Functionally graded（FG） carbon nanotubes（CNT） and nano-silicon carbide（nSiC） reinforced aluminium（Al）matrix composites have been successfully fabricated using high-energy ball milling followed by solid-state s...Functionally graded（FG） carbon nanotubes（CNT） and nano-silicon carbide（nSiC） reinforced aluminium（Al）matrix composites have been successfully fabricated using high-energy ball milling followed by solid-state spark plasma sintering processes.The CNTs were well-dispersed in the Al particles using the nSiC as a solid mixing agent.Two different types of multi-walled CNTs were used to add different amounts of CNTs in the same volume.The ball milled Al—CNT—nSiC and Al—CNT powder mixtures were fully densified and demonstrated good adhesion with no serious microcracks and pores within an FG multilayer composite.Each layer contained different amounts of the CNTs,and the nSiC additions showed different microstructures and hardness.It is possible to control the characteristics of the FG multilayer composite through the efficient design of an Al—CNT—nSiC gradient layer.This concept offers a feasible approach for fabricating the dualnanoparticulate-reinforced Al matrix nanocomposites and can be applied to other scenarios such as polymer and ceramic systems.展开更多
Copper matrix composites have received more attentions as possible candidate for thermal and electrical conductive materials to be used in electrical contact applications. In this study, five-layered Cu/YSZ （yttria-s...Copper matrix composites have received more attentions as possible candidate for thermal and electrical conductive materials to be used in electrical contact applications. In this study, five-layered Cu/YSZ （yttria-stabilized zirconia） functionally graded material （FGM） and copper matrix composite specimens containing 3 and 5 vol% YSZ particles plus pure Cu specimen were synthesized using powder metallurgy （PM） route and spark plasma sintering （SPS） consolidation process. The microstructural and some physical, mechanical features of all specimens were characterized. Microscopic examinations showed that ultrafine YSZ particles were distributed in the copper matrix almost homoge- neously. An appropriate interface was observed at each layer of FGM. The density measurement indicated that the graded structure of the composite could be well densified after the SPS process. The microhardness values of various layers of Cu/ YSZ FGM specimen were gradually altered from 56.3 （pure copper side） to 75.2 HV （Cu-5 vol% YSZ side）. The increase of YSZ content resulted in a decrease in electrical conductivity. Additionally, thermal conductivity of Cu/YSZ FGM specimen [308.0 W/（m K）] was determined to be higher than that of the Cu-5 vol% YSZ composite specimen [260.7 W/ （m K）]. Accordingly, it can be concluded that the Cu/YSZ FGM can be a good candidate for the electrical applications, like sliding electrical contacts, where different material characteristics in the same component are required.展开更多
W/Cu functionally gradient material (FGM) has excellent mechanical properties since it can effectively relax interlayer thermal stresses caused by the mismatch between their thermal expansion coefficients. W/Cu FGM co...W/Cu functionally gradient material (FGM) has excellent mechanical properties since it can effectively relax interlayer thermal stresses caused by the mismatch between their thermal expansion coefficients. W/Cu FGM combines the advantages of tungsten such as high melting point and service strength, with heat conductivity and plasticity of copper at room temperature. Thus it demonstrates satisfactory heat corrosion and thermal shock resistance and will be a promising candidate as divertor component in thermonuclear device. Owing to the dramatic difference of melting point between tungsten and copper, conventional processes meet great difficulties in fabricating this kind of FGMs. A new approach termed graded sintering under ultra-high pressure (GSUHP) is proposed, with which a near 96% relative density of W/Cu FGM that contains a full distribution spectrum (0-100%W) has been successfully fabricated. Suitable amount of transition metals (such as nickel, zirconium, vanadium) is employed as additives to activate tungsten's sintering, enhance phase wettability and bonding strength between W and Cu. Densification effects of different layer of FGM were investigated. Microstructure morphology and interface elements distribution were observed and analyzed. The thermal shock performance of W/Cu FGM was also preliminarily tested.展开更多
The carburized graded cemented carbide with the addition of some（Ti,Ta） C was analyzed in detail.The micro-structure and element distribution were measured by using optical microscopy and X-ray photoelectron spectro...The carburized graded cemented carbide with the addition of some（Ti,Ta） C was analyzed in detail.The micro-structure and element distribution were measured by using optical microscopy and X-ray photoelectron spectrometry along the gradient direction.The experimental results showed that a large amount of solid solution phases were formed and distributed like clusters in the surface layer of cemented carbide.The cobalt migration was not very notable and the Co-rich layer was close to the surface of cemented carbide.展开更多
In INs study, the fabrication of multilayer AI（Zn）-A1203 with different volume fractions of A1203 was investigated. A1 and ZnO powders were milled by a plaaetaxy ball mill, after which five-layer functionally graded...In INs study, the fabrication of multilayer AI（Zn）-A1203 with different volume fractions of A1203 was investigated. A1 and ZnO powders were milled by a plaaetaxy ball mill, after which five-layer functionally graded samples were produced flarough hot pressing at 580~C and 90 MPa pressure for 30 min. Formation of reinforcing A1203 particles occurred in the aluminum matrix via the aluminolkermic reaction. Determination of the ignition temperature of the aluminolkennic reaction was accomplished using differential lkermal and lkermo- gravimelric amlyses. Scaaming electron microscopy, energy dispersive spectroscopy, and X-ray diffractometery amlyses were utilized to characterize the specimens. The lkermal amlysis results showed that the ignition temperatures for the aluminolkennic reaction of layers with the highest and lowest ZnO contents were 667 and 670~C, respectively. Microslxuctural observation and chemical amlysis confirmed the fa- brication of AI（Zn）-A1203 functionally graded materials composites with precipitation of additional Zn in the matrix. Moreover, nearly dense functionally graded samples demonstrated minimum and maximum hacdness values of HV 75 and HV 130, respectively.展开更多
文摘Functionally graded（FG） carbon nanotubes（CNT） and nano-silicon carbide（nSiC） reinforced aluminium（Al）matrix composites have been successfully fabricated using high-energy ball milling followed by solid-state spark plasma sintering processes.The CNTs were well-dispersed in the Al particles using the nSiC as a solid mixing agent.Two different types of multi-walled CNTs were used to add different amounts of CNTs in the same volume.The ball milled Al—CNT—nSiC and Al—CNT powder mixtures were fully densified and demonstrated good adhesion with no serious microcracks and pores within an FG multilayer composite.Each layer contained different amounts of the CNTs,and the nSiC additions showed different microstructures and hardness.It is possible to control the characteristics of the FG multilayer composite through the efficient design of an Al—CNT—nSiC gradient layer.This concept offers a feasible approach for fabricating the dualnanoparticulate-reinforced Al matrix nanocomposites and can be applied to other scenarios such as polymer and ceramic systems.
