The modeling and self-excited vibration mechanism in the magnetic levitation-collision interface coupling system are investigated.The effects of the control and interface parameters on the system's stability are a...The modeling and self-excited vibration mechanism in the magnetic levitation-collision interface coupling system are investigated.The effects of the control and interface parameters on the system's stability are analyzed.The frequency range of self-excited vibrations is investigated from the energy point of view.The phenomenon of self-excited vibrations is elaborated with the phase trajectory.The corresponding control strategies are briefly analyzed with respect to the vibration mechanism.The results show that when the levitation objects collide with the mechanical interface,the system's vibration frequency becomes larger with the decrease in the collision gap;when the vibration frequency exceeds the critical frequency,the electromagnetic system continues to provide energy to the system,and the collision interface continuously dissipates energy so that the system enters the self-excited vibration state.展开更多
The effect of the Y spacer layer on the phase composition,coercivity,and magnetization reversal processes of La-Nd-Fe-B films has been investigated.The addition of a 10 nm Y spacer layer increases the coercivity of th...The effect of the Y spacer layer on the phase composition,coercivity,and magnetization reversal processes of La-Nd-Fe-B films has been investigated.The addition of a 10 nm Y spacer layer increases the coercivity of the film to 1.36 T at 300 K and remains 0.938 T at 380 K.As the thickness of the Y spacer layer increases,Y participates in the formation of the main phase in the film,and further regulates the formation of La-B phases.The results of the first-order reversal curve(FORC)and micromagnetic fitting show that the coercivity of all the films is dominated by nucleation mechanism.The c-axis preferred orientation,good magnetic microstructure parameters and the largest dipole interaction enhance the coercivity.Therefore,the introduction of the Y spacer layer can be an effective way to improve the coercivity of La-Nd-Fe-B film over a wide temperature range of 150 K-380 K.展开更多
The adverse effects of eutrophication have prompted the use of various remediation techniques for phosphate(PO_(4)^(3-))removal owing to it being the major causative agent.Herein,the influence of different solvents an...The adverse effects of eutrophication have prompted the use of various remediation techniques for phosphate(PO_(4)^(3-))removal owing to it being the major causative agent.Herein,the influence of different solvents and ratios of 2-aminoterepthalicacid on the efficiency of magnetic biomass metal-organic framework composites based on the in situ growth of NH_(2)-MIL-101(Fe)onto magnetized peanut husks towards PO_(4)^(3-)removal was assessed via the adsorption technique.The magnetic biocomposite labelled as MPN@NH2-MIL-101(Fe)exhibited the best efficiency owing to its mesoporous structures and presence of abundant oxygen and nitrogen possessing functional groups.Adsorption results confirmed MPN@NH2-MIL-101(Fe)to have a high adsorption capacity of(14.0±0.3)mg·L^(-1)at a PO43-concentration of 20 mg·L^(-1)with an associated high stability within pH 2-10.The adsorption kinetics for the process was well described by both Elovich and pseudo-second-order kinetic models and was mediated by both internal diffusion and liquid film diffusion.The Temkin and Freundlich models fitted the equilibrium data well signifying occurrence of both physical and chemical adsorption on a heterogeneous surface.It is concluded that MPN@NH2-MIL-101(Fe)is a promising adsorbent for the effective removal of phosphate from a water body.展开更多
To clarify the corrosion mechanism associated with the precipitate of T1(Al2CuLi)in Al-Li alloys,the simulated bulk precipitate of T1 was fabricated through melting and casting.Its electrochemical behavior and couplin...To clarify the corrosion mechanism associated with the precipitate of T1(Al2CuLi)in Al-Li alloys,the simulated bulk precipitate of T1 was fabricated through melting and casting.Its electrochemical behavior and coupling behavior with α(Al)in 3.5% NaCl solution were investigated.Meanwhile,the simulated Al alloy containing T1 particle was prepared and its corrosion morphology was observed.The results show that there exists a dynamic conversion corrosion mechanism associated with the precipitate of T1.At the beginning,the precipitate of T1 is anodic to the alloy base and corrosion occurs on its surface.However,during its corrosion process,its potential moves to a positive direction with immersion time increasing,due to the preferential dissolution of Li and the enrichment of Cu.As a result,the corroded T1 becomes cathodic to the alloy base at a later stage,leading to the anodic dissolution and corrosion of the alloy base at its adjacent periphery.It is suggested that the localized corrosion associated with the precipitate of T1 in Al-Li alloys is caused by the alternate anodic dissolution of the T1 precipitate and the alloy base at its adjacent periphery.展开更多
Precipitates play an important role in determining the mechanical and magnetic properties of silicon steel. This paper aims to investigate the growth kinetics of precipitates in commercial silicon steel by analyzing i...Precipitates play an important role in determining the mechanical and magnetic properties of silicon steel. This paper aims to investigate the growth kinetics of precipitates in commercial silicon steel by analyzing its magnetic properties during isothermal annealing at 200℃. The growth of precipitates was studied by optical microscopy, scanning electron microscopy, transmission electron microscopy, and magnetic measurements. In combination with the coercive field and initial susceptibility, this technique offers the advantage of being non-destructive and providing quantitative information about the number, mean radius of precipitates, and fraction of transformation. An ob- served decrease in the number of precipitated particles indicates that the transformation starts from particles of appreciable initial size.展开更多
