Nanometer powders of Al Fe alloy were prepared by gas evaporation. The formation regularity of the phases in the as prepared powders and the morphology of the particles were examined. The experimental results show tha...Nanometer powders of Al Fe alloy were prepared by gas evaporation. The formation regularity of the phases in the as prepared powders and the morphology of the particles were examined. The experimental results show that chemical composition of the master alloy is the key factor which controls the chemical composition of the compound phases in nanometer powders at given evaporating temperature, the compound phases with high Fe mole fraction will form with increasing of Fe content in master alloy. Only Al 13 Fe 4, FeAl 2 and Al 2Fe compound phases form in nanometer powders in present experiment, changing of the pressure of Ar can only alter relative amounts of the compound phases in the powders. Nanometer particles with inhomogeneous tissue were obtained, which is very different from that of pure Al and Fe nanometer particles. When mole fraction of Fe in particles increases, the inhomogeneity is enhanced. [展开更多
Bismuth-doped tin dioxide nanometer powders were prepared by co-precipitation method using SnCl4 and Bi（NO3）3 as raw materials. The effects of calcining temperature and doping ratio on the particle size, composition...Bismuth-doped tin dioxide nanometer powders were prepared by co-precipitation method using SnCl4 and Bi（NO3）3 as raw materials. The effects of calcining temperature and doping ratio on the particle size, composition, spectrum selectivity of bismuth-doped tin dioxide and the phase transition of Bi-Sn precursor at different temperatures were studied by means of X-ray diffraction, transmission electron microscopy, ultraviolet-visual-near infrared diffuse reflection spectrum and the thermogravimetric-differential scanning calorimetry. The results show that prepared bismuth-doped tin dioxide powders have excellent characteristics with a single-phase tetragonal structure, good dispersibility, good absorbency for ultraviolet ray and average particle size less than 10 nm. The optimum conditions for preparing bismuth-doped tin dioxide nanometer powders are as follows: calcining temperature of 600℃, ratio of bismuth-doped in a range of 0.10-0.30, and Bi-Sn precursor being dispersed by ultrasonic wave and refluxed azeotropic and distillated with mixture of n-butanol and benzene. The mechanism of phase transition of Bi-Sn precursor is that Bi 3+ enters Sn-vacancy and then forms Sn—O—Bi bond.展开更多
A serials of Fe based nanometer powders were fabricated by reduced pressure gas evaporation process with induction current as the heating source. The formation regularities of the phases in as prepared powders and the...A serials of Fe based nanometer powders were fabricated by reduced pressure gas evaporation process with induction current as the heating source. The formation regularities of the phases in as prepared powders and the structures of the nanometer particles were investigated. Pure Fe nanometer powders with about 70% γ Fe phase is prepared in present study by using the powder collector with good cooling effect. In the nanometer powders of Fe Ni alloy, solid solution phase γ (Fe,Ni) and α Fe phase form, but for Fe Cr alloys only solid solution phase α (Fe,Cr) forms. In the nanometer powders of Fe Cu alloy, only pure metal phases of γ Fe and Cu form, and no compound or solid solution phase exists. The formation regularity of the phases in the nanometer powders of alloys obeys the common phase laws in bulk alloy state.展开更多
Low cost silicon carbon nanometer powder was synthesized by carbothermal reduction method with nanometer SiO2 and carbon as raw material. Its synthesis thermodynamics were discussed. The influence of La on TG-DSC curv...Low cost silicon carbon nanometer powder was synthesized by carbothermal reduction method with nanometer SiO2 and carbon as raw material. Its synthesis thermodynamics were discussed. The influence of La on TG-DSC curve was also analyzed. It indicated that the synthesis process of SiC powder had two steps. In the first step two medial productions of SiOg and COg formed, and in the second step, β-SiC was finally synthesized. After 0.3% La added, at the first step, the initiatory forming temperature of producing SiO(g) and CO(g) declined from 1351.4 to 1250.9 ℃, and the thermal activation energy decreased from 223.6 to 34.7 J·g-1; at the second step the initiatory forming temperature of synthesizing β-SiC powder declined from 1526.5 to 1357.8 ℃, and the thermal activation energy decreased from 693.7 to 295.7 J·g-1. Without La added, the best synthesis technology for β-SiC powder was 1550 ℃ for 120 min, average powder diameter was bigger about 150 nm. With La added, the best synthesis technology was 1500 ℃ for 120 min, average powder diameter was about 100 nm.展开更多
