Internal Microstructure Research Articles

Comparison between microstructural analysis of GFRP and CFRP rebars using micro computed tomography (μCT), scanning electron microscope (SEM), and acoustic emission (AE) techniques

The internal micro-structure of glass and carbon fibre-reinforced polymer (FRP) rebars subjected to tensile loading was investigated using micro computed tomography (μCT) and scanning electron microscopy (SEM) images. Three dimensional (3D) and two dimensional (2D) reconstructed μCT images were used to study and quantify the void volume and its distribution along with FRP rebar samples after being subjected to tensile loads. The void volume was observed to increase in all samples as the tensile load on the samples was increased. Acoustic emission (AE) monitoring during the tensile loading was also employed to establish a correlation between the AE parameters and damage evolution in the FRP samples. Cumulative energy of AE signal in frequency domain was used to monitor the progression of the internal damage in the FRP reinforcing rebars. A high correlation was observed between the void volume measured by μCT and SEM and the cumulative energy of the AE signal.

The hidden biotic face of microbialite morphogenesis – a case study from Laguna de Los Cisnes, southernmost Patagonia (Chile)

ABSTRACTMicrobialites provide geological evidence into Earth's early ecosystems, recording long‐standing interactions between co‐evolving life and the environment. Yet, after more than 100 years of research, the complex interplay between environmental and biological forces involved in microbialite growth is still debated. Laguna de Los Cisnes, located in Chilean Tierra del Fuego, Patagonia, provides a unique opportunity to study these interactions. This lake, which became ice‐free around 10 000 years ago, features carbonate microbialites developed by algal–microbial communities. Macroscopically, the organo‐sedimentary deposits exhibit a consistent primary crater‐like architecture, showcasing macrostructural variations such as dish‐shaped, hemispherical, columnar and lenticular morphologies. This study explores the environmental and biological factors shaping microbialite macrostructure by analysing the distribution of dominant morphotypes across the basin. Concurrently, it examines the internal mesostructure and microstructure of microbialites in association with prevailing algal–microbial communities. The incremental development of these communities contributes to the distinct crater‐like morphology observed in microbialites from Laguna de Los Cisnes. The mineral encrustation of the green alga Percursaria percursa emerges as a primary driver of lithification, evidenced by the preservation of microfossils within the microstructure of the microbialites. Simultaneously, physical environmental factors, including waves, Langmuir cells and accommodation space influence the location of the algal–microbial carbonate factory, determining the spatial distribution and temporal succession of different crater architecture variants. Laguna de Los Cisnes, hosting well‐preserved subfossil outcrops and living microbialites, serves as a remarkable living laboratory for understanding microbialite morphogenesis. This study contributes to a novel model that captures the fundamental role of algal–microbial communities in determining the primary macrostructural architecture of microbialites before environmental factors come into play, merely reshaping this architecture into different morphotypes.

Treatment activity of hydrogels loaded with metal–organic frameworks of bleomycin on hemangioma

In the current paper, through utilizing two symmetrical pentacarboxylate ligands, namely, 3,5-di(2′,5′-dicarboxylphenyl)benzoic (H5L1) and 3,5-di(2′,4′ dicarboxylphenyl)benzoic acid (H5L2), two fresh Co(II)-basd coordination polymers (CPs), [Co5(μ3-H2O)2(L1)2]·3DMA·4H2O (1, DMA is N,N-dimethylacetamide) along with [Co3(μ3-OH)L2(H2O)3]·H2O (2) have been synthesized under the conditions of solvothermal. With hyaluronic acid (HA) and carboxymethyl chitosan (CMCS) as raw materials, HA/CMCS hydrogel was prepared by chemical synthesis and its internal microstructure was observed by scanning electron microscope. Using bleomycin as a drug model, we designed and synthesized two metallogel particle frameworks encapsulating bleomycin drugs and compared the effects of the two metallogel particle frameworks as drug carriers for delivering bleomycin drugs for the treatment of hemangiomas.

