We experimentally study the dynamic characteristics of a miniaturized spin-exchange relaxation-free(SERF) magnetometer based on uniform light field. The ceramic ferrule is used to expand the Gaussian beam to improve l...We experimentally study the dynamic characteristics of a miniaturized spin-exchange relaxation-free(SERF) magnetometer based on uniform light field. The ceramic ferrule is used to expand the Gaussian beam to improve light intensity uniformity, while the volume of the sensor is also reduced. This scheme makes the magnetometer have better sensitivity when the detected light intensity is less than 3.16 m W/cm^(2) at 120℃. When the temperature rises to 150℃ the sensitivity under the action of uniform light field is 18.5 f T/Hz^(1/2). The bandwidth of the sensor remains at the original level and meets application needs. The proposed structure improves transverse polarization uniformity within the miniaturized sensor, which is ideal for the magnetoencephalography and magnetocardiography imaging systems.展开更多
Prostatic hyperplasia and tumor are common diseases,and the minimally invasive surgery inserting the instruments through the urethra into the prostate is commonly conducted.Taking the robotic manipulator for such surg...Prostatic hyperplasia and tumor are common diseases,and the minimally invasive surgery inserting the instruments through the urethra into the prostate is commonly conducted.Taking the robotic manipulator for such surgery into consideration,this paper analyses the workspace of the end effector,and proposes the distribution error of the fixed point and the tracking error of manipulator end effector on the cone bottom surface of the workspace as the basis for control implementation of the manipulator.The D-H coordinate system of the manipulator is established and the trajectory planning of the end effector in the Cartesian space is carried out.The digital model was established,and dynamics simulation was performed in Solidworks and Matlab/Simulink environment to guide the manipulator design.Trajectory mapping and synchronization control between virtual model and the actual manipulator are realized based on digital twin technique.The virtual manipulator can reflect the real-time state of the manipulator with data interaction by comparing the dynamics simulation results with the motor current values obtained by experiment.Experiment was carried out with PD feedback control and Newton-Euler dynamics based feedforward control to get the trajectory tracking characteristic of each motor,errors of the fixed point and tracking performance of the end effector of the manipulator.The results show that compared with PD feedback control,feed forward control implementation can achieve a reduction of 30.0%in the average error of the fixed point of the manipulator and a reduction of 33.3%in the maximum error.展开更多
As a promising cathode material for sodium ion batteries,honeycomb-ordered layered Na_(3)Ni_(2)Sb O_(6)still suffers from rapid capacity fading because of partially irreversible phase transition.Herein,a substitution ...As a promising cathode material for sodium ion batteries,honeycomb-ordered layered Na_(3)Ni_(2)Sb O_(6)still suffers from rapid capacity fading because of partially irreversible phase transition.Herein,a substitution of Na+by Rb+with a larger ionic radius in honeycomb layered Na_(3)-xRbxNi_(2)Sb O_(6)is proposed to modulate the interlayer structure.The results unveil that biphasic transition reversibility of the intermediate P′3phase is substantially enhanced,and the structure evolution behavior during the charge/discharge process changes due to the structural modulation,which contributes to a suppression of the unfavorable O_(1)phase and an alleviation of the lattice distortion.Moreover,Rb substituted samples exhibited an improved Na+(de)intercalation thermodynamics and kinetics.Attributed to the modifications,the sample with optimized Rb content delivers superior cycle stability and rate capacity,demonstrating a feasible strategy for suppressing irreversible phase transition and developing high-performance honeycomb layered materials for sodium ion batteries.展开更多
