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Keywords = in situ ultrasonic characterization

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13 pages, 3600 KiB  
Article
The Effects of Water Flow on the Swimming Behavior of the Large Yellow Croaker (Larimichthys crocea) in a Large Sea Cage
by Xiaorun Zhang, Yong Tang, Xinyi Hu, Chonghuan Liu, Yonghu Liu, Xin Zhuang, Guang Xu and Jing Liu
Fishes 2025, 10(6), 250; https://doi.org/10.3390/fishes10060250 - 26 May 2025
Viewed by 374
Abstract
This study aims to clarify the influence of water flow on the behavior of the large yellow croaker (Larimichthys crocea). Although L. crocea is a key species in marine cage aquaculture, and the industry is increasingly adopting large-scale sea cages, the [...] Read more.
This study aims to clarify the influence of water flow on the behavior of the large yellow croaker (Larimichthys crocea). Although L. crocea is a key species in marine cage aquaculture, and the industry is increasingly adopting large-scale sea cages, the behavioral adaptations of this species under such conditions remain insufficiently characterized. To solve this problem, the study implemented an ultrasonic biotelemetry system to monitor the in situ swimming behavior of L. crocea across varying current velocities and tidal phases. The results indicated that the tagged fish predominantly occupied water depths of 1 to 2.6 m, with no observable circular swimming behavior along the cage periphery. Additionally, the spatial distribution of L. crocea within the large-scale cage seemed to correlate with the direction of the current. Furthermore, both the frequency of appearance and swimming speed of L. crocea were higher in the center of the cage compared to the peripheral regions during flood and ebb tides, whereas the opposite trend was observed during slack water. This study provides novel insights into the behavioral ecology of L. crocea in large-scale aquaculture systems. Full article
(This article belongs to the Section Fishery Facilities, Equipment, and Information Technology)
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13 pages, 4612 KiB  
Article
Balancing Conductivity and Morphology in Aniline-Tuned Biopolymer–Starch Composites
by Mohammed E. Ali Mohsin and Suleiman Mousa
Polymers 2025, 17(4), 497; https://doi.org/10.3390/polym17040497 - 14 Feb 2025
Cited by 2 | Viewed by 723
Abstract
This work investigates the optimization of aniline content in polyaniline (PANI)/sago starch blends prepared via in situ oxidative polymerization under ultrasonic irradiation. Building upon our previous optimizations of pH and sonication time, this study focuses on the effect of aniline concentration (5–65 wt%) [...] Read more.
This work investigates the optimization of aniline content in polyaniline (PANI)/sago starch blends prepared via in situ oxidative polymerization under ultrasonic irradiation. Building upon our previous optimizations of pH and sonication time, this study focuses on the effect of aniline concentration (5–65 wt%) on electrical conductivity, morphological dispersion, and thermal stability. Various characterization techniques, including field emission scanning electron microscopy (FE-SEM), ultraviolet–visible (UV–Vis) spectroscopy, Fourier transform infrared (FT–IR) spectroscopy, and thermogravimetric analysis (TGA), confirm that a well-connected, conductive network forms at about 35 wt% aniline. Electrical conductivity measurements reveal a pronounced rise from ~1.6 × 10−8 to ~2.2 × 10−3 S/cm between 5 wt% and 35 wt% aniline. Conductivity stabilizes above this threshold due to PANI agglomeration. Morphological assessments confirm a shift from smooth, uniform blends at low aniline to rougher, void-filled surfaces when aniline exceeds 50 wt%. TGA shows improved thermal stability with increasing aniline content. These findings highlight an optimum aniline loading of ~35 wt% to achieve synergy between conductivity and structural integrity in biopolymer-based PANI/sago starch composites, offering a pathway to sustainable, high-performance biopolymer-based conductors for applications in sensors, flexible electronics, and electromagnetic shielding. Full article
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22 pages, 9065 KiB  
Article
Lignin Particle Size Affects the Properties of PLA Composites Prepared by In Situ Ring-Opening Polymerization
by Sofia P. Makri, Eleftheria Xanthopoulou, Panagiotis A. Klonos, Alexios Grigoropoulos, Apostolos Kyritsis, Ioanna Deligkiozi, Alexandros Zoikis-Karathanasis, Nikolaos Nikolaidis, Dimitrios Bikiaris and Zoi Terzopoulou
Polymers 2024, 16(24), 3542; https://doi.org/10.3390/polym16243542 - 19 Dec 2024
Cited by 1 | Viewed by 2112
Abstract
The present work focuses on the synthesis and characterization of biobased lignin-poly(lactic) acid (PLA) composites. Organosolv lignin, extracted from beechwood, was used as a filler at 0.5, 1.0, and 2.5 wt% loadings, with ultrasonication reducing the lignin particle size to ~700 nm. The [...] Read more.
