Materials

18 pages, 2749 KiB

Open AccessArticle

Macroscopic and Microscopic Investigation of Gypsum Slag Cement-Stabilized Recycled Aggregate Base Layers

by Changdong Zhou, Pengcheng Shi, Hao Huang and Junan Shen

Materials 2024, 17(6), 1450; https://doi.org/10.3390/ma17061450 - 21 Mar 2024

Viewed by 1038

The purpose of this study is to investigate the macro and micro properties of stabilized recycled aggregate base layers using gypsum slag cement (GSC) and compare them with ordinary Portland cement (OPC). To achieve this, four levels of recycled aggregate content (0%, 50%, [...] Read more.

The purpose of this study is to investigate the macro and micro properties of stabilized recycled aggregate base layers using gypsum slag cement (GSC) and compare them with ordinary Portland cement (OPC). To achieve this, four levels of recycled aggregate content (0%, 50%, 60%, 70%) and three levels of binder materials (3.5%, 4.5%, 5.5%) were designed, where the binding materials included OPC and GSC. When GSC is used as the binding material with 0% recycled content, two scenarios for the ratio of slag to activator are considered: 4:1 and 4:2. For recycled content of 50%, 60%, and 70%, only the 4:1 ratio is considered. The macro-mechanical properties of the composite material were studied through compaction tests, unconfined compressive strength tests, and indirect tensile strength tests. Microscopic properties were investigated through X-ray diffraction (XRD) and scanning electron microscopy (SEM). Macroscopic test results indicate that, at an equal binder content, GSC exhibits a higher moisture content and maximum dry density compared to OPC. Moreover, the unconfined compressive strength and indirect tensile strength of GSC are higher than those of OPC. Microscopic test results reveal that the hydration products of both binding materials are essentially similar; however, under identical curing conditions, the hydration products of GSC are more abundant than those of OPC. Full article

(This article belongs to the Special Issue Concrete in Structural Engineering: Fabrication and Mechanical Behavior ‖)

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17 pages, 3978 KiB

Open AccessArticle

Foaming and Physico-Mechanical Properties of Geopolymer Pastes Manufactured from Post-Metallurgical Recycled Slag

by Mateusz Sitarz, Tomasz Zdeb, Katarzyna Mróz, Izabela Hager and Kinga Setlak

Materials 2024, 17(6), 1449; https://doi.org/10.3390/ma17061449 - 21 Mar 2024

Viewed by 1017

Abstract

This paper presents a research program aimed towards developing a method of producing lightweight, porous geopolymer composites for the construction industry based on industrial wastes. A direct method involving the addition of chemicals is currently most commonly used to produce the porous mineral [...] Read more.

This paper presents a research program aimed towards developing a method of producing lightweight, porous geopolymer composites for the construction industry based on industrial wastes. A direct method involving the addition of chemicals is currently most commonly used to produce the porous mineral structure of a geopolymer matrix. This relies on a reaction in a highly alkaline environment of the geopolymer to produce a gas (usually hydrogen or oxygen) that forms vesicles and creates a network of pores. This paper demonstrates the feasibility of producing a slag-based geopolymer paste foamed with aluminum powder, taking into account different parameters of fresh paste production: the mixing duration, its speed and the timing of foaming agent addition. The foaming process of the fresh paste in terms of the volumetric changes and temperature development of the fresh paste during the curing of the material are observed. After hardening, the physical properties (density and porosity) as well as the mechanical parameters (compressive strength and work of damage) are determined for the nine manufactured foamed pastes. Image analysis software was used to assess the porosity distribution of the material across the cross-section of the samples. The results enabled the design of the mixing procedure to be adopted during the manufacture of such composites. Full article

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11 pages, 4244 KiB

Open AccessArticle

Methylated Biochemical Fulvic Acid-Derived Hydrogels with Improved Swelling Behavior and Water Retention Capacity

by Chunhui Shi, Xifeng Lv, Jingfan Peng, Jikui Zhu, Fengqin Tang and Libing Hu

Materials 2024, 17(6), 1448; https://doi.org/10.3390/ma17061448 - 21 Mar 2024

Viewed by 1112

Abstract

Although humic acids (HAs) have been used to prepare absorbent hydrogels, their applications in many areas, such as agriculture, wastewater treatment and hygienic products, are not satisfactory due to their low solubility in organic solvents. In this work, biochemical fulvic acid (BFA), as [...] Read more.

Although humic acids (HAs) have been used to prepare absorbent hydrogels, their applications in many areas, such as agriculture, wastewater treatment and hygienic products, are not satisfactory due to their low solubility in organic solvents. In this work, biochemical fulvic acid (BFA), as a kind of HA, was initially methylated for preparation of the methylated BFA (M-BFA), which contributed to enhancing the solubility in organic solvents. Then, M-BFA reacted with N,N′-methylene diacrylamide (MBA) in the N,N-Dimethylacrylamide (DMAA) solution, and the expected hydrogel (M-BFA/DMAA) was successfully obtained. XPS confirmed that there were more C=O and C-N groups in M-BFA/DMAA than in DMAA; thus, M-BFA/DMAA was able to offer more reactive sites for the water adsorption process than DMAA. The combined results of BET and SEM further demonstrated that M-BFA/DMAA possessed a larger BET surface area, a larger pore volume and a more porous structure, which were favorable for the transfer of water and accessibility of water to active sites, facilitating water adsorption and storage. In addition, the swelling ratio and water retention were investigated in deionized (DI) water at different conditions, including test times, temperatures and