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Photoinduced effects on the magnetic properties of the (Fe <sub/>0.2</sub> Cr <sub/>0.8</sub> ) <sub/>1.5</sub> [Cr(CN) <sub/>6</sub> ] Prussian blue analogue.
摘要： One of the most attractive characteristics of some Prussian blue derivatives is the sensitivity of their magnetic properties to the irradiation with light. In this work photoinduced effects in the (Fe0.2Cr0.8)1.5 [Cr(CN)6]·15 H2O PBA have been studied by means of X ray-based spectroscopies and magnetometry. It is found that the photosensitivity of this compound is mostly centred on the Fe cations: the exposure to green light induces a transfer of electrons from them to the Cr that provokes a reversal of the previously existing linkage isomerization and increases the elastic strain caused by the mis?t of the unit cells of the Fe–NC–Cr and Cr–NC–Cr sublattices. The green light also quenches the magnetism of the FeII high-spin (HS) ions present in the sample and reduces the magnetic moments of most of the Cr cations except for CrII HS. Our study highlights the important role played by the mismatch between the unit cells of the coexisting sub-lattices in ternary Prussian blue analogues.
关键词： magnetometry,photoinduced effects,magnetic properties,elastic strain,X-ray spectroscopies,Prussian blue analogues,linkage isomerization
更新于2025-09-19 17:15:36
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Effect of tungsten doping on structural and optical properties of rutile TiO2 and band gap narrowing
摘要： Pure and W doped nanocrystalline rutile TiO2 samples were synthesized using high energy ball milling process. Rietveld refinement results of X-ray diffraction data confirmed that pure sample exhibited rutile TiO2 phase whereas doped samples contained both rutile TiO2 and a secondary Ti0.54W0.46O2 phase. Different models of Williamson–Hall method were employed to evaluate crystallite size and strain in the samples. The crystallite size was found to decrease from 50 to 47 nm with increase in the dopant concentration. The pure TiO2 exhibited tensile microstrain which became compressive and increased upon doping. A blue shift in A1g Raman mode with doping of W also indicated the increase in the compressive strain. The HR-TEM images also confirmed the presence of higher strain in doped samples compared to un-doped sample. The observed decrease in band gap from 3 to 2.83 eV with dopant concentration, as calculated from UV–vis spectroscopy data, may be attributed to the increased strain. The decrease in the intensity of photoluminescence emission indicated the increase in number of defects and oxygen vacancies with increasing dopant concentration. This is further, supported by the rise in Urbach energy, a signature of increased number of defects in doped samples. This study shows that the dopant induced strain plays significant role in band gap narrowing.
关键词： Strain,Peak profile analysis,Band gap narrowing,Rutile TiO2 nanoparticles,High energy ball milling
更新于2025-09-19 17:15:36
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Dynamic and quasi-static signal separation method for bridges under moving loads based on long-gauge FBG strain monitoring
摘要： Structural health monitoring is an important means of obtaining the state information of bridges, and the extracted quasi-static strain signal can reflect the stress state of bridges directly. However, the strain signals acquired during the operation stage of bridges are dynamic, and the strain gauges used in the health monitoring system are short (no more than 10 cm), which means they are easily affected by small damage at the installation parts of bridges and thereby the monitoring signal abnormalities occur. A type of externally affixed long-gauge fiber strain gauge is used to monitor the health of bridges, and the dynamic and quasi-static signal separation method for long-gauge strain sensors is studied under different vehicle loads; at the same time, the dynamic monitoring performance of the long-gauge sensor is investigated in this paper. The quasi-static strain signal extracted from the dynamic macro-strain signal can be used to directly monitor the stress status of the bridge. The results show that the method proposed in this paper is feasible for extracting the quasi-static macro-strain from a dynamic long-gauge strain signal.
