Hydraulic simulation is one of the critical methods to research the filling mechanism of molten metal in the casting process.However,it only performs on test pieces with relatively simple structures due to the limitat...Hydraulic simulation is one of the critical methods to research the filling mechanism of molten metal in the casting process.However,it only performs on test pieces with relatively simple structures due to the limitation of the preparation method.In this study,the method of photocuring additive manufacturing was used to prepare the complex casting mould from transparent photosensitive resin.The pouring test was carried out under different centrifugal conditions,and the filling process of the gating system,support bars and other positions in the vertical direction was recorded and analyzed.The experimental results show that the internal liquid level and the filling process of the test piece prepared by this method can be observed clearly.The angle between the liquid surface and the horizontal plane in the test piece gradually increases as the centrifugal rotational speed increases,which means the filling process is carried out from outside to inside at high rotational speed.The velocity of the fluid entering the runner increases with the increase of rotational speed,but the filling speeds is less affected by the centrifugal speed at other positions.The liquid flow is continuous and stable during the forward filling process,without splashing or interruption of liquid droplets.展开更多
Industrial water splitting has long been suppressed by the sluggish kinetics of the oxygen evolution reaction(OER),which requires a catalyst to be efficient.Herein,we propose a molecular-level proton acceptor strategy...Industrial water splitting has long been suppressed by the sluggish kinetics of the oxygen evolution reaction(OER),which requires a catalyst to be efficient.Herein,we propose a molecular-level proton acceptor strategy to produce an efficient OER catalyst that can boost industrial-scale water splitting.Molecular-level phosphate(-PO_(4))group is introduced to modify the surface of PrBa_(0.5)Ca_(0.5)Co_(2)O_(5)+δ(PBCC).The achieved catalyst(PO_(4)-PBCC)exhibits significantly enhanced catalytic performance in alkaline media.Based on the X-ray absorption spectroscopy results and density functional theory(DFT)calculations,the PO_(4)on the surface,which is regarded as the Lewis base,is the key factor to overcome the kinetic limitation of the proton transfer process during the OER.The use of the catalyst in a membrane electrode assembly(MEA)is further evaluated for industrial-scale water splitting,and it only needs a low voltage of 1.66 V to achieve a large current density of 1 A cm^(-2).This work provides a new molecular-level strategy to develop highly efficient OER electrocatalysts for industrial applications.展开更多
Electrodeposition of aluminum from benzene-tetrahydrofuran-Al Cl3-Li Al H4 was studied at room temperature. Galvanostatic electrolysis was used to investigate the effect of various parameters on deposit morphology and...Electrodeposition of aluminum from benzene-tetrahydrofuran-Al Cl3-Li Al H4 was studied at room temperature. Galvanostatic electrolysis was used to investigate the effect of various parameters on deposit morphology and crystal size, including current density, temperature, molar ratio of benzene/tetrahydrofuran and stirring speed. The deposit microstructure was adjusted by changing the parameters, and the optimum operating conditions were determined. Dense, bright and adherent aluminum coatings were obtained over a wide range of current densities(10-25 m A/cm2), molar ratio of benzene and tetrahydrofuran(4:1 to 7:8) and stirring speeds(200-500 r/min). Smaller grain sizes and well-adhered deposits were obtained at lower temperatures. Aluminum-magnesium alloys could potentially be used as hydrogen storage materials. A novel method for Al-Mg deposition was proposed by using pure Mg anodes in the organic solvents system benzene-tetrahydrofuran-Al Cl3-Li Al H4. XRD shows that the aluminum-magnesium alloys are mainly Al3Mg2 and Al12Mg17.展开更多
Determination of dissolution rate of alumina is one of the classical problems in aluminum electrolysis. A novel method which can measure the dissolution rate of alumina was presented. Effect of factors on dissolution ...Determination of dissolution rate of alumina is one of the classical problems in aluminum electrolysis. A novel method which can measure the dissolution rate of alumina was presented. Effect of factors on dissolution rate of alumina was studied intuitively and roundly using transparent quartz electrobath and image analysis techniques. Images about dissolution process of alumina were taken at an interval of fixed time from transparent quartz electrobath of double rooms. Gabor wavelet transforms were used for extracting and describing the texture features of each image. After subsampling several times, the dissolution rate of alumina was computed using these texture features in local neighborhood of samples. Regression equation of the dissolution rate of alumina was obtained using these dissolution rates. Experiments show that the regression equation of the dissolution rate of alumina is y=-0.000 5x^3＋0.024 0x^2-0.287 3x＋ 1.276 7 for Na3AIF6-AIF3-Al2O3-CaF2-LiF- MgF2 system at 920 ℃.展开更多
Electrochemical deposition of aluminum on W electrode from AlCl3-NaCl melts was studied by cyclic voltammetry and chronopotentiometry. The results show that Al ( Ⅲ) is reduced in two consecutive steps, i.e., 4Al2Cl7-...Electrochemical deposition of aluminum on W electrode from AlCl3-NaCl melts was studied by cyclic voltammetry and chronopotentiometry. The results show that Al ( Ⅲ) is reduced in two consecutive steps, i.e., 4Al2Cl7-+3e-→Al+7AlCl4- and then AlCl4-+3e-→Al+4Cl-. The electrochemical reaction of 4Al2Cl7-+3e-→Al+7AlCl4- is reversible. Certain nucleation overpotential is required during the deposition of aluminum on W electrode. Chronopotentiometry analysis also shows that Al (Ⅲ ) is reduced in two consecutive steps under certain current density, which is in reasonable agreement with cyclic voltammograms. By using constant current deposition, the electrodeposits on Al substrate obtained at between 50 and 100 mA/cm2 are quite dense and well adherent to the Al substrate. The electrochemical deposition of aluminum on Cu substrate in AlCl3-NaCl melts indicates that the intermetallic compounds are formed. The intermetallic compounds are AlCu and Al2Cu.展开更多
