Materials

13 pages, 5201 KiB

Open AccessArticle

Influence of Hollow Glass Microspheres (HGM) on Properties of Alkali-Activated Slag Lightweight High-Strength Concrete Under Varying Lightweight Aggregate (LWA) Dosages

by Liankun Wang, Zefeng Lu, Long Cheng, Jun Sun, Yao Huang, Xin Cheng and Minrong Wang

Materials 2025, 18(14), 3233; https://doi.org/10.3390/ma18143233 (registering DOI) - 9 Jul 2025

Abstract

As a promising and sustainable construction material, alkali-activated slag lightweight high-strength concrete (AAS-LWHSC) may be influenced by lightweight aggregate (LWA) content. In this study, the effects of hollow glass microspheres (HGM) replacing granulated ground blast furnace slag (GGBFS) under varying LWA dosages on [...] Read more.

As a promising and sustainable construction material, alkali-activated slag lightweight high-strength concrete (AAS-LWHSC) may be influenced by lightweight aggregate (LWA) content. In this study, the effects of hollow glass microspheres (HGM) replacing granulated ground blast furnace slag (GGBFS) under varying LWA dosages on the workability, dry apparent density, mechanical properties, and microstructure of AAS-LWHSC were investigated. The results indicated that the dry density of concrete was significantly reduced by HGM, while the “ball-bearing” effect of HGM was observed to enhance workability at a dosage of 6%. The 7-day mechanical properties of AAS-LWHSC were found to decline progressively with increasing HGM content. However, at the shale ceramsite sand replacement rates of 35% and 65%, the incorporation of 6% HGM slightly improved the 28-day mechanical properties. Due to the absence of the water-releasing effect from shale ceramsite, the pozzolanic reactions of HGM were restricted, resulting in coarse hydration products and a reduction in the mechanical performance of AAS-LWHSC. Full article

(This article belongs to the Topic Green Construction Materials and Construction Innovation)

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14 pages, 2168 KiB

Open AccessArticle

Engineering Ultra-Low Thermal Conductivity in (Pb_0.8Ge_0.2Te)_0.95-x(PbSe)_0.05(PbS)_x Quaternary Lead Chalcogenides Through PbS-Induced Phase Segregation

by Dianta Ginting, Hadi Pronoto, Nurato, Kontan Tarigan, Sagir Alva, Muhamad Fitri, Dwi Nanto, Ai Nurlela, Mashadi, Yunasfi, Toto Sudiro, Jumril Yunas and Jong-Soo Rhyee

Materials 2025, 18(14), 3232; https://doi.org/10.3390/ma18143232 (registering DOI) - 9 Jul 2025

Abstract

The shortage of tellurium and toxicity of lead are major obstacles to scaling mid-temperature thermoelectric generators. We engineer quaternary lead chalcogenides with composition (Pb_0.8Ge_0.2Te)_0.95-_x(PbSe)_0.05(PbS)_x (0 ≤ x ≤ 0.25), where Pb is lead, [...] Read more.

The shortage of tellurium and toxicity of lead are major obstacles to scaling mid-temperature thermoelectric generators. We engineer quaternary lead chalcogenides with composition (Pb_0.8Ge_0.2Te)_0.95-_x(PbSe)_0.05(PbS)_x (0 ≤ x ≤ 0.25), where Pb is lead, Ge is germanium, Te is tellurium, Se is selenium, S is sulfur, and x denotes the molar fraction of lead sulfide (PbS). The primary novelty lies in achieving ultra-low thermal conductivity through controlled phase segregation induced by systematic PbS incorporation. X-ray diffraction analysis reveals single-phase solid solutions up to x ≈ 0.10, with secondary PbS precipitates forming beyond this threshold. These PbS-rich phases create hierarchical microstructures that scatter phonons across multiple length scales, suppressing total thermal conductivity to 0.6 Wm⁻¹K⁻¹ at x = 0.15—approximately 84% lower than pristine lead telluride (PbTe) and approaching glass-like thermal conductivity values. Electrical transport measurements demonstrate sulfur’s role as an electron donor, enabling carrier-type control from p-type to n-type conduction. Despite moderate electrical power factors, the optimized composition (x = 0.20) achieves a peak dimensionless figure of merit ZT ≈ 0.34 at 650 K. This work demonstrates an effective strategy for tellurium-lean, lead-reduced thermoelectric materials through sulfur-induced phase segregation, providing practical design guidelines for sustainable waste heat recovery applications. Full article

(This article belongs to the Section Energy Materials)

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11 pages, 1625 KiB

Open AccessArticle

Optimization of Electron Transport Layer Inkjet Printing Towards Fully Solution-Processable OLEDs

by Riccardo Manfredi, Carmela Tania Prontera, Fabrizio Mariano, Marco Pugliese, Antonio Maggiore, Alessandra Zizzari, Marco Cinquino, Iolena Tarantini, Giuseppe Gigli and Vincenzo Maiorano

Materials 2025, 18(14), 3231; https://doi.org/10.3390/ma18143231 (registering DOI) - 9 Jul 2025

Abstract

The fabrication of high-performance organic optoelectronic devices using solution-based techniques, in particular inkjet printing, is both a desirable and challenging goal. Organic light-emitting diodes (OLEDs) are multilayer devices that have demonstrated great potential in display applications, with ongoing efforts aimed at extending their [...] Read more.

