Materials

12 pages, 4303 KiB

Open AccessArticle

The Influence of Aging Temperature and Cryogenic Treatment on the Mechanical Properties and Microstructure of Extruded Mg-8Gd-3Y-0.4Zr Alloy

by Haoran Pang, Lunyuan Tang, Xiaojun Wang, Min Ma and Liwei Lu

Materials 2025, 18(12), 2922; https://doi.org/10.3390/ma18122922 - 19 Jun 2025

Viewed by 386

Abstract

This investigation implemented an integrated aging–cryogenic thermal processing method for extruded Mg-8Gd-3Y-0.4Zr alloy to further improve its performance and broaden its scope of application, employing a characterization approach combining optical microscopy (OM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), and transmission electron microscopy [...] Read more.

This investigation implemented an integrated aging–cryogenic thermal processing method for extruded Mg-8Gd-3Y-0.4Zr alloy to further improve its performance and broaden its scope of application, employing a characterization approach combining optical microscopy (OM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The comprehensive microstructure characterization was systematically correlated with mechanical property evolution to establish structure–property relationships. The results show that aging combined with cryogenic treatment significantly enhances the hardness and improves the microstructure of magnesium alloys. Specimens aged at 210 °C for 20 h followed by one-hour cryogenic treatment exhibited the highest average hardness (113.5 HV), representing a 11.2–25% improvement compared to those aged at lower temperatures. This enhancement can be attributed to the elevated aging temperature promoting substantial precipitation and subsequent growth of second phases such as Mg₃(Gd,Y), which benefit from sufficient thermal activation energy. The increased density and larger dimensions of these second phases contribute to enhanced hardness through elevated internal stress generation. However, their non-uniform distribution may induce localized stress concentration, consequently reducing hardness uniformity. Notably, specimens subjected solely to 210 °C aging for 20 h showed marginally lower hardness compared to their cryogenically treated counterparts, suggesting that although cryogenic treatment may refine grain structures and introduce dislocation defects to enhance hardness, its concurrent reduction in residual stresses might limit the overall improvement magnitude. Full article

(This article belongs to the Section Metals and Alloys)

► Show Figures

Graphical abstract

14 pages, 1366 KiB

Open AccessArticle

Screw Coating as a Solution to Solve Screw Loosening Complications: An In Vitro Study

by Lara Coelho, Maria-Cristina Manzanares-Céspedes, Joana Mendes, Carlos Aroso and José Manuel Mendes

Materials 2025, 18(12), 2921; https://doi.org/10.3390/ma18122921 - 19 Jun 2025

Viewed by 371

Abstract

Background: This study aimed to evaluate the influence of a screw coating on the screw preload and removal torque value (RTV) with and without the application of a cyclic load (CL) to make screws with greater untightening resistance to prevent screw loosening. Methods [...] Read more.

Background: This study aimed to evaluate the influence of a screw coating on the screw preload and removal torque value (RTV) with and without the application of a cyclic load (CL) to make screws with greater untightening resistance to prevent screw loosening. Methods: Ninety complexes composed of implants, abutments, and prosthetic screws were examined and tested under CL oral conditions (n = 45) and non-CL conditions (nCL, n = 45). Each group was divided into three subgroups (n = 15): a control group (CG) without a screw coating, a GapSeal^®-coated screw group (GG), and a polytetrafluoroethylene (PTFE) tape-wrapped screw group (PG). All screws were tightened at 30 Ncm, and the preload was recorded. In the nCL group, the screws were untightened to record the RTV. In the CL group, the screws were tightened, subjected to a CL in distillated water at a temperature of 37 °C, and then untightened to record the RTV. Micro-Ct analysis was conducted on two samples from each group before CL. SEM analyses of two samples per subgroup before and after CL were also performed. Results: The preload in the PG was significantly lower under nCL (29.92 Ncm) compared with CG (30.95 Ncm) and GG (31.19 Ncm) and also under a CL (PG: 30.92 Ncm) compared with CG (31.72 Ncm) and GG (31.42 Ncm). The RTVs of the PG were significantly lower under nCL (15.30 Ncm) compared with CG (27.98 Ncm) and GG (28.46 Ncm). Under CL, the RTVs of the PG were significantly higher (31.50 Ncm) compared with CG (26.00 Ncm) and GG (27.44 Ncm). Conclusions: Wrapping the screw with PTFE tape significantly reduced the preload but resulted in a significantly greater RTV under CL conditions in the simulated oral environment, suggesting that this could be a solution to decrease the risk of screw loosening. Full article

(This article belongs to the Special Issue Advanced Coating Research for Metal Surface Protection)

► Show Figures

Figure 1

13 pages, 8452 KiB

Open AccessArticle

Could Tack-Curing Influence Margin Continuity and Conversion Degree of a Universal Dual-Curing Cement?

by Leila Es Sebar, Andrea Baldi, Allegra Comba, Isabella Sannino, Leonardo Iannucci, Sabrina Grassini, Tolou Shokuhfar and Nicola Scotti

Materials 2025, 18(12), 2920; https://doi.org/10.3390/ma18122920 - 19 Jun 2025

Viewed by 360

Abstract

Proper polymerization protocol is crucial for the long-term success of full-ceramic crown restorations. This study investigates the margin continuity and degree of conversion (DC) of a universal dual-curing cement under full-ceramic crowns subjected to different polymerization protocols and thermal aging. Intact human upper [...] Read more.

Proper polymerization protocol is crucial for the long-term success of full-ceramic crown restorations. This study investigates the margin continuity and degree of conversion (DC) of a universal dual-curing cement under full-ceramic crowns subjected to different polymerization protocols and thermal aging. Intact human upper central incisors and canines were prepared for crowns, digitally designed, and milled from reinforced lithium silicate (Celtra Duo, Dentsply). Crowns were cemented using a universal dual-curing cement (G-Cem One, GC) with two polymerization protocols: (G1) microbrush excess removal, 1 min waiting, and 20 s light curing per side; (G2) 5 s tack curing per side, excess removal with a scaler, and 20 s light curing. Marginal adaptation was assessed using micro-computed tomography, and DC was evaluated with Raman spectroscopy before and after artificial thermal aging (10,000 cycles between 5 °C and 55 °C). Statistical comparisons were performed with significance set at p < 0.05. Results showed significantly poorer marginal adaptation in the tack-curing group, with no post-aging differences between groups. Baseline DC was high in all samples, with no protocol-dependent variations; nevertheless, aging increased DC in G1. These findings highlight the importance of selecting an appropriate polymerization protocol to ensure optimal marginal adaptation and polymerization efficiency. Full article

(This article belongs to the Special Issue Advanced Materials for Oral Application (3rd Edition))

► Show Figures

Figure 1

48 pages, 7715 KiB

Open AccessReview

Next-Generation Bioplastics for Food Packaging: Sustainable Materials and Applications

by Xiaokun Shi, Lijuan Cui, Chao Xu and Shuping Wu

Materials 2025, 18(12), 2919; https://doi.org/10.3390/ma18122919 - 19 Jun 2025

Viewed by 1065

Abstract

As the global plastic pollution problem intensifies and the environmental hazards of traditional petroleum-based plastics become increasingly significant, the development of sustainable alternative materials has become an urgent need. This paper systematically reviews the research progress, application status and future trends of new [...] Read more.