Three types of tungsten powders were prepared by hydrogen reduction of three precursor powders at low temperature, which were used as samples, and were then characterized by Brunauer-Emmer-Teller （BET） method, scann...Three types of tungsten powders were prepared by hydrogen reduction of three precursor powders at low temperature, which were used as samples, and were then characterized by Brunauer-Emmer-Teller （BET） method, scanning electron microscopy （SEM）, transmission electronic microscopy （TEM）, small angle X-ray scattering （SAXS）, and field-emission scanning election microscopy （FESEM） respectively. The results showed that although BET and SEM could not characterize the particle size of nanometer powders, they were important means of assistance to exclude non-nanometer powders. TEM and FESEM could directly measure the particle size of nanometer powders, but this needs a lot of time, to count the average particle size and particle size distribution. SAXS could not describe the state of agglomeration. By the combination of FESEM and SAXS, the particle size, particle size distribution, and particle shape of nanometer powders could be precisely characterized.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
GaN powder of nanometer scale was prepared by metal organic chemical vapor deposition using diethylgallium azide as precursor. The resulting powder was characterized by XRD and TEM. It has been found that the particle...GaN powder of nanometer scale was prepared by metal organic chemical vapor deposition using diethylgallium azide as precursor. The resulting powder was characterized by XRD and TEM. It has been found that the particle size of the powder obtained is affected by the deposition temperature, and the fine crystals formed in temperature range 500 similar to 650 degrees C were hexagonal.展开更多
A novel process for synthesizing nano-ceramics powders, named mechanical & therm al activation processing, is discussed in the present paper. It is a processing based on thermal activation in liquid phase (molten ...A novel process for synthesizing nano-ceramics powders, named mechanical & therm al activation processing, is discussed in the present paper. It is a processing based on thermal activation in liquid phase (molten salt) after mechanical activ ation. The nanometer-sized TiC particles (15-20nm) have been synthesized by the method, and analyzed by X-ray diffraction (XRD), transmission electron microscop e (TEM), scanning electron microscopy (SEM) and energy dispersion X-ray (EDX) sp ectroscopy. An interface interaction between liquid (molten salt) and solid (fin al product particles) phases plays a dominating role for the control of product particles size. The mechanism for the formation of nanometer-sized TiC particles has been discussed.展开更多
Sb-doped SnO2 （ATO） nanometer powders were synthesized by hydrolysis of alkoxides, using SnCl4·5H2O and SbCl3 as raw materials. Some dehydrating processes, such as n-butanol/xylene mixed solvent heterogeneous a...Sb-doped SnO2 （ATO） nanometer powders were synthesized by hydrolysis of alkoxides, using SnCl4·5H2O and SbCl3 as raw materials. Some dehydrating processes, such as n-butanol/xylene mixed solvent heterogeneous azeotropic distillation, organic dehydrating agent and other dehydrating processes, were used to treat the wet colloids for preparing nonagglomerated ATO nanoparticles. The influences of dehydrating processes on the particle size, agglomeration and resistance were investigated using X-ray diffraction （XRD）, transmission electron microscopy （TEM） and Brunauer-Emmet-Teller （BET）. It is indicated that the dehydrating methods have great influences on the products properties, and that n-butanol/xylene mixed solvent heterogeneous azeotropic distillation processing and organic dehydrating agent can effectively remove the residual H2O molecules in wet colloids, and be used to prepare powders with high surface areas, about 85.32 m2/g, low agglomeration and good conductivity.展开更多
To study the effect of the particle size of industrial alumina powder on the properties of active alumina micropowder(α-Al_(2)O_(3) micropowder),the fine powders with the median diameter of 50,30,10,and 5 pm,respecti...To study the effect of the particle size of industrial alumina powder on the properties of active alumina micropowder(α-Al_(2)O_(3) micropowder),the fine powders with the median diameter of 50,30,10,and 5 pm,respectively,were obtained by grinding industrial alumina powder(the median diameter of 80 pm),and the active alumina micropowders were prepared by firing the industrial alumina powders before and after grinding at 1320℃ for 5 h.The effect of the particle size of the industrial alumina powder on the microstructure and properties of the active alumina micropowder was researched.The results indicate that the initial particle size of the industrial alumina powder has a great influence on the grain morphology of the active alumina micropowder;when the median diameter is larger than 30 pm,the α-Al_(2)O_(3) grains show wormlike aggregates state after calcination and when it is around or less than 10 pm,the α-Al_(2)O_(3) are round,spherical and well dispersed grains with the particle size of 0.3-1.0 pm.With the initial particle size of the industrial alumina powder decreasing,the α-Al_(2)O_(3) phase transition rate increases and the true density gradually increases;moreover,the α-Al_(2)O_(3) powder shows better dispersity and flowability.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
