Structure Of Materials Research Articles

Improvement of charge trapping memory performance by modulating band alignment with oxygen plasma

Metal-oxide charge trapping memory (CTM) integration into amorphous and organic flexible devices encounters challenges due to high-temperature treatment. Our approach enhances memory performance via room-temperature oxygen plasma treatment, subtly adjusting surface band alignment without changing the original material structure and surface roughness. Infiltration of oxygen plasma induces band alignment bending, creating a barrier for charge trapping. The device with oxygen plasma treatment exhibits an impressive 19.06 V memory window and a charge trapping density of 3.58 × 1013/cm2. In comparison, the memory window of untreated device only has 5.56 V, demonstrating that oxygen plasma treatment significantly improves memory characteristics. The charge retention rate exhibits outstanding stability, potentially reaching 94% after a decade. It should be noted that careful control during plasma treatment is crucial to maintaining optimal memory effects. This facile, efficient technique, applicable to various oxide layers, offers a way for future advancements in metal-oxide CTM technology.

Sol-gel synthesis and research of inorganic compounds, hybrid functional materials and disperse systems

The results are summarised of the Seventh International Conference of CIS countries “Sol-gel synthesis and research of inorganic compounds, hybrid functional materials and disperse systems “Sol-gel 2023”, the key reports are discussed within the scientific sections: Theoretical aspects of sol-gel process; Films, coatings and membranes obtained using sol-gel technology; Hybrid organic-inorganic sol-gel materials; Xerogels, glasses and bulk ceramic materials synthesized by sol-gel method; Nano- and microstructured materials, nanotechnology; Methods of research of structure and properties of materials obtained using sol-gel synthesis.

Integrating an urban fire model into an operational wildland fire model to simulate one dimensional wildland–urban interface fires: a parametric study

Background Wildland fires that occur near communities, in the wildland–urban interface (WUI), can inflict significant damage to urban structures. Although computational models are vital in wildfires, they often focus solely on wildland landscapes. Aim We conducted a computational study to investigate WUI fire spread, encompassing both urban and wildland landscapes. Methods We developed a 1D landscape-scale semi-physical model by integrating a semi-physical urban fire spread model into an Eulerian level set model of wildfire. The model includes ignition and spread through radiation, direct flame contact and ember deposition. Key results Through a parametric study, we compare the relative change of spread rate from various structural properties and landscape layouts represented by model parameters, highlighting the significant impact of fire-resistant structure materials over surface treatments. Layout configurations play a pivotal role in fire spread, with isolated islands of combustibles effective in reducing spread rate, aligning with existing mitigation strategies. Conclusion Despite using a 1D domain and limitations on spatial and temporal variability, our model provides insights into underlying phenomena observed in WUI fires and their mitigation. It offers early-stage development of strategies for managing structure materials and landscape layouts. Implications Our model and findings provide insights into WUI fire dynamics, paving the way for advanced mitigation strategies.

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.

Preparation of microalgae-based carbon materials with Ni(OH)2 doping and their electrochemical performance

Supercapacitors are a new type of energy storage devices with many advantages. In this study a novel composite material named NiC were synthesized to improved their electrochemical performance in supercapacitors. It was composite of Ni(OH)2 and microalgae-based N-doped activated carbon materials. Activated carbon material prepared from defatted microalgae was excellent electrode material because of their nitrogen-rich characterization and porous structure. The Ni(OH)2 as a metallic material could provide considerable pseudo-capacitance for capacitors. In this study, Ni(OH)2 was successfully doped into carbon materials using a hydrothermal method at a temperature of 150 °C for 4 h. The flower-like structure of metallic materials was observed in SEM images and two forms of elemental Ni ions (Ni3+ and Ni2+) were detected in XPS. The porosity of the composite materials NiC was retained to some extent (specific surface area of 502 m2/g for sample NiC10). Moreover, the specific capacitance value of composite material NiC20 was increased by 190 % compared to its parent carbon material, indicating that the capacitive performance of the composite materials was significantly improved. The capacitance retention of NiC20//NiC20 in a two-electrode system was up to 75.29 % over 5000 cycles. This research will provide necessary information for high-performance electrochemical materials based on microalgae-based carbon materials.

