Materials

12 pages, 865 KB

Open AccessArticle

Effect of Collar Diameter and Simulated Aging on the Orthogonal Load Resistance of Orthodontic Miniscrews

by Maria Francesca Sfondrini, Giuseppe Merlati, Maurizio Pascadopoli, Letizia Valceschini, Simone Ricchio, Mattia Maria Torchia, Leonardo Del Corso and Andrea Scribante

Materials 2026, 19(2), 262; https://doi.org/10.3390/ma19020262 - 8 Jan 2026

Abstract

The use of miniscrews as Temporary Skeletal Anchorage Devices (TSAD) in orthodontics has allowed clinicians to perform challenging tooth movements by dissipating undesired forces into the bone structure; thus, avoiding unwanted movement of the adjacent teeth. It is essential for miniscrews to be [...] Read more.

The use of miniscrews as Temporary Skeletal Anchorage Devices (TSAD) in orthodontics has allowed clinicians to perform challenging tooth movements by dissipating undesired forces into the bone structure; thus, avoiding unwanted movement of the adjacent teeth. It is essential for miniscrews to be highly resistant to fracture during clinical use. While many studies have analysed torsional loads, none have measured the changes in flexural and bending strength of miniscrews before and after an ageing process. This study aims to analyse the resistance to orthogonal forces of miniscrews with different diameters, focusing on both new and aged materials, the latter subjected to thermocycling and autoclaving laboratory processes to simulate a 3- and a 6-month exposure to the oral environment. A total of 105 pristine miniscrews have been tested; specimens were divided into seven groups based on the different endosseous body diameters. Each group was further subdivided into three subgroups, according to the simulated ageing of the miniscrews (intact, 3 months of ageing and 6 months of ageing, respectively). An Instron Universal Testing Machine has been used to measure deflection at 0.1 mm and 0.2 mm, as well as maximum load at fracture. The results evidenced that miniscrews respond differently to cutting forces; in particular, the resistance to orthogonal loads increases as the diameter of the miniscrews increases. Linear regression analysis revealed a significant influence between all the dependent variables—maximum load, 0.1 mm deflection load, and 0.2 mm deflection load—and the independent variables, such as diameter and thermocycling (p < 0.05). Both new and aged miniscrews are suitable for orthodontic and orthopaedic loads; moreover, ageing up to 6 months does not seem to significantly decrease the resistance to shear forces for the same diameter. Linear regression analysis of the miniscrews subjected to experimental ageing showed a slight but significant decrease in resistance to orthogonal loading. Full article

(This article belongs to the Special Issue Materials and Techniques in Dentistry, Oral Surgery and Orthodontics (Second Edition))

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13 pages, 2134 KB

Open AccessArticle

Performance of Repair Mortars Composed of Calcium Sulfoaluminate and Amorphous Calcium Aluminate

by Seungtae Lee and Seho Park

Materials 2026, 19(2), 261; https://doi.org/10.3390/ma19020261 - 8 Jan 2026

Abstract

Extensive research has addressed concrete deterioration and its countermeasures; however, studies on responsive repair methods and materials remain comparatively limited and less systematic. In this study, six mixtures of repair mortars (RMs) were formulated using aluminate-based binders, specifically calcium sulfoaluminate (CSA) and amorphous [...] Read more.

Extensive research has addressed concrete deterioration and its countermeasures; however, studies on responsive repair methods and materials remain comparatively limited and less systematic. In this study, six mixtures of repair mortars (RMs) were formulated using aluminate-based binders, specifically calcium sulfoaluminate (CSA) and amorphous calcium aluminate (ACA) cements. The experiment evaluated the mechanical properties and freeze–thaw resistance of these mortars. To accelerate hydration, a controlled amount of anhydrite gypsum was incorporated into each mixture. The fluidity and setting time of fresh RMs were measured, whereas the compressive strength, flexural strength, and ultrasonic pulse velocity (UPV) of hardened RMs were evaluated at 1, 7, and 28 days. In addition, freeze–thaw resistance was assessed as per ASTM C666 by determining the relative dynamic modulus of elasticity. Additionally, the hydration products and microstructural characteristics of paste specimens were qualitatively analyzed. The mechanical performance, including strength and UPV, and freeze–thaw resistance of RMs containing ACA were superior to those of RMs containing CSA. In particular, compared to the CSA-containing specimens exposed to freeze–thaw action were significantly deteriorated, the ACA-containing specimens showed excellent resistance with relatively less cracking and spalling. This may imply that ACA is effective as rapid repair materials for concrete structures in cold regions. Microstructural observations revealed variations in hydration products depending on the aluminate binder employed, which significantly influenced the mechanical and durability properties of the RMs. These results may aid the selection of optimal repair materials for deteriorated concrete structures. Full article

