The exceptional properties of graphene make it ideal as a reinforcement to enhance the properties of aluminum matrices and this critically depends on uniform dispersion. In this study, the dispersion issue was address...The exceptional properties of graphene make it ideal as a reinforcement to enhance the properties of aluminum matrices and this critically depends on uniform dispersion. In this study, the dispersion issue was addressed by sonication and non-covalent surface functionalization of graphite nanoplatelets(GNPs) using two types of surfactant: anionic(sodium dodecyl benzene sulfate(SDBS)) and non-ionic polymeric(ethyl cellulose(EC)). After colloidal mixing with Al powder, consolidation was performed at two sintering temperatures(550 and 620°C). The structure, density, mechanical and wear properties of the nanocomposite samples were investigated and compared with a pure Al and a pure GNPs/Al nanocomposite sample. Noticeably, EC-based 0.5 wt% GNPs/Al samples showed the highest increment of 31% increase in hardness with reduced wear rate of 98.25% at 620°C, while a 22% increase in hardness with reduced wear rate of 96.98% at 550°C was observed, as compared to pure Al. Microstructural analysis and the overall results validate the use of EC-based GNPs/Al nanocomposites as they performed better than pure Al and pure GNPs/Al nanocomposite at both sintering temperatures.展开更多
In the present investigation the possibility of using exfoliated graphite nanoplatelets (xGnP) as reinforcement in order to enhance the mechanical properties of Cu-based metal matrix composites is explored. Cu-based m...In the present investigation the possibility of using exfoliated graphite nanoplatelets (xGnP) as reinforcement in order to enhance the mechanical properties of Cu-based metal matrix composites is explored. Cu-based metal matrix composites reinforced with different amounts of xGnP were fabricated by powder metallurgy route. The microstructure, sliding wear behaviour and mechanical properties of the Cu-xGnP composites were investigated. xGnP has been synthesized from the graphite intercalation compounds (GIC) through rapid evaporation of the intercalant at an elevated temperature. The thermally exfoliated graphite was later sonicated for a period of 5 h in acetone in order to achieve further exfoliation. The xGnP synthesized was characterized using SEM, HRTEM, X-ray diffraction, Raman spectroscopy and Fourier transform infrared spectroscopy. The Cu and xGnP powder mixtures were consolidated under a load of 565 MPa followed by sintering at 850°C for 2 h in inert atmosphere. Cu-1, 2, 3 and 5 wt% xGnP composites were developed. Results of the wear test show that there is a significant improvement in the wear resistance of the composites up to addition of 2 wt% of xGnP. Hardness, tensile strength and strain at failure of the various Cu-xGnP composites also show improvement upto the addition of 2 wt% xGnP beyond which there is a decrease in these properties. The density of the composites decreases with the addition of higher wt% of xGnP although addition of higher wt% of xGnP leads to higher sinterability and densification of the composites, resulting in higher relative density values. The nature of fracture in the pure Cu as well as the various Cu-xGnP composites was found to be ductile. Nanoplatelets of graphite were found firmly embedded in the Cu matrix in case of Cu-xGnP composites containing low wt% of xGnP.展开更多
Epoxy/graphene nanoplatelets(GNPs) powder coatings were fabricated using ultrasonic predispersion of GNPs and melt-blend extrusion method. The isothermal curing kinetics of epoxy/GNPs powder coating were monitored b...Epoxy/graphene nanoplatelets(GNPs) powder coatings were fabricated using ultrasonic predispersion of GNPs and melt-blend extrusion method. The isothermal curing kinetics of epoxy/GNPs powder coating were monitored by means of real-time Fourier transform infrared spectroscopy(FT-IR) with a heating cell. The mechanical properties of the epoxy/GNPs cured coatings had been investigated, by evaluating their fracture surfaces with field-emission scanning electron microscopy(FE-SEM) after three-point-bending tests. The thermal stability of the epoxy/GNPs cured coatings was studied by thermo-gravimetric analysis(TGA). The isothermal curing kinetics result showed that the GNPs would not affect the autocatalytic reaction mechanism, but the loading of GNPs below 1.0 wt % additive played a prompting role in the curing of the epoxy/GNPs powder coatings. The fracture strain, fracture toughness and impact resistance of the epoxy/GNPs cured coatings increased dramatically at low levels of GNPs loading(1 wt %), indicating that the GNPs could improve the toughness of the epoxy/GNPs powder coatings. Furthermore, from FE-SEM studies of the fracture surfaces, the possible toughening mechanisms of the epoxy/GNPs cured coatings were proposed. TGA result showed that the incorporation of GNPs improved the thermal stability of the cured coatings. Hence, the GNPs modified epoxy can be an efficient approach to toughen epoxy powder coating along with improving their thermal stability.展开更多
