The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
D Ugarte - One of the best experts on this subject based on the ideXlab platform.
-
correlation between quantum conductance and Atomic Arrangement of Atomic size silver nanowires
Web Science, 2012Co-Authors: Maureen J Lagos, Pedro A S Autreto, Douglas S Galvao, D UgarteAbstract:We have studied the effect of thermal effects on the structural and transport response of Ag Atomic-size nanowires (NWs) generated by mechanical elongation. Our study involves both time-resolved Atomic resolution transmission electron microscopy imaging and quantum conductance measurement using an ultra-high-vacuum mechanically controllable break junction. We have observed drastic changes in conductance and structural properties of Ag nanowires generated at different temperatures (150 and 300 K). By combining electron microscopy images, electronic transport measurements, and quantum transport calculations, we have been able to obtain a consistent correlation between the conductance and structural properties of Ag NWs. In particular, our study has revealed the formation of metastable rectangular rod-like Ag wire (3/3) along the [001] crystallographic direction, whose formation is enhanced. These results illustrate the high complexity of analyzing structural and quantum conductance behaviour of metal Atomic...
-
temperature effects on the Atomic Arrangement and conductance of Atomic size gold nanowires generated by mechanical stretching
Nanotechnology, 2010Co-Authors: Maureen J Lagos, Varlei Rodrigues, Fernando Sato, Pedro A S Autreto, Douglas S Galvao, D UgarteAbstract:We have studied the changes induced by thermal effects in the structural and transport response of Au nanowires generated by mechanical elongation. We have used time-resolved Atomic resolution transmission electron microscopy imaging and quantum conductance measurement using a mechanically controllable break junction. Our results showed remarkable differences in the NW evolution for experiments realized at 150 and 300 K, which modifies drastically the conductance response during elongation. Molecular dynamics and electronic transport calculations were used to consistently correlate the observed structural and conductance behavior. These results emphasize that it is essential to take into account the precise Atomic Arrangement of nanocontacts generated by mechanical stretching to understand electrical transport properties. Also, our study shows that much care must be taken when comparing results obtained in different experimental conditions, mainly different temperatures.
-
metal nanowires Atomic Arrangement and electrical transport properties
Nanotechnology, 2002Co-Authors: Varlei Rodrigues, D UgarteAbstract:We have studied the Atomic Arrangement and defect formation in metal nanowires (NWs) generated by mechanical elongation using in situ high resolution transmission electron microscopy. It has been observed that the narrowest constriction of gold and platinum NWs is crystalline and defect-free; in particular, gold NWs adopt only three kinds of Atomic Arrangement. A model correlating these gold structures and the quantum conductance behaviour is proposed, which showed a remarkable agreement with ultrahigh-vacuum mechanically controllable break junction electrical transport measurements.
Seok Woo Lee - One of the best experts on this subject based on the ideXlab platform.
-
Atomic Arrangement and mechanical properties of chemical-vapor-deposited amorphous boron
Materials & Design, 2020Co-Authors: Jessica M. Maita, Gyuho Song, Mariel Colby, Seok Woo LeeAbstract:Abstract Amorphous boron can be synthesized by chemical vapor deposition (CVD) onto a tungsten wire substrate, and this core-shell fiber has been widely used in high-performance composites due to its superior mechanical properties. Although the amorphous boron coating makes a significant contribution to the high fracture strength, its mechanical properties have not been studied rigorously due to its thin thickness and strong adhesion to the substrate. Furthermore, the medium-range Atomic ordering of CVD amorphous boron has not been clearly understood, and the determination of the closest crystalline structure has been a challenge. In this study, high-resolution transmission electron microscopy (HRTEM), nanoindentation, and in-situ micropillar compression were performed to investigate the Atomic Arrangement and mechanical properties. Electron diffraction and autocorrelation function analysis revealed α-rhombohedral boron ordering as the closest crystalline structure. Micropillar compression displayed near-ideal yield strength (~13 GPa), but nanoindentation a relatively moderate Young's modulus (~320 GPa), leading to a modulus of resilience (2.64 × 108 J/m3) unprecedentedly higher than most advanced engineering materials. Our structural and mechanical data will be discussed in terms of lattice point spacing and the influence of surface defects on fracture strength, respectively. Our results will be potentially useful to improve mechanical properties of amorphous boron core-shell fibers and related composites.
