With the microscopic phase-field dynamic model, the effects of temperature and concentration on the nucleation incubation time of Ni75AlxV25-x alloy were studied and the relation between the incubation time and precip...With the microscopic phase-field dynamic model, the effects of temperature and concentration on the nucleation incubation time of Ni75AlxV25-x alloy were studied and the relation between the incubation time and precipitation mechanism was investigated by using the atomic occupation probability picture and average order parameter curve. The simulation results demonstrate that there exists the incubation time for different precipitation mechanisms~ such as non-classical nucleation, the mixed style of non-classical nucleation and spinodal decomposition, and spinodal ordering; and the incubation time shortens in turn for the three kinds of mechanisms. With the increase of Al content of Ni75AlxV25-x alloy, the incubation time of Llz phases shortens continuously and that of DOzz phases is prolonged. The effects of temperature on the incubation time of Llz and DOzz phases are accordant, i.e. the incuba- tion time is greatly prolonged with the temperature rising.展开更多
The solution diffusion coefficient is a great important intrinsical parameter in crystal growth.On earth,it is impossible to accurately determine the diffusion coefficient since there is nature convection.One of the m...The solution diffusion coefficient is a great important intrinsical parameter in crystal growth.On earth,it is impossible to accurately determine the diffusion coefficient since there is nature convection.One of the marked charateristics of space-crystal growth is to eleminate nature convection,so that purely diffusion-controlled condition of crystal growth could be realized and precise measurement of the diffusion coefficient should be approved.展开更多
Carbon nanotube formation exemplifies atomically precise self-assembly,where atomic interactions dynamically engineer nanoscale architectures with emergent properties that transcend classical material boundaries.Howev...Carbon nanotube formation exemplifies atomically precise self-assembly,where atomic interactions dynamically engineer nanoscale architectures with emergent properties that transcend classical material boundaries.However,elucidating the transient molecular intermediates remains a critical mechanistic frontier.This study investigates the atomic-scale nucleation process of single-walled carbon nanotubes(SWCNTs)from acetylene on iron(Fe)clusters,utilizing GFN(-x)TB-based nanoreactor molecular dynamics simulations.The simulations reveal a consistent nucleation pathway,regardless of iron cluster size(Fe_(13),Fe_(38),Fe_(55)),where the chemisorption and dissociation of acetylene molecules on the Fe clusters lead to the formation of C_(2)H and C_(2)intermediates.These species then undergo oligomerization,initiating the growth of carbon chains.As the chains cross-link and cyclize,five-membered carbon rings are preferentially formed,which eventually evolve into six-membered rings and more complex sp2-hybridized carbon networks,resembling the cap structures of nascent SWCNTs.Although the nucleation mechanism remains similar across all cluster sizes,larger clusters show enhanced catalytic activity,leading to higher molecular weight hydrocarbons and more extensive carbocyclic networks due to their higher density of active sites per reacting molecule.Crucially,the study highlights the role of C_(2)H as the key active species in the carbon network formation process.These findings offer critical insights into the initial stages of SWCNT nucleation,contributing to a deeper understanding of the mechanisms driving SWCNT growth and guiding the development of optimized synthetic strategies.展开更多
The goethite residue generated from zinc hydrometallurgy is classified as hazardous solid waste,produced in large quantities,and results in significant zinc loss.The study was conducted on removing iron from FeSO_(4)-...The goethite residue generated from zinc hydrometallurgy is classified as hazardous solid waste,produced in large quantities,and results in significant zinc loss.The study was conducted on removing iron from FeSO_(4)-ZnSO_(4) solution,employing seed-induced nucleation methods.Analysis of the iron removal rate,residue structure,morphology,and elemental composition involved ICP,XRD,FT-IR,and SEM.The existing state of zinc was investigated by combining step-by-step dissolution using hydrochloric acid.Concurrently,iron removal tests were extended to industrial solutions to assess the influence of seeds and solution pH on zinc loss and residue yield.The results revealed that seed addition increased the iron removal rate by 3%,elevated the residual iron content by 6.39%,and mitigated zinc loss by 29.55%in the simulated solution.Seed-induced nucleation prevented excessive nuclei formation,fostering crystal stable growth and high crystallinity.In addition,the zinc content of surface adsorption and crystal internal embedding in the residue was determined,and the zinc distribution on the surface was dense.In contrast,the total amount of zinc within the crystal was higher.The test results in the industrial solution demonstrated that the introduction of seeds expanded the pH range for goethite formation and growth,and the zinc loss per ton of iron removed was reduced by 50.91 kg(34.12%)and the iron residue reduced by 0.17 t(8.72%).展开更多