Due to the extensive application of Al-Si alloys in the automotive and aerospace industries as structural components, an understanding of their microstructural formation, such as dendrite and(Al+Si) eutectic, is of gr...Due to the extensive application of Al-Si alloys in the automotive and aerospace industries as structural components, an understanding of their microstructural formation, such as dendrite and(Al+Si) eutectic, is of great importance to control the desirable microstructure, so as to modify the performance of castings. Since previous major themes of microstructural simulation are dendrite and regular eutectic growth, few efforts have been paid to simulate the irregular eutectic growth. Therefore, a multiphase cellular automaton(CA) model is developed and applied to simulate the time-dependent Al-Si irregular eutectic growth. Prior to model establishment, related experiments were carried out to investigate the influence of cooling rate and Sr modification on the growth of eutectic Si. This CA model incorporates several aspects, including growth algorithms and nucleation criterion, to achieve the competitive and cooperative growth mechanism for nonfaceted-faceted Al-Si irregular eutectic. The growth kinetics considers thermal undercooling, constitutional undercooling, and curvature undercooling, as well as the anisotropic characteristic of eutectic Si growth. The capturing rule takes into account the effects of modification on the silicon growth behaviors.The simulated results indicate that for unmodified alloy, the higher eutectic undercooling results in the higher eutectic growth velocity, and a more refined eutectic microstructure as well as narrower eutectic lamellar spacing. For modified alloy, the eutectic silicon tends to be obvious fibrous morphology and the morphology of eutectic Si is determined by both chemical modifier and cooling rate. The predicted microstructure of Al-7Si alloy under different solidification conditions shows that this proposed model can successfully reproduce both dendrite and eutectic microstructures.展开更多
The influences of surfactant type and concentration on the content and uniformity of SiC particles in Ni-SiC deposit were studied in this paper. The electrochemical behavior of preparing Ni-SiC composite coating was i...The influences of surfactant type and concentration on the content and uniformity of SiC particles in Ni-SiC deposit were studied in this paper. The electrochemical behavior of preparing Ni-SiC composite coating was investigated using the cyclic voltammetry method. Then the impact of surfactants on the deposition potential of Ni-SiC coating was analyzed. Electrochemical studies showed that the cathode overvoltage increases gradually with increasing SDS（Sodium dodecyl sulfate） concentration. The CV curve showed the shift towards a lower current at a given potential with increasing SDS concentration. Ni-SiC composite coatings were prepared by electrodeposition. The experimental results show that the dispersion of 40 nm SiC in Ni-SiC coating obtained in the electrolyte containing SDS is superior that containing CTAB（cetyltrimethyl ammonium bromide）. CTAB increases the content of 40 nm SiC particles in the Ni-SiC coating, but the uniformity of 40 nm SiC particles in Ni-SiC composite coating is poor. SiC particles are still agglomerated. Compared with the anionic surfactant SDS and the cationic surfactant CTAB, surfactant SDS makes the particles better dispersed. But the contribution of surfactant SDS for co-deposition amount of SiC particles is negligible. The cationic surfactant CTAB can effectively improve the suspension performance of SiC particles and promote the co-deposition of SiC particles and metallic nickel. But there is still some reunion of SiC.展开更多
Ti/TiN multilayer film was deposited on uranium surface by arc ion plating technique to improve fretting wear behavior. The morphology, structure and element distribution of the film were measured by scanning electric...Ti/TiN multilayer film was deposited on uranium surface by arc ion plating technique to improve fretting wear behavior. The morphology, structure and element distribution of the film were measured by scanning electric microscopy（SEM）, X-ray diffractometry（XRD） and Auger electron spectroscopy（AES）. Fretting wear tests of uranium and Ti/TiN multilayer film were carried out using pin-on-disc configuration. The fretting tests of uranium and Ti/TiN multilayer film were carried out under normal load of 20 N and various displacement amplitudes ranging from 5 to 100 μm. With the increase of the displacement amplitude, the fretting changed from partial slip regime（PSR） to slip regime（SR）. The coefficient of friction（COF） increased with the increase of displacement amplitude. The results indicated that the displacement amplitude had a strong effect on fretting wear behavior of the film. The damage of the film was very slight when the displacement amplitude was below 20 μm. The observations indicated that the delamination was the main wear mechanism of Ti/TiN multilayer film in PSR. The main wear mechanism of Ti/TiN multilayer film in SR was delamination and abrasive wear.展开更多
Ceramic cores are widely used in investment casting,and ideal properties of cores are essential for high-quality castings.Under the circumstances requiring thick cores,solid cores are likely to encounter deformation a...Ceramic cores are widely used in investment casting,and ideal properties of cores are essential for high-quality castings.Under the circumstances requiring thick cores,solid cores are likely to encounter deformation and cracking defects due to the accumulation of shrinkage.Therefore,with the superiority of ceramic stereolithography in producing complex ceramic parts,hollow cores with lattice structures were designed and fabricated.The dimensional accuracy and properties of the green and sintered bodies were evaluated.Results show the dimensional accuracy of sintered cores is controlled within±0.25 mm benefited from the precise green bodies.The mechanical properties are not obviously deteriorated.The bending strength reaches 11.94 MPa at room temperature and 12.87 MPa at 1,500℃ with a creep deformation of 0.345 mm.Furthermore,casting verifications prove that the hollow cores meet the requirements of investment casting.Smooth casting surfaces are obtained,at the same time,the core-removal efficiency is improved by over 3 times.展开更多
