Heterogeneous Materials Research Articles

Three-Dimensional Reconstruction of Retaining Structure Defects from Crosshole Ground Penetrating Radar Data Using a Generative Adversarial Network

Crosshole ground penetrating radar (GPR) is an efficient method for ensuring the quality of retaining structures without the need for excavation. However, interpreting crosshole GPR data is time-consuming and prone to inaccuracies. To address this challenge, we proposed a novel three-dimensional (3D) reconstruction method based on a generative adversarial network (GAN) to recover 3D permittivity distributions from crosshole GPR images. The established framework, named CGPR2VOX, integrates a fully connected layer, a residual network, and a specialized 3D decoder in the generator to effectively translate crosshole GPR data into 3D permittivity voxels. The discriminator was designed to enhance the generator’s performance by ensuring the physical plausibility and accuracy of the reconstructed models. This adversarial training mechanism enables the network to learn non-linear relationships between crosshole GPR data and subsurface permittivity distributions. CGPR2VOX was trained using a dataset generated through finite-difference time-domain (FDTD) simulations, achieving precision, recall and F1-score of 91.43%, 96.97% and 94.12%, respectively. Model experiments validate that the relative errors of the estimated positions of the defects were 1.67%, 1.65%, and 1.30% in the X-, Y-, and Z-direction, respectively. Meanwhile, the method exhibits noteworthy generalization capabilities under complex conditions, including condition variations, heterogeneous materials and electromagnetic noise, highlighting its reliability and effectiveness for practical quality assurance of retaining structures.

Analysis of Stress Corrosion Cracking Growth Rate in the Heat-Affected Zone of 316L Based on the Heterogeneity of the Mechanical Properties

The heterogeneity of the microstructure and mechanical properties of safe-end dissimilar metal welded joints (DMWJs) presents a challenge to the quantitative prediction of the stress corrosion cracking (SCC) growth rate directly from laboratory data. This study investigates the effect of the heterogeneity of the mechanical properties of the 316L-welded heat-affected zone (HAZ) in safe-end DWMJs on the SCC tip stress-strain field and the SCC growth rate. First, based on the analysis of microstructures in localized regions within the 316L-welded HAZ and the acquisition of material mechanical properties through microhardness testing, a user-defined material subroutine was developed to characterize the heterogeneous material properties within the 316L-welded HAZ. Then, using this finite element model with an inhomogeneous distribution of the mechanical properties of the material, the crack tip strain rates (CTSRs) at different locations within the 316L-welded HAZ were obtained. In conjunction with the FRI model, the SCC growth rates at various locations within the HAZ were determined. The results show that the closer to the 52Mw/316L fusion boundary within the 316L-welded HAZ, the greater the yield strength of the material and the higher the CTSR and predicted SCC growth rates at the characteristic distance.

Basic design of artificial membrane-less organelles using condensation-prone proteins in plant cells

Membrane-less organelles, formed by the condensation of biomolecules, play a pivotal role in eukaryotes. Artificial membrane-less organelles and condensates are effective tools for the creation of new cellular functions. However, it is poorly understood how to control the properties that affect condensate function, particularly in plants. Here, we report the construction of model artificial condensates using the condensation-prone proteins OsJAZ2 and AtFCA in a transient assay using rice (Oryza sativa) cells, and how condensate properties, such as subcellular localization, protein mobility, and size can be altered. We showed that proteins of interest can be recruited to condensates using nanobodies or chemically induced dimerization. Furthermore, by combining two types of condensation-prone proteins, we demonstrated that artificial hybrid condensates with heterogeneous material properties could be constructed. Finally, we showed that modified artificial condensates can be constructed in transgenic Arabidopsis thaliana plants. These results provide a framework for the basic design of synthetic membrane-less organelles in plants.

Detecting Multi-Scale Defects in Material Extrusion Additive Manufacturing of Fiber-Reinforced Thermoplastic Composites: A Review of Challenges and Advanced Non-Destructive Testing Techniques