As the global plastic pollution problem intensifies and the environmental hazards of traditional petroleum-based plastics become increasingly significant, the development of sustainable alternative materials has become an urgent need. This paper systematically reviews the research progress, application status and future trends of new generation bioplastics in the field of food packaging. Bioplastics are categorized into three main groups according to their sources and degradability: biobased biodegradable materials (e.g., polylactic acid PLA, polyhydroxy fatty acid ester PHA, chitosan, and cellulose-based materials); biobased non-biodegradable materials (e.g., Bio-PE, Bio-PET); and non-biobased biodegradable materials (e.g., PBAT, PCL, PBS). Different processing technologies, such as thermoforming, injection molding, extrusion molding and coating technologies, can optimize the mechanical properties, barrier properties and freshness retention of bioplastics and promote their application in scenarios such as food containers, films and smart packaging. Although bioplastics still face challenges in terms of cost, degradation conditions and industrial support, promising future directions are found in the development of the large-scale utilization of non-food raw materials (e.g., agricultural waste, algae), nano-composite technology to enhance the performance, and the development of intelligent packaging functions. Through technological innovation and industry chain integration, bioplastics are expected to transform from an environmentally friendly alternative to a mainstream packaging material, helping to realize the goal of global carbon neutrality. Full article

(This article belongs to the Section Green Materials)

► Show Figures

Graphical abstract

22 pages, 1719 KiB

Open AccessArticle

Selection of High-Performance Sorbent for H₂S Removal and Regulation of Reaction Products via Thermodynamic Simulation

by Yanni Xuan, Shuaicheng Peng, Hong Tian, Zhangmao Hu, Yanshan Yin and Haitao Gao

Materials 2025, 18(12), 2918; https://doi.org/10.3390/ma18122918 - 19 Jun 2025

Viewed by 382

Abstract

Thermodynamic simulations of the H₂S removal from blast furnace gas by metal oxides were conducted to select a suitable metal desulfurizer. Notably, the Mn oxides demonstrated themselves as the optimal H₂S removal agents. They are characterized by the absence [...] Read more.

Thermodynamic simulations of the H₂S removal from blast furnace gas by metal oxides were conducted to select a suitable metal desulfurizer. Notably, the Mn oxides demonstrated themselves as the optimal H₂S removal agents. They are characterized by the absence of radioactive pollution, high cost-effectiveness, high sulfur fixation potential, and non-reactivity with CO₂, CO, and CH₄. Through a comprehensive comparison of Mn oxides, the sulfur fixation potential and sulfur capacity were elucidated as follows: Mn₃O₄ > Mn₂O₃ > MnO₂ > MnO. The higher-valence manganese oxides were shown to have stronger oxidation ability, larger sulfur capacity, and the advantage of producing elemental sulfur with high utilization value during the reaction. After selecting Mn oxides as the optimal H₂S removal agents, an equilibrium component analysis of the regeneration process of the sulfided MnS was carried out. The results indicate that an oxygen amount that is 1.5 times that of MnS is the optimal dosage, and such an amount can oxidize all of the MnS at a relatively low temperature. Conversely, a diluted oxygen concentration can further reduce the temperature of the regeneration process, preventing the sintering of the regenerated desulfurizer and thus maintaining its reusability. This research provides a sufficient theoretical basis for the use of Mn oxides as active components of desulfurizers to remove H₂S from blast furnace gas and for the regeneration of MnS after desulfurization. Full article

(This article belongs to the Section Materials Physics)

► Show Figures

Figure 1

12 pages, 2393 KiB

Open AccessArticle

Influence of PVP and PEG on the Electrochemical Synthesis of Magnesium Hydroxide

by Shengqing Wang, Fangyang Liu, Zongliang Zhang, Jun Wang and Liangxing Jiang

Materials 2025, 18(12), 2917; https://doi.org/10.3390/ma18122917 - 19 Jun 2025

Viewed by 247

Abstract

The functional performance of magnesium hydroxide (Mg(OH)₂) is intrinsically governed by its crystallographic morphology. Herein, we demonstrate an electrochemical deposition strategy to synthesize Mg(OH)₂ from abandoned MgCl₂ resources in salt lakes, achieving simultaneous waste valorization and morphology control. Systematic [...] Read more.

The functional performance of magnesium hydroxide (Mg(OH)₂) is intrinsically governed by its crystallographic morphology. Herein, we demonstrate an electrochemical deposition strategy to synthesize Mg(OH)₂ from abandoned MgCl₂ resources in salt lakes, achieving simultaneous waste valorization and morphology control. Systematic investigations were conducted on the effects of polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) as surfactants on electrochemical parameters (cell voltage, pH, current efficiency, and energy consumption) and morphological evolution (XRD, SEM, and laser particle size analysis). Results show that the cell voltage and pH increased proportionally with surfactant concentration, with a current efficiency of 93.86% and an optimal energy consumption of 4.15 kW h·t⁻¹ at an optimal PVP concentration of 6 g·L⁻¹. PEG addition exhibited a similar trend in process parameter modulation. Morphological evolution analysis revealed that appropriate PEG dosage promoted the transformation of irregular Mg(OH)₂ flakes into near-spherical platelets, accompanied by a measurable increase in particle size. This work establishes structure–property relationships between surfactant molecular design and Mg(OH)₂ crystallization, providing theoretical support for the controllable electrochemical preparation of magnesium hydroxide with different morphologies. Furthermore, it opens up a novel and innovative technical pathway to promote the high-value utilization of abandoned magnesium resources in salt lakes. Full article

(This article belongs to the Section Advanced Materials Characterization)

► Show Figures

Figure 1

20 pages, 5705 KiB

Open AccessArticle

Polyacrylic Surfactant-Enabled Engineering of Co₃O₄ Electrodes for Enhanced Asymmetric Supercapacitor Performance

by Rutuja U. Amate, Pritam J. Morankar, Mrunal K. Bhosale, Aviraj M. Teli, Sonali A. Beknalkar and Chan-Wook Jeon

Materials 2025, 18(12), 2916; https://doi.org/10.3390/ma18122916 - 19 Jun 2025

Viewed by 329

Abstract

In this work, we report a facile and tunable electrodeposition approach for engineering polyacrylic acid (PAA)-modified Co₃O₄ electrodes on nickel foam for high-performance asymmetric pouch-type supercapacitors. By systematically varying the PAA concentration (0.5 wt %, 1 wt %, and 1.5 [...] Read more.

In this work, we report a facile and tunable electrodeposition approach for engineering polyacrylic acid (PAA)-modified Co₃O₄ electrodes on nickel foam for high-performance asymmetric pouch-type supercapacitors. By systematically varying the PAA concentration (0.5 wt %, 1 wt %, and 1.5 wt %), we demonstrate that the CO-1 sample (1 wt % PAA) exhibited the most optimized structure and electrochemical behavior. The CO-1 electrode delivered a remarkable areal capacitance of 3467 mF/cm² at 30 mA/cm², attributed to its interconnected nanosheet morphology, enhanced ion diffusion, and reversible Co²⁺/Co³⁺/Co⁴⁺ redox transitions. Electrochemical impedance spectroscopy confirmed low internal resistance (0.4267 Ω), while kinetic analysis revealed a dominant diffusion-controlled charge storage contribution of 91.7%. To evaluate practical applicability, an asymmetric pouch-type supercapacitor device was assembled using CO-1 as the positive electrode and activated carbon as the negative electrode. The device operated efficiently within a 1.6 V window, achieving an impressive areal capacitance of 157 mF/cm², an energy density of 0.056 mWh/cm², a power density of 1.9 mW/cm², and excellent cycling stability. This study underscores the critical role of polymer-assisted growth in tailoring electrode architecture and provides a promising route for integrating cost-effective and scalable supercapacitor devices into next-generation energy storage technologies. Full article

(This article belongs to the Special Issue Emerging Electrode Materials for Energy Harvesting and Storage Applications)

► Show Figures

Figure 1

23 pages, 10093 KiB

Open AccessArticle

Phase Evolution and Synthesis of Be₁₂ Nb Intermetallic Compound in the 800–1300 °C Temperature Range

by Sergey Udartsev, Inesh E. Kenzhina, Timur Kulsartov, Kuanysh Samarkhanov, Zhanna Zaurbekova, Yuriy Ponkratov, Alexandr Yelishenkov, Meiram Begentayev, Saulet Askerbekov, Aktolkyn Tolenova, Manarbek Kylyshkanov, Mikhail Podoinikov, Ainur Kaynazarova and Oleg Obgolts

Materials 2025, 18(12), 2915; https://doi.org/10.3390/ma18122915 - 19 Jun 2025

Viewed by 376

Abstract

Beryllium-based intermetallic compounds, such as Be₁₂Nb, are attracting growing interest for their high thermal stability and potential to replace pure beryllium as neutron reflectors and multipliers in both fission and future fusion reactors, with additional applications in metallurgy, aerospace, and hydrogen [...] Read more.

