Intrinsic Material Characteristics Research Articles

A numerical study of Mullins softening effects on mode I crack propagation in viscoelastic solids

This paper presents a finite element analysis of steady-state crack propagation in viscoelastic soft solids exhibiting Mullins softening. A cohesive-zone model is employed to simulate the localized processes at the tip of a Mode I crack in materials governed by viscoelastic behavior and damage-induced Mullins effects. The study numerically evaluates the intrinsic dissipation characteristics of typical rubber-like materials, focusing on the influence of key factors such as Mullins damage, relaxation modulus, and relaxation time. The impact of these factors on material toughening is examined, with particular emphasis on their role in crack propagation. The results reveal that crack propagation velocity is highly sensitive to the interplay between energy dissipation mechanisms. Specifically, Mullins damage parameters are shown to increase fracture toughness by raising the local energy release rate threshold at the crack tip. Additionally, the relaxation modulus enhances viscous dissipation, further elevating this threshold and subsequently reducing crack propagation velocity. Interestingly, an inverse relationship between relaxation time and crack propagation velocity is observed. The study provides a detailed analysis of the dissipation mechanisms at the crack tip, offering valuable insights for improving material toughness.

Light-Driven Multidirectional Bending in Artificial Muscles.

Using light to drive polymer actuators can enable spatially selective complex motions, offering a wealth of opportunities for wireless control of soft robotics and active textiles. Here, the integration of photothermal components is reported into shape memory polymer actuators. The fabricated twist-coiled artificial muscles show on-command multidirectional bending, which can be controlled by both the illumination intensity, as well as the chirality, of the prepared artificial muscles. Importantly, the direction in which these artificial muscles bend does not depend on intrinsic material characteristics. Instead, this directionality is achieved by localized untwisting of the actuator, driven by selective irradiation. The reaction times of this bending system are significantly - at least two orders of magnitude - faster than heliotropic biological systems, with a response time up to one second. The programmability of the artificial muscles is further demonstrated for selective, reversible, and sustained actuation when integrated in butterfly-shaped textiles, along with the capacity to autonomously orient toward a light source. This functionality is maintained even on a rotating platform, with angular velocities of 6°/s, independent of the rotation direction. These attributes collectively represent a breakthrough in the field of artificial muscles, intended to adaptive shape-changing soft systems and biomimetic technologies.

Solving Spectrum Unmixing as a Multi-Task Bayesian Inverse Problem with Latent Factors for Endmember Variability

With the increasing customization of spectrometers, spectral unmixing has become a widely used technique in fields such as remote sensing, textiles, and environmental protection. However, endmember variability is a common issue for unmixing, where changes in lighting, atmospheric, temporal conditions, or the intrinsic spectral characteristics of materials, can all result in variations in the measured spectrum. Recent studies have employed deep neural networks to tackle endmember variability. However, these approaches rely on generic networks to implicitly resolve the issue, which struggles with the ill-posed nature and lack of effective convergence constraints for endmember variability. This paper proposes a streamlined multi-task learning model to rectify this problem, incorporating abundance regression and multi-label classification with Unmixing as a Bayesian Inverse Problem, denoted as BIPU. To address the issue of the ill-posed nature, the uncertainty of unmixing is quantified and minimized through the Laplace approximation in a Bayesian inverse solver. In addition, to improve convergence under the influence of endmember variability, the paper introduces two types of constraints. The first separates background factors of variants from the initial factors for each endmember, while the second identifies and eliminates the influence of non-existent endmembers via multi-label classification during convergence. The effectiveness of this model is demonstrated not only on a self-collected near-infrared spectral textile dataset (FENIR), but also on three commonly used remote sensing hyperspectral image datasets, where it achieves state-of-the-art unmixing performance and exhibits strong generalization capabilities.