The research on the rock burst prediction was made on the basis of seismology,rock mechanics and the data from Dongguashan Copper Mine(DCM) ,the deepest metal mine in China.The seismic responses to mining in DCM were ...The research on the rock burst prediction was made on the basis of seismology,rock mechanics and the data from Dongguashan Copper Mine(DCM) ,the deepest metal mine in China.The seismic responses to mining in DCM were investigated through the analyses of the spatio-temporal distribution of hypocenters,apparent stress and displacement of seismic events,and the process of the generation of hazardous seismicity in DCM was studied in the framework of the theory of asperity in the seismic source mechanism.A method of locating areas with hazardous seismicity and a conceptual model of hazardous seismic nucleation in DCM were proposed.A criterion of rockburst prediction was analyzed theoretically in the framework of unstable failure theories,and consequently,the rate of change in the ratio of the seismic stiffness of rock in a seismic nucleation area to that in surrounding area,dS/dt,is defined as an index of the rockburst prediction.The possibility of a rockburst will increase if dS/dt>0,and the possibility of rock burst will decrease if dS/dt<0.The correctness of these methods is demonstrated by analyses of rock failure cases in DCM.展开更多
In order to expand the application of the basic magnesium carbonate in the field of flame retardant,the plate-like basic magnesium carbonate(Mg5(CO3)4(OH)2.4H2O)was prepared successfully by template-mediated/homogeneo...In order to expand the application of the basic magnesium carbonate in the field of flame retardant,the plate-like basic magnesium carbonate(Mg5(CO3)4(OH)2.4H2O)was prepared successfully by template-mediated/homogeneous precipitation method,using magnesium chloride hexahydrate(MgCl2.6H2O)and urea(CO(NH2)2)as reaction materials.Phase and morphology of the product were characterized by X-ray diffraction(XRD),scanning electron microscope(SEM)and atomic force microscope(AFM),respectively.The results showed that well-crystallized plate-like Mg5(CO3)4(OH)2.4H2O can be prepared at the water bath temperature of 100°C,water bath time of 24 h,the aging time of 5 h after adding organic template agent.The investigation on organic template mediated mechanism shows that the template affects the crystal morphology by changing surface energy of different crystal plane.Through a preliminary study on the growth mechanism of the product,it is found that the generation of the plate-like Mg5(CO3)4(OH)2.4H2O could be explained by two-dimensional nucleation/step growth mechanism.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
To prepare the porous NC-based(nitrocellulose-based) gun propellants,the batch foaming process of using supercritical CO_2 as the physical blowing agent is used.The solubilities of CO_2 in the single-base propellants ...To prepare the porous NC-based(nitrocellulose-based) gun propellants,the batch foaming process of using supercritical CO_2 as the physical blowing agent is used.The solubilities of CO_2 in the single-base propellants and TEGDN(trimethyleneglycol dinitrate) propellants are measured by the gravimetric method,and SEM(scanning electron microscope) is used to observe the morphology of foamed propellants.The result shows that a large amount of CO_2 could be dissolved in NC-based propellants.The experimental results also reveal that the energetic plasticizer TEGDN exerts an important influence on the pore structure.The triaxial tensile failure mechanism for solid-state nucleation is used to explain the nucleation of NC-based propellants in the sol id state.Since some specific foaming behaviors of NC-based propellants can not be explained by the failure mechanism,a solid-state nucleation mechanism which revises the triaxial tensile failure mechanism is proposed and discussed.展开更多
In order to obtain an effective and reliable grain refiner for Mg-Al alloys, 1% （mass fraction） Mg3N2 was added into AZ31 Mg alloy. The microstructures of the Mg alloys were studied by optical microscopy, scan elect...In order to obtain an effective and reliable grain refiner for Mg-Al alloys, 1% （mass fraction） Mg3N2 was added into AZ31 Mg alloy. The microstructures of the Mg alloys were studied by optical microscopy, scan electron microscopy and X-ray energy dispersive spectroscopy, and the mechanical properties were determined. The results show that adding a small amount of Mg3N2 to AZ31 Mg alloy can refine the grain size from 103 to 58 μm. The ultimate tensile strength and elongation of AZ31 Mg alloy are 174.1MPa and 8.3%, respectively. After the addition of 1% Mg3N2, the ultimate tensile strength and elongation of AZ31 Mg alloy are increased up to 198.7 MPa and 11.8%, respectively. The grain refinement mechanism is that AIN is formed after Mg3N2 is added. Both AIN and Mg phases are of HCP lattice structure, and the disregistry between Mg phases and AIN along （0001）Mg//（0001）AIN is 3.04%, which is very effective for heterogeneous nucleation.展开更多
To improve the thermal properties of aluminum(Al)in the energetic system,a coated structure with ammonium perchlorate(AP)was prepared by a facile approach.And N,N-Dimethylformamide(DMF)was chosen as an ideal solvent b...To improve the thermal properties of aluminum(Al)in the energetic system,a coated structure with ammonium perchlorate(AP)was prepared by a facile approach.And N,N-Dimethylformamide(DMF)was chosen as an ideal solvent based on heterogeneous nucleation theory and molecular dynamics simulation.This coated structure could enlarge the contact area and improve the reaction environment to enhance the thermal properties.The addition of AP could accelerate oxidation temperature of Al with around 17.5°C.And the heat release of 85@15 composition rises to 26.13 k J/g and the reaction degree is97.6%with higher peak pressure(254.6 k Pa)and rise rate(1.397 MPa/s).An ideal ratio with 15 wt%AP was probed primarily.The high energy laser-induced shockwave experiment was utilized to simulate the reaction behavior in hot field.And the larger activated mixture of coated powder could release more energy to promote the growth of shockwave with higher speed up to 518.7±55.9 m/s.In conclusion,85@15 composition is expected to be applied in energetic system as a novel metal fuel.展开更多
