Materials

26 pages, 9237 KiB

Open AccessArticle

Early Detection and Analysis of Cavity Defects in Concrete Columns Based on Infrared Thermography and Finite Element Analysis

by Fan Yang, Xianwang Zeng, Qilong Xia, Ligui Yang, Haonan Cai and Chongsheng Cheng

Materials 2025, 18(7), 1686; https://doi.org/10.3390/ma18071686 - 7 Apr 2025

Viewed by 445

Abstract

Concrete, known for its high strength, durability, and flexibility, is a core material in construction. However, defects such as voids and honeycombing often occur due to improper pouring or vibration, weakening the concrete’s strength and affecting its long-term performance. These defects typically require [...] Read more.

Concrete, known for its high strength, durability, and flexibility, is a core material in construction. However, defects such as voids and honeycombing often occur due to improper pouring or vibration, weakening the concrete’s strength and affecting its long-term performance. These defects typically require costly repairs. Therefore, timely identification and repair of such early defects is crucial for improving construction quality. This paper proposes a method for non-destructive detection of honeycomb defects in concrete using infrared thermography (IR) during the hydration stage. By analyzing the temperature differences between defect and non-defect areas based on the temperature distribution generated during hydration, defects can be detected. Furthermore, the study uses the COMSOL finite element model to explore the relationship between defect size, ambient temperature, formwork thickness, and thermal contrast. The results show that IR technology can effectively and reliably detect honeycomb defects, especially during the hydration phase. As a convenient and feasible non-destructive testing method, IR technology has significant potential for application and development in concrete defect detection. Full article

(This article belongs to the Special Issue Numerical Methods and Modeling Applied for Composite Structures)

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16 pages, 6992 KiB

Open AccessArticle

Micromagnetic and Quantitative Prediction of Hardness and Impact Energy in Martensitic Stainless Steels Using Mutual Information Parameter Screening and Random Forest Modeling Methods

by Changjie Xu, Haijiang Dong, Zhengxiang Yan, Liting Wang, Mengshuai Ning, Xiucheng Liu and Cunfu He

Materials 2025, 18(7), 1685; https://doi.org/10.3390/ma18071685 - 7 Apr 2025

Viewed by 318

Abstract

This study proposes a novel modelling approach that integrates mutual information (MI)-based parameter screening with random forest (RF) modelling to achieve an accurate quantitative prediction of surface hardness and impact energy in two martensitic stainless steels (1Cr13 and 2Cr13). Preliminary analyses indicated that [...] Read more.

This study proposes a novel modelling approach that integrates mutual information (MI)-based parameter screening with random forest (RF) modelling to achieve an accurate quantitative prediction of surface hardness and impact energy in two martensitic stainless steels (1Cr13 and 2Cr13). Preliminary analyses indicated that the magnetic parameters derived from Barkhausen noise (MBN), and the incremental permeability (IP) measurements showed limited linear correlations with the target properties (surface hardness and impact energy). To address this challenge, an MI feature screening method has been developed to identify both the linear and non-linear parameter dependencies that are critical for predicting target mechanical properties. The selected features were then fed into an RF model, which outperformed traditional multiple linear regression in handling the complex, non-monotonic relationships between magnetic signatures and mechanical performance. A key advantage of the proposed MI-RF framework lies in its robustness to small sample sizes, where it achieved high prediction accuracy (e.g., R² > 0.97 for hardness, and R² > 0.86 for impact energy) using limited experimental data. By leveraging MI’s ability to capture multivariate dependencies and RF’s ensemble learning power, it effectively mitigates overfitting and improves generalisation. In addition to demonstrating a promising tool for the non-destructive evaluation of martensitic steels, this study also provides a transferable paradigm for the quantitative assessment of other mechanical properties by magnetic feature fusion. Full article

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14 pages, 8696 KiB

Open AccessArticle

The Effect of Aging Time at 600 °C on Tensile Properties of the 0.3Nb FeCrAl Alloy

by Liping Tang, Hongying Sun, Guijun Wu, Zhangquan Lv and Yi Xiong

Materials 2025, 18(7), 1684; https://doi.org/10.3390/ma18071684 - 7 Apr 2025

Viewed by 343

Abstract

This study examines the impact of aging at 600 °C on the tensile properties of 0.3NbFeCrAl alloy at various temperatures, including room temperature (RT), 300 °C, 350 °C, and 400 °C, as well as the corresponding changes in microstructure. Results demonstrate that as [...] Read more.

This study examines the impact of aging at 600 °C on the tensile properties of 0.3NbFeCrAl alloy at various temperatures, including room temperature (RT), 300 °C, 350 °C, and 400 °C, as well as the corresponding changes in microstructure. Results demonstrate that as aging time increases, the grain size remains relatively stable, while the amount of precipitate gradually increases and becomes uniformly distributed. The tensile strength (R_m) also increases steadily with aging time, reaching its maximum after 1000 h of aging. This can be attributed to the precipitation strengthening effect of the Laves phase after 1000 h of aging. The yield strength (R_p0.2) remains constant when the specimen is stretched at room temperature, but gradually increases with both the stretching temperature and aging time. Additionally, the section shrinkage ratio (Z) exhibits a decreasing trend with aging time, except for stretching at room temperature. Nevertheless, Z remains above 50% in all other cases, indicating that the toughness of the aged specimens is maintained well. While fracture shrinkage is significant for tensile tests at RT, it exhibits minimal change with increasing aging time. Furthermore, a notable increase in the number of dimples and a decrease in their size is observed on the tensile fracture surface with aging. Full article

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32 pages, 4722 KiB

Open AccessArticle

Comparative Analysis of Energy Viability of Crop Residue from Different Corn Varieties

by Raquel García-Mateos, María Teresa Miranda, José Ignacio Arranz, Pilar Romero, Francisco José Sepúlveda and Santiago Cuellar-Borrego

Materials 2025, 18(7), 1683; https://doi.org/10.3390/ma18071683 - 7 Apr 2025

Viewed by 533

Abstract

The valorization of agricultural residues assumes a pivotal position in the circular economy by transforming waste into a useful and environmentally friendly product, with the cultivation of corn, as one of the world’s predominant crops, being crucial. This article aimed to investigate the [...] Read more.

The valorization of agricultural residues assumes a pivotal position in the circular economy by transforming waste into a useful and environmentally friendly product, with the cultivation of corn, as one of the world’s predominant crops, being crucial. This article aimed to investigate the feasibility of using residues from corn crop as biofuels, going more in-depth into determining the effect that crop variety may have on its thermal qualities. Specifically, 12 samples of corn crop residues were studied in three main groups: conventional, forage, and transgenic varieties. To achieve this, proximate and ultimate analyses, thermogravimetric analyses, and differential scanning calorimetry were conducted, along with a study of gas emissions and a statistical comparison of different varieties. From the results obtained, it is worth highlighting the low ash content in all the samples (between 5.55% and 8.42%) and high calorific values (higher than 17 MJ/kg in all cases), as well as optimal thermal results for all the samples studied in both pyrolysis and combustion processes. Significant differences were found between the different varieties; in particular, it was observed that the forage variety presented more optimal conditions for its application in both processes. This may represent a potential competitive advantage for the forage varieties. Full article

(This article belongs to the Special Issue Innovative Utilization of Biomass for Sustainable Energy Production)

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9 pages, 1633 KiB

Open AccessCommunication

Identification and Visualization Textile Fibers by Raman Imaging

by Kaili Liu and Huacai Chen

Materials 2025, 18(7), 1682; https://doi.org/10.3390/ma18071682 - 7 Apr 2025

Viewed by 341

Abstract

Textile fibers are an essential component of daily necessities and are often used as forensic evidence, making their characterization crucial in forensic science. Different types of textile fibers can be identified using their unique Raman spectral characteristic peaks. In this study, we achieved [...] Read more.