Mechanism of mean stress sensitivity in Ti-6Al-4V under different stress ratios in high cycle fatigue

Initially, this article precisely determines that the “facet” on the fracture surface of the Ti-6Al-4V alloy during high cycle fatigue (HCF) loading under positive stress ratios, as determined by white light interferometry and transmission Kikuchi diffraction (TKD), originates from cracking along the slip planes that exhibit a grain orientated α grain in the loading direction, predominantly involving shear deformation along the crystallographic planes. The article emphasizes the crack initiation mechanisms in Ti-6Al-4V alloy related to internal microstructures under positive stress ratio HCF loading, elucidating relationship between texture-induced crack initiation and growth, and anomalous mean stress sensitivity. Under positive stress ratio fatigue loading, preferentially orientated texture regions tend to generate irreversible dislocations parallel to the basal plane, gradually accumulating within multiple locations to form persistent slip bands (PSBs), which, under the influence of internal stresses, sequentially collapse and rupture, leading to nucleation of microcracks. Upon encountering unfavorably oriented texture regions or grains, PSBs or existing microcracks experience dislocation accumulation, which in turn induce grain refinement, thereby causing further crack nucleation. Consequently, microcracks, through aggregation and coalescence during the fatigue loading sequence, form the main crack, ultimately precipitating fatigue failure and engendering the anomalous mean stress sensitivity observed in the Ti-6Al-4V alloy.

Designing Lightweight 3D-Printable Bioinspired Structures for Enhanced Compression and Energy Absorption Properties.

Recent progress in additive manufacturing, also known as 3D printing, has offered several benefits, including high geometrical freedom and the ability to create bioinspired structures with intricate details. Mantis shrimp can scrape the shells of prey molluscs with its hammer-shaped stick, while beetles have highly adapted forewings that are lightweight, tough, and strong. This paper introduces a design approach for bioinspired lattice structures by mimicking the internal microstructures of a beetle's forewing, a mantis shrimp's shell, and a mantis shrimp's dactyl club, with improved mechanical properties. Finite element analysis (FEA) and experimental characterisation of 3D printed polylactic acid (PLA) samples with bioinspired structures were performed to determine their compression and impact properties. The results showed that designing a bioinspired lattice with unit cells parallel to the load direction improved quasi-static compressive performance, among other lattice structures. The gyroid honeycomb lattice design of the insect forewings and mantis shrimp dactyl clubs outperformed the gyroid honeycomb design of the mantis shrimp shell, with improvements in ultimate mechanical strength, Young's modulus, and drop weight impact. On the other hand, hybrid designs created by merging two different designs reduced bending deformation to control collapse during drop weight impact. This work holds promise for the development of bioinspired lattices employing designs with improved properties, which can have potential implications for lightweight high-performance applications.

Thermomechanical transitions of meat-analog based fried foods batter coating

This study aimed to characterize the thermomechanical transitions of meat-analog (MA) based coated fried foods. Wheat and rice flour-based batters were used to coat the MA and fried at 180 °C in canola oil for 2, 4 and 6 min. Glass-transition-temperature (Tg) of the coatings were assessed by differential scanning calorimetry, directly after frying or after post-fry holding. Mechanical texture analyzer and X-ray microtomography were employed to assess textural attributes and internal microstructure, respectively. Batter-formulation substantially impacted the Tg of fried foods coating i.e., crust. Tg of fried foods crust were ranged between −20 °C to −24 °C. Tg was positively correlated with frying time and internal microporosity (%), whereas negatively correlated with moisture content. Internal microstructure greatly influenced the textural attributes (hardness, brittleness, crispiness). Post-fry textural stability considerably impacted by Tg. Negative Tg value explains post-fry textural changes (hard-to-soft, brittle-to-ductile, crispy-to-soggy) of MA-based coated products at room-temperature (25 °C) and under IR-heating (65 °C).

