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-ra...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.展开更多
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 coppe...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 μm 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°C 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 interfacial reaction between glass and chip gives high adhesion.展开更多
The auto-evolved ultrafine copper powders were synthesized via a novel electrodeposition route performed by ultrasonic dispersion of the electrolyte. The properties of the samples obtained were characterized by X-ray ...The auto-evolved ultrafine copper powders were synthesized 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 Cu2+ 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%.展开更多
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 th...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.展开更多
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 c...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.展开更多
A novel process was developed to produce spherical copper powder for multilayer ceramic capacitors (MLCC). Spherical ultrafine cuprous oxide (Cu2O) powder was prepared by glucose reduction of Cu(OH)2. The Cu2O particl...A novel process was developed to produce spherical copper powder for multilayer ceramic capacitors (MLCC). Spherical ultrafine cuprous oxide (Cu2O) powder was prepared by glucose reduction of Cu(OH)2. The Cu2O 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 Cu2O 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.展开更多
An approach to fabricate sintered copper with high green strength and high sintered density using nonaqueous gelcasting technology is presented in this study. The effects of various gelcasting processing parameters su...An approach to fabricate sintered copper with high green strength and high sintered density using nonaqueous gelcasting technology 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°C.展开更多
In order to study the properties of sintered copper powder shaped charge liner, the copper powder, whose particle size was below 20 μm, was chosen as the main material. The mixed powders were directly pressed into th...In order to study the properties of sintered copper powder shaped charge liner, the copper powder, whose particle size was below 20 μm, was chosen as the main material. The mixed powders were directly pressed into the desired shape of the shaped charge liner by the top direct-pressure way. The microscopic morphology of the spinning shaped charge liner, the sintered and non-sintered powder liners, and the particle properties of the copper powder were studied with scanning electron microscopy. The experimental results showed that the irregular copper powder could get together effectively and sintering could improve the compactness of the powder liner effectively. The wall thickness and density of the non-sintered and sintered liner were also tested, and it shows that sintering causes the wall thickness thinned and the density improved. The penetration depths of non-sintered powder liner, sintered powder liner and the spinning copper plate liner were tested with different standoff respectively, showing that the penetration properties of sintered powder liner are well.展开更多
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...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.展开更多
For the preparation of copper nanoparticles several methods, i.e., thermal reduction, mechanical attrition, chemical reduction metal vapour synthesis, radiation methods, laser ablation and micro emulsion techniques we...For the preparation of copper nanoparticles several methods, i.e., thermal reduction, mechanical attrition, chemical reduction metal vapour synthesis, radiation methods, laser ablation and micro emulsion techniques were developed in the past. Electrolytic deposition is one of the most suitable, simplest and low cost methods which are used for wide range of materials. In the present investigations, efforts were put to produce copper nano powder using electrolytic technique. It could be possible to obtain near nano copper powder of 258 nm size using high cathode current density of 1100 A/m2 in sulphate bath. The specific surface area and shape of the particles were found to be 23.2 m2/g and irregular, respectively.展开更多
In the study, the common copper powder is used as sample, the ultrafine copper powder is researched by a new process of high energy ball milling. The influence of the milling time, the milling intensity, the milling m...In the study, the common copper powder is used as sample, the ultrafine copper powder is researched by a new process of high energy ball milling. The influence of the milling time, the milling intensity, the milling medium, the ratio of ball to material, the dry milling and the wet milling on copper powder size are studied and the rule of every factors influencing properties of copper particle size and specific surface area under the best experimental conditions are acquired. By the regressive analysis of experimental results under the best conditions, the characteristic equation of copper particle prepared by high energy milling is confirmed.展开更多