The present work focuses on the synthesis and characterization of biobased lignin-poly(lactic) acid (PLA) composites. Organosolv lignin, extracted from beechwood, was used as a filler at 0.5, 1.0, and 2.5 wt% loadings, with ultrasonication reducing the lignin particle size to ~700 nm. The PLA–lignin composites were prepared via in situ ring-opening polymerization (ROP) of L-lactide in the presence of lignin. This method ensured uniform lignin dispersion in the PLA matrix due to grafting of PLA chains onto lignin particles, preventing aggregation. Strong polymer–filler interactions were confirmed through spectroscopic analysis (FTIR and XPS) and their effects on static and dynamic glass transitions (DSC). These interactions enhanced mechanical properties, including a two-fold increase in tensile strength and elongation at 1 wt% lignin. Crystallization was suppressed due to shorter PLA chains, and a 15% drop in dynamical fragility was observed via Broadband Dielectric Spectroscopy (BDS). Antioxidant activity improved significantly, with PLA–2.5% ultrasonicated organosolv lignin reducing DPPH• content to 7% after 8 h, while UV-blocking capability increased with lignin content. Full article
(This article belongs to the Section Biobased and Biodegradable Polymers)
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12 pages, 5961 KiB  
Article
In Situ Ultrasonic Characterization of Hydrogen Damage Evolution in X80 Pipeline Steel
by Bing Chen, Feifei Qiu, Li Xia, Lintao Xu, Junjun Jin and Guoqing Gou
Materials 2024, 17(23), 5891; https://doi.org/10.3390/ma17235891 - 1 Dec 2024
Cited by 2 | Viewed by 943
Abstract
A nondestructive evaluation of the hydrogen damage of materials in a hydrogen environment is important for monitoring the running conditions of various pieces of equipment. In this work, a new thermostatic electrolytic hydrogenation in situ ultrasonic test system (In Situ TEH-UT) was developed. [...] Read more.
A nondestructive evaluation of the hydrogen damage of materials in a hydrogen environment is important for monitoring the running conditions of various pieces of equipment. In this work, a new thermostatic electrolytic hydrogenation in situ ultrasonic test system (In Situ TEH-UT) was developed. The system operates by combining cross-correlation delay estimation and frequency domain amplitude estimation and hence improves measurement accuracy with respect to ultrasonic propagation time and amplitude, allowing in situ ultrasonic evaluation of the hydrogen-charging process in X80 pipeline steel. The experimental results show that under a 30 mA/cm2 hydrogen-charging current, the hydrogen saturation time of X80 pipeline steel is 800 min. Between 0 and 800 min, the attenuation coefficient and amplitude attenuation both demonstrate a strong linear relationship with the hydrogen-charging time. After 800 min, the attenuation coefficient and amplitude attenuation do not change further, while the attenuation coefficient fluctuates greatly. Through the characterization of the microstructures of the materials analyzed, it was found that hydrogen-induced cracks (HICs) constituted the main reason for the change in the ultrasonic parameters, and the mechanism behind the hydrogen-induced damage layer (HIDL) was determined. This study provides reference significance for clarifying the change mechanism of ultrasonic parameters under hydrogen damage conditions and determining the extent of hydrogen damage using an ultrasonic technique. Full article
(This article belongs to the Special Issue Advancements in Ultrasonic Testing for Metallurgical Materials)
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16 pages, 11263 KiB  
Article
Optimizing Building Rehabilitation through Nondestructive Evaluation of Fire-Damaged Steel-Fiber-Reinforced Concrete
by Anastasios C. Mpalaskas, Violetta K. Kytinou, Adamantis G. Zapris and Theodore E. Matikas
Sensors 2024, 24(17), 5668; https://doi.org/10.3390/s24175668 - 31 Aug 2024
Cited by 13 | Viewed by 1733
Abstract
Fire incidents pose significant threats to the structural integrity of reinforced concrete buildings, often necessitating comprehensive rehabilitation to restore safety and functionality. Effective rehabilitation of fire-damaged structures relies heavily on accurate damage assessment, which can be challenging with traditional invasive methods. This paper [...] Read more.
