Compound(Ph_4P)[V_3MP_6](MPH_2=o-HOC_6H_4SH)was obtained by reaction of VCl_3 and Na_2MP in ethanol in the presence of Ph_4PBr.It is triclinic and crystallizes in space group P1,fw=1237.3,a=14.127(4), b=14.342(4),c=15...Compound(Ph_4P)[V_3MP_6](MPH_2=o-HOC_6H_4SH)was obtained by reaction of VCl_3 and Na_2MP in ethanol in the presence of Ph_4PBr.It is triclinic and crystallizes in space group P1,fw=1237.3,a=14.127(4), b=14.342(4),c=15.878(4);α=65.08(2),β=73.09(2),T=78.68(2)°;V=2781.3~3, Z=2,d_c=1.48 g/cm^3.Final R factor is 0.063.The three vanadium atoms are linearly arranged and bridged by the oxygen atoms and terminally chelated by the thiolato-atoms of the six MP^2-ligands in pseudo-S_6 symmetry.展开更多
Li3V2-2/3xMnx（PO4）3（0≤x≤0.12） powders were synthesized by sol-gel method. The effect of Mn2＋-doping on the structure and electrochemical performances of Li3V2（PO4）3/C was characterized by XRD, SEM, XPS, galva...Li3V2-2/3xMnx（PO4）3（0≤x≤0.12） powders were synthesized by sol-gel method. The effect of Mn2＋-doping on the structure and electrochemical performances of Li3V2（PO4）3/C was characterized by XRD, SEM, XPS, galvanostatic charge /discharge and electrochemical impedance spectroscopy（EIS）. The XRD study shows that a small amount of Mn2＋-doped does not alter the structure of Li3V2（PO4）3/C materials, and all Mn2＋-doped samples are of pure single phase with a monoclinic structure （space group P21/n）. The XPS analysis indicates that valences state of V and Mn are ＋3 and ＋2 in Li3V1.94Mn0.09（PO4）3/C, respectively, and the citric acid in raw materials was decomposed into carbon during calcination, and residual carbon exists in Li3V1.94Mn0.09（PO4）/C. The results of electrochemical measurements show that Mn2＋-doping can improve the cyclic stability and rate performance of these cathode materials. The Li3V1.94Mn0.09（PO4）3/C cathode material shows the best cyclic stability and rate performance. For example, at the discharge current density of 40 mA/g, after 100 cycles, the discharge capacity of Li3V1.94Mn0.09（PO4）3/C declines from initial 158.8 mA·h/g to 120.5 mA·h/g with a capacity retention of 75.9%; however, that of the Mn-undoed sample declines from 164.2 mA·h/g to 72.6 mA·h/g with a capacity retention of 44.2%. When the discharge current is increased up to 1C, the intial discharge capacity of Li3V1.94Mn0.09（PO4）3/C still reaches 146.4 mA·h/g, and the discharge capacity maintains at 107.5 mA·h/g after 100 cycles. The EIS measurement indicates that Mn2＋-doping with a appropriate amount of Mn2＋ decreases the charge transfer resistance, which is favorable for the insertion/extraction of Li＋.展开更多
The tribological behaviors of TiN coating and TiN+TiC+Ti(C, N)/diamond like carbon (DLC), TiN/DLC, TiC/DLC multilayers on Ti 6Al 4V alloy prepared by plasma based ion implantation (PBII) were compared. Under the test ...The tribological behaviors of TiN coating and TiN+TiC+Ti(C, N)/diamond like carbon (DLC), TiN/DLC, TiC/DLC multilayers on Ti 6Al 4V alloy prepared by plasma based ion implantation (PBII) were compared. Under the test conditions of counterbody AISI 52100, load 1 N and speed 0.05 m/s, the tribological properties of the alloy are improved by these films in the order of TiN, TiC/DLC, TiN/DLC and TiN+TiC+Ti(C,N)/DLC. Tribological behavior is affected by the conditions of surface modification and triboexperiments. The appearance of “peaks” in the wear dynamic resistance profiles may be due or correspond to the process of formation and breaking apart of transition films. The breakthrough of the DLC coated samples may start from partially wearing out, and end with joining piece dilamination. There are transition films on all counterbodies AISI 52100. When AISI 52100 counterbody is changed to Ti 6Al 4V, the wear of most modified samples is changed from only disc to both disc and ball abrasive dominated.展开更多
Y-doped Li3V2（PO4）3 cathode materials were prepared by a carbothermal reduction（CTR） process.The properties of the Y-doped Li3V2（PO4）3 were investigated by X-ray diffraction（XRD） and electrochemical measuremen...Y-doped Li3V2（PO4）3 cathode materials were prepared by a carbothermal reduction（CTR） process.The properties of the Y-doped Li3V2（PO4）3 were investigated by X-ray diffraction（XRD） and electrochemical measurements.XRD studies showed that the Y-doped Li3V2（PO4）3 had the same monoclinic structure as the undoped Li3V2（PO4）3.The Y-doped Li3V2（PO4）3 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram（CV）, and electrochemical impedance spectra（EIS）.The optimal doping content of Y was x=0.03 in Li3V2-xYx（PO4）3 system.The Y-doped Li3V2（PO4）3 samples showed a better cyclic ability.The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Y-doping.The improved electrochemical perormances of the Y-doped Li3V2（PO4）3 cathode materials were attributed to the addition of Y3＋ ion by stabilizing the monoclinic structure.展开更多
A semi-insulating layer is obtained in n-type 4H-SiC by vanadium-ion implantation. A little higher resistivity is obtained by increasing the annealing temperature from 1450 to 1650 ℃. The resistivity at room temperat...A semi-insulating layer is obtained in n-type 4H-SiC by vanadium-ion implantation. A little higher resistivity is obtained by increasing the annealing temperature from 1450 to 1650 ℃. The resistivity at room temperature is as high as 7.6 ×10^6 Ω. cm. Significant redistribution of vanadium is not observed even after 1650 ℃ annealing. Temperaturedependent resistivity and optical absorption of V-implanted samples are measured. The activation energy of vanadium acceptor level is observed to be at about Ec - 1.1 eV.展开更多
