Gas atomization was usually regarded as a good method for producing the spherical or approximate spherical powders. We found a lot of non-spherical powders in production processes, especially in larger particle size d...Gas atomization was usually regarded as a good method for producing the spherical or approximate spherical powders. We found a lot of non-spherical powders in production processes, especially in larger particle size distribution area. The causes of producing non-spherical powders are explained and some analyses are done in order to find a better condition of producing spherical powders in this paper. The following morphologies were obtained by atomized Fe50 Co50 and pure iron and investigated by scanning electron microscopy （SEM）.展开更多
Under certain conditions of proper temperature and pH value, sodium silicate was hydrolyzed in liquid ammonia chloride, and spherical microfine SiO2 powder in micrometer-size was prepared. In this experiment, the rela...Under certain conditions of proper temperature and pH value, sodium silicate was hydrolyzed in liquid ammonia chloride, and spherical microfine SiO2 powder in micrometer-size was prepared. In this experiment, the relationship between needed time and proper pH value, temperature, density of the solution, and its current capacity were found .The optimum conditions are pH 8.5, 70 ~C, and the concentration of sodium silicate is 0.6 mol/L for the density of the solution. The structure of spherical microfine silicon was characterized by SEM and XRD.展开更多
In order to tackle the shortcomings of high brittleness,hard graphitization,and poor oxidation resistance resulted from carbonization of phenolic resin of Mg O- C refractories, effects of 2 mass% spherical Ni, and2 ma...In order to tackle the shortcomings of high brittleness,hard graphitization,and poor oxidation resistance resulted from carbonization of phenolic resin of Mg O- C refractories, effects of 2 mass% spherical Ni, and2 mass% spherical Ni plus 7. 5 mass% Al composite powder on microstructure of the secondary carbon in Mg O- C refractories matrix were investigated. The results show that a large number of carbon whiskers form after the carbonization of phenolic resin with Ni powder;in the Mg O- C refractories matrix with only Ni powder,the carbon microspheres form at all treatment temperatures and change slightly with the temperature rising;the carbon whiskers begin to generate in the specimens with composite powder at 1 000 ℃,the diameter of the carbon whiskers is about 0. 4- 0. 5 μm,and the length is about 3- 4 μm,and the formed carbon whiskers increase gradually with the temperature rising.展开更多
Cubic phase spherical zirconia nano-powder was prepared by a direct template route in the lamellar liquid crystal formed by polyoxyethylene tert-octylphenyl ether(Triton X-100)/sodium dodecyl sulfate(SDS)/H_2O.The pre...Cubic phase spherical zirconia nano-powder was prepared by a direct template route in the lamellar liquid crystal formed by polyoxyethylene tert-octylphenyl ether(Triton X-100)/sodium dodecyl sulfate(SDS)/H_2O.The precursor powder and zirconia powder were characterized by XRD,FT-IR,TG/DSC,TEM,and SEM methods.Results show that the stability of the lamellar liquid crystal is controlled by NH_3·H_2O concentration.The size of nanoparticles is greatly affected by NH_3·H_2O and ZrOCl_2·8H_2O concentrations.The zirconia nanoparticles show narrow particle size distribution of 10-30 nm.展开更多
SiC magnetic abrasive is used to polish surfaces of precise, complex parts which are hard, brittle and highly corrosion-resistant in magnetic abrasive finishing（MAF）. Various techniques are employed to produce this ...SiC magnetic abrasive is used to polish surfaces of precise, complex parts which are hard, brittle and highly corrosion-resistant in magnetic abrasive finishing（MAF）. Various techniques are employed to produce this magnetic abrasive, but few can meet production demands because they are usually time-consuming, complex with high cost, and the magnetic abrasives made by these techniques have irregular shape and low bonding strength that result in low processing efficiency and shorter service life. Therefore, an attempt is made by combining gas atomization and rapid solidification to fabricate a new iron-based SiC spherical composite magnetic abrasive. The experimental system to prepare this new magnetic abrasive is constructed according to the characteristics of gas atomization and rapid solidification process and the performance requirements of magnetic abrasive. The new iron-based SiC spherical composite magnetic abrasive is prepared successfully when the machining parameters and the composition proportion of the raw materials are controlled properly. Its morphology, microstructure, phase composition are characterized by scanning electron microscope（SEM） and X-ray diffraction（XRD） analysis. The MAF tests on plate of mold steel S136 are carried out without grinding lubricant to assess the finishing performance and service life of this new SiC magnetic