Fire incidents pose significant threats to the structural integrity of reinforced concrete buildings, often necessitating comprehensive rehabilitation to restore safety and functionality. Effective rehabilitation of fire-damaged structures relies heavily on accurate damage assessment, which can be challenging with traditional invasive methods. This paper explores the impact of severe damage due to fire exposure on the mechanical behavior of steel-fiber-reinforced concrete (SFRC) using nondestructive evaluation (NDE) techniques. After being exposed to direct fire, the SFRC specimens are subjected to fracture testing to assess their mechanical properties. NDE techniques, specifically acoustic emission (AE) and ultrasonic pulse velocity (UPV), are employed to assess fire-induced damage. The primary aim of this study is to reveal that AE parameters—such as amplitude, cumulative hits, and energy—are strongly correlated with mechanical properties and damage of SFRC due to fire. Additionally, AE monitoring is employed to assess structural integrity throughout the loading application. The distribution of AE hits and the changes in specific AE parameters throughout the loading can serve as valuable indicators for differentiating between healthy and thermally damaged concrete. Compared to the well-established relationship between UPV and strength in bending and compression, the sensitivity of AE to fracture events shows its potential for in situ application, providing new characterization capabilities for evaluating the post-fire mechanical performance of SFRC. The test results of this study reveal the ability of the examined NDE methods to establish the optimum rehabilitation procedure to restore the capacity of the fire-damaged SFRC structural members. Full article
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26 pages, 10395 KiB  
Article
Hybrid Nanocomposites Based on Poly(3,6-dianiline-2,5-dichloro-1,4-benzoquinone): Synthesis, Structure and Properties
by Svetlana G. Kiseleva, Galina N. Bondarenko, Andrey V. Orlov, Dmitriy G. Muratov, Vladimir V. Kozlov, Andrey A. Vasilev and Galina P. Karpacheva
Polymers 2024, 16(13), 1832; https://doi.org/10.3390/polym16131832 - 27 Jun 2024
Cited by 2 | Viewed by 1396
Abstract
Hybrid nanocomposites based on poly(3,6-dianiline-2,5-dichloro-1,4-benzoquinone) (PDACB) in salt form and graphene oxide (GO) have been obtained for the first time, and the significant influence of the preparation method on the composition and structure of nanocomposites and their functional properties has been demonstrated. Nanocomposites [...] Read more.
