Ceramic particles reinforced copper matrix composites manufactured by advanced powder metallurgy:preparation, performance, and mechanisms

Copper matrix composites doped with ceramic particles are known to effectively enhance the mechanical properties,thermal expansion behavior and high-temperature stability of copper while maintaining high thermal and electrical conductivity.This greatly expands the applications of copper as a functional material in thermal and conductive components,including electronic packaging materials and heat sinks,brushes,integrated circuit lead frames.So far,endeavors have been focusing on how to choose suitable ceramic components and fully exert strengthening effect of ceramic particles in the copper matrix.This article reviews and analyzes the effects of preparation techniques and the characteristics of ceramic particles,including ceramic particle content,size,morphology and interfacial bonding,on the diathermancy,electrical conductivity and mechanical behavior of copper matrix composites.The corresponding models and influencing mechanisms are also elaborated in depth.This review contributes to a deep understanding of the strengthening mechanisms and microstructural regulation of ceramic particle reinforced copper matrix composites.By more precise design and manipulation of composite microstructure,the comprehensive properties could be further improved to meet the growing demands of copper matrix composites in a wide range of application fields.

Preparation of fine copper powders and their application in BME-MLCC

The preparation of fine copper powders by chemical reduction method was investigated. The reaction of [Cu（NH3）4]2^＋ complex with hydrazine hydrate gives spherical monodispersed fine copper powders. The spherical copper powder with a uniform size of 3.5 ± 0.5 μtm was processed to obtain flake copper powder having a uniform size of 8-10 μm, excellent dispersibility and uniform shape. The spherical copper powder of 2.5 ±0.3 μm in size, flake copper, glass frit and vehicle were mixed to prepare copper paste, which was fired in 910-920℃ to obtain BME-MLCC （base metal multilayer ceramic capacitor） with a dense surface of end termination, high adhesion and qualified electrical behavior. Polarized light photo and SEM were employed to observe the copper end termination of BME-MLCC. The rough interface from the interracial reaction between glass and chip gives high adhesion.

Preparation and characterization of molybdenum powders with copper coating by the electroless plating technique

Molybdenum powders with a diameter of approximately 3 μn were coated with copper using the electroless plating technique in the pH 12.5-13 and temperature range of 55-75℃. The optimization of the electroless copper bath was evaluated through the combination of process parameters like pH and temperature. The optimized values ofpH and temperature were found to be 12.5 and 60℃, respectively, which attributes to the bright maroon color of the coating with an increase in weight of 46%. The uncoated and coated powders were subjected to microstructural studies using scanning electron microscope （SEM） and the phases were analyzed using X-my diffrction （XRD）. An attempt was made to understand the growth mechanism of the coating. The diffusion-shrinkage autocatalytic model was suggested for copper growth on the molybdenum surface.

Preparation of electrolytic copper powders with high current efficiency enhanced by super gravity field and its mechanism

Super gravity field was employed to enhance electrolytic reaction for the preparation of copper powders.The morphology, microstructure and size of copper powders were characterized by scanning electron microscopy,X-ray diffractometry and laser particle analysis.The results indicated that current efficiencies of electrolytic copper powders under super gravity field increased by more than 20% compared with that under normal gravity condition.Cell voltage under super gravity field was also much lower.The size of copper powders decreased with the increase of gravity coefficient(G).The increase of current efficiency can be contributed to the disturbance of electrode/electrolyte interface and enhanced mass transfer of Cu2+ in super gravity field.Meanwhile,the huge gravity acceleration would promote the detachment of copper powders from electrode surface during electrolytic process,which can prevent the growth of copper powders.

Microstructure and thermal properties of dissimilar M300–CuCr1Zr alloys by multi-material laser-based powder bed fusion

Multi-material laser-based powder bed fusion (PBF-LB) allows manufacturing of parts with 3-dimensional gradient and additional functionality in a single step. This research focuses on the combination of thermally-conductive CuCr1Zr with hard M300 tool steel.Two interface configurations of M300 on CuCr1Zr and CuCr1Zr on M300 were investigated. Ultra-fine grains form at the interface due to the low mutual solubility of Cu and steel. The material mixing zone size is dependent on the configurations and tunable in the range of0.1–0.3 mm by introducing a separate set of parameters for the interface layers. Microcracks and pores mainly occur in the transition zone.Regardless of these defects, the thermal diffusivity of bimetallic parts with 50vol% of CuCr1Zr significantly increases by 70%–150%compared to pure M300. The thermal diffusivity of CuCr1Zr and the hardness of M300 steel can be enhanced simultaneously by applying the aging heat treatment.