Cr-doped Li3V2（PO4）3 cathode materials Li3V2-xCr（PO4）3 were prepared by a carbothermal reduction（CTR） process. The properties of the Cr-doped Li3V2（PO4）3 were investigated by X-ray diffraction （XRD）, scannin...Cr-doped Li3V2（PO4）3 cathode materials Li3V2-xCr（PO4）3 were prepared by a carbothermal reduction（CTR） process. The properties of the Cr-doped Li3V2（PO4）3 were investigated by X-ray diffraction （XRD）, scanning electron microscopic （SEM）, and electrochemical measurements Results show that the Cr-doped Li3V2（PO4）3 has the same monoclinic structure as the undoped Li3V2（PO4）3, and the particle size of Cr-doped Li3V2（PO4）3 is smaller than that of the undoped Li3V2（PO4）3 and the smallest particle size is only about 1 1μm. The Cr-doped Li3V2（PO4）3 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram （CV）, and electrochemical impedance spectra（EIS）. The optimal doping content of Cr was that x=0.04 in the Li3V2-xCrx（PO4）3 samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Cr-doping. The improved electrochemical performances of the Cr-doped Li3V2（PO4）3 cathode materials are attributed to the addition of Cr^3＋ ion by stabilizing the monoclinic structure.展开更多
The composition and structure of Ti 6Al 4V alloy plasma based ion implanted with nitrogen was investigated.The nitrogen depth distribution shows more antiballistic with distribution peak heightened with increased i...The composition and structure of Ti 6Al 4V alloy plasma based ion implanted with nitrogen was investigated.The nitrogen depth distribution shows more antiballistic with distribution peak heightened with increased implantation time(dose),and more like a parabola at the low implantation pulse voltage.When implantation pulse voltage is increased,the implantation depth increased with the nitrogen distribution peak being deepened,widened and lowered somewhat.TiN,TiN+Ti 2N,or Ti 2N second phases were formed in the implanted layer.The relative percentage of nitrogen content in the form of TiN increases when going deeper into the implanted(TiN formed) layer.The increase of implantation pulse width and/or time is favourable for the formation of TiN rather than Ti 2N.It is unfavourable for formation of any nitrides when implantation pulse voltage is decreased to 30kV or less.Tiny crystalline particles (made mainly of Ti 2N and a smaller percentage of TiO 2 phases) of regular shapes such as triangle and tetragon, etc .(about 20 nm) are found distrbuted dispersively in the near surface region of samples implanted at the high implantation pulse voltage (75kV).展开更多
The dynamic corrosion behaviors of Ti-6Al-4V alloy in acid artificial saliva containing fluoride ion were traced using electrochemical techniques,optical microscope,scanning electron microscopy,energy dispersive spect...The dynamic corrosion behaviors of Ti-6Al-4V alloy in acid artificial saliva containing fluoride ion were traced using electrochemical techniques,optical microscope,scanning electron microscopy,energy dispersive spectrometer and roughness tester.The experimental results indicate that a negative shift of corrosion potential as well as a continuous decrease in impedance for the alloy exists with increasing immersion time,and the degradation rate of the alloy presents the trend of first increase then decrease following the dissolution of passivation film and the formation of corrosion products.The accumulated fluoride ion on the alloy surface accelerates the fracture of passivation film,and the occurrence and development of corrosion of alloy are mainly located at the sites where the formation and shedding of white particles are composed of fluoride compounds,resulting in the decrease of corrosion resisting property of the alloy.A possible model is proposed to elaborate the dynamic corrosion behavior of the alloy.展开更多
Presents the investigation of the effect of implantation time and pre or post implantation aging on nitrogen distribution and microhardness with the following findings: the colour of the surface is modified after impl...Presents the investigation of the effect of implantation time and pre or post implantation aging on nitrogen distribution and microhardness with the following findings: the colour of the surface is modified after implantation and it gets darker with the increase of implantation time, and is not affected by pre or post implantation aging; for every implanted sample, a peak is found in the near surface region of the nitrogen concentration depth profile determined by X ray photoelectron spectroscopy (XPS); The position of the peak is not affected by implantation time and pre or post implantation aging used; With the increase of implantation time, the surface nitrogen concentration increases, and the peak is heightened, but the speed of heightening decreases; The surface structure formed after the implantation may be more unstable and more readily oxidized in its subsequent exposure to air; The implanted samples can be protected against oxidation by immersing them in pure alcohol; and the immersion causes the surface nitrogen concentration to increase somewhat and the surface oxygen concentration to decrease in comparison with the exposure to air. The implanted samples exhibit higher hardness improvement factor especially at low plastic penetrations. The exposure to air causes the hardness improvement factor to increase. As the implantation time is increased, the hardness improvement factor increases (but at a decreased speed). Over long implantation time can induce a softening process because the hardness improvement effects are then unable to follow the effect of strength loss.展开更多