abrasive. The surface roughness（Ra） of the plate worked is rapidly reduced to 0.051 μm from an initial value of 0.372 μm within 5 min. The MAF test is carried on to find that the service life of this new SiC magnetic abrasive reaches to 155 min. The results indicate that this process presented is feasible to prepare the new SiC magnetic abrasive; and compared with previous magnetic abrasives, the new SiC spherical composite magnetic abrasive has excellent finishing performance, high processing efficiency and longer service life. The presented method to fabricate magnetic abrasive through gas atomization and rapid solidification presented can significantly improve the finishing performance and service life of magnetic abrasive, and provide a more practical approach for large-scale industrial production of magnetic abrasive.展开更多
Characteristics of spherical particles on copper powder and changing sizes were studied in a ball mill under various experimental conditions,such as different ball diameters,high rotation speeds,and milling times,usin...Characteristics of spherical particles on copper powder and changing sizes were studied in a ball mill under various experimental conditions,such as different ball diameters,high rotation speeds,and milling times,using a discrete element method(DEM)simulation.This experiment has investigated the characteristics of spherical particle morphology evolution involved in the mechanical alloying of copper powder.The morphological evolution of the copper particle was analyzed using scanning electron microscopy(SEM).A spherical copper particle was shown with a roundness value using imageJ software.The DEM was used to simulate the ball motion in a planetary ball mill,and the impact energy and shear energy generated during the collision were analyzed to estimate the contact number between the ball and the ball wall.Therefore,as the size of the ball decreased,the number of ball-to-ball and ball-to-wall contacts increased accordingly,and the spherical shape of the copper powder changed.展开更多
A dry mechanical surface treatment was described, in which irregularly shaped metal powders were impacted and sphericized by using high speed airflow impact method particles composite system(PCS). The optimum technolo...A dry mechanical surface treatment was described, in which irregularly shaped metal powders were impacted and sphericized by using high speed airflow impact method particles composite system(PCS). The optimum technological parameters for the metal powders processed were determined according to the treatment effect under different conditions. The results show that the irregularly shaped metal powders are impacted into dense spherical particles, the bulk density and tap density of the metal powders increase noticeably. The combination property of metal powders is improved greatly.展开更多
Monodispersed spherical Ru powders are essential for fabricating high-performance Ru sputtering targets,which have applications in very-large-scale integration circuits and magnetic recording devices.However,the synth...Monodispersed spherical Ru powders are essential for fabricating high-performance Ru sputtering targets,which have applications in very-large-scale integration circuits and magnetic recording devices.However,the synthesis of such powders remains a major challenge.Here,we reported the synthesis of monodispersed spherical Ru powders through controlling the molar ratio of SO_(4)^(2-)to Ru^(3+)in urea homogeneous precipitation solution and the annealing conditions.Without the addition of(NH4)2SO_(4)into the reaction solution,only gel-like precipitation particles were obtained.Once introducing(NH_(4))_(2)SO_(4) into the reaction solution and controlling the molar ratio of SO_(4)^(2-)to Ru3+between 0.50 and 1.00,monodispersed spherical precursor powders were obtained.The nucleation and growth of monodispersed spherical precursor particles in solution were found to conform to LaMer's model.Through controlled annealing at 450℃in a hydrogen atmosphere,the obtained metallic Ru powder with an average particle size of 135 nm inherited the spherical morphology and excellent dispersity from the monodispersed spherical precursor powders.These results and findings would deepen the understanding of the preparation of monodispersed Ru and Ru-like powders.展开更多
Spherical Tb_(0.5)Dy_(0.5)(Fe_(1-x)Mn_(x))_(1.92)(x=0,0.05,0.10 and 0.15)single-crystal particles were prepared.The magnetic anisotropy of the alloy decreases as x increases from 0 to 0.15.Subsequently,we prepared gia...Spherical Tb_(0.5)Dy_(0.5)(Fe_(1-x)Mn_(x))_(1.92)(x=0,0.05,0.10 and 0.15)single-crystal particles were prepared.The magnetic anisotropy of the alloy decreases as x increases from 0 to 0.15.Subsequently,we prepared giant magnetostrictive composites with these spherical Tb_(0.5)Dy_(0.5)(Fe_(1-x)Mn_(x))_(1.92)single-crystal particles.As a consequence,well<111>-orie nted Tb_(0.5)Dy_(0.5)(Fe_(1-x)Mn_(x))_(1.92)composites with 55 vol%Tb_(0.5)Dy_(0.5)(Fe_(1-x)Mn_(x))_(1.92)particles were obtained.The Tb_(0.5)Dy_(0.5)(Fe_(0.9)Mn_(0.1))_(2)composite manifests a good low-field magnetostrictive property and saturation magnetostriction at an axial pressure of 10 MPa,λ_(‖,saturation)≈2100 ppm,which is larger than that of the commercially available Terfenol-D(1400-1800 ppm).The preparation of composites with single crystal spherical powders may be an effective solution of developing high-performance magnetostrictive composites.展开更多