A new hydrothermal process--hydrothermal salt solution pressure-relief--was introduced, and ZnO powder with the size of 15 nm and ZnO fiber with length/diameter=16∶1 were prepared by this process. The change of parti...A new hydrothermal process--hydrothermal salt solution pressure-relief--was introduced, and ZnO powder with the size of 15 nm and ZnO fiber with length/diameter=16∶1 were prepared by this process. The change of particle size of ZnO powder and the formation mechanism of ZnO fiber were investigated. It is proposed that the main factor affecting the particle size of powders is nucleation rate, that is, the bigger the nucleation rate is, the smaller the particle is; the main factors affecting the formation of fiber include whether hydrothermal reaction proceeds under the condition of pressure-relief or not and the crystallization degree of powders before pressure-relief.展开更多
W-2 wt.%Y2O3 composite material with uniform distribution of yttrium element was fabricated through processes of mechanical alloying （MA） and spark plasma sintering （SPS）. The relevant productions were characteriz...W-2 wt.%Y2O3 composite material with uniform distribution of yttrium element was fabricated through processes of mechanical alloying （MA） and spark plasma sintering （SPS）. The relevant productions were characterized by scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. The XRD showed that the W-2 wt.%Y2O3 composite powder, including tungsten matrix and Y2O3 particles, was refined to nanometer sizes during the MA process. The SEM and TEM micrographs showed that the MA produced composite powder presented a lamellar morphology and contained many dislocations and microcracks. The EDS showed that the Y and O elements were uniformly distributed in the W matrix after mechanically alloying for 15 h. The W-2 wt.%Y2O3 composite material with uniform distribution of yttrium was obtained by sintering of the MA produced composite powder.展开更多
文摘Nanometer powders of Al Fe alloy were prepared by gas evaporation. The formation regularity of the phases in the as prepared powders and the morphology of the particles were examined. The experimental results show that chemical composition of the master alloy is the key factor which controls the chemical composition of the compound phases in nanometer powders at given evaporating temperature, the compound phases with high Fe mole fraction will form with increasing of Fe content in master alloy. Only Al 13 Fe 4, FeAl 2 and Al 2Fe compound phases form in nanometer powders in present experiment, changing of the pressure of Ar can only alter relative amounts of the compound phases in the powders. Nanometer particles with inhomogeneous tissue were obtained, which is very different from that of pure Al and Fe nanometer particles. When mole fraction of Fe in particles increases, the inhomogeneity is enhanced. [
基金Project(GC200603) supported by the Open Fund of Guangdong Provincial Key Laboratory for Green Chemicals projectsupported by the Key Laboratory of Enhanced Heat Transfer and Energy Conservation of Ministry of Education of China
文摘Bismuth-doped tin dioxide nanometer powders were prepared by co-precipitation method using SnCl4 and Bi（NO3）3 as raw materials. The effects of calcining temperature and doping ratio on the particle size, composition, spectrum selectivity of bismuth-doped tin dioxide and the phase transition of Bi-Sn precursor at different temperatures were studied by means of X-ray diffraction, transmission electron microscopy, ultraviolet-visual-near infrared diffuse reflection spectrum and the thermogravimetric-differential scanning calorimetry. The results show that prepared bismuth-doped tin dioxide powders have excellent characteristics with a single-phase tetragonal structure, good dispersibility, good absorbency for ultraviolet ray and average particle size less than 10 nm. The optimum conditions for preparing bismuth-doped tin dioxide nanometer powders are as follows: calcining temperature of 600℃, ratio of bismuth-doped in a range of 0.10-0.30, and Bi-Sn precursor being dispersed by ultrasonic wave and refluxed azeotropic and distillated with mixture of n-butanol and benzene. The mechanism of phase transition of Bi-Sn precursor is that Bi 3+ enters Sn-vacancy and then forms Sn—O—Bi bond.
