Various novel double metal cyanide (DMC) catalysts were successfully prepared by modifying the central metal (M) and one of cyanide ion (CN-) in Zna[M(CN)b]c complex. Such modifications have significant impact...Various novel double metal cyanide (DMC) catalysts were successfully prepared by modifying the central metal (M) and one of cyanide ion (CN-) in Zna[M(CN)b]c complex. Such modifications have significant impact on the catalytic efficiency as well as the polymer selectivity for the reaction of PO/CO2. Zn-Ni(Ⅱ) DMC is a potential catalyst for alternating copolymerization of PO/CO2,and DMC catalysts based on Zn3[Co(CN)5X]2 (X = Br^- and N3^-) exhibit moderate efficiency for the production of polycarbonates.This research presents the preliminary exploration of novel DMC complex via chemical modification of its central metal and ligand.展开更多
Copolymerization of propylene oxide (PO) and ethylene oxide (EO) using double metal cyanide (DMC) complex as the catalyst was carried out. The structure of random copolymers was confirmed by C-13-NMR and IR spectra. H...Copolymerization of propylene oxide (PO) and ethylene oxide (EO) using double metal cyanide (DMC) complex as the catalyst was carried out. The structure of random copolymers was confirmed by C-13-NMR and IR spectra. H-1-NMR analysis shows that the EO content in the copolymer is the same as that in the initial monomer feed. Moderate molecular weight copolymers with various EO content were obtained and their values of molecular weight distribution (MWD) fell in the range of 1.21-1.55. It was found that the molecular weight of copolymers is controlled by the mass ratio of EO+PO to initiator moles used, The reaction rate as well as polymer yield decrease with increasing EO content in the feed composition.展开更多
MXene,an emerging two-dimensional(2D)layered material,has received worldwide attention in various energy storage systems because of its excellent properties.Nevertheless,the low capacity of pristine MXene restricts it...MXene,an emerging two-dimensional(2D)layered material,has received worldwide attention in various energy storage systems because of its excellent properties.Nevertheless,the low capacity of pristine MXene restricts its application in energy storage devices especially for the lithium-ion batteries(LIBs).To address the above issue,herein,a stable and highly conductive double transition metal MXene(Ti_(2)NbC_(2)T_(x)) is successfully fabricated,which provides enlarged interlayer spacing and excellent conductivity for fast ion diffusion and charge transfer.Taking the Ti_(2)NbC_(2)T_(x)s anode for LIBs,a superior specific capacity of 196.2 mAh·g-1and an excellent long-term cycling stability of~100%after 400cycles under 0.1 A·g^(-1) are achieved for LIBs.In particular,Ti_(2)NbC_(2)T_(x) delivers an impressive capacity retention of 81%over 4000 cycle under 1 A·g^(-1),outperforming the Ti_(3)C_(2)T_(x) and various previously reported MXene-based materials.Our results offer an attractive strategy for the future application of MXene-based materials.展开更多
Joining of aluminum to steel has attracted significant attention from the welding research community,automotive and rail transportation industries.Many current welding methods have been developed and applied,however,t...Joining of aluminum to steel has attracted significant attention from the welding research community,automotive and rail transportation industries.Many current welding methods have been developed and applied,however,they can not precisely control the heat input to work-piece,they are high costs,low efficiency and consist lots of complex welding devices,and the generated intermetallic compound layer in weld bead interface is thicker.A novel pulsed double electrode gas metal arc welding(Pulsed DE-GMAW)method is developed.To achieve a stable welding process for joining of aluminum to steel,a mathematical model of coupled arc is established,and a new control scheme that uses the average feedback arc voltage of main loop to adjust the wire feed speed to control coupled arc length is proposed and developed.Then,the impulse control simulation of coupled arc length,wire feed speed and wire extension is conducted to demonstrate the mathematical model and predict the stability of welding process by changing the distance of contact tip to work-piece(CTWD).To prove the proposed PSO based PID control scheme’s feasibility,the rapid prototyping experimental system is setup and the bead-on-plate control experiments are conducted to join aluminum to steel.The impulse control simulation shows that the established model can accurately represent the variation of coupled arc length,wire feed speed and the average main arc voltage when the welding process is disturbed,and the developed controller has a faster response and adjustment,only runs about 0.1 s.The captured electric signals show the main arc voltage gradually closes to the supposed arc voltage by adjusting the wire feed speed in 0.8 s.The obtained typical current waveform demonstrates that the main current can be reduced by controlling the bypass current under maintaining a relative large total current.The control experiment proves the accuracy of proposed model and feasibility of new control scheme further.The beautiful and smooth weld beads are also obtained by this method.Pulsed DE-GMAW can thus be considered as an alternative method for low cost,high efficiency joining of aluminum to steel.展开更多
