A novel technology using Fe powder as reducing agent for Ge and Cu recovery from precipitating vitriol supernatant in Zn hydrometallurgical plant was investigated. The results show that reaction time, temperature, agi...A novel technology using Fe powder as reducing agent for Ge and Cu recovery from precipitating vitriol supernatant in Zn hydrometallurgical plant was investigated. The results show that reaction time, temperature, agitation speed, initial pH value of solution and the amount of reducing Fe have significant effects on recovering Ge and Cu, and the optimum process operating parameters are established as follows： time 120 min, initial pH value 1.5, the dosage of reducing Fe powder 4 g/L, agitation speed 600 r/min and temperature 80 °C. Under these experimental conditions, the recovery ratios of Ge and Cu from precipitating vitriol supernatant in Zn hydrometallurgical plant can reach 96% and 100%, respectively. The content of Ge in the reduced residue reaches up to 2.06% （mass fraction）, indicating that the separation and enrichment of Ge from the Zn sulfate solution is realized. The grade of Ge and Cu can reach up to 4.88% and 56.75%, respectively, when the reduced residue is further processed.展开更多
Precipitation-strengthened HEAs exhibit outstanding integration of strength and toughness at ambient temperature.Nevertheless,precipitates generally reduce the localized corrosion resistance in aggressive solution env...Precipitation-strengthened HEAs exhibit outstanding integration of strength and toughness at ambient temperature.Nevertheless,precipitates generally reduce the localized corrosion resistance in aggressive solution environments.To solve this problem,a strategy of introducing nano-sized L12 precipitates in CoCrFeNiAlTi HEAs has been proposed in this work.Results demonstrate the pitting corrosion potential can be elevated from 258 mVSCE to 603 mVSCE by increasing the precipitate content to 38 wt.%.Such an improvement in localized corrosion resistance can be attributed to two aspects.Firstly,L12 precipitates tend to be dissolved during the corrosion process,which promotes the heterogeneous nucleation of protective Cr2 O3 due to the rapid deposition of oxides/hydroxides of Al/Ti,and improves the passive film stability due to the Crrich FCC matrix.Secondly,the dissolution kinetic inside the pits can be suppressed on account of the enrichment of Cr element in the FCC matrix,thus inhibiting the pitting growth.In summary,the current work not only reveals the mechanisms of the nano-sized L12 precipitates upon the corrosion behavior,but also provides a strategy for designing corrosion-resistant HEA.展开更多
The influence of the precipitating reagents and dispersants on the formation of nano-aluminum hydroxide from sodium aluminate solution by chemical precipitation was investigated. The influence of the dispersed seeds o...The influence of the precipitating reagents and dispersants on the formation of nano-aluminum hydroxide from sodium aluminate solution by chemical precipitation was investigated. The influence of the dispersed seeds on the decomposi-tion process was investigated too. The alkaline aluminate solutions were used as original solutions with a concentration of Al2O3 having 14.78 g/dm3, αk—1.6 and127 g/dm3, αk—1.6. For the precipitation processes there were used follow-ing precipitating reagents—solutions HCl, NaHCO3 and NH4HCO3 with a concentration of 80 g/dm3, dispersants—PEG 6000, (NaPO3)6 and Tween 20. For the decomposition process the dispersed seeds and factories seeds were used. Structural studies of the aluminum hydroxide particles were carried out by means of the electron-probe microanalysis and scanning electron microscopy, and phase composition of products was determined by means of X-ray diffraction analysis. Ammonium bicarbonate and Tween 20 were determined as the optimal precipitating reagent and dispersant, correspondingly, resulting in dispersed aluminum hydroxide, which is used as a seed in the decomposition process. It was established that this product in form of dispersed seed considerably reduces the duration of the decomposition process;the maximal decomposition of solution (73.9%) was observed after injection of dispersеd aluminum hydroxide into solution. The final aluminum hydroxide having 90% of particles less than 100 nanometers was obtained within 7 hours of steady decreasing temperature from 70°C to 48°C.展开更多
Calculation of the influence of soft precipitating electrons on the polar ionosphere was carried out. The primary results are: (1) During summer time when the sunlight is the main source of upper atmosphere ionization...Calculation of the influence of soft precipitating electrons on the polar ionosphere was carried out. The primary results are: (1) During summer time when the sunlight is the main source of upper atmosphere ionization, the additional soft electron precipitation can increase the NmF2. The daily variation of NmF2 is mainly controlled by solar EUV radiation. (2) At wintertime, when only soft electron precipitation ionization is considered, a peak at the height of F2 layer also appears. The altitude profile of electron density is different frorn that when the sunlit ionization is taken into account.展开更多
The precursors organic cerium deposits were obtained by a stripping precipitation method from cerium-loaded P507 organic phase using oxalic acid as a precipitating agent and nano-sized ceria particles were prepared by...The precursors organic cerium deposits were obtained by a stripping precipitation method from cerium-loaded P507 organic phase using oxalic acid as a precipitating agent and nano-sized ceria particles were prepared by calcining the precursors at 500 ℃. The morphologies, phase structure of the precursors and ceria particles were characterized by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD）, thermogravimetric analysis （TG-DSC） and infrared spectroscopy analysis （FTIR）. The results indicated that the concentration of oxalic acid had a little impact on the morphology of the precursors, which was blocky-shape Ce2（C2O4）3：10H2O with a monoclinic lattice structure. With the volume ratio of organic phase and oxalic acid aqueous solution （aqueous phase） varied from 1：3 to 1：6, the morphologies of the precursors Ce2（C2O4）3· 10H2O precipitates gradually changed from inhomogeneous blocky-shape to uniform spherical particles. The precursors could be turned to CeO2 crystal particles with a fluorite structure by calcining, and the products ceria particles were similar in the size and morphology to the precursors.展开更多