Hybrid nanocomposites based on poly(3,6-dianiline-2,5-dichloro-1,4-benzoquinone) (PDACB) in salt form and graphene oxide (GO) have been obtained for the first time, and the significant influence of the preparation method on the composition and structure of nanocomposites and their functional properties has been demonstrated. Nanocomposites were prepared in three ways: via ultrasonic mixing of PDACB and GO; via in situ oxidative polymerization of 3,6-dianiline-2,5-dichloro-1,4-benzoquinone (DACB) in the presence of GO; and by heating a suspension of previously prepared PDACB and GO in DMF with the removal of the solvent. The results of the study of the composition, chemical structure, morphology, thermal stability and electrical properties of nanocomposites obtained via various methods are presented. Nanocomposites obtained by mixing the components in an ultrasonic field demonstrated strong intermolecular interactions between PDACB and GO both due to the formation of hydrogen bonds and π-stacking, as well as through electrostatic interactions. Under oxidative polymerization of DACB in the presence of GO, the latter participated in the oxidative process, being partially reduced. At the same time, a PDACB polymer film was formed on the surface of the GO. Prolonged heating for 4 h at 85 °C of a suspension of PDACB and GO in DMF led to the dedoping of PDACB with the transition of the polymer to the base non-conductive form and the reduction of GO. Regardless of the preparation method, all nanocomposites showed an increase in thermal stability compared to PDACB. All nanocomposites were characterized by a hopping mechanism of conductivity. Direct current (dc) conductivity σdc values varied within two orders of magnitude depending on the preparation conditions. Full article
(This article belongs to the Special Issue Advances in Polymer Composites II)
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15 pages, 11307 KiB  
Article
The Evolution of Grain Microstructure in Friction Stir Welding of Dissimilar Al/Mg Alloys with Ultrasonic Assistance
by Junjie Zhao, Bo Zhao, Chuansong Wu and Sachin Kumar
Materials 2024, 17(13), 3073; https://doi.org/10.3390/ma17133073 - 22 Jun 2024
Cited by 1 | Viewed by 1397
Abstract
The process of grain refinement during welding significantly influences both the final microstructure and performance of the weld joint. In the present work, merits of acoustic addition in the conventional Frictions Stir Welding (FSW) process were evaluated for joining dissimilar Al/Mg alloys. To [...] Read more.
The process of grain refinement during welding significantly influences both the final microstructure and performance of the weld joint. In the present work, merits of acoustic addition in the conventional Frictions Stir Welding (FSW) process were evaluated for joining dissimilar Al/Mg alloys. To capture the near “in situ” structure around the exit hole, an “emergency stop” followed by rapid cooling using liquid nitrogen was employed. Electron Backscatter Diffraction analysis was utilized to characterize and examine the evolution of grain microstructure within the aluminum matrix as the material flowed around the exit hole. The findings reveal that two mechanisms, continuous dynamic recrystallization (CDRX) and geometric dynamic recrystallization (GDRX), jointly or alternatively influence the grain evolution process. In conventional FSW, CDRX initially governs grain evolution, transitioning to GDRX as material deformation strain and temperature increase. Subsequently, as material deposition commences, CDRX reasserts dominance. Conversely, in acoustic addition, ultrasonic vibration accelerates GDRX, promoting its predominance by enhancing material flow and dislocation movements. Even during the material deposition, GDRX remains the dominant mechanism. Full article
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13 pages, 6044 KiB  
Article
Preparation of ZnO Ultrasonic Transducer by Radio-Frequency Sputtering and Its Application in Bolt Preload Detection
by Yi Xu, Yanghui Jiang, Kai Tan, Wenrui Yang, Jie Lv, Daijun Deng, Dengguo Zheng, Changsheng Li, Jun Zhang and Bing Yang
Coatings 2024, 14(6), 718; https://doi.org/10.3390/coatings14060718 - 5 Jun 2024
Viewed by 1196
Abstract
Accurate detection of the preload force of tower crane bolts is of great significance for the stable and safe operation of the equipment. The method of contact ultrasonic detection of bolt preload has always been the focus of attention, which can realize rapid [...] Read more.