Denvid Lau - One of the best experts on this subject based on the ideXlab platform.
-
Atomic Arrangement in cuzr based metallic glass composites under tensile deformation
Physical Chemistry Chemical Physics, 2020Co-Authors: Huali Hao, Wenzhao Zhou, Denvid LauAbstract:Lacking macroscopic plasticity severely limits structure applications of bulk metallic glasses (BMGs). In general, particle-reinforced BMGs have an enhanced ductility but show reduced strength, whereas body-centered-cubic CuZr phase (B2 phase)-reinforced bulk MGs display improved ductility and strength. The underlying reason for the improvement in B2 phase-reinforced BMGs is still ambiguous. Herein, the Atomic Arrangement in Cu48Zr48Al4 BMGs with and without the B2 phase under tensile deformation is studied using molecular dynamics simulation. Different from pure MG where shear transformation zones (STZs) are activated along the same direction to form the domain shear band, STZs in the B2 phase-reinforced MG are activated along different directions disturbing the formation of a domain shear band. More plastic deformation and increased stress are allowed because of the phase transformations of B2 phases. The revealed deformation mechanism of B2 phase-reinforced MGs enables us to design heterogeneous structures with excellent strength and toughness.
Wenjie Zhong - One of the best experts on this subject based on the ideXlab platform.
-
Direct observation of the changes in Atomic Arrangement of Cu50Zr50 metallic glass during tensile deformation by EXAFS
Journal of Alloys and Compounds, 2006Co-Authors: Toshio Nasu, Yohei Onodera, Masaki Sakurai, Takeshi Usuki, Akihisa Inoue, Sadayuki Takahashi, Isao Ajiki, Zhang Wei, Wenjie ZhongAbstract:Abstract The purpose of this research is to investigate the micro-mechanism of anelastic behavior of metallic glass. The changes of Atomic Arrangement in Cu 50 Zr 50 metallic glass were observed directly by EXAFS method during tensile deformation. The transmission-mode EXAFS measurements around Zr K-edge and Cu K-edge of the sample in various amounts of tensile deformation conditions were done. The interAtomic distance between Cu–Zr increased, and that between Zr–Zr decreased simultaneously, with the amount of tensile deformation increase of the sample at first stage of deformation. When the Atomic distances reached certain values, respectively, they recovered to the initial values of no tensile deformation condition at first stage, and then the Atomic distances changed in same manner as the first stage of deformation, respectively.
Jessica M. Maita - One of the best experts on this subject based on the ideXlab platform.
-
Atomic Arrangement and mechanical properties of chemical-vapor-deposited amorphous boron
Materials & Design, 2020Co-Authors: Jessica M. Maita, Gyuho Song, Mariel Colby, Seok Woo LeeAbstract:Abstract Amorphous boron can be synthesized by chemical vapor deposition (CVD) onto a tungsten wire substrate, and this core-shell fiber has been widely used in high-performance composites due to its superior mechanical properties. Although the amorphous boron coating makes a significant contribution to the high fracture strength, its mechanical properties have not been studied rigorously due to its thin thickness and strong adhesion to the substrate. Furthermore, the medium-range Atomic ordering of CVD amorphous boron has not been clearly understood, and the determination of the closest crystalline structure has been a challenge. In this study, high-resolution transmission electron microscopy (HRTEM), nanoindentation, and in-situ micropillar compression were performed to investigate the Atomic Arrangement and mechanical properties. Electron diffraction and autocorrelation function analysis revealed α-rhombohedral boron ordering as the closest crystalline structure. Micropillar compression displayed near-ideal yield strength (~13 GPa), but nanoindentation a relatively moderate Young's modulus (~320 GPa), leading to a modulus of resilience (2.64 × 108 J/m3) unprecedentedly higher than most advanced engineering materials. Our structural and mechanical data will be discussed in terms of lattice point spacing and the influence of surface defects on fracture strength, respectively. Our results will be potentially useful to improve mechanical properties of amorphous boron core-shell fibers and related composites.