以7075铝合金为基体,采用有机溶剂体系,以无水氯化铝和无水氯化镍为溶质,四氢呋喃及苯为溶剂,石墨烯作为第二项添加剂,制备铝-镍-石墨烯复合镀层。镀液组成为Li Al H_(4)0.25 mol/L,AlCl_(3)0.75 mol/L,THF 150 m L,C_(6)H_(6)100 m L,N...以7075铝合金为基体,采用有机溶剂体系,以无水氯化铝和无水氯化镍为溶质,四氢呋喃及苯为溶剂,石墨烯作为第二项添加剂,制备铝-镍-石墨烯复合镀层。镀液组成为Li Al H_(4)0.25 mol/L,AlCl_(3)0.75 mol/L,THF 150 m L,C_(6)H_(6)100 m L,NiCl_(2)0.075 mol/L。通过SEM、EDS、拉曼光谱进行微观表征,通过显微硬度计检测硬度。结果表明:镍及石墨烯存在且均匀分散在7075铝合金的表面,铝-镍-石墨烯显微硬度最高256 HV,摩擦系数最低0.47。展开更多
采用正交试验法研究了半固态搅拌法制造铝—石墨复合材料的工艺参数——搅拌速度、开始搅拌温度、搅拌时间、石墨预热时间对石墨分散、吸收及基体组织的影响。试验结果说明,搅拌速度700r/min,开始搅拌温度550℃、搅拌时间7 min、石墨预...采用正交试验法研究了半固态搅拌法制造铝—石墨复合材料的工艺参数——搅拌速度、开始搅拌温度、搅拌时间、石墨预热时间对石墨分散、吸收及基体组织的影响。试验结果说明,搅拌速度700r/min,开始搅拌温度550℃、搅拌时间7 min、石墨预热时间5 min 为最佳工艺参数。所研究的因素中影响最显著的是开始搅拌温度,其它依次为搅拌速度、搅拌时间、石墨预热时间。展开更多
Graphite, used as a carbon source in a conventional magnesia-carbon(MgO-C) refractory, was modified with an acid reagent, resulting in a negative charge on the surface of graphite, to enhance the coating efficiency of...Graphite, used as a carbon source in a conventional magnesia-carbon(MgO-C) refractory, was modified with an acid reagent, resulting in a negative charge on the surface of graphite, to enhance the coating efficiency of aluminum(Al) phase, which was compared to the pristine graphite through its dispersibity and oxidation behavior. The graphite particles with and without surface modification were added, respecticely, in an Al(NO3)3 suspension used as a coating reagent, and then filtered at room temperature. The modified graphite shows better disperbility than the pristine graphite, indicating that the coating efficiency of Al precursor is enhanced in the modified graphite. With respect to oxidation behavior, the modified graphite without the coating layer is totally reacted with oxygen at heat treatment of 900 °C in air. However, the Al-coated graphite starts to react with oxygen at heat treatment of 900 °C and fully reacted with oxygen at heat treatment of 1000 °C, showing the gray and white colors, respectively. It is verified that the Al layer is individually and uniformly formed on the surface of graphite and the oxidation resistance of graphite is enhanced owing to the increased coating efficiency of Al precursor.展开更多
30-50 wt.%graphite nanoflakes(GNFs)/6061Al matrix composites were fabricated via spark plasma sintering(SPS)at 610℃.The effects of the sintering pressure and GNF content on the microstructure and properties of the co...30-50 wt.%graphite nanoflakes(GNFs)/6061Al matrix composites were fabricated via spark plasma sintering(SPS)at 610℃.The effects of the sintering pressure and GNF content on the microstructure and properties of the composites were investigated.The results indicated that interfacial reactions were inhibited during SPS because no Al4C3 was detected.Moreover,the agglomeration of the GNFs increased,and the distribution orientation of the GNFs decreased with increasing the GNF content.The relative density,bending strength,and coefficient of thermal expansion(CTE)of the composites decreased,while the thermal conductivity(TC)in the X−Y direction increased.As the sintering pressure increased,the GNFs deagglomerated and were distributed preferentially in the X−Y direction,which increased the relative density,bending strength and TC,and decreased the CTE of the composites.The 50wt.%GNFs/6061Al matrix composite sintered at 610℃ under 55 MPa demonstrated the best performance,i.e.,bending strength of 72 MPa,TC and CTE(RT−100℃)of 254 W/(m·K)and 8.5×10^(−6)K^(−1)in the X−Y direction,and 55 W/(m·K)and 9.7×10^(−6)K^(−1)in the Z direction,respectively.展开更多