The techniques for surface analysis including AES,XPS and SIMS were employed to study the chemical composition and bond valence of nitrogen ion implanted surface of surgical implantation service alloy Ti6Al4V.The dept...The techniques for surface analysis including AES,XPS and SIMS were employed to study the chemical composition and bond valence of nitrogen ion implanted surface of surgical implantation service alloy Ti6Al4V.The depth of implanted nitrogen ions and the sputtering rate of argon beams were determined using a profilometer.It was found that the combination of injected nitrogen ions with titanium resulted in the formation of hard TiN particles and the profile of nitrogen concentration approximately displayed gaussian distribution.The total depth of implanted nitrogen is about 350 nm and its maximum concentration appears in the depth of about 140 nm from the surface,in which the concentration ratio of nitrogen to titanium may be up to 1.1.展开更多
The nitrogen-doped porous TiO2 layer on Ti6Al4V substrate was fabricated by plasma-based ion implantation of He, O and N. In order to increase the photodegradation efficiency of TiO2 layer, two methods were used in th...The nitrogen-doped porous TiO2 layer on Ti6Al4V substrate was fabricated by plasma-based ion implantation of He, O and N. In order to increase the photodegradation efficiency of TiO2 layer, two methods were used in the process by forming mesopores to increase the specific surface area and by nitrogen doping to increase visible light absorption. Importantly, TiO2 formation, porosity architectures and nitrogen doping can be performed by implantation of He, O and N in one step. After implantation, annealing at 650 ℃ leads to a mixing phase of anatase with a little rutile in the implanted layer. By removing the near surface compact layer using argon ion sputtering, the meso-porous structure was exposed on surfaces. Nitrogen doping enlarges the photo-response region of visible light. Moreover, the nitrogen dose of 8×1015 ion/cm2 induces a stronger visible light absorption. The photodegradation of rhodamine B solution with visible light sources indicates that the mesopores on surfaces and nitrogen doping contribute to an apparent increase of photocatalysis efficiency.展开更多
in order to achieve increased layer thickness, and wearing resistance, enhanced ion implantation with nitrogen has been carried out at temperatures of 100, 200, 400, and 600℃ with a dose of 4x 1018 ions' cm-2. U...in order to achieve increased layer thickness, and wearing resistance, enhanced ion implantation with nitrogen has been carried out at temperatures of 100, 200, 400, and 600℃ with a dose of 4x 1018 ions' cm-2. Using the Plasma Source ion Implantation (PSII) device, specimens of Ti6Al4V alloy were implanted at elevated temperatures, using the ion flux as the heating source. Auger Electron Spectroscopy (AES), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), micro-hardness measurements and pin-on-disk wearing tester were utilized to evaluate the surface property improvements. The thickness of the implanted layer increased by about an order of magnitude when the temperature was elevated from 100 to 600℃. Higher surface hardness and wearing resistance was also obtained in implantation under higher temperature. XRD image showed the presence of titanium nitrides on the implanted surface.展开更多
Na_(3)V_(2)(PO_(4))_(3)(NVP)cathode material of the sodium ion battery(1 C=117 mAh g-1)has a NASICON-type structure,which not only facilitates the rapid migration of sodium ions,but also has a small volume deformation...Na_(3)V_(2)(PO_(4))_(3)(NVP)cathode material of the sodium ion battery(1 C=117 mAh g-1)has a NASICON-type structure,which not only facilitates the rapid migration of sodium ions,but also has a small volume deformation during sodium ion de-intercalation and the main frame mechanism remains unchanged,and thus is seen as an energy storage material for a wide range of applications,but has a limited electronic conductivity due to its structure.In this paper,NVP cathode materials with finer primary particles are successfully prepared using a simple hydrothermal treatment-assisted sol-gel method.The increased pore size of the NVP materials prepared under the hydrothermal process allows for more active sites and more effective resistance to the volume deformation of sodium ions during insertion/extraction processes,effectively facilitating the diffusion of ions and electrons.The Na_(3)V_(2)(PO_(4))_(3) material obtained by the optimized process exhibited good crystallinity in XRD characterization,as well as superior electrochemical properties in a series of electrochemical tests.A specific capacitance of 106.3 mAh g^(-1) at 0.2 C is demonstrated,compared to 96.5 mAh g^(-1) for Na_(3)V_(2)(PO_(4))_(3) without hydrothermal treatment,and cycling performance is also improved with 93%capacity retention.The calculated sodium ion diffusion coefficient(DNa=5.68×10^(-14))obtained after EIS curve fitting of the improved sample illustrates that the pore structure is beneficial to the performance of the Na_(3)V_(2)(PO_(4))_(3)cathode material.展开更多