In this study,a composite powder capillary wick is prepared,manufactured by sintering copper powder and surface treated by low-temperature thermal oxidation.It is used to improve the performance of the capillary wick....In this study,a composite powder capillary wick is prepared,manufactured by sintering copper powder and surface treated by low-temperature thermal oxidation.It is used to improve the performance of the capillary wick.The forced flow method and infrared imaging method are used to test the permeability and capillary performance of the samples.The effects of different oxidation temperatures on the performance of capillary wick are investigated.The experimental results show that the wetting performance of the oxidized samples is significantly enhanced.With the increase of oxidation temperature,the permeability decreases.The capillary height and velocity of the thermally oxidized samples are significantly higher than those of the untreated capillary wick.However,the oxidation temperature needs to be adjusted to obtain the best capillary performance.The highest capillary performance is found at oxidation temperature of 300℃,with an increase of 46% compared to the untreated ones.Comparisons with other composite wicks show that the sample with an oxidation temperature of 300℃ has competitive capillary performance,making it a favorable alternative to two-phase heat transfer device.This study shows that combining low-temperature thermal oxidation technology with powder sintering is a convenient and effective method to improve the capillary performance of powder wicks.展开更多
High power electronics units generate high-density heat flux,which poses a significant threat to the reliability of these devices.The vapor chamber(VC)has a very high heat transfer rate and has a wide range of applica...High power electronics units generate high-density heat flux,which poses a significant threat to the reliability of these devices.The vapor chamber(VC)has a very high heat transfer rate and has a wide range of applications in the heat dissipation of electronic products.VCs with sintered copper powder wicks sized as irregular shape copper powder 50μm(I-50μm),I-75μm,I-110μm,I-150μm were studied in this paper.The effect of liquid filling ratio was discussed.The results indicated that the thermal resistance of all VCs decreased with the increase of heating power.The capillary performance of wick was the dominant factor for the heat transfer performance of VCs with different kinds of wick.A capillary performance factor was proposed to evaluate the capillary performance of VCs.The capillary performance factor of VC with the wick of I-75μm was much higher than that of the other types of VC in this study.The heat source surface temperature of VCs could be affected by filling ratio and wick structure.But,it should be insensitive to the filling ratio when a better capillary performance factor was obtained.With the same heating area and similar structure,the maximum heat flux density of the VC would decrease as the height of vapor cavity decreased.展开更多
Oxide-reduced copper powder can be produced efficiently at low cost. The volume shrinkage, porosity, maximum pore size, permeability and thermal conductivity of wicks sintered from two oxide-reduced (OR) powders were ...Oxide-reduced copper powder can be produced efficiently at low cost. The volume shrinkage, porosity, maximum pore size, permeability and thermal conductivity of wicks sintered from two oxide-reduced (OR) powders were compared with one from water-atomized (WA) powder. The green specimens were sintered at temperatures from 800 to 1000 ?C in a tube furnace under a reduction stream of 10% hydrogen and 90% argon. The results show that the property variations of OR ? 100 and WA wicks due to porosity changes have a similar tendency and range. Nine hundred degree celsius is a recommended sintering temperature for producing ideal wicks for use in heat pipes. A smaller maximum pore size can be obtained by increasing the green density.展开更多
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 log...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.展开更多
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 s...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.展开更多
Direct electroreduction of solid cuprous chloride to prepare copper powder in a"neutral"ambient-temperature ionic liquid,1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid(BMIMBF4)was investigated.Cy...Direct electroreduction of solid cuprous chloride to prepare copper powder in a"neutral"ambient-temperature ionic liquid,1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid(BMIMBF4)was investigated.Cyclic voltammetry of the CuCl powder in a Pt-powder cavity microelectrode exhibited that solid CuCl can be electrochemical reduced in the ionic liquid.Chronoamperometry of the salt powder filled Mo-cavity electrode(current collector)in the ionic liquid further demonstrated the conversion of chloride to metal inside the cavity,as confirmed by scanning electron microscopy,energy-dispersive X-ray,and X-ray diffraction spectra.展开更多
Molybdenum powders with a diameter of approximately 3 μm were coated with copper using the electroless plating technique in the pH 12.5-13 and temperature range of 55-75°C. The optimization of the electroless co...Molybdenum powders with a diameter of approximately 3 μm were coated with copper using the electroless plating technique in the pH 12.5-13 and temperature range of 55-75°C. The optimization of the electroless copper bath was evaluated through the combination of process parameters like pH and temperature. The optimized values of pH and temperature were found to be 12.5 and 60°C, respectively, which at-tributes to the bright maroon color of the coating with an increase in weight of 46%. The uncoated and coated powders were subjected to mi-crostructural studies using scanning electron microscope (SEM) and the phases were analyzed using X-ray diffraction (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.展开更多
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...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...展开更多
基金Projects(50804043, 50674011) supported by the National Natural Science Foundation of ChinaProject(KZCX2-YW-412-2) supported the Knowledge Innovation Program of Chinese Academy of Sciences
文摘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.