The characteristics and generation mechanism of(Ti,Nb,V)(C,N) precipitates larger than 2 μm in Nb-containing H13 bar steel were studied. The results show that two types of(Ti,Nb,V)(C,N) phases exist—a Ti-V-r...The characteristics and generation mechanism of(Ti,Nb,V)(C,N) precipitates larger than 2 μm in Nb-containing H13 bar steel were studied. The results show that two types of(Ti,Nb,V)(C,N) phases exist—a Ti-V-rich one and an Nb-rich one—in the form of single or complex precipitates. The sizes of the single Ti-V-rich(Ti,Nb,V)(C,N) precipitates are mostly within 5 to 10 μm, whereas the sizes of the single Nb-rich precipitates are mostly 2–5 μm. The complex precipitates are larger and contain an inner Ti-V-rich layer and an outer Nb-rich layer. The compositional distribution of(Ti,Nb,V)(C,N) is concentrated. The average composition of the single Ti-V-rich phase is(Ti_(0.511)V_(0.356)Nb_(0.133))(CxNy), whereas that for the single Nb-rich phase is(Ti_(0.061)V_(0.263)Nb_(0.676))(C_xN_y). The calculation results based on the Scheil–Gulliver model in the Thermo-Calc software combining with the thermal stability experiments show that the large phases precipitate during the solidification process. With the development of solidification, the Ti-V-rich phase precipitates first and becomes homogeneous during the subsequent temperature reduction and heat treatment processes. The Nb-rich phase appears later.展开更多
To clarify the localized corrosion mechanism associated with precipitates containing Mg in Al alloys, the simulated bulk precipitates of S and β were synthesized through melting and casting. Their electrochemical beh...To clarify the localized corrosion mechanism associated with precipitates containing Mg in Al alloys, the simulated bulk precipitates of S and β were synthesized through melting and casting. Their electrochemical behaviors and coupling behaviors with α(Al) in NaCl solution were measured. Meanwhile, simulated Al alloys containing S and β particles were prepared and their corrosion morphologies were observed. It’s found that there exist two kinds of corrosion mechanisms associated with precipitates containing Mg. The precipitate of β is anodic to the alloy base, resulting in its anodic dissolution and corrosion during the whole corrosion process. While, there exists a corrosion conversion mechanism associated with the S precipitate, which contains active element Mg and noble element Cu simultaneously. At an initial stage, S is anodic to the alloy matrix at its periphery and the corrosion occurs on its surface. However, during its corrosion process, Mg is preferentially dissolved and noble Cu is enriched in the remnants. This makes S become cathodic to α(Al) and leads to anodic dissolution and corrosion on the alloy base at its periphery at a later stage.展开更多
During the process of directional solidification,laser remelting/solidification in the layer on sintered magnets, die-upsetting of cast magnets,or die-upsetting of nano-composites,the arrangements of the easy-magnetiz...During the process of directional solidification,laser remelting/solidification in the layer on sintered magnets, die-upsetting of cast magnets,or die-upsetting of nano-composites,the arrangements of the easy-magnetization-axes of the hard magnetic phases(Nd2Fe14B,SmCo5 or Sm2Co17 type)in their designed directions have been studied.In Fe-Pt nano-composite magnets,attempts have been taken to promote phase transformation from disordered,soft magnetic A1 to ordered,hard magnetic L10 FePt phase at reduced temperatures.The dependence of the magnetization and reversal magnetization processes on the microstructures,involving the morphology and three critical sizes of particles of the FePt nano-composite magnets,are summarized. With the decrease of the nominal thickness of the anisotropic FePt film epitaxially grown on the single crystal MgO(001)substrate, the reversal magnetization process firstly changes from full domain wall displacement to partial magnetic wall pinning related to the morphology change,where the coercive force increases abruptly.The reversal magnetization process secondly changes from magnetic wall pinning to incoherent magnetization rotation associated with the particles being below the first critical size at which multi-domain particles turn into single domain ones,where the coercive force is still increased.And the reversal magnetization mode thirdly changes from incoherent to coherent rotation referred to the second critical size,where the increase of the coercive force keeps on.However,when the particle size decreases to approach the third critical size where the particles turn into the supperparamagnetic state,the coercive force begins to decrease due to the interplay of the size effect and the incomplete ordering induced by the size effect.Meanwhile,due to the size effect,Curie temperature of the ultra-small FePt particles reduces.展开更多
The martensitic transformation,mechanical,and magnetic properties of the Ni_(2)Mn_(1.5-x)Cu_(x)Ti_(0.5) (x=0.125,0.25,0.375,0.5) and Ni_(2-y)Co_(y)Mn_(1.5-x)Cu_(x)Ti_(0.5)[(x=0.125,y=0.125,0.25,0.375,0.5) and (x=0.125...The martensitic transformation,mechanical,and magnetic properties of the Ni_(2)Mn_(1.5-x)Cu_(x)Ti_(0.5) (x=0.125,0.25,0.375,0.5) and Ni_(2-y)Co_(y)Mn_(1.5-x)Cu_(x)Ti_(0.5)[(x=0.125,y=0.125,0.25,0.375,0.5) and (x=0.125,0.25,0.375,y=0.625)]alloys were systematically studied by the first-principles calculations.For the formation energy,the martensite is smaller than the austenite,the Ni–(Co)–Mn–Cu–Ti alloys studied in this work can undergo martensitic transformation.The austenite and non-modulated (NM) martensite always present antiferromagnetic state in the Ni_(2)Mn_(1.5-x)Cu_(x)Ti_(0.5) and Ni_(2-y)Co_(y)Mn_(1.5-x)Cu_(x)Ti_(0.5) (y<0.625) alloys.When y=0.625 in the Ni_(2-y)Co_(y)Mn_(1.5-x)Cu_(x)Ti_(0.5) series,the austenite presents ferromagnetic state while the NM martensite shows antiferromagnetic state.Cu doping can decrease the thermal hysteresis and anisotropy of the Ni–(Co)–Mn–Ti alloy.Increasing Mn and decreasing Ti content can improve the shear resistance and normal stress resistance,but reduce the toughness in the Ni–Mn–Cu–Ti alloy.And the ductility of the Co–Cu co-doping alloy is inferior to that of the Ni–Mn–Cu–Ti and Ni–Co–Mn–Ti alloys.The electronic density of states was studied to reveal the essence of the mechanical and magnetic properties.展开更多
The microstructures and properties of hot-rolled low-carbon ferritic steel have been investigated by optical microscopy, field-emission scanning electron microscopy, transmission electron microscopy, and tensile tests...The microstructures and properties of hot-rolled low-carbon ferritic steel have been investigated by optical microscopy, field-emission scanning electron microscopy, transmission electron microscopy, and tensile tests after isothermal transformation from 600°C to 700°C for 60 min. It is found that the strength of the steel decreases with the increment of isothermal temperature, whereas the hole expansion ratio and the fraction of high-angle grain boundaries increase. A large amount of nanometer-sized carbides were homogeneously distributed throughout the material, and fine(Ti, Mo)C precipitates have a significant precipitation strengthening effect on the ferrite phase because of their high density. The nanometer-sized carbides have a lattice parameter of 0.411-0.431 nm. After isothermal transformation at 650°C for 60 min, the ferrite phase can be strengthened above 300 MPa by precipitation strengthening according to the Ashby-Orowan mechanism.展开更多