Accurate detection of the preload force of tower crane bolts is of great significance for the stable and safe operation of the equipment. The method of contact ultrasonic detection of bolt preload has always been the focus of attention, which can realize rapid in situ detection without damaging the parts. In order to improve the accuracy and convenience of ultrasonic measurement of bolt preload and meet the urgent needs of the actual industrial site for high-precision measurement of bolt preload, we propose to prepare ZnO piezoelectric coatings as functional layers for ultrasonic transducers using magnetron sputtering and deposit them directly on bolts. The growth behavior of the ZnO coatings is investigated by varying the sputtering power, sputtering gas pressure and target substrate distance, and the morphology, structure, and properties are characterized and analyzed. The ZnO piezoelectric coatings with high c-axis optimal growth orientation and excitation of ultrasonic longitudinal waves were finally obtained and verified to be effective and stable when applied to the bolts. Full article
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37 pages, 3927 KiB  
Review
Imaging of Structural Timber Based on In Situ Radar and Ultrasonic Wave Measurements: A Review of the State-of-the-Art
by Narges Pahnabi, Thomas Schumacher and Arijit Sinha
Sensors 2024, 24(9), 2901; https://doi.org/10.3390/s24092901 - 1 May 2024
Cited by 10 | Viewed by 3913
Abstract
With the rapidly growing interest in using structural timber, a need exists to inspect and assess these structures using non-destructive testing (NDT). This review article summarizes NDT methods for wood inspection. After an overview of the most important NDT methods currently used, a [...] Read more.
With the rapidly growing interest in using structural timber, a need exists to inspect and assess these structures using non-destructive testing (NDT). This review article summarizes NDT methods for wood inspection. After an overview of the most important NDT methods currently used, a detailed review of Ground Penetrating Radar (GPR) and Ultrasonic Testing (UST) is presented. These two techniques can be applied in situ and produce useful visual representations for quantitative assessments and damage detection. With its commercial availability and portability, GPR can help rapidly identify critical features such as moisture, voids, and metal connectors in wood structures. UST, which effectively detects deep cracks, delaminations, and variations in ultrasonic wave velocity related to moisture content, complements GPR’s capabilities. The non-destructive nature of both techniques preserves the structural integrity of timber, enabling thorough assessments without compromising integrity and durability. Techniques such as the Synthetic Aperture Focusing Technique (SAFT) and Total Focusing Method (TFM) allow for reconstructing images that an inspector can readily interpret for quantitative assessment. The development of new sensors, instruments, and analysis techniques has continued to improve the application of GPR and UST on wood. However, due to the hon-homogeneous anisotropic properties of this complex material, challenges remain to quantify defects and characterize inclusions reliably and accurately. By integrating advanced imaging algorithms that consider the material’s complex properties, combining measurements with simulations, and employing machine learning techniques, the implementation and application of GPR and UST imaging and damage detection for wood structures can be further advanced. Full article
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22 pages, 4364 KiB  
Article
Online and Ex Situ Damage Characterization Techniques for Fiber-Reinforced Composites under Ultrasonic Cyclic Three-Point Bending
by Aravind Premanand, Mario Prescher, Michael Rienks, Lutz Kirste and Frank Balle
Polymers 2024, 16(6), 803; https://doi.org/10.3390/polym16060803 - 13 Mar 2024
Cited by 6 | Viewed by 2096
Abstract
With ultrasonic fatigue testing (UFT), it is possible to investigate the damage initiation and accumulation from the weakest link of the composite material in the very high cycle fatigue (VHCF) regime in a shorter time frame than conventional fatigue testing. However, the thermal [...] Read more.
