Nano-mechanisms of crystal lattice deformation on the interface of dissimilar materials (Cu-Nb), joined by vacuum rolling in solid phase under high temperature (950℃) were studied by means of high resolution electron...Nano-mechanisms of crystal lattice deformation on the interface of dissimilar materials (Cu-Nb), joined by vacuum rolling in solid phase under high temperature (950℃) were studied by means of high resolution electron microscopy. Input of carriers of rotation modes—nano-dipoles of partial disclinations and nano-twist disclinations in the form of double spirals in deformation mechanisms were analyzed. The role of these mechanisms in decrease of shear stability of the interface areas and in production of high-quality rolled metal is discussed.展开更多
The defect structures of s = ±1/2 twist disclinations in twisted nematic and twisted chiral liquid crystals have been investigated within the Landau-de Gennes theory numerically. Our results show that there exist...The defect structures of s = ±1/2 twist disclinations in twisted nematic and twisted chiral liquid crystals have been investigated within the Landau-de Gennes theory numerically. Our results show that there exists eigenvalue exchange across the defect core of both the two models. The defect core is essentially biaxial and never isotropic. The defect centre is uniaxial and is surrounded by a strong biaxial region.展开更多
A new liquid crystalline polyacetylene containing a phenyl benzoate mesogen (5) is synthesized,whose mesomorphic properties are found to be easily 'tunab1e' by simple mechanical perturbation. Thepolymerization...A new liquid crystalline polyacetylene containing a phenyl benzoate mesogen (5) is synthesized,whose mesomorphic properties are found to be easily 'tunab1e' by simple mechanical perturbation. Thepolymerization of 10- [ 4 - (4' -methoxyphenoxycarbonyl )phenoxycarbonyl] - 1 -decyne (4 ) in itiated by theWCl_6-Ph_4Sn/dioxane complex yields polymer 5 with a M_w of 28400. The molecular structure of 5 ischaracterized by NMR, IR, and UV spectroscopy and its liquid crystalline behavior is investigated by DSC,POM, and XRD analysis. Upon mechanical perturbation, 5 exhibits unusual agitation-induced high-strengthdisclinations, shear-induced inversion walls, and solidification-induced banded textures. Such phenomenahave been observed in the main-chain liquid crystalline polymers with rigid backbones, but have seldom beenreported for the side-chain liquid crystalline polymers with flexible backbones, suggesting that the rigidpolyacetylene backbone of 5 plays a constructive role in inducing the novel molecular alignments.展开更多
By using topological current theory, this paper studies the inner topological structure of disclinations during the melting of two-dimensional systems. From two-dimensional elasticity theory, it finds that there are t...By using topological current theory, this paper studies the inner topological structure of disclinations during the melting of two-dimensional systems. From two-dimensional elasticity theory, it finds that there are topological currents for topological defects in homogeneous equation. The evolution of disclinations is studied, and the branch conditions for generating, annihilating, crossing, splitting and merging of disclinations are given.展开更多
Elemental powders of Cu and Fe were ball milled for various time durations up to 100 h. The various stages of forced alloying by ball milling, leading to instability of elemental crystalline phases and formation of qu...Elemental powders of Cu and Fe were ball milled for various time durations up to 100 h. The various stages of forced alloying by ball milling, leading to instability of elemental crystalline phases and formation of quasicrystalline phases were monitored using X-ray diffraction. Diffusion of Fe into the Cu matrix is proposed as the cause which triggers the instability of crystalline phases and leads to the formation of quasicrystalline phases after 10 h of milling. Milling for 100 h resulted in two different quasicrystalline phases with different lattice constants. Role of the nanocrystalline microstructure as an important criterion for the destabilisation of crystalline phases is explained. It is suggested that the formation of nanocrystalline microstructure and their subsequent transformation into quasicrystalline phases may be associated with a continuous increase in the disclination content of the system, which had formed as a result of continued milling and mechanical deformation.展开更多
Topological defects(including disclinations and dislocations)which commonly exist in various materials have shown an amazing ability to produce excellent mechanical and physical properties of matters.In this paper,dis...Topological defects(including disclinations and dislocations)which commonly exist in various materials have shown an amazing ability to produce excellent mechanical and physical properties of matters.In this paper,disclinations are introduced into topological nontrivial elastic phononic plates.The deformation of the lattice yielded by disclinations produces a pentagonal core with the local five-fold symmetry.The topological bound states are well localized around the boundaries of the pentagonal cores with and without hollow regions.The topological bound states immunize against the finite sizes and the moderate imperfects of plates,essentially differing from the trivial defect states.The discovery of topological bound states unveils a new horizon in topological mechanics and physics,and it provides a novel platfonn to implement large-scale elastic devices with topologically protected resonances.展开更多
文摘Nano-mechanisms of crystal lattice deformation on the interface of dissimilar materials (Cu-Nb), joined by vacuum rolling in solid phase under high temperature (950℃) were studied by means of high resolution electron microscopy. Input of carriers of rotation modes—nano-dipoles of partial disclinations and nano-twist disclinations in the form of double spirals in deformation mechanisms were analyzed. The role of these mechanisms in decrease of shear stability of the interface areas and in production of high-quality rolled metal is discussed.