The fabrication of high-performance organic optoelectronic devices using solution-based techniques, in particular inkjet printing, is both a desirable and challenging goal. Organic light-emitting diodes (OLEDs) are multilayer devices that have demonstrated great potential in display applications, with ongoing efforts aimed at extending their use to the lighting sector. A key objective in this context is the reduction in production costs, for which printing techniques offer a promising pathway. The main obstacle to fully printed OLEDs lies in the difficulty of depositing new layers onto pre-existing ones while maintaining high film quality and avoiding damage to the underlying layers. In a bottom-emitting OLED, the electron transport layer (ETL) is the final organic layer to be deposited, making its printing particularly challenging, a process for which only a few successful examples have been reported. In this work, we report on the optimization of a 2,2′,2″-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi)-based ink formulation for ETL printing on an emitting layer composed of 5,10-Bis(4-(3,6-di-tert-butyl-9H-carbazol-9-yl)-2,6-dimethylphenyl)-5,10-dihydroboranthrene (tBuCzDBA). A specific ratio of methanol to diethyl ether was identified as the most suitable for printing the ETL without compromising the integrity of the underlying layer. The printed ETL was successfully integrated into an OLED device, which exhibited a maximum current efficiency of 6.8 cd/A and a peak luminance of about 8700 cd/m². These results represent a significant step toward the development of a fully printed OLED architecture. Full article

(This article belongs to the Special Issue Advanced Materials, Structures, and Technologies for Thin-Film Light-Emitting Diodes)

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42 pages, 15713 KiB

Open AccessArticle

A Novel Method for Determining the Contact Pattern Area in Gear Meshing Based on Computer Processing of Pressure Measurement Film Images

by Paweł Fudali, Patrycja Ewa Jagiełowicz, Adam Kalina, Piotr Połowniak, Mariusz Sobolak and Waldemar Witkowski

Materials 2025, 18(14), 3230; https://doi.org/10.3390/ma18143230 - 8 Jul 2025

Abstract

The contact pattern between gear teeth is one of the most significant indicators of proper gear operation. This paper presents an analysis of the contact pattern of gears with a sinusoidal profile. The gear geometry was obtained through direct solid simulation of the [...] Read more.

The contact pattern between gear teeth is one of the most significant indicators of proper gear operation. This paper presents an analysis of the contact pattern of gears with a sinusoidal profile. The gear geometry was obtained through direct solid simulation of the machining process. Generally, analytical, numerical, and experimental methods are used for contact pattern analysis in gearboxes. This article presents contact pattern investigations using numerical methods and a novel experimental method that utilizes pressure measurement films. A proprietary program using image analysis was used for the contact pattern analysis. The numerical studies utilized the Finite Element Method (FEM) and the CAD method. The results obtained from the presented methods show good convergence. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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17 pages, 946 KiB

Open AccessArticle

Analysis of Fatigue and Residual Strength Estimation of Polymer Matrix Composites Using the Theory of the Markov Chain Method

by Rafał Chatys, Mariusz Kłonica and Ilmars Blumbergs

Materials 2025, 18(14), 3229; https://doi.org/10.3390/ma18143229 - 8 Jul 2025

Abstract

This paper deals with an important issue, which is the influence of failure caused by the quality of matrix post-curing on the strength of complex and difficult materials of the “new generation” such as fibre composites, particularly with a polymer matrix. In recent [...] Read more.

This paper deals with an important issue, which is the influence of failure caused by the quality of matrix post-curing on the strength of complex and difficult materials of the “new generation” such as fibre composites, particularly with a polymer matrix. In recent years, significant advances in the field of adhesive materials chemistry have led to the constant development of bonding technology. The effectiveness of bonding depends, to a large extent, on the suitable selection of the adhesive and the use of appropriate surface treatment technology. It is difficult to imagine virtually any modern industry without adhesive joints, be it the aircraft, aerospace or automotive industries, which simultaneously highlights the great importance of adhesives and adhesive materials for the present-day economy. In modern technology, it is extremely important to obtain the right combination of modern construction materials. The statistical analysis of the components showed the complexity of the layered composite structure. The proposed model of the weakest micro-volume developed in this study indirectly reflects the experimentally based curing variables that affect the stresses of the components in the composite (laminate) structure. The strength of fibrous composite structures based on the Markov chain theory considers technological aspects during hardening. The model proposed in the paper was validated on the basis of examples from the literature and experimental data obtained in the research project. The numerical results are in good agreement with the literature database and measurement data. The presented model could be a novel method, which allows better insight into the curing process of epoxy resins. Full article