Owing to its high production costs, complexity of equipment, and difficulty in controlling parameters, spherical or subglobose tungsten powder preparation method cannot meet the demand of industrial production. Tungst...Owing to its high production costs, complexity of equipment, and difficulty in controlling parameters, spherical or subglobose tungsten powder preparation method cannot meet the demand of industrial production. Tungstic oxide powder was treated by particle composite system and its effects were studied. Morphologies of par- ticles were investigated by scanning electron microscopy （SEM）. Particle size analysis was carried out and the related mechanism was discussed. The results show that the processing effect is best when the rotational speed is set at 4,000 r.min-1 for 15 rain： the powder particles become nearly spherical and their sharp edge angles are rounded off and reshaped. When the processing time is 60 min, the powders smash to pieces because of too much energy inputting. So the test results, such as grain size distribution, can be explained well. Nearly spherical tungsten powder is obtained after reduction at 780 ℃ for 2 h and its flow ability is significantly improved.展开更多
Four types of hollow spherical micro- and nano-szied powders of ZrO2-7wt.%Y2O3(7YSZ), ZrO2-7wt.%Y2O3, Al2O3-13 wt.% TiO2(AT) and WC as well as one type of core/shell structured powder of ZrB2-30 wt.%Mo Si2 were prepar...Four types of hollow spherical micro- and nano-szied powders of ZrO2-7wt.%Y2O3(7YSZ), ZrO2-7wt.%Y2O3, Al2O3-13 wt.% TiO2(AT) and WC as well as one type of core/shell structured powder of ZrB2-30 wt.%Mo Si2 were prepared via plasma processing. In addition, the formation mechanisms of hollow spherical and core/shell structured powders prepared via plasma processing were also proposed.展开更多
ZrO_(2) spherical nanometer powders containing 3.5 mol%Y_(2)O_(3) have been prepared via the coupling route of water/oil(W/O)emulsion with dimethyl oxalate homogenous precipitation.ZrO_(2) powders and their precursor ...ZrO_(2) spherical nanometer powders containing 3.5 mol%Y_(2)O_(3) have been prepared via the coupling route of water/oil(W/O)emulsion with dimethyl oxalate homogenous precipitation.ZrO_(2) powders and their precursor powders have been characterized by XRD,TEM and SEM.According to the XRD result,phase volume fractions of powders were calculated by comparing the peaks’intensities of spectrum.Furthermore,phase crystal lattice constants were obtained using crystal interplanar spacing formula and Bragg equation.With these results,the theoretical density of powders was analyzed.Finally,powders’spherical degree was revealed via the method of comparison between theoretical density and actual density.展开更多
In additive manufacturing(also known as 3D printing),a layer-by-layer buildup process is used for manufacturing parts.Modern laser 3D printers can work with various materials including metal powders.In particular,mixi...In additive manufacturing(also known as 3D printing),a layer-by-layer buildup process is used for manufacturing parts.Modern laser 3D printers can work with various materials including metal powders.In particular,mixing various-sized spherical powders of titanium alloys is considered most promising for the aerospace industry.To achieve desired mechanical properties of the final product,it is necessary to maintain a certain proportional ratio between different powder fractions.In this paper,a modeling approach for filling up a rectangular 3D volume by unequal spheres in a layer-by-layer manner is proposed.A relative number of spheres of a given radius(relative frequency)are known and have to be fulfilled in the final packing.A fast heuristic has been developed to solve this special packing problem.Numerical results are compared with experimental findings for titanium alloy spherical powders.The relative frequencies obtained by using the imposed algorithm are very close to those obtained by the experiment.This provides an opportunity for using a cheap numerical modeling instead of expensive experimental study.展开更多
文摘Gas atomization was usually regarded as a good method for producing the spherical or approximate spherical powders. We found a lot of non-spherical powders in production processes, especially in larger particle size distribution area. The causes of producing non-spherical powders are explained and some analyses are done in order to find a better condition of producing spherical powders in this paper. The following morphologies were obtained by atomized Fe50 Co50 and pure iron and investigated by scanning electron microscopy （SEM）.