Textile fibers are an essential component of daily necessities and are often used as forensic evidence, making their characterization crucial in forensic science. Different types of textile fibers can be identified using their unique Raman spectral characteristic peaks. In this study, we achieved the visualization of single-component, multi-component, and dyed blended fibers through Raman spectral imaging, demonstrating the spatial distribution of different types of textile fibers within the same area. Furthermore, by merging Raman images of fibers from non-confocal planes, we achieved accurate visual identification, providing more possibilities for characterizing fibers with special morphological features using Raman spectral imaging. In conclusion, Raman spectral imaging enables the successful visualization and identification of different types of fibers. Full article

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22 pages, 5425 KiB

Open AccessArticle

Diffusion Mechanism in Running-Water and CFD-DEM Numerical Simulation of Expandable Particulate Grouting Material

by Zhipeng Zhang, Chenyang Ma, Chen Zhao, Zhuo Zheng, Wei Li, Rentai Liu, Xiuhao Li and Hongyan Wang

Materials 2025, 18(7), 1681; https://doi.org/10.3390/ma18071681 - 7 Apr 2025

Viewed by 258

Abstract

In order to study the diffusion and sealing mechanism of an innovative grouted material tentatively called “expandable particulate grout material”, the diffusion process was simulated by the numerical method of CFD-DEM coupling. A numerical model was established for a grouting process in an [...] Read more.

In order to study the diffusion and sealing mechanism of an innovative grouted material tentatively called “expandable particulate grout material”, the diffusion process was simulated by the numerical method of CFD-DEM coupling. A numerical model was established for a grouting process in an individual fracture based on the basic physical parameters of expandable particles. The numerical model of the expandable particulate slurry flow was established. The interaction between particles and water in different conditions, such as different grouting times, different volume fractions of the particle, and different velocities, was investigated. The differences in the diffusion process and in the running-water sealing mechanism of expandable particles, cement slurry, and cement-sodium silicate slurry in the crack (in a, in b, and in c) were analyzed. The influence of expandable particles on the streamline of the grout and the drag force in the interaction process under the fracture were analyzed. This is summarized The influence of the velocity ratio of grout to water on different physical quantities, such as diffusion opening degree, diffusion velocity, and diffusion distance, was summarized. It is of significant theoretical and practical value to further develop and improve the grouting technology. Full article

(This article belongs to the Special Issue Advances in Material Structural Analysis: Finite Element Analysis and Numerical Modelling)

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31 pages, 5436 KiB

Open AccessArticle

Study of the Relationship Between the Structures and Biological Activity of Herbicides Derived from Phenoxyacetic Acid

by Grzegorz Świderski, Natalia Kowalczyk, Gabriela Tyniecka, Monika Kalinowska, Renata Łyszczek, Aleksandra Bocian, Ewa Ciszkowicz, Leszek Siergiejczyk, Małgorzata Pawłowska and Jacek Czerwiński

Materials 2025, 18(7), 1680; https://doi.org/10.3390/ma18071680 - 7 Apr 2025

Viewed by 362

Abstract

Chloroderivatives of phenoxyacetic acid are a group of compounds commonly used as plant protection products. Differences in the molecular structure of these compounds are related to varying substitution and the number of chlorine atoms in the aromatic ring. Different molecular structures may affect [...] Read more.

Chloroderivatives of phenoxyacetic acid are a group of compounds commonly used as plant protection products. Differences in the molecular structure of these compounds are related to varying substitution and the number of chlorine atoms in the aromatic ring. Different molecular structures may affect the activity of these compounds, their physicochemical properties, as well as their toxicity and biological effects. A group of 6 chemical compounds derived from phenoxyacetic acid was tested. The molecular structure was analysed using spectroscopic methods (FTIR, FTRaman, UV-VIS, ¹HNMR, ¹³CNMR) and quantum chemical computational methods (DFT). The reactivity of the tested compounds was determined using DFT calculations and experimentally in reaction with a hydroxyl radical. The electronic charge distribution of NBO, CHelpG and ESP was analysed and aromaticity indices were calculated for theoretically modeled structures and structures examined by X-ray diffraction (data obtained from the CSD database). Phenoxyacetic acid derivatives were tested for antimicrobial activity on soil bacterial strains. Cytotoxicity tests were performed on normal human skin fibroblasts (BJ CRL-2522) and the human prostate cancer cell line (DU-145 HTB-81). The purpose of this study was to investigate the relationship between the molecular structure of phenoxyacetic acid derivatives and their reactivity and biological activity. Full article

(This article belongs to the Special Issue From Molecular to Supramolecular Materials)

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17 pages, 5690 KiB

Open AccessArticle

Evaluation of the Accuracy of a Fused Deposition Modeling Process in the Production of Low-Density ABS Lattice Structures

by Gianluca Parodo, Luca Sorrentino, Sandro Turchetta and Giuseppe Moffa

Materials 2025, 18(7), 1679; https://doi.org/10.3390/ma18071679 - 7 Apr 2025

Viewed by 327

Abstract

Fused Deposition Modeling (FDM) has emerged as one of the most widely adopted additive manufacturing (AM) technologies due to its broad material availability and low production costs, enabling the efficient production of complex geometries and customized components. Among the materials commonly used in [...] Read more.

Fused Deposition Modeling (FDM) has emerged as one of the most widely adopted additive manufacturing (AM) technologies due to its broad material availability and low production costs, enabling the efficient production of complex geometries and customized components. Among the materials commonly used in AM, Acrylonitrile Butadiene Styrene (ABS) is particularly notable for its favorable mechanical properties, ease of processing, and versatility. While moderate-to-high-density lattice configurations have been extensively studied, low relative density lattice structures remain largely unexplored. This study investigates the feasibility of fabricating Cuboidal Body-Centered Cubic (BCC) lattice structures with relative densities of 5%, 10%, and 15% using FDM. The geometrical/dimensional accuracy of the printed samples is thoroughly assessed to quantify fabrication-induced deviations, focusing on strut geometry and overall lattice consistency. Results show that while smaller lattice configurations, particularly those with 5% relative density, exhibit significant geometrical inaccuracies due to printing limitations (e.g., strut waviness, material deposition inconsistencies, layer misalignment), larger configurations demonstrate improved dimensional and geometrical fidelity and structural integrity. A framework is proposed for assessing geometrical/dimensional fidelity, which can enhance the predictive modeling of these structures and optimize manufacturing processes. These findings clarify low relative density lattice manufacturability, guiding research on mechanical performance for lightweight aerospace applications. Full article

(This article belongs to the Special Issue Nonconventional Technology in Materials Processing-3rd Edition)

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30 pages, 4998 KiB

Open AccessArticle

A Material Study of Persian-Period Silver Coins and Hacksilber from Samaria

by Dana Ashkenazi, Maayan Cohen, Haim Gitler, Mati Johananoff and Oren Tal

Materials 2025, 18(7), 1678; https://doi.org/10.3390/ma18071678 - 7 Apr 2025

Viewed by 454

Abstract

An assembly of fourth-century BCE Samarian silver coins and late-fifth-century BCE Samarian cut silver sheets, Sidonian and Philistian coins from a hacksilber hoard allegedly found in the region of Samaria belonging to the David and Jemima Jeselsohn collection, were characterized by metallurgical analyses. [...] Read more.