Polymers typically have intrinsic thermal conductivity much lower than other materials. Enhancement of this property may be obtained by the addition of conductive fillers. In this research, epoxy nanocomposites with e...Polymers typically have intrinsic thermal conductivity much lower than other materials. Enhancement of this property may be obtained by the addition of conductive fillers. In this research, epoxy nanocomposites with exfoliated graphite nanoplatelets are prepared and characterized. The chosen approach requires no surface treatment and no sophisticated equipments allowing one to produce composites on a pilot scale. A significant increase of the thermal conductivity with the increasing of the graphite fillers content is nevertheless observed on 4 mm thick specimens. Our results viewed in the latest scientific findings suggest that the choice of resin is an important parameter to move towards composite materials with high thermal conductivity.展开更多
Graphite nanoplatelets were prepared by a novel magnetic-grinding method using self-made equipments. Under a variant magnetic field, magnetic needles collided at a high rotating speed and exfoliated pristine graphite ...Graphite nanoplatelets were prepared by a novel magnetic-grinding method using self-made equipments. Under a variant magnetic field, magnetic needles collided at a high rotating speed and exfoliated pristine graphite into graphite nanoplatelets with high efficiency. The obtained graphite nanoplatelets are highly crystalline, and the thickness is less than 10 nm. Moreover, the surface area could reached 738.1 m^2/g with a grinding time of 4 h. Silanized graphite nanoplatelets can disperse well in SG 15W-40 engine oil and serve as lubricant additive. Tribological results indicate that the friction coefficient and wear-scar of the friction pairs are lower than 76% and 41%, respectively, by adding 1.5‰(mass fraction) of silanized graphite nanoplatelets. Notably, the functionalized graphite nanoplatelets can realize large-scale production and commercial application.展开更多
Waste is the main problem for the environment.Handling waste for various useful applications has a benefit for the future.This work has been studied for handling pineapple peel waste to make composite film bacterial c...Waste is the main problem for the environment.Handling waste for various useful applications has a benefit for the future.This work has been studied for handling pineapple peel waste to make composite film bacterial cellulose nanocomposite membrane(BCNM)with addition graphite nanoplatelet(GNP).The concentration of GNP in the membrane influence the membrane properties.The bacterial cellulose(BC)pellicle was synthesized by using media from pineapple peel waste extract.BC pellicle is cleaned with water and NaOH solution to be free from impactors.BCNM is synthesized through the mechanical disintegration stage.The results of disintegration using high pressure homogenizer at 150 bar and five cycles.BCNM/GNP is synthesized with varying addition of GNP of 2.5,5.0,10 and 100 wt%of dry bacterial nanocellulose(BNC).The BC and GNP solution were dried in an oven for 14 h at 80℃.BCNM morphology was observed using SEM.GNP is dispersed and distributed in the BC matrix as reinforcement.FTIR analysis shows many peaks of BNC less pronounced with increasing of GNP.The higher concentration of GNP,the rougher of BCNM.The optimum tensile strength of BCNM was achieved after addition GNP of 2.5 wt%.展开更多
In this study, high-density polyethylene (HDPE)/exfoliated graphite nanoplatelet (xGnP) composites reinforced with a 2 wt.% concentration of nano-magnesia (n-MgO) were fabricated using an injection moulding machine. T...In this study, high-density polyethylene (HDPE)/exfoliated graphite nanoplatelet (xGnP) composites reinforced with a 2 wt.% concentration of nano-magnesia (n-MgO) were fabricated using an injection moulding machine. The thermal properties and morphological structures of the composites were investigated. The XRD results showed the peaks of xGnP and n-MgO, where the intensity of the xGnP peaks became stronger with adding increasing amounts of xGnP into the polymermatrix. In terms of morphology, some agglomeration of particles was observed within the matrix, and the agglomeration decreased the thermal properties of the composites. The nanocomposites showed less thermal stability than the pristine polymer. The reduction in the onset temperature compared to that of neat HDPE was attributed to less adhesion between the fillers and the matrix. In addition, the crystallinity was reduced by the addition of fillers.展开更多