基金the National Innovation Foundation of China (No. 04C26225120227)
文摘Under certain conditions of proper temperature and pH value, sodium silicate was hydrolyzed in liquid ammonia chloride, and spherical microfine SiO2 powder in micrometer-size was prepared. In this experiment, the relationship between needed time and proper pH value, temperature, density of the solution, and its current capacity were found .The optimum conditions are pH 8.5, 70 ~C, and the concentration of sodium silicate is 0.6 mol/L for the density of the solution. The structure of spherical microfine silicon was characterized by SEM and XRD.
文摘In order to tackle the shortcomings of high brittleness,hard graphitization,and poor oxidation resistance resulted from carbonization of phenolic resin of Mg O- C refractories, effects of 2 mass% spherical Ni, and2 mass% spherical Ni plus 7. 5 mass% Al composite powder on microstructure of the secondary carbon in Mg O- C refractories matrix were investigated. The results show that a large number of carbon whiskers form after the carbonization of phenolic resin with Ni powder;in the Mg O- C refractories matrix with only Ni powder,the carbon microspheres form at all treatment temperatures and change slightly with the temperature rising;the carbon whiskers begin to generate in the specimens with composite powder at 1 000 ℃,the diameter of the carbon whiskers is about 0. 4- 0. 5 μm,and the length is about 3- 4 μm,and the formed carbon whiskers increase gradually with the temperature rising.
文摘Cubic phase spherical zirconia nano-powder was prepared by a direct template route in the lamellar liquid crystal formed by polyoxyethylene tert-octylphenyl ether(Triton X-100)/sodium dodecyl sulfate(SDS)/H_2O.The precursor powder and zirconia powder were characterized by XRD,FT-IR,TG/DSC,TEM,and SEM methods.Results show that the stability of the lamellar liquid crystal is controlled by NH_3·H_2O concentration.The size of nanoparticles is greatly affected by NH_3·H_2O and ZrOCl_2·8H_2O concentrations.The zirconia nanoparticles show narrow particle size distribution of 10-30 nm.
基金supported by National Natural Science Foundation of China(Grant No. 50775133)
文摘SiC magnetic abrasive is used to polish surfaces of precise, complex parts which are hard, brittle and highly corrosion-resistant in magnetic abrasive finishing（MAF）. Various techniques are employed to produce this magnetic abrasive, but few can meet production demands because they are usually time-consuming, complex with high cost, and the magnetic abrasives made by these techniques have irregular shape and low bonding strength that result in low processing efficiency and shorter service life. Therefore, an attempt is made by combining gas atomization and rapid solidification to fabricate a new iron-based SiC spherical composite magnetic abrasive. The experimental system to prepare this new magnetic abrasive is constructed according to the characteristics of gas atomization and rapid solidification process and the performance requirements of magnetic abrasive. The new iron-based SiC spherical composite magnetic abrasive is prepared successfully when the machining parameters and the composition proportion of the raw materials are controlled properly. Its morphology, microstructure, phase composition are characterized by scanning electron microscope（SEM） and X-ray diffraction（XRD） analysis. The MAF tests on plate of mold steel S136 are carried out without grinding lubricant to assess the finishing performance and service life of this new SiC magnetic abrasive. The surface roughness（Ra） of the plate worked is rapidly reduced to 0.051 μm from an initial value of 0.372 μm within 5 min. The MAF test is carried on to find that the service life of this new SiC magnetic abrasive reaches to 155 min. The results indicate that this process presented is feasible to prepare the new SiC magnetic abrasive; and compared with previous magnetic abrasives, the new SiC spherical composite magnetic abrasive has excellent finishing performance, high processing efficiency and longer service life. The presented method to fabricate magnetic abrasive through gas atomization and rapid solidification presented can significantly improve the finishing performance and service life of magnetic abrasive, and provide a more practical approach for large-scale industrial production of magnetic abrasive.