Magnetizing roasting of oolitic hematite ore from western Hubei Province was investigated.The mechanism for reduction roasting of oolitic hematite ore was discussed and analyzed.It is found that flash magnetizing roas...Magnetizing roasting of oolitic hematite ore from western Hubei Province was investigated.The mechanism for reduction roasting of oolitic hematite ore was discussed and analyzed.It is found that flash magnetizing roasting-magnetic separation process is a promising approach for the processing of oolitic hematite ore from western Hubei Province.展开更多
To study the precipitation mechanism of α-Cr phase in Inconel 718 alloy, the samples after long-time aging at 650 and 677℃ were examined by microstructural observations and chemical phase analysis methods. Combining...To study the precipitation mechanism of α-Cr phase in Inconel 718 alloy, the samples after long-time aging at 650 and 677℃ were examined by microstructural observations and chemical phase analysis methods. Combining the thermodynamics and kinetics calculation results, α-Cr always precipitates in the vicinity of δ phase, because δ phase rejects Cr into the γ-matrix when growing. The selected area diffraction patterns confirm that the crystallographic relationships of α-Cr with 6 phase are (010)d/(1- 10)a.Cr and [100]d/If 11 ]α-Cr- A graphic model is also presented to show the crystallographic relation between α-Cr and δ phases.展开更多
The shape change of the γ' precipitates of cast Ni-based superalloy K52 after aging treatment under a high magnetic field was investigated. The results show that duplex γ' precipitates are present in the γ matrix...The shape change of the γ' precipitates of cast Ni-based superalloy K52 after aging treatment under a high magnetic field was investigated. The results show that duplex γ' precipitates are present in the γ matrix after aging treatment with or without the magnetic field. One is the coarse particles with average size of 500 nm; the other is fine spherical γ' precipitates with average of 100 nm in diameter. The application of a 10T magnetic field only results in the shape of the coarse γ' particles changing from spherical to cuboidal when the alloys subjected to the same heat treatments. This shape change was mainly discussed based on the strain energy increase caused by the difference in magnetostriction between the γ matrix and γ' precipitates. The fine γ' particles still keep spherical. Further TEM observations shows that a number of γ particles in nano-scale precipitate in the coarse γ' particles in the specimens treated without the magnetic field. In addition, it was found that the magnetic field caused the decrease of the hardness in the alloy, and the hardness was associated with the field direction.展开更多
Optical microscope(OM),scanning electron microscope(SEM),transmission electron microscope(TEM)and tensile machine were used to characterize the microstructures and mechanical properties of as-forged and aged Mg-9.5Gd-...Optical microscope(OM),scanning electron microscope(SEM),transmission electron microscope(TEM)and tensile machine were used to characterize the microstructures and mechanical properties of as-forged and aged Mg-9.5Gd-3.8Y-0.6Zr alloys.The results show that a novel kind of dislocation arrays,comprising parallel arranged dislocations,were obtained in the forged alloy.The arrays tend to extend parallel and are heterogeneously distributed with adjacent distances varying from 0.3μm to 1.4μm.After aging the alloy at 265°C,a large number of preferential-oriented phases were precipitated on the dislocation arrays,forming a structure of"precipitation chains"(PCs),which results in simultaneous increments of strength and ductility.展开更多
The coercivity mechanism of Nd Fe B magnets prepared by combination of strip casting with hydrogen decrepitation techniques was investigated. The microstructure of (Nd 0.935 Dy 0.065 ) 14.5 Fe 79.4 ...The coercivity mechanism of Nd Fe B magnets prepared by combination of strip casting with hydrogen decrepitation techniques was investigated. The microstructure of (Nd 0.935 Dy 0.065 ) 14.5 Fe 79.4 B 6.1 magnet was observed. The average grain size is about 6~12 μm. The magnetizing field dependence of the hardmagnetic properties for the (Nd 0.935 Dy 0.065 ) 14.5 Fe 79.4 B 6.1 and the temperature dependence of the coercivity for the Nd 14.5 Fe 79.4 B 6.1 were investigated. Results show that the coercivity for magnets prepared by the combination of strip casting with hydrogen decrepitation techniques is controlled by the nucleation mechanism.展开更多
The microstructures of B2-ordered NiA1 containing α-Fe precipitates have been investigated in terms of transmission electron microscopy. Fine precipitation of α-Fe (bcc structure) occurs in NiA1 by aging around 973...The microstructures of B2-ordered NiA1 containing α-Fe precipitates have been investigated in terms of transmission electron microscopy. Fine precipitation of α-Fe (bcc structure) occurs in NiA1 by aging around 973K. The aging behavior was investigated by microhandness measurements and the temperature dependence of the yield strength of precipitate- comaining B2- ordered NiA1 was investigated by compression tests over the temperature range of 673-1273K. The fine precipitation of α-Fe was found to enhance greatly the low and intermediate temperature yield strength. When the deformation temperature is over 1073K, the strength of precipitate- containing NiA1 was comparable to ternary solid solution hardening NiA1-Fe. Dislocations bypass the particles during deformation and typical Orowan loops were observed surrounding the or-Fe particles after deformation.展开更多
The rectangle-like pulsed magnetic field acted on the rubbing pair was presented through analyzing the exciting property in the reciprocating travel. The test of wear in NG-x tester shows that the wear between the ele...The rectangle-like pulsed magnetic field acted on the rubbing pair was presented through analyzing the exciting property in the reciprocating travel. The test of wear in NG-x tester shows that the wear between the electromagnetic core and down magnetic board distributes in the high velocity slip region of reciprocating travel, and the adhesive wear in the low velocity slip region nearby up and down dead points is depressed owing to the presence of high flux magnetic field. The lubrication by magnetic fluid with high permeability effectively reduces the friction and wear of high flux rubbing pair, and improves the conducting property of magnetic circuit constructed by the rubbing pair, which is beneficial to increase the operation performance of magnetic driving mechanism.展开更多