Finite element simulation investigation of warping deformation during baking temperature cycle of dissimilar materials sandwich adhesive bonded structures of car body

Adhesive bonding is crucial for joining lightweight, mixed-material car bodies but can cause distortion due to changes in adhesive properties during heat curing. In this paper, based on the characteristics of the roller-hemming structures, a sandwich adhesive bonded structure of aluminum-steel dissimilar materials was designed. A viscoelastic model for the hemming adhesive was developed, and a coupled thermal-chemical-structural model was implemented in ABAQUS. Baking experiments validated the model. Stress and strain variations were analyzed to understand warping mechanisms during the temperature cycle. Further analysis results showed that decreasing heating rate, holding temperature, or increasing cooling rate can reduce deformation.

Soft-templating of biomass derivatives into edge-N doped 3D-interconnected hierarchical porous carbon for multi-scenario supercapacitive energy storage

Rational design of the pore structure for carbon materials is of great significance for solving the low specific capacitance and poor rate capability of supercapacitors. A novel soft-templating strategy is proposed by using biomass-derived sodium lignosulphonate as a carbon precursor and sublimable hexamethylenetetramine as a soft template. The hexamethylenetetramine nanoparticles are formed in the confined spaces of the precursor, and then these templates sublime to leave mesopores after the lignosulfonate transformed from linear structure to bulk structure by thermostabilization treatment. A high nitrogen content of 40 wt% in hexamethylenetetramine is also beneficial for the subsequent in-situ N-doping. The as-obtained nitrogen-doped hierarchical porous carbon microspheres possess a high specific surface area of 1416 m2 g−1 with an N-doping content of 4.32 % (86.26 % edge-N). In a two-electrode system, the soft-templating carbon exhibits a decent specific capacitance of 234 F g−1 at 0.1 A g−1, an excellent rate capability of 62.4 % at 50 A g−1, and a high energy density of 8.1 Wh kg−1 at 15.0 kW kg−1 in 6 M KOH aqueous electrolyte. Moreover, advanced additive manufacturing technology of direct ink writing was applied to construct a quasi-solid-state in-plane interdigital microsupercapacitor by using the soft-templating carbon, and it presents a superior areal/volumetric capacitance, rate performance, mechanical stability, and flexibility with PVA/H2SO4 gel electrolyte. This work broadens the pore structure engineering methodology by novel soft-templating biocarbon for multi-functional and multi-scenario energy storage systems.

Ultra-broadband and large angle metamaterial absorber based on 3D anisotropic resistive structure and magnetic material

Ultra-broadband and large angle metamaterial absorber based on 3D anisotropic resistive structure and magnetic material

Application of Kolmogorov-Sinai's Metric Entropy for the Analysis of Mechanical Properties in the Bending Test of Epoxy-Rubber-Glass Composites.

The article presents an analysis of the results obtained during the three-point bending test for seven variants of epoxy rubber-glass composites manufactured according to innovative technology. Different contents of rubber recyclate (3, 5, and 7%) and different methods of distribution of the recyclate in the composite structure (1, 2, and 3 layers with a constant share of 5% of the recyclate) were used in the tested materials. To determine the stress values at which critical failures of the tested materials are initiated in the bending test, an analysis was carried out using the Kolmogorov-Sinai (EK-S) metric entropy calculations. The analysis results showed that for each of the above-mentioned variants of the tested epoxy-glass composites, the onset of critical changes occurring in the material structure occurs below the recorded values of the flexural strength Rmg. The decrease in the RmgK-S value in relation to Rmg is different for different material variants and depends mainly on the % content of rubber recyclate and the amount and method of decomposition of rubber recyclate in the layers of the analyzed materials. The research showed that the introduction of rubber recyclate into the composition of composites has a positive effect on their strength properties. This process allows for the efficient use of hard to degrade waste and opens up the possibility of using the newly developed materials in many industrial sectors.

