Based on the alloy Cu55Ni45 (at pct), holding the proportion of Cu to Ni in constant and in the temperature range of 1233~1573 K, the wetting angles of CuNi-0~56 at pct Ti alloys on Si3N4 have been measured by the ses...Based on the alloy Cu55Ni45 (at pct), holding the proportion of Cu to Ni in constant and in the temperature range of 1233~1573 K, the wetting angles of CuNi-0~56 at pct Ti alloys on Si3N4 have been measured by the sessile drop method. With the increase of Ti content, the wetting angles decreased. The equilibrium wetting angle was 5° when Ti content ≥32 at pct.In the case of same Ti content, the activity of Ti in CuNiTi alloy was weaker than that in CuTi alloy The cross-section of the CuNiTi-Si3N4 interface and the elements distribution were examined by scanning electron microscope with X-ray wave-dispersion spectrometer, and the reaction products formed at the interface were determined by X-ray diffiaction analysis method.展开更多
Reaction products of 2,4,6-tris(4-phenyl-phenoxy)-1,3,5-triazine derived from 4-phenylphenol cyanate ester and phenyl glycidyl ether were analyzed. In addition to an isocyanurate compound and an oxazolidone compound w...Reaction products of 2,4,6-tris(4-phenyl-phenoxy)-1,3,5-triazine derived from 4-phenylphenol cyanate ester and phenyl glycidyl ether were analyzed. In addition to an isocyanurate compound and an oxazolidone compound which were well known as reaction products of cyanate esters and epoxy resins, compounds with hybrid ring structure of cyanurate/isocyanurate were determined. Gibbs free energies of the compound having hybrid ring structure of cyanurate/isocyanurate with two isocyanurate moiety were found to be lower than that of the compound with cyanurate ring structure through calculations. Calculation data supported the existence of hybrid ring structure of cy-anurate/isocyanurate. It was revealed that isomerization from cyanurate to isocyanurate occurs via hybrid ring structure of cyanurate/isocyanurate in the reaction of aryl cyanurate and epoxy.展开更多
Using the highly accurate G4 method, we computed the thermodynamic data of 1287 possible reaction products under a wide range of reaction conditions in the Fischer-Tropcsh synthesis (FTS) process. These accurate therm...Using the highly accurate G4 method, we computed the thermodynamic data of 1287 possible reaction products under a wide range of reaction conditions in the Fischer-Tropcsh synthesis (FTS) process. These accurate thermodynamic data provide basic thermodynamic quantities for the actual chemical engineering process and are useful in analyzing product distribution because FTS demonstrates many features of an equilibrium-controlled system. Our results show that the number of thermodynamically allowed products to increase when lowering temperature, raising pressure, and raising H2/CO ratio. At low temperature, high pressure and high H2/CO ratio, many products are thermodynamically allowed and the selectivity of product has to be controlled by kinetic factors. On the other hand, high selectivity of lighter products can be realized in thermodynamics by raising temperature and lowering pressure. We found that the equilibrium product yield will reach a maximum and remain unchanged when lowering temperature, raising pressure, and raising H2/CO ratio to some limits, implying that optimizing reaction conditions has no effect on equilibrium product yields beyond these limits. The thermodynamic analysis is also useful in designing and evaluating FTS reaction mechanisms. We found that reaction pathways through formaldehyde should be discarded because of its extremely low equilibrium yield. Recently, in the FTS process using metal-oxide-zeolite catalysts for the highly selective production of C2-C4 olefins and aromatic hydrocarbons, there are several guesses on the possible reaction intermediates entering the zeolite channel. Our results show that ketene, methanol, and dimethyl ether are three possible reaction intermediates.展开更多