(This article belongs to the Special Issue Eco-Friendly Intelligent Infrastructures Materials)

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28 pages, 6027 KB

Open AccessArticle

Acoustic Performance of Stone Mastic Asphalts with Crumb Rubber and Polymeric Additives in Warm, Dry Climates

by Jesús Campuzano-Ríos and Juan José Jorquera-Lucerga

Materials 2026, 19(2), 260; https://doi.org/10.3390/ma19020260 - 8 Jan 2026

Abstract

Traffic noise is one of the main sources of environmental problems and a growing challenge for national traffic authorities. It is widely accepted that tire-pavement interaction is the main cause of traffic noise at speeds between 40 and 90 km/h. Typically, noise attenuation [...] Read more.

Traffic noise is one of the main sources of environmental problems and a growing challenge for national traffic authorities. It is widely accepted that tire-pavement interaction is the main cause of traffic noise at speeds between 40 and 90 km/h. Typically, noise attenuation strategies include earthworks, tree belts, or noise barriers. However, a solution that is almost always viable is the use of low-noise pavements, which are characterized by their porous macrotexture, such as Stone Mastic Asphalt (SMA) mixtures. These mixtures are increasingly used for heavy traffic volumes because of their many advantages, including drainage properties and mechanical strength. Based on the experimental results obtained on different roads in southern Spain, this paper compares noise reduction in an SMA standard mixture due to the incorporation of different additives, such as crumb rubber and polymeric additives. According to the analysis, increasing the additives content by 1% reduces CPX by 1.18 decibels, approximately, and none of the analyzed sections shows increases greater than 3 dB within 24 months. Additionally, the paper proposes design recommendations regarding macrotexture and the percentage of voids for zones with warm, dry climates, such as Mediterranean Spain. Full article

(This article belongs to the Special Issue Eco-Friendly Intelligent Infrastructures Materials)

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31 pages, 2516 KB

Open AccessArticle

Study on Vibration Compaction Behavior of Fresh Concrete Mixture with Ternary Aggregate Grading

by Liping He, Fazhang Li, Huidong Qu, Zhenghong Tian, Weihao Shen and Changyue Luo

Materials 2026, 19(2), 259; https://doi.org/10.3390/ma19020259 - 8 Jan 2026

Abstract

The vibration compaction behavior of fully graded fresh concrete differs fundamentally from that of conventional two-graded concrete. Based on measured vibration responses of an internal vibrator and sinking-ball tests, an energy transfer model for fully graded concrete was established by incorporating the effects [...] Read more.

The vibration compaction behavior of fully graded fresh concrete differs fundamentally from that of conventional two-graded concrete. Based on measured vibration responses of an internal vibrator and sinking-ball tests, an energy transfer model for fully graded concrete was established by incorporating the effects of aggregate-specific surface area, paste–aggregate ratio, dynamic damping, and natural frequency, and the spatiotemporal attenuation of vibration energy in fresh concrete was systematically analyzed. Experimental results indicate that fully graded concrete exhibits a higher energy absorption capacity during the early stage of vibration, with a maximum energy absorption rate of 423 W and a peak energy transfer efficiency of 76.3%, both of which are significantly higher than those of two-graded concrete at the same slump. However, as a dense aggregate skeleton rapidly forms, the energy absorption efficiency of fully graded concrete decreases more rapidly during the middle and later stages of vibration, showing a characteristic pattern of “high initial absorption followed by rapid attenuation.” Through segregation assessment and porosity analysis, a safe vibration energy range for fully graded concrete was quantitatively determined, with lower and upper energy thresholds of 159.7 J·kg⁻¹ and 538.5 J·kg⁻¹, respectively. In addition, the experiments identified recommended vibration durations of 30–65 s and effective vibration influence radii of 22–85 mm for fully graded concrete under different slump conditions. These findings provide a quantitative basis for the control of vibration parameters and energy-oriented construction of fully graded concrete. Full article

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

18 pages, 2709 KB

Open AccessArticle

Stability of a Compressed Bar Resting on an Elastic Substrate with Stepwise Changes in Parameters

by Mirosław Sadowski, Jakub Marcinowski and Volodymyr Sakharov

Materials 2026, 19(2), 258; https://doi.org/10.3390/ma19020258 - 8 Jan 2026

Abstract

The study presents a stability analysis of an axially compressed column resting on a Winkler foundation with a stepwise variation in stiffness. The solution is based on an energy approach using the Rayleigh quotient, and the original buckling mode function is proposed to [...] Read more.

