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Pulickel M Ajayan - One of the best experts on this subject based on the ideXlab platform.

  • sharp burnout failure observed in high current carrying double walled Carbon Nanotube fibers
    Nanotechnology, 2012
    Co-Authors: Jinquan Wei, Robert Vajtai, Pulickel M Ajayan, Li Song, Geza Toth, Zheng Liu, Wei Gao, Morinobu Endo
    Abstract:

    We report on the current-carrying capability and the high-current-induced thermal burnout failure modes of 5–20 μm diameter Double-Walled Carbon Nanotube (DWNT) fibers made by an improved dry-spinning method. It is found that the electrical conductivity and maximum current-carrying capability for these DWNT fibers can reach up to 5.9 × 10 5 Sm −1 and over 1 × 10 5 Ac m −2 in air. In comparison, we observed that standard Carbon fiber tended to be oxidized and burnt out into cheese-like morphology when the maximum current was reached, while DWNT fiber showed a much slower breakdown behavior due to the gradual burnout in individual Nanotubes. The electron microscopy observations further confirmed that the failure process of DWNT fibers occurs at localized positions, and while the individual Nanotubes burn they also get aligned due to local high temperature and electrostatic field. In addition a finite element model was constructed to gain better understanding of the failure behavior of DWNT fibers.

  • multifunctional macroarchitectures of double walled Carbon Nanotube fibers
    Advanced Materials, 2007
    Co-Authors: Niramol Punbusayakul, Jinquan Wei, Robert Vajtai, Saikat Talapatra, Pulickel M Ajayan
    Abstract:

    Many applications are envisioned that will ultimately utilize macroarchitectures fabricated by using Carbon Nanotubes (CNTs) as building blocks, because these architectures (for example CNT films and fibers) possess a number of superb properties, such as high strength, low density, high specific surface area, and excellent thermal and electrical conductivity. These properties make these macrostructures potential engineering materials for developing applications in a variety of fields, such as composites, field-emission display devices, electrochemical sensing, and electrochemical energy storage. For these reasons, the last several years have seen a growing popularity for spinning CNT fibers. Long CNT strands or fibers could be directly drawn out of a chemical vapor deposition (CVD) furnace. By mimicking the process of drawing silk out of cocoon, continuous CNT yarns were assembled from a vertically aligned multi-walled CNT (MWNT) film. In general, CNT products are powderlike, and fabricating macroscopic fibers from these powders is a challenging task. Several successful attempts for spinning single-walled CNT (SWNT) fibers from CNT solutions (i.e., SWNT/surfactant solution and SWNT/super-acid solution) by a coagulation process have been reported in the literature, however, these processes are costly. In this Communication, we report a simple and cheap process for spinning Double-Walled CNT (DWNT) fibers out of DWNT cotton. DWNTs consist of two concentric graphene layers, and some of their properties are similar to those of SWNTs. However, DWNTs have a higher structural stability than SWNTs, with the onset temperature for oxidation ca. 200 °C higher than for SWNTs because of the coaxial structure. In our previous research, we have shown that DWNTs can be mass-produced by a sulfur-promoted floating catalyst CVD method, with the as-grown Nanotube products in a cottonlike form (Nanotube cotton). Developing a technique to spin yarns from the Nanotube cotton by mimicking the ancient cotton-spinning process is very practical and promising for the large-scale production of DWNT fibers. Here, a drawing–drying process is reported for the fabrication of DWNT fibers. We have also investigated some of the properties of these fibers to show their multifunctional capabilities. Centimeter-long DWNT strands could be peeled off from the as-grown Nanotube cotton. However, it was not easy to pull out a long fiber continuously from the as-grown Nanotube cotton, perhaps because of the strong adhesion between the Nanotube bundles. After the purification process (as described in the Experimental section), we occasionally found that a long Nanotube fiber could be drawn from the wet Nanotube cotton. A drawing–drying process to spin Nanotube yarns from the wet DWNT cotton was developed (see Experimental section), which was very efficient in producing continuous fibers of DWNT. Figure 1 shows a schematic illustration of the spinning process, and an optical image of the as-spun DWNT fibers. After the spinning process, heat treatment under argon gas was performed for one hour at 150 °C to completely remove water content inside the fibers. This process further compacted the Nanotube bundles.