Nanosized copper powders prepared by gel-casting method and their application in lubricating oil

Nanosized copper powders were prepared by a gel-casting method using copper nitrate, acrylamide（AM） and N, N′-methylenebisacrylamide（MBAM） as the main raw materials. The as-prepared copper powders were characterized by X-ray diffractometry and scanning electron microscopy, and then added into a 48# industrial white oil. Dispersion and wear properties of the compounded lubricating oil were tested. The results show that the copper powders prepared are of high purity, fine dispersibility with mean particle size of about 60 nm and with a narrow particle size distribution. The nanosized copper powders can be well dispersed in the lubricating oil. The addition of the copper powders obviously improves the anti-wear properties of the lubricating oil owing to their good self-repairing performance. Compared with 48# industrial white lubricating oil, the friction coefficient of GCr15 steel with the compounded oil containing 0.6% copper powders reduces by 0.07 and nearly no wear chippings are found in the scratches of the friction counter parts.

Preparation of copper-coated fine molybdenum powders with electroless technique

The molybdenum powders with average particle size of 3 μm were coated with copper by electroless plating. The influence of pretreatment, solution composition and plating conditions on electroless copper plating was studied. The copper-coated molybdenum powders were examined by SEM and XRD. Results indicate that a series of optimization methods is used to add activated sites before electroless copper plating. Taking TEA and EDTA as chief and assistant complex agents respectively, 2,2＇-bipyridyl and PEG as double stabilizers, the Mo powders are coated with copper successfully with little Cu20 contained, at the same time, Mo-Cu composite powders with copper content of 15 - 85 wt% can be obtained. The optimal values of pH, temperature and HCHO concentration are 12 -13, 60 -65 ℃ and 22 -26 mL/L, respectively.

Development of copper coatings on molybdenum powders by electroless plating technique

Mo powders with average particle size of 3 μm were attempted to coat with copper by electroless plating technique. The effect of the solution composition and plating conditions on the electroless copper plating was studied. The uncoated and coated powders were subjected to the microstructural studies by SEM and the phases were analyzed by XRD. The results indicate that the Mo powders are coated with copper,at the same time,Mo-Cu composite powders with Cu content ranging from 15% to 85%(mass fraction) can be obtained. The optimal values of pH,HCHO concentration and temperature are in the ranges of 12-13,22-26 ml/L and 60-65 ℃,respectively. The diffusion-shrinkage autocatalytic model is suggested for the growth mechanism of electroless coating over the surface.

Effect of process parameters on microstructure and mechanical properties of a nickel-aluminum-bronze alloy fabricated by laser powder bed fusion

This work investigated the effect of process parameters on densification,microstructure,and mechanical properties of a nickel-aluminum-bronze(NAB)alloy fabricated by laser powder bed fusion(LPBF)additive manufacturing.The LPBF-printed NAB alloy samples with relative densities of over 98.5%were obtained under the volumetric energy density range of 200−250 J/mm^(3).The microstructure of the NAB alloy printed in both horizontal and vertical planes primarily consisted ofβ'martensitic phase and bandedαphase.In particular,a coarser-columnar grain structure and stronger crystallographic texture were achieved in the vertical plane,where the maximum texture intensity was 30.56 times greater than that of random textures at the(100)plane.Increasing the volumetric energy density resulted in a decrease in the columnar grain size,while increasing the amount ofαphase.Notably,β_(1)'martensitic structures with nanotwins and nanoscaleκ-phase precipitates were identified in the microstructure of LPBF-printed NAB samples with a volumetric energy density of 250 J/mm^(3).Furthermore,under optimal process parameters with a laser power of 350 W and scanning speed of 800 mm/s,significant improvements were observed in the microhardness(HV 386)and ultimate tensile strength(671 MPa),which was attributed to an increase in refined acicular martensite.

Structural Characteristics and Properties of Precious Metal Powders and Copper Powder Prepared by High-speed Centrifugal Atomization Technique

The principle and characteristics of the rapidly solidified centrifugal atomization technique are studied in present paper.It has been widely used to make fine,rapidly solidified precious metal powders for application as the electrical engineering materials,conductive coatings for electromagnetic shielding and brazing alloys.The silver powder,copper powder and some precious metal alloys powders are prepared by the new method.A comparative analysis is carried out with the conventional electrolytic silver powder and chemical deposition silver powder.The results show that rapidly solidified powders are fine and have higher solid solubility of the alloying elements,and their alloys have excellent properties in various aspects.