文摘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 μm 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°C 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 interfacial reaction between glass and chip gives high adhesion.
基金Project(08JJ3104) support by Hunan Provincial Natural Science Foundation of China
文摘The auto-evolved ultrafine copper powders were synthesized 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 Cu2+ 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%.
文摘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.
文摘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.
文摘A novel process was developed to produce spherical copper powder for multilayer ceramic capacitors (MLCC). Spherical ultrafine cuprous oxide (Cu2O) powder was prepared by glucose reduction of Cu(OH)2. The Cu2O 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 Cu2O 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.
基金financially supported by the National Science Foundation of China (Grant No. 51274041)
文摘An approach to fabricate sintered copper with high green strength and high sintered density using nonaqueous gelcasting technology 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°C.
基金Funded by the National Natural Science Foundation of China(No.11072222)
文摘In order to study the properties of sintered copper powder shaped charge liner, the copper powder, whose particle size was below 20 μm, was chosen as the main material. The mixed powders were directly pressed into the desired shape of the shaped charge liner by the top direct-pressure way. The microscopic morphology of the spinning shaped charge liner, the sintered and non-sintered powder liners, and the particle properties of the copper powder were studied with scanning electron microscopy. The experimental results showed that the irregular copper powder could get together effectively and sintering could improve the compactness of the powder liner effectively. The wall thickness and density of the non-sintered and sintered liner were also tested, and it shows that sintering causes the wall thickness thinned and the density improved. The penetration depths of non-sintered powder liner, sintered powder liner and the spinning copper plate liner were tested with different standoff respectively, showing that the penetration properties of sintered powder liner are well.
基金Project supported by national high technology research and development program(863)of China(2001AA337080).
文摘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.
文摘For the preparation of copper nanoparticles several methods, i.e., thermal reduction, mechanical attrition, chemical reduction metal vapour synthesis, radiation methods, laser ablation and micro emulsion techniques were developed in the past. Electrolytic deposition is one of the most suitable, simplest and low cost methods which are used for wide range of materials. In the present investigations, efforts were put to produce copper nano powder using electrolytic technique. It could be possible to obtain near nano copper powder of 258 nm size using high cathode current density of 1100 A/m2 in sulphate bath. The specific surface area and shape of the particles were found to be 23.2 m2/g and irregular, respectively.
文摘In the study, the common copper powder is used as sample, the ultrafine copper powder is researched by a new process of high energy ball milling. The influence of the milling time, the milling intensity, the milling medium, the ratio of ball to material, the dry milling and the wet milling on copper powder size are studied and the rule of every factors influencing properties of copper particle size and specific surface area under the best experimental conditions are acquired. By the regressive analysis of experimental results under the best conditions, the characteristic equation of copper particle prepared by high energy milling is confirmed.