  • vertically aligned large diameter double walled Carbon Nanotube arrays having ultralow density
    Journal of Physical Chemistry C, 2007
    Co-Authors: Robert Vajtai, Pulickel M Ajayan
    Abstract:

    We have selectively synthesized ultralow density (0.015 ± 0.002 g/cm3) Double-Walled Carbon Nanotube (DWNT) arrays. The low mass density is due to the large diameter and low-site density of DWNTs in the arrays. The diameter of the as-grown DWNTs varies from 4.5 to 14.8 nm with a mean value of 7.9 nm. The role of the thickness of Fe catalyst layer is evaluated for the selective growth of large-diameter DWNTs. Our DWNT arrays have promising applications in areas such as solar absorbers and super-hydrophobic surfaces.

  • double walled Carbon Nanotube electrodes for electrochemical sensing
    Electrochemical and Solid State Letters, 2007
    Co-Authors: Niramol Punbusayakul, Saikat Talapatra, Werasak Surareungchai, Pulickel M Ajayan
    Abstract:

    We report on the electrochemical properties of electrodes fabricated using spun fibers of purified Double-Walled Nanotubes (DWNTs). These electrodes show reversible and faster electron-transfer kinetics in electrochemical reactions compared to multiwalled Nanotubes (MWNTs) and standard glassy Carbon electrodes (GCE). The detection capabilities of the DWNT electrodes for chemical species such as hydrogen peroxide, ascorbic acid (AA), and electroactive neurotransmitters such as dopamine are presented and compared with the detection abilities for these species using GCE and MWNT. These electrodes also show excellent selective sensing properties (with observed detection limits as low as 20 μM of DA in 1 mM of AA) and can be developed for active components in electrochemical sensors.

Jinquan Wei - One of the best experts on this subject based on the ideXlab platform.

  • significantly enhanced thermoelectric properties of ultralong double walled Carbon Nanotube bundle
    Applied Physics Letters, 2013
    Co-Authors: Tingting Miao, Xing Zhang, Jinquan Wei, Jialin Sun
    Abstract:

    A T-type method is developed to comprehensively evaluate the thermoelectric properties of materials. The thermoelectric properties, including thermal conductivity, thermopower, and electrical conductivity of an ultralong Double-Walled Carbon Nanotube bundle are studied from 240 K to 340 K by applying the T-type method. The determined figure of merit achieves 10−3 which is significantly larger than that reported for Carbon Nanotubes samples. The bundle consists of thousands of Nanotubes aligned along the long axis with low levels of impurities, and the thermal conductivity is significantly reduced compared to that of individual Double-Walled Nanotube, while the electrical conductivity is superior to most of the Carbon Nanotubes samples.

  • fabrication of double walled Carbon Nanotube film cu2o nanoparticle film tio2 Nanotube array heterojunctions for photosensors
    Applied Physics Letters, 2012
    Co-Authors: Mingjie Yang, Jinquan Wei, Jialin Sun, Wei Liu, Jialin Zhu
    Abstract:

    A structure for visible photosensors based on Double-Walled Carbon Nanotube (DWCNT) film/Cu2O nanoparticle (NP) film/TiO2 Nanotube array (TNA) heterojunctions has been fabricated. Cu2O nanoparticles reduce dark current and enhance photoresponse of the heterojunctions. Consequently, the optoelectric performance is significantly enhanced compared to that of the heterojunctions without Cu2O nanoparticles. The photocurrent-to-dark current ratio reaches ∼1 × 104 under illumination at 405 nm and ∼3 × 104 under illumination at 532 nm, which is two orders of magnitude higher than the results of Double-Walled Carbon Nanotube film/TiO2 Nanotube array heterojunctions under the same illumination density. Moreover, the response speed of the heterojunctions is greatly improved.