Metal-free catalyst for photocatalytic production of H_(2)O_(2)is highly desirable with the long-term vision of artificial photosynthesis of solar fuel.In particular,the specific chemical bonds for selective H_(2)O_(2...Metal-free catalyst for photocatalytic production of H_(2)O_(2)is highly desirable with the long-term vision of artificial photosynthesis of solar fuel.In particular,the specific chemical bonds for selective H_(2)O_(2)photosynthesis via 2e–oxygen reduction reactions(ORR)remain to be explored for understanding the forming mechanism of active sites.Herein,we report a facile doping method to introduce boron-nitrogen(B–N)bonds into the structure of graphitic carbon nitride(g-C_(3)N_(4))nanosheets(denoted as BCNNS)to provide significant photocatalytic activity,selectivity and stability.The theoretical calculation and experimental results reveal that the electron-deficient B–N units serving as electron acceptors improve photogenerated charge separation and transfer.The units are also proved to be superior active sites for selective O_(2)adsorption and activation,reducing the energy barrier for*OOH formation,and thereby enabling an efficient 2e–ORR pathway to H_(2)O_(2).Consequently,with only bare loss of activity during repeated cycles,the optimal H2O2 production rate by BCNNS photocatalysts reaches 1.16 mmol·L^(–1)·h^(–1)under 365 nm-monochrome light emitting diode(LED365nm)irradiation,increasing nearly 2–5 times as against the state-of-art metal-free photocatalysts.This work gives the first example of applying B–N bonds to enhance the photocatalytic H_(2)O_(2)production as well as unveiling the underlying reaction pathway for efficient solar-energy transformations.展开更多
Aging of a solid composite propellant containing HTPB/AP/AL was performed in order to validate the conformance of the accelerated aging data to the Arrhenius law. The main objective of the work was to examine the infl...Aging of a solid composite propellant containing HTPB/AP/AL was performed in order to validate the conformance of the accelerated aging data to the Arrhenius law. The main objective of the work was to examine the influence of the aziridine bonding agents family on the propellant aging. Aging of the prepared propellant samples was conducted as follows: 1. Four samples, one free of bonding agents, and three containing aziridine based bonding agents MAPO,HX-752, MAT4 were aged at 65°C. 2. Another four samples based on HX-752, MAT4 with different curing agents were aged at 65°C. The measured mechanical properties of the free bonding agent propellant samples were very far from the specifications and this illustrates the importance of the bonding agents in both the preparation and the aging phases.The prepared bonding agent 'MAT4' gave remarkable improvements of the mechanical properties comparing with HX-752 and MAPO. The aziridine bonding agents family inhibited the rate of decomposition of the propellant during the aging periods and supported the propellant matrix against decomposition at the elevate temperatures. Using of HMDI as curing agent gave slight better mechanical properties to the IPDI.展开更多
Electrochemical nitrate reduction reaction(NO_(3)RR)towards ammonia,as an emerging and appealing technology alternative to the energy-intensive Haber-Bosch process and inefficient nitrogen reduction reaction,has recen...Electrochemical nitrate reduction reaction(NO_(3)RR)towards ammonia,as an emerging and appealing technology alternative to the energy-intensive Haber-Bosch process and inefficient nitrogen reduction reaction,has recently aroused wide concern and research.However,the current research of the NO_(3)RR towards ammonia lacks the overall performance comparison of various electrocatalysts.Given this,we here make a comparison of 12 common transition metal oxide catalysts for the NO_(3)RR under a high cathodic current density of 0.25 A·cm^(-2),wherein Co_(3)O_(4) catalyst displays the highest ammonia Faradaic efficiency(85.15%)and moderate activity(ca.-0.25 V vs.reversible hydrogen electrode).Other external factors,such as nitrate concentrations in the electrolyte and applied potential ranges,have also been specifically investigated for the NO_(3)RR.展开更多
B4Cp/6061Al composites have become important structural and functional materials and can be fabricated by powder metallurgy and subsequent hot rolling. In this work, the effects of the hot-pressing temperature on micr...B4Cp/6061Al composites have become important structural and functional materials and can be fabricated by powder metallurgy and subsequent hot rolling. In this work, the effects of the hot-pressing temperature on microstructures and mechanical behaviors of the B4Cp/6061Al composites were investigated. The results showed that compared with the T4 heat treated B4Cp/6061Al composite hot pressed at 560℃, the yield strength and failure strain of the composites hot pressed at 580℃ were increased to 235 MPa and 18.4%, respectively. This was associated with the interface bonding strength between the B4C particles and the matrix. However, the reaction products, identified to be MgAl2O4 phases, were detected in the composites hot pressed at 600℃. The formation of the MgAl2O4 phases resulted in the Mg depletion, thus reducing the yield strength to 203.5 MPa after the T4 heat treatment due to the effect of the solid solution strengthening being weakened. In addition, the variation of hardness and electrical conductivity was mainly related to the Mg content in the matrix. Based on the as-rolled microstructures observed by SEM, SR-μCT and fracture surfaces, the deformation schematic diagram was depicted to reflect the tensile deformation process of the composites.展开更多