An assembly of fourth-century BCE Samarian silver coins and late-fifth-century BCE Samarian cut silver sheets, Sidonian and Philistian coins from a hacksilber hoard allegedly found in the region of Samaria belonging to the David and Jemima Jeselsohn collection, were characterized by metallurgical analyses. The aims of the research were to identify the items’ composition and manufacturing processes. We affirmed that the Samarian coins were made of silver–copper alloy produced by a controlled process. The microstructural and elemental analyses revealed that the sheets were produced from various materials, including pure silver, silver–copper, and silver–copper–gold alloys, whereas the Sidonian and Philistian coins were made of silver–copper alloy. Continuity in style and production techniques was observed. This information provides a better understanding of the material culture and technological skills in the Persian-period province of Samaria. Full article

(This article belongs to the Section Metals and Alloys)

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30 pages, 20540 KiB

Open AccessArticle

Study on Lateral-Load Resisting Mechanism and Capacities of Steel Frame Infilled with Composite Plate Shear Wall Under Cyclic Loading

by Hui Li, Yi Qi, Tongyang Kang and Huafei Wang

Materials 2025, 18(7), 1677; https://doi.org/10.3390/ma18071677 - 6 Apr 2025

Viewed by 303

Abstract

Steel frame infilled with composite plate shear wall (SF-CPSW) is an effective structure for lateral-load resisting. In the structural design, the vertical loads are primarily carried by the boundary SF, while the horizontal loads are expected to be totally carried by CPSW. CPSW [...] Read more.

Steel frame infilled with composite plate shear wall (SF-CPSW) is an effective structure for lateral-load resisting. In the structural design, the vertical loads are primarily carried by the boundary SF, while the horizontal loads are expected to be totally carried by CPSW. CPSW incorporates the steel web and the concrete encasements. For the CPSW bays, the boundary SF also inevitably withstands the lateral-loads due to the coordinated deformations between boundary SF and CPSW. The available researches, however, have not given a certain shear force assignment between the boundary SF and CPSW. Furthermore, their interactions under the cyclic lateral-loading are unclear. This paper conducted a study on the load-resisting mechanism of SF-CPSW by a structural model test and finite element analyses. The deformation pattern, failure mode, internal forces, and interactions of structural members were investigated. The effects of steel web and concrete thicknesses, cross-sections of boundary SF, and axial compression ratio on the lateral-load resistance of SF-CPSW were assessed. The results indicated that the interactions of CPSW and boundary SF caused significant normal stresses at the corners of CPSW, reducing the shear strength of steel web. However, the concrete encasements and boundary SF compensate it and mutually improved the stiffness and ductility. According to the analysis results, the formulas of the lateral stiffness and strengths of SF-CPSW were proposed for its seismic design. Full article

(This article belongs to the Section Construction and Building Materials)

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27 pages, 7046 KiB

Open AccessArticle

Design, Optimization, and Realization of a Magnetic Multi-Layer Quasi-Zero-Stiffness Isolation Platform Supporting Different Loads

by Shuaijie Yang, Xiuting Sun, Jiawei Qian, Jian Xu and Kaixiang Li

Materials 2025, 18(7), 1676; https://doi.org/10.3390/ma18071676 - 6 Apr 2025

Viewed by 366

Abstract

This study presents a Multi-layer Quasi-Zero-Stiffness (ML-QZS) vibration isolation platform for variable loads in large-amplitude and low-frequency dynamic environments. In one isolation mount of the proposed ML-QZS isolation platform, Multi-layer permanent magnets are constructed to generate discontinuous Multi-layer negative-stiffness regions. The first design [...] Read more.

This study presents a Multi-layer Quasi-Zero-Stiffness (ML-QZS) vibration isolation platform for variable loads in large-amplitude and low-frequency dynamic environments. In one isolation mount of the proposed ML-QZS isolation platform, Multi-layer permanent magnets are constructed to generate discontinuous Multi-layer negative-stiffness regions. The first design criterion is to achieve the low-frequency and wide-amplitude vibration isolation range for different loads. The second design criterion is carried out for the dynamic performances of transient and steady states. Since both structural design and damping determine vibration transient time and the displacement transmissibility, which often exhibit contradictions depending on system parameters, a bi-objective Pareto optimization criterion is proposed to balance the vibration transients between different layers while ensuring significant isolation effectiveness in one layer. Finally, the relevant experimental prototype is constructed, and the results verify the design principle of Multi-layer double magnetic ring construction and optimization criterions for structural parameters and damping coefficients. This study provides an advanced nonlinear isolation platform with a wide QZS range for different loads, and the optimization method to coordinate the vibration performances, which provides important theoretical and experimental guidance for the design and realization of isolation platforms in practical engineering applications for large-amplitude and low-frequency dynamic environments. Full article

(This article belongs to the Special Issue Synthesis, Functionalization, and Applications of Advanced Magnetic Materials)

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17 pages, 7517 KiB

Open AccessArticle

Molecular Simulation Study on the Impact of a Cross-Linked Network Structure on the Tensile Mechanical Properties of PBT Substrates

by Renlong Huang, Kang Zhao, Peng Cao, Liang Cao, Hongjun Liao and Xianqiong Tang

Materials 2025, 18(7), 1675; https://doi.org/10.3390/ma18071675 - 6 Apr 2025

Viewed by 291

Abstract

This study investigates the correlation between the cross-linked network structure and the macroscopic mechanical properties of 3,3-bis(azidomethyl)oxetane-tetrahydrofuran copolymer (PBT)-based solid propellants through molecular dynamics (MD) simulations. A multi-component system comprising PBT molecular chains, toluene diisocyanate (TDI), trimethylolpropane (TMP), tetraethylene glycol (TEG), and sodium [...] Read more.