The effects of Ni coating on the mechanical behaviors of single graphene sheet and their embedded Al matrix composites under axial tension are investigated using molecular dynamics （MD） simulation method. The result...The effects of Ni coating on the mechanical behaviors of single graphene sheet and their embedded Al matrix composites under axial tension are investigated using molecular dynamics （MD） simulation method. The results show that the Young＇s moduli and tensile strength of graphene obviously decrease after Ni coating. The results also show that the mechanical properties of Al matrix can be obviously increased by embedding a single graphene sheet. From the simulation, we also find that the Young＇s modulus and tensile strength of the Ni-coated graphene/Al composite is obviously larger than those of the uncoated graphene/Al composite. The increased magnitude of the Young＇s modulus and tensile strength of graphene/Al composite are 52.27% and 32.32% at 0.01 K, respectively, due to Ni coating. By exploring the effects of temperature on the mechanical properties of single graphene sheet and their embedded Al matrix composites, it is found that the higher temperature leads to the lower critical strain and tensile strength.展开更多
The kinetics of potassium intercalating into graphite in molten KF at 1 163 K was investigated by means of cyclic voltammetry and chronoamperometry.Cyclic voltammetry results indicate that intercalaltion/deintercalati...The kinetics of potassium intercalating into graphite in molten KF at 1 163 K was investigated by means of cyclic voltammetry and chronoamperometry.Cyclic voltammetry results indicate that intercalaltion/deintercalation of potassium into/from graphite involve kinetic limitations.The intercalation process of potassium was further confirmed to be governed by both the diffusion of potassium ion in graphite bulk and the phase transition kinetics through the analyses of current-time transient curves with reversible and quasi-reversible equations.The transfer coefficient of the intercalation reaction was calculated to be 0.364 according to the parameters resulting from nonlinear fitting of the current-time transient curves with a quasi-reversible equation.Analysis with scanning electron microscope shows that graphite matrix was severely eroded by intercalation of potassium.展开更多
The wettability of pure aluminium on filter materials and on inclusions is believed to be an important factor affecting the filtration of aluminium. The contact angles of molten aluminium on alumina, SiC and graphite ...The wettability of pure aluminium on filter materials and on inclusions is believed to be an important factor affecting the filtration of aluminium. The contact angles of molten aluminium on alumina, SiC and graphite were measured under 10-8 bar high vacuum in the temperature range of 1000-1300 °C. To describe the wetting behaviour of the Al on ceramic at lower temperatures used in filtration and casting aluminium, a semi-empirical calculation was employed. The calculated contact angles at 700 °C were around 97° for alumina, 92° for vitreous graphite, 126° for single- and poly-crystal graphite, and 79° for single crystal SiC, respectively. This indicates that aluminium does not wet alumina or graphite （or Al4C3） around the casting temperature, but wets SiC at this temperature. Thus a priming height is required for aluminium to infiltrate an alumina filter. Increasing temperature can also improve the wettability of Al on ceramic.展开更多
5.0 vol.% graphene nanoplatelets(GNPs) and aluminum powders were mixed to prepare GNPs/Al composites via high-energy ball milling(HEBM). The mixed powders were subjected to spark plasma sintering(SPS) and subsequent h...5.0 vol.% graphene nanoplatelets(GNPs) and aluminum powders were mixed to prepare GNPs/Al composites via high-energy ball milling(HEBM). The mixed powders were subjected to spark plasma sintering(SPS) and subsequent hot extrusion. The microstructure and mechanical properties of extruded composites were investigated by X-ray photoelectron spectroscopy(XPS), transmission electron microscopy(TEM) and tensile tests. In the extruded composites, 5.0 vol.% GNPs were dispersed homogeneously and no serious GNP-Al interfacial reaction occurred. As a result, the yield strength and ultimate tensile strength of the extruded GNPs/Al composites reached 462 and 479 MPa, which were 62% and 60% higher than those of the extruded Al matrix, respectively. The enhanced mechanical properties were attributed to the effective load transfer capacity of dispersed GNPs. This demonstrated that it may be promising to introduce dispersed high-content GNPs via HEBM, SPS and hot extrusion techniques and GNP-Al interfacial reaction can be controlled.展开更多