文摘A serials of Fe based nanometer powders were fabricated by reduced pressure gas evaporation process with induction current as the heating source. The formation regularities of the phases in as prepared powders and the structures of the nanometer particles were investigated. Pure Fe nanometer powders with about 70% γ Fe phase is prepared in present study by using the powder collector with good cooling effect. In the nanometer powders of Fe Ni alloy, solid solution phase γ (Fe,Ni) and α Fe phase form, but for Fe Cr alloys only solid solution phase α (Fe,Cr) forms. In the nanometer powders of Fe Cu alloy, only pure metal phases of γ Fe and Cu form, and no compound or solid solution phase exists. The formation regularity of the phases in the nanometer powders of alloys obeys the common phase laws in bulk alloy state.
基金Project supported by the National Natural Science Foundation of China (50672060 and 50372041)Projectof Liaoning Province Government (20052002)
文摘Low cost silicon carbon nanometer powder was synthesized by carbothermal reduction method with nanometer SiO2 and carbon as raw material. Its synthesis thermodynamics were discussed. The influence of La on TG-DSC curve was also analyzed. It indicated that the synthesis process of SiC powder had two steps. In the first step two medial productions of SiOg and COg formed, and in the second step, β-SiC was finally synthesized. After 0.3% La added, at the first step, the initiatory forming temperature of producing SiO(g) and CO(g) declined from 1351.4 to 1250.9 ℃, and the thermal activation energy decreased from 223.6 to 34.7 J·g-1; at the second step the initiatory forming temperature of synthesizing β-SiC powder declined from 1526.5 to 1357.8 ℃, and the thermal activation energy decreased from 693.7 to 295.7 J·g-1. Without La added, the best synthesis technology for β-SiC powder was 1550 ℃ for 120 min, average powder diameter was bigger about 150 nm. With La added, the best synthesis technology was 1500 ℃ for 120 min, average powder diameter was about 100 nm.
文摘Three types of tungsten powders were prepared by hydrogen reduction of three precursor powders at low temperature, which were used as samples, and were then characterized by Brunauer-Emmer-Teller （BET） method, scanning electron microscopy （SEM）, transmission electronic microscopy （TEM）, small angle X-ray scattering （SAXS）, and field-emission scanning election microscopy （FESEM） respectively. The results showed that although BET and SEM could not characterize the particle size of nanometer powders, they were important means of assistance to exclude non-nanometer powders. TEM and FESEM could directly measure the particle size of nanometer powders, but this needs a lot of time, to count the average particle size and particle size distribution. SAXS could not describe the state of agglomeration. By the combination of FESEM and SAXS, the particle size, particle size distribution, and particle shape of nanometer powders could be precisely characterized.
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.
文摘GaN powder of nanometer scale was prepared by metal organic chemical vapor deposition using diethylgallium azide as precursor. The resulting powder was characterized by XRD and TEM. It has been found that the particle size of the powder obtained is affected by the deposition temperature, and the fine crystals formed in temperature range 500 similar to 650 degrees C were hexagonal.
基金The project was supported by China Postdoctoral Science Foundation(No.2003034452)National Natural Science Foundation of China(No.50371027).
文摘A novel process for synthesizing nano-ceramics powders, named mechanical & therm al activation processing, is discussed in the present paper. It is a processing based on thermal activation in liquid phase (molten salt) after mechanical activ ation. The nanometer-sized TiC particles (15-20nm) have been synthesized by the method, and analyzed by X-ray diffraction (XRD), transmission electron microscop e (TEM), scanning electron microscopy (SEM) and energy dispersion X-ray (EDX) sp ectroscopy. An interface interaction between liquid (molten salt) and solid (fin al product particles) phases plays a dominating role for the control of product particles size. The mechanism for the formation of nanometer-sized TiC particles has been discussed.