Photoelectrochemical oxygen reduction reaction(ORR)toward H_(2)O_(2)is highly desirable because only sunlight,O_(2)and water are required in the process.However,the corresponding studies are still at its infancy becau...Photoelectrochemical oxygen reduction reaction(ORR)toward H_(2)O_(2)is highly desirable because only sunlight,O_(2)and water are required in the process.However,the corresponding studies are still at its infancy because of the lack of suitable photocathodes,especially inorganic semiconductor photocathodes.In this work,we report CuBi_(2)O_(4)/CuO(CBO/CuO)heterojunction submicrocrystalline film photocathodes with efficient ORR activity for H_(2)O_(2)production.The heterojunction film photocathodes were prepared through thermal evaporation of Cu and Bi metals under vacuum and subsequent annealing treatment.Furthermore,the doping of Gd^(3+)ions into CBO/CuO could significantly enhance the yield of H_(2)O_(2).As a result,the concentration of H_(2)O_(2)could reach 1.3 mM within 30 min,which is 6 times higher than that obtained on the pristine CBO/CuO photocathode.The theoretical calculations suggested that the introduction of Gd could adjust the electronic structure of CBO surface and promote 2e ORR pathway for selective production of H_(2)O_(2).Our work not only provides a new strategy for designing highly efficient photocathode for H_(2)O_(2)production but also will evoke more interest in photoelectrocatalytic ORR through inorganic semiconductor photocathode.展开更多
Direct C—H functionalization of quinoline N-oxides with arylboronic acids is achieved using KMnOas the sole and efficient oxidative system.This method provides an efficient protocol to construct regioselectively 2-ar...Direct C—H functionalization of quinoline N-oxides with arylboronic acids is achieved using KMnOas the sole and efficient oxidative system.This method provides an efficient protocol to construct regioselectively 2-arylquinoline N-oxides via radical cross-coupling reaction in moderated to good yields under mild conditions.展开更多
Peroxymonosulfate(PMS)decomposition,hydroxyl radical(·OH)generation,and acetaminophen(ACT)degradation by the Co/PMS system using homogeneous(dissolved cobalt)and heterogeneous(suspended Co3O4)cobalt were assessed...Peroxymonosulfate(PMS)decomposition,hydroxyl radical(·OH)generation,and acetaminophen(ACT)degradation by the Co/PMS system using homogeneous(dissolved cobalt)and heterogeneous(suspended Co3O4)cobalt were assessed.For the homogeneous process,>99%PMS decomposition was observed and 10 mmol/L of·OH generation was produced using 5 mmol/L of PMS and different dissolved cobalt concentrations after 30 min.A dissolved cobalt concentration of 0.2 mmol/L was used to achieve>99%ACT degradation using the homogeneous process.For the heterogeneous process,60%PMS decomposition and negligible·OH generation were observed for 5 mmol/L of the initial PMS concentration using 0.1 and 0.2 g/L of Co3O4.Degradation of ACT greater than 80%was achieved for all experimental runs using 5 mmol/L of the initial PMS concentration independently of the initial Co3O4 load used.For the heterogeneous process,the best experimental conditions for ACT degradation were found to be 3 mmol/L of PMS and 0.2 g/L of Co3O4,for which>99%ACT degradation was achieved after 10 min.Because negligible·OH was produced by the Co3O4/PMS process,a second-order kinetic model was proposed for sulfur-based free radical production to allow fair comparison between homogeneous and heterogeneous processes.Using the kinetic data and the reaction by-products identified,a mechanistic pathway for ACT degradation is suggested.展开更多
文摘Based on the alloy Cu55Ni45 (at pct), holding the proportion of Cu to Ni in constant and in the temperature range of 1233~1573 K, the wetting angles of CuNi-0~56 at pct Ti alloys on Si3N4 have been measured by the sessile drop method. With the increase of Ti content, the wetting angles decreased. The equilibrium wetting angle was 5° when Ti content ≥32 at pct.In the case of same Ti content, the activity of Ti in CuNiTi alloy was weaker than that in CuTi alloy The cross-section of the CuNiTi-Si3N4 interface and the elements distribution were examined by scanning electron microscope with X-ray wave-dispersion spectrometer, and the reaction products formed at the interface were determined by X-ray diffiaction analysis method.