(This article belongs to the Special Issue Material Surface Topography Measurement, Analysis and Characterization)

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20 pages, 5198 KiB

Open AccessArticle

Damage Behaviour of Shot-Peened 7075 Aluminium Alloy Based on Temperature Evolution and Digital Image Correlation Methods

by Yutong Tang, Aifeng Jiang, Lei Li, Yanliang Dong and Le Chang

Materials 2025, 18(14), 3228; https://doi.org/10.3390/ma18143228 - 8 Jul 2025

Abstract

The peening process plays a pivotal role in enhancing the properties of aluminium alloys across various industries, including aerospace, automotive, and construction. Among the critical factors influencing this process, the shot peening time is of paramount importance for studying material characteristics. In the [...] Read more.

The peening process plays a pivotal role in enhancing the properties of aluminium alloys across various industries, including aerospace, automotive, and construction. Among the critical factors influencing this process, the shot peening time is of paramount importance for studying material characteristics. In the present study, we undertook a comprehensive investigation into the mechanical properties, surface roughness, and damage evolution behaviour of 7075 aluminium alloy subjected to different shot peening durations. This investigation was conducted using a microhardness tester, laser confocal microscope, scanning electron microscope, and other advanced equipment, in conjunction with digital image correlation methods and temperature evolution analysis. Our findings demonstrate that the shot peening time has a profound impact on the mechanical properties of the 7075 alloy. Specifically, the microhardness, tensile strength, and surface roughness of the alloy increased with increasing shot peening time, whereas the elongation rate exhibited a non-monotonic trend, initially decreasing and then increasing. Utilising DIC and temperature evolution analysis, we analysed the influence of shot peening time on the damage evolution behaviour of the alloy and developed tensile damage evolution equations tailored to different shot peening durations. The damage evolution of the 7075 alloy under various shot peening times was observed to proceed through two distinct stages: smooth development and rapid damage. Notably, the damage evolution laws derived from both techniques exhibited good consistency and agreement. The present study serves as a theoretical foundation for exploring the surface peening and damage evolution of 7075 aluminium alloy, which holds significant implications for optimising peening parameters and predicting material life in engineering applications. Full article

(This article belongs to the Special Issue Fatigue, Damage and Fracture of Alloys)

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21 pages, 4603 KiB

Open AccessArticle

Hybrid Binders Through Alkaline Activation of Fine Construction and Demolition Waste

by Manuel Retamal-Rojas, Diego Aponte, William Valencia-Saavedra, Rafael Robayo-Salazar and Marilda Barra-Bizinotto

Materials 2025, 18(14), 3227; https://doi.org/10.3390/ma18143227 - 8 Jul 2025

Abstract

The use of construction and demolition waste (CDW) as an alternative binder to ordinary Portland cement presents a promising solution through alkaline activation. This study evaluates the physical, mechanical, and microstructural behaviour of pastes and mortars produced with CDW—specifically concrete (RH) and ceramic [...] Read more.

The use of construction and demolition waste (CDW) as an alternative binder to ordinary Portland cement presents a promising solution through alkaline activation. This study evaluates the physical, mechanical, and microstructural behaviour of pastes and mortars produced with CDW—specifically concrete (RH) and ceramic (RC) waste—activated with NaOH and Na₂SiO₃ (SS) solutions. Mortars were prepared with NaOH/SS ratios of 0.2 and 0.3 and an activator-to-precursor (AA/P) ratio of 0.2. Results showed that higher NaOH content accelerated alkaline activation, reducing setting times from 6.2 h to 3.7 h for RC and from 4.6 h to 3.2 h for RH. Conversely, increasing Na₂SiO₃ content led to greater drying shrinkage, from −0.42% to −0.49% in RC and from −0.46% to −0.52% in RH. Compressive strength values at 28 days ranged from 7.6 to 8.2 MPa. X-ray diffraction (XRD) revealed the presence of non-reactive crystalline phases in both precursors, while Fourier transform infrared (FTIR) spectroscopy indicated the formation of CASH, CSH, and/or (N)CASH gels. This study highlights the potential of CDW as a sustainable alternative binder and the usefulness of the proposed method for optimising alkali-activated systems, contributing to circular economy strategies in the construction sector. Full article

(This article belongs to the Special Issue Recycled Materials in Concrete: Towards a Circular Economy in Construction)

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19 pages, 5562 KiB

Open AccessArticle

Research on the Milling Characteristics of SBS Modified Asphalt Pavement with Different Service Years Using the Discrete Element Method

by Xiujun Li, Zhipeng Zhang, Hao Liu, Hao Feng, Heng Zhang, Fangzhi Shi and Zhi Gou

Materials 2025, 18(14), 3226; https://doi.org/10.3390/ma18143226 - 8 Jul 2025

Abstract

The service years of the milled pavement are varied in numerous SBS modified asphalt pavement milling assignments. To investigate the milling characteristics of SBS (styrene–butadiene–styrene) modified asphalt pavements with different service years, the values of the bonding parameters were calibrated and verified and [...] Read more.