The effect of pre-recovery on the recrystallization kinetics of a supersaturated Al–Mn alloy annealed at 530°C was investigated.The results show that the pre-recovery treatment can lead to faster recrystallizati...The effect of pre-recovery on the recrystallization kinetics of a supersaturated Al–Mn alloy annealed at 530°C was investigated.The results show that the pre-recovery treatment can lead to faster recrystallization kinetics at the initial stage but cause sluggish recrystallization at the later stage.This different recrystallization behavior is explained by the formation of precipitates-free zones and the consumption of driving force during the pre-recovery treatment.The promoted recrystallization at the early stage can be interpreted by the promotion of recrystallization nucleation through sub-grain growth to a critical size inside precipitates-free zones.A simple model is presented to describe the nucleation of recrystallization with pre-recovery treatment in the supersaturated Al–Mn alloys.展开更多
Rapidly solidified Al87Ni7Cu3Nd3 amorphous alloy was prepared by using melt spinning. Its calorimetric behavior was characterized by using differential scanning calorimeter in a continuous or isothermal heating mode. ...Rapidly solidified Al87Ni7Cu3Nd3 amorphous alloy was prepared by using melt spinning. Its calorimetric behavior was characterized by using differential scanning calorimeter in a continuous or isothermal heating mode. phase transformation was investigated, with a special interest in primary crystallization, by using an in-situ examination of X-ray diffractometry （XRD） and high resolution transmission electron microscopy （HRTEM）. The results show that, the whole devitrification of rapidly solidified Al87NiyCu3Nd3 amorphous alloy involves two main processes of primary crystallization and secondary crystallization that consist mainly of two reactions. For primary crystallization, the apparent activation energies, EIso and EKis and growth activation energies Eg are about 153, 166 and 288 kJ/mol, respectively. The interdiffusion of Al atoms is a rate-controlled step of formation of the a（Al） particles, but slow diffusion of Ni and Nd atoms plays a significant role in retarding growth of the α （Al） particles. For secondary crystallization, EIso, EKis and Eg of the first reaction are about 291,208 and 290 kJ/mol, and those of the second reaction are about 367, 269 and 372 kJ/mol. The two reactions of secondary crystallization are controlled mainly in an interface-controlled three-dimensional mode, depending mainly on slow diffusion of Ni and Nd atoms.展开更多
Diamond films were deposited on high-speed steel substrates by hot filament chemical vapor deposition （HFCVD） method. To minimize the early formation of graphite and to enhance the diamond film adhesion, a WC-Co coa...Diamond films were deposited on high-speed steel substrates by hot filament chemical vapor deposition （HFCVD） method. To minimize the early formation of graphite and to enhance the diamond film adhesion, a WC-Co coating was used as an interlayer on the steel substrates by high velocity oxy-fuel spraying. The effects of methane content on nucleation, quality, residual stress and adhesion of diamond films were investigated. The results indicate that the increasing methane content leads to the increase in nucleation density, residual stress, the degradation of quality and adhesion of diamond films. Diamond films deposited on high-speed steel （HSS） substrate with a WC-Co interlayer exhibit high nucleation density and good adhesion under the condition of the methane content initially set to be a higher value （4%, volume fraction） for 30 min, and then reduced to 2% for subsequent growth at pressure of 3 kPa and substrate temperature of 800 ℃.展开更多
Two-dimensional(2D)semiconductors offer an atomic thickness that facilitates superior gate field penetration and enables transistors to maintain shrinking with suppressed short-channel effects,thereby being considered...Two-dimensional(2D)semiconductors offer an atomic thickness that facilitates superior gate field penetration and enables transistors to maintain shrinking with suppressed short-channel effects,thereby being considered as channel materials for future transistors in the post-Moore era.As a member of high-mobility 2D semiconductors,the air-stable Bi_(2)O_(2)Se with a moderate bandgap has drawn significant attention.Distinguished from other 2D materials,Bi_(2)O_(2)Se can be oxidized layer-by-layer to form a high-k native-oxide dielectric,Bi2SeO5,with an atomically sharp interface,similar to Si/SiO2 in the semiconductor industry.These characteristics make Bi_(2)O_(2)Se an ideal material platform for fabricating various devices with excellent performance,such as transistors,thermoelectrics,optoelectronics,sensors,flexible devices and memory devices.To realize advanced applications of 2D Bi_(2)O_(2)Se,it is essential to develop scalable and high-quality preparation methods with relatively low cost.Chemical vapor deposition(CVD)has shown promise in meeting these requirements.Over the past years,CVD has been widely used to synthesize 2D Bi_(2)O_(2)Se despite some remaining challenges.In this review,we summarize the recent progress in the controlled growth of 2D Bi_(2)O_(2)Se via the CVD method.We begin by introducing the crystal structure and properties of Bi_(2)O_(2)Se.Next,we focus on the morphology control of 2D Bi_(2)O_(2)Se,including various nucleation modes and different dimensionalities by carefully manipulating the CVD process.In terms of nucleation modes,in-plane and vertical epitaxial growth of Bi_(2)O_(2)Se,achieved by controlling the interaction between epitaxial layer and substrate,are reviewed.Wafer-scale continuous Bi_(2)O_(2)Se film facilitates the device integration while vertical 2D fins pave the way for fabricating high-performance fin field-effect-transistors(FinFET).As for the dimensionality control,the transition from 2D nanoplates to 1D nanoribbons is investigated.Parameters such as precursor ratio,growth temperature and types of catalyst play a key role in such transition.We then discuss the construction of ordered arrays of Bi_(2)O_(2)Se with the above morphology by selective growth and post treatment for potential device integration.In addition,we highlight the electrical quality improvement of the grown material via defect control and strain release.For example,both the Se poor growth condition and the out-of-plane strain-free growth contribute to higher mobility of Bi_(2)O_(2)Se.Lastly,we propose potential strategies for precise control of Bi_(2)O_(2)Se structures and quality.In order to meet the demands of advanced electronic applications,more efforts are expected to made to achieve uniform,transferable and site-specific preparation of high-quality single-crystal Bi_(2)O_(2)Se on a large scale.展开更多