The study presents a stability analysis of an axially compressed column resting on a Winkler foundation with a stepwise variation in stiffness. The solution is based on an energy approach using the Rayleigh quotient, and the original buckling mode function is proposed to capture the localization of deformations in the region of foundation discontinuity. The theoretical model was verified numerically for rectangular-section columns by comparing the results with simulations performed in COSMOS/M and ABAQUS systems. The differences in critical load values did not exceed 1.7%. The investigation showed that increasing the stiffness contrast leads to stronger buckling localization within the weaker foundation segment. The developed model can be used for preliminary assessment of the load-carrying capacity of structural elements interacting with a non-homogeneous distributed foundation. Full article

(This article belongs to the Special Issue Modelling of Deformation Characteristics of Materials or Structures)

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16 pages, 1668 KB

Open AccessArticle

Prediction and Analysis of Creep Rupture Life of 9Cr Martensitic-Ferritic Heat-Resistant Steel by Neural Networks

by Muhammad Ishtiaq, Seungmin Hwang, Won-Seok Bang, Sung-Gyu Kang and Nagireddy Gari Subba Reddy

Materials 2026, 19(2), 257; https://doi.org/10.3390/ma19020257 - 8 Jan 2026

Abstract

Thermal and nuclear power systems require materials capable of sustaining high mechanical and thermal loads over prolonged service durations. Among these, 9Cr heat-resistant steels are particularly attractive due to their superior mechanical strength and extended creep rupture life, making them suitable for extreme [...] Read more.

Thermal and nuclear power systems require materials capable of sustaining high mechanical and thermal loads over prolonged service durations. Among these, 9Cr heat-resistant steels are particularly attractive due to their superior mechanical strength and extended creep rupture life, making them suitable for extreme environments. In this study, multiple machine learning models were explored to predict the creep rupture life of 9Cr heat-resistant steels. A comprehensive dataset of 913 samples, compiled from experimental results and literature, included eight input variables—covering chemical composition, stress, and temperature—and one output variable, the creep rupture life. The optimized artificial neural network (ANN) model achieved the highest predictive accuracy with a regularization coefficient of 0.01, 10,000 training iterations, and five hidden layers with 30 neurons per layer, attaining an R² of 0.9718 for the test dataset. Beyond accurate prediction, single- and two-variable sensitivity analyses were used to elucidate statistically meaningful trends and interactions among the input parameters governing creep rupture life. The analyses indicated that among all variables, test conditions—particularly the test temperature—exert a pronounced negative effect on creep life, significantly reducing durability at elevated temperatures. Additionally, an optimization module enables identification of input conditions to achieve desired creep life, while the Index of Relative Importance (I_RI) and quantitative effect analysis enhance interpretability. This framework represents a robust and reliable tool for long-term creep life assessment and the design of 9Cr steels for high-temperature applications. Full article

(This article belongs to the Section Metals and Alloys)

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25 pages, 3497 KB

Open AccessArticle

Effect of Functionally Graded Material on the Dynamic Stability of Three-Layered Annular Plates

by Dorota Pawlus

Materials 2026, 19(2), 256; https://doi.org/10.3390/ma19020256 - 8 Jan 2026

Abstract

This study considers the dynamic stability of a three-layered annular plate, whose facings are made of functionally graded material in the radial direction. The plate is subjected to linearly increasing in-plane forces applied at either the inner or outer edge. The effect of [...] Read more.

This study considers the dynamic stability of a three-layered annular plate, whose facings are made of functionally graded material in the radial direction. The plate is subjected to linearly increasing in-plane forces applied at either the inner or outer edge. The effect of the heterogeneity of the plate-facing material on the dynamic response is analyzed in detail. The main parameters defining the stability state—such as critical dynamic load, critical time, maximum deflection, and buckling mode—are specifically evaluated. The problem is analyzed using two approximation methods: the finite difference method and the finite element method. Numerical calculations were carried out using two approaches: the author’s program following analytical calculations, and the ABAQUS system. The results show the importance of modeling the plate with an appropriate material function describing the radial gradation, which significantly affects the plate’s dynamic stability response and critical parameters. Full article

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

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12 pages, 4080 KB

Open AccessArticle

Aging Structure, Mechanical Properties, and ZnO Piezoelectric Coating-Based Ultrasonic Response of 15CrMo Steel

by Huayong Hu, Yanbing Zhang, Xiangdong Ma, Zhiping Fu, Jie Liu, Jun Zhang and Bing Yang

Materials 2026, 19(2), 255; https://doi.org/10.3390/ma19020255 - 8 Jan 2026

Abstract

The ZnO piezoelectric coatings were deposited on the surface of 15CrMo steels by magnetron sputtering to directly excite the ultrasonic signal, effectively solving the coupling problem between the traditional probe and the pipe surface. The microstructure, mechanical properties, and ultrasonic longitudinal wave velocity [...] Read more.