Anisotropic MXene/Poly(vinyl alcohol) Composite Hydrogels with Vertically Oriented Channels and Modulated Surface Topography for Efficient Solar-Driven Water Evaporation and Purification.

Hierarchical structure and surface topography play pivotal roles in developing high-performance solar-driven evaporators for clean water production; however, there exists a notable gap in research addressing simultaneous modulation of internal microstructure and surface topography in hydrogels to enhance both solar steam generation performance and desalination efficiency. Herein, anisotropic poly(vinyl alcohol)/MXene composite hydrogels for efficient solar-driven water evaporation and wastewater purification are fabricated using a template-assisted directional freezing approach followed by precise surface wettability modulation. The resultant composite hydrogels exhibit vertically oriented channels that ensure fast water supply during evaporation, and their poly(vinyl alcohol) skeletons can reduce the vaporization enthalpy of the water in the hydrogels. The incorporation of MXene sheets enables efficient solar light absorption and solar-thermal conversion while providing structural reinforcement to the hydrogels. More importantly, the as-created undulating solar-thermal surface, featuring modulated hydrophilic troughs and hydrophobic crests, significantly enhances solar-thermal conversion efficiency, thereby boosting solar evaporation performances. As a result, the fabricated hydrogel-based evaporator exhibits an impressive evaporation rate of 2.55 kg m-2 h-1 under 1 sun irradiation, coupled with long-term durability and desalination stability. Notably, the outstanding mechanical robustness of the hydrogel further enables high portability through a readily achievable process of reversible dehydration/hydration.

Voltage‐Driven Molecular Orientation with Optical Synergy in Rare Earth Doped Polymer Dispersed Liquid Crystals

AbstractAchieving reversible large‐span photoluminescence regulation still faces difficulties due to limitations in the design or preparation conditions of related materials. Herein, a universal strategy that combines voltage‐driven molecular orientation with optical synergy between rare earth (RE) doped materials and polymer dispersed liquid crystals (PDLC) is proposed to achieve large‐span reversible opto‐electrically synergistic induced multi‐response photoluminescence regulation. The obtained Eu(tta)3phen/PDLC composites can exhibit different emission colors reversible transform from purple to purplish‐pink depending on the excitation wavelength and the applied electric voltage. The interaction between PDLC and Eu(tta)3phen is analyzed and the field distribution of internal microstructures is simulated using the finite‐difference time‐domain method, providing a theoretical basis for the voltage‐dependent photon interactions. The potential applications of Eu(tta)3phen/PDLC composites for anticounterfeiting is suggested by demonstrating a proof‐of‐concept anticounterfeiting system based on the composites. The strategy of opto‐electrically synergistic induced multi‐response photoluminescence regulation, with general applicability, can be easily extended to other RE doped materials and PDLC systems, opening up new possibilities for photoluminescence regulation research.

A novel cost-effective method for self-estimation of crack occur time by piezoelectric measurement of glass powder-modified cementitious mortar

This study investigated the usability of ground glass waste powders (GP) in cementitious mortars. For this purpose, 4 cm × 4 cm x 16 cm mortars were produced with 0%, 5%, 10%, and 20% GP additives by weight (instead of cement). The mortars’ hydration temperature and moisture (%) values were recorded during one day (for every minute), and various comparisons were made. To investigate the effects of alternating current (AC) on the internal temperature, physical, mechanical features, and microstructure of mortars, 20V AC was applied to fresh mortars for 24 h. It was found that the optimum ratio of GP in both current-applied and non-current-applied mortars was 5%. It was observed that the 28-day compressive strengths of the mortars decreased by 4.81%, 19.97%, 30.89%, and 40.10%, respectively, compared to the reference mortar when 5%, 10%, 15%, and 20% GP were added. Another result obtained in the study is that crack formation level can be predicted by measuring vibration in mortars. Thus, this study is critical especially in predicting the damage stages of the structures due to earthquakes.

A new Cd(II) Complex: Fluorescence Performances, Loading with Budesonide-hydrogels on Pediatric Asthma and Molecular Docking.