关键词： signal processing,bridge engineering,empirical mode decomposition method,macro-strain,Bridge health monitoring
更新于2025-09-19 17:15:36
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Superior and Anti-fatigue Electro-strain in Bi <sub/>0.5</sub> Na <sub/>0.5</sub> TiO <sub/>3</sub> -based Polycrystalline Relaxor Ferroelectrics
摘要： For eco-friendly bismuth sodium titanate (Bi0.5Na0.5TiO3)-based materials, ultrahigh poling strain (Spol) is always accompanied with a sizable remnant strain (Srem), which severely restricts the cycling reliability of their superior electro-strain. Composition engineering is an effective way of eliminating Srem, but Spol will be sacrificed as well, leading to the overall inferior electro-strain. Here, by composition engineering and subtle criticality confinement, a giant recoverable electro-strain (S>0.7%, realizing the Srem modulation without Spol sacrifice) with reduced hysteresis is reported in BNT-based relaxor ferroelectrics, which can be kept at a high level (<2% variation) even after 105 fatigue cycles. As disclosed by the detailed electric field-dependent multi-scales analyses, the electro-strain behaviors are tightly associated with the agglomeration and deagglomeration process of polar clusters. More efficient release of mechanical mismatch stress among interacting polar entities is suggested to facilitate the deagglomeration process of polar clusters, ensuring a faster restoration of the electric field-induced ferroelectric state when the electric field is removed, which is responsible for the reduced hysteresis and the excellent fatigue performance. These results indicate the significance of 'subtle criticality confinement', and the insight for the design of polycrystalline ceramics with giant and anti-fatigue electro-strain may be useful to develop the new generation of eco-friendly actuators.
关键词： Lead-free Bi0.5Na0.5TiO3,Subtle criticality,Relaxor ferroelectrics,Giant and anti-fatigue electro-strain
更新于2025-09-19 17:15:36
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A Strain Distribution Sensing System for Bone-Implant Interfaces Based on Digital Speckle Pattern Interferometry
摘要： This paper aims to provide an effective measurement method for the distribution of deformations and strains focusing on the response to external loading of bone-implant interfaces. To achieve this target, a novel speckle interference imaging method is proposed by introducing phosphate buffer saline medium, in which the samples were completely placed into a phosphate buffer saline solution medium to stable the water molecules. The stability of interferometry imaging is analyzed by using the concepts of co-occurrence matrix and moment of inertia. A series of experiments to measure load-driven deformation and strain in the bone-implant interface was carried out, and the experiments results were analyzed and discussed. It shows that the proposed method is feasible and effective for the no-contact strain measurements of biomaterials in a physiological condition. The proposed strain distribution sensing system will contribute to evaluating computational simulations and improving selection of implant designs and materials.
关键词： digital speckle pattern interferometry,speckle interference imaging,phosphate buffer saline solution,strain distribution detection,bone-implant interface
更新于2025-09-19 17:15:36
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Designing Morphotropic Phase Composition in BiFeO <sub/>3</sub>
摘要： In classical morphotropic piezoelectric materials, rhombohedral and tetragonal phase variants can energetically compete to form a mixed phase regime with improved functional properties. While the discovery of morphotropic-like phases in multiferroic BiFeO3 films has broadened this definition, accessing these phase spaces is still typically accomplished through isovalent substitution or heteroepitaxial strain which do not allow for continuous modification of phase composition post-synthesis. Here, we show that it is possible to use low-energy helium implantation to tailor morphotropic phases of epitaxial BiFeO3 films post-synthesis in a continuous and iterative manner. Applying this strain doping approach to morphotropic films creates a new phase space based on internal and external lattice stress that can be seen as an analogue to temperature – composition phase diagrams of classical morphotropic ferroelectric systems.
关键词： ferroelectrics,metastability,implantation,strain,Morphotropic phases
更新于2025-09-19 17:15:36
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Metal Mesh as a Transparent Omnidirectional Strain Sensor
摘要： Metal Mesh as a Transparent Omnidirectional Strain Sensor Weixin Zhou, Yi Li,* Pan Li, Jun Chen, Rongqing Xu,* Shanshan Yao, Zheng Cui, Ronald Booth, Baoxiu Mi, Dan Wang, Yanwen Ma,* and Wei Huang Thin metal films can be engineered to fabricate strain sensors by conquering their stiffness using wavy, buckle, or wrinkle topography. However, these structures usually operate in uniaxial or biaxial stretching directions, limiting their application in the omnidirectional model. Here a strain sensor is con- structed by using metal mesh with honeycomb lattices and multiple domains as the sensitive unit, which simultaneously provides good stretchability and direction independence. Besides, the metal mesh structure makes it possible to obtain a transparent sensor with a sheet resistance of 26 Ω sq?1 at a trans- mittance of 79%. The sensor exhibits a highly sensitive resistance change with tension strain, demonstrated by quick response when monitoring the finger and muscle motion. The sensor also shows promising potential application in detecting periodic oscillation with selected frequency and even complex mechanical oscillation like glass vibration.