文摘Reaction products of 2,4,6-tris(4-phenyl-phenoxy)-1,3,5-triazine derived from 4-phenylphenol cyanate ester and phenyl glycidyl ether were analyzed. In addition to an isocyanurate compound and an oxazolidone compound which were well known as reaction products of cyanate esters and epoxy resins, compounds with hybrid ring structure of cyanurate/isocyanurate were determined. Gibbs free energies of the compound having hybrid ring structure of cyanurate/isocyanurate with two isocyanurate moiety were found to be lower than that of the compound with cyanurate ring structure through calculations. Calculation data supported the existence of hybrid ring structure of cy-anurate/isocyanurate. It was revealed that isomerization from cyanurate to isocyanurate occurs via hybrid ring structure of cyanurate/isocyanurate in the reaction of aryl cyanurate and epoxy.
基金the National Natural Science Foundation of China (No.91645201, No.21873019 and No.21573044).
文摘Using the highly accurate G4 method, we computed the thermodynamic data of 1287 possible reaction products under a wide range of reaction conditions in the Fischer-Tropcsh synthesis (FTS) process. These accurate thermodynamic data provide basic thermodynamic quantities for the actual chemical engineering process and are useful in analyzing product distribution because FTS demonstrates many features of an equilibrium-controlled system. Our results show that the number of thermodynamically allowed products to increase when lowering temperature, raising pressure, and raising H2/CO ratio. At low temperature, high pressure and high H2/CO ratio, many products are thermodynamically allowed and the selectivity of product has to be controlled by kinetic factors. On the other hand, high selectivity of lighter products can be realized in thermodynamics by raising temperature and lowering pressure. We found that the equilibrium product yield will reach a maximum and remain unchanged when lowering temperature, raising pressure, and raising H2/CO ratio to some limits, implying that optimizing reaction conditions has no effect on equilibrium product yields beyond these limits. The thermodynamic analysis is also useful in designing and evaluating FTS reaction mechanisms. We found that reaction pathways through formaldehyde should be discarded because of its extremely low equilibrium yield. Recently, in the FTS process using metal-oxide-zeolite catalysts for the highly selective production of C2-C4 olefins and aromatic hydrocarbons, there are several guesses on the possible reaction intermediates entering the zeolite channel. Our results show that ketene, methanol, and dimethyl ether are three possible reaction intermediates.
基金supported by the Jiangsu Provincial Double-Innovation Doctor Program(JSSCBS20210996).
