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In Situ Measurement of Phase Boundary Kinetics during Initial Lithiation of Crystalline Silicon through Picosecond Ultrasonics
摘要： Studying the kinetics of phase transformation and phase boundary propagation during initial lithiation of silicon electrodes in lithium ion batteries is relevant to understanding their performance. Such studies are usually challenging due to the difficulties in measuring the phase boundary velocity in the interior of the sample. Here we introduce a non-invasive, in situ method to measure the progression of the phase boundary in a planar specimen geometry while maintaining well-controlled lithium flux and potential. We developed an apparatus integrating an electrochemical cell with picosecond ultrasonics to probe the propagating phase boundary in real time. Phase propagation during initial lithiation of crystalline silicon, which is an example of a high capacity anode, is investigated. The primary objective of this manuscript is to report on the experimental technique development and some preliminary results. For lithiation normal to the (100) plane, we observe the phase boundary velocity to be approximately 12 pm/s and x to be 3.73 in LixSi under galvanostatic lithiation with a current density of 40 μA/cm2. The growth rate of the lithiated phase and the reaction rate coefficient are examined using a Deal-Grove type model.
关键词： Lithium ion battery,In situ,Phase boundary propagation,Crystalline silicon,Picosecond ultrasonics
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE International Ultrasonics Symposium (IUS) - Kobe, Japan (2018.10.22-2018.10.25)] 2018 IEEE International Ultrasonics Symposium (IUS) - Looking at the Skull in a New Light: Rayleigh-Lamb Waves in Cranial Bone
摘要： Current knowledge on the ultrasound wave propagation in the cranial bone is restricted to far-field observations. In order to extend our understanding on how ultrasound waves propagate in the skull, we use short laser pulses to excite ultrasound waves in water-immersed ex vivo mouse and human skulls and explored their near-field. The laser pulses ( 10 ns duration) of 532 nm are absorbed by a small layer of black burnish deposited on the skull’s inner surface and generate ultrasound waves due to the thermoelastic effect. The acoustic near-field is mapped using a needle hydrophone close to the skull surface, following a three-dimensional scanning path derived from a previous pulse-echo scan of the skull with a spherically focused ultrasound transducer. The results for mouse and human skulls show different wave propagation regimes according to their differences in size, thickness, and internal structure. Leaky and non-leaky waves have been observed for both skull samples. Zero order Lamb modes were observed in the mouse skull, whereas Rayleigh-Lamb higher order modes can be observed in the human skull sample, presumably propagating in the outer cortical bone layer. Good agreement is found between the experiments and the multilayered flat plate model.
关键词： Skull Bone,Lamb Waves,Near Field,Surface Acoustic Waves,Rayleigh Waves,Plate waves,Laser ultrasonics
更新于2025-09-23 15:22:29
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Visible Light Driven Catalytic Properties Over Methyl Orange by Novel PtSe2/Graphene Nanocomposites
摘要： High efficient graphene based platinum selenide composite photocatalyst were synthesized by ultrasonic assisted method. The “as-prepared” nanocomposites are further characterized by X-ray diffraction, scanning electron microscopy with an energy dispersive X-ray analysis, transmission electron microscopy, UV-visible absorbance spectra analysis and diffuse reflectance spectra analysis. The photocatalytic activities of the composites are investigated by the degradation of methyl orange as a standard dye. The results showed that the photocatalytic activity of PtSe2 was significantly enhanced by the loading of graphene in the composites.
