The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
Martin Wegener - One of the best experts on this subject based on the ideXlab platform.
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Micro-Structured Two-Component 3D Metamaterials with Negative Thermal-Expansion Coefficient from Positive Constituents
Scientific Reports, 2017Co-Authors: Jingyuan Qu, Andreas Naber, Muamer Kadic, Martin WegenerAbstract:Controlling the thermal Expansion of materials is of great technological importance. Uncontrolled thermal Expansion can lead to failure or irreversible destruction of structures and devices. In ordinary crystals, thermal Expansion is governed by the asymmetry of the microscopic binding potential, which cannot be adjusted easily. In artificial crystals called metamaterials, thermal Expansion can be controlled by structure. Here, following previous theoretical work, we fabricate three-dimensional (3D) two-component polymer micro-lattices by using gray-tone laser lithography. We perform cross-correlation analysis of optical microscopy images taken at different sample temperatures. The derived displacement-vector field reveals that the thermal Expansion and resulting bending of the bi-material beams leads to a rotation of the 3D chiral crosses arranged onto a 3D checkerboard pattern within one metamaterial unit cell. These rotations can compensate the Expansion of the all positive constituents, leading to an effectively near-zero thermal length-Expansion Coefficient, or over-compensate the Expansion, leading to an effectively negative thermal length-Expansion Coefficient. This evidences a striking level of thermal-Expansion control.
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micro structured two component 3d metamaterials with negative thermal Expansion Coefficient from positive constituents
arXiv: Materials Science, 2016Co-Authors: Jingyuan Qu, Andreas Naber, Muamer Kadic, Martin WegenerAbstract:Controlling the thermal Expansion of materials is of great technological importance. Uncontrolled thermal Expansion can lead to failure or irreversible destruction of structures and devices. In ordinary crystals, thermal Expansion is governed by the asymmetry of the microscopic binding potential, which cannot be adjusted easily. In artificial crystals called metamaterials, thermal Expansion can be controlled by structure. Here, following previous theoretical work, we fabricate three-dimensional two-component polymer microlattices by using gray-tone laser lithography. We perform cross-correlation analysis of optical microscopy images taken at different sample temperatures. The derived displacement-vector field reveals that the thermal Expansion and resulting bending of the bi-material beams leads to a rotation of the 3D chiral crosses arranged onto a 3D checkerboard pattern within one metamaterial unit cell. These rotations can over-compensate the Expansion and lead to an effectively negative thermal length-Expansion Coefficient for all positive constituents evidencing a striking level of thermal-Expansion control.
Jingyuan Qu - One of the best experts on this subject based on the ideXlab platform.
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Micro-Structured Two-Component 3D Metamaterials with Negative Thermal-Expansion Coefficient from Positive Constituents
Scientific Reports, 2017Co-Authors: Jingyuan Qu, Andreas Naber, Muamer Kadic, Martin WegenerAbstract:Controlling the thermal Expansion of materials is of great technological importance. Uncontrolled thermal Expansion can lead to failure or irreversible destruction of structures and devices. In ordinary crystals, thermal Expansion is governed by the asymmetry of the microscopic binding potential, which cannot be adjusted easily. In artificial crystals called metamaterials, thermal Expansion can be controlled by structure. Here, following previous theoretical work, we fabricate three-dimensional (3D) two-component polymer micro-lattices by using gray-tone laser lithography. We perform cross-correlation analysis of optical microscopy images taken at different sample temperatures. The derived displacement-vector field reveals that the thermal Expansion and resulting bending of the bi-material beams leads to a rotation of the 3D chiral crosses arranged onto a 3D checkerboard pattern within one metamaterial unit cell. These rotations can compensate the Expansion of the all positive constituents, leading to an effectively near-zero thermal length-Expansion Coefficient, or over-compensate the Expansion, leading to an effectively negative thermal length-Expansion Coefficient. This evidences a striking level of thermal-Expansion control.
