Materials

17 pages, 3346 KiB

Open AccessEditor’s ChoiceArticle

The Use of 3D Printing Filaments to Build Moisture Sensors in Porous Materials

by Magdalena Paśnikowska-Łukaszuk, Joanna Szulżyk-Cieplak, Magda Wlazło, Jarosław Zubrzycki, Ewa Łazuka, Arkadiusz Urzędowski and Zbigniew Suchorab

Materials 2025, 18(1), 115; https://doi.org/10.3390/ma18010115 - 30 Dec 2024

Viewed by 728

Abstract

This study explores the application of materials used in 3D printing to manufacture the housings of non-invasive sensors employed in measurements using a TDR (Time Domain Reflectometry) meter. The research investigates whether sensors designed with 3D printing technology can serve as viable alternatives [...] Read more.

This study explores the application of materials used in 3D printing to manufacture the housings of non-invasive sensors employed in measurements using a TDR (Time Domain Reflectometry) meter. The research investigates whether sensors designed with 3D printing technology can serve as viable alternatives to conventional invasive and non-invasive sensors. This study focuses on innovative approaches to designing humidity sensors, utilizing Fused Deposition Modeling (FDM) technology to create housings for non-invasive sensors compatible with TDR devices. The paper discusses the use of 3D modeling technology in sensor design, with particular emphasis on materials used in 3D printing, notably polylactic acid (PLA). Environmental factors, such as moisture in building materials, are characterized, and the need for dedicated sensor designs is highlighted. The software utilized in the 3D modeling and printing processes is also described. The Materials and Methods Section provides a detailed account of the construction process for the non-invasive sensor housing and the preparation for moisture measurement in silicate materials using the designed sensor. A prototype sensor was successfully fabricated through 3D printing. Using the designed sensor, measurements were conducted on silicate samples soaked in aqueous solutions with water absorption levels ranging from 0% to 10%. Experimental validation involved testing silicate samples with the prototype sensor to evaluate its effectiveness. The electrical permittivity of the material was calculated, and the root-mean-square error (RMSE) was determined using classical computational methods and machine learning techniques. The RMSE obtained using the classical method was 0.70. The results obtained were further analyzed using machine learning models, including Gaussian Process Regression (GPR) and Support Vector Machine (SVM). The GPR model achieved an RMSE of 0.15, while the SVM model yielded an RMSE of 0.25. These findings confirm the sensor’s effectiveness and its potential for further research and practical applications. Full article

(This article belongs to the Special Issue 3D-Printed Composite Structures: Design, Properties and Application)

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14 pages, 2561 KiB

Open AccessEditor’s ChoiceArticle

Surface Hydrophilic Modification of Polypropylene by Nanosecond Pulsed Ar/O₂ Dielectric Barrier Discharge

by Yang Zhou, Zhi Fang, Yi Zhang, Tingting Li and Feng Liu

Materials 2025, 18(1), 95; https://doi.org/10.3390/ma18010095 - 29 Dec 2024

Viewed by 821

Abstract

Polypropylene (PP) membranes have found diverse applications, such as in wastewater treatment, lithium-ion batteries, and pharmaceuticals, due to their low cost, excellent mechanical properties, thermal stability, and chemical resistance. However, the intrinsic hydrophobicity of PP materials leads to membrane fouling and filtration flux [...] Read more.

Polypropylene (PP) membranes have found diverse applications, such as in wastewater treatment, lithium-ion batteries, and pharmaceuticals, due to their low cost, excellent mechanical properties, thermal stability, and chemical resistance. However, the intrinsic hydrophobicity of PP materials leads to membrane fouling and filtration flux reduction, which greatly hinders the applications of PP membranes. Dielectric barrier discharge (DBD) is an effective technique for surface modification of materials because it generates a large area of low-temperature plasma at atmospheric pressure. In this study, O₂ was added to nanosecond pulsed Ar DBD to increase its reactivity. Electrical and optical diagnostic techniques were used to study the discharge characteristics of the DBD at varying O₂ contents. The uniformity of the discharge was quantitatively analyzed using the observed discharge images. Water contact angle measurements were used to assess the surface hydrophilicity of polypropylene. The surface morphology and chemical composition of the PP materials before and after treatment were analyzed using field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The results show that the moderate addition of O₂ enhances surface hydrophilicity and the uniformity of the modification. By increasing the O₂ addition from 0% to 0.1%, the average power increased from 4.19 W to 5.79 W, and the energy efficiency increased from 17.78% to 21.51%. The water contact angle of the DBD-treated PP showed a tendency to decrease and then increase with increasing O₂ content, with the optimum O₂ addition determined to be 0.1%. Under this condition, the water contact angle of the PP surface decreased by 31.88°, which is 52.31% lower than the untreated surface. O₂ increases the number of oxygen-containing polar groups (-OH, C=O, and O-C=O) on the surface of the material, and deepens and densifies the grooves on the surface of the PP material, resulting in an increase in the hydrophilicity of the PP surface. Full article

(This article belongs to the Special Issue Advances in Design and Characterization of Graded and Hierarchical Honeycomb Materials)

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15 pages, 3877 KiB

Open AccessEditor’s ChoiceArticle

Unveiling the Influence of Hot Carriers on Photovoltage Formation in Perovskite Solar Cells

by Muhammad Mujahid, Aurimas Čerškus, Jonas Gradauskas, Asta Grigucevičienė, Raimondas Giraitis, Konstantinas Leinartas, Andžej Lučun, Kazimieras Petrauskas, Algirdas Selskis, Algirdas Sužiedėlis, Aldis Šilėnas, Edmundas Širmulis and Steponas Ašmontas

Materials 2025, 18(1), 85; https://doi.org/10.3390/ma18010085 - 28 Dec 2024

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Abstract

The experimental and theoretical study of photovoltage formation in perovskite solar cells under pulsed laser excitation at 0.53 μm wavelength is presented. Two types of solar cells were fabricated on the base of cesium-containing triple cation perovskite films: (1) Cs_x(FA_0.83 [...] Read more.

The experimental and theoretical study of photovoltage formation in perovskite solar cells under pulsed laser excitation at 0.53 μm wavelength is presented. Two types of solar cells were fabricated on the base of cesium-containing triple cation perovskite films: (1) Cs_x(FA_0.83MA_0.17)_(1−x)Pb(I_0.83Br_0.17)₃ and (2) Cs_x(FA_0.83MA_0.17)_(1−x)Pb_0.8Sn_0.2(I_0.83Br_0.17)₃. It is found that photovoltage across the solar cells consists of two components, U = U_ph + U_f. The first one, U_ph, is the traditional photovoltage arising due to laser radiation-induced electron-hole pair generation. The second one, U_f, is the fast component following the laser pulse and has a polarity opposite to that of U_ph. It is shown that the fast photovoltage component results from the laser radiation-caused heating of free carriers. The transient photovoltage measurements show that the values of the fast component U_f are nearly the same in both types of perovskite solar cells. The magnitude of the traditional photovoltage of mixed Pb-Sn perovskite solar cells is lower than that of Pb-based cells. Full article

(This article belongs to the Special Issue Advances in Photoelectric Materials: Preparation, Properties, and Applications)

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22 pages, 9096 KiB

Open AccessEditor’s ChoiceArticle

Assessment of Steel Storage Tank Thickness Obtained from the API 650 Design Procedure Through Nonlinear Dynamic Analysis, Accounting for Large Deformation Effects

by Sobhan Fallah Daryavarsari and Roberto Nascimbene

Materials 2025, 18(1), 66; https://doi.org/10.3390/ma18010066 - 27 Dec 2024

Cited by 1 | Viewed by 1362

Abstract

This study evaluates the API 650 design procedure for steel storage tanks, incorporating nonlinear dynamic analysis with large deformation effects. Focusing on seismic vulnerability, the case study examines storage tanks proposed for construction in Naples, Italy, assessing their performance under site-specific seismic conditions. [...] Read more.

This study evaluates the API 650 design procedure for steel storage tanks, incorporating nonlinear dynamic analysis with large deformation effects. Focusing on seismic vulnerability, the case study examines storage tanks proposed for construction in Naples, Italy, assessing their performance under site-specific seismic conditions. A target spectrum and 20 earthquake records were selected to reflect regional seismic characteristics. Initial tank thicknesses were calculated using API 650 guidelines and subsequently analyzed through nonlinear time-history simulations in SAP2000. Results reveal that thicknesses derived from API 650s linear average spectrum equations are insufficient for real seismic demands. Through a trial-and-error methodology, optimal thicknesses were determined to ensure satisfactory performance across all seismic records. Key findings highlight significant variations in mode participation, the frequent occurrence of elephant-foot buckling in tanks with lower

H / R

ratios, and the limitations of linear spectral analysis for realistic earthquake scenarios. Given the vital role of storage tanks in the oil and gas industry, this study emphasizes the need to integrate nonlinear time history analysis into design processes to enhance seismic resilience, particularly in high-risk regions. Full article

(This article belongs to the Special Issue Advances in the Nonlinear Vibration and Structure Dynamics of Composite Materials)

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26 pages, 14474 KiB

Open AccessEditor’s ChoiceArticle

Development of a Stable Process for Wire Embedding in Fused Filament Fabrication Printing Using a Geometric Correction Model

by Valentin Wilhelm Mauersberger, Fabian Ziervogel, Linda Weisheit, Lukas Boxberger and Welf-Guntram Drossel

Materials 2025, 18(1), 41; https://doi.org/10.3390/ma18010041 - 26 Dec 2024

Viewed by 572

Abstract

Using a newly developed tool head with an additional rotational axis and a wire feed, wires can be directly processed in the fused filament fabrication (FFF) process. Thus, electrical structures such as conductive paths, coils, heating elements, or sensors can be integrated into [...] Read more.

Using a newly developed tool head with an additional rotational axis and a wire feed, wires can be directly processed in the fused filament fabrication (FFF) process. Thus, electrical structures such as conductive paths, coils, heating elements, or sensors can be integrated into polymer parts. However, the accuracy of the wire deposition in curved sections of the print track is insufficient. To improve the wire position, a geometric correction model was set up, converted into G-code, and validated using test prints for different wire parameters. For this, a sample of printed arcs was evaluated regarding wire position and embedding quality using various visual methods. This also determined the optimal cooling time for the model. The process parameters extrusion coefficient and feed were then varied to identify optimal process parameters for a stable and at the same time efficient process. By varying the wire (copper, constantan) and polymer material (PLA, PETG), the model was checked for general validity. It was found that the position of the ø 0.2 mm wire can be improved with the correction model. Different sets of parameters can be found that enable good quality of embedding and wire position. Full article

(This article belongs to the Special Issue Current and Future Trends in Additive Manufacturing)

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17 pages, 5985 KiB

Open AccessEditor’s ChoiceArticle

The Effect of the Chamber-Filling Ratio in Vibratory Shot Peening on Selected Surface Layer Properties of 30HGSA

by Agnieszka Skoczylas and Kazimierz Zaleski

Materials 2025, 18(1), 8; https://doi.org/10.3390/ma18010008 - 24 Dec 2024

Viewed by 430

Abstract

This study investigated the influence of the filling ratio of the working chamber and ball diameter in vibratory shot peening (VSP) on select properties of the surface layer. The tested material was 30HGSA steel, which is effectively used in the aviation industry. The [...] Read more.

This study investigated the influence of the filling ratio of the working chamber and ball diameter in vibratory shot peening (VSP) on select properties of the surface layer. The tested material was 30HGSA steel, which is effectively used in the aviation industry. The following were analyzed: the surface roughness parameters, the shape of the Abbott–Firestone curve, the bearing area ratio Smr_(c=50%), the microhardness distribution, the microhardness on the surface, and the residual stress σ on the surface. A change in the ratio of peaks and valleys in the maximum height of the profile was observed. After VSP, the valleys were dominant over the peaks. The most favorable values of the analyzed roughness parameters (Sz, Sp, and Sv) were obtained for d = 9.4 mm and k_d = 33%. The bearing area ratio Smr_(c=50%) was approximately 50 times higher than before VSP (the most favorable for d = 9.4 mm and k_d = 33%). The largest thickness of the strengthened layer of 200 μm and the greatest increase in the microhardness equal to ΔHV 0.05 = 109 were obtained after VSP was conducted using the ball diameter d = 14.3 mm k_d = 33%. Regardless of the VSP conditions, the absolute value of compressive stresses increased; the highest σ stresses were obtained for d = 3.0 mm and k_d = 33%, and they were 88% higher than before the treatment. It was concluded that the recommended chamber-filling ratio for beneficial properties is k_d = 33%. Full article

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

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28 pages, 13465 KiB

Open AccessEditor’s ChoiceArticle

Innovative Approaches on the Estimation of the Effective Permittivity of Fibrous Media

by Jesus Nain Camacho Hernandez and Guido Link

Materials 2025, 18(1), 14; https://doi.org/10.3390/ma18010014 - 24 Dec 2024

Viewed by 593

Abstract

Estimating the effective permittivity of anisotropic fibrous media is critical for advancing electromagnetic applications, requiring detailed microstructural and orientation analyses. This study introduces innovative approaches for disclosing the orientation and microstructure of fibers, leading to mixing relations. It particularly focuses on two specific [...] Read more.