The ZnO piezoelectric coatings were deposited on the surface of 15CrMo steels by magnetron sputtering to directly excite the ultrasonic signal, effectively solving the coupling problem between the traditional probe and the pipe surface. The microstructure, mechanical properties, and ultrasonic longitudinal wave velocity of the aged samples were carried out systematically. The spheroidization grade of pearlite, evolution of carbide morphology, hardness, strength, and ultrasonic wave velocity were systematically analyzed. As the degree of aging intensifies, the material undergoes significant pearlite spheroidization and carbide coarsening. The Vickers hardness drops from 158 HV in the original state to 134.2 HV, and the yield strength and tensile strength decrease by 22.7% and 17.9%, respectively. The ultrasonic longitudinal wave velocity shows a monotonically upward trend with the increase in spheroidization grade, increasing from 5925.6 m/s in the original state to 5976 m/s at the highest spheroidization grade. Full article

(This article belongs to the Section Metals and Alloys)

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17 pages, 4657 KB

Open AccessArticle

Study on the Immobilization of Horseradish Peroxidase on a Multi-Level Composite Carrier SiO₂@MnO₂@MAF-7

by Mengjie Huang, Baihui Zhang, Xiangyu Jiang, Maojie Jiang, Peng Yin, Xuan Fang, Yanna Lin and Fuqiang Ma

Materials 2026, 19(2), 254; https://doi.org/10.3390/ma19020254 - 8 Jan 2026

Abstract

This study addresses the issues of poor stability and difficulty in recovery of free horseradish peroxidase (HRP) by developing a multi-level composite immobilized carrier that combines high loading capacity with long-term stability. The SiO₂@MnO₂@MAF-7 core–shell structured carrier was prepared [...] Read more.

This study addresses the issues of poor stability and difficulty in recovery of free horseradish peroxidase (HRP) by developing a multi-level composite immobilized carrier that combines high loading capacity with long-term stability. The SiO₂@MnO₂@MAF-7 core–shell structured carrier was prepared via a solvothermal self-assembly method. Three immobilization strategies—adsorption, covalent cross-linking, and encapsulation—were systematically compared for their immobilization efficacy on HRP. The material structure was analyzed using techniques such as specific surface area analysis (BET), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) to characterize the material structure. Enzyme kinetic parameter determination experiments were conducted to systematically evaluate the performance advantages of the immobilized enzyme. BET analysis showed that SiO₂@MnO₂@MAF-7 had a specific surface area of 251.99 m²/g and a mesoporous area of 12.47 nm, and its HRP loading was 50.37 U/mg (immobilization efficiency 85.03%). Compared with free HRP, the Km value of the immobilized enzyme was decreased by 42%, the activity retention rate was increased by 35–50% at 80 °C and pH 4–9, and the activity was maintained by 65% after five repeated uses. In this study, MAF-7 was combined with MnO₂/SiO₂ for HRP immobilization for the first time, and the triple effect of rigid support-catalytic synergy-confined protection synergistically improved the stability of the enzyme, providing a new strategy for the industrial application of oxidoreductases. Full article

(This article belongs to the Section Advanced Composites)

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18 pages, 6172 KB

Open AccessArticle

Predicting the Effect of Mould Material and Design on the Efficiency of the LLDPE Rotational Moulding Process: Thermal and Time Analyses

by Karolina Głogowska and Janusz Wojciech Sikora

Materials 2026, 19(2), 253; https://doi.org/10.3390/ma19020253 - 8 Jan 2026

Abstract

This study evaluates the effect of mould material and mould wall thickness on the thermal behaviour and cycle time of the LLDPE rotational moulding process by using RotoSim-based numerical simulation. This study was performed using three different metallic materials (low-carbon steel, brass, and [...] Read more.

