A stable δ- and β-bismuth trioxide was prepared at room temperature by vacuum vapor-phase oxidation. The average crystal size of products was 14.6 nm (by XRD), the d(0.5) value was in the range from 62 nm to 69 nm, ...A stable δ- and β-bismuth trioxide was prepared at room temperature by vacuum vapor-phase oxidation. The average crystal size of products was 14.6 nm (by XRD), the d(0.5) value was in the range from 62 nm to 69 nm, and geometric standard deviation(GSD) was from 1.42 to 1.64. The results show that δ-Bi2O3 is formed when quenching rates is rapid and β-Bi2O3 is formed when it is slow. The size of grains increases with rising reaction temperature, flow rate of carrier gas, residual pressure of system and longer growing time of grains.展开更多
Zinc oxide nanometer powders were prepared by the sol-gel process.The sol and the powders characteristic of absorbing ultraviolet light is detected by the ultraviolet spectrometer.The results indicate the concentratio...Zinc oxide nanometer powders were prepared by the sol-gel process.The sol and the powders characteristic of absorbing ultraviolet light is detected by the ultraviolet spectrometer.The results indicate the concentration of zinc acetate dihydrate in isopropyl alcohol solution and the final pH value of the aqueous sol have effect on the UV absorption of the sol. The nanometer zinc oxide has strong absorption at 200 nm～360 nm,and over 90% ultraviolet in the range of 200 nm～360 nm wavelength are absorbed.The characteristic of absorbing ultraviolet light of zinc oxide increases as the particle size of zinc oxide decreases.展开更多
The decomposed characteristic of nanometer ZnO precursor compound was studied. From the research, the decomposed temperature of nanometer precursor compound of ZnO is about 230 ℃ and it may be completely decompounded...The decomposed characteristic of nanometer ZnO precursor compound was studied. From the research, the decomposed temperature of nanometer precursor compound of ZnO is about 230 ℃ and it may be completely decompounded at 350 ℃. By means of the kinetics theory, the dynamics equation of precursor compound of nanometer ZnO was obtained. Activation energy is approximately 789.83±40 J·mol -1, reaction order is about 3, and pre-exponential factor is 0.0696 mg·s -1.展开更多
Nanometer oxides La1-xSrxMnO3 were synthesized by absolute alcohol as solvent.The desired metal cations were chelated in a solution using citric acid as the chelating agents.In order to get the optimum preparation con...Nanometer oxides La1-xSrxMnO3 were synthesized by absolute alcohol as solvent.The desired metal cations were chelated in a solution using citric acid as the chelating agents.In order to get the optimum preparation condition for La1-xSrxMnO3,the pH of primal commix solution,the molar fraction of citric acid and baking temperature of predecessor block were researched by orthogonal test design method with different x.The thermal decomposition of the metal carboxylate precursor gels was studied by TG/DTA and the products derived from calcinations of the gels were characterized by XRD and TEM.The polarization curves were acquired on an electrochemical work station(LK98)and the discharge curves were acquired on a testing instrument of batteries(DC-5)with a constant current discharge under 120 mA/cm2.The results reveal that the nanometer oxides can be achieved by absolute alcohol as solvent and it has better catalytic activity.展开更多
The nanometer yttrium oxides were obtained through precipitation in aqueous solution by reaction with ammonium bicarbonate. The reaction between yttrium chloride and ammonium bicarbonate, the effect of surfactants on ...The nanometer yttrium oxides were obtained through precipitation in aqueous solution by reaction with ammonium bicarbonate. The reaction between yttrium chloride and ammonium bicarbonate, the effect of surfactants on particle size and the methods of controlling agglomeration were studied. Compared to other methods, the method of controlling the agglomeration by adding surfactant is one of the best methods for controlling the agglomeration of nanometer particles in wet-chemical process. Increasing surfactants in process of precipitation deduced particle size, obtained narrow size distribution of primary particles. As for the concentration range studied, excess surfactants increased the particle size on the contrary. Characteristics of the thermal decomposition of yttrium carbonate were studied. It indicated that the approximate chemical composition of the precipitate was Y（OH）Clx（CO3） （1-x/2） ·3H2O,the cubic Y2O3 was obtained above 600℃, the specific surface and the remain chloride of nanometer Y2O3 was decreased with calcinating temperature rising. The spherical nanometer yttrium oxide was gained with primary particles<50 nm,agglomerate distribution D 50 <150 nm, BET>35 m2/g,agglomerate constant （D 50 /D BET ）<6.展开更多