Additive manufacturing (AM) defects present significant challenges in fiber-reinforced thermoplastic composites (FRTPCs), directly impacting both their structural and non-structural performance. In structures produced through material extrusion-based AM, specifically fused filament fabrication (FFF), the layer-by-layer deposition can introduce defects such as porosity (up to 10–15% in some cases), delamination, voids, fiber misalignment, and incomplete fusion between layers. These defects compromise mechanical properties, leading to reduction of up to 30% in tensile strength and, in some cases, up to 20% in fatigue life, severely diminishing the composite’s overall performance and structural integrity. Conventional non-destructive testing (NDT) techniques often struggle to detect such multi-scale defects efficiently, especially when resolution, penetration depth, or material heterogeneity pose challenges. This review critically examines manufacturing defects in FRTPCs, classifying FFF-induced defects based on morphology, location, and size. Advanced NDT techniques, such as micro-computed tomography (micro-CT), which is capable of detecting voids smaller than 10 µm, and structural health monitoring (SHM) systems integrated with self-sensing fibers, are discussed. The role of machine-learning (ML) algorithms in enhancing the sensitivity and reliability of NDT methods is also highlighted, showing that ML integration can improve defect detection by up to 25–30% compared to traditional NDT techniques. Finally, the potential of self-reporting FRTPCs, equipped with continuous fibers for real-time defect detection and in situ SHM, is investigated. By integrating ML-enhanced NDT with self-reporting FRTPCs, the accuracy and efficiency of defect detection can be significantly improved, fostering broader adoption of AM in aerospace applications by enabling the production of more reliable, defect-minimized FRTPC components.

A Multi-Scale Model for Predicting Physically Short Crack and Long Crack Behavior in Metals

The fatigue behavior of metal specimens is influenced by defects, material properties, and loading. This study aims to establish a multi-scale fatigue crack growth model that describes physically short crack (PSC) and long crack (LC) behavior. The model allows the calculation of crack growth rates for uniaxial loading at different stress ratios based on the material properties and specimen geometry. Furthermore, the model integrates the Gaussian distribution theory to consider material heterogeneity and the experimental measurement errors that cause fatigue scatter. The crack growth rate and fatigue life of metal specimens with different notch geometry were predicted. The curves generated by the multi-scale model were mainly consistent with the test data from the published literature at the PSC and LC stages.

Heterogeneous Catalytic Materials for Carbon dioxide Transformation: Efficient Carboxylation Cyclization to Cyclic Carbonates and Oxazolidinones

The exacerbation of environmental issues is increasingly attributed to the anthropogenic emissions of carbon dioxide (CO2) . CO2 is a cost‐effective and readily available C1 source. The conversion of CO2 into value‐added organic chemicals, such as cyclic carbonate and 2‐oxazolidinone, through carboxylation cyclization reactions shows promise in reducing carbon emissions and combating climate change. The use of catalysts can facilitate this process, with heterogeneous catalysts emerging as favorable due to their advantages of easy recovery and structural stability. This paper provides a comprehensive review of heterogeneous catalysts that have been utilized for the carboxylation cyclization of CO2 to afford cyclic carbonates and oxazolidinones in recent years. The catalysts include metal organic frameworks, covalent organic frameworks, super‐crosslinked polymers, conjugated microporous polymers, porous ionic organic polymers, and composite materials. We give a detailed synthesis route for each type of catalysts. Furthermore, the characteristics of the catalysts, such as BET specific surface area, CO2 adsorption capacity, and catalytic performance, is summarized and analyzed to offer insights for improving heterogeneous catalysts for CO2 conversion via carboxylation cyclization reactions in future research.

Small Strain Stiffness of Sand‐Rubber Mixtures With Particle Size Disparity Effect

ABSTRACTThis study systematically investigates the small‐strain stiffness of sand‐rubber mixtures, focusing on combined particle disparity—both larger sand with smaller rubber and smaller sand with larger rubber—using the discrete element method. The effectiveness of various state variables in capturing stiffness behavior across different rubber contents and size disparities (SDs) is evaluated. Conventional state variables developed for natural sands, such as void ratio and mechanical void ratio were found to be less effective in describing the small‐strain stiffness characteristics of sand‐rubber mixtures due to distinct properties of rubber. This study then demonstrates that the stiffness contribution of rubber materials could be negligible, emphasizing that particle property disparity is more significant than SD between sand and rubber materials. Therefore, an adapted state variable, considering only active sand particles, shows improved performance for capturing the correlation between small‐strain stiffness with increasing rubber contents, suggesting its potential utility over conventional variables. Additionally, a refined void ratio, including inactive sand particles but excluding rubber, offers a practical alternative for capturing small‐strain stiffness in experimental and engineering practices, aligning with previous experimental observations. These findings underscore the need for developing more effective state variables that accurately reflect the interactions within heterogeneous materials like sand‐rubber mixtures.

A Review of the Biomimetic Structural Design of Sandwich Composite Materials.