Double slag process was adopted to produce low-phosphorus steel from middle-phosphorus hot metal.To achieve a stable dephosphorization operation,conventional process was modified as follows:the blowing time was exten...Double slag process was adopted to produce low-phosphorus steel from middle-phosphorus hot metal.To achieve a stable dephosphorization operation,conventional process was modified as follows:the blowing time was extended by approximately 1min by reducing the oxygen supply flow rate;calcium ferrite pellets were added to adjust the slag composition and viscosity;the dumping temperature was lowered by 30-50°C by the addition of calcium ferrite pellets during the double slag process to prevent phosphorus in the slag from returning to the molten steel;and the bottom-blown gas flow was increased during the blowing process.For 40 heats of comparative experiments,the rate of dephosphorization reached 91% and ranged between 87% and 95%;the phosphorus,sulfur,manganese,and oxygen contents calculated according to the compositions of molten steel and slag as well as the temperature of molten steel at the end-point of the basic oxygen furnace process were similar to the equilibrium values for the reaction between the slag and the steel.Less free calcium oxide and metallic iron were present in the final slag,and the surface of the slag mineral phase was smooth,clear,and well developed,which showed that the slag exhibited better melting effects than that produced using the conventional slag process.A steady phosphorus capacity in the slag and stable dephosphorization effects were achieved.展开更多
The action of the composite heat source model in DE-GMAW has been carried out according to the characteristics of the DE-GMA W process, and the distribution of surface and body heat source was analyzed. The weld tempe...The action of the composite heat source model in DE-GMAW has been carried out according to the characteristics of the DE-GMA W process, and the distribution of surface and body heat source was analyzed. The weld temperature field distribution has been derived from the appropriate boundary conditions and the thermal physical property parameters by COMSOL software. The effects of the positions of the surface and body heat source on the cross- sectional shape were investigated by studying the experimental welding thermal cycle curve. The simulated results are fully compliant with the experimental data under the same conditions. This illustrates that the composite heat source model is correct. It reflects the thermal mechanism of DE-GMA W process, and reveals the internal influence of weld shaping.展开更多
A new double alkali metal borate,LiRbB8O13,has been obtained in the sealed system.Its structure consists of two kinds of independent interpenetrating 3D frameworks composed of the fundamental building block,[B8O16]8–...A new double alkali metal borate,LiRbB8O13,has been obtained in the sealed system.Its structure consists of two kinds of independent interpenetrating 3D frameworks composed of the fundamental building block,[B8O16]8–.It crystallizes in the P21/c space group with a=10.950(6),b=7.689(4),c=11.375(7)?,β=96.653(7)°,V=951.2(9)?3,Z=4,F(000)=736,Dc=2.702 g/cm3,Mr=386.89 andμ=5.289 mm–1.The final R=0.0547 and w R=0.1224.The UV-Vis-NIR diffuse reflectance spectrum,infrared spectrum and the first-principle theoretical studies show that the title compound possesses a short cut-off edge and large birefringence.展开更多
Non-enzymatic electrochemical sensors for the determination of hydrogen peroxide(H_(2)O_(2))have attracted more and more concerns.A series of nickel and cobalt double oxides(Ni_(x)Co_(y)-DO)with the different ratios o...Non-enzymatic electrochemical sensors for the determination of hydrogen peroxide(H_(2)O_(2))have attracted more and more concerns.A series of nickel and cobalt double oxides(Ni_(x)Co_(y)-DO)with the different ratios of Ni/Co have been prepared by a polyol-mediated solvothermal method for H_(2)O_(2)detection.The obtained products exhibit honeycomb-like open porous microtubes constituted with the low-dimensional nanostructured Ni_(x)Co_(y)-DO blocks after the calcination treatment.Compared with nickel oxides,the introduced Co ions in Ni_(x)Co_(y)-DO can induce the production of surficial oxygen vacancies,and further enhance the electrode surface activity.In particular,the NiCo-DO sample(with an atomic ratio of Ni/Co=4:3)shows the richest surficial oxygen vacancies and presents the highest H_(2)O_(2)detection activity among all the as-prepared samples,demonstrating an excellent sensitivity of698.60μAL mmol^(-1)cm^(-2)(0~0.4 mmol/L),low detection limit(0.28μmol/L,S/N=3),as well as long stability,high selectivity and good reproducibility.This work lends a new impetus to the potential application of double metal oxides for the next generation of non-enzymatic sensors.展开更多