Beryllium-based intermetallic compounds, such as Be₁₂Nb, are attracting growing interest for their high thermal stability and potential to replace pure beryllium as neutron reflectors and multipliers in both fission and future fusion reactors, with additional applications in metallurgy, aerospace, and hydrogen technology. The paper presents the results of an investigation of the thermal treatment and phase formation of the intermetallic compound Be₁₂Nb from a mixture of niobium and beryllium powders in the temperature range of 800–1300 °C. The phase evolution was assessed as a function of sintering temperature and time. A nearly single-phase Be₁₂Nb composition was achieved at 1100 °C, while decomposition into lower-order beryllides such as Be₁₇Nb₂ occurred at temperatures ≥1200 °C, indicating thermal instability of Be₁₂Nb under vacuum. Careful handling of sintering in low vacuum minimized oxidation, though signs of possible BeO formation were noted. The findings complement and extend earlier reports on Be₁₂Nb synthesis via plasma sintering, mechanical alloying, and other powder metallurgy routes, providing broader insight into phase formation and synthesis. These results provide a foundation for optimizing the manufacturing parameters required to produce homogeneous Be₁₂Nb-based components and billets at an industrial scale. Additionally, they help define the operational temperature limits necessary to preserve the material’s phase integrity during application. Full article

(This article belongs to the Section Advanced Materials Characterization)

► Show Figures

Figure 1

12 pages, 4646 KiB

Open AccessArticle

Dielectric Properties and Defect Chemistry of Tb/Ho-Co-Doped BaTiO₃ Ceramics

by Junwei Liu, Xin Wei, Qiaoli Liu, Yupei Ran, Guoqi Xu and Qi Liu

Materials 2025, 18(12), 2914; https://doi.org/10.3390/ma18122914 - 19 Jun 2025

Viewed by 338

Abstract

Co-doping at Ba and Ti sites with double rare-earth elements has proven an effective strategy for enhancing the dielectric properties of BaTiO₃ ceramics. Among intermediate-sized rare-earth ions, Tb and Ho exhibit amphoteric behavior, occupying both Ba and Ti sites. Investigating the site [...] Read more.

Co-doping at Ba and Ti sites with double rare-earth elements has proven an effective strategy for enhancing the dielectric properties of BaTiO₃ ceramics. Among intermediate-sized rare-earth ions, Tb and Ho exhibit amphoteric behavior, occupying both Ba and Ti sites. Investigating the site occupation, defect chemistry, and dielectric effects of Tb and Ho in BaTiO₃ is therefore valuable. In this work, Tb/Ho-co-doped BaTiO₃ ceramics with the composition (Ba_1−xTb_x)(Ti_1−xHo_x)O₃ (x = 0.01~0.10) were fabricated at 1400 °C via solid-state reaction, and their solid solubility and crystal structures are confirmed. Microstructure, dielectric properties, photoluminescence, and valence states of samples with a single phase were systematically studied. Both the lattice parameter a and unit cell volume increase with doping level. The ceramic with x = 0.02 meets the X5S dielectric specification. Ho and Tb ions both demonstrate amphoteric site occupancy: Ho exists solely as Ho³⁺ at both Ba and Ti sites, while Tb exhibits mixed valence states as Ba-site Tb³⁺ and Ti-site Tb⁴⁺. As the doping content increases, the concentration of Tb⁴⁺ at Ti sites decreases, and the quantity of Ba-site Ho³⁺ ions initially increases to a maximum before decreasing. Defect compensation mechanisms within the samples are also discussed. Full article

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

► Show Figures

Figure 1

15 pages, 1882 KiB

Open AccessArticle

Predicting Rheological Properties of Asphalt Modified with Mineral Powder: Bagging, Boosting, and Stacking vs. Single Machine Learning Models

by Haibing Huang, Zujie Xu, Xiaoliang Li, Bin Liu, Xiangyang Fan, Haonan Ding and Wen Xu

Materials 2025, 18(12), 2913; https://doi.org/10.3390/ma18122913 - 19 Jun 2025

Viewed by 335

Abstract

This study systematically compares the predictive performance of single machine learning (ML) models (KNN, Bayesian ridge regression, decision tree) and ensemble learning methods (bagging, boosting, stacking) for quantifying the rheological properties of mineral powder-modified asphalt, specifically the complex shear modulus (G*) and the [...] Read more.

This study systematically compares the predictive performance of single machine learning (ML) models (KNN, Bayesian ridge regression, decision tree) and ensemble learning methods (bagging, boosting, stacking) for quantifying the rheological properties of mineral powder-modified asphalt, specifically the complex shear modulus (G*) and the phase angle (δ). We used two emulsifiers and three mineral powders for fabricating modified emulsified asphalt and conducting rheological property tests, respectively. Dynamic shear rheometer (DSR) test data were preprocessed using the local outlier factor (LOF) algorithm, followed by K-fold cross-validation (K = 5) and Bayesian optimization to tune model hyperparameters. This framework uniquely employs cross-validated predictions from base models as input features for the meta-learner, reducing information leakage and enhancing generalization. Traditional single ML models struggle to characterize accurately as a result, and an innovative stacking model was developed, integrating predictions from four heterogeneous base learners—KNN, decision tree (DT), random forest (RF), and XGBoost—with a Bayesian ridge regression meta-learner. Results demonstrate that ensemble models outperform single models significantly, with the stacking model achieving the highest accuracy (R² = 0.9727 for G* and R² = 0.9990 for δ). Shapley additive explanations (SHAP) analysis reveals temperature and mineral powder type as key factors, addressing the “black box” limitation of ML in materials science. This study validates the stacking model as a robust framework for optimizing asphalt mixture design, offering insights into material selection and pavement performance improvement. Full article

(This article belongs to the Special Issue Modeling and Analysis of Composite Materials and Structures in Civil Engineering (Second Edition))

► Show Figures

Graphical abstract

22 pages, 8327 KiB

Open AccessArticle

Surface Evaluation of a Novel Acid-Etching Solution for Zirconia and Lithium Disilicate

by Clint Conner, Fabio Andretti, Alfredo I. Hernandez, Silvia Rojas-Rueda, Francisco X. Azpiazu-Flores, Brian R. Morrow, Franklin Garcia-Godoy, Carlos A. Jurado and Abdulrahman Alshabib

Materials 2025, 18(12), 2912; https://doi.org/10.3390/ma18122912 - 19 Jun 2025

Viewed by 372

Abstract

The current investigation evaluated a novel acid-etching solution containing hydrochloric acid (HCl), hydrofluoric acid (HF), nitric acid (HNO₃), orthophosphoric acid (H₃PO₄), and sulfuric acid (H₂SO₄) designed for etching zirconia ceramics. Achieving reliable bonding [...] Read more.