文摘Metal-free catalyst for photocatalytic production of H_(2)O_(2)is highly desirable with the long-term vision of artificial photosynthesis of solar fuel.In particular,the specific chemical bonds for selective H_(2)O_(2)photosynthesis via 2e–oxygen reduction reactions(ORR)remain to be explored for understanding the forming mechanism of active sites.Herein,we report a facile doping method to introduce boron-nitrogen(B–N)bonds into the structure of graphitic carbon nitride(g-C_(3)N_(4))nanosheets(denoted as BCNNS)to provide significant photocatalytic activity,selectivity and stability.The theoretical calculation and experimental results reveal that the electron-deficient B–N units serving as electron acceptors improve photogenerated charge separation and transfer.The units are also proved to be superior active sites for selective O_(2)adsorption and activation,reducing the energy barrier for*OOH formation,and thereby enabling an efficient 2e–ORR pathway to H_(2)O_(2).Consequently,with only bare loss of activity during repeated cycles,the optimal H2O2 production rate by BCNNS photocatalysts reaches 1.16 mmol·L^(–1)·h^(–1)under 365 nm-monochrome light emitting diode(LED365nm)irradiation,increasing nearly 2–5 times as against the state-of-art metal-free photocatalysts.This work gives the first example of applying B–N bonds to enhance the photocatalytic H_(2)O_(2)production as well as unveiling the underlying reaction pathway for efficient solar-energy transformations.
文摘Aging of a solid composite propellant containing HTPB/AP/AL was performed in order to validate the conformance of the accelerated aging data to the Arrhenius law. The main objective of the work was to examine the influence of the aziridine bonding agents family on the propellant aging. Aging of the prepared propellant samples was conducted as follows: 1. Four samples, one free of bonding agents, and three containing aziridine based bonding agents MAPO,HX-752, MAT4 were aged at 65°C. 2. Another four samples based on HX-752, MAT4 with different curing agents were aged at 65°C. The measured mechanical properties of the free bonding agent propellant samples were very far from the specifications and this illustrates the importance of the bonding agents in both the preparation and the aging phases.The prepared bonding agent 'MAT4' gave remarkable improvements of the mechanical properties comparing with HX-752 and MAPO. The aziridine bonding agents family inhibited the rate of decomposition of the propellant during the aging periods and supported the propellant matrix against decomposition at the elevate temperatures. Using of HMDI as curing agent gave slight better mechanical properties to the IPDI.
基金supported by the Fundamental Research Funds for the Central Universities,China(No.20720210010)the National Natural Science Foundation of China(Nos.22001081,22075236)the Science and Technology Projects of Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province(IKKEM,No.HRTP-[2022]-7).
文摘Electrochemical nitrate reduction reaction(NO_(3)RR)towards ammonia,as an emerging and appealing technology alternative to the energy-intensive Haber-Bosch process and inefficient nitrogen reduction reaction,has recently aroused wide concern and research.However,the current research of the NO_(3)RR towards ammonia lacks the overall performance comparison of various electrocatalysts.Given this,we here make a comparison of 12 common transition metal oxide catalysts for the NO_(3)RR under a high cathodic current density of 0.25 A·cm^(-2),wherein Co_(3)O_(4) catalyst displays the highest ammonia Faradaic efficiency(85.15%)and moderate activity(ca.-0.25 V vs.reversible hydrogen electrode).Other external factors,such as nitrate concentrations in the electrolyte and applied potential ranges,have also been specifically investigated for the NO_(3)RR.
基金financial support of National Key Research and Development Program of China (No. 2017YFA0403803)the National Natural Science Foundation of China (Nos.51525401, 51774065, 51601028, 51690163)+1 种基金Dalian Support Plan for Innovation of High-level Talents (Top and Leading Talents, 2015R013)fundamental research funds for the central universities (Nos. DUT18RC(3)042, DUT17RC(3)108)
文摘B4Cp/6061Al composites have become important structural and functional materials and can be fabricated by powder metallurgy and subsequent hot rolling. In this work, the effects of the hot-pressing temperature on microstructures and mechanical behaviors of the B4Cp/6061Al composites were investigated. The results showed that compared with the T4 heat treated B4Cp/6061Al composite hot pressed at 560℃, the yield strength and failure strain of the composites hot pressed at 580℃ were increased to 235 MPa and 18.4%, respectively. This was associated with the interface bonding strength between the B4C particles and the matrix. However, the reaction products, identified to be MgAl2O4 phases, were detected in the composites hot pressed at 600℃. The formation of the MgAl2O4 phases resulted in the Mg depletion, thus reducing the yield strength to 203.5 MPa after the T4 heat treatment due to the effect of the solid solution strengthening being weakened. In addition, the variation of hardness and electrical conductivity was mainly related to the Mg content in the matrix. Based on the as-rolled microstructures observed by SEM, SR-μCT and fracture surfaces, the deformation schematic diagram was depicted to reflect the tensile deformation process of the composites.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.21673160 and 12075154)Natural Science Foundation of Zhejiang for Distinguished Young Scholars(No.LR16B010002)startup funds of Shaoxing University.
