Thermodynamic and kinetic aspects of Sn nucleation and growth processes onto a glassy carbon electrode from SnCl2·2H2O dissolved in ethylene glycol solutions were studied.Typical reduction and oxidation peaks obs...Thermodynamic and kinetic aspects of Sn nucleation and growth processes onto a glassy carbon electrode from SnCl2·2H2O dissolved in ethylene glycol solutions were studied.Typical reduction and oxidation peaks observed in voltammograms have demonstrated the capability of ethylene glycol solutions to electrodeposit Sn.The temperature-dependence of diffusion coefficient values derived from potentiodynamic and potentiostatic studies helped to determine and validate estimations of the activation energy for Sn(II)bulk diffusion.Chronoamperometric results have identified that,the suitable model to describe the early stage of Sn electrodeposition could be composed of Sn three-dimensional nucleation and diffusion-controlled growth and water reduction contributions,which was duly validated by theoretical and experimental approaches.From the model,typical kinetic parameters such as the nucleation frequency of Sn(A),number density of Sn nuclei(N_(0)),and diffusion coefficient of Sn(II)ions(D),were determined.The presence of Sn nuclei with excellent quality and their structures were verified using SEM,EDX,and XRD techniques.展开更多
A Ni layer with a thickness of about 100 nm was sputtered on Cu substrates,followed by an ultrasonic seeding with nanodiamond suspension.High-quality diamond film with its crystalline grains close to thermal equilibri...A Ni layer with a thickness of about 100 nm was sputtered on Cu substrates,followed by an ultrasonic seeding with nanodiamond suspension.High-quality diamond film with its crystalline grains close to thermal equilibrium shape was deposited on Cu substrates by hot-filament chemical vapor deposition（HF-CVD）,and the sp2 carbon content was less than 5.56%.The nucleation and growth of diamond film were investigated by micro-Raman spectroscopy,scanning electron microscopy,and X-ray diffraction.The results show that the nucleation density of diamond on the Ni-modified Cu substrates is 10 times higher than that on blank Cu substrates.The enhancement mechanism of the nucleation kinetics by Ni modification layer results from two effects：namely,the nanometer rough Ni-modified surface shows an improved absorption of nanodiamond particles that act as starting points for the diamond nucleation during HF-CVD process;the strong catalytic effect of the Ni-modified surface causes the formation of graphite layer that acts as an intermediate to facilitate diamond nucleation quickly.展开更多
In order to solve the problems of environment pollution and high cost in traditional process of bismuth subcarbonate preparation, a new process using ball-milling transformation method from NH4HCO3 and Bi2O3 was propo...In order to solve the problems of environment pollution and high cost in traditional process of bismuth subcarbonate preparation, a new process using ball-milling transformation method from NH4HCO3 and Bi2O3 was proposed. Additionally, the kinetics of bismuth subcarbonate preparation was studied. Effects of reaction temperature, particle size of bismuth oxide, solid-to-liquid ratio and concentrations of ammonium bicarbonate on the conversion rate of bismuth oxide were studied. The results indicate that the conversion rate of bismuth oxide significantly increased under the conditions of higher temperature, smaller particle size, higher concentration of ammonium bicarbonate and smaller solid-to-liquid ratio. The XRD and ICP-AES analyses show that the purity of product is high. The reaction kinetics with activation energy of 9.783 kJ/mol was analyzed by shrinking core model, and the whole transformation process is controlled by solid product layer diffusion. A semi-empirical kinetics equation was obtained to describe the conversion process.展开更多
For understanding the rock microscopic damage and dynamic mechanical properties subjected to recurrent freeze-thaw cycles, experiments for five groups of homogeneous sandstone under different freeze-thaw cycles were c...For understanding the rock microscopic damage and dynamic mechanical properties subjected to recurrent freeze-thaw cycles, experiments for five groups of homogeneous sandstone under different freeze-thaw cycles were conducted. After freezethaw, nuclear magnetic resonance(NMR) tests and impact loading tests were carried out, from which microscopic damage characteristics of sandstone and dynamic mechanical parameters were obtained. The results indicate that the porosity increases with the increase of cycle number, the rate of porosity growth descends at the beginning of freeze-thaw, yet accelerates after a certain number of cycles. The proportion of pores with different sizes changes dynamically and the multi-scale distribution of pores tends to develop on pore structure with the continuing impact of freeze-thaw and thawing. Dynamic compressive stress-strain curve of sandstone undergoing freeze-thaw can be divided into four phases, and the phase of compaction is inconspicuous compared with the static curve. Elastic modulus and dynamic peak intensity of sandstone gradually decrease with freeze-thaw cycles, while peak strain increases. The higher the porosity is, the more serious the degradation of dynamic intensity is. The porosity is of a polynomial relationship with the dynamic peak intensity.展开更多