基金convergence research financial program for instructors,graduate students and professors in 2023.
文摘Characteristics of spherical particles on copper powder and changing sizes were studied in a ball mill under various experimental conditions,such as different ball diameters,high rotation speeds,and milling times,using a discrete element method(DEM)simulation.This experiment has investigated the characteristics of spherical particle morphology evolution involved in the mechanical alloying of copper powder.The morphological evolution of the copper particle was analyzed using scanning electron microscopy(SEM).A spherical copper particle was shown with a roundness value using imageJ software.The DEM was used to simulate the ball motion in a planetary ball mill,and the impact energy and shear energy generated during the collision were analyzed to estimate the contact number between the ball and the ball wall.Therefore,as the size of the ball decreased,the number of ball-to-ball and ball-to-wall contacts increased accordingly,and the spherical shape of the copper powder changed.
基金Project(50474003) supported by the National Natural Science Foundation of China
文摘A dry mechanical surface treatment was described, in which irregularly shaped metal powders were impacted and sphericized by using high speed airflow impact method particles composite system(PCS). The optimum technological parameters for the metal powders processed were determined according to the treatment effect under different conditions. The results show that the irregularly shaped metal powders are impacted into dense spherical particles, the bulk density and tap density of the metal powders increase noticeably. The combination property of metal powders is improved greatly.
基金financially supported by the National Natural Science Foundation of China (Nos.51977027 and51967008)Yunnan Key Research and Development Program (No.202102AB080008)+2 种基金the Fundamental Research Funds for the Central Universities (Nos.N2002007 and N182508026)the Open Project of Yunnan Precious Metals Laboratory Co.,Ltd. (No.YPML-2023050250)the State Key Laboratory of AdvancedTechnologies for Comprehensive Utilization of Platinum Metals (No.SKL-SPM-202014 and SKL-SPM-202015)。
文摘Monodispersed spherical Ru powders are essential for fabricating high-performance Ru sputtering targets,which have applications in very-large-scale integration circuits and magnetic recording devices.However,the synthesis of such powders remains a major challenge.Here,we reported the synthesis of monodispersed spherical Ru powders through controlling the molar ratio of SO_(4)^(2-)to Ru^(3+)in urea homogeneous precipitation solution and the annealing conditions.Without the addition of(NH4)2SO_(4)into the reaction solution,only gel-like precipitation particles were obtained.Once introducing(NH_(4))_(2)SO_(4) into the reaction solution and controlling the molar ratio of SO_(4)^(2-)to Ru3+between 0.50 and 1.00,monodispersed spherical precursor powders were obtained.The nucleation and growth of monodispersed spherical precursor particles in solution were found to conform to LaMer's model.Through controlled annealing at 450℃in a hydrogen atmosphere,the obtained metallic Ru powder with an average particle size of 135 nm inherited the spherical morphology and excellent dispersity from the monodispersed spherical precursor powders.These results and findings would deepen the understanding of the preparation of monodispersed Ru and Ru-like powders.