This study investigates the correlation between the cross-linked network structure and the macroscopic mechanical properties of 3,3-bis(azidomethyl)oxetane-tetrahydrofuran copolymer (PBT)-based solid propellants through molecular dynamics (MD) simulations. A multi-component system comprising PBT molecular chains, toluene diisocyanate (TDI), trimethylolpropane (TMP), tetraethylene glycol (TEG), and sodium perchlorate (AP) was constructed. Perl script programming was utilized to precisely control the dynamic cross-linking reaction. Molecular models with cross-linking densities of 0%, 50%, 60%, 70%, 80%, and 90% were established, and their mechanical properties were analyzed under varying cross-link densities and strain rates through uniaxial tensile simulations. The results indicate that the formation of the cross-linked network significantly alters the energy distribution and microstructural characteristics of the system. As the cross-linking density increases from 50% to 90%, the total energy of the system decreases by approximately 40%, primarily due to reductions in non-bonded energy. The radial distribution function (RDF) and root mean square displacement (MSD) curves reveal that the cross-linking reaction enhances covalent bond formation between molecular chains, reduces their degrees of freedom, and increases the glass transition temperature (Tg). Under identical strain conditions, the models with higher cross-link densities exhibit greater stress resistance. Specifically, the stress growth rate of the 90% cross-link density system increases by 42.1% as the stretching rate rises from 1.0 × 10¹¹ s⁻¹ to 2.0 × 10¹¹ s⁻¹, compared to an 18.7% increase for the 50% cross-link density system. These findings have significant implications for optimizing processing parameters and predicting the mechanical properties of propellants. Full article

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16 pages, 1291 KiB

Open AccessArticle

Extreme Behaviors in Fibrous Material Remodeling: Auxetic to Non-Auxetic Transition and Phase Segregation

by Andrea Rodella

Materials 2025, 18(7), 1674; https://doi.org/10.3390/ma18071674 - 6 Apr 2025

Viewed by 352

Abstract

Fibrous materials, prevalent in biological tissues and engineered composites, undergo remodeling in response to mechanical loads, leading to plastic changes in fiber orientation. A previously developed continuum model describes this remodeling process. Building on that framework, the present study examines the extreme behaviors [...] Read more.

Fibrous materials, prevalent in biological tissues and engineered composites, undergo remodeling in response to mechanical loads, leading to plastic changes in fiber orientation. A previously developed continuum model describes this remodeling process. Building on that framework, the present study examines the extreme behaviors of such materials. Analytical results for the homogeneous response under tensile loading reveal three distinct classes: in class

(A)

, fibers asymptotically approach a specific angle; in class

(B)

, fibers align perpendicularly to the load direction; and in class

(C)

, fibers align either with the load direction or perpendicularly, depending on their initial orientation. Numerical simulations are employed to analyze the non-homogeneous material response in a standard tensile test, demonstrating how differences in behavior arise from the material class and the initial fiber orientation distribution. This investigation focuses on the extreme behaviors of material classes

(A)

and

(C)

, emphasizing phase segregation and transitions between auxetic and non-auxetic behavior. Full article

(This article belongs to the Special Issue Advances in Modelling and Simulation of Materials in Applied Sciences)

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22 pages, 10415 KiB

Open AccessArticle

Forming Process Prediction Model and Application of Laser Cladding for Remanufactured Screw Pump Rotors

by Haiying Zu, Yongpeng Liu, Sihui Chen, Xiang Jin, Weidong Ye, Mingyuan Sun, Zhongmin Xiao and Liming Yao

Materials 2025, 18(7), 1673; https://doi.org/10.3390/ma18071673 - 5 Apr 2025

Viewed by 421

Abstract

In order to achieve high-quality repair of complex curved parts, a remanufacturing process method utilizing laser cladding and reverse engineering technology is proposed to be implemented by robots. This study focuses on the oscillating helical surface of a screw pump rotor. A single-pass [...] Read more.

In order to achieve high-quality repair of complex curved parts, a remanufacturing process method utilizing laser cladding and reverse engineering technology is proposed to be implemented by robots. This study focuses on the oscillating helical surface of a screw pump rotor. A single-pass laser cladding test is conducted using Response Surface Methodology (RSM) to construct a predictive model and identify optimal process parameters. The model’s accuracy is validated through analysis of variance (ANOVA) and index verification, while the optimal lap rate is determined through multi-pass laser cladding testing. Using reverse engineering technology, the generation of laser cladding paths for complex surfaces is explored, and the trajectory planning for the laser cladding robot is carried out. Simulations and experiments of robotic laser cladding on complex surfaces are performed, with the optimal process parameters guiding both the experiment and simulation. The optimum single-pass cladding layer, with a lap rate of 25.6%, is achieved when the laser power is 2217 W, the powder feed rate is 2.86 r/min, and the scanning speed is 400 mm/min. The study successfully plans the path for laser cladding on complex curved parts, verifying its feasibility and effectiveness, verifying that there is good metallurgical bonding between the cladding layer and the substrate, and helping to select the appropriate process parameters that are consistent with the requirements of a particular application, thus providing valuable guidance for the remanufacture of failed metal parts. Full article

(This article belongs to the Special Issue Rising Stars in Additive Manufacturing)

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14 pages, 7055 KiB

Open AccessArticle

The Influence of Selected Solid Lubricants on the Wear of the Rolling–Sliding Interface in the Wheel–Rail System According to the Standard PN-EN 15427-2-1:2022

by Wioletta Cebulska, Henryk Bąkowski and Damian Hadryś

Materials 2025, 18(7), 1672; https://doi.org/10.3390/ma18071672 - 5 Apr 2025

Viewed by 325

Abstract

This article presents the influence of lubricant on selected tribological properties of the rolling–sliding association, i.e., the wheel–rail system. Three solid lubricants were tested: soybean grease, molybdenum disulfide and graphite grease. Under specific operating conditions, a beneficial influence of lubrication of the above-mentioned [...] Read more.

This article presents the influence of lubricant on selected tribological properties of the rolling–sliding association, i.e., the wheel–rail system. Three solid lubricants were tested: soybean grease, molybdenum disulfide and graphite grease. Under specific operating conditions, a beneficial influence of lubrication of the above-mentioned friction node was observed. This is valuable information for rolling stock owners, track operation or maintenance workers when making decisions about lubrication or its absence on a given section of railway track. In this way, tangible financial benefits (savings) are obtained by extending the durability of the wheel rim and rail, and, through extended periods of wheel set reprofiling, we significantly reduce operating costs. Solid lubricants (lubricating sticks) intended for the lubrication of railway wheel flanges must meet the requirements specified in the PN-EN 15427-2-1:2022 standard. Annex H. The wear patterns were observed and analyzed using both optical microscopy and scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS). The test results indicate that graphite is characterized by the lowest and most stable coefficient of friction over time, which makes it the most effective lubricant in terms of friction reduction. Soybean grease also shows stability and a low level of friction, but with a slight increase in value over a longer period of time. However, grease containing molybdenum disulfide, despite its initial effectiveness, loses its lubricating properties over time, resulting in a significant increase in friction. Full article

(This article belongs to the Special Issue Advances in Tribological and Other Functional Properties of Materials)

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19 pages, 7143 KiB

Open AccessArticle

Substrate Bias-Driven Structural and Mechanical Evolution of AlCrN and AlCrSiN Coatings via Reactive Magnetron Sputtering

by Du-Cheng Tsai, Rong-Hsin Huang, Zue-Chin Chang, Erh-Chiang Chen, Yen-Lin Huang and Fuh-Sheng Shieu

Materials 2025, 18(7), 1671; https://doi.org/10.3390/ma18071671 - 5 Apr 2025

Viewed by 260

Abstract

AlCrN and AlCrSiN coatings were deposited via reactive magnetron sputtering. This study investigates the effects of radio frequency (RF) substrate bias, ranging from 0 V to 200 V, on the chemical composition, microstructure, and mechanical properties of the coatings. All crystalline coatings exhibited [...] Read more.