The significant clinical feature of bisphosphonate-related osteonecrosis of the jaw(BRONJ)is the exposure of the necrotic jaw.Other clinical manifestations include jaw pain,swelling,abscess,and skin fistula,which seri...The significant clinical feature of bisphosphonate-related osteonecrosis of the jaw(BRONJ)is the exposure of the necrotic jaw.Other clinical manifestations include jaw pain,swelling,abscess,and skin fistula,which seriously affect the patients’life,and there is no radical cure.Thus,new methods need to be found to prevent the occurrence of BRONJ.Here,a novel nanoparticle,t FNA-KLT,was successfully synthesized by us,in which the nanoparticle tetrahedral framework nucleic acid(tFNA)was used for carrying angiogenic peptide,KLT,and then further enhanced angiogenesis.TFNA-KLT possessed the same characteristics as tFNA,such as simple synthesis,stable structure,and good biocompatibility.Meanwhile,tFNA enhanced the stability of KLT and carried more KLT to interact with endothelial cells.First,it was confirmed that tFNA-KLT had the superior angiogenic ability to tFNA and KLT both in vitro and in vivo.Then we apply tFNA-KLT to the prevention of BRONJ.The results showed that tFNA-KLT can effectively prevent the occurrence of BRONJ by accelerating angiogenesis.In summary,the prepared novel nanoparticle,tFNA-KLT,was firstly synthesized by us.It was also firstly confirmed by us that tFNA-KLT significantly enhanced angiogenesis and can effectively prevent the occurrence of BRONJ by accelerating angiogenesis,thus providing a new avenue for the prevention of BRONJ and a new choice for therapeutic angiogenesis.展开更多
Grain boundary diffusion process(GBDP)serves as a promising approach in improving magnetic properties and thermal stability of Nd FeB permanent magnets.Herein,non-heavy rare earth Pr-Zn films deposited on the magnet s...Grain boundary diffusion process(GBDP)serves as a promising approach in improving magnetic properties and thermal stability of Nd FeB permanent magnets.Herein,non-heavy rare earth Pr-Zn films deposited on the magnet surface using DC-magnetron sputtering system are reported.The thermal stability and coercivity enhancement mechanism of Pr-Zn GBDP magnets were investigated.Results show that the coercivity of Pr-Zn GBDP magnet increases from 963.96 kA m^-1 to 1317.14 kA m^-1 without any remanence reduction.Notably,the demagnetization curve of Pr-Zn GBDP magnet still remains a high squareness ratio.The temperature coefficient of coercivity and anti-demagnetization ability of Pr-Zn GBDP magnet under high temperatures are improved after GBDP treatment.The well-optimized rare earth-rich(RE-rich)grain boundary phases and high effective anisotropy field of(Nd,RE)2 Fe14 B magnetic hardening layers surrounding main grains are the key factors to impact the magnetic properties and thermal stability of Nd FeB permanent magnets via GBDP treatment.展开更多
Choroidal neovascularization(CNV)is a common pathological feature of various eye diseases and an important cause of visual impairment in middle-aged and elderly patients.In previous studies,tetrahedral framework nucle...Choroidal neovascularization(CNV)is a common pathological feature of various eye diseases and an important cause of visual impairment in middle-aged and elderly patients.In previous studies,tetrahedral framework nucleic acids(tFNAs)showed good carrier performance.In this experiment,we developed microRNA-155-equipped tFNAs(T-155)and explored its biological effects on CNV.Based on the results of in-vitro experiments,T-155 could regulate macrophages into the antiangiogenic M1 type.Then,we injected T-155 into the vitreous of laser-induced CNV model mice and found that T-155 significantly reduced the size and area of CNV,inhibited blood vessel leakage.In summary,we prove that T-155 could regulate the inflammatory process of CNV by polarizing macrophages,thereby improving the symptoms of CNV.Thus,T-155 might become a new DNA-based drug with great potential for treating CNV.展开更多
We consider optimal shape design in Stokes flow using H^(1) shape gradient flows based on the distributed Eulerian derivatives.MINI element is used for discretizations of Stokes equation and Galerkin finite element is...We consider optimal shape design in Stokes flow using H^(1) shape gradient flows based on the distributed Eulerian derivatives.MINI element is used for discretizations of Stokes equation and Galerkin finite element is used for discretizations of distributed and boundary H^(1) shape gradient flows.Convergence analysis with a priori error estimates is provided under general and different regularity assumptions.We investigate the performances of shape gradient descent algorithms for energy dissipation minimization and obstacle flow.Numerical comparisons in 2D and 3D show that the distributed H1 shape gradient flow is more accurate than the popular boundary type.The corresponding distributed shape gradient algorithm is more effective.展开更多