The problem was found that the nucleation and growth of diamond are different on each side of flaky catalyst in the cubic high pressure diamond synthesis system. Some theories explainning this difference were introduc...The problem was found that the nucleation and growth of diamond are different on each side of flaky catalyst in the cubic high pressure diamond synthesis system. Some theories explainning this difference were introduced in the paper. The synthesis cavity and the forces on flaky ctalyst were analysed. The results show that the stress makes the transmission velocity of carbon different on each side of catalyst slice, which causes the difference of nucleation density of diamond between two sides of the slice.展开更多
Based upon the thermodynamic analysis of the nucleation of d iamond crystal, the effects of synthesis temperature and pressure on the nucleat ion of diamond crystal, diamond growth and output of diamond crystal, parti...Based upon the thermodynamic analysis of the nucleation of d iamond crystal, the effects of synthesis temperature and pressure on the nucleat ion of diamond crystal, diamond growth and output of diamond crystal, particle s ize and strength were discussed. The results show that the excess pressure has a n important effect on the critical radius of nucleation and thermodynamic b a rrier in the formation of a critical nucleus. Considering the excess pressure, t he expression of diamond nucleation rate was obtained.展开更多
Nucleation mechanism and technological process for Ni-Fe co-deposition with a relatively high Fe^(2+)concentration surrounded were described,and the effects of Fe^(2+) concentration,solution pH,temperature,and sodium ...Nucleation mechanism and technological process for Ni-Fe co-deposition with a relatively high Fe^(2+)concentration surrounded were described,and the effects of Fe^(2+) concentration,solution pH,temperature,and sodium dodecyl sulfonate concentration were investigated.Electrochemical experiments demonstrate that iron's electrodeposition plays a leading role in the Ni-Fe co-deposition process,and the co-deposition nucleation mechanism accords with a progressive nucleation.Temperature increase does favor in increasing nickel content in the ferronickel(Ni-Fe co-deposition products),while Fe^(2+) concentration increase does not.When solution pH is higher than 3.5,nickel content in the ferronickel decreases with pH because of the hydrolysis of Fe^(2+).With the current density of 180 A/m^2,Na_2SO_4 concentration of 100 g/L and Ni^(2+) concentration of 60 g/L,a smooth ferronickel deposit containing 96.21% Ni can be obtained under the conditions of temperature of 60 °C,Fe^(2+) concentration of 0.3 g/L,solution pH of 3 and sodium dodecyl sulfonate concentration of 40 mg/L.展开更多
The development of the recrystallization texture of the alloy AA3104 was investigated by analysis of orientation distribution functions determined by X-ray diffraction,supported by EBSD local texture analysis.A typic...The development of the recrystallization texture of the alloy AA3104 was investigated by analysis of orientation distribution functions determined by X-ray diffraction,supported by EBSD local texture analysis.A typical β-fiber with nearly 20%Bs orientation {011}211 was detected in the final hot rolled sheet.At the beginning of annealing at 350 ℃,the cube component{001}100 got a sharp increase.TEM results show that the growth of both number and size of precipitation appears to inhibit the advantage of Cube orientation {001}100 notably after annealing at 350 ℃ for 15 min.Finally,it comes out to be a random distributed orientation by full recry stallization.展开更多
This study aims to develop a paraffin-based phase change material(PCM) emulsion with a low extent of supercooling for thermal energy storage(TES) systems to improve the cooling efficiency.Hexadecane-water emulsions we...This study aims to develop a paraffin-based phase change material(PCM) emulsion with a low extent of supercooling for thermal energy storage(TES) systems to improve the cooling efficiency.Hexadecane-water emulsions were prepared and characterized. Multi-wall carbon nanotubes(MWCNTs) were dispersed in the emulsion as a nucleating agent to reduce the supercooling. The MWCNTs were chemically modified with carboxyl groups to improve the dispersion of the tubular particles in the organic liquid. Thermal analyses of the emulsions by differential scanning calorimeter(DSC) indicated that the extent of supercooling was significantly reduced. The concentration of the nucleating agent for an effective supercooling suppression as found to be very low, in agreement with previous findings, and there appeared to be a minimum concentration for the supercooling reduction.展开更多
文摘With the microscopic phase-field dynamic model, the effects of temperature and concentration on the nucleation incubation time of Ni75AlxV25-x alloy were studied and the relation between the incubation time and precipitation mechanism was investigated by using the atomic occupation probability picture and average order parameter curve. The simulation results demonstrate that there exists the incubation time for different precipitation mechanisms~ such as non-classical nucleation, the mixed style of non-classical nucleation and spinodal decomposition, and spinodal ordering; and the incubation time shortens in turn for the three kinds of mechanisms. With the increase of Al content of Ni75AlxV25-x alloy, the incubation time of Llz phases shortens continuously and that of DOzz phases is prolonged. The effects of temperature on the incubation time of Llz and DOzz phases are accordant, i.e. the incuba- tion time is greatly prolonged with the temperature rising.