The effects of small additions of calcium (0.1%and 0.5%~1) on the dynamic recrystallization behavior and mechanical properties of asextruded Mg-1Mn-0.5Al alloys were investigated.Calcium microalloying led to the forma...The effects of small additions of calcium (0.1%and 0.5%~1) on the dynamic recrystallization behavior and mechanical properties of asextruded Mg-1Mn-0.5Al alloys were investigated.Calcium microalloying led to the formation of Al_(2)Ca in as-cast Mg-1Mn-0.5Al-0.1Ca alloy and both Mg_(2)Ca and Al_(2)Ca phases in Mg-1Mn-0.5Al-0.5Ca alloy.The formed Al_(2)Ca particles were fractured during extrusion process and distributed at grain boundary along extrusion direction (ED).The Mg_(2)Ca phase was dynamically precipitated during extrusion process,hindering dislocation movement and reducing dislocation accumulation in low angle grain boundaries (LAGBs) and hindering the transformation of high density of LAGBs into high angle grain boundaries (HAGBs).Therefore,a bimodal structure composed of fine dynamically recrystallized (DRXed) grains and coarse un DRXed regions was formed in Ca-microalloyed Mg-1Mn-0.5Al alloys.The bimodal structure resulted in effective hetero-deformation-induced (HDI) strengthening.Additionally,the fine grains in DRXed regions and the coarse grains in un DRXed regions and the dynamically precipitated Mg_(2)Ca phase significantly enhanced the tensile yield strength from 224 MPa in Mg-1Mn-0.5Al to335 MPa and 352 MPa in Mg-1Mn-0.5Al-0.1Ca and Mg-1Mn-0.5Al-0.5Ca,respectively.Finally,a yield point phenomenon was observed in as-extruded Mg-1Mn-0.5Al-x Ca alloys,more profound with 0.5%Ca addition,which was due to the formation of (■) extension twins in un DRXed regions.展开更多
Nowadays,having an effective technique in preparing semi-solid slurries for rheocasting process seems to be an essential requirement.In this study,semi-solid slurry of A356 aluminum alloy was prepared by three-phase a...Nowadays,having an effective technique in preparing semi-solid slurries for rheocasting process seems to be an essential requirement.In this study,semi-solid slurry of A356 aluminum alloy was prepared by three-phase annular electromagnetic stirring(A-EMS)technique under different conditions.The effects of stirring current,pouring temperature and stirring time on microstructural evolution,mean particle size,shape factor and solid fraction were investigated.The rheocasting process was carried out by using a drop weight setup and to inject the prepared semi-solid slurry in optimal conditions into the step-die cavity.The filling behavior and mechanical properties of parts were studied.Microstructural evolution showed that the best semi-solid slurry which had fine spherical particles with the average size of~27μm and a shape factor of~0.8 was achieved at the stirring current of 70 A,melt pouring temperature of 670℃,and stirring time of 30 s.Under these conditions,the step-die cavity was completely filled at die preheating temperature of 470℃.The hardness increases by decreasing step thickness as well as die preheating temperature.Moreover,the tensile properties are improved at lower die preheating temperatures.The fracture surface,which consists of a complex topography,indicates a typical ductile fracture.展开更多
Loess disintegration can lead to geotechnical engineering problems,e.g.,slope erosion,wetting-induced landslide,and hydroconsolidation.Microbially induced calcite precipitation(MICP)technique is a potential loess rein...Loess disintegration can lead to geotechnical engineering problems,e.g.,slope erosion,wetting-induced landslide,and hydroconsolidation.Microbially induced calcite precipitation(MICP)technique is a potential loess reinforcing method.This study investigated the physical-mechanical properties of MICP-treated loess and then explored the mechanism of loess modification by MICP.Here,loess first underwent MICP treatment,i.e.,mixing loess with Sporosarcina pasteurii and cementation solution(CS).Then,the effects of the CS concentration(0.2,0.6,0.8,and 1 M)on the physical and mechanical properties of the MICP-treated loess were tested.Finally,the static contact angle test,scanning electron microscopy(SEM),and X-ray diffractometry(XRD)were conducted to study the mechanism of MICP treatment on loess.Results showed the following property changes of loess after MICP treatment:the liquid limit decreased by 1.7%,the average particle size increased from 6 to 47μm,the specific gravity decreased from 2.65 to 2.43,the unconfined compressive strength increased from 37 to 71 k Pa,and the disintegration time increased from 10 to 25 min.Besides,the shear strength also increased,and the shear strength parameters(cohesion c and internal friction angle?)varied with the CS concentration.The static contact angle tests indicated that the water absorption ability of loess was reduced after MICP treatment.SEM and XRD results verified that the CaCO_(3)from MICP was attributed to the above results.The above findings explained the mechanism of MICP treatment of loess:the CaCO_(3)coats and cements the particles,and fills the pores of loess,improving the strength and water stability of loess.展开更多
基金Project supported by the National Natural Science Foundation of China(No.12372005)。
文摘The modeling and self-excited vibration mechanism in the magnetic levitation-collision interface coupling system are investigated.The effects of the control and interface parameters on the system's stability are analyzed.The frequency range of self-excited vibrations is investigated from the energy point of view.The phenomenon of self-excited vibrations is elaborated with the phase trajectory.The corresponding control strategies are briefly analyzed with respect to the vibration mechanism.The results show that when the levitation objects collide with the mechanical interface,the system's vibration frequency becomes larger with the decrease in the collision gap;when the vibration frequency exceeds the critical frequency,the electromagnetic system continues to provide energy to the system,and the collision interface continuously dissipates energy so that the system enters the self-excited vibration state.
