Tungsten was plated on the surface of diamond by using thermal diffusion method.Different process parameters were employed to prepare the composites with tungsten,diamond and copper.The micro morphology of different s...Tungsten was plated on the surface of diamond by using thermal diffusion method.Different process parameters were employed to prepare the composites with tungsten,diamond and copper.The micro morphology of different samples was observed,and the thermal conductivity of samples was measured by laser flash method.The optimal process parameters for preparing diamond/copper composites with high thermal conductivity were investigated.The results indicated that plating tungsten on diamond could modify the interface bonding.When the diamond was plated for 60 min,the coating appeared intact,uniform and flat,and the thermal conductivity of the sample could reach as high as 486 W/(m·K).The integrity and uniformity were more important than thickness for the coating.When the tungsten-plated diamond was further annealed,the metallurgical bonding between the coating and the diamond was enhanced,and the thermal conductivity rose to 559 W/(m·K).展开更多
In order to impart electrical conductivity to the magnesium alloy micro-arc oxidation(MAO)coating,the electroless copper plating was performed.Effects of plating temperature and complexing agent concentration on the p...In order to impart electrical conductivity to the magnesium alloy micro-arc oxidation(MAO)coating,the electroless copper plating was performed.Effects of plating temperature and complexing agent concentration on the properties of the electroless copper plating layers were studied by measuring their microstructure,corrosion resistance and electrical conductivity.It was found that the optimized plating temperature was 60°C,and the most suitable value of the complexing agent concentration was 30 g/L.Under this condition,a complete and dense plating layer could be obtained.The formation mechanism of the plating layer on magnesium alloy MAO coating was analyzed.A three-stage model of the plating process was proposed.The square resistance of the plated specimen was finally reduced to 0.03Ω/□after the third stage.Through electroless copper plating,the MAO coated sample obtained excellent electrical conductivity without significantly reducing its corrosion resistance.展开更多
Graphene-reinforced copper composites recently have attracted more attention, since they exhibited excellent mechanical properties and could be used widely in many fields. Few-layer graphene （FLG） and copper powder ...Graphene-reinforced copper composites recently have attracted more attention, since they exhibited excellent mechanical properties and could be used widely in many fields. Few-layer graphene （FLG） and copper powder were mixed by ball milling to produce homogeneous composite powders. Then, FLG-reinforced copper composites （FLG/Cu） were fabricated by spark plasma sintering （SPS） using the composite powders with a FLG volume fraction of 2.4 vol%. The effects of the rotating speed and the time of ball milling were analyzed based on the microstructure evolution and properties of the FLG/Cu composites. Obvious strengthening effect of FLG was found for the composites, and the conductance of the composite reaches 70.4% of IACS. The yield strength of the composite produced by ball milling at a speed of 100 r/rain for 4 h is 376 MPa, which is 2.5 times higher than that of copper and higher than that of copper composite enhanced by 5 vol% CNTs （360 MPa）. The defects produced in FLG with the increase of rotating speed and time could reduce the mechanical and conductive properties of the composites.展开更多
Purpose To reduce the beam coupling impedance of the vacuum chamber made of poorly conducting material,a layer of high-conductivity metal,such as copper,is often coated on its inner surface.As the natural bunch length...Purpose To reduce the beam coupling impedance of the vacuum chamber made of poorly conducting material,a layer of high-conductivity metal,such as copper,is often coated on its inner surface.As the natural bunch length of modern accelerators is about several millimeters,its beam spectrum can reach tens of GHz.In this case,the skin depth of copper is of the same order of magnitude as its surface roughness,and its electrical properties can be different from that in DC,which will influence the beam coupling impedance.Therefore,the electrical property of copper coating at high frequency needs to be investigated.Methods In this paper,the method of resonant cavity is adopted to measure the coating conductivity,which is based on the relation between the quality factor of the cavity and material conductivity.Results Three different resonant modes are tested in the measurement,among which the H011 mode shows the best performance.The results also indicate that surface roughness of copper can have an influence on its effective conductivity at high frequency.Conclusion The H011 mode is suitable for measuring high-conductivity materials.When the skin depth of copper is comparable to or larger than its surface roughness,its effective conductivity will be significantly reduced.展开更多
采用电场压力激活辅助合成工艺(Field activated and pressure assisted synthesis process (FAPAS))制备铜基石墨烯复合材料,研究不同的石墨烯含量对铜基体材料的微观结构和性能的影响机理。结果表明,石墨烯的添加能提高材料的位错密...采用电场压力激活辅助合成工艺(Field activated and pressure assisted synthesis process (FAPAS))制备铜基石墨烯复合材料,研究不同的石墨烯含量对铜基体材料的微观结构和性能的影响机理。结果表明,石墨烯的添加能提高材料的位错密度、阻止位错在晶界移动,硬度提升17.6%;由于石墨烯添加量少,对铜基复合材料的位错密度和晶粒尺寸影响有限,片状的石墨烯能有效地弥补制备产生的缺陷,使材料的热导率和电导率分别提升2.9%和4.4%;石墨烯的添加使腐蚀电池两极间的电位差减小,降低了铜离子在氧化膜中的扩散能力,使复合材料的阻抗提升5.3%,腐蚀电流密度下降28.2%,有效地提升了铜基复合材料的耐腐蚀性能。铜基石墨烯复合材料的石墨烯最佳添加量为0.5 wt.%。展开更多
基金supported by the National Natural Science Foundation of China(No.11802125)。
文摘Tungsten was plated on the surface of diamond by using thermal diffusion method.Different process parameters were employed to prepare the composites with tungsten,diamond and copper.The micro morphology of different samples was observed,and the thermal conductivity of samples was measured by laser flash method.The optimal process parameters for preparing diamond/copper composites with high thermal conductivity were investigated.The results indicated that plating tungsten on diamond could modify the interface bonding.When the diamond was plated for 60 min,the coating appeared intact,uniform and flat,and the thermal conductivity of the sample could reach as high as 486 W/(m·K).The integrity and uniformity were more important than thickness for the coating.When the tungsten-plated diamond was further annealed,the metallurgical bonding between the coating and the diamond was enhanced,and the thermal conductivity rose to 559 W/(m·K).