文摘The solution diffusion coefficient is a great important intrinsical parameter in crystal growth.On earth,it is impossible to accurately determine the diffusion coefficient since there is nature convection.One of the marked charateristics of space-crystal growth is to eleminate nature convection,so that purely diffusion-controlled condition of crystal growth could be realized and precise measurement of the diffusion coefficient should be approved.
基金supported by the National Key R&D Program of China(2022YFA1604100)the National Natural Science Foundation of China(22302220,22372187,1972157,21972160,22402218)+2 种基金the National Science Fund for Distinguished Young Scholars of China(22225206)the Fundamental Research Program of Shanxi Province(202203021222403)the Youth Innovation Promotion Association CAS(2020179)。
文摘Carbon nanotube formation exemplifies atomically precise self-assembly,where atomic interactions dynamically engineer nanoscale architectures with emergent properties that transcend classical material boundaries.However,elucidating the transient molecular intermediates remains a critical mechanistic frontier.This study investigates the atomic-scale nucleation process of single-walled carbon nanotubes(SWCNTs)from acetylene on iron(Fe)clusters,utilizing GFN(-x)TB-based nanoreactor molecular dynamics simulations.The simulations reveal a consistent nucleation pathway,regardless of iron cluster size(Fe_(13),Fe_(38),Fe_(55)),where the chemisorption and dissociation of acetylene molecules on the Fe clusters lead to the formation of C_(2)H and C_(2)intermediates.These species then undergo oligomerization,initiating the growth of carbon chains.As the chains cross-link and cyclize,five-membered carbon rings are preferentially formed,which eventually evolve into six-membered rings and more complex sp2-hybridized carbon networks,resembling the cap structures of nascent SWCNTs.Although the nucleation mechanism remains similar across all cluster sizes,larger clusters show enhanced catalytic activity,leading to higher molecular weight hydrocarbons and more extensive carbocyclic networks due to their higher density of active sites per reacting molecule.Crucially,the study highlights the role of C_(2)H as the key active species in the carbon network formation process.These findings offer critical insights into the initial stages of SWCNT nucleation,contributing to a deeper understanding of the mechanisms driving SWCNT growth and guiding the development of optimized synthetic strategies.
基金Project(2018YFC1900403) supported by the National Key Research and Development Program of ChinaProject(CX20210197) supported by the Postgraduate Scientific Research Innovation Project of Hunan Province,China+1 种基金Project(202206370103) supported by the China Scholarship CouncilProject(2021zzts0115) supported by the Fundamental Research Funds for the Central Universities,China。
文摘The goethite residue generated from zinc hydrometallurgy is classified as hazardous solid waste,produced in large quantities,and results in significant zinc loss.The study was conducted on removing iron from FeSO_(4)-ZnSO_(4) solution,employing seed-induced nucleation methods.Analysis of the iron removal rate,residue structure,morphology,and elemental composition involved ICP,XRD,FT-IR,and SEM.The existing state of zinc was investigated by combining step-by-step dissolution using hydrochloric acid.Concurrently,iron removal tests were extended to industrial solutions to assess the influence of seeds and solution pH on zinc loss and residue yield.The results revealed that seed addition increased the iron removal rate by 3%,elevated the residual iron content by 6.39%,and mitigated zinc loss by 29.55%in the simulated solution.Seed-induced nucleation prevented excessive nuclei formation,fostering crystal stable growth and high crystallinity.In addition,the zinc content of surface adsorption and crystal internal embedding in the residue was determined,and the zinc distribution on the surface was dense.In contrast,the total amount of zinc within the crystal was higher.The test results in the industrial solution demonstrated that the introduction of seeds expanded the pH range for goethite formation and growth,and the zinc loss per ton of iron removed was reduced by 50.91 kg(34.12%)and the iron residue reduced by 0.17 t(8.72%).