Estimating the effective permittivity of anisotropic fibrous media is critical for advancing electromagnetic applications, requiring detailed microstructural and orientation analyses. This study introduces innovative approaches for disclosing the orientation and microstructure of fibers, leading to mixing relations. It particularly focuses on two specific fiber configurations: 1. wave-curved fibers and 2. a collection of interconnected fibers. The first approach uses sinusoidal wave fibers, considering their curvature and direction. Conversely, the approach for the interconnected fibers operates on the principle of representing fibers as a collection of straight segments. Investigations on fibrous media for both approaches were performed using numerical calculations at the microwave frequency of 2.45 GHz. Each fibrous medium was treated as an effective medium by using fibers significantly smaller than the microwave wavelength. A thorough comparison was made between the proposed mixing relations, numerical data, and state-of-the-art mixing relations to assess their consistency and validity. The comparison of the proposed approaches with traditional models shows an improved accuracy of up to 70% and 8% for the real and imaginary components of the permittivity, respectively. Additionally, the root-mean-square errors were determined as 0.001 + j0.003 and 0.001 – j0.007 for the sinusoidal and interconnected straight fibers approaches, respectively. In addition, a woven alumina fabric was used to compare the experimental resonance frequency with that from simulations using the permittivity of the fabric estimated by the interconnected straight fibers approach. These findings advance the predictive accuracy of permittivity estimation in fibrous media, providing a robust foundation for engineering applications. Full article

(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Advanced Materials Characterization)

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15 pages, 11668 KiB

Open AccessEditor’s ChoiceArticle

Analysis of the Properties of Anticorrosion Systems Used for Structural Component Protection in Truck Trailers

by Wojciech Skotnicki and Dariusz Jędrzejczyk

Materials 2024, 17(24), 6303; https://doi.org/10.3390/ma17246303 - 23 Dec 2024

Viewed by 687

Abstract

The article compares the properties of coatings (cataphoretic, hot-dip zinc, and thermo-diffusion zinc) applied to steel components used in the automotive industry. The research focused on the analysis of corrosion resistance, hardness measurements, and tribological properties conducted on steel guides used in trailer [...] Read more.

The article compares the properties of coatings (cataphoretic, hot-dip zinc, and thermo-diffusion zinc) applied to steel components used in the automotive industry. The research focused on the analysis of corrosion resistance, hardness measurements, and tribological properties conducted on steel guides used in trailer and truck body structures as well as fasteners (M12 × 40 bolts). The base surfaces were cleaned chemically. Corrosion resistance was tested in a salt chamber, while coating thickness was measured using the magnetic induction method. Coating hardness (HV 0.02) was assessed with a microhardness tester, and tribological properties were tested under dry friction conditions. The results showed that the zinc coatings demonstrated corrosion resistance far superior to paint coatings. Full article

(This article belongs to the Special Issue Metal Coatings for Wear and Corrosion Applications (Second Edition))

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20 pages, 37498 KiB

Open AccessEditor’s ChoiceArticle

Analysis of the Deburring Efficiency of EN-AW 7075 Aluminum Alloy Parts with Complex Geometric Shapes Considering the Tool Path Strategy During Multi-Axis Brushing

by Jakub Matuszak, Andrzej Kawalec and Michał Gdula

Materials 2024, 17(24), 6267; https://doi.org/10.3390/ma17246267 - 21 Dec 2024

Viewed by 716

Abstract

The paper presents the results of an analysis of the effect of brushing on the edge condition of workpieces with complex geometric shapes, formed during milling, on a five-axis DMU 100 monoBLOCK machining center. A set of EN-AW 7075 aluminum alloy specimens with [...] Read more.

The paper presents the results of an analysis of the effect of brushing on the edge condition of workpieces with complex geometric shapes, formed during milling, on a five-axis DMU 100 monoBLOCK machining center. A set of EN-AW 7075 aluminum alloy specimens with curvilinear edges requiring multi-axis machining was prepared. The change of edge condition after the milling process was realized using Xebec tools with flexible ceramic fibers. The effects of brush fiber type and parameters related to tool design were analyzed. Different brushing strategies were employed on the five-axis machining center. It was shown that, for curvilinear edges, there were different effects for concave and convex edges depending on the employed tool strategy, including the type of tool, its configuration, and its orientation towards the workpiece. For a lead angle of β = 0°, the machined edge was characterized by variable chamfer widths, in spite of maintaining other machining parameters constant. The use of a lead angle β > 0 produced a stable edge with repeatable characteristics. The range of fiber interaction increased with increasing the lead angle and fiber working length. Full article

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

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15 pages, 3706 KiB

Open AccessEditor’s ChoiceArticle

Chemical Compositions and Chromatic Mechanism of High-Temperature Iron-Series Glazed Wares from the Guangyuan Kiln in Sichuan Province, Southwest China During the Song Dynasty

by Lin Wu, Yourongtian Nie, Jinwei Li, Junming Wu, Wei Shi, Yanfang Wu and Yueguang Jiang

Materials 2024, 17(24), 6221; https://doi.org/10.3390/ma17246221 - 19 Dec 2024

Viewed by 518

Abstract

The Guangyuan kiln, located in the Sichuan Province, Southwest China during the Song Dynasty (960–1279 A.D.), is renowned for its high-temperature iron-series glazed wares, including pure black glazed ware, hare’s fur glazed ware, glossy brown glazed ware, and matte brown glazed ware. To [...] Read more.

The Guangyuan kiln, located in the Sichuan Province, Southwest China during the Song Dynasty (960–1279 A.D.), is renowned for its high-temperature iron-series glazed wares, including pure black glazed ware, hare’s fur glazed ware, glossy brown glazed ware, and matte brown glazed ware. To elucidate the raw materials, processing techniques, and coloration mechanisms of these wares, multiple analytical experiments were employed to investigate chemical composition, microstructure, and the phase of Fe-bearing minerals. We found that glossy brown glazed ware has the highest Fe₂O₃ content in the glaze (7.67 wt% on average), while pure black glazed ware exhibits the lowest (4.84 wt% on average). Higher Fe₂O₃ content leads to more iron for Fe-bearing mineral crystallization and larger ε-Fe₂O₃ precipitation. Based on microscopic observations, pure black glazed ware has numerous 100–250 nm crystalline grains, while hare’s fur glaze ware features dendritic crystal flowers (200–400 nm), which exhibited liquid-liquid phase separation within the glaze, suggesting localized phase separation inducing iron oxide crystallization. Glossy brown glazed ware contains well-developed ε-Fe₂O₃ crystals (25 µm), and matte brown glazed ware, with the highest CaO and total flux, has acicular anorthite crystals alongside ε-Fe₂O₃ crystals. In summary, the decorative effect of four different types of iron-series glazed wares is determined by their chemical composition, phase composition, and microscopic structure. The findings offer valuable insights for the study of ancient iron-glazed ware. Full article

(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Advanced Materials Characterization)

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29 pages, 6836 KiB

Open AccessEditor’s ChoiceReview

Advanced Characterization of Solid-State Battery Materials Using Neutron Scattering Techniques

by Eric Novak, Luke Daemen and Niina Jalarvo

Materials 2024, 17(24), 6209; https://doi.org/10.3390/ma17246209 - 19 Dec 2024

Viewed by 917

Abstract

Advanced batteries require advanced characterization techniques, and neutron scattering is one of the most powerful experimental methods available for studying next-generation battery materials. Neutron scattering offers a non-destructive method to probe the complex structural and chemical processes occurring in batteries during operation in [...] Read more.

Advanced batteries require advanced characterization techniques, and neutron scattering is one of the most powerful experimental methods available for studying next-generation battery materials. Neutron scattering offers a non-destructive method to probe the complex structural and chemical processes occurring in batteries during operation in truly in situ/in operando measurements with a high sensitivity to battery-relevant elements such as lithium. Neutrons have energies comparable to the energies of excitations in materials and wavelengths comparable to atomic distances in the solid state, thus giving access to study structural and dynamical properties of materials on an atomic scale. In this review, a broad overview of selected neutron scattering techniques is presented to illustrate how neutron scattering can be used to gain invaluable information of solid-state battery materials, with a focus on in situ/in operando methods. These techniques span multiple decades of length and time scales to uncover the complex processes taking place fundamentally on the atomic scale and to determine how these processes impact the macroscale properties and performance of functional battery systems. This review serves the solid-state battery research community by examining how the unique capabilities of neutron scattering can be applied to answer critical and unresolved questions of materials research in this field. A thorough and broad perspective is provided with numerous practical examples showing these techniques in action for battery research. Full article

(This article belongs to the Special Issue Local Structure Characterization for Complex Functional Materials)

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19 pages, 8834 KiB

Open AccessEditor’s ChoiceArticle

Protective Properties of Silane Composite Coatings Modified with Poly(3,4-ethylenedioxythiophene) with Heteropolyacid on X20Cr13 and 41Cr4 Steel

by Aleksandra Kucharczyk-Kotlewska, Lidia Adamczyk, Krzysztof Miecznikowski and Agata Dudek

Materials 2024, 17(24), 6177; https://doi.org/10.3390/ma17246177 - 18 Dec 2024

Viewed by 512

Abstract

This paper describes the methodology of the preparation and analyses of the structure and anticorrosion properties of silane coatings modified with poly(3,4-ethylenedioxythiophene) (PEDOT) with phosphododecamolybdic acid (PMo₁₂). Protective coatings, consisting of vinyltrimethoxysilane (VTMS), PEDOT powder with PMo₁₂ admixture (at different [...] Read more.

This paper describes the methodology of the preparation and analyses of the structure and anticorrosion properties of silane coatings modified with poly(3,4-ethylenedioxythiophene) (PEDOT) with phosphododecamolybdic acid (PMo₁₂). Protective coatings, consisting of vinyltrimethoxysilane (VTMS), PEDOT powder with PMo₁₂ admixture (at different concentrations), and ethanol, were deposited on X20Cr13 and 41Cr4 steels by immersion. The physicochemical properties of these silane coatings (e.g., surface morphology, thickness, roughness, and adhesion to the substrate) were elucidated using a digital microscope, a Fourier transform infrared spectrophotometer with attenuated total reflectance, and various electrochemical diagnostic techniques. Protective properties were assessed in acidified sulfate solutions with and without chloride ions (pH 2). Experimental results have shown that this coating displayed the effective protection of steel against general and pitting corrosion, stabilized the corrosion potential in the passive state, and provided barrier protection. Full article

(This article belongs to the Special Issue Fabrication and Properties of Functional Coatings Under Extreme Conditions)

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14 pages, 3148 KiB

Open AccessEditor’s ChoiceArticle

Liquid Structure of Magnesium Aluminates

by Viviana Cristiglio, Irina Pozdnyakova, Aleksei Bytchkov, Gabriel J. Cuello, Sandro Jahn, Didier Zanghi, Séverine Brassamin, James W. E. Drewitt and Louis Hennet

Materials 2024, 17(24), 6173; https://doi.org/10.3390/ma17246173 - 17 Dec 2024

Viewed by 635

Abstract

Magnesium aluminates (MgO)_x(Al₂O₃)_1−x belong to a class of refractory materials with important applications in glass and glass–ceramic technologies. Typically, these materials are fabricated from high-temperature molten phases. However, due to the difficulties in making measurements [...] Read more.