Recent progress in transmissive and reflective electrochromic devices for multi-color modulation

Multi-color electrochromic devices (M-ECDs), which dynamically and reversibly regulate the visible optical properties of the objects, have received significant interest in various fields such as displays, flexible intelligent electronics, smart windows and military camouflage. This review provides comprehensive summaries of the latest advances in inorganic electrochromic materials and M-ECDs. We discuss the basic principles for achieving M-ECDs, from the intrinsic multicolor characteristics of materials to a combination with optical structures. The progress on the construction of multicolor electrochromic thin-films and associated devices are unfolded in detail based on their transmissive or reflective working scenarios. Moreover, the limitations and challenges are also outlined for consideration for the future development of M-ECDs.

Dirac fermions in monolayer blue phosphorus: A multi-orbital tight-binding investigation

This work is a theoretical investigation of the energy dispersion bands of blue phosphorus (buk-P) system within the multi-orbital tight-binding (MOTB) approach. The aim is to corroborate the presence of Dirac fermions, as observed in a recent experimental study. The existence of the Dirac cone at the high-symmetry K point primarily arises from the contributions of elemental phosphorus (P) s, px, and py atomic orbitals. Note that the Fermi velocity of the monolayer buk-P system (vf≈ 2.2 × 106 m s−1) is approximately 3 times higher than that of graphene (G). This discovery classifies monolayer buk-P as a novel and scarce two-dimensional Dirac material. Furthermore, it has been reported that these Dirac fermions exhibit remarkable adaptability along the Γ–K region while preserving their degeneracy intact.Here, we quantitatively improve the overall tight-binding (TB) picture of the monolayer buk-P throughout the Brillouin zone (BZ) by engaging more neighboring interacting sites up to the fifth intra-layer nearest-neighbors (5NN). However, our models reproduce the computations based on the DFT approach and the experimental findings quite accurately.To the best of our knowledge, this work is the first to systematically investigate the presence of Dirac cone in monolayer buk-P system within the MOTB model. This rigorous analytical approach, along with the experimental observations and DFT computations, holds significant promise for exploring the intrinsic characteristics of Dirac materials beyond buk-P. Moreover, the observed electronic properties and high Fermi velocity make this material a highly promising candidate for future high-performance nano-electronic devices.

Scanning Tunneling Spectroscopy Method for the Prediction of Semiconductor Heterojunction Performance as a Prequel for Device Development.

The prediction of semiconductor device performance is a persistent challenge in materials science, and the ability to anticipate useful specifications prior to construction is crucial for enhancing the overall efficiency. In this study, we investigate the constituents of a solar cell by employing scanning tunneling microscopy (STM) and spectroscopy (STS). Through our observations, we identify a spatial distribution of the dopant type in thin films of materials that were designed to present major p-doping for germanium sulfide (GeS) and dominant n-doping for tin disulfide (SnS2). By generating separate STS maps for each semiconductor film and conducting a statistical analysis of the gap and doping distribution, we determine intrinsic limitations for the solar cell efficiency that must be understood prior to processing. Subsequently, we fabricate a solar cell utilizing these materials (GeS and SnS2) via vapor phase deposition and carry out a characterization using standard J-V curves under both dark/illuminated irradiance conditions. Our devices corroborate the expected reduced efficiency due to doping fluctuation but exhibit stable photocurrent responses. As originally planned, quantum efficiency measurements reveal that the peak efficiency of our solar cell coincides with the range where the standard silicon solar cells sharply decline. Our STS method is suggested as a prequel to device development in novel material junctions or deposition processes where fluctuations of doping levels are retrieved due to intrinsic material characteristics such as the occurrence of defects, roughness, local chemical segregation, and faceting or step bunching.