TiN,which is ubiquitous in Ti-bearing steel,has a critical influence on both the mechanical properties and the welding process of steel,and therefore researche on the precipitation behavior of TiN in molten steel bath...TiN,which is ubiquitous in Ti-bearing steel,has a critical influence on both the mechanical properties and the welding process of steel,and therefore researche on the precipitation behavior of TiN in molten steel bath is of great significance.In this paper,Ti-bearing peritectic steel was taken as the study object and FactSage was adopted to explore how the precipitation behavior of typical inclusions in steel was affected by the steel composition.Furthermore,microsegregation models were used to analyze the precipitation process of TiN at solidification front,and the calculation results were finally verified by scanning electron microscope(SEM).Research showed that a multitude of dispersed particles of high melting oxide MgAl2O4 or MgO always existed in molten steel after magnesium treatment.In consideration of the segregation and enrichment of solute elements at the solidification front,the Ohnaka microsegregation model was employed to compute the precipitation during solidification.In the event of the solid fraction reaching 0.95 or more,the concentration product of[Ti][N]at the solidification front exceeded the equilibrium concentration product,then TiN began to precipitate.MgO or MgAl2O4 cores were generally found in TiN particles of peritectic steel after the magnesium treatment,which was consistent with the thermodynamic calculation results.Moreover,the average size of TiN particles was reduced by approximately 49%.This demonstrated that Mg-rich high melting inclusions were formed after the magnesium treatment,by which the heterogeneous nucleation of TiN was promoted it;therefore,favorable nucleation sites were provided for further refining the high-temperature ferrite phase.展开更多
The distribution of ^(125)I recombinant E. coli L-asparaginase in tissues ororgans and the excretion in urine, feces and bile were studied with in vivo radioactive tracertechnique. The amount of radioactivity excreted...The distribution of ^(125)I recombinant E. coli L-asparaginase in tissues ororgans and the excretion in urine, feces and bile were studied with in vivo radioactive tracertechnique. The amount of radioactivity excreted in urine, feces and bile within 24 h afterintravenous administration of ^(125)I recombinant E. col L-asparaginase to rats was 68.95% ,4.44%and 5.36% of the dose respectively. ^(125)I recombinant E. coli L-asparaginase in plasma samples wasdetermined. The levels of structural intact molecule in plasma samples were evaluated by SDS-PAGEand bio-imaging analyzer system. Pharmacokinetic parameters were assessed with a model-dependentmethod. The concentration-time curves of recombinant E. coli L-asparaginase after intravenousinjection at 1 250 IU·kg^(-1), 2 500, IU·kg^(-1), 5 000 IU·kg^(-1) to rats were consistent withthe two-compartment model. The first and terminal elimination t_(1/2) were 0.52 ~ 0.63 h and 2.39 ~2.76 h respectively. AUC was linearly related to the doses. The results of distribution in tissuesor organs and excretion in urine suggested that the metabolites of the enzyme were cleared bymechanisms of urinary excretion. Pharmacokinetics parameters of recombinant E. coli L- asparaginasein rats are warranted for the design of future clinical trials.展开更多
Phosphogypsum(PG)is a potential resource for rare earth elements(REEs).Several studies have been carried out on REE leaching from PG.However,few in-depth studies have investigated the kinetics of this leaching process...Phosphogypsum(PG)is a potential resource for rare earth elements(REEs).Several studies have been carried out on REE leaching from PG.However,few in-depth studies have investigated the kinetics of this leaching process.In this study,the leaching kinetics of REEs from PG in nitric acid at different temperatures were explored in depth.The experiments show that the maximum leaching recovery for ΣREE was 58.5%,75.9%and 83.4%at 30,60 and 80℃,respectively.Additionally,among La,Ce,Y and Nd,Y had the highest leaching rate.A new shrinking core model(SCM)based on the dissolution reaction of a cylindrical solid particle with interfacial transfer and diffusion across the product layer as the rate-controlling step was deduced and could well fit the leaching process of REEs from PG.The activation energies for the leaching of La,Ce,Y and Nd were determined on the basis of the new cylindrical SCM.In summary,the cylindrical SCM was a more suitable fitting model than the spherical SCM,and the interfacial transfer and diffusion across the product layer were the rate-controlling step for REE leaching from the PG sample.展开更多