This article investigates the colloidal study for water and ethylene glycol based nanofluids.The effects of Lorentz forces and thermal radiation are considered.The process of non-dimensionalities of governing equation...This article investigates the colloidal study for water and ethylene glycol based nanofluids.The effects of Lorentz forces and thermal radiation are considered.The process of non-dimensionalities of governing equations is carried out successfully by means of similarity variables.Then,the resultant nonlinear nature of flow model is treated numerically via Runge-Kutta scheme.The characteristics of various pertinent flow parameters on the velocity,temperature,streamlines and isotherms are discussed graphically.It is inspected that the Lorentz forces favors the rotational velocity and rotational parameter opposes it.Intensification in the nanofluids temperature is observed for volumetric fraction and thermal radiation parameter and dominating trend is noted for γ-aluminum nanofluid.Furthermore,for higher rotational parameter,reverse flow is investigated.To provoke the validity of the present work,comparison between current and literature results is presented which shows an excellent agreement.It is examined that rotation favors the velocity of the fluid and more radiative fluid enhances the fluid temperature.Moreover,it is inspected that upturns in volumetric fraction improves the thermal and electrical conductivities.展开更多
Nanometer sized SnO 2 particles were prepared by a sol gel method using inorganic salt as a precursor material. Its crystallization was investigated by means of TG DTA,IR absorption spectra, X ray diffractometry ...Nanometer sized SnO 2 particles were prepared by a sol gel method using inorganic salt as a precursor material. Its crystallization was investigated by means of TG DTA,IR absorption spectra, X ray diffractometry and TEM as well as its resistivity change and the gas sensitivity varied with temperature were measured in various reducing gas. The results indicate that well crystallized nano sized SnO 2 with size around 15nm can be obtained at annealing temperature 600℃. The activation energy for the growth of nano SnO 2 was calculated to be 26.55kJ.mol 1 when the annealing temperature was higher than 500℃. The measurements also show that there is a peculiar resistance change varied with temperature for nano SnO 2.It has relevance to the increase in surface adsorbed oxygen. The selective detectivities to C 4H 10 and petrol can be increased when ruthenium ion was doped in nano SnO 2 as a catalyst and so do the gas sensitivity to CO,CH 4,H 2 etc. when rhodium ion was doped in.The detection to the several reducing gas can be realized when the temperature ranged from 260℃ to 400℃.展开更多
The nanometer yellow iron oxide was prepared by oxidizing Fe（OH）2 with air, which was verified with XRD and TEM. The result shows that nanometer yellow iron oxide is spindle-shaped and well-distributed with a long a...The nanometer yellow iron oxide was prepared by oxidizing Fe（OH）2 with air, which was verified with XRD and TEM. The result shows that nanometer yellow iron oxide is spindle-shaped and well-distributed with a long axis of 150-200 nm and short axis of 40-50 nm. Ultraviolet （UV） transmittance of the iron oxide shows the great effect of concentration on both transparency and UV ab- sorption, and it has been proven that iron oxide with a concentration of 0.025wt% is preferred. The spectrum of XRD indicates that it is goethite. When the yellow iron is dispersed in sol, given that the wavelength of UV is less than 300 nm, its UV absorption capacity is superior to those of ZnO and TiO2. The absorption capacity of the yellow iron is less than TiO2 and more than ZnO as the wavelength of UV is 300-400 nm.展开更多
The mechanism of the improvement of heat affected zone(HAZ) toughness with nanometer precipitates is discussed in this paper.The austenite grain growth during welding process can be effectively prevented with the aid ...The mechanism of the improvement of heat affected zone(HAZ) toughness with nanometer precipitates is discussed in this paper.The austenite grain growth during welding process can be effectively prevented with the aid of the pinning effect of fine particles,so that the steel plate can be improved in large-heat input welding performance.The oxide metallurgy technology with strong deoxidizers is developed in Baosteel.Large number of nanometer precipitates are formed during deoxidation,solidification and phase transformation processes.With the pinning effect of these fine particles,after welding with large-heat input of 400 kJ/cm,the average austenite grain size is 61μm in HAZ,the average energy absorbed value is 142 J for V-notch Charpy test at - 20℃.展开更多