AlCrN and AlCrSiN coatings were deposited via reactive magnetron sputtering. This study investigates the effects of radio frequency (RF) substrate bias, ranging from 0 V to 200 V, on the chemical composition, microstructure, and mechanical properties of the coatings. All crystalline coatings exhibited a single wurtzite-type hexagonal close-packed (hcp) structure. At a 0 V substrate bias, the AlCrN coating consisted of porous V-shaped columnar crystallites, while the AlCrSiN coating exhibited a porous, fiber-like amorphous structure. As the substrate bias increased, crystal growth was promoted, void density decreased, and the surface morphology transitioned from a textured to a more rounded appearance. Additionally, the preferred orientation shifted toward the (101) direction. However, at excessively high substrate bias, re-nucleation occurred, leading to grain refinement and increased film densification, which in turn caused a further shift in the preferred orientation toward the (002) plane. Due to its multi-element composition and the low solubility of Si in nitrides, AlCrSiN coatings tend to exhibit an amorphous growth tendency during sputtering. As a result, their microstructure is more sensitive to substrate bias. This sensitivity results in the formation of a highly dense structure with an optimal crystallite size at a substrate bias of 100 V, leading to a hardness of 22.6 GPa—surpassing that of the AlCrN coating. Full article

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6 pages, 184 KiB

Open AccessEditorial

Advanced Composites Manufacturing and Plastics Processing

by Patricia Krawczak and Ludwig Cardon

Materials 2025, 18(7), 1670; https://doi.org/10.3390/ma18071670 - 5 Apr 2025

Viewed by 282

Abstract

Environmental and energy concerns and digitalization are currently profoundly reshaping the plastics and composites industry [...] Full article

(This article belongs to the Topic Advanced Composites Manufacturing and Plastics Processing)

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31 pages, 7519 KiB

Open AccessArticle

An Experimental Investigation into Trochoidal Milling for High-Quality GFRP Machining

by Ondřej Bílek, Martin Řezníček, Andrzej Matras, Tomáš Solařík and Lubomír Macků

Materials 2025, 18(7), 1669; https://doi.org/10.3390/ma18071669 - 5 Apr 2025

Viewed by 355

Abstract

This study investigates the effectiveness of trochoidal (adaptive) milling in machining Glass Fiber Reinforced Polymer (GFRP), emphasizing its potential advantages over conventional milling. Six coated solid carbide end mills, each with distinct geometries, were evaluated under identical conditions to assess the cutting forces, [...] Read more.

This study investigates the effectiveness of trochoidal (adaptive) milling in machining Glass Fiber Reinforced Polymer (GFRP), emphasizing its potential advantages over conventional milling. Six coated solid carbide end mills, each with distinct geometries, were evaluated under identical conditions to assess the cutting forces, surface quality, dimensional accuracy, burr formation, chip size distribution, and tool wear. Trochoidal milling demonstrated shorter cycle times—up to 23% faster—and higher material removal rates (MRRs), while conventional milling provided superior dimensional control and smoother surfaces in certain fiber-sensitive regions. A four-tooth cutter with a low helix angle (10°) and aluminum-oxide coating delivered the best overall performance, balancing minimal tool wear with high-quality finishes (arithmetic mean roughness, Ra, as low as 1.36 μm). The results indicate that although conventional milling can exhibit a 25%-lower RMS cutting force, its peak forces and extended machining times may limit the throughput. Conversely, trochoidal milling, when coupled with an appropriately robust tool, effectively manages the cutting forces, improves the surface quality, and reduces the machining time. Most chips produced were less than 11 μm in size, highlighting the need for suitable dust extraction. Notably, a hybrid approach—trochoidal roughing followed by conventional finishing—offers a promising method for achieving both efficient material removal and enhanced dimensional accuracy in GFRP components. Full article

(This article belongs to the Special Issue Research on Metal Cutting, Casting, Forming, and Heat Treatment)

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16 pages, 8657 KiB

Open AccessArticle

Impact of NaHCO₃/Na₂CO₃ Buffer Reagent on Mitigating the Corrosion of C110 Steel in Water-Based Annulus Protection Fluid at Ultrahigh Temperature

by Zhi Zhang, Mifeng Zhao, Yan Li, Junfeng Xie, Wenwen Song, Juantao Zhang, Mengkai Wang, Jie Zhou, Yuan Wang, Xiaowei Lei and Danping Li

Materials 2025, 18(7), 1668; https://doi.org/10.3390/ma18071668 - 5 Apr 2025

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Abstract

The drilling of ultradeep oil wells brings many challenges to the downhole tubular materials, where corrosion induced by halide annulus protection fluid is one major problem. In this work, the Na₂CO₃/NaHCO₃ buffer system is employed to mitigate the [...] Read more.

The drilling of ultradeep oil wells brings many challenges to the downhole tubular materials, where corrosion induced by halide annulus protection fluid is one major problem. In this work, the Na₂CO₃/NaHCO₃ buffer system is employed to mitigate the corrosion of C110 steel in NaBr annulus protection fluid at 220 °C. Weight loss tests, corrosion morphologies characterizations, and electrochemical measurements were used to investigate the inhibition effect. X-ray diffraction and X-ray photo-electron spectroscopy were employed to analyze the surface phase compositions. It is found that the Na₂CO₃/NaHCO₃ buffer reagents effectively inhibit the corrosion of C110 steel, and the inhibition efficiency can reach 96.1%. The higher pH leads to the better inhibition performance, and, particularly, the buffer system is more effective in the corrosion environment of greater aggressivity. Without buffer reagents, the steel substrate is subjected to higher degree of uniform etching and pitting corrosion due to the formation of loose and porous corrosion products. In contrast, the addition of buffer reagents facilitates the formation of thinner but denser and more protective Fe₃O₄ passive film, contributing the high corrosion inhibition efficiency. Our work paves the way for the safe service of NaBr annulus protection fluid at 220 °C in ultradeep oil wells. Full article

(This article belongs to the Special Issue Advances in Corrosion and Protection of Metallic Materials)

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16 pages, 18153 KiB

Open AccessArticle

Effect of Mo and B on Microstructure and Impact Toughness of Coarse Grain Heat-Affected Zone in Low-Carbon V-Ti-N Micro-Alloyed Steel

by Mingliang Qiao, Huibing Fan, Shibiao Wang, Yixin Huang, Qingfeng Wang and Riping Liu

Materials 2025, 18(7), 1667; https://doi.org/10.3390/ma18071667 - 4 Apr 2025

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Abstract

This study investigates the effects of molybdenum (Mo) and boron (B) on the microstructures and impact properties in the coarse grain heat-affected zone (CGHAZ) of a low-carbon V-Ti-N steel. The results demonstrate that, at a heat input of up to 75 kJ/cm, the [...] Read more.

