Using XRD,TEM and VSM methods,the phase,morphology and magnetic property of iron hydroxide oxide(FeOOH) which has been prepared by low-temperature neutralization reaction under different magnetic fields were analyzed....Using XRD,TEM and VSM methods,the phase,morphology and magnetic property of iron hydroxide oxide(FeOOH) which has been prepared by low-temperature neutralization reaction under different magnetic fields were analyzed.It can be found that the magnetic field had a great influence on the product.Acicular goethite(α-FeOOH) was synthetized without magnetic field.When the magnetic flux density was increased to 0.1T,γ-FeOOH was obtained.If the magnetic field intensity was raised to 0.5T,the product was all composed of δ-FeOOH.Moreover,the crystallization of FeOOH was greatly influenced by magnetic field as well.Thermodynamic calculation results show that the magnetic free energy of chemical reaction reached to more than hundreds KJ/mol when the magnetic field is applied.It meaned that the application of magnetic field was conducived to producing the products with higher susceptibility.Even under the low magnetic field,due to the stability of the reaction products was broken by the magnetic field,the magnetic free energy was also effective.展开更多
Cu/ZnO catalysts were prepared by the co-precipitation method with the addition of OP-10 （polyoxyethylene octylphenol ether） and were chemically and structurally characterized by means of XRD, BET, H2-TPR, CO-TPD an...Cu/ZnO catalysts were prepared by the co-precipitation method with the addition of OP-10 （polyoxyethylene octylphenol ether） and were chemically and structurally characterized by means of XRD, BET, H2-TPR, CO-TPD and N20-titration. The effect of OP-10 addition on the activity of Cu/ZnO for the slurry phase methanol synthesis at 150℃ was evaluated. The results showed that Cu/ZnO prepared with addition of 8% OP-10 （denoted as C8） exhibited the promoted activity for the methanol synthesis. The conversion of CO and the STY （space time yield） of methanol were 42.5% and 74.6% higher than those of Cu/ZnO prepared without addition of OP-10 （denoted as CO）, respectively. The precursor of C8 contained more aurichalcite and rosasite, and the concerted effect of Cu-Zn in C8 was found to be stronger than that in CO. Compared with CO, C8 showed smaller particle size, lower reduction temperature and larger BET and Cu surface areas.展开更多
Rechargeable magnesium batteries(RMBs),as one of the most promising candidates for efficient energy storage devices with high energy,power density and high safety,have attracted increasing attention.However,searching ...Rechargeable magnesium batteries(RMBs),as one of the most promising candidates for efficient energy storage devices with high energy,power density and high safety,have attracted increasing attention.However,searching for suitable cathode materials with fast diffusion kinetics and exploring their magnesium storage mechanisms remains a great challenge.Cu S submicron spheres,made by a facile low-temperature synthesis strategy,were applied as the high-performance cathode for RMBs in this work,which can deliver a high specific capacity of 396mAh g^(-1)at 20 mA g^(-1) and a remarkable rate capacity of 250 m Ah g^(-1)at 1000 mA g^(-1).The excellent rate performance can be assigned to the nano needle-like particles on the surface of Cu S submicron spheres,which can facilitate the diffusion kinetics of Mg^(2+).Further storage mechanism investigations illustrate that the Cu S cathodes experience a two-step conversion reaction controlled by diffusion during the electrochemical reaction process.This work could make a contribution to the study of the enhancement of diffusion kinetics of Mg2+and the reaction mechanism of RMBs.展开更多
In this study,the temperature of the low-temperature reduction-diffusion(LTRD)process was successfully decreased to below 600℃by introducing LiClKCl eutectic molten salt with a low eutectic point(352℃)as a solvent f...In this study,the temperature of the low-temperature reduction-diffusion(LTRD)process was successfully decreased to below 600℃by introducing LiClKCl eutectic molten salt with a low eutectic point(352℃)as a solvent for Ca reductant.Therefore,the Sm-Fe binary compounds,which were synthesizable at previously-unexplored low temperatures by the LTRD process using LiCl-KCl eutectic molten salt,were investigated,including whether a new metastable or ThMn_(12)-type Sm-Fe binary phase was formed.The Sm-Fe phase transitions of the SmFe binary compounds at a low temperature were identified,and it was found that MgCu_(2)-type Sm-Fe,PuNi_(3)-type SmFe and TbCu_(7)-type Sm-Fe phases were synthesized and stable at 400,500 and 550℃respectively.Although no new metastable Sm-Fe and ThMn_(12)-type Sm-Fe compounds were discovered in this study,this work can demonstrate that it is possible to synthesize the Sm-Fe phase at very low temperatures by the LTRD process for the first time.展开更多
Alcohol-assisted low-temperature methanol synthesis was conducted over Cu/ZnO;catalysts while varying the copper content（X）. Unlike conventional methanol synthesis, ethanol acted as both solvent and reaction interme...Alcohol-assisted low-temperature methanol synthesis was conducted over Cu/ZnO;catalysts while varying the copper content（X）. Unlike conventional methanol synthesis, ethanol acted as both solvent and reaction intermediate in this reaction, creating a different reaction pathway. The formation of crystalline phases and characteristic morphology of the co-precipitated precursors during the co-precipitation step were important factors in obtaining an efficient Cu/ZnO catalyst with a high dispersion of metallic copper,which is one of the main active sites for methanol synthesis. The acidic properties of the Cu/ZnO catalyst were also revealed as important factors, since alcohol esterification is considered the rate-limiting step in alcohol-assisted low-temperature methanol synthesis. As a consequence, bifunctionality of the Cu/ZnO catalyst such as metallic copper and acidic properties was required for this reaction. In this respect, the copper content（X） strongly affected the catalytic activity of the Cu/ZnO;catalysts, and accordingly, the Cu/ZnO;.5 catalyst with a high copper dispersion and sufficient acid sites exhibited the best catalytic performance in this reaction.展开更多