Magnesium aluminates (MgO)_x(Al₂O₃)_1−x belong to a class of refractory materials with important applications in glass and glass–ceramic technologies. Typically, these materials are fabricated from high-temperature molten phases. However, due to the difficulties in making measurements at very high temperatures, information on liquid-state structure and properties is limited. In this work, we employed the method of aerodynamic levitation with CO₂ laser heating at large scale facilities to study the structure of liquid magnesium aluminates in the system (MgO)_x(Al₂O₃)_1−x, with x = 0.33, 0.5, and 0.75, using X-ray and neutron diffraction. We determined the structure factors and corresponding pair distribution functions, providing detailed information on the short-range structural order in the liquid state. The local structures were similar across the range of compositions studied, with average coordination numbers of

{\bar{n}}_{A l}^{O} \sim 4.5

and

{\bar{n}}_{M g}^{O} \sim 5.1

and interatomic distances of

r_{AlO} = 1.76 - 1.78 Å

and

r_{MgO} = 1.93 - 1.95 Å

. The results are in good agreement with previous molecular dynamics simulations. For the spinel endmember MgAl₂O₄ (x = 0.5), the average Mg-O and Al-O coordination numbers gave rise to conflicting values for the inversion coefficient χ, indicating that the structural formula used to describe the solid-state order-disorder transition is not applicable in the liquid state. Full article

(This article belongs to the Section Materials Physics)

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10 pages, 1345 KiB

Open AccessEditor’s ChoiceArticle

Conversion of Oil-Containing Residue from Waste Oil Recycling Plant into Porous Carbon Materials Through Activation Method with Phosphoric Acid

by Li-An Kuo, Wen-Tien Tsai, Chien-Chen Pan, Ya-Chen Ye and Chi-Hung Tsai

Materials 2024, 17(24), 6161; https://doi.org/10.3390/ma17246161 - 17 Dec 2024

Cited by 1 | Viewed by 567

Abstract

In the waste oil recycling industry, large amounts of oil-containing sludge are still generated, thus posing a resource depletion issue when disposed of or incinerated without energy recovery or residual oil utilization. In this work, chemical activation experiments using phosphoric acid (H₃ [...] Read more.

In the waste oil recycling industry, large amounts of oil-containing sludge are still generated, thus posing a resource depletion issue when disposed of or incinerated without energy recovery or residual oil utilization. In this work, chemical activation experiments using phosphoric acid (H₃PO₄) were performed at a low temperature (600 °C) for 30 min to produce porous carbon products. From the results of the pore property analysis, an increasing trend with an increasing impregnation ratio from 0.5 to 2.0 was observed. Based on the Brunauer–Emmett–Teller (BET) model, the maximal BET surface area was about 70 m²/g, which was indicative of the hysteresis loop and the type IV isotherms in the resulting carbon product. In addition, the enhancement in the pore properties of the carbon products obtained through acid-washing was superior to that achieved through water-washing and without post-washing. From observations made using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), the carbon products featured a porous structure and inherent magnetism due to their richness of iron oxides. In this regard, they can be used as efficient adsorbents or catalyst supports due to their simple recovery (or separation) when exhausted. Full article

(This article belongs to the Special Issue Obtaining and Characterization of New Materials (5th Edition))

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23 pages, 9728 KiB

Open AccessEditor’s ChoiceArticle

Investigation of the Photocatalytic Activity of Copper-Modified Commercial Titania (P25) in the Process of Carbon Dioxide Photoreduction

by Konrad Sebastian Sobczuk, Iwona Pełech, Daniel Sibera, Piotr Staciwa, Agnieszka Wanag, Ewa Ekiert, Joanna Kapica-Kozar, Katarzyna Ćmielewska, Ewelina Kusiak-Nejman, Antoni Waldemar Morawski and Urszula Narkiewicz

Materials 2024, 17(24), 6139; https://doi.org/10.3390/ma17246139 - 15 Dec 2024

Viewed by 766

Abstract

The photocatalytic reduction of CO₂ to useful products is an area of active research because it shows a potential to be an efficient tool for mitigating climate change. This work investigated the modification of titania with copper(II) nitrate and its impact on [...] Read more.

The photocatalytic reduction of CO₂ to useful products is an area of active research because it shows a potential to be an efficient tool for mitigating climate change. This work investigated the modification of titania with copper(II) nitrate and its impact on improving the CO₂ reduction efficiency in a gas-phase batch photoreactor under UV–Vis irradiation. The investigated photocatalysts were prepared by treating P25-copper(II) nitrate suspensions (with various Cu²⁺ concentrations), alkalized with ammonia water, in a microwave-assisted solvothermal reactor. The titania-based photocatalysts were characterized by SEM, EDS, ICP-OES, XRD and UV-Vis/DR methods. Textural properties were measured by the low-temperature nitrogen adsorption/desorption studies at 77 K. P25 photocatalysts modified with copper(II) nitrate used in the process of carbon dioxide reduction allowed for a higher efficiency both for the photocatalytic reduction of CO₂ to CH₄ and for the photocatalytic water decomposition to hydrogen as compared to a reference. Similarly, modified samples showed significantly higher selectivity towards methane in the CO₂ conversion process than the unmodified sample (a change from 30% for a reference sample to 82% for the P25-R-Cu-0.1 sample after the 6 h process). It was found that smaller loadings of Cu are more beneficial for increasing the photocatalytic activity of a sample. Full article

(This article belongs to the Special Issue Advances in Photocatalyst Materials and Green Chemistry)

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11 pages, 1686 KiB

Open AccessEditor’s ChoiceArticle

Theoretical Investigation of Single-Atom Catalysts for Hydrogen Evolution Reaction Based on Two-Dimensional Tetragonal Mo₃C₂

by Bo Xue, Qingfeng Zeng, Shuyin Yu and Kehe Su

Materials 2024, 17(24), 6134; https://doi.org/10.3390/ma17246134 - 15 Dec 2024

Cited by 1 | Viewed by 655

Abstract

Developing highly efficient and cost-competitive electrocatalysts for the hydrogen evolution reaction (HER), which can be applied to hydrogen production by water splitting, is of great significance in the future of the zero-carbon economy. Here, by means of first-principles calculations, we have scrutinized the [...] Read more.

Developing highly efficient and cost-competitive electrocatalysts for the hydrogen evolution reaction (HER), which can be applied to hydrogen production by water splitting, is of great significance in the future of the zero-carbon economy. Here, by means of first-principles calculations, we have scrutinized the HER catalytic capacity of single-atom catalysts (SACs) by embedding transition-metal atoms in the C and Mo vacancies of a tetragonal Mo₃C₂ slab, where the transition-metal atoms refer to Ti, V, Cr, Mn, Fe, Co, Ni and Cu. All the Mo₃C₂-based SACs exhibit excellent electrical conductivity, which is favorable to charge transfer during HER. An effective descriptor, Gibbs free energy difference (ΔG_H*) of hydrogen adsorption, is adopted to evaluate catalytic ability. Apart from SACs with Cr, Mn and Fe located at C vacancies, all the other SACs can act as excellent catalysts for HER. Full article

(This article belongs to the Special Issue Advances in Multicomponent Catalytic Materials)

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19 pages, 7232 KiB

Open AccessEditor’s ChoiceArticle

Finite Element Simulation of Acoustic Emissions from Different Failure Mechanisms in Composite Materials

by Manoj Rijal, David Amoateng-Mensah and Mannur J. Sundaresan

Materials 2024, 17(24), 6085; https://doi.org/10.3390/ma17246085 - 12 Dec 2024

Cited by 1 | Viewed by 1079

Abstract

Damage in composite laminates evolves through complex interactions of different failure modes, influenced by load type, environment, and initial damage, such as from transverse impact. This paper investigates damage growth in cross-ply polymeric matrix laminates under tensile load, focusing on three primary failure [...] Read more.

Damage in composite laminates evolves through complex interactions of different failure modes, influenced by load type, environment, and initial damage, such as from transverse impact. This paper investigates damage growth in cross-ply polymeric matrix laminates under tensile load, focusing on three primary failure modes: transverse matrix cracks, delaminations, and fiber breaks in the primary loadbearing 0-degree laminae. Acoustic emission (AE) techniques can monitor and quantify damage in real time, provided the signals from these failure modes can be distinguished. However, directly observing crack growth and related AE signals is challenging, making numerical simulations a useful alternative. AE signals generated by the three failure modes were simulated using modified step impulses of appropriate durations based on incremental crack growth. Linear elastic finite element analysis (FEA) was applied to model the AE signal propagating as Lamb waves. Experimental attenuation data were used to modify the simulated AE waveforms by designing arbitrary magnitude response filters. The propagating waves can be detected as surface displacements or surface strains depending upon the type of sensor employed. This paper presents the signals corresponding to surface strains measured by surface-bonded piezoelectric sensors. Fiber break events showed higher-order Lamb wave modes with frequencies over 2 MHz, while matrix cracks primarily exhibited the fundamental S₀ and A₀ modes with frequencies ranging up to 650 kHz, with delaminations having a dominant A₀ mode and frequency content less than 250 kHz. The amplitude and frequency content of signals from these failure modes are seen to change significantly with source–sensor distance, hence requiring an array of dense sensors to acquire the signals effectively. Furthermore, the reasonable correlation between the simulated waveforms and experimental acoustic emission signals obtained during quasi-static tensile test highlights the effectiveness of FEA in accurately modeling these failure modes in composite materials. Full article

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

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1 pages, 24225 KiB

Open AccessEditor’s ChoiceArticle

Multiscale Concurrent Topology Optimization and Mechanical Property Analysis of Sandwich Structures

by Zihao Li, Shiqiang Li and Zhihua Wang

Materials 2024, 17(24), 6086; https://doi.org/10.3390/ma17246086 - 12 Dec 2024

Viewed by 967

Abstract

Based on the basic theoretical framework of the Bi-directional Evolutionary Structural Optimization method (BESO) and the Solid Isotropic Material with Penalization method (SIMP), this paper presents a multiscale topology optimization method for concurrently optimizing the sandwich structure at the macro level and the [...] Read more.

Based on the basic theoretical framework of the Bi-directional Evolutionary Structural Optimization method (BESO) and the Solid Isotropic Material with Penalization method (SIMP), this paper presents a multiscale topology optimization method for concurrently optimizing the sandwich structure at the macro level and the core layer at the micro level. The types of optimizations are divided into macro and micro concurrent topology optimization (MM), macro and micro gradient concurrent topology optimization (MMG), and macro and micro layered gradient concurrent topology optimization (MMLG). In order to compare the multiscale optimization method with the traditional macroscopic optimization method, the sandwich simply supported beam is illustrated as a numerical example to demonstrate the functionalities and superiorities of the proposed method. Moreover, several samples are printed through micro-nano 3D printing technology, and then the static three-point bending experiments and the numerical simulations are carried out. The mechanical properties of the optimized structures in terms of deformation modes, load-bearing capacity, and energy absorption characteristics are compared and analyzed in detail. Finally, the multiscale optimization methods are extended to the design of 2D sandwich cantilever beams and 3D sandwich fully clamped beams. Full article

(This article belongs to the Section Advanced Materials Characterization)

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14 pages, 2706 KiB

Open AccessEditor’s ChoiceArticle

Evolution of Chemical, Structural, and Mechanical Properties of Titanium Nitride Films with Different Thicknesses Fabricated Using Pulsed DC Magnetron Sputtering

by Wei Mao, Runze Qi, Jiali Wu, Zhe Zhang and Zhanshan Wang

Materials 2024, 17(24), 6067; https://doi.org/10.3390/ma17246067 - 12 Dec 2024

Viewed by 607

Abstract

Considering the application of titanium nitride (TiN) films as a release layer in producing Wolter-I X-ray telescope mirror shells by the electroformed nickel replication (ENR) technique, this research pays attention to the influence of nanometer-scale thickness variation in the microstructure and physical properties [...] Read more.