Sandwich composites are widely used in engineering due to their excellent mechanical properties. Accordingly, the problem of interface bonding between their panels and core layers has always been a hot research topic. The emergence of biomimetic technology has enabled the integration of the structure and function of biological materials from living organisms or nature into the design of sandwich composites, greatly improving the interface bonding and overall performance of heterogeneous materials. In this paper, we review the most commonly used biomimetic structures and the fusion design of multi-biomimetic structures in the engineering field. They are analyzed with respect to their mechanical properties, and several biomimetic structures derived from abstraction in plants and animals are highlighted. Their structural advantages are further discussed specifically. Regarding the optimization of different interface combinations of multilayer composites, this paper explores the optimization of simulations and the contributions of molecular dynamics, machine learning, and other techniques used for optimization. Additionally, the latest molding methods for sandwich composites based on biomimetic structural design are introduced, and the materials applicable to different processes, as well as their advantages and disadvantages, are briefly analyzed. Our research results can help improve the mechanical properties of sandwich composites and promote the application of biomimetic structures in engineering.

Molybdenum Disulfide Induced Phase Control Synthesis of Multi‐dimensional Co3S4‐MoS2 Heteronanostructures via Cation Exchange

AbstractPhase control over cation exchange (CE) reactions has emerged as an important approach for the synthesis of nanomaterials (NMs), enabling precise determination of their reactivity and properties. Although factors such as crystal structure and morphology have been studied for the phase engineering of CE reactions in NMs, there remains a lack of systematic investigation to reveal the impact for the factors in heterogeneous materials. Herein, we report a molybdenum disulfide induced phase control method for synthesizing multidimensional Co3S4‐MoS2 heteronanostructures (HNs) via cation exchange. MoS2 in parent Cu1.94S‐MoS2 HNs are proved to affect the thermodynamics and kinetics of CE reactions, and facilitate the formation of Co3S4‐MoS2 HNs with controlled phase. This MoS2 induced phase control method can be extended to other parent HNs with multiple dimensions, which shows its diversity. Further, theoretical calculations demonstrate that Co3S4 (111)/MoS2 (001) exhibits a higher adhesion work, providing further evidence that MoS2 enables phase control in the HNs CE reactions, inducing the generation of novel Co3S4‐MoS2 HNs. As a proof‐of‐concept application for crystal phase‐ and dimensionality‐dependent of cobalt sulfide based HNs, the obtained Co3S4‐MoS2 heteronanoplates (HNPls) show remarkable performance in hydrogen evolution reactions (HER) under alkaline media. This synthetic methodology provides a unique design strategy to control the crystal structure and fills the gap in the study of heterogeneous materials on CE reaction over phase engineering that are otherwise inaccessible.

The Feasibility of Using Electrostatic Interactions for Immobilizing Ru-bda Catalysts in Covalent Organic Framework: A Proof-of-concept.

Heterogenetization of molecular catalysts effectively resolves the separation issues of homogeneous catalysts and expands their application scenarios. In recent years, more and more studies have been using non-covalent interactions to achieve the heterogenization of molecular catalysts. Herein, electrostatic attraction was used to immobilize molecular catalysts, Ru-bda small molecular catalysts in COF materials, where the charged Ru-bda catalysts were immobilized in the oppositely charged COF with a high [Ru] loading content of ~0.2 mmol [Ru] g-1 COF. The leakage experiment verified that the immobilization of Ru-bda catalysts in COF by electrostatic interactions is stable in 0.1 M HClO4 and less than 5% of molecular Ru-bda catalysts were leached into the solution in 2 hours. The chemical water oxidation experiment was conducted as a model catalysis reaction to verify the feasibility of using electrostatic interactions for immobilizing Ru-bda catalysts in COFs. The prepared Ru(bda)@COFs demonstrate a high catalytic activity of 268 μmol L-1 s-1 O2 for chemical water oxidation, illustrating the electrostatic attractions between COF and small molecules that can be used to immobilize homogeneous catalysts in heterogeneous materials. However, the robustness of COF material itself under catalytic conditions should be considered in practical applications.

Asymptotic analysis of sign-changing transmission problems with rapidly oscillating interface

We study the asymptotic behavior of a sign-changing transmission problem, stated in a symmetric oscillating domain obtained by gluing together a positive and a negative material, separated by an imperfect and rapidly oscillating interface. The interface separating the two heterogeneous materials has a periodic microstructure and is a small perturbation of a flat interface. The solution of the transmission problem is continuous and its flux has a jump on the oscillating interface. Under certain conditions on the properties of the two materials, we derive the limit problem and we prove the convergence result. The T-coercivity method is used to handle the lack of coercivity for both the microscopic and the macroscopic limit problems. For more information see https://ejde.math.txstate.edu/Volumes/2024/60/abstr.html