关键词： Graphene,Ultrasonics,Nanocomposites,Photocatalysis,Methyl orange
更新于2025-09-23 15:21:01
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Parametric optimization of pulse-echo laser ultrasonic system for inspection of thick polymer matrix composites
摘要： One of the main challenges of using laser ultrasonic techniques for non-destructive testing applications is the typically low signal-to-noise ratio of the laser ultrasonic signals. In the case of thick composite structures, this is even more problematic since composite materials have very strong sound attenuation. This article investigates the effects of laser beam size and profile to the amplitude of pulse-echo laser ultrasonic signals with the constraint that the peak energy density (fluence) must be kept constant under the thermal damage threshold of material like polymer matrix composites. Such constraint is very important for the non-destructive feature of non-destructive testing, yet in a number of the existing parameter studies of laser ultrasonics, it was not fully investigated. In this article, a series of A-scan and C-scan experiments on thick composite specimens shows that the amplitude of the direct waves and the reflected waves increases with the increase in laser beam size with constant peak energy density. This amplitude enhancement significantly improves the propagation depth, thereby optimizing the system for inspection of thick composite structures. The validity of experimental results is verified theoretically by solving the thermoelastic model of epicenter displacement using Laplace–Hankel transformation.
关键词： epicenter displacement,Laser thermoelastic model,thick composite structures,pulse-echo laser ultrasonics
更新于2025-09-23 15:19:57
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A Basic Complete Numerical Toolbox for Picosecond Ultrasonics
摘要： A complete numerical complete toolbox is proposed concerning the simulation of photo-induced propagative mechanical wave, and concerning the optical re?ectometric measured response of the material, which is initially exposed to a ?rst pump laser beam that photo-induces the acoustic wavefronts. The deformation ?eld and its propagation into a bulk material are simulated. Based on this ?eld expression, the complex transient re?ectivity is given for a medium considered as homogeneous. The real part of this quantity permits afterwards to propose a numerical simulation of the transient re?ectivity, which corresponds to the optical signal measured during experimental works. The frequency acoustic spectrum is simulated and successfully compared to the measured frequency spectrum. For the ?rst time, numerical complete developments are explicitly proposed and fully-developed under the SciLab R(cid:13) environment, related to the simulation of laser-induced picosecond acoustic wavefront photogenerated through an opto-acoustic transduction process (ultrasonics and pretersonics).
关键词： simulation,computational acoustics,laser ultrasonics,acoustic waves,optical re?ectivity,pretersonics
更新于2025-09-19 17:15:36
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[IEEE 2019 Far East NDT New Technology & Application Forum (FENDT) - Qingdao, Shandong province, China (2019.6.24-2019.6.27)] 2019 Far East NDT New Technology & Application Forum (FENDT) - Phased-Array Laser Ultrasonic Testing with Sparse Total Focusing Imaging Method
摘要： In order to further improve the detectability of laser ultrasonic testing method for internal defects of materials, this paper studies a new phased array laser ultrasonic detection and imaging method based on the full matrix capture technology and total focusing method. Based on the finite element method, a numerical model of full matrix laser ultrasonic detection and signal sampling is developed to acquire the signal data of full matrix laser ultrasonic testing, and then the corresponding program of the total focusing method algorithm is developed to realize the visual imaging detection of different defects in the specimen based on the total focusing method. Subsequently, in order to improve the efficiency of laser ultrasonic testing with full matrix phased array, a full matrix laser ultrasonic testing method with sparse array is proposed, and a signal reproduction method based on sparse array is developed to expand sparse array to dense array signal, thus achieving high quality imaging of internal defects, and effectively improving the detection efficiency of this method.
关键词： Sparse array,Total focusing method,Laser ultrasonics,Full matrix capture
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE International Ultrasonics Symposium (IUS) - Glasgow, United Kingdom (2019.10.6-2019.10.9)] 2019 IEEE International Ultrasonics Symposium (IUS) - Laser Ultrasonic Sensing of Oxidation-Induced Microstructural Changes in Nuclear Graphites
摘要： Serving both as a structural and as a functional material, nuclear graphites have a range of useful mechanical, chemical and radiation-related behaviors that are important for nuclear applications. The raw materials used as feedstock along with the manufacturing processes used for production of these materials results in a complicated microstructure composed of graphite filler, graphitized pitch binder, and voids/defects that include porosity and microcracks. These heavily influence the overall elastic moduli of nuclear graphites and must be taken into account when interpreting ultrasonic measurements. Indeed, the measured elastic moduli are generally close to the Reuss limits – the theoretical, lower bounds for the moduli – but no attempts have been made to explain these results within the broader context of elasticity in porous materials containing microcracks. In this work, we report ultrasonic measurements of elastic moduli for nuclear graphites as a function of the bulk porosity and interpret them using relatively simple, physics-based models that describe the effects of porosity and microcracking on modulus. Modifications to these models are explored to account for microstructure-related effects on modulus such as those that are associated with oxidation-induced porosity. These models can be used to interpret a broad range of ultrasonic measurements reported previously for nuclear graphites, and the insight gained into the elastic responses of these materials can be used to guide the use of ultrasonic methods to assess the structural integrity of nuclear graphites.
