Materials

21 pages, 3370 KB

Open AccessArticle

Understanding Mechanical Properties of Nothofagus alpina (Poepp. & Endl.) Oerst. Wood Through Controlled Freeze–Heat Treatments: Linking Physical, Chemical, and Structural Changes

by Rodrigo Valle, Romina E. Inostroza, Luis Soto-Cerda, Wilmer Bueno-Silva, Marcelo Muñoz-Vera, Víctor Tuninetti and Ricardo I. Castro

Materials 2026, 19(6), 1275; https://doi.org/10.3390/ma19061275 - 23 Mar 2026

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Abstract

Wood is a versatile material; however, it is susceptible to changes when exposed to extreme temperatures. This study investigated the physical, chemical, and mechanical properties of raulí (Nothofagus alpina) under different thermal stress conditions. The results showed that the moisture content at [...] Read more.

Wood is a versatile material; however, it is susceptible to changes when exposed to extreme temperatures. This study investigated the physical, chemical, and mechanical properties of raulí (Nothofagus alpina) under different thermal stress conditions. The results showed that the moisture content at temperatures below 5 °C exhibited a significant reduction from 9.7% to 7.5% within the first 20 days. Conversely, under extreme cold (−20 °C), significant changes only occurred after 60 days, with an increase from 9.7% to 11%. At higher temperatures (50 °C, 95 °C, and 120 °C), moisture content dropped sharply after 40 days, nearing 0%. Additionally, analysis showed minor color changes in samples at low temperatures: RW2 (20 d; 5 °C, ΔE* = 3.46) and RW7 (40 d; 5 °C, ΔE* = 0.61); however, color changes were observed at higher temperatures (95–120 °C). RW15 (60 d; 120 °C, ΔE* = 37.16), indicating the degradation of cell wall polymers. Mechanical testing using three-point bending demonstrated that controlled heat treatments can improve the modulus of elasticity (MOE), modulus of rupture (MOR), and fracture energy. The most significant improvements were obtained at 120 °C for 60 days, with increases in MOE, MOR, and fracture energy of 22%, 60%, and 118%, respectively, compared to untreated wood. Full article

(This article belongs to the Special Issue Development and Application of Wood-Based Materials)

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15 pages, 4210 KB

Open AccessArticle

Tool Wear and Surface Finish in AISI 304 Stainless Steel Dry Turning with Cermet Inserts

by Laurence Colares Magalhães, Nelson Antenor Sorte, Marcelo Tramontin Souza and Armando Marques

Materials 2026, 19(6), 1274; https://doi.org/10.3390/ma19061274 - 23 Mar 2026

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Abstract

The present study investigates the surface integrity and flank wear of uncoated cermet inserts during dry turning of AISI 304 stainless steel. Three-dimensional metrology techniques were employed to assess both surface roughness and cutting-tool flank wear. Cutting speed and feed rate were the [...] Read more.

The present study investigates the surface integrity and flank wear of uncoated cermet inserts during dry turning of AISI 304 stainless steel. Three-dimensional metrology techniques were employed to assess both surface roughness and cutting-tool flank wear. Cutting speed and feed rate were the process parameters varied in the experiments. Both parameters exhibited a significant influence on the final surface quality. Specifically, increasing the cutting speed resulted in a deterioration of the surface finish under the evaluated conditions. Considering an average flank wear (VBB) of 0.1 mm as the tool life criterion, tool lives of 15 min and 9 min were achieved at cutting speeds of 120 m/min (lowest level) and 150 m/min (highest level), respectively. At lower cutting speeds, abrasive wear and adhesion were the predominant wear mechanisms, whereas chipping and diffusion became more pronounced at the higher cutting speed. The dry turning of AISI 304 stainless steel with uncoated cermet inserts proved viable in terms of sustainability and surface integrity; however, effective chip evacuation remains a critical concern. The use of compressed air or minimum quantity lubrication (MQL) may help mitigate this issue. Full article

(This article belongs to the Section Metals and Alloys)

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28 pages, 34091 KB

Open AccessArticle

Effects of Titanium Gypsum and Flue Gas Desulfurization Gypsum on the Hydration and Mechanical Properties of Anhydrite–Phosphogypsum-Based Supersulfated Cement

by Youquan Xie, Li Yang, Xiaodong Li, Jiaqing Wang, Yanbo Li, Hao Zhou and Yueyang Hu

Materials 2026, 19(6), 1273; https://doi.org/10.3390/ma19061273 - 23 Mar 2026

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Abstract

Supersulfated cement (SSC) is an environmentally friendly cementitious material with a low clinker content, in which industrial byproduct gypsum serves as the sulfate source, thereby enabling the valorization of solid waste. The hydration process, pore structure, microstructure, and hydration products were investigated using [...] Read more.

Supersulfated cement (SSC) is an environmentally friendly cementitious material with a low clinker content, in which industrial byproduct gypsum serves as the sulfate source, thereby enabling the valorization of solid waste. The hydration process, pore structure, microstructure, and hydration products were investigated using paste samples by means of isothermal calorimetry, X-ray diffraction (XRD), thermogravimetric analysis (TG–DTG), Fourier transform–infrared spectroscopy (FT-IR), mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM), while compressive strength was evaluated using mortar specimens. Compared with ordinary Portland cement (OPC), SSC offers clear advantages in reducing energy consumption and greenhouse gas emissions. In this study, the effects of titanium gypsum (TG) and flue gas desulfurization gypsum (FGD) on the hydration behavior, fluidity, mechanical properties, and microstructural evolution of an anhydrite (AH)–phosphogypsum (PG)-based SSC were systematically investigated. The results indicate that the incorporation of 11% TG and FGD mitigates the strong sulfate environment caused by the rapid dissolution of soluble AH, thereby regulating the hydration process. As the proportion of TG and FGD increased, the cumulative heat release within 72 h gradually decreased. When AH was completely replaced, the cumulative heat release of TG4 and FG4 decreased by approximately 19.7% and 28.6%, respectively. TG and FGD exhibited opposite effects on the fluidity of SSC while both promoting strength development. Among all mixtures, TG2 and FG2 showed the best performance, with the highest 28-day compressive strengths of 50.15 MPa and 51.95 MPa, respectively. Microstructural analysis reveals that differences in particle size distribution and dissolution kinetics among gypsums governed the sulfate release characteristics and slag activation mechanisms, thus leading to distinct hydration pathways, pore structure evolution, and microstructural densification. This study provides a theoretical basis for the efficient utilization of various industrial byproduct gypsums and offers important guidance for the controllable design of SSC performance. Full article

(This article belongs to the Special Issue Advances in Hydration Chemistry for Low-Carbon Cementitious Materials)

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14 pages, 3565 KB

Open AccessArticle

Decarburization Control of H13 Steel Under Varying Process Pressures During Austenitization

by Gi-Hoon Kwon, Byoungho Choi, Su-Young Choi, Kyoung Jun An and Kyoung Il Moon

Materials 2026, 19(6), 1272; https://doi.org/10.3390/ma19061272 - 23 Mar 2026

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Abstract

Decarburization during austenitization degrades the surface integrity and mechanical performance of tool steels, yet the quantitative influence of process pressure remains unclear. In this study, the effect of process pressure on the decarburization behavior of H13 tool steel was investigated. Specimens were austenitized [...] Read more.

