The high temperature chemical reaction process of La2O3 in H3BO3-C system was studied by means of XRD and TG-DTA.The results showed that dehydration reaction of H3BO3 occurred in the temperature range of 82~390 ℃;La...The high temperature chemical reaction process of La2O3 in H3BO3-C system was studied by means of XRD and TG-DTA.The results showed that dehydration reaction of H3BO3 occurred in the temperature range of 82~390 ℃;La2O3 and B2O3 reacted to form LaB3O6,LaBO3,and B4C in the temperature range of 836~1400℃;at 1450 ℃,B4C and LaBO3 further reacted to form LaB4,and partial LaB4 and B reacted to form LaB6;at 1500 ℃,LaB4 and B reacting into LaB6 was the main reaction,and the content of LaB6 increased with prolonging time.展开更多
Singular perturbation reaction-diffusion problem with Dirichlet boundary condition is considered. It is a multi-scale problem. Presence of small parameter leads to boundary layer phenomena in both sides of the region....Singular perturbation reaction-diffusion problem with Dirichlet boundary condition is considered. It is a multi-scale problem. Presence of small parameter leads to boundary layer phenomena in both sides of the region. A non-equidistant finite difference method is presented according to the property of boundary layer. The region is divided into an inner boundary layer region and an outer boundary layer region according to transition point of Shishkin. The steps sizes are equidistant in the outer boundary layer region. The step sizes are gradually increased in the inner boundary layer region such that half of the step sizes are different from each other. Truncation error is estimated. The proposed method is stable and uniformly convergent with the order higher than 2. Numerical results are given, which are in agreement with the theoretical result.展开更多
A unidirectional reaction for synthesis of the high T_c superconductor YBa_2Cu_3O_x has been proposed, Its T_c is 90-94.5 K and △T is 1 K. The phase relationships in the system Y_2BaCuO_5-Y_2Cu_2O_5-CuO-YBa_2Cu_3O_x ...A unidirectional reaction for synthesis of the high T_c superconductor YBa_2Cu_3O_x has been proposed, Its T_c is 90-94.5 K and △T is 1 K. The phase relationships in the system Y_2BaCuO_5-Y_2Cu_2O_5-CuO-YBa_2Cu_3O_x were studied and discussed.展开更多
The equilibrating problem for intermediate-high energy reaction is studied by themicroscopic kinetic model.The calculations are carried out for reaction 830 MeV p+Fe.Thetime evolution of the squared momentum component...The equilibrating problem for intermediate-high energy reaction is studied by themicroscopic kinetic model.The calculations are carried out for reaction 830 MeV p+Fe.Thetime evolution of the squared momentum components and the kinetic energy density shows thatquasi equilibrium is reached.展开更多
Aspects of BURSTS and Spallation reactions induced by high-energy heavy ions in thick targets (>10 cm thick) will be investigated: BURSTS are reviewed from a historical and phenomenological point-of-view. Details o...Aspects of BURSTS and Spallation reactions induced by high-energy heavy ions in thick targets (>10 cm thick) will be investigated: BURSTS are reviewed from a historical and phenomenological point-of-view. Details of interactions in nuclear emulsions will be compared for irradiations of 72 GeV 22Ne-ions from Dubna with irradiations of 72 GeV 40Ar-ions from Berkeley. Measured correlations in individual interactions between multiplicities of “minimum ionizing particles”, ns, and “black prongs”, nb, will be shown as “ns-vs.-nb” per event for BURSTS and separately for Spallation in interactions of 72 GeV 22Ne-ions. Monte Carlo calculations, based on the MCNPX 2.7 code, have been carried out for 72 GeV 22Ne interacting in nuclear emulsions: The correlation between ns and nb in Spallation reactions could be understood. However, “ns-vs.-nb” correlations from BURST-interactions could not be reproduced with this model for events with small numbers of heavy prongs nh ≤ 10. For large numbers of heavy prongs with nh > 10 one could find some agreement between experiments and calculations, however, not in all details. Further experimental and theoretical studies are necessary before one has a complete understanding of BURST interactions in high-energy heavy ion reactions.展开更多
The NiFe2O4-10NiO powder for inert anode of aluminium electrolysis was prepared by high temperature solid state reaction. The microstructural evolution from the raw materials NiO and Fe2O3 to the NiFe2O4-10NiO powder ...The NiFe2O4-10NiO powder for inert anode of aluminium electrolysis was prepared by high temperature solid state reaction. The microstructural evolution from the raw materials NiO and Fe2O3 to the NiFe2O4-10NiO powder was studied by SEM. The results show that the domain structure making up of the agglomerate particles of Fe2O3 remains after high temperature solid state reaction, and the diffusion of Ni2+ into Fe2O3 structure is the control step of the reaction process. A microstructure with compact structure and fine grain inside the particle results from the sintering of NiFe2O4-10NiO powder.展开更多
