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
This study investigated the effects of adding graphene nanoplates(GNPs)and carbon nanotubes(CNTs)into the Al7075 matrix via the stir casting method on the microstructure and mechanical properties of the fabricated com...This study investigated the effects of adding graphene nanoplates(GNPs)and carbon nanotubes(CNTs)into the Al7075 matrix via the stir casting method on the microstructure and mechanical properties of the fabricated composites.By increasing the volume fraction of rein-forcements,the fraction of porosity increased.The X-ray diffraction results showed that the addition of reinforcements into the Al7075 changed the dominant crystal orientation from(002)to(111).Field emission scanning electron microscopy images also showed the distribution of clustered reinforcements in the matrix.Between the two reinforcements,the addition of CNTs generated a lower fraction of porosities.Through the addition of 0.52vol%GNPs into the matrix,the hardness,ultimate tensile strength and uniform elongation increased by 44%,32%,and 180%,respectively.Meanwhile,the presence of 0.71vol%CNTs in the matrix increased the hardness,tensile strength and uniform elongation by 108%,129%,and 260%,respectively.展开更多
In this study,nano-graphene reinforced titanium matrix composites(GNPs/Ti)with a honeycomb porous structure were fabricated by selective laser melting(SLM).The effects of graphene on the microstructure,mechanical prop...In this study,nano-graphene reinforced titanium matrix composites(GNPs/Ti)with a honeycomb porous structure were fabricated by selective laser melting(SLM).The effects of graphene on the microstructure,mechanical properties and corrosion performance of the SLM GNPs/Ti were systematically investigated.Results of microstructure characterization show that:1)the density of the SLM GNPs/Ti was improved as compared to that of the SLM Ti;2)abundant TiC particles were formed in the SLM GNPs/Ti.The hardness and compressive strength of the composite increased by 90%(from HV 236 to HV 503)and 14%(from 277 MPa to 316 MPa),respectively,attributed to the uniformly distributed TiC and fine GNPs in the Ti matrix.Electrochemical tests reveal that the corrosion current density of the SLM GNPs/Ti is only 0.328μA/cm^(2),that is about 25%less than that of the SLM Ti.The results indicate that the incorporation of nano-graphene is a potential method to strengthen the Ti by SLM.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
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
Classical powder metallurgy followed by either hot isostatic pressing（HIPing） or repressing–annealing process was used to produce Cu–graphene nanoplatelets（GNPs） nanocomposites in this work. A wet mixing method ...Classical powder metallurgy followed by either hot isostatic pressing（HIPing） or repressing–annealing process was used to produce Cu–graphene nanoplatelets（GNPs） nanocomposites in this work. A wet mixing method was used to disperse the graphene within the matrix. The results show that a uniform dispersion of GNPs at low graphene contents could be achieved, whereas agglomeration of graphene was revealed at higher graphene contents. Density evaluations showed that the relative density of pure copper and copper composites increased by using the post-processing techniques.However, it should be noticed that the efficiency of HIPing was remarkably higher than repressing–annealing process, and through the HIPing, fully dense samples were achieved. The Vickers hardness results showed that the reconsolidation steps can improve the mechanical strength of the specimens up to 50% owing to the progressive porosity elimination after reconsolidation. The thermal conductivity results of pure copper and composites at high temperatures showed that the postprocessing techniques could enhance the conductivity of materials significantly.展开更多
This work uses refined first-order shear theory to analyze the free vibration and transient responses of double-curved sandwich two-layer shells made of auxetic honeycomb core and laminated three-phase polymer/GNP/fib...This work uses refined first-order shear theory to analyze the free vibration and transient responses of double-curved sandwich two-layer shells made of auxetic honeycomb core and laminated three-phase polymer/GNP/fiber surface subjected to the blast load.Each of the two layers that make up the double-curved shell structure is made up of an auxetic honeycomb core and two laminated sheets of three-phase polymer/GNP/fiber.The exterior is supported by a Kerr elastic foundation with three characteristics.The key innovation of the proposed theory is that the transverse shear stresses are zero at two free surfaces of each layer.In contrast to previous first-order shear deformation theories,no shear correction factor is required.Navier's exact solution was used to treat the double-curved shell problem with a single title boundary,while the finite element technique and an eight-node quadrilateral were used to address the other boundary requirements.To ensure the accuracy of these results,a thorough comparison technique is employed in conjunction with credible statements.The problem model's edge cases allow for this kind of analysis.The study's findings may be used in the post-construction evaluation of military and civil works structures for their ability to sustain explosive loads.In addition,this is also an important basis for the calculation and design of shell structures made of smart materials when subjected to shock waves or explosive loads.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This study investigated the effects of adding graphene nanoplates(GNPs)and carbon nanotubes(CNTs)into the Al7075 matrix via the stir casting method on the microstructure and mechanical properties of the fabricated composites.By increasing the volume fraction of rein-forcements,the fraction of porosity increased.The X-ray diffraction results showed that the addition of reinforcements into the Al7075 changed the dominant crystal orientation from(002)to(111).Field emission scanning electron microscopy images also showed the distribution of clustered reinforcements in the matrix.Between the two reinforcements,the addition of CNTs generated a lower fraction of porosities.Through the addition of 0.52vol%GNPs into the matrix,the hardness,ultimate tensile strength and uniform elongation increased by 44%,32%,and 180%,respectively.Meanwhile,the presence of 0.71vol%CNTs in the matrix increased the hardness,tensile strength and uniform elongation by 108%,129%,and 260%,respectively.