The service years of the milled pavement are varied in numerous SBS modified asphalt pavement milling assignments. To investigate the milling characteristics of SBS (styrene–butadiene–styrene) modified asphalt pavements with different service years, the values of the bonding parameters were calibrated and verified and then used to build three simulation models for the milling of old asphalt pavements with service years of 2~3 years, 7~8 years, and 11~12 years, respectively. The milling characteristics of SBS modified asphalt pavements with different service years were investigated using the moving speed

v

and rotating speed

ω

of the milling rotor as test factors, and the particle bonding ratio (

R_{b}

) and rotor average force (

F_{a}

) as test indexes. The results demonstrate that the following: The regularity of the effects of milling rotor moving speed and rotating speed on the particle bonding ratio and milling rotor average forces remained consistent overall as the pavement age increased. For the same milling parameters, the particle bonding ratio and the rotor average force are reduced. From 2~3 years old pavements to 7~8 years old pavements, the overall reduction in the particle bonding ratio indicator is about 12%, and the average force on the milling rotor is about 24%. From 7~8 years old pavements to 11~12 years old pavements, the overall reduction in the particle bonding ratio indicator is about 3%, and the average force on the milling rotor is about 15%. Full article

(This article belongs to the Special Issue Materials Informatics and Machine Learning in Pavement Engineering)

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18 pages, 5065 KiB

Open AccessArticle

Thermally Induced Phase Transformation of Ni-Exchanged LTA Zeolite as an Alternative Route of Obtaining Stable Ni-Spinel Pigment

by Miomir Krsmanović, Aleksandar Popović, Smilja Marković, Bojana Milićević, Dušan Bučevac, Marjetka Savić and Mia Omerašević

Materials 2025, 18(14), 3225; https://doi.org/10.3390/ma18143225 - 8 Jul 2025

Abstract

This study investigates the thermally induced phase transformation of Ni-exchanged LTA zeolite as a dual-purpose method for nickel immobilization and the synthesis of stable ceramic pigments. The process describes a cost-effective and sustainable alternative to conventional pigment production, aligning with circular economy principles. [...] Read more.

This study investigates the thermally induced phase transformation of Ni-exchanged LTA zeolite as a dual-purpose method for nickel immobilization and the synthesis of stable ceramic pigments. The process describes a cost-effective and sustainable alternative to conventional pigment production, aligning with circular economy principles. Upon thermal treatment at temperatures ranging between 900 °C and 1300 °C, Ni-exchanged LTA zeolite undergoes a transformation to NiAl₂O₄ spinel, confirmed by XRPD, FTIR, and thermal analysis. Initially, NiO is formed, but as the temperature increases, it dissolves and transforms into NiAl₂O₄. Colorimetric studies revealed intensified blue pigmentation with increasing temperature, correlating with crystallite growth and structural evolution. SEM analysis showed morphological changes from cubic particles to sintered agglomerates, enhancing pigment stability and hardness. The Ni-LTA sample calcined at 1300 °C showed the highest hue angle, which was consistent with the formation of over 99 wt.% of the nickel aluminate crystalline phase at this temperature. The results demonstrate that Ni-LTA zeolite can be effectively transformed into durable greenish-blue pigments suitable for application in porcelain. This transformation is especially evident at 1300 °C, where a spinel phase (NiAlSi₂O₄) forms, with colorimetric values: L = 58.94, a* = –16.08, and b* = –15.90. Full article

(This article belongs to the Section Advanced and Functional Ceramics and Glasses)

14 pages, 3439 KiB

Open AccessArticle

Electrospun Parallel, Crossed Fibers for Promoting Cell Adhesion and Migration

by Xiang Gao, Jingjun Peng, Linjie Huang, Xiaoquan Peng, Yanjun Cheng, Wei Zhang and Wei Jia

Materials 2025, 18(14), 3224; https://doi.org/10.3390/ma18143224 - 8 Jul 2025

Abstract

Electrospun fibers, possessing biomimetic characteristics similar to fibrous extracellular matrices, have attracted widespread attention as scaffold materials for skin tissue engineering. The topographical structure of electrospun fibers plays a critical role in determining cell behavior. However, the effects of fiber topography on human [...] Read more.