High Nb containing TiAl alloy was fabricated in argon atmosphere by reactive hot pressing process. Reaction mechanism was investigated by means of microstructural analyses and thermodynamic calculations. The results s...High Nb containing TiAl alloy was fabricated in argon atmosphere by reactive hot pressing process. Reaction mechanism was investigated by means of microstructural analyses and thermodynamic calculations. The results show that it is feasible to prepare high Nb containing TiAl alloy with fine lamellar colonies by reactive hot pressing process. The reaction between Ti and Al powders is dominant in Ti-Al-Nb system. Nb powders dissolve into the Ti-Al matrix by diffusion. Pore nests are formed in situ after Nb powders diffusion. The hot pressing atmosphere is optimized by thermodynamic calculations. Vacuum or argon protective atmosphere should be adopted.展开更多
Though water electrolysis is effective in generating high-quality hydrogen gas,it requires effective electrocatalysts for hydrogen evolution reaction(HER).CoS_2 have been considered as a promising HER electrocatalyst ...Though water electrolysis is effective in generating high-quality hydrogen gas,it requires effective electrocatalysts for hydrogen evolution reaction(HER).CoS_2 have been considered as a promising HER electrocatalyst because of its high ctalytic activity.However,the key limitation for CoS_2 nanomaterial as HER electrocatalyst is its poor stability,which may be due to the structural breakdown of CoS_2 nanostructure or the evolution of S during H_2 evolution in acid media.Coating porous carbon thin layer for protection from structural breakdown and evolution of S is a good way to improve catalytic stability.In addition,coating carbon layer can change electronic structure of CoS_2 for the moderated hydrogen adsorption energy,leading to enhanced catalytic activity.Here,CoS_2 yolk-shell spheres coated with carbon thin layers exhibit superior catalytic performance for HER with low overpotential,small Tafel slope,and excellent stability.展开更多
To describe properties of the high frequency gravitational wave (HFGW) propagating through the vacuum gravitational field in Robertson-Walker background space-time,we calculated its energy momentum pseudo-tensor (EMPT...To describe properties of the high frequency gravitational wave (HFGW) propagating through the vacuum gravitational field in Robertson-Walker background space-time,we calculated its energy momentum pseudo-tensor (EMPT) in the limit of short wavelengths by taking the Brill-Hartle average on the second order perturbation of the Einstein tensor over several wavelengths. By rewriting the EMPT as a form of perfect fluid,the dynamical back-reaction of HFGW on the background space-time was discussed. The result shows that the energy density of HFGW,which is in the gauge we chose,is positive definite. The HFGW serves as a source for curving the background space-time and affects the dynamical evolution and time evolution of the scale factor of the Robertson-Walker metric.展开更多
In the present study, Ti-45Al-(6, 7, 8)Nb(at%) and Ti-45Al-8Nb-0.5(Mn, Si, Y, B) alloys were prepared by arc melting and casting into Zr O2(Y2O3 stabilized) ceramic moulds to study the effect of alloying elements Nb a...In the present study, Ti-45Al-(6, 7, 8)Nb(at%) and Ti-45Al-8Nb-0.5(Mn, Si, Y, B) alloys were prepared by arc melting and casting into Zr O2(Y2O3 stabilized) ceramic moulds to study the effect of alloying elements Nb and Mn, Si, Y, B on the interfacial reaction between casting Ti Al alloys and ceramic moulds by SEM, and the elements' distribution in the interface reaction layer by line scanning. The results showed that with an increase in Nb content, the interfacial reaction weakened and the thickness of the reaction layer decreased gradually. The interface reaction thickness of the alloys with Nb content of 6, 7, 8at% were 60, 34 and 26 μm, respectively. Clearly, the addition of 8at% Nb to Ti-45 Al is the best for the thickness of the reaction layer. The addition of Nb would form a Nb-rich film in the reaction layer, which could reduce the solubility of oxygen in the interface, and suppress further diffusion of oxygen to the matrix. If the same content of Mn, Si, Y, or B alloying elements were added respectively to Ti-45Al-8Nb, the thickness of the interface reaction layer from large to small was as follows: Mn>Si>Y>B. The interface reaction thickness increased after 0.5at% Mn added, had no obvious change after 0.5at% Si addition, and decreased after adding 0.5at% Y or B. The introduced elements, which formed a protective film or/and promoted the formation of a dense aluminum oxide layer, would be of benefit to the resistance of interfacial reaction.展开更多
基金Project supported by the National Natural Science Foundation of China(5057403)Scientific Research Special Foundation of Doctor Subject of Chinese University(20030145015)
文摘The high temperature chemical reaction process of La2O3 in H3BO3-C system was studied by means of XRD and TG-DTA.The results showed that dehydration reaction of H3BO3 occurred in the temperature range of 82~390 ℃;La2O3 and B2O3 reacted to form LaB3O6,LaBO3,and B4C in the temperature range of 836~1400℃;at 1450 ℃,B4C and LaBO3 further reacted to form LaB4,and partial LaB4 and B reacted to form LaB6;at 1500 ℃,LaB4 and B reacting into LaB6 was the main reaction,and the content of LaB6 increased with prolonging time.