This study evaluates the effect of mould material and mould wall thickness on the thermal behaviour and cycle time of the LLDPE rotational moulding process by using RotoSim-based numerical simulation. This study was performed using three different metallic materials (low-carbon steel, brass, and aluminium), mould wall thicknesses of 3, 5, and 8 mm, and oven temperatures of 230, 250, and 270 °C. The simulations demonstrate that both mould material and wall thickness significantly influence the temperature evolution in the mould cavity and the overall cycle duration. Aluminium moulds provided the mould-cavity temperature closest to the oven conditions, the longest time with the polymer in the plastic/molten state, and the shortest total cycle time compared with steel and brass moulds. Increasing the mould wall thickness prolonged the cycle time for all materials, with the extension occurring primarily during the cooling stage. For a 3 mm wall thickness at 230 °C, the shortest cycle time was 2900 s (Al/3/230) and the longest was 3300 s (S/3/230). For an 8 mm wall thickness at 270 °C, the shortest cycle time was 4400 s (Al/8/270) and the longest was 4900 s (S/8/270). These results indicate that selecting an appropriate mould material and wall thickness can be an effective approach to shortening the cycle time and improving the efficiency of LLDPE rotational moulding. Full article

(This article belongs to the Special Issue Advances in Polymers and Their Composites: Processing, Properties and Numerical Simulation)

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13 pages, 5612 KB

Open AccessArticle

Effects of Corrugated Flat Rolling Process on the Bonding Interface, Microstructure, and Properties of Mg/Al Clad Plates

by Lifang Pan, Zhiyuan Zhu, Huanhuan Wang, Yong Chen, Sha Li, Cuirong Liu and Guangming Liu

Materials 2026, 19(2), 252; https://doi.org/10.3390/ma19020252 - 8 Jan 2026

Abstract

In this paper, an AZ31B Mg/Al clad plate with 5052 aluminum alloy as the cladding was successfully prepared by a new composite process of corrugated roll roughing + flat roll finishing. First, finite element simulation software was used to predict and analyze the [...] Read more.

In this paper, an AZ31B Mg/Al clad plate with 5052 aluminum alloy as the cladding was successfully prepared by a new composite process of corrugated roll roughing + flat roll finishing. First, finite element simulation software was used to predict and analyze the rolling process. Subsequently, experimental research was carried out according to the simulation results, and clad plate samples under single corrugated rolling and corrugated–flat rolling processes were prepared. Finally, the differences between the two clad plates in shape quality, interface bonding state, and mechanical properties were systematically compared and analyzed. The results show that, compared with the traditional corrugated rolling process, the sheet formed by corrugated–flat rolling composite rolling has a flatter shape with no warpage, and its interface bonding quality is better. The specific performance is as follows: the mechanical properties were significantly improved, and the tensile strength and elongation reached 259.96 MPa and 8.11%, respectively, in the transverse direction (TD). This study provides a new strategy for the preparation of high-performance Mg/Al clad plates. Full article

(This article belongs to the Section Advanced Materials Characterization)

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17 pages, 2910 KB

Open AccessArticle

Antimicrobial Properties of Polymer-Based Nanocomposites Modified by Nanoparticles Produced by Green Chemistry

by Anna Wasilewska, Magda Bielicka, Urszula Klekotka, Grzegorz Markiewicz, Marek Jałbrzykowski, Wioleta Lewandowska, Izabela Swiecicka and Beata Kalska-Szostko

Materials 2026, 19(2), 251; https://doi.org/10.3390/ma19020251 - 8 Jan 2026

Abstract

A significant driving force in nanotechnology development is the environmentally friendly synthesis of nanomaterials using natural extracts as reducing and stabilizing agents. In this study, silver and copper nanoparticles were synthesized and compared using two approaches: (1) a green synthesis pathway employing beetroot [...] Read more.

A significant driving force in nanotechnology development is the environmentally friendly synthesis of nanomaterials using natural extracts as reducing and stabilizing agents. In this study, silver and copper nanoparticles were synthesized and compared using two approaches: (1) a green synthesis pathway employing beetroot extract as a natural bio-reductant and stabilizer, and (2) a conventional chemical reduction method. The resulting nanoparticles were extensively characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-Vis spectroscopy, and dynamic light scattering (DLS). The study revealed that the green synthesis route produced nanoparticles with well-defined morphology, high stability, and strong antimicrobial potential, outperforming those obtained via conventional chemical synthesis. Copper nanoparticles synthesized using beetroot extract exhibited particularly enhanced fungicidal and bactericidal properties, demonstrating the effectiveness of plant-based reducing agents in producing functional nanostructures. To further evaluate potential applications, the green-synthesized nanoparticles were incorporated into a polypropylene matrix, confirming their integrity and activity within the composite system. This work emphasizes the role of green synthesis in designing high-performance nanomaterials and highlights the promising capabilities of beetroot extract as a sustainable and efficient reducing and stabilizing medium for silver and copper nanoparticle production. Full article

