The Experts below are selected from a list of 1671 Experts worldwide ranked by ideXlab platform

Mohammad F Islam - One of the best experts on this subject based on the ideXlab platform.

  • graphene coating makes carbon nanotube aerogels Superelastic and resistant to fatigue
    Nature Nanotechnology, 2012
    Co-Authors: Youngseok Oh, Mohammad F Islam
    Abstract:

    A mechanically fragile aerogel made of single-walled carbon nanotubes can be transformed into a Superelastic Material by coating it with graphene.

  • Graphene coating makes carbon nanotube aerogels Superelastic and resistant to fatigue
    Nature Nanotechnology, 2012
    Co-Authors: Kyu Hun Kim, Mohammad F Islam
    Abstract:

    A mechanically fragile aerogel made of single-walled carbon nanotubes can be transformed into a Superelastic Material by coating it with graphene. Lightweight Materials that are both highly compressible and resilient under large cyclic strains can be used in a variety of applications^ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 . Carbon nanotubes offer a combination of elasticity, mechanical resilience and low density^ 9 , and these properties have been exploited in nanotube-based foams^ 10 , 11 , 12 , 13 , 14 and aerogels^ 15 , 16 . However, all nanotube-based foams and aerogels developed so far undergo structural collapse^ 15 or significant plastic deformation with a reduction in compressive strength^ 10 , 11 , 13 , 14 when they are subjected to cyclic strain. Here, we show that an inelastic aerogel made of single-walled carbon nanotubes can be transformed into a Superelastic Material by coating it with between one and five layers of graphene nanoplates. The graphene-coated aerogel exhibits no change in mechanical properties after more than 1 × 10^6 compressive cycles, and its original shape can be recovered quickly after compression release. Moreover, the coating does not affect the structural integrity of the nanotubes or the compressibility and porosity of the nanotube network. The coating also increases Young's modulus and energy storage modulus by a factor of ∼6, and the loss modulus by a factor of ∼3. We attribute the Superelasticity and complete fatigue resistance to the graphene coating strengthening the existing crosslinking points or ‘nodes’ in the aerogel.

Kyu Hun Kim - One of the best experts on this subject based on the ideXlab platform.

  • Graphene coating makes carbon nanotube aerogels Superelastic and resistant to fatigue
    Nature Nanotechnology, 2012
    Co-Authors: Kyu Hun Kim, Mohammad F Islam
    Abstract:

    A mechanically fragile aerogel made of single-walled carbon nanotubes can be transformed into a Superelastic Material by coating it with graphene. Lightweight Materials that are both highly compressible and resilient under large cyclic strains can be used in a variety of applications^ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 . Carbon nanotubes offer a combination of elasticity, mechanical resilience and low density^ 9 , and these properties have been exploited in nanotube-based foams^ 10 , 11 , 12 , 13 , 14 and aerogels^ 15 , 16 . However, all nanotube-based foams and aerogels developed so far undergo structural collapse^ 15 or significant plastic deformation with a reduction in compressive strength^ 10 , 11 , 13 , 14 when they are subjected to cyclic strain. Here, we show that an inelastic aerogel made of single-walled carbon nanotubes can be transformed into a Superelastic Material by coating it with between one and five layers of graphene nanoplates. The graphene-coated aerogel exhibits no change in mechanical properties after more than 1 × 10^6 compressive cycles, and its original shape can be recovered quickly after compression release. Moreover, the coating does not affect the structural integrity of the nanotubes or the compressibility and porosity of the nanotube network. The coating also increases Young's modulus and energy storage modulus by a factor of ∼6, and the loss modulus by a factor of ∼3. We attribute the Superelasticity and complete fatigue resistance to the graphene coating strengthening the existing crosslinking points or ‘nodes’ in the aerogel.

Tao Cheng - One of the best experts on this subject based on the ideXlab platform.

  • Deformation Induced Solid−Solid Phase Transitions in Gamma Boron
    Chemistry of Materials, 2014
    Co-Authors: William A Goddard, Hai Xiao, Tao Cheng
    Abstract:

    We predict three new polymorphs of boron by applying density functional theory (PBE flavor) to large shear deformations starting from the recently discovered γ-B_(28) boron phase (stable above 9 GPa and 1000 K). We find that continuous deformation along the (100)/⟨001⟩ slip system leads to two new phases, named here as γ-B_(12)–(B_(2))_(6) and γ-B_(12)–(B···B)_(6). We show that these γ-B_(12)–(B_(2))_(6) and γ-B_(12)–(B···B)_(6) phases can also be obtained from uniaxial tensile and compressive deformations of the γ-B28 phase along the ⟨101⟩ direction, respectively. However, the reverse compressive loading on the newly formed γ-B_(12)–(B_(2))_(6) phase transforms it to itself, not the γ-B28 phase, because of the transferability of the three-center two-electron bond under deformation. This makes the new phase γ-B_(12)–(B_(2))_(6) a special type of Superelastic Material. In addition, application of reverse tensile deformation on the newly formed γ-B_(12)–(B···B)_(6) phase, transforms it to a third new phase, named α-B_(12)–BB, that is metallic, suggesting increased ductility that might make α-B_(12)–BB important for applications in electronic devices. We compared the structural character, mechanical properties, and electronic properties of these new phases to each other and to other phases of boron. We show that the three new phases are dynamically stable at zero pressure. These results show how modifying the connections between boron icosahedra using one to two atom chains can lead to dramatically different mechanical and electronic properties.