Sodium-ion batteries （SIBs） have attracted increasing attention in the past decades, because of high over-all abundance of precursors, their even geographical distribution, and low cost. Na3V2（PO4）3 （NVP）, atypi...Sodium-ion batteries （SIBs） have attracted increasing attention in the past decades, because of high over-all abundance of precursors, their even geographical distribution, and low cost. Na3V2（PO4）3 （NVP）, atypical sodium super ion conductor （NASlCON）-based electrode material, exhibits pronounced structuralstability, exceptionally high ion conductivity, rendering it a most promising electrode for sodium storage.However. the comparatively low electronic conductivity makes the theoretical capacity of NVP cannot befully accessible even at comparatively low rates, presenting a major drawback for further practical ap-plications, especially when high rate capability is especially important. Thus, many endeavors have beenconformed to increase the surface and intrinsic electrical conductivity of NVP by coating the active mate-rials with a conductive carbon layer, downsizing the NVP particles, combining the NVP particle with vari-ous carbon materials and ion doping strategy. In this review, to get a better understanding on the sodiumstorage in NVP, we firstly present 4 distinct crystal structures in the temperature range of-30℃-225℃ namely α-NVP, β-NVP, β′-NVP and γ-NVP. Moreover, we give an overview of recent approaches to en-hance the surface electrical conductivity and intrinsic electrical conductivity of NVP. Finally, some poten-tial applications of NVP such as in all-climate environment and PHEV, EV fields have been prospected.展开更多
Li3V2（PO4）3 samples were synthesized by sol-gel route and high temperature solid-state reaction. The influence of Li3V2（PO4）3 as cathode materials for lithium-ion batteries on electrochemical performances was inve...Li3V2（PO4）3 samples were synthesized by sol-gel route and high temperature solid-state reaction. The influence of Li3V2（PO4）3 as cathode materials for lithium-ion batteries on electrochemical performances was investigated. The structure of Li3Va（PO4）3 as cathode materials for lithium-ion batteries and morphology of Li3V2（PO4）3 were characterized by X-ray diffractometry （XRD） and scanning electron microscopy （SEM）. Electrochemical performances were characterized by charge/discharge and AC impedance measurements. Li3V2（PO4）3 with smaller grain size shows better performances in terms of the discharge capacity and cycle stability. The improved electrochemical properties of Li3V2（PO4）3 are attributed to the refined grains and enhanced electrical conductivity. AC impedance measurements also show that the Li3V2（PO4）3 synthesized by sol-gel route exhibits significantly decreased charge-transfer resistance and shortened migration distance of lithium ions.展开更多
With the development of stable alkali metal anodes,V_(2)O_(5) is gaining traction as a cathode material due to its high theoretical capacity and the ability to intercalate Li,Na and K ions.Herein,we report a method fo...With the development of stable alkali metal anodes,V_(2)O_(5) is gaining traction as a cathode material due to its high theoretical capacity and the ability to intercalate Li,Na and K ions.Herein,we report a method for synthesizing structured orthorhombic V_(2)O_(5) microspheres and investigate Li intercalation/deintercalation into this material.For industry adoption,the electrochemical behavior of V_(2)O_(5) as well as structural and phase transformation attributing to Li intercalation reaction must be further investigated.Our synthesized V_(2)O_(5) microspheres consisted of small primary particles that were strongly joined together and exhibited good cycle stability and rate capability,triggered by reversible volume change and rapid Li ion diffusion.In addition,the reversibility of phase transformation(a,e,d,c and xLixV_(2)O_(5))and valence state evolution(5+,4+,and 3.5+)during intercalation/de-intercalation were studied via in-situ X-ray powder diffraction and X-ray absorption near edge structure analyses.展开更多
Ti6Al4V alloy‒CoCrMo alloy pair is commonly applied for modular head‒neck interfaces for artificial hip joint.Unfortunately,the fretting corrosion damage at this interface seriously restricts its lifespan.This work st...Ti6Al4V alloy‒CoCrMo alloy pair is commonly applied for modular head‒neck interfaces for artificial hip joint.Unfortunately,the fretting corrosion damage at this interface seriously restricts its lifespan.This work studied the fretting corrosion of Ti6Al4V‒CoCrMo pair in calf serum solution.We established this material pair’s running condition fretting map(RCFM)regarding load and displacement,and revealed the damage mechanism of this material pair in various fretting regimes,namely partial slip regime(PSR),mixed fretting regime(MFR),and gross slip regime(GSR).The damage mechanism of Ti6Al4V alloy was mainly abrasive wear induced by CoCrMo alloy and tribocorrosion.Adhesive wear(material transfer)also existed in MFR.The damage mechanism of CoCrMo alloy was mainly abrasive wear induced by metal oxides and tribocorrosion in GSR and MFR,while no apparent damage in PSR.Furthermore,a dense composite material layer with high hardness was formed in the middle contacting area in GSR,which reduced the corrosion and wear of Ti alloys and exacerbated damage to Co alloys.Finally,the ion concentration maps for Ti and Co ions were constructed,which displayed the transition in the amount of released Ti and Co ions under different displacements and loads.展开更多
文摘Compound(Ph_4P)[V_3MP_6](MPH_2=o-HOC_6H_4SH)was obtained by reaction of VCl_3 and Na_2MP in ethanol in the presence of Ph_4PBr.It is triclinic and crystallizes in space group P1,fw=1237.3,a=14.127(4), b=14.342(4),c=15.878(4);α=65.08(2),β=73.09(2),T=78.68(2)°;V=2781.3~3, Z=2,d_c=1.48 g/cm^3.Final R factor is 0.063.The three vanadium atoms are linearly arranged and bridged by the oxygen atoms and terminally chelated by the thiolato-atoms of the six MP^2-ligands in pseudo-S_6 symmetry.