基金financially supported by the National Key Research and Development Program of China(No.2016YFB0301105)the National Natural Science Foundation of China(No.51804190)+4 种基金the Shandong Provincial Natural Science Foundation,China(No.ZR2021ME240)the Youth Science Funds of Shandong Academy of Sciences,China(No.2020QN0022)the Shandong Province Key Research and Development Plan,China(Nos.2019GHZ019 and 2019JZZY020329)the Jinan Science&Technology Bureau,China(No.2019GXRC030)the Innovation Pilot Project for Fusion of Science,Education and Industry(International Cooperation)from Qilu University of Technology(Shandong Academy of Sciences),China(No.2020KJC-GH03)。
文摘In order to impart electrical conductivity to the magnesium alloy micro-arc oxidation(MAO)coating,the electroless copper plating was performed.Effects of plating temperature and complexing agent concentration on the properties of the electroless copper plating layers were studied by measuring their microstructure,corrosion resistance and electrical conductivity.It was found that the optimized plating temperature was 60°C,and the most suitable value of the complexing agent concentration was 30 g/L.Under this condition,a complete and dense plating layer could be obtained.The formation mechanism of the plating layer on magnesium alloy MAO coating was analyzed.A three-stage model of the plating process was proposed.The square resistance of the plated specimen was finally reduced to 0.03Ω/□after the third stage.Through electroless copper plating,the MAO coated sample obtained excellent electrical conductivity without significantly reducing its corrosion resistance.
基金financially supported by the National Basic Research Program of China (No.2011CB612200)Program of Qinghai Science and Technology Department (2012-Z701)+1 种基金China Scholarship Council (No.201206125006)Harbin Key Technologies R&D Program (2012DB2CP029)
文摘Graphene-reinforced copper composites recently have attracted more attention, since they exhibited excellent mechanical properties and could be used widely in many fields. Few-layer graphene （FLG） and copper powder were mixed by ball milling to produce homogeneous composite powders. Then, FLG-reinforced copper composites （FLG/Cu） were fabricated by spark plasma sintering （SPS） using the composite powders with a FLG volume fraction of 2.4 vol%. The effects of the rotating speed and the time of ball milling were analyzed based on the microstructure evolution and properties of the FLG/Cu composites. Obvious strengthening effect of FLG was found for the composites, and the conductance of the composite reaches 70.4% of IACS. The yield strength of the composite produced by ball milling at a speed of 100 r/rain for 4 h is 376 MPa, which is 2.5 times higher than that of copper and higher than that of copper composite enhanced by 5 vol% CNTs （360 MPa）. The defects produced in FLG with the increase of rotating speed and time could reduce the mechanical and conductive properties of the composites.
基金supported by the National Natural Science Foundation of China(No.11775239).
文摘Purpose To reduce the beam coupling impedance of the vacuum chamber made of poorly conducting material,a layer of high-conductivity metal,such as copper,is often coated on its inner surface.As the natural bunch length of modern accelerators is about several millimeters,its beam spectrum can reach tens of GHz.In this case,the skin depth of copper is of the same order of magnitude as its surface roughness,and its electrical properties can be different from that in DC,which will influence the beam coupling impedance.Therefore,the electrical property of copper coating at high frequency needs to be investigated.Methods In this paper,the method of resonant cavity is adopted to measure the coating conductivity,which is based on the relation between the quality factor of the cavity and material conductivity.Results Three different resonant modes are tested in the measurement,among which the H011 mode shows the best performance.The results also indicate that surface roughness of copper can have an influence on its effective conductivity at high frequency.Conclusion The H011 mode is suitable for measuring high-conductivity materials.When the skin depth of copper is comparable to or larger than its surface roughness,its effective conductivity will be significantly reduced.
文摘采用电场压力激活辅助合成工艺(Field activated and pressure assisted synthesis process (FAPAS))制备铜基石墨烯复合材料,研究不同的石墨烯含量对铜基体材料的微观结构和性能的影响机理。结果表明,石墨烯的添加能提高材料的位错密度、阻止位错在晶界移动,硬度提升17.6%;由于石墨烯添加量少,对铜基复合材料的位错密度和晶粒尺寸影响有限,片状的石墨烯能有效地弥补制备产生的缺陷,使材料的热导率和电导率分别提升2.9%和4.4%;石墨烯的添加使腐蚀电池两极间的电位差减小,降低了铜离子在氧化膜中的扩散能力,使复合材料的阻抗提升5.3%,腐蚀电流密度下降28.2%,有效地提升了铜基复合材料的耐腐蚀性能。铜基石墨烯复合材料的石墨烯最佳添加量为0.5 wt.%。