The current investigation evaluated a novel acid-etching solution containing hydrochloric acid (HCl), hydrofluoric acid (HF), nitric acid (HNO₃), orthophosphoric acid (H₃PO₄), and sulfuric acid (H₂SO₄) designed for etching zirconia ceramics. Achieving reliable bonding to zirconia is challenging due to its chemical inertia, unlike lithium disilicate, which can be effectively conditioned with HF etching. One hundred and twenty specimens of zirconia and lithium disilicate underwent etching with the experimental solution for six different durations: control, 20 s, 60 s, 5 min, 30 min, and 1 h. Surface roughness was assessed using 3D optical profilometry and scanning electron microscopy (SEM). The roughness of both materials increased with etching time; however, lithium disilicate demonstrated a significantly greater response, with Ra values rising from 0.18 µm (control) to 1.26 µm (1 h), while zirconia increased from 0.21 µm to 0.60 µm. ANOVA revealed significant effects depending on the ceramic type, time, and their interaction (p < 0.001). SEM images revealed non-selective etching of lithium disilicate, suggesting potential over-etching. The novel acid-etching solution improved surface roughness, especially in lithium disilicate ceramics. An application duration of one hour appears optimal for zirconia, improving surface characteristics while reducing damage; however, further research is required to assess its clinical safety and long-term effects on the mechanical properties of this dental ceramic. Full article

(This article belongs to the Special Issue Characteristics of Dental Ceramics)

► Show Figures

Figure 1

25 pages, 3478 KiB

Open AccessArticle

Silicon Oxycarbide Thin Films Produced by Hydrogen-Induced CVD Process from Cyclic Dioxa-Tetrasilacyclohexane

by Agnieszka Walkiewicz-Pietrzykowska, Krzysztof Jankowski, Jan Kurjata, Rafał Dolot, Romuald Brzozowski, Joanna Zakrzewska and Paweł Uznanski

Materials 2025, 18(12), 2911; https://doi.org/10.3390/ma18122911 - 19 Jun 2025

Viewed by 454

Abstract

Silicon oxycarbide coatings are the subject of research due to their exceptional optical, electronic, anti-corrosion, etc., properties, which make them attractive for a number of applications. In this article, we present a study on the synthesis and characterization of thin SiOC:H silicon oxycarbide [...] Read more.

Silicon oxycarbide coatings are the subject of research due to their exceptional optical, electronic, anti-corrosion, etc., properties, which make them attractive for a number of applications. In this article, we present a study on the synthesis and characterization of thin SiOC:H silicon oxycarbide films with the given composition and properties from a new organosilicon precursor octamethyl-1,4-dioxatetrasilacyclohexane (²D₂) and its macromolecular equivalent—poly(oxybisdimethylsily1ene) (POBDMS). Layers from ²D₂ precursor with different SiOC:H structure, from polymeric to ceramic-like, were produced in the remote microwave hydrogen plasma by CVD method (RHP-CVD) on a heated substrate in the temperature range of 30–400 °C. SiOC:H polymer layers from POEDMS were deposited from solution by spin coating and then crosslinked in RHP via the breaking of the Si-Si silyl bonds initiated by hydrogen radicals. The properties of SiOC:H layers obtained by both methods were compared. The density of the cross-linked materials was determined by the gravimetric method, elemental composition by means of XPS, chemical structure by FTIR spectroscopy, and NMR spectroscopy (¹³C, ²⁹Si). Photoluminescence analyses and ellipsometric measurements were also performed. Surface morphology was characterized by AFM. Based on the obtained results, a mechanism of initiation, growth, and cross-linking of the CVD layers under the influence of hydrogen radicals was proposed. Full article

(This article belongs to the Special Issue Advances in Plasma Treatment of Materials)

► Show Figures

Figure 1

21 pages, 4884 KiB

Open AccessArticle

Sandwich Panels Subjected to Point Loads: Design Approach Using Effective Widths in Elastic Range

by Niklas Ardelmann and Bernd Naujoks

Materials 2025, 18(12), 2910; https://doi.org/10.3390/ma18122910 - 19 Jun 2025

Viewed by 253

Abstract

Sandwich panels have established themselves as self-supporting and isolating construction elements for room closures in hall construction. As a result of subsequently installed photovoltaic (PV) systems or cladding, sandwich panels are subjected to point loads at the connection points to the substructure of [...] Read more.

Sandwich panels have established themselves as self-supporting and isolating construction elements for room closures in hall construction. As a result of subsequently installed photovoltaic (PV) systems or cladding, sandwich panels are subjected to point loads at the connection points to the substructure of additional systems. In the case of pressure-suction changes from wind, a cyclical local load also occurs. Therefore, for sandwich panels—which are designed and dimensioned for uniform surface loads (dead weight, wind, snow, temperature constraints)—the question must be answered as to how this local load introduction affects the load-bearing behaviour and stress distribution in the sandwich panel. To quantify any stress concentrations across the width of the panel, the method of effective widths is used here, based on stress distributions in the elastic range determined through component tests and numerical models. The results of these test series, along with the resulting design concept based on effective widths in the elastic range, as well as the failure under the ultimate load condition, are documented in this paper. Full article

(This article belongs to the Special Issue Experimental and Numerical Analysis of Sandwich Structures)

► Show Figures

Figure 1

14 pages, 2967 KiB

Open AccessArticle

Gradient Joule Heating Curing Performance of Steel-Fiber-Reinforced High-Performance Concrete in Severe Cold Environments: A Preliminary Attempt for Deep-Cold Concrete Construction

by Xinyu Liu, Jinghui Wang, Zheng Zhou, Lei Zhang and Qiang Fu

Materials 2025, 18(12), 2909; https://doi.org/10.3390/ma18122909 - 19 Jun 2025

Viewed by 273

Abstract

Winter concrete construction in cold regions faces significant challenges due to extreme subzero temperatures, and the harsh environment presents new requirement for cement-based materials to resist this hostile external condition. To address this gap, this study proposes gradient Joule heating (GJH) curing for [...] Read more.

Winter concrete construction in cold regions faces significant challenges due to extreme subzero temperatures, and the harsh environment presents new requirement for cement-based materials to resist this hostile external condition. To address this gap, this study proposes gradient Joule heating (GJH) curing for steel-fiber-reinforced high-performance concrete (SFR-HPC) in subzero environments (−20 °C to −60 °C). Compared to room-temperature (RT) curing, GJH enabled specimens at −20 °C to −50 °C to achieve equivalent mechanical properties within a short curing duration; the compressive strength of the specimens cured at such low environmental temperature still reached up to that of the specimen cured by RT curing. Moreover, the compressive strength of the specimens cured at −60 °C retained >60 MPa despite reduced performance. Specifically, the specimens cured at −20 °C, −30 °C, −40 °C, and −50 °C for 2 days exhibited compressive strengths of 75.8 MPa, 79.2 MPa, 77.6 MPa, and 75.4 MPa, respectively. FTIR/XRD confirmed that the specimens cured by GJH showed hydration product integrity akin to RT-cured specimens. Moreover, it should be noted that early pore structure deteriorated with decreasing temperatures, but prolonged curing mitigated these differences. These results validate GJH as a viable method for in situ HPC production in extreme cold, addressing critical limitations of conventional winter construction techniques. Full article

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

► Show Figures

Figure 1

20 pages, 54673 KiB

Open AccessArticle

Mechanical Properties of Repaired Welded Pipe Joints Made of Heat-Resistant Steel P92

by Filip Vučetić, Branislav Đorđević, Dorin Radu, Stefan Dikić, Lazar Jeremić, Nikola Milovanović and Aleksandar Sedmak

Materials 2025, 18(12), 2908; https://doi.org/10.3390/ma18122908 - 19 Jun 2025

Viewed by 324

Abstract

This research provides a detailed investigation into the mechanical properties and microstructural evolution of heat-resistant steel P92 subjected to both initial (i) welding procedures and simulated (ii) repair welding. The study addresses the influence of critical welding parameters, including preheating temperature, heat input, [...] Read more.