基金supported by the Educational Department Foundation of Fujian Province of China(Nos. JA08140 and A0610025)the Scientific Research Foundation of Zhejiang University of Scienceand Technology (No. 2008050)the National Natural Science Foundation of China (No. 50679074)
文摘Singular perturbation reaction-diffusion problem with Dirichlet boundary condition is considered. It is a multi-scale problem. Presence of small parameter leads to boundary layer phenomena in both sides of the region. A non-equidistant finite difference method is presented according to the property of boundary layer. The region is divided into an inner boundary layer region and an outer boundary layer region according to transition point of Shishkin. The steps sizes are equidistant in the outer boundary layer region. The step sizes are gradually increased in the inner boundary layer region such that half of the step sizes are different from each other. Truncation error is estimated. The proposed method is stable and uniformly convergent with the order higher than 2. Numerical results are given, which are in agreement with the theoretical result.
文摘A unidirectional reaction for synthesis of the high T_c superconductor YBa_2Cu_3O_x has been proposed, Its T_c is 90-94.5 K and △T is 1 K. The phase relationships in the system Y_2BaCuO_5-Y_2Cu_2O_5-CuO-YBa_2Cu_3O_x were studied and discussed.
基金The project supported in part by the National Natural Science Foundation of China and Nuclear Industry Science Foundation of China
文摘The equilibrating problem for intermediate-high energy reaction is studied by themicroscopic kinetic model.The calculations are carried out for reaction 830 MeV p+Fe.Thetime evolution of the squared momentum components and the kinetic energy density shows thatquasi equilibrium is reached.
文摘Aspects of BURSTS and Spallation reactions induced by high-energy heavy ions in thick targets (>10 cm thick) will be investigated: BURSTS are reviewed from a historical and phenomenological point-of-view. Details of interactions in nuclear emulsions will be compared for irradiations of 72 GeV 22Ne-ions from Dubna with irradiations of 72 GeV 40Ar-ions from Berkeley. Measured correlations in individual interactions between multiplicities of “minimum ionizing particles”, ns, and “black prongs”, nb, will be shown as “ns-vs.-nb” per event for BURSTS and separately for Spallation in interactions of 72 GeV 22Ne-ions. Monte Carlo calculations, based on the MCNPX 2.7 code, have been carried out for 72 GeV 22Ne interacting in nuclear emulsions: The correlation between ns and nb in Spallation reactions could be understood. However, “ns-vs.-nb” correlations from BURST-interactions could not be reproduced with this model for events with small numbers of heavy prongs nh ≤ 10. For large numbers of heavy prongs with nh > 10 one could find some agreement between experiments and calculations, however, not in all details. Further experimental and theoretical studies are necessary before one has a complete understanding of BURST interactions in high-energy heavy ion reactions.
基金Project(2005CB623703) supported by the National Basic Research Program of China
文摘The NiFe2O4-10NiO powder for inert anode of aluminium electrolysis was prepared by high temperature solid state reaction. The microstructural evolution from the raw materials NiO and Fe2O3 to the NiFe2O4-10NiO powder was studied by SEM. The results show that the domain structure making up of the agglomerate particles of Fe2O3 remains after high temperature solid state reaction, and the diffusion of Ni2+ into Fe2O3 structure is the control step of the reaction process. A microstructure with compact structure and fine grain inside the particle results from the sintering of NiFe2O4-10NiO powder.