Biosorption of copper ions from dilute aqueous solutions on base treated rubber (Hevea brasiliensis) leaves powder: kinetics, isotherm, and biosorption mechanisms

The effciency of sodium hydroxide treated rubber (Hevea brasiliensis) leaves powder (NHBL) for removing copper ions from aqueous solutions has been investigated. The e?ects of physicochemical parameters on biosorption capacities such as stirring speed, pH, biosorbent dose, initial concentrations of copper, and ionic strength were studied. The biosorption capacities of NHBL increased with increase in pH, stirring speed and copper concentration but decreased with increase in biosorbent dose and ionic strength. The isotherm study indicated that NHBL fitted well with Langmuir model compared to Freundlich and Dubinin-Radushkevich models. The maximum biosorption capacity determined from Langmuir isotherm was 14.97 mg/g at 27°C. The kinetic study revealed that pseudo- second order model fitted well the kinetic data, while Boyd kinetic model indicated that film diffusion was the main rate determining step in biosorption process. Based on surface area analysis, NHBL has low surface area and categorized as macroporous. Fourier transform infrared (FT-IR) analyses revealed that hydroxyl, carboxyl, and amino are the main functional groups involved in the binding of copper ions. Complexation was one of the main mechanisms for the removal of copper ions as indicated by FT-IR spectra. Ion exchange was another possible mechanism since the ratio of adsorbed cations (Cu2+ and H+) to the released cations (Na+, Ca2+, and Mg2+) from NHBL was almost unity. Copper ions bound on NHBL were able to be desorbed at > 99% using 0.05 mol/L HCl, 0.01 mol/L HNO3, and 0.01 mol/L EDTA solutions.

DYNAMIC COMPACTION OF PURE COPPER POWDER USING PULSED MAGNETIC FORCE

The compaction of pure Cu powder was carried out through a series of experiments using dynamic magnetic pulse compaction, and the effects of process parameters, such as discharge energy and compacting direction, on the homogeneity and the compaction density of compacted specimens were presented and discussed. The results indicated that the compaction density of specimens increased with the augment of discharge voltage and time. During unidirectional compaction, there was a density gradient along the loading direction in the compacted specimen, and the minimum compaction density was localized to the center of the bottom of the specimen. The larger the aspect ratio of a powder body, the higher the compaction density of the compacted specimen. And high conductivity drivers were beneficial to the increase of the compaction density. The iterative and the double direction compaction were efficient means to manufacture the homogeneous and high-density powder parts.

Sintering microstructure and properties of copper powder prepared by electrolyzation and atomization

The almost completely dense copper was prepared by ultrafine copper powder prepared with both methods of electrolysis and novel water-gas atomization through cold isostatic pressing(CIP)and sintering under atmospheric hydrogen.Fine copper powder possesses the higher sintering driving force,thereby promoting shrinkage and densification during the sintering process.The grain size of sintered samples by electrolytic copper powder is smaller than that prepared by the atomized copper powder,and the twin crystals are particularly prone to forming in the former sintered microstructure due to the raw powder with low oxygen content and high residual stress originating from the CIP process.The relative density of samples by electrolytic and atomized powder at 1000℃ sintering temperature achieves 99.3%and 97.4%,respectively,significantly higher than that of the powder metallurgy copper parts reported in the literature.Correspondingly,the ultimate tensile strength and yield strength of samples by both kinds of copper powder are approximately similar,while the elongation of the sintered sample by the electrolytic powder(60%)is apparently higher than the atomized powder(44%).The superior performance of samples fabricated by electrolytic powder is inferred from the full density and low oxygen level for there is no cuprous oxide in the grain boundaries.

Characterization of ultrafine copper powder prepared by novel electrodeposition method

The auto-evolved ultrafine copper powders were synlhesized via a novel electrodeposition route performed by ultrasonic dispersion of the electrolyte. The properties of the samples obtained were characterized by X-ray powder diffractometry （XRD）, transmission electron microscopy （TEM）, scanning electron microscopy （SEM） and laser size distribution analyzer （SL） respectively. The formation mechanisms of the powders and the efficiency of the elctrodeposition were discussed. The results show that the as-prepared powders are high-purity copper nanoparticles with the fcc structure taking a mixture of fishbone-like and irregular shapes When the concentration of Cu^2＋ increases from 0.03 to 0.09 mol/L, the average size of copper particles increases from 0.92 to 1.80 μm, and current efficiency of electrodeposition linearly changes from 66.5% to 91.3%.

Preparation of spherical ultrafine copper powder via hydrogen reduction-densification of Mg(OH)_2-coated Cu_2O powder

A novel process was developed to produce spherical copper powder for multilayer ceramic capacitors （MLCC）. Spherical ultrafine cuprous oxide （Cu20） powder was prepared by glucose reduction of Cu（OH）2. The Cu20 particles were coated by Mg（OH）2 and reduced to metallic copper particles. At last, the copper particles were densified by high-temperature heat treatment. The products were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, tap density, and thermogravimetry （TG）. It is found that the shape and size distribution of the copper powder are determined by the Cu20 powder and the copper particles do not agglomerate during high-temperature heat treatment because of the existence of Mg（OH）2 coating. After densification at high temperature, the particle tap density increases from 3.30 to 4.18 g/cm3 and the initial oxidation temperature rises from 125 to 150~C.