Superconducting vanadium nitride （VN） is successfully synthesized by a solid-state reaction of vanadium pentox- ide, sodium amide and sulfur in an autoclave at a relatively low temperature （240-400℃）. The obtaine...Superconducting vanadium nitride （VN） is successfully synthesized by a solid-state reaction of vanadium pentox- ide, sodium amide and sulfur in an autoclave at a relatively low temperature （240-400℃）. The obtained samples are characterized by x-ray diffraction, x-ray photoelectron spectroscopy and transmission electron microscopy. The result of the magnetization of the obtained VN product as a function of temperature indicates that the onset superconducting transition temperature is about 8.4K. Furthermore, the possible reaction mechanism is also discussed.展开更多
Small-diameter ZnO nanorods with lengths of 35-50 nm were synthesized by solvothermal treatment route at low temperature(70℃)for 48,96 and 144 hours using polyvinylpyrrolidone(PVP)as stabilizing agent.The optical ban...Small-diameter ZnO nanorods with lengths of 35-50 nm were synthesized by solvothermal treatment route at low temperature(70℃)for 48,96 and 144 hours using polyvinylpyrrolidone(PVP)as stabilizing agent.The optical band gap energy of nanorods was calculated by Tauc’s approximation,obtaining values of 3.30-3.21 eV.By X-ray diffraction(XRD)it was determined that ZnO samples crystallize in Wurtzite hexagonal structure and present changes in lattice parameters.Also XRD patterns reveal a preferential growth of ZnO nanostructures along the plane with Miller indices(002).Stabilization process of ZnO nanoparticles and nanorods was studied by Fourier-transform infrared(FT-IR)spectroscopy,determining that the presence of amide group in polymer structure confers the ability to interact electrostatically with ZnO nanostructures surface.FT-IR results revealed that O and N atoms of amide group interact strongly with the surface of ZnO nanostructures.The length/diameter ratio of ZnO nanorods at 48 and 96 hours of reflux was 2.3 and 2.7,respectively.展开更多
Plasma-assisted ball milling was carried out on the Al+C3H6N6 system and Al+C_(4)H_(4)N_(4) system,respectively.The phase structure,functional groups and synthesis mechanism were analyzed by XRD and FT-IR,and the diff...Plasma-assisted ball milling was carried out on the Al+C3H6N6 system and Al+C_(4)H_(4)N_(4) system,respectively.The phase structure,functional groups and synthesis mechanism were analyzed by XRD and FT-IR,and the differences in the synthesis process of nano-AlN with different solid nitrogen sources were discussed.The results show that C3H6N6 has a stable triazine ring structure,and its chemical bond is firm and difficult to break,so AlN cannot be synthesized directly by solid-solid reaction at room temperature.However,there are a large number of nitrile groups(-CN)and amino groups(-NH_(2))in C_(4)H_(4)N_(4) molecules.Under the combined action of plasma bombardment and mechanical energy activation,C_(4)H_(4)N_(4) molecules undergo polycondensation and deamination,so that the ball milling tank is filled with a large number of active nitrogen-containing groups such as N=,≡N,etc.These groups and ball milling activated Al can synthesize nano-AlN at room temperature,with a conversion rate of 92%.SEM,DSC/TG analysis showed that the powder obtained by ball milling was formed by soft agglomeration of many fine primary particles about 50–80 nm.The surface morphology of the powder was loose and porous,and it had strong activity.After annealing at 800℃,the conversion rate of the Al+C_(4)H_(4)N_(4) system reached 99%.展开更多
The component synthesis active vibration suppression method （CSVS） can be applied to suppress the vibration of flexible systems. By this method, several same or similar time-varying components are arranged according...The component synthesis active vibration suppression method （CSVS） can be applied to suppress the vibration of flexible systems. By this method, several same or similar time-varying components are arranged according to certain rules along the time axis. The synthesized command can suppress the arbitrary unwanted vibration harmonic while achieving the desired rigid body motion. The number of the components increases rapidly when the number of harmonic vibration is growing. In this article, the CSVS based on zero-placement technique is used to construct the synthesized command to suppress the multi-harmonics simultaneously in the discrete domain. The nature of zero-placement method is to put enough zeros to cancel system poles at necessary points. The designed synthesized command has equal time intervals between each component and which is much easier to be implemented. Using this method, the number of components increases linearly with the increasing of the number of being suppressed harmonics. For the spacecraft with flexible appendages, CSVS based on zero-placement is used to design the time optimal large angle maneuver control strategy. Simulations have verified the validity and superiority of the proposed approach.展开更多
Many methods are proposed to deal with the type synthesis of parallel kinematic mechanisms（PKMs）, but most of them are less intuitive to some extent. Thus, to propose a concise and intuitive type synthesis method fo...Many methods are proposed to deal with the type synthesis of parallel kinematic mechanisms（PKMs）, but most of them are less intuitive to some extent. Thus, to propose a concise and intuitive type synthesis method for engineering application is a very challenging issue, which should be further studied in the field. Grassmann line geometry, which can investigate the dimensions of spatial line-clusters in a concise way, is taken as the mathematic foundation. Atlas method is introduced to visually describe the degrees of freedom（DOFs） and constraints of a mechanism, and the dual rule is brought in to realize the mutual conversion of the freedom-space and constraint-space. Consequently, a systematic method based on Grassmann line geometry and Atlas method is generated and the entire type synthesis process is presented. Three type 4-DOF PKMs, i.e., 1T3R, 2T2R and 3T1R（T： translational DOF; R： rotational DOF）, are classified according to the different combinations of the translational DOFs and rotational DOFs. The type synthesis of 4-DOF PKMs is carried out and the possible configurations are thoroughly investigated. Some new PKMs with useful functions are generated during this procedure. The type synthesis method based on Grassmann line geometry and Atlas method is intuitive and concise, and can reduce the complexity of the PKMs＇ type synthesis. Moreover, this method can provide theoretical guidance for other PKMs＇ type synthesis and engineering application. A novel type synthesis method is proposed, which solves the existing methods＇ problems in terms of complicated, not intuitive and unsuitable for practical application.展开更多
