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Adhi Dwi Hatmanto - One of the best experts on this subject based on the ideXlab platform.

  • the kinetics of Lattice Distortion introduction and Lattice relaxation at the surface of thermally oxidized 4h sic 0001
    Applied Physics Express, 2019
    Co-Authors: Adhi Dwi Hatmanto, Koji Kita
    Abstract:

    The kinetics of Lattice Distortion introduction and Lattice relaxation at the surface of thermally-oxidized 4H-SiC (0001) were investigated. Our results suggested that Lattice Distortion introduction and Lattice relaxation seem to follow zeroth and second order rate laws, respectively. The obtained activation energy of ~3.9 eV for Lattice Distortion introduction and ~1 eV for its relaxation indicate that the Lattice Distortion is determined by a bond rearrangement or movement process with a relatively low activation energy. Furthermore, the formation of byproducts which remain at the surface region of 4H-SiC was predicted to be a possible origin of the significant Lattice Distortion.

  • thermal oxidation induced local Lattice Distortion at surface of 4h sic 0001 characterized by in plane x ray diffractometry
    Applied Physics Express, 2018
    Co-Authors: Adhi Dwi Hatmanto
    Abstract:

    Local Lattice Distortions at the surface of 4H-SiC(0001) after various thermal oxidation processes were investigated by in-plane X-ray diffractometry. Our results showed that dry oxidation induced Lattice Distortion, observed as the increase of interplanar spacing, became higher with increasing oxidation time. Lattice constant changes of up to ~0.4% were observed by increasing the oxide thickness to 44 nm. This Lattice Distortion was not recovered after removal of the SiO2 layer by chemical etching, although it was partially reduced by Ar gas annealing, suggesting that strain relaxation requires removal of oxidation-induced defects in the 4H-SiC surface region.

Yuji Ikeda - One of the best experts on this subject based on the ideXlab platform.

  • element resolved local Lattice Distortion in complex concentrated alloys an observable signature of electronic effects
    Acta Materialia, 2021
    Co-Authors: Khorgolkhuu Odbadrakh, Yuji Ikeda, Fritz Kormann, Chengjun Sun, Heh Sang Ahn, Kook Noh Yoon, Cemal Cem Tasan, T Egami
    Abstract:

    Complex concentrated alloys (CCAs) are of growing interest due to their outstanding mechanical properties that exceed the property limits of conventional alloys. Whereas the superior properties are often attributed to severe Lattice Distortion, to date it is not clear what controls the Lattice Distortion and how it affects the mechanical properties of CCAs. In this work, we study the element-resolved local Lattice Distortion (ELLD) in CCAs of 3d transition-metal elements (3d CCAs) by the extended X-ray absorption fine structure experiment and the density-functional theory calculations. We show that ELLD is primarily dependent upon charge transfer among elements and affects the properties through atomic-level pressure and orbital transition. The ELLD provides a qualitative measure of the effective atomic size for explaining element-specific properties and macroscopic properties.

  • ultrastrong medium entropy single phase alloys designed via severe Lattice Distortion
    Advanced Materials, 2019
    Co-Authors: Seok Su Sohn, Alisson Kwiatkowski Da Silva, Yuji Ikeda, Fritz Kormann, Wonseok Choi, Baptiste Gault, Dirk Ponge, Jorg Neugebauer
    Abstract:

    Severe Lattice Distortion is a core effect in the design of multiprincipal element alloys with the aim to enhance yield strength, a key indicator in structural engineering. Yet, the yield strength values of medium- and high-entropy alloys investigated so far do not substantially exceed those of conventional alloys owing to the insufficient utilization of Lattice Distortion. Here it is shown that a simple VCoNi equiatomic medium-entropy alloy exhibits a near 1 GPa yield strength and good ductility, outperforming conventional solid-solution alloys. It is demonstrated that a wide fluctuation of the atomic bond distances in such alloys, i.e., severe Lattice Distortion, improves both yield stress and its sensitivity to grain size. In addition, the dislocation-mediated plasticity effectively enhances the strength-ductility relationship by generating nanosized dislocation substructures due to massive pinning. The results demonstrate that severe Lattice Distortion is a key property for identifying extra-strong materials for structural engineering applications.

Fritz Kormann - One of the best experts on this subject based on the ideXlab platform.

  • element resolved local Lattice Distortion in complex concentrated alloys an observable signature of electronic effects
    Acta Materialia, 2021
    Co-Authors: Khorgolkhuu Odbadrakh, Yuji Ikeda, Fritz Kormann, Chengjun Sun, Heh Sang Ahn, Kook Noh Yoon, Cemal Cem Tasan, T Egami
    Abstract:

    Complex concentrated alloys (CCAs) are of growing interest due to their outstanding mechanical properties that exceed the property limits of conventional alloys. Whereas the superior properties are often attributed to severe Lattice Distortion, to date it is not clear what controls the Lattice Distortion and how it affects the mechanical properties of CCAs. In this work, we study the element-resolved local Lattice Distortion (ELLD) in CCAs of 3d transition-metal elements (3d CCAs) by the extended X-ray absorption fine structure experiment and the density-functional theory calculations. We show that ELLD is primarily dependent upon charge transfer among elements and affects the properties through atomic-level pressure and orbital transition. The ELLD provides a qualitative measure of the effective atomic size for explaining element-specific properties and macroscopic properties.