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micro structured two component 3d metamaterials with negative thermal Expansion Coefficient from positive constituents
arXiv: Materials Science, 2016Co-Authors: Jingyuan Qu, Andreas Naber, Muamer Kadic, Martin WegenerAbstract:Controlling the thermal Expansion of materials is of great technological importance. Uncontrolled thermal Expansion can lead to failure or irreversible destruction of structures and devices. In ordinary crystals, thermal Expansion is governed by the asymmetry of the microscopic binding potential, which cannot be adjusted easily. In artificial crystals called metamaterials, thermal Expansion can be controlled by structure. Here, following previous theoretical work, we fabricate three-dimensional two-component polymer microlattices by using gray-tone laser lithography. We perform cross-correlation analysis of optical microscopy images taken at different sample temperatures. The derived displacement-vector field reveals that the thermal Expansion and resulting bending of the bi-material beams leads to a rotation of the 3D chiral crosses arranged onto a 3D checkerboard pattern within one metamaterial unit cell. These rotations can over-compensate the Expansion and lead to an effectively negative thermal length-Expansion Coefficient for all positive constituents evidencing a striking level of thermal-Expansion control.
E P George - One of the best experts on this subject based on the ideXlab platform.
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temperature dependencies of the elastic moduli and thermal Expansion Coefficient of an equiatomic single phase cocrfemnni high entropy alloy
Journal of Alloys and Compounds, 2015Co-Authors: G Laplanche, P Gadaud, O Horst, F Otto, G Eggeler, E P GeorgeAbstract:Abstract The equiatomic CoCrFeMnNi alloy is now regarded as a model face-centered cubic single-phase high-entropy alloy. Therefore, determination of its intrinsic properties such as the temperature dependencies of elastic moduli and thermal Expansion Coefficient are important to improve understanding of this new class of material. These temperature dependencies were measured over a large temperature range (200–1270 K) in this study.
Yuri Shvydko - One of the best experts on this subject based on the ideXlab platform.
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ultraprecise studies of the thermal Expansion Coefficient of diamond using backscattering x ray diffraction
Physical Review B, 2011Co-Authors: Stanislav Stoupin, Yuri ShvydkoAbstract:The linear thermal Expansion Coefficient of diamond crystals of type IIa and type Ia was measured in the temperature range from 10 to 295 K. Neither negative thermal Expansion nor any substantial difference in the thermal Expansion Coefficient in crystals of the different types were observed. An empirical expression was obtained that approximates the temperature dependence of the thermal Expansion Coefficient of diamond. The T{sup 3} temperature dependence of a Debye solid holds below {approx}100 K with an accuracy of {approx}10{sup -8} K{sup -1}. A slight increase in the value of the lattice parameter was found for the Ia-type crystal, which suggests lattice dilatation by nitrogen impurity. The measurements were performed using Bragg diffraction in backscattering from diamond crystals of highly monochromatic 23.7 keV x rays with the recently demonstrated high relative accuracy of 1.2 x 10{sup -8} in the determination of the lattice parameter [S. Stoupin and Yu. Shvyd'ko Phys. Rev. Lett. 104 085901 (2010)].
Qichuan Jiang - One of the best experts on this subject based on the ideXlab platform.
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size effects on debye temperature einstein temperature and volume thermal Expansion Coefficient of nanocrystals
Solid State Communications, 2006Co-Authors: C C Yang, M X Xiao, W Li, Qichuan JiangAbstract:Based on a size-dependent root of mean square amplitude (rms) model, the size-dependent Debye temperatures of nanocrystals are modeled without any adjustable parameter by considering both Lindemann’s criterion and Mott’s equation. In terms of this model, the Debye temperatures depend on both size and interface conditions, which lead to related applications on size effects of the Einstein temperature and the volume thermal Expansion Coefficient. It is found that the model’s predictions are in good agreement with available experimental and computer simulation results.