基金This work was supported by the National Natural Science Foundation of China coal joint fund key projects ＂Large section roadway fast driving and supporting basic research （no. 51134012）＂ and the Anhui Provincial Program for the Tackling Key Problem （07010302189） and the Program for the Provincial Innovation Research and Development of Anhui Mil- itary and Civilian Projects （Anhui Provincial Financial Enterprises [2013] 1202）. And the authors are grateful to the Anhui Provincial Educational Office Key Program （KJ2010A102）.
文摘Sb-doped SnO2 （ATO） nanometer powders were synthesized by hydrolysis of alkoxides, using SnCl4·5H2O and SbCl3 as raw materials. Some dehydrating processes, such as n-butanol/xylene mixed solvent heterogeneous azeotropic distillation, organic dehydrating agent and other dehydrating processes, were used to treat the wet colloids for preparing nonagglomerated ATO nanoparticles. The influences of dehydrating processes on the particle size, agglomeration and resistance were investigated using X-ray diffraction （XRD）, transmission electron microscopy （TEM） and Brunauer-Emmet-Teller （BET）. It is indicated that the dehydrating methods have great influences on the products properties, and that n-butanol/xylene mixed solvent heterogeneous azeotropic distillation processing and organic dehydrating agent can effectively remove the residual H2O molecules in wet colloids, and be used to prepare powders with high surface areas, about 85.32 m2/g, low agglomeration and good conductivity.
文摘To study the effect of the particle size of industrial alumina powder on the properties of active alumina micropowder(α-Al_(2)O_(3) micropowder),the fine powders with the median diameter of 50,30,10,and 5 pm,respectively,were obtained by grinding industrial alumina powder(the median diameter of 80 pm),and the active alumina micropowders were prepared by firing the industrial alumina powders before and after grinding at 1320℃ for 5 h.The effect of the particle size of the industrial alumina powder on the microstructure and properties of the active alumina micropowder was researched.The results indicate that the initial particle size of the industrial alumina powder has a great influence on the grain morphology of the active alumina micropowder;when the median diameter is larger than 30 pm,the α-Al_(2)O_(3) grains show wormlike aggregates state after calcination and when it is around or less than 10 pm,the α-Al_(2)O_(3) are round,spherical and well dispersed grains with the particle size of 0.3-1.0 pm.With the initial particle size of the industrial alumina powder decreasing,the α-Al_(2)O_(3) phase transition rate increases and the true density gradually increases;moreover,the α-Al_(2)O_(3) powder shows better dispersity and flowability.
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.
文摘A new hydrothermal process--hydrothermal salt solution pressure-relief--was introduced, and ZnO powder with the size of 15 nm and ZnO fiber with length/diameter=16∶1 were prepared by this process. The change of particle size of ZnO powder and the formation mechanism of ZnO fiber were investigated. It is proposed that the main factor affecting the particle size of powders is nucleation rate, that is, the bigger the nucleation rate is, the smaller the particle is; the main factors affecting the formation of fiber include whether hydrothermal reaction proceeds under the condition of pressure-relief or not and the crystallization degree of powders before pressure-relief.
文摘W-2 wt.%Y2O3 composite material with uniform distribution of yttrium element was fabricated through processes of mechanical alloying （MA） and spark plasma sintering （SPS）. The relevant productions were characterized by scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. The XRD showed that the W-2 wt.%Y2O3 composite powder, including tungsten matrix and Y2O3 particles, was refined to nanometer sizes during the MA process. The SEM and TEM micrographs showed that the MA produced composite powder presented a lamellar morphology and contained many dislocations and microcracks. The EDS showed that the Y and O elements were uniformly distributed in the W matrix after mechanically alloying for 15 h. The W-2 wt.%Y2O3 composite material with uniform distribution of yttrium was obtained by sintering of the MA produced composite powder.