文摘The defect structures of s = ±1/2 twist disclinations in twisted nematic and twisted chiral liquid crystals have been investigated within the Landau-de Gennes theory numerically. Our results show that there exists eigenvalue exchange across the defect core of both the two models. The defect core is essentially biaxial and never isotropic. The defect centre is uniaxial and is surrounded by a strong biaxial region.
基金This project was in part supported by the Hong Kong Research Grants Council(HKUST597/95P&6149/97P)
文摘A new liquid crystalline polyacetylene containing a phenyl benzoate mesogen (5) is synthesized,whose mesomorphic properties are found to be easily 'tunab1e' by simple mechanical perturbation. Thepolymerization of 10- [ 4 - (4' -methoxyphenoxycarbonyl )phenoxycarbonyl] - 1 -decyne (4 ) in itiated by theWCl_6-Ph_4Sn/dioxane complex yields polymer 5 with a M_w of 28400. The molecular structure of 5 ischaracterized by NMR, IR, and UV spectroscopy and its liquid crystalline behavior is investigated by DSC,POM, and XRD analysis. Upon mechanical perturbation, 5 exhibits unusual agitation-induced high-strengthdisclinations, shear-induced inversion walls, and solidification-induced banded textures. Such phenomenahave been observed in the main-chain liquid crystalline polymers with rigid backbones, but have seldom beenreported for the side-chain liquid crystalline polymers with flexible backbones, suggesting that the rigidpolyacetylene backbone of 5 plays a constructive role in inducing the novel molecular alignments.
基金supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry of Chinathe Interdisciplinary Innovation Research Fund for Young Scholars,Lanzhou University
文摘By using topological current theory, this paper studies the inner topological structure of disclinations during the melting of two-dimensional systems. From two-dimensional elasticity theory, it finds that there are topological currents for topological defects in homogeneous equation. The evolution of disclinations is studied, and the branch conditions for generating, annihilating, crossing, splitting and merging of disclinations are given.
文摘Elemental powders of Cu and Fe were ball milled for various time durations up to 100 h. The various stages of forced alloying by ball milling, leading to instability of elemental crystalline phases and formation of quasicrystalline phases were monitored using X-ray diffraction. Diffusion of Fe into the Cu matrix is proposed as the cause which triggers the instability of crystalline phases and leads to the formation of quasicrystalline phases after 10 h of milling. Milling for 100 h resulted in two different quasicrystalline phases with different lattice constants. Role of the nanocrystalline microstructure as an important criterion for the destabilisation of crystalline phases is explained. It is suggested that the formation of nanocrystalline microstructure and their subsequent transformation into quasicrystalline phases may be associated with a continuous increase in the disclination content of the system, which had formed as a result of continued milling and mechanical deformation.
基金supported by the National Natural Science Foundation of China(Grant Nos.12072108 and 51621004)Hunan Provincial Natural Science Foundation of China(Grant No.2021JJ40626).
文摘Topological defects(including disclinations and dislocations)which commonly exist in various materials have shown an amazing ability to produce excellent mechanical and physical properties of matters.In this paper,disclinations are introduced into topological nontrivial elastic phononic plates.The deformation of the lattice yielded by disclinations produces a pentagonal core with the local five-fold symmetry.The topological bound states are well localized around the boundaries of the pentagonal cores with and without hollow regions.The topological bound states immunize against the finite sizes and the moderate imperfects of plates,essentially differing from the trivial defect states.The discovery of topological bound states unveils a new horizon in topological mechanics and physics,and it provides a novel platfonn to implement large-scale elastic devices with topologically protected resonances.