基金Project supported by the National Key Research and Development Program of China(Grant No.2021YFB3500303)the National Natural Science Foundation of China(Grant Nos.52031014 and 51971219).
文摘The effect of the Y spacer layer on the phase composition,coercivity,and magnetization reversal processes of La-Nd-Fe-B films has been investigated.The addition of a 10 nm Y spacer layer increases the coercivity of the film to 1.36 T at 300 K and remains 0.938 T at 380 K.As the thickness of the Y spacer layer increases,Y participates in the formation of the main phase in the film,and further regulates the formation of La-B phases.The results of the first-order reversal curve(FORC)and micromagnetic fitting show that the coercivity of all the films is dominated by nucleation mechanism.The c-axis preferred orientation,good magnetic microstructure parameters and the largest dipole interaction enhance the coercivity.Therefore,the introduction of the Y spacer layer can be an effective way to improve the coercivity of La-Nd-Fe-B film over a wide temperature range of 150 K-380 K.
基金supported by the National Key Research and Development Program of China (2018YFD0401402–04)Zhongyuan Scholars Foundation (202101510005).
文摘The adverse effects of eutrophication have prompted the use of various remediation techniques for phosphate(PO_(4)^(3-))removal owing to it being the major causative agent.Herein,the influence of different solvents and ratios of 2-aminoterepthalicacid on the efficiency of magnetic biomass metal-organic framework composites based on the in situ growth of NH_(2)-MIL-101(Fe)onto magnetized peanut husks towards PO_(4)^(3-)removal was assessed via the adsorption technique.The magnetic biocomposite labelled as MPN@NH2-MIL-101(Fe)exhibited the best efficiency owing to its mesoporous structures and presence of abundant oxygen and nitrogen possessing functional groups.Adsorption results confirmed MPN@NH2-MIL-101(Fe)to have a high adsorption capacity of(14.0±0.3)mg·L^(-1)at a PO43-concentration of 20 mg·L^(-1)with an associated high stability within pH 2-10.The adsorption kinetics for the process was well described by both Elovich and pseudo-second-order kinetic models and was mediated by both internal diffusion and liquid film diffusion.The Temkin and Freundlich models fitted the equilibrium data well signifying occurrence of both physical and chemical adsorption on a heterogeneous surface.It is concluded that MPN@NH2-MIL-101(Fe)is a promising adsorbent for the effective removal of phosphate from a water body.
基金Project(50401012) supported by the National Natural Science Foundation of China
文摘To clarify the corrosion mechanism associated with the precipitate of T1(Al2CuLi)in Al-Li alloys,the simulated bulk precipitate of T1 was fabricated through melting and casting.Its electrochemical behavior and coupling behavior with α(Al)in 3.5% NaCl solution were investigated.Meanwhile,the simulated Al alloy containing T1 particle was prepared and its corrosion morphology was observed.The results show that there exists a dynamic conversion corrosion mechanism associated with the precipitate of T1.At the beginning,the precipitate of T1 is anodic to the alloy base and corrosion occurs on its surface.However,during its corrosion process,its potential moves to a positive direction with immersion time increasing,due to the preferential dissolution of Li and the enrichment of Cu.As a result,the corroded T1 becomes cathodic to the alloy base at a later stage,leading to the anodic dissolution and corrosion of the alloy base at its adjacent periphery.It is suggested that the localized corrosion associated with the precipitate of T1 in Al-Li alloys is caused by the alternate anodic dissolution of the T1 precipitate and the alloy base at its adjacent periphery.
文摘Precipitates play an important role in determining the mechanical and magnetic properties of silicon steel. This paper aims to investigate the growth kinetics of precipitates in commercial silicon steel by analyzing its magnetic properties during isothermal annealing at 200℃. The growth of precipitates was studied by optical microscopy, scanning electron microscopy, transmission electron microscopy, and magnetic measurements. In combination with the coercive field and initial susceptibility, this technique offers the advantage of being non-destructive and providing quantitative information about the number, mean radius of precipitates, and fraction of transformation. An ob- served decrease in the number of precipitated particles indicates that the transformation starts from particles of appreciable initial size.