This research provides a detailed investigation into the mechanical properties and microstructural evolution of heat-resistant steel P92 subjected to both initial (i) welding procedures and simulated (ii) repair welding. The study addresses the influence of critical welding parameters, including preheating temperature, heat input, and post-weld heat treatment (PWHT), with a particular emphasis on the metallurgical consequences arising from the application of repair welding thermal cycles. Through the analysis of three welding probes—initially welded pipes using the PF (vertical upwards) and PC (horizontal–vertical) welding positions, and a PF-welded pipe undergoing a simulated repair welding (also in the PF position)—the research compares microstructure in the parent material (PM), weld metal (WM), and heat-affected zone (HAZ). Recognizing the practical limitations and challenges associated with achieving complete removal of the original WM under the limited (in-field) repair welding, this study provides a comprehensive comparative analysis of uniaxial tensile properties, impact toughness evaluated via Charpy V-notch testing, and microhardness measurements conducted at room temperature. Furthermore, the research critically analyzes the influence of the complex thermal cycles experienced during both the initial welding and repair welding procedures to elucidate the practical application limits of this high-alloyed, heat-resistant P92 steel in demanding service conditions. Full article

► Show Figures

Figure 1

14 pages, 2670 KiB

Open AccessCommunication

The Potential of MN₄-GPs (M = Mn, Fe, Co, Ni, Cu, Mo) as Adsorbents for the Efficient Separation of CH₄ from CO₂ and H₂S

by Shiqian Wei, Xinyu Tian, Zhen Rao, Chunxia Wang, Rui Tang, Ying He, Yu Luo, Qiang Fan, Weifeng Fan and Yu Hu

Materials 2025, 18(12), 2907; https://doi.org/10.3390/ma18122907 - 19 Jun 2025

Viewed by 289

Abstract

Carbon dioxide (CO₂) and hydrogen sulfide (H₂S) as harmful gases are always associated with methane (CH₄) in natural gas, biogas, and landfill gas. Given that chemisorption and physisorption are the key gas separation technologies in industry, selecting [...] Read more.

Carbon dioxide (CO₂) and hydrogen sulfide (H₂S) as harmful gases are always associated with methane (CH₄) in natural gas, biogas, and landfill gas. Given that chemisorption and physisorption are the key gas separation technologies in industry, selecting appropriate adsorbents is crucial to eliminate these harmful gases. The adsorption of CH₄, CO₂, and H₂S has been studied based on the density functional theory (DFT) in this work to evaluate the feasibility of transition metal (M = Mn, Fe, Co, Ni, Cu, Mo) porphyrin-like moieties embedded in graphene sheets (MN₄-GPs) as adsorbents. It was found that the interactions between gas molecules and MN₄-GPs (M = Mn, Fe, Co, Ni, Cu, Mo) are different. The weaker interactions between CH₄ and MN₄-GPs (M = Co, Ni, Cu, Mo) than those between CO₂ and MN₄-GPs or between H₂S and MN₄-GPs are beneficial to the separation of CH₄ from CO₂ and H₂S. The maximum difference in the interactions between gas molecules and MoN₄-GPs means that MoN₄-GPs have the greatest potential to become adsorbents. The different interfacial interactions are related to the amount of charge transfer, which could promote the formation of bonds between gas molecules and MN₄-GPs to effectively enhance the interfacial interactions. Full article

► Show Figures

Figure 1

22 pages, 6543 KiB

Open AccessArticle

Impact Resistance Study of Fiber–Metal Hybrid Composite Laminate Structures: Experiment and Simulation

by Zheyi Zhang, Haotian Guo, Yang Lan and Libin Zhao

Materials 2025, 18(12), 2906; https://doi.org/10.3390/ma18122906 - 19 Jun 2025

Viewed by 394

Abstract

Thermoplastic carbon fiber/aluminum alloy hybrid composite laminates fully integrate the advantages of fiber-reinforced composites and metallic materials, exhibiting high fatigue resistance and impact resistance, with broad applications in fields such as national defense, aerospace, automotive engineering, and marine engineering. In this paper, thermoplastic [...] Read more.

Thermoplastic carbon fiber/aluminum alloy hybrid composite laminates fully integrate the advantages of fiber-reinforced composites and metallic materials, exhibiting high fatigue resistance and impact resistance, with broad applications in fields such as national defense, aerospace, automotive engineering, and marine engineering. In this paper, thermoplastic carbon fiber/aluminum alloy hybrid composite laminates were first prepared using a hot-press machine; then, high-velocity impact tests were conducted on the specimens using a first-stage light gas gun test system. Comparative experimental analyses were performed to evaluate the energy absorption performance of laminates with different ply thicknesses and layup configurations. High-speed cameras and finite element analysis software were employed to analyze the failure process and modes of the laminates under impact loading. The results demonstrate that fiber–metal laminates exhibit higher specific energy absorption than carbon fiber composite laminates. Meanwhile, the numerical simulation results can effectively reflect the experimental outcomes in terms of the velocity–time relationship, failure modes during the laminate impact process, and failure patterns after the laminate impact. Full article

(This article belongs to the Special Issue Experimental Testing, Manufacturing and Numerical Modelling of Composite and Sandwich Structures (Second Edition))

► Show Figures

Figure 1

17 pages, 3940 KiB

Open AccessArticle

Influence of Post-Printing Polymerization Time on the Elution of Residual Monomers and Water Sorption of 3D-Printed Resin Composite

by Shaima Alharbi, Abdulrahman Alshabib, Hamad Algamaiah, Muath Aldosari and Abdullah Alayad

Materials 2025, 18(12), 2905; https://doi.org/10.3390/ma18122905 - 19 Jun 2025

Viewed by 371

Abstract

This study evaluated the effect of post-printing polymerization time on residual monomer elution and water sorption in a 3D-printed resin composite. Eighty samples were fabricated and assigned to four groups based on post-curing duration: 0, 20, 40, and 60 min. Each group was [...] Read more.

This study evaluated the effect of post-printing polymerization time on residual monomer elution and water sorption in a 3D-printed resin composite. Eighty samples were fabricated and assigned to four groups based on post-curing duration: 0, 20, 40, and 60 min. Each group was subdivided according to two storage conditions (distilled water and 75% ethanol–water solution), and evaluated at 1 and 7 days. High-performance liquid chromatography (HPLC) quantified eluted monomers. Additionally, 40 specimens underwent a 4-month sorption/desorption cycle for water sorption and solubility assessment. Data were statistically analyzed using kernel regression (monomer data) and Welch ANOVA (water sorption and solubility) at a significance level of p < 0.05. BisEMA was the only monomer detected, with significantly higher elution recorded in ethanol-based storage. Increasing post-curing time notably reduced both monomer release and water sorption/solubility (p < 0.001); however, the optimal results were observed at 40 min post-curing. These findings suggest that extending post-curing beyond an optimal threshold does not further improve composite properties, underscoring the importance of identifying precise curing parameters in order to enhance durability and material performance. Full article

(This article belongs to the Special Issue Advanced Resin-Based Materials and Composites)

► Show Figures

Figure 1

20 pages, 7536 KiB

Open AccessArticle

Study on the Micro-Mechanism of Corrosion Deterioration of Concrete Under Sulfate Attack Environment

by Yuzhou Sun, Mengjie You, Xiaosan Yin, Dongchang Hou, Jimin Li and Xiangming Zhou

Materials 2025, 18(12), 2904; https://doi.org/10.3390/ma18122904 - 19 Jun 2025

Viewed by 291

Abstract

To investigate the influence of the water–cement ratio and erosion patterns on the deterioration of concrete in a sulfate corrosion environment, concrete specimens with different water–cement ratios were immersed in Na₂SO₄ solutions of varying concentrations (0%, 5%, and 8%). The [...] Read more.

To investigate the influence of the water–cement ratio and erosion patterns on the deterioration of concrete in a sulfate corrosion environment, concrete specimens with different water–cement ratios were immersed in Na₂SO₄ solutions of varying concentrations (0%, 5%, and 8%). The immersion times were set at 0 days, 30 days, 60 days, and 90 days. Macro-scale compressive strength tests and micro-scale performance tests were conducted to obtain the damage morphology, micro-scale elastic modulus, and hardness of eroded concrete. Additionally, K-means clustering analysis was used to analyze the micro-mineral phases of the specimens, and SEM and XRD were employed to reveal the degradation mechanisms of sulfate erosion on the microstructure of concrete. The results indicated that the erosion products of calcium aluminate and gypsum in concrete gradually increased with the increase in Na₂SO₄ solution concentration and immersion time. In the early stages of erosion, the compressive strength and corrosion resistance coefficient of concrete showed a temporary upward trend, which then decreased as the erosion depth increased. From a microstructural perspective, erosion had a significant impact on the internal structure of concrete, while the elastic modulus and hardness of hydrated calcium silicate and calcium hydroxide under erosion showed relatively minor changes, both exhibiting a gradual decrease. The volume fraction of microporous pores gradually increased, further exacerbating the depth and extent of erosion. Full article

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

► Show Figures

Figure 1

29 pages, 9234 KiB

Open AccessArticle

Dual-Functional Organosilicon Additives Containing Methacrylate and Trimethoxysilyl Groups Enhancing Impact Toughness of Polylactide (PLA): Structure–Property Relationship

by Julia Głowacka, Miłosz Frydrych, Eliza Romańczuk-Ruszuk, Yi Gao, Hui Zhou, Robert E. Przekop and Bogna Sztorch

Materials 2025, 18(12), 2903; https://doi.org/10.3390/ma18122903 - 19 Jun 2025

Viewed by 582

Abstract

The demands of the green economy necessitate modern polymer materials that are not only environmentally friendly but also durable and capable of long service life. Bio-based polylactide (PLA) polyesters have gained significant traction in various industrial markets; however, their application in specialized sectors [...] Read more.