The effect of synthesis methods on the activity of V/Ce/WTi catalysts was investigated for the selective catalytic reduction（SCR） of NO_x by NH_3. V/Ce/WTi-DP（deposition precipitation） catalyst showed excellent NH...The effect of synthesis methods on the activity of V/Ce/WTi catalysts was investigated for the selective catalytic reduction（SCR） of NO_x by NH_3. V/Ce/WTi-DP（deposition precipitation） catalyst showed excellent NH_3-SCR performance, especially the better medium-temperature activity and the less N_2O formation than V/Ce/WTi-IMP（impregnation）. These catalysts were characterized by X-ray diffraction（XRD）, Brumauer-Emmett-Teller（BET）, X-ray photoelectron spectroscopy（XPS）, temperature-programmed reduction（H_2-TPR）, and in situ DRIFTS techniques. The XPS and H_2-TPR results revealed that V/Ce/WTi-DP exhibited more surface Ce species, higher level of Oα and higher reducibility of Ce species. Reflected by in situ DRIFTS results, the deposition precipitation method（DP） contributed to a greater amount of weakly adsorbed NO_2, monodentate nitrate and NH_3 species with better reactive activity. Meanwhile, the cis-N_2O_2^（2-） species, an intermediate for N_2O formation, was very limited. As a result, these advantages brought about the superior SCR activity and N_2 selectivity for V/Ce/WTi-DP.展开更多
Using cetyltrimethylammonium bromide （CTAB） as the template agent, cerium nitrate as the cerium resource, yttrium nitrate as the yttrium resource, and ammonium carbonate as the precipitating agent, mesoporous CeO2 p...Using cetyltrimethylammonium bromide （CTAB） as the template agent, cerium nitrate as the cerium resource, yttrium nitrate as the yttrium resource, and ammonium carbonate as the precipitating agent, mesoporous CeO2 powders doped with different yttrium contents were successfully synthesized using a chemical precipitation method, under an alkalescent condition. Properties of the obtained samples were characterized and analyzed with X-ray diffraction （XRD）, energy dispersive analysis of X-rays （EDAX）, transmission electron microscopy （TEM）, infrared （IR） absorbance, and the BET method. For the prepared samples with 20% （molar ratio） Y-doped content, a BET specific surface area of 106. 6 m^2 · g^- 1, with an average pore size of3~27 nm were obtained. XRD patterns showed that the doped samples were with a cubic fluorite structure. TEM micrographs revealed that the doped samples showed a spherical morphology with a diameter ranging from 20 to 30 nm and a round pore shape. IR results indicated that the Ce-O-Ce vibration intensity decreased as the Y-doped content increased. N2 adsorption-desorption isotherms showed that the samples possessed typical mesopore characteristics. The average pore size of the samples decreased alter mesoporous CeO2 was doped with yttrium, and the average pore size decreased largely as the Y-doped content increased.展开更多
SiO2-CaO-MgO glass and glass-ceramic powder doped with Nd3＋ were synthesized with sol-gel method. Tetraethylorthosilicate （TEOS）, Ca（NO3）2？4H2O, Mg（NO3）2？6H2O, Nd（NO3）3？6H2O, ethanol, distilled water, and ...SiO2-CaO-MgO glass and glass-ceramic powder doped with Nd3＋ were synthesized with sol-gel method. Tetraethylorthosilicate （TEOS）, Ca（NO3）2？4H2O, Mg（NO3）2？6H2O, Nd（NO3）3？6H2O, ethanol, distilled water, and HNO3 were used as starting materials. The synthesized powder’s properties were examined with simultaneous thermal analysis （STA）, X-ray diffraction （XRD）, photoluminescence （PL） and scanning electron microscopy （SEM） analysis. The STA curves showed that the softening point and crystallization temperatures were shifted to higher temperatures with increasing dopant content. Regarding XRD patterns of glass samples, Nd was found to act as an intermediate oxide in glass matrix. The XRD patterns of glass-ceramic samples indicated that bredigite and akermanite crystallized in the glass matrix after heat treating at 900 oC. The fluorescence spectra showed that glass-ceramics emitted much stronger irradiation than glasses with the same dopant content. The SEM images illustrated uniform and homogeneous distribution of applied oxides in glass and glass-ceramic compositions.展开更多
Lithium-ion batteries(LIBs)have evolved into the mainstream power source of ene rgy sto rage equipment by reason of their advantages such as high energy density,high power,long cycle life and less pollution.With the e...Lithium-ion batteries(LIBs)have evolved into the mainstream power source of ene rgy sto rage equipment by reason of their advantages such as high energy density,high power,long cycle life and less pollution.With the expansion of their applications in deep-sea exploration,aerospace and military equipment,special working conditions have placed higher demands on the low-temperature performance of LIBs.However,at low temperatures,the severe polarization and inferior electrochemical activity of electrode materials cause the acute capacity fading upon cycling,which greatly hindered the further development of LIBs.In this review,we summarize the recent important progress of LIBs in low-temperature operations and introduce the key methods and the related action mechanisms for enhancing the capacity of the various cathode and anode materials.It aims to promote the development of high-performance electrode materials and broaden the application range of LIBs.展开更多
The current type synthesis of the redundant actuated parallel mechanisms is adding active-actuated kinematic branches on the basis of the traditional parallel mechanisms,or using screw theory to perform multiple getti...The current type synthesis of the redundant actuated parallel mechanisms is adding active-actuated kinematic branches on the basis of the traditional parallel mechanisms,or using screw theory to perform multiple getting intersection and union to complete type synthesis.The number of redundant parallel mechanisms obtained by these two methods is limited.In this paper,based on Grassmann line geometry and Atlas method,a novel and effective method for type synthesis of redundant actuated parallel mechanisms(PMs)with closed-loop units is proposed.Firstly,the degree of freedom(DOF)and constraint line graph of the moving platform are determined successively,and redundant lines are added in constraint line graph to obtain the redundant constraint line graph and their equivalent line graph,and a branch constraint allocation scheme is formulated based on the allocation criteria.Secondly,a scheme is selected and redundant lines are added in the branch chains DOF graph to construct the redundant actuated branch chains with closed-loop units.Finally,the branch chains that meet the requirements of branch chains configuration criteria and F&C(degree of freedom&constraint)line graph are assembled.In this paper,two types of 2 rotational and 1 translational(2R1T)redundant actuated parallel mechanisms and one type of 2 translational and 1 rotational(2T1R)redundant actuated parallel mechanisms with few branches and closed-loop units were taken as examples,and 238,92 and 15 new configurations were synthesized.All the mechanisms contain closed-loop units,and the mechanisms and the actuators both have good symmetry.Therefore,all the mechanisms have excellent comprehensive performance,in which the two rotational DOFs of the moving platform of 2R1T redundant actuated parallel mechanism can be independently controlled.The instantaneous analysis shows that all mechanisms are not instantaneous,which proves the feasibility and practicability of the method.展开更多