关键词： breath-figure,wearable devices,strain sensors,transparent stretchable electronics,omnidirectional detection
更新于2025-09-19 17:15:36
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The formation of intermediate layers in covered Ge/Si heterostructures with low-temperature quantum dots: a study using high-resolution transmission electron microscopy and Raman spectroscopy
摘要： The method of software analysis of high-resolution TEM images using the peak pairs algorithm in combination with Raman spectroscopy was employed to study lattice deformations in Ge/Si(001) structures with low-temperature Ge quantum dots. It was found that the stresses do not spread in a thick Si layer above quantum dots, but completely relax via the formation of a thin boundary layer of mixed composition. However, intermixing of Ge and Si is absent beneath the Ge layer in samples with a Ge coverage of 10 ?A. Besides intermixing was not observed at all, both beneath and above the Ge layer, in samples with a Ge coverage of 6 ?A or less. This may be due to the predominance of Ge di?usion into the Si matrix from the {105} facets of Ge huts, not from the Ge wetting layer, at low temperatures of the Ge/Si structure deposition. The critical thickness of Si coverage at which the intense stress-induced di?usion takes place is determined to lie in the range from 5 to 8 nm.
关键词： lattice strain,Ge/Si quantum dots,peak-pairs analysis,HR TEM,Raman scattering,strain relaxation
更新于2025-09-19 17:13:59
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Ultrasensitive MWCNT/PDMS composite strain sensor fabricated by laser ablation process
摘要： Flexible ultrasensitive piezoresistive strain sensors were fabricated by CO2 Laser ablating of the surface of the multiwall carbon nanotube/ polydimethylsiloxane (MWCNT/PDMS) composite film prepared by a coating process. The effects of the MWCNT content and the applied laser power on the electrical and sensing performances of the MWCNT/PDMS composite strain sensor were systematically investigated. It is found that, after laser ablating, the electrical conductivity and the sensing gauge factor of the MWCNT/PDMS film were greatly improved only by the addition of 1.0 wt.% of MWCNT, which is below the percolation threshold of the MWCNT in the PDMS matrix. A novel boscage-like structure at the surface of the film formed by the ablation of the PDMS and the rearrangement of the MWCNT during the laser ablating process was found responsible for the ultrahigh gauge factor of the composite strain sensor, which is about 513 at the strain of 5.0%. The facile and cost-effective fabrication process of the flexible ultrasensitive strain sensor could be simply extended to other polymer composites for the development of new multifunctional and wearable electronic devices.
关键词： Laser ablation,Strain sensor,PDMS,MWCNT
更新于2025-09-19 17:13:59
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Development of a non-contact and non-destructive laser speckle imaging system for remote sensing of anisotropic deformation around fastener holes
摘要： Strain sensing around the fastener holes is fundamentally significant in structural health monitoring and failure detections. Conventional non-destructive testing (NDT) techniques typically have limitations in performing reliable and efficient inspections. Here, a laser speckle imaging system (LSIS) has been developed to achieve non-contact, non-destructive and remote strain sensing. Methods for determining optimal laser speckle patterns have been investigated to achieve remote sensing of strain up to a working distance of 5 m. This LSIS was applied to study the anisotropic properties of un-notched and circular notched specimens in cold-rolled aluminium sheet, an important material for the construction of lightweight aircraft structures. The results showed that strain distributions determined by LSIS are consistent with finite element (FE) predictions in which the evolution of strain concentrations not only depends on the notch size but also on material anisotropy. This study demonstrates the potential application of LSIS as an effective NDT technique for full-field, non-contact and remote sensing of anisotropic deformation around fastener holes.
关键词： Non-destructive testing,Digital image correlation,Laser speckle imaging,Remote strain sensing
更新于2025-09-19 17:13:59