Application of the FDTD Method to Analyze the Influence of Brick Complexity on Electromagnetic Wave Propagation

This article presents a numerical analysis of the effects related to the propagation of electromagnetic waves in an area containing a non-ideal, non-uniform, and absorbing dielectric. The analysis concerns the influence of electrical parameters, the structure of the building material, and the layering of the wall on the values of the electric field intensity. A multivariate analysis was carried out with different conductivity values. Homogeneous materials (e.g., solid brick) can be analyzed using the analytical method. In the case of complex materials containing, e.g., hollows (brick with hollows, hollow block), it is necessary to use the numerical method. The FDTD (finite difference time domain) method was used to assess the dependence of the electric field intensity on the layering, the length of hollows in bricks, and the material loss. In order to check the correctness of the adopted numerical assumptions, a series of tests related to the discretization of the model was carried out. The article also presents the influence of changing the length of hollows in bricks on the values of the electric field intensity at a frequency of 2.4 GHz. The instantaneous field distributions and maximum values of the electric field intensity are presented. In the model with a two-layer wall, regardless of the conductivity, the field values were the same for the two models, where the difference in the percentage of ceramic mass in the brick was 8%. A 12% decrease in the percentage of ceramic mass in the brick resulted in a 15% increase in the value of the area between a single-layer and a double-layer wall made of clinker bricks. At a conductivity of 0.04 S/m for a single-layer wall, the field values were similar for all brick variants.

Monitoring of historical structural materials with computed tomography

AbstractComputed tomography (CT) is an excellent tool to solve certain engineering problems connected to material science (such as sulfate swelling, internal degradation due to freezing, and alkali silicate swelling) and to understand specific processes (frost peeling, acid action). Albeit borne and mostly used in the medical domain, CT is increasingly used in the examination of the internal structure of building materials, where degradation processes occur to the detriment of their mechanical performance and durability. This paper presents five engineering problems concerning concrete freezing and thawing, concrete at high temperatures, timber charring, spalling in asbestos‐cement pipes, and deterioration in prestressed concrete pipes due to the corrosion of metallic inserts. In each case, the degradation processes are monitored via CT, something that may be crucial in the renovation and preservation of historical structures.

Epitaxial Growth of a Three-Dimensional Hollow and Chestnut Shell Photothermal p-n Junction Photoanode.

The p-n junction, a widely studied semiconductor material structure, offers only limited improvements in photoelectrochemical (PEC) efficiency. Herein, a three-dimensional (3D) p-n junction h-Ta3N5@CoN featuring a stable chestnut shell hollow sphere structure and photothermal effect was synthesized by using an epitaxial growth strategy. The fine fibers within the sphere induce Rayleigh scattering, which scatters unabsorbed light, thereby enabling secondary absorption and enhancing light utilization. The quantum confinement effects generated by CoN fine fibers, which are sized in a few nanometers, inhibit the recombination of electron-hole pairs. Moreover, the lattice matching between Ta3N5 and CoN allows for smoother movement of carriers and nonradiative relaxation phonons along the lattice, thereby enhancing the transport of both carriers and heat. The obtained h-Ta3N5@CoN/FTO p-n junction photoanode, under near-infrared (NIR) auxiliary irradiation, demonstrates a photocurrent of 8.71 mA cm-2 at 1.23 VRHE. Moreover, the h-Ta3N5@CoN+NIR/FTO photoanode can sustain operation for 168 h, which, to my knowledge, surpasses the operational durations of all other Ta3N5-based photoanodes. This study synthesizes three-dimensional hollow chestnut shell photothermal p-n heterojunctions through an epitaxial growth strategy, endowing the material with a more efficient carrier separation and photothermal transfer efficiency.

Assessment of Physical and Mechanical Parameters of Spun-Bond Nonwoven Fabric.

The selection of an appropriate fabric for technical applications, such as protective masks, hinges on a thorough understanding of the fabric's physical and mechanical properties. This study addresses the challenge of selecting the optimal material structure for the upper layer of a protective mask, aiming to ensure adequate breathability while providing effective filtration against airborne particles and contaminants. We assessed and compared the physical-mechanical properties of five polymer spun-bond nonwoven fabrics from different suppliers. Our comprehensive evaluation included, as follows: a visual inspection; light permeability analysis; mass and thickness measurements; elongation and tensile strength tests; breathing resistance assessments; and filter penetration tests with paraffin oil. The results revealed significant variations in performance among the samples, with one fabric consistently outperforming the others across multiple parameters. Notably, this top-performing fabric met or exceeded the EN 149:2001+A1:2009 standard for breathing resistance and filtration efficiency and, in combination with additional filter layers, met the requirements or exceeded class FFP2 (filtering face piece). This study underscores the importance of meticulous material selection and quality control in optimizing PPE (personal protective equipment) performance and user safety, providing valuable insights for mask manufacturers and healthcare professionals.