Herein,we prepared a bimetallic layered double hydroxide(FeCo LDH)featuring a dandelion-like structure.Anchoring of CeO_(2)onto FeCo LDH produced interfaces between the functionalizing CeO_(2)and the parent LDH.Compar...Herein,we prepared a bimetallic layered double hydroxide(FeCo LDH)featuring a dandelion-like structure.Anchoring of CeO_(2)onto FeCo LDH produced interfaces between the functionalizing CeO_(2)and the parent LDH.Comparative electrochemical studies were carried out.Onset potential,overpotential,and Tafel slope point to the superior oxygen-evolving performance of CeO_(2)-FeCo LDH with respect to FeCo LDH,therefore,demonstrating the merits of CeO_(2)functionalization.The electronic structures of Fe,Co,and Ce were analyzed by X-ray photoelectron spectroscopy(XPS)and electron energy loss spectroscopy(EELS)from which the increase of Co^(3+)and the concurrent lowering of Ce^(4+)were established.With the use of CeO_(2)-FeCo LDH,accelerated formation at a sizably reduced potential of Co-OOH,one of the key intermediates preceding the release of O_(2)was observed by in situ Raman spectroscopy.We now have the atomic-level and location-specific evidence,the increase of the active Co^(3+)across the interface to correlate the enhanced catalytic performance with CeO_(2)functionalization.展开更多
基金the National Natural Science Foundation of China(No.50273031)China Postdoctoral Science Foundation(No.20060400339).
文摘Various novel double metal cyanide (DMC) catalysts were successfully prepared by modifying the central metal (M) and one of cyanide ion (CN-) in Zna[M(CN)b]c complex. Such modifications have significant impact on the catalytic efficiency as well as the polymer selectivity for the reaction of PO/CO2. Zn-Ni(Ⅱ) DMC is a potential catalyst for alternating copolymerization of PO/CO2,and DMC catalysts based on Zn3[Co(CN)5X]2 (X = Br^- and N3^-) exhibit moderate efficiency for the production of polycarbonates.This research presents the preliminary exploration of novel DMC complex via chemical modification of its central metal and ligand.
文摘Copolymerization of propylene oxide (PO) and ethylene oxide (EO) using double metal cyanide (DMC) complex as the catalyst was carried out. The structure of random copolymers was confirmed by C-13-NMR and IR spectra. H-1-NMR analysis shows that the EO content in the copolymer is the same as that in the initial monomer feed. Moderate molecular weight copolymers with various EO content were obtained and their values of molecular weight distribution (MWD) fell in the range of 1.21-1.55. It was found that the molecular weight of copolymers is controlled by the mass ratio of EO+PO to initiator moles used, The reaction rate as well as polymer yield decrease with increasing EO content in the feed composition.
基金supported by the National Science,Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources&Institutional Development,Research and Innovation(No.B05F640153)the National Research Council of Thailand(NRCT)(No.NRCT5-RSA63001-19)+2 种基金the National Natural Science Foundation of China(No.52125405)the National Key R&D Program of China(No.2018YFA0703602)financially supporting from the Second Century Fund(C2F),Chulalongkorn University。
文摘MXene,an emerging two-dimensional(2D)layered material,has received worldwide attention in various energy storage systems because of its excellent properties.Nevertheless,the low capacity of pristine MXene restricts its application in energy storage devices especially for the lithium-ion batteries(LIBs).To address the above issue,herein,a stable and highly conductive double transition metal MXene(Ti_(2)NbC_(2)T_(x)) is successfully fabricated,which provides enlarged interlayer spacing and excellent conductivity for fast ion diffusion and charge transfer.Taking the Ti_(2)NbC_(2)T_(x)s anode for LIBs,a superior specific capacity of 196.2 mAh·g-1and an excellent long-term cycling stability of~100%after 400cycles under 0.1 A·g^(-1) are achieved for LIBs.In particular,Ti_(2)NbC_(2)T_(x) delivers an impressive capacity retention of 81%over 4000 cycle under 1 A·g^(-1),outperforming the Ti_(3)C_(2)T_(x) and various previously reported MXene-based materials.Our results offer an attractive strategy for the future application of MXene-based materials.