Considering the application of titanium nitride (TiN) films as a release layer in producing Wolter-I X-ray telescope mirror shells by the electroformed nickel replication (ENR) technique, this research pays attention to the influence of nanometer-scale thickness variation in the microstructure and physical properties of TiN films deposited by the pulsed direct current (DC) magnetron sputtering method. This topic has received limited attention in the existing literature. TiN films (9.8 nm to 42.9 nm) were fabricated to comprehensively analyze the evolution in microstructure, depth distribution of elements, surface morphology, and intrinsic stress. With increasing thickness, TiN transitioned from amorphous to (200) and (111)–(200) mixed-oriented crystallization, explaining inflection points in the increasing roughness curve. Elements (C, N, O, Si, and Ti) and chemical bond proportions (Ti-N, Ti-N-O, and Ti-O) varied with film depth, and the fitting of film density can be optimized according to these variations. Crystallite size increased with thickness, which led to a reduction in intrinsic stress. It is evident that as film thickness increases, TiN forms a stable crystal structure, thereby reducing intrinsic stress, but resulting in increased roughness. Considering the impact of changes in thin film thickness on physical properties such as roughness, crystallinity, and intrinsic stress, a TiN film with a thickness of approximately 25 nm is deemed suitable for application as a release layer. Full article

(This article belongs to the Special Issue Advances in Thin Films Materials: Properties, Characterization, Physical Vapor Deposition and Application)

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19 pages, 17330 KiB

Open AccessEditor’s ChoiceArticle

Effects of Building Orientation and Raster Angle on the Mechanical Properties of Selected Materials Used in FFF Techniques

by Piotr Dziewit, Kamil Rajkowski and Paweł Płatek

Materials 2024, 17(24), 6076; https://doi.org/10.3390/ma17246076 - 12 Dec 2024

Viewed by 620

Abstract

Advances in the development of additive manufacturing materials (AM) and the low availability of studies on the impact response of AM specimens are the main reasons for this paper. Therefore, the influence of building orientation (vertical and horizontal) and the angle of the [...] Read more.

Advances in the development of additive manufacturing materials (AM) and the low availability of studies on the impact response of AM specimens are the main reasons for this paper. Therefore, the influence of building orientation (vertical and horizontal) and the angle of the raster (15°/−75°, 30°/−60°, 45°/−45°, and 0°/90°) on the tensile and impact strength of AM specimens was investigated. The polylactic acid (PLA)-PolyMax, Mediflex and acrylonitrile-butadiene-styrene (ABS) filaments were chosen to provide a comprehensive characterization of AM materials with versatile mechanical properties. The experimental results of this study show that the tensile strength and toughness of PolyMax PLA specimens are comparable to ABS specimens, while Mediflex samples are characterized by their higher toughness, but lower impact force needed to break the samples. The Mediflex Charpy fracture surfaces exhibit a ductile character compared to those of brittle ABS and PLA. Furthermore, fracture surface morphology shows the allocation of voids, which helps us to understand differences in mechanical properties, and allows one to properly interpret the results of the geometrical accuracy of AM specimens with various printing settings. Full article

(This article belongs to the Special Issue Mechanical Properties of Polymeric, Metallic, and Composite Materials)

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34 pages, 1503 KiB

Open AccessEditor’s ChoiceArticle

The Generalized Phase Rule, the Extended Definition of the Degree of Freedom, the Component Rule and the Seven Independent Non-Compositional State Variables: To the 150th Anniversary of the Phase Rule of Gibbs

by George Kaptay

Materials 2024, 17(24), 6048; https://doi.org/10.3390/ma17246048 - 10 Dec 2024

Viewed by 1198

Abstract

The phase rule of Gibbs is one of the basic equations in phase equilibria. Although it has been with us for 150 years, discussions, interpretations and extensions have been published. Here, the following new content is provided: (i). the choice of independent components [...] Read more.

The phase rule of Gibbs is one of the basic equations in phase equilibria. Although it has been with us for 150 years, discussions, interpretations and extensions have been published. Here, the following new content is provided: (i). the choice of independent components is discussed, and the component rule is introduced, (ii). independent state variables are divided into compositional and non-compositional ones, (iii). the generalized phase rule is derived replacing number two in the original phase rule by the number of independent non-compositional state variables introduced above, (iv). the degree of freedom is decreased by the number of compositional constraints in special points (azeotrope and congruent melting) of phase diagrams, (v). a rule is derived connecting the maximum number of coexisting phases with the dimensions of the phase diagram, (vi). examples show how to apply the phase rule to unary, binary and ternary phase diagrams and their sections, (vii). the same is extended with the discussion of calculable and not calculable phase fractions, (viii). it is shown that the current definition of the degree of freedom is not sufficient in the number of cases, (ix). the current definition of the degree of freedom is extended, (x). the application of the generalized phase rule is demonstrated when other non-compositional state variables are applied for nano-phase diagrams, and/or for phase diagrams under the influence of electric potential difference, external magnetic field, mechanical strain or the gravitational field. Full article

(This article belongs to the Section Materials Chemistry)

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15 pages, 2348 KiB

Open AccessEditor’s ChoiceArticle

Fine Tuning the Glass Transition Temperature and Crystallinity by Varying the Thiophene-Quinoxaline Copolymer Composition

by Xun Pan and Mats R. Andersson

Materials 2024, 17(24), 6031; https://doi.org/10.3390/ma17246031 - 10 Dec 2024

Viewed by 749

Abstract

In recent years, the design and synthesis of high-performing conjugated materials for the application in organic photovoltaics (OPVs) have achieved lab-scale devices with high power conversion efficiency. However, most of the high-performing materials are still synthesised using complex multistep procedures, resulting in high [...] Read more.

In recent years, the design and synthesis of high-performing conjugated materials for the application in organic photovoltaics (OPVs) have achieved lab-scale devices with high power conversion efficiency. However, most of the high-performing materials are still synthesised using complex multistep procedures, resulting in high cost. For the upscaling of OPVs, it is also important to focus on conjugated polymers that can be made via fewer simple synthetic steps. Therefore, an easily synthesised amorphous thiophene−quinoxaline donor polymer, TQ1, has attracted our attention. An analogue, TQ-EH that has the same polymer backbone as TQ1 but with short branched side-chains, was previously reported as a donor polymer with increased crystallinity. We have synthesised copolymers with varied ratios between octyloxy and branched (2-ethylhexyl)oxy-substituted quinoxaline units having the same polymer backbone, with the aim to control the aggregation/crystallisation behaviour of the resulting copolymers. The optical properties, glass transition temperatures and degree of crystallinity of the new copolymers were systematically examined in relation to their copolymer composition, revealing that the composition can be used to fine-tune these properties of conjugated polymers. In addition, multiple sub-T_g transitions were found from some of the polymers, which are not commonly or clearly seen in other conjugated polymers. The new copolymers were tested in photovoltaic devices with a fullerene derivative as the acceptor, achieving slightly higher performances compared to the homopolymers. This work demonstrates that side-chain modification by copolymerisation can fine-tune the properties of conjugated polymers without requiring complex organic synthesis, thereby expanding the number of easily synthesised polymers for future upscaling of OPVs. Full article

(This article belongs to the Special Issue Advanced Photovoltaic Materials: Synthesis, Properties and Applications)

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16 pages, 4200 KiB

Open AccessEditor’s ChoiceArticle

Dielectric, Electric, and Pyroelectric Properties of Ba_1−xCa_xTiO₃ Ceramics

by Kamil Feliksik, Jolanta Makowska, Joanna A. Bartkowska, Tomasz Pikula, Rafał Panek, Oliwia Starczewska and Małgorzata Adamczyk-Habrajska

Materials 2024, 17(24), 6040; https://doi.org/10.3390/ma17246040 - 10 Dec 2024

Viewed by 826

Abstract

In this study, we investigate the dielectric, electric, and pyroelectric properties of Ba_1−xCa_xTiO₃ (BCT) ceramics with compositions of x = 0.2, 0.25, and 0.3. The ceramics were synthesized using the solid-state reaction method. A microstructural analysis was performed [...] Read more.

In this study, we investigate the dielectric, electric, and pyroelectric properties of Ba_1−xCa_xTiO₃ (BCT) ceramics with compositions of x = 0.2, 0.25, and 0.3. The ceramics were synthesized using the solid-state reaction method. A microstructural analysis was performed using scanning electron microscopy (SEM), revealing that calcium concentration influences grain size and morphology, with BCT20 showing larger, hexagonal grains, while BCT25 and BCT30 exhibited smaller, irregular grains. Phase composition and crystalline structure were characterized via X-ray diffraction (XRD), which confirmed the absence of secondary phases and a predominantly tetragonal P4mm structure for BCT20 and BCT25. However, BCT30 showed an additional orthorhombic (Pbam) phase at 5.9 wt. % alongside the dominant tetragonal phase. Dielectric measurements revealed that increasing the calcium concentration shifts the temperature of dielectric permittivity maximum to lower values, correlating with a shift in the ferroelectric–paraelectric phase transition. Pyroelectric measurements indicated the highest pyroelectric current for BCT25, while BCT30 showed the maximum thermally stimulated depolarization current. Full article

(This article belongs to the Special Issue Ferromagnetic and Ferroelectric Materials: Synthesis, Applications, and Techniques (Second Edition))

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18 pages, 9431 KiB

Open AccessEditor’s ChoiceArticle

Enhanced Wear Resistance and Thermal Dissipation of Copper–Graphene Composite Coatings via Pulsed Electrodeposition for Circuit Breaker Applications

by Daniele Almonti, Daniel Salvi, Nadia Ucciardello and Silvia Vesco

Materials 2024, 17(23), 6017; https://doi.org/10.3390/ma17236017 - 9 Dec 2024

Viewed by 941

Abstract

Copper, though highly conductive, requires improved wear resistance and thermal dissipation in applications that involve continuous movement and current-induced vibrations, such as power breakers. Conventional solutions, such as copper–tungsten alloys or lubricant use, face limitations in durability, friction, or environmental impact. This study [...] Read more.

Copper, though highly conductive, requires improved wear resistance and thermal dissipation in applications that involve continuous movement and current-induced vibrations, such as power breakers. Conventional solutions, such as copper–tungsten alloys or lubricant use, face limitations in durability, friction, or environmental impact. This study explores the development of copper–graphene (Cu-GNPs) composite coatings using pulsed electrodeposition to enhance the tribological, thermal, and mechanical properties of circuit breaker components by adopting an industrially scalable technique. The influence of deposition bath temperature, duty cycle, and frequency on coating morphology, hardness, wear resistance, and heat dissipation was systematically evaluated using a 2³ full factorial design and an Analysis of Variance (ANOVA). The results revealed that optimized pulsed electrodeposition significantly improved coating performance: hardness increased by 76%, wear volume decreased by more than 99%, and friction coefficient stabilized at 0.2, reflecting effective graphene integration. The addition of graphene further improved thermal diffusivity by 19.5%, supporting superior heat dissipation. These findings suggest that pulsed copper–graphene composite coatings offer a promising alternative to traditional copper alloys, enhancing the lifespan and reliability of electronic components through improved wear resistance, lower friction, and superior heat transfer. Full article

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

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30 pages, 7774 KiB

Open AccessEditor’s ChoiceReview

Perovskite in Triboelectric Nanogenerator and the Hybrid Energy Collection System

by Tong Wu, Zequan Zhao, Yin Lu, Hanzhang Yang, Xiaoning Liu, Xia Cao and Ning Wang

Materials 2024, 17(23), 6019; https://doi.org/10.3390/ma17236019 - 9 Dec 2024

Cited by 1 | Viewed by 1140

Abstract

In the context of escalating energy demands and environmental sustainability, the paradigm of global energy systems is undergoing a transformative shift to innovative and reliable energy-harvesting techniques ranging from solar cells to triboelectric nanogenerators (TENGs) to hybrid energy systems, where a fever in [...] Read more.

In the context of escalating energy demands and environmental sustainability, the paradigm of global energy systems is undergoing a transformative shift to innovative and reliable energy-harvesting techniques ranging from solar cells to triboelectric nanogenerators (TENGs) to hybrid energy systems, where a fever in the study of perovskite materials has been set off due to the excellent optoelectronic properties and defect tolerance features. This review begins with the basic properties of perovskite materials and the fundamentals of TENGs, including their working principles and general developing strategy, then delves into the key role of perovskite materials in promoting TENG-based hybrid technologies in terms of energy conversion. While spotlighting the coupling of triboelectric–optoelectronic effects in harnessing energy from a variety of sources, thereby transcending the limitations inherent to single-source energy systems, this review pays special attention to the strategic incorporation of perovskite materials into TENGs and TENG-based energy converting systems, which heralds a new frontier in enhancing efficiency, stability, and adaptability. At the end, this review highlights the remaining challenges such as stability, efficiency, and functionality for applications in TENG-based energy-harvesting systems, aiming to provide a comprehensive overview of the current landscape and the prospective trajectory of the role of perovskite materials in TENG-based energy-harvesting technologies within the renewable energy sector. Full article

(This article belongs to the Special Issue Featured Papers and Reviews of Advanced Materials for Sensing, Energy Conversion and Storage)

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11 pages, 2574 KiB

Open AccessEditor’s ChoiceArticle

Photo-Excited Carrier Dynamics in Ammonothermal Mn-Compensated GaN Semiconductor

by Patrik Ščajev, Paweł Prystawko, Robert Kucharski and Irmantas Kašalynas

Materials 2024, 17(23), 5995; https://doi.org/10.3390/ma17235995 - 7 Dec 2024

Viewed by 856

Abstract

We investigated the carrier dynamics of ammonothermal Mn-compensated gallium nitride (GaN:Mn) semiconductors by using sub-bandgap and above-bandgap photo-excitation in a photoluminescence analysis and pump–probe measurements. The contactless probing methods elucidated their versatility for the complex analysis of defects in GaN:Mn crystals. The impurities [...] Read more.