  • sharp burnout failure observed in high current carrying double walled Carbon Nanotube fibers
    Nanotechnology, 2012
    Co-Authors: Jinquan Wei, Robert Vajtai, Pulickel M Ajayan, Li Song, Geza Toth, Zheng Liu, Wei Gao, Morinobu Endo
    Abstract:

    We report on the current-carrying capability and the high-current-induced thermal burnout failure modes of 5–20 μm diameter Double-Walled Carbon Nanotube (DWNT) fibers made by an improved dry-spinning method. It is found that the electrical conductivity and maximum current-carrying capability for these DWNT fibers can reach up to 5.9 × 10 5 Sm −1 and over 1 × 10 5 Ac m −2 in air. In comparison, we observed that standard Carbon fiber tended to be oxidized and burnt out into cheese-like morphology when the maximum current was reached, while DWNT fiber showed a much slower breakdown behavior due to the gradual burnout in individual Nanotubes. The electron microscopy observations further confirmed that the failure process of DWNT fibers occurs at localized positions, and while the individual Nanotubes burn they also get aligned due to local high temperature and electrostatic field. In addition a finite element model was constructed to gain better understanding of the failure behavior of DWNT fibers.

  • Tailoring the intrinsic metallic states of Double-Walled Nanotube films by self-soldered laser welding
    Applied Physics Letters, 2007
    Co-Authors: Yong Zhang, Jinquan Wei, Tao Gong, Yi Jia, Wenjin Liu, Kunlin Wang, Minlin Zhong, Anyuan Cao
    Abstract:

    The metallic state and resistivity of interconnected Double-Walled Carbon Nanotube bundles have been tuned by modifying two major components, including (1) structure of the bundles and (2) contacts at the heterojunctions between the bundles. Infrared laser illumination at controlled intensity on the Nanotubes produces an amorphous Carbon coating that subsequently serves as the solder material to weld the bundles at their heterojunction sites. The results show that without selective etching of metallic or semiconductor species, the crossover temperature at which metallic behavior changes to semiconducting can be tuned within a wide range (25–150K).

  • double walled Carbon Nanotube solar cells
    Nano Letters, 2007
    Co-Authors: Jinquan Wei, Yi Jia, Kunlin Wang, Qinke Shu, Zhicheng Wang, Jianbin Luo, Daming Zhuang, Gong Zhang, And Anyuan Cao
    Abstract:

    We directly configured Double-Walled Carbon Nanotubes as energy conversion materials to fabricate thin-film solar cells, with Nanotubes serving as both photogeneration sites and a charge carriers collecting/transport layer. The solar cells consist of a semitransparent thin film of Nanotubes conformally coated on a n-type crystalline silicon substrate to create high-density p-n heterojunctions between Nanotubes and n-Si to favor charge separation and extract electrons (through n-Si) and holes (through Nanotubes). Initial tests have shown a power conversion efficiency of >1%, proving that DWNTs-on-Si is a potentially suitable configuration for making solar cells. Our devices are distinct from previously reported organic solar cells based on blends of polymers and nanomaterials, where conjugate polymers generate excitons and Nanotubes only serve as a transport path.

Alain Peigney - One of the best experts on this subject based on the ideXlab platform.

