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Influence of compression strains on photon absorption of silicene and germanene
摘要： In this paper, optical properties of silicene and germanene under compressive homogeneous strain are investigated within the density function theory. Results show that the optical-field response are strongly depend on the amount of applied strain. As the strain increases, the amount of optical absorption increases. In fact, by applying the compressive strain in the silicene and germanene, the band gap at the Dirac points decreases where ultimately reaches zero. Depending on the amount of strain, absorption peak shows red and blue shifts by increasing the strain. This can be realized by considering the change of the band gap energy and transition rates by the strain. In both of these graphene-like structures, the light absorption along zigzag direction is greater than that of the armchair direction.
关键词： Graphene-like structures,Compressive strain,Density functional theory,Optical properties
更新于2025-09-23 15:23:52
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Effect of laser forming on mechanical properties of multiple-phase steels by using a thermal–microstructure–mechanical model
摘要： Based on a forming temperature-controlled mixed strain-hardening law, a temperature-controlled thermal–microstructure–mechanical model was developed to predict the deformation in ferrite–martensite dual-phase steel before and after complex laser forming. Phase transformation in dual phase steel was predicted by coupling a kinetic transformation model with the developed model during laser forming. The corresponding algorithm of the constitutive model was used in three-dimensional finite element method to simulate the material deformation and mechanical properties during the laser forming. The simulated results agree well with the experimental results. Laser forming influences the mechanical properties of the material significantly, leads to bending deformation of the scanned sample and induces a ferrite-to-martensite transformation. The influence of scanning line number on the tensile strength and bending deformation of the scanned specimen was investigated. The tensile strength and bending angle are related positively to the number of scanning lines on the sample.
关键词： Stress-strain curve,Phase transformation,Thermal–microstructure–mechanical model,Sheet metal,Laser forming
更新于2025-09-23 15:23:52
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Strain-Induced Metastable Phase Stabilization in Ga2O3 Thin Films
摘要： It is well known that metastable and transient structures in bulk can be stabilized in thin films via epitaxial strain (heteroepitaxy) and appropriate growth conditions that are often far from equilibrium. However, the mechanism of heteroepitaxy, particularly how the nominally unstable or metastable phase gets stabilized, remains largely unclear. This is especially intriguing for thin film Ga2O3, where multiple crystal phases may exist under varied growth conditions with spatial and dimensional constraints. Herein, the development and distribution of epitaxial strain at the Ga2O3/Al2O3 film-substrate interfaces is revealed down to the atomic resolution along different orientations, with an aberration-corrected scanning transmission electron microscope (STEM). Just a few layers of metastable α-Ga2O3 structure were found to accommodate the misfit strain in direct contact with the substrate. Following an epitaxial α-Ga2O3 structure of about couple unit cells, several layers (4~5) of transient phase appear as the intermediate structure to release the misfit strain. Subsequent to this transient crystal phase, the nominally unstable κ-Ga2O3 phase is stabilized as the major thin film phase form. We show that the epitaxial strain is gracefully accommodated by rearrangement of the oxygen polyhedra. When the structure is under large compressive strain, Ga3+ ions occupy only the oxygen octahedral sites to form a dense structure. With gradual release of the compressive strain, more and more Ga3+ ions occupy the oxygen tetrahedral sites, leading to volumetric expansion and the phase transformation. The structure of the transition phase is identified by high resolution electron microscopy (HREM) observation, complemented by the density functional theory (DFT) calculations. This study provides insights from the atomic scale and their implications for the design of functional thin film materials using epitaxial engineering.
关键词： κ-Ga2O3,misfit strain,α-Ga2O3,metastable phase,aberration-corrected scanning transmission electron microscopy
更新于2025-09-23 15:23:52
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Sheath-Core Fiber Strain Sensors Driven by In-Situ Crack and Elastic Effects in Graphite Nanoplate Composites
摘要： The flexible and stretchable electronics, e.g., graphite nanoplatelets (GNPs) based nanocomposite devices, have attracted great interest due to their potential application in healthcare, robotics, and mechatronics technology. However, the deficient sensors with manipulation of low sensitivity, sluggish responsivity, sophisticated fabrication process and poor repeatability notoriously limit their industrial applications. To enhance the spontaneous sensitivity, flexibility and wearability in GNPs based strain sensors, in this report, the synergistic crack and elastic effects engineering is employed and in turn significantly enhances the sensitivity with the gauge factor of 20 at the strain of 30% and the stability in our developed sheath-core fiber (SCF) strain sensors. Upon reliable devices integration, it is demonstrated that the developed SCF strain sensor could detect the movement of human joint effectively with generating a resistance change rate ΔR/R0 up to 600%. Furthermore, a controlling devices system based on SCF strain sensor has been manufactured in circuit level to realize the real-time control of a robot hand, such as copying gestures and playing piano.