The demands of the green economy necessitate modern polymer materials that are not only environmentally friendly but also durable and capable of long service life. Bio-based polylactide (PLA) polyesters have gained significant traction in various industrial markets; however, their application in specialized sectors is hindered by high brittleness. This study extensively examines the effects of 1–5% of synthetically obtained tetracyclosiloxane (CS) and octaspherosilicate (OSS) derivatives with methacrylate (MA) and trimethoxysilyl (TMOS) groups as functional modifiers for PLA. The research provides a detailed characterization of PLA/CS and PLA/OSS materials, including a comparative analysis of mechanical properties such as tensile, flexural, and dynamic resistance. Notably, incorporating 5% CS-2MA-2TMOS into PLA resulted in a remarkable 104% increase in impact resistance. The study further evaluates the influence of these modifications on thermal properties (DSC, TGA), heat deflection temperature (HDT), and surface character (WCA). The miscibility between the organosilicon additives and PLA was assessed using oscillatory rheometry and SEM-EDS analysis. The melt-rheology analysis explained the mechanisms behind the interaction between the CS and OSS additives with the PLA matrix, highlighting their lubricating effects on the melt flow behavior. The study was complemented by XRD structural analysis and verification of the structure of PLA-based materials by optical microscopy and SEM analysis, demonstrating a plasticizing effect and uniform distribution of the modifiers. The findings strongly suggest that, even at low concentrations, organosilicon additives serve as effective impact modifiers for PLA. Full article

(This article belongs to the Special Issue Sustainable Materials: Preparation, Characterization and Applications)

► Show Figures

Graphical abstract

28 pages, 6157 KiB

Open AccessArticle

Towards a Sustainable Material Protection: Olanzapine Drugs and Their Derivatives as Corrosion Inhibitors for C1018 Steel in 1 M Hydrochloric Acid

by Habibah M. A. Omar, Nestor Ankah, Mohamed S. Gomaa, Malak Y. Alkhaldi, Nadir M. A. Osman, Abdullah R. Al-Subaie, Ibrahim Aldossary, Irshad Baig, Ashraf A. Bahraq, Marwah Aljohani, Ihsan Ulhaq Toor and Aeshah H. Alamri

Materials 2025, 18(12), 2902; https://doi.org/10.3390/ma18122902 - 19 Jun 2025

Viewed by 419

Abstract

This study investigates the synthesis process and characterization methods and evaluates the inhibition behavior of olanzapine (2-methyl-4-(4-methyl-1-piperazinyl)-10H-thieno-[2,3-b] 1,5]benzodiazepine (OLZ)) and its derivatives, such as 3-(2-methyl-4-(4-methylpiperazin-1-yl)-10H-benzo[b]thieno[2,3-e] [1,4]diazepin-10-yl) propenamide (OLZ1) and Ethyl 2-(2-methyl-4-(4-methylpiperazin-1-yl)-10H-benzo[b]thieno[2,3-e][1,4]diazepin-10 yl) acetate (OLZ2) for carbon steel (C1018) in a 1 M HCl [...] Read more.

This study investigates the synthesis process and characterization methods and evaluates the inhibition behavior of olanzapine (2-methyl-4-(4-methyl-1-piperazinyl)-10H-thieno-[2,3-b] 1,5]benzodiazepine (OLZ)) and its derivatives, such as 3-(2-methyl-4-(4-methylpiperazin-1-yl)-10H-benzo[b]thieno[2,3-e] [1,4]diazepin-10-yl) propenamide (OLZ1) and Ethyl 2-(2-methyl-4-(4-methylpiperazin-1-yl)-10H-benzo[b]thieno[2,3-e][1,4]diazepin-10 yl) acetate (OLZ2) for carbon steel (C1018) in a 1 M HCl acidic solution. Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR) were employed to verify their molecular structures and functional groups, which characterized the derivatives after synthesis. Their corrosion inhibition potential for C1018 steel in acidic media was estimated by weight loss (WL) and electrochemical techniques, such as electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), and potentiodynamic polarization (PDP), accompanied by surface analysis methods. The findings revealed that all three derivatives demonstrated exceptional inhibition performance, achieving maximum efficiencies of 88.83%, 91.20%, and 91.82% for OLZ, OLZ1, and OLZ2 at 300 ppm, respectively. Weight loss experiments across different temperatures further explored their inhibitory behavior. Although inhibition efficiency decreased with a temperature increase to 318 K, the derivatives still displayed notable performance, with maximum efficiencies of 74.75% for OLZ, 81.63% for OLZ1, and 79.44% for OLZ2. Polarization studies identified the corrosion inhibition mechanisms as an anodic type. Surface characterization of the C1018 steel coupons, both with and without the inhibitors, was performed using FTIR and scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX). These analyses indicated the creation of a protective inhibitor layer on the carbon steel surface, reducing corrosion in the acidic environment. Overall, this study underscores the potential of these drug derivatives as corrosion inhibitors, combining structural insights and performance assessments to support their industrial application. Full article

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

► Show Figures

Figure 1

13 pages, 2262 KiB

Open AccessArticle

Application of Bioinspired Structural Ceramics with High-Temperature Electrical Insulation and High Adhesion in K-Type Coaxial Thermocouples

by Zhenyin Hai, Yue Chen, Zhixuan Su, Yemin Wang, Shigui Gong, Yihang Zhang, Shanmin Gao, Chengfei Zhang, Zhangquan Wang, Hongwei Ji, Chenyang Xue and Zhichun Liu

Materials 2025, 18(12), 2901; https://doi.org/10.3390/ma18122901 - 19 Jun 2025

Viewed by 289

Abstract

Surface erosion of the coaxial thermocouple probe initiates continuous bridging of thermoelectric materials on the insulation layer surface, forming new temperature measurement junctions. This inherent ability to measure continuous self-erosion ensures the operational reliability of the coaxial thermocouples in high-temperature ablative environments. However, [...] Read more.

Surface erosion of the coaxial thermocouple probe initiates continuous bridging of thermoelectric materials on the insulation layer surface, forming new temperature measurement junctions. This inherent ability to measure continuous self-erosion ensures the operational reliability of the coaxial thermocouples in high-temperature ablative environments. However, the fabrication of a high-temperature electrical insulation layer and a high-adhesion insulating layer in the coaxial thermocouples remains a challenge. Inspired by calcium carbonate/oxalate crystals in jujube leaves that strengthen the leaves, a bioinspired structural ceramic (BSC) mimicking these needle-like crystals is designed. This BSC demonstrates excellent high-temperature insulation (with insulation impedance of 2.55 kΩ at 1210 °C) and adhesion strength (35.3 Newtons). The BSC is successfully used as the insulating layer in a K-type coaxial thermocouple. The generation rules for surface junctions are systematically studied, revealing that stable and reliable measurement junctions can be created when the sandpaper grit does not exceed 600#. Static test results show that the K-type coaxial thermocouple ranges from 200 °C to 1200 °C with an accuracy of 1.1%, a drift rate better than 0.0137%/h, and hysteresis better than 0.81%. Dynamic test results show that the response time is 1.08 ms. The K-type coaxial thermocouple can withstand a high-temperature flame impact for 300 s at 1200 °C, as well as over forty cycles of high-power laser thermal shock, while maintaining good response characteristics. Therefore, the K-type coaxial thermocouple designed in this study provides an ideal solution for long-term temperature monitoring of the thermal components of aerospace engines under extremely high-temperature, high-speed, and strong thermal shock conditions. Full article

(This article belongs to the Special Issue Multi-Scale Bionic Materials: Interfacial Design, Effective Fabrication and Functional Application)

► Show Figures

Figure 1

16 pages, 2143 KiB

Open AccessArticle

Effect of a Polyhexanide-Based Antiseptic Composition on Dentin Microhardness and Mechanical Properties: An In Vitro Study

by Zurab Khabadze, Yulia Generalova and Oleg Mordanov

Materials 2025, 18(12), 2900; https://doi.org/10.3390/ma18122900 - 19 Jun 2025

Viewed by 320

Abstract

The effect of root canal irrigants on the mechanical properties of dentin is crucial in endodontic treatment planning. While antiseptics such as sodium hypochlorite and EDTA are widely used, their potential to weaken dentin structure remains a concern. Polyhexanide-based formulations may offer a [...] Read more.