High external quantum efficiency photodetector based on Ga2O3/CH3NH3PbI3

In this paper, Ga2O3/CH3NH3PbI3 photodetector (PD) with high external quantum efficiency (EQE) was successfully prepared by spin coating CH3NH3PbI3 on the film surface of Ga2O3/Au MSM PD. Compared with Ga2O3 film device, the dark current of heterojunction device decreased from 5.20 to 0.09nA, and the responsivity increased from 0.18 to 14.01 A/W at 40 V bias. It is worth noting that under the same bias voltage (40 V), the EQE of Ga2O3/CH3NH3PbI3 PD is as high as 6686 %, which is 78 times of Ga2O3/Au PD (85.89 %). The high EQE is attributed to collision ionization doubling caused by the effect of an applied electric field. In addition, the construction of heterojunction speeds up the response speed of PD. This work has important implications for the selection of heterogeneous materials and the construction of PDs to optimize device performance.

Extremely Low Thermal Resistance of β-Ga2O3 MOSFETs by Co-integrated Design of Substrate Engineering and Device Packaging.

Gallium oxide (Ga2O3) emerges as a promising ultrawide bandgap semiconductor, which is expected to surpass the performance of current wide bandgap materials, like GaN and SiC, in electronic devices. However, widespread application of Ga2O3 is hindered by its extremely low thermal conductivity and lack of effective device-level thermal management strategies. In this work, Ga2O3 metal-oxide-semiconductor field-effect transistors (MOSFETs) are fabricated by conducting co-integrated design of substrate engineering with layer transferring and device packaging. 3D Raman thermography is introduced as a novel method to analyze the temperature distribution within the device, which provides valuable insights into their thermal performances. A high-quality Ga2O3-SiC heterogeneous integrated material is successfully fabricated with an extremely low interface thermal resistance of 6.67 ± 2 m2·K/GW. Compared to the homoepitaxial Ga2O3 MOSFETs, the degradation of Ion/Ioff in Ga2O3-SiC MOSFETs is decreased by 1.5 orders of magnitude, and that of Ron is decreased by 31%, showing the great thermal stability of Ga2O3-SiC MOSFETs. With the additional device packaging, a significant one order-of-magnitude reduction in the thermal resistance of the Ga2O3-SiC MOSFET is achieved, reaching a record-low value of 4.45 K·mm/W in the reported Ga2O3 MOSFETs. This work demonstrates an efficient strategy for device-level thermal management in next-generation Ga2O3 power and RF applications.

Adjusting the Structure-Activity Relationship of MOFs to Obtain Electrocatalysts with Higher Hydrogen Evolution and Urea Oxidation Performance by Introducing Different Linkers.

Three kinds of metal-organic frameworks possessing analogous structures were prepared by regulating the structure units of organic linkers. MOF/nickel foam electrocatalysts were formed by in situ hydrothermal growth of MOFs on a clean supported substrate nickel foam (NF), and the corresponding composites were prepared. We phosphatated them and obtained the heterojunction catalyst. Different structure units in the ligand have significant influences on the phosphating, resulting in heterogeneous materials that are not quite the same. Among them, heterogeneous materials with Co2P and NiP have the best catalytic performance. We also studied the urea oxidation reaction (UOR) properties of the materials and proved that it is feasible to improve the UOR performance of MOF/NF composites by regulating the structure units in the organic linkers. The results provided an idea for the reasonable selection of organic ligands to construct MOFs to regulate the electrocatalytic performance.

Estimation of local variation in Young's modulus over a gold nanocontact using microscopic nanomechanical measurement method.

Nanoscale materials tend to have a single crystal domain, leading to not only size dependence but also orientation dependence of their mechanical properties. Recently, we developed a microscopic nanomechanical measurement method (MNMM), which enabled us to obtain equivalent spring constants (force gradients) of nanocontacts while observing their atomic structures by transmission electron microscopy (TEM). Therein, we evaluated Young's modulus based on a model that a newly introduced layer at the thinnest section of a nanocontact determined the change in the measured equivalent spring constant, and discussed their size dependence. However, this model is not general for other nanomaterials that do not exhibit the introduction of a new atomic layer while stretching. In this study, using MNMM, we propose a new analytical method to directly retrieve the local Young's modulus of nanomaterials by measuring initial lattice spacing and its displacement of a local region in the TEM image during the stretching of the nanocontact. This reveals the size dependence of local Young's modulus at various positions of the nanocontact at once. As a result, our estimated Young's modulus for a gold [111] nanocontact showed a size dependence similar to the one previously reported. This indicates that this analytical method benefits in revealing the mechanical properties of not only nanomaterials but also structurally heterogeneous materials such as high-entropy alloys.&#xD.