With the recent advancement in nanotechnology,nanoparticles(NPs)offer an ample variety of smart functions than conventional materials in various aspects.As compared to larger particles,NPs possess unique characteristi...With the recent advancement in nanotechnology,nanoparticles(NPs)offer an ample variety of smart functions than conventional materials in various aspects.As compared to larger particles,NPs possess unique characteristics and excellent abilities,such as low toxicity,chemical stability,surface functionality,and biocompatibility.These advantageous properties allow them to be widely utilized in many applications,including biomedical applications,energy applications,IT applications,and industrial applications.In order to fulfill the increasing demands of NP applications,existing NP synthesis methods need to be improved based on the requirements of different applications to further their usage.A comprehensive understanding of the relationships between synthesis parameters and properties of NPs can help us better fine-tune them with designed properties and minimal toxicity.This review paper will discuss the commonly used synthesis methods of functionalized NPs,as well as future directions and challenges to develop various synthesis methods further.展开更多
High quality potassium hexatitanate whiskers were hydrothermally synthesized in one step under moderate temperature and pressure conditions. Effects of the titanium source and reaction conditions on the hydrothermal r...High quality potassium hexatitanate whiskers were hydrothermally synthesized in one step under moderate temperature and pressure conditions. Effects of the titanium source and reaction conditions on the hydrothermal reaction rate, product phase component, and morphology of whiskers were investigated. The results show that the reactivity of hydrated titania, anatase TiO2, and rutile TiO2 with KOH decreases in turn, and with hydrated titania as titanium source, it is difficult to obtain potassium hexatitanate whiskers with good morphology. In contrast, uniform potassium hexatitanate whiskers with a length of 10-20 μm and a diameter of 200-700 nm were obtained using anatase TiO2 as titanium source. The investigation demonstrates that the initial KOH concentration, annealing temperature and time, molar ratio of K2O/TiO2, etc. significantly affect the morphology of the as-synthesized whiskers. The optimized synthesis condition is as follows： anatase as a titanium source 10 wt.% KOH solution; annealing temperature and time of 300℃ and 5 h, respectively; K2O/TiO2 molar ratio of 5, etc. A rhombic potassium hexatitanate was prepared under the optimum condition and the whisker grew along the [110] direction. The reaction mechanism was discussed.展开更多
We used a chemical reduction method to synthesize the catalysts of cobalt(Co) and cobalt-ruthenium(Co-Ru) bifunctional supported on carbon nanotubes(CNTs) for Fischer–Tropsch synthesis(FTS) in a fixedbed reactor. The...We used a chemical reduction method to synthesize the catalysts of cobalt(Co) and cobalt-ruthenium(Co-Ru) bifunctional supported on carbon nanotubes(CNTs) for Fischer–Tropsch synthesis(FTS) in a fixedbed reactor. These Co-Ru/CNTs catalysts were synthesized with various weight proportions of Ru/Co(0.1 to 0.4 wt%) with keeping a fixed amount of cobalt(10 wt%). Moreover, for comparison purpose, CNTs supported Co-and Co(Ru)-based catalysts at same loading as the above catalysts were prepared through impregnation method. We characterize the present catalysts through the various techniques such as Energy–dispersive X-ray(EDX), Transmission Electron Microscopy(TEM), Brunauer–Emmett–Teller(BET),Hydrogen-Temperature-Programmed Reduction(H_2-TPR), Hydrogen-Temperature-Programmed Desorption(H_2-TPD) and O_2 titration. Thus using the chemical reduction method, a narrow particle size distribution was obtained so that the small cobalt particles were confined inside the CNTs. The Co-based catalyst prepared by impregnation was compared with the Co-Ru catalysts at the same loading. The results demonstrated that the use of chemical reduction method led to decrease the average Co oxide cluster size to8.7 nm so that the reduction enhanced about 24% and stabilized an earlier time at the stream. Among the prepared catalysts, the results indicated that the Co-Ru/CNTs catalysts demonstrated high catalytic activity with the highest long-chain hydrocarbons(C_(5+)), selectivity up to 74.76%, which was higher than those we obtained by the Co-Ru/γ-Al_2O_3(61._20%), Co/CNTs(43.68%) and Co/γ-Al_2O_3(37.69%). At the same time, comparing with those catalyst synthesized by impregnation, the use of chemical reduction led to enhancement of the C_(5+) selectivity from 59.30% to 68.83% and increment in FTS rate about 11% for the Co-Ru/CNTs catalyst.展开更多
For at least the past five decades,structural synthesis has been used as a main means of finding better mechanisms with some predefined function.In structural synthesis,isomorphism identification is still a problem un...For at least the past five decades,structural synthesis has been used as a main means of finding better mechanisms with some predefined function.In structural synthesis,isomorphism identification is still a problem unsolved well,and to solve this problem is very significant to the design of new mechanisms.According to the given degree of freedom（DOF） and link connection property of planar closed chain mechanisms,vertex assortment is obtained.For solving the isomorphism problem,a method of the adding sub-chains is proposed with the detailed steps and algorithms in the synthesizing process.Employing this method,the identification code and formation code of every topological structure are achieved,therefore many isomorphic structures could be eliminated in time during structural synthesis by comparing those codes among different topological graphs,resulting in the improvement of synthesizing efficiency and accuracy,and the approach for eliminating rigid sub-chains in and after the synthesizing process is also presented.Some examples are given,including how to add sub-chains,how to detect simple rigid sub-chains and how to obtain identification codes and formulation codes et al.Using the adding sub-chain method,the relative information of some common topological graphs is given in the form of table.The comparison result is coincident with many literatures,so the correctness of the adding sub-chain method is convinced.This method will greatly improve the synthesizing efficiency and accuracy,and has a good potential for application.展开更多