The relationship between the thermal/electrical conductivity enhancement in graphite nanoplatelets (GNPs) composites and the properties of filling graphite nanoplatelets is studied. The effective thermal and electri...The relationship between the thermal/electrical conductivity enhancement in graphite nanoplatelets (GNPs) composites and the properties of filling graphite nanoplatelets is studied. The effective thermal and electrical conductivity enhancements of GNP-oil nanofluids and GNP-polyimide composites are measured. By taking into account the particle shape, the volume fraction, the thermal conductivity of filling particles and the base fluids, the thermal and electrical conductivity enhancements of GNP nanofluids are theoretically predicted by the generalized effective medium theory. Both the nonlinear dependence of effective thermal conductivity on the GNP volume fraction in nanofhiids and the very low percolation threshold for GNP-polyimide composites are well predicted. The theoretical predications are found to be in reasonably good agreement with the experimental data. The generalized effective medium theory can be used for predicting the thermal and electrical properties of GNP composites and it is still available for most of the thermal/electrical modifications in two-phase composites.展开更多
A powder thixoforging route combined with slurry based mixing process was proposed to fabricate graphene nanoplatelets(GNPs) reinforced magnesium matrix composites(MgMCs). The originally spherical and ball-milled ZK60...A powder thixoforging route combined with slurry based mixing process was proposed to fabricate graphene nanoplatelets(GNPs) reinforced magnesium matrix composites(MgMCs). The originally spherical and ball-milled ZK60 powders were used as matrices, respectively.The mixing of 0.05 wt.% GNPs with the spherical powder led to GNPs clusters and degraded the mechanical properties of the composite.In contrast, with the addition of an optimal content(0.1 wt.%) of GNPs, the composite fabricated from ball-milled powder achieved a joint enhancement in tensile yield strength(52%) and fracture toughness(19%), demonstrating a pronounced strengthening efficiency of 650% and a good balance between strength and toughness. The ball-milled powder endowed the composite with a homogenous distribution of GNPs and a denser microstructure with reduced Mg-Zn eutectics, and the thixoforging process offered a well-bonded Mg/GNP interface, making full use of the strengthening and toughening potential of GNPs. Theoretical predication based on a modified shear-lag model suggested that load transfer dominated the strengthening mechanisms. In-situ tensile tests verified that crack deflection, secondary cracks and GNPs bridging mainly accounted for the toughening mechanisms. A numerical model with consideration of GNPs orientations was also established to understand the toughening effect from GNPs bridging.展开更多
The integration of lightweight and high-modulus magnesium-based materials is becoming increasingly valued as structural materials due to the complexity and intelligence of industrial products like automobiles and elec...The integration of lightweight and high-modulus magnesium-based materials is becoming increasingly valued as structural materials due to the complexity and intelligence of industrial products like automobiles and electronics.In this study,the graphene nanoplatelets(GNPs)/Mg-Zn-Zr composites with 0.5 wt%GNPs were successfully prepared by the combination of multidirectional forging(MDF)and hot extrusion(Ex).The newly-developed composites after multi-step deformation possessed excellent strength and modulus,with a tensile strength exceeding 375 MPa and an elastic modulus reaching 54 GPa.The results revealed that the stripping and thinning of GNPs bands parallel to the extrusion direction occurred after MDF+Ex,which promoted the dynamic recrystallization and the formation of numerous fine grains.The significant improvement in comprehensive mechanical performances of the composites could be primarily ascribed to the refinement of grain size caused by the optimized distribution of GNPs,and efficient load transfer facilitated by the tight interface.展开更多
Ultrathin graphitic carbon nitride nanoplatelets (UGCNPs) are synthesized by a facile manner via an efficient and eco-friendly ball milling approach. The obtained UGCNPs are 2-6 nm in size and 0.35-0.7 nm in thickne...Ultrathin graphitic carbon nitride nanoplatelets (UGCNPs) are synthesized by a facile manner via an efficient and eco-friendly ball milling approach. The obtained UGCNPs are 2-6 nm in size and 0.35-0.7 nm in thickness, with improved specific surface area over that of bulk graphitic carbon nitride. Photochemical experiments show that the UGCNPs are highly active in visible-light water splitting, with a hydrogen evolution rate of 1,365 μmol·h^-1·g^-1, which is 13.7-fold greater than that of their bulk counterparts. The notable improvement in the hydrogen evolution rate observed with UGCNPs under visible light is due to the synergistic effects derived from the increased specific surface area, reduced thickness, and a negative shift in the conduction band concomitant with the exfoliation of bulk graphitic carbon nitride into UGCNPs. In addition to metal- free visible-light-driven photocatalytic hydrogen production, the UGCNPs find attractive applications in biomedical imaging and optoelectronics because of their superior luminescence characteristics.展开更多