Inverse Problem of Thermal Diagnostics of Multiply Connected Structures with Heterogeneous Materials

Inverse Problem of Thermal Diagnostics of Multiply Connected Structures with Heterogeneous Materials

A Closer Look at Heritage Systems from Medieval Colors to Modern and Contemporary Artworks

This microreview, conducted by interdisciplinary teams, examines complex heritage material systems, such as medieval colors and modern and contemporary artworks. Our multi-analytical approach, a significant aspect of our research, is a means to this end. The conservation of works of art is our shared goal, as it ensures their accessibility and the transfer of cultural heritage to future generations. We seek to interpret the damage, usefulness, and innovation of the experimental design in this context. As Jan Wouters rightly points out, “The terminology used nowadays to describe the potential damage to objects caused by analysis should be refined beyond the destructiveness/non-invasiveness polarization. A terminology should include at least degree level intervention (low, medium, high), usefulness, and innovation”. Complementing micro- or sub-micro-sampling with the appropriate analytical methods is crucial, as exemplified in medieval, modern, and contemporary collections studies. Finally, a novel perspective for exploring the information contained in the multiscale heterogeneity of organic historical materials is envisaged, and it includes UV/Visible photoluminescence spectral imaging using a low-intensity ultraviolet synchrotron beam.

VBO3/V2O3@C heterogeneous anode material with high-specific-capacity and high-stability for lithium-ion batteries

The design and synthesis of high-performance anode materials is the key to further improve the performance of lithium-ion batteries. In this study, VBO3/V2O3 heterogeneous material with high crystallinity was prepared in vacuum quartz tubes by a facile high-temperature solid-phase method, and the electron transport capacity of VBO3/V2O3 was further improved by ball-milling with conductive carbon. As a result, the obtained VBO3/V2O3@C heterogeneous anode material delivers an initial discharge specific capacity of 927 mAh·g−1 and good cycling stability. Even at −20 °C, VBO3/V2O3@C still presents a discharge specific capacity of 432 mAh·g−1. In addition, ex-situ XRD and ex-situ XPS measurements reveal the conversion reaction and (de)intercalation reaction mechanism during charge/discharge. This work deepens the understanding of the structure-activity relationship of borate/oxide heterogeneous anode materials.

Enhancing strength and ductility of CuCrZr high-conductivity alloy via lamellar heterostructures on grain boundaries

Heterogeneous lamellar structure materials have attracted extensive attention due to their exceptional strength and ductility. In this study, Y element was introduced into CuCrZr alloys to adjust the liquid phase formation temperature of the CuZrY phase during the solution annealing process. By employing cold rolling deformation prior to annealing to elongate the grains, the liquid phase was promoted to wet the elongated grain boundaries during the annealing process, ultimately forming lamellar CuZrY heterostructures distributed along the grain boundaries. The heterogeneous lamellar structure, the grain boundary distribution characteristics, and the effect of Y on stacking fault energy enhanced the hetero-deformation induced working hardening, thereby improving both the strength and ductility of the CuCrZrY alloy. Besides, the investigated CuCrZrY alloy achieved an excellent combination of tensile strength, uniform elongation, electrical conductivity and thermal conductivity, with values of 527 MPa, 10.66%, 83% IACS and 335.5 W/(m·K), respectively. Therefore, the method of controlling liquid phase temperature through composition adjustment and liquid phase infiltration path through grain deformation offers new possibilities for the design of heterogeneous lamellar structure materials.

Subsurface Spectroscopy of Thermal Degradation Inside an Inert Plastic Bonded Explosive (PBX) Simulant Using Feedback-Assisted Wavefront Shaping.

We characterize the subsurface thermal degradation of an inert analog of high-explosive molecular crystals (Eu:Y(acac)3(DPEPO)) (EYAD) embedded inside of a plastic bonded explosive simulant using feedback-assisted wavefront shaping-based fluorescence and Raman spectroscopies. This technique utilizes wavefront shaping to focus pump light inside a heterogeneous material onto a target particle, which significantly improves its spectroscopic signature. We find that embedding the EYAD crystals in the heterogeneous polymer results in improved thermal stability, relative to bare crystal measurements, with the crystal remaining fluorescent to >612 K inside of the heterogeneous material, while the bare crystal's fluorescence is fully quenched by 500 K. We hypothesize that this improvement is due to the polymer restricting the effects of EYAD melting, which occurs at 400 K and is the primary mechanism for spectroscopic changes in the temperature range explored.