Ceria(CeO_(2))nanoparticles were successfully synthesized via a simple complex-precipitation route that employs cerium chloride as cerium source and citric acid as precipitant.The elemental analysis results of carbon,...Ceria(CeO_(2))nanoparticles were successfully synthesized via a simple complex-precipitation route that employs cerium chloride as cerium source and citric acid as precipitant.The elemental analysis results of carbon,hydrogen,oxygen,and cerium in the precursors were calculated,and the results revealed that the precursors were composed of Ce(OH)_(3),Ce(H_(2)Cit)_(3),or CeCit.X-ray diffraction analysis showed that all ceria nanoparticles had a face-centered cubic structure.With the molar ratio of citric acid to Ce^(3)+(n)of 0.25 and pH of 5.5,the specific surface area of the sample reached the maximum value of 83.17 m^(2)/g.Ceria nanoparticles were observed by scanning electron microscopy.Selected area electron diffraction patterns of several samples were obtained by transmission electron microscopy,and the crystal plane spacing of each low-exponent crystal plane was calculated.The ultraviolet(UV)–visible transmittance curve showed that ceria can absorb UV light and pass through visible light.Among all samples,the minimum average transmittance of ultraviolet radiation a(UVA)was 4.42%,and that of ultraviolet radiation b(UVB)was 1.56%.展开更多
Since ultraviolet(UV)light,as well as blue light,which is part of visible light,is harmful to skin,samarium-cerium compounds containing Sm_(2)O_(2)S were synthesized by co-precipitation method.This kind of compounds b...Since ultraviolet(UV)light,as well as blue light,which is part of visible light,is harmful to skin,samarium-cerium compounds containing Sm_(2)O_(2)S were synthesized by co-precipitation method.This kind of compounds blocks not only UV light,but also blue light.The minimum values of average transmittance(360-450 nm)and band gap of samarium-cerium compounds were 8.90%and 2.76 eV,respectively,which were less than 13.96%and 3.01 eV of CeO_(2).Elemental analysis(EA),X-ray diffraction(XRD),Fourier transformation infrared(FTIR),and Raman spectra determined that the samples contained Ce_(4)O_(7),Sm_(2)O_(2)S,Sm_(2)O_(3),and Sm_(2)O_(2)SO_(4).The microstructure of samples was analyzed by scanning and transmission electron microscopies(SEM and TEM).X-ray photoelectron spectrum(XPS)showed that cerium had Ce^(3+)and Ce^(4+) valence states,and oxygen was divided into lattice oxygen and oxygen vacancy,which was the direct cause of the decrease of average transmittance and band gap.展开更多
Solvent extraction experiments of La(III) with di-(2-ethylhexyl)phosphoric acid (P204) from chloride solution in the presence of a complexing agent (lactic acid) have been performed. The effective separation factors c...Solvent extraction experiments of La(III) with di-(2-ethylhexyl)phosphoric acid (P204) from chloride solution in the presence of a complexing agent (lactic acid) have been performed. The effective separation factors can be achieved when the complexing agent is added to the aqueous phase of the extraction system. The complexing agent lactic acid can be effectively recycled using tributyl phosphate (TBP) as extractant, by the use of a countercurrent extraction process, and the chemical oxygen demand (COD) value in the raffinate is 57.7 mg/L, which meets the emission standards of pollutants from rare earths industry. Thus, the simple and environment-friendly complexing method has been proved to be an effective strategy for separating light rare earths, and provides a positive influence on the purification of La(III).展开更多
Isoconversional methods combined with thermogravimetry were applied to investigate the decomposition kinetics of bastnaesite concentrates with different amounts of calcium hydroxide added.The apparent activation energ...Isoconversional methods combined with thermogravimetry were applied to investigate the decomposition kinetics of bastnaesite concentrates with different amounts of calcium hydroxide added.The apparent activation energy was calculated,and the results indicate that the overall reaction involves more than one single step.The reaction with a lower content(<15 wt%)of calcium hydroxide can be divided into two steps,while the reaction with a higher content(>15 wt%)involves another step which denotes the decomposition of newly formed calcium carbonate during roasting.The activation energy increases with increasing amount of calcium hydroxide in the lower range(0-15 wt%).This is due to the resistance of calcium hydroxide to heat and mass transport,However,more calcium can promote the decomposition reaction more effectively and thus reduce the activation energy.Nonlinear fitting was performed by fitting the experimental data to Avrami-Erofeev model to determine the reaction model and pre-exponential factor.The theoretical models were proven to be reliable for kinetic prediction.展开更多