基金Supported by National Natural Science Foundation of China(Grant No.51165023)Project of International Cooperation and Exchanges of National Natural Science Foundation of China(Grant No.51210105024)+1 种基金Financial Commission of Gansu Province of Chinathe Hong Liu Outstanding Talent Training Plan of Lanzhou University of Technology,China(Grant No.J201201)
文摘Joining of aluminum to steel has attracted significant attention from the welding research community,automotive and rail transportation industries.Many current welding methods have been developed and applied,however,they can not precisely control the heat input to work-piece,they are high costs,low efficiency and consist lots of complex welding devices,and the generated intermetallic compound layer in weld bead interface is thicker.A novel pulsed double electrode gas metal arc welding(Pulsed DE-GMAW)method is developed.To achieve a stable welding process for joining of aluminum to steel,a mathematical model of coupled arc is established,and a new control scheme that uses the average feedback arc voltage of main loop to adjust the wire feed speed to control coupled arc length is proposed and developed.Then,the impulse control simulation of coupled arc length,wire feed speed and wire extension is conducted to demonstrate the mathematical model and predict the stability of welding process by changing the distance of contact tip to work-piece(CTWD).To prove the proposed PSO based PID control scheme’s feasibility,the rapid prototyping experimental system is setup and the bead-on-plate control experiments are conducted to join aluminum to steel.The impulse control simulation shows that the established model can accurately represent the variation of coupled arc length,wire feed speed and the average main arc voltage when the welding process is disturbed,and the developed controller has a faster response and adjustment,only runs about 0.1 s.The captured electric signals show the main arc voltage gradually closes to the supposed arc voltage by adjusting the wire feed speed in 0.8 s.The obtained typical current waveform demonstrates that the main current can be reduced by controlling the bypass current under maintaining a relative large total current.The control experiment proves the accuracy of proposed model and feasibility of new control scheme further.The beautiful and smooth weld beads are also obtained by this method.Pulsed DE-GMAW can thus be considered as an alternative method for low cost,high efficiency joining of aluminum to steel.
基金financially supported by the Beijing Natural Science Foundation of China(No.2172057)
文摘Double slag process was adopted to produce low-phosphorus steel from middle-phosphorus hot metal.To achieve a stable dephosphorization operation,conventional process was modified as follows:the blowing time was extended by approximately 1min by reducing the oxygen supply flow rate;calcium ferrite pellets were added to adjust the slag composition and viscosity;the dumping temperature was lowered by 30-50°C by the addition of calcium ferrite pellets during the double slag process to prevent phosphorus in the slag from returning to the molten steel;and the bottom-blown gas flow was increased during the blowing process.For 40 heats of comparative experiments,the rate of dephosphorization reached 91% and ranged between 87% and 95%;the phosphorus,sulfur,manganese,and oxygen contents calculated according to the compositions of molten steel and slag as well as the temperature of molten steel at the end-point of the basic oxygen furnace process were similar to the equilibrium values for the reaction between the slag and the steel.Less free calcium oxide and metallic iron were present in the final slag,and the surface of the slag mineral phase was smooth,clear,and well developed,which showed that the slag exhibited better melting effects than that produced using the conventional slag process.A steady phosphorus capacity in the slag and stable dephosphorization effects were achieved.
基金supported by the National Natural Science Foundation of China(Grant No.51165023)
文摘The action of the composite heat source model in DE-GMAW has been carried out according to the characteristics of the DE-GMA W process, and the distribution of surface and body heat source was analyzed. The weld temperature field distribution has been derived from the appropriate boundary conditions and the thermal physical property parameters by COMSOL software. The effects of the positions of the surface and body heat source on the cross- sectional shape were investigated by studying the experimental welding thermal cycle curve. The simulated results are fully compliant with the experimental data under the same conditions. This illustrates that the composite heat source model is correct. It reflects the thermal mechanism of DE-GMA W process, and reveals the internal influence of weld shaping.
基金supported by the National Natural Science Foundation of China(61835014,U1703127,51972336)Shanghai Cooperation Organization Science and Technology Partnership Program(2020E01019)+1 种基金Xinjiang Outstanding Young Talents in Science and Technology(2018Q004)Fujian Institute of Innovation,CAS。
文摘A new double alkali metal borate,LiRbB8O13,has been obtained in the sealed system.Its structure consists of two kinds of independent interpenetrating 3D frameworks composed of the fundamental building block,[B8O16]8–.It crystallizes in the P21/c space group with a=10.950(6),b=7.689(4),c=11.375(7)?,β=96.653(7)°,V=951.2(9)?3,Z=4,F(000)=736,Dc=2.702 g/cm3,Mr=386.89 andμ=5.289 mm–1.The final R=0.0547 and w R=0.1224.The UV-Vis-NIR diffuse reflectance spectrum,infrared spectrum and the first-principle theoretical studies show that the title compound possesses a short cut-off edge and large birefringence.
基金supported by the National Natural Science Foundation of China(Nos.51432003,51802011 and 51125007)the Start-Up Fund for Talent Introduction of Beijing University of Chemical Technology(No.buctrc201806)the Fundamental Research Funds for the Central Universities(No.JD2010)。
文摘Non-enzymatic electrochemical sensors for the determination of hydrogen peroxide(H_(2)O_(2))have attracted more and more concerns.A series of nickel and cobalt double oxides(Ni_(x)Co_(y)-DO)with the different ratios of Ni/Co have been prepared by a polyol-mediated solvothermal method for H_(2)O_(2)detection.The obtained products exhibit honeycomb-like open porous microtubes constituted with the low-dimensional nanostructured Ni_(x)Co_(y)-DO blocks after the calcination treatment.Compared with nickel oxides,the introduced Co ions in Ni_(x)Co_(y)-DO can induce the production of surficial oxygen vacancies,and further enhance the electrode surface activity.In particular,the NiCo-DO sample(with an atomic ratio of Ni/Co=4:3)shows the richest surficial oxygen vacancies and presents the highest H_(2)O_(2)detection activity among all the as-prepared samples,demonstrating an excellent sensitivity of698.60μAL mmol^(-1)cm^(-2)(0~0.4 mmol/L),low detection limit(0.28μmol/L,S/N=3),as well as long stability,high selectivity and good reproducibility.This work lends a new impetus to the potential application of double metal oxides for the next generation of non-enzymatic sensors.
基金This work was financially supported by Shenzhen Nobel Prize Scientists Laboratory Project(No.C17213101)Guangdong Provincial Key Laboratory of Catalysis(No.2020B121201002)+6 种基金Guangdong Provincial Key Laboratory of Energy Materials for Electric Power(No.2018B030322001)China Postdoctoral Science Foundation(No.2018M642133,X.Y.Z.)Post-doctorate Scientific Research Fund for staying(coming to)Shenzhen(No.K21217502,X.Y.Z.)the National Natural Science Foundation of China(No.21671096,Z.G.L.)Shenzhen Key Laboratory of Interfacial Science and Engineering of Materials(No.ZDSYS20200421111401738,Z.G.L.)The authors also acknowledge the assistance of Southern University of Science and Technology Core Research Facilities(SUSTech CRF)Key Laboratory of Energy Conversion and Storage Technologies(Southern University of Science and Technology).
文摘Herein,we prepared a bimetallic layered double hydroxide(FeCo LDH)featuring a dandelion-like structure.Anchoring of CeO_(2)onto FeCo LDH produced interfaces between the functionalizing CeO_(2)and the parent LDH.Comparative electrochemical studies were carried out.Onset potential,overpotential,and Tafel slope point to the superior oxygen-evolving performance of CeO_(2)-FeCo LDH with respect to FeCo LDH,therefore,demonstrating the merits of CeO_(2)functionalization.The electronic structures of Fe,Co,and Ce were analyzed by X-ray photoelectron spectroscopy(XPS)and electron energy loss spectroscopy(EELS)from which the increase of Co^(3+)and the concurrent lowering of Ce^(4+)were established.With the use of CeO_(2)-FeCo LDH,accelerated formation at a sizably reduced potential of Co-OOH,one of the key intermediates preceding the release of O_(2)was observed by in situ Raman spectroscopy.We now have the atomic-level and location-specific evidence,the increase of the active Co^(3+)across the interface to correlate the enhanced catalytic performance with CeO_(2)functionalization.