy composite, whose reversible specific capacity is 1300 mAh/g with 85% coulombic efficiency at 1st cycle, shows not only great cycling stability with 84% retention at 0.5 C after 100th cycles but also high rate capability with 91% of capacities retention at 7C (vs. 0.2C). These remarkable electrochemical properties come from a-silicon characteristics and formation of either Fe-Si or Cu-Si alloys with reactions of a-Si, leading to improve the structural integrity with porosity. This silicon-based ternary alloy composite have also succeeded in increasing the tap density as high as 0.8 g/cm3. Furthermore, the electrode was swollen only 42% after 100th cycles. In these regards, the silicon-based ternary alloy composite will contribute to the progress of practical use of silicon anode for next generation LIBs.

Synthesis and characterization in AuCu–Si nanostructures

Au/Cu bilayers with different Au:Cu concentrations (25:75, 50:50 and 75:25at.%) were deposited on Si(100) substrates by thermal evaporation. The thicknesses of all Au/Cu bilayers were 150nm. The alloys were prepared by thermal diffusion into a vacuum oven with argon atmosphere at 690K during 1h. X-ray diffraction analysis revealed different phases of AuCu and CuSi alloys in the samples after annealing process. CuSi alloys were mainly obtained for 25:75at.% samples, meanwhile the AuCuII phase dominates for samples prepared with 50:50at.%. Additionally, the Au:Cu alloys with 75:25at.%, produce Au2Cu3 and Au3Cu phases. The formed alloys were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) to study the morphology and the elemental concentration of the formed alloys.

Boron Removal from MG-Si by Slag Treatment with Copper Addition

The effect of slag treatment with Copper addition in silicon purification by metallurgical methods was examined in this paper. The microstructures and contents of Si-Cu alloy after slag refining were investigated by XRD and ICP, respectively. The majority phases in the Si-Cu alloy were Cu3Si and Si. The partition ratio of boron (LB) between slag and silicon was studied with and without Cu addition. Experimental results show that slag treatment with Cu addition can improve the LBin CaO-SiO2-CaF2slag system, where a maximum boron removal ratio of 85% could be achieved.

Effect of Reductants on Valuable Metals Separation and Recovery from Copper Cliff Converter Slag

AbstractThe aim of the project is to investigate new material as a reductant in nickel extraction and purification processes. The analyzed reductants were coke, pig iron, ferrosilicon and two copper-silicon alloys. The mixture with the slag and reductant was poured into a cylindrical alumina crucible and kept in a furnace for one hour at 1573 K (1300 °C). After settling, the solidified sample consisted of the matte settled at the bottom of the sample separated from the slag at the top. Ferrosilicon was found to be the most effective reductant for cobalt recovery while 70wt%Cu-30wt%Si alloy facilitated 72% copper and 87% nickel recovery. The highest copper recovery is achieved with 90wt%Cu-10wt%Si reductant. Due to low melting point, high exothermicity and suitable density, Cu-Si alloys could be an ideal choice for the pyrometallurgical converting processes.