关键词： Graphite nanoplatelets (GNPs),Robotic mechatronics,Sheath–core structure,Strain sensors,Crack and elastic effects
更新于2025-09-23 15:23:52
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Highly sensitive strain sensor based on a novel Mach–Zehnder mode interferometer with TCF-PCF-TCF structure
摘要： We have demonstrated a high-sensitivity strain sensor based on a novel photonic crystal fiber (PCF) interferometer by means of splicing two sections of thin core fibers (TCF) with a piece of PCF between two single mode fibers (SMFs). The proposed MZI has exhibited an excellent fringe visibility as high as 21 dB in air. Particularly, the measurement range was up to 4 m ε and a strain sensitivity of ?1.89 pm/με was achieved. It was found that the strain sensitivity of the MZI was weekly dependent on the PCF length. The measured sensitivities of the MZI with 25 mm, 30 mm and 35 mm PCF at ～1590 nm were ?1.83 pm/με, ?1.85 pm/με and ?1.77 pm/με, respectively. Moreover, the temperature characteristics of the sensor were also investigated. Additionally, the sensor has advantages of simplicity of fabrication, low cost, compact size as well as large strain measurement range.
关键词： Strain sensor,Mach–Zehnder interferometer (MZI),Photonic crystal fiber (PCF),Thin core fiber (TCF)
更新于2025-09-23 15:23:52
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Cation disorder and epitaxial strain modulated Drude–Smith type terahertz conductivity and Hall-carrier switching in Ca <sub/> 1? <i>x</i> </sub> Ce <sub/><i>x</i> </sub> RuO <sub/>3</sub> thin films
摘要： The CaRuO3 is a non-Fermi liquid pseudo-cubic perovskite with a magnetic ground state on the verge of phase transition and it lies in the vicinity of the quantum critical point. To understand the sensitivity of its ground state, the effects of subtle aliovalent chemical disorder on the static and high frequency dynamic conductivity in the coherently strained structures were explored. The Ce-doped Ca1?xCexRuO3 (0 ? x ? 0.1) thin films were deposited on LaAlO3 (1 0 0) and SrTiO3 (1 0 0) substrates and studies for low-energy terahertz (THz) carrier dynamics, dc transport and Hall effect. These compositions exhibited a very effective and unusual Hall-carrier switching in both compressive and tensile strain induced epitaxial thin films. The dc resistivity depicts a switching from a non-Fermi liquid to a Fermi liquid behavior without any magnetic phase transition. A discernible and gradual crossover from Drude to Drude–Smith THz dynamic optical conductivity was observed while traversing from pure to 10% Ce-doped CaRuO3 films. Overall, a nearly Fermi liquid behavior, effective carrier switching and unusual features in THz conductivity, were all novel features realized for the first time in physically and/or chemically modified CaRuO3. These new phases highlight the novel subtleties and versatility of the systems lying near the quantum critical point.