The effect of root canal irrigants on the mechanical properties of dentin is crucial in endodontic treatment planning. While antiseptics such as sodium hypochlorite and EDTA are widely used, their potential to weaken dentin structure remains a concern. Polyhexanide-based formulations may offer a safer alternative. To assess the impact of a polyhexanide-based antiseptic composition, compared to standard irrigants, on the microhardness, Young’s modulus, and elastic deformation energy of dentin. Sixty extracted human teeth were sectioned and polished to prepare dentin samples. Baseline measurements of Vickers microhardness, Young’s modulus, and elastic deformation work were performed using a Microhardness Tester (CSM Instruments, Switzerland) with a Berkovich indenter. Samples were then divided into six groups (n = 10 per group) and exposed to different irrigants (NaCl 0.9%, NaOCl 3%, chlorhexidine 2%, EDTA 17%, and polyhexanide-based solutions—0.1% and 0.2% Lavasept). Post-treatment measurements were performed. Statistical analysis was conducted using non-parametric tests with Bonferroni correction. Sodium hypochlorite (3%) caused the most pronounced reduction in dentin microhardness and mechanical strength, though not always statistically significant. Polyhexanide-based solutions (0.1% and 0.2% Lavasept) showed a milder effect, with statistically significant changes observed only in elastic deformation energy for 0.2% polyhexanide. EDTA treatment led to severe surface destruction, precluding reliable post-treatment measurements. Polyhexanide-based irrigants demonstrated a more favorable impact on dentin mechanical properties compared to traditional irrigants, supporting their potential use in endodontic protocols aimed at preserving dentin integrity. Full article

(This article belongs to the Section Biomaterials)

► Show Figures

Figure 1

18 pages, 3874 KiB

Open AccessArticle

Organic and Ionic Liquids Electrolyte Solutions as Versatile Media for Metallic Lithium Recovery

by Mihai Tudor Olaru, Alexandru Matei, Irina Atkinson, Adelina Ionela Matei, Elena Bacalum, Miruna Iota and Ana-Maria Popescu

Materials 2025, 18(12), 2899; https://doi.org/10.3390/ma18122899 - 19 Jun 2025

Viewed by 410

Abstract

For various applications, particularly in battery technology, there is a significant demand for uniform, high-quality lithium or lithium-coated materials. The use of electrodeposition techniques to obtain such materials has not proven practical or economical due to the low solubility of most lithium salts [...] Read more.

For various applications, particularly in battery technology, there is a significant demand for uniform, high-quality lithium or lithium-coated materials. The use of electrodeposition techniques to obtain such materials has not proven practical or economical due to the low solubility of most lithium salts in suitable solvents. In this study, we propose efficient lithium electrodeposition processes and baths that can be operated at low temperatures and relatively low costs. We utilized organic solvents such as dimethyl acetamide (DMA), dimethylforamide (DMF), and dimethyl sulfoxide (DMSO), as well as a mixture of DMSO and ionic liquid [1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide BMIMTFSI]. Lithium salts such as LiCl, Li₂CO₃, and LiNO₃ were tested. Lithium metal was deposited on copper substrates at different temperatures and selected current densities within an argon-filled glovebox using a DC power source or a PARSTAT-4000A potentiostat. Cyclic voltammetry (CV) was employed to determine and compare the deposition processes. The obtained deposits were analyzed through visual inspection (photography) and scanning electron microscopy (SEM). Chemical analysis (ICP-OES) and XRD confirmed the presence of lithium and occasionally lithium hydroxide in the deposits. The best results were achieved with the deposition of lithium from DMSO-LiNO₃ and DMSO-BMIMTFSI-LiNO₃ systems. Full article

(This article belongs to the Section Electronic Materials)

► Show Figures

Figure 1

28 pages, 11508 KiB

Open AccessArticle

Non-Destructive Integrity Assessment of Austenitic Stainless-Steel Membranes via Magnetic Property Measurements

by Haeng Sung Heo, Jinheung Park, Jehyun You, Shin Hyung Rhee and Myoung-Gyu Lee

Materials 2025, 18(12), 2898; https://doi.org/10.3390/ma18122898 - 19 Jun 2025

Viewed by 351

Abstract

This study proposes a novel non-destructive methodology for assessing structural integrity in liquefied natural gas (LNG) carrier cargo containment systems (CCSs), addressing limitations of conventional inspection techniques like visual inspection and vacuum box testing. The method leverages strain-induced martensitic transformation (SIMT) in austenitic [...] Read more.

This study proposes a novel non-destructive methodology for assessing structural integrity in liquefied natural gas (LNG) carrier cargo containment systems (CCSs), addressing limitations of conventional inspection techniques like visual inspection and vacuum box testing. The method leverages strain-induced martensitic transformation (SIMT) in austenitic stainless steel (SUS304L), widely used in CCS membranes, quantifying magnetic permeability increase via a Feritscope to evaluate deformation history and damage. To analyze SUS304L SIMT behavior, uniaxial tensile (UT) and equi-biaxial tensile (EBT) tests were conducted, as these stress states predominate in CCS membranes. Microstructural evolution was examined using X-ray diffraction (XRD) and electron backscatter diffraction (EBSD), allowing a quantitative assessment of the transformed martensite volume fraction versus plastic strain. Subsequently, Feritscope measurements under the same conditions were calibrated against the XRD-measured martensite volume fraction for accuracy. Based on testing, this study introduces three complementary Feritscope approaches for evaluating CCS health: outlier detection, quantitative damaged area analysis, and time-series analysis. The methodology integrates data-driven quantitative assessment with conventional qualitative inspection, enhancing safety and maintenance efficiency. Full article

(This article belongs to the Special Issue Non-Destructive Testing of Materials and Parts: Techniques, Case Studies and Practical Applications—2nd Edition)

► Show Figures

Figure 1

19 pages, 4961 KiB

Open AccessArticle

Modification of Chabazite Using Hexadecyltrime-Thylammonium Bromide (HDTMA-Br) for Chromium(VI) Removal from Water Solutions

by Agata L. Skwarczynska-Wojsa, Paulina Sobolewska, Marcin Chutkowski and Jolanta Warchol

Materials 2025, 18(12), 2897; https://doi.org/10.3390/ma18122897 - 18 Jun 2025

Viewed by 438

Abstract

Chabazite, a tectosilicate mineral, belongs to the zeolite group and has been widely used for the adsorptive removal of a number of cationic contaminants from the aqueous phase. However, a negatively charged chabazite surface can be altered by chemical modification in order to [...] Read more.