文摘以7075铝合金为基体,采用有机溶剂体系,以无水氯化铝和无水氯化镍为溶质,四氢呋喃及苯为溶剂,石墨烯作为第二项添加剂,制备铝-镍-石墨烯复合镀层。镀液组成为Li Al H_(4)0.25 mol/L,AlCl_(3)0.75 mol/L,THF 150 m L,C_(6)H_(6)100 m L,NiCl_(2)0.075 mol/L。通过SEM、EDS、拉曼光谱进行微观表征,通过显微硬度计检测硬度。结果表明:镍及石墨烯存在且均匀分散在7075铝合金的表面,铝-镍-石墨烯显微硬度最高256 HV,摩擦系数最低0.47。
文摘采用正交试验法研究了半固态搅拌法制造铝—石墨复合材料的工艺参数——搅拌速度、开始搅拌温度、搅拌时间、石墨预热时间对石墨分散、吸收及基体组织的影响。试验结果说明,搅拌速度700r/min,开始搅拌温度550℃、搅拌时间7 min、石墨预热时间5 min 为最佳工艺参数。所研究的因素中影响最显著的是开始搅拌温度,其它依次为搅拌速度、搅拌时间、石墨预热时间。
基金Project(2011-0030058) supported by the National Research Foundation of Korea(NRF)Project(20134030200220) supported by the Human Resources Development Program of the Korea Institute of Energy Technology Evaluation,Korea+1 种基金Project supported by the Planning (KETEP) Grant Funded by the Korea Government Ministry of Trade,Industry and Energy and POSCO 2012,KoreaProject(10043795) supported by the Technology Innovation Program of the Ministry of Knowledge Economy Korea
文摘Graphite, used as a carbon source in a conventional magnesia-carbon(MgO-C) refractory, was modified with an acid reagent, resulting in a negative charge on the surface of graphite, to enhance the coating efficiency of aluminum(Al) phase, which was compared to the pristine graphite through its dispersibity and oxidation behavior. The graphite particles with and without surface modification were added, respecticely, in an Al(NO3)3 suspension used as a coating reagent, and then filtered at room temperature. The modified graphite shows better disperbility than the pristine graphite, indicating that the coating efficiency of Al precursor is enhanced in the modified graphite. With respect to oxidation behavior, the modified graphite without the coating layer is totally reacted with oxygen at heat treatment of 900 °C in air. However, the Al-coated graphite starts to react with oxygen at heat treatment of 900 °C and fully reacted with oxygen at heat treatment of 1000 °C, showing the gray and white colors, respectively. It is verified that the Al layer is individually and uniformly formed on the surface of graphite and the oxidation resistance of graphite is enhanced owing to the increased coating efficiency of Al precursor.
基金financial support from the International Science&Technology Cooperation Program of China(No.2014DFA50860)。
文摘30-50 wt.%graphite nanoflakes(GNFs)/6061Al matrix composites were fabricated via spark plasma sintering(SPS)at 610℃.The effects of the sintering pressure and GNF content on the microstructure and properties of the composites were investigated.The results indicated that interfacial reactions were inhibited during SPS because no Al4C3 was detected.Moreover,the agglomeration of the GNFs increased,and the distribution orientation of the GNFs decreased with increasing the GNF content.The relative density,bending strength,and coefficient of thermal expansion(CTE)of the composites decreased,while the thermal conductivity(TC)in the X−Y direction increased.As the sintering pressure increased,the GNFs deagglomerated and were distributed preferentially in the X−Y direction,which increased the relative density,bending strength and TC,and decreased the CTE of the composites.The 50wt.%GNFs/6061Al matrix composite sintered at 610℃ under 55 MPa demonstrated the best performance,i.e.,bending strength of 72 MPa,TC and CTE(RT−100℃)of 254 W/(m·K)and 8.5×10^(−6)K^(−1)in the X−Y direction,and 55 W/(m·K)and 9.7×10^(−6)K^(−1)in the Z direction,respectively.