This study investigates the effects of molybdenum (Mo) and boron (B) on the microstructures and impact properties in the coarse grain heat-affected zone (CGHAZ) of a low-carbon V-Ti-N steel. The results demonstrate that, at a heat input of up to 75 kJ/cm, the addition of Mo alters the microstructure of the CGHAZ, transforming it from a polygonal ferrite (PF) + degraded pearlite (DP) composition to a granular bainite (GB) + a small amount of acicular ferrite (AF). This transformation increases the impact energy from 20 J to 35 J. Furthermore, with the Mo/B composite addition, the CGHAZ microstructure was refined due to the formation of a large number of acicular ferrites, and the mean equivalent diameter (MED_MTA≥15°) decreased from 7.9 μm to 4.2 μm. Consequently, the impact toughness of the CGHAZ increased from 35 J to 111 J. The correlation between the Mo/B elements, microstructure and impact toughness was investigated in detail. The findings of this study have the potential to generate novel ideas for the advancement of steel materials in the context of high heat input welding. Full article

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17 pages, 8754 KiB

Open AccessArticle

Investigating Fireside Corrosion Behavior and Mechanism of Low-Alloy Water Wall Tube of Ultra-Supercritical Power Plant

by Yifan Ni, Weijie Weng, Zuogui Zhang, Jianning Li and Chenghao Fan

Materials 2025, 18(7), 1666; https://doi.org/10.3390/ma18071666 - 4 Apr 2025

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Abstract

The corrosion thinning behavior and mechanism of low-alloy water wall tubes of an ultra-supercritical power plant was investigated via SEM, EPMA, XRD, TEM, and laboratory simulation experiments. Fireside corrosion was first initiated by chemical potential- and concentration-governed transportation and diffusion, sequentially facilitated by [...] Read more.

The corrosion thinning behavior and mechanism of low-alloy water wall tubes of an ultra-supercritical power plant was investigated via SEM, EPMA, XRD, TEM, and laboratory simulation experiments. Fireside corrosion was first initiated by chemical potential- and concentration-governed transportation and diffusion, sequentially facilitated by sensitization, which was observed by TEM in terms of the carbide matrix precipitation on the grain boundary, and finally accelerated by the kinetic controlled growth, leading to the final thinning behavior. Laboratory experiments revealed that the reduced atmosphere corrosion kinetic simulation followed the linear law, as well as a different corrosion scale structure layer, compared to the furnace corrosion sample; the reduced atmosphere condition in the laboratory experiment inhibited the oxidation process and layer growth. The frequent shift between the oxidizing and reducing properties of the atmosphere around the water wall tubes during boiler operation may contribute to the delaminated oxidation layer. Full article

(This article belongs to the Special Issue Microstructures and Properties of Corrosion-Resistant Alloys)

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19 pages, 5369 KiB

Open AccessArticle

Interactions of Terahertz Photons with Phonons of Two-Dimensional van der Waals MoS₂/WSe₂/MoS₂ Heterostructures and Thermal Responses

by Jingwen Huang, Ningsheng Xu, Yumao Wu, Xue Ran, Yue Fang, Hongjia Zhu, Weiliang Wang, Huanjun Chen and Shaozhi Deng

Materials 2025, 18(7), 1665; https://doi.org/10.3390/ma18071665 - 4 Apr 2025

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Abstract

The interaction between terahertz (THz) photons and phonons of materials is crucial for the development of THz photonics. In this work, typical two-dimensional (2D) van der Waals (vdW) transition metal chalcogenide (TMD) layers and heterostructures are used in THz time-domain spectroscopy (TDS) measurements, [...] Read more.

The interaction between terahertz (THz) photons and phonons of materials is crucial for the development of THz photonics. In this work, typical two-dimensional (2D) van der Waals (vdW) transition metal chalcogenide (TMD) layers and heterostructures are used in THz time-domain spectroscopy (TDS) measurements, low-wavenumber Raman spectroscopy measurements, calculation of 2D materials’ phonon spectra, and theoretical analysis of thermal responses. The TDS results reveal strong absorption of THz photons in the frequency range of 2.5–10 THz. The low-wavenumber Raman spectra show the phonon vibration characteristics and are used to establish phonon energy bands. We also set up a computational simulation model for thermal responses. The temperature increases and distributions in the individual layers and their heterostructures are calculated, showing that THz photon absorption results in significant increases in temperature and differences in the heterostructures. These give rise to interesting photothermal effects, including the Seebeck effect, resulting in voltages across the heterostructures. These findings provide valuable guidance for the potential optoelectronic application of the 2D vdW heterostructures. Full article

(This article belongs to the Special Issue Terahertz Vibrational Spectroscopy in Advanced Materials)

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13 pages, 4809 KiB

Open AccessArticle

Optimization of Hybrid Composite–Metal Joints: Single Pin

by Ruopu Bian, Bin Wang, Hongying Yang, Jiazhi Ren, Lujun Cui and Oluwamayokun B. Adetoro

Materials 2025, 18(7), 1664; https://doi.org/10.3390/ma18071664 - 4 Apr 2025

Viewed by 322

Abstract

Deepening the understanding of composite and metal joint methodologies applied in the aerospace industry is crucial for minimizing operational expenditures. Current investigations are focusing on innovative joining techniques that incorporate additive manufactured rivet pins. This research aims to analyze the mechanical strength of [...] Read more.

Deepening the understanding of composite and metal joint methodologies applied in the aerospace industry is crucial for minimizing operational expenditures. Current investigations are focusing on innovative joining techniques that incorporate additive manufactured rivet pins. This research aims to analyze the mechanical strength of these joints for the effective optimization of pin profiles. Through extensive study of the impact of pin geometry on joint performance, we derived the optimal pin design, considering various initial parameters with the objective of minimizing stress concentration in the pin structure. The joint configurations of metal to composite interfaces were systematically examined using finite element analysis and lap shear testing, which included a singular pin and an adhesive-bonding layer. Numerical simulations reveal that the maximum shear stress in the pin is located at the junction between the base of the pin and the metal plate. By optimizing the shape and dimensions of the pin, both the shear and axial stresses can be significantly mitigated. Following the numerical optimization process, a series of enhanced pins have been produced via additive manufacturing techniques to facilitate mechanical testing. The experimental data obtained align closely with the simulation results, thereby reinforcing the validity of the optimization. The optimal configuration for a single pin, involving a 60° angle and a total height of 3.43 mm, achieves the minimum shear stress. Based on these findings, further investigations are underway to explore optimized designs utilizing multiple pins. This paper presents the results of the single pin study, whereas the findings pertaining to the ongoing investigation on the multi-pin configuration will be disseminated in subsequent publications. Full article

(This article belongs to the Section Materials Simulation and Design)

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13 pages, 2614 KiB

Open AccessArticle

Rheological Investigation of Polydimethylsiloxane with Glass Beads: A Model for Compression-Stiffening Effects in Soft Tissue Engineering

by Dawid Łysik and Joanna Mystkowska

Materials 2025, 18(7), 1663; https://doi.org/10.3390/ma18071663 - 4 Apr 2025

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Abstract

This study explores the rheological properties of polydimethylsiloxane (PDMS) composites with glass beads (GBs) to replicate the compression-stiffening behavior of biological tissues. The mechanical properties of soft tissues arise from interactions between the extracellular matrix (ECM) and embedded cells. To mimic this, PDMS [...] Read more.