A kind of ferrofluid containing Fe-Al oxide composite nanometer particles was synthesized. The ferrofluid made of Fe-Al oxide composite nanometer particles which ratio was Fe:Al2O3 = 3:1 and thermally treated at 300&#...A kind of ferrofluid containing Fe-Al oxide composite nanometer particles was synthesized. The ferrofluid made of Fe-Al oxide composite nanometer particles which ratio was Fe:Al2O3 = 3:1 and thermally treated at 300°C showed Faraday effect approximate linearity versus the magnetic field B, and a relatively excellent Faraday effect without saturation in varying 0 - 1.5T magnetic field, which provided a method for synthesizing the ferrofluid of Faraday rotation still continuing in a relatively high magnetic field.展开更多
The nanometer CeO2 powder was prepared by the method of microwave-assisted heating hydrolysis,and the nanometer CeO2-supported or ordinary CeO2-supported vanadia catalysts with different vanadium loadings(atomic ratio...The nanometer CeO2 powder was prepared by the method of microwave-assisted heating hydrolysis,and the nanometer CeO2-supported or ordinary CeO2-supported vanadia catalysts with different vanadium loadings(atomic ratios:100V/Ce=0.1,1,4,10,and 20) were prepared by an incipient-wetness impregnation method.Spectroscopic techniques(XRD,FT-IR,Raman and UV-Vis DRS) were utilized to characterize the structures of VOx/CeO2 catalysts.The results showed that the structures of CeO2-supported vanadium oxide catalysts de...展开更多
A series of Au/CuOx-TiO2 with various Cu/Ti ratios were prepared. CuOx/TiO2 was prepared by incipient-wetness im- pregnation with aqueous solution of copper nitrate. Au catalysts were prepared by deposition-precipitat...A series of Au/CuOx-TiO2 with various Cu/Ti ratios were prepared. CuOx/TiO2 was prepared by incipient-wetness im- pregnation with aqueous solution of copper nitrate. Au catalysts were prepared by deposition-precipitation method at pH 7 and 338 K. The catalysts were characterized by inductively-coupled plasma-mass spectrometry, temperature pro- gramming reduction, X-ray diffraction, transmission electron microscopy, high-resolution transmission electron mi- croscopy and X-ray photoelectron spectroscopy. The reaction was carried out in a fixed bed reactor with a feed con- taining 1% CO in air at WHSV of 120,000 mL/h·g. High gold dispersion and narrow size distribution was obtained. The addition of CuOx in Au/TiO2 enhanced the activity on CO oxidation significantly. CuOx was in amorphous state which could stabilize the Au nanoparticles. Cu was in Cu1+ state. Cu donated partial electrons to Au. The interactions among Au, Cu1+ and TiO2 account for the high catalytic activity for CO oxidation. The significant promotional effect of CuOx on CO oxidation at low temperature was demonstrated.展开更多
基金Project(03SSY4056) supported by the Bureau of Science and Technology of Hunan Province, China Project(04C034) supported by the Bureau of Education of Hunan Province, China
文摘A stable δ- and β-bismuth trioxide was prepared at room temperature by vacuum vapor-phase oxidation. The average crystal size of products was 14.6 nm (by XRD), the d(0.5) value was in the range from 62 nm to 69 nm, and geometric standard deviation(GSD) was from 1.42 to 1.64. The results show that δ-Bi2O3 is formed when quenching rates is rapid and β-Bi2O3 is formed when it is slow. The size of grains increases with rising reaction temperature, flow rate of carrier gas, residual pressure of system and longer growing time of grains.
文摘Zinc oxide nanometer powders were prepared by the sol-gel process.The sol and the powders characteristic of absorbing ultraviolet light is detected by the ultraviolet spectrometer.The results indicate the concentration of zinc acetate dihydrate in isopropyl alcohol solution and the final pH value of the aqueous sol have effect on the UV absorption of the sol. The nanometer zinc oxide has strong absorption at 200 nm～360 nm,and over 90% ultraviolet in the range of 200 nm～360 nm wavelength are absorbed.The characteristic of absorbing ultraviolet light of zinc oxide increases as the particle size of zinc oxide decreases.