We investigated the carrier dynamics of ammonothermal Mn-compensated gallium nitride (GaN:Mn) semiconductors by using sub-bandgap and above-bandgap photo-excitation in a photoluminescence analysis and pump–probe measurements. The contactless probing methods elucidated their versatility for the complex analysis of defects in GaN:Mn crystals. The impurities of Mn were found to show photoconductivity and absorption bands starting at the 700 nm wavelength threshold and a broad peak located at 800 nm. Here, we determined the impact of Mn-induced states and Mg acceptors on the relaxation rates of charge carriers in GaN:Mn based on a photoluminescence analysis and pump–probe measurements. The electrons in the conduction band tails were found to be responsible for both the photoconductivity and yellow luminescence decays. The slower red luminescence and pump–probe decays were dominated by Mg acceptors. After photo-excitation, the electrons and holes were quickly thermalized to the conduction band tails and Mg acceptors, respectively. The yellow photoluminescence decays exhibited a 1 ns decay time at low laser excitations, whereas, at the highest ones, it increased up to 7 ns due to the saturation of the nonradiative defects, resembling the photoconductivity lifetime dependence. The fast photo-carrier decay time observed in ammonothermal GaN:Mn is of critical importance in high-frequency and high-voltage device applications. Full article

(This article belongs to the Special Issue Optical Properties of Crystalline Semiconductors and Nanomaterials)

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15 pages, 7639 KiB

Open AccessEditor’s ChoiceArticle

Superhydrophobic Surfaces as a Potential Skin Coating to Prevent Jellyfish Stings: Inhibition and Anti-Tentacle Adhesion in Nematocysts of Jellyfish Nemopilema nomurai

by Yichen Xie, Yuanyuan Sun, Rongfeng Li, Song Liu, Ronge Xing, Pengcheng Li and Huahua Yu

Materials 2024, 17(23), 5983; https://doi.org/10.3390/ma17235983 - 6 Dec 2024

Viewed by 810

Abstract

The development of skin-protective materials that prevent the adhesion of cnidarian nematocysts and enhance the mechanical strength of these materials is crucial for addressing the issue of jellyfish stings. This study aimed to construct superhydrophobic nanomaterials capable of creating a surface that inhibits [...] Read more.

The development of skin-protective materials that prevent the adhesion of cnidarian nematocysts and enhance the mechanical strength of these materials is crucial for addressing the issue of jellyfish stings. This study aimed to construct superhydrophobic nanomaterials capable of creating a surface that inhibits nematocyst adhesion, therefore preventing jellyfish stings. We investigated wettability and nematocyst adhesion on four different surfaces: gelatin, polydimethylsiloxane (PDMS), dodecyl trichlorosilane (DTS)-modified SiO₂, and perfluorooctane triethoxysilane (PFOTS)-modified TiO₂. Our findings revealed that an increase in hydrophobicity significantly inhibited nematocyst adhesion. Furthermore, DTS-modified sprayed SiO₂ and PFOTS-modified sprated TiO₂ were further enhanced with low-surface-energy substances—cellulose nanofibers (CNF) and chitin nanocrystals (ChNCs)—to improve both hydrophobicity and mechanical strength. After incorporating CNF and ChNCs, the surface of s-TiO₂-ChNCs exhibited a contact angle of 153.49° even after undergoing abrasion and impact tests, and it maintained its hydrophobic properties with a contact angle of 115.21°. These results indicate that s-TiO₂-ChNCs can serve as an effective skin coating to resist tentacle friction. In conclusion, this study underscores the importance of utilizing hydrophobic skin materials to inhibit the adhesion of tentacle nematocysts, providing a novel perspective for protection against jellyfish stings. Full article

(This article belongs to the Special Issue Superhydrophobic Coating Materials: Preparation, Strategy and Application)

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18 pages, 14812 KiB

Open AccessEditor’s ChoiceArticle

Influence of the Cooling Method on Cutting Force and Recurrence Analysis in Polymer Composite Milling

by Krzysztof Ciecieląg

Materials 2024, 17(23), 5981; https://doi.org/10.3390/ma17235981 - 6 Dec 2024

Cited by 1 | Viewed by 758

Abstract

This work investigates the milling of the surface of glass and carbon fiber-reinforced plastics using tools with a polycrystalline diamond insert. The milling process was conducted under three different conditions, namely without the use of a cooling liquid, with oil mist cooling, and [...] Read more.

This work investigates the milling of the surface of glass and carbon fiber-reinforced plastics using tools with a polycrystalline diamond insert. The milling process was conducted under three different conditions, namely without the use of a cooling liquid, with oil mist cooling, and with emulsion cooling. The milling process of composites was conducted with variable technological parameters. The variable milling parameters were feed per tooth and cutting speed. The novelty of this work is the use of recurrence methods based on the cutting force signal to analyze the milling of composites with three types of cooling. The primary aim of the study was to determine the effect of variable technological milling parameters on cutting force and to select recurrence quantifications that would be sensitive to the cooling method. It has been shown that recurrence quantifications such as determinism (DET), laminarity (LAM), averaged diagonal length (L), trapping time (TT), recurrence time of the second type (T₂), and entropy (ENTR) are sensitive to the cooling methods applied for the tested composite materials. The results have shown that it is possible to determine common ranges of changes in sensitive recurrence quantifications for the two tested variables parameters of milling: 0.63–0.94 (DET), 0.69–0.97 (LAM), 7.30–13.48 (L), 2.92–4.98 (TT), 17.01–38.25 (T₂), 2.02–3.16 (ENTR). The ANOVA analysis results have confirmed that the studied variables have a significant impact on the recurrence quantifications. Full article

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

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9 pages, 4243 KiB

Open AccessEditor’s ChoiceArticle

Phase Evolution in Mn_1.6Zn_0.2Ni_0.6Mg_0.2Al_0.4O₄ High-Entropy Oxide Films by Heat Treatment

by Wei Ren, Xianhai Liu, Wenting Wu and Weili Wang

Materials 2024, 17(23), 5967; https://doi.org/10.3390/ma17235967 - 5 Dec 2024

Viewed by 590

Abstract

In this work, Mn-Zn-Ni-Mg-Al multi-layer films were annealed in air at different temperatures to form spinel-structured Mn_1.6Zn_0.2Ni_0.6Mg_0.2Al_0.4O₄ high-entropy oxide films. X-ray diffraction results demonstrate that the films possess a polycrystalline spinel phase [...] Read more.

In this work, Mn-Zn-Ni-Mg-Al multi-layer films were annealed in air at different temperatures to form spinel-structured Mn_1.6Zn_0.2Ni_0.6Mg_0.2Al_0.4O₄ high-entropy oxide films. X-ray diffraction results demonstrate that the films possess a polycrystalline spinel phase as well as impurity phases: when annealed at 650 °C and 750 °C, MnO₂ and Al₂O₃ impurity phases exist; at 950 °C, an Al₂O₃ impurity phase exists. Only at 850 °C does a pure spinel phase exist. However, the film at 750 °C exhibits the best conductive behavior, which indicates that the impurity phases may not have to be removed to maintain the best electrical properties of the film. Full article

(This article belongs to the Special Issue New Technique for Preparing Thin Film: Characteristic and Further Development)

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14 pages, 5593 KiB

Open AccessEditor’s ChoiceArticle

Influence of Selected Factors of Vibratory Work Hardening Machining on the Properties of CuZn30 Brass

by Damian Bańkowski, Anna Kiljan, Irena M. Hlaváčová and Piotr Młynarczyk

Materials 2024, 17(23), 5913; https://doi.org/10.3390/ma17235913 - 3 Dec 2024

Viewed by 634

Abstract

The purpose of this study was to determine the effect of selected vibratory strengthening machining factors on the properties of CuZn30 brass. Vibratory strengthening machining was carried out using metal media dedicated to polishing processes, which also contributed to strengthening the treated surfaces. [...] Read more.

The purpose of this study was to determine the effect of selected vibratory strengthening machining factors on the properties of CuZn30 brass. Vibratory strengthening machining was carried out using metal media dedicated to polishing processes, which also contributed to strengthening the treated surfaces. The test samples were cut with an abrasive water jet and recrystallized to obtain a soft microstructure. An orthogonal, two-factor five-level plan was used for the study. The effect of vibration frequency and vibratory machining time on selected changes in parameters of the geometric structure of the surface and hardness of the surface layer was determined using Statistica software version 10 (64-bit). Higher vibration frequencies for vibratory machining increased the hardness of machined surfaces by as much as 50 HV_0.02. The arithmetic mean deviation of the height of surface irregularities from the reference plane, Sa, decreases with increasing the time of vibratory machining. A value of Sa = 0.168 µm was obtained after 87 min of consolidation, compared to an initial surface of S_a = 0.65 µm. Full article

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

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18 pages, 3164 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Bioactive Compounds from Banana Leaf Extracts: Influence of Extraction Methodologies and Their Integration into Knitted Hemp Fabrics

by Joana Mota Gomes, João Mariz, Catarina Rodrigues, Ana Luísa Alves, Joana Moreira, Bárbara Vieira, Rosa Maria Silva, Andrea Zille and Carla Joana Silva

Materials 2024, 17(23), 5884; https://doi.org/10.3390/ma17235884 - 30 Nov 2024

Viewed by 1493

Abstract

This study explores the bioactive potential of banana leaf extracts and their innovative integration into knitted hemp fabrics. To obtain the extracts, distinct extraction methodologies were employed, namely conventional extraction, ultrasound-assisted extraction, and pressurized-liquid extraction. Aqueous and hydroethanolic solvents, namely 20% (v [...] Read more.

This study explores the bioactive potential of banana leaf extracts and their innovative integration into knitted hemp fabrics. To obtain the extracts, distinct extraction methodologies were employed, namely conventional extraction, ultrasound-assisted extraction, and pressurized-liquid extraction. Aqueous and hydroethanolic solvents, namely 20% (v/v) and 50% (v/v), were employed during the extraction process. Furthermore, the cationization and functionalization of knitted hemp fabrics with the banana leaf extracts was achieved through padding. The extracts’ phenolic content and antioxidant activity were evaluated using the Folin–Ciocalteu (FC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays, respectively. The results indicated that both ultrasound-assisted extraction and pressurized-assisted extraction substantially enhanced the yield of phenolic compounds in comparison to conventional extraction, while employing 50% EtOH as a solvent also improved extraction yields for all extraction methodologies. The functionalized knits were further characterized concerning their antioxidant activity by DPPH, assessing their antimicrobial properties through ATCC TM-100 standard against three microorganisms (Staphylococcus aureus, Candida Krusei, and Candida albicans), and UV protection according to the standard AS/NZS 4399:2017. Antioxidant activity was highest in knits functionalized with extracts obtained via ultrasound-assisted extraction, while antimicrobial properties were most pronounced in knits treated with hydroalcoholic extracts, particularly those derived from assisted methods. The UV protection was enhanced in extracts with higher ethanol concentrations obtained through ultrasound-assisted extraction, with these knits exhibiting the highest Ultraviolet Protection Factor (UPF). This research not only highlights the efficacy of the alternative extraction technologies but also offers valuable insights for the development of innovative, biocompatible materials with enhanced bioactive properties for diverse applications in the textile and healthcare sectors, paving the way for sustainable applications. Full article

(This article belongs to the Special Issue Leather, Textiles and Bio-Based Materials)

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14 pages, 5465 KiB

Open AccessEditor’s ChoiceArticle

Thin and Flexible PANI/PMMA/CNF Forest Films Produced via a Two-Step Floating Catalyst Chemical Vapor Deposition

by Foteini-Maria Papadopoulou, Spyros Soulis, Aikaterini-Flora A. Trompeta and Costas A. Charitidis

Materials 2024, 17(23), 5812; https://doi.org/10.3390/ma17235812 - 27 Nov 2024

Viewed by 934

Abstract

In this paper, we explore a straightforward two-step method to produce high-purity, vertically aligned multi-walled carbon nanofibres (MWCNFs) via chemical vapor deposition (CVD). Two distinct solutions are utilized for this CVD method: a catalytic solution consisting of ferrocene and acetonitrile (ACN) and a [...] Read more.