基金financial support for this research from the National Natural Science Foundation of China (52006040 and 51876044)the Natural Science Foundation of Guangdong Province(2019B090905005)the International Science and Technology Projects of Huangpu District of Guangzhou City(2020GH08)。
文摘In this study,a composite powder capillary wick is prepared,manufactured by sintering copper powder and surface treated by low-temperature thermal oxidation.It is used to improve the performance of the capillary wick.The forced flow method and infrared imaging method are used to test the permeability and capillary performance of the samples.The effects of different oxidation temperatures on the performance of capillary wick are investigated.The experimental results show that the wetting performance of the oxidized samples is significantly enhanced.With the increase of oxidation temperature,the permeability decreases.The capillary height and velocity of the thermally oxidized samples are significantly higher than those of the untreated capillary wick.However,the oxidation temperature needs to be adjusted to obtain the best capillary performance.The highest capillary performance is found at oxidation temperature of 300℃,with an increase of 46% compared to the untreated ones.Comparisons with other composite wicks show that the sample with an oxidation temperature of 300℃ has competitive capillary performance,making it a favorable alternative to two-phase heat transfer device.This study shows that combining low-temperature thermal oxidation technology with powder sintering is a convenient and effective method to improve the capillary performance of powder wicks.
基金supported by Fundamental Research Funds for the Central Universities(2018JBZ108)National Natural Science Foundation of China(No.51776015).
文摘High power electronics units generate high-density heat flux,which poses a significant threat to the reliability of these devices.The vapor chamber(VC)has a very high heat transfer rate and has a wide range of applications in the heat dissipation of electronic products.VCs with sintered copper powder wicks sized as irregular shape copper powder 50μm(I-50μm),I-75μm,I-110μm,I-150μm were studied in this paper.The effect of liquid filling ratio was discussed.The results indicated that the thermal resistance of all VCs decreased with the increase of heating power.The capillary performance of wick was the dominant factor for the heat transfer performance of VCs with different kinds of wick.A capillary performance factor was proposed to evaluate the capillary performance of VCs.The capillary performance factor of VC with the wick of I-75μm was much higher than that of the other types of VC in this study.The heat source surface temperature of VCs could be affected by filling ratio and wick structure.But,it should be insensitive to the filling ratio when a better capillary performance factor was obtained.With the same heating area and similar structure,the maximum heat flux density of the VC would decrease as the height of vapor cavity decreased.
文摘Oxide-reduced copper powder can be produced efficiently at low cost. The volume shrinkage, porosity, maximum pore size, permeability and thermal conductivity of wicks sintered from two oxide-reduced (OR) powders were compared with one from water-atomized (WA) powder. The green specimens were sintered at temperatures from 800 to 1000 ?C in a tube furnace under a reduction stream of 10% hydrogen and 90% argon. The results show that the property variations of OR ? 100 and WA wicks due to porosity changes have a similar tendency and range. Nine hundred degree celsius is a recommended sintering temperature for producing ideal wicks for use in heat pipes. A smaller maximum pore size can be obtained by increasing the green density.
文摘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.
基金Project (50301017) supported by the National Natural Science Foundation of China
文摘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.
基金the financial support of the National Natural Science Foundation of China(51204080,51274108,21263007)the Natural Science Foundation of Yunnan Province(2011FA009)the Application Foundation Research of Yunnan Province(2011FZ020)
文摘Direct electroreduction of solid cuprous chloride to prepare copper powder in a"neutral"ambient-temperature ionic liquid,1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid(BMIMBF4)was investigated.Cyclic voltammetry of the CuCl powder in a Pt-powder cavity microelectrode exhibited that solid CuCl can be electrochemical reduced in the ionic liquid.Chronoamperometry of the salt powder filled Mo-cavity electrode(current collector)in the ionic liquid further demonstrated the conversion of chloride to metal inside the cavity,as confirmed by scanning electron microscopy,energy-dispersive X-ray,and X-ray diffraction spectra.
文摘Molybdenum powders with a diameter of approximately 3 μm were coated with copper using the electroless plating technique in the pH 12.5-13 and temperature range of 55-75°C. The optimization of the electroless copper bath was evaluated through the combination of process parameters like pH and temperature. The optimized values of pH and temperature were found to be 12.5 and 60°C, respectively, which at-tributes to the bright maroon color of the coating with an increase in weight of 46%. The uncoated and coated powders were subjected to mi-crostructural studies using scanning electron microscope (SEM) and the phases were analyzed using X-ray diffraction (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.
基金Universiti Sains Malaysia for the financial support under Short Term Research Grant(Grant No.304/PKIMIA/638056)
文摘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...
