11 research outputs found

    Photoconductive CdSe Nanowire Arrays, Serpentines, and Loops Formed by Electrodeposition on Self-Organized Carbon Nanotubes

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    Semiconducting nanowires frequently have enhanced properties and unique functionality compared to their bulk counterparts. Controlling the geometry of nanowires is crucial for their integration into nanoscale devices because the shape of a device component can dictate its functionality, such as in the case of a mechanical spring or an antenna. We demonstrate a novel synthetic method for making polycrystalline CdSe nanowires with controlled geometries by using self-organized single-walled carbon nanotubes as a template for the selective electrodeposition of nanowires. Nanowires of up to hundreds of micrometers in length are formed as high-density straight arrays, as well as in the shape of serpentines and loops. These nanowires exhibit significant photoluminescence and photoconductivity applicable to photodetectors and respond to illumination up to 2 orders of magnitude faster than single crystalline CdSe

    Microstructure versus Flaw: Mechanisms of Failure and Strength in Nanostructures

    No full text
    Understanding failure in nanomaterials is critical for the design of reliable structural materials and small-scale devices with nanoscale components. No consensus exists on the effect of flaws on fracture at the nanoscale, but proposed theories include nanoscale flaw tolerance and maintaining macroscopic fracture relationships at the nanoscale with scarce experimental support. We explore fracture in nanomaterials using nanocrystalline Pt nanocylinders with prefabricated surface notches created using a “paused” electroplating method. In situ scanning electron microscopy (SEM) tension tests demonstrate that the majority of these samples failed at the notches, but that tensile failure strength is independent of whether failure occurred at or away from the flaw. Molecular dynamics simulations verify these findings and show that local plasticity is able to reduce stress concentration ahead of the notch to levels comparable with the strengths of microstructural features (e.g., grain boundaries). Thus, failure occurs at the stress concentration with the highest local stress whether this is at the notch or a microstructural feature

    Microstructure versus Flaw: Mechanisms of Failure and Strength in Nanostructures

    No full text
    Understanding failure in nanomaterials is critical for the design of reliable structural materials and small-scale devices with nanoscale components. No consensus exists on the effect of flaws on fracture at the nanoscale, but proposed theories include nanoscale flaw tolerance and maintaining macroscopic fracture relationships at the nanoscale with scarce experimental support. We explore fracture in nanomaterials using nanocrystalline Pt nanocylinders with prefabricated surface notches created using a “paused” electroplating method. In situ scanning electron microscopy (SEM) tension tests demonstrate that the majority of these samples failed at the notches, but that tensile failure strength is independent of whether failure occurred at or away from the flaw. Molecular dynamics simulations verify these findings and show that local plasticity is able to reduce stress concentration ahead of the notch to levels comparable with the strengths of microstructural features (e.g., grain boundaries). Thus, failure occurs at the stress concentration with the highest local stress whether this is at the notch or a microstructural feature

    Microstructure versus Flaw: Mechanisms of Failure and Strength in Nanostructures

    No full text
    Understanding failure in nanomaterials is critical for the design of reliable structural materials and small-scale devices with nanoscale components. No consensus exists on the effect of flaws on fracture at the nanoscale, but proposed theories include nanoscale flaw tolerance and maintaining macroscopic fracture relationships at the nanoscale with scarce experimental support. We explore fracture in nanomaterials using nanocrystalline Pt nanocylinders with prefabricated surface notches created using a “paused” electroplating method. In situ scanning electron microscopy (SEM) tension tests demonstrate that the majority of these samples failed at the notches, but that tensile failure strength is independent of whether failure occurred at or away from the flaw. Molecular dynamics simulations verify these findings and show that local plasticity is able to reduce stress concentration ahead of the notch to levels comparable with the strengths of microstructural features (e.g., grain boundaries). Thus, failure occurs at the stress concentration with the highest local stress whether this is at the notch or a microstructural feature

    Microstructure versus Flaw: Mechanisms of Failure and Strength in Nanostructures

    No full text
    Understanding failure in nanomaterials is critical for the design of reliable structural materials and small-scale devices with nanoscale components. No consensus exists on the effect of flaws on fracture at the nanoscale, but proposed theories include nanoscale flaw tolerance and maintaining macroscopic fracture relationships at the nanoscale with scarce experimental support. We explore fracture in nanomaterials using nanocrystalline Pt nanocylinders with prefabricated surface notches created using a “paused” electroplating method. In situ scanning electron microscopy (SEM) tension tests demonstrate that the majority of these samples failed at the notches, but that tensile failure strength is independent of whether failure occurred at or away from the flaw. Molecular dynamics simulations verify these findings and show that local plasticity is able to reduce stress concentration ahead of the notch to levels comparable with the strengths of microstructural features (e.g., grain boundaries). Thus, failure occurs at the stress concentration with the highest local stress whether this is at the notch or a microstructural feature