文摘The characteristics and generation mechanism of(Ti,Nb,V)(C,N) precipitates larger than 2 μm in Nb-containing H13 bar steel were studied. The results show that two types of(Ti,Nb,V)(C,N) phases exist—a Ti-V-rich one and an Nb-rich one—in the form of single or complex precipitates. The sizes of the single Ti-V-rich(Ti,Nb,V)(C,N) precipitates are mostly within 5 to 10 μm, whereas the sizes of the single Nb-rich precipitates are mostly 2–5 μm. The complex precipitates are larger and contain an inner Ti-V-rich layer and an outer Nb-rich layer. The compositional distribution of(Ti,Nb,V)(C,N) is concentrated. The average composition of the single Ti-V-rich phase is(Ti_(0.511)V_(0.356)Nb_(0.133))(CxNy), whereas that for the single Nb-rich phase is(Ti_(0.061)V_(0.263)Nb_(0.676))(C_xN_y). The calculation results based on the Scheil–Gulliver model in the Thermo-Calc software combining with the thermal stability experiments show that the large phases precipitate during the solidification process. With the development of solidification, the Ti-V-rich phase precipitates first and becomes homogeneous during the subsequent temperature reduction and heat treatment processes. The Nb-rich phase appears later.
基金Project(50401012) supported by the National Natural Science Foundation of China
文摘To clarify the localized corrosion mechanism associated with precipitates containing Mg in Al alloys, the simulated bulk precipitates of S and β were synthesized through melting and casting. Their electrochemical behaviors and coupling behaviors with α(Al) in NaCl solution were measured. Meanwhile, simulated Al alloys containing S and β particles were prepared and their corrosion morphologies were observed. It’s found that there exist two kinds of corrosion mechanisms associated with precipitates containing Mg. The precipitate of β is anodic to the alloy base, resulting in its anodic dissolution and corrosion during the whole corrosion process. While, there exists a corrosion conversion mechanism associated with the S precipitate, which contains active element Mg and noble element Cu simultaneously. At an initial stage, S is anodic to the alloy matrix at its periphery and the corrosion occurs on its surface. However, during its corrosion process, Mg is preferentially dissolved and noble Cu is enriched in the remnants. This makes S become cathodic to α(Al) and leads to anodic dissolution and corrosion on the alloy base at its periphery at a later stage.
基金Project(2004CCA04000)supported by the National Basic Research Program of ChinaProject(50744014)supported by the National Natural Science Foundation of China+3 种基金Project(2008C21046)supported by Science and Technology Department of Zhejiang Province,ChinaProject(Y406389)supported by Zhejiang Provincial Natural Science Foundation of ChinaProject(2006B100054)supported by Ningbo Bureau of Science and Technology,ChinaProject supported by K.C.Wong Magna Found in Ningbo University,China
文摘During the process of directional solidification,laser remelting/solidification in the layer on sintered magnets, die-upsetting of cast magnets,or die-upsetting of nano-composites,the arrangements of the easy-magnetization-axes of the hard magnetic phases(Nd2Fe14B,SmCo5 or Sm2Co17 type)in their designed directions have been studied.In Fe-Pt nano-composite magnets,attempts have been taken to promote phase transformation from disordered,soft magnetic A1 to ordered,hard magnetic L10 FePt phase at reduced temperatures.The dependence of the magnetization and reversal magnetization processes on the microstructures,involving the morphology and three critical sizes of particles of the FePt nano-composite magnets,are summarized. With the decrease of the nominal thickness of the anisotropic FePt film epitaxially grown on the single crystal MgO(001)substrate, the reversal magnetization process firstly changes from full domain wall displacement to partial magnetic wall pinning related to the morphology change,where the coercive force increases abruptly.The reversal magnetization process secondly changes from magnetic wall pinning to incoherent magnetization rotation associated with the particles being below the first critical size at which multi-domain particles turn into single domain ones,where the coercive force is still increased.And the reversal magnetization mode thirdly changes from incoherent to coherent rotation referred to the second critical size,where the increase of the coercive force keeps on.However,when the particle size decreases to approach the third critical size where the particles turn into the supperparamagnetic state,the coercive force begins to decrease due to the interplay of the size effect and the incomplete ordering induced by the size effect.Meanwhile,due to the size effect,Curie temperature of the ultra-small FePt particles reduces.
基金financially supported by the National Natural Science Foundation of China(No.51771044)the Natural Science Foundation of Hebei Province(No.E2019501061)+3 种基金the Performance subsidy fund for Key Laboratory of Dielectric and Electrolyte Functional Material Hebei Province(No.22567627H)the Fundamental Research Funds for the Central Universities(No.N2223025)the State Key Lab of Advanced Metals and Materials(No.2022-Z02)Programme of Introducing Talents of Discipline Innovation to Universities 2.0(the 111 Project of China 2.0,No.BP0719037)。
文摘The martensitic transformation,mechanical,and magnetic properties of the Ni_(2)Mn_(1.5-x)Cu_(x)Ti_(0.5) (x=0.125,0.25,0.375,0.5) and Ni_(2-y)Co_(y)Mn_(1.5-x)Cu_(x)Ti_(0.5)[(x=0.125,y=0.125,0.25,0.375,0.5) and (x=0.125,0.25,0.375,y=0.625)]alloys were systematically studied by the first-principles calculations.For the formation energy,the martensite is smaller than the austenite,the Ni–(Co)–Mn–Cu–Ti alloys studied in this work can undergo martensitic transformation.The austenite and non-modulated (NM) martensite always present antiferromagnetic state in the Ni_(2)Mn_(1.5-x)Cu_(x)Ti_(0.5) and Ni_(2-y)Co_(y)Mn_(1.5-x)Cu_(x)Ti_(0.5) (y<0.625) alloys.When y=0.625 in the Ni_(2-y)Co_(y)Mn_(1.5-x)Cu_(x)Ti_(0.5) series,the austenite presents ferromagnetic state while the NM martensite shows antiferromagnetic state.Cu doping can decrease the thermal hysteresis and anisotropy of the Ni–(Co)–Mn–Ti alloy.Increasing Mn and decreasing Ti content can improve the shear resistance and normal stress resistance,but reduce the toughness in the Ni–Mn–Cu–Ti alloy.And the ductility of the Co–Cu co-doping alloy is inferior to that of the Ni–Mn–Cu–Ti and Ni–Co–Mn–Ti alloys.The electronic density of states was studied to reveal the essence of the mechanical and magnetic properties.