Next-gen strain sensors: Self-healing, ultra-sensitive, lightweight, and durable MWCNT-silicone rubber for advanced human motion tracking

Strain sensors that have flexible wearable forms can be applied in different aspects, such as in soft robotics, human-computer interaction, motion monitoring, and medical treatment process. The main challenge is creating lightweight, flexible sensors with high sensitivity. In this study, we developed flexible strain sensors using a simple sandwich manufacturing method. To achieve this, multi-walled carbon nanotubes (MWCNTs) were chosen for their excellent conductivity, while silicone rubber (SR) provided a flexible and durable substrate. Advanced SEM-EDX and FTIR analyses were conducted to assess the material structure. Furthermore, the electromechanical performance of the sensors was thoroughly evaluated, highlighting their potential in real-world applications. Electromechanical performance evaluation showed that the SR/0.7-MWCNT/SR sensor in the 0–90 % strain range had a sensitivity of 34.47, an increase of 53.35 %, and a linearity of 0.978, an increase of 10 % compared to the SR/0.5-MWCNT/SR sensor. In addition, the sensor has extremely fast response and recovery times of 65 ms and 60 ms, respectively. The sensor is also able to withstand up to 1.200 cycles of stretching, twisting, and bending. The sensor also exhibited good autonomous electromechanical self-healing properties against physical damage. The sensor developed in the present study are proven to be used to detect human movements such as finger bending, wrist, elbow, and knee movements.

Prediction of crystal structure, phase group, and stability of 2D materials through data science coupled with DFT

Two-dimensional materials offer unique mechanical strength, electrical conductivity, and tunable electronic properties, driving advancements in electronics, energy storage, and catalysis. The crystal structure of the materials is fundamental to several properties. In this study, we employ solely the elemental features to construct a random forest classification model achieving an 82.56 % accuracy in predicting the crystal structure of the compounds. Additionally, one vs rest binary classifiers are developed for each crystal structure within our 2D materials dataset, with accuracies ranging from 86 % to 99 %, enhancing their practical utility. Features based on stoichiometric norms have been found to play a major role in the prediction because of the fact that certain crystal structures are associated with more balanced compositions, leading to lower norm values, while others with imbalances have higher norm values. It has also been observed that material compositions with an overall higher amount of p valence electrons tend to show monoclinic, orthorhombic and triclinic crystal structures. Moreover, in compounds with a lower total electronegativity of the constituent elements, the occurrence of trigonal and tetragonal systems has been found to be more probable. In a similar fashion, hexagonal crystal systems have been more often found in compounds where the sum of Van Der Waals radius of the constituent atoms is lower. To validate our model, Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) method, and Density Functional Theory (DFT) are utilized to predict the crystal structure, phase group, and stability of a 2D material.

On the feasibility of a predictive model of mechanical properties of AM Inconel 718 thin wallets produced by DED-LB process monitored with thermal methods

AbstractNickel-based superalloys are widely used in applications requiring resistance to high temperatures and high strain rates. Various additive manufacturing (AM) processes, such as Laser Metal Deposition (LMD), a Directed Energy Deposition (DED) process, can be used to produce these components. The quality of the components depends on the process parameters, so it is crucial to investigate the influence of each parameter and their combinations through extensive experimental campaigns. In this scenario, it would be very important to predict the mechanical properties of the produced components through the online monitoring of the process parameters using non-destructive techniques, such as thermography. The aim of this work was to explore the feasibility to predict the mechanical properties of Inconel 718 thin wallets around 10 mm produced by DED-LB, based on the extraction of suitable thermal features directly during the production. An experimental campaign analysed the effect of different process parameters (laser power, scan speed, powder flow rate, and energy density) on the mechanical properties achieved. All sample production was monitored with an infrared uncooled camera integrated with the laser head moving at the same scan speed. After the process, hardness measurements and tensile tests in both growth directions were carried out for each sample to evaluate the mechanical behaviour of the "as-built" coupons and the influence of selected process parameters. Macrographic analyses of the material structure were performed to determine the morphology of the passes and the degree of overlap between different passes and layers. Various thermal features and statistical models were considered to demonstrate the possibility of establishing a predictive model. The obtained results demonstrated the correlation between the hardness and the apparent temperature assuming a confidence level of 95%, and the possibility of predicting in this sense the final macrostructure and the mechanical behaviour of the printed material considering an empirical model with the R2 coefficient around 0.8.