基金Project (20771100) supported by the National Natural Science Foundation of China
文摘Li3V2-2/3xMnx（PO4）3（0≤x≤0.12） powders were synthesized by sol-gel method. The effect of Mn2＋-doping on the structure and electrochemical performances of Li3V2（PO4）3/C was characterized by XRD, SEM, XPS, galvanostatic charge /discharge and electrochemical impedance spectroscopy（EIS）. The XRD study shows that a small amount of Mn2＋-doped does not alter the structure of Li3V2（PO4）3/C materials, and all Mn2＋-doped samples are of pure single phase with a monoclinic structure （space group P21/n）. The XPS analysis indicates that valences state of V and Mn are ＋3 and ＋2 in Li3V1.94Mn0.09（PO4）3/C, respectively, and the citric acid in raw materials was decomposed into carbon during calcination, and residual carbon exists in Li3V1.94Mn0.09（PO4）/C. The results of electrochemical measurements show that Mn2＋-doping can improve the cyclic stability and rate performance of these cathode materials. The Li3V1.94Mn0.09（PO4）3/C cathode material shows the best cyclic stability and rate performance. For example, at the discharge current density of 40 mA/g, after 100 cycles, the discharge capacity of Li3V1.94Mn0.09（PO4）3/C declines from initial 158.8 mA·h/g to 120.5 mA·h/g with a capacity retention of 75.9%; however, that of the Mn-undoed sample declines from 164.2 mA·h/g to 72.6 mA·h/g with a capacity retention of 44.2%. When the discharge current is increased up to 1C, the intial discharge capacity of Li3V1.94Mn0.09（PO4）3/C still reaches 146.4 mA·h/g, and the discharge capacity maintains at 107.5 mA·h/g after 100 cycles. The EIS measurement indicates that Mn2＋-doping with a appropriate amount of Mn2＋ decreases the charge transfer resistance, which is favorable for the insertion/extraction of Li＋.
文摘The tribological behaviors of TiN coating and TiN+TiC+Ti(C, N)/diamond like carbon (DLC), TiN/DLC, TiC/DLC multilayers on Ti 6Al 4V alloy prepared by plasma based ion implantation (PBII) were compared. Under the test conditions of counterbody AISI 52100, load 1 N and speed 0.05 m/s, the tribological properties of the alloy are improved by these films in the order of TiN, TiC/DLC, TiN/DLC and TiN+TiC+Ti(C,N)/DLC. Tribological behavior is affected by the conditions of surface modification and triboexperiments. The appearance of “peaks” in the wear dynamic resistance profiles may be due or correspond to the process of formation and breaking apart of transition films. The breakthrough of the DLC coated samples may start from partially wearing out, and end with joining piece dilamination. There are transition films on all counterbodies AISI 52100. When AISI 52100 counterbody is changed to Ti 6Al 4V, the wear of most modified samples is changed from only disc to both disc and ball abrasive dominated.
基金supported by Guangxi Natural Science Foundation (0832259)Program to Sponsor Teams for Innovation in the Construction of Talent Highlands in Guangxi Institutions of Higher Learning (GuiJiaoRen [2007]71)Research Funds of the Guangxi Key Laboratory of Environmental Engineering, Protection and Assessment
文摘Y-doped Li3V2（PO4）3 cathode materials were prepared by a carbothermal reduction（CTR） process.The properties of the Y-doped Li3V2（PO4）3 were investigated by X-ray diffraction（XRD） and electrochemical measurements.XRD studies showed that the Y-doped Li3V2（PO4）3 had the same monoclinic structure as the undoped Li3V2（PO4）3.The Y-doped Li3V2（PO4）3 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram（CV）, and electrochemical impedance spectra（EIS）.The optimal doping content of Y was x=0.03 in Li3V2-xYx（PO4）3 system.The Y-doped Li3V2（PO4）3 samples showed a better cyclic ability.The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Y-doping.The improved electrochemical perormances of the Y-doped Li3V2（PO4）3 cathode materials were attributed to the addition of Y3＋ ion by stabilizing the monoclinic structure.
