The mechanical and tribological properties of Cu-based powder metallurgy （P/M） friction composites containing 10wt%-50wt% oxide-dispersion-strengthened （ODS） Cu reinforced with nano-Al2O3 were investigated. Additi...The mechanical and tribological properties of Cu-based powder metallurgy （P/M） friction composites containing 10wt%-50wt% oxide-dispersion-strengthened （ODS） Cu reinforced with nano-Al2O3 were investigated. Additionally, the friction and wear behaviors as well as the wear mechanism of the Cu-based composites were characterized by scanning electron microscopy （SEM） in conjunction with energy-dispersive X-ray spectroscopy （EDS） elemental mapping. The results indicated that the Cu-based friction composite containing 30wt% ODS Cu exhibited the highest hardness and shear strength. The average and instantaneous friction coefficient curves of this sample, when operated in a high-speed train at a speed of 300 km/h, were similar to those of a commercial disc brake pad produced by Knorr-Bremse AG （Germany）. Additionally, the lowest linear wear loss of the obtained samples was （0.008 ± 0.001） mm per time per face, which is much lower than that of the Knorr-Bremse pad （（0.01 ± 0.001） mm）. The excellent performance of the developed pad is a consequence of the formation of a dense oxide composite layer and its close combination with the pad body.展开更多
Fe3O4@SiO2 core–shell composite nanoparticles were successfully prepared by a one-pot process. Tetraethyl-orthosilicate was used as a surfactant to synthesize Fe3O4@SiO2 core–shell structures from prepared Fe3O4 nan...Fe3O4@SiO2 core–shell composite nanoparticles were successfully prepared by a one-pot process. Tetraethyl-orthosilicate was used as a surfactant to synthesize Fe3O4@SiO2 core–shell structures from prepared Fe3O4 nanoparticles. The properties of the Fe3O4 and Fe3O4@SiO2 composite nanoparticles were studied by X-ray diffraction, transmission electron microscopy, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy. The prepared Fe3O4 particles were approximately 12 nm in size, and the thickness of the SiO2 coating was approximately 4 nm. The magnetic properties were studied by vibrating sample magnetometry. The results show that the maximum saturation magnetization of the Fe3O4@SiO2 powder（34.85 A·m^2·kg^–1） was markedly lower than that of the Fe3O4 powder（79.55 A·m^2·kg^–1）, which demonstrates that Fe3O4 was successfully wrapped by SiO2. The Fe3O4@SiO2 composite nanoparticles have broad prospects in biomedical applications; thus, our next study will apply them in magnetic resonance imaging.展开更多
Anodized composite films containing Si C nanoparticles were synthesized on Ti6Al4 V alloy by anodic oxidation procedure in C4O6H4Na2 electrolyte. Scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS) ...Anodized composite films containing Si C nanoparticles were synthesized on Ti6Al4 V alloy by anodic oxidation procedure in C4O6H4Na2 electrolyte. Scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS) and X-ray photoelectron spectroscopy(XPS) were employed to characterize the morphology and composition of the films fabricated in the electrolytes with and without addition of Si C nanoparticles. Results show that Si C particles can be successfully incorporated into the oxide film during the anodizing process and preferentially concentrate within internal cavities and micro-cracks. The ball-on-disk sliding tests indicate that Si C-containing oxide films register much lower wear rate than the oxide films without Si C under dry sliding condition. Si C particles are likely to melt and then are oxidized by frictional heat during sliding tests. Potentiodynamic polarization behavior reveals that the anodized alloy with Si C nanoparticles results in a reduction in passive current density to about 1.54×10-8 A/cm2, which is more than two times lower than that of the Ti O2 film(3.73×10-8 A/cm2). The synthesized composite film has good anti-wear and anti-corrosion properties and the growth mechanism of nanocomposite film is also discussed.展开更多
Direct carbon solid oxide fuel cells(DC-SOFCs)are promising,green,and efficient power-generating devices that are fueled by solid carbons and comprise all-solid-state structures.Developing suitable anode materials for...Direct carbon solid oxide fuel cells(DC-SOFCs)are promising,green,and efficient power-generating devices that are fueled by solid carbons and comprise all-solid-state structures.Developing suitable anode materials for DC-SOFCs is a substantial scientific challenge.Herein we investigated the use of La_(0.75)Sr_(0.25)Cr_(0.5)Mn_(0.5)O_(3)-δ−Ce_(0.8)Gd_(0.2)O_(1.9)(LSCM−GDC)composite electrodes as anodes for La_(0.9)Sr_(0.1)Ga_(0.8)Mg_(0.2)O_(3)-δelectrolyte-based DC-SOFCs,with Camellia oleifera shell char as the carbon fuel.The LSCM−GDC-anode DC-SOFC delivered a maximum power density of 221 mW/cm^(2) at 800℃ and it significantly improved to 425 mW/cm^(2) after Ni nanoparticles were introduced into the LSCM−GDC anode through wet impregnation.The microstructures of the prepared anodes were characterized,and the stability of the anode in a DC-SOFC and the influence of catalytic activity on open circuit voltage were studied.The above results indicate that LSCM–GDC anode is promising to be applied in DC-SOFCs.展开更多
Hybrid CuO-Co_(3)O_(4)nanosphere building blocks have been embedded between the layered nanosheets of reduced graphene oxides with a three dimensional(3D)hybrid architecture(CuO-Co_(3)O_(4)-RGO),which are successfully...Hybrid CuO-Co_(3)O_(4)nanosphere building blocks have been embedded between the layered nanosheets of reduced graphene oxides with a three dimensional(3D)hybrid architecture(CuO-Co_(3)O_(4)-RGO),which are successfully applied as enhanced anodes for lithium-ion batteries(LIBs).The CuO-Co_(3)O_(4)-RGO sandwiched nanostructures exhibit a reversible capacity of~847 mA·h·g^(-1)after 200 cycles’cycling at 100 mA·g^(-1)with a capacity retention of 79%.The CuO-Co_(3)O_(4)-RGO compounds show superior electrochemical properties than the comparative CuO-Co_(3)O_(4),Co_(3)O_(4)and CuO anodes,which may be ascribed to the following reasons:the hybridizing multicomponent can probably give the complementary advantages;the mutual benefit of uniformly distributing nanospheres across the layered RGO nanosheets can avoid the agglomeration of both the RGO nanosheets and the CuO-Co_(3)O_(4) nanospheres;the 3D storage structure as well as the graphene wrapped composite could enhance the electrical conductivity and reduce volume expansion effect associated with the discharge-charge process.展开更多
Platinum and palladium(PtPd)alloy nanoparticles(NPs)are excellent catalysts for direct methanol fuel cells.In this study,we developed PtPd alloy NPs through the co‐reduction of K2PtCl4and Na2PdCl4in a polyol synthesi...Platinum and palladium(PtPd)alloy nanoparticles(NPs)are excellent catalysts for direct methanol fuel cells.In this study,we developed PtPd alloy NPs through the co‐reduction of K2PtCl4and Na2PdCl4in a polyol synthesis environment.During the reaction,the feed molar ratio of the two precursors was carried over to the final products,which have a narrow size distribution with a mean size of approximately4nm.The catalytic activity for methanol oxidation reactions possible depends closely on the composition of as‐prepared PtPd alloy NPs,and the NPs with a Pt atomic percentage of approximately75%result in higher activity and stability with a mass specific activity that is7times greater than that of commercial Pt/C catalysts.The results indicate that through composition control,PtPd alloy NPs can improve the effectiveness of catalytic performance.展开更多
In recent years, energy-retrofitting is becoming an imperative aim for existing buildings worldwide and increased interest has focused on the development of nanoparticle blended concretes with adequate mechanical...In recent years, energy-retrofitting is becoming an imperative aim for existing buildings worldwide and increased interest has focused on the development of nanoparticle blended concretes with adequate mechanical properties and durability performance, through the optimization of concrete permeability and the incorporation of the proper nanoparticle type in the concrete matrix. In order to investigate the potential use of nanocomposites as dense barriers against the permeation of liquids into the concrete, three types of nanoparticles including Zinc Oxide (ZnO), Magnesium Oxide (MgO), and composite nanoparticles were used in the present study as partial replacement of cement. Besides, the effect of adding these nanoparticles on both pore structure and mechanical strengths of the concrete at different ages was determined, and scanning electron microscopy (SEM) images were then used to illustrate the uniformity dispersion of nanoparticles in cement paste. It was demonstrated that the addition of a small number of nanoparticles effectively enhances the mechanical properties of concrete and consequently reduces the extent of the water permeation front. Finally, the behavioral models using Genetic Algorithm (GA) programming were developed to describe the time-dependent behavioral characteristics of nanoparticle blended concrete samples in various compressive and tensile stress states at different ages.展开更多
Pt/Ni catalysts modified with CeO2 nanoparticles were prepared by simple composite electrodeposition of Ni and CeO2,and spontaneous Ni partial replacement by Pt processes.The as-prepared CeO2-modified Pt/Ni catalysts ...Pt/Ni catalysts modified with CeO2 nanoparticles were prepared by simple composite electrodeposition of Ni and CeO2,and spontaneous Ni partial replacement by Pt processes.The as-prepared CeO2-modified Pt/Ni catalysts showed enhanced catalytic performance for ethanol electro-oxidation compared with pure Pt/Ni,and acetate species were proposed to be the main products of the oxidation when using these catalysts.The content of CeO2 in the as-prepared catalysts influenced their catalytic activity,with Pt/NiCe2（obtained from an electrolyte containing 100 mg/L CeO2 nanoparticles） exhibiting higher activity and relatively better stability in ethanol electro-oxidation.This was mainly due to the oxygen storage capacity of CeO2,the interaction between Pt and CeO2/Ni,and the relatively small contact and charge transfer resistances.The results of this work thus suggest that electrocatalysts with low price and high activity can be rationally designed and produced by a simple route for use in direct ethanol fuel cells.展开更多
Electrodeposited Ni matrix/Al microparticles or nanoparticles dispersed composite coatings (termed as EMCCs or ENCCs) are developed from a Ni-based electrolyte bath. The Al microparticles are in a size range of 1 -5 ...Electrodeposited Ni matrix/Al microparticles or nanoparticles dispersed composite coatings (termed as EMCCs or ENCCs) are developed from a Ni-based electrolyte bath. The Al microparticles are in a size range of 1 -5 μm and the Al nanoparticles in an average size of 75 nm. The Al content in coatings increases with increase in the particle content in the bath. Particle size effect on the degree of codeposition is not significant. However, codeposition of Al nanoparticles instead of microparticles promotes more homogenous growth of Ni deposits on {111}, {200} and {220} planes. The oxidation at 1 050 ℃ of the as-deposited composite coatings shows that at a comparable Al content, ENCC of Ni-Al exhibits a better oxidation resistance than EMCC of Ni-Al due to the fast formation of an alumina scale during the transient stage of oxidation.展开更多
基金financially supported by the National High Technology Research and Development Program of China (No. 2013AA031104)
文摘The mechanical and tribological properties of Cu-based powder metallurgy （P/M） friction composites containing 10wt%-50wt% oxide-dispersion-strengthened （ODS） Cu reinforced with nano-Al2O3 were investigated. Additionally, the friction and wear behaviors as well as the wear mechanism of the Cu-based composites were characterized by scanning electron microscopy （SEM） in conjunction with energy-dispersive X-ray spectroscopy （EDS） elemental mapping. The results indicated that the Cu-based friction composite containing 30wt% ODS Cu exhibited the highest hardness and shear strength. The average and instantaneous friction coefficient curves of this sample, when operated in a high-speed train at a speed of 300 km/h, were similar to those of a commercial disc brake pad produced by Knorr-Bremse AG （Germany）. Additionally, the lowest linear wear loss of the obtained samples was （0.008 ± 0.001） mm per time per face, which is much lower than that of the Knorr-Bremse pad （（0.01 ± 0.001） mm）. The excellent performance of the developed pad is a consequence of the formation of a dense oxide composite layer and its close combination with the pad body.
基金the National Natural Science Foundation of China (No.51274039)the State Key Lab of Advanced Metals and Materials (No.2013-ZD05)the Guangdong Foundation of Research (No.2014B090901003)
文摘Fe3O4@SiO2 core–shell composite nanoparticles were successfully prepared by a one-pot process. Tetraethyl-orthosilicate was used as a surfactant to synthesize Fe3O4@SiO2 core–shell structures from prepared Fe3O4 nanoparticles. The properties of the Fe3O4 and Fe3O4@SiO2 composite nanoparticles were studied by X-ray diffraction, transmission electron microscopy, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy. The prepared Fe3O4 particles were approximately 12 nm in size, and the thickness of the SiO2 coating was approximately 4 nm. The magnetic properties were studied by vibrating sample magnetometry. The results show that the maximum saturation magnetization of the Fe3O4@SiO2 powder（34.85 A·m^2·kg^–1） was markedly lower than that of the Fe3O4 powder（79.55 A·m^2·kg^–1）, which demonstrates that Fe3O4 was successfully wrapped by SiO2. The Fe3O4@SiO2 composite nanoparticles have broad prospects in biomedical applications; thus, our next study will apply them in magnetic resonance imaging.
基金Project(51271012)supported by the National Natural Science Foundation of China
文摘Anodized composite films containing Si C nanoparticles were synthesized on Ti6Al4 V alloy by anodic oxidation procedure in C4O6H4Na2 electrolyte. Scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS) and X-ray photoelectron spectroscopy(XPS) were employed to characterize the morphology and composition of the films fabricated in the electrolytes with and without addition of Si C nanoparticles. Results show that Si C particles can be successfully incorporated into the oxide film during the anodizing process and preferentially concentrate within internal cavities and micro-cracks. The ball-on-disk sliding tests indicate that Si C-containing oxide films register much lower wear rate than the oxide films without Si C under dry sliding condition. Si C particles are likely to melt and then are oxidized by frictional heat during sliding tests. Potentiodynamic polarization behavior reveals that the anodized alloy with Si C nanoparticles results in a reduction in passive current density to about 1.54×10-8 A/cm2, which is more than two times lower than that of the Ti O2 film(3.73×10-8 A/cm2). The synthesized composite film has good anti-wear and anti-corrosion properties and the growth mechanism of nanocomposite film is also discussed.
基金Project(2019YFC1907405)supported by the National Key R&D Program of ChinaProject(GJJ200809)supported by the Education Department Project Fund of Jiangxi Province,ChinaProject(2020BAB214021)supported by the Natural Science Foundation of Jiangxi Province,China。
文摘Direct carbon solid oxide fuel cells(DC-SOFCs)are promising,green,and efficient power-generating devices that are fueled by solid carbons and comprise all-solid-state structures.Developing suitable anode materials for DC-SOFCs is a substantial scientific challenge.Herein we investigated the use of La_(0.75)Sr_(0.25)Cr_(0.5)Mn_(0.5)O_(3)-δ−Ce_(0.8)Gd_(0.2)O_(1.9)(LSCM−GDC)composite electrodes as anodes for La_(0.9)Sr_(0.1)Ga_(0.8)Mg_(0.2)O_(3)-δelectrolyte-based DC-SOFCs,with Camellia oleifera shell char as the carbon fuel.The LSCM−GDC-anode DC-SOFC delivered a maximum power density of 221 mW/cm^(2) at 800℃ and it significantly improved to 425 mW/cm^(2) after Ni nanoparticles were introduced into the LSCM−GDC anode through wet impregnation.The microstructures of the prepared anodes were characterized,and the stability of the anode in a DC-SOFC and the influence of catalytic activity on open circuit voltage were studied.The above results indicate that LSCM–GDC anode is promising to be applied in DC-SOFCs.
基金financially supported by the National Natural Science Foundation of China (21471100, 22005199)the Shenzhen Natural Science Fundation (20200813081943001)the Natural Science Foundation of Guangdong Province,China(2021A1515010241, 2021A1515010142)
文摘Hybrid CuO-Co_(3)O_(4)nanosphere building blocks have been embedded between the layered nanosheets of reduced graphene oxides with a three dimensional(3D)hybrid architecture(CuO-Co_(3)O_(4)-RGO),which are successfully applied as enhanced anodes for lithium-ion batteries(LIBs).The CuO-Co_(3)O_(4)-RGO sandwiched nanostructures exhibit a reversible capacity of~847 mA·h·g^(-1)after 200 cycles’cycling at 100 mA·g^(-1)with a capacity retention of 79%.The CuO-Co_(3)O_(4)-RGO compounds show superior electrochemical properties than the comparative CuO-Co_(3)O_(4),Co_(3)O_(4)and CuO anodes,which may be ascribed to the following reasons:the hybridizing multicomponent can probably give the complementary advantages;the mutual benefit of uniformly distributing nanospheres across the layered RGO nanosheets can avoid the agglomeration of both the RGO nanosheets and the CuO-Co_(3)O_(4) nanospheres;the 3D storage structure as well as the graphene wrapped composite could enhance the electrical conductivity and reduce volume expansion effect associated with the discharge-charge process.
基金supported by the National Natural Science Foundation of China (21373272)~~
文摘Platinum and palladium(PtPd)alloy nanoparticles(NPs)are excellent catalysts for direct methanol fuel cells.In this study,we developed PtPd alloy NPs through the co‐reduction of K2PtCl4and Na2PdCl4in a polyol synthesis environment.During the reaction,the feed molar ratio of the two precursors was carried over to the final products,which have a narrow size distribution with a mean size of approximately4nm.The catalytic activity for methanol oxidation reactions possible depends closely on the composition of as‐prepared PtPd alloy NPs,and the NPs with a Pt atomic percentage of approximately75%result in higher activity and stability with a mass specific activity that is7times greater than that of commercial Pt/C catalysts.The results indicate that through composition control,PtPd alloy NPs can improve the effectiveness of catalytic performance.
文摘In recent years, energy-retrofitting is becoming an imperative aim for existing buildings worldwide and increased interest has focused on the development of nanoparticle blended concretes with adequate mechanical properties and durability performance, through the optimization of concrete permeability and the incorporation of the proper nanoparticle type in the concrete matrix. In order to investigate the potential use of nanocomposites as dense barriers against the permeation of liquids into the concrete, three types of nanoparticles including Zinc Oxide (ZnO), Magnesium Oxide (MgO), and composite nanoparticles were used in the present study as partial replacement of cement. Besides, the effect of adding these nanoparticles on both pore structure and mechanical strengths of the concrete at different ages was determined, and scanning electron microscopy (SEM) images were then used to illustrate the uniformity dispersion of nanoparticles in cement paste. It was demonstrated that the addition of a small number of nanoparticles effectively enhances the mechanical properties of concrete and consequently reduces the extent of the water permeation front. Finally, the behavioral models using Genetic Algorithm (GA) programming were developed to describe the time-dependent behavioral characteristics of nanoparticle blended concrete samples in various compressive and tensile stress states at different ages.
基金supported by the National Natural Science Foundation of China (21307038 and 21577046)Key Project of Chinese Ministry of Education (212115)Physical Chemistry Experiment of Huanggang Normal University (2015CK12)~~
文摘Pt/Ni catalysts modified with CeO2 nanoparticles were prepared by simple composite electrodeposition of Ni and CeO2,and spontaneous Ni partial replacement by Pt processes.The as-prepared CeO2-modified Pt/Ni catalysts showed enhanced catalytic performance for ethanol electro-oxidation compared with pure Pt/Ni,and acetate species were proposed to be the main products of the oxidation when using these catalysts.The content of CeO2 in the as-prepared catalysts influenced their catalytic activity,with Pt/NiCe2（obtained from an electrolyte containing 100 mg/L CeO2 nanoparticles） exhibiting higher activity and relatively better stability in ethanol electro-oxidation.This was mainly due to the oxygen storage capacity of CeO2,the interaction between Pt and CeO2/Ni,and the relatively small contact and charge transfer resistances.The results of this work thus suggest that electrocatalysts with low price and high activity can be rationally designed and produced by a simple route for use in direct ethanol fuel cells.
文摘Electrodeposited Ni matrix/Al microparticles or nanoparticles dispersed composite coatings (termed as EMCCs or ENCCs) are developed from a Ni-based electrolyte bath. The Al microparticles are in a size range of 1 -5 μm and the Al nanoparticles in an average size of 75 nm. The Al content in coatings increases with increase in the particle content in the bath. Particle size effect on the degree of codeposition is not significant. However, codeposition of Al nanoparticles instead of microparticles promotes more homogenous growth of Ni deposits on {111}, {200} and {220} planes. The oxidation at 1 050 ℃ of the as-deposited composite coatings shows that at a comparable Al content, ENCC of Ni-Al exhibits a better oxidation resistance than EMCC of Ni-Al due to the fast formation of an alumina scale during the transient stage of oxidation.
