Higher initial(de)hydrogenation temperature and sluggish kinetics are the main bottlenecks to develop Mg-based hydrogen storage alloys with high hydrogen capacity.One of the effective methods of solv ing these problem...Higher initial(de)hydrogenation temperature and sluggish kinetics are the main bottlenecks to develop Mg-based hydrogen storage alloys with high hydrogen capacity.One of the effective methods of solv ing these problems is introducing additives to enhance(de)hydrogenation kinetics and decrease par ticle sizes to lower(de)hydrogenation temperatures.In this work,Mg85-Ni10-La4.5-Y0.5 alloy doped with Cu@C nanoparticles is prepared,which could enhance(de)hydrogenation kinetics via introducing Cu nanoparticles as a catalyst and reduce the alloy particle sizes via acting as a grinding agent to lowe(de)hydrogenation temperature.The results indicate the dehydrogenation temperature of the modified Mg85-Ni10-La4.5-Y0.5 composite could be decreased to 308.5℃,absorb 4.73 wt%H_(2)at 220℃ within1 min and release 5.01 wt%H_(2)within 4 min at 300℃.Moreover,the capacity retention could be main tained around 98.8%after 10 cycles at 300℃,superior than those of Mg85-Ni10-La4.5-Y0.5 and milled Mg85-Ni10-La4.5-Y0.5.DFT results and characterizations suggest that in-situ formed Mg_(2)Cu could acceler ate the dissociation of Mg-H bonds and the presence of amorphous carbon in Mg-Ni-La-Y-Cu system wil further synergistically improve the(de)hydrogenation kinetics of Mg85-Ni10-La4.5-Y0.5.Reduced particle sizes under the aid of carbon frameworks also help introduce boundaries of the particles and shorten hydrogen diffusion pathways.展开更多
Copper based catalysts have high potential for the substituent of noble-metal based catalysts as their high selectivity and moderate activity for selective hydrogenation reaction;however,achieving further high catalyt...Copper based catalysts have high potential for the substituent of noble-metal based catalysts as their high selectivity and moderate activity for selective hydrogenation reaction;however,achieving further high catalytic stability is very difficult.In this work,the carbonization process of Cu-based organic frameworks was explored for the synthesis of highly-dispersed Cu supported by hierarchically porous carbon with high catalytic performance for selective hydrogenation of 1,3-butadiene.The porous hierarchy of carbon support and the dispersion of copper nanoparticles can be precisely tuned by controlling the carbonization process.The resultant catalyst carbonized at 600°C exhibits a rather low reaction temperature at 75°C for 100%butadiene conversion with 100%selectivity to butenes,due to its reasonable porous hierarchy and highly-dispersed copper sites.More importantly,unprecedentedly stability of the corresponding Cu catalyst was firstly observed for selective 1,3-butadiene hydrogenation,with both 100%butadiene conversion and 100%butenes selectivity over 120 h of reaction at 75°C.This study verifies that a simply control the carbonization process of metal organic frameworks can be an effective way to obtain Cu-based catalysts with superior catalytic performance for selective hydrogenation reaction.展开更多
Samples of the Cu-C composite coatings were produced by high-speed ion-plasma magnetron sputtering (HiPMS) with mosaic target (MT). Nanostructure, roughness, mechanical properties as well as electric properties of coa...Samples of the Cu-C composite coatings were produced by high-speed ion-plasma magnetron sputtering (HiPMS) with mosaic target (MT). Nanostructure, roughness, mechanical properties as well as electric properties of coatings depend on carbon-cooper ratio. So 10% - 15% cooper con centration (atomic) results in to dry friction coefficient decrease up to 0.1 and wear resistance increase up to 10<sup>-17</sup> m3/N·m. The HiPMS method allowed us to effectively sputter very different materials like carbon and cooper at the same velocity with required proportion. At the same time, one could obtain a uniform mixture of ingredients on the atomic level. The coating corresponds to a mixture of nano-sized phases of carbon and cooper. Crystalline dispersion of samples depends on carbon concentration. The obtained products are characterized by XRD, UV (257 nm) and visible (514 nm) Raman spectroscopy. The morphologies are studied with TEM and AFM. Mechanical properties were investigated with friction coefficient and micro hardness tests. There was no chemical interaction during Cu-C precipitation on hot substrate (625 - 725 K). The mechanical properties can be explained by free electrons capture with carbon nanostructures and space charge formation.展开更多