In this paper, we explore a straightforward two-step method to produce high-purity, vertically aligned multi-walled carbon nanofibres (MWCNFs) via chemical vapor deposition (CVD). Two distinct solutions are utilized for this CVD method: a catalytic solution consisting of ferrocene and acetonitrile (ACN) and a carbon source solution with camphor and ACN. The vapors of the catalytic solution inserted in the reaction chamber through external boiling result in a floating catalyst CVD approach that produces vertically aligned CNFs in a consistent manner. CNFs are grown in a conventional CVD horizontal reactor at 850 °C under atmospheric pressure and characterized by Raman spectroscopy, scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Coating the MWCNTs with polymethyl methacrylate (PMMA) while still on the Si substrate retains the structure and results in a flexible, conductive thin film suitable for flexible electrodes. The film is 62 μm thick and stable in aqueous solutions, capable of withstanding further processing, such as electropolymerization with polyaniline, to be used for energy storage applications. Full article

(This article belongs to the Special Issue Emerging Technologies for Development of Novel Materials Systems and Coatings (Volume 2))

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14 pages, 2827 KiB

Open AccessEditor’s ChoiceArticle

The Coloring Mechanism of Opaque Glazes from the Changsha Kiln of the Tang Dynasty

by Lala Jia, Maolin Zhang, Yongqiang Yu, Zihan Li and Yongbin Yu

Materials 2024, 17(23), 5803; https://doi.org/10.3390/ma17235803 - 27 Nov 2024

Viewed by 879

Abstract

The Changsha Kiln of the Tang Dynasty was a major site for celadon production, yet the mechanisms behind the unique coloring of its opaque glazes remain inadequately explored. Prior research has largely focused on the general composition of these glazes, with limited understanding [...] Read more.

The Changsha Kiln of the Tang Dynasty was a major site for celadon production, yet the mechanisms behind the unique coloring of its opaque glazes remain inadequately explored. Prior research has largely focused on the general composition of these glazes, with limited understanding of the specific processes contributing to their distinct visual characteristics. This gap in knowledge hinders efforts to accurately replicate these historical glazes and fully appreciate their technological significance. In this study, we analyze the chemical composition and microstructure of opaque glaze specimens from the Changsha Kiln using advanced techniques such as EDXRF, SEM-EDS, and ultra-deep field microscopy. Our findings reveal that the opaque glazes are high-calcium compositions where phase separation and the presence of coloring ions like Cu²⁺, Cu⁺, and Fe³⁺ play critical roles in determining the glaze’s color. The interplay between chemical coloring and phase separation processes is shown to produce the distinct blue-green and creamy white hues observed in the glazes. These results provide a deeper understanding of the coloring mechanisms in Changsha Kiln glazes, contributing to the broader field of ceramic research and aiding in the preservation and accurate reproduction of these historic artifacts. Full article

(This article belongs to the Special Issue Advanced Characterization Approaches Applied to the Field of Cultural Heritage: From Conservation to Divulgation)

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18 pages, 4444 KiB

Open AccessEditor’s ChoiceArticle

Toward Sustainable 3D-Printed Sensor: Green Fabrication of CNT-Enhanced PLA Nanocomposite via Solution Casting

by Javid Sharifi, Ghaus Rizvi and Haniyeh (Ramona) Fayazfar

Materials 2024, 17(23), 5782; https://doi.org/10.3390/ma17235782 - 25 Nov 2024

Viewed by 914

Abstract

The current study explores, for the first time, an eco-friendly solution casting method using a green solvent, ethyl acetate, to prepare feedstock/filaments from polylactic acid (PLA) biopolymer reinforced with carbon nanotubes (CNTs), followed by 3D printing and surface activation for biosensing applications. Comprehensive [...] Read more.

The current study explores, for the first time, an eco-friendly solution casting method using a green solvent, ethyl acetate, to prepare feedstock/filaments from polylactic acid (PLA) biopolymer reinforced with carbon nanotubes (CNTs), followed by 3D printing and surface activation for biosensing applications. Comprehensive measurements of thermal, electrical, rheological, microstructural, and mechanical properties of developed feedstock and 3D-printed parts were performed and analyzed. Herein, adding 2 wt.% CNTs to the PLA matrix marked the electrical percolation, achieving conductivity of 8.3 × 10⁻³ S.m⁻¹, thanks to the uniform distribution of CNTs within the PLA matrix facilitated by the solution casting method. Rheological assessments paralleled these findings; the addition of 2 wt.% CNTs transitioned the nanocomposite from liquid-like to a solid-like behavior with a percolated network structure, significantly elevating rheological properties compared to the composite with 1 wt.% CNTs. Mechanical evaluations of the printed samples revealed improvement in tensile strength and modulus compared to virgin PLA by a uniform distribution of 2 wt.% CNTs into PLA, with an increase of 14.5% and 10.3%, respectively. To further enhance the electrical conductivity and sensing capabilities of the developed samples, an electrochemical surface activation treatment was applied to as-printed nanocomposite samples. The field-emission scanning electron microscopy (FE-SEM) analysis confirmed that this surface activation effectively exposed the CNTs to the surface of 3D-printed parts by removing a thin layer of polymer from the surface, thereby optimizing the composite’s electroconductivity performance. The findings of this study underscore the potential of the proposed eco-friendly method in developing advanced 3D-printed bio-nanocomposites based on carbon nanotubes and biopolymers, using a green solution casting and cost-effective material extrusion 3D-printing method, for electrochemical-sensing applications. Full article

(This article belongs to the Special Issue The Application of Materials in Modern Manufacturing Processes: Design, Performance and Applied Research)

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14 pages, 11006 KiB

Open AccessEditor’s ChoiceArticle

The Influence of the Steam Sterilization Process on Selected Properties of Polymer Samples Produced in MEX and JMT Processes

by Małgorzata Zaborniak, Janusz Kluczyński, Jakub Stańko and Tomasz Ślęzak

Materials 2024, 17(23), 5763; https://doi.org/10.3390/ma17235763 - 25 Nov 2024

Viewed by 843

Abstract

Polymeric materials are widely used in medical engineering, and with the dynamic development of additive manufacturing (AM) technology, increasing attention is being paid to research on the mechanical strength of composite polymer structures. At the same time, the impact of sterilization on, for [...] Read more.

Polymeric materials are widely used in medical engineering, and with the dynamic development of additive manufacturing (AM) technology, increasing attention is being paid to research on the mechanical strength of composite polymer structures. At the same time, the impact of sterilization on, for example, surgical templates and the influence of the sterilization process on the geometry of these parts have not been sufficiently studied. In this work, the effect of steam sterilization on samples made of polymer materials for medical applications was presented. This research was carried out on samples with normative geometry made of polyetheretherketone (PEEK) polymers produced using the Material Extrusion (MEX) AM process and acrylic formulation (MED610) produced by Jetting Modeling Technology (JMT). These materials provide biocompatibility, which makes them suitable for potential medical applications. Steam sterilization was performed in an autoclave at temperatures of 121 °C and 134 °C. The three-point bending strength properties were determined according to ISO 178 standards. An INSTRON 5967 strength testing machine was used for those tests. Surface roughness analysis (according to ISO 21920) was performed and presented in 2D and 3D surface views using the Mountains Map Software (version 6.0). Full article

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

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21 pages, 23836 KiB

Open AccessEditor’s ChoiceArticle

Electron Beam Welding of Dissimilar Stainless Steel and Maraging Steel Joints

by Matúš Geľatko, Radoslav Vandžura, František Botko and Michal Hatala

Materials 2024, 17(23), 5769; https://doi.org/10.3390/ma17235769 - 25 Nov 2024

Cited by 2 | Viewed by 762

Abstract

The incorporation of additive manufactured (AM) metal parts to real assemblies is a crucial issue for the increasing of their industrial utilization. The presented research is devoted to the electron beam welding (EBW) of dissimilar steel joints. Dissimilarity is defined by the various [...] Read more.

The incorporation of additive manufactured (AM) metal parts to real assemblies is a crucial issue for the increasing of their industrial utilization. The presented research is devoted to the electron beam welding (EBW) of dissimilar steel joints. Dissimilarity is defined by the various types of steel and manufacturing processes used for the creation of specimens. Conventional AISI 316 stainless steel, selective laser melted (SLM) SS 316L stainless steel, and SLM M300 maraging steel were welded at variable parameters in the form of a welding current and a welding velocity. EBW joints were evaluated considering the macroscopic and microscopic characteristics, as well as a reached microhardness. The obtained preliminary results represent important input data for the follow-up experiments focused on the setting of optimal EBW parameters of welding the dissimilar joints including SLM products, with the consideration of their basic macroscopical and microscopical characteristics, mechanical properties, and residual stresses. Full article

(This article belongs to the Special Issue Advanced Production, Processing and Characterization of Industrial Materials)

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15 pages, 7876 KiB

Open AccessEditor’s ChoiceArticle

Gas-Sensing Properties of Co₉S₈ Films Toward Formaldehyde, Ethanol, and Hydrogen Sulfide

by Myeong Gyu Kim and Yun-Hyuk Choi

Materials 2024, 17(23), 5743; https://doi.org/10.3390/ma17235743 - 24 Nov 2024

Viewed by 786

Abstract

The chemiresistive gas-sensing properties of pristine Co₉S₈ film are little known despite its potential as a promising gas sensor material due to its intrinsic characteristics. In this study, a pristine polycrystalline Co₉S₈ film (approximately 440 nm in [...] Read more.

The chemiresistive gas-sensing properties of pristine Co₉S₈ film are little known despite its potential as a promising gas sensor material due to its intrinsic characteristics. In this study, a pristine polycrystalline Co₉S₈ film (approximately 440 nm in thickness) is fabricated by depositing a Co₃O₄ film followed by sulfidation to investigate its gas-sensing properties. The prepared Co₉S₈ film sensor is found to exhibit high responsiveness towards formaldehyde (HCHO), ethanol (C₂H₅OH), and hydrogen sulfide (H₂S) at operating temperatures of 300 °C and 400 °C, with strong concentration dependence. On the other hand, the sensor shows very low or no responsiveness towards hydrogen (H₂), acetone (CH₃COCH₃), and nitrogen dioxide (NO₂). These results enhance our understanding of the intrinsic gas-sensing properties of Co₉S₈, aiding in the design and fabrication of high-performance chemiresistive gas sensors based on Co₉S₈. Full article

(This article belongs to the Section Materials Chemistry)

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15 pages, 2341 KiB

Open AccessEditor’s ChoiceArticle

Green Synthesis of CuO Nanoparticles—Structural, Morphological, and Dielectric Characterization

by Joana Neiva, Zohra Benzarti, Sandra Carvalho and Susana Devesa

Materials 2024, 17(23), 5709; https://doi.org/10.3390/ma17235709 - 22 Nov 2024

Cited by 1 | Viewed by 1043

Abstract

This study investigates the structural, chemical, and morphological properties of CuO nanoparticles synthesized via a green synthesis route using Opuntia ficus-indica cladode extract, with a focus on the effects of stepwise versus direct calcination. Raman spectroscopy revealed the presence of CuO, [...] Read more.