Lighter and more powerful next generation vehicles and other rotary machinery demand bearings to operate in harsher conditions for higher efficiency,and the continuous development of advanced low-wear and friction mat...Lighter and more powerful next generation vehicles and other rotary machinery demand bearings to operate in harsher conditions for higher efficiency,and the continuous development of advanced low-wear and friction materials is thus becoming even more important to meet these requirements.New aluminium composites reinforced with high performance lubricate phases such as graphene nanoplatelets(GNPs)are very promising and have been vigorously investigated.By maintaining a low coefficient of friction(COF)and offering great strength against wear due to their self-lubricating capability,the solid lubricant like GNPs protect the bearing surface from wear damage and prevent change in metallurgical properties during temperature fluctuations.This paper first studies the high-temperature tribological performance of aluminium matrix composites reinforced with GNP,consolidated via powder metallurgy,then elucidates their tribological mechanism.We report that the best tribological performance is achieved by the composite containing 2.0 wt%GNP,with an extraordinarily low COF of 0.09 and a specific wear rate of 3.5×10^(−2)mm^(3)·N^(−1)·m^(−1),which represent 75%and 40%reduction respectively,against the plain aluminium consolidated under identical conditions.The in-track and out-of-track Raman analysis have confirmed the role of GNPs in creating a tribofilm on the counterpart surface which contributed to the excellent performance.展开更多
文摘The exceptional properties of graphene make it ideal as a reinforcement to enhance the properties of aluminum matrices and this critically depends on uniform dispersion. In this study, the dispersion issue was addressed by sonication and non-covalent surface functionalization of graphite nanoplatelets(GNPs) using two types of surfactant: anionic(sodium dodecyl benzene sulfate(SDBS)) and non-ionic polymeric(ethyl cellulose(EC)). After colloidal mixing with Al powder, consolidation was performed at two sintering temperatures(550 and 620°C). The structure, density, mechanical and wear properties of the nanocomposite samples were investigated and compared with a pure Al and a pure GNPs/Al nanocomposite sample. Noticeably, EC-based 0.5 wt% GNPs/Al samples showed the highest increment of 31% increase in hardness with reduced wear rate of 98.25% at 620°C, while a 22% increase in hardness with reduced wear rate of 96.98% at 550°C was observed, as compared to pure Al. Microstructural analysis and the overall results validate the use of EC-based GNPs/Al nanocomposites as they performed better than pure Al and pure GNPs/Al nanocomposite at both sintering temperatures.
文摘In the present investigation the possibility of using exfoliated graphite nanoplatelets (xGnP) as reinforcement in order to enhance the mechanical properties of Cu-based metal matrix composites is explored. Cu-based metal matrix composites reinforced with different amounts of xGnP were fabricated by powder metallurgy route. The microstructure, sliding wear behaviour and mechanical properties of the Cu-xGnP composites were investigated. xGnP has been synthesized from the graphite intercalation compounds (GIC) through rapid evaporation of the intercalant at an elevated temperature. The thermally exfoliated graphite was later sonicated for a period of 5 h in acetone in order to achieve further exfoliation. The xGnP synthesized was characterized using SEM, HRTEM, X-ray diffraction, Raman spectroscopy and Fourier transform infrared spectroscopy. The Cu and xGnP powder mixtures were consolidated under a load of 565 MPa followed by sintering at 850°C for 2 h in inert atmosphere. Cu-1, 2, 3 and 5 wt% xGnP composites were developed. Results of the wear test show that there is a significant improvement in the wear resistance of the composites up to addition of 2 wt% of xGnP. Hardness, tensile strength and strain at failure of the various Cu-xGnP composites also show improvement upto the addition of 2 wt% xGnP beyond which there is a decrease in these properties. The density of the composites decreases with the addition of higher wt% of xGnP although addition of higher wt% of xGnP leads to higher sinterability and densification of the composites, resulting in higher relative density values. The nature of fracture in the pure Cu as well as the various Cu-xGnP composites was found to be ductile. Nanoplatelets of graphite were found firmly embedded in the Cu matrix in case of Cu-xGnP composites containing low wt% of xGnP.