文摘The decomposed characteristic of nanometer ZnO precursor compound was studied. From the research, the decomposed temperature of nanometer precursor compound of ZnO is about 230 ℃ and it may be completely decompounded at 350 ℃. By means of the kinetics theory, the dynamics equation of precursor compound of nanometer ZnO was obtained. Activation energy is approximately 789.83±40 J·mol -1, reaction order is about 3, and pre-exponential factor is 0.0696 mg·s -1.
文摘Nanometer oxides La1-xSrxMnO3 were synthesized by absolute alcohol as solvent.The desired metal cations were chelated in a solution using citric acid as the chelating agents.In order to get the optimum preparation condition for La1-xSrxMnO3,the pH of primal commix solution,the molar fraction of citric acid and baking temperature of predecessor block were researched by orthogonal test design method with different x.The thermal decomposition of the metal carboxylate precursor gels was studied by TG/DTA and the products derived from calcinations of the gels were characterized by XRD and TEM.The polarization curves were acquired on an electrochemical work station(LK98)and the discharge curves were acquired on a testing instrument of batteries(DC-5)with a constant current discharge under 120 mA/cm2.The results reveal that the nanometer oxides can be achieved by absolute alcohol as solvent and it has better catalytic activity.
基金Project supported by key project of science and technology research of guangdong province(2002A1070108)
文摘The nanometer yttrium oxides were obtained through precipitation in aqueous solution by reaction with ammonium bicarbonate. The reaction between yttrium chloride and ammonium bicarbonate, the effect of surfactants on particle size and the methods of controlling agglomeration were studied. Compared to other methods, the method of controlling the agglomeration by adding surfactant is one of the best methods for controlling the agglomeration of nanometer particles in wet-chemical process. Increasing surfactants in process of precipitation deduced particle size, obtained narrow size distribution of primary particles. As for the concentration range studied, excess surfactants increased the particle size on the contrary. Characteristics of the thermal decomposition of yttrium carbonate were studied. It indicated that the approximate chemical composition of the precipitate was Y（OH）Clx（CO3） （1-x/2） ·3H2O,the cubic Y2O3 was obtained above 600℃, the specific surface and the remain chloride of nanometer Y2O3 was decreased with calcinating temperature rising. The spherical nanometer yttrium oxide was gained with primary particles<50 nm,agglomerate distribution D 50 <150 nm, BET>35 m2/g,agglomerate constant （D 50 /D BET ）<6.
文摘This article investigates the colloidal study for water and ethylene glycol based nanofluids.The effects of Lorentz forces and thermal radiation are considered.The process of non-dimensionalities of governing equations is carried out successfully by means of similarity variables.Then,the resultant nonlinear nature of flow model is treated numerically via Runge-Kutta scheme.The characteristics of various pertinent flow parameters on the velocity,temperature,streamlines and isotherms are discussed graphically.It is inspected that the Lorentz forces favors the rotational velocity and rotational parameter opposes it.Intensification in the nanofluids temperature is observed for volumetric fraction and thermal radiation parameter and dominating trend is noted for γ-aluminum nanofluid.Furthermore,for higher rotational parameter,reverse flow is investigated.To provoke the validity of the present work,comparison between current and literature results is presented which shows an excellent agreement.It is examined that rotation favors the velocity of the fluid and more radiative fluid enhances the fluid temperature.Moreover,it is inspected that upturns in volumetric fraction improves the thermal and electrical conductivities.
文摘Nanometer sized SnO 2 particles were prepared by a sol gel method using inorganic salt as a precursor material. Its crystallization was investigated by means of TG DTA,IR absorption spectra, X ray diffractometry and TEM as well as its resistivity change and the gas sensitivity varied with temperature were measured in various reducing gas. The results indicate that well crystallized nano sized SnO 2 with size around 15nm can be obtained at annealing temperature 600℃. The activation energy for the growth of nano SnO 2 was calculated to be 26.55kJ.mol 1 when the annealing temperature was higher than 500℃. The measurements also show that there is a peculiar resistance change varied with temperature for nano SnO 2.It has relevance to the increase in surface adsorbed oxygen. The selective detectivities to C 4H 10 and petrol can be increased when ruthenium ion was doped in nano SnO 2 as a catalyst and so do the gas sensitivity to CO,CH 4,H 2 etc. when rhodium ion was doped in.The detection to the several reducing gas can be realized when the temperature ranged from 260℃ to 400℃.