This study explores the rheological properties of polydimethylsiloxane (PDMS) composites with glass beads (GBs) to replicate the compression-stiffening behavior of biological tissues. The mechanical properties of soft tissues arise from interactions between the extracellular matrix (ECM) and embedded cells. To mimic this, PDMS was used as a polymeric matrix, while rigid GBs acted as non-deformable inclusions facilitating stress redistribution. PDMS composites with 10%, 20%, and 30% GB concentrations were fabricated. Rheological analysis revealed that GBs significantly enhanced the storage modulus (G′), with stiffness increasing linearly under compression. The stiffening rate rose from 300 Pa/% (pure PDMS) to 387 Pa/%, 836 Pa/%, and 2035 Pa/% for 10%, 20%, and 30% GB, respectively, marking a sevenfold increase at the highest concentration. Similarly, the apparent Young’s modulus increased from 150 kPa (pure PDMS) to 200 kPa, 300 kPa, and 380 kPa for composites with 10%, 20%, and 30% GB, respectively. PDMS-GB composites successfully reproduce the compression-stiffening effect observed in biological tissues, which may aid research in mechanobiology and tissue engineering. Full article

(This article belongs to the Special Issue 3D Tissue Models and Biomaterials for Oral Soft Tissue Regeneration)

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20 pages, 8605 KiB

Open AccessArticle

Effect of Bio-Cementation Level and Rainfall Intensity on Surface Erosion Resistance of Biotreated Slope Using PEICP Method

by Yuyuan Chen, Hemanta Hazarika and Nadella Marchelina

Materials 2025, 18(7), 1662; https://doi.org/10.3390/ma18071662 - 4 Apr 2025

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Abstract

Biomineralization technology is a promising method for soil cementation, enhancing its mechanical properties. However, its application in mitigating slope surface erosion caused by rainfall has not been fully explored. This study experimentally examined the feasibility of using plant-based enzyme-induced carbonate precipitation (PEICP) to [...] Read more.

Biomineralization technology is a promising method for soil cementation, enhancing its mechanical properties. However, its application in mitigating slope surface erosion caused by rainfall has not been fully explored. This study experimentally examined the feasibility of using plant-based enzyme-induced carbonate precipitation (PEICP) to reduce slope surface rainfall erosion through simulated rainfall tests. The effects of biotreatment cycles (N) and rainfall intensity (R_i) on erosion resistance were evaluated. The results demonstrated that increasing the biotreatment cycles improved the bio-cementation level, as evidenced by enhanced surface strength, increased calcium carbonate content (CCC) and thicker crust layers. Specifically, as the biotreatment cycles (N) increased from 2 to 6, the crust layer thickness expanded from 5.2 mm to 15.7 mm, with surface strength rising from 38.3 kPa to 244.3 kPa. Likewise, the CCC increased significantly from 1.09% to 5.32%, further reinforcing the soil structure and enhancing erosion resistance. Slopes treated with six biotreatment cycles exhibited optimal erosion resistance across rainfall intensities ranging from 45 to 100 mm/h. Compared to untreated slopes, biotreated slopes showed significant reductions in soil loss, with a decrease to below 10% at N = 4 and near-complete erosion resistance at N = 6. These findings highlight the potential of PEICP technology for improving slope stability under rainfall conditions. Full article

(This article belongs to the Special Issue Advances in Biomass-Based Materials and Their Applications (2nd Edition))

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32 pages, 11378 KiB

Open AccessArticle

Preparation and Characterization of Char Carbon Obtained by Carbonization of Unused Cigarette Filter Rods: The Product Application Assessment

by Bojan Janković, Dejan Cvetinović, Milena Milošević, Filip Veljković, Vladimir Rajić, Marija Janković and Vladimir Dodevski

Materials 2025, 18(7), 1661; https://doi.org/10.3390/ma18071661 - 4 Apr 2025

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Abstract

The development of carbonaceous materials such as biochar has triggered a hot spot in materials application. In this study, a new type of char carbon was developed from raw cigarette filter rods (CFRs) via a carbonization process under moderate conditions (T = [...] Read more.

The development of carbonaceous materials such as biochar has triggered a hot spot in materials application. In this study, a new type of char carbon was developed from raw cigarette filter rods (CFRs) via a carbonization process under moderate conditions (T = 550 °C; t_res = 1 h) (CFR char carbon). The produced char was characterized by ATR-FTIR (Attenuated total reflectance—Fourier-transform infrared) spectroscopy, XRD (X-ray diffraction) analysis, GC-MS (Gas Chromatography–Mass Spectrometry), FESEM-EDS (Field-Emission Scanning Electron Microscopy—Energy-dispersive X-ray spectroscopy) technique, XPS (X-ray photoelectron spectroscopy), and N₂ adsorption/desorption (BET) measurements. The obtained carbon material is rich in oxygen-containing functional groups (i.e., C=O, C–O, –C(=O)–CH₃, C–O–C, C–OH, and O=C–O, with chemisorbed oxygen), containing significant amounts of calcium (that originates from CaCO₃) and silicon (Si), generated by reduction of SiO₂. It was found that the formation of char(C)/n-alkane composite material makes that CFR char have a high compressive strength improvement. Moderate carbonization has contributed to the creation of such material that has a fairly high specific surface area (320.93 m²/g), exhibiting a complex hierarchical structure that was characterized by composite Type I/IV(a) isotherm, associated with micro-/mesoporous carbon material. In addition, more directional extensions of this research for future work were proposed, including the implementation of electrochemical research. Full article

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19 pages, 3236 KiB

Open AccessArticle

Comprehensive Characterization of the Molecular Structure and Properties of Pitch-like Products from Coal Dissolution at Mild Temperature Using Heavy Solvents of Coal and Petroleum Origin

by Peter Kuznetsov, Budeebazar Avid, Ludmila Kuznetsova, Xing Fan, Jian-Fang Xu, Evgeniy Kamenskiy and Sergey Lyrschikov

Materials 2025, 18(7), 1660; https://doi.org/10.3390/ma18071660 - 4 Apr 2025

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Abstract

The chemical composition and molecular structure of the pitch-like products obtained by liquid-phase reaction of bituminous coal with heavy hydrocarbon fractions of coal and petroleum origin as solvents at a moderate temperature were comprehensively characterized in terms of a new aromatic feedstock for [...] Read more.