With ultrasonic fatigue testing (UFT), it is possible to investigate the damage initiation and accumulation from the weakest link of the composite material in the very high cycle fatigue (VHCF) regime in a shorter time frame than conventional fatigue testing. However, the thermal influence on the mechanical fatigue of composites and the scatter in fatigue data for composites under ultrasonic cyclic three-point bending loading still need to be investigated. In this study, we conducted interrupted constant-amplitude fatigue experiments on a carbon-fiber satin-fabric reinforced in poly-ether-ketone-ketone (CF-PEKK) composite material. These experiments were carried out using a UFT system, which operates at a cyclic frequency of 20 kHz with a pulse–pause sequence. Various parameters, such as the CF-PEKK specimen’s surface temperature, acoustic activity, and the ultrasonic generator’s input resonance parameters, were measured during cyclic loading. During experiment interruption, stiffness measurement and volumetric damage characterization in the CF-PEKK specimens using 3D X-ray microscopy (XRM) were performed. The locations of damage initiation and accumulation and their influence on the changes in in situ parameters were characterized. Under fixed loading conditions, damage accumulation occurred at different locations, leading to scattering in fatigue life data. Further, the damage population decreased from the surface to the bulk of the composite material. Full article
(This article belongs to the Special Issue Damage and Failure Analysis of Polymer-Based Composites)
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19 pages, 5818 KiB  
Article
Reliability Estimation of the Compressive Concrete Strength Based on Non-Destructive Tests
by Andrea Miano, Hossein Ebrahimian, Fatemeh Jalayer and Andrea Prota
Sustainability 2023, 15(19), 14644; https://doi.org/10.3390/su151914644 - 9 Oct 2023
Cited by 11 | Viewed by 2486
Abstract
The uncertainty in the concrete compressive strength is one of the most challenging issues in safety checking of existing reinforced concrete (RC) buildings. The concrete compressive strength used in the assessment can highly influence the vulnerability results and thus the retrofit strategies. The [...] Read more.
The uncertainty in the concrete compressive strength is one of the most challenging issues in safety checking of existing reinforced concrete (RC) buildings. The concrete compressive strength used in the assessment can highly influence the vulnerability results and thus the retrofit strategies. The need to use less expensive and less invasive in situ measurements such as the non-destructive tests should be balanced with a careful check of their structural reliability. The compressive concrete strength is characterized herein based on a large database of both in situ destructive and non-destructive results measured on the same structural members. The data are obtained from existing RC buildings mainly located in the Campania region, Southern Italy. Probabilistic linear and multilinear regression models are developed for calculating the compressive concrete strength based on non-destructive tests. Furthermore, the implementation of the concrete strength based on ultrasonic test results are investigated together with the relative measurement error through a fully probabilistic workflow. Accordingly, the relative weights of non-destructive data for calculating concrete compressive strength are estimated and compared with those recommended by the Italian national code. The results demonstrate that the effective weights of the non-destructive data are very close to the code-based recommendation. Full article
(This article belongs to the Special Issue Sustainable Assessment and Modelling in Seismic Risk Mitigation)
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14 pages, 4085 KiB  
Article
Complementary Methods for the Assessment of the Porosity of Laser Additive-Manufactured Titanium Alloy
by Silviu Mihai Petrișor, Adriana Savin, Mariana Domnica Stanciu, Zdenek Prevorovsky, Marian Soare, František Nový and Rozina Steigmann
Materials 2023, 16(19), 6383; https://doi.org/10.3390/ma16196383 - 24 Sep 2023
Cited by 3 | Viewed by 1761
Abstract
The method of making parts through additive manufacturing (AM) is becoming more and more widespread due to the possibility of the direct manufacturing of components with complex geometries. However, the technology’s capacity is limited by the appearance of micro-cracks/discontinuities during the layer-by-layer thermal [...] Read more.