Electrospun fibers, possessing biomimetic characteristics similar to fibrous extracellular matrices, have attracted widespread attention as scaffold materials for skin tissue engineering. The topographical structure of electrospun fibers plays a critical role in determining cell behavior. However, the effects of fiber topography on human skin fibroblasts (HSFs) remain unclear. In this study, electrospinning technology was employed to investigate how parallel and crossed fiber architectures influence the spreading morphology, proliferation, and migration of HSFs. The results demonstrated that cells exhibited spindle-shaped elongation along single fibers; on closely spaced parallel fibers, cells formed cross-adhesions between adjacent fibers, with a fiber spacing of 30–60 μm serving as the threshold range for distinguishing individual cell behaviors. At fiber intersections, a characteristic spacing of 100 μm distinguished three distinct cellular responses: anchoring, turning, and bridging. The probability of a cell altering its preexisting migration path depended on its ability to extend laterally and reach adjacent fibers, which was constrained by the upper limit of the cell body’s minor axis. This study elucidated the unique role of the electrospun fiber topography in guiding cellular decision-making in complex microenvironments, provided important insights into topography-triggered cell migration, and highlighted the practical significance of material-guided strategies in tissue engineering. Full article

(This article belongs to the Special Issue Surface Modification of Materials for Multifunctional Applications)

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23 pages, 2548 KiB

Open AccessReview

Incorporation of Waste Glass Powder in the Sustainable Development of Concrete

by Arvindan Sivasuriyan and Eugeniusz Koda

Materials 2025, 18(14), 3223; https://doi.org/10.3390/ma18143223 - 8 Jul 2025

Abstract

The steep incline in the rising need for sustainable construction materials has marked the emerging trend of comprehensive research on utilizing waste glass powder (WGP) as a partial substitute for fine aggregates, such as cement, and coarse aggregates in concrete preparation. This review [...] Read more.

The steep incline in the rising need for sustainable construction materials has marked the emerging trend of comprehensive research on utilizing waste glass powder (WGP) as a partial substitute for fine aggregates, such as cement, and coarse aggregates in concrete preparation. This review thoroughly examines WGP-incorporated concrete in terms of its mechanical and durability properties. It explores compressive, tensile, and flexural strength, as well as its resistance to freeze–thaw cycles, sulfate attack, and chloride ion penetration. The characteristic microstructure densification, strength development, and durability performance can be attributed to the pozzolanic activity of WGP that forms additional calcium silicate hydrate (C-S-H). The review also highlights the optimal replacement levels of WGP to balance mechanical performance and long-term stability while addressing potential challenges, such as alkali–silica reaction (ASR) and reduced workability at high replacement ratios. By consolidating recent research findings, this study highlights the feasibility of WGP as a sustainable supplementary cementitious material (SCM), promoting eco-friendly construction while mitigating environmental concerns associated with glass waste disposal. Full article

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

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33 pages, 1541 KiB

Open AccessReview

A Review of External Confinement Methods for Enhancing the Strength of Concrete Columns

by Oliwia Sikora and Krzysztof Adam Ostrowski

Materials 2025, 18(14), 3222; https://doi.org/10.3390/ma18143222 - 8 Jul 2025

Abstract

The growing application of carbon fiber-reinforced polymers (CFRPs) in construction opens new possibilities for replacing traditional materials such as steel, particularly in strengthening and retrofitting concrete structures. CFRP materials offer notable advantages, including high tensile strength, low self-weight, corrosion resistance, and the ability [...] Read more.

The growing application of carbon fiber-reinforced polymers (CFRPs) in construction opens new possibilities for replacing traditional materials such as steel, particularly in strengthening and retrofitting concrete structures. CFRP materials offer notable advantages, including high tensile strength, low self-weight, corrosion resistance, and the ability to be tailored to complex geometries. This paper provides a comprehensive review of current technologies used to strengthen concrete columns, with a particular focus on the application of fiber-reinforced polymer (FRP) tubes in composite column systems. The manufacturing processes of FRP composites are discussed, emphasizing the influence of resin types and fabrication methods on the mechanical properties and durability of composite elements. This review also analyzes how factors such as fiber type, orientation, thickness, and application method affect the load-bearing capacity of both newly constructed and retrofitted damaged concrete elements. Furthermore, the paper identifies research gaps concerning the use of perforated CFRP tubes as internal reinforcement components. Considering the increasing interest in innovative column strengthening methods, this paper highlights future research directions, particularly the application of perforated CFRP tubes combined with external composite strengthening and self-compacting concrete (SCC). Full article

(This article belongs to the Special Issue Advanced Methods for Estimating Mechanical Properties, Constructional and Performance of Fiber-Reinforced Concrete Materials)

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Graphical abstract

21 pages, 2734 KiB

Open AccessArticle

Influence of Crossrib Configuration on Bond-Slip Behavior for High-Strength Reinforcement in Concrete

by Sisi Chao

Materials 2025, 18(14), 3221; https://doi.org/10.3390/ma18143221 - 8 Jul 2025

Abstract

In the present study, the mechanical properties of high-strength steel rebar with different crossrib spacing that affect the bond behavior between steel rebar and concrete is investigated. To reveal the effects of crossrib spacing on the bond behavior of 630 MPa high-strength steel [...] Read more.