Temperature‐Dependent Phase Transition in WS2 for Reinforcing Band‐to‐Band Tunneling and Photoreactive Random Access Memory Application

In the era of big data, negative differential resistance (NDR) devices have attracted significant attention as a means of handling massive amounts of information. While 2D materials have been used to achieve NDR behavior, their intrinsic material characteristics have produced limited performance improvements. In this article, a facile phase modification method is presented via a plasma‐assisted sulfidation process to synthesize multiphased WS2 thin films, including distorted 1 T (D‐1 T) phase and 2 H phases for photoreactive NDR devices with p‐Si. The D‐1 T phase offers a feasible route to achieve high‐performance NDR devices with excellent stability and semimetallic properties. A comprehensive investigation of experimental and computational analyses elucidates the phase transition mechanism with various temperatures and electrical properties of D‐1 T WS2. In addition, optimizing electron tunneling in the multiple‐phased tungsten disulfide (MP‐WS2)/p‐Si heterojunction at MP‐WS2 with 77.4% D‐1 T phase results in superior NDR performance with a peak‐to‐valley current ratio of 13.8 and reliable photoreactive random‐access memory. This unique phase engineering process via plasma‐assisted sulfidation provides a pioneering perspective in functionalization and reliability for next‐generation nanoelectronics.

A comparative study on silicon-based negatrode materials in metallic cavity electrode and button half cell — Uncovering unseen microscopic and dynamic features

The electrochemical characterization of lithium storage materials using the button cell is commonplace, but it is also tedious and time-consuming. Also, the results are often affected by the use of the binders and separator membranes, and by the electrode forming and cell assembly methods. To study the changes in materials before and after dis-/charging, one has to break up the button cell and disturb the packing structure of electrode. In this work, the metallic cavity electrode made of copper (Cu-MCE) was used to study silicon-based negative electrode (negatrode) materials during electrochemical de-/lithiation. The initial apparent reaction area (i.e. the contacting area between the Cu substrate and the active materials, 0.785 mm2) of the Cu-MCE was much smaller than that of the half-button cell (153.86 mm2), reducing significantly the overall current and hence polarization in the Cu-MCE. Powders of commercial silicon and phosphorus-doped silicon (P-doped Si) were tested in the Cu-MCE and a conventional button cell. Cyclic voltammograms (CVs) recorded using the Cu-MCE showed full activation in the first cycle, unlike the button cell whose CVs expanded continuously beyond 5 cycles. Current peaks on the CVs of the Cu-MCE agreed with the expected redox reactions but were more pronounced. The subtle differences between P-doped Si and pure Si could also be revealed by the Cu-MCE with the current peaks becoming more obvious, apparently due to modification in material structures and improved ion transport dynamics. The peak currents on the CVs of the Cu-MCE were plotted against the square root of scan rate (v1/2), showing non-linearity for the two oxidation peaks at 0.35 and 0.54 V, indicating both diffusion and surface of the delithiation processes. Linear plots were obtained for the two reduction peaks at 0.165 and 0.245 V with comparable slopes (−0.024 and 0.029 mA mV−1/2 s1/2), confirming diffusion control with insignificant polarization. However, similar analyses of the button cell revealed diffusion control in both oxidation and reduction, indicating slower dynamics with large polarization to delithiation. More importantly, the Cu-MCE can be inspected directly after dis-/charging without any disturbance, and provides unseen variation in the packing structure, particle morphology, and elemental information of the active materials. It is hoped that the higher accuracy, better details, and greater efficiency offered by the Cu-MCE for studying the intrinsic electrode reaction characteristics of Si-based electrode materials can be extended to other powdery materials for charge storage.

The perspectives and trends of THz technology in material research for future communication - a comprehensive review

In recent years, the realm of terahertz (THz) has seen a new paradigm of unprecedented development and offered new possibilities to strengthen the communication sector by studying the dielectric properties of different materials. The aim of this article is to present a comprehensive review of various THz technologies that have been employed to investigate the intrinsic characteristics of different materials. In addition, the study highlights the significance use of THz wave guides with some discussion on sources, and detectors and components. Towards the end, it highlights the future trends of THz technology and the challenges. The paper concludes that THz technology has a promising potential and offer new opportunities for applications in characterization of composite materials.