This study investigates the structural, chemical, and morphological properties of CuO nanoparticles synthesized via a green synthesis route using Opuntia ficus-indica cladode extract, with a focus on the effects of stepwise versus direct calcination. Raman spectroscopy revealed the presence of CuO, Na₂CO₃, and Na₂SO₃, with the latter two being associated with elements inherited from the cactus extracts. XRD patterns confirmed the presence of crystalline CuO and Na₂CO₃ phases, with the low content of Na₂SO₃ inferred to be amorphous. Rietveld refinement estimated a CuO content of approximately 77% in the stepwise-calcined sample and 75% in the directly calcined sample, with lattice parameters closely aligning with reference values. SEM micrographs revealed a tendency for CuO nanoparticles to aggregate, likely due to high surface energy and interaction with the viscous plant extract used in the green synthesis. Crystallite size estimates, along with morphological observations, suggest that stepwise calcination enhances crystallinity and particle definition without altering the fundamental nanoparticle morphology. These findings highlight the influence of calcination method and natural extracts on the composition and morphology of green-synthesized CuO nanoparticles, offering insights into potential applications, namely in microelectronics, due to their promising dielectric properties. Full article

(This article belongs to the Special Issue Synthesis and Characterization Techniques for Nanomaterials)

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21 pages, 3260 KiB

Open AccessEditor’s ChoiceArticle

Amber “Alchemy”: Recreating and Investigating Yellow Glass Formulations

by Catarina Reis Santos, Andreia Ruivo, Ana Carneiro, João Pedro Veiga, Teresa Palomar and Inês Coutinho

Materials 2024, 17(23), 5699; https://doi.org/10.3390/ma17235699 - 21 Nov 2024

Viewed by 905

Abstract

Amber glass has been produced since at least the 6th century BC. Its value derives from its ability to mimic natural amber and, later, from its ultraviolet filtering properties. Until the 19th century, amber glass was widely used for the storage of food [...] Read more.

Amber glass has been produced since at least the 6th century BC. Its value derives from its ability to mimic natural amber and, later, from its ultraviolet filtering properties. Until the 19th century, amber glass was widely used for the storage of food and medicines because its protective properties had been empirically recognized. This study investigates historical methods of amber glass production by using glass recipes from four Portuguese arcana (1793–1975) and focusing on Fe-S and Fe-Mn chromophores. Five recipes were reproduced under controlled laboratory conditions, resulting in 21 experiments. Of these, only 10 produced amber glasses were with different shades. Chemical compositions were analysed by WDXRF, while DSC and dilatometry were used to assess thermal properties. Vickers hardness tests and UV–visible absorption spectroscopy provided insight into mechanical strength and chromophore presence. The study found that FeS amber glass was more difficult to produce than Fe-Mn amber glass, given the complex variables involved in the former, such as SO₃ volatility affecting the final product. Reproduction of historical recipes showed that, even without modern chemical knowledge, historical glassmakers developed practical, empirical methods for making amber glass. These findings contribute to a broader understanding of glass conservation and highlight the importance of historical glass recipes for the interpretation and conservation of glass objects. Full article

(This article belongs to the Special Issue Materials in Cultural Heritage: Analysis, Testing, and Preservation)

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18 pages, 4439 KiB

Open AccessEditor’s ChoiceArticle

The Influence of Horsetail (Equisetum arvense L.) Powder and Horsetail-Based Silica on the Crystallization Kinetics of Polylactide

by Olga Mysiukiewicz, Joanna Szulc and Andrzej Miklaszewski

Materials 2024, 17(23), 5697; https://doi.org/10.3390/ma17235697 - 21 Nov 2024

Viewed by 812

Abstract

Biogenic silica (SiO₂) sourced from living organisms, especially plants such as rice and other cereals, has recently been successfully applied in different polymeric compositions. Another rich source of biogenic silica is common horsetail (Equisetum arvense L.), containing up to 25% [...] Read more.

Biogenic silica (SiO₂) sourced from living organisms, especially plants such as rice and other cereals, has recently been successfully applied in different polymeric compositions. Another rich source of biogenic silica is common horsetail (Equisetum arvense L.), containing up to 25% SiO₂ in the dry matter. In this study, biogenic silica was obtained from horsetail powder by acid leaching in sulfuric acid and calcination at 400 °C. The analysis, including measurements of specific surface area using the Brunauer–Emmett–Teller method, assessment of crystallinity by X-ray diffraction, as well as chemical content analysis by Fourier-transform infrared spectroscopy showed that high-purity, high-surface mesoporous silica was obtained. The biogenic silica and horsetail powders were also introduced to polylactide (PLA) to determine their influence on the polymer’s crystallization, which was studied in both non-isothermal and isothermal conditions by differential scanning calorimetry. The crystallization parameters were calculated according to the Avrami method based on isothermal crystallization curves at 100, 110 and 120 °C. The crystalline structures were observed by optical microscopy in polarized light. It was found that both fillers improve the crystallization of PLA, especially in low-supercooling conditions, so they can be successfully utilized in industrial applications, when high crystallinity of polylactide is needed. Full article

(This article belongs to the Special Issue Advanced Designs of Materials, Machines and Processes in a Circular Economy)

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19 pages, 3453 KiB

Open AccessEditor’s ChoiceReview

Opportunities and Challenges for Predicting the Service Status of SLM Metal Parts Under Big Data and Artificial Intelligence

by Xiaoling Yan and Huiwen Fu

Materials 2024, 17(22), 5648; https://doi.org/10.3390/ma17225648 - 19 Nov 2024

Viewed by 923

Abstract

Selective laser melting (SLM) technology is a high-end dual-use technology that is implemented in aerospace and medical equipment, as well as the automotive industry and other military and civilian industries, and is urgently needed for major equipment manufacturing and national defense industries. This [...] Read more.

Selective laser melting (SLM) technology is a high-end dual-use technology that is implemented in aerospace and medical equipment, as well as the automotive industry and other military and civilian industries, and is urgently needed for major equipment manufacturing and national defense industries. This paper examines the challenges of uncontrollable service states and the inability to ensure service safety of SLM metal parts under nonlinear and complex operating conditions. An overview of the prediction of the service status of SLM metal parts was introduced, and an effective approach solving the problem was provided in this paper. In this approach, the cross-scale coupling mechanism between mesoscopic damage evolution and macroscopic service state evolution is clarified by tracking the mesoscopic damage evolution process of SLM metal parts based on ultrasonic nonlinear responses. The failure mechanism is organically integrated with hidden information from monitoring big data, and a “chimeric” model to accurately evaluate the service status of SLM metal parts is constructed. Combining nonlinear ultrasound technology with big data and artificial intelligence to construct a “chimeric” model and consummate the corresponding methods and theories for evaluating the service status of SLM metal parts is an effective way to reveal the mesoscopic damage evolution and service status evolution mechanisms of SLM metal parts under complex factor coupling, and to accurately describe and characterize the service status of parts under complex operating conditions. The proposed approach will provide a theoretical basis and technical guarantee for the precise management of SLM parts’ service safety in key equipment fields such as aerospace, medical equipment, and the automotive industry. Full article

(This article belongs to the Section Advanced Materials Characterization)

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13 pages, 5392 KiB

Open AccessEditor’s ChoiceArticle

Exploring Light Stability and Trapping Mechanisms in Organic Thin-Film Transistors for High-Brightness MicroLED Integration

by Chia-Hung Tsai, Yang-En Wu, Chuan-Wei Kuo, Ting-Chang Chang, Li-Yin Chen, Fang-Chung Chen and Hao-Chung Kuo

Materials 2024, 17(22), 5643; https://doi.org/10.3390/ma17225643 - 19 Nov 2024

Cited by 1 | Viewed by 818

Abstract

Organic thin-film transistors (OTFTs), benefiting from a low-temperature process (≤120 °C), offer a promising approach for the monolithic integration of MicroLED structures through organic-last integration. Previous research has demonstrated that small-molecule/polymer binder-based organic semiconductor deposition, utilizing the vertical phase separation mechanism, can achieve [...] Read more.

Organic thin-film transistors (OTFTs), benefiting from a low-temperature process (≤120 °C), offer a promising approach for the monolithic integration of MicroLED structures through organic-last integration. Previous research has demonstrated that small-molecule/polymer binder-based organic semiconductor deposition, utilizing the vertical phase separation mechanism, can achieve good device uniformity while preserving high field-effect carrier mobility. However, the stability of OTFTs under light exposure at the device level remains underexplored. This study investigates the effects of various light irradiation conditions on OTFTs and delves into the underlying mechanisms of the light-trapping effect. Based on these findings, we propose an optimal OTFT design tailored for driving MicroLED displays at high operational brightness, ensuring both performance and stability. Full article

(This article belongs to the Special Issue Advanced Materials for Organic Semiconductors and Their Applications)

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25 pages, 5749 KiB

Open AccessEditor’s ChoiceArticle

A Statistical Assessment of Drilling Effects on Glass Fiber-Reinforced Polymeric Composites

by Ana Martins, Alda Carvalho, Ivo M. F. Bragança, Inês C. J. Barbosa, Joaquim Infante Barbosa and Maria A. R. Loja

Materials 2024, 17(22), 5631; https://doi.org/10.3390/ma17225631 - 18 Nov 2024

Viewed by 853

Abstract

Fiber-reinforced composites are extensively used in many components and structures in various industry sectors, and the need to connect and assemble such types of components may require drilling operations. Although drilling is a common machining process; when dealing with fiber-reinforced composite materials, additional [...] Read more.

Fiber-reinforced composites are extensively used in many components and structures in various industry sectors, and the need to connect and assemble such types of components may require drilling operations. Although drilling is a common machining process; when dealing with fiber-reinforced composite materials, additional and specific problems may arise that can com-promise mechanical integrity. So, the main goal of this work is to assess how various input variables impact two main outcomes in the drilling process: the exit-adjusted delamination factor and the maximum temperature on the bottom surface where the drilling tool exits. The input variables include the type of drilling tools used, the operating speeds, and the thickness of the plates being drilled. By using Analysis of Variance (ANOVA), the analysis aims to identify which factors significantly influence damage and exit temperature. The results demonstrate that the influence of tools and drilling parameters is critical, and those selections impact the quality of the hole and the extent of the induced damage to the surrounding area. In concrete, considering the initially selected set of tools, the BZT03 tool does not lead to high-quality holes when drilling medium- and high-thickness plates. In contrast, the Dagger tool shows potential to reduce exit hole damage while also lowering temperature. Full article

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

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11 pages, 3705 KiB

Open AccessEditor’s ChoiceArticle

Zirconium Oxide as a Novel Material for Post-Endodontically Treated Teeth: Comparative Fracture Behavior of 3D-Printed Cobalt–Chromium, Milled Zirconium Oxide, and Quartz Fiber Posts

by Armin Sokolowski, Fernando Gustavo Warchomicka, Lukas Seebacher, Bernhard Remschmidt, Marcus Rieder, Lumnije Kqiku-Biblekaj and Alwin Sokolowski

Materials 2024, 17(22), 5611; https://doi.org/10.3390/ma17225611 - 17 Nov 2024

Viewed by 1148

Abstract

This study evaluates the mechanical properties of materials used in the post-endodontic restoration of root-treated teeth and examines their performance under stress to provide insights for material selection in clinical applications. Particular attention is given to zirconium oxide, which demonstrates promising characteristics due [...] Read more.

This study evaluates the mechanical properties of materials used in the post-endodontic restoration of root-treated teeth and examines their performance under stress to provide insights for material selection in clinical applications. Particular attention is given to zirconium oxide, which demonstrates promising characteristics due to its esthetic color and favorable material properties, positioning it as a potential material for future use in post-endodontic treatments. Three materials—prefabricated quartz fiber-reinforced composite, milled zirconium oxide, and additively manufactured cobalt–chromium—were evaluated using compressive-deflection tests. The specimens were subjected to a 45° compressive load extending 5 mm from a metal core. Their mechanical properties were analyzed using one-way ANOVA and Tukey’s post hoc test. Significant differences were observed among the materials. Quartz fiber posts, with the lowest force resistance, buckled at lower loads (143.3 ± 9.9 N), while zirconia posts failed in a brittle manner at higher forces (246.1 ± 97.2 N). Cobalt–chromium posts demonstrated the highest maximal force (323.2 ± 10.5 N, p < 0.001) and, unlike the other materials, bent rather than fractured. The failure patterns of the tested materials underscore the importance of careful material selection when restoring root-treated teeth. Despite displaying distinct fracture characteristics, zirconium oxide, due to its color, rigidity, and hardness, stands out as a promising material for future dental applications. Further research through randomized clinical trials is recommended to refine treatment approaches and optimize clinical outcomes. Full article

(This article belongs to the Special Issue Recent Research in Restorative Dental Materials)

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18 pages, 5642 KiB

Open AccessEditor’s ChoiceArticle

A New Slicer-Based Method to Generate Infill Inspired by Sandwich-Patterns for Reduced Material Consumption

by Patrick Steck, Dominik Schuler, Christian Witzgall and Sandro Wartzack

Materials 2024, 17(22), 5596; https://doi.org/10.3390/ma17225596 - 15 Nov 2024

Viewed by 881

Abstract

This work presents a novel infill method for additive manufacturing, specifically designed to optimize material use and enhance stiffness in fused filament fabrication (FFF) parts through a geometry-aware, corrugated design inspired by sandwich structures. Unlike standard infill patterns, which typically employ uniform, space-filling [...] Read more.