The strength of traditional commercially pure titanium(CP-Ti) alloys often fails to meet the demand of structural materials. In order to enhance their mechanical properties, the cold-rolled CP-Ti alloys were annealed ...The strength of traditional commercially pure titanium(CP-Ti) alloys often fails to meet the demand of structural materials. In order to enhance their mechanical properties, the cold-rolled CP-Ti alloys were annealed at different temperatures, and the recrystallization behavior and texture evolution were investigated. It was found that the bimodal microstructure(equiaxed and elongated grains) was formed after partial recrystallization, and the corresponding sample exhibited an excellent combination of ultimate tensile strength(702 MPa) and total elongation(36.4%). The recrystallization nucleation of CP-Ti sheets occurred preferentially in the high strain and the high-angle grain boundaries(HAGBs) regions. Meanwhile, the internal misorientations of the deformed heterogeneous grains increased and transformed into HAGBs, which further promoted the recrystallization nucleation. The main recrystallization texture was basal TD-split texture transformed from cold-rolled basal RD-split texture, and the oriented nucleation played a dominated role during recrystallization.展开更多
In this work,the solidification of liquid iron with or without external magnetic field was investigated by using two molecular dynamics methods,namely direct cooling and two-phase simulation.The influence of external ...In this work,the solidification of liquid iron with or without external magnetic field was investigated by using two molecular dynamics methods,namely direct cooling and two-phase simulation.The influence of external magnetic field on the solidification is characterized by the critical temperature and radial distribution functions.Our computational results show that under external magnetic field,the solidification point tends to decrease significantly.By further analyzing the diffusion coefficients and viscosity,we attribute the effect to the stronger fluctuation of liquid iron atoms driven by the external magnetic field.展开更多
文摘Thermodynamic and kinetic aspects of Sn nucleation and growth processes onto a glassy carbon electrode from SnCl2·2H2O dissolved in ethylene glycol solutions were studied.Typical reduction and oxidation peaks observed in voltammograms have demonstrated the capability of ethylene glycol solutions to electrodeposit Sn.The temperature-dependence of diffusion coefficient values derived from potentiodynamic and potentiostatic studies helped to determine and validate estimations of the activation energy for Sn(II)bulk diffusion.Chronoamperometric results have identified that,the suitable model to describe the early stage of Sn electrodeposition could be composed of Sn three-dimensional nucleation and diffusion-controlled growth and water reduction contributions,which was duly validated by theoretical and experimental approaches.From the model,typical kinetic parameters such as the nucleation frequency of Sn(A),number density of Sn nuclei(N_(0)),and diffusion coefficient of Sn(II)ions(D),were determined.The presence of Sn nuclei with excellent quality and their structures were verified using SEM,EDX,and XRD techniques.
基金Project(20110933K) supported by the State Key Laboratory of Powder Metallurgy,ChinaProject(2012QNZT002) supported by the Freedom Explore Program of Central South University,ChinaProject(CSUZC2012024) supported by the Open-End Fund for the Valuable and Precision Instruments of Central South University,China
文摘A Ni layer with a thickness of about 100 nm was sputtered on Cu substrates,followed by an ultrasonic seeding with nanodiamond suspension.High-quality diamond film with its crystalline grains close to thermal equilibrium shape was deposited on Cu substrates by hot-filament chemical vapor deposition（HF-CVD）,and the sp2 carbon content was less than 5.56%.The nucleation and growth of diamond film were investigated by micro-Raman spectroscopy,scanning electron microscopy,and X-ray diffraction.The results show that the nucleation density of diamond on the Ni-modified Cu substrates is 10 times higher than that on blank Cu substrates.The enhancement mechanism of the nucleation kinetics by Ni modification layer results from two effects：namely,the nanometer rough Ni-modified surface shows an improved absorption of nanodiamond particles that act as starting points for the diamond nucleation during HF-CVD process;the strong catalytic effect of the Ni-modified surface causes the formation of graphite layer that acts as an intermediate to facilitate diamond nucleation quickly.