Synergistic regulation of current-carrying wear performance of resin matrix carbon brush composites with tungsten copper composite powder

Resin matrix carbon brush composites(RMCBCs)are critical materials for high-powered electric tools.However,effectively improving their wear resistance and heat dissipation remains a challenge.RMCBCs prepared with flake graphite powders that were evenly loaded with tungsten copper composite powder(RMCBCs-W@Cu)exhibited a low wear rate of 1.63 mm^(3)/h,exhibiting 48.6%reduction in the wear rate relative to RCMBCs without additives(RMCBCs-0).In addition,RMCBCs-W@Cu achieved a low friction coefficient of 0.243 and low electric spark grade.These findings indicate that tungsten copper composite powders provide particle reinforcement and generate a gradation effect for the epoxy resin(i.e.,connecting phase)in RMCBCs,which weakens the wear of RMCBCs caused by fatigue under a cyclic current-carrying wear.

Thermodynamic equilibrium calculation on preparation of copper oxalate precursor powder

According to the principles of simultaneous equilibrium and mass balance,a series of thermodynamic equilibrium equations of Cu2+-C2O42--NH3-NH4+-H2O system at ambient temperature were deduced theoretically and the logarithm concentration versus pH value(lg[Cu 2+ ]T—pH)diagrams at different solution compositions were drawn.The results show that when pH is below 5.0,copper ion reacts with C2O42-directly and the morphology of copper precursor powder is of pie-shape;when pH is above 5.0,copper ion coordinates with ammonia,and the precipitation proceeds slowly accompanying with the release of copper ions from the multi-coordinated2+ 3Cu(NH) n (n=1,2,···,5)and the morphologies of copper precursor powder are respectively of rod aggregation shape(when 5.0<pH<8.0)and of rod-shape(when pH>8.0).Some experiments were performed to confirm the relation between the total concentration of copper ion and pH value.It is shown that the thermodynamic mathematical model is correct and the calculated values are basically accurate.

Comparison of effective parameters for copper powder production via electrorefining and electrowinning cells and improvement using DOE methods

The influences of cupric ion concentration （5-35 g/L）,current density （500-2000 A/m2）,circulation rate of the electrolyte solution （15-120 mL/min）,and temperature （25-60℃） on the physical and chemical properties of copper powders obtained in electrolysis cells were investigated.Two industrial processes,electrorefining （ER） cells with a synthetic electrolyte and electrowinning （EW） cells with an original solution of coppermineral leaching,were utilized to produce copper powders.Finally,the statistical full factorial method of design of experiments （DOE） was employed to investigate the interaction or the main effects of processes.The results show that increasing the copper concentration and temperature can increase the grain size,apparent density,and electrical energy consumption.On the other hand,increasing the current density and circulation rate of the electrolyte can decrease them.This production process is optimized via DOE to control the interactive and main effects to produce copper powders with favorable properties.

Synthesis and characterization of copper foams through a powder metallurgy route using a compressible and lubricant space-holder material

In the present work,a compressible and lubricating space-holder material commonly known as "acrawax" was used to process Cu foams with various pore sizes and various porosities.The foams were processed without using binders to avoid contamination of their metal matrices.The lubricant space-holder material was found to facilitate more uniform flow and distribution of metal powder around the surface of the space holder.In addition,the use of acrawax as a space-holder material yielded considerably dense cell walls,which are an essential prerequisite for better material properties.The foams processed with a smaller-sized space holder were found to exhibit better electrical and mechanical properties than those processed with a coarser-sized space holder.The isotropic pore shape,uniform pore distribution throughout the metal matrix,and uniform cell wall thickness were found to enhance the properties pertaining to fine-pore foam samples.The processed foams exhibit properties similar to those of the foams processed through the lost-carbonate sintering process.

Effects of process parameters on nonaqueous gelcasting for copper powder

An approach to fabricate sintered copper with high green strength and high sintered density using nonaqueous gelcasting technol- ogy is presented in this study. The effects of various gelcasting processing parameters such as monomer content, monomer/crosslinker ratio, initiator content, dispersant dosage, and temperature on the flexural strength of dried green bodies and the relative density of sintered bodies were studied to obtain better microstructures and properties. The appropriate process parameters obtained for copper gelcasting are as follows monomer content, 20vol%-30vol% （based on the total volume of reagents）; monomer/crosslinker ratio, 10：1 to 20：1; initiator content, 3vol%-4vol% （based on the volume of the monomer）; dispersant dosage, 1.5wt%-2.5wt% （based on the mass of the copper powder）; and reaction temperature, 65-75℃.