基金Project(2010CB732004) supported by the National Basic Research Program of ChinaProject(50490274) supported by the National Natural Science Foundation of China
文摘The research on the rock burst prediction was made on the basis of seismology,rock mechanics and the data from Dongguashan Copper Mine(DCM) ,the deepest metal mine in China.The seismic responses to mining in DCM were investigated through the analyses of the spatio-temporal distribution of hypocenters,apparent stress and displacement of seismic events,and the process of the generation of hazardous seismicity in DCM was studied in the framework of the theory of asperity in the seismic source mechanism.A method of locating areas with hazardous seismicity and a conceptual model of hazardous seismic nucleation in DCM were proposed.A criterion of rockburst prediction was analyzed theoretically in the framework of unstable failure theories,and consequently,the rate of change in the ratio of the seismic stiffness of rock in a seismic nucleation area to that in surrounding area,dS/dt,is defined as an index of the rockburst prediction.The possibility of a rockburst will increase if dS/dt>0,and the possibility of rock burst will decrease if dS/dt<0.The correctness of these methods is demonstrated by analyses of rock failure cases in DCM.
基金Project(51374155)supported by the National Natural Science Foundation of ChinaProject(2014BCB034)supported by the Hubei Province Key Technology R&D Program,ChinaProject(2014CFB796)supported by the Natural Science Foundation of Hubei Province of China
文摘In order to expand the application of the basic magnesium carbonate in the field of flame retardant,the plate-like basic magnesium carbonate(Mg5(CO3)4(OH)2.4H2O)was prepared successfully by template-mediated/homogeneous precipitation method,using magnesium chloride hexahydrate(MgCl2.6H2O)and urea(CO(NH2)2)as reaction materials.Phase and morphology of the product were characterized by X-ray diffraction(XRD),scanning electron microscope(SEM)and atomic force microscope(AFM),respectively.The results showed that well-crystallized plate-like Mg5(CO3)4(OH)2.4H2O can be prepared at the water bath temperature of 100°C,water bath time of 24 h,the aging time of 5 h after adding organic template agent.The investigation on organic template mediated mechanism shows that the template affects the crystal morphology by changing surface energy of different crystal plane.Through a preliminary study on the growth mechanism of the product,it is found that the generation of the plate-like Mg5(CO3)4(OH)2.4H2O could be explained by two-dimensional nucleation/step growth mechanism.
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funded by the priority academic program development of Jiangsu Higher Education Institutions
文摘To prepare the porous NC-based(nitrocellulose-based) gun propellants,the batch foaming process of using supercritical CO_2 as the physical blowing agent is used.The solubilities of CO_2 in the single-base propellants and TEGDN(trimethyleneglycol dinitrate) propellants are measured by the gravimetric method,and SEM(scanning electron microscope) is used to observe the morphology of foamed propellants.The result shows that a large amount of CO_2 could be dissolved in NC-based propellants.The experimental results also reveal that the energetic plasticizer TEGDN exerts an important influence on the pore structure.The triaxial tensile failure mechanism for solid-state nucleation is used to explain the nucleation of NC-based propellants in the sol id state.Since some specific foaming behaviors of NC-based propellants can not be explained by the failure mechanism,a solid-state nucleation mechanism which revises the triaxial tensile failure mechanism is proposed and discussed.
基金Project(E2013402056)supported by the Natural Science Foundation of Hebei Province,ChinaProject(QN2014002)supported by the Science and Technology Research Foundation of Hebei Education Department for Young Teachers in University,ChinaProject(51601053)supported by the National Natural Science Foundation of China
基金Project(2007430023)supported by the Office of Education,Henan Province,ChinaProject(0612002500)supported by the Excellent Young Scientists Foundation of Henan Province,China
文摘In order to obtain an effective and reliable grain refiner for Mg-Al alloys, 1% （mass fraction） Mg3N2 was added into AZ31 Mg alloy. The microstructures of the Mg alloys were studied by optical microscopy, scan electron microscopy and X-ray energy dispersive spectroscopy, and the mechanical properties were determined. The results show that adding a small amount of Mg3N2 to AZ31 Mg alloy can refine the grain size from 103 to 58 μm. The ultimate tensile strength and elongation of AZ31 Mg alloy are 174.1MPa and 8.3%, respectively. After the addition of 1% Mg3N2, the ultimate tensile strength and elongation of AZ31 Mg alloy are increased up to 198.7 MPa and 11.8%, respectively. The grain refinement mechanism is that AIN is formed after Mg3N2 is added. Both AIN and Mg phases are of HCP lattice structure, and the disregistry between Mg phases and AIN along （0001）Mg//（0001）AIN is 3.04%, which is very effective for heterogeneous nucleation.