In the present study, the mechanical properties of high-strength steel rebar with different crossrib spacing that affect the bond behavior between steel rebar and concrete is investigated. To reveal the effects of crossrib spacing on the bond behavior of 630 MPa high-strength steel rebar (T63) in concrete, 42 bonding specimens were designed using T63 rebars and T63 rebars with increased crossrib spacing (TB63). The bond properties of two kinds of steel rebar with concrete were investigated by pull-out test and the failure modes, bond strengths, relative slippages, and bond-slip curves were obtained. Based on analysis of bond-slip curves, the applicability of the existing bond-slip constitutive model to describe T63 and TB63 rebars was discussed. It was found that 30–50% increase in crossrib spacing had little effect on the bond failure mode and bond strength of T63 rebar. The bond-slip curves of the two types of bonding specimens were similar and there is a 1.3 to 1.5-fold increase in peak slippage with TB63. The calculation method of critical bond length in Chinese code (GB 50010-2010) is applicable to T63 and TB63 rebars, and the bond-slip characteristics of T63 rebar with different crossrib spacings was reliably described by the bond-slip constitutive model. The research results can be used as the basis for the application of T63 reinforcement and can also be used as a reference for optimizing of rebar ribs outline. Full article

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

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12 pages, 3441 KiB

Open AccessArticle

Mechanical Strength and Hydration Characteristic of Multiple Common Waste-Blended Cement-Based Materials Cured by Electric-Induced Heating Curing Under Severely Cold Environments

by Lei Zhang, Ruisen Li, Sheng Li, Han Wang and Qiang Fu

Materials 2025, 18(14), 3220; https://doi.org/10.3390/ma18143220 - 8 Jul 2025

Abstract

To address the challenges of concrete construction in polar regions, this study investigates the feasibility of fabricating cement-based materials under severely low temperatures using electric-induced heating curing methods. Cement mortars incorporating fly ash (FA-CM), ground granulated blast furnace slag (GGBS-CM), and metakaolin (MK-CM) [...] Read more.

To address the challenges of concrete construction in polar regions, this study investigates the feasibility of fabricating cement-based materials under severely low temperatures using electric-induced heating curing methods. Cement mortars incorporating fly ash (FA-CM), ground granulated blast furnace slag (GGBS-CM), and metakaolin (MK-CM) were cured at environmental temperatures of −20 °C, −40 °C, and −60 °C. The optimal carbon fiber (CF) contents were determined using the initial electric resistivity to ensure a consistent electric-induced heating curing process. The thermal profiles during curing were monitored, and mechanical strength development was systematically evaluated. Hydration characteristics were elucidated through thermogravimetric analysis (TG), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR) to identify phase compositions and reaction products. Results demonstrate that electric-induced heating effectively mitigates the adverse effect caused by the ultra-low temperature constraints, with distinct differences in the strength performance and hydration kinetics among supplementary cementitious materials. MK-CM exhibited superior early strength development with strength increasing rates above 10% compared to the Ref. specimen, which was attributed to the accelerated pozzolanic reactions. Microstructural analyses further verified the macroscopic strength test results that showed that electric-induced heating curing can effectively promote the performance development even under severely cold environments with a higher hydration degree and refined micro-pore structure. This work proposes a viable strategy for polar construction applications. Full article

(This article belongs to the Special Issue Advanced Cement-Based Composite Materials and Composite Intelligent Design)

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13 pages, 3428 KiB

Open AccessArticle

Multi-Parametric Study on Flexural Behavior of Wool–Flax Hybrid Composites Under Thermal Conditions

by Tsegaye Lemmi, David Ranz and Clara Luna Martin

Materials 2025, 18(14), 3219; https://doi.org/10.3390/ma18143219 - 8 Jul 2025

Abstract

The increasing demand for sustainable materials has intensified the interest in natural fiber-reinforced composites (NFRCs) as environmentally friendly alternatives to synthetic composites. However, NFRCs often face limitations in thermal stability, restricting their use in high-temperature environments. To address this, the present study explores [...] Read more.

The increasing demand for sustainable materials has intensified the interest in natural fiber-reinforced composites (NFRCs) as environmentally friendly alternatives to synthetic composites. However, NFRCs often face limitations in thermal stability, restricting their use in high-temperature environments. To address this, the present study explores the hybridization of cellulosic flax fibers with protein-based wool fibers to improve thermal stability without compromising mechanical integrity. Wool–flax hybrid composites were fabricated using a bio-based epoxy resin through a resin infusion technique with different fiber proportions. The flexural properties of these composites were evaluated under varying temperature conditions to assess the influence of fiber composition and thermal conditions. This study specifically examined the impact of wool fiber content on the flexural performance of the composites under thermal conditions, including behavior near and above the matrix’s glass transition temperature. The results showed that the flexural properties of the hybrid biocomposites were significantly affected by temperature. Compared with specimens tested at room temperature, the flexural modulus of all variants decreased by 85–94%, while the flexural strength declined by 79–85% at 120 °C, depending on the variant. The composite variant with a higher wool content (variant 3W) exhibited enhanced flexural performance, demonstrating an average of 15% greater flexural strength than other variants at 60 °C and 5% higher at 120 °C. These findings suggest that incorporating wool fibers into flax-based composites can effectively improve thermal stability while maintaining flexural properties, supporting the development of sustainable biocomposites for structural applications. Full article