Scalable pressureless sintering of nanocrystalline alumina(Al2O_(3))ceramics is a challenging problem with great scientific and technological interest.This challenge was addressed in our recent works utilizing ultrafi...Scalable pressureless sintering of nanocrystalline alumina(Al2O_(3))ceramics is a challenging problem with great scientific and technological interest.This challenge was addressed in our recent works utilizing ultrafine a-Al2O_(3) nanopowders with exceptional sinterability combined with two-step sintering technique.Here the sintering mechanism and kinetic parameters(grain boundary diffusivity and its activation energy)were analyzed from constant heating-rate sintering experiments by three different sintering models and compared with existing sintering data in the literature.We found that the lowtemperature sintering of 4.7 nm a-Al2O_(3) nanopowders can be well explained by conventional sintering mechanism via grain boundary diffusion,with reasonable activation energy of 4e5 eV that is smaller than that of coarse Al2O_(3) powders and enhanced diffusivity.However,unphysically small activation energy could be obtained if an inappropriate model was used.Lastly,successful two-step sintering was demonstrated under different heating rates.Our work illustrates that the exceptional sinterability of ultrafine a-Al2O_(3) nanopowders are most likely contributed by small size(short diffusion distance),large surface area(large sintering driving force)and good dispersity rather than new sintering mechanism,and highlights the importance of fast firing and the non-equilibrium nature for the low-temperature sintering of such nanopowders.展开更多
In view of the uneven distribution of the core-shell structure of sintered Nd-Fe-B magnets after grain boundary diffusion,this study proposes to use high-melting-point and reactive element titanium(Ti)as an additive t...In view of the uneven distribution of the core-shell structure of sintered Nd-Fe-B magnets after grain boundary diffusion,this study proposes to use high-melting-point and reactive element titanium(Ti)as an additive to increase the diffusion channels and to enhance the diffusion of heavy rare earth elements along the grain boundary phase.By adding Ti element,the diffusion depth and hence the intrinsic coercivity of magnets are increased significantly.The addition of Ti increases the coercivity at two stages:initially from 16.07 to 16.29 kOe by addition effect,and then from 16.29 to 25.16 kOe by facilitating the diffusion of Tb element.The formation of TiB_(2) phase improves the periodic arrangement of the crystal structure in the surroundings of the grain boundary phase and enhances its activity.The improved grain boundary diffusion and better core-shell structure distribution provide a theoretical guidance fo r solving the problem of diffusion depth in bulk magnets.展开更多
Low-cost and efficient oxygen reduction reaction(ORR)electrocatalysts are the key to developing Zn-air batteries for renewable energy storage.Herein,the Mn-N-P doped carbon sphere was prepared through polymerization o...Low-cost and efficient oxygen reduction reaction(ORR)electrocatalysts are the key to developing Zn-air batteries for renewable energy storage.Herein,the Mn-N-P doped carbon sphere was prepared through polymerization of hexachlorotripolyphosphazene(HCCP)and phloroglucinol,and then followed the calcination at 900°C.Theory calculations demonstrated the introduction of Mn in N-P doped carbon could lower the dissociation barrier of O2into O*and promote the ORR through a 4e-pathway.The asprepared catalysts exhibited a half-wave potential of 0.82 V vs.RHE and limiting current density of 5.2 m A/cm^(2)toward ORR,which was comparable to those of the commercial Pt/C catalysts.In addition,Zn-air batteries with 0.05 Mn-N-P-C catalysts showed a high specific capacity of 830 m Ah/gZnand excellent cycle stability.This facile approach demonstrated herein could be a solution to develop optimum non-precious metal catalysts for the application in cathodes of proton exchange membrane fuel cells.This study also provides new insight to design the catalysts of multi-heteroatom coordinated metal in the carbon matrix for both fundamental researches and practical applications.展开更多
Joule-heating reactors have the higher energy efficiency and product selectivity compared with the reactors based on radiative heating.Current Joule-heating reactors are constructed with electrically-conductive metals...Joule-heating reactors have the higher energy efficiency and product selectivity compared with the reactors based on radiative heating.Current Joule-heating reactors are constructed with electrically-conductive metals or carbon materials,and therefore suffer from stability issue due to the presence of corrosive or oxidizing gases during high-temperature reactions.In this study,chemicallystable and electrically-conductive(La_(0.80)Sr_(0.20))_(0.95)FeO_(3)(LSF)/Gd_(0.1)Ce_(0.9)O_(2)(GDC)ceramics have been used to construct Joule-heating reactors for the first time.Taking the advantage of the resistance decrease