基金supported by National Natural Science Foundation of China[No.21975024]。
文摘To improve the thermal properties of aluminum(Al)in the energetic system,a coated structure with ammonium perchlorate(AP)was prepared by a facile approach.And N,N-Dimethylformamide(DMF)was chosen as an ideal solvent based on heterogeneous nucleation theory and molecular dynamics simulation.This coated structure could enlarge the contact area and improve the reaction environment to enhance the thermal properties.The addition of AP could accelerate oxidation temperature of Al with around 17.5°C.And the heat release of 85@15 composition rises to 26.13 k J/g and the reaction degree is97.6%with higher peak pressure(254.6 k Pa)and rise rate(1.397 MPa/s).An ideal ratio with 15 wt%AP was probed primarily.The high energy laser-induced shockwave experiment was utilized to simulate the reaction behavior in hot field.And the larger activated mixture of coated powder could release more energy to promote the growth of shockwave with higher speed up to 518.7±55.9 m/s.In conclusion,85@15 composition is expected to be applied in energetic system as a novel metal fuel.
基金Project(2016YFB0300901)supported by National Key R&D Program of ChinaProject(51421001)supported by the National Natural Science Foundation of ChinaProject(106112015CDJXY130003)supported by the Fundamental Research Funds for the Central Universities,China
文摘The effect of pre-recovery on the recrystallization kinetics of a supersaturated Al–Mn alloy annealed at 530°C was investigated.The results show that the pre-recovery treatment can lead to faster recrystallization kinetics at the initial stage but cause sluggish recrystallization at the later stage.This different recrystallization behavior is explained by the formation of precipitates-free zones and the consumption of driving force during the pre-recovery treatment.The promoted recrystallization at the early stage can be interpreted by the promotion of recrystallization nucleation through sub-grain growth to a critical size inside precipitates-free zones.A simple model is presented to describe the nucleation of recrystallization with pre-recovery treatment in the supersaturated Al–Mn alloys.
基金Project(2005-5) supported by the Postdoctoral Foundation of Central South University, ChinaProject(2005038560) supported by the Postdoctoral Science Foundation of China
文摘Rapidly solidified Al87Ni7Cu3Nd3 amorphous alloy was prepared by using melt spinning. Its calorimetric behavior was characterized by using differential scanning calorimeter in a continuous or isothermal heating mode. phase transformation was investigated, with a special interest in primary crystallization, by using an in-situ examination of X-ray diffractometry （XRD） and high resolution transmission electron microscopy （HRTEM）. The results show that, the whole devitrification of rapidly solidified Al87NiyCu3Nd3 amorphous alloy involves two main processes of primary crystallization and secondary crystallization that consist mainly of two reactions. For primary crystallization, the apparent activation energies, EIso and EKis and growth activation energies Eg are about 153, 166 and 288 kJ/mol, respectively. The interdiffusion of Al atoms is a rate-controlled step of formation of the a（Al） particles, but slow diffusion of Ni and Nd atoms plays a significant role in retarding growth of the α （Al） particles. For secondary crystallization, EIso, EKis and Eg of the first reaction are about 291,208 and 290 kJ/mol, and those of the second reaction are about 367, 269 and 372 kJ/mol. The two reactions of secondary crystallization are controlled mainly in an interface-controlled three-dimensional mode, depending mainly on slow diffusion of Ni and Nd atoms.
基金Project(1343-74236000005) supported by the Innovation Foundation for Postgraduates of Hunan Province, ChinaProject(ZKJ2008001) supported by the Open Fund for Valuable Instruments of Central South University, ChinaProject(2008112048) supported by the Open Fund of State Key Laboratory of Metallurgy, China
文摘Diamond films were deposited on high-speed steel substrates by hot filament chemical vapor deposition （HFCVD） method. To minimize the early formation of graphite and to enhance the diamond film adhesion, a WC-Co coating was used as an interlayer on the steel substrates by high velocity oxy-fuel spraying. The effects of methane content on nucleation, quality, residual stress and adhesion of diamond films were investigated. The results indicate that the increasing methane content leads to the increase in nucleation density, residual stress, the degradation of quality and adhesion of diamond films. Diamond films deposited on high-speed steel （HSS） substrate with a WC-Co interlayer exhibit high nucleation density and good adhesion under the condition of the methane content initially set to be a higher value （4%, volume fraction） for 30 min, and then reduced to 2% for subsequent growth at pressure of 3 kPa and substrate temperature of 800 ℃.