(This article belongs to the Special Issue Fabrication, Characteristics and Applications of Multifunctional Polymer Nanocomposites)

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20 pages, 3240 KB

Open AccessArticle

Sustainable Rubberized Concrete-Filled Square Steel Tubular Columns Under Eccentric Compression

by Yanhua Liu, Yong Bao, Senyan Jiang, Qingxin Ren, Yu Liu and Tong Li

Materials 2026, 19(2), 250; https://doi.org/10.3390/ma19020250 - 8 Jan 2026

Abstract

This study examined rubberized concrete-filled steel tubular (RuCFST) columns as a sustainable option for structural applications. Eccentric compression tests were conducted on eight groups of square specimens, with two identical specimens per group. The main parameters were slenderness ratio, load eccentricity, and rubber [...] Read more.

This study examined rubberized concrete-filled steel tubular (RuCFST) columns as a sustainable option for structural applications. Eccentric compression tests were conducted on eight groups of square specimens, with two identical specimens per group. The main parameters were slenderness ratio, load eccentricity, and rubber replacement level for fine aggregates. Full load–displacement and load-strain curves were obtained. Results indicated that rubber particles inhibit concrete cracking. Increasing slenderness ratio reduces bearing capacity, with ductility peaking at moderate slenderness. Eccentricity significantly degrades bearing capacity and stiffness. A higher rubber replacement ratio lowers capacity but optimizes particle interaction and distribution, leading to stiffness recovery at higher ratios. Filling the steel tube with core concrete transforms it into a composite member, substantially improving load-bearing performance. Comparisons with seven design standards (including GB 50936-2014, CECS 254:2012, Eurocode 4, and AISC 360-16) revealed that Eurocode 4 provided the most reliable predictions, whereas AISC was the most cautious. None of the codes accounts for the effect of rubber on core concrete behavior. These results offer useful guidance for incorporating recycled rubber particles into composite columns to promote sustainable building practices. Full article

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

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9 pages, 1999 KB

Open AccessCommunication

A Rapid Spheroidizing Annealing Process for High-Carbon Steel

by Bei Li, Zhi Tong, Mengying Zhao, Xinlang Wu and Wenyue Zheng

Materials 2026, 19(2), 249; https://doi.org/10.3390/ma19020249 - 8 Jan 2026

Abstract

Spheroidizing annealing is a critical heat treatment process for high-carbon steels to balance hardness and machinability. This study develops a rapid spheroidizing annealing process by employing low-temperature pretreatment followed by subcritical heating. The key is to utilize carbide precipitates from non-equilibrium phases (e.g., [...] Read more.

Spheroidizing annealing is a critical heat treatment process for high-carbon steels to balance hardness and machinability. This study develops a rapid spheroidizing annealing process by employing low-temperature pretreatment followed by subcritical heating. The key is to utilize carbide precipitates from non-equilibrium phases (e.g., martensite/lower bainite) as nucleation sites, thereby accelerating spheroidization. At an optimized pretreatment temperature of 400 °C, the process achieves a homogeneous spheroidized microstructure with a hardness of 206.7 HV, comparable to that obtained via conventional prolonged annealing. This method significantly reduces processing time and energy consumption. Full article

(This article belongs to the Special Issue Additive Manufacturing and Forming Technologies of Alloy: Mechanical Properties and Microstructure Evaluation)

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14 pages, 3535 KB

Open AccessArticle

Reduction Behavior and Melting Characteristics of Blast Furnace Iron Ore Mixed with Carbon-Rich Iron Particles

by Jyun-Ming Shen, Chi-Ming Lin, You-Ren Hong, Shao-Feng Luo, Yu-Yang Chen, Jia-Shyan Shiau and Weite Wu

Materials 2026, 19(2), 248; https://doi.org/10.3390/ma19020248 - 8 Jan 2026

Abstract

The currently available hot briquetted iron (HBI) typically contains approximately 1 wt.% carbon. In the CO–CO₂ atmosphere of a blast furnace, carbon loss from iron is significant, accompanied by overoxidation. Based on the high metallicity of HBI, this study designed iron particles [...] Read more.