Heat-resistant aluminum alloys are widely used in aerospace and automotive fields for manufacturing hot components due to their advantages in lightweight design and energy conservation.However,the high-temperature str...Heat-resistant aluminum alloys are widely used in aerospace and automotive fields for manufacturing hot components due to their advantages in lightweight design and energy conservation.However,the high-temperature strength of existing cast aluminum alloys is always limited to about 100 MPa at 350℃due to coarsening and transformation of strengthening phases.Here,we reveal that the yield strength and ultimate tensile strength of the T6 state Al-8.4Cu-2.3Ce-1.0Mn-0.5Ni-0.2Zr alloy at 400◦C increase by 34%and 44%after re-aging at 300℃for 100 h,and its thermal strength exhibits distinguished ad-vantage over traditional heat-resistant aluminum alloys.The enhanced elevated-temperature strength is attributed to the reprecipitation of the Ni-bearing T-Al_(20)Cu_(2)Mn_(3)phase,whose number density increases over one time.The significant segregation of Ni,Ce,and Zr elements at the interfaces helps improve the thermal stability of the T phase.The thermostable T phase effectively strengthens the matrix by in-hibiting dislocation motion.Meanwhile,a highly interconnected 3D intermetallic network along the grain boundaries can still remain after long-term re-aging at 300℃,which is conducive to imposing a drag on the grain boundaries at high temperatures.This finding offers a viable route for enhancing the elevated-temperature strength of heat-resistant aluminum alloys,which could provide expanded opportunities for higher-temperature applications.展开更多
Carbides in a series of cold-welding weld metals were studied by means of SEM, TEM and EPMA, and the forming mechanism of carbide was proposed according to their distribution and morphology. Due to their different car...Carbides in a series of cold-welding weld metals were studied by means of SEM, TEM and EPMA, and the forming mechanism of carbide was proposed according to their distribution and morphology. Due to their different carbide-forming tendency, Nb and Ti could combine with C to form particulate carbide in liquid weld metai and depleted the carbon content in matrix, while V induced the carbide precipitated along grain boundary. But too much Nb or Ti alone resulted in coarse carbide and poor strengthened matrix. When suitabie amount of Nb, Ti and V coexisted in weld metai, both uniformly distributed particulate carbide and well strengthened matrix could be achieved. It was proposed that the carbide nucleated on the oxlde which dispersed in liquid weld metai, and then grew into multi-layer complex carbide particies by epitaxial grovvth. At different sites, carbide particies may present as different morphologies.展开更多
Spray deposition is a novel process which is used to manufacture rapidly solidified bulk and near-net-shape preforms. In this study, AI-20Si-5Fe-3Mn-3Cu-1Mg alloy was synthesized by spray deposition technique. The agi...Spray deposition is a novel process which is used to manufacture rapidly solidified bulk and near-net-shape preforms. In this study, AI-20Si-5Fe-3Mn-3Cu-1Mg alloy was synthesized by spray deposition technique. The aging process of the alloy was investigated by differential scanning calorimetry (DSC) analysis and transmission electron microscopy (TEM). The results show that two kinds of phases, i.e. S(Al2CuMg) and σ(Al5Cu6Mg2), precipitate from matrix and improve the tensile strength of the alloy efficiently at both the ambient and elevated temperatures (300℃). In addition, the σ-Al5Cu6Mg2 is a relatively stable phase which improves microstructural stability of the alloy.展开更多
The grain size and precipitate amount which are affected by heat treatment have significant impact on the properties of high nitrogen austenitic stainless steel.In this study,Cr18Mn18 high nitrogen steel sheet is empl...The grain size and precipitate amount which are affected by heat treatment have significant impact on the properties of high nitrogen austenitic stainless steel.In this study,Cr18Mn18 high nitrogen steel sheet is employed to investigate the effects of precipitate on austenitic grain size.It can be seen that the lamella precipitates which are rich in nitrogen and chromium nucleate in the austenite grain boundary and grow inward into grain when aged at 800℃through electron probe micro-analyzer.The transmission electron microscopy results demonstrate that the precipitate is Cr2N and its morphology are detected as ellipsoid-like with major axis of 100-300 nm and minor axis of 50-100 nm roughly.The experiment show that coarsen of the austenite grain is quite critical at 1000-1100℃.However,the samples which pre-precipitated at 800℃for 240 min to obtain the most nitride precipitate exhibits much smaller grain size than the as-rolled samples after solid solution treated at 1000,1050 and 1100℃for 240 min.The results show that the nitride precipitates in the grain boundary can effectively pin the austenite grain boundary and inhibit the grain growth.展开更多
The effect of tempering temperature on the microstrocture and precipitating evolution and the resultant mechanical properties of newly developed high-strength microalloyed steel plate was investigated by optical micro...The effect of tempering temperature on the microstrocture and precipitating evolution and the resultant mechanical properties of newly developed high-strength microalloyed steel plate was investigated by optical microscopy （OM） and transmission electron microscopy （TEM）. The steel mainly consists of fine lath martensite and lower bainite. The width of the martensitic laths in as-hot-rolled state is about 120 nm,and increases from 120 nm to 150 nm and 180 nm after tempering at 200 ℃ and 250℃ for 2 h respectively with no change in its morphology. Of special interest is the phenomenon that both tensile strength and impact toughness of the steel plate decrease with the increase of the tempering temperature, which might be attributed to the combination of lath martensite broadening and the coarsening of needle-like carbides located on the boundaries of lath martensite and within bainitic ferrite. It is suggested that the existence of the complex carbonitride larger than 100 nm in bainitic ferrite is one of the reasons.展开更多
The Cu0.9Cr0.1Zr alloy was deformed through continuous equal channel angular pressing(C-ECAP)through Route A,followed by liquid nitrogen cryogenic rolling(CR)and aging treated at 450℃.The microstructure,mechanical pr...The Cu0.9Cr0.1Zr alloy was deformed through continuous equal channel angular pressing(C-ECAP)through Route A,followed by liquid nitrogen cryogenic rolling(CR)and aging treated at 450℃.The microstructure,mechanical properties,and conductivity of the alloy were detected by electron back-scattered diffractometer,energy dispersive spectroscope,X-ray diffractometer,scanning electron microscope,and transmission electron microscope.The evolution mechanism of the texture during the deformation process and its influence on mechanical properties were analyzed.The results show that directional shear bands form in the CuCrZr alloy during the C-ECAP process,and the preferred orientation of the microstructure is consistent with the rolling direction.After deformation,the number of precipitated phases(mainly Cr)increases with the prolongation of aging time,accompanied by the appearance of micro-nanostructured fibrous structure in the alloy.After C-ECAP for three passes,75%CR deformation,and aging at 450℃ for 2 h,the tensile strength,microhardness,and conductivity reach 538 MPa,168 HV,and 80%IACS,respectively.CR,aging heat treatment,and formation of recrystallization texture are all conducive to the improvement of conductivity.展开更多