文摘Two-dimensional(2D)semiconductors offer an atomic thickness that facilitates superior gate field penetration and enables transistors to maintain shrinking with suppressed short-channel effects,thereby being considered as channel materials for future transistors in the post-Moore era.As a member of high-mobility 2D semiconductors,the air-stable Bi_(2)O_(2)Se with a moderate bandgap has drawn significant attention.Distinguished from other 2D materials,Bi_(2)O_(2)Se can be oxidized layer-by-layer to form a high-k native-oxide dielectric,Bi2SeO5,with an atomically sharp interface,similar to Si/SiO2 in the semiconductor industry.These characteristics make Bi_(2)O_(2)Se an ideal material platform for fabricating various devices with excellent performance,such as transistors,thermoelectrics,optoelectronics,sensors,flexible devices and memory devices.To realize advanced applications of 2D Bi_(2)O_(2)Se,it is essential to develop scalable and high-quality preparation methods with relatively low cost.Chemical vapor deposition(CVD)has shown promise in meeting these requirements.Over the past years,CVD has been widely used to synthesize 2D Bi_(2)O_(2)Se despite some remaining challenges.In this review,we summarize the recent progress in the controlled growth of 2D Bi_(2)O_(2)Se via the CVD method.We begin by introducing the crystal structure and properties of Bi_(2)O_(2)Se.Next,we focus on the morphology control of 2D Bi_(2)O_(2)Se,including various nucleation modes and different dimensionalities by carefully manipulating the CVD process.In terms of nucleation modes,in-plane and vertical epitaxial growth of Bi_(2)O_(2)Se,achieved by controlling the interaction between epitaxial layer and substrate,are reviewed.Wafer-scale continuous Bi_(2)O_(2)Se film facilitates the device integration while vertical 2D fins pave the way for fabricating high-performance fin field-effect-transistors(FinFET).As for the dimensionality control,the transition from 2D nanoplates to 1D nanoribbons is investigated.Parameters such as precursor ratio,growth temperature and types of catalyst play a key role in such transition.We then discuss the construction of ordered arrays of Bi_(2)O_(2)Se with the above morphology by selective growth and post treatment for potential device integration.In addition,we highlight the electrical quality improvement of the grown material via defect control and strain release.For example,both the Se poor growth condition and the out-of-plane strain-free growth contribute to higher mobility of Bi_(2)O_(2)Se.Lastly,we propose potential strategies for precise control of Bi_(2)O_(2)Se structures and quality.In order to meet the demands of advanced electronic applications,more efforts are expected to made to achieve uniform,transferable and site-specific preparation of high-quality single-crystal Bi_(2)O_(2)Se on a large scale.
文摘The problem was found that the nucleation and growth of diamond are different on each side of flaky catalyst in the cubic high pressure diamond synthesis system. Some theories explainning this difference were introduced in the paper. The synthesis cavity and the forces on flaky ctalyst were analysed. The results show that the stress makes the transmission velocity of carbon different on each side of catalyst slice, which causes the difference of nucleation density of diamond between two sides of the slice.
文摘Based upon the thermodynamic analysis of the nucleation of d iamond crystal, the effects of synthesis temperature and pressure on the nucleat ion of diamond crystal, diamond growth and output of diamond crystal, particle s ize and strength were discussed. The results show that the excess pressure has a n important effect on the critical radius of nucleation and thermodynamic b a rrier in the formation of a critical nucleus. Considering the excess pressure, t he expression of diamond nucleation rate was obtained.
基金Project(51574135)supported by the National Natural Science Foundation of ChinaProject(KKPT201563022)supported by Collaborative Innovation Center of Kunming University of Science and Technology,China
文摘Nucleation mechanism and technological process for Ni-Fe co-deposition with a relatively high Fe^(2+)concentration surrounded were described,and the effects of Fe^(2+) concentration,solution pH,temperature,and sodium dodecyl sulfonate concentration were investigated.Electrochemical experiments demonstrate that iron's electrodeposition plays a leading role in the Ni-Fe co-deposition process,and the co-deposition nucleation mechanism accords with a progressive nucleation.Temperature increase does favor in increasing nickel content in the ferronickel(Ni-Fe co-deposition products),while Fe^(2+) concentration increase does not.When solution pH is higher than 3.5,nickel content in the ferronickel decreases with pH because of the hydrolysis of Fe^(2+).With the current density of 180 A/m^2,Na_2SO_4 concentration of 100 g/L and Ni^(2+) concentration of 60 g/L,a smooth ferronickel deposit containing 96.21% Ni can be obtained under the conditions of temperature of 60 °C,Fe^(2+) concentration of 0.3 g/L,solution pH of 3 and sodium dodecyl sulfonate concentration of 40 mg/L.
文摘The development of the recrystallization texture of the alloy AA3104 was investigated by analysis of orientation distribution functions determined by X-ray diffraction,supported by EBSD local texture analysis.A typical β-fiber with nearly 20%Bs orientation {011}211 was detected in the final hot rolled sheet.At the beginning of annealing at 350 ℃,the cube component{001}100 got a sharp increase.TEM results show that the growth of both number and size of precipitation appears to inhibit the advantage of Cube orientation {001}100 notably after annealing at 350 ℃ for 15 min.Finally,it comes out to be a random distributed orientation by full recry stallization.
基金Supported by the Research Grant Council of the Hong Kong SAR government(GRF PolyU 5241/11E)
文摘This study aims to develop a paraffin-based phase change material(PCM) emulsion with a low extent of supercooling for thermal energy storage(TES) systems to improve the cooling efficiency.Hexadecane-water emulsions were prepared and characterized. Multi-wall carbon nanotubes(MWCNTs) were dispersed in the emulsion as a nucleating agent to reduce the supercooling. The MWCNTs were chemically modified with carboxyl groups to improve the dispersion of the tubular particles in the organic liquid. Thermal analyses of the emulsions by differential scanning calorimeter(DSC) indicated that the extent of supercooling was significantly reduced. The concentration of the nucleating agent for an effective supercooling suppression as found to be very low, in agreement with previous findings, and there appeared to be a minimum concentration for the supercooling reduction.