基金Item Sponsored by the National Natural Science Foundation of China(Key Basic Project,No.51034010)International cooperation project from Shanghai Science and Technology Commission(No.075207015)Key Basic Project from Science and Technology Commission of Shanghai Municipality(No.08JC1410000)
文摘Using XRD,TEM and VSM methods,the phase,morphology and magnetic property of iron hydroxide oxide(FeOOH) which has been prepared by low-temperature neutralization reaction under different magnetic fields were analyzed.It can be found that the magnetic field had a great influence on the product.Acicular goethite(α-FeOOH) was synthetized without magnetic field.When the magnetic flux density was increased to 0.1T,γ-FeOOH was obtained.If the magnetic field intensity was raised to 0.5T,the product was all composed of δ-FeOOH.Moreover,the crystallization of FeOOH was greatly influenced by magnetic field as well.Thermodynamic calculation results show that the magnetic free energy of chemical reaction reached to more than hundreds KJ/mol when the magnetic field is applied.It meaned that the application of magnetic field was conducived to producing the products with higher susceptibility.Even under the low magnetic field,due to the stability of the reaction products was broken by the magnetic field,the magnetic free energy was also effective.
基金supported by the Chinese Ministry of Science & Technology (2005CCA00700)Spring Scenery Plan (2006) and Program for New Century Excellent Talents in University (NCET-08-0872) from the Chinese Ministry of Education
文摘Cu/ZnO catalysts were prepared by the co-precipitation method with the addition of OP-10 （polyoxyethylene octylphenol ether） and were chemically and structurally characterized by means of XRD, BET, H2-TPR, CO-TPD and N20-titration. The effect of OP-10 addition on the activity of Cu/ZnO for the slurry phase methanol synthesis at 150℃ was evaluated. The results showed that Cu/ZnO prepared with addition of 8% OP-10 （denoted as C8） exhibited the promoted activity for the methanol synthesis. The conversion of CO and the STY （space time yield） of methanol were 42.5% and 74.6% higher than those of Cu/ZnO prepared without addition of OP-10 （denoted as CO）, respectively. The precursor of C8 contained more aurichalcite and rosasite, and the concerted effect of Cu-Zn in C8 was found to be stronger than that in CO. Compared with CO, C8 showed smaller particle size, lower reduction temperature and larger BET and Cu surface areas.
基金the support from the Fundamental Research Funds for the Central Universities of Chongqing University(No.2020CDCGCL005)。
文摘Rechargeable magnesium batteries(RMBs),as one of the most promising candidates for efficient energy storage devices with high energy,power density and high safety,have attracted increasing attention.However,searching for suitable cathode materials with fast diffusion kinetics and exploring their magnesium storage mechanisms remains a great challenge.Cu S submicron spheres,made by a facile low-temperature synthesis strategy,were applied as the high-performance cathode for RMBs in this work,which can deliver a high specific capacity of 396mAh g^(-1)at 20 mA g^(-1) and a remarkable rate capacity of 250 m Ah g^(-1)at 1000 mA g^(-1).The excellent rate performance can be assigned to the nano needle-like particles on the surface of Cu S submicron spheres,which can facilitate the diffusion kinetics of Mg^(2+).Further storage mechanism investigations illustrate that the Cu S cathodes experience a two-step conversion reaction controlled by diffusion during the electrochemical reaction process.This work could make a contribution to the study of the enhancement of diffusion kinetics of Mg2+and the reaction mechanism of RMBs.
基金financially supported by"Adaptable and Seamless Technology Transfer Program through Target-Driven R&D(A-STEP),(No.JPMJTM20EB)commissioned by the Japan Science and Technology Agency(JST)。
文摘In this study,the temperature of the low-temperature reduction-diffusion(LTRD)process was successfully decreased to below 600℃by introducing LiClKCl eutectic molten salt with a low eutectic point(352℃)as a solvent for Ca reductant.Therefore,the Sm-Fe binary compounds,which were synthesizable at previously-unexplored low temperatures by the LTRD process using LiCl-KCl eutectic molten salt,were investigated,including whether a new metastable or ThMn_(12)-type Sm-Fe binary phase was formed.The Sm-Fe phase transitions of the SmFe binary compounds at a low temperature were identified,and it was found that MgCu_(2)-type Sm-Fe,PuNi_(3)-type SmFe and TbCu_(7)-type Sm-Fe phases were synthesized and stable at 400,500 and 550℃respectively.Although no new metastable Sm-Fe and ThMn_(12)-type Sm-Fe compounds were discovered in this study,this work can demonstrate that it is possible to synthesize the Sm-Fe phase at very low temperatures by the LTRD process for the first time.
基金supported by C1 Gas Refinery Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science,ICT & Future Planning (2015M3D3A1A01064908)
文摘Alcohol-assisted low-temperature methanol synthesis was conducted over Cu/ZnO;catalysts while varying the copper content（X）. Unlike conventional methanol synthesis, ethanol acted as both solvent and reaction intermediate in this reaction, creating a different reaction pathway. The formation of crystalline phases and characteristic morphology of the co-precipitated precursors during the co-precipitation step were important factors in obtaining an efficient Cu/ZnO catalyst with a high dispersion of metallic copper,which is one of the main active sites for methanol synthesis. The acidic properties of the Cu/ZnO catalyst were also revealed as important factors, since alcohol esterification is considered the rate-limiting step in alcohol-assisted low-temperature methanol synthesis. As a consequence, bifunctionality of the Cu/ZnO catalyst such as metallic copper and acidic properties was required for this reaction. In this respect, the copper content（X） strongly affected the catalytic activity of the Cu/ZnO;catalysts, and accordingly, the Cu/ZnO;.5 catalyst with a high copper dispersion and sufficient acid sites exhibited the best catalytic performance in this reaction.