of the ceramic reactors with temperature increase,the ceramic reactors heated under current control mode achieved the automatic adjustment of heating to stabilize reactor temperatures.In addition,the electrical resistance of LSF/GDC reactors can be tuned by the content of the highconductive LSF in composite ceramics and ceramic density via sintering temperature,which offers flexibility to control reactor temperatures.The ceramic reactors with dendritic channels(less than 100μm in diameter)showed the catalytic activity for CO oxidation,which was further improved by coating efficient MnO_(2)nanocatalyst on reactor channel wall.The Joule-heating ceramic reactors achieved complete CO oxidation at a low temperature of 165℃.Therefore,robust ceramic reactors have successfully demonstrated effective Joule heating for CO oxidation,which are potentially applied in other high-temperature catalytic reactions.展开更多
Rapid and simultaneous in situ detection of multi-components is extremely crucial for the real-time monitoring of nutrients in fruits.Herein,a facile and user-friendly poly(carboxybetaine methacrylate)-coated paper-ba...Rapid and simultaneous in situ detection of multi-components is extremely crucial for the real-time monitoring of nutrients in fruits.Herein,a facile and user-friendly poly(carboxybetaine methacrylate)-coated paper-based microfluidic device(pCBMA-μPAD)has been exploited to synchronously identify and semi-quantify vitamin C.glucose,sucro se and fructose in fruits.The pCBMA was successfully grafted from the surface of paper sensor using a co nvenient and robust method,which was confirmed by Fourier transform infrared spectroscopy(FT-IR)and X-ray photoelectron spectrometry(XPS).The superior hydrophilicity and ultra-low fouling of pCBMA endowed the pCBMA-μPAD with remarkably rapid response(3 min),high sensitivity,good linear relationship and low detection limit(LOD)(vitamin C:y=33.809+5.175 x,R^2=0.993,LOD=0.179 mmol/L;glucose:y=-0.113+30.0661 g(x),R^2=0.988,LOD=0.095 mmol/L;sucrose:y--5.334+34.858 lg(x),R^2=0.996,LOD=0.097 mmol/L;fructose:y=4.996+23.325 lg(x),R^2=0.994,LOD=0.140 mmol/L).Furthermore,satisfactory results were yielded in the detection of these nutrients in 9 fruits,which were much agreed well with those obtained by spectrophotometry.Such a portable and versatile pCBMA-μPAD will pro foundly shape the future of food analysis,especially for the assessment of food quality and nutrition in the process of agricultural production and marketing.展开更多
It is still a challenge to simultaneously enhance coercivity(H_(cj))and remanence(J_(r))of hot-deformed Nd-Fe-B magnet due to the coercivity-remanence trade-off dilemma.Here,we achieved this balance between H_(cj)and ...It is still a challenge to simultaneously enhance coercivity(H_(cj))and remanence(J_(r))of hot-deformed Nd-Fe-B magnet due to the coercivity-remanence trade-off dilemma.Here,we achieved this balance between H_(cj)and Jr by flake Cu powder assisted DyF_(3)interflake addition.The Hcj increases from 1218 to 1496 kA/m and Jr increases from 1.32 to 1.34 T compared with the original magnet.Results show that the width of coarse grain layers reduces because of the introduction of flake Cu,which increases the contact areas of the adjacent grains at ribbon interfaces and suppresses the excessive growth of grains.The stronger degree of texture and higher density compared with the original magnet should take the responsibility for the increase of J_(r).Additionally,the aggregation regions of rare earth rich(RE-rich)phase reduce and the betterment of the microstructure is another reason for the enhancement of Jr in the flake Cu aided DyF_(3)hot-deformed magnet.This strategy of using flake powder additives provides a promising method for optimizing microstructure and enhancing magnetic properties of hot-deformed Nd-Fe-B magnets.展开更多
基金the National Natural Science Foundation of China (Grant No. 62003020)。
文摘We experimentally study the dynamic characteristics of a miniaturized spin-exchange relaxation-free(SERF) magnetometer based on uniform light field. The ceramic ferrule is used to expand the Gaussian beam to improve light intensity uniformity, while the volume of the sensor is also reduced. This scheme makes the magnetometer have better sensitivity when the detected light intensity is less than 3.16 m W/cm^(2) at 120℃. When the temperature rises to 150℃ the sensitivity under the action of uniform light field is 18.5 f T/Hz^(1/2). The bandwidth of the sensor remains at the original level and meets application needs. The proposed structure improves transverse polarization uniformity within the miniaturized sensor, which is ideal for the magnetoencephalography and magnetocardiography imaging systems.