Four polyaniline-tea saponin (PTS) nanocomposites were prepared by an in-situ polymerization with tea saponin (TS) as a biosurfactant,and they were used to remove organic dyes from aqueous solution.The PTS nanocomposi...Four polyaniline-tea saponin (PTS) nanocomposites were prepared by an in-situ polymerization with tea saponin (TS) as a biosurfactant,and they were used to remove organic dyes from aqueous solution.The PTS nanocomposites were characterized by using field emission scanning electron microscopy,the Fourier transform infrared spectroscopy,the Ultraviolet-visible spectroscopy,and the thermogravimetric analysis.The adsorption performances of the PTS nanocomposites for organic dyes were studied by a static adsorption method.The experimental results reveal that adsorption capacities of the PTS nanocomposites are higher than that of pure polyaniline.Especially,the PTS nanocomposites exhibit excellent adsorption performances for anionic dyes because of the electrostatic interaction between the positively charged nitrogen atoms on the PTS chains and the negatively charged sulfonate ions in the anionic dyes.According to the adsorption kinetics and thermodynamics results,the adsorption processes of PTS20 for CR and AB74 follow well with the pseudo second-order and Langmuir isotherm models.It is indicated that TS should be very useful in the preparation of PTS nanocomposite and in removal of toxic dyes from waste water.展开更多
The adsorption of fibrinogen can be used as a quick indicator of surface haemocompatibility because of its prominent role in coagulation and platelet adhesion. In this work the molecular interaction between fibrinogen...The adsorption of fibrinogen can be used as a quick indicator of surface haemocompatibility because of its prominent role in coagulation and platelet adhesion. In this work the molecular interaction between fibrinogen and a modified titanium oxide surface/platelet has been studied by quartz crystal microbalanee with dissipation （QCM-D） in situ. In order to further characterize the conformation of adsorbed fibrinogen, αC and γ-chain antibody were used to check the orientation and denaturation of fibrinogen on solid surface. QCM-D investiga- tions revealed the fibrinogen have the trend to adsorb on hydropllilic surface in a side-on orientation by positively charged αC domains, which would reduce the exposure of platelet bonding site on γ chain and enable less platelet adhesion and be activated. These obser- vations suggest that certain conformations of adsorbed fibrinogen are less platelet adhesive than others, which opens a possibility for creating a non-platelet adhesive substrates.展开更多
Side reactions and dendrite growth triggered by the unstable interface and inhomogeneous deposition have become the biggest obstacle to the commercialization for lithium metal batteries.In this study,a highly-chlorina...Side reactions and dendrite growth triggered by the unstable interface and inhomogeneous deposition have become the biggest obstacle to the commercialization for lithium metal batteries.In this study,a highly-chlorinated organic-inorganic hybrid interfacial protective layer is developed by rationally tuning the interfacial passivation and robustness to achieve the convenient and efficient Li metal anode.The polyvinyl chloride(PVC)can effectively resist water and oxygen,which is confirmed by density functional theory.The organic-dominant solid electrolyte interphases(SEI)with lithium chloride are investigated by the X-ray photoelectron spectroscopy(XPS)with little mineralization of oxide,such as Li_(2)O and Li_(2)CO_(3).With such artificial SEI,a uniform and dense lithium deposition morphology are formed and an ultra-long stable cycle of over 500 h are achieved even at an ultra-high current density of 10 m A/cm^(2).Moreover,the simple and convenient protected anode also exhibits excellent battery stability when paired with the LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)and LiFePO_(4)(LFP)cathode,showing great potential for the commercial application of lithium metal batteries.展开更多
Electrochemical energy systems such as fuel cells and metal–air batteries can be used as clean power sources in the field of electric transportation and possess great potential in the reduction of various energy and ...Electrochemical energy systems such as fuel cells and metal–air batteries can be used as clean power sources in the field of electric transportation and possess great potential in the reduction of various energy and environmental issues.In these systems,the oxygen reduction reaction(ORR)at the cathode is the rate-determining factor for overall system performance,and up to now,platinum group metals supported on carbon materials,especially Pt,remain the highest performing and the most practical ORR electrocatalysts.However,corresponding carbonaceous catalyst supports are extremely susceptible to corrosion under electrochemical operation,and therefore,the extensive exploration of alternative stable materials for ORR electrocatalysts with both high electrochemical stability and catalytic performance is essential.Here,noncarbon materials with high corrosion resistance have been explored to substitute traditional carbon supports or even act directly as low-cost non-noble metal electrocatalysts,and based on this,this review will present a comprehensive overview and deep analysis of the recent progress in noncarbon materials,including metals,oxides,nitrides,carbides,sulfides,and so on.Overall,general attributes associated with noncarbon materials include high corrosion resistance,strong metal–support interaction,and impressive porous structure retention.However,major drawbacks include low electrical conductivity,insufficient chemical stability in acidic or alkaline media,and poor electrochemical stability at ORR electrode potentials.To overcome these challenges,this review will also summarize efficient strategies such as combining with highly conductive materials,introducing dopants and forming vacancies to result in promising electrocatalytic ORR performances.Finally,this review will propose possible research directions to facilitate future research and development toward the practical application of noncarbon-based ORR electrocatalysts.展开更多