(This article belongs to the Section Advanced Composites)

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33 pages, 24073 KiB

Open AccessArticle

Concentration Dependence of Optical Properties of Double-Doped LiTaO₃:Cr³⁺:Nd³⁺ Crystals

by Nikolay V. Sidorov, Lyubov A. Bobreva, Alexander Yu. Pyatyshev, Mikhail N. Palatnikov, Olga V. Palatnikova, Alexander V. Skrabatun, Andrei A. Teslenko and Mikhail K. Tarabrin

Materials 2025, 18(14), 3218; https://doi.org/10.3390/ma18143218 - 8 Jul 2025

Abstract

LiTaO₃ crystals doped with Cr³⁺ and Nd³⁺ ions are promising for developing active nonlinear laser media. In this work, the defect structure of LiTaO₃ crystals, including those doped with Cr³⁺ and Nd³⁺, is examined. X-ray patterns [...] Read more.

LiTaO₃ crystals doped with Cr³⁺ and Nd³⁺ ions are promising for developing active nonlinear laser media. In this work, the defect structure of LiTaO₃ crystals, including those doped with Cr³⁺ and Nd³⁺, is examined. X-ray patterns of all six investigated LiTaO₃:Cr:Nd crystals are identical and correspond to a highly perfect structure. Using optical microscopy, the presence of defects of various shapes, microinhomogeneities, and lacunae was revealed. The optical absorption and Raman scattering spectra of a series of nonlinear, optical, double-doped LiTaO₃:Cr³⁺:Nd³⁺ (0.06 ≤ [Cr³⁺] ≤ 0.2; 0.2 ≤ [Nd³⁺] ≤ 0.45 wt%) crystals showed that at concentrations of doping Cr³⁺ ions less than 0.09 wt% and Nd³⁺ ions less than 0.25 wt%, the crystal structure is characterized by a low level of defects, and the optical transmission spectra characterized by narrow lines corresponding to electron transitions in Nd³⁺ ions. In this case, for the radiative transition in the cation sublattice, the existence of three nonequivalent neodymium centers is observed, and for the radiative transition, two nonequivalent centers are observed. IR absorption spectroscopy in the OH⁻-stretching vibration range revealed two main spectral regions: 3463–3465 cm⁻¹, associated with stoichiometry changes, and 3486–3490 cm⁻¹, linked to complex defects such as (V^-_Li)-OH and (Ta⁴⁺_Li)-OH. A distinct low-intensity line at ~3504 cm⁻¹ was observed only in doped crystals, attributed to (Nd²⁺_Li)-OH defects that significantly distort the oxygen-octahedral clusters due to the larger ionic radius of Nd³⁺ compared to Ta⁵⁺. In contrast, Cr-related defects cause only minor distortions. The Klauer method indicated that the highest concentration of OH⁻-groups occurs in the LiTaO₃:Cr³⁺ (0.09 wt%):Nd³⁺ (0.25 wt%) crystal, where multiple complex defects are present. Full article

(This article belongs to the Special Issue Advanced Materials in Photoelectrics and Photonics)

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15 pages, 1244 KiB

Open AccessArticle

Shrinkage Behavior of Strength-Gradient Multilayered Zirconia Materials

by Andrea Coldea, John Meinen, Moritz Hoffmann, Adham Elsayed and Bogna Stawarczyk

Materials 2025, 18(14), 3217; https://doi.org/10.3390/ma18143217 - 8 Jul 2025

Abstract

To investigate the sintering shrinkage behavior of multigeneration, multilayer zirconia materials using geometrical measurements. Seven zirconia CAD/CAM materials were analyzed, comprising two mono-generation zirconia (HTML: Katana Zr, HTML Plus, 3Y-TZP; UTML: Katana Zr, UTML, 5Y-TZP) and five strength-gradient multilayer zirconia (AIDI: optimill 3D [...] Read more.