基金Project(50774099)supported by the National Natural Science Foundation of China
文摘In order to solve the problems of environment pollution and high cost in traditional process of bismuth subcarbonate preparation, a new process using ball-milling transformation method from NH4HCO3 and Bi2O3 was proposed. Additionally, the kinetics of bismuth subcarbonate preparation was studied. Effects of reaction temperature, particle size of bismuth oxide, solid-to-liquid ratio and concentrations of ammonium bicarbonate on the conversion rate of bismuth oxide were studied. The results indicate that the conversion rate of bismuth oxide significantly increased under the conditions of higher temperature, smaller particle size, higher concentration of ammonium bicarbonate and smaller solid-to-liquid ratio. The XRD and ICP-AES analyses show that the purity of product is high. The reaction kinetics with activation energy of 9.783 kJ/mol was analyzed by shrinking core model, and the whole transformation process is controlled by solid product layer diffusion. A semi-empirical kinetics equation was obtained to describe the conversion process.
基金Project(2013YQ17046310)supported by the National Key Scientific Instrument and Equipment Development Project of ChinaProject(2013M542138)supported by China Postdoctoral Science FoundationProjects(20130162110010,20130162120012)supported by Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘For understanding the rock microscopic damage and dynamic mechanical properties subjected to recurrent freeze-thaw cycles, experiments for five groups of homogeneous sandstone under different freeze-thaw cycles were conducted. After freezethaw, nuclear magnetic resonance(NMR) tests and impact loading tests were carried out, from which microscopic damage characteristics of sandstone and dynamic mechanical parameters were obtained. The results indicate that the porosity increases with the increase of cycle number, the rate of porosity growth descends at the beginning of freeze-thaw, yet accelerates after a certain number of cycles. The proportion of pores with different sizes changes dynamically and the multi-scale distribution of pores tends to develop on pore structure with the continuing impact of freeze-thaw and thawing. Dynamic compressive stress-strain curve of sandstone undergoing freeze-thaw can be divided into four phases, and the phase of compaction is inconspicuous compared with the static curve. Elastic modulus and dynamic peak intensity of sandstone gradually decrease with freeze-thaw cycles, while peak strain increases. The higher the porosity is, the more serious the degradation of dynamic intensity is. The porosity is of a polynomial relationship with the dynamic peak intensity.
基金Projects(51774208,52074186,U1860205)supported by the National Natural Science Foundation of China。
文摘TiN,which is ubiquitous in Ti-bearing steel,has a critical influence on both the mechanical properties and the welding process of steel,and therefore researche on the precipitation behavior of TiN in molten steel bath is of great significance.In this paper,Ti-bearing peritectic steel was taken as the study object and FactSage was adopted to explore how the precipitation behavior of typical inclusions in steel was affected by the steel composition.Furthermore,microsegregation models were used to analyze the precipitation process of TiN at solidification front,and the calculation results were finally verified by scanning electron microscope(SEM).Research showed that a multitude of dispersed particles of high melting oxide MgAl2O4 or MgO always existed in molten steel after magnesium treatment.In consideration of the segregation and enrichment of solute elements at the solidification front,the Ohnaka microsegregation model was employed to compute the precipitation during solidification.In the event of the solid fraction reaching 0.95 or more,the concentration product of[Ti][N]at the solidification front exceeded the equilibrium concentration product,then TiN began to precipitate.MgO or MgAl2O4 cores were generally found in TiN particles of peritectic steel after the magnesium treatment,which was consistent with the thermodynamic calculation results.Moreover,the average size of TiN particles was reduced by approximately 49%.This demonstrated that Mg-rich high melting inclusions were formed after the magnesium treatment,by which the heterogeneous nucleation of TiN was promoted it;therefore,favorable nucleation sites were provided for further refining the high-temperature ferrite phase.