基金Supported by the Natural Science Foundation of Jiangsu Province under Grant No BK20160292the Natural Science Foundation of the Higher Educations Institutions of Jiangsu Province under Grant No 16KJB150013+1 种基金the National Natural Science Foundation of China under Grant No U1404505the Program for Innovative Talent in University of Henan Province under Grant No16HASTIT010
文摘Superconducting vanadium nitride （VN） is successfully synthesized by a solid-state reaction of vanadium pentox- ide, sodium amide and sulfur in an autoclave at a relatively low temperature （240-400℃）. The obtained samples are characterized by x-ray diffraction, x-ray photoelectron spectroscopy and transmission electron microscopy. The result of the magnetization of the obtained VN product as a function of temperature indicates that the onset superconducting transition temperature is about 8.4K. Furthermore, the possible reaction mechanism is also discussed.
文摘Small-diameter ZnO nanorods with lengths of 35-50 nm were synthesized by solvothermal treatment route at low temperature(70℃)for 48,96 and 144 hours using polyvinylpyrrolidone(PVP)as stabilizing agent.The optical band gap energy of nanorods was calculated by Tauc’s approximation,obtaining values of 3.30-3.21 eV.By X-ray diffraction(XRD)it was determined that ZnO samples crystallize in Wurtzite hexagonal structure and present changes in lattice parameters.Also XRD patterns reveal a preferential growth of ZnO nanostructures along the plane with Miller indices(002).Stabilization process of ZnO nanoparticles and nanorods was studied by Fourier-transform infrared(FT-IR)spectroscopy,determining that the presence of amide group in polymer structure confers the ability to interact electrostatically with ZnO nanostructures surface.FT-IR results revealed that O and N atoms of amide group interact strongly with the surface of ZnO nanostructures.The length/diameter ratio of ZnO nanorods at 48 and 96 hours of reflux was 2.3 and 2.7,respectively.
基金The study was supported by the Education and Research Project for Young and Middle-Aged Teachers in Fujian Province(JAT201167).
文摘Plasma-assisted ball milling was carried out on the Al+C3H6N6 system and Al+C_(4)H_(4)N_(4) system,respectively.The phase structure,functional groups and synthesis mechanism were analyzed by XRD and FT-IR,and the differences in the synthesis process of nano-AlN with different solid nitrogen sources were discussed.The results show that C3H6N6 has a stable triazine ring structure,and its chemical bond is firm and difficult to break,so AlN cannot be synthesized directly by solid-solid reaction at room temperature.However,there are a large number of nitrile groups(-CN)and amino groups(-NH_(2))in C_(4)H_(4)N_(4) molecules.Under the combined action of plasma bombardment and mechanical energy activation,C_(4)H_(4)N_(4) molecules undergo polycondensation and deamination,so that the ball milling tank is filled with a large number of active nitrogen-containing groups such as N=,≡N,etc.These groups and ball milling activated Al can synthesize nano-AlN at room temperature,with a conversion rate of 92%.SEM,DSC/TG analysis showed that the powder obtained by ball milling was formed by soft agglomeration of many fine primary particles about 50–80 nm.The surface morphology of the powder was loose and porous,and it had strong activity.After annealing at 800℃,the conversion rate of the Al+C_(4)H_(4)N_(4) system reached 99%.
文摘The component synthesis active vibration suppression method （CSVS） can be applied to suppress the vibration of flexible systems. By this method, several same or similar time-varying components are arranged according to certain rules along the time axis. The synthesized command can suppress the arbitrary unwanted vibration harmonic while achieving the desired rigid body motion. The number of the components increases rapidly when the number of harmonic vibration is growing. In this article, the CSVS based on zero-placement technique is used to construct the synthesized command to suppress the multi-harmonics simultaneously in the discrete domain. The nature of zero-placement method is to put enough zeros to cancel system poles at necessary points. The designed synthesized command has equal time intervals between each component and which is much easier to be implemented. Using this method, the number of components increases linearly with the increasing of the number of being suppressed harmonics. For the spacecraft with flexible appendages, CSVS based on zero-placement is used to design the time optimal large angle maneuver control strategy. Simulations have verified the validity and superiority of the proposed approach.
基金supported by National Natural Science Foundation of China(Grant No.51135008)National Basic Research Program of China(973 Program,Grant No.2013CB035400)China Postdoctoral Science Foundation(Grant Nos.2012M520256,2013T60107)
文摘Many methods are proposed to deal with the type synthesis of parallel kinematic mechanisms（PKMs）, but most of them are less intuitive to some extent. Thus, to propose a concise and intuitive type synthesis method for engineering application is a very challenging issue, which should be further studied in the field. Grassmann line geometry, which can investigate the dimensions of spatial line-clusters in a concise way, is taken as the mathematic foundation. Atlas method is introduced to visually describe the degrees of freedom（DOFs） and constraints of a mechanism, and the dual rule is brought in to realize the mutual conversion of the freedom-space and constraint-space. Consequently, a systematic method based on Grassmann line geometry and Atlas method is generated and the entire type synthesis process is presented. Three type 4-DOF PKMs, i.e., 1T3R, 2T2R and 3T1R（T： translational DOF; R： rotational DOF）, are classified according to the different combinations of the translational DOFs and rotational DOFs. The type synthesis of 4-DOF PKMs is carried out and the possible configurations are thoroughly investigated. Some new PKMs with useful functions are generated during this procedure. The type synthesis method based on Grassmann line geometry and Atlas method is intuitive and concise, and can reduce the complexity of the PKMs＇ type synthesis. Moreover, this method can provide theoretical guidance for other PKMs＇ type synthesis and engineering application. A novel type synthesis method is proposed, which solves the existing methods＇ problems in terms of complicated, not intuitive and unsuitable for practical application.
基金supported by the Grant from the China Huadian Science and Technology Institute(CHDI.KJ-20)the National High-Tech Research and Development Program of China(863,2011AA03A405)
文摘The effect of synthesis methods on the activity of V/Ce/WTi catalysts was investigated for the selective catalytic reduction（SCR） of NO_x by NH_3. V/Ce/WTi-DP（deposition precipitation） catalyst showed excellent NH_3-SCR performance, especially the better medium-temperature activity and the less N_2O formation than V/Ce/WTi-IMP（impregnation）. These catalysts were characterized by X-ray diffraction（XRD）, Brumauer-Emmett-Teller（BET）, X-ray photoelectron spectroscopy（XPS）, temperature-programmed reduction（H_2-TPR）, and in situ DRIFTS techniques. The XPS and H_2-TPR results revealed that V/Ce/WTi-DP exhibited more surface Ce species, higher level of Oα and higher reducibility of Ce species. Reflected by in situ DRIFTS results, the deposition precipitation method（DP） contributed to a greater amount of weakly adsorbed NO_2, monodentate nitrate and NH_3 species with better reactive activity. Meanwhile, the cis-N_2O_2^（2-） species, an intermediate for N_2O formation, was very limited. As a result, these advantages brought about the superior SCR activity and N_2 selectivity for V/Ce/WTi-DP.
基金Project supported by the International Cooperation of Science and Technology Ministry PRC (2005DFBA028)the National Natural Science Foundation of China (59925412)
文摘Using cetyltrimethylammonium bromide （CTAB） as the template agent, cerium nitrate as the cerium resource, yttrium nitrate as the yttrium resource, and ammonium carbonate as the precipitating agent, mesoporous CeO2 powders doped with different yttrium contents were successfully synthesized using a chemical precipitation method, under an alkalescent condition. Properties of the obtained samples were characterized and analyzed with X-ray diffraction （XRD）, energy dispersive analysis of X-rays （EDAX）, transmission electron microscopy （TEM）, infrared （IR） absorbance, and the BET method. For the prepared samples with 20% （molar ratio） Y-doped content, a BET specific surface area of 106. 6 m^2 · g^- 1, with an average pore size of3~27 nm were obtained. XRD patterns showed that the doped samples were with a cubic fluorite structure. TEM micrographs revealed that the doped samples showed a spherical morphology with a diameter ranging from 20 to 30 nm and a round pore shape. IR results indicated that the Ce-O-Ce vibration intensity decreased as the Y-doped content increased. N2 adsorption-desorption isotherms showed that the samples possessed typical mesopore characteristics. The average pore size of the samples decreased alter mesoporous CeO2 was doped with yttrium, and the average pore size decreased largely as the Y-doped content increased.
基金supported by the Iran Nanotechnology Initiative Council(INIC)
文摘SiO2-CaO-MgO glass and glass-ceramic powder doped with Nd3＋ were synthesized with sol-gel method. Tetraethylorthosilicate （TEOS）, Ca（NO3）2？4H2O, Mg（NO3）2？6H2O, Nd（NO3）3？6H2O, ethanol, distilled water, and HNO3 were used as starting materials. The synthesized powder’s properties were examined with simultaneous thermal analysis （STA）, X-ray diffraction （XRD）, photoluminescence （PL） and scanning electron microscopy （SEM） analysis. The STA curves showed that the softening point and crystallization temperatures were shifted to higher temperatures with increasing dopant content. Regarding XRD patterns of glass samples, Nd was found to act as an intermediate oxide in glass matrix. The XRD patterns of glass-ceramic samples indicated that bredigite and akermanite crystallized in the glass matrix after heat treating at 900 oC. The fluorescence spectra showed that glass-ceramics emitted much stronger irradiation than glasses with the same dopant content. The SEM images illustrated uniform and homogeneous distribution of applied oxides in glass and glass-ceramic compositions.
基金supported by the National Natural Science Foundation of China(NSFC,Nos.51772205,51572192,51772208,51472179)the General Program of Municipal Natural Science Foundation of Tianjin(Nos.17JCYBJC17000,17JCYBJC22700)。
文摘Lithium-ion batteries(LIBs)have evolved into the mainstream power source of ene rgy sto rage equipment by reason of their advantages such as high energy density,high power,long cycle life and less pollution.With the expansion of their applications in deep-sea exploration,aerospace and military equipment,special working conditions have placed higher demands on the low-temperature performance of LIBs.However,at low temperatures,the severe polarization and inferior electrochemical activity of electrode materials cause the acute capacity fading upon cycling,which greatly hindered the further development of LIBs.In this review,we summarize the recent important progress of LIBs in low-temperature operations and introduce the key methods and the related action mechanisms for enhancing the capacity of the various cathode and anode materials.It aims to promote the development of high-performance electrode materials and broaden the application range of LIBs.
基金Supported by National Natural Science Foundation of China(Grant No.51875499).