文摘Photoelectrochemical oxygen reduction reaction(ORR)toward H_(2)O_(2)is highly desirable because only sunlight,O_(2)and water are required in the process.However,the corresponding studies are still at its infancy because of the lack of suitable photocathodes,especially inorganic semiconductor photocathodes.In this work,we report CuBi_(2)O_(4)/CuO(CBO/CuO)heterojunction submicrocrystalline film photocathodes with efficient ORR activity for H_(2)O_(2)production.The heterojunction film photocathodes were prepared through thermal evaporation of Cu and Bi metals under vacuum and subsequent annealing treatment.Furthermore,the doping of Gd^(3+)ions into CBO/CuO could significantly enhance the yield of H_(2)O_(2).As a result,the concentration of H_(2)O_(2)could reach 1.3 mM within 30 min,which is 6 times higher than that obtained on the pristine CBO/CuO photocathode.The theoretical calculations suggested that the introduction of Gd could adjust the electronic structure of CBO surface and promote 2e ORR pathway for selective production of H_(2)O_(2).Our work not only provides a new strategy for designing highly efficient photocathode for H_(2)O_(2)production but also will evoke more interest in photoelectrocatalytic ORR through inorganic semiconductor photocathode.
基金supported by the Department of Henan Province Natural Science and Technology Foundation(No.142102210410)Natural Science Foundation in Henan Province Department of Education(No.17A150005)+1 种基金the Program for Innovative Research Team from Zhengzhou(No.131PCXTD605)Project of Youth Backbone Teachers of Henan University of Technology
文摘Direct C—H functionalization of quinoline N-oxides with arylboronic acids is achieved using KMnOas the sole and efficient oxidative system.This method provides an efficient protocol to construct regioselectively 2-arylquinoline N-oxides via radical cross-coupling reaction in moderated to good yields under mild conditions.
基金the economic support of Universidad de Guanajuato,(Grant No.18,Convocatoria Institucional de Apoyo a la Investigación Científica 2018)CONACyT for a graduate fellowship(Grant No.562419)。
文摘Peroxymonosulfate(PMS)decomposition,hydroxyl radical(·OH)generation,and acetaminophen(ACT)degradation by the Co/PMS system using homogeneous(dissolved cobalt)and heterogeneous(suspended Co3O4)cobalt were assessed.For the homogeneous process,>99%PMS decomposition was observed and 10 mmol/L of·OH generation was produced using 5 mmol/L of PMS and different dissolved cobalt concentrations after 30 min.A dissolved cobalt concentration of 0.2 mmol/L was used to achieve>99%ACT degradation using the homogeneous process.For the heterogeneous process,60%PMS decomposition and negligible·OH generation were observed for 5 mmol/L of the initial PMS concentration using 0.1 and 0.2 g/L of Co3O4.Degradation of ACT greater than 80%was achieved for all experimental runs using 5 mmol/L of the initial PMS concentration independently of the initial Co3O4 load used.For the heterogeneous process,the best experimental conditions for ACT degradation were found to be 3 mmol/L of PMS and 0.2 g/L of Co3O4,for which>99%ACT degradation was achieved after 10 min.Because negligible·OH was produced by the Co3O4/PMS process,a second-order kinetic model was proposed for sulfur-based free radical production to allow fair comparison between homogeneous and heterogeneous processes.Using the kinetic data and the reaction by-products identified,a mechanistic pathway for ACT degradation is suggested.