关键词： epitaxial strain,terahertz,allovalent doping,Hall carrier switching
更新于2025-09-23 15:23:52
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On the mechanisms of tip-force induced switching in ferroelectric thin films: The crossover of depolarization, shear strain and flexoelectricity
摘要： The recent observation of mechanical switching of ferroelectric polarization has placed the mechanical manipulation of ferroelectrics on an equal footing with the conventional electrical manipulation. However, discussions on the exact switching mechanisms due to mechanical loads are ongoing for the complexity in experimental situations. In this work, based on continuum mechanical and thermodynamic modeling and simulation, we analyze the mechanisms of tip-force induced switching in ferroelectric thin films. The roles of depolarization, shear strain and flexoelectricity in mechanical switching, both in normal and sliding loading modes, are separated out and the switching characteristics are analyzed. The depolarization field in the film is demonstrated to enable bidirectional switching. The coupling between shear strain and polarization components is shown to be important in the sliding loading mode. A great influence of flexoelectricity-modified polarization boundary condition on the switching process is revealed. The previous speculation that the switching process experiences an intermediate paraelectric phase is proved. The regulation of loading force, misfit strain, temperature and film thickness on the switching are further given for each mechanism. Taking all of the three mechanisms into account, we present the phase diagrams of mechanical switching for films in an initial upward or downward polarization state. The revealed characteristics of various switching mechanisms should provide useful guidelines for their verification in experiments, and the tunability of the switching by various influencing factors is instructive for the design and optimization of ferroelectric devices via mechanical engineering.
关键词： shear strain,mechanical switching,ferroelectrics,flexoelectricity,depolarization
更新于2025-09-23 15:23:52
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Fiber Bragg grating-based experimental and numerical investigations of CO <sub/>2</sub> migration front in saturated sandstone under subcritical and supercritical conditions
摘要： Carbon dioxide (CO2) can be at risk of leakage during its storage in deep saline aquifers due to stress field changes in the reservoir. The aim of this study was to investigate the effects of CO2 injection pressure on dynamic strain response of the reservoir and the CO2 migration process. A series of core flooding experiments was performed with the-state-of-art fiber Bragg grating sensors. The results show that the surface strain response was linearly correlated with CO2 injection pressure. Carbon dioxide migration velocity can be estimated from the strain response time differences among three gratings. The migration velocity of supercritical CO2 is higher than that of liquid CO2 but lower than gaseous CO2. Finally, numerical simulation was applied to model the CO2 migration process and the simulated values were compatible with those of experiments.
关键词： reservoir sandstone,core flooding,CO2 geological storage,CO2 migration front,fiber Bragg grating,strain response
更新于2025-09-23 15:23:52
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[IEEE 2018 International Multi-Conference on Industrial Engineering and Modern Technologies (FarEastCon) - Vladivostok, Russia (2018.10.3-2018.10.4)] 2018 International Multi-Conference on Industrial Engineering and Modern Technologies (FarEastCon) - Experimental Study of the Stress-Strain State Features of Outlet Guide Vane Made From Polymer Composite Material Using Fiber Optic Sensors
摘要： An estimation technique for the stress-strain state of the outlet guide vane design of an aircraft propulsion system made of polymer composite materials (PCM) using fiber-optic sensors is proposed. Fiber-optic sensors allow creating details with the possibility of self-diagnosis and forecasting the resource of work. This issue is particularly relevant when using PCM in highly loaded aircraft engine elements. The object of the study is the outlet guide vane (OGV) made of an equally strong carbon cloth on an epoxy binder. The tests were carried out on a universal servo-hydraulic machine. The data from fiber-optic sensors was carried out using an interrogator ASTRO X327. The comparison of the experiment and the numerical calculation were performed using the software package ANSYS.
关键词： polymer composite material,fiber optic sensors,numerical calculations,stress-strain state
更新于2025-09-23 15:23:52
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[IEEE 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Shanghai (2018.8.8-2018.8.11)] 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Graphene-like Monolayer Yttrium Nitride: A Moderate Semiconductor and Pronounced Electronic Insensitivity to Strain
摘要： It is extremely important to explore two-dimensional materials with excellent properties due to their potential applications in future electronic devices. In the present study, a 2D hexagonal YN (h-YN) is predicted based on theoretical calculations. By assessing the phonon spectrum, ab initio molecule dynamics and elastic constants, the h-YN monolayer is proved to own satisfying thermal, dynamic and mechanical stability. Distinguishing from the most reported 2D transition metal mononitrides which exhibit metallic, monolayer h-YN presents a semiconducting characteristic with a indirect bandgap of 1.144 eV. In particular, h-YN presents unusually insensitive responses of electronic structures to tensile or compressive strain due to the valence orbital hybridization. Moderate bandgap together with insensitive electronic responses to strain endow h-YN a promising candidate in future nanoscale electronic devices in high-strain conditions.
关键词： nano-electronics,strain condition,band structure,two-dimensional
更新于2025-09-23 15:22:29