The currently available hot briquetted iron (HBI) typically contains approximately 1 wt.% carbon. In the CO–CO₂ atmosphere of a blast furnace, carbon loss from iron is significant, accompanied by overoxidation. Based on the high metallicity of HBI, this study designed iron particles with varying carbon contents. These pellets were mixed with three typical blast furnace iron ores–sinter, pellet, and lump– and subjected to thermogravimetric analysis reduction experiments. The investigation explored the effects of substituting 15 wt.% sinter with HBI containing different carbon contents and assessed the resulting impact on the temperature difference between iron and slag melting, ultimately determining the optimal carbon content for blast furnace operations. The findings showed that the addition of iron particles with carbon contents exceeding 1.6 wt.% achieved reduction rates and iron–slag melting characteristics similar to those of typical blast furnace charges. When iron particles containing 3.6 wt.% carbon were added, the iron oxides of various valence states in the charge and pellets exhibited the highest availability of carbon for both direct and indirect reduction. Consequently, the slag melting temperature rose to 1398 °C. Due to the presence of unreacted carbon, the molten iron melted at approximately 1530 °C, while the iron–slag dripping temperature range narrowed to 132 °C, achieving the optimal temperature range for blast furnace application. Full article

(This article belongs to the Section Metals and Alloys)

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26 pages, 4979 KB

Open AccessArticle

Chloride-Induced Corrosion Performance of ASR-Contaminated Concrete: Coupled Analysis Using Resistance Variation and NT Build 492 Method

by Tianxing Shi, Shami Nejadi and Harry Far

Materials 2026, 19(2), 247; https://doi.org/10.3390/ma19020247 - 8 Jan 2026

Abstract

This study examines how the Alkali–Silica Reaction (ASR) modifies chloride transport and chloride-induced corrosion (CIC) in reinforced concrete beams. Non-reactive and reactive concrete beams were cast with blue metal and dacite aggregates and subjected to a two-stage exposure: (i) alkali-rich immersion at 38 [...] Read more.

This study examines how the Alkali–Silica Reaction (ASR) modifies chloride transport and chloride-induced corrosion (CIC) in reinforced concrete beams. Non-reactive and reactive concrete beams were cast with blue metal and dacite aggregates and subjected to a two-stage exposure: (i) alkali-rich immersion at 38 °C to induce ASR, and (ii) impressed-current CIC and NT BUILD 492 chloride migration testing. Microstructural changes were characterized using SEM–EDS and TGA. The reactive specimens developed extensive surface cracking, but after one year of ASR exposure, exhibited 47–53% lower non-steady-state migration coefficients (Dnssm: 7.03–8.02 × 10⁻¹² m²/s) than the non-reactive beam (15.09 × 10⁻¹² m²/s). After two years, Dnssm was reduced by approximately 37–56% (4.78–6.93 vs. 10.92 × 10⁻¹² m²/s). Crack mapping confirmed higher crack density and width in reactive beams, while SEM–EDS and TGA evidenced Ca depletion and the formation of C–(N,K)–S–H gels, which fill cracks and refine the pore structure. Electrical resistance monitoring showed earlier corrosion initiation in ASR-damaged beams but less pronounced resistance loss during the propagation phase. Overall, the results indicate that ASR can initially accelerate corrosion initiation through microcracking and reduced resistivity, but long-term gel deposition can partially seal transport paths and lower chloride migration under the specific conditions of this study. Full article

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

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17 pages, 16588 KB

Open AccessArticle

The Governing Role of Si/Al Ratio in the Structural Evolution and Mechanical Properties of N-A-S-H Gel

by Min Hu, Jiayun Chen, Bo Xia and Jiejin Chen

Materials 2026, 19(2), 246; https://doi.org/10.3390/ma19020246 - 7 Jan 2026

Abstract

Alkali-activated cementitious materials are environmentally friendly alternatives to traditional cement. The structure of their core product, sodium aluminosilicate hydrate (N-A-S-H) gel, is regulated by the silicon-to-aluminum (Si/Al) ratio; however, the atomic-scale mechanism underlying this influence remains unclear. Integrating reactive force field molecular dynamics [...] Read more.