基金This work was financially supported by the Construct Plan of Cooperation Project from the Beijing Education Committee (No.XK100080432).
文摘The nanometer yellow iron oxide was prepared by oxidizing Fe（OH）2 with air, which was verified with XRD and TEM. The result shows that nanometer yellow iron oxide is spindle-shaped and well-distributed with a long axis of 150-200 nm and short axis of 40-50 nm. Ultraviolet （UV） transmittance of the iron oxide shows the great effect of concentration on both transparency and UV ab- sorption, and it has been proven that iron oxide with a concentration of 0.025wt% is preferred. The spectrum of XRD indicates that it is goethite. When the yellow iron is dispersed in sol, given that the wavelength of UV is less than 300 nm, its UV absorption capacity is superior to those of ZnO and TiO2. The absorption capacity of the yellow iron is less than TiO2 and more than ZnO as the wavelength of UV is 300-400 nm.
文摘The mechanism of the improvement of heat affected zone(HAZ) toughness with nanometer precipitates is discussed in this paper.The austenite grain growth during welding process can be effectively prevented with the aid of the pinning effect of fine particles,so that the steel plate can be improved in large-heat input welding performance.The oxide metallurgy technology with strong deoxidizers is developed in Baosteel.Large number of nanometer precipitates are formed during deoxidation,solidification and phase transformation processes.With the pinning effect of these fine particles,after welding with large-heat input of 400 kJ/cm,the average austenite grain size is 61μm in HAZ,the average energy absorbed value is 142 J for V-notch Charpy test at - 20℃.
文摘A kind of ferrofluid containing Fe-Al oxide composite nanometer particles was synthesized. The ferrofluid made of Fe-Al oxide composite nanometer particles which ratio was Fe:Al2O3 = 3:1 and thermally treated at 300°C showed Faraday effect approximate linearity versus the magnetic field B, and a relatively excellent Faraday effect without saturation in varying 0 - 1.5T magnetic field, which provided a method for synthesizing the ferrofluid of Faraday rotation still continuing in a relatively high magnetic field.
基金supported by the National Natural Science Foundation of China (20803093,20833011,20525621)the Doctor Select Foundation for the University of State Education Ministry (200804251016)+1 种基金the Beijing Outstanding Ph.D.Thesis Foundation (YB 20091141401)the Hi-Tech Research and Development Program (863) of China (SQ2009AA06Z3488052)
文摘The nanometer CeO2 powder was prepared by the method of microwave-assisted heating hydrolysis,and the nanometer CeO2-supported or ordinary CeO2-supported vanadia catalysts with different vanadium loadings(atomic ratios:100V/Ce=0.1,1,4,10,and 20) were prepared by an incipient-wetness impregnation method.Spectroscopic techniques(XRD,FT-IR,Raman and UV-Vis DRS) were utilized to characterize the structures of VOx/CeO2 catalysts.The results showed that the structures of CeO2-supported vanadium oxide catalysts de...
文摘A series of Au/CuOx-TiO2 with various Cu/Ti ratios were prepared. CuOx/TiO2 was prepared by incipient-wetness im- pregnation with aqueous solution of copper nitrate. Au catalysts were prepared by deposition-precipitation method at pH 7 and 338 K. The catalysts were characterized by inductively-coupled plasma-mass spectrometry, temperature pro- gramming reduction, X-ray diffraction, transmission electron microscopy, high-resolution transmission electron mi- croscopy and X-ray photoelectron spectroscopy. The reaction was carried out in a fixed bed reactor with a feed con- taining 1% CO in air at WHSV of 120,000 mL/h·g. High gold dispersion and narrow size distribution was obtained. The addition of CuOx in Au/TiO2 enhanced the activity on CO oxidation significantly. CuOx was in amorphous state which could stabilize the Au nanoparticles. Cu was in Cu1+ state. Cu donated partial electrons to Au. The interactions among Au, Cu1+ and TiO2 account for the high catalytic activity for CO oxidation. The significant promotional effect of CuOx on CO oxidation at low temperature was demonstrated.