    Microstructure versus Flaw: Mechanisms of Failure and Strength in Nanostructures

    No full text
    Understanding failure in nanomaterials is critical for the design of reliable structural materials and small-scale devices with nanoscale components. No consensus exists on the effect of flaws on fracture at the nanoscale, but proposed theories include nanoscale flaw tolerance and maintaining macroscopic fracture relationships at the nanoscale with scarce experimental support. We explore fracture in nanomaterials using nanocrystalline Pt nanocylinders with prefabricated surface notches created using a “paused” electroplating method. In situ scanning electron microscopy (SEM) tension tests demonstrate that the majority of these samples failed at the notches, but that tensile failure strength is independent of whether failure occurred at or away from the flaw. Molecular dynamics simulations verify these findings and show that local plasticity is able to reduce stress concentration ahead of the notch to levels comparable with the strengths of microstructural features (e.g., grain boundaries). Thus, failure occurs at the stress concentration with the highest local stress whether this is at the notch or a microstructural feature

    Microstructure versus Flaw: Mechanisms of Failure and Strength in Nanostructures

    No full text
    Understanding failure in nanomaterials is critical for the design of reliable structural materials and small-scale devices with nanoscale components. No consensus exists on the effect of flaws on fracture at the nanoscale, but proposed theories include nanoscale flaw tolerance and maintaining macroscopic fracture relationships at the nanoscale with scarce experimental support. We explore fracture in nanomaterials using nanocrystalline Pt nanocylinders with prefabricated surface notches created using a “paused” electroplating method. In situ scanning electron microscopy (SEM) tension tests demonstrate that the majority of these samples failed at the notches, but that tensile failure strength is independent of whether failure occurred at or away from the flaw. Molecular dynamics simulations verify these findings and show that local plasticity is able to reduce stress concentration ahead of the notch to levels comparable with the strengths of microstructural features (e.g., grain boundaries). Thus, failure occurs at the stress concentration with the highest local stress whether this is at the notch or a microstructural feature

    Microstructure versus Flaw: Mechanisms of Failure and Strength in Nanostructures

    No full text
    Understanding failure in nanomaterials is critical for the design of reliable structural materials and small-scale devices with nanoscale components. No consensus exists on the effect of flaws on fracture at the nanoscale, but proposed theories include nanoscale flaw tolerance and maintaining macroscopic fracture relationships at the nanoscale with scarce experimental support. We explore fracture in nanomaterials using nanocrystalline Pt nanocylinders with prefabricated surface notches created using a “paused” electroplating method. In situ scanning electron microscopy (SEM) tension tests demonstrate that the majority of these samples failed at the notches, but that tensile failure strength is independent of whether failure occurred at or away from the flaw. Molecular dynamics simulations verify these findings and show that local plasticity is able to reduce stress concentration ahead of the notch to levels comparable with the strengths of microstructural features (e.g., grain boundaries). Thus, failure occurs at the stress concentration with the highest local stress whether this is at the notch or a microstructural feature

    Microstructure versus Flaw: Mechanisms of Failure and Strength in Nanostructures

    No full text
    Understanding failure in nanomaterials is critical for the design of reliable structural materials and small-scale devices with nanoscale components. No consensus exists on the effect of flaws on fracture at the nanoscale, but proposed theories include nanoscale flaw tolerance and maintaining macroscopic fracture relationships at the nanoscale with scarce experimental support. We explore fracture in nanomaterials using nanocrystalline Pt nanocylinders with prefabricated surface notches created using a “paused” electroplating method. In situ scanning electron microscopy (SEM) tension tests demonstrate that the majority of these samples failed at the notches, but that tensile failure strength is independent of whether failure occurred at or away from the flaw. Molecular dynamics simulations verify these findings and show that local plasticity is able to reduce stress concentration ahead of the notch to levels comparable with the strengths of microstructural features (e.g., grain boundaries). Thus, failure occurs at the stress concentration with the highest local stress whether this is at the notch or a microstructural feature

    Effects of Helium Implantation on the Tensile Properties and Microstructure of Ni<sub>73</sub>P<sub>27</sub> Metallic Glass Nanostructures

    No full text
    We report fabrication and nanomechanical tension experiments on as-fabricated and helium-implanted ∼130 nm diameter Ni<sub>73</sub>P<sub>27</sub> metallic glass nanocylinders. The nanocylinders were fabricated by a templated electroplating process and implanted with He<sup>+</sup> at energies of 50, 100, 150, and 200 keV to create a uniform helium concentration of ∼3 atom % throughout the nanocylinders. Transmission electron microscopy imaging and through-focus analysis reveal that the specimens contained ∼2 nm helium bubbles distributed uniformly throughout the nanocylinder volume. In situ tensile experiments indicate that helium-implanted specimens exhibit enhanced ductility as evidenced by a 2-fold increase in plastic strain over as-fabricated specimens with no sacrifice in yield and ultimate tensile strengths. This improvement in mechanical properties suggests that metallic glasses may actually exhibit a favorable response to high levels of helium implantation
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