  • double walled Carbon Nanotube zirconia composites preparation by spark plasma sintering electrical conductivity and mechanical properties
    Ceramics International, 2015
    Co-Authors: Anne Kasperski, Alicia Weibel, Claude Estournès, C Laurent, Dalya Alkattan, Alain Peigney
    Abstract:

    Double-Walled Carbon Nanotube/yttria-stabilized zirconia composite powders with Carbon contents up to 6.3 wt% are prepared by soft covalent functionalization of Carbon Nanotubes (CNTs) followed by mixing with a nanometric yttria-stabilized zirconia (YSZ) powder. Composites are densified by spark plasma sintering (SPS). The composites present an electrical conductivity (0.09–0.88 S cm−1) which is among the highest values reported in the literature. Both the fracture strength (σf) and the single-edged notched beam fracture toughness (KIc) are measured for the first time on CNT/YSZ composites. The best mechanical properties (σf=694 MPa; KIc=7 MPa m1/2), obtained for low Carbon contents (up to 1.2 wt%), are among the highest reported up to now. However, the fracture toughness is lower than that of the YSZ ceramic (KIc=10.3 MPa m1/2) whose mechanical properties are outstanding, taking into account its very fine microstructure.

  • Double-Walled Carbon Nanotube/zirconia composites: Preparation by spark plasma sintering, electrical conductivity and mechanical properties
    Ceramics International, 2015
    Co-Authors: Anne Kasperski, Alicia Weibel, Claude Estournès, Christophe Laurent, Dalya Alkattan, Alain Peigney
    Abstract:

    Double-Walled Carbon Nanotube/yttria-stabilized zirconia composite powders with Carbon contents up to 6.3 wt% are prepared by soft covalent functionalization of Carbon Nanotubes (CNTs) followed by mixing with a nanometric yttria-stabilized zirconia (YSZ) powder. Composites are densified by spark plasma sintering (SPS). The composites present an electrical conductivity (0.09–0.88 S cm−1) which is among the highest values reported in the literature. Both the fracture strength (σf) and the single-edged notched beam fracture toughness (KIc) are measured for the first time on CNT/YSZ composites. The best mechanical properties (σf=694 MPa; KIc=7 MPa m1/2), obtained for low Carbon contents (up to 1.2 wt%), are among the highest reported up to now. However, the fracture toughness is lower than that of the YSZ ceramic (KIc=10.3 MPa m1/2) whose mechanical properties are outstanding, taking into account its very fine microstructure.

  • the preparation of double walled Carbon Nanotube cu composites by spark plasma sintering and their hardness and friction properties
    Carbon, 2011
    Co-Authors: Christophe Guiderdoni, Alicia Weibel, Claude Estournès, Alain Peigney, Viviane Turq, C Laurent
    Abstract:

    Abstract Double-Walled Carbon Nanotube (DWCNT)/copper composite powders were prepared by a rapid route involving freeze-drying without oxidative acidic treatment or ball-milling. The DWCNTs are not damaged and are homogeneously dispersed in the matrix. Dense specimens were prepared by spark plasma sintering. The Vickers microhardness is doubled, the wear against a steel or an alumina ball seems very low and the average friction coefficient is decreased by a factor of about 4 compared to pure copper. The best results are obtained for a Carbon loading (5 vol%) significantly lower than those reported when using multi-walled Carbon Nanotubes (10–20 vol%). Maximum Hertzian contact pressure data could indicate that the surface DWCNTs and bundles of them are deformed and broken, possibly resulting in the formation of a graphitized lubricating tribofilm in the contact.

  • toughening and hardening in double walled Carbon Nanotube nanostructured magnesia composites
    Carbon, 2010
    Co-Authors: Alain Peigney, Alicia Weibel, Claude Estournès, Felipe Legorreta Garcia, C Laurent
    Abstract:

    Abstract Dense Double-Walled Carbon Nanotube (DWCNT)/nanostructured MgO composites were prepared using an in situ route obviating any milling step for the synthesis of powders and consolidation by spark-plasma-sintering. An unambiguous increase in both toughness and microhardness is reported. The mechanisms of crack-bridging on an unprecedented scale, crack-deflection and DWCNT pullout have been evidenced. The very long DWCNTs, which appear to be mostly undamaged, are very homogeneously dispersed at the grain boundaries of the matrix, greatly inhibiting the grain growth during sintering. These results arise because the unique microstructure (low content of long DWCNTs, nanometric matrix grains and grain boundary cohesion) provides the appropriate scale of the reinforcement to make the material tough.