The water-quenched(WQ)2195 Al−Li alloy was subjected to stretching at different temperatures,from room temperature(RT)to−196℃(CT),to investigate the effect of cryogenic deformation on the aging precipitation behavior...The water-quenched(WQ)2195 Al−Li alloy was subjected to stretching at different temperatures,from room temperature(RT)to−196℃(CT),to investigate the effect of cryogenic deformation on the aging precipitation behaviors and mechanical properties.The precipitation kinetics of the T1 phase and the microstructures in peak aging state were investigated through the differential scanning calorimetric(DSC)tests and electron microscopy observation.The results show that−196℃deformation produces a high dislocation density,which promotes the precipitation of the T1 phase and refines its sizes significantly.In addition,the grain boundary precipitates(GBPs)of−196℃-stretched samples are suppressed considerably due to the high dislocation density in the grain interiors,which increases the ductility.In comparison,the strength remains nearly constant.Thus,it is indicated that cryogenic forming has the potential to provide the shape and property control for the manufacture of critical components of aluminum alloys.展开更多
Manganese is a major impurity in acidic vanadium-bearing leaching solutions,but its effects on vanadium precipitation via hydrolysis and acidic ammonium salts remain unclear.In this study,vanadium-bearing leachates wi...Manganese is a major impurity in acidic vanadium-bearing leaching solutions,but its effects on vanadium precipitation via hydrolysis and acidic ammonium salts remain unclear.In this study,vanadium-bearing leachates with varying manganese concentrations(VL-cMn)were prepared through calcium,a calcium-manganese composite,and manganese-based roasting of vanadium slag(VS)to investigate the influence of manganese on vanadium precipitation behavior during hydrolysis precipitation(HP)and ammonium salt precipitation(AP),as well as the microscopic characteristics and purity of the resulting V_(2)O_(5) products.The results showed that increasing the pH mitigated the negative effects of Mn on the V precipitation rate during HP.However,as the manganese concentration increased from 5.69 to 15.38 g/L,the V precipitation rate gradually declined at higher temperatures and longer reaction times.The precipitates exhibited increased microstructural density,which might had contributed to the formation of Mn-bearing phases.Additionally,the average grain size of V_(2)O_(5) was reduced and the particles were increasingly agglomerated,leading to a 2.55%decrease in product purity.For AP,as manganese concentration increased,raising the pH counteracted the negative impact of Mn on the V precipitation rate and reduced the required amount of ammonium sulfate.Moreover,Mn was unevenly adsorbed on the surface of the precipitates.Although V_(2)O_(5) grains gradually shrank and became denser,there was no significant effect on the final product purity,which remained above 99.3%.In conclusion,roasting with added manganese salts influenced the hydrolysis of vanadium but had no significant effect on acidic ammonium salt precipitation.展开更多
Enzyme-induced carbonate precipitation(EICP)is a potential ground improvement method that can reduce the permeability of sands.However,the traditional mathematical models are hard to accurately predict the permeabilit...Enzyme-induced carbonate precipitation(EICP)is a potential ground improvement method that can reduce the permeability of sands.However,the traditional mathematical models are hard to accurately predict the permeability of EICP-treated sands.In this study,the mathematical model was established for predicting the permeability of EICP-treated sands based on Kozeny-Carman equation.The effects of calcium carbonate precipitation on the porosity,tortuosity,and specific surface area of the EICP-treated sands were considered in the model.To validate the model,the bio-cemented sand column tests with different grain size distributions(coarse,medium,and fine sands)and treatment numbers(6,8,and 10 times)were conducted.The calcium carbonate content(CCC)and permeability of EICP-treated sands were measured.The validation of the model was confirmed through a comparative analysis of theoretical and experimental results.Furthermore,the impacts of porosity,particle size,CCC,and specific surface area on the hydraulic conductivity of EICP-treated sands were analyzed.The results showed that the model can reflect the hydraulic conductivity of EICP-treated sands under different particle size distributions and degrees of cementation,demonstrating broad applicability.Parametric analysis indicated the hydraulic conductivity gradually decreases with increasing CCC and specific surface area.Conversely,the hydraulic conductivity gradually increases with increasing porosity(n)and particle size(d50),with porosity exhibiting a significantly higher sensitivity than particle size.In summary,this study contributes theoretical foundations for the practical implementation of EICP technology in reducing soil permeability.展开更多
Enzyme-Induced Carbonate Precipitation(EICP)is an innovative technique to improve soil strength and reduce permeability.However,the use of EICP for reinforcing underwater sand beds remains largely unexplored.To advanc...Enzyme-Induced Carbonate Precipitation(EICP)is an innovative technique to improve soil strength and reduce permeability.However,the use of EICP for reinforcing underwater sand beds remains largely unexplored.To advance EICP implementation in various geotechnical applications,this paper develops a model box system to investigate the effectiveness of the EICP technique in reinforcing underwater sand beds.An"injection-extraction"system is designed to facilitate the flow of the EICP solution through underwater sand layers.Key parameters,including conductivity,pH,and Ca^(2+)concentration of the solution,are measured and analyzed.Electrical resistivity tomography(ERT)is utilized to evaluate the reinforcement effect in the underwater sand bed.The permeability of the model is tested to verify the feasibility of EICP technology for strengthening underwater sands.Furthermore,scanning electron microscope(SEM)is performed to investigate the growth mechanisms of calcium carbonate(CaCO_(3))crystals.The results show that the permeability of the model decreases from 1.28×10^(-2)m/s to 9.66×10^(-5)m/s,representing a reduction of approximately three orders of magnitude.This verifies that the EICP technology can greatly reduce the permeability of underwater sand beds.With increasing grouting cycles,the resistivity of the underwater sand initially decreases and then increases.This variation in sand resistivity is significantly influenced by the ion concentration in the solution,resulting in marked differences in resistivity at various depths and positions within the sand.The findings from this study offer a theoretical basis for the application of EICP technology in reinforcing seabed foundations and supporting marine infrastructure such as offshore pipelines,wind turbines,and oil platforms.展开更多