Theory, Method and Practice of Metal Deformation Instability: A Review

Deformation instability is a macroscopic and microscopic phenomenon of non-uniformity and unstable deformation of materials under stress loading conditions, and it is affected by the intrinsic characteristics of materials, the structural geometry of materials, stress state and environmental conditions. Whether deformation instability is positive and constructive or negative and destructive, it objectively affects daily life at all times and the deformation instability based on metal-bearing analysis in engineering design has always been the focus of attention. Currently, the literature on deformation instability in review papers mainly focuses on the theoretical analysis of deformation instability (instability criteria). However, there are a limited number of papers that comprehensively classify and review the subject from the perspectives of material characteristic response, geometric structure response, analysis method and engineering application. Therefore, this paper aims to provide a comprehensive review of the existing literature on metal deformation instability, covering its fundamental principles, analytical methods, and engineering practices. The phenomenon and definition of deformation instability, the principle and viewpoint of deformation instability, the theoretical analysis, experimental research and simulation calculation of deformation instability, and the engineering application and prospect of deformation instability are described. This will provide a reference for metal bearing analysis and deformation instability design according to material deformation instability, structural deformation instability and localization conditions of deformation instability, etc. From the perspective of practical engineering applications, regarding the key problems in researching deformation instability, using reverse thinking to deduce and analyze the characteristics of deformation instability is the main trend of future research.

Dimension-dependent intrinsic point defect characteristics of binary photovoltaic materials

Because the absorption layer materials in solar cells have different dimensions, they have different material properties. Defect formation energy can increase with the increase of material dimensions.

Research advance of lithium-rich cathode materials in all-solid-state lithium batteries

The development of all-solid-state lithium batteries with high energy density, long cycle life, low cost and high safety is one of the important directions for the developing next-generation lithium-ion batteries. Lithium-rich cathode materials have been widely used in liquid lithium batteries for their higher discharge specific capacity (> 250 mAh/g) and energy density (> 900 Wh/kg), high thermal stability and low raw material cost. With the rapid development of high-performance lithium-rich cathode materials and solid-state electrolytes in all-solid-state lithium batteries, the application of lithium-rich cathode materials in all-solid-state lithium batteries is expected to make a breakthrough toward the target of 500 Wh/kg energy density of lithium-ion batteries. In this review, first, we elaborate the failure mechanism of lithium-rich cathode materials in all-solid-state lithium batteries. The poor electronic conductivity, irreversible redox reaction of anionic oxygen and structute transformation during the electrochemical cycling of lithium-rich cathode materials result in the low initial coulomb efficiency, poor cycling stability and voltage decay. In addition, the high operating voltage of lithium-rich cathode materials (> 4.5 V <i>vs</i>. Li/Li<sup>+</sup>) triggers off not only the conventional interfacial chemical reactions between anode and electrolyte, but also the release of oxygen, aggravating the interfacial electrochemical reactions, which reduces the stability of the cathode/electrolyte interface. Therefore, the intrinsic characteristics of lithium-rich cathode materials and the severe interfacial reaction of lithium-rich cathode/electrolyte greatly limit the application of lithium-rich cathode materials in all-solid-state lithium batteries. Then, we review the research progress of lithium-rich cathode materials in various solid-state electrolyte systems in recent years. The higher room temperature ionic conductivity and wider voltage window of inorganic solid-state electrolytes provide opportunities for the application of lithium-rich cathode materials in all-solid-state lithium batteries. At present, the application of lithium-rich cathode materials in all-solid-state lithium batteries is explored on the basis of sulfide, halide and oxide solid-state electrolyte systems, and important progress has been made in the studies of composite cathode preparation methods, interfacial reaction mechanisms and activation mechanisms. Finally, we summarize the current research hotspot of lithium-rich cathode all-solid-state lithium batteries and propose several strategies for their future studies, such as the regulation of cathode material components, the construction of lithium ion and electron transport pathways within the composite cathode, and the interfacial modification of cathode materials that have been shown to have significant effects in solving the failure problem.