Chabazite, a tectosilicate mineral, belongs to the zeolite group and has been widely used for the adsorptive removal of a number of cationic contaminants from the aqueous phase. However, a negatively charged chabazite surface can be altered by chemical modification in order to change its adsorption abilities towards anions. This study reports the potential for the removal of hexavalent chromium ions from aqueous solutions by modified chabazite. In this regard, natural chabazite was modified by the immobilization of HDTMA-Br to achieve double-layer coverage on its surface, defined as the double external cation exchange capacity. Next, a batch adsorption system was applied to study the adsorption of inorganic Cr(VI) anions from aqueous solutions. The process equilibrium was described by 11 theoretical isotherm equations, while 6 adsorption kinetics were represented by four models. Among those tested, the most appropriate model for the description of the studied process kinetics was the pseudo-second order irreversible model. The obtained results suggest that Cr(VI) adsorption takes place according to a complex mechanism comprising both Langmuir-type sorption with the maximum adsorption capacity of modified chabazite, approx. 9.3–9.9 mg g⁻¹, and the trapping of Cr(VI) inside the capillaries of the amorphous sorbent, making it a viable option for water treatment applications. Full article

(This article belongs to the Special Issue Environmentally Friendly Adsorption Materials (2nd Edition))

► Show Figures

Figure 1

21 pages, 4098 KiB

Open AccessArticle

Gas Sensor Properties of (CuO/WO₃)-CuWO₄ Heterostructured Nanocomposite Materials

by Michael Castaneda Mendoza, Carlos A. Parra Vargas, Miryam Rincón Joya, Adenilson J. Chiquito and Angela M. Raba-Páez

Materials 2025, 18(12), 2896; https://doi.org/10.3390/ma18122896 - 18 Jun 2025

Viewed by 423

Abstract

In this work, we report the evaluation of a (CuO/WO₃)-CuWO₄ heterostructured system as a methanol and acetone gas sensor in different configurations, contrasted with the pure oxides CuO and WO₃. The samples were synthesized using a modified precipitation [...] Read more.

In this work, we report the evaluation of a (CuO/WO₃)-CuWO₄ heterostructured system as a methanol and acetone gas sensor in different configurations, contrasted with the pure oxides CuO and WO₃. The samples were synthesized using a modified precipitation route followed by a single thermal treatment step to induce multiphase simultaneous crystallization. The structural characterization by XRD showed that all the materials presented the formation of monoclinic CuO and WO₃ and triclinic CuWO₄. No additional phases were detected in the samples, and a reduction in the crystallite size of the CuO phase after the crystallization in the heterostructured system was observed. FE-SEM analysis made it possible to directly observe the morphology and the structures of the samples at the nanometer scale, showing a heterogeneous grain formation and supporting the formation of a heterostructure. UV-Vis DRS was used to study the optical properties of the materials, and the presence of two optical band gaps was successfully determined, which provides further evidence of heterostructure formation via this modified synthesis route. The variation in the resistance of the materials was observed in the presence of methanol and acetone vapors, where the heterostructure exhibited a substantial change in performance in the configuration with 40% copper precursor (Cu40:W60), the sample that presented the highest response as a sensor against these VOCs. To our knowledge, this is the first time that this system has been reported as a gas sensor, using the multiple configurations of the (CuO/WO₃)-CuWO₄ heterostructured system. Full article

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

► Show Figures

Figure 1

17 pages, 2894 KiB

Open AccessArticle

Identification of Laser Parameters Acting on an Axisymmetric Domain Using an Artificial Immune System

by Arkadiusz Poteralski and Jolanta Dziatkiewicz

Materials 2025, 18(12), 2895; https://doi.org/10.3390/ma18122895 - 18 Jun 2025

Viewed by 311

Abstract

The paper presents the control of the ablated gap of required dimensions in an axisymmetric domain made of metal. For this purpose, two parameters of the laser interacting on this layer were identified, which means laser intensity and characteristic time of the laser [...] Read more.

The paper presents the control of the ablated gap of required dimensions in an axisymmetric domain made of metal. For this purpose, two parameters of the laser interacting on this layer were identified, which means laser intensity and characteristic time of the laser pulse. A hyperbolic two-temperature model was applied. This is a model in which there are two coupled equations for electrons and phonons. The model was supplemented with appropriate boundary and initial conditions. The direct problem was solved using the finite difference method with a staggered grid. An artificial immune system was used for the identification process. Full article

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

► Show Figures

Figure 1

15 pages, 1913 KiB

Open AccessArticle

Influence of Moisture and Tool Temperature on the Maximum Stretch and Process Stability in High-Speed 3D Paper Forming

by Heike Stotz, Matthias Klauser, Johannes Rauschnabel and Marek Hauptmann

Materials 2025, 18(12), 2894; https://doi.org/10.3390/ma18122894 - 18 Jun 2025

Viewed by 334

Abstract

This study investigates how moisture preconditioning and thermal parameters affect the stretchability of paper in 3D forming, with the goal of extending geometric forming limits and enhancing process stability. Multidimensional tensile tests were performed on FibreForm Duo (310 g/m²) using a [...] Read more.

This study investigates how moisture preconditioning and thermal parameters affect the stretchability of paper in 3D forming, with the goal of extending geometric forming limits and enhancing process stability. Multidimensional tensile tests were performed on FibreForm Duo (310 g/m²) using a hemispherical punch. Key variables included water bath dwell time, punch temperature, and contact time, simulating industrial conditions in high-speed packaging. A short duration of water bath immersion (1–3 s) led to rapid moisture uptake (−20%), resulting in significantly improved formability. Compared to unconditioned samples, the maximum stretch increased by up to 3.5 percentage points. The process window identified (3.03 s dwell time; 70 °C punch temperature; 1.08 s contact time to punch) yielded a predicted stretch of 16.5%, representing a notable expansion of the material’s geometric forming capacity. Regression analysis (R² = 0.8946) confirmed the strong statistical significance of all parameters. Full article

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

► Show Figures

Graphical abstract

29 pages, 6989 KiB

Open AccessArticle

Numerical and Fracture Mechanical Evaluation of Safety Monitoring Indexes and Crack Resistance in High RCC Gravity Dams Under Hydraulic Fracture Risk

by Mohamed Ramadan, Jinsheng Jia, Lei Zhao, Xu Li and Yangfeng Wu

Materials 2025, 18(12), 2893; https://doi.org/10.3390/ma18122893 - 18 Jun 2025

Viewed by 356

Abstract

High concrete gravity dams, particularly Roller-Compacted Concrete (RCC) types, face long-term safety challenges due to weak interlayer formation and crack propagation. This study presented a comprehensive evaluation of safety monitoring indexes for the Guxian high RCC dam (currently under construction) using both numerical [...] Read more.

High concrete gravity dams, particularly Roller-Compacted Concrete (RCC) types, face long-term safety challenges due to weak interlayer formation and crack propagation. This study presented a comprehensive evaluation of safety monitoring indexes for the Guxian high RCC dam (currently under construction) using both numerical and mathematical models. A finite element method (FEM) is employed with a strength reduction approach to assess dam stability considering weak layers. In parallel, a fracture mechanical model is used to investigate the safety of the Guxian dam based on failure assessment diagrams (FADs) for calculating the safety factor and the residual strength curve for calculating critical crack depth for two different crack locations, single-edge and center-through crack, to investigate the high possible risk associated with crack location on the dam safety. Additionally, the Guxian dam’s resistance to hydraulic fracture is assessed under two fracture mechanic failure modes, Mode I (open type) and Mode II (in-plane shear), by computing the ultimate overload coefficient using a proposed novel derived formula. The results show that weak layers reduce the dam’s safety index by approximately 20%, especially in lower sections with extensive interfaces. Single-edge cracks pose greater risk, decreasing the safety factor by 10% and reducing critical crack depth by 40% compared to center cracks. Mode II demonstrates higher resistance to hydraulic fracture due to greater shear strength and fracture energy, whereas Mode I represents the most critical failure scenario. The findings highlight the urgent need to incorporate weak layer behavior and hydraulic fracture mechanisms into dam safety monitoring, and to design regulations for high RCC gravity dams. Full article

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

► Show Figures

Figure 1

Journal Menu

Journal Browser

Materials, Volume 18, Issue 12 (June-2 2025) – 252 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI