Currently,the carbothermal reduction-nitridation(CRN)process is the predominant method for preparing aluminum nitride(AlN)powder.Although AlN powder prepared by CRN process exhibits high purity and excellent sintering...Currently,the carbothermal reduction-nitridation(CRN)process is the predominant method for preparing aluminum nitride(AlN)powder.Although AlN powder prepared by CRN process exhibits high purity and excellent sintering activity,it also presents challenges such as the necessity for high reaction temperatures and difficulties in achieving uniform mixing of its raw materials.This study presents a comprehensive investigation into preparation process of AlN nanopowders using a combination of hydrothermal synthesis and CRN.In the hydrothermal reaction,a homogeneous composite precursor consisting of carbon and boehmite(γ-AlOOH)is synthesized at 200℃using aluminum nitrate as the aluminum source,sucrose as the carbon source,and urea as the precipitant.During the hydrothermal process,the precursor develops a core-shell structure,with boehmite tightly coated with carbon(γ-AlOOH@C)due to electrostatic attraction.Compared with conventional precursor,the hydrothermal hybrid offers many advantages,such as ultrafine particles,uniform particle size distribution,good dispersion,high reactivity,and environmental friendliness.The carbon shell enhances thermodynamic stability of γ-Al_(2)O_(3) compared to the corundum phase(α-Al_(2)O_(3))by preventing the loss of the surface area in alumina.This stability enables γ-Al_(2)O_(3) to maintain high reactivity during CRN process,which initiates at 1300℃,and concludes at 1400℃.The underlying mechanisms are substantiated through experiments and thermodynamic calculations.This research provides a robust theoretical and experimental foundation for the hydrothermal combined carbothermal preparation of non-oxide ceramic nanopowders.展开更多
To enhance the overall performance of cyclotrimethylenetrinitramine(RDX),a modification strategy for RDX via in situ coordination with monometallic polydopamine(PDA)coatings(PDA-Fe,PDA-Cu,and PDA-Pb)was developed.The ...To enhance the overall performance of cyclotrimethylenetrinitramine(RDX),a modification strategy for RDX via in situ coordination with monometallic polydopamine(PDA)coatings(PDA-Fe,PDA-Cu,and PDA-Pb)was developed.The thermal properties of pristine RDX and its modified variants(RDX@PDA-Fe,RDX@PDA-Cu,RDX@PDA-Pb)were characterized using differential scanning calorimetry(DSC)and accelerating rate calorimetry(ARC).The impact sensitivity of these materials was evaluated via the characteristic drop-height method.The results demonstrate that PDA-metal metal coatings—formed through coordination between PDA and single metal ions(Fe^(3+),Cu^(2+),or Pb^(2+))—significantly enhance RDX′s thermal stability while attenuating its mechanical sensitivity.These coatings act as energy-absorbing barriers against external stimuli,effectively mitigating RDX′s sensitivity.Furthermore,they elevate RDX′s thermal stability by increasing its decomposition onset temperature and accelerating its decomposition kinetics.The monometallic coatings also catalyze RDX′s thermal decomposition and combustion,with Cu and Pb exhibiting particularly distinct catalytic effects.展开更多
The mechanism of stability of Co-doped spinel λ-MnO_2 that is referred to as spinel Li_xMn_2O_4 (x=0) was studied by using the first-principle calculation method. The total energy and formation enthalpy can be decrea...The mechanism of stability of Co-doped spinel λ-MnO_2 that is referred to as spinel Li_xMn_2O_4 (x=0) was studied by using the first-principle calculation method. The total energy and formation enthalpy can be decreased remarkably due to the Co substation, resulting in a more stable structure of λ-Mn_xCr_(2-x)O_4. The bond order and DOS analysis were given in detail to explain the nature of stability improvement. The calculated results show that as the content of Co dopant increases, the bond order of Mn—O becomes larger and the peak of density of states around Fermi level shifts toward lower energy. The charge density distribution illustrates that the Mn—O bonding is ionic and partially covalent, and the covalent Mn-O bonding becomes stronger with the increase of Co dopant content. The results confirm that the Codoping will enhance the stability of λ-MnO_2 and hence improve the electrochemistry performance of Li_xMn_2O_4.展开更多
Based on the first-principles calculations of density functional theory,co-adsorption models of C or CO with Cl2 on rutile TiO2(100)surface were established.The adsorption structures and electronic properties during c...Based on the first-principles calculations of density functional theory,co-adsorption models of C or CO with Cl2 on rutile TiO2(100)surface were established.The adsorption structures and electronic properties during chlorination process were predicted.Then,the adsorption energy,charge density,electron density difference and density of state of the adsorption structures were calculated and analyzed.The stabilities of the adsorption structures and the charge distributions between atoms were studied.It was found that both C and CO could promote the adsorption reactions of Cl2 on TiO2(100)surface,and C was more favorable to the adsorption process.The results show that the adsorption process of Cl2 on TiO2(100)surface was physisorption,and the co-adsorption processes of C or CO with Cl2 on TiO2(100)surface were chemisorptions.展开更多
Ground improvement has been used on many construction sites to densify granular materials, in other word, to improve soil properties and reduce potential settlement. This work presents a case study of ground improveme...Ground improvement has been used on many construction sites to densify granular materials, in other word, to improve soil properties and reduce potential settlement. This work presents a case study of ground improvement using rapid impact compaction （RIC）. The research site comprises the construction of workshop and depots as part of railway development project at Batu Gajah-Ipoh, Malaysia. In-situ testing results show that the subsurface soil comprises mainly of sand and silty sand through the investigated depth extended to 10 m. Groundwater is approximately 0.5 m below the ground surface. Evaluation of improvement was based on the results of pre- and post-improvement cone penetration test （CPT）. Interpretation software has been used to infer soil properties. Load test was conducted to estimate soil settlement. It is found that the technique succeeds in improving soil properties namely the relative density increases from 45% to 70%, the friction angle of soil is increased by an average of 3°, and the soil settlement is reduced by 50%： The technique succeeds in improving soil properties to approximately 5.0 m in depth depending on soil uniformity with depth.展开更多
The electric double layer with the transmission of particles was presented based on the principle of electrochemistry.In accordance with this theory,the cavitation catalysis removal mechanism of ultrasonic-pulse elect...The electric double layer with the transmission of particles was presented based on the principle of electrochemistry.In accordance with this theory,the cavitation catalysis removal mechanism of ultrasonic-pulse electrochemical compound machining(UPECM) based on particles was proposed.The removal mechanism was a particular focus and was thus validated by experiments.The principles and experiments of UPECM were introduced,and the removal model of the UPECM based on the principles of UPECM was established.Furthermore,the effects of the material removal rate for the main processing parameters,including the particles size,the ultrasonic vibration amplitude,the pulse voltage and the minimum machining gap between the tool and the workpiece,were also studied through UPECM.The results show that the particles promote ultrasonic-pulse electrochemical compound machining and thus act as the catalyzer of UPECM.The results also indicate that the processing speed,machining accuracy and surface quality can be improved under UPECM compound machining.展开更多
Transition metal dichalcogenides are interesting candidates as photocatalysts for hydrogen evolution reaction.The MnPSe_(3)/WS_(2) heterostructure is hence studied here with first principles calculations by exploring ...Transition metal dichalcogenides are interesting candidates as photocatalysts for hydrogen evolution reaction.The MnPSe_(3)/WS_(2) heterostructure is hence studied here with first principles calculations by exploring its electronic properties under the application of an electric field.It is discovered that the band gap will decrease from the WS_(2) monolayer to the MnPSe_(3)/WS_(2) heterostructure with Perdew-Burke-Ernzerhof functional,while increase slightly when electron correlation is involved.The conduction band minimum of the heterostructure is determined by the MnPSe3 layer,while the valence band maximum is contributed by the WS_(2)layer.The band edges and band gap suggest that the heterostructure will have good photocatalytic properties for water splitting.Moreover,comparing to monolayer WS_(2),the light absorption in both the ultraviolet and visible regions will be enhanced.When an electric field is present,a linear relation is observed between the electric field and the band gap within specific range,which can thus modulate the photocatalytic performance of this heterostructure.展开更多
Ab initio calculations are used to understand the fundamental mechanism of the solid solution softening/hardening of the Mo-binary system.The results reveal that the Mo-Ti,Mo-Ta,Mo-Nb,and Mo-W interactions are primari...Ab initio calculations are used to understand the fundamental mechanism of the solid solution softening/hardening of the Mo-binary system.The results reveal that the Mo-Ti,Mo-Ta,Mo-Nb,and Mo-W interactions are primarily attractive with negative heats of formation,while the interactions of Mo-Re,and Mo-Zr would be mainly repulsive with positive heats of formation.It is also shown that the addition of Re and Zr would cause the solid solution softening of Mo by the decrease of the unstable stacking fault energy and the increase of ductility.On the contrary,the elements of W,Ta,Ti,and Nb could bring about the solid-solution hardening of Mo through the impediment of the slip of the dislocation and the decrease of ductility.Electronic structures indicate that the weaker/stronger chemical bonding due to the alloying elements should fundamentally induce the solid solution softening/hardening of Mo.The results are discussed and compared with available evidence in literatures,which could deepen the fundamental understanding of the solid solution softening/hardening of the binary metallic system.展开更多
Alastraet： The gas-based direct reduction of iron ore pellets was carried out by simulating the typical gas composition in coal gasification process, Midrex and HyMII processes. The influences of gas composition and ...Alastraet： The gas-based direct reduction of iron ore pellets was carried out by simulating the typical gas composition in coal gasification process, Midrex and HyMII processes. The influences of gas composition and temperature on reduction were studied. Results show that the increasing of HE proportion is helpful to improve the reduction rate. However, when ~o（H2）：~o（CO）〉1.6：1, changes of HE content have little influence on it. Appropriate reduction temperature is about 950 ℃, and higher temperature （1 000 ℃） may unfavorably slow the reduction rate. From the kinetics analysis at 950 ℃, the most part of reduction course is likely controlled by interfacial chemical reaction mechanism and in the final stage controlled by a combined effect of gaseous diffusion and interfacial chemical reaction mechanisms. From the utilizations study of different reducing gases at 950 ℃, the key step in reduction course is the 3rd stage （FeO→Fe）, and the utilization of reducing gas increases with the rise of HE proportion.展开更多
Pyrite （FeS2） bulk and （100） surface properties and the oxygen adsorption on the surface were studied by using density functional theory methods. The results show that in the formation of FeS2 （100） surface, the...Pyrite （FeS2） bulk and （100） surface properties and the oxygen adsorption on the surface were studied by using density functional theory methods. The results show that in the formation of FeS2 （100） surface, there exists a process of electron transfer from Fe dangling bond to S dangling bond. In this situation, surface Fe and S atoms have more ionic properties. Both Fe2+ and S2- have high electrochemistry reduction activity, which is the base for oxygen adsorption. From the viewpoint of adsorption energy, the parallel form oxygen adsorption is in preference. The result also shows that the state of oxygen absorbed on FeS2 surface acts as peroxides rather than O2.展开更多
The redox initiation system for polyacrylate sodium of high molecular mass was designed and its effect with varying component dosage on the degree of polymerization was investigated. The results show that the proper t...The redox initiation system for polyacrylate sodium of high molecular mass was designed and its effect with varying component dosage on the degree of polymerization was investigated. The results show that the proper type and amount of inorganic salt, as well as amine initiator, are conductive to the increase of degree of polymerization. The fine ingredient of the initiation system is as follows:the dosages of amine, persulphate and inorganic salt are 0.75%, 0.10% and 1.00% by mass based on acryl acid respectively, the molar ratio of sulphite to the persulphate is 1:1. Under such conditions the degree of polyacrylate can reach 7.43×107 with a acceptable polymerization time for industrial production.展开更多
First-principles calculations based on the density-functional theory were employed to study the crystal structure of vanadium phosphide compounds,such as V3P,V2P,VP,VP2 and VP4. Cohesive energy of five types of vanadi...First-principles calculations based on the density-functional theory were employed to study the crystal structure of vanadium phosphide compounds,such as V3P,V2P,VP,VP2 and VP4. Cohesive energy of five types of vanadium phosphide compounds was calculated to assess their structural stability. The charge density distribution and densities of states of vanadium phosphides were discussed to study further their electronic structures. The results show that the structure of metal-rich compounds is considerably more stable than the phosphorus-rich compositions,and covalent bond exists between the V and P atoms of V3P,V2P,VP,VP2 and VP4.展开更多
The selective catalytic reduction reaction belongs to the gas-solid multiphase reaction, and the adsorption of NH3 and NO on CuO/γ-Al2O3 catalysts plays an important role in the reaction. Performance of the CuO/γ-Al...The selective catalytic reduction reaction belongs to the gas-solid multiphase reaction, and the adsorption of NH3 and NO on CuO/γ-Al2O3 catalysts plays an important role in the reaction. Performance of the CuO/γ-Al2O3 catalysts was explored in a fixed bed adsorption system. The catalysts maintain nearly 100% NO conversion efficiency at 350℃. Comprehensive tests were carried out to study the adsorption behavior of NH3 and NO over the catalysts. The desorption experiments prove that NH3 and NO are adsorbed on CuO/γ-Al2O3 catalysts. The adsorption behaviors of NH3 and NO were also studied with the in-situ diffusion reflectance infrared Fourier transform spectroscopy methods. The results show that NH3 could be strongly adsorbed on the catalysts, resulting in coordinated NH3 and NH4＋. NO adsorption leads to the formation of bridging bidentate nitrate, chelating bidentate nitrate, and chelating nitro. The interaction of NH3 and NO molecules with the Cu2＋ present on the CAl2O3 （100） surface was investigated by using a periodic density functional theory. The results show that the adsorption of all the molecules on the Cu2＋ site is energetically favorable, whereas NO bound is stronger than that of NH3 with the adsorption site, and key information about the structural and energetic properties was also addressed.展开更多
The electronic structure and optical properties of the tetragonal phase quaternary arsenide oxides YZnAsO and LaZnAsO were studied using density-functional theory(DFT) within generalized gradient approximation(GGA).Th...The electronic structure and optical properties of the tetragonal phase quaternary arsenide oxides YZnAsO and LaZnAsO were studied using density-functional theory(DFT) within generalized gradient approximation(GGA).The band structure along the higher symmetry axes in the Brillouin zone,the density of states(DOS) and the partial density of states(PDOS) were presented.The calculated energy band structures show that both YZnAsO and LaZnAsO are indirect gap semiconductors with band gap of 1.173 1 eV and 1.166 5 eV,respectively.The DOS and PDOS show the hybridization of Y-O/La-O atom orbits and Zn-As atom orbits.The dielectric function,reflectivity,absorption coefficient,refractive index,electron energy-loss function and optical conductivity were presented in an energy range from 0 to 25 eV for discussing the optical properties of YZnAsO and LaZnAsO.展开更多
The electronic structures,chemical bonding,elastic and optical properties of the novel hP24 phase WB3 were investigated by using density-functional theory(DFT) within generalized gradient approximation(GGA).The calcul...The electronic structures,chemical bonding,elastic and optical properties of the novel hP24 phase WB3 were investigated by using density-functional theory(DFT) within generalized gradient approximation(GGA).The calculated energy band structures show that the hP24 phase WB3 is metallic material.The density of state(DOS) and the partial density of state(PDOS) calculations show that the DOS near the Fermi level is mainly from the W 5d and B 2p states.Population analysis suggests that the chemical bonding in hP24-WB3 has predominantly covalent characteristics with mixed covalent-ionic characteristics.Basic physical properties,such as lattice constant,bulk modulus,shear modulus and elastic constants Cij were calculated.The elastic modulus E and Poisson ratio υ were also predicted.The results show that hP24-WB3 phase is mechanically stable and behaves in a brittle manner.Detailed analysis of all optical functions reveals that WB3 is a better dielectric material,and reflectivity spectra show that WB3 can be promised as good coating material in the energy regions of 8.5-11.4 eV and 14.5-15.5 eV.展开更多
To make sure the intermediate products of the carbothermic reduction of Al2O3 process, such as Al4CO4, Al2CO and Al4C3,and the interaction of AlCl, AlCl2, AlCl3 with Al4CO4, Al2CO and Al4C3, respectively, thermodynami...To make sure the intermediate products of the carbothermic reduction of Al2O3 process, such as Al4CO4, Al2CO and Al4C3,and the interaction of AlCl, AlCl2, AlCl3 with Al4CO4, Al2CO and Al4C3, respectively, thermodynamic analyses were used to study the chloride reaction production of them under the vacuum situation. The stable structures and electronic properties of AlCl, AlCl2 and AlCl3 adsorbed on Al4CO4, Al2CO and Al4C3 were calculated by first-principles calculations by the CASTEP module in the Materials Studio program. The results show that the AlCl3 and AlCl2 molecules have decomposed on the plane of Al4C3（001）, while there are no obvious decomposition of AlCl3 and AlCl2 on Al4CO4（001） and Al2CO（001） planes. The adsorption of AlCl on the Al4CO4（001）and Al2CO（001） planes is stronger than that on the Al4C3（001） plane. The interaction strength of AlCl3, as well as AlCl2, with Al4CO4,Al2CO and Al4C3 is in the sequence of Al4CO4Al2CO〉Al4C3.展开更多
The equilibrium lattice parameters, electronic structure, bulk modulus, Debye temperature, heat capacity and Gibbs energy of TiB and TiB2 were investigated using the pseudopotential plane-wave method based on density ...The equilibrium lattice parameters, electronic structure, bulk modulus, Debye temperature, heat capacity and Gibbs energy of TiB and TiB2 were investigated using the pseudopotential plane-wave method based on density functional theory (DFT) and the improved quasi-harmonic Debye method. The results show that the total density of states (DOS) of TiB2 is mainly provided by the orbit hybridization of Ti-3d and B-2p states, and the total DOS of TiB is mainly provided by the hybrids bond of Ti-3d and B-2p below the Fermi level and Ti—Ti bond up to the Fermi level. The Ti—B hybrid bond in TiB2 is stronger than that in TiB. Finally, the enthalpy of formation at 0 K, heat capacity and Gibbs free energy of formation at various temperatures were determined. The calculated results are in excellent agreement with the available experimental data.展开更多
基金National Key Research and Development Program of China(2022YFB3708500,2023YFB3611000)Fujian Science&Technology Innovation Laboratory for Optoelectronic Information of China(2020ZZ109)。
文摘Currently,the carbothermal reduction-nitridation(CRN)process is the predominant method for preparing aluminum nitride(AlN)powder.Although AlN powder prepared by CRN process exhibits high purity and excellent sintering activity,it also presents challenges such as the necessity for high reaction temperatures and difficulties in achieving uniform mixing of its raw materials.This study presents a comprehensive investigation into preparation process of AlN nanopowders using a combination of hydrothermal synthesis and CRN.In the hydrothermal reaction,a homogeneous composite precursor consisting of carbon and boehmite(γ-AlOOH)is synthesized at 200℃using aluminum nitrate as the aluminum source,sucrose as the carbon source,and urea as the precipitant.During the hydrothermal process,the precursor develops a core-shell structure,with boehmite tightly coated with carbon(γ-AlOOH@C)due to electrostatic attraction.Compared with conventional precursor,the hydrothermal hybrid offers many advantages,such as ultrafine particles,uniform particle size distribution,good dispersion,high reactivity,and environmental friendliness.The carbon shell enhances thermodynamic stability of γ-Al_(2)O_(3) compared to the corundum phase(α-Al_(2)O_(3))by preventing the loss of the surface area in alumina.This stability enables γ-Al_(2)O_(3) to maintain high reactivity during CRN process,which initiates at 1300℃,and concludes at 1400℃.The underlying mechanisms are substantiated through experiments and thermodynamic calculations.This research provides a robust theoretical and experimental foundation for the hydrothermal combined carbothermal preparation of non-oxide ceramic nanopowders.
基金National Natural Science Foundation of China(No.22405249)Open Project of Key Laboratory of Rubber Research Institute,Chinese Academy of Tropical Agricultural Science in 2025(No.RRI-KLOF202402)。
文摘To enhance the overall performance of cyclotrimethylenetrinitramine(RDX),a modification strategy for RDX via in situ coordination with monometallic polydopamine(PDA)coatings(PDA-Fe,PDA-Cu,and PDA-Pb)was developed.The thermal properties of pristine RDX and its modified variants(RDX@PDA-Fe,RDX@PDA-Cu,RDX@PDA-Pb)were characterized using differential scanning calorimetry(DSC)and accelerating rate calorimetry(ARC).The impact sensitivity of these materials was evaluated via the characteristic drop-height method.The results demonstrate that PDA-metal metal coatings—formed through coordination between PDA and single metal ions(Fe^(3+),Cu^(2+),or Pb^(2+))—significantly enhance RDX′s thermal stability while attenuating its mechanical sensitivity.These coatings act as energy-absorbing barriers against external stimuli,effectively mitigating RDX′s sensitivity.Furthermore,they elevate RDX′s thermal stability by increasing its decomposition onset temperature and accelerating its decomposition kinetics.The monometallic coatings also catalyze RDX′s thermal decomposition and combustion,with Cu and Pb exhibiting particularly distinct catalytic effects.
基金Project(20376086) supported by National Natural Science Foundation of China
文摘The mechanism of stability of Co-doped spinel λ-MnO_2 that is referred to as spinel Li_xMn_2O_4 (x=0) was studied by using the first-principle calculation method. The total energy and formation enthalpy can be decreased remarkably due to the Co substation, resulting in a more stable structure of λ-Mn_xCr_(2-x)O_4. The bond order and DOS analysis were given in detail to explain the nature of stability improvement. The calculated results show that as the content of Co dopant increases, the bond order of Mn—O becomes larger and the peak of density of states around Fermi level shifts toward lower energy. The charge density distribution illustrates that the Mn—O bonding is ionic and partially covalent, and the covalent Mn-O bonding becomes stronger with the increase of Co dopant content. The results confirm that the Codoping will enhance the stability of λ-MnO_2 and hence improve the electrochemistry performance of Li_xMn_2O_4.
基金Projects(51674052,51974046)supported by the National Natural Science Foundation of ChinaProject(cstc2018jcyjAX0003)supported by the Chongqing Research Program of Basic Research and Frontier Technology,China。
文摘Based on the first-principles calculations of density functional theory,co-adsorption models of C or CO with Cl2 on rutile TiO2(100)surface were established.The adsorption structures and electronic properties during chlorination process were predicted.Then,the adsorption energy,charge density,electron density difference and density of state of the adsorption structures were calculated and analyzed.The stabilities of the adsorption structures and the charge distributions between atoms were studied.It was found that both C and CO could promote the adsorption reactions of Cl2 on TiO2(100)surface,and C was more favorable to the adsorption process.The results show that the adsorption process of Cl2 on TiO2(100)surface was physisorption,and the co-adsorption processes of C or CO with Cl2 on TiO2(100)surface were chemisorptions.
基金Projects(RG148/12AET,RG086/10AET) supported by the UMRG,MalaysiaProject(PS05812010B) supported by the Post Graduate Research Fund,Malaysia
文摘Ground improvement has been used on many construction sites to densify granular materials, in other word, to improve soil properties and reduce potential settlement. This work presents a case study of ground improvement using rapid impact compaction （RIC）. The research site comprises the construction of workshop and depots as part of railway development project at Batu Gajah-Ipoh, Malaysia. In-situ testing results show that the subsurface soil comprises mainly of sand and silty sand through the investigated depth extended to 10 m. Groundwater is approximately 0.5 m below the ground surface. Evaluation of improvement was based on the results of pre- and post-improvement cone penetration test （CPT）. Interpretation software has been used to infer soil properties. Load test was conducted to estimate soil settlement. It is found that the technique succeeds in improving soil properties namely the relative density increases from 45% to 70%, the friction angle of soil is increased by an average of 3°, and the soil settlement is reduced by 50%： The technique succeeds in improving soil properties to approximately 5.0 m in depth depending on soil uniformity with depth.
基金Project(51275116)supported by the National Natural Science Foundation of ChinaProject(2012ZE77010)supported by the Aero Science Foundation of ChinaProject(LBH-Q11090)supported by the Postdoctoral Science Research Development Foundation of Heilongjiang Province,China
文摘The electric double layer with the transmission of particles was presented based on the principle of electrochemistry.In accordance with this theory,the cavitation catalysis removal mechanism of ultrasonic-pulse electrochemical compound machining(UPECM) based on particles was proposed.The removal mechanism was a particular focus and was thus validated by experiments.The principles and experiments of UPECM were introduced,and the removal model of the UPECM based on the principles of UPECM was established.Furthermore,the effects of the material removal rate for the main processing parameters,including the particles size,the ultrasonic vibration amplitude,the pulse voltage and the minimum machining gap between the tool and the workpiece,were also studied through UPECM.The results show that the particles promote ultrasonic-pulse electrochemical compound machining and thus act as the catalyzer of UPECM.The results also indicate that the processing speed,machining accuracy and surface quality can be improved under UPECM compound machining.
基金Project(2682019CX06)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2019KY23)supported by Research Start-up Fund from the Southwest Jiaotong University,China+2 种基金Projects(20ZDYF0236,20ZDYF0490)supported by the Key R&D Projects in the Field of High and new Technology of Sichuan,ChinaProject(52072311)supported by the National Natural Science Foundation of ChinaProject(2019JDJQ0009)supported by the Outstanding Young Scientific and Technical Talents in Sichuan Province,China。
文摘Transition metal dichalcogenides are interesting candidates as photocatalysts for hydrogen evolution reaction.The MnPSe_(3)/WS_(2) heterostructure is hence studied here with first principles calculations by exploring its electronic properties under the application of an electric field.It is discovered that the band gap will decrease from the WS_(2) monolayer to the MnPSe_(3)/WS_(2) heterostructure with Perdew-Burke-Ernzerhof functional,while increase slightly when electron correlation is involved.The conduction band minimum of the heterostructure is determined by the MnPSe3 layer,while the valence band maximum is contributed by the WS_(2)layer.The band edges and band gap suggest that the heterostructure will have good photocatalytic properties for water splitting.Moreover,comparing to monolayer WS_(2),the light absorption in both the ultraviolet and visible regions will be enhanced.When an electric field is present,a linear relation is observed between the electric field and the band gap within specific range,which can thus modulate the photocatalytic performance of this heterostructure.
基金Project(51801129)supported by the National Natural Science Foundation of ChinaProject supported by the State Key Laboratory of Powder Metallurgy,China。
文摘Ab initio calculations are used to understand the fundamental mechanism of the solid solution softening/hardening of the Mo-binary system.The results reveal that the Mo-Ti,Mo-Ta,Mo-Nb,and Mo-W interactions are primarily attractive with negative heats of formation,while the interactions of Mo-Re,and Mo-Zr would be mainly repulsive with positive heats of formation.It is also shown that the addition of Re and Zr would cause the solid solution softening of Mo by the decrease of the unstable stacking fault energy and the increase of ductility.On the contrary,the elements of W,Ta,Ti,and Nb could bring about the solid-solution hardening of Mo through the impediment of the slip of the dislocation and the decrease of ductility.Electronic structures indicate that the weaker/stronger chemical bonding due to the alloying elements should fundamentally induce the solid solution softening/hardening of Mo.The results are discussed and compared with available evidence in literatures,which could deepen the fundamental understanding of the solid solution softening/hardening of the binary metallic system.
基金Project(50725416) supported by National Natural Science Funds for Distinguished Young Scholars of China
文摘Alastraet： The gas-based direct reduction of iron ore pellets was carried out by simulating the typical gas composition in coal gasification process, Midrex and HyMII processes. The influences of gas composition and temperature on reduction were studied. Results show that the increasing of HE proportion is helpful to improve the reduction rate. However, when ~o（H2）：~o（CO）〉1.6：1, changes of HE content have little influence on it. Appropriate reduction temperature is about 950 ℃, and higher temperature （1 000 ℃） may unfavorably slow the reduction rate. From the kinetics analysis at 950 ℃, the most part of reduction course is likely controlled by interfacial chemical reaction mechanism and in the final stage controlled by a combined effect of gaseous diffusion and interfacial chemical reaction mechanisms. From the utilizations study of different reducing gases at 950 ℃, the key step in reduction course is the 3rd stage （FeO→Fe）, and the utilization of reducing gas increases with the rise of HE proportion.
文摘Pyrite （FeS2） bulk and （100） surface properties and the oxygen adsorption on the surface were studied by using density functional theory methods. The results show that in the formation of FeS2 （100） surface, there exists a process of electron transfer from Fe dangling bond to S dangling bond. In this situation, surface Fe and S atoms have more ionic properties. Both Fe2+ and S2- have high electrochemistry reduction activity, which is the base for oxygen adsorption. From the viewpoint of adsorption energy, the parallel form oxygen adsorption is in preference. The result also shows that the state of oxygen absorbed on FeS2 surface acts as peroxides rather than O2.
基金Project(G199906490 2) supported by the National Key Fundamental Research and Development Program of China
文摘The redox initiation system for polyacrylate sodium of high molecular mass was designed and its effect with varying component dosage on the degree of polymerization was investigated. The results show that the proper type and amount of inorganic salt, as well as amine initiator, are conductive to the increase of degree of polymerization. The fine ingredient of the initiation system is as follows:the dosages of amine, persulphate and inorganic salt are 0.75%, 0.10% and 1.00% by mass based on acryl acid respectively, the molar ratio of sulphite to the persulphate is 1:1. Under such conditions the degree of polyacrylate can reach 7.43×107 with a acceptable polymerization time for industrial production.
基金Project(20871101)supported by the National Natural Science Foundation of ChinaProject(09C945)supported by the Scientific Research Fund of Hunan Provincial Education Department,China
文摘First-principles calculations based on the density-functional theory were employed to study the crystal structure of vanadium phosphide compounds,such as V3P,V2P,VP,VP2 and VP4. Cohesive energy of five types of vanadium phosphide compounds was calculated to assess their structural stability. The charge density distribution and densities of states of vanadium phosphides were discussed to study further their electronic structures. The results show that the structure of metal-rich compounds is considerably more stable than the phosphorus-rich compositions,and covalent bond exists between the V and P atoms of V3P,V2P,VP,VP2 and VP4.
基金Projects(50806025, 51021065, 50976038) supported by the National Natural Science Foundation of ChinaProject(20100480893) supported by the China Postdoctoral Science FoundationProject(1001022B) supported by the Postdoctoral Research Fund of Jiangsu Province, China
文摘The selective catalytic reduction reaction belongs to the gas-solid multiphase reaction, and the adsorption of NH3 and NO on CuO/γ-Al2O3 catalysts plays an important role in the reaction. Performance of the CuO/γ-Al2O3 catalysts was explored in a fixed bed adsorption system. The catalysts maintain nearly 100% NO conversion efficiency at 350℃. Comprehensive tests were carried out to study the adsorption behavior of NH3 and NO over the catalysts. The desorption experiments prove that NH3 and NO are adsorbed on CuO/γ-Al2O3 catalysts. The adsorption behaviors of NH3 and NO were also studied with the in-situ diffusion reflectance infrared Fourier transform spectroscopy methods. The results show that NH3 could be strongly adsorbed on the catalysts, resulting in coordinated NH3 and NH4＋. NO adsorption leads to the formation of bridging bidentate nitrate, chelating bidentate nitrate, and chelating nitro. The interaction of NH3 and NO molecules with the Cu2＋ present on the CAl2O3 （100） surface was investigated by using a periodic density functional theory. The results show that the adsorption of all the molecules on the Cu2＋ site is energetically favorable, whereas NO bound is stronger than that of NH3 with the adsorption site, and key information about the structural and energetic properties was also addressed.
基金Project(50474051) supported by the National Natural Science Foundation of China
文摘The electronic structure and optical properties of the tetragonal phase quaternary arsenide oxides YZnAsO and LaZnAsO were studied using density-functional theory(DFT) within generalized gradient approximation(GGA).The band structure along the higher symmetry axes in the Brillouin zone,the density of states(DOS) and the partial density of states(PDOS) were presented.The calculated energy band structures show that both YZnAsO and LaZnAsO are indirect gap semiconductors with band gap of 1.173 1 eV and 1.166 5 eV,respectively.The DOS and PDOS show the hybridization of Y-O/La-O atom orbits and Zn-As atom orbits.The dielectric function,reflectivity,absorption coefficient,refractive index,electron energy-loss function and optical conductivity were presented in an energy range from 0 to 25 eV for discussing the optical properties of YZnAsO and LaZnAsO.
基金Project(11271121)supported by the National Natural Science Foundation of ChinaProject(11JJ2002)supported by the Natural Science Foundation of Hunan Province,China+1 种基金Project(11K038)supported by Key Laboratory of Computational and Stochastic Mathematics of Ministry of Education of ChinaProject(2013GK3130)supported by the Scientific and Technological Plan of Hunan Province,China
文摘The electronic structures,chemical bonding,elastic and optical properties of the novel hP24 phase WB3 were investigated by using density-functional theory(DFT) within generalized gradient approximation(GGA).The calculated energy band structures show that the hP24 phase WB3 is metallic material.The density of state(DOS) and the partial density of state(PDOS) calculations show that the DOS near the Fermi level is mainly from the W 5d and B 2p states.Population analysis suggests that the chemical bonding in hP24-WB3 has predominantly covalent characteristics with mixed covalent-ionic characteristics.Basic physical properties,such as lattice constant,bulk modulus,shear modulus and elastic constants Cij were calculated.The elastic modulus E and Poisson ratio υ were also predicted.The results show that hP24-WB3 phase is mechanically stable and behaves in a brittle manner.Detailed analysis of all optical functions reveals that WB3 is a better dielectric material,and reflectivity spectra show that WB3 can be promised as good coating material in the energy regions of 8.5-11.4 eV and 14.5-15.5 eV.
基金Projects(51104078,51264023)supported by the National Natural Science Foundation of ChinaProject(2010CD022)supported by Yunnan Provincial Applied Basic Research Fund,China+2 种基金Project(IRT1250)supported by the Program for Innovative Research Team in University of Ministry of Education of ChinaProject(U1202271)supported by the National Natural Science Foundation of China-Yunnan United FundProject(KKZ3201252020)supported by Fund of Kunming University of Science and Technology for Talent Training,China
文摘To make sure the intermediate products of the carbothermic reduction of Al2O3 process, such as Al4CO4, Al2CO and Al4C3,and the interaction of AlCl, AlCl2, AlCl3 with Al4CO4, Al2CO and Al4C3, respectively, thermodynamic analyses were used to study the chloride reaction production of them under the vacuum situation. The stable structures and electronic properties of AlCl, AlCl2 and AlCl3 adsorbed on Al4CO4, Al2CO and Al4C3 were calculated by first-principles calculations by the CASTEP module in the Materials Studio program. The results show that the AlCl3 and AlCl2 molecules have decomposed on the plane of Al4C3（001）, while there are no obvious decomposition of AlCl3 and AlCl2 on Al4CO4（001） and Al2CO（001） planes. The adsorption of AlCl on the Al4CO4（001）and Al2CO（001） planes is stronger than that on the Al4C3（001） plane. The interaction strength of AlCl3, as well as AlCl2, with Al4CO4,Al2CO and Al4C3 is in the sequence of Al4CO4Al2CO〉Al4C3.
基金Project(07JJ3102)supported by the Natural Science Foundation of Hunan Province,ChinaProject(k0902132-11)supported by the Changsha Municipal Science and Technology,China
文摘The equilibrium lattice parameters, electronic structure, bulk modulus, Debye temperature, heat capacity and Gibbs energy of TiB and TiB2 were investigated using the pseudopotential plane-wave method based on density functional theory (DFT) and the improved quasi-harmonic Debye method. The results show that the total density of states (DOS) of TiB2 is mainly provided by the orbit hybridization of Ti-3d and B-2p states, and the total DOS of TiB is mainly provided by the hybrids bond of Ti-3d and B-2p below the Fermi level and Ti—Ti bond up to the Fermi level. The Ti—B hybrid bond in TiB2 is stronger than that in TiB. Finally, the enthalpy of formation at 0 K, heat capacity and Gibbs free energy of formation at various temperatures were determined. The calculated results are in excellent agreement with the available experimental data.