基金Project supported by the National Natural Science Foundation of China （Grant No 60376001）, the National Basic Research Program of China （Grant No 2002CB311904） and the National Defense Basic Research Program of China （Grant No 51327020202）. Acknowledgments The authors would like to thank Li Cheng-Ji and Ye Xiao-Ling of Institute of Semiconductors, Chinese Academy of Sciences for measuring the temperaturedependent resistivity and absorption, respectively, and they also thank Ma Nong-Nong at the Centre of Electronic Materials Characterization of Tianjin Electronic Materials Research Institute for performing SIMS measurements.
文摘A semi-insulating layer is obtained in n-type 4H-SiC by vanadium-ion implantation. A little higher resistivity is obtained by increasing the annealing temperature from 1450 to 1650 ℃. The resistivity at room temperature is as high as 7.6 ×10^6 Ω. cm. Significant redistribution of vanadium is not observed even after 1650 ℃ annealing. Temperaturedependent resistivity and optical absorption of V-implanted samples are measured. The activation energy of vanadium acceptor level is observed to be at about Ec - 1.1 eV.
基金Funded by the Guangxi Natural Science Foundation(No. 0832259)the National Basic Research Program of China (No. 2007CB613607)
文摘Cr-doped Li3V2（PO4）3 cathode materials Li3V2-xCr（PO4）3 were prepared by a carbothermal reduction（CTR） process. The properties of the Cr-doped Li3V2（PO4）3 were investigated by X-ray diffraction （XRD）, scanning electron microscopic （SEM）, and electrochemical measurements Results show that the Cr-doped Li3V2（PO4）3 has the same monoclinic structure as the undoped Li3V2（PO4）3, and the particle size of Cr-doped Li3V2（PO4）3 is smaller than that of the undoped Li3V2（PO4）3 and the smallest particle size is only about 1 1μm. The Cr-doped Li3V2（PO4）3 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram （CV）, and electrochemical impedance spectra（EIS）. The optimal doping content of Cr was that x=0.04 in the Li3V2-xCrx（PO4）3 samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Cr-doping. The improved electrochemical performances of the Cr-doped Li3V2（PO4）3 cathode materials are attributed to the addition of Cr^3＋ ion by stabilizing the monoclinic structure.
文摘The composition and structure of Ti 6Al 4V alloy plasma based ion implanted with nitrogen was investigated.The nitrogen depth distribution shows more antiballistic with distribution peak heightened with increased implantation time(dose),and more like a parabola at the low implantation pulse voltage.When implantation pulse voltage is increased,the implantation depth increased with the nitrogen distribution peak being deepened,widened and lowered somewhat.TiN,TiN+Ti 2N,or Ti 2N second phases were formed in the implanted layer.The relative percentage of nitrogen content in the form of TiN increases when going deeper into the implanted(TiN formed) layer.The increase of implantation pulse width and/or time is favourable for the formation of TiN rather than Ti 2N.It is unfavourable for formation of any nitrides when implantation pulse voltage is decreased to 30kV or less.Tiny crystalline particles (made mainly of Ti 2N and a smaller percentage of TiO 2 phases) of regular shapes such as triangle and tetragon, etc .(about 20 nm) are found distrbuted dispersively in the near surface region of samples implanted at the high implantation pulse voltage (75kV).
基金Funded by the National Natural Science Foundation of China(No.50801057)the Engineering Research Center of Nano-Geo Materials of Ministry of Education,China University of Geosciences(No.NGM2018KF015)。
文摘The dynamic corrosion behaviors of Ti-6Al-4V alloy in acid artificial saliva containing fluoride ion were traced using electrochemical techniques,optical microscope,scanning electron microscopy,energy dispersive spectrometer and roughness tester.The experimental results indicate that a negative shift of corrosion potential as well as a continuous decrease in impedance for the alloy exists with increasing immersion time,and the degradation rate of the alloy presents the trend of first increase then decrease following the dissolution of passivation film and the formation of corrosion products.The accumulated fluoride ion on the alloy surface accelerates the fracture of passivation film,and the occurrence and development of corrosion of alloy are mainly located at the sites where the formation and shedding of white particles are composed of fluoride compounds,resulting in the decrease of corrosion resisting property of the alloy.A possible model is proposed to elaborate the dynamic corrosion behavior of the alloy.