By applying the phosphonic acid ligand to the solvothermal reaction of nitrobenzylphosphonic acid (H2L) with Cd(NO3)2·4H2O in a mixed solvent of water and DMF, a novel Cd(II)-based coordination polymer, {[Cd(L)(H2O)2](H2O)}n (1), was successfully synthesized in this study. The excellent fluorescence performance of complex 1 was confirmed through fluorescence spectroscopy testing, and the obtained CIE standard coordinates (0.1599, 0.0786) positioned it in the blue fluorescence region. Transparent hyaluronic acid/carboxymethyl chitosan hydrogels were prepared using chemical synthesis, and their internal microstructure was observed. Using budesonide as a drug model, a new budesonide metal gel was prepared, and its therapeutic efficacy in treating pediatric asthma was evaluated. Molecular docking simulations indicated that the Cd complex formed three hydrogen bonding interactions with the target protein through its nitro group, revealing the potential origin of its biological activity.

A review of the interfacial transition zones in concrete: Identification, physical characteristics, and mechanical properties

Interfacial Transition Zones (ITZ) with high porosity are easier pathways for damage initiation and propagation. However, their mechanical performance has hardly been examined owing to the length scale of the microregions, as well as the heterogeneous and opaque constituent properties, which have been increasingly studied in recent years. This study presents a comprehensive review of the ITZ, determining strategies at the meso-micro level, quantitative characterization, and physical features. It focuses on the effects of various casting and material composition factors on the microstructural and mechanical properties of the ITZ, including porosity, thickness, volume, and elastic modulus. The correlations between the microstructures and the essential mechanical properties are discussed in detail. The weak bonding properties of the ITZ can be tailored by the material composition, which changes its internal microstructure, enhances the adhesion of the paste to aggregates, and fills micropores in cement. Several approaches can be employed to achieve this, such as adding minerals, increasing the curing age, and adjusting the water-cement ratio and sand fineness. The content of the weak ITZ can be reduced by optimizing the size distribution and volume fraction of the aggregates. Furthermore, modelling the gradient distribution of the ITZ thickness and elastic modulus is crucial in numerical simulations to enable an accurate investigation of the damage accumulation process in concrete. This study also identifies the challenges in the mechanical behavior of ITZ and serves as an engineering design guide for more advanced fracture-resistant concrete structures.

The influence of industrial solid waste in conjunction with lepidolite tailings on the mechanical properties and microstructure of cemented backfill materials

The global demand for lithium resources continues to increase, resulting in significant solid waste generation, including tailings, during the process of lithium mining. To maintain a consistent 80% solid content and a cement-to-solid waste ratio of 1:12 in cementitious backfill (CB), an orthogonal experimental design was employed. The curing periods were set at 7 and 14 days respectively. Uniaxial compressive strength tests were conducted on specimens of CB containing varying proportions of desulfurization gypsum (DG), fly ash (FA), steel slag (SS), and lepidolite tailings (LT). Mechanical properties and microstructure were studied and analyzed using scanning electron microscopy (SEM), gray value analysis, as well as other equipment and methods. The results indicate that:(1)The compressive strength of CB specimens cured for 7 days ranged between 1.28 and 3.05 MPa, while those cured for 14 days exhibited compressive strengths ranging from 2.14 to 3.17 MPa, with the optimal solid waste mix ratio being 2:4:4:3. (2) The predominant macroscopic failure modes of the CB specimens are tensile failure and a combination of tensile and shear failure. The entire failure process encompasses four stages: initial pore compaction, linear elastic deformation, micro-crack propagation, and post-peak failure development. (3) Appropriately increasing the content of DG, FA, and LT and appropriately reducing the content of SS can effectively improve the mechanical properties of CB samples and contribute to the formation of hydration products by hydration reaction. The internal hydration products within the CB specimens encompass ettringite AFt (3CaO·Al₂O₃·3CaSO₄·32 H₂O) and C-(A)-S-H gel, with the latter demonstrating superior binding properties compared to AFt. As the curing age increases, the quantity of hydration products correspondingly grows. Furthermore, CB samples prepared with an optimal solid waste ratio exhibit a more compact internal microstructure. This work provides theoretical support for seeking the best proportions of multiple industrial solid wastes, such as lithium mica mine tailings, as backfill materials, while significantly reducing the cement costs associated with conventional filling and the handling burden of tailings generated from lithium mine extraction.