The chemical composition and molecular structure of the pitch-like products obtained by liquid-phase reaction of bituminous coal with heavy hydrocarbon fractions of coal and petroleum origin as solvents at a moderate temperature were comprehensively characterized in terms of a new aromatic feedstock for needle coke and other valuable high-tech carbon materials. The molecular parameters of the products were characterized by using FTIR, ¹H NMR, ¹³C NMR and XPS. Liquid-phase chromatography was used to analyze benzo(a)pyrene (BaP) as a carcinogenicity marker. The chemical composition and the characteristics of the molecular structure of the products were shown to depend greatly on the solvent used. The product obtained using coal tar as a solvent was highly aromatic, its polyaromatic nuclei consisted predominantly of protonated and pericondensed cycles sparsely substituted by CH₃ and occasionally CH₂ groups. The product obtained using petroleum-derived heavy gas oil as solvent was much less aromatic and prone to autogenous surface oxidation. Its aromatic nuclei contained mainly protonated and highly alkylated catacondensed chains. The intermediate structural parameters were characteristic of the product obtained using binary solvent. A remarkable feature of the pitch-like products obtained was a reduced BaP concentration (up to 40 times compared to typical coal-tar pitch). In terms of the molecular structure, the pitch-like products obtained by low-temperature dissolution of coal can serve as a new polyaromatic feedstock with a reduced carcinogenicity for the production of valuable high-tech carbon materials, needle coke, in particular. Full article

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21 pages, 14258 KiB

Open AccessArticle

Biomass, Phyto-Ash, and Biochar from Beech Wood as Functional Additives for Natural Rubber-Based Elastomer Composites

by Justyna Miedzianowska-Masłowska, Marcin Masłowski and Krzysztof Strzelec

Materials 2025, 18(7), 1659; https://doi.org/10.3390/ma18071659 - 4 Apr 2025

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Abstract

The growing interest in renewable resource-based materials has driven efforts to develop elastomeric biocomposites using biomass, phyto-ash, and biochar as fillers. These bio-additives, derived from beech wood through various processing methods, were incorporated into natural rubber (NR) at varying weight ratios. The primary [...] Read more.

The growing interest in renewable resource-based materials has driven efforts to develop elastomeric biocomposites using biomass, phyto-ash, and biochar as fillers. These bio-additives, derived from beech wood through various processing methods, were incorporated into natural rubber (NR) at varying weight ratios. The primary objective of this study was to assess how the type and content of each bio-filler influence the structural, processing, and performance properties of the biocomposites. Mechanical properties, including tensile strength and hardness, were evaluated, while crosslink density of the vulcanizates was determined using equilibrium swelling in solvents. Additionally, the composites underwent thermogravimetric analysis (TGA) to determine the decomposition temperature of individual components within the polymer matrix. Bio-fillers influenced rheological and mechanical properties, with phyto-ash reducing viscosity and cross-linking density, and biochar and biomass increasing stiffness and maximum torque. Biochar extended curing time due to the absorption of curing agents, whereas phyto-ash accelerated vulcanization. Mechanical tests showed that all bio-filled composites were stiffer than the reference, with biochar and biomass (30 phr) exhibiting the highest hardness (45.8 °ShA and 49.1 °ShA, respectively) and cross-link density (2.68 × 10⁻⁵ mol/cm³ and 2.77 × 10⁻⁵ mol/cm³, respectively), contributing to improved tensile strength, in particular in the case of biochar, where the TS was 17.6 MPa. The study also examined the effects of thermal-oxidative aging on the samples, providing insights into the changes in the mechanical properties of the biocomposites under simulated aging conditions. Full article

(This article belongs to the Special Issue Advances in Bio-Polymer and Polymer Composites)

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16 pages, 3746 KiB

Open AccessArticle

Synthesis, Characterization, and Investigation of the Properties of a New Promising Poly(Azomethine) Organic Semiconductor Material

by Jihane Ismaili, Chouki Zerrouki, Najla Fourati, Stephanie Leroy-Lhez, Daniel Montplaisir, Nicolas Villandier and Rachida Zerrouki

Materials 2025, 18(7), 1658; https://doi.org/10.3390/ma18071658 - 4 Apr 2025

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Abstract

A new poly(azomethine) with improved solubility was successfully prepared by the polycondensation of terephthalaldehyde and 2,2-Bis[4-(4-aminophenoxy)phenyl]-hexafluoropropane (4-BDAF) under green chemistry conditions. This new polymer containing hexafluoroisopropylidene was compared with a polymer containing isopropylidenediphenyl to study the influence of the presence of fluorine atoms [...] Read more.

A new poly(azomethine) with improved solubility was successfully prepared by the polycondensation of terephthalaldehyde and 2,2-Bis[4-(4-aminophenoxy)phenyl]-hexafluoropropane (4-BDAF) under green chemistry conditions. This new polymer containing hexafluoroisopropylidene was compared with a polymer containing isopropylidenediphenyl to study the influence of the presence of fluorine atoms on the properties of the polymer. Both were characterized by nuclear magnetic resonance (NMR), their molecular weight was measured by gel permeation chromatography (GPC), and their morphology was studied by X-ray diffraction (XRD). The two polymers obtained were soluble in most polar aprotic solvents and even in less polar solvents, which are practical and easily accessible solvents. Their thermal properties were determined by a thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). These two new polymers showed high resistance to thermal decomposition up to 490 °C, with a glass transition temperature (Tg) of 180 °C. The photophysical properties were studied by UV/Visible absorption. The polymers were doped and then deposited on cellulose filaments, an approach that made it possible to produce self-supporting conductive composites thanks to their mechanical properties. The topography of the resulting materials was characterized at submicron scales before estimating their electronic conductivity and gap energy by diffuse reflection spectroscopy. Full article

(This article belongs to the Special Issue Latest Advances in Functional Polymeric Materials for Environmental and Biomedical Applications)

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15 pages, 4526 KiB

Open AccessArticle

Dielectric Properties of Isotactic Polypropylene with Lignocellulose-Based Biomass Filler

by Dragana D. Cerovic, Ivan M. Petronijevic, Filip S. Marinkovic, Slavica B. Maletic and Dusan M. Popovic

Materials 2025, 18(7), 1657; https://doi.org/10.3390/ma18071657 - 4 Apr 2025

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Abstract

The ecological aspect of substituting synthetic materials with natural materials is of great interest nowadays. This paper examines the percentage of lignocellulose-based fillers that can be added to a synthetic polymer matrix to ensure the resulting biocomposite maintains its dielectric properties. Biocomposites were [...] Read more.

The ecological aspect of substituting synthetic materials with natural materials is of great interest nowadays. This paper examines the percentage of lignocellulose-based fillers that can be added to a synthetic polymer matrix to ensure the resulting biocomposite maintains its dielectric properties. Biocomposites were made from isotactic polypropylene (iPP) and various proportions (20%, 30%, and 40%) of oats, rye, wheat, and barley bran and granules from corn cobs using a Brabender plastograph and a hydraulic hot press. From a morphological analysis, it was noted that the particles were well incorporated into the polymer matrix. The frequency-dependent behavior of the dielectric properties was analyzed across a frequency range from 30 Hz to 60 kHz at a room temperature of 23 °C and 35% relative humidity. The obtained results showed that the incorporation of biomasses into the iPP matrix increased the values of the dielectric properties across the entire measured frequency range. The samples with wheat showed the most stable values of the dielectric parameters with frequency changes, for all three concentrations. A linear regression analysis showed a very high coefficient of determination (R² = 0.997) between the effective dielectric permeability and filler concentration at 30 Hz for the samples with wheat. Furthermore, the biocomposite iPP/20% wheat showed a desirable balance of dielectric properties for electronic applications. The results showed that biocomposites obtained by adding cheap lignocellulose-based biomass, such as bran or granules from corn cobs, to a synthetic polymer matrix have a great potential for use as electrically insulating materials because their dielectric parameters are comparable to those of standard insulating materials. Full article

(This article belongs to the Special Issue Physics and Chemistry of Polymers and Sustainable Polymer-Based Materials)

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