基金financial support by the National Natural Science Foundation of China (No. 51271035)the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20110006110007)
文摘The microstructures and properties of hot-rolled low-carbon ferritic steel have been investigated by optical microscopy, field-emission scanning electron microscopy, transmission electron microscopy, and tensile tests after isothermal transformation from 600°C to 700°C for 60 min. It is found that the strength of the steel decreases with the increment of isothermal temperature, whereas the hole expansion ratio and the fraction of high-angle grain boundaries increase. A large amount of nanometer-sized carbides were homogeneously distributed throughout the material, and fine(Ti, Mo)C precipitates have a significant precipitation strengthening effect on the ferrite phase because of their high density. The nanometer-sized carbides have a lattice parameter of 0.411-0.431 nm. After isothermal transformation at 650°C for 60 min, the ferrite phase can be strengthened above 300 MPa by precipitation strengthening according to the Ashby-Orowan mechanism.
文摘Magnetizing roasting of oolitic hematite ore from western Hubei Province was investigated.The mechanism for reduction roasting of oolitic hematite ore was discussed and analyzed.It is found that flash magnetizing roasting-magnetic separation process is a promising approach for the processing of oolitic hematite ore from western Hubei Province.
基金supported by the National Natural Science Foundation of China (No50771011)
文摘To study the precipitation mechanism of α-Cr phase in Inconel 718 alloy, the samples after long-time aging at 650 and 677℃ were examined by microstructural observations and chemical phase analysis methods. Combining the thermodynamics and kinetics calculation results, α-Cr always precipitates in the vicinity of δ phase, because δ phase rejects Cr into the γ-matrix when growing. The selected area diffraction patterns confirm that the crystallographic relationships of α-Cr with 6 phase are (010)d/(1- 10)a.Cr and [100]d/If 11 ]α-Cr- A graphic model is also presented to show the crystallographic relation between α-Cr and δ phases.
基金supported by the National Natural Science Foundation of China under grant No. 10477006the Key Project of Chinese Ministry of Education undergrant No. 106055
文摘The shape change of the γ' precipitates of cast Ni-based superalloy K52 after aging treatment under a high magnetic field was investigated. The results show that duplex γ' precipitates are present in the γ matrix after aging treatment with or without the magnetic field. One is the coarse particles with average size of 500 nm; the other is fine spherical γ' precipitates with average of 100 nm in diameter. The application of a 10T magnetic field only results in the shape of the coarse γ' particles changing from spherical to cuboidal when the alloys subjected to the same heat treatments. This shape change was mainly discussed based on the strain energy increase caused by the difference in magnetostriction between the γ matrix and γ' precipitates. The fine γ' particles still keep spherical. Further TEM observations shows that a number of γ particles in nano-scale precipitate in the coarse γ' particles in the specimens treated without the magnetic field. In addition, it was found that the magnetic field caused the decrease of the hardness in the alloy, and the hardness was associated with the field direction.
基金The authors are grateful to the financial support from the National Basic Research Program of China(Grant no.2013 CB632200)the National Natural Science Foundation of China(Grant no.51574291)the Fund amental Research Funds for the Central Universities of Central South University(Grant no.502220002).
文摘Optical microscope(OM),scanning electron microscope(SEM),transmission electron microscope(TEM)and tensile machine were used to characterize the microstructures and mechanical properties of as-forged and aged Mg-9.5Gd-3.8Y-0.6Zr alloys.The results show that a novel kind of dislocation arrays,comprising parallel arranged dislocations,were obtained in the forged alloy.The arrays tend to extend parallel and are heterogeneously distributed with adjacent distances varying from 0.3μm to 1.4μm.After aging the alloy at 265°C,a large number of preferential-oriented phases were precipitated on the dislocation arrays,forming a structure of"precipitation chains"(PCs),which results in simultaneous increments of strength and ductility.
文摘The coercivity mechanism of Nd Fe B magnets prepared by combination of strip casting with hydrogen decrepitation techniques was investigated. The microstructure of (Nd 0.935 Dy 0.065 ) 14.5 Fe 79.4 B 6.1 magnet was observed. The average grain size is about 6~12 μm. The magnetizing field dependence of the hardmagnetic properties for the (Nd 0.935 Dy 0.065 ) 14.5 Fe 79.4 B 6.1 and the temperature dependence of the coercivity for the Nd 14.5 Fe 79.4 B 6.1 were investigated. Results show that the coercivity for magnets prepared by the combination of strip casting with hydrogen decrepitation techniques is controlled by the nucleation mechanism.
文摘The microstructures of B2-ordered NiA1 containing α-Fe precipitates have been investigated in terms of transmission electron microscopy. Fine precipitation of α-Fe (bcc structure) occurs in NiA1 by aging around 973K. The aging behavior was investigated by microhandness measurements and the temperature dependence of the yield strength of precipitate- comaining B2- ordered NiA1 was investigated by compression tests over the temperature range of 673-1273K. The fine precipitation of α-Fe was found to enhance greatly the low and intermediate temperature yield strength. When the deformation temperature is over 1073K, the strength of precipitate- containing NiA1 was comparable to ternary solid solution hardening NiA1-Fe. Dislocations bypass the particles during deformation and typical Orowan loops were observed surrounding the or-Fe particles after deformation.
文摘The rectangle-like pulsed magnetic field acted on the rubbing pair was presented through analyzing the exciting property in the reciprocating travel. The test of wear in NG-x tester shows that the wear between the electromagnetic core and down magnetic board distributes in the high velocity slip region of reciprocating travel, and the adhesive wear in the low velocity slip region nearby up and down dead points is depressed owing to the presence of high flux magnetic field. The lubrication by magnetic fluid with high permeability effectively reduces the friction and wear of high flux rubbing pair, and improves the conducting property of magnetic circuit constructed by the rubbing pair, which is beneficial to increase the operation performance of magnetic driving mechanism.
基金funded by the National Natural Science Foundation of China (Project 52271092)the Chongqing Science and Technology Commission (cstc2021jcyj-msxm X0814,CSTB2022NSCQ-MSX0891)+1 种基金the Chongqing Municipal Education Commission (KJQN202101523)the support from The Ohio State University。
文摘The effects of small additions of calcium (0.1%and 0.5%~1) on the dynamic recrystallization behavior and mechanical properties of asextruded Mg-1Mn-0.5Al alloys were investigated.Calcium microalloying led to the formation of Al_(2)Ca in as-cast Mg-1Mn-0.5Al-0.1Ca alloy and both Mg_(2)Ca and Al_(2)Ca phases in Mg-1Mn-0.5Al-0.5Ca alloy.The formed Al_(2)Ca particles were fractured during extrusion process and distributed at grain boundary along extrusion direction (ED).The Mg_(2)Ca phase was dynamically precipitated during extrusion process,hindering dislocation movement and reducing dislocation accumulation in low angle grain boundaries (LAGBs) and hindering the transformation of high density of LAGBs into high angle grain boundaries (HAGBs).Therefore,a bimodal structure composed of fine dynamically recrystallized (DRXed) grains and coarse un DRXed regions was formed in Ca-microalloyed Mg-1Mn-0.5Al alloys.The bimodal structure resulted in effective hetero-deformation-induced (HDI) strengthening.Additionally,the fine grains in DRXed regions and the coarse grains in un DRXed regions and the dynamically precipitated Mg_(2)Ca phase significantly enhanced the tensile yield strength from 224 MPa in Mg-1Mn-0.5Al to335 MPa and 352 MPa in Mg-1Mn-0.5Al-0.1Ca and Mg-1Mn-0.5Al-0.5Ca,respectively.Finally,a yield point phenomenon was observed in as-extruded Mg-1Mn-0.5Al-x Ca alloys,more profound with 0.5%Ca addition,which was due to the formation of (■) extension twins in un DRXed regions.
基金Central Applied Research Laboratory(CARL)Center of Materials ResearchDepartment of Materials Science and Metallurgy,Shahid Bahonar University of Kerman(SBUK)for support of this work。
文摘Nowadays,having an effective technique in preparing semi-solid slurries for rheocasting process seems to be an essential requirement.In this study,semi-solid slurry of A356 aluminum alloy was prepared by three-phase annular electromagnetic stirring(A-EMS)technique under different conditions.The effects of stirring current,pouring temperature and stirring time on microstructural evolution,mean particle size,shape factor and solid fraction were investigated.The rheocasting process was carried out by using a drop weight setup and to inject the prepared semi-solid slurry in optimal conditions into the step-die cavity.The filling behavior and mechanical properties of parts were studied.Microstructural evolution showed that the best semi-solid slurry which had fine spherical particles with the average size of~27μm and a shape factor of~0.8 was achieved at the stirring current of 70 A,melt pouring temperature of 670℃,and stirring time of 30 s.Under these conditions,the step-die cavity was completely filled at die preheating temperature of 470℃.The hardness increases by decreasing step thickness as well as die preheating temperature.Moreover,the tensile properties are improved at lower die preheating temperatures.The fracture surface,which consists of a complex topography,indicates a typical ductile fracture.
基金funded by the Beijing Natural Science Foundation(No.8214060)the National Natural Science Foundation of China(No.42107164)the 2021 Graduate Innovation Fund Project of China University of Geosciences,Beijing(No.ZD2021YC059)。
文摘Loess disintegration can lead to geotechnical engineering problems,e.g.,slope erosion,wetting-induced landslide,and hydroconsolidation.Microbially induced calcite precipitation(MICP)technique is a potential loess reinforcing method.This study investigated the physical-mechanical properties of MICP-treated loess and then explored the mechanism of loess modification by MICP.Here,loess first underwent MICP treatment,i.e.,mixing loess with Sporosarcina pasteurii and cementation solution(CS).Then,the effects of the CS concentration(0.2,0.6,0.8,and 1 M)on the physical and mechanical properties of the MICP-treated loess were tested.Finally,the static contact angle test,scanning electron microscopy(SEM),and X-ray diffractometry(XRD)were conducted to study the mechanism of MICP treatment on loess.Results showed the following property changes of loess after MICP treatment:the liquid limit decreased by 1.7%,the average particle size increased from 6 to 47μm,the specific gravity decreased from 2.65 to 2.43,the unconfined compressive strength increased from 37 to 71 k Pa,and the disintegration time increased from 10 to 25 min.Besides,the shear strength also increased,and the shear strength parameters(cohesion c and internal friction angle?)varied with the CS concentration.The static contact angle tests indicated that the water absorption ability of loess was reduced after MICP treatment.SEM and XRD results verified that the CaCO_(3)from MICP was attributed to the above results.The above findings explained the mechanism of MICP treatment of loess:the CaCO_(3)coats and cements the particles,and fills the pores of loess,improving the strength and water stability of loess.