基金Funded by the National Natural Science Foundation of China(No.51473104)
文摘Epoxy/graphene nanoplatelets(GNPs) powder coatings were fabricated using ultrasonic predispersion of GNPs and melt-blend extrusion method. The isothermal curing kinetics of epoxy/GNPs powder coating were monitored by means of real-time Fourier transform infrared spectroscopy(FT-IR) with a heating cell. The mechanical properties of the epoxy/GNPs cured coatings had been investigated, by evaluating their fracture surfaces with field-emission scanning electron microscopy(FE-SEM) after three-point-bending tests. The thermal stability of the epoxy/GNPs cured coatings was studied by thermo-gravimetric analysis(TGA). The isothermal curing kinetics result showed that the GNPs would not affect the autocatalytic reaction mechanism, but the loading of GNPs below 1.0 wt % additive played a prompting role in the curing of the epoxy/GNPs powder coatings. The fracture strain, fracture toughness and impact resistance of the epoxy/GNPs cured coatings increased dramatically at low levels of GNPs loading(1 wt %), indicating that the GNPs could improve the toughness of the epoxy/GNPs powder coatings. Furthermore, from FE-SEM studies of the fracture surfaces, the possible toughening mechanisms of the epoxy/GNPs cured coatings were proposed. TGA result showed that the incorporation of GNPs improved the thermal stability of the cured coatings. Hence, the GNPs modified epoxy can be an efficient approach to toughen epoxy powder coating along with improving their thermal stability.
文摘Polymers typically have intrinsic thermal conductivity much lower than other materials. Enhancement of this property may be obtained by the addition of conductive fillers. In this research, epoxy nanocomposites with exfoliated graphite nanoplatelets are prepared and characterized. The chosen approach requires no surface treatment and no sophisticated equipments allowing one to produce composites on a pilot scale. A significant increase of the thermal conductivity with the increasing of the graphite fillers content is nevertheless observed on 4 mm thick specimens. Our results viewed in the latest scientific findings suggest that the choice of resin is an important parameter to move towards composite materials with high thermal conductivity.
基金Project(ZR2011BL005)supported by the Natural Science Foundation of Shandong Province,China
文摘Graphite nanoplatelets were prepared by a novel magnetic-grinding method using self-made equipments. Under a variant magnetic field, magnetic needles collided at a high rotating speed and exfoliated pristine graphite into graphite nanoplatelets with high efficiency. The obtained graphite nanoplatelets are highly crystalline, and the thickness is less than 10 nm. Moreover, the surface area could reached 738.1 m^2/g with a grinding time of 4 h. Silanized graphite nanoplatelets can disperse well in SG 15W-40 engine oil and serve as lubricant additive. Tribological results indicate that the friction coefficient and wear-scar of the friction pairs are lower than 76% and 41%, respectively, by adding 1.5‰(mass fraction) of silanized graphite nanoplatelets. Notably, the functionalized graphite nanoplatelets can realize large-scale production and commercial application.
基金the Universitas Negeri Malang through the PNBP Research Grant 2021 with PUI/CAMRY scheme by Contract No.5.3.837/UN32.14.1/LT2021.