Decarburization during austenitization degrades the surface integrity and mechanical performance of tool steels, yet the quantitative influence of process pressure remains unclear. In this study, the effect of process pressure on the decarburization behavior of H13 tool steel was investigated. Specimens were austenitized at 920–1020 °C for 60 min under pressures ranging from 0.01 to 760 Torr. Carbon concentration profiles were measured by electron probe microanalysis, and hardness degradation and mass loss were evaluated. A one-dimensional diffusion model with a Robin boundary condition was applied to describe the coupled effects of carbon diffusion and surface reaction. High-vacuum conditions suppressed decarburization, whereas increasing pressure accelerated carbon loss, leading to deeper decarburized layers and pronounced hardness reduction. The model reproduced the experimental results and revealed a pressure-dependent transition in the dominant decarburization mechanism. Full article

(This article belongs to the Section Metals and Alloys)

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25 pages, 2455 KB

Open AccessArticle

Physics-Informed Machine Learning for Carbonation Depth Prediction in Concrete

by Moutaman M. Abbas and Alina Bărbulescu

Materials 2026, 19(6), 1271; https://doi.org/10.3390/ma19061271 - 23 Mar 2026

Viewed by 347

Abstract

The durability of reinforced concrete structures is significantly affected by the carbonation process, which decreases the alkalinity of the pore solution and initiates corrosion of the steel reinforcement. However, the square roots of time equations, which are Fickian diffusion-based, are not able to [...] Read more.

The durability of reinforced concrete structures is significantly affected by the carbonation process, which decreases the alkalinity of the pore solution and initiates corrosion of the steel reinforcement. However, the square roots of time equations, which are Fickian diffusion-based, are not able to accurately capture the nonlinear interactions of material properties with environmental factors. To overcome this limitation, this research introduces a novel hybrid model based on the integration of a physics-informed neural network (PINN) with residual regression via CatBoost, a categorical boosting algorithm. Using an expanded dataset of 6000 samples, the first stage of the model, which is based on the physics-informed neural network, is able to learn the underlying physics of the diffusion process by imposing monotonicity constraints. The second stage of the model, which is based on the CatBoost algorithm, is able to learn the residuals of the nonlinear interactions of factors such as the curing time, water–cement ratio, and supplementary cementitious material reactivity, which are not captured by the underlying physics of the diffusion law. Data augmentation via physics-based resampling increased the dataset from 3000 to 6000 samples. Validation of the model using 1200 samples resulted in R² = 0.871, MAE = 15.362, and RMSE = 24.37. SHAP confirmed that the model was physically consistent with the principles of concrete technology, reversing the counterintuitive linear correlations to accurately capture the protective effect of longer curing times. The suggested framework offers a practical method for enhancing durability evaluation and aiding the maintenance and service-life management of reinforced concrete structures. Full article

(This article belongs to the Special Issue Recent Progress in Sustainable Construction Materials)

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13 pages, 2158 KB

Open AccessArticle

A Broad-Band Self-Powered Photodetector Based on a MoTe₂/Bi₂Te₃ Heterojunction for Optical Imaging and Bias-Controlled Signal Modulation

by Shaoxiong Du, Kunle Li, Weijie Li, Jiahui Feng, Yunwei Sheng, Lili Tao, Zhaoqiang Zheng, Wei Song and Yu Zhao

Materials 2026, 19(6), 1270; https://doi.org/10.3390/ma19061270 - 23 Mar 2026

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Abstract

Self-powered photodetectors are highly demanded in applications but often suffer from limited spectral absorption, slow response speed, and high dark currents. Two-dimensional van der Waals heterostructures have emerged as promising candidates owing to their designable structures and excellent performance. Herein, we construct a [...] Read more.

Self-powered photodetectors are highly demanded in applications but often suffer from limited spectral absorption, slow response speed, and high dark currents. Two-dimensional van der Waals heterostructures have emerged as promising candidates owing to their designable structures and excellent performance. Herein, we construct a MoTe₂/Bi₂Te₃ heterostructure and investigate its photoelectric properties. At zero bias, it exhibits a broad photovoltaic response ranging from 405 to 1550 nm. Benefiting from the interfacial built-in electric field, it achieves a responsivity of 1.38 A/W and a detectivity of 1.90 × 10¹² Jones at 532 nm and retains 174.56 mA/W and 2.4 × 10¹¹ Jones at 1060 nm, together with a low dark current of 1.6 × 10⁻¹² A. Upon a reverse bias of −1 V and 532 nm laser illumination at an intensity of 19.0 W/m², the responsivity is further boosted to 36.22 A/W, accompanied by rise and decay times of 32 ms and 33 ms, respectively. Taking advantage of the distinct optical switching ratios at zero/non-zero biases, application in optical imaging and bias-controlled signal modulation is realized, highlighting the heterojunction’s potential as a broadband self-powered photodetector. Full article

(This article belongs to the Special Issue Two-Dimensional Semiconductors—Advancements in Material Growth and Characterization)

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17 pages, 14248 KB

Open AccessArticle

Research on the Mechanism of Hydrogen Plasma Heating and Reduction of Acidic Pellets

by Zihao Fan, Xiaoping Zhang, Chuanwen Geng, Xingyue Jin, Lin Li, Peng Zhao, Baoliang Wen and Jialong Yang

Materials 2026, 19(6), 1269; https://doi.org/10.3390/ma19061269 - 23 Mar 2026

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Abstract

Hydrogen plasma heating, a unique method for heating and reducing iron ore, is distinguished by its high heat, rapid reduction, and high efficiency, making it a promising technique in the metallurgy field. In this study, a non-transferred arc plasma heating system was used [...] Read more.

Hydrogen plasma heating, a unique method for heating and reducing iron ore, is distinguished by its high heat, rapid reduction, and high efficiency, making it a promising technique in the metallurgy field. In this study, a non-transferred arc plasma heating system was used with Ar-H₂ as the working gas and acidic pellets as the raw material. The microstructures and elemental distributions of the slag and iron phases during the reduction process were examined using electron microscopy and energy-dispersive X-ray. The variation patterns of Fe-containing phases in the reduction products were found using X-ray diffraction and full-spectrum fitting refinement. The conversion rate of the oxidized pellets and the deoxidation conversion rate per area were estimated for various gas flow rates and reduction times. A reaction kinetics model was also used to study the reaction controlling step. The results showed that during the reduction process, with an H₂ flow rate of 4.5 L min⁻¹ and a 40 min reduction, the conversion(α) reached 99.89% and the purity of the reduced metallic iron reached 99.9%, achieving the industrial-grade 3N standard. Si and Al in the melt bath generated fayalite (Fe₂SiO₄) and hercynite (FeAl₂O₄) with Fe_xO. The deoxidation conversion rate per unit area was 1.11 g (cm² min)⁻¹. A three-dimensional diffusion-controlled model was used to describe the reduction process, and the mechanism function was 2/3(1 + α)^3/2[(1 + α)^1/3]⁻¹. The values of the reduction reaction rate constant (K) were 12.6 × 10⁻² s⁻¹ and 12.8 × 10⁻² s⁻¹ when the flow rates of H₂ gas were 3 and 4.5 L min⁻¹, respectively. The apparent activation energy was 21.9 kJ mol⁻¹. The empirical equation for the specific reduction rate was calculated as ln r = −2637.5/T − 0.407. Full article

(This article belongs to the Section Metals and Alloys)

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26 pages, 1601 KB

Open AccessArticle

Performance Control and Mechanism Analysis of DCLR-Based Composite High-Modulus Asphalt Based on Synergistic Modification Effect

by Bin Xu, Xinjie Yu, Aodong Gao, Guanjun Bu and Kaiji Lu

Materials 2026, 19(6), 1268; https://doi.org/10.3390/ma19061268 - 23 Mar 2026

Viewed by 261

Abstract

To address the prominent problem of early rutting distress in asphalt pavements under heavy-load traffic in China, this study proposes a composite modifier consisting of direct coal liquefaction residue (DCLR), styrene–butadiene–styrene block copolymer (SBS), and styrene–butadiene rubber (SBR). The preparation process and formula [...] Read more.