The method of making parts through additive manufacturing (AM) is becoming more and more widespread due to the possibility of the direct manufacturing of components with complex geometries. However, the technology’s capacity is limited by the appearance of micro-cracks/discontinuities during the layer-by-layer thermal process. The ultrasonic (US) method is often applied to detect and estimate the location and size of discontinuities in the metallic parts obtained by AM as well as to identify local deterioration in structures. The Ti6Al4V (Ti64) alloy prepared by AM needed to acquire a high-quality densification if remarkable mechanical properties were to be pursued. Ultrasonic instruments employ a different type of scanning for the studied samples, resulting in extremely detailed images comparable to X-rays. Automated non-destructive testing with special algorithms is widely used in the industry today. In general, this means that there is a trend towards automation and data sharing in various technological and production sectors, including the use of intelligent systems at the initial stage of production that can exclude defective construction materials, prevent the spread of defective products, and identify the causes of certain instances of damage. Placing the non-destructive testing on a completely new basis will create the possibility for a broader analysis of the primary data and thus will contribute to the improvement of both inspection reliability and consistency of the results. The paper aims to present the C-scan method, using ultrasonic images in amplitude or time-of-flight to emphasize discontinuities of Ti64 samples realized by laser powder-bed fusion (L-PBF) technology. The analysis of US maps offers the possibility of information correlation, mainly as to flaws in certain areas, as well as distribution of a specific flaw in the volume of the sample (flaws and pores). Final users can import C-scan results as ASCII files for further processing and comparison with other methods of analysis (e.g., non-linear elastic wave spectroscopy (NEWS), multi-frequency eddy current, and computer tomography), leading to specific results. The precision of the flight time measurement ensures the possibility of estimating the types of discontinuities, including volumetric ones, offering immediate results of the inspection. In situ monitoring allows the detection, characterization, and prediction of defects, which is suitable for robotics. Detailing the level of discontinuities at a certain location is extremely valuable for making maintenance and management decisions. Full article
(This article belongs to the Special Issue Developments in Additive Manufacturing and 3D Printing)
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18 pages, 6871 KiB  
Article
Ultrasonication-Tailored Graphene Oxide of Varying Sizes in Multiple-Equilibrium-Route-Enhanced Adsorption for Aqueous Removal of Acridine Orange
by Zhaoyang Han, Ling Sun, Yingying Chu, Jing Wang, Chenyu Wei, Yifang Liu, Qianlei Jiang, Changbao Han, Hui Yan and Xuemei Song
Molecules 2023, 28(10), 4179; https://doi.org/10.3390/molecules28104179 - 18 May 2023
Cited by 4 | Viewed by 2387
Abstract
Graphene oxide (GO) has shown remarkable performance in the multiple-equilibrium-route adsorption (MER) process, which is characterized by further activation of GO through an in-situ reduction process based on single-equilibrium-route adsorption (SER), generating new adsorption sites and achieving an adsorption capacity increase. However, the [...] Read more.
Graphene oxide (GO) has shown remarkable performance in the multiple-equilibrium-route adsorption (MER) process, which is characterized by further activation of GO through an in-situ reduction process based on single-equilibrium-route adsorption (SER), generating new adsorption sites and achieving an adsorption capacity increase. However, the effect of GO on MER adsorption in lateral size and thickness is still unclear. Here, GO sheets were sonicated for different lengths of time, and the adsorption of MER and SER was investigated at three temperatures to remove the typical cationic dye, acridine orange (AO). After sonication, we found that freshly prepared GO was greatly reduced in lateral size and thickness. In about 30 min, the thickness of GO decreased dramatically from several atomic layers to fewer atomic layers to a single atomic layer, which was completely stripped off; after that, the monolayer lateral size reduction dominated until it remained constant. Surface functional sites, such as hydroxyl groups, showed little change in the experiments. However, GO mainly reduces the C=O and C-O bonds in MER, except for the conjugated carbon backbone (C-C). The SER adsorption kinetics of all temperatures fitted the pseudo-first-order and pseudo-second-order models, yet room temperature preferred the latter. An overall adsorption enhancement appeared as sonication time, but the equilibrium capacity of SER GO generally increased with thickness and decreased with the single-layer lateral size, while MER GO conversed concerning the thickness. The escalated temperature facilitated the exfoliation of GO regarding the adsorption mechanism. Thus, the isotherm behaviors of the SER GO changed from the Freundlich model to Langmuir as size and temperature changed, while the MER GO were all of the Freundlich. A record capacity of ~4.3 g of AO per gram of GO was obtained from the MER adsorption with a sixty-minute ultrasonicated GO at 313.15 K. This work promises a cornerstone for MER adsorption with GO as an adsorbent. Full article
(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)
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11 pages, 2562 KiB  
Article
Significance of Annealing Twins in Laser Ultrasonic Measurements of Grain Size in High-Strength Low-Alloy Steels
by Tuomo Nyyssönen, Mikael Malmström, David Lindell, Anton Jansson, Johan Lönnqvist, Linda Bäcke and Bevis Hutchinson
Appl. Sci. 2023, 13(6), 3901; https://doi.org/10.3390/app13063901 - 19 Mar 2023
Cited by 5 | Viewed by 1875
Abstract
In this study, we demonstrate the significance of austenite annealing twin boundaries when calibrating laser ultrasonic measurements for gauging austenite grain size in situ during the thermomechanical processing of high-strength low-alloy steels. Simple calculations show how differences in twinning density can lead to [...] Read more.