Intelligent Control of SMART Materials for Energy Harvesting and Storage Devices

The investigation of innovative materials and intelligent control systems has been motivated by the desire to provide sustainable energy solutions, with the aim of improving the efficiency and adaptability of energy harvesting and storage devices. This study introduces an innovative methodology to tackle this issue by combining SMART (Self-Monitoring, Analysing, and Reporting Technology) materials with sophisticated intelligent control approaches. The system under consideration utilises the intrinsic material characteristics of SMART materials, including piezoelectric, thermoelectric, and shape memory alloys, with the objective of capturing and transforming ambient energy into electrical power that can be effectively utilised. In order to fully harness the capabilities of SMART materials, a novel control framework is proposed that integrates machine learning algorithms, real-time sensor data, and adaptive control procedures. The intelligent control system enhances the effectiveness and durability of energy harvesting and storage devices by effectively adjusting to different operational situations and optimising energy conversion and storage processes. The findings demonstrate significant enhancements in energy conversion efficiency as well as notable advancements in the longevity and dependability of energy systems utilising SMART materials. Furthermore, the capacity of the control system to adjust to various environmental circumstances and energy sources situates this research at the forefront of cutting-edge energy technology.

Mesoporous Silica and Oligo (Ethylene Glycol) Methacrylates-Based Dual-Responsive Hybrid Nanogels.

Polymeric-inorganic hybrid nanomaterials have emerged as novel multifunctional platforms because they combine the intrinsic characteristics of both materials with unexpected properties that arise from synergistic effects. In this work, hybrid nanogels based on mesoporous silica nanoparticles, oligo (ethylene glycol) methacrylates, and acidic moieties were developed employing ultrasound-assisted free radical precipitation/dispersion polymerization. Chemical structure was characterized by infrared spectroscopy and nuclear magnetic resonance. Hydrodynamic diameters at different temperatures were determined by dynamic light scattering, and cloud point temperatures were determined by turbidimetry. Cell viability in fibroblast (NIH 3T3) and human prostate cancer (LNCaP) cell lines were studied by a standard colorimetric assay. The synthetic approach allows covalent bonding between the organic and inorganic components. The composition of the polymeric structure of hybrid nanogels was optimized to incorporate high percentages of acidic co-monomer, maintaining homogeneous nanosized distribution, achieving appropriate volume phase transition temperature values for biomedical applications, and remarkable pH response. The cytotoxicity assays show that cell viability was above 80% even at the highest nanogel concentration. Finally, we demonstrated the successful cell inhibition when they were treated with camptothecin-loaded hybrid nanogels.

Evolution of PEKK crystallization measured in laser sintering

The rising popularity of laser sintering (LS) technology has increased by the broadening of available materials for this process. Kepstan 6002 poly (ether ketone ketone) (PEKK) was recently launched as a high-performance polymer grade with a lower processing temperature and unique crystallization kinetics. This study aims to understand the progress of crystallization on samples manufactured throughout the laser sintering process. These results were compared with isothermal and dynamic differential scanning calorimetry (DSC) experiments with different cooling rates. Kepstan 6002 PEKK processed by high-temperature laser sintering (HT-LS) presents a kinetics of crystallization in the order of ∼10 times slower than its crystallized samples in the DSC. This result highlights the need for a part-based crystallization investigation rather than isothermal models to describe the crystallization in LS. The transmission electron microscopy (TEM) analysis reveals smaller spherulites in the samples subjected to prolonged cooling times and an almost amorphous structure for the PEKK samples exposed to almost no cooling. This experiment identified the surroundings of laser sintered particles as preferential sites for crystallization initiation, which grows as the particles penetrate the molten layers and spherulites are formed. The slower kinetics of crystallization of Kepstan 6002 PEKK grade improve the adhesion between layers in laser sintering and enable tailoring its properties according to the application. Understanding the relationship between intrinsic material characteristics and the resulting final properties is vital to optimizing the process and controlling the final performance of PEKK for different applications.