Precipitation events,which follow a life cycle of initiation,development,and decay,represent the fundamental form of precipitation.Comprehensive and accurate detection of these events is crucial for effective water re...Precipitation events,which follow a life cycle of initiation,development,and decay,represent the fundamental form of precipitation.Comprehensive and accurate detection of these events is crucial for effective water resource management and flood control.However,current investigations on their spatio-temporal patterns remain limited,largely because of the lack of systematic detection indices that are specifically designed for precipitation events,which constrains event-scale research.In this study,we defined a set of precipitation event detection indices(PEDI)that consists of five conventional and fourteen extreme indices to characterize precipitation events from the perspectives of intensity,duration,and frequency.Applications of the PEDI revealed the spatial patterns of hourly precipitation events in China and its first-and second-order river basins from 2008 to 2017.Both conventional and extreme precipitation events displayed spatial distribution patterns that gradually decreased in intensity,duration,and frequency from southeast to northwest China.Compared with those in northwest China,the average values of most PEDIs in southeast China were usually 2-10 times greater for first-order river basins and 3-15 times greater for second-order basins.The PEDI could serve as a reference method for investigating precipitation events at global,regional,and basin scales.展开更多
To reveal the influence mechanism of Nb/Ti microalloying on the mechanical property of ferritic stainless steel,the grain size,phase composition,microhardness,mechanical properties and fracture morphology are characte...To reveal the influence mechanism of Nb/Ti microalloying on the mechanical property of ferritic stainless steel,the grain size,phase composition,microhardness,mechanical properties and fracture morphology are characterized and analyzed for ferritic stainless steel with single addition of Ti stabilizing element and composite addition of Nb and Ti stabilizing elements.The influence mechanism of Ti and Nb stabilizing elements is elucidated on microstructure and mechanical properties of ferritic stainless steel.Results indicate that the grains are bigger(20-60µm)for ferritic stainless steel containing 0.09 wt.%Ti(F-Ti-ss).The average grain size is about 43.9µm.Meanwhile,there are many granular TiN precipitates with big size.For ferritic stainless steel with Nb and Ti stabilizing elements(F-Nb-Ti-ss),the grains are small(8-22µm),and average grain size is about 17.3µm.There are a few granular TiN precipitates with small size.Furthermore,many nanoscale(Fe,Cr,Nb)C phases precipitate at grain boundary,which plays a role in refining grain size.Compared with mechanical properties of F-Ti-ss(506 MPa and 28.2%),both the ultimate tensile strength and elongation are improved for F-Nb-Ti-ss(573 MPa and 30.5%).The ultimate tensile strength is increased by 13.2%.The main reason is that grains are obviously refined and a large number of nanoscale phases precipitate at grain boundary for F-Nb-Ti-ss.Therefore,strengthening effect is obvious and grain deformation is more uniform during tensile test.展开更多
China launched its first spaceborne Precipitation Measurement Radar(PMR)on the FY-3G satellite in April 2023.To achieve the scientific goal of measuring the three-dimensional precipitation structure,evaluating the qua...China launched its first spaceborne Precipitation Measurement Radar(PMR)on the FY-3G satellite in April 2023.To achieve the scientific goal of measuring the three-dimensional precipitation structure,evaluating the quantitative measurement ability of the PMR is critical.China operates more than 250 weather radars over the mainland.Consistency of the spaceborne radar with ground-based radars will enhance precipitation measurement ability,especially over oceans and mountains where observations are sparse.Additionally,the spaceborne radar can be used to evaluate the spatial and temporal homogeneity of the ground-based radar network.This paper focuses on comparing the PMR onboard the FY-3G satellite with S-band China New Generation Weather Radars(CINRADs).A comparison algorithm between the PMR and CINRADs has been developed,incorporating detailed quality control,attenuation correction,data optimization,spatiotemporal matching,non-uniform beam filling constraint,uniformity constraint,and frequency correction.The matched data in typical months of four seasons were selected to carry out the comparison.The data consistency between the PMR and CINRADs was analyzed.The correlation coefficient is 0.87,the deviation is 0.89 dB,and the standard deviation is 2.50 dB,based on 98226 matching samples.The results show the radar reflectivity of the PMR is quite comparable to that of the CINRADs,demonstrating that the PMR data quality is satisfactory and can be used to verify and correct data consistency among multiple ground-based radars.This work also paves the way for data fusion and joint application of satellite and ground radars in the future.展开更多
基金Project(2011TT2057)supported by Science&Technology Department of Hunan Province,China
文摘A novel technology using Fe powder as reducing agent for Ge and Cu recovery from precipitating vitriol supernatant in Zn hydrometallurgical plant was investigated. The results show that reaction time, temperature, agitation speed, initial pH value of solution and the amount of reducing Fe have significant effects on recovering Ge and Cu, and the optimum process operating parameters are established as follows： time 120 min, initial pH value 1.5, the dosage of reducing Fe powder 4 g/L, agitation speed 600 r/min and temperature 80 °C. Under these experimental conditions, the recovery ratios of Ge and Cu from precipitating vitriol supernatant in Zn hydrometallurgical plant can reach 96% and 100%, respectively. The content of Ge in the reduced residue reaches up to 2.06% （mass fraction）, indicating that the separation and enrichment of Ge from the Zn sulfate solution is realized. The grade of Ge and Cu can reach up to 4.88% and 56.75%, respectively, when the reduced residue is further processed.
