A novel approach of decorating graphene surface with graphene quantum dots(abbreviated as GQDs@Gr)was presented to achieve superior tribological properties in Gr/Cu composites.The prepared GQDs@Gr hybrid reinforcement...A novel approach of decorating graphene surface with graphene quantum dots(abbreviated as GQDs@Gr)was presented to achieve superior tribological properties in Gr/Cu composites.The prepared GQDs@Gr hybrid reinforcement possessed superior dispersion and had achieved strong interface bonding with Cu matrix.GQDs@Gr/Cu composite showed a good combination of wear resistance and electrical conductivity due to the synergistic effect of GQDs and Gr.Specifically,the coefficient of friction(COF)was reduced to 0.3,the wear rate(WR)was 2.13×10^(-5) mm^(3)·N^(−1)·m^(−1)(only a quarter of pure copper),and maintained the electrical conductivity of 96.5%IACS(international annealed copper standard).As a result,delamination,fracture,and plow furrows on the wear surface of Gr/Cu composite indicate that fatigue and abrasive adhesive wear are the main wear mechanisms.Wear surface lubrication film and strong interface bonding ensure better comprehensive performance of GQDs@Gr/Cu composite.展开更多
The NO gas is easily oxidized to form toxic by-products(NO_(2))during the oxidation process,which are adsorbed on the catalyst surface and inhibit the subsequent reaction.For photocatalytic NO removal,a significant ch...The NO gas is easily oxidized to form toxic by-products(NO_(2))during the oxidation process,which are adsorbed on the catalyst surface and inhibit the subsequent reaction.For photocatalytic NO removal,a significant challenge is to achieve catalytic stability while maintaining high conversion efficiency.Here,we fabricated a(BiO)_(2)CO_(3)/β-Bi_(2)O_(3)heterostructure that enables efficient charge transfer and promotes the NO removal.We propose that the catalytic stability depends on the heterojunction structure,which is able to generate interfacial charge transfer channels.In addition,we further introduce graphene quantum dots on the heterojunction structure,which further strengthens the interfacial charge transfer dynamics and finally realizes that the NO_(2)byproduct could gain electrons and convert to the final product(nitrite or nitrate).This composite structure not only exhibits high activity for NO removal but also maintains long-term stability under visible light.展开更多
The configuration and quality of reinforcements, as well as the robustness of interfacial bonding,holding a critical significance in determining the concurrence between electrical conductivity and mechanical strength ...The configuration and quality of reinforcements, as well as the robustness of interfacial bonding,holding a critical significance in determining the concurrence between electrical conductivity and mechanical strength in metal matrix composites. In this study, citric acid was employed as the precursor for synthesizing multiscale carbon nanomaterials(graphene quantum dots and graphene, abbreviated as GQDs and GN). The GQDs@GN/Cu composites were fabricated through a segmented ball milling process in conjunction with subsequent spark plasma sintering(SPS). The intragranular GQDs and intergranular GQDs@GN had synergistically reinforced Cu composites through Orowan strengthening, load transfer strengthening and refinement strengthening. Furthermore,the robust interface bonding between GQDs@GN and Cu effectively mitigated interfacial impedance stemming from electron-boundary scattering. The yield strength and ultimate tensile strength of the GQDs@GN/Cu composites were recorded as 270 and 314 MPa, respectively, representing an improvement of 92 and 28% over pure Cu, while maintaining electrical conductivity at a level comparable to that of pure Cu. This study advances the understanding of the possibility of realizing a synergistic compatibility between electrical conductivity and mechanical strength in Cu composites.展开更多
Nanocomposites of graphene quantum dots(GQDs)modified gadolinium oxide(Gd_(2)O_(3))particles were successfully synthesized.In addition,the effects of the amount of GQDs and the particle size of Gd_(2)O_(3)on the prope...Nanocomposites of graphene quantum dots(GQDs)modified gadolinium oxide(Gd_(2)O_(3))particles were successfully synthesized.In addition,the effects of the amount of GQDs and the particle size of Gd_(2)O_(3)on the properties of nanocomposites were investigated.The structures and properties of nanoparticles were characterized by X-ray diffraction,X-ray photoelectron spectroscopy,Fourier transform infrared spectroscopy,field emission scanning electron microscopy,transmission electron microscopy,photoluminescence spectrometry,and magnetic resonance imaging.The results show that the synthesized particles Gd_(2)O_(3)/GQD are spherical with a diameter of approximately 40 nm and have excellent fluorescence and magnetic property,and its relaxation rate(r_(1)=25.18(mmol/L)^(-1)/s)is higher than that of the typical commercial contrast agents Gd-DTPA(r_(1)=4.5(mmol/L)^(-1)/s),The fluorescence property of Gd_(2)O_(3)/GQD is optimized by varying the V_(GQDs):V_(Gd2O3)ratio,and 1:1 ratio of V_(GQDs):V_(Gd2O3)results in the best fluorescence property.The large particles of Gd_(2)O_(3)improve the relaxation property of nanocomposites.Therefore,the nanocomposites Gd_(2)O_(3)/GQD with magnetic and fluorescence characteristics can be used in biological imaging,drug targeting,and in-vivo diagnostic analysis.展开更多
基金supported by Yunnan Fundamental Research Projects(No.202401CF070085)Yunnan Engineering Research Projects(No.2023-XMDJ-00617273)+1 种基金Industrial Support Plan Project of Gansu Provincial Education Department(No.2024CYZC-22)the National Natural Science Foundation of China(No.52064032).
文摘A novel approach of decorating graphene surface with graphene quantum dots(abbreviated as GQDs@Gr)was presented to achieve superior tribological properties in Gr/Cu composites.The prepared GQDs@Gr hybrid reinforcement possessed superior dispersion and had achieved strong interface bonding with Cu matrix.GQDs@Gr/Cu composite showed a good combination of wear resistance and electrical conductivity due to the synergistic effect of GQDs and Gr.Specifically,the coefficient of friction(COF)was reduced to 0.3,the wear rate(WR)was 2.13×10^(-5) mm^(3)·N^(−1)·m^(−1)(only a quarter of pure copper),and maintained the electrical conductivity of 96.5%IACS(international annealed copper standard).As a result,delamination,fracture,and plow furrows on the wear surface of Gr/Cu composite indicate that fatigue and abrasive adhesive wear are the main wear mechanisms.Wear surface lubrication film and strong interface bonding ensure better comprehensive performance of GQDs@Gr/Cu composite.
基金supported by the National Natural Science Foundation of China(Nos.22172019,52002054)the Sichuan Science and Technology Program(No.2022JDRC0084)。
文摘The NO gas is easily oxidized to form toxic by-products(NO_(2))during the oxidation process,which are adsorbed on the catalyst surface and inhibit the subsequent reaction.For photocatalytic NO removal,a significant challenge is to achieve catalytic stability while maintaining high conversion efficiency.Here,we fabricated a(BiO)_(2)CO_(3)/β-Bi_(2)O_(3)heterostructure that enables efficient charge transfer and promotes the NO removal.We propose that the catalytic stability depends on the heterojunction structure,which is able to generate interfacial charge transfer channels.In addition,we further introduce graphene quantum dots on the heterojunction structure,which further strengthens the interfacial charge transfer dynamics and finally realizes that the NO_(2)byproduct could gain electrons and convert to the final product(nitrite or nitrate).This composite structure not only exhibits high activity for NO removal but also maintains long-term stability under visible light.
基金financially supported by the National Natural Science Foundation of China (Nos.52174345 and 52064032)the Science and Technology Major Project of Yunnan Province (No.202202AG050004)。
文摘The configuration and quality of reinforcements, as well as the robustness of interfacial bonding,holding a critical significance in determining the concurrence between electrical conductivity and mechanical strength in metal matrix composites. In this study, citric acid was employed as the precursor for synthesizing multiscale carbon nanomaterials(graphene quantum dots and graphene, abbreviated as GQDs and GN). The GQDs@GN/Cu composites were fabricated through a segmented ball milling process in conjunction with subsequent spark plasma sintering(SPS). The intragranular GQDs and intergranular GQDs@GN had synergistically reinforced Cu composites through Orowan strengthening, load transfer strengthening and refinement strengthening. Furthermore,the robust interface bonding between GQDs@GN and Cu effectively mitigated interfacial impedance stemming from electron-boundary scattering. The yield strength and ultimate tensile strength of the GQDs@GN/Cu composites were recorded as 270 and 314 MPa, respectively, representing an improvement of 92 and 28% over pure Cu, while maintaining electrical conductivity at a level comparable to that of pure Cu. This study advances the understanding of the possibility of realizing a synergistic compatibility between electrical conductivity and mechanical strength in Cu composites.
基金Project supported by Guizhou Provincial Education Department Project(2017016)Guizhou Science and Technology Project(20192165)。
文摘Nanocomposites of graphene quantum dots(GQDs)modified gadolinium oxide(Gd_(2)O_(3))particles were successfully synthesized.In addition,the effects of the amount of GQDs and the particle size of Gd_(2)O_(3)on the properties of nanocomposites were investigated.The structures and properties of nanoparticles were characterized by X-ray diffraction,X-ray photoelectron spectroscopy,Fourier transform infrared spectroscopy,field emission scanning electron microscopy,transmission electron microscopy,photoluminescence spectrometry,and magnetic resonance imaging.The results show that the synthesized particles Gd_(2)O_(3)/GQD are spherical with a diameter of approximately 40 nm and have excellent fluorescence and magnetic property,and its relaxation rate(r_(1)=25.18(mmol/L)^(-1)/s)is higher than that of the typical commercial contrast agents Gd-DTPA(r_(1)=4.5(mmol/L)^(-1)/s),The fluorescence property of Gd_(2)O_(3)/GQD is optimized by varying the V_(GQDs):V_(Gd2O3)ratio,and 1:1 ratio of V_(GQDs):V_(Gd2O3)results in the best fluorescence property.The large particles of Gd_(2)O_(3)improve the relaxation property of nanocomposites.Therefore,the nanocomposites Gd_(2)O_(3)/GQD with magnetic and fluorescence characteristics can be used in biological imaging,drug targeting,and in-vivo diagnostic analysis.