基金Supported by National Natural Science Foundation of China(Grant No.51675400).
文摘Prostatic hyperplasia and tumor are common diseases,and the minimally invasive surgery inserting the instruments through the urethra into the prostate is commonly conducted.Taking the robotic manipulator for such surgery into consideration,this paper analyses the workspace of the end effector,and proposes the distribution error of the fixed point and the tracking error of manipulator end effector on the cone bottom surface of the workspace as the basis for control implementation of the manipulator.The D-H coordinate system of the manipulator is established and the trajectory planning of the end effector in the Cartesian space is carried out.The digital model was established,and dynamics simulation was performed in Solidworks and Matlab/Simulink environment to guide the manipulator design.Trajectory mapping and synchronization control between virtual model and the actual manipulator are realized based on digital twin technique.The virtual manipulator can reflect the real-time state of the manipulator with data interaction by comparing the dynamics simulation results with the motor current values obtained by experiment.Experiment was carried out with PD feedback control and Newton-Euler dynamics based feedforward control to get the trajectory tracking characteristic of each motor,errors of the fixed point and tracking performance of the end effector of the manipulator.The results show that compared with PD feedback control,feed forward control implementation can achieve a reduction of 30.0%in the average error of the fixed point of the manipulator and a reduction of 33.3%in the maximum error.
基金funded by the NSFC Grant(52177213)supported through NSFC Committee of Chinathe foundation(2020A1414010346 and 2019622163008)supported through the Science and Technology Bureau of Guangdong Governmentsponsored by the Student Research Program(X202110561688)supported through South China University of Technology。
文摘As a promising cathode material for sodium ion batteries,honeycomb-ordered layered Na_(3)Ni_(2)Sb O_(6)still suffers from rapid capacity fading because of partially irreversible phase transition.Herein,a substitution of Na+by Rb+with a larger ionic radius in honeycomb layered Na_(3)-xRbxNi_(2)Sb O_(6)is proposed to modulate the interlayer structure.The results unveil that biphasic transition reversibility of the intermediate P′3phase is substantially enhanced,and the structure evolution behavior during the charge/discharge process changes due to the structural modulation,which contributes to a suppression of the unfavorable O_(1)phase and an alleviation of the lattice distortion.Moreover,Rb substituted samples exhibited an improved Na+(de)intercalation thermodynamics and kinetics.Attributed to the modifications,the sample with optimized Rb content delivers superior cycle stability and rate capacity,demonstrating a feasible strategy for suppressing irreversible phase transition and developing high-performance honeycomb layered materials for sodium ion batteries.
基金the National Key R&D Program of China(2019YFA0110600)the National Natural Science Foundation of China(81970916,81870746)the support of State Key Laboratory of Oral Diseases,National Clinical Research Center for Oral Diseases,Department of Oral&Maxillofacial Surgery,West China Hospital of Stomatology,Sichuan University。
文摘The significant clinical feature of bisphosphonate-related osteonecrosis of the jaw(BRONJ)is the exposure of the necrotic jaw.Other clinical manifestations include jaw pain,swelling,abscess,and skin fistula,which seriously affect the patients’life,and there is no radical cure.Thus,new methods need to be found to prevent the occurrence of BRONJ.Here,a novel nanoparticle,t FNA-KLT,was successfully synthesized by us,in which the nanoparticle tetrahedral framework nucleic acid(tFNA)was used for carrying angiogenic peptide,KLT,and then further enhanced angiogenesis.TFNA-KLT possessed the same characteristics as tFNA,such as simple synthesis,stable structure,and good biocompatibility.Meanwhile,tFNA enhanced the stability of KLT and carried more KLT to interact with endothelial cells.First,it was confirmed that tFNA-KLT had the superior angiogenic ability to tFNA and KLT both in vitro and in vivo.Then we apply tFNA-KLT to the prevention of BRONJ.The results showed that tFNA-KLT can effectively prevent the occurrence of BRONJ by accelerating angiogenesis.In summary,the prepared novel nanoparticle,tFNA-KLT,was firstly synthesized by us.It was also firstly confirmed by us that tFNA-KLT significantly enhanced angiogenesis and can effectively prevent the occurrence of BRONJ by accelerating angiogenesis,thus providing a new avenue for the prevention of BRONJ and a new choice for therapeutic angiogenesis.