基金supported by the National Natural Science Foun-dation of China(Nos.U1908219,52171163)the Key Research Program of the Chinese Academy of Sciences(No.ZDRW-CN-2021-2-2)+1 种基金the Applied Basic Research Program of Liaoning Province(grant no.2022JH2/101300005)the Central Guidance for Local Science and Technology Development Funds of Liaoning Province(grant no.2023JH6/100100016).
文摘Precipitation-strengthened HEAs exhibit outstanding integration of strength and toughness at ambient temperature.Nevertheless,precipitates generally reduce the localized corrosion resistance in aggressive solution environments.To solve this problem,a strategy of introducing nano-sized L12 precipitates in CoCrFeNiAlTi HEAs has been proposed in this work.Results demonstrate the pitting corrosion potential can be elevated from 258 mVSCE to 603 mVSCE by increasing the precipitate content to 38 wt.%.Such an improvement in localized corrosion resistance can be attributed to two aspects.Firstly,L12 precipitates tend to be dissolved during the corrosion process,which promotes the heterogeneous nucleation of protective Cr2 O3 due to the rapid deposition of oxides/hydroxides of Al/Ti,and improves the passive film stability due to the Crrich FCC matrix.Secondly,the dissolution kinetic inside the pits can be suppressed on account of the enrichment of Cr element in the FCC matrix,thus inhibiting the pitting growth.In summary,the current work not only reveals the mechanisms of the nano-sized L12 precipitates upon the corrosion behavior,but also provides a strategy for designing corrosion-resistant HEA.
文摘The influence of the precipitating reagents and dispersants on the formation of nano-aluminum hydroxide from sodium aluminate solution by chemical precipitation was investigated. The influence of the dispersed seeds on the decomposi-tion process was investigated too. The alkaline aluminate solutions were used as original solutions with a concentration of Al2O3 having 14.78 g/dm3, αk—1.6 and127 g/dm3, αk—1.6. For the precipitation processes there were used follow-ing precipitating reagents—solutions HCl, NaHCO3 and NH4HCO3 with a concentration of 80 g/dm3, dispersants—PEG 6000, (NaPO3)6 and Tween 20. For the decomposition process the dispersed seeds and factories seeds were used. Structural studies of the aluminum hydroxide particles were carried out by means of the electron-probe microanalysis and scanning electron microscopy, and phase composition of products was determined by means of X-ray diffraction analysis. Ammonium bicarbonate and Tween 20 were determined as the optimal precipitating reagent and dispersant, correspondingly, resulting in dispersed aluminum hydroxide, which is used as a seed in the decomposition process. It was established that this product in form of dispersed seed considerably reduces the duration of the decomposition process;the maximal decomposition of solution (73.9%) was observed after injection of dispersеd aluminum hydroxide into solution. The final aluminum hydroxide having 90% of particles less than 100 nanometers was obtained within 7 hours of steady decreasing temperature from 70°C to 48°C.
文摘Calculation of the influence of soft precipitating electrons on the polar ionosphere was carried out. The primary results are: (1) During summer time when the sunlight is the main source of upper atmosphere ionization, the additional soft electron precipitation can increase the NmF2. The daily variation of NmF2 is mainly controlled by solar EUV radiation. (2) At wintertime, when only soft electron precipitation ionization is considered, a peak at the height of F2 layer also appears. The altitude profile of electron density is different frorn that when the sunlit ionization is taken into account.
基金Project supported by the National High Technology Research and Development Program of China (863 Program) (2010AA03A407)Project of Beijing Educational Committee (PXM2012_014204_00_000160)
文摘The precursors organic cerium deposits were obtained by a stripping precipitation method from cerium-loaded P507 organic phase using oxalic acid as a precipitating agent and nano-sized ceria particles were prepared by calcining the precursors at 500 ℃. The morphologies, phase structure of the precursors and ceria particles were characterized by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD）, thermogravimetric analysis （TG-DSC） and infrared spectroscopy analysis （FTIR）. The results indicated that the concentration of oxalic acid had a little impact on the morphology of the precursors, which was blocky-shape Ce2（C2O4）3：10H2O with a monoclinic lattice structure. With the volume ratio of organic phase and oxalic acid aqueous solution （aqueous phase） varied from 1：3 to 1：6, the morphologies of the precursors Ce2（C2O4）3· 10H2O precipitates gradually changed from inhomogeneous blocky-shape to uniform spherical particles. The precursors could be turned to CeO2 crystal particles with a fluorite structure by calcining, and the products ceria particles were similar in the size and morphology to the precursors.