Cathode erosion of graphite and Cu/C was studied in direct current arcs, which were ignited between two electrodes comprised of two kinds of carbon materials and a tungsten anode in air. The arced zones on the cathode...Cathode erosion of graphite and Cu/C was studied in direct current arcs, which were ignited between two electrodes comprised of two kinds of carbon materials and a tungsten anode in air. The arced zones on the cathode surface were investigated by a scanning electron microscope. Also, the cathode erosion rates of the investigated materials were measured. The results show that two distinct zone can be seen on both cathodes. The eroded area was located at the zone just opposite to the anode and surrounded by a white zone. The arced surface on the Cu/C containing 9.3 % Cu is rougher than that of the pure graphite. Many particles with various sizes distributed on the Cu/C. The vaporization of Cu can lower the surface temperature and reduce the cathode erosion. Therefore, the cathode erosion rate of the Cu/C is lower than that of the pure graphite.展开更多
Through modular pressing and sintering, the Cu C powder metallurgy samples were made and the process was investigated. The results show that there exist expanding mechanism and shrinking mechanism in sintering process...Through modular pressing and sintering, the Cu C powder metallurgy samples were made and the process was investigated. The results show that there exist expanding mechanism and shrinking mechanism in sintering process, and whether the sintering body is shrinking or expanding depends on the interacting between the two mechanisms, and the HD sintering model is in keeping with the actual sintering process. [展开更多
Carbon-coated Cu nanocomposites (Cu@C NCs) consisting of core-shell nanoparticles and nanorods weresynthesized by arc discharge plasma under an atmosphere of He and H_(2) gas, and the N-doping of themwas achieved by a...Carbon-coated Cu nanocomposites (Cu@C NCs) consisting of core-shell nanoparticles and nanorods weresynthesized by arc discharge plasma under an atmosphere of He and H_(2) gas, and the N-doping of themwas achieved by a post-treatment process using ureal as the precursor. The concentration of N in the Ndoped samples varies in the range of 0.62%-2.31 % (in mole), with a transformation from pyrrolic N tographitic N when increasing the relative content of ureal. Dielectric properties of the NCs without or withN-doping in the microwave and THz bands were investigated. The N-doped samples achieve theenhanced dielectric loss in both microwave and THz bands. In the microwave band, dielectric loss wasdominated by interfacial polarization, dipolar polarization, and conduction loss, while in the THz band,plasma resonance, ionic polarization and conduction loss are responsible for the dielectric loss, with astrong absorption characteristic dominated by conductive effect.展开更多
The in situ direct-current conductance behaviors of Cu/C_(60) nano-scale granular films have been investigated experimentally.The results show that the incorporation of Cu into Ceo greatly increases the conductance of...The in situ direct-current conductance behaviors of Cu/C_(60) nano-scale granular films have been investigated experimentally.The results show that the incorporation of Cu into Ceo greatly increases the conductance of the film.The orientational phase transition that exists in pure C_(60) single crystals still retains in the Cu/C_(60) co-evaporated Elms,while the transition temperature range is significantly widened.The interactions between the nano-scale Cu clusters and C_(60) grains are discussed.展开更多
基金funded by National Key R&D Program of China(No.2021YFB4000604)the National Natural Science Foundations of China(No.52261041)+3 种基金Key R&D projects of Jilin Provincial Science and Technology Development Plan(No.20230201125GX)Youth Growth Science and Technology Program of Jilin Province(No.20220508001RC)Youth Innovation Promotion Association CAS(No.2022225)Independent Research Project of the State Key Laboratory of Rare Earth Resources Utilization,and Changchun Institute of Applied Chemistry,Chinese Academy of Sciences(No.110000RL86)。
文摘Higher initial(de)hydrogenation temperature and sluggish kinetics are the main bottlenecks to develop Mg-based hydrogen storage alloys with high hydrogen capacity.One of the effective methods of solv ing these problems is introducing additives to enhance(de)hydrogenation kinetics and decrease par ticle sizes to lower(de)hydrogenation temperatures.In this work,Mg85-Ni10-La4.5-Y0.5 alloy doped with Cu@C nanoparticles is prepared,which could enhance(de)hydrogenation kinetics via introducing Cu nanoparticles as a catalyst and reduce the alloy particle sizes via acting as a grinding agent to lowe(de)hydrogenation temperature.The results indicate the dehydrogenation temperature of the modified Mg85-Ni10-La4.5-Y0.5 composite could be decreased to 308.5℃,absorb 4.73 wt%H_(2)at 220℃ within1 min and release 5.01 wt%H_(2)within 4 min at 300℃.Moreover,the capacity retention could be main tained around 98.8%after 10 cycles at 300℃,superior than those of Mg85-Ni10-La4.5-Y0.5 and milled Mg85-Ni10-La4.5-Y0.5.DFT results and characterizations suggest that in-situ formed Mg_(2)Cu could acceler ate the dissociation of Mg-H bonds and the presence of amorphous carbon in Mg-Ni-La-Y-Cu system wil further synergistically improve the(de)hydrogenation kinetics of Mg85-Ni10-La4.5-Y0.5.Reduced particle sizes under the aid of carbon frameworks also help introduce boundaries of the particles and shorten hydrogen diffusion pathways.