基金Project(704008) supported by the Key Grant Project of Chinese Ministry of Education Project(NCET-04-01017) supported by the Program for New Century Excellent Talents in University, China
文摘High Nb containing TiAl alloy was fabricated in argon atmosphere by reactive hot pressing process. Reaction mechanism was investigated by means of microstructural analyses and thermodynamic calculations. The results show that it is feasible to prepare high Nb containing TiAl alloy with fine lamellar colonies by reactive hot pressing process. The reaction between Ti and Al powders is dominant in Ti-Al-Nb system. Nb powders dissolve into the Ti-Al matrix by diffusion. Pore nests are formed in situ after Nb powders diffusion. The hot pressing atmosphere is optimized by thermodynamic calculations. Vacuum or argon protective atmosphere should be adopted.
基金supported by the National Basic Research Program of China(Nos.2015CB932304,2016YFA0202603)the Natural Science Foundation of China (No.91645104)+1 种基金the Natural Science Foundation of Guangdong Province(Nos.S2013020012833,2016A010104004)the Fundamental Research Fund for the Central Universities(No.16lgjc67)
文摘Though water electrolysis is effective in generating high-quality hydrogen gas,it requires effective electrocatalysts for hydrogen evolution reaction(HER).CoS_2 have been considered as a promising HER electrocatalyst because of its high ctalytic activity.However,the key limitation for CoS_2 nanomaterial as HER electrocatalyst is its poor stability,which may be due to the structural breakdown of CoS_2 nanostructure or the evolution of S during H_2 evolution in acid media.Coating porous carbon thin layer for protection from structural breakdown and evolution of S is a good way to improve catalytic stability.In addition,coating carbon layer can change electronic structure of CoS_2 for the moderated hydrogen adsorption energy,leading to enhanced catalytic activity.Here,CoS_2 yolk-shell spheres coated with carbon thin layers exhibit superior catalytic performance for HER with low overpotential,small Tafel slope,and excellent stability.
基金the National Basic Research Program of China (No.2003 CB 716300)the National Natural Science Foundation of China (No.10575140)+1 种基金the Nature Science Foundation of Chongqing (No. 8562)the Foundation of China Academy of Engineering Physics.
文摘To describe properties of the high frequency gravitational wave (HFGW) propagating through the vacuum gravitational field in Robertson-Walker background space-time,we calculated its energy momentum pseudo-tensor (EMPT) in the limit of short wavelengths by taking the Brill-Hartle average on the second order perturbation of the Einstein tensor over several wavelengths. By rewriting the EMPT as a form of perfect fluid,the dynamical back-reaction of HFGW on the background space-time was discussed. The result shows that the energy density of HFGW,which is in the gauge we chose,is positive definite. The HFGW serves as a source for curving the background space-time and affects the dynamical evolution and time evolution of the scale factor of the Robertson-Walker metric.
基金supported by the National Basic Research Program of China(973 Program,No.2011CB605500)the"Fundamental Research Funds for the Central Universities"(FRF-MP-10-005B)the National Natural Science Foundation of China under Contract No.51171015
文摘In the present study, Ti-45Al-(6, 7, 8)Nb(at%) and Ti-45Al-8Nb-0.5(Mn, Si, Y, B) alloys were prepared by arc melting and casting into Zr O2(Y2O3 stabilized) ceramic moulds to study the effect of alloying elements Nb and Mn, Si, Y, B on the interfacial reaction between casting Ti Al alloys and ceramic moulds by SEM, and the elements' distribution in the interface reaction layer by line scanning. The results showed that with an increase in Nb content, the interfacial reaction weakened and the thickness of the reaction layer decreased gradually. The interface reaction thickness of the alloys with Nb content of 6, 7, 8at% were 60, 34 and 26 μm, respectively. Clearly, the addition of 8at% Nb to Ti-45 Al is the best for the thickness of the reaction layer. The addition of Nb would form a Nb-rich film in the reaction layer, which could reduce the solubility of oxygen in the interface, and suppress further diffusion of oxygen to the matrix. If the same content of Mn, Si, Y, or B alloying elements were added respectively to Ti-45Al-8Nb, the thickness of the interface reaction layer from large to small was as follows: Mn>Si>Y>B. The interface reaction thickness increased after 0.5at% Mn added, had no obvious change after 0.5at% Si addition, and decreased after adding 0.5at% Y or B. The introduced elements, which formed a protective film or/and promoted the formation of a dense aluminum oxide layer, would be of benefit to the resistance of interfacial reaction.