文摘Presents the investigation of the effect of implantation time and pre or post implantation aging on nitrogen distribution and microhardness with the following findings: the colour of the surface is modified after implantation and it gets darker with the increase of implantation time, and is not affected by pre or post implantation aging; for every implanted sample, a peak is found in the near surface region of the nitrogen concentration depth profile determined by X ray photoelectron spectroscopy (XPS); The position of the peak is not affected by implantation time and pre or post implantation aging used; With the increase of implantation time, the surface nitrogen concentration increases, and the peak is heightened, but the speed of heightening decreases; The surface structure formed after the implantation may be more unstable and more readily oxidized in its subsequent exposure to air; The implanted samples can be protected against oxidation by immersing them in pure alcohol; and the immersion causes the surface nitrogen concentration to increase somewhat and the surface oxygen concentration to decrease in comparison with the exposure to air. The implanted samples exhibit higher hardness improvement factor especially at low plastic penetrations. The exposure to air causes the hardness improvement factor to increase. As the implantation time is increased, the hardness improvement factor increases (but at a decreased speed). Over long implantation time can induce a softening process because the hardness improvement effects are then unable to follow the effect of strength loss.
文摘The techniques for surface analysis including AES,XPS and SIMS were employed to study the chemical composition and bond valence of nitrogen ion implanted surface of surgical implantation service alloy Ti6Al4V.The depth of implanted nitrogen ions and the sputtering rate of argon beams were determined using a profilometer.It was found that the combination of injected nitrogen ions with titanium resulted in the formation of hard TiN particles and the profile of nitrogen concentration approximately displayed gaussian distribution.The total depth of implanted nitrogen is about 350 nm and its maximum concentration appears in the depth of about 140 nm from the surface,in which the concentration ratio of nitrogen to titanium may be up to 1.1.
基金Project(20040213048) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of ChinaProject(20090450737) supported by the China Postdoctoral Science Foundation
文摘The nitrogen-doped porous TiO2 layer on Ti6Al4V substrate was fabricated by plasma-based ion implantation of He, O and N. In order to increase the photodegradation efficiency of TiO2 layer, two methods were used in the process by forming mesopores to increase the specific surface area and by nitrogen doping to increase visible light absorption. Importantly, TiO2 formation, porosity architectures and nitrogen doping can be performed by implantation of He, O and N in one step. After implantation, annealing at 650 ℃ leads to a mixing phase of anatase with a little rutile in the implanted layer. By removing the near surface compact layer using argon ion sputtering, the meso-porous structure was exposed on surfaces. Nitrogen doping enlarges the photo-response region of visible light. Moreover, the nitrogen dose of 8×1015 ion/cm2 induces a stronger visible light absorption. The photodegradation of rhodamine B solution with visible light sources indicates that the mesopores on surfaces and nitrogen doping contribute to an apparent increase of photocatalysis efficiency.
基金This item was supported by the Defense Science Foundation with Grant No.98JS50.3.3 HZ5801.
文摘in order to achieve increased layer thickness, and wearing resistance, enhanced ion implantation with nitrogen has been carried out at temperatures of 100, 200, 400, and 600℃ with a dose of 4x 1018 ions' cm-2. Using the Plasma Source ion Implantation (PSII) device, specimens of Ti6Al4V alloy were implanted at elevated temperatures, using the ion flux as the heating source. Auger Electron Spectroscopy (AES), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), micro-hardness measurements and pin-on-disk wearing tester were utilized to evaluate the surface property improvements. The thickness of the implanted layer increased by about an order of magnitude when the temperature was elevated from 100 to 600℃. Higher surface hardness and wearing resistance was also obtained in implantation under higher temperature. XRD image showed the presence of titanium nitrides on the implanted surface.
文摘Na_(3)V_(2)(PO_(4))_(3)(NVP)cathode material of the sodium ion battery(1 C=117 mAh g-1)has a NASICON-type structure,which not only facilitates the rapid migration of sodium ions,but also has a small volume deformation during sodium ion de-intercalation and the main frame mechanism remains unchanged,and thus is seen as an energy storage material for a wide range of applications,but has a limited electronic conductivity due to its structure.In this paper,NVP cathode materials with finer primary particles are successfully prepared using a simple hydrothermal treatment-assisted sol-gel method.The increased pore size of the NVP materials prepared under the hydrothermal process allows for more active sites and more effective resistance to the volume deformation of sodium ions during insertion/extraction processes,effectively facilitating the diffusion of ions and electrons.The Na_(3)V_(2)(PO_(4))_(3) material obtained by the optimized process exhibited good crystallinity in XRD characterization,as well as superior electrochemical properties in a series of electrochemical tests.A specific capacitance of 106.3 mAh g^(-1) at 0.2 C is demonstrated,compared to 96.5 mAh g^(-1) for Na_(3)V_(2)(PO_(4))_(3) without hydrothermal treatment,and cycling performance is also improved with 93%capacity retention.The calculated sodium ion diffusion coefficient(DNa=5.68×10^(-14))obtained after EIS curve fitting of the improved sample illustrates that the pore structure is beneficial to the performance of the Na_(3)V_(2)(PO_(4))_(3)cathode material.