Study on the rheological properties and compressive strength mechanism of geopolymer cementitious materials for solid waste

The large-scale storage of industrial solid waste can cause serious environmental pollution issues. Utilizing industrial solid waste to produce green cementitious materials is an effective alternative to cement. This study utilizes steel slag (SS) and calcium carbide residue (CCR) as alkaline activators, combining them with blast furnace slag (BFS) and fly ash (FA) to create SCBF cementitious materials. Investigate the flowability, setting time, rheological properties, compressive strength, pore structure, and microscopic morphology of SCBF cementitious materials under different conditions and conduct molecular dynamics simulations. The research findings indicate that with an increase in BFS content, the flow performance of SCBF decreases, setting time shortens, plastic viscosity and yield stress gradually increase, UCS increases, and the proportion of harmful pores inside the samples decreases. When SS:CCR:BFS:FA is at a ratio of 25:25:30:20, with an increase in curing temperature, the UCS of samples shows a trend of first increasing and then decreasing. The proportion of harmful pores follows a pattern of initial decrease followed by an increase. When the curing temperature is 30 °C, the proportion of harmful pores is 0.31 %, reaching a local minimum, and the UCS strength reaches 13.83 MPa. In the raw materials, SiO2 and Al2O3 aggregate with Ca2+ in an alkaline environment to form C-(A)-S-H three-dimensional network gel. The potential energy, kinetic energy, non-bonding energy, and total energy of Tobermorite 14 Å crystals gradually increase with higher curing temperatures, with the most intense molecular motion occurring at 60 °C. The research findings are beneficial for promoting the use of industrial solid waste to manufacture green cementitious materials as substitutes for cement-based materials. They also provide a theoretical basis for the industrial application of high-temperature-cured solid waste cementitious materials.

Microscopic Analysis of Structure and Wear for Metallic Materials Using SEM

Microscopic Analysis of Structure and Wear for Metallic Materials Using SEM

Solar-Adaptive Cooling Blocks Composed of Recycled Fabric.

Radiative cooling technologies have had a significant impact on advancing carbon neutrality efforts by significantly improving the passive cooling efficiency. The tandem of conduction and radiation enables solar-adaptive radiative cooling through the insulating effect of materials along with solar absorption, which affects the thermal state of materials and enhances radiative thermal transfer from the surface under solar irradiation. This enhancement is achieved by utilizing the porous polymeric structure of materials, which facilitates improved conduction pathways along with solar reflectance, while maintaining the effective emission of thermal radiation. In this particular scenario, blocks, which were made of recycled fibers, offer a great opportunity as solar-adaptive cooling materials, enabling their easy deployment for cooling applications. Herein, we have fabricated a porous block using fiber wastes that combines strong solar reflectance (92%) at the 1 μm region and high thermal infrared emittance (∼75%) at the 10 μm region. The combination of effective solar reflection and thermal infrared emission allows the fiber block to achieve a high cooling performance of approximately 68 W/m2 under solar irradiation. In addition, the fiber block works effectively for insulation during the night, thereby enhancing its heat retention capabilities. The economic and environmental advantages of the fiber block make it a cost-competitive and sustainable choice for near-market cooling technologies. This design is anticipated to expand the practical application range of passive cooling.

Gradient and De-Clustered Anionic Redox Enabled Undetectable O2 Formation in 4.5V Sodium Manganese Oxide Cathodes.

Anionic redox chemistry presents a promising approach to enhancing the energy density of oxide cathode materials. However, anionic redox reactions invariably lead to O2 formation, either as free gaseous O2 or trapped molecular O2, which destabilizes the material's structure. Here, this critical challenge is addressed by constructing a crystal structure with both gradient redox activity and de-clustered redox-active oxygen. This design strategy is directly validated by operando differential electrochemical mass spectrometry and ex situ 50K electron paramagnetic resonance, revealing no release of O2 or trapped O2 in the 4.5V P2-type sodium manganese-based layered oxide. Notably, the material exhibits a highly reversible capacity of 247mAhg-1 at 20mAg-1 and exceptional capacity retention of 91.4% after 300 cycles at 300mAg-1. In situ X-ray diffraction further suggests that the absence of O2 formation suppresses the typical P2-O2 phase transition, resulting in a minimal lattice volume change of only 0.5%. Ex situ neutron diffraction studies and theoretical calculations further elucidate that the locally ordered lattice is well-preserved, attributable to reduced cationic migrations during cycling.