Mechanical strength and microstructure of ultra‐high‐performance cementitious composite with glass powder substituted cement/silica fume

AbstractUltra‐high‐performance cementitious composite (UHPCC) incurs higher economic costs and resource wastage due to its high cement/silica fume (SF) content. The paper aims to achieve sustainability and environmental friendliness of UHPCC by substituting cement/SF with glass powder (GP). The influence of various GP particle sizes and substitution levels on the mechanical properties of UHPCC was investigated. X‐ray diffraction and scanning electron microscopy were employed to analyze the impact of GP on the hydration process of UHPCC from a microscopic perspective. In addition, the internal damage pattern of GP‐UHPCC was simulated by the RFPA3D program. The results show that the addition of GP could achieve superior fluidity than GP‐0. Compared to conventional UHPCC, GP‐20 exhibits improved strength, initial flexural toughness, and residual flexural toughness. Furthermore, finer GP particle sizes contribute to enhanced matrix strength and flexural energy absorption capacity to some extent. Additionally, the incorporation of 5%–20% GP leads to an increase in the characteristic peaks of hydrated lime and C‐S‐H gel, which are beneficial to improving the internal microstructure of the matrix. Based on the RFPA3D program, the crack area, principal stress distribution, and acoustic emission energy of specimens with 15%–25% GP substitution levels were significantly higher than those of specimens with low substitution levels (0%–10%). Generally speaking, a GP substitution level of 15%–25% is found the most effective range for improving strength, and toughness behavior in this study.

Nanomechanical Analysis of Living Small Extracellular Vesicles to Identify Gastric Cancer Cell Malignancy Based on a Biomimetic Peritoneum.

Gastric cancer is one of the most prevalent digestive malignancies. The lack of effective in vitro peritoneal models has hindered the exploration of the potential mechanisms behind gastric cancer's peritoneal metastasis. An accumulating body of research indicates that small extracellular vesicles (sEVs) play an indispensable role in peritoneal metastasis of gastric cancer cells. In this study, a biomimetic peritoneum was constructed. The biomimetic model is similar to real peritoneum in internal microstructure, composition, and primary function, and it enables the recurrence of peritoneal metastasis process in vitro. Based on this model, the association between the mechanical properties of sEVs and the invasiveness of gastric cancer was identified. By performing nanomechanical analysis on sEVs, we found that the Young's modulus of sEVs can be utilized to differentiate between malignant clinical samples (ascites) and nonmalignant clinical samples (peritoneal lavage). Furthermore, patients' ascites-derived sEVs were verified to stimulate the mesothelial-to-mesenchymal transition, thereby promoting peritoneal metastasis. In summary, nanomechanical analysis of living sEVs could be utilized for the noninvasive diagnosis of malignant degree and peritoneal metastasis of gastric cancer. This finding is expected to contribute future treatments.

Theoretical and experimental study on the radiative properties of Parachlorella kessleri: considering the effect of internal microstructure.

A microalgal cell model with multiple organelles considering both the irregular overall shape and internal microstructure was proposed. The radiative properties of Parachlorella kessleri during the normal phase, starch-rich phase, and lipid-rich phase were calculated by the discrete dipole approximation method in the visible wavelengths. The accuracy of the model is verified with experimental measurements. The results showed that the theoretical calculation of the established microalgal cell model is more accurate than those of the equal volume spheres, such as the homogeneous sphere and the coated sphere, with the errors of the scattering cross-section reduced by more than 10.7%. The calculated scattering phase function of the multi-component model is basically in good agreement with the experimental results. Compared to the normal growth phase, the lipid enrichment during the lipid-rich phase leads to a sharp increase in the scattering cross-section by three to four times, while the absorption cross-section remains stable. Remarkably, in the starch-rich phase, the abundant production of starch results in a reduction of two to three times in the absorption cross-section compared to the normal growth phase, while the scattering cross-section varies little. The results can provide basic data and theoretical support for the design and optimization of photobioreactors.