文摘Heat-resistant aluminum alloys are widely used in aerospace and automotive fields for manufacturing hot components due to their advantages in lightweight design and energy conservation.However,the high-temperature strength of existing cast aluminum alloys is always limited to about 100 MPa at 350℃due to coarsening and transformation of strengthening phases.Here,we reveal that the yield strength and ultimate tensile strength of the T6 state Al-8.4Cu-2.3Ce-1.0Mn-0.5Ni-0.2Zr alloy at 400◦C increase by 34%and 44%after re-aging at 300℃for 100 h,and its thermal strength exhibits distinguished ad-vantage over traditional heat-resistant aluminum alloys.The enhanced elevated-temperature strength is attributed to the reprecipitation of the Ni-bearing T-Al_(20)Cu_(2)Mn_(3)phase,whose number density increases over one time.The significant segregation of Ni,Ce,and Zr elements at the interfaces helps improve the thermal stability of the T phase.The thermostable T phase effectively strengthens the matrix by in-hibiting dislocation motion.Meanwhile,a highly interconnected 3D intermetallic network along the grain boundaries can still remain after long-term re-aging at 300℃,which is conducive to imposing a drag on the grain boundaries at high temperatures.This finding offers a viable route for enhancing the elevated-temperature strength of heat-resistant aluminum alloys,which could provide expanded opportunities for higher-temperature applications.
基金This work was supported by the Natural Science Foundation of Shandong Province under grant No.Y99F01.
文摘Carbides in a series of cold-welding weld metals were studied by means of SEM, TEM and EPMA, and the forming mechanism of carbide was proposed according to their distribution and morphology. Due to their different carbide-forming tendency, Nb and Ti could combine with C to form particulate carbide in liquid weld metai and depleted the carbon content in matrix, while V induced the carbide precipitated along grain boundary. But too much Nb or Ti alone resulted in coarse carbide and poor strengthened matrix. When suitabie amount of Nb, Ti and V coexisted in weld metai, both uniformly distributed particulate carbide and well strengthened matrix could be achieved. It was proposed that the carbide nucleated on the oxlde which dispersed in liquid weld metai, and then grew into multi-layer complex carbide particies by epitaxial grovvth. At different sites, carbide particies may present as different morphologies.
基金support from Chinese High-Tech Project(715-09-03)
文摘Spray deposition is a novel process which is used to manufacture rapidly solidified bulk and near-net-shape preforms. In this study, AI-20Si-5Fe-3Mn-3Cu-1Mg alloy was synthesized by spray deposition technique. The aging process of the alloy was investigated by differential scanning calorimetry (DSC) analysis and transmission electron microscopy (TEM). The results show that two kinds of phases, i.e. S(Al2CuMg) and σ(Al5Cu6Mg2), precipitate from matrix and improve the tensile strength of the alloy efficiently at both the ambient and elevated temperatures (300℃). In addition, the σ-Al5Cu6Mg2 is a relatively stable phase which improves microstructural stability of the alloy.
基金National Nature Science Foundation of China(50974014)
文摘The grain size and precipitate amount which are affected by heat treatment have significant impact on the properties of high nitrogen austenitic stainless steel.In this study,Cr18Mn18 high nitrogen steel sheet is employed to investigate the effects of precipitate on austenitic grain size.It can be seen that the lamella precipitates which are rich in nitrogen and chromium nucleate in the austenite grain boundary and grow inward into grain when aged at 800℃through electron probe micro-analyzer.The transmission electron microscopy results demonstrate that the precipitate is Cr2N and its morphology are detected as ellipsoid-like with major axis of 100-300 nm and minor axis of 50-100 nm roughly.The experiment show that coarsen of the austenite grain is quite critical at 1000-1100℃.However,the samples which pre-precipitated at 800℃for 240 min to obtain the most nitride precipitate exhibits much smaller grain size than the as-rolled samples after solid solution treated at 1000,1050 and 1100℃for 240 min.The results show that the nitride precipitates in the grain boundary can effectively pin the austenite grain boundary and inhibit the grain growth.
文摘The effect of tempering temperature on the microstrocture and precipitating evolution and the resultant mechanical properties of newly developed high-strength microalloyed steel plate was investigated by optical microscopy （OM） and transmission electron microscopy （TEM）. The steel mainly consists of fine lath martensite and lower bainite. The width of the martensitic laths in as-hot-rolled state is about 120 nm,and increases from 120 nm to 150 nm and 180 nm after tempering at 200 ℃ and 250℃ for 2 h respectively with no change in its morphology. Of special interest is the phenomenon that both tensile strength and impact toughness of the steel plate decrease with the increase of the tempering temperature, which might be attributed to the combination of lath martensite broadening and the coarsening of needle-like carbides located on the boundaries of lath martensite and within bainitic ferrite. It is suggested that the existence of the complex carbonitride larger than 100 nm in bainitic ferrite is one of the reasons.