基金ProjectsupportedbytheNationalNinth FivePlanKeyProjectFoundation No 96 90 2 0 1 2 5
文摘The distribution of ^(125)I recombinant E. coli L-asparaginase in tissues ororgans and the excretion in urine, feces and bile were studied with in vivo radioactive tracertechnique. The amount of radioactivity excreted in urine, feces and bile within 24 h afterintravenous administration of ^(125)I recombinant E. col L-asparaginase to rats was 68.95% ,4.44%and 5.36% of the dose respectively. ^(125)I recombinant E. coli L-asparaginase in plasma samples wasdetermined. The levels of structural intact molecule in plasma samples were evaluated by SDS-PAGEand bio-imaging analyzer system. Pharmacokinetic parameters were assessed with a model-dependentmethod. The concentration-time curves of recombinant E. coli L-asparaginase after intravenousinjection at 1 250 IU·kg^(-1), 2 500, IU·kg^(-1), 5 000 IU·kg^(-1) to rats were consistent withthe two-compartment model. The first and terminal elimination t_(1/2) were 0.52 ~ 0.63 h and 2.39 ~2.76 h respectively. AUC was linearly related to the doses. The results of distribution in tissuesor organs and excretion in urine suggested that the metabolites of the enzyme were cleared bymechanisms of urinary excretion. Pharmacokinetics parameters of recombinant E. coli L- asparaginasein rats are warranted for the design of future clinical trials.
基金Project(51904104) supported by the National Natural Science Foundation of ChinaProject(2020JJ5174) supported by the Natural Science Foundation of Hunan Province,China+2 种基金Project(2019M662780) supported by China Postdoctoral Science FoundationProject(19C0746) supported by Scientific Research Fund of Hunan Provincial Education Department,ChinaProject(2021-2843) supported by College Student Innovation and Entrepreneurship Training Program of Hunan Province,China。
文摘Phosphogypsum(PG)is a potential resource for rare earth elements(REEs).Several studies have been carried out on REE leaching from PG.However,few in-depth studies have investigated the kinetics of this leaching process.In this study,the leaching kinetics of REEs from PG in nitric acid at different temperatures were explored in depth.The experiments show that the maximum leaching recovery for ΣREE was 58.5%,75.9%and 83.4%at 30,60 and 80℃,respectively.Additionally,among La,Ce,Y and Nd,Y had the highest leaching rate.A new shrinking core model(SCM)based on the dissolution reaction of a cylindrical solid particle with interfacial transfer and diffusion across the product layer as the rate-controlling step was deduced and could well fit the leaching process of REEs from PG.The activation energies for the leaching of La,Ce,Y and Nd were determined on the basis of the new cylindrical SCM.In summary,the cylindrical SCM was a more suitable fitting model than the spherical SCM,and the interfacial transfer and diffusion across the product layer were the rate-controlling step for REE leaching from the PG sample.
基金financially supported by the National Natural Science Foundation of China (No.52104372)the Fundamental Research Funds for the Central Universities,China (No.N2107001)the China Postdoctoral Science Foundation (No.2019M651129)。
文摘The strength of traditional commercially pure titanium(CP-Ti) alloys often fails to meet the demand of structural materials. In order to enhance their mechanical properties, the cold-rolled CP-Ti alloys were annealed at different temperatures, and the recrystallization behavior and texture evolution were investigated. It was found that the bimodal microstructure(equiaxed and elongated grains) was formed after partial recrystallization, and the corresponding sample exhibited an excellent combination of ultimate tensile strength(702 MPa) and total elongation(36.4%). The recrystallization nucleation of CP-Ti sheets occurred preferentially in the high strain and the high-angle grain boundaries(HAGBs) regions. Meanwhile, the internal misorientations of the deformed heterogeneous grains increased and transformed into HAGBs, which further promoted the recrystallization nucleation. The main recrystallization texture was basal TD-split texture transformed from cold-rolled basal RD-split texture, and the oriented nucleation played a dominated role during recrystallization.
基金funded by the National Natural Science Foundation of China(No.22173057 for Yongle Li and No.51690164 for Xi Li)the Foundation of Shanghai Science and Technology Commission(No.21JC1402700 and No.21DZ2304900 for Yongle Li)supported by Open Project of State Key Laboratory of Advanced Special Steel,Shanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University。
文摘In this work,the solidification of liquid iron with or without external magnetic field was investigated by using two molecular dynamics methods,namely direct cooling and two-phase simulation.The influence of external magnetic field on the solidification is characterized by the critical temperature and radial distribution functions.Our computational results show that under external magnetic field,the solidification point tends to decrease significantly.By further analyzing the diffusion coefficients and viscosity,we attribute the effect to the stronger fluctuation of liquid iron atoms driven by the external magnetic field.