基金supported by the National Natural Science Foundation of China(51671102 and 11475086)。
文摘Spherical Tb_(0.5)Dy_(0.5)(Fe_(1-x)Mn_(x))_(1.92)(x=0,0.05,0.10 and 0.15)single-crystal particles were prepared.The magnetic anisotropy of the alloy decreases as x increases from 0 to 0.15.Subsequently,we prepared giant magnetostrictive composites with these spherical Tb_(0.5)Dy_(0.5)(Fe_(1-x)Mn_(x))_(1.92)single-crystal particles.As a consequence,well<111>-orie nted Tb_(0.5)Dy_(0.5)(Fe_(1-x)Mn_(x))_(1.92)composites with 55 vol%Tb_(0.5)Dy_(0.5)(Fe_(1-x)Mn_(x))_(1.92)particles were obtained.The Tb_(0.5)Dy_(0.5)(Fe_(0.9)Mn_(0.1))_(2)composite manifests a good low-field magnetostrictive property and saturation magnetostriction at an axial pressure of 10 MPa,λ_(‖,saturation)≈2100 ppm,which is larger than that of the commercially available Terfenol-D(1400-1800 ppm).The preparation of composites with single crystal spherical powders may be an effective solution of developing high-performance magnetostrictive composites.
基金financially supported by the International Science and Technology Cooperation Program of China(No.2010DFR50360)
文摘Owing to its high production costs, complexity of equipment, and difficulty in controlling parameters, spherical or subglobose tungsten powder preparation method cannot meet the demand of industrial production. Tungstic oxide powder was treated by particle composite system and its effects were studied. Morphologies of par- ticles were investigated by scanning electron microscopy （SEM）. Particle size analysis was carried out and the related mechanism was discussed. The results show that the processing effect is best when the rotational speed is set at 4,000 r.min-1 for 15 rain： the powder particles become nearly spherical and their sharp edge angles are rounded off and reshaped. When the processing time is 60 min, the powders smash to pieces because of too much energy inputting. So the test results, such as grain size distribution, can be explained well. Nearly spherical tungsten powder is obtained after reduction at 780 ℃ for 2 h and its flow ability is significantly improved.
基金National "973" program (2012CB625100)"863" program (2012AA03A512) for their financial support
文摘Four types of hollow spherical micro- and nano-szied powders of ZrO2-7wt.%Y2O3(7YSZ), ZrO2-7wt.%Y2O3, Al2O3-13 wt.% TiO2(AT) and WC as well as one type of core/shell structured powder of ZrB2-30 wt.%Mo Si2 were prepared via plasma processing. In addition, the formation mechanisms of hollow spherical and core/shell structured powders prepared via plasma processing were also proposed.
基金The authors acknowledge the support of the National Natural Science Foundation of China(Grant Nos.51004046 and 51075129)the State Key Development Program for Basic Research of China(Project No.2010CB635107)the National Natural Science Foundation of Hubei Province of China(Project No.2010CDB05806).
文摘ZrO_(2) spherical nanometer powders containing 3.5 mol%Y_(2)O_(3) have been prepared via the coupling route of water/oil(W/O)emulsion with dimethyl oxalate homogenous precipitation.ZrO_(2) powders and their precursor powders have been characterized by XRD,TEM and SEM.According to the XRD result,phase volume fractions of powders were calculated by comparing the peaks’intensities of spectrum.Furthermore,phase crystal lattice constants were obtained using crystal interplanar spacing formula and Bragg equation.With these results,the theoretical density of powders was analyzed.Finally,powders’spherical degree was revealed via the method of comparison between theoretical density and actual density.
文摘In additive manufacturing(also known as 3D printing),a layer-by-layer buildup process is used for manufacturing parts.Modern laser 3D printers can work with various materials including metal powders.In particular,mixing various-sized spherical powders of titanium alloys is considered most promising for the aerospace industry.To achieve desired mechanical properties of the final product,it is necessary to maintain a certain proportional ratio between different powder fractions.In this paper,a modeling approach for filling up a rectangular 3D volume by unequal spheres in a layer-by-layer manner is proposed.A relative number of spheres of a given radius(relative frequency)are known and have to be fulfilled in the final packing.A fast heuristic has been developed to solve this special packing problem.Numerical results are compared with experimental findings for titanium alloy spherical powders.The relative frequencies obtained by using the imposed algorithm are very close to those obtained by the experiment.This provides an opportunity for using a cheap numerical modeling instead of expensive experimental study.