Alkali-activated cementitious materials are environmentally friendly alternatives to traditional cement. The structure of their core product, sodium aluminosilicate hydrate (N-A-S-H) gel, is regulated by the silicon-to-aluminum (Si/Al) ratio; however, the atomic-scale mechanism underlying this influence remains unclear. Integrating reactive force field molecular dynamics simulations and experiments, this study systematically reveals the regulation mechanism of the Si/Al ratio (1.0–2.0) on the microstructure and macroscopic properties of N-A-S-H gels. Starting from well-defined PS and PSS oligomers, the simulation results demonstrate that the Si/Al ratio governs the polymerization pathway, aluminum coordination environment (especially the content of pentacoordinate aluminum), and evolution of nanoporosity. When the Si/Al ratio is approximately 1.8, the system exhibits the highest silicate polymerization degree, lowest nanoporosity, and densest three-dimensional (3D) network structure; deviation from this ratio leads to structural degradation due to charge imbalance or excessive polymerization. These computational findings are validated by experiments on fly ash-based geopolymers: the material achieves the highest compressive strength at a Si/Al ratio of 1.8. The consistency between simulations and experiments collectively reveals a cross-scale action mechanism: the Si/Al ratio determines the macroscopic mechanical properties by regulating the nanoscale packing density and defect distribution of the gel. This study provides critical atomic-scale insights for the rational design of high-performance geopolymers. Full article

(This article belongs to the Topic Novel Cementitious Materials)

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20 pages, 4822 KB

Open AccessArticle

Impact of Waste-HydroChar on the Rheological Behavior, Physical Properties, and Aging Resistance of Bitumen

by Nadka Tz. Dintcheva, Rosalia Teresi, Francesco Graziano, Giulia Infurna, Maurizio Volpe, Antonio Messineo and Clara Celauro

Materials 2026, 19(2), 245; https://doi.org/10.3390/ma19020245 - 7 Jan 2026

Abstract

In line with circular principles and the reuse of waste products, this study investigates the use of a waste-derived additive sourced from civil waste to modify the rheological and physical properties, as well as the aging resistance, of bitumen. Different dosages of waste-hydrochar [...] Read more.

In line with circular principles and the reuse of waste products, this study investigates the use of a waste-derived additive sourced from civil waste to modify the rheological and physical properties, as well as the aging resistance, of bitumen. Different dosages of waste-hydrochar (HC), produced via hydrothermal carbonization of digested sewage sludge, specifically 2%, 4%, and 10% by weight, were introduced to the bitumen, and the materials were characterized in terms of their rheological, physical, and aging behavior. Two aging protocols, e.g., short-term thermal aging and UV irradiation aging, were followed to evaluate the aging resistance of the bitumen with and without waste-hydrochar. The results obtained suggest that bitumen containing waste-hydrochar exhibits similar rheological and physical properties to bitumen without an additive, indicating the potential for using this waste material as a suitable bitumen additive. Furthermore, the presence of waste-hydrochar does not reduce the short-term thermal or UV irradiation resistance of bitumen, again suggesting the potential for using this waste material as a suitable bitumen additive. Finally, the results obtained have been compared with those of bitumen containing high-cost biochar, highlighting the potential to replace high-cost biochar with low-cost, waste-hydrochar. Full article

(This article belongs to the Special Issue Advances in Hybrid Energy Harvesting: Materials, Structures and Applications)

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21 pages, 5184 KB

Open AccessArticle

Effect of Argon Injection into the Down-Leg of RH on the Inclusion Removal in Industrial Trials

by Yukang Pan, Yanhui Sun, Yang He, Xiaodong Yang, Baohui Yuan and Jianhua Liu

Materials 2026, 19(2), 244; https://doi.org/10.3390/ma19020244 - 7 Jan 2026

Abstract

The novel industrial trial is conducted to investigate the effect of argon injection into the down-leg of the RH degasser on the inclusion removal. The ‘cold steel plate dipping’ is used to take samples of molten steel and argon bubbles from the RH [...] Read more.

The novel industrial trial is conducted to investigate the effect of argon injection into the down-leg of the RH degasser on the inclusion removal. The ‘cold steel plate dipping’ is used to take samples of molten steel and argon bubbles from the RH ladle. The industrial CT detection and electron microscope observation are applied to analyze the bubble characteristics. The results show that the size of bubbles generated by argon injection in the down-leg ranges from 7 to 1430 μm. Among them, the number density of bubbles with a diameter of 60 μm is the largest, reaching 0.1 per mm³. After adopting the down-leg argon injection technology, the average oxygen activity at the end of the RH process decreases by 2.35 ppm, and the surface defects of cold-rolled sheets of all grades are reduced. Based on the theoretical analysis of bubble collision and adhesion to inclusions, the small-sized bubbles have a relatively high capture probability for inclusions smaller than 10 μm. Comprehensively analyzing the experimental results, it is found that the down-leg argon injection technology has an obvious effect on removing inclusions. Full article

(This article belongs to the Special Issue Fundamental Metallurgy: From Impact Solutions to New Insight)

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