The thermal decomposition of CeCl3·7 H2O was studied from room temperature to 800 ℃. Analysis was performed by applying TG-DTA, XRD, FESEM, EDXS, and TG-MS technologies to investigate the thermal decomposition m...The thermal decomposition of CeCl3·7 H2O was studied from room temperature to 800 ℃. Analysis was performed by applying TG-DTA, XRD, FESEM, EDXS, and TG-MS technologies to investigate the thermal decomposition mechanism of CeCl3·7 H2O in air atmosphere. Multiple forms of hydrated cerium chloride compound were observed in the dehydration products. The CeCl3hydrolysis product was separated by a continuous centrifugation method and the phase composition was identified as CeO2,Ce(OH)3,and CeCl3·4 H2O by XRD analysis. The evolved gas composition was identified as CI2and HCI by TG-MS system. Based on the analysis of the experimental results, the mechanism of thermal decomposition of CeCl3·7 H2O was proposed with completion of the dehydration reaction at 224 ℃,the hydrolysis reaction at 170-480 ℃,and the oxidation reaction of CeCl3above 480 ℃.展开更多
"New"electro-optical(EO)crystals are hard to find,"old"EO crystals are scarce and each has its own problems,and the demand for high-performance EO crystals by higher power,higher repetition rate,an..."New"electro-optical(EO)crystals are hard to find,"old"EO crystals are scarce and each has its own problems,and the demand for high-performance EO crystals by higher power,higher repetition rate,and narrower pulse width laser is realistic and urgent.The EO performance of KTP was recognized as soon as it was discovered,but after more than 40 years of development,the reports,and products of EO devices based on KTP are less than those of other EO crystals,even though KTP is now almost the cheapest nonlinear optical crystal material.In this paper,based on our understanding of the crystal structure of predecessors and ourselves,especially the understanding and practice of quasi-one-dimensional ionic conduction mechanism,we think that crystal growth is the most important reason that affects the controllability of crystal performance.Through a series of science and technology,we realize the growth of large-size crystals with high-optical uniformity,then reduce the absorption of KTP to a very low level,and grow crystals with resistance to electric damage and laser damage.On this basis,reducing the conductivity and improving the uniformity of optical,electrical,piezoelectric,and ferroelectric properties are emphasized.The extinction ratio,piezoelectric ringing effect,and thermal influence of the EO switch based on KTP crystal are tested,and some publicly available progress of using KTP EO devices in high-repetition rate laser is listed.Finally,we are looking forward to the development of KTP EO crystal for the laser system to EO generator for integrated optics.展开更多
This paper deals with the structural analysis problem of dynamic lumped process high-index differential algebraic equations(DAE)models.The existing graph theoretical method depends on the change in the relative positi...This paper deals with the structural analysis problem of dynamic lumped process high-index differential algebraic equations(DAE)models.The existing graph theoretical method depends on the change in the relative position of underspecified and overspecified subgraphs and has an effect to the value of the differential index for complex models.In this paper,we consider two methods for index reduction of such models by differentiation:Pryce’s method and the symbolic differential elimination algorithm rifsimp.They can remedy the above drawbacks.Discussion and comparison of these methods are given via a class of fundamental process simulation examples.In particular,the efficiency of Pryce’s method is illustrated as a function of the number of tanks in process design.Moreover,a range of nontrivial problems are demonstrated by the symbolic differential elimination algorithm and fast prolongation.展开更多