This work presents a novel infill method for additive manufacturing, specifically designed to optimize material use and enhance stiffness in fused filament fabrication (FFF) parts through a geometry-aware, corrugated design inspired by sandwich structures. Unlike standard infill patterns, which typically employ uniform, space-filling grids that often disregard load-specific requirements, this method generates a cavity inside the component to be printed and fill the space between inner and outer contours with continuous, adaptable extrusion paths. This design enables consistent support and improved load distribution, making it particularly effective for parts under bending stresses, as it enhances structural resilience without requiring additional material. Simulations performed on a 10 cm³ test part using this method showed potential reductions in material consumption by up to 77% and a decrease in print time by 78%, while maintaining stiffness comparable to parts using conventional 100% grid infill. Additionally, simulations demonstrated that the new corrugated infill pattern provides near-isotropic stiffness, addressing the anisotropic limitations often seen in traditional infill designs that are sensitive to load orientation. This geometry-aware infill strategy thus contributes to balanced stiffness across complex geometries, enhancing reliability under mechanical loads. By integrating directly with slicer software, this approach simplifies advanced stiffness optimization without the necessity of finite element analysis-based topology optimization. Full article

(This article belongs to the Special Issue Advanced Additive Manufacturing and Application)

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16 pages, 2999 KiB

Open AccessEditor’s ChoiceArticle

Modification of Poly(3-Hydroxybutyrate) with a Linear Polyurethane Modifier and Organic Nanofiller—Preparation and Structure–Property Relationship

by Iwona Zarzyka, Beata Krzykowska, Karol Hęclik, Wiesław Frącz, Grzegorz Janowski, Łukasz Bąk, Tomasz Klepka, Jarosław Bieniaś, Monika Ostapiuk, Aneta Tor-Świątek, Magda Droździel-Jurkiewicz, Adam Tomczyk, Anna Falkowska and Michał Kuciej

Materials 2024, 17(22), 5542; https://doi.org/10.3390/ma17225542 - 13 Nov 2024

Viewed by 842

Abstract

The growing demand for products made of polymeric materials, including the commonly used polypropylene (PP), is accompanied by the problem of storing and disposing of non-biodegradable waste, increasing greenhouse gas emissions, climate change and the creation of toxic products that constitute a health [...] Read more.

The growing demand for products made of polymeric materials, including the commonly used polypropylene (PP), is accompanied by the problem of storing and disposing of non-biodegradable waste, increasing greenhouse gas emissions, climate change and the creation of toxic products that constitute a health hazard of all living organisms. Moreover, most of the synthetic polymers used are made from petrochemical feedstocks from non-renewable resources. The use of petrochemical raw materials also causes degradation of the natural environment. A potential solution to these problems is the use of biopolymers. Biopolymers include biodegradable or biosynthesizable polymers, i.e., obtained from renewable sources or produced synthetically but from raw materials of natural origin. One of them is the poly(3-hydroxybutyrate) (P3HB) biopolymer, whose properties are comparable to PP. Unfortunately, it is necessary to modify its properties to improve its processing and operational properties. In the work, hybrid polymer nanobiocomposites based on P3HB, with the addition of chain, uncross-linked polyurethane (PU) and layered aluminosilicate modified with organic salts (Cloisite^®30B) were produced by extrusion process. The introduction of PU and Cloisite^®30B to the polymer matrix (P3HB) influenced the processing parameters beneficially and resulted in a decrease in the extrusion temperature of more than 10 °C. The influence of the simultaneous addition of a constant amount of PU (10 m/m%) and the different amounts of nanoadditives (1, 2 and 3 m/m%) on the compatibility, morphology and static mechanical properties of the resulted nanobiocomposites were examined. The component interactions by Fourier transformation infrared spectroscopy (FTIR) analysis, nano- and microscale structure studies using small-angle X-ray scattering (SAXS) and morphology by scanning electron microscopy (SEM) were carried out, and the hardness and tensile strength of the obtained polymer nanobiocomposites were determined. FTIR analysis identified the compatibility of the polyester matrix, PU, and organomodified montmorillonite, the greatest being 3 m/m% Cloisite30B content. The addition of PU to the polyester elasticizes the material and decreases the material’s strength and ductility. The presence of nanoclay enhanced the mechanical properties of nanobiocomposites. The resulting nanobiocomposites can be used in the production of short-life materials applied in gardening or agriculture. Full article

(This article belongs to the Special Issue Progressive Technologies and Materials in Mechanical and Materials Engineering)

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13 pages, 7008 KiB

Open AccessEditor’s ChoiceArticle

Si Characterization on Thinning and Singulation Processes for 2.5/3D HBM Package Integration

by MiKyeong Choi, SeaHwan Kim, TaeJoon Noh, DongGil Kang and SeungBoo Jung

Materials 2024, 17(22), 5529; https://doi.org/10.3390/ma17225529 - 13 Nov 2024

Viewed by 1007

Abstract

As stacking technologies, such as 2.5D and 3D packages, continue to accelerate in advanced semiconductor components, the singulation and thinning of Si wafers are becoming increasingly critical. Despite their importance in producing thinner and more reliable Si chips, achieving high reliability remains a [...] Read more.

As stacking technologies, such as 2.5D and 3D packages, continue to accelerate in advanced semiconductor components, the singulation and thinning of Si wafers are becoming increasingly critical. Despite their importance in producing thinner and more reliable Si chips, achieving high reliability remains a challenge, and comprehensive research on the effects of these processing techniques on Si chip integrity is lacking. In this study, the impacts of wafer thinning and singulation on the fracture strength of Si wafers were systematically compared. Three different grinding processes, namely fine grinding, poly-grinding, and polishing, were used for thinning, and the resulting surface morphology and roughness were analyzed using scanning electron microscopy and an interferometer. In addition, the residual mechanical stress on the wafer surface was measured using Raman spectroscopy. The fracture strength of Si wafers and chips was assessed through three-point bending tests. Singulation, including blade dicing, laser dicing, and stealth dicing, was evaluated for its impact on fracture strength. Among these processes, polishing for wafer thinning exhibited the lowest full-width half maximum and intensity ratio of Raman shifts (I480/I520), indicating minimal residual stress and surface defects. Consequently, Si wafers and chips processed through polishing demonstrated the highest fracture strength. Moreover, the 60 µm thick Si wafers and chips showed the highest fracture strength compared with those with thicknesses of 90 and 120 µm, possibly because of the increased flexibility, which mitigates stress. Among the singulation methods, stealth dicing yielded the highest fracture strength, outperforming blade and laser dicing. The combination of wafer thinning via polishing and singulation via stealth dicing presents an optimal solution for producing highly reliable Si chips for 2.5D and 3D packaging. These findings may be valuable in selecting optimal processing technologies for high-reliability Si chip production in industrial settings. Full article

(This article belongs to the Section Advanced Materials Characterization)

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26 pages, 16106 KiB

Open AccessEditor’s ChoiceArticle

Physicochemical Characterization and Kinetics Study of Polymer Carriers with Vitamin C for Controlled Release Applications

by Magdalena Bańkosz

Materials 2024, 17(22), 5502; https://doi.org/10.3390/ma17225502 - 12 Nov 2024

Viewed by 925

Abstract

This study focuses on the selection and evaluation of a kinetic model for the release of vitamin C from different delivery systems, including microcapsules, hydrogels, and a hybrid system combining both. The microcapsules were synthesized from a 2% sodium alginate solution and with [...] Read more.

This study focuses on the selection and evaluation of a kinetic model for the release of vitamin C from different delivery systems, including microcapsules, hydrogels, and a hybrid system combining both. The microcapsules were synthesized from a 2% sodium alginate solution and with vitamin C incorporated in selected formulations. Hydrogels were obtained through photopolymerization using poly(ethylene glycol) diacrylate and polyvinyl alcohol, with and without the addition of vitamin C. The hybrid system incorporated the vitamin C-containing microcapsules within the hydrogel matrix. Physicochemical properties, such as density, porosity, and water vapor transmission rate (WVTR), were evaluated. Kinetic studies of vitamin C release were conducted under dynamic and static conditions, and the experimental data were fitted to six different kinetic models: zero-order, first-order, second-order, Higuchi, Korsmeyer–Peppas, and Hixson–Crowell. The Higuchi and Korsmeyer–Peppas models provided the best fit for most systems, indicating that the release is predominantly controlled by diffusion and, in dynamic conditions, swelling of the matrix. The hybrid system, while exhibiting slower release than the microcapsules and hydrogel alone, demonstrated more controlled and sustained release, which is advantageous for applications requiring prolonged action. Full article

(This article belongs to the Special Issue Research of Organic Molecules and Materials for Biological Application)

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39 pages, 8550 KiB

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Enhancement of Magnetic Shielding Based on Low-Noise Materials, Magnetization Control, and Active Compensation: A Review

by Yijin Liu, Jianzhi Yang, Fuzhi Cao, Xu Zhang and Shiqiang Zheng

Materials 2024, 17(22), 5469; https://doi.org/10.3390/ma17225469 - 8 Nov 2024

Cited by 3 | Viewed by 2368

Abstract

Magnetic-shielding technologies play a crucial role in the field of ultra-sensitive physical measurement, medical imaging, quantum sensing, etc. With the increasing demand for the accuracy of magnetic measurement, the performance requirements of magnetic-shielding devices are also higher, such as the extremely weak magnetic [...] Read more.

Magnetic-shielding technologies play a crucial role in the field of ultra-sensitive physical measurement, medical imaging, quantum sensing, etc. With the increasing demand for the accuracy of magnetic measurement, the performance requirements of magnetic-shielding devices are also higher, such as the extremely weak magnetic field, gradient, and low-frequency noise. However, the conventional method to improve the shielding performance by adding layers of materials is restricted by complex construction and inherent materials noise. This paper provides a comprehensive review about the enhancement of magnetic shielding in three aspects, including low-noise materials, magnetization control, and active compensation. The generation theorem and theoretical calculation of materials magnetic noise is summarized first, focusing on the development of spinel ferrites, amorphous, and nanocrystalline. Next, the principles and applications of two magnetization control methods, degaussing and magnetic shaking, are introduced. In the review of the active magnetic compensation system, the forward and inverse design methods of coil and the calculation method of the coupling effect under the ferromagnetic boundary of magnetic shield are explained in detail, and their applications, especially in magnetocardiography (MCG) and magnetoencephalogram (MEG), are also mainly described. In conclusion, the unresolved challenges of different enhancement methods in materials preparation, optimization of practical implementation, and future applications are proposed, which provide comprehensive and instructive references for corresponding research. Full article

(This article belongs to the Special Issue Preparation, Electromagnetic Absorption and Shielding Properties of Electromagnetic Functional Materials)

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22 pages, 3931 KiB

Open AccessEditor’s ChoiceReview

Securing Rare Earth Permanent Magnet Needs for Sustainable Energy Initiatives

by Dan-Cristian Popa and Loránd Szabó

Materials 2024, 17(22), 5442; https://doi.org/10.3390/ma17225442 - 7 Nov 2024

Viewed by 1580

Abstract

Rare earth permanent magnets are vital in various sectors, including renewable energy conversion, where they are widely used in permanent magnet generators. However, the global supply and availability of these materials present significant risks, and their mining and processing have raised serious environmental [...] Read more.

Rare earth permanent magnets are vital in various sectors, including renewable energy conversion, where they are widely used in permanent magnet generators. However, the global supply and availability of these materials present significant risks, and their mining and processing have raised serious environmental concerns. This paper reviews the necessary legislative, economic, and technological measures that must be implemented to address these issues. While it may not be feasible to eliminate the risks associated with the availability of rare earth materials, researchers in the field of electrical generators can play a crucial role in significantly reducing the demand for newly mined and processed such materials, thereby mitigating the negative environmental impacts of their extraction and production. Full article

(This article belongs to the Special Issue Advances in Sustainable Energy Materials and Devices)

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