  • Double-Walled Carbon Nanotube dispersion via surfactant substitution
    Journal of Materials Chemistry, 2009
    Co-Authors: Vitaliy Datsyuk, Perine Landois, Juliette Fitremann, Alain Peigney, Anne Marie Galibert, Brigitte Soula, Emmanuel Flahaut
    Abstract:

    A new approach for the stabilisation of Double-Walled Carbon Nanotubes in aqueous media was developed. A low molecular weight surfactant was used in the first stage for the debundling of the Nanotubes followed by substitution with a higher molecular weight surfactant or non-ionic surfactants. Dispersions were characterized by optical density measurements, SEM and DLS. The presence of remaining low molecular weight surfactant was investigated by FT-IR. Double walled Carbon Nanotube dispersions showed good dispersion stability and non-detectable amounts of the initial surfactant, which was completely removed. Such a method could be useful for preparation of stable aqueous dispersions of Carbon Nanotubes with low concentration of surfactants, which is especially important for toxicity studies.

Claude Estournès - One of the best experts on this subject based on the ideXlab platform.

  • High strength - High conductivity Double-Walled Carbon Nanotube - Copper composite wires
    Carbon, 2016
    Co-Authors: Claire Arnaud, David Mesguich, Florence Lecouturier, Alicia Weibel, Geoffroy Chevallier, Claude Estournès, Nelson Ferreira, Christophe Laurent
    Abstract:

    Double-Walled Carbon Nanotube - copper composite macroscopic wires are prepared using a combination of spark plasma sintering and room-temperature wire drawing. The Carbon content in the samples is low (0.5 vol.%). Compared to the corresponding pure copper wires, the electrical resistivity at 77 K of the composite wires is increased by only about 12% whereas their ultimate tensile strength at 293 K (560 MPa) and 77 K (710 MPa) is increased by about 10%.

  • High strength – High conductivity Double-Walled Carbon Nanotube – Copper composite wires
    Carbon, 2016
    Co-Authors: Claire Arnaud, David Mesguich, Florence Lecouturier, Alicia Weibel, Geoffroy Chevallier, Claude Estournès, Nelson Ferreira, Christophe Laurent
    Abstract:

    Double-Walled Carbon Nanotube – copper composite macroscopic wires are prepared using a combination of spark plasma sintering and room-temperature wire drawing. The Carbon content in the samples is low (0.5 vol.%). Compared to the corresponding pure copper wires, the electrical resistivity at 77 K of the composite wires is increased by only about 12% whereas their ultimate tensile strength at 293 K (560 MPa) and 77 K (710 MPa) is increased by about 10%

  • double walled Carbon Nanotube zirconia composites preparation by spark plasma sintering electrical conductivity and mechanical properties
    Ceramics International, 2015
    Co-Authors: Anne Kasperski, Alicia Weibel, Claude Estournès, C Laurent, Dalya Alkattan, Alain Peigney
    Abstract:

    Double-Walled Carbon Nanotube/yttria-stabilized zirconia composite powders with Carbon contents up to 6.3 wt% are prepared by soft covalent functionalization of Carbon Nanotubes (CNTs) followed by mixing with a nanometric yttria-stabilized zirconia (YSZ) powder. Composites are densified by spark plasma sintering (SPS). The composites present an electrical conductivity (0.09–0.88 S cm−1) which is among the highest values reported in the literature. Both the fracture strength (σf) and the single-edged notched beam fracture toughness (KIc) are measured for the first time on CNT/YSZ composites. The best mechanical properties (σf=694 MPa; KIc=7 MPa m1/2), obtained for low Carbon contents (up to 1.2 wt%), are among the highest reported up to now. However, the fracture toughness is lower than that of the YSZ ceramic (KIc=10.3 MPa m1/2) whose mechanical properties are outstanding, taking into account its very fine microstructure.