基金financially supported by the Major State Basic Research Development Program of China(No.2012CBA01205)the National Natural Science Foundation of China(No.51274060)。
文摘Ceria(CeO_(2))nanoparticles were successfully synthesized via a simple complex-precipitation route that employs cerium chloride as cerium source and citric acid as precipitant.The elemental analysis results of carbon,hydrogen,oxygen,and cerium in the precursors were calculated,and the results revealed that the precursors were composed of Ce(OH)_(3),Ce(H_(2)Cit)_(3),or CeCit.X-ray diffraction analysis showed that all ceria nanoparticles had a face-centered cubic structure.With the molar ratio of citric acid to Ce^(3)+(n)of 0.25 and pH of 5.5,the specific surface area of the sample reached the maximum value of 83.17 m^(2)/g.Ceria nanoparticles were observed by scanning electron microscopy.Selected area electron diffraction patterns of several samples were obtained by transmission electron microscopy,and the crystal plane spacing of each low-exponent crystal plane was calculated.The ultraviolet(UV)–visible transmittance curve showed that ceria can absorb UV light and pass through visible light.Among all samples,the minimum average transmittance of ultraviolet radiation a(UVA)was 4.42%,and that of ultraviolet radiation b(UVB)was 1.56%.
基金financially supported by the Major State Basic Research Development Program of China(973 Program)(No.2012CBA01205)the National Natural Science Foundation of China(No.51274060)。
文摘Since ultraviolet(UV)light,as well as blue light,which is part of visible light,is harmful to skin,samarium-cerium compounds containing Sm_(2)O_(2)S were synthesized by co-precipitation method.This kind of compounds blocks not only UV light,but also blue light.The minimum values of average transmittance(360-450 nm)and band gap of samarium-cerium compounds were 8.90%and 2.76 eV,respectively,which were less than 13.96%and 3.01 eV of CeO_(2).Elemental analysis(EA),X-ray diffraction(XRD),Fourier transformation infrared(FTIR),and Raman spectra determined that the samples contained Ce_(4)O_(7),Sm_(2)O_(2)S,Sm_(2)O_(3),and Sm_(2)O_(2)SO_(4).The microstructure of samples was analyzed by scanning and transmission electron microscopies(SEM and TEM).X-ray photoelectron spectrum(XPS)showed that cerium had Ce^(3+)and Ce^(4+) valence states,and oxygen was divided into lattice oxygen and oxygen vacancy,which was the direct cause of the decrease of average transmittance and band gap.
文摘Solvent extraction experiments of La(III) with di-(2-ethylhexyl)phosphoric acid (P204) from chloride solution in the presence of a complexing agent (lactic acid) have been performed. The effective separation factors can be achieved when the complexing agent is added to the aqueous phase of the extraction system. The complexing agent lactic acid can be effectively recycled using tributyl phosphate (TBP) as extractant, by the use of a countercurrent extraction process, and the chemical oxygen demand (COD) value in the raffinate is 57.7 mg/L, which meets the emission standards of pollutants from rare earths industry. Thus, the simple and environment-friendly complexing method has been proved to be an effective strategy for separating light rare earths, and provides a positive influence on the purification of La(III).
基金Project supported by the National Basic Research Program(973 Program,2012CBA01205)。
文摘Isoconversional methods combined with thermogravimetry were applied to investigate the decomposition kinetics of bastnaesite concentrates with different amounts of calcium hydroxide added.The apparent activation energy was calculated,and the results indicate that the overall reaction involves more than one single step.The reaction with a lower content(<15 wt%)of calcium hydroxide can be divided into two steps,while the reaction with a higher content(>15 wt%)involves another step which denotes the decomposition of newly formed calcium carbonate during roasting.The activation energy increases with increasing amount of calcium hydroxide in the lower range(0-15 wt%).This is due to the resistance of calcium hydroxide to heat and mass transport,However,more calcium can promote the decomposition reaction more effectively and thus reduce the activation energy.Nonlinear fitting was performed by fitting the experimental data to Avrami-Erofeev model to determine the reaction model and pre-exponential factor.The theoretical models were proven to be reliable for kinetic prediction.