文摘Waste is the main problem for the environment.Handling waste for various useful applications has a benefit for the future.This work has been studied for handling pineapple peel waste to make composite film bacterial cellulose nanocomposite membrane(BCNM)with addition graphite nanoplatelet(GNP).The concentration of GNP in the membrane influence the membrane properties.The bacterial cellulose(BC)pellicle was synthesized by using media from pineapple peel waste extract.BC pellicle is cleaned with water and NaOH solution to be free from impactors.BCNM is synthesized through the mechanical disintegration stage.The results of disintegration using high pressure homogenizer at 150 bar and five cycles.BCNM/GNP is synthesized with varying addition of GNP of 2.5,5.0,10 and 100 wt%of dry bacterial nanocellulose(BNC).The BC and GNP solution were dried in an oven for 14 h at 80℃.BCNM morphology was observed using SEM.GNP is dispersed and distributed in the BC matrix as reinforcement.FTIR analysis shows many peaks of BNC less pronounced with increasing of GNP.The higher concentration of GNP,the rougher of BCNM.The optimum tensile strength of BCNM was achieved after addition GNP of 2.5 wt%.
文摘In this study, high-density polyethylene (HDPE)/exfoliated graphite nanoplatelet (xGnP) composites reinforced with a 2 wt.% concentration of nano-magnesia (n-MgO) were fabricated using an injection moulding machine. The thermal properties and morphological structures of the composites were investigated. The XRD results showed the peaks of xGnP and n-MgO, where the intensity of the xGnP peaks became stronger with adding increasing amounts of xGnP into the polymermatrix. In terms of morphology, some agglomeration of particles was observed within the matrix, and the agglomeration decreased the thermal properties of the composites. The nanocomposites showed less thermal stability than the pristine polymer. The reduction in the onset temperature compared to that of neat HDPE was attributed to less adhesion between the fillers and the matrix. In addition, the crystallinity was reduced by the addition of fillers.
基金The National Natural Science Foundation of China(No.50906073,31070517)China Postdoctoral Science Foundation(No.20110491332)+1 种基金Jiangsu Planned Projects for Postdoctoral Research Funds(No.1101009B)the Science and Technology Development Plan of North Jiangsu(No.BC2012444)
文摘The relationship between the thermal/electrical conductivity enhancement in graphite nanoplatelets (GNPs) composites and the properties of filling graphite nanoplatelets is studied. The effective thermal and electrical conductivity enhancements of GNP-oil nanofluids and GNP-polyimide composites are measured. By taking into account the particle shape, the volume fraction, the thermal conductivity of filling particles and the base fluids, the thermal and electrical conductivity enhancements of GNP nanofluids are theoretically predicted by the generalized effective medium theory. Both the nonlinear dependence of effective thermal conductivity on the GNP volume fraction in nanofhiids and the very low percolation threshold for GNP-polyimide composites are well predicted. The theoretical predications are found to be in reasonably good agreement with the experimental data. The generalized effective medium theory can be used for predicting the thermal and electrical properties of GNP composites and it is still available for most of the thermal/electrical modifications in two-phase composites.
基金financially supported by the National natural Science Foundation of China (Grant No.51761028)。
文摘A powder thixoforging route combined with slurry based mixing process was proposed to fabricate graphene nanoplatelets(GNPs) reinforced magnesium matrix composites(MgMCs). The originally spherical and ball-milled ZK60 powders were used as matrices, respectively.The mixing of 0.05 wt.% GNPs with the spherical powder led to GNPs clusters and degraded the mechanical properties of the composite.In contrast, with the addition of an optimal content(0.1 wt.%) of GNPs, the composite fabricated from ball-milled powder achieved a joint enhancement in tensile yield strength(52%) and fracture toughness(19%), demonstrating a pronounced strengthening efficiency of 650% and a good balance between strength and toughness. The ball-milled powder endowed the composite with a homogenous distribution of GNPs and a denser microstructure with reduced Mg-Zn eutectics, and the thixoforging process offered a well-bonded Mg/GNP interface, making full use of the strengthening and toughening potential of GNPs. Theoretical predication based on a modified shear-lag model suggested that load transfer dominated the strengthening mechanisms. In-situ tensile tests verified that crack deflection, secondary cracks and GNPs bridging mainly accounted for the toughening mechanisms. A numerical model with consideration of GNPs orientations was also established to understand the toughening effect from GNPs bridging.