  • Double-Walled Carbon Nanotube/zirconia composites: Preparation by spark plasma sintering, electrical conductivity and mechanical properties
    Ceramics International, 2015
    Co-Authors: Anne Kasperski, Alicia Weibel, Claude Estournès, Christophe Laurent, Dalya Alkattan, Alain Peigney
    Abstract:

    Double-Walled Carbon Nanotube/yttria-stabilized zirconia composite powders with Carbon contents up to 6.3 wt% are prepared by soft covalent functionalization of Carbon Nanotubes (CNTs) followed by mixing with a nanometric yttria-stabilized zirconia (YSZ) powder. Composites are densified by spark plasma sintering (SPS). The composites present an electrical conductivity (0.09–0.88 S cm−1) which is among the highest values reported in the literature. Both the fracture strength (σf) and the single-edged notched beam fracture toughness (KIc) are measured for the first time on CNT/YSZ composites. The best mechanical properties (σf=694 MPa; KIc=7 MPa m1/2), obtained for low Carbon contents (up to 1.2 wt%), are among the highest reported up to now. However, the fracture toughness is lower than that of the YSZ ceramic (KIc=10.3 MPa m1/2) whose mechanical properties are outstanding, taking into account its very fine microstructure.

  • the preparation of double walled Carbon Nanotube cu composites by spark plasma sintering and their hardness and friction properties
    Carbon, 2011
    Co-Authors: Christophe Guiderdoni, Alicia Weibel, Claude Estournès, Alain Peigney, Viviane Turq, C Laurent
    Abstract:

    Abstract Double-Walled Carbon Nanotube (DWCNT)/copper composite powders were prepared by a rapid route involving freeze-drying without oxidative acidic treatment or ball-milling. The DWCNTs are not damaged and are homogeneously dispersed in the matrix. Dense specimens were prepared by spark plasma sintering. The Vickers microhardness is doubled, the wear against a steel or an alumina ball seems very low and the average friction coefficient is decreased by a factor of about 4 compared to pure copper. The best results are obtained for a Carbon loading (5 vol%) significantly lower than those reported when using multi-walled Carbon Nanotubes (10–20 vol%). Maximum Hertzian contact pressure data could indicate that the surface DWCNTs and bundles of them are deformed and broken, possibly resulting in the formation of a graphitized lubricating tribofilm in the contact.

Alicia Weibel - One of the best experts on this subject based on the ideXlab platform.

  • High strength - High conductivity Double-Walled Carbon Nanotube - Copper composite wires
    Carbon, 2016
    Co-Authors: Claire Arnaud, David Mesguich, Florence Lecouturier, Alicia Weibel, Geoffroy Chevallier, Claude Estournès, Nelson Ferreira, Christophe Laurent
    Abstract:

    Double-Walled Carbon Nanotube - copper composite macroscopic wires are prepared using a combination of spark plasma sintering and room-temperature wire drawing. The Carbon content in the samples is low (0.5 vol.%). Compared to the corresponding pure copper wires, the electrical resistivity at 77 K of the composite wires is increased by only about 12% whereas their ultimate tensile strength at 293 K (560 MPa) and 77 K (710 MPa) is increased by about 10%.