关键词： porosity,laser ultrasonics characterization,elastic modulus,material property
更新于2025-09-19 17:13:59
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Detection and imaging of local ply angle in carbon fiber reinforced plastics using laser ultrasound and tilt filter processing
摘要： Wrinkles in carbon-fiber reinforced plastics (CFRP) are extremely dangerous, dramatically changing the performance of a composite structure. However, wrinkles are one of the most difficult defects to detect and characterize with ultrasound since they do not produce large echoes like other flaws. Recent developments in laser-ultrasound (LU) have enabled non-contact, high-resolution imaging of CFRPs, providing sub-ply resolution and detailed visualization of CFRP structures. In this paper, we demonstrate that the superior resolution of LU systems can be used to help track ply orientation variations in composites. To improve the signal-to-noise ratio of LU generated signals, we propose a local cross-correlation based tilt-filtration procedure for coherent spatial signal averaging that accounts for the shape of subsequent layers. In addition, local ply angle is a straightforward output of the proposed processing, which can be used directly as an indicator of wrinkle severity.
关键词： D. Non-destructive testing,A. Carbon fibers,B. Directional orientation,D. Ultrasonics
更新于2025-09-11 14:15:04
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Monitoring of Thermal Aging of Aluminum Alloy via Nonlinear Propagation of Acoustic Pulses Generated and Detected by Lasers
摘要： Nonlinear acoustic techniques are established tools for the characterization of micro-inhomogeneous materials with higher sensitivity, compared to linear ultrasonic techniques. In particular, the evaluation of material elastic quadratic nonlinearity via the detection of the second harmonic generation by acoustic waves is known to provide an assessment of the state variation of heat treated micro-structured materials. We report on the first application for non-destructive diagnostics of material thermal aging of finite-amplitude longitudinal acoustic pulses generated and detected by lasers. Finite-amplitude longitudinal pulses were launched in aluminum alloy samples by deposited liquid-suspended carbon particles layer irradiated by a nanosecond laser source. An out-of-plane displacement at the epicenter of the opposite sample surface was measured by an interferometer. This laser ultrasonic technique provided an opportunity to study the propagation in aluminum alloys of finite-amplitude acoustic pulses with a strain up to 5 × 10?3. The experiments revealed a signature of the hysteretic quadratic nonlinearity of micro-structured material manifested in an increase of the duration of detected acoustic pulses with an increase of their amplitude. The parameter of the hysteretic quadratic nonlinearity of the aluminum alloy (Al6061) was found to be of the order of 100 and to exhibit more than 50% variations in the process of the alloy thermal aging. By comparing the measured parameter of the hysteretic quadratic nonlinearity in aluminum alloys that were subjected to heat-treatment at 220 ?C for different times (0 min, 20 min, 40 min, 1 h, 2 h, 10 h, 100 h, and 1000 h), with measurements of yield strength in same samples, it was established that the extrema in the dependence of the hysteretic nonlinearity and of the yield strength of this alloy on heat treatment time are correlated. This experimental observation provides the background for future research with the application goal of suggested nonlinear laser ultrasonic techniques for non-destructive evaluation of alloys’ strength and rigidity in the process of their heat treatment.
关键词： laser ultrasonics,thermal aging,hysteretic acoustic nonlinearity,nonlinear acoustics
更新于2025-09-11 14:15:04