文摘Copper based catalysts have high potential for the substituent of noble-metal based catalysts as their high selectivity and moderate activity for selective hydrogenation reaction;however,achieving further high catalytic stability is very difficult.In this work,the carbonization process of Cu-based organic frameworks was explored for the synthesis of highly-dispersed Cu supported by hierarchically porous carbon with high catalytic performance for selective hydrogenation of 1,3-butadiene.The porous hierarchy of carbon support and the dispersion of copper nanoparticles can be precisely tuned by controlling the carbonization process.The resultant catalyst carbonized at 600°C exhibits a rather low reaction temperature at 75°C for 100%butadiene conversion with 100%selectivity to butenes,due to its reasonable porous hierarchy and highly-dispersed copper sites.More importantly,unprecedentedly stability of the corresponding Cu catalyst was firstly observed for selective 1,3-butadiene hydrogenation,with both 100%butadiene conversion and 100%butenes selectivity over 120 h of reaction at 75°C.This study verifies that a simply control the carbonization process of metal organic frameworks can be an effective way to obtain Cu-based catalysts with superior catalytic performance for selective hydrogenation reaction.
文摘Samples of the Cu-C composite coatings were produced by high-speed ion-plasma magnetron sputtering (HiPMS) with mosaic target (MT). Nanostructure, roughness, mechanical properties as well as electric properties of coatings depend on carbon-cooper ratio. So 10% - 15% cooper con centration (atomic) results in to dry friction coefficient decrease up to 0.1 and wear resistance increase up to 10<sup>-17</sup> m3/N·m. The HiPMS method allowed us to effectively sputter very different materials like carbon and cooper at the same velocity with required proportion. At the same time, one could obtain a uniform mixture of ingredients on the atomic level. The coating corresponds to a mixture of nano-sized phases of carbon and cooper. Crystalline dispersion of samples depends on carbon concentration. The obtained products are characterized by XRD, UV (257 nm) and visible (514 nm) Raman spectroscopy. The morphologies are studied with TEM and AFM. Mechanical properties were investigated with friction coefficient and micro hardness tests. There was no chemical interaction during Cu-C precipitation on hot substrate (625 - 725 K). The mechanical properties can be explained by free electrons capture with carbon nanostructures and space charge formation.
基金the National Natural Science Foundation of China (Nos. 50702045, 50871078, 51172182)the Program for New Century Excellent Talents in University (No. NCET-08-0460)Basic Research Foundation of NWPU (No. JC20100227)
文摘Cathode erosion of graphite and Cu/C was studied in direct current arcs, which were ignited between two electrodes comprised of two kinds of carbon materials and a tungsten anode in air. The arced zones on the cathode surface were investigated by a scanning electron microscope. Also, the cathode erosion rates of the investigated materials were measured. The results show that two distinct zone can be seen on both cathodes. The eroded area was located at the zone just opposite to the anode and surrounded by a white zone. The arced surface on the Cu/C containing 9.3 % Cu is rougher than that of the pure graphite. Many particles with various sizes distributed on the Cu/C. The vaporization of Cu can lower the surface temperature and reduce the cathode erosion. Therefore, the cathode erosion rate of the Cu/C is lower than that of the pure graphite.
文摘Through modular pressing and sintering, the Cu C powder metallurgy samples were made and the process was investigated. The results show that there exist expanding mechanism and shrinking mechanism in sintering process, and whether the sintering body is shrinking or expanding depends on the interacting between the two mechanisms, and the HD sintering model is in keeping with the actual sintering process. [
基金financially supported by the National Natural Science Foundation of China(NOs.U1908220 and 51331006).
文摘Carbon-coated Cu nanocomposites (Cu@C NCs) consisting of core-shell nanoparticles and nanorods weresynthesized by arc discharge plasma under an atmosphere of He and H_(2) gas, and the N-doping of themwas achieved by a post-treatment process using ureal as the precursor. The concentration of N in the Ndoped samples varies in the range of 0.62%-2.31 % (in mole), with a transformation from pyrrolic N tographitic N when increasing the relative content of ureal. Dielectric properties of the NCs without or withN-doping in the microwave and THz bands were investigated. The N-doped samples achieve theenhanced dielectric loss in both microwave and THz bands. In the microwave band, dielectric loss wasdominated by interfacial polarization, dipolar polarization, and conduction loss, while in the THz band,plasma resonance, ionic polarization and conduction loss are responsible for the dielectric loss, with astrong absorption characteristic dominated by conductive effect.
基金Supported by the National Natural Science Foundation of China under Grant Nos.59529204 and 19734002.
文摘The in situ direct-current conductance behaviors of Cu/C_(60) nano-scale granular films have been investigated experimentally.The results show that the incorporation of Cu into Ceo greatly increases the conductance of the film.The orientational phase transition that exists in pure C_(60) single crystals still retains in the Cu/C_(60) co-evaporated Elms,while the transition temperature range is significantly widened.The interactions between the nano-scale Cu clusters and C_(60) grains are discussed.