Advanced analysis of disintegrating pharmaceutical compacts using deep learning-based segmentation of time-resolved micro-tomography images

The mechanism governing pharmaceutical tablet disintegration is far from fully understood. Despite the importance of controlling a formulation's disintegration process to maximize the active pharmaceutical ingredient's bioavailability and ensure predictable and consistent release profiles, the current understanding of the process is based on indirect or superficial measurements. Formulation science could, therefore, additionally deepen the understanding of the fundamental physical principles governing disintegration based on direct observations of the process. We aim to help bridge the gap by generating a series of time-resolved X-ray micro-computed tomography (μCT) images capturing volumetric images of a broad range of mini-tablet formulations undergoing disintegration. Automated image segmentation was a prerequisite to overcoming the challenges of analyzing multiple time series of heterogeneous tomographic images at high magnification. We devised and trained a convolutional neural network (CNN) based on the U-Net architecture for autonomous, rapid, and consistent image segmentation. We created our own μCT data reconstruction pipeline and parameterized it to deliver image quality optimal for our CNN-based segmentation. Our approach enabled us to visualize the internal microstructures of the tablets during disintegration and to extract parameters of disintegration kinetics from the time-resolved data. We determine by factor analysis the influence of the different formulation components on the disintegration process in terms of both qualitative and quantitative experimental responses. We relate our findings to known formulation component properties and established experimental results. Our direct imaging approach, enabled by deep learning-based image processing, delivers new insights into the disintegration mechanism of pharmaceutical tablets.

Rheological Characterization of a Thixotropic Semisolid Slurry by Means of Numerical Simulations of Squeeze-Flow Experiments

We propose a methodology for the rheological characterization of a semisolid metal slurry using experimental squeeze-flow data. The slurry is modeled as a structural thixotropic viscoplastic material, obeying the regularized Herschel–Bulkley constitutive equation. All rheological parameters are assumed to vary with the structure parameter that is governed by first-order kinetics accounting for the material structure breakdown and build-up. The squeeze flow is simulated using finite elements in a Lagrangian framework. The evolution of the sample height has been studied for wide ranges of the Bingham and Reynolds numbers, the power-law exponent as well as the kinetics parameters of the structure parameter. Systematic comparisons have been carried out with available experimental data on a semisolid aluminum alloy (A356), where the sample is compressed from its top side under a specified strain of 80% at a temperature of 582 °C, while the bottom side remains fixed. Excellent agreement with the experimental data could be achieved provided that at the initial instances (up to 0.01 s) of the experiment, the applied load is much higher than the nominal experimental load and that the yield stress and the power-law exponent vary linearly with the structure parameter. The first assumption implies that a different model, such as an elastoviscoplastic one, needs to be employed during the initial stages of the experiment. As for the second one, the evolution of the sample height can be reproduced allowing the yield stress to vary from 0 (no structure) to a maximum nominal value (full structure) and the power-law exponent from 0.2 to 1.4, i.e., from the shear-thinning to the shear-thickening regime. These variations are consistent with the internal microstructure variation pattern known to be exhibited by semisolid slurries.