基金Gansu Provincial Department of Education Industrial Support Program Project(2025CYZC-069)Central Government-Guided Local Science and Technology Development Fund Project(25ZYJE002)National Natural Science Foundation of China(51861022,51261016)。
文摘The Cu0.9Cr0.1Zr alloy was deformed through continuous equal channel angular pressing(C-ECAP)through Route A,followed by liquid nitrogen cryogenic rolling(CR)and aging treated at 450℃.The microstructure,mechanical properties,and conductivity of the alloy were detected by electron back-scattered diffractometer,energy dispersive spectroscope,X-ray diffractometer,scanning electron microscope,and transmission electron microscope.The evolution mechanism of the texture during the deformation process and its influence on mechanical properties were analyzed.The results show that directional shear bands form in the CuCrZr alloy during the C-ECAP process,and the preferred orientation of the microstructure is consistent with the rolling direction.After deformation,the number of precipitated phases(mainly Cr)increases with the prolongation of aging time,accompanied by the appearance of micro-nanostructured fibrous structure in the alloy.After C-ECAP for three passes,75%CR deformation,and aging at 450℃ for 2 h,the tensile strength,microhardness,and conductivity reach 538 MPa,168 HV,and 80%IACS,respectively.CR,aging heat treatment,and formation of recrystallization texture are all conducive to the improvement of conductivity.
基金financially supported by the National Key Research and Development Program of China (No. 2019YFA0708801)the National Natural Science Foundation of China (No. 51875125)。
文摘The water-quenched(WQ)2195 Al−Li alloy was subjected to stretching at different temperatures,from room temperature(RT)to−196℃(CT),to investigate the effect of cryogenic deformation on the aging precipitation behaviors and mechanical properties.The precipitation kinetics of the T1 phase and the microstructures in peak aging state were investigated through the differential scanning calorimetric(DSC)tests and electron microscopy observation.The results show that−196℃deformation produces a high dislocation density,which promotes the precipitation of the T1 phase and refines its sizes significantly.In addition,the grain boundary precipitates(GBPs)of−196℃-stretched samples are suppressed considerably due to the high dislocation density in the grain interiors,which increases the ductility.In comparison,the strength remains nearly constant.Thus,it is indicated that cryogenic forming has the potential to provide the shape and property control for the manufacture of critical components of aluminum alloys.
基金supported by National Natural Science Foundation of China(Nos.52204309,52174277 and 52374300)Fundamental Funds for the Central Universities(No.N2425026)。
文摘Manganese is a major impurity in acidic vanadium-bearing leaching solutions,but its effects on vanadium precipitation via hydrolysis and acidic ammonium salts remain unclear.In this study,vanadium-bearing leachates with varying manganese concentrations(VL-cMn)were prepared through calcium,a calcium-manganese composite,and manganese-based roasting of vanadium slag(VS)to investigate the influence of manganese on vanadium precipitation behavior during hydrolysis precipitation(HP)and ammonium salt precipitation(AP),as well as the microscopic characteristics and purity of the resulting V_(2)O_(5) products.The results showed that increasing the pH mitigated the negative effects of Mn on the V precipitation rate during HP.However,as the manganese concentration increased from 5.69 to 15.38 g/L,the V precipitation rate gradually declined at higher temperatures and longer reaction times.The precipitates exhibited increased microstructural density,which might had contributed to the formation of Mn-bearing phases.Additionally,the average grain size of V_(2)O_(5) was reduced and the particles were increasingly agglomerated,leading to a 2.55%decrease in product purity.For AP,as manganese concentration increased,raising the pH counteracted the negative impact of Mn on the V precipitation rate and reduced the required amount of ammonium sulfate.Moreover,Mn was unevenly adsorbed on the surface of the precipitates.Although V_(2)O_(5) grains gradually shrank and became denser,there was no significant effect on the final product purity,which remained above 99.3%.In conclusion,roasting with added manganese salts influenced the hydrolysis of vanadium but had no significant effect on acidic ammonium salt precipitation.
基金supported by the National Youth Top-notch Talent Support Program of China(Grant No.00389335)the National Natural Science Foundation of China(Grant No.52378392)the“Foal Eagle Program”Youth Top-notch Talent Project of Fujian Province,China(Grant No.00387088).
文摘Enzyme-induced carbonate precipitation(EICP)is a potential ground improvement method that can reduce the permeability of sands.However,the traditional mathematical models are hard to accurately predict the permeability of EICP-treated sands.In this study,the mathematical model was established for predicting the permeability of EICP-treated sands based on Kozeny-Carman equation.The effects of calcium carbonate precipitation on the porosity,tortuosity,and specific surface area of the EICP-treated sands were considered in the model.To validate the model,the bio-cemented sand column tests with different grain size distributions(coarse,medium,and fine sands)and treatment numbers(6,8,and 10 times)were conducted.The calcium carbonate content(CCC)and permeability of EICP-treated sands were measured.The validation of the model was confirmed through a comparative analysis of theoretical and experimental results.Furthermore,the impacts of porosity,particle size,CCC,and specific surface area on the hydraulic conductivity of EICP-treated sands were analyzed.The results showed that the model can reflect the hydraulic conductivity of EICP-treated sands under different particle size distributions and degrees of cementation,demonstrating broad applicability.Parametric analysis indicated the hydraulic conductivity gradually decreases with increasing CCC and specific surface area.Conversely,the hydraulic conductivity gradually increases with increasing porosity(n)and particle size(d50),with porosity exhibiting a significantly higher sensitivity than particle size.In summary,this study contributes theoretical foundations for the practical implementation of EICP technology in reducing soil permeability.
基金supported by the National Youth Top-notch Talent Support Program of China(Grant No.00389335)the National Natural Science Foundation of China(Grant No.52378392)+1 种基金the“Foal Eagle Program”Youth Top-notch Talent Project of Fujian Province(Grant No.00387088)supports are gratefully acknowledged.