基金financial support from the National Natural Science Foundation of China (No.21501171,51403209,21406221,51177156/E0712)
文摘Sodium-ion batteries （SIBs） have attracted increasing attention in the past decades, because of high over-all abundance of precursors, their even geographical distribution, and low cost. Na3V2（PO4）3 （NVP）, atypical sodium super ion conductor （NASlCON）-based electrode material, exhibits pronounced structuralstability, exceptionally high ion conductivity, rendering it a most promising electrode for sodium storage.However. the comparatively low electronic conductivity makes the theoretical capacity of NVP cannot befully accessible even at comparatively low rates, presenting a major drawback for further practical ap-plications, especially when high rate capability is especially important. Thus, many endeavors have beenconformed to increase the surface and intrinsic electrical conductivity of NVP by coating the active mate-rials with a conductive carbon layer, downsizing the NVP particles, combining the NVP particle with vari-ous carbon materials and ion doping strategy. In this review, to get a better understanding on the sodiumstorage in NVP, we firstly present 4 distinct crystal structures in the temperature range of-30℃-225℃ namely α-NVP, β-NVP, β′-NVP and γ-NVP. Moreover, we give an overview of recent approaches to en-hance the surface electrical conductivity and intrinsic electrical conductivity of NVP. Finally, some poten-tial applications of NVP such as in all-climate environment and PHEV, EV fields have been prospected.
基金Projects(0991025,0842003-5 and 0832259) supported by Natural Science Foundation of Guangxi Province,ChinaProject supported by the Joint Graduate Innovation Talent Cultivation Base of Guangxi Province,ChinaProject(GuiJiaoRen[2007]71) supported by the Research Funds of the Guangxi Key Laboratory of Environmental Engineering,Protection and Assessment Program to Sponsor Teams for Innovation in the Construction of Talent Highlands in Guangxi Institutions of Higher Learning,China
文摘Li3V2（PO4）3 samples were synthesized by sol-gel route and high temperature solid-state reaction. The influence of Li3V2（PO4）3 as cathode materials for lithium-ion batteries on electrochemical performances was investigated. The structure of Li3Va（PO4）3 as cathode materials for lithium-ion batteries and morphology of Li3V2（PO4）3 were characterized by X-ray diffractometry （XRD） and scanning electron microscopy （SEM）. Electrochemical performances were characterized by charge/discharge and AC impedance measurements. Li3V2（PO4）3 with smaller grain size shows better performances in terms of the discharge capacity and cycle stability. The improved electrochemical properties of Li3V2（PO4）3 are attributed to the refined grains and enhanced electrical conductivity. AC impedance measurements also show that the Li3V2（PO4）3 synthesized by sol-gel route exhibits significantly decreased charge-transfer resistance and shortened migration distance of lithium ions.
基金supported by both the Technology Innovation Program(20004958,Development of ultra-high performance supercapacitor and high power module)funded by the Ministry of Trade,Industry and Energy(MOTIE)the R&D Convergence Program(CAP-15-02-KBSI)of the National Research Council of Science&Technology,Republic of Korea。
文摘With the development of stable alkali metal anodes,V_(2)O_(5) is gaining traction as a cathode material due to its high theoretical capacity and the ability to intercalate Li,Na and K ions.Herein,we report a method for synthesizing structured orthorhombic V_(2)O_(5) microspheres and investigate Li intercalation/deintercalation into this material.For industry adoption,the electrochemical behavior of V_(2)O_(5) as well as structural and phase transformation attributing to Li intercalation reaction must be further investigated.Our synthesized V_(2)O_(5) microspheres consisted of small primary particles that were strongly joined together and exhibited good cycle stability and rate capability,triggered by reversible volume change and rapid Li ion diffusion.In addition,the reversibility of phase transformation(a,e,d,c and xLixV_(2)O_(5))and valence state evolution(5+,4+,and 3.5+)during intercalation/de-intercalation were studied via in-situ X-ray powder diffraction and X-ray absorption near edge structure analyses.
基金supported by the National Natural Science Foundation of China(Nos.52035012 and 52275215)the Natural Science Foundation of Sichuan Province(No.2022NSFSC1940).
文摘Ti6Al4V alloy‒CoCrMo alloy pair is commonly applied for modular head‒neck interfaces for artificial hip joint.Unfortunately,the fretting corrosion damage at this interface seriously restricts its lifespan.This work studied the fretting corrosion of Ti6Al4V‒CoCrMo pair in calf serum solution.We established this material pair’s running condition fretting map(RCFM)regarding load and displacement,and revealed the damage mechanism of this material pair in various fretting regimes,namely partial slip regime(PSR),mixed fretting regime(MFR),and gross slip regime(GSR).The damage mechanism of Ti6Al4V alloy was mainly abrasive wear induced by CoCrMo alloy and tribocorrosion.Adhesive wear(material transfer)also existed in MFR.The damage mechanism of CoCrMo alloy was mainly abrasive wear induced by metal oxides and tribocorrosion in GSR and MFR,while no apparent damage in PSR.Furthermore,a dense composite material layer with high hardness was formed in the middle contacting area in GSR,which reduced the corrosion and wear of Ti alloys and exacerbated damage to Co alloys.Finally,the ion concentration maps for Ti and Co ions were constructed,which displayed the transition in the amount of released Ti and Co ions under different displacements and loads.