  • ultrastrong medium entropy single phase alloys designed via severe Lattice Distortion
    Advanced Materials, 2019
    Co-Authors: Seok Su Sohn, Alisson Kwiatkowski Da Silva, Yuji Ikeda, Fritz Kormann, Wonseok Choi, Baptiste Gault, Dirk Ponge, Jorg Neugebauer
    Abstract:

    Severe Lattice Distortion is a core effect in the design of multiprincipal element alloys with the aim to enhance yield strength, a key indicator in structural engineering. Yet, the yield strength values of medium- and high-entropy alloys investigated so far do not substantially exceed those of conventional alloys owing to the insufficient utilization of Lattice Distortion. Here it is shown that a simple VCoNi equiatomic medium-entropy alloy exhibits a near 1 GPa yield strength and good ductility, outperforming conventional solid-solution alloys. It is demonstrated that a wide fluctuation of the atomic bond distances in such alloys, i.e., severe Lattice Distortion, improves both yield stress and its sensitivity to grain size. In addition, the dislocation-mediated plasticity effectively enhances the strength-ductility relationship by generating nanosized dislocation substructures due to massive pinning. The results demonstrate that severe Lattice Distortion is a key property for identifying extra-strong materials for structural engineering applications.

Rui Yang - One of the best experts on this subject based on the ideXlab platform.

  • unconventional non uniform local Lattice Distortion in dilute ti mo solid solution
    Social Science Research Network, 2020
    Co-Authors: Rui Yang
    Abstract:

    The substitutional solute atom induced local Lattice Distortion (LLD) in dilute metal solid solution was believed to be uniform because the solute atom was supposed to occupy the high symmetry Lattice site without breaking the point group symmetry of the crystal Lattice. Contrary to this conventional picture, we report in this paper that substitutional Mo atom in Ti-Mo solid solution occupies an off-center position instead of the high symmetry Lattice site and leads to highly non-uniform LLD, as evidenced by our first principles calculations. The physics underlying the off-center occupation and non-uniform LLD are shown to be the Jahn-Teller splitting of the degenerated d states of Mo atom. With which, the solid-solutions suffering from non-uniform LLD are predicted. The non-uniform LLD challenges the application of classical solid solution hardening model based on uniform LLD and spherical stress tensor assumption to this kind of solid solutions. This work also questions the traditional view that elementary substitutional solute atoms in metal solid solutions should not induce anelastic relaxation and internal friction.

  • unconventional non uniform local Lattice Distortion in dilute ti mo solid solution
    arXiv: Materials Science, 2020
    Co-Authors: Rui Yang
    Abstract:

    The substitutional solute atom induced local Lattice Distortion (LLD) in dilute metal solid solution was believed to be uniform that may even be modeled by using soap bubble raft. Contrary to this conventional picture, we report in this manuscript that the Mo induced LLD in dilute Ti-Mo solid solution is highly non-uniform as evidenced by our first principles calculations. The non-uniform LLD is ascribed to the Jahn-Teller splitting of the degenerated d states of Mo atom. We propose that the substitutional solid solutions with non-uniform LLD should satisfy two conditions. With which, the solid-solutions suffering from non-uniform LLD are predicted. The non-uniform LLD is expected to result in non-spherical stress field around the solute atom, and, therefore, challenges the application of classical solid solution hardening model to this kind of solid solutions.

L H Dai - One of the best experts on this subject based on the ideXlab platform.

  • chemical composition dependent local Lattice Distortions and magnetism in high entropy alloys
    Intermetallics, 2021
    Co-Authors: Yuanyuan Tan, Lirong Zheng, Yu Gong, Zhoucan Xie, Zhongjun Chen, Zhan Shi, Haiying Wang, L H Dai
    Abstract:

    Abstract A distinguish feature of high-entropy alloys (HEAs) is well-defined crystalline structure with chemical disorder. While, local Lattice Distortion is a longstanding issue in HEAs and more challenging than traditional alloys. However, reports on local Lattice Distortion of HEAs are rarely related to chemical compositions. Here, we use synchrotron radiation facility based XRD and X-ray absorption fine structure (XAFS) to examine averaged Lattice Distortion and element specified local Lattice Distortions in CrCoNi medium-entropy alloy (MEA), CrFeCoNi and CrMnFeCoNi HEAs. The results showed that averaged Lattice Distortions observed from XRD patterns are subtle. The Distortion magnitude centred around certain alloying element observed in XAFS spectra keeps in the same order, generally, Ni > Co > Fe > Cr > Mn. The observed positive strains are proposed to counteract negative strains and thus leading to observation of subtle averaged Lattice Distortion. The XANES results suggested that local electron structure flexibility of element might be one factor that contributes to local Lattice Distortions. The magnetic measurements indicated a paramagnetic state of all the studied alloys at ambient conditions. This study provides key information on local Lattice Distortion and its correlations with chemical compositions in HEAs, which is of crucial importance in tailoring properties of advanced HEAs and other multicomponent alloys.