Construction of the Aerogel Thermal Conductivity Model based on k×k Sierpinski Carpet Fractal Units

With the characteristics of low density, high specific surface area, and high porosity, aerogel boasts prominent advantages in the field of thermal protection. The thermal insulation performance of aerogel has a significant relationship with its internal microstructure. In this study, the thermal conduction model of Sierpinski aerogel filled with solid in ga
 With the characteristics of low density, high specific surface area, and high porosity, aerogel boasts prominent advantages in the field of thermal protection. The thermal insulation performance of aerogel has a significant relationship with its internal microstructure. In this study, the thermal conduction model of Sierpinski aerogel filled with solid in gas is established based on the equivalent circuit method. We calculated the optimal fractal unit structure of the aerogel via its porosity, applied it to the thermal conductivity calculation of four types of aerogels, and revealed the average relative error of less than 11.58%, which is lower than the calculation results of the thermal conductivity model of the aerogel with the fractal unit structure of , indicating the effectiveness and reliability of the proposed thermal conductivity prediction model.
 s is established based on the equivalent circuit method. We calculated the optimal fractal unit structure of the aerogel via its porosity, applied it to the thermal conductivity calculation of four types of aerogels, and revealed the average relative error of less than 11.58%, which is lower than the calculation results of the thermal conductivity model of the aerogel with the fractal unit structure of , indicating the effectiveness and reliability of the proposed thermal conductivity prediction model.

Effect of Process Parameters in Additively Manufactured Sensors prepared via Material Extrusion Processes: Correlation among Electrical, Mechanical and Microstructure Properties

Fusion-based Material Extrusion (MEX) Additive Manufacturing (AM) processes have been extensively used for the fabrication of smart structures with embedded sensors, proving to have several benefits such as reduction in cost, manufacturing time, and assembly. A major issue negatively affecting 3D printed sensors is related to their poor electrical conductivity, as well as inconsistent electrical performance, which leads to electrical power losses amongst other issues. In the present paper, a set of process parameters (ironing, printing temperature, and infill overlap) has been analyzed by performing a Design of Experiment (DoE) factorial plan to minimize the electrical resistance. The best process parameters configuration involves a remarkable reduction of electrical resistance of 47.9%, as well as an improvement of mechanical properties of 31.9% (ultimate tensile strength), 25.8% (elongation at break) and 28.14% (flexural stress). The microstructure of the obtained results has also been analyzed by employing a high-resolution, X-ray Computed Tomography (X-Ray CT) system showing a reduction of intralayer voids of 19.5%. This work demonstrates a clear correlation between process parameters and the corresponding electrical properties, mechanical properties, and internal microstructure. In the present research, it has been shown that i) it is possible to significantly improve the overall 3D printed sensors performance by process parameter selection, and ii) small changes in the microstructure lead to remarkable improvements in electrical and mechanical performance.

Experimental investigation on efficient thermal management of autonomous underwater vehicle battery packs using anisotropic expanded graphite/paraffin composite materials

The thermal safety issue of battery packs is very prominent in the field of electrically powered AUVs. However, there has been few previous studies for AUV battery thermal management. In this study, anisotropic high-performance CENG/PCM composite materials were prepared and their internal microstructure was characterized by SEM, XRD, Raman spectroscopy, and TEM. A modified correlation was proposed to predict the latent heat and thermal conductivity of CPCM. In addition, the systematic experimental study was conducted on the thermal management of AUV battery modules using CENG/PCM. A new criterion called available mass energy density considering the weight and temperature control performance of CENG/PCM has been proposed to evaluate the comprehensive thermal management performance of battery packs. The results show that CENG can significantly improve the thermal conductivity of PCM. When the CENG density is 0.3 g/cm3, the thermal conductivity of CENG/PCM in the perpendicular and parallel compression directions is 118.7 and 31 times higher than that of pure PCM, respectively. CENG/PCM has demonstrated excellent thermal management performance. Compared to the battery module without CENG/PCM, the maximum temperature of the battery module with CENG/PCM decreased by 29.9 % and the temperature difference decreased by 55.3 % at 2C discharge rate. The optimal thickness of CENG/PCM is recommended to be 30 mm, and when the mass of the battery module increases by 16.84 %, the available mass energy density increases by 63.55 %. The findings of this study contribute to promoting the commercial application of CENG/PCM composite materials in thermal management of autonomous underwater vehicle battery packs.