文摘Enzyme-Induced Carbonate Precipitation(EICP)is an innovative technique to improve soil strength and reduce permeability.However,the use of EICP for reinforcing underwater sand beds remains largely unexplored.To advance EICP implementation in various geotechnical applications,this paper develops a model box system to investigate the effectiveness of the EICP technique in reinforcing underwater sand beds.An"injection-extraction"system is designed to facilitate the flow of the EICP solution through underwater sand layers.Key parameters,including conductivity,pH,and Ca^(2+)concentration of the solution,are measured and analyzed.Electrical resistivity tomography(ERT)is utilized to evaluate the reinforcement effect in the underwater sand bed.The permeability of the model is tested to verify the feasibility of EICP technology for strengthening underwater sands.Furthermore,scanning electron microscope(SEM)is performed to investigate the growth mechanisms of calcium carbonate(CaCO_(3))crystals.The results show that the permeability of the model decreases from 1.28×10^(-2)m/s to 9.66×10^(-5)m/s,representing a reduction of approximately three orders of magnitude.This verifies that the EICP technology can greatly reduce the permeability of underwater sand beds.With increasing grouting cycles,the resistivity of the underwater sand initially decreases and then increases.This variation in sand resistivity is significantly influenced by the ion concentration in the solution,resulting in marked differences in resistivity at various depths and positions within the sand.The findings from this study offer a theoretical basis for the application of EICP technology in reinforcing seabed foundations and supporting marine infrastructure such as offshore pipelines,wind turbines,and oil platforms.
基金National Key Research and Development Program of China,No.2023YFC3206605,No.2021YFC3201102National Natural Science Foundation of China,No.41971035。
文摘Precipitation events,which follow a life cycle of initiation,development,and decay,represent the fundamental form of precipitation.Comprehensive and accurate detection of these events is crucial for effective water resource management and flood control.However,current investigations on their spatio-temporal patterns remain limited,largely because of the lack of systematic detection indices that are specifically designed for precipitation events,which constrains event-scale research.In this study,we defined a set of precipitation event detection indices(PEDI)that consists of five conventional and fourteen extreme indices to characterize precipitation events from the perspectives of intensity,duration,and frequency.Applications of the PEDI revealed the spatial patterns of hourly precipitation events in China and its first-and second-order river basins from 2008 to 2017.Both conventional and extreme precipitation events displayed spatial distribution patterns that gradually decreased in intensity,duration,and frequency from southeast to northwest China.Compared with those in northwest China,the average values of most PEDIs in southeast China were usually 2-10 times greater for first-order river basins and 3-15 times greater for second-order basins.The PEDI could serve as a reference method for investigating precipitation events at global,regional,and basin scales.
基金the National Key Research and Development Program of China(Grant No.2023YFB3712400)the National Natural Science Foundation of China(Grant Nos.52027805 and 52204381)Fundamental Research Funds for the Central Universities(Grant No.FRF-TP-24-002A).
文摘To reveal the influence mechanism of Nb/Ti microalloying on the mechanical property of ferritic stainless steel,the grain size,phase composition,microhardness,mechanical properties and fracture morphology are characterized and analyzed for ferritic stainless steel with single addition of Ti stabilizing element and composite addition of Nb and Ti stabilizing elements.The influence mechanism of Ti and Nb stabilizing elements is elucidated on microstructure and mechanical properties of ferritic stainless steel.Results indicate that the grains are bigger(20-60µm)for ferritic stainless steel containing 0.09 wt.%Ti(F-Ti-ss).The average grain size is about 43.9µm.Meanwhile,there are many granular TiN precipitates with big size.For ferritic stainless steel with Nb and Ti stabilizing elements(F-Nb-Ti-ss),the grains are small(8-22µm),and average grain size is about 17.3µm.There are a few granular TiN precipitates with small size.Furthermore,many nanoscale(Fe,Cr,Nb)C phases precipitate at grain boundary,which plays a role in refining grain size.Compared with mechanical properties of F-Ti-ss(506 MPa and 28.2%),both the ultimate tensile strength and elongation are improved for F-Nb-Ti-ss(573 MPa and 30.5%).The ultimate tensile strength is increased by 13.2%.The main reason is that grains are obviously refined and a large number of nanoscale phases precipitate at grain boundary for F-Nb-Ti-ss.Therefore,strengthening effect is obvious and grain deformation is more uniform during tensile test.
基金jointly supported by the National Natural Science Foundation of China(Grant U2442214)the China Meteorological Administration Youth Innovation Team(Grant No.CMA2024QN10)+1 种基金the National Defense Science and Technology Bureau’s 14th Five-Year Civil Aerospace Preresearch Project(Grant Nos.D030303 and D040204)the International Space Water Cycle Observation Constellation Program(Grant No.183311KYSB20200015).
文摘China launched its first spaceborne Precipitation Measurement Radar(PMR)on the FY-3G satellite in April 2023.To achieve the scientific goal of measuring the three-dimensional precipitation structure,evaluating the quantitative measurement ability of the PMR is critical.China operates more than 250 weather radars over the mainland.Consistency of the spaceborne radar with ground-based radars will enhance precipitation measurement ability,especially over oceans and mountains where observations are sparse.Additionally,the spaceborne radar can be used to evaluate the spatial and temporal homogeneity of the ground-based radar network.This paper focuses on comparing the PMR onboard the FY-3G satellite with S-band China New Generation Weather Radars(CINRADs).A comparison algorithm between the PMR and CINRADs has been developed,incorporating detailed quality control,attenuation correction,data optimization,spatiotemporal matching,non-uniform beam filling constraint,uniformity constraint,and frequency correction.The matched data in typical months of four seasons were selected to carry out the comparison.The data consistency between the PMR and CINRADs was analyzed.The correlation coefficient is 0.87,the deviation is 0.89 dB,and the standard deviation is 2.50 dB,based on 98226 matching samples.The results show the radar reflectivity of the PMR is quite comparable to that of the CINRADs,demonstrating that the PMR data quality is satisfactory and can be used to verify and correct data consistency among multiple ground-based radars.This work also paves the way for data fusion and joint application of satellite and ground radars in the future.