基金Supported by National Natural Science Foundation of China under Grant No.10902083the Natural Science Foundation of Shannxi Province under Grant No.2009GM1007
文摘The effects of Ni coating on the mechanical behaviors of single graphene sheet and their embedded Al matrix composites under axial tension are investigated using molecular dynamics （MD） simulation method. The results show that the Young＇s moduli and tensile strength of graphene obviously decrease after Ni coating. The results also show that the mechanical properties of Al matrix can be obviously increased by embedding a single graphene sheet. From the simulation, we also find that the Young＇s modulus and tensile strength of the Ni-coated graphene/Al composite is obviously larger than those of the uncoated graphene/Al composite. The increased magnitude of the Young＇s modulus and tensile strength of graphene/Al composite are 52.27% and 32.32% at 0.01 K, respectively, due to Ni coating. By exploring the effects of temperature on the mechanical properties of single graphene sheet and their embedded Al matrix composites, it is found that the higher temperature leads to the lower critical strain and tensile strength.
基金Project(1343-74236000004)supported by the Hunan Province Innovation Foundation for Postgraduate
文摘The kinetics of potassium intercalating into graphite in molten KF at 1 163 K was investigated by means of cyclic voltammetry and chronoamperometry.Cyclic voltammetry results indicate that intercalaltion/deintercalation of potassium into/from graphite involve kinetic limitations.The intercalation process of potassium was further confirmed to be governed by both the diffusion of potassium ion in graphite bulk and the phase transition kinetics through the analyses of current-time transient curves with reversible and quasi-reversible equations.The transfer coefficient of the intercalation reaction was calculated to be 0.364 according to the parameters resulting from nonlinear fitting of the current-time transient curves with a quasi-reversible equation.Analysis with scanning electron microscope shows that graphite matrix was severely eroded by intercalation of potassium.
基金Project (179947/I40) supported by the Norwegian Research Council (NRC) funded BIP RIRA (Remelting and Inclusion Refining of Aluminium)
文摘The wettability of pure aluminium on filter materials and on inclusions is believed to be an important factor affecting the filtration of aluminium. The contact angles of molten aluminium on alumina, SiC and graphite were measured under 10-8 bar high vacuum in the temperature range of 1000-1300 °C. To describe the wetting behaviour of the Al on ceramic at lower temperatures used in filtration and casting aluminium, a semi-empirical calculation was employed. The calculated contact angles at 700 °C were around 97° for alumina, 92° for vitreous graphite, 126° for single- and poly-crystal graphite, and 79° for single crystal SiC, respectively. This indicates that aluminium does not wet alumina or graphite （or Al4C3） around the casting temperature, but wets SiC at this temperature. Thus a priming height is required for aluminium to infiltrate an alumina filter. Increasing temperature can also improve the wettability of Al on ceramic.
基金financial supports from National Key R&D Program of China (2017YFB0703103)Key Area R&D Program of Guangdong Province,China (2019B010942001)。
文摘5.0 vol.% graphene nanoplatelets(GNPs) and aluminum powders were mixed to prepare GNPs/Al composites via high-energy ball milling(HEBM). The mixed powders were subjected to spark plasma sintering(SPS) and subsequent hot extrusion. The microstructure and mechanical properties of extruded composites were investigated by X-ray photoelectron spectroscopy(XPS), transmission electron microscopy(TEM) and tensile tests. In the extruded composites, 5.0 vol.% GNPs were dispersed homogeneously and no serious GNP-Al interfacial reaction occurred. As a result, the yield strength and ultimate tensile strength of the extruded GNPs/Al composites reached 462 and 479 MPa, which were 62% and 60% higher than those of the extruded Al matrix, respectively. The enhanced mechanical properties were attributed to the effective load transfer capacity of dispersed GNPs. This demonstrated that it may be promising to introduce dispersed high-content GNPs via HEBM, SPS and hot extrusion techniques and GNP-Al interfacial reaction can be controlled.