  • High strength – High conductivity Double-Walled Carbon Nanotube – Copper composite wires
    Carbon, 2016
    Co-Authors: Claire Arnaud, David Mesguich, Florence Lecouturier, Alicia Weibel, Geoffroy Chevallier, Claude Estournès, Nelson Ferreira, Christophe Laurent
    Abstract:

    Double-Walled Carbon Nanotube – copper composite macroscopic wires are prepared using a combination of spark plasma sintering and room-temperature wire drawing. The Carbon content in the samples is low (0.5 vol.%). Compared to the corresponding pure copper wires, the electrical resistivity at 77 K of the composite wires is increased by only about 12% whereas their ultimate tensile strength at 293 K (560 MPa) and 77 K (710 MPa) is increased by about 10%

  • double walled Carbon Nanotube zirconia composites preparation by spark plasma sintering electrical conductivity and mechanical properties
    Ceramics International, 2015
    Co-Authors: Anne Kasperski, Alicia Weibel, Claude Estournès, C Laurent, Dalya Alkattan, Alain Peigney
    Abstract:

    Double-Walled Carbon Nanotube/yttria-stabilized zirconia composite powders with Carbon contents up to 6.3 wt% are prepared by soft covalent functionalization of Carbon Nanotubes (CNTs) followed by mixing with a nanometric yttria-stabilized zirconia (YSZ) powder. Composites are densified by spark plasma sintering (SPS). The composites present an electrical conductivity (0.09–0.88 S cm−1) which is among the highest values reported in the literature. Both the fracture strength (σf) and the single-edged notched beam fracture toughness (KIc) are measured for the first time on CNT/YSZ composites. The best mechanical properties (σf=694 MPa; KIc=7 MPa m1/2), obtained for low Carbon contents (up to 1.2 wt%), are among the highest reported up to now. However, the fracture toughness is lower than that of the YSZ ceramic (KIc=10.3 MPa m1/2) whose mechanical properties are outstanding, taking into account its very fine microstructure.

  • Double-Walled Carbon Nanotube/zirconia composites: Preparation by spark plasma sintering, electrical conductivity and mechanical properties
    Ceramics International, 2015
    Co-Authors: Anne Kasperski, Alicia Weibel, Claude Estournès, Christophe Laurent, Dalya Alkattan, Alain Peigney
    Abstract:

    Double-Walled Carbon Nanotube/yttria-stabilized zirconia composite powders with Carbon contents up to 6.3 wt% are prepared by soft covalent functionalization of Carbon Nanotubes (CNTs) followed by mixing with a nanometric yttria-stabilized zirconia (YSZ) powder. Composites are densified by spark plasma sintering (SPS). The composites present an electrical conductivity (0.09–0.88 S cm−1) which is among the highest values reported in the literature. Both the fracture strength (σf) and the single-edged notched beam fracture toughness (KIc) are measured for the first time on CNT/YSZ composites. The best mechanical properties (σf=694 MPa; KIc=7 MPa m1/2), obtained for low Carbon contents (up to 1.2 wt%), are among the highest reported up to now. However, the fracture toughness is lower than that of the YSZ ceramic (KIc=10.3 MPa m1/2) whose mechanical properties are outstanding, taking into account its very fine microstructure.

  • the preparation of double walled Carbon Nanotube cu composites by spark plasma sintering and their hardness and friction properties
    Carbon, 2011
    Co-Authors: Christophe Guiderdoni, Alicia Weibel, Claude Estournès, Alain Peigney, Viviane Turq, C Laurent
    Abstract:

    Abstract Double-Walled Carbon Nanotube (DWCNT)/copper composite powders were prepared by a rapid route involving freeze-drying without oxidative acidic treatment or ball-milling. The DWCNTs are not damaged and are homogeneously dispersed in the matrix. Dense specimens were prepared by spark plasma sintering. The Vickers microhardness is doubled, the wear against a steel or an alumina ball seems very low and the average friction coefficient is decreased by a factor of about 4 compared to pure copper. The best results are obtained for a Carbon loading (5 vol%) significantly lower than those reported when using multi-walled Carbon Nanotubes (10–20 vol%). Maximum Hertzian contact pressure data could indicate that the surface DWCNTs and bundles of them are deformed and broken, possibly resulting in the formation of a graphitized lubricating tribofilm in the contact.