基金Projects(51504191,51671152,51874225)supported by the National Natural Science Foundation of ChinaProject(2019GY-188)supported by the Key R&D Projects of Shaanxi,China+2 种基金Project(18JC019)supported by the Industrialization Project of Shaanxi Education Department,ChinaProject(PMMSLKL-901)supported by the State Key Laboratory of Metal Porous Materials,ChinaProject(2020ZDLGY13-10)supported by the Science&Technology Project of Shaanxi,China。
文摘In this study,nano-graphene reinforced titanium matrix composites(GNPs/Ti)with a honeycomb porous structure were fabricated by selective laser melting(SLM).The effects of graphene on the microstructure,mechanical properties and corrosion performance of the SLM GNPs/Ti were systematically investigated.Results of microstructure characterization show that:1)the density of the SLM GNPs/Ti was improved as compared to that of the SLM Ti;2)abundant TiC particles were formed in the SLM GNPs/Ti.The hardness and compressive strength of the composite increased by 90%(from HV 236 to HV 503)and 14%(from 277 MPa to 316 MPa),respectively,attributed to the uniformly distributed TiC and fine GNPs in the Ti matrix.Electrochemical tests reveal that the corrosion current density of the SLM GNPs/Ti is only 0.328μA/cm^(2),that is about 25%less than that of the SLM Ti.The results indicate that the incorporation of nano-graphene is a potential method to strengthen the Ti by SLM.
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.
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.
文摘Classical powder metallurgy followed by either hot isostatic pressing（HIPing） or repressing–annealing process was used to produce Cu–graphene nanoplatelets（GNPs） nanocomposites in this work. A wet mixing method was used to disperse the graphene within the matrix. The results show that a uniform dispersion of GNPs at low graphene contents could be achieved, whereas agglomeration of graphene was revealed at higher graphene contents. Density evaluations showed that the relative density of pure copper and copper composites increased by using the post-processing techniques.However, it should be noticed that the efficiency of HIPing was remarkably higher than repressing–annealing process, and through the HIPing, fully dense samples were achieved. The Vickers hardness results showed that the reconsolidation steps can improve the mechanical strength of the specimens up to 50% owing to the progressive porosity elimination after reconsolidation. The thermal conductivity results of pure copper and composites at high temperatures showed that the postprocessing techniques could enhance the conductivity of materials significantly.
文摘This work uses refined first-order shear theory to analyze the free vibration and transient responses of double-curved sandwich two-layer shells made of auxetic honeycomb core and laminated three-phase polymer/GNP/fiber surface subjected to the blast load.Each of the two layers that make up the double-curved shell structure is made up of an auxetic honeycomb core and two laminated sheets of three-phase polymer/GNP/fiber.The exterior is supported by a Kerr elastic foundation with three characteristics.The key innovation of the proposed theory is that the transverse shear stresses are zero at two free surfaces of each layer.In contrast to previous first-order shear deformation theories,no shear correction factor is required.Navier's exact solution was used to treat the double-curved shell problem with a single title boundary,while the finite element technique and an eight-node quadrilateral were used to address the other boundary requirements.To ensure the accuracy of these results,a thorough comparison technique is employed in conjunction with credible statements.The problem model's edge cases allow for this kind of analysis.The study's findings may be used in the post-construction evaluation of military and civil works structures for their ability to sustain explosive loads.In addition,this is also an important basis for the calculation and design of shell structures made of smart materials when subjected to shock waves or explosive loads.