  • deformation induced solid solid phase transitions in gamma boron
    Chemistry of Materials, 2014
    Co-Authors: Q An, William A Goddard, Hai Xiao, Tao Cheng
    Abstract:

    We predict three new polymorphs of boron by applying density functional theory (PBE flavor) to large shear deformations starting from the recently discovered γ-B_(28) boron phase (stable above 9 GPa and 1000 K). We find that continuous deformation along the (100)/⟨001⟩ slip system leads to two new phases, named here as γ-B_(12)–(B_(2))_(6) and γ-B_(12)–(B···B)_(6). We show that these γ-B_(12)–(B_(2))_(6) and γ-B_(12)–(B···B)_(6) phases can also be obtained from uniaxial tensile and compressive deformations of the γ-B28 phase along the ⟨101⟩ direction, respectively. However, the reverse compressive loading on the newly formed γ-B_(12)–(B_(2))_(6) phase transforms it to itself, not the γ-B28 phase, because of the transferability of the three-center two-electron bond under deformation. This makes the new phase γ-B_(12)–(B_(2))_(6) a special type of Superelastic Material. In addition, application of reverse tensile deformation on the newly formed γ-B_(12)–(B···B)_(6) phase, transforms it to a third new phase, named α-B_(12)–BB, that is metallic, suggesting increased ductility that might make α-B_(12)–BB important for applications in electronic devices. We compared the structural character, mechanical properties, and electronic properties of these new phases to each other and to other phases of boron. We show that the three new phases are dynamically stable at zero pressure. These results show how modifying the connections between boron icosahedra using one to two atom chains can lead to dramatically different mechanical and electronic properties.

Youngseok Oh - One of the best experts on this subject based on the ideXlab platform.

William A Goddard - One of the best experts on this subject based on the ideXlab platform.

  • Deformation Induced Solid−Solid Phase Transitions in Gamma Boron
    Chemistry of Materials, 2014
    Co-Authors: William A Goddard, Hai Xiao, Tao Cheng
    Abstract:

    We predict three new polymorphs of boron by applying density functional theory (PBE flavor) to large shear deformations starting from the recently discovered γ-B_(28) boron phase (stable above 9 GPa and 1000 K). We find that continuous deformation along the (100)/⟨001⟩ slip system leads to two new phases, named here as γ-B_(12)–(B_(2))_(6) and γ-B_(12)–(B···B)_(6). We show that these γ-B_(12)–(B_(2))_(6) and γ-B_(12)–(B···B)_(6) phases can also be obtained from uniaxial tensile and compressive deformations of the γ-B28 phase along the ⟨101⟩ direction, respectively. However, the reverse compressive loading on the newly formed γ-B_(12)–(B_(2))_(6) phase transforms it to itself, not the γ-B28 phase, because of the transferability of the three-center two-electron bond under deformation. This makes the new phase γ-B_(12)–(B_(2))_(6) a special type of Superelastic Material. In addition, application of reverse tensile deformation on the newly formed γ-B_(12)–(B···B)_(6) phase, transforms it to a third new phase, named α-B_(12)–BB, that is metallic, suggesting increased ductility that might make α-B_(12)–BB important for applications in electronic devices. We compared the structural character, mechanical properties, and electronic properties of these new phases to each other and to other phases of boron. We show that the three new phases are dynamically stable at zero pressure. These results show how modifying the connections between boron icosahedra using one to two atom chains can lead to dramatically different mechanical and electronic properties.

  • deformation induced solid solid phase transitions in gamma boron
    Chemistry of Materials, 2014
    Co-Authors: Q An, William A Goddard, Hai Xiao, Tao Cheng
    Abstract:

    We predict three new polymorphs of boron by applying density functional theory (PBE flavor) to large shear deformations starting from the recently discovered γ-B_(28) boron phase (stable above 9 GPa and 1000 K). We find that continuous deformation along the (100)/⟨001⟩ slip system leads to two new phases, named here as γ-B_(12)–(B_(2))_(6) and γ-B_(12)–(B···B)_(6). We show that these γ-B_(12)–(B_(2))_(6) and γ-B_(12)–(B···B)_(6) phases can also be obtained from uniaxial tensile and compressive deformations of the γ-B28 phase along the ⟨101⟩ direction, respectively. However, the reverse compressive loading on the newly formed γ-B_(12)–(B_(2))_(6) phase transforms it to itself, not the γ-B28 phase, because of the transferability of the three-center two-electron bond under deformation. This makes the new phase γ-B_(12)–(B_(2))_(6) a special type of Superelastic Material. In addition, application of reverse tensile deformation on the newly formed γ-B_(12)–(B···B)_(6) phase, transforms it to a third new phase, named α-B_(12)–BB, that is metallic, suggesting increased ductility that might make α-B_(12)–BB important for applications in electronic devices. We compared the structural character, mechanical properties, and electronic properties of these new phases to each other and to other phases of boron. We show that the three new phases are dynamically stable at zero pressure. These results show how modifying the connections between boron icosahedra using one to two atom chains can lead to dramatically different mechanical and electronic properties.