基金financially supported by the National Natural Science Foundation of China(No.51561009)the General Program of National Natural Science Foundation of Jiangxi Province(No.20192BAB206004)+2 种基金the Higher School Science and Technology Landing Project of Jiangxi Province(No.KJLD14043)the Doctoral Start-up Foundation of Jiangxi University of Science and Technology(No.3401223391)the China Scholarship Council(No.201703000006)for funding to visit Nanyang Technological University,Singapore.
文摘Grain boundary diffusion process(GBDP)serves as a promising approach in improving magnetic properties and thermal stability of Nd FeB permanent magnets.Herein,non-heavy rare earth Pr-Zn films deposited on the magnet surface using DC-magnetron sputtering system are reported.The thermal stability and coercivity enhancement mechanism of Pr-Zn GBDP magnets were investigated.Results show that the coercivity of Pr-Zn GBDP magnet increases from 963.96 kA m^-1 to 1317.14 kA m^-1 without any remanence reduction.Notably,the demagnetization curve of Pr-Zn GBDP magnet still remains a high squareness ratio.The temperature coefficient of coercivity and anti-demagnetization ability of Pr-Zn GBDP magnet under high temperatures are improved after GBDP treatment.The well-optimized rare earth-rich(RE-rich)grain boundary phases and high effective anisotropy field of(Nd,RE)2 Fe14 B magnetic hardening layers surrounding main grains are the key factors to impact the magnetic properties and thermal stability of Nd FeB permanent magnets via GBDP treatment.
基金supported by the National Key R&D Program of China(2019YFA0110600)National Natural Science Foundation of China(81970916,81671031)The National Major Scientific Equipment program(Grant No.2012YQ12008005).
文摘Choroidal neovascularization(CNV)is a common pathological feature of various eye diseases and an important cause of visual impairment in middle-aged and elderly patients.In previous studies,tetrahedral framework nucleic acids(tFNAs)showed good carrier performance.In this experiment,we developed microRNA-155-equipped tFNAs(T-155)and explored its biological effects on CNV.Based on the results of in-vitro experiments,T-155 could regulate macrophages into the antiangiogenic M1 type.Then,we injected T-155 into the vitreous of laser-induced CNV model mice and found that T-155 significantly reduced the size and area of CNV,inhibited blood vessel leakage.In summary,we prove that T-155 could regulate the inflammatory process of CNV by polarizing macrophages,thereby improving the symptoms of CNV.Thus,T-155 might become a new DNA-based drug with great potential for treating CNV.
基金This work was supported in part by the National Natural Science Foundation of China under grants(No.11571115 and No.12071149)Natural Science Foundation of Shanghai(No.19ZR1414100)Science and Technology Commission of Shanghai Municipality(No.18dz2271000).
文摘We consider optimal shape design in Stokes flow using H^(1) shape gradient flows based on the distributed Eulerian derivatives.MINI element is used for discretizations of Stokes equation and Galerkin finite element is used for discretizations of distributed and boundary H^(1) shape gradient flows.Convergence analysis with a priori error estimates is provided under general and different regularity assumptions.We investigate the performances of shape gradient descent algorithms for energy dissipation minimization and obstacle flow.Numerical comparisons in 2D and 3D show that the distributed H1 shape gradient flow is more accurate than the popular boundary type.The corresponding distributed shape gradient algorithm is more effective.
基金the support by the National Natural Science Foundation of China(No.51551201 and 51772137)the Fundamental Research Funds for the Central Universities(No.lzujbky-2019-sp03).
文摘Scalable pressureless sintering of nanocrystalline alumina(Al2O_(3))ceramics is a challenging problem with great scientific and technological interest.This challenge was addressed in our recent works utilizing ultrafine a-Al2O_(3) nanopowders with exceptional sinterability combined with two-step sintering technique.Here the sintering mechanism and kinetic parameters(grain boundary diffusivity and its activation energy)were analyzed from constant heating-rate sintering experiments by three different sintering models and compared with existing sintering data in the literature.We found that the lowtemperature sintering of 4.7 nm a-Al2O_(3) nanopowders can be well explained by conventional sintering mechanism via grain boundary diffusion,with reasonable activation energy of 4e5 eV that is smaller than that of coarse Al2O_(3) powders and enhanced diffusivity.However,unphysically small activation energy could be obtained if an inappropriate model was used.Lastly,successful two-step sintering was demonstrated under different heating rates.Our work illustrates that the exceptional sinterability of ultrafine a-Al2O_(3) nanopowders are most likely contributed by small size(short diffusion distance),large surface area(large sintering driving force)and good dispersity rather than new sintering mechanism,and highlights the importance of fast firing and the non-equilibrium nature for the low-temperature sintering of such nanopowders.
基金Project supported by the National Natural Science Foundation of China(51801085)Jiangxi Province Science and Technology Cooperation Key Project(20212BDH80007)。
文摘In view of the uneven distribution of the core-shell structure of sintered Nd-Fe-B magnets after grain boundary diffusion,this study proposes to use high-melting-point and reactive element titanium(Ti)as an additive to increase the diffusion channels and to enhance the diffusion of heavy rare earth elements along the grain boundary phase.By adding Ti element,the diffusion depth and hence the intrinsic coercivity of magnets are increased significantly.The addition of Ti increases the coercivity at two stages:initially from 16.07 to 16.29 kOe by addition effect,and then from 16.29 to 25.16 kOe by facilitating the diffusion of Tb element.The formation of TiB_(2) phase improves the periodic arrangement of the crystal structure in the surroundings of the grain boundary phase and enhances its activity.The improved grain boundary diffusion and better core-shell structure distribution provide a theoretical guidance fo r solving the problem of diffusion depth in bulk magnets.
基金financial supports from the National Key Research and Development Program of China(2019YFA0210103 and 2017YFA0104302)the National Natural Science Foundation of China(81901873,51832001,and 81971701)+2 种基金the National Key Laboratory of Science and Technology on Strong Electromagnetic Environment Simulation and Protection(6142205190402)the Natural Science Foundation of Jiangsu Province(BK20201352)the Program of Jiangsu Specially Appointed Professor。
基金financially supported by the Science and Technology Program of University of Jinan(Nos.XKY2103,XKY2105)National Natural Science Foundation of China(Nos.51902130,52072085)Key Research and Development project of Shandong Province(No.2019GGX102087)。
文摘Low-cost and efficient oxygen reduction reaction(ORR)electrocatalysts are the key to developing Zn-air batteries for renewable energy storage.Herein,the Mn-N-P doped carbon sphere was prepared through polymerization of hexachlorotripolyphosphazene(HCCP)and phloroglucinol,and then followed the calcination at 900°C.Theory calculations demonstrated the introduction of Mn in N-P doped carbon could lower the dissociation barrier of O2into O*and promote the ORR through a 4e-pathway.The asprepared catalysts exhibited a half-wave potential of 0.82 V vs.RHE and limiting current density of 5.2 m A/cm^(2)toward ORR,which was comparable to those of the commercial Pt/C catalysts.In addition,Zn-air batteries with 0.05 Mn-N-P-C catalysts showed a high specific capacity of 830 m Ah/gZnand excellent cycle stability.This facile approach demonstrated herein could be a solution to develop optimum non-precious metal catalysts for the application in cathodes of proton exchange membrane fuel cells.This study also provides new insight to design the catalysts of multi-heteroatom coordinated metal in the carbon matrix for both fundamental researches and practical applications.
基金Prof.Dehua DONG acknowledges the financial support by the National Natural Science Foundation of China(51872123)Jinan Science and Technology Bureau(2020GXRC033).
文摘Joule-heating reactors have the higher energy efficiency and product selectivity compared with the reactors based on radiative heating.Current Joule-heating reactors are constructed with electrically-conductive metals or carbon materials,and therefore suffer from stability issue due to the presence of corrosive or oxidizing gases during high-temperature reactions.In this study,chemicallystable and electrically-conductive(La_(0.80)Sr_(0.20))_(0.95)FeO_(3)(LSF)/Gd_(0.1)Ce_(0.9)O_(2)(GDC)ceramics have been used to construct Joule-heating reactors for the first time.Taking the advantage of the resistance decrease of the ceramic reactors with temperature increase,the ceramic reactors heated under current control mode achieved the automatic adjustment of heating to stabilize reactor temperatures.In addition,the electrical resistance of LSF/GDC reactors can be tuned by the content of the highconductive LSF in composite ceramics and ceramic density via sintering temperature,which offers flexibility to control reactor temperatures.The ceramic reactors with dendritic channels(less than 100μm in diameter)showed the catalytic activity for CO oxidation,which was further improved by coating efficient MnO_(2)nanocatalyst on reactor channel wall.The Joule-heating ceramic reactors achieved complete CO oxidation at a low temperature of 165℃.Therefore,robust ceramic reactors have successfully demonstrated effective Joule heating for CO oxidation,which are potentially applied in other high-temperature catalytic reactions.
基金financially supported by the National Natural Science Foundation of China(Nos.31701678,31801638)the Key Project of Shanghai Agriculture Prosperity through Science and Technology(No.2019-02-08-00-15-F01147)+1 种基金the Key Science and Technology Project of Henan(No.172102310586)China Post-Doctoral Science Foundation(No.2018T110338)。
文摘Rapid and simultaneous in situ detection of multi-components is extremely crucial for the real-time monitoring of nutrients in fruits.Herein,a facile and user-friendly poly(carboxybetaine methacrylate)-coated paper-based microfluidic device(pCBMA-μPAD)has been exploited to synchronously identify and semi-quantify vitamin C.glucose,sucro se and fructose in fruits.The pCBMA was successfully grafted from the surface of paper sensor using a co nvenient and robust method,which was confirmed by Fourier transform infrared spectroscopy(FT-IR)and X-ray photoelectron spectrometry(XPS).The superior hydrophilicity and ultra-low fouling of pCBMA endowed the pCBMA-μPAD with remarkably rapid response(3 min),high sensitivity,good linear relationship and low detection limit(LOD)(vitamin C:y=33.809+5.175 x,R^2=0.993,LOD=0.179 mmol/L;glucose:y=-0.113+30.0661 g(x),R^2=0.988,LOD=0.095 mmol/L;sucrose:y--5.334+34.858 lg(x),R^2=0.996,LOD=0.097 mmol/L;fructose:y=4.996+23.325 lg(x),R^2=0.994,LOD=0.140 mmol/L).Furthermore,satisfactory results were yielded in the detection of these nutrients in 9 fruits,which were much agreed well with those obtained by spectrophotometry.Such a portable and versatile pCBMA-μPAD will pro foundly shape the future of food analysis,especially for the assessment of food quality and nutrition in the process of agricultural production and marketing.
基金Project supported by the National Key Research and Development Program of China(2022YFB3505201,2022YFB3505400)the National Natural Science Foundation of China(52261034)the Natural Science Foundation of Jiangxi Province(20224BAB204015)。
文摘It is still a challenge to simultaneously enhance coercivity(H_(cj))and remanence(J_(r))of hot-deformed Nd-Fe-B magnet due to the coercivity-remanence trade-off dilemma.Here,we achieved this balance between H_(cj)and Jr by flake Cu powder assisted DyF_(3)interflake addition.The Hcj increases from 1218 to 1496 kA/m and Jr increases from 1.32 to 1.34 T compared with the original magnet.Results show that the width of coarse grain layers reduces because of the introduction of flake Cu,which increases the contact areas of the adjacent grains at ribbon interfaces and suppresses the excessive growth of grains.The stronger degree of texture and higher density compared with the original magnet should take the responsibility for the increase of J_(r).Additionally,the aggregation regions of rare earth rich(RE-rich)phase reduce and the betterment of the microstructure is another reason for the enhancement of Jr in the flake Cu aided DyF_(3)hot-deformed magnet.This strategy of using flake powder additives provides a promising method for optimizing microstructure and enhancing magnetic properties of hot-deformed Nd-Fe-B magnets.