基金supported by the Fundamental Research Program of Shanxi Province (Grant Nos.202203021221088 and 202103021223043)the Fund Program for the Scientific Activities of Selected Returned Overseas Professionals in Shanxi Province (Grant No.20230010)+5 种基金the Shanxi Provincial Science and Technology Major Special Project plan of"Taking the lead in unveiling the list" (Grant No.202201050201012)the Research Project Supported by Shanxi Scholarship Council of China (Grant No.2023-063)the National Natural Science Foundation of China (Grant Nos.51771129,52271109 and 51771128)the National Key Research and Development Program for Young Scientists (Grant No.2021YFB3703300)the Special Fund Project for Guiding Local Science and Technology Development by the Central Government (Grant No.YDZJSX2021B019)the Open Foundation of State Key Laboratory of Compressor Technology (Compressor Technology Laboratory of Anhui Province) (Grant No.SKL-YSJ202103).
文摘The integration of lightweight and high-modulus magnesium-based materials is becoming increasingly valued as structural materials due to the complexity and intelligence of industrial products like automobiles and electronics.In this study,the graphene nanoplatelets(GNPs)/Mg-Zn-Zr composites with 0.5 wt%GNPs were successfully prepared by the combination of multidirectional forging(MDF)and hot extrusion(Ex).The newly-developed composites after multi-step deformation possessed excellent strength and modulus,with a tensile strength exceeding 375 MPa and an elastic modulus reaching 54 GPa.The results revealed that the stripping and thinning of GNPs bands parallel to the extrusion direction occurred after MDF+Ex,which promoted the dynamic recrystallization and the formation of numerous fine grains.The significant improvement in comprehensive mechanical performances of the composites could be primarily ascribed to the refinement of grain size caused by the optimized distribution of GNPs,and efficient load transfer facilitated by the tight interface.
基金This project is sponsored by NSFC (Nos. 21325415, 21174019, 21301018, 51161120361), National Basic Research Program of China (2011CB013000), Basic Research Foundation of Beijing Institute of Technology (20121942008), Fok Ying Tong Education Foundation (No. 131043), the 111 Project B07012, Beijing Natural Science Foundation (2152028) and the Beijing Key Laboratory for Chemical Power Source and Green Catalysis under the contract no. 2013CX02031.
文摘Ultrathin graphitic carbon nitride nanoplatelets (UGCNPs) are synthesized by a facile manner via an efficient and eco-friendly ball milling approach. The obtained UGCNPs are 2-6 nm in size and 0.35-0.7 nm in thickness, with improved specific surface area over that of bulk graphitic carbon nitride. Photochemical experiments show that the UGCNPs are highly active in visible-light water splitting, with a hydrogen evolution rate of 1,365 μmol·h^-1·g^-1, which is 13.7-fold greater than that of their bulk counterparts. The notable improvement in the hydrogen evolution rate observed with UGCNPs under visible light is due to the synergistic effects derived from the increased specific surface area, reduced thickness, and a negative shift in the conduction band concomitant with the exfoliation of bulk graphitic carbon nitride into UGCNPs. In addition to metal- free visible-light-driven photocatalytic hydrogen production, the UGCNPs find attractive applications in biomedical imaging and optoelectronics because of their superior luminescence characteristics.
基金supported by the“The Royal Society”(INF\PHD\180005).
文摘Lighter and more powerful next generation vehicles and other rotary machinery demand bearings to operate in harsher conditions for higher efficiency,and the continuous development of advanced low-wear and friction materials is thus becoming even more important to meet these requirements.New aluminium composites reinforced with high performance lubricate phases such as graphene nanoplatelets(GNPs)are very promising and have been vigorously investigated.By maintaining a low coefficient of friction(COF)and offering great strength against wear due to their self-lubricating capability,the solid lubricant like GNPs protect the bearing surface from wear damage and prevent change in metallurgical properties during temperature fluctuations.This paper first studies the high-temperature tribological performance of aluminium matrix composites reinforced with GNP,consolidated via powder metallurgy,then elucidates their tribological mechanism.We report that the best tribological performance is achieved by the composite containing 2.0 wt%GNP,with an extraordinarily low COF of 0.09 and a specific wear rate of 3.5×10^(−2)mm^(3)·N^(−1)·m^(−1),which represent 75%and 40%reduction respectively,against the plain aluminium consolidated under identical conditions.The in-track and out-of-track Raman analysis have confirmed the role of GNPs in creating a tribofilm on the counterpart surface which contributed to the excellent performance.