文摘Copper matrix composites have received more attentions as possible candidate for thermal and electrical conductive materials to be used in electrical contact applications. In this study, five-layered Cu/YSZ （yttria-stabilized zirconia） functionally graded material （FGM） and copper matrix composite specimens containing 3 and 5 vol% YSZ particles plus pure Cu specimen were synthesized using powder metallurgy （PM） route and spark plasma sintering （SPS） consolidation process. The microstructural and some physical, mechanical features of all specimens were characterized. Microscopic examinations showed that ultrafine YSZ particles were distributed in the copper matrix almost homoge- neously. An appropriate interface was observed at each layer of FGM. The density measurement indicated that the graded structure of the composite could be well densified after the SPS process. The microhardness values of various layers of Cu/ YSZ FGM specimen were gradually altered from 56.3 （pure copper side） to 75.2 HV （Cu-5 vol% YSZ side）. The increase of YSZ content resulted in a decrease in electrical conductivity. Additionally, thermal conductivity of Cu/YSZ FGM specimen [308.0 W/（m K）] was determined to be higher than that of the Cu-5 vol% YSZ composite specimen [260.7 W/ （m K）]. Accordingly, it can be concluded that the Cu/YSZ FGM can be a good candidate for the electrical applications, like sliding electrical contacts, where different material characteristics in the same component are required.
基金China National Committee of High Technology New Materials under grant No.863-715-011-0230.]
文摘W/Cu functionally gradient material (FGM) has excellent mechanical properties since it can effectively relax interlayer thermal stresses caused by the mismatch between their thermal expansion coefficients. W/Cu FGM combines the advantages of tungsten such as high melting point and service strength, with heat conductivity and plasticity of copper at room temperature. Thus it demonstrates satisfactory heat corrosion and thermal shock resistance and will be a promising candidate as divertor component in thermonuclear device. Owing to the dramatic difference of melting point between tungsten and copper, conventional processes meet great difficulties in fabricating this kind of FGMs. A new approach termed graded sintering under ultra-high pressure (GSUHP) is proposed, with which a near 96% relative density of W/Cu FGM that contains a full distribution spectrum (0-100%W) has been successfully fabricated. Suitable amount of transition metals (such as nickel, zirconium, vanadium) is employed as additives to activate tungsten's sintering, enhance phase wettability and bonding strength between W and Cu. Densification effects of different layer of FGM were investigated. Microstructure morphology and interface elements distribution were observed and analyzed. The thermal shock performance of W/Cu FGM was also preliminarily tested.
基金Funded by the Natural Science Foundation of Shanxi Province(2013011024-5)
文摘The carburized graded cemented carbide with the addition of some（Ti,Ta） C was analyzed in detail.The micro-structure and element distribution were measured by using optical microscopy and X-ray photoelectron spectrometry along the gradient direction.The experimental results showed that a large amount of solid solution phases were formed and distributed like clusters in the surface layer of cemented carbide.The cobalt migration was not very notable and the Co-rich layer was close to the surface of cemented carbide.
文摘In INs study, the fabrication of multilayer AI（Zn）-A1203 with different volume fractions of A1203 was investigated. A1 and ZnO powders were milled by a plaaetaxy ball mill, after which five-layer functionally graded samples were produced flarough hot pressing at 580~C and 90 MPa pressure for 30 min. Formation of reinforcing A1203 particles occurred in the aluminum matrix via the aluminolkermic reaction. Determination of the ignition temperature of the aluminolkennic reaction was accomplished using differential lkermal and lkermo- gravimelric amlyses. Scaaming electron microscopy, energy dispersive spectroscopy, and X-ray diffractometery amlyses were utilized to characterize the specimens. The lkermal amlysis results showed that the ignition temperatures for the aluminolkennic reaction of layers with the highest and lowest ZnO contents were 667 and 670~C, respectively. Microslxuctural observation and chemical amlysis confirmed the fa- brication of AI（Zn）-A1203 functionally graded materials composites with precipitation of additional Zn in the matrix. Moreover, nearly dense functionally graded samples demonstrated minimum and maximum hacdness values of HV 75 and HV 130, respectively.