In this study, we demonstrate the significance of austenite annealing twin boundaries when calibrating laser ultrasonic measurements for gauging austenite grain size in situ during the thermomechanical processing of high-strength low-alloy steels. Simple calculations show how differences in twinning density can lead to errors in grain size measurements if twins are disregarded during calibration and the method is used for a broad range of steels. Conversely, when calibration is performed using alloys with a metastable austenite microstructure at room temperature, the same calibration is suitable for a broad range of HSLA steels, provided that annealing twins are taken into account. Since light optical microscopy does not allow the characterization of annealing twins in low-alloy steel, the verification of the laser ultrasonic results was conducted using the novel approach of comparing the twinned grain sizes obtained using the ultrasonic method in low-alloy steels with the austenite grain maps reconstructed from martensite orientation maps measured using electron backscatter diffraction. Finally, we show how differences in twinning density occur even for alloys with a roughly similar stacking fault energy, further highlighting the importance of annealing twins in the calibration of laser ultrasonic measurements for industrial use. Full article
(This article belongs to the Section Materials Science and Engineering)
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14 pages, 1860 KiB  
Article
Assessment and Non-Destructive Evaluation of the Influence of Residual Solvent on a Two-Part Epoxy-Based Adhesive Using Ultrasonics
by Gonzalo Seisdedos, Edgar Viamontes, Eduardo Salazar, Mariana Ontiveros, Cristian Pantea, Eric S. Davis, Tommy Rockward, Dwayne McDaniel and Benjamin Boesl
Appl. Sci. 2023, 13(6), 3883; https://doi.org/10.3390/app13063883 - 18 Mar 2023
Cited by 8 | Viewed by 2646
Abstract
Polymers are increasingly being used in higher demanding applications due to their ability to tailor the properties of structures while allowing for a weight and cost reduction. Solvents play an important role in the manufacture of polymeric structures since they allow for a [...] Read more.
Polymers are increasingly being used in higher demanding applications due to their ability to tailor the properties of structures while allowing for a weight and cost reduction. Solvents play an important role in the manufacture of polymeric structures since they allow for a reduction in the polymer’s viscosity or assist with the dispersion of fillers into the polymer matrix. However, the incorrect removal of the solvent affects both the physical and chemical properties of polymeric materials. The presence of residual solvent can also negatively affect the curing kinetics and the final quality of polymers. Destructive testing is mainly performed to characterize the properties of these materials. However, this type of testing involves using lab-type equipment that cannot be taken in-field to perform in situ testing and requires a specific sample preparation. Here, a method is presented to non-destructively evaluate the curing process and final viscoelastic properties of polymeric materials using ultrasonics. In this study, changes in longitudinal sound speed were detected during the curing of an aerospace epoxy adhesive as a result of variations in polymer chemistry. To simulate the presence of residual solvent, samples containing different weight percentages of isopropyl alcohol were manufactured and tested using ultrasonics. Thermogravimetric analysis was used to show changes in the decomposition of the adhesive due to the presence of IPA within the polymer structure. Adding 2, 4, and 6 wt.% of IPA decreased the adhesive’s lap shear strength by 40, 58, and 71%, respectively. Ultrasonics were used to show how the solvent influenced the curing process and the final sound speed of the adhesive. Young’s modulus and Poisson’s ratio were determined using both the longitudinal and shear sound speeds of the adhesive. Using ultrasonics has the potential to non-invasively characterize the quality of polymers in both an in-field and manufacturing settings, ensuring their reliability during use in demanding applications. Full article
(This article belongs to the Special Issue Non-destructive Testing of Materials and Structures - Volume II)
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