The Er3+doped double perovskite Ba_(2)CaWO_(6) crystal is a promising ratiometric thermometer based on the fluorescence intensity ratio(FIR) of transitions from ^(2)H_(11/2) and ^(4)S_(3/2) to the lowered ^(4)I_(15/2)...The Er3+doped double perovskite Ba_(2)CaWO_(6) crystal is a promising ratiometric thermometer based on the fluorescence intensity ratio(FIR) of transitions from ^(2)H_(11/2) and ^(4)S_(3/2) to the lowered ^(4)I_(15/2) level.However,the Ca^(2+) vacancy defect caused by the charge difference between rare-earth ions and the substituted alkaline-earth ions gives rise to the non-radiative probability and limits the thermal sensitivity.Here,the up-conversion luminescence and thermometric performance of Er^(3+),Yb^(3+) dopedBa_(2)CaWO_(6) are tuned by tri-doping with alkaline ions.The Ca^(2+) vacancy defect can be eliminated by the introduction of Na^(+),which occupies the Ca^(2+) site when it is doped into Ba_(2)CaWO_(6) with Er^(3+) and Yb^(3+).On the contrary,the doping of Cs^(+) into Ba_(2)CaWO_(6) with Er^(3+) and Yb^(3+) enhances the defect concentration because it occupies the site of Ba^(2+).Thus,the tri-doping of Na^(+) reduces the non-radiative probability and enhances the quantum efficiency of Er^(3+),leading to the improvement of the thermometric sensitivity of Ba_(2)CaWO_(6).As a result,we get an excellent thermometric Ba_(2)CaWO_(6):8%Yb^(3+),3.5%Er^(3+),6%Na^(+) powder with a luminescence lifetime of 515 μs and maximum thermal sensitivity(S_(r)) of 1.45%/K,which is more than three times higher than that of the BCWO:Er^(3+) powder.展开更多
By doping Ni into YBa2Fe308＋w （YBFO） system, we obtained the phase YBa2Fe3-xNixO8＋w （YBFNO, x=0, 0.05, 0.10, 0.15, 0.30, 0.50, 1.00）. This paper discusses the changes in crystal structural, resistivity and magne...By doping Ni into YBa2Fe308＋w （YBFO） system, we obtained the phase YBa2Fe3-xNixO8＋w （YBFNO, x=0, 0.05, 0.10, 0.15, 0.30, 0.50, 1.00）. This paper discusses the changes in crystal structural, resistivity and magnetoresistivity （MR） of YBFO samples due to the incorporation of transition metal Ni. The results show that Ni substitution for partial Fe in YBFO does not substantially transform the structure of parent phase, but results in tiny changes in the lat- tice parameters. The YBFO crystal with Ni doped is semiconducting.展开更多
Li metal anodes have attracted tremendous attention in the last decade because of their high theoretical capacities and low electrochemical potentials.However,until now,there has only been limited success in improving...Li metal anodes have attracted tremendous attention in the last decade because of their high theoretical capacities and low electrochemical potentials.However,until now,there has only been limited success in improving the interfacial and structural stabilities and in realizing the highly controllable and large-scale fabrication of this emerging material;these limitations have posed great obstacles to further performing fundamental and applied studies in Li metal anodes.In this review,we focus on summarizing the existing challenges of Li metal anodes based on the leap from coin cells to pouch cells and on outlining typical methods for designing Li metal anodes on demand;we controllably engineer their surface protection layers and structure sizes by encapsulating structured Li metal inside a variety of synthetic protection layers.We aim to provide a comprehensive understanding and serve as a strategic guide for designing and fabricating practicable Li metal anodes for use in pouch batteries.Challenges and opportunities regarding this burgeoning field are critically evaluated at the end of this review.展开更多
The development of lithium-metal batteries(LMBs)is seriously restricted by the out-of-control dendrites growth and infinite volume expansion.Herein,a pervasive organic-inorganic layer construction strategy is reported...The development of lithium-metal batteries(LMBs)is seriously restricted by the out-of-control dendrites growth and infinite volume expansion.Herein,a pervasive organic-inorganic layer construction strategy is reported for the composite lithium metal anode with congener-derived organic-inorganic solid electrolyte interphase(SEI).In this strategy,the organic-inorganic Ag@polydopamine(Ag@PDA)layer is coated on the arbitrary substrates by a simple two-step method.The thin and stable congener-derived SEI is insitu formed with fewer inorganic components and more organic components during charging/discharging.The polydopamine with sufficient adhesion groups and lithiophilic Ag layer realize near-zero nucleation overpotential during lithium deposition.The low interface resistance and stable lithium deposition are achieved.Moreover,the practical areal and volumetric capacities of the composite anode with three-dimensional copper(3DCu)as the substrate are 10 mAh/cm^(2)and 1538 mAh/cm^3(vs.the mass of anode).The symmetrical cell shows very low polarization voltage(10 mV)and more than 2500 h cycles life at 1 mA/cm^(2)(1 mAh/cm^(2)).The LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)-based full cells show improved capacity retention(82%)after 100 cycles at 0.5 C.The modified lithiophilic anode with congener-derived interphase provides a promising strategy to realize the next-generation dendrite-free LMBs.展开更多
基金This work was financially supported by the National Science and Technology Major Project of China(Grant No.J2019-Ⅶ-0002-0142)the National Natural Science Foundation of China(Grant No.52175333).
文摘Hydraulic simulation is one of the critical methods to research the filling mechanism of molten metal in the casting process.However,it only performs on test pieces with relatively simple structures due to the limitation of the preparation method.In this study,the method of photocuring additive manufacturing was used to prepare the complex casting mould from transparent photosensitive resin.The pouring test was carried out under different centrifugal conditions,and the filling process of the gating system,support bars and other positions in the vertical direction was recorded and analyzed.The experimental results show that the internal liquid level and the filling process of the test piece prepared by this method can be observed clearly.The angle between the liquid surface and the horizontal plane in the test piece gradually increases as the centrifugal rotational speed increases,which means the filling process is carried out from outside to inside at high rotational speed.The velocity of the fluid entering the runner increases with the increase of rotational speed,but the filling speeds is less affected by the centrifugal speed at other positions.The liquid flow is continuous and stable during the forward filling process,without splashing or interruption of liquid droplets.
基金supported by the National Natural Sci-ence Foundation of China(22272081),Jiangsu Provincial Specially Appointed Professors Foundation.
文摘Industrial water splitting has long been suppressed by the sluggish kinetics of the oxygen evolution reaction(OER),which requires a catalyst to be efficient.Herein,we propose a molecular-level proton acceptor strategy to produce an efficient OER catalyst that can boost industrial-scale water splitting.Molecular-level phosphate(-PO_(4))group is introduced to modify the surface of PrBa_(0.5)Ca_(0.5)Co_(2)O_(5)+δ(PBCC).The achieved catalyst(PO_(4)-PBCC)exhibits significantly enhanced catalytic performance in alkaline media.Based on the X-ray absorption spectroscopy results and density functional theory(DFT)calculations,the PO_(4)on the surface,which is regarded as the Lewis base,is the key factor to overcome the kinetic limitation of the proton transfer process during the OER.The use of the catalyst in a membrane electrode assembly(MEA)is further evaluated for industrial-scale water splitting,and it only needs a low voltage of 1.66 V to achieve a large current density of 1 A cm^(-2).This work provides a new molecular-level strategy to develop highly efficient OER electrocatalysts for industrial applications.
基金Projects(51101104,51372156)supported by the National Natural Science Foundation of ChinaProject(LJQ2015074)supported by the Program for Liaoning Excellent Talents in University,China
文摘Electrodeposition of aluminum from benzene-tetrahydrofuran-Al Cl3-Li Al H4 was studied at room temperature. Galvanostatic electrolysis was used to investigate the effect of various parameters on deposit morphology and crystal size, including current density, temperature, molar ratio of benzene/tetrahydrofuran and stirring speed. The deposit microstructure was adjusted by changing the parameters, and the optimum operating conditions were determined. Dense, bright and adherent aluminum coatings were obtained over a wide range of current densities(10-25 m A/cm2), molar ratio of benzene and tetrahydrofuran(4:1 to 7:8) and stirring speeds(200-500 r/min). Smaller grain sizes and well-adhered deposits were obtained at lower temperatures. Aluminum-magnesium alloys could potentially be used as hydrogen storage materials. A novel method for Al-Mg deposition was proposed by using pure Mg anodes in the organic solvents system benzene-tetrahydrofuran-Al Cl3-Li Al H4. XRD shows that the aluminum-magnesium alloys are mainly Al3Mg2 and Al12Mg17.
基金Projects(51101104,51072121) supported by the National Natural Science Foundation of ChinaProject(LS2010109) supported by the Key Laboratory Foundation of Liaoning Province,China
文摘Determination of dissolution rate of alumina is one of the classical problems in aluminum electrolysis. A novel method which can measure the dissolution rate of alumina was presented. Effect of factors on dissolution rate of alumina was studied intuitively and roundly using transparent quartz electrobath and image analysis techniques. Images about dissolution process of alumina were taken at an interval of fixed time from transparent quartz electrobath of double rooms. Gabor wavelet transforms were used for extracting and describing the texture features of each image. After subsampling several times, the dissolution rate of alumina was computed using these texture features in local neighborhood of samples. Regression equation of the dissolution rate of alumina was obtained using these dissolution rates. Experiments show that the regression equation of the dissolution rate of alumina is y=-0.000 5x^3＋0.024 0x^2-0.287 3x＋ 1.276 7 for Na3AIF6-AIF3-Al2O3-CaF2-LiF- MgF2 system at 920 ℃.
基金Project(50672060) supported by the National Natural Science Foundation of ChinaProject(2007CB210305) supported by the National Basic Research Program of China
文摘Electrochemical deposition of aluminum on W electrode from AlCl3-NaCl melts was studied by cyclic voltammetry and chronopotentiometry. The results show that Al ( Ⅲ) is reduced in two consecutive steps, i.e., 4Al2Cl7-+3e-→Al+7AlCl4- and then AlCl4-+3e-→Al+4Cl-. The electrochemical reaction of 4Al2Cl7-+3e-→Al+7AlCl4- is reversible. Certain nucleation overpotential is required during the deposition of aluminum on W electrode. Chronopotentiometry analysis also shows that Al (Ⅲ ) is reduced in two consecutive steps under certain current density, which is in reasonable agreement with cyclic voltammograms. By using constant current deposition, the electrodeposits on Al substrate obtained at between 50 and 100 mA/cm2 are quite dense and well adherent to the Al substrate. The electrochemical deposition of aluminum on Cu substrate in AlCl3-NaCl melts indicates that the intermetallic compounds are formed. The intermetallic compounds are AlCu and Al2Cu.
基金financially supported by the National Basic Research Program of China(Grant No.2011CB706801)the National Natural Science Foundation of China(Grant No.51374137,51171089)the National Science and Technology Major Projects(Grant No.2012ZX04012-011,2011ZX04014-052)
文摘Due to the extensive application of Al-Si alloys in the automotive and aerospace industries as structural components, an understanding of their microstructural formation, such as dendrite and(Al+Si) eutectic, is of great importance to control the desirable microstructure, so as to modify the performance of castings. Since previous major themes of microstructural simulation are dendrite and regular eutectic growth, few efforts have been paid to simulate the irregular eutectic growth. Therefore, a multiphase cellular automaton(CA) model is developed and applied to simulate the time-dependent Al-Si irregular eutectic growth. Prior to model establishment, related experiments were carried out to investigate the influence of cooling rate and Sr modification on the growth of eutectic Si. This CA model incorporates several aspects, including growth algorithms and nucleation criterion, to achieve the competitive and cooperative growth mechanism for nonfaceted-faceted Al-Si irregular eutectic. The growth kinetics considers thermal undercooling, constitutional undercooling, and curvature undercooling, as well as the anisotropic characteristic of eutectic Si growth. The capturing rule takes into account the effects of modification on the silicon growth behaviors.The simulated results indicate that for unmodified alloy, the higher eutectic undercooling results in the higher eutectic growth velocity, and a more refined eutectic microstructure as well as narrower eutectic lamellar spacing. For modified alloy, the eutectic silicon tends to be obvious fibrous morphology and the morphology of eutectic Si is determined by both chemical modifier and cooling rate. The predicted microstructure of Al-7Si alloy under different solidification conditions shows that this proposed model can successfully reproduce both dendrite and eutectic microstructures.
基金the Program for Liaoning Excellent Talents in University(LJQ2015074)the Shenyang Science and Technology Plan(17-231-1-15)
文摘The influences of surfactant type and concentration on the content and uniformity of SiC particles in Ni-SiC deposit were studied in this paper. The electrochemical behavior of preparing Ni-SiC composite coating was investigated using the cyclic voltammetry method. Then the impact of surfactants on the deposition potential of Ni-SiC coating was analyzed. Electrochemical studies showed that the cathode overvoltage increases gradually with increasing SDS（Sodium dodecyl sulfate） concentration. The CV curve showed the shift towards a lower current at a given potential with increasing SDS concentration. Ni-SiC composite coatings were prepared by electrodeposition. The experimental results show that the dispersion of 40 nm SiC in Ni-SiC coating obtained in the electrolyte containing SDS is superior that containing CTAB（cetyltrimethyl ammonium bromide）. CTAB increases the content of 40 nm SiC particles in the Ni-SiC coating, but the uniformity of 40 nm SiC particles in Ni-SiC composite coating is poor. SiC particles are still agglomerated. Compared with the anionic surfactant SDS and the cationic surfactant CTAB, surfactant SDS makes the particles better dispersed. But the contribution of surfactant SDS for co-deposition amount of SiC particles is negligible. The cationic surfactant CTAB can effectively improve the suspension performance of SiC particles and promote the co-deposition of SiC particles and metallic nickel. But there is still some reunion of SiC.
基金Projects(U1530136,51375407) supported by the National Natural Science Foundation of ChinaProject(2017TD0017) supported by the Young Scientific Innovation Team of Science and Technology of Sichuan Province,China
文摘Ti/TiN multilayer film was deposited on uranium surface by arc ion plating technique to improve fretting wear behavior. The morphology, structure and element distribution of the film were measured by scanning electric microscopy（SEM）, X-ray diffractometry（XRD） and Auger electron spectroscopy（AES）. Fretting wear tests of uranium and Ti/TiN multilayer film were carried out using pin-on-disc configuration. The fretting tests of uranium and Ti/TiN multilayer film were carried out under normal load of 20 N and various displacement amplitudes ranging from 5 to 100 μm. With the increase of the displacement amplitude, the fretting changed from partial slip regime（PSR） to slip regime（SR）. The coefficient of friction（COF） increased with the increase of displacement amplitude. The results indicated that the displacement amplitude had a strong effect on fretting wear behavior of the film. The damage of the film was very slight when the displacement amplitude was below 20 μm. The observations indicated that the delamination was the main wear mechanism of Ti/TiN multilayer film in PSR. The main wear mechanism of Ti/TiN multilayer film in SR was delamination and abrasive wear.
基金supported by the National Natural Science Foundation of China (Grant No. 52175333)Tribology Science Fund of the State Key Laboratory of Tribology,Tsinghua University (Grant No. SKLT2021B05)+1 种基金Foshan Science and Technology Innovation Team Project (Grant No. 2018IT100142)National Science and Technology Major Project of China (Grant No. J2019-VII-0002-0142)
文摘Ceramic cores are widely used in investment casting,and ideal properties of cores are essential for high-quality castings.Under the circumstances requiring thick cores,solid cores are likely to encounter deformation and cracking defects due to the accumulation of shrinkage.Therefore,with the superiority of ceramic stereolithography in producing complex ceramic parts,hollow cores with lattice structures were designed and fabricated.The dimensional accuracy and properties of the green and sintered bodies were evaluated.Results show the dimensional accuracy of sintered cores is controlled within±0.25 mm benefited from the precise green bodies.The mechanical properties are not obviously deteriorated.The bending strength reaches 11.94 MPa at room temperature and 12.87 MPa at 1,500℃ with a creep deformation of 0.345 mm.Furthermore,casting verifications prove that the hollow cores meet the requirements of investment casting.Smooth casting surfaces are obtained,at the same time,the core-removal efficiency is improved by over 3 times.
文摘Four polyaniline-tea saponin (PTS) nanocomposites were prepared by an in-situ polymerization with tea saponin (TS) as a biosurfactant,and they were used to remove organic dyes from aqueous solution.The PTS nanocomposites were characterized by using field emission scanning electron microscopy,the Fourier transform infrared spectroscopy,the Ultraviolet-visible spectroscopy,and the thermogravimetric analysis.The adsorption performances of the PTS nanocomposites for organic dyes were studied by a static adsorption method.The experimental results reveal that adsorption capacities of the PTS nanocomposites are higher than that of pure polyaniline.Especially,the PTS nanocomposites exhibit excellent adsorption performances for anionic dyes because of the electrostatic interaction between the positively charged nitrogen atoms on the PTS chains and the negatively charged sulfonate ions in the anionic dyes.According to the adsorption kinetics and thermodynamics results,the adsorption processes of PTS20 for CR and AB74 follow well with the pseudo second-order and Langmuir isotherm models.It is indicated that TS should be very useful in the preparation of PTS nanocomposite and in removal of toxic dyes from waste water.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.9732011CB606200 and No.81330031） and Fundamentat Research Funds for the Central Universities （No.SWJTU11CX054）. The authors gratefully acknowledge assistance of Mr. Hai-bei Liu at Qsense company for consulting.
文摘The adsorption of fibrinogen can be used as a quick indicator of surface haemocompatibility because of its prominent role in coagulation and platelet adhesion. In this work the molecular interaction between fibrinogen and a modified titanium oxide surface/platelet has been studied by quartz crystal microbalanee with dissipation （QCM-D） in situ. In order to further characterize the conformation of adsorbed fibrinogen, αC and γ-chain antibody were used to check the orientation and denaturation of fibrinogen on solid surface. QCM-D investiga- tions revealed the fibrinogen have the trend to adsorb on hydropllilic surface in a side-on orientation by positively charged αC domains, which would reduce the exposure of platelet bonding site on γ chain and enable less platelet adhesion and be activated. These obser- vations suggest that certain conformations of adsorbed fibrinogen are less platelet adhesive than others, which opens a possibility for creating a non-platelet adhesive substrates.
基金supported by the National Key Research and Development Program of China(2020YFA0710303)the National Natural Science Foundation of China(52002072,U1905215,52072076)the Natural Science Foundation of Fujian Province(2021J01589,2023J05082)。
基金supported primarily by National Natural Science Foundation of China(Nos.22109025,51972061)National Key Research and Development Program of China(No.2020YFA0710303)Natural Science Foundation of Fujian Province,China(No.2021J05121)。
文摘Side reactions and dendrite growth triggered by the unstable interface and inhomogeneous deposition have become the biggest obstacle to the commercialization for lithium metal batteries.In this study,a highly-chlorinated organic-inorganic hybrid interfacial protective layer is developed by rationally tuning the interfacial passivation and robustness to achieve the convenient and efficient Li metal anode.The polyvinyl chloride(PVC)can effectively resist water and oxygen,which is confirmed by density functional theory.The organic-dominant solid electrolyte interphases(SEI)with lithium chloride are investigated by the X-ray photoelectron spectroscopy(XPS)with little mineralization of oxide,such as Li_(2)O and Li_(2)CO_(3).With such artificial SEI,a uniform and dense lithium deposition morphology are formed and an ultra-long stable cycle of over 500 h are achieved even at an ultra-high current density of 10 m A/cm^(2).Moreover,the simple and convenient protected anode also exhibits excellent battery stability when paired with the LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)and LiFePO_(4)(LFP)cathode,showing great potential for the commercial application of lithium metal batteries.
基金the Natural Science Foundation of China(Grant Nos.21606149,21832004,U1905215,and 51672046)Shanghai Rising-Star Program(18QB1404400)National Key Research and Development Program/Key Scientific Issues of Transformative Technology(2020YFA0710303).
文摘Electrochemical energy systems such as fuel cells and metal–air batteries can be used as clean power sources in the field of electric transportation and possess great potential in the reduction of various energy and environmental issues.In these systems,the oxygen reduction reaction(ORR)at the cathode is the rate-determining factor for overall system performance,and up to now,platinum group metals supported on carbon materials,especially Pt,remain the highest performing and the most practical ORR electrocatalysts.However,corresponding carbonaceous catalyst supports are extremely susceptible to corrosion under electrochemical operation,and therefore,the extensive exploration of alternative stable materials for ORR electrocatalysts with both high electrochemical stability and catalytic performance is essential.Here,noncarbon materials with high corrosion resistance have been explored to substitute traditional carbon supports or even act directly as low-cost non-noble metal electrocatalysts,and based on this,this review will present a comprehensive overview and deep analysis of the recent progress in noncarbon materials,including metals,oxides,nitrides,carbides,sulfides,and so on.Overall,general attributes associated with noncarbon materials include high corrosion resistance,strong metal–support interaction,and impressive porous structure retention.However,major drawbacks include low electrical conductivity,insufficient chemical stability in acidic or alkaline media,and poor electrochemical stability at ORR electrode potentials.To overcome these challenges,this review will also summarize efficient strategies such as combining with highly conductive materials,introducing dopants and forming vacancies to result in promising electrocatalytic ORR performances.Finally,this review will propose possible research directions to facilitate future research and development toward the practical application of noncarbon-based ORR electrocatalysts.
基金Project supported by the National Natural Science Foundation of China (51972061,22109025,22171045,52072076)。
文摘The Er3+doped double perovskite Ba_(2)CaWO_(6) crystal is a promising ratiometric thermometer based on the fluorescence intensity ratio(FIR) of transitions from ^(2)H_(11/2) and ^(4)S_(3/2) to the lowered ^(4)I_(15/2) level.However,the Ca^(2+) vacancy defect caused by the charge difference between rare-earth ions and the substituted alkaline-earth ions gives rise to the non-radiative probability and limits the thermal sensitivity.Here,the up-conversion luminescence and thermometric performance of Er^(3+),Yb^(3+) dopedBa_(2)CaWO_(6) are tuned by tri-doping with alkaline ions.The Ca^(2+) vacancy defect can be eliminated by the introduction of Na^(+),which occupies the Ca^(2+) site when it is doped into Ba_(2)CaWO_(6) with Er^(3+) and Yb^(3+).On the contrary,the doping of Cs^(+) into Ba_(2)CaWO_(6) with Er^(3+) and Yb^(3+) enhances the defect concentration because it occupies the site of Ba^(2+).Thus,the tri-doping of Na^(+) reduces the non-radiative probability and enhances the quantum efficiency of Er^(3+),leading to the improvement of the thermometric sensitivity of Ba_(2)CaWO_(6).As a result,we get an excellent thermometric Ba_(2)CaWO_(6):8%Yb^(3+),3.5%Er^(3+),6%Na^(+) powder with a luminescence lifetime of 515 μs and maximum thermal sensitivity(S_(r)) of 1.45%/K,which is more than three times higher than that of the BCWO:Er^(3+) powder.
基金supported by Funds from Center University of the Education Ministry (No. SWJTU09ZT24)
文摘By doping Ni into YBa2Fe308＋w （YBFO） system, we obtained the phase YBa2Fe3-xNixO8＋w （YBFNO, x=0, 0.05, 0.10, 0.15, 0.30, 0.50, 1.00）. This paper discusses the changes in crystal structural, resistivity and magnetoresistivity （MR） of YBFO samples due to the incorporation of transition metal Ni. The results show that Ni substitution for partial Fe in YBFO does not substantially transform the structure of parent phase, but results in tiny changes in the lat- tice parameters. The YBFO crystal with Ni doped is semiconducting.
基金supported by the National Natural Science Foundation of China(Nos.52071227,22109025)the Key Scientific Research Project in Shanxi Province(Grant No.201805D121003)+5 种基金the Special Found Projects for Central Government Guidance to Local Science and Technology Developmentthe Science and Technology Major Projects of Shanxi Province(20191102004)the Fundamental Research Program of Shanxi Province(202103021222006)the Natural Science Foundation of Shanxi Province(2019D111102)the Research Project Supported by Shanxi Scholarship Council of China(HGKY2019085)the Natural Science Foundation of Fujian Province,China(2021J05121).
文摘Li metal anodes have attracted tremendous attention in the last decade because of their high theoretical capacities and low electrochemical potentials.However,until now,there has only been limited success in improving the interfacial and structural stabilities and in realizing the highly controllable and large-scale fabrication of this emerging material;these limitations have posed great obstacles to further performing fundamental and applied studies in Li metal anodes.In this review,we focus on summarizing the existing challenges of Li metal anodes based on the leap from coin cells to pouch cells and on outlining typical methods for designing Li metal anodes on demand;we controllably engineer their surface protection layers and structure sizes by encapsulating structured Li metal inside a variety of synthetic protection layers.We aim to provide a comprehensive understanding and serve as a strategic guide for designing and fabricating practicable Li metal anodes for use in pouch batteries.Challenges and opportunities regarding this burgeoning field are critically evaluated at the end of this review.
基金financially supported by the National Key Research and Development Program/Key Scientific Issues of Transformative Technology (2020YFA0710303)the National Natural Science Foundation of China (U1905215 and 52072076)+1 种基金Fujian Science Foundation Grant (2022J01554)the Key Project of Science and Technology Innovation of Fujian Provincial Department of Education (2022G02002)。
基金supported primarily by the National Natural Science Foundation of China(No.22109025)National Key Research and Development Program of China(No.2020YFA0710303)Natural Science Foundation of Fujian Province,China(No.2021J05121)。
文摘The development of lithium-metal batteries(LMBs)is seriously restricted by the out-of-control dendrites growth and infinite volume expansion.Herein,a pervasive organic-inorganic layer construction strategy is reported for the composite lithium metal anode with congener-derived organic-inorganic solid electrolyte interphase(SEI).In this strategy,the organic-inorganic Ag@polydopamine(Ag@PDA)layer is coated on the arbitrary substrates by a simple two-step method.The thin and stable congener-derived SEI is insitu formed with fewer inorganic components and more organic components during charging/discharging.The polydopamine with sufficient adhesion groups and lithiophilic Ag layer realize near-zero nucleation overpotential during lithium deposition.The low interface resistance and stable lithium deposition are achieved.Moreover,the practical areal and volumetric capacities of the composite anode with three-dimensional copper(3DCu)as the substrate are 10 mAh/cm^(2)and 1538 mAh/cm^3(vs.the mass of anode).The symmetrical cell shows very low polarization voltage(10 mV)and more than 2500 h cycles life at 1 mA/cm^(2)(1 mAh/cm^(2)).The LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)-based full cells show improved capacity retention(82%)after 100 cycles at 0.5 C.The modified lithiophilic anode with congener-derived interphase provides a promising strategy to realize the next-generation dendrite-free LMBs.