文摘The current type synthesis of the redundant actuated parallel mechanisms is adding active-actuated kinematic branches on the basis of the traditional parallel mechanisms,or using screw theory to perform multiple getting intersection and union to complete type synthesis.The number of redundant parallel mechanisms obtained by these two methods is limited.In this paper,based on Grassmann line geometry and Atlas method,a novel and effective method for type synthesis of redundant actuated parallel mechanisms(PMs)with closed-loop units is proposed.Firstly,the degree of freedom(DOF)and constraint line graph of the moving platform are determined successively,and redundant lines are added in constraint line graph to obtain the redundant constraint line graph and their equivalent line graph,and a branch constraint allocation scheme is formulated based on the allocation criteria.Secondly,a scheme is selected and redundant lines are added in the branch chains DOF graph to construct the redundant actuated branch chains with closed-loop units.Finally,the branch chains that meet the requirements of branch chains configuration criteria and F&C(degree of freedom&constraint)line graph are assembled.In this paper,two types of 2 rotational and 1 translational(2R1T)redundant actuated parallel mechanisms and one type of 2 translational and 1 rotational(2T1R)redundant actuated parallel mechanisms with few branches and closed-loop units were taken as examples,and 238,92 and 15 new configurations were synthesized.All the mechanisms contain closed-loop units,and the mechanisms and the actuators both have good symmetry.Therefore,all the mechanisms have excellent comprehensive performance,in which the two rotational DOFs of the moving platform of 2R1T redundant actuated parallel mechanism can be independently controlled.The instantaneous analysis shows that all mechanisms are not instantaneous,which proves the feasibility and practicability of the method.
文摘With the recent advancement in nanotechnology,nanoparticles(NPs)offer an ample variety of smart functions than conventional materials in various aspects.As compared to larger particles,NPs possess unique characteristics and excellent abilities,such as low toxicity,chemical stability,surface functionality,and biocompatibility.These advantageous properties allow them to be widely utilized in many applications,including biomedical applications,energy applications,IT applications,and industrial applications.In order to fulfill the increasing demands of NP applications,existing NP synthesis methods need to be improved based on the requirements of different applications to further their usage.A comprehensive understanding of the relationships between synthesis parameters and properties of NPs can help us better fine-tune them with designed properties and minimal toxicity.This review paper will discuss the commonly used synthesis methods of functionalized NPs,as well as future directions and challenges to develop various synthesis methods further.
文摘High quality potassium hexatitanate whiskers were hydrothermally synthesized in one step under moderate temperature and pressure conditions. Effects of the titanium source and reaction conditions on the hydrothermal reaction rate, product phase component, and morphology of whiskers were investigated. The results show that the reactivity of hydrated titania, anatase TiO2, and rutile TiO2 with KOH decreases in turn, and with hydrated titania as titanium source, it is difficult to obtain potassium hexatitanate whiskers with good morphology. In contrast, uniform potassium hexatitanate whiskers with a length of 10-20 μm and a diameter of 200-700 nm were obtained using anatase TiO2 as titanium source. The investigation demonstrates that the initial KOH concentration, annealing temperature and time, molar ratio of K2O/TiO2, etc. significantly affect the morphology of the as-synthesized whiskers. The optimized synthesis condition is as follows： anatase as a titanium source 10 wt.% KOH solution; annealing temperature and time of 300℃ and 5 h, respectively; K2O/TiO2 molar ratio of 5, etc. A rhombic potassium hexatitanate was prepared under the optimum condition and the whisker grew along the [110] direction. The reaction mechanism was discussed.
文摘We used a chemical reduction method to synthesize the catalysts of cobalt(Co) and cobalt-ruthenium(Co-Ru) bifunctional supported on carbon nanotubes(CNTs) for Fischer–Tropsch synthesis(FTS) in a fixedbed reactor. These Co-Ru/CNTs catalysts were synthesized with various weight proportions of Ru/Co(0.1 to 0.4 wt%) with keeping a fixed amount of cobalt(10 wt%). Moreover, for comparison purpose, CNTs supported Co-and Co(Ru)-based catalysts at same loading as the above catalysts were prepared through impregnation method. We characterize the present catalysts through the various techniques such as Energy–dispersive X-ray(EDX), Transmission Electron Microscopy(TEM), Brunauer–Emmett–Teller(BET),Hydrogen-Temperature-Programmed Reduction(H_2-TPR), Hydrogen-Temperature-Programmed Desorption(H_2-TPD) and O_2 titration. Thus using the chemical reduction method, a narrow particle size distribution was obtained so that the small cobalt particles were confined inside the CNTs. The Co-based catalyst prepared by impregnation was compared with the Co-Ru catalysts at the same loading. The results demonstrated that the use of chemical reduction method led to decrease the average Co oxide cluster size to8.7 nm so that the reduction enhanced about 24% and stabilized an earlier time at the stream. Among the prepared catalysts, the results indicated that the Co-Ru/CNTs catalysts demonstrated high catalytic activity with the highest long-chain hydrocarbons(C_(5+)), selectivity up to 74.76%, which was higher than those we obtained by the Co-Ru/γ-Al_2O_3(61._20%), Co/CNTs(43.68%) and Co/γ-Al_2O_3(37.69%). At the same time, comparing with those catalyst synthesized by impregnation, the use of chemical reduction led to enhancement of the C_(5+) selectivity from 59.30% to 68.83% and increment in FTS rate about 11% for the Co-Ru/CNTs catalyst.
基金supported by National Natural Science Foundation of China (Grant No. 51075079)National Hi-tech Research and Development Program of China(863 Program,Grant No. 2008AA04Z202)
文摘For at least the past five decades,structural synthesis has been used as a main means of finding better mechanisms with some predefined function.In structural synthesis,isomorphism identification is still a problem unsolved well,and to solve this problem is very significant to the design of new mechanisms.According to the given degree of freedom（DOF） and link connection property of planar closed chain mechanisms,vertex assortment is obtained.For solving the isomorphism problem,a method of the adding sub-chains is proposed with the detailed steps and algorithms in the synthesizing process.Employing this method,the identification code and formation code of every topological structure are achieved,therefore many isomorphic structures could be eliminated in time during structural synthesis by comparing those codes among different topological graphs,resulting in the improvement of synthesizing efficiency and accuracy,and the approach for eliminating rigid sub-chains in and after the synthesizing process is also presented.Some examples are given,including how to add sub-chains,how to detect simple rigid sub-chains and how to obtain identification codes and formulation codes et al.Using the adding sub-chain method,the relative information of some common topological graphs is given in the form of table.The comparison result is coincident with many literatures,so the correctness of the adding sub-chain method is convinced.This method will greatly improve the synthesizing efficiency and accuracy,and has a good potential for application.