Evaluating the potential use of recycled glass fibers for the development of gypsum-based composites

The concerns on the recyclability of composites are rising. Finding ways to reuse composite materials is fundamental given their huge availability worldwide. However, the intrinsic characteristics of composite materials make it hard to recover their primary constituents. Therefore, the incorporation of these materials after their typical life span into other applications is of great importance towards their circularity and valorisation. In this paper we evaluate the possibility of recycled fiberglass sheets to be used for the creation of gypsum-based composites, aiming at improving the mechanical properties when compared to conventional gypsum. We benchmark the effect of adding recycled fibers against the use of virgin ones. Neat gypsum plaster was used as the matrix and reinforced with both commercial E-glass and recycled fibers. The addition of recycled fibers into the gypsum matrix modified the material behaviour, preventing a purely brittle behaviour, and increasing the flexural strength by 66 % when 6 wt. % was added. The addition of virgin E-glass fibers not only allows for massive plastic deformation of the composite but also increases its flexural strength by nearly 290 % when a mass fraction of 12 wt. % of E-glass was added.

Exploring the Alişar IV Pottery in Anatolia

This paper discusses some of the major problems concerning Alişar IV pottery. The question of the origin of this peculiar pottery typology is far from solved and it now requires a new approach based on its intrinsic material characteristics. The lack of a unique definition and the absence up until now of clear primary finding contexts make the reconstruction of the production of Alişar IV even more complex. Given this, the study of the different steps of production, the so-called chaîne opératoire, can bring to light new and important information. It might permit the identification of possible workshops and a better understanding of the phenomena of trade and exchange within the local and regional context of Anatolia during the Middle Iron Age. In addition, important new data has come from the site of Uşaklı Höyük (Yozgat) located in central-northern Anatolia. The assemblage of Alişar IV pottery discovered on this site adds some interesting observations regarding the elements of variability involved in this kind of production that could be related to a multiregional and polycentric system of distribution.

Superior High-Temperature Strength in a Supersaturated Refractory High-Entropy Alloy.

Refractory high-entropy alloys (RHEAs) show promising applications at high temperatures. However, achieving high strengths at elevated temperatures above 1173K is still challenging due to heat softening. Using intrinsic material characteristics as the alloy-design principles, a single-phase body-centered-cubic (BCC) CrMoNbV RHEA with high-temperature strengths (beyond 1000MPa at 1273 K) is designed, superior to other reported RHEAs as well as conventional superalloys. The origin of the high-temperature strength is revealed by in situ neutron scattering, transmission-electron microscopy, and first-principles calculations. The CrMoNbV's elevated-temperature strength retention up to 1273 K arises from its large atomic-size and elastic-modulus mismatches, the insensitive temperature dependence of elastic constants, and the dominance of non-screw character dislocations caused by the strong solute pinning, which makes the solid-solution strengthening pronounced. The alloy-design principles and the insights in this study pave the way to design RHEAs with outstanding high-temperature strength.

Compressed acoustic sealing foam optimization investigation using statistical approach

In industry segments such as automotive and industrial equipment the use of compressed porous materials is well known to improve the global acoustic performance of the complete system. Such porous materials should be designed in a specific way in order to reach a significant acoustic sealing performance at different compression rates. Unfortunately, there are no standard measurement procedures nor predefined material characteristics that allow the selection of the right material with the optimal acoustic performance. The main goal of this research is to link acoustic performance of compressed porous materials with intrinsic material characteristics using statistical techniques.

Non-destructive defect level analysis of graphene using amplitude-modulated discharge current analysis

The intrinsic characteristics of novel devices and materials are often misunderstood due to the characterization methods which are developed to analyze existing devices or materials. Even though graphene is a very well-known material, there hasn't been a proper method to assess the density and energy levels of defects in graphene non-destructively, especially after the device fabrication. Here, we report a new non-destructive defect analysis method, amplitude-modulated discharge current analysis (AMDCA). The validity of this method was confirmed using a graphene field effect transistor with physically predefined defect densities in the channel. Charge trap densities (Nct) of the order of ∼1012 cm−2 were observed at the defect level in the range of 0.15–0.29 eV. This method can be very useful for the in-depth study of graphene devices as well as other two-dimensional materials that don't have a body contact.