The severe degradation of electrochemical performance for lithium-ion batteries(LIBs)at low temperatures poses a significant challenge to their practical applications.Consequently,extensive efforts have been contribut...The severe degradation of electrochemical performance for lithium-ion batteries(LIBs)at low temperatures poses a significant challenge to their practical applications.Consequently,extensive efforts have been contributed to explore novel anode materials with high electronic conductivity and rapid Li^(+)diffusion kinetics for achieving favorable low-temperature performance of LIBs.Herein,we try to review the recent reports on the synthesis and characterizations of low-temperature anode materials.First,we summarize the underlying mechanisms responsible for the performance degradation of anode materials at subzero temperatures.Second,detailed discussions concerning the key pathways(boosting electronic conductivity,enhancing Li^(+)diffusion kinetics,and inhibiting lithium dendrite)for improving the low-temperature performance of anode materials are presented.Third,several commonly used low-temperature anode materials are briefly introduced.Fourth,recent progress in the engineering of these low-temperature anode materials is summarized in terms of structural design,morphology control,surface&interface modifications,and multiphase materials.Finally,the challenges that remain to be solved in the field of low-temperature anode materials are discussed.This review was organized to offer valuable insights and guidance for next-generation LIBs with excellent low-temperature electrochemical performance.展开更多
FVS1212/FVS0812 material was prepared by adding FVS1212 powder into FVS0812 powder. The structure and mechanical properties of materials were studied by means of X-Ray, tensile measurement, OM and SEM. The results sho...FVS1212/FVS0812 material was prepared by adding FVS1212 powder into FVS0812 powder. The structure and mechanical properties of materials were studied by means of X-Ray, tensile measurement, OM and SEM. The results show that adding proper content FVS1212 powders can improve the tensile strength of FVS0812 aluminum at room temperature and elevated temperature, and that the elongation of FVS1212/FVS0812 material is better than that of FVS1212 aluminum.展开更多
It is economically advantageous to cast wrought aluminum alloys directly into near-net-shape components.The objective of the present work is to take advantage of the rheoforming with 7075 alloy to improve the competit...It is economically advantageous to cast wrought aluminum alloys directly into near-net-shape components.The objective of the present work is to take advantage of the rheoforming with 7075 alloy to improve the competitiveness of this emerging technology in the manufacture of wrought aluminum alloy.High quality semi-solid slurry was produced,in which primary α(Al) presents in diameter of 62 μm and shape factor of 0.78 and features no eutectics entrapped.Higher forming pressure results in small grain size,improved shape factor and higher density.Especially,rheoforming can effectively reduce the occurrence of hot tearing.The average yield strength and elongation of the rheoformed samples in the T6 condition are 483 MPa and 8%,respectively.展开更多
The semi-solid slurry of wrought aluminum alloy 2024 was prepared by a well developed rheocasting process, low superheat pouring with shearing field(LSPSF). The appreciate combination of pouring temperature and rotati...The semi-solid slurry of wrought aluminum alloy 2024 was prepared by a well developed rheocasting process, low superheat pouring with shearing field(LSPSF). The appreciate combination of pouring temperature and rotation speed of barrel, can give rise to a transition of the growth morphology of primary α(Al) from coarse-dendritic to coarse-particle-like and further to fine-globular. The combined effects of both localized rapid cooling and vigorous mixing during the initial stage of solidification can enhance wall nucleation and nuclei survival, which leads to the formation of fine-globular primary α(Al). By using semi-solid slurry prepared by LSPSF, direct squeeze cast cup-shaped component with improved mechanical properties such as yield strength of 198 MPa, ultimate tensile strength of 306 MPa and elongation of 10.4%, can be obtained.展开更多
Eutectic alloy Sn-9Zn is an attractive candidate for lead-free solders. However, its wettability to copper is poor thus,its development was limited. Effects of less than 1% (mass fraction) additions of mischmetal cons...Eutectic alloy Sn-9Zn is an attractive candidate for lead-free solders. However, its wettability to copper is poor thus,its development was limited. Effects of less than 1% (mass fraction) additions of mischmetal consisting mainly of La and Ce, heavy rare earth Y, pure P, Al, Mg and Ti elements on the wetting/adhesion behavior of Sn-9Zn alloy to copper, as well as the associated oxidation and solidification morphology of this alloy were examined. The results show that harmful effect on the wettability can be found when adding Al and Ti elements, while the wettability can be improved slightly by adding Mg and Y elements. The adhesion of the alloy to copper can be decreased by Mg element. The RE and P are found to significantly improve the wettability. In addition, oxidation of the alloy can be increased by adding RE, while little effect on the oxidation behavior can be found by adding P element. As-solidified Sn-9Zn alloy has a rough surface with protrusions and cavities shaped by coarse needle-like crystallites, while the Sn-37Pb sample has a rather smooth surface, which indicates the different solidification behavior of Sn-9Zn alloy and the Sn-37Pb one. The additions of the different elements investigated in this study do not alter Sn-9Zn's as-solidified morphology.展开更多
The microstructure characteristics and mechanical properties of 2024 wrought aluminum alloy produced by a new rheoforming technique under as-cast and optimized heat treatment conditions were investigated. The present ...The microstructure characteristics and mechanical properties of 2024 wrought aluminum alloy produced by a new rheoforming technique under as-cast and optimized heat treatment conditions were investigated. The present rheoforming combined the independently developed rheocasting process, named as LSPSF (low superheat pouring with a shear field) process, and the existing squeeze casting process. The experimental results show that LSPSF can be used to prepare sound semi-solid slurry within 25 s to fully meet the production rate of squeeze casting. The primary α(Al) presents in mean equivalent diameter of 69 μm and shape factor of 0.76, and features zero-entrapped eutectics. Compared with conventional squeeze casting, the present LSPSF rheoforming can improve the microstructures and mechanical properties. An optimized heat treatment results in substantial reduction of microsegregation and significant improvement of mechanical properties, such as yield strength of 321 MPa, ultimate tensile strength of 428 MPa and elongation of 12%.展开更多
To make the ferroelectric BaTiO3 possess ferromagnetism simultaneously,magnetic Fe was doped into BaTiO3 ceramics at doping levels up to 10%(molar fraction).Both tetragonal and hexagonal phases coexisted in the Fe-dop...To make the ferroelectric BaTiO3 possess ferromagnetism simultaneously,magnetic Fe was doped into BaTiO3 ceramics at doping levels up to 10%(molar fraction).Both tetragonal and hexagonal phases coexisted in the Fe-doped BaTiO3 ceramics except at 1% doping level.X-ray diffraction analysis indicated that higher doping level of Fe,higher sintering temperature and longer sintering time promoted the formation of hexagonal phases in Fe-doped BaTiO3 ceramics.Ferroelectricity was observed in all samples at room temperature,but it was greatly depressed by Fe doping.Except at doping level of 1%,room-temperature ferromagnetism was observed in the BaTiO3 ceramics.The dependence of the saturation magnetization and coercivities of the Fe-doped BaTiO3 ceramics on doping level was systematically studied.Both the saturation magnetization and magnetic coercivities were found to be dependent on the doping level as well as the fraction of the hexagonal phase in the ceramics.展开更多
A novel cationic photosensitive resin(3 DSLR-01) for stereolithography 3 D printing was prepared with 3,4-epoxycyclohexylmethyl-3’,4’-epoxycyclohexane carboxylate(2021 P),1,4-cyclohexanedimethanol glycidyl ether(JX-...A novel cationic photosensitive resin(3 DSLR-01) for stereolithography 3 D printing was prepared with 3,4-epoxycyclohexylmethyl-3’,4’-epoxycyclohexane carboxylate(2021 P),1,4-cyclohexanedimethanol glycidyl ether(JX-026), diglycidyl 4,5-epoxycyclohexane-1,2-dicarboxylate(S-186), polycaprolactone polyol(Polyol-0305), novolac epoxy resin(F-51), bis(3-ethyl-3-oxetanylmethyl) ether(S-221) and a mixture of triarylsulfonium hexafluoroantimonate salts solution(UVI-6976). The properties of the photosensitive resin and its UV-cured films were investigated by some instruments and equipment.The experimental results show that the critical exposure(Ec) of the photosensitive resin is 16.3 mJ/cm^2, the penetration depth(Dp) is 0.14 mm, and the optical property of the photosensitive resin is excellent. Rectangle plates were printed by using a stereolithography apparatus(HRPL-150 A) with the photosensitive resin as the manufacturing material, and the shrinkage rates of the plates were less than 0.60%, which showed that the accuracy of the manufactured plates was very high.展开更多
Particle reinforced Sn-Zn based composite solders were obtained by adding Cu powders to Sn-9Zn melts. The microstructure analysis reveals that in situ CusZn8 particles are formed and distributed uniformly in the compo...Particle reinforced Sn-Zn based composite solders were obtained by adding Cu powders to Sn-9Zn melts. The microstructure analysis reveals that in situ CusZn8 particles are formed and distributed uniformly in the composite solders. The strength and plasticity of the composite solders were improved, and creep resistance was considerably enhanced. The wettability of these composite solders is also better than that of Sn-9Zn.展开更多
There remains growing interest in magnesium(Mg)and its alloys,as they are the lightest structural metallic materials and potential metallic biomaterials.In spite of the greatest historical Mg usage at present,the wide...There remains growing interest in magnesium(Mg)and its alloys,as they are the lightest structural metallic materials and potential metallic biomaterials.In spite of the greatest historical Mg usage at present,the wider use of Mg alloys remains restricted by the poor corrosion resistance.A nano amorphous film,as the composition of Al2O3,had now been deposited on the AZ31 Mg alloy substrate by atomic layer deposition(ALD).Grazing incidence X-ray diffraction(GIXRD),X-ray reflectivity(XRR),X-ray photoelectron spectroscopy(XPS),atomic force microscope(AFM)and scanning electron microscopy(SEM)had been employed to identify the chemical compositions,microstructure and Al2O3/Mg interface of specimens firstly.Then corrosion behavior had been evaluated by neutral salt spray test and electrochemical measurement.The results showed that nano amorphous film made a homogeneous cover on Mg alloy.The film could improve the corrosion resistance of Mg alloy greatly,not only with a positive shift in Ecorr and a decrease in icorr,but also with a more uniform corroded mode.Furthermore,the roughness was found to be an important factor for corrosion resistant,in the way that rougher surface was corroded worse,and greater improvement would be in corrosion resistant after nano amorphous film deposition.展开更多
Ce^(3+)/Tb^(3+) co-doped and Ce^(3+)/Tb^(3+)/Eu^(3+) tri-doped β-NaYF_(4) photoluminescent microcrystals using oleic acid as surfactant were synthesized using the solvothermal method.Their microstructural characteris...Ce^(3+)/Tb^(3+) co-doped and Ce^(3+)/Tb^(3+)/Eu^(3+) tri-doped β-NaYF_(4) photoluminescent microcrystals using oleic acid as surfactant were synthesized using the solvothermal method.Their microstructural characteristics and photoluminescence properties were investigated in detail.They have the shape of hexagonal prism bipyramids with uniform particle size,which decreases with the concentrations of Tb^(3+) and Eu^(3+).The energy transfer processes of both the Ce^(3+)→Tb^(3+) and the Ce^(3+)→Tb^(3+)→Eu^(3+) were systematically studied.Compared with Eu^(3+) or Tb^(3+) single-doped β-NaYF_(4) microcrystals,the sensitization by Ce^(3+) for the photoluminescence of Tb^(3+) and Eu^(3+) leads to a broad excitation spectral bandwidth in the ultraviolet (UV) range.Meanwhile,the corresponding optical absorption efficiency is greatly enhanced.High energy transfer efficiencies have been observed from Ce^(3+) to Tb^(3+) and from Tb^(3+) to Eu^(3+).展开更多
Tetrapod-shaped ZnO whiskers and microrods were synthesized in one crucible by thermal evaporation of Zn/C mixtures at 930 ℃ in air without any catalyst.The digital camera,optical microscopy,scanning electron microsc...Tetrapod-shaped ZnO whiskers and microrods were synthesized in one crucible by thermal evaporation of Zn/C mixtures at 930 ℃ in air without any catalyst.The digital camera,optical microscopy,scanning electron microscopy,energy dispersive X-ray spectroscopy,and X-ray diffraction techniques were used to study the morphologies and crystal structures of these tetrapod-shaped ZnO microcrystals.The results show that these two types of ZnO tetrapods are grown at different heights within the same crucible.The legs of these tetrapod-shaped ZnO crystals are hexagonally faceted.Some tetrapod-shaped ZnO whiskers show hierarchical structures.A short button-like hexagonal ZnO microcrystal is observed at the triple junctions of some tetrapod-shaped ZnO whiskers.The tetrapod-shaped ZnO microrods are capped by two sets of hexagonal pyramids with two different groups of crystal planes for the surfaces.These two types of tetrapod-shaped ZnO microcrystals have different side faces and aspect ratio,which are believed to be the result of their different growth behaviors.The octa-twin model was used to discuss the different growth behaviors of these two types of ZnO tetrapods.The crystal planes of the legs and the pyramids were determined.展开更多
The potential of using a hypoeutectic, instead of eutectic, Sn-Zn alloy as a lead-free solder has been discussed. The nonequilibrium melting behaviors of a series of Sn-Zn alloys were examined by differential thermal ...The potential of using a hypoeutectic, instead of eutectic, Sn-Zn alloy as a lead-free solder has been discussed. The nonequilibrium melting behaviors of a series of Sn-Zn alloys were examined by differential thermal analysis. It was found that at a heating rate of 5℃/min, Sn-6.SZn exhibited no melting range. Dipping and spreading tests were carried out to characterize the wettability of Sn-Zn alloys on Cu. Both tests exhibited that Sn-6.5Zn has significantly better wettability on Cu than Sn-9Zn. The reaction layers formed during the spreading tests were examined. When the Zn concentration fell between 2.5wt%-9wt%, two reaction layers were formed at the interface, a thick and flat Cu5Zn8 adjacent to Cu and a thin and irregular Cu-Zn-Sn layer adjacent to the alloy. Only a Cu0Sn5 layer was formed when the Zn concentration decreased to 0.5wt%. The total thickness of the reaction layer(s) between the alloy and Cu was found to increase linearly with the Zn concentration.展开更多
BaTiO3/epoxy composites consisting of two three-dimensionally interpenetrating networks of BaTiO3 and epoxy phases were prepared using a new approach. The BaTiO3/epoxy composites exhibit a colossal dielectric constant...BaTiO3/epoxy composites consisting of two three-dimensionally interpenetrating networks of BaTiO3 and epoxy phases were prepared using a new approach. The BaTiO3/epoxy composites exhibit a colossal dielectric constant, low dielectric loss and high flexural strength. In the BaTiO3 networks, chemically bonded grain boundaries between neighboring BaTiO3 grains were established, and they are responsible for the colossal dielectric constant and high flexural strength of the BaTiO3/epoxy composites. Furthermore, unlike the conventional ceramic/polymer composites, this approach also makes high loadings of BaTiO3 contents possible for the BaTiO3/epoxy composites without compromising their high flexural strength.展开更多
Several samples of manganese oxides La(1-x)2/3Ca1/3MnO3 (V-LCMO) and (La0.7-xY0.3)2/3Ca1/3MnO3 (x<0.15) (V-LYCMO) with vacancies at La-site (La-vacancy) were prepared by solid-state reaction method. The X-ray diffr...Several samples of manganese oxides La(1-x)2/3Ca1/3MnO3 (V-LCMO) and (La0.7-xY0.3)2/3Ca1/3MnO3 (x<0.15) (V-LYCMO) with vacancies at La-site (La-vacancy) were prepared by solid-state reaction method. The X-ray diffraction(XRD) patterns refined by Rietveld confirm that these compounds exhibit single phase structure with orthorhombic symmetry (Pnma). The lattice parameters, Mn—O bond length and Mn—O—Mn bond angle vary with La-vacancy concentration, as an indication of the occurrence of the local Jahn-Teller effect. The measurement result of V-LCMO compounds shows that the maximum magnetoresistance(MR) is about 220% at TIM=268 K and La-vacancy content x=0.04. For V-LYCMO compounds, there exists metal-insulator transition at about 50 K, and a very large MR (over 106%) is observed at the temperature ranging from 40 K to 50 K.展开更多
Physical-chemical characteristics of the band sawing dusts regarding to recovery of pure silicon from them were investigated.The experimental results show 50vol%-60vol% amorphous phases exist in the dusts,which is mos...Physical-chemical characteristics of the band sawing dusts regarding to recovery of pure silicon from them were investigated.The experimental results show 50vol%-60vol% amorphous phases exist in the dusts,which is mostly amorphous silica.The as-received saw dusts are found to form hard agglomerates of larger than 50 microns in diameter.The iron-based inclusions collected by magnets are found to match well with the band saw material in XRD patterns.Weight loss in heating was observed by thermal gravity tests,up to 900 ℃,presumably due to reaction of the amorphous silica with carbon contaminant in the dusts.The saw dusts were variously treated to examine their physical-chemical responses,and the results were also presented.展开更多
A compound,3-ethyl-3-hydroxymethyloxetane(EHO),was synthesized with diethyl carbonate and trihydroxypropane as raw materials,3-ethyl-3-allylmethoxy oxetane(EAMO)was synthesized with EHO and allyl bromide,and 1,1,3,3,5...A compound,3-ethyl-3-hydroxymethyloxetane(EHO),was synthesized with diethyl carbonate and trihydroxypropane as raw materials,3-ethyl-3-allylmethoxy oxetane(EAMO)was synthesized with EHO and allyl bromide,and 1,1,3,3,5,5-hexamethyl-1,5-bis[(3-ethyl-3-methoxyoxetane)propyl]trisiloxane(HMBEMOPTS)was synthesized with EAMO and 1,1,3,3,5,5-hexamethyltrisiloxane(HMTS).HMBEMOPTS is a novel UV-curable oligomer.The test of photo-DSC shows the photosensitivity of HMBEMOPTS is better than the ordinary oxetane,3-ethyl-3-[(3-ethyloxetan-3-yl)methoxymethyl]oxetane.HMBEMOPTS was mixed with bisphenol A type epoxy resin E-51 to prepare a cationic UV-curable system,and triarylsulfonium hexafluoroantimonate(UV-6976)was used as a cationic photoinitiator.The mechanical tests of coating films prove that when the mass fraction of HMBEMOPTS is 50%,the mechanical properties of the curing system are the best.The impact strength of the UV-curable films is measured to be 40 kg·cm and the flexibility is 2 mm;the tensile strength and flexural strength of the prepared specimens are 20.74 MPa and 13.43 MPa,respectively.The experimental results show that HMBEMOPTS can effectively improve photosensitivity and flexibility of the photosensitive resin.展开更多
B_2O_3-SiO_2-ZnO-BaO-Al_2O_3 glass with different Al_2O_3 contents(1mol%, 3mol%, 5mol%, and 7mol%) was prepared, and it was intended to be used as lead-free and low-melting glass sealants for solid oxide fuel cells....B_2O_3-SiO_2-ZnO-BaO-Al_2O_3 glass with different Al_2O_3 contents(1mol%, 3mol%, 5mol%, and 7mol%) was prepared, and it was intended to be used as lead-free and low-melting glass sealants for solid oxide fuel cells. The effects of Al_2O_3 content on the structures, thermal properties, and sintering behaviors of the B_2O_3-SiO_2-ZnO-BaO-Al_2O_3 glass were investigated in detail. The Al_2O_3 content largely influenced the structures and thermal properties of the glass. When the Al_2O_3 content 5mol%, the transition temperature of the glass decreased with the Al_2O_3 content, while the crystallization temperature increased with the Al_2O_3 content. However, higher Al_2O_3 content degraded the stability of the glass. The B_2O_3-SiO_2-ZnO-BaO-Al_2O_3 glass with 5 mol% Al_2O_3 content exhibits the optimal sintering densification characteristics and can be used as glass sealants for solid oxide fuel cells.展开更多
基金supported by the National Key Research and Development Program of China(No.2019YFA0705601)the National Natural Science Foundation of China(No.U23A20122,52101267)the Key Science and Technology Special Project of Henan Province(No.201111311400).
文摘The severe degradation of electrochemical performance for lithium-ion batteries(LIBs)at low temperatures poses a significant challenge to their practical applications.Consequently,extensive efforts have been contributed to explore novel anode materials with high electronic conductivity and rapid Li^(+)diffusion kinetics for achieving favorable low-temperature performance of LIBs.Herein,we try to review the recent reports on the synthesis and characterizations of low-temperature anode materials.First,we summarize the underlying mechanisms responsible for the performance degradation of anode materials at subzero temperatures.Second,detailed discussions concerning the key pathways(boosting electronic conductivity,enhancing Li^(+)diffusion kinetics,and inhibiting lithium dendrite)for improving the low-temperature performance of anode materials are presented.Third,several commonly used low-temperature anode materials are briefly introduced.Fourth,recent progress in the engineering of these low-temperature anode materials is summarized in terms of structural design,morphology control,surface&interface modifications,and multiphase materials.Finally,the challenges that remain to be solved in the field of low-temperature anode materials are discussed.This review was organized to offer valuable insights and guidance for next-generation LIBs with excellent low-temperature electrochemical performance.
文摘FVS1212/FVS0812 material was prepared by adding FVS1212 powder into FVS0812 powder. The structure and mechanical properties of materials were studied by means of X-Ray, tensile measurement, OM and SEM. The results show that adding proper content FVS1212 powders can improve the tensile strength of FVS0812 aluminum at room temperature and elevated temperature, and that the elongation of FVS1212/FVS0812 material is better than that of FVS1212 aluminum.
基金Projects(50804023,50474007) supported by the National Natural Science Foundation of ChinaProject(GJJ08006) supported by the Jiangxi Provincial Education Department,China
文摘It is economically advantageous to cast wrought aluminum alloys directly into near-net-shape components.The objective of the present work is to take advantage of the rheoforming with 7075 alloy to improve the competitiveness of this emerging technology in the manufacture of wrought aluminum alloy.High quality semi-solid slurry was produced,in which primary α(Al) presents in diameter of 62 μm and shape factor of 0.78 and features no eutectics entrapped.Higher forming pressure results in small grain size,improved shape factor and higher density.Especially,rheoforming can effectively reduce the occurrence of hot tearing.The average yield strength and elongation of the rheoformed samples in the T6 condition are 483 MPa and 8%,respectively.
基金Project(50474007) supported by the National Natural Science Foundation of ChinaProject(0450050) supported by the Natural Science Foundation of Jiangxi Province, China Projects(GanJiaoZi[2005]2, 24) supported by the Science and Technology Program of Education Department of Jiangxi Province, China
文摘The semi-solid slurry of wrought aluminum alloy 2024 was prepared by a well developed rheocasting process, low superheat pouring with shearing field(LSPSF). The appreciate combination of pouring temperature and rotation speed of barrel, can give rise to a transition of the growth morphology of primary α(Al) from coarse-dendritic to coarse-particle-like and further to fine-globular. The combined effects of both localized rapid cooling and vigorous mixing during the initial stage of solidification can enhance wall nucleation and nuclei survival, which leads to the formation of fine-globular primary α(Al). By using semi-solid slurry prepared by LSPSF, direct squeeze cast cup-shaped component with improved mechanical properties such as yield strength of 198 MPa, ultimate tensile strength of 306 MPa and elongation of 10.4%, can be obtained.
文摘Eutectic alloy Sn-9Zn is an attractive candidate for lead-free solders. However, its wettability to copper is poor thus,its development was limited. Effects of less than 1% (mass fraction) additions of mischmetal consisting mainly of La and Ce, heavy rare earth Y, pure P, Al, Mg and Ti elements on the wetting/adhesion behavior of Sn-9Zn alloy to copper, as well as the associated oxidation and solidification morphology of this alloy were examined. The results show that harmful effect on the wettability can be found when adding Al and Ti elements, while the wettability can be improved slightly by adding Mg and Y elements. The adhesion of the alloy to copper can be decreased by Mg element. The RE and P are found to significantly improve the wettability. In addition, oxidation of the alloy can be increased by adding RE, while little effect on the oxidation behavior can be found by adding P element. As-solidified Sn-9Zn alloy has a rough surface with protrusions and cavities shaped by coarse needle-like crystallites, while the Sn-37Pb sample has a rather smooth surface, which indicates the different solidification behavior of Sn-9Zn alloy and the Sn-37Pb one. The additions of the different elements investigated in this study do not alter Sn-9Zn's as-solidified morphology.
基金Project(50474007) supported by the National Natural Science Foundation of ChinaProject(0450050) supported by the Natural Science Foundation of Jiangxi Province, ChinaProject(GJJ 08006) supported by the Science & Technology Program of Education Department of Jiangxi Province, China
文摘The microstructure characteristics and mechanical properties of 2024 wrought aluminum alloy produced by a new rheoforming technique under as-cast and optimized heat treatment conditions were investigated. The present rheoforming combined the independently developed rheocasting process, named as LSPSF (low superheat pouring with a shear field) process, and the existing squeeze casting process. The experimental results show that LSPSF can be used to prepare sound semi-solid slurry within 25 s to fully meet the production rate of squeeze casting. The primary α(Al) presents in mean equivalent diameter of 69 μm and shape factor of 0.76, and features zero-entrapped eutectics. Compared with conventional squeeze casting, the present LSPSF rheoforming can improve the microstructures and mechanical properties. An optimized heat treatment results in substantial reduction of microsegregation and significant improvement of mechanical properties, such as yield strength of 321 MPa, ultimate tensile strength of 428 MPa and elongation of 12%.
基金Project(60661001) supported by the National Natural Science Foundation of China
文摘To make the ferroelectric BaTiO3 possess ferromagnetism simultaneously,magnetic Fe was doped into BaTiO3 ceramics at doping levels up to 10%(molar fraction).Both tetragonal and hexagonal phases coexisted in the Fe-doped BaTiO3 ceramics except at 1% doping level.X-ray diffraction analysis indicated that higher doping level of Fe,higher sintering temperature and longer sintering time promoted the formation of hexagonal phases in Fe-doped BaTiO3 ceramics.Ferroelectricity was observed in all samples at room temperature,but it was greatly depressed by Fe doping.Except at doping level of 1%,room-temperature ferromagnetism was observed in the BaTiO3 ceramics.The dependence of the saturation magnetization and coercivities of the Fe-doped BaTiO3 ceramics on doping level was systematically studied.Both the saturation magnetization and magnetic coercivities were found to be dependent on the doping level as well as the fraction of the hexagonal phase in the ceramics.
基金Funded by the National Natural Science Foundation of China(No.51563017)
文摘A novel cationic photosensitive resin(3 DSLR-01) for stereolithography 3 D printing was prepared with 3,4-epoxycyclohexylmethyl-3’,4’-epoxycyclohexane carboxylate(2021 P),1,4-cyclohexanedimethanol glycidyl ether(JX-026), diglycidyl 4,5-epoxycyclohexane-1,2-dicarboxylate(S-186), polycaprolactone polyol(Polyol-0305), novolac epoxy resin(F-51), bis(3-ethyl-3-oxetanylmethyl) ether(S-221) and a mixture of triarylsulfonium hexafluoroantimonate salts solution(UVI-6976). The properties of the photosensitive resin and its UV-cured films were investigated by some instruments and equipment.The experimental results show that the critical exposure(Ec) of the photosensitive resin is 16.3 mJ/cm^2, the penetration depth(Dp) is 0.14 mm, and the optical property of the photosensitive resin is excellent. Rectangle plates were printed by using a stereolithography apparatus(HRPL-150 A) with the photosensitive resin as the manufacturing material, and the shrinkage rates of the plates were less than 0.60%, which showed that the accuracy of the manufactured plates was very high.
基金Funded by the Major Scientific and Technical Project Program of Jiangxi Province (No.2005008) the Science & Technology Project of Education Department of Jiangxi Province (No.[2007]53 and No.GJJ09416)
文摘Particle reinforced Sn-Zn based composite solders were obtained by adding Cu powders to Sn-9Zn melts. The microstructure analysis reveals that in situ CusZn8 particles are formed and distributed uniformly in the composite solders. The strength and plasticity of the composite solders were improved, and creep resistance was considerably enhanced. The wettability of these composite solders is also better than that of Sn-9Zn.
基金This work was supported by National Key Research and Development Program(Nos.2016YFB0701201,2016YFB0701203)National Natural Science Foundation of China(Nos.51671101)+3 种基金Domain Foundation of Equipment Advance Research of 13th Five-year Plan(No.61409220118)Natural Science Foundation of JiangXi Province(Nos.20171BCD40003)Key Research and Development Program of JiangXi Province(No GJJ150010)Nanchang University Graduate Innovation Special Fund(No.CX2018038).
文摘There remains growing interest in magnesium(Mg)and its alloys,as they are the lightest structural metallic materials and potential metallic biomaterials.In spite of the greatest historical Mg usage at present,the wider use of Mg alloys remains restricted by the poor corrosion resistance.A nano amorphous film,as the composition of Al2O3,had now been deposited on the AZ31 Mg alloy substrate by atomic layer deposition(ALD).Grazing incidence X-ray diffraction(GIXRD),X-ray reflectivity(XRR),X-ray photoelectron spectroscopy(XPS),atomic force microscope(AFM)and scanning electron microscopy(SEM)had been employed to identify the chemical compositions,microstructure and Al2O3/Mg interface of specimens firstly.Then corrosion behavior had been evaluated by neutral salt spray test and electrochemical measurement.The results showed that nano amorphous film made a homogeneous cover on Mg alloy.The film could improve the corrosion resistance of Mg alloy greatly,not only with a positive shift in Ecorr and a decrease in icorr,but also with a more uniform corroded mode.Furthermore,the roughness was found to be an important factor for corrosion resistant,in the way that rougher surface was corroded worse,and greater improvement would be in corrosion resistant after nano amorphous film deposition.
基金Funded by the National Natural Science Foundation of China(Nos.21571095,51362020)the Jiangxi Provincial Department of Education(No.KJLD13008)the Scientific Research Projects of Hunan Education Department(No.18C1442)。
文摘Ce^(3+)/Tb^(3+) co-doped and Ce^(3+)/Tb^(3+)/Eu^(3+) tri-doped β-NaYF_(4) photoluminescent microcrystals using oleic acid as surfactant were synthesized using the solvothermal method.Their microstructural characteristics and photoluminescence properties were investigated in detail.They have the shape of hexagonal prism bipyramids with uniform particle size,which decreases with the concentrations of Tb^(3+) and Eu^(3+).The energy transfer processes of both the Ce^(3+)→Tb^(3+) and the Ce^(3+)→Tb^(3+)→Eu^(3+) were systematically studied.Compared with Eu^(3+) or Tb^(3+) single-doped β-NaYF_(4) microcrystals,the sensitization by Ce^(3+) for the photoluminescence of Tb^(3+) and Eu^(3+) leads to a broad excitation spectral bandwidth in the ultraviolet (UV) range.Meanwhile,the corresponding optical absorption efficiency is greatly enhanced.High energy transfer efficiencies have been observed from Ce^(3+) to Tb^(3+) and from Tb^(3+) to Eu^(3+).
基金Project(0061)supported by the Doctorate Foundation of Nanchang University,ChinaProject(2006015)supported by the Center for Analysis and Testing,Nanchang University,China
文摘Tetrapod-shaped ZnO whiskers and microrods were synthesized in one crucible by thermal evaporation of Zn/C mixtures at 930 ℃ in air without any catalyst.The digital camera,optical microscopy,scanning electron microscopy,energy dispersive X-ray spectroscopy,and X-ray diffraction techniques were used to study the morphologies and crystal structures of these tetrapod-shaped ZnO microcrystals.The results show that these two types of ZnO tetrapods are grown at different heights within the same crucible.The legs of these tetrapod-shaped ZnO crystals are hexagonally faceted.Some tetrapod-shaped ZnO whiskers show hierarchical structures.A short button-like hexagonal ZnO microcrystal is observed at the triple junctions of some tetrapod-shaped ZnO whiskers.The tetrapod-shaped ZnO microrods are capped by two sets of hexagonal pyramids with two different groups of crystal planes for the surfaces.These two types of tetrapod-shaped ZnO microcrystals have different side faces and aspect ratio,which are believed to be the result of their different growth behaviors.The octa-twin model was used to discuss the different growth behaviors of these two types of ZnO tetrapods.The crystal planes of the legs and the pyramids were determined.
文摘The potential of using a hypoeutectic, instead of eutectic, Sn-Zn alloy as a lead-free solder has been discussed. The nonequilibrium melting behaviors of a series of Sn-Zn alloys were examined by differential thermal analysis. It was found that at a heating rate of 5℃/min, Sn-6.SZn exhibited no melting range. Dipping and spreading tests were carried out to characterize the wettability of Sn-Zn alloys on Cu. Both tests exhibited that Sn-6.5Zn has significantly better wettability on Cu than Sn-9Zn. The reaction layers formed during the spreading tests were examined. When the Zn concentration fell between 2.5wt%-9wt%, two reaction layers were formed at the interface, a thick and flat Cu5Zn8 adjacent to Cu and a thin and irregular Cu-Zn-Sn layer adjacent to the alloy. Only a Cu0Sn5 layer was formed when the Zn concentration decreased to 0.5wt%. The total thickness of the reaction layer(s) between the alloy and Cu was found to increase linearly with the Zn concentration.
基金Funded by the National Natural Science Foundation of China(Nos.21571095 and 51362020)the Jiangxi Provincial Department of Education(KJLD13008)
文摘BaTiO3/epoxy composites consisting of two three-dimensionally interpenetrating networks of BaTiO3 and epoxy phases were prepared using a new approach. The BaTiO3/epoxy composites exhibit a colossal dielectric constant, low dielectric loss and high flexural strength. In the BaTiO3 networks, chemically bonded grain boundaries between neighboring BaTiO3 grains were established, and they are responsible for the colossal dielectric constant and high flexural strength of the BaTiO3/epoxy composites. Furthermore, unlike the conventional ceramic/polymer composites, this approach also makes high loadings of BaTiO3 contents possible for the BaTiO3/epoxy composites without compromising their high flexural strength.
基金Project(0150014) supported by the Natural Science Foundation of Jiangxi Province, China
文摘Several samples of manganese oxides La(1-x)2/3Ca1/3MnO3 (V-LCMO) and (La0.7-xY0.3)2/3Ca1/3MnO3 (x<0.15) (V-LYCMO) with vacancies at La-site (La-vacancy) were prepared by solid-state reaction method. The X-ray diffraction(XRD) patterns refined by Rietveld confirm that these compounds exhibit single phase structure with orthorhombic symmetry (Pnma). The lattice parameters, Mn—O bond length and Mn—O—Mn bond angle vary with La-vacancy concentration, as an indication of the occurrence of the local Jahn-Teller effect. The measurement result of V-LCMO compounds shows that the maximum magnetoresistance(MR) is about 220% at TIM=268 K and La-vacancy content x=0.04. For V-LYCMO compounds, there exists metal-insulator transition at about 50 K, and a very large MR (over 106%) is observed at the temperature ranging from 40 K to 50 K.
基金Funded by the LDK Solar(TC-NU-0004)the Science & Technology Project of Education Department of Jiangxi Province(No.GJJ10034)
文摘Physical-chemical characteristics of the band sawing dusts regarding to recovery of pure silicon from them were investigated.The experimental results show 50vol%-60vol% amorphous phases exist in the dusts,which is mostly amorphous silica.The as-received saw dusts are found to form hard agglomerates of larger than 50 microns in diameter.The iron-based inclusions collected by magnets are found to match well with the band saw material in XRD patterns.Weight loss in heating was observed by thermal gravity tests,up to 900 ℃,presumably due to reaction of the amorphous silica with carbon contaminant in the dusts.The saw dusts were variously treated to examine their physical-chemical responses,and the results were also presented.
基金Funded by the National Natural Science Foundation of China(No.21865017)。
文摘A compound,3-ethyl-3-hydroxymethyloxetane(EHO),was synthesized with diethyl carbonate and trihydroxypropane as raw materials,3-ethyl-3-allylmethoxy oxetane(EAMO)was synthesized with EHO and allyl bromide,and 1,1,3,3,5,5-hexamethyl-1,5-bis[(3-ethyl-3-methoxyoxetane)propyl]trisiloxane(HMBEMOPTS)was synthesized with EAMO and 1,1,3,3,5,5-hexamethyltrisiloxane(HMTS).HMBEMOPTS is a novel UV-curable oligomer.The test of photo-DSC shows the photosensitivity of HMBEMOPTS is better than the ordinary oxetane,3-ethyl-3-[(3-ethyloxetan-3-yl)methoxymethyl]oxetane.HMBEMOPTS was mixed with bisphenol A type epoxy resin E-51 to prepare a cationic UV-curable system,and triarylsulfonium hexafluoroantimonate(UV-6976)was used as a cationic photoinitiator.The mechanical tests of coating films prove that when the mass fraction of HMBEMOPTS is 50%,the mechanical properties of the curing system are the best.The impact strength of the UV-curable films is measured to be 40 kg·cm and the flexibility is 2 mm;the tensile strength and flexural strength of the prepared specimens are 20.74 MPa and 13.43 MPa,respectively.The experimental results show that HMBEMOPTS can effectively improve photosensitivity and flexibility of the photosensitive resin.
基金Funded by the Jiangxi Provincial Department of Education(KJLD13008)the National Natural Science Foundation of China(number 51362020)the Research Fund for the Doctoral Program of Higher Education(20123601110006)
文摘B_2O_3-SiO_2-ZnO-BaO-Al_2O_3 glass with different Al_2O_3 contents(1mol%, 3mol%, 5mol%, and 7mol%) was prepared, and it was intended to be used as lead-free and low-melting glass sealants for solid oxide fuel cells. The effects of Al_2O_3 content on the structures, thermal properties, and sintering behaviors of the B_2O_3-SiO_2-ZnO-BaO-Al_2O_3 glass were investigated in detail. The Al_2O_3 content largely influenced the structures and thermal properties of the glass. When the Al_2O_3 content 5mol%, the transition temperature of the glass decreased with the Al_2O_3 content, while the crystallization temperature increased with the Al_2O_3 content. However, higher Al_2O_3 content degraded the stability of the glass. The B_2O_3-SiO_2-ZnO-BaO-Al_2O_3 glass with 5 mol% Al_2O_3 content exhibits the optimal sintering densification characteristics and can be used as glass sealants for solid oxide fuel cells.