基金Project supported by the National Natural Science Foundation of China(51274060)National Sci-Tech Support Plan(2012BAE01B02)Basic scientific research business expenses(N150204019)
文摘The thermal decomposition of CeCl3·7 H2O was studied from room temperature to 800 ℃. Analysis was performed by applying TG-DTA, XRD, FESEM, EDXS, and TG-MS technologies to investigate the thermal decomposition mechanism of CeCl3·7 H2O in air atmosphere. Multiple forms of hydrated cerium chloride compound were observed in the dehydration products. The CeCl3hydrolysis product was separated by a continuous centrifugation method and the phase composition was identified as CeO2,Ce(OH)3,and CeCl3·4 H2O by XRD analysis. The evolved gas composition was identified as CI2and HCI by TG-MS system. Based on the analysis of the experimental results, the mechanism of thermal decomposition of CeCl3·7 H2O was proposed with completion of the dehydration reaction at 224 ℃,the hydrolysis reaction at 170-480 ℃,and the oxidation reaction of CeCl3above 480 ℃.
基金supported by the National Natural ScienceFoundation of China(51890864 and 60378032)the National High-tech R&D Programof China(2006AA030110)+2 种基金the National Key R&D Program of China(SQ2021YFB3600023,SQ2020YFF0405730)the Scientific Research and Technology Development Program of Guangxi(1348018-7,10123002-14,0630004-3B,AA17204068,and AD17195087)the Science and technology Development Plan of China Nonferrous Metal Mining Group(2018KUJH08,and 2014KJJH03).
文摘"New"electro-optical(EO)crystals are hard to find,"old"EO crystals are scarce and each has its own problems,and the demand for high-performance EO crystals by higher power,higher repetition rate,and narrower pulse width laser is realistic and urgent.The EO performance of KTP was recognized as soon as it was discovered,but after more than 40 years of development,the reports,and products of EO devices based on KTP are less than those of other EO crystals,even though KTP is now almost the cheapest nonlinear optical crystal material.In this paper,based on our understanding of the crystal structure of predecessors and ourselves,especially the understanding and practice of quasi-one-dimensional ionic conduction mechanism,we think that crystal growth is the most important reason that affects the controllability of crystal performance.Through a series of science and technology,we realize the growth of large-size crystals with high-optical uniformity,then reduce the absorption of KTP to a very low level,and grow crystals with resistance to electric damage and laser damage.On this basis,reducing the conductivity and improving the uniformity of optical,electrical,piezoelectric,and ferroelectric properties are emphasized.The extinction ratio,piezoelectric ringing effect,and thermal influence of the EO switch based on KTP crystal are tested,and some publicly available progress of using KTP EO devices in high-repetition rate laser is listed.Finally,we are looking forward to the development of KTP EO crystal for the laser system to EO generator for integrated optics.
基金supported by the National Basic Research Program of China(2011CB302402)the National Natural Science Foundation of China(Grant Nos.91118001,11171053)+1 种基金the West Light Foundation of the Chinese Academy of Sciences,China Postdoctoral Science Foundation Funded Project(Grant No.2012M521692)the Chinese Academy of Sciences Visiting Professorship for Senior International Scientists(Grant No.2010T2G31)。
文摘This paper deals with the structural analysis problem of dynamic lumped process high-index differential algebraic equations(DAE)models.The existing graph theoretical method depends on the change in the relative position of underspecified and overspecified subgraphs and has an effect to the value of the differential index for complex models.In this paper,we consider two methods for index reduction of such models by differentiation:Pryce’s method and the symbolic differential elimination algorithm rifsimp.They can remedy the above drawbacks.Discussion and comparison of these methods are given via a class of fundamental process simulation examples.In particular,the efficiency of Pryce’s method is illustrated as a function of the number of tanks in process design.Moreover,a range of nontrivial problems are demonstrated by the symbolic differential elimination algorithm and fast prolongation.