To investigate the sintering shrinkage behavior of multigeneration, multilayer zirconia materials using geometrical measurements. Seven zirconia CAD/CAM materials were analyzed, comprising two mono-generation zirconia (HTML: Katana Zr, HTML Plus, 3Y-TZP; UTML: Katana Zr, UTML, 5Y-TZP) and five strength-gradient multilayer zirconia (AIDI: optimill 3D PRO Zir; PRIT: Priti multidisc ZrO₂ multicolor; UPCE: Explore Esthetic; ZCPC: IPS e.max ZirCAD Prime; ZYML: Katana YML) materials. Cubes (10 × 10 × 10 mm³) were milled in varying positions within the disks. Geometrical measurements were applied before and after dense sintering using a micrometer screw gauge, light microscopy, as well as surface scans and shrinkages were calculated. Data were analyzed using Kolmogorov–Smirnov, five-way ANOVA followed by the Scheffé post hoc test, and partial eta squared, as well as the Kruskal–Wallis test, including Bonferroni correction (p < 0.05). The highest influence on the shrinkage was exerted by the zirconia material (^η_P² = 0.893, p < 0.001), followed by the test method (^η_P² = 0.175, p < 0.001), while the vertical and horizontal position and measurement point showed no impact on the shrinkage results (p = 0.195–0.763) in the global analysis. Depending on the test method, the pooled shrinkage values of all tested zirconia materials varied between 17.7 and 20.2% for micrometer screw gauge, 17.7 and 20.1% for light microscopy, and 17.8 and 21.1% for surface scan measurements. The shrinkage values measured in the upper, middle, and lower multilayered vertical direction did not differ significantly in the global analysis for the multilayer materials. Therefore, a uniform shrinkage of these strength-gradient multilayer zirconia materials within clinically relevant restorations can be assumed. Full article

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25 pages, 17922 KiB

Open AccessArticle

Application of Food Waste in Biodegradable Composites: An Ecological Alternative in Tribology

by Łukasz Wojciechowski, Zuzanna Sydow, Karol Bula and Tomasz Runka

Materials 2025, 18(14), 3216; https://doi.org/10.3390/ma18143216 - 8 Jul 2025

Abstract

Biodegradable composite materials enhanced with food waste for tribological applications are proposed in this article. Polymer materials used as matrices included polypropylene and polylactic acid, which, according to the manufacturers’ claims, were made entirely or partially from biodegradable raw materials. Additionally, the matrices [...] Read more.

Biodegradable composite materials enhanced with food waste for tribological applications are proposed in this article. Polymer materials used as matrices included polypropylene and polylactic acid, which, according to the manufacturers’ claims, were made entirely or partially from biodegradable raw materials. Additionally, the matrices were enhanced with three types of waste materials: powders derived from cherry and plum stones, and pomace extracted from flax seeds. The composites differed in the percentage content of filler (15 or 25 wt.%) and particle size (d < 400 µm or d > 400 µm). Thirty-minute block-on-ring friction tests were performed to determine frictional behaviour (when pairing with steel), and the wear mechanisms were analysed using optical microscopy and scanning electron microscopy, supplemented with Raman spectroscopy. A notable effect of cherry and plum stone fillers was observed as a reduction in motion resistance, as measured by the friction coefficient. This reduction was evident across all material configurations in polypropylene-based composites and was significant at the lowest concentrations and granulation in polylactic acid composites. The effect of flaxseed pomace filler was ambiguous for both composite bases. Full article

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

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19 pages, 4319 KiB

Open AccessArticle

Investigation of Corrosion Resistance of 60Si2MnA Spring Steel Coated with Zn-Al in Atmospheric Environments

by Yurong Wang, Hui Xiao, Baolong Liu, Shilong Chen, Xiaofei Jiao, Shuwei Song, Wenyue Zhang and Ying Jin

Materials 2025, 18(14), 3215; https://doi.org/10.3390/ma18143215 - 8 Jul 2025

Abstract

To investigate the corrosion resistance of 60Si2MnA spring steel coated with Zn-Al in a domestic atmospheric environment containing harmful salts, the corrosion environmental factors (temperature, humidity, deposited salts, and pH) were obtained through field research. The deliquescence and weathering behavior of harmful salts [...] Read more.

To investigate the corrosion resistance of 60Si2MnA spring steel coated with Zn-Al in a domestic atmospheric environment containing harmful salts, the corrosion environmental factors (temperature, humidity, deposited salts, and pH) were obtained through field research. The deliquescence and weathering behavior of harmful salts were studied using impedance methods to establish their characteristic curves. Additionally, a self-designed salt deposition test apparatus was employed to conduct accelerated atmospheric corrosion tests under constant salt deposition (10 g/m²) and controlled temperature and humidity conditions (20 °C/75% RH and 40 °C/75% RH) over different corrosion periods. The results show that noticeable red rust appeared on the samples after one month of corrosion. As the temperature increased, the consumption of the coating accelerated. XRD and Raman analyses reveal that the main corrosion products of the coating materials were ZnO, Zn(OH)₂, and Zn₅(CO₃)₂(OH)₆, while the red rust primarily consisted of iron oxides and hydroxides. In the early stages of corrosion, the self-corrosion current density was relatively low due to the protective effects of the coating and the corrosion product layer, indicating good corrosion resistance. However, in the later stages, the integrity of the coating and the corrosion product layer deteriorated, leading to a significant increase in the self-corrosion current density and a decline in corrosion resistance. This study provides a data foundation for understanding the corrosion behavior of Zn-Al-coated spring steel in atmospheric environments and offers theoretical insights for developing more corrosion-resistant coatings and optimizing anti-corrosion measures. Full article

(This article belongs to the Section Metals and Alloys)

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