To address the prominent problem of early rutting distress in asphalt pavements under heavy-load traffic in China, this study proposes a composite modifier consisting of direct coal liquefaction residue (DCLR), styrene–butadiene–styrene block copolymer (SBS), and styrene–butadiene rubber (SBR). The preparation process and formula were optimized through single-factor experiments and orthogonal tests. Systematic investigations were conducted on its conventional performance, water damage resistance, aging resistance, fatigue performance, rheological properties, and microscopic mechanism, with comparisons made against base asphalt, single DCLR-modified asphalt, SBS-modified asphalt, and SBS/SBR-modified asphalt. The results indicate that the optimal preparation process for the novel composite high-modulus modified asphalt is as follows: DCLR particle size of 0.3 mm, addition in molten state, shear temperature of 170 °C, shear rate of 5000 r·min⁻¹, shear time of 50 min. The optimal formula is 10% DCLR + 3% SBS + 2% SBR + 3% compatibilizer, with the addition sequence of “DCLR → SBS + compatibilizer → SBR”. This asphalt exhibits a softening point of 77.8 ± 2.1 °C, a Brookfield viscosity at 135 °C of 1.928 ± 0.105 Pa·s, and a grading of 5 for adhesion to aggregates; the rutting factor at 64 °C reaches 10.8 ± 0.9 kPa (6.43 times that of the base asphalt), the creep stiffness at −12 °C is 136 ± 12.5 MPa, and the low-temperature limit temperature is −17 °C; the freeze–thaw splitting strength ratio (TSR) is 94.6 ± 1.8%, and both aging resistance and water damage resistance are significantly superior to those of the control group asphalts (p < 0.05). The novel composite high-modulus modified asphalt showed improved overall laboratory performance and may be suitable for heavy-load traffic and complex climatic conditions, however, field validation is needed. Full article

(This article belongs to the Special Issue Mechanical Property Research of Advanced Asphalt-Based Materials—Second Edition)

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16 pages, 1228 KB

Open AccessReview

The Methods for Estimating State of Charge in Lithium-Ion Batteries

by Peilin Xu and Ruyan Zhou

Materials 2026, 19(6), 1267; https://doi.org/10.3390/ma19061267 - 23 Mar 2026

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Abstract

It is of great significance in real time to accurately monitor the internal state parameters of lithium-ion batteries toy ensure the safety, reliability and lasting efficiency of battery energy storage systems. The battery management system can monitor the working state, prevent overcharge or [...] Read more.

It is of great significance in real time to accurately monitor the internal state parameters of lithium-ion batteries toy ensure the safety, reliability and lasting efficiency of battery energy storage systems. The battery management system can monitor the working state, prevent overcharge or overdischarge, and make the working process more safe and reliable. The state of charge (SOC) is one of the most important indicators to monitor a working battery, and its accurate estimation is the most important work at present. SOC cannot be measured directly, so the state estimation problem of batteries is transformed into a state estimation problem of time-varying nonlinear systems, the core of which is how to obtain a more accurate and reasonable state estimation value in real time. This paper introduces the definition of battery charge state, summarizes common estimation methods and disadvantages of the ampere-hour integration method and open-circuit voltage method, and finally points out the future development direction of battery charge state estimation methods. Full article

(This article belongs to the Section Energy Materials)

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13 pages, 1894 KB

Open AccessArticle

Circular Approach to Composite Materials: Synthesis of Carbon Nanomaterials from Polymer Recycling Liquid By-Products

by Evangelos Tsimis, Stefania Termine, Maria Modestou, Aikaterini-Flora Trompeta, Szymon Sobek, Marcin Sajdak, Jakub Adamek, Sebastian Werle and Costas Charitidis

Materials 2026, 19(6), 1266; https://doi.org/10.3390/ma19061266 - 23 Mar 2026

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Abstract

The growing volume of fiber-reinforced polymer composite waste creates an urgent need for efficient recycling technologies. While solvolysis effectively breaks down thermoset matrices for fiber reinforcement recovery, the process generates hydrocarbon-rich liquid by-products that require further management. This study validates the use of [...] Read more.

The growing volume of fiber-reinforced polymer composite waste creates an urgent need for efficient recycling technologies. While solvolysis effectively breaks down thermoset matrices for fiber reinforcement recovery, the process generates hydrocarbon-rich liquid by-products that require further management. This study validates the use of these liquid recycling streams—derived from the solvolysis of unsaturated polyester and epoxy resins—as sustainable carbon precursors for the growth of carbon nanomaterials. Synthesis was performed via catalytic chemical vapor deposition (CVD) at 850 °C using iron nanoparticles impregnated on a zeolite substrate. Morphological analysis confirmed the production of one-dimensional nanostructures (carbon nanotubes/nanofibers), with average diameters below 100 nm. Raman spectroscopy revealed a high degree of graphitization, with I_D/I_G ratios ranging from 0.25 to 0.58, which is comparable to structures synthesized from conventional precursors. Thermogravimetric analysis (TGA) demonstrated high thermal stability and carbon purity reaching up to 90.3%. These findings demonstrate a viable upcycling pathway that enhances the economic attractiveness of composite recycling by transforming waste into advanced nanomaterials. Full article

(This article belongs to the Special Issue Carbonaceous Materials: Fabrication, Characterization and Applications—Second Edition)

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13 pages, 3590 KB

Open AccessArticle

Optical Properties and Growth of the (100) Crystal-Faced MAPbBr₃ Film on TiN-Buffered MgO Substrate

by Tzu-Lung Chang, Yu-Chen Lin, Yu-Li Hsieh, Hsueh-Hsing Hung and Hui-Huang Hsieh

Materials 2026, 19(6), 1265; https://doi.org/10.3390/ma19061265 - 23 Mar 2026

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Abstract

The growth of MAPbBr₃ crystal-faced films is a critical challenge for advancing optoelectronic devices. This study presents a methodology for fabricating a (100) crystal-faced MAPbBr₃ film on a lattice-matched MgO/TiN composite substrate using a localized thermally driven inverse temperature crystallization technique. [...] Read more.

The growth of MAPbBr₃ crystal-faced films is a critical challenge for advancing optoelectronic devices. This study presents a methodology for fabricating a (100) crystal-faced MAPbBr₃ film on a lattice-matched MgO/TiN composite substrate using a localized thermally driven inverse temperature crystallization technique. The metallic TiN buffer layer offers a 0.66% lattice mismatch to MAPbBr₃, minimizing interfacial strain. Furthermore, the orientation enhancement of the film induced by post-annealing was confirmed by X-ray diffraction, with the (200) peak FWHM decreasing from 0.042° to 0.028° and the intensity ratio of the (100) to (110) peaks increasing from 6.89 to 19.00. These structural improvements directly translate into enhanced optical performance. The annealed sample exhibited sharper Raman phonon modes at 49 cm⁻¹ and 151 cm⁻¹, a 1.8-fold photoluminescence intensity enhancement, and a 20.8% narrowing of the PL FWHM at 536 nm. Additionally, UV-Vis spectroscopy confirms the bandgap of MAPbBr₃, displaying a steeper absorption edge with a bandgap of 2.30 eV. These metrics provide compelling evidence of suppressed non-radiative recombination and improved optical homogeneity after annealing. By integrating TiN as an electron-transport and buffer layer to reduce strain and lattice mismatch, the MgO/TiN/MAPbBr₃ architecture offers a scalable, scientifically grounded pathway to improve MAPbBr₃’s optical performance. Full article

(This article belongs to the Section Thin Films and Interfaces)

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24 pages, 4071 KB

Open AccessArticle

Detecting Critical Damage in Concrete by Taking Advantage of Acoustic Events with an Amplitude Exceeding Their Mean Value

by Dimos Triantis, Ilias Stavrakas, Ermioni D. Pasiou and Stavros K. Kourkoulis

Materials 2026, 19(6), 1264; https://doi.org/10.3390/ma19061264 - 23 Mar 2026

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Abstract

A novel approach for detecting preliminary signals designating upcoming entrance of a loaded system to the critical stage of impending fracture is assessed. The approach is based on the analysis of a time series of the cumulative number of acoustic events, the amplitude [...] Read more.

A novel approach for detecting preliminary signals designating upcoming entrance of a loaded system to the critical stage of impending fracture is assessed. The approach is based on the analysis of a time series of the cumulative number of acoustic events, the amplitude of which exceeds the respective average value of all the events recorded during loading. Using the “sliding window” technique, the average slope of the evolution of this time series is quantified, either against conventional or natural time (the latter provides a more detailed view of the stage before macroscopic fracture, during which the “information” gathered is very densely packed in a short interval). For the needs of this study, data from a previously published experimental protocol are exploited. The protocol comprised notched, beam-shaped specimens, made of either plain or fiber-reinforced concrete, under three-point bending. It is concluded that the slope of the evolution of the above time series systematically attains a value equal to unity slightly before the applied load attains its peak value. The results of the present analysis are in qualitative agreement with the respective ones based on either the instantaneous frequency of generation of acoustic events or the Euclidean distance between the sources of acoustic signals. Full article

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

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2 pages, 1332 KB

Open AccessCorrection

Correction: Srichanachaichok, W.; Pissuwan, D. Micro/Nano Structural Investigation and Characterization of Mussel Shell Waste in Thailand as a Feasible Bioresource of CaO. Materials 2023, 16, 805

by Wiranchana Srichanachaichok and Dakrong Pissuwan

Materials 2026, 19(6), 1263; https://doi.org/10.3390/ma19061263 - 23 Mar 2026

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Abstract

In the original publication [...] Full article

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16 pages, 3873 KB

Open AccessArticle

Dependence of Wenzel–Cassie Transition on Droplet Size: The Critical Water Droplet

by Mengdan You, Yanfei Wang, Yuzhen Liu and Qiang Sun

Materials 2026, 19(6), 1262; https://doi.org/10.3390/ma19061262 - 23 Mar 2026

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Abstract

In this work, molecular dynamics (MD) simulations are applied to investigate the dependence of the Wenzel–Cassie transition on water droplet size. During the Wenzel–Cassie transition, the critical water droplet and corresponding critical roughness may be expected, which are respectively described as the critical [...] Read more.

In this work, molecular dynamics (MD) simulations are applied to investigate the dependence of the Wenzel–Cassie transition on water droplet size. During the Wenzel–Cassie transition, the critical water droplet and corresponding critical roughness may be expected, which are respectively described as the critical radius (R_Droplet,c) and wetting parameter (W_Roughness,c). From the work, R_Droplet,c may be termed as the smallest droplet size at which the Cassie state is expected for the corresponding W_Roughness,c. In combination with the structural study of water, it is due to the structural competition between interfacial and bulk water. Additionally, R_Droplet,c may be dependent on the W_Roughness,c. It is found that the R_Droplet,c is influenced by the distribution and geometric characteristics of surface roughness. A denser distribution of roughness is expected to result in a lower R_Droplet,c. Consequently, superhydrophobicity may be influenced by the characteristics of surface roughness and the size of the water droplet. The Cassie state is achieved when the wetting parameter of roughness is less than the W_Roughness,c and the water droplet is larger than the R_Droplet,c. Full article

(This article belongs to the Special Issue Superhydrophobic Interfaces and Surfaces: Preparation, Characterization, and Applications)

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15 pages, 5536 KB

Open AccessArticle

Impact of M-POSS on Selected Properties of Experimental Methacrylate Matrices and Composites

by Kinga Bociong, Barbara Kosior, Norbert Soboń, Monika Domarecka, Jerzy Sokołowski, Aleksandra Zimon, Michał Krasowski and Agata Szczesio-Wlodarczyk

Materials 2026, 19(6), 1261; https://doi.org/10.3390/ma19061261 - 23 Mar 2026

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Abstract

Methacrylate-POSS (M-POSS) is a novel organic–inorganic additive shown to reinforce dental composites and reduce polymerization shrinkage. This study aimed to evaluate the influence of M-POSS addition (0.5, 2, 10, or 15 wt.%) on the mechanical properties of an experimental polymer matrix (bis-GMA/UDMA/TEGDMA/HEMA = [...] Read more.

Methacrylate-POSS (M-POSS) is a novel organic–inorganic additive shown to reinforce dental composites and reduce polymerization shrinkage. This study aimed to evaluate the influence of M-POSS addition (0.5, 2, 10, or 15 wt.%) on the mechanical properties of an experimental polymer matrix (bis-GMA/UDMA/TEGDMA/HEMA = 35/35/20/10 wt.%) and a dental resin composite (45 wt.% silanized silica as filler). Vickers hardness (HV), three-point bending strength (FS), diametral tensile strength (DTS), and shrinkage stress generated during polymerization were studied. The results show HV values between 16 and 18 compared to 15 ± 1 in the control group. Hardness in the control composite was 34 ± 4, and after modification, it showed similar or slightly lower values between 32 and 35. FS increased from 90 ± 4 MPa before modification to 100 ± 5 MPa for 2 wt.% M-POSS, and then decreased to 78 ± 5 MPa for materials containing 15 wt.% M-POSS. FS of composites were within the range of 61–77 MPa, with a similar tendency in variation to that of matrices. DTS values decreased after M-POSS addition, from 37 ± 4 MPa before modification to 31–33 MPa after modification. Flexural modulus decreases after modification, both for matrices and composites. The morphology of composites with >10 wt. % M-POSS showed visible surface irregularities. In conclusion, M-POSS affects matrix hardness, resulting in an increase in HV. The addition of M-POSS also increases FS values of the matrix, but only up to a certain concentration. However, the introduction of M-POSS does not significantly affect the HV or bending strength of the composites. Although DTS values decreased, this change was not statistically significant. Finally, contraction stress was significantly reduced for groups containing 2 wt.% and 10 wt.% M-POSS, representing an anticipated and promising improvement. Full article

(This article belongs to the Special Issue Advanced Dental Materials: From Design to Application, Third Edition)

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24 pages, 11341 KB

Open AccessArticle

An RSM-Based Investigation on the Process–Performance Correlation and Microstructural Evolution of Friction Stir Welded 7055 Al/2195 Al-Li Dissimilar T-Joints

by Binbin Lin, Yanjie Han, Duquan Zuo, Nannan Wang, Yuanxiu Zhang, Haoran Fu and Chong Gao

Materials 2026, 19(6), 1260; https://doi.org/10.3390/ma19061260 - 23 Mar 2026

Viewed by 318

Abstract

Friction stir welding (FSW) is a key technology for manufacturing T-shaped thin-walled structures and avoiding fusion welding defects. However, the quantitative relationship between its process parameters and the microstructure properties of the joint remains unclear. To address this, this study established regression models [...] Read more.

Friction stir welding (FSW) is a key technology for manufacturing T-shaped thin-walled structures and avoiding fusion welding defects. However, the quantitative relationship between its process parameters and the microstructure properties of the joint remains unclear. To address this, this study established regression models via response surface methodology (RSM) relating rotational speed (w), welding speed (v), and plunge depth (h) to the mechanical properties of T-joints. The optimal process parameters (400 rpm, 60 mm/min, 0.21 mm) were determined, under which the ultimate tensile strength (UTS) and weld nugget hardness (WNH) of the joint reached 74.1% (377 MPa) and 94.4% (153 Hv) of the base materials (BM) respectively, with v showing the most significant influence on joint mechanical properties. Microstructural observations revealed that from the BM to the stirring zone (SZ), the grains underwent a continuous evolution from coarsening, partial recrystallization to complete dynamic recrystallization (DRX). In the SZ, due to severe plastic deformation and high heat input, the continuous dynamic recrystallization (CDRX) was the dominant mechanism, and the grain was significantly refined. The heat input in the thermomechanical affected zone (TMAZ) is relatively low, mainly geometric dynamic recrystallization (GDRX). DRX-driven grain refinement was the primary strengthening factor in the joint, with hardness closely related to grain size. However, thermal cycling induced softening in the heat-affected zone (HAZ) and promoted the precipitation of brittle compounds such as Al₃Mg₂ and MgZn₂, which caused crack initiation exhibiting intergranular brittle fracture. Subsequently, under stress drive, it extends to SZ, mainly characterized by ductile fracture. Full article

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17 pages, 1440 KB

Open AccessArticle

Mechanical and Environmental Performance of Concrete Incorporating Post-Consumer Plastics and E-Waste

by Madiha Ammari, Halil Sezen and Jose Castro

Materials 2026, 19(6), 1259; https://doi.org/10.3390/ma19061259 - 23 Mar 2026

Viewed by 261

Abstract

A significant portion of plastic products is not accepted by curbside recycling companies and goes to landfills or incineration, causing an adverse impact on the environment. This study investigated the effects of utilizing post-consumer plastic and e-waste in concrete. A plastic product made [...] Read more.

A significant portion of plastic products is not accepted by curbside recycling companies and goes to landfills or incineration, causing an adverse impact on the environment. This study investigated the effects of utilizing post-consumer plastic and e-waste in concrete. A plastic product made of thermoplastic polypropylene (PP) was ground into fine particles and used for 10% volumetric replacement of sand, while bare printed circuit boards (PCBs) were pulverized into powder and used for 10% cement replacement by mass. This study introduces a unique utilization of grounded powder PCBs by partially replacing cement in concrete. Furthermore, reinforced concrete beams with the replacements were constructed and tested under flexure for structural behavior evaluation. The results of this study show an average of 11% reduction in both the compressive strength of concrete and the maximum load capacity of the beams incorporating plastic products. A life cycle assessment study was conducted using a functional unit of 1.0 cubic yard concrete production. The system boundary for the environmental assessment of the concrete in this study includes only the production phase, which is from the cradle to the end gate of the ready-mix concrete plant. The environmental impact estimation of a 10% reduction in constituents of concrete showed a 10% reduction in most LCA measures where cement was replaced compared to a 1% effect for the fine aggregate replacement. Full article

(This article belongs to the Special Issue Reinforced Concrete: Mechanical Properties and Materials Design)

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20 pages, 4441 KB

Open AccessArticle

Metal-Enhanced Fluorescence of Nanocomplexes

by Alexander N. Yakunin, Sergey V. Zarkov, Yuri A. Avetisyan, Garif G. Akchurin and Valery V. Tuchin

Materials 2026, 19(6), 1258; https://doi.org/10.3390/ma19061258 - 22 Mar 2026

Viewed by 310

Abstract

Metal-enhanced fluorescence (MEF) has found widespread application in biomedical sensing and in vivo tissue imaging systems. To enhance MEF efficiency, it is necessary to optimize the interaction between the metal nanoparticle plasmon and the fluorophore molecule. The size and shape of the nanoparticle, [...] Read more.

Metal-enhanced fluorescence (MEF) has found widespread application in biomedical sensing and in vivo tissue imaging systems. To enhance MEF efficiency, it is necessary to optimize the interaction between the metal nanoparticle plasmon and the fluorophore molecule. The size and shape of the nanoparticle, the nanoscale gap between the fluorescent molecule and the nanoparticle, and the excitation wavelength are critical parameters. In this study, we propose a model for a more complete and accurate description of the processes of molecular excitation and generation of the fluorescence spectral response, introducing a new concept of effective properties for the field enhancement factor, quantum yield, and fluorescence enhancement factor. The influence of the spectral properties of both the nanostructure plasmon and the fluorophore molecule on the optimal tuning of fluorescent complexes is studied. Particular attention is paid to the analysis of the spectral properties of plasmon resonance and calculations of the near-field intensity enhancement of the plasmonic nanostructure’s excitation field. Numerical results for optimizing the MEF of fluorescent complexes based on TagRFP and gold (silver) nanorod composites are presented. The advantages of the proposed model for the optimal design of new nanomaterials with unique fluorescent properties are discussed. Full article

(This article belongs to the Special Issue Fluorescence Spectroscopy for Materials Characterization)

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21 pages, 4567 KB

Open AccessArticle

Asymmetric Supercapacitor Based on Biomass-Derived Carbon Electrodes Functionalized with NdFeB

by Ahmad Reshad Delawary, Constantin Bubulinca, Natalia E. Kazantseva, Petr Saha, Quoc Bao Le, Ram K. Gupta and Rudolf Kiefer

Materials 2026, 19(6), 1257; https://doi.org/10.3390/ma19061257 - 22 Mar 2026

Viewed by 377

Abstract

Supercapacitors (SCs) are highly attractive energy storage devices, and modern research is focused on using waste materials to reduce environmental impact. This study processed biowaste from local brewery production to produce a highly specific mesoporous activated carbon (AC) for SC electrode scaffolds. Polyaniline [...] Read more.

Supercapacitors (SCs) are highly attractive energy storage devices, and modern research is focused on using waste materials to reduce environmental impact. This study processed biowaste from local brewery production to produce a highly specific mesoporous activated carbon (AC) for SC electrode scaffolds. Polyaniline (PANI) was synthesized and incorporated into the AC scaffold, thereby enhancing performance. The AC and PANI combination (ACP) achieved a specific capacitance of 173.7 F/g at 1 A/g, with 92% retention after 5000 cycles. Using NdFeB (ACN) particles, the anode showed a specific capacitance of 127 F/g and over 99% retention. An asymmetrical ACN//ACP cell demonstrated promising performance with 70% efficiency. This study highlights the potential of using biowaste for high-performance SC electrodes and the effective synergy between AC and PANI. Full article

(This article belongs to the Special Issue Performance of Supercapacitors for Energy Technologies and Applications)

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14 pages, 6694 KB

Open AccessArticle

Cracking Mechanism and Life-Cycle Performance Evaluation of Early-Age Concrete Based on Environment-Damage Coupling

by Min Yuan, Zhiqiang Xie, Jiazheng Li, Yun Dong and Sheng Qiang

Materials 2026, 19(6), 1256; https://doi.org/10.3390/ma19061256 - 22 Mar 2026

Viewed by 271

Abstract

Concrete is accelerating its transition towards green and low-carbon development, but its performance throughout its entire life cycle is significantly influenced by environmental changes, which remains a key technical challenge currently faced. The effects of early-age concrete tensile damage on thermal conductivity and [...] Read more.

Concrete is accelerating its transition towards green and low-carbon development, but its performance throughout its entire life cycle is significantly influenced by environmental changes, which remains a key technical challenge currently faced. The effects of early-age concrete tensile damage on thermal conductivity and moisture transport properties, as well as their coupling mechanism, remain unclear, leading to severe cracking. To explore the cracking mechanism of early-age concrete under the coupled conditions of environment and damage and to evaluate its performance throughout its lifecycle, this article conducts comparative experiments on the performance of concrete under high temperature, varying humidity, and damage conditions in the early age stage. The variation law of temperature, humidity, and strain of concrete is studied, and the evolution of microstructure and composition of concrete is explored. The response of porosity to ambient humidity exhibits opposite trends between restrained and unrestrained specimens, with rates of change of +0.0353%/RH and −0.0245%/RH, respectively. Furthermore, the study identified a critical turning point in ambient relative humidity (50% RH), which significantly alters the degree of hydration (Ca/Si ratio) of the concrete. The research results may provide theoretical and technical support for cracking risk assessment and crack control throughout the entire life cycle of concrete thin-walled structures. Full article

(This article belongs to the Special Issue Next-Generation Sustainable Materials for Green Manufacturing and Circular Economy)

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20 pages, 12398 KB

Open AccessArticle

Comparison of Surface Morphology and Topography of Additively Manufactured SS 316L Steel After AWJM in Dependence on Layer Orientation

by Radoslav Vandžura, Matúš Geľatko, Marek Čornanič, Vladimír Simkulet and František Botko

Materials 2026, 19(6), 1255; https://doi.org/10.3390/ma19061255 - 22 Mar 2026

Viewed by 319

Abstract

Additively manufactured stainless steels are gaining considerable attention in the production of complex components, especially in the aerospace, food production, energy, and biomedical industries. Machining and achieving the desired surface properties of such materials remains a challenge. Abrasive waterjet machining technology appears to [...] Read more.

Additively manufactured stainless steels are gaining considerable attention in the production of complex components, especially in the aerospace, food production, energy, and biomedical industries. Machining and achieving the desired surface properties of such materials remains a challenge. Abrasive waterjet machining technology appears to be one of the options due to the advantages it brings. Removing support structures and separating individual parts is also one of the possible applications of this technology. This study investigates the effects of process parameters for individual cut qualities (Q1–Q5) of abrasive waterjet on the surface properties of additively manufactured stainless steel (SS 316L) specimens, considering the different mechanical properties of the material due to the direction of layering of the material during its production. Experimental specimens were prepared by selective laser melting technology with parameters ensuring the best possible quality of the resulting part. The results of the study showed changes in the topography of the machined surface, especially in the roughness parameters. Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy analysis proved the presence of fragmented abrasive particles in the cut areas. Full article

(This article belongs to the Special Issue Advanced Abrasive Processing Technology and Applications (Second Edition))

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21 pages, 1787 KB

Open AccessReview

Integrating Multifunctional Hydrogen-Bonded Organic Frameworks into Intelligent Packaging: Mechanisms, Design and Challenges

by Yabo Fu, Yubing Zhang, Congyao Wang, Jingmei Guan, Jiazi Shi, Hui Liu and Bo Lu

Materials 2026, 19(6), 1254; https://doi.org/10.3390/ma19061254 - 22 Mar 2026

Viewed by 364

Abstract

The transition from passive containment to active, responsive management is defining the next generation of intelligent packaging. This evolution creates a critical demand for materials that can be precisely engineered to monitor, regulate, and protect. Hydrogen-bonded organic frameworks (HOFs) have emerged as a [...] Read more.

The transition from passive containment to active, responsive management is defining the next generation of intelligent packaging. This evolution creates a critical demand for materials that can be precisely engineered to monitor, regulate, and protect. Hydrogen-bonded organic frameworks (HOFs) have emerged as a uniquely versatile platform in this regard, owing to their synthetically tunable porosity, inherent biocompatibility, and exceptional solution processability derived from reversible supramolecular assembly. This review moves beyond cataloging applications to dissect the fundamental mechanisms by which HOFs enable smart packaging functions, including the following: (i) selective gas capture and atmosphere tailoring via molecular recognition within designed pores; (ii) high-sensitivity optical and electrochemical sensing for real-time quality and safety signaling; and (iii) stimuli-responsive release of active agents (e.g., antimicrobials). We further explore the frontier of integrating HOFs as functional fillers or coatings within polymeric matrices, a key step toward practical devices. Despite challenges such as structural stability and maintaining permanent porosity due to relatively weak hydrogen bonds, this work aims to provide a design blueprint for advancing HOFs from laboratory curiosities to core components of sustainable, multifunctional packaging systems. Full article

(This article belongs to the Section Green Materials)

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11 pages, 1141 KB

Open AccessArticle

Analysis of High-Field-Induced Processes with Enthalpy Release in Martensite–Austenite MnCo(Fe)(GeSi) Alloys: Solving PPMS Artifact and Recovery of Heat Capacity

by Antonio Vidal-Crespo, F. Javier Romero, Jhon J. Ipus and Javier S. Blázquez

Materials 2026, 19(6), 1253; https://doi.org/10.3390/ma19061253 - 22 Mar 2026

Viewed by 288

Abstract

The relaxation calorimeter option in the commercial Physical Property Measurement System (PPMS) has become widely used. Since its introduction, the capabilities of this technique for specific heat measurements have been critically discussed, particularly to avoid misinterpretation of data near phase transitions. Traditional methods [...] Read more.

The relaxation calorimeter option in the commercial Physical Property Measurement System (PPMS) has become widely used. Since its introduction, the capabilities of this technique for specific heat measurements have been critically discussed, particularly to avoid misinterpretation of data near phase transitions. Traditional methods rely on cooling curves after sample excitation, where sharp latent heat contributions during heating lead to clear deviations from the fitting model. However, subtle but extended enthalpy contributions (e.g., strain release) may mask these effects, allowing both heating and cooling curves to be well fitted using the standard PPMS protocol. In this work, we develop a procedure that assumes a constant extra power supplied due to subtle enthalpy contributions, enabling consistent interpretation of both heating and cooling curves. This procedure allows: (1) correction of specific heat measurements; and (2) quantification of the enthalpy involved in the transition. The procedure is applied to a magnetic-field-induced transformation in MnCo(Fe)Ge(Si) alloys. Two samples were studied: a single-phase austenite without any field-induced transition, used as a reference, and a mixed austenite-martensite sample, in which apparent deviations in the conductance of the wires evidence the presence of the anomaly. Full article

(This article belongs to the Section Metals and Alloys)

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16 pages, 1782 KB

Open AccessArticle

Charge Transport and Thermoelectric Properties of Bornite with Fe-Site Off-Stoichiometry

by Hyemin Oh, Seungmin Lee, Hyeon-Sik O and Il-Ho Kim

Materials 2026, 19(6), 1252; https://doi.org/10.3390/ma19061252 - 22 Mar 2026

Viewed by 271

Abstract

The effects of Fe non-stoichiometry on crystal structure, microstructural evolution, and thermoelectric transport properties were systematically investigated in bornite (Cu₅Fe_1+yS₄; −0.06 ≤ y ≤ 0.06) synthesized by mechanical alloying followed by hot pressing. X-ray diffraction analysis confirmed [...] Read more.

The effects of Fe non-stoichiometry on crystal structure, microstructural evolution, and thermoelectric transport properties were systematically investigated in bornite (Cu₅Fe_1+yS₄; −0.06 ≤ y ≤ 0.06) synthesized by mechanical alloying followed by hot pressing. X-ray diffraction analysis confirmed the formation of a single-phase orthorhombic bornite structure over the entire composition range. Anisotropic lattice distortion was observed with increasing Fe non-stoichiometry, manifested as contraction along the a-axis and expansion along the b- and c-axes, with a non-linear dependence on composition. Crystallite sizes estimated from Lorentzian peak fitting increased from 64.1 nm for the stoichiometric composition to 70.6–76.3 nm for Fe-deficient samples and 73.2–90.9 nm for Fe-excess samples. Hall-effect measurements revealed p-type semiconducting behavior for the stoichiometric composition, degenerate p-type transport with increased hole concentration under Fe-deficient conditions, and a transition to n-type behavior with reduced carrier mobility under Fe-excess conditions. While Fe-deficient samples retained high electrical conductivity and positive Seebeck coefficients, Fe-excess samples exhibited negative Seebeck coefficients at low temperatures with sign reversal at elevated temperatures. As a consequence, the power factor of Fe-deficient samples was enhanced by approximately 20–30% relative to the stoichiometric composition. In addition, the total thermal conductivity remained below 0.8 W·m⁻¹·K⁻¹ for all samples, and Fe non-stoichiometry effectively suppressed lattice thermal conductivity. Consequently, the Cu₅Fe_0.94S₄ composition achieved a maximum dimensionless figure of merit of ZT = 0.61 at 673 K, representing a performance enhancement of approximately 30–70% compared with the stoichiometric composition (ZT = 0.36 at 673 K and 0.47 at 723 K). Full article

(This article belongs to the Special Issue Advanced Thermoelectric Materials and Micro/Nanoscale Heat Transfer)

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18 pages, 8085 KB

Open AccessArticle

Investigation of Microstructural Characterization and Tensile Deformation Mechanisms in Inconel 617 Welded Joints Produced by GTAW

by Mingyang Zhao, Lang Wang, Wenhao Ren, Yuxin Wang, Tao Zhang and Zhengzong Chen

Materials 2026, 19(6), 1251; https://doi.org/10.3390/ma19061251 - 21 Mar 2026

Viewed by 304

Abstract

The microstructural evolution and tensile behavior of Inconel 617 welded joints produced by gas tungsten arc welding (GTAW) with ERNiCrCoMo-1 filler were systematically investigated. Detailed microstructural characterization revealed that Cr-rich M₂₃C₆ and Ti-rich MC carbides are the dominant precipitates, while [...] Read more.

The microstructural evolution and tensile behavior of Inconel 617 welded joints produced by gas tungsten arc welding (GTAW) with ERNiCrCoMo-1 filler were systematically investigated. Detailed microstructural characterization revealed that Cr-rich M₂₃C₆ and Ti-rich MC carbides are the dominant precipitates, while Mo-rich M₆C forms locally along grain boundaries after thermal exposure. The fusion and weld zones exhibit fine dendritic morphologies with uniformly distributed precipitates, resulting in significant strengthening through precipitation and dislocation–pinning mechanisms. Owing to the low heat input and compositional compatibility between the weld and base metals, the heat-affected zone remains extremely narrow and free of compositional transitions. The welded joint attains tensile strengths of 920 MPa at room temperature and 605.5 MPa at 750 °C, corresponding to joint efficiencies of 117% and 121%, respectively, with fracture consistently occurring in the base metal. Deformation analysis shows that plasticity at room temperature is governed by planar slip and dislocation entanglement, whereas deformation twinning predominates at elevated temperatures owing to the reduced stacking-fault energy and the pinning effect of M₂₃C₆ carbides. These results provide key insights into the deformation and strengthening mechanisms controlling the high-temperature performance of GTAW-welded Inconel 617 joints and offer guidance for their application in advanced nuclear and high-temperature energy systems. Full article

(This article belongs to the Section Metals and Alloys)

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22 pages, 1702 KB

Open AccessArticle

Evaluation of Solid and Hollow Sand Brick Properties with Partial Replacement of Fine Aggregates by Ground Granulated Blast Furnace Slag

by Kamal Hosen and Alina Bărbulescu

Materials 2026, 19(6), 1250; https://doi.org/10.3390/ma19061250 - 21 Mar 2026

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Abstract

Ground granulated blast furnace slag (GGBFS), an industrial by-product of steel manufacturing, can be utilized as a partial replacement for natural fine aggregate in clay brick production. Although widely used in cementitious systems, its incorporation into sand bricks and its effects on key [...] Read more.

Ground granulated blast furnace slag (GGBFS), an industrial by-product of steel manufacturing, can be utilized as a partial replacement for natural fine aggregate in clay brick production. Although widely used in cementitious systems, its incorporation into sand bricks and its effects on key performance parameters remain insufficiently investigated. To fill in the gap, sand bricks containing 0–35% GGBFS (at 5% intervals) were tested for compressive strength, water absorption, thermal conductivity, and efflorescence. Optimal performance was achieved at 25% replacement. Compressive strength increased from 17.5 MPa (control) to 24 MPa (28.5% improvement). Water absorption decreased from 11.67% to 8.20% (29.7% reduction), and thermal conductivity decreased from 1.08 to 0.85 W/m·°C. No efflorescence was observed at 25% GGBFS, whereas higher replacement levels (30% and 35%) exhibited increased efflorescence. The results confirm that 25% GGBFS replacement enhances mechanical and durability-related properties of clay bricks, demonstrating its technical feasibility as an alternative fine aggregate. Full article

(This article belongs to the Special Issue Recovered or Recycled Materials for Composites and Other Materials)

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15 pages, 8850 KB

Open AccessArticle

Enhancing Self-Healing Performance of Cement-Based Materials Through Sodium Silicate and SAP Composite Incorporation

by Yumei Kang, Rongbao Wu, Yu Qiao and Chang Xu

Materials 2026, 19(6), 1249; https://doi.org/10.3390/ma19061249 - 21 Mar 2026

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Abstract

Conventional admixture-based self-healing technologies are often limited by inadequate internal water supply and a scarcity of unhydrated gel particles. Therefore, this study proposes a new self-healing method that leverages the synergistic interplay between the chemical repair of sodium silicate and the physical clogging [...] Read more.

Conventional admixture-based self-healing technologies are often limited by inadequate internal water supply and a scarcity of unhydrated gel particles. Therefore, this study proposes a new self-healing method that leverages the synergistic interplay between the chemical repair of sodium silicate and the physical clogging of superabsorbent polymers (SAPs) to overcome the aforementioned limitations. The healing efficiency of cement mortar was assessed through compressive strength recovery, capillary water absorption, and ultrasonic pulse velocity (UPV). Microstructural evolution and healing mechanisms were elucidated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results indicate that at an optimal dosage (0.5 wt.% for both admixtures), the healing performance is significantly enhanced: the compressive strength recovery rate reaches 103.1%, the capillary water absorption coefficient decreases by 16.57 × 10⁻³, and the UPV recovery achieves 95.4%. Microstructural analysis reveals that sodium silicate facilitates the reaction between

{Ca}^{2 +}

and

{S i O}_{3}^{2 -}

ions, leading to the in situ precipitation of dense C-S-H gel at the crack interface, thereby enabling chemical repair. In contrast, SAP contributes to physical sealing via a swelling and release mechanism. Full article

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

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20 pages, 3091 KB

Open AccessArticle

Hybrid Steel Fiber Design in Ultra-High-Performance Concrete Containing Coarse Aggregate Using Pore Size Distribution Within Coarse Aggregate Skeleton

by Rui Tang, Yinfei Du, Jian Zhang and Lingxiang Kong

Materials 2026, 19(6), 1248; https://doi.org/10.3390/ma19061248 - 21 Mar 2026

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Abstract

To address the challenge of coarse aggregates hindering steel fiber dispersion and reducing toughening efficiency in ultra-high-performance concrete containing coarse aggregate (UHPC-CA), this study proposes a hybrid fiber design method based on reverse adaptation to the aggregate structure: a paradigm where fiber proportions [...] Read more.

To address the challenge of coarse aggregates hindering steel fiber dispersion and reducing toughening efficiency in ultra-high-performance concrete containing coarse aggregate (UHPC-CA), this study proposes a hybrid fiber design method based on reverse adaptation to the aggregate structure: a paradigm where fiber proportions are inversely designed to match the quantified void size distribution within the coarse aggregate skeleton. Industrial X-ray computed tomography (X-CT) was employed to capture the internal structure of UHPC-CA. Digital image processing techniques were used to quantitatively characterize the size distribution within the coarse aggregate skeleton gap. Based on this distribution, the blending proportions of multi-scale (3–16 mm) copper-plated steel fibers were systematically determined. Three fiber configurations were compared: mono-sized 13 mm fibers (Type A), an empirical model based on aggregate size (Type B), and a quantitatively designed blend based on skeleton gap distribution (Type C). At the same fiber volume fraction, the mechanical property test results show that the C type achieves approximately 18.6% higher flexural strength and 29.1% higher splitting tensile strength compared to the A type, while showing 5.3% and 6.7% improvements over the B type, and the compressive strength also increased slightly (about 3.0%). The microanalysis further confirms that the fiber distribution in the C-type design was more uniform, and the bridging effect and crack resistance were more sufficient. The proposed gap-adaptive fiber design paradigm offers an effective approach for optimizing reinforcement distribution in composites, providing theoretical and practical value for high-performance UHPC-CA applications. Full article

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

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12 pages, 2203 KB

Open AccessCommunication

Theoretical Investigation of Stiffness and Vibration Frequency Enhancement in Novel Membrane-Wrapped Lattice Beams

by Peiyao Xi, Hao Zhou, Canghai Tan, Chuang Shi, Rongqiang Liu and Jianzhong Yang

Materials 2026, 19(6), 1247; https://doi.org/10.3390/ma19061247 - 21 Mar 2026

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Abstract

Bending-dominated lattice structures offer superior stability but suffer from low stiffness and natural frequencies, posing resonance risks in aerospace applications. To address this, a novel Membrane-Wrapped Lattice (MWL) encapsulated by a micrometer-scale metallic film is proposed. A theoretical framework based on the tension-compression [...] Read more.

Bending-dominated lattice structures offer superior stability but suffer from low stiffness and natural frequencies, posing resonance risks in aerospace applications. To address this, a novel Membrane-Wrapped Lattice (MWL) encapsulated by a micrometer-scale metallic film is proposed. A theoretical framework based on the tension-compression asymmetry of the membrane is established to analyze the influence of membrane thickness on the neutral axis shift, ultimately deriving analytical formulations for flexural stiffness and natural frequencies. MWL specimens with varying membrane thicknesses (0–50 μm) were fabricated via selective laser melting and adhesive bonding, then subjected to three-point bending and vibration tests. Results demonstrate that wrapping with a 50 μm 316 L stainless steel membrane increases the flexural stiffness by 128% and the fundamental natural frequency by 85%. The experimental measurements align well with theoretical and numerical predictions, validating this lightweight, high-stiffness design strategy. Full article

(This article belongs to the Section Porous Materials)

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23 pages, 4123 KB

Open AccessArticle

Transient Contact Elastic–Plastic Characteristics Analysis of Rail Welded Joints in Heavy-Haul Railways

by Chen Liu and Zhiqiang Wang

Materials 2026, 19(6), 1246; https://doi.org/10.3390/ma19061246 - 21 Mar 2026

Viewed by 313

Abstract

This study investigates the transient wheel–rail contact mechanics of welded joints in heavy-haul rails via a validated 3D finite element model, and analyzes the stick-slip behavior, dynamic response and elastoplastic characteristics in the base material zone, heat-affected zone and weld bead zone. Results [...] Read more.

This study investigates the transient wheel–rail contact mechanics of welded joints in heavy-haul rails via a validated 3D finite element model, and analyzes the stick-slip behavior, dynamic response and elastoplastic characteristics in the base material zone, heat-affected zone and weld bead zone. Results show a distinct contact state transition from stick-slip in the base material to predominant slip within the welded zones, indicating higher wear susceptibility. Dynamic response analysis reveals the highest and lowest contact-point acceleration amplitudes in the base material and heat-affected zone, respectively, due to material heterogeneity. Plastic deformation consistently initiates at the rail surface, where stress and strain concentrate, establishing it as the primary site for damage nucleation. A systematic parametric study shows that plastic deformation can be effectively mitigated by increasing the yield strength and elastic modulus of the welded joint material, or reducing the wheelset velocity, unsprung mass and wheel–rail friction coefficient. In contrast, adjusting the primary suspension and fastener parameters exerts a negligible influence on plastic deformation control. These findings provide a mechanistic basis for optimizing the performance and maintenance of welded joints in heavy-haul rail operations. This study reveals the coupling law of multiple mechanisms among contact behavior, dynamic response and material failure during the damage initiation process of rail welded joints from the mechanistic perspective, which provides a theoretical basis for the structural optimization, condition assessment and maintenance of rail welded joints in heavy-haul railways. Full article

(This article belongs to the Special Issue Road and Rail Construction Materials: Development and Prospects)

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Materials, Volume 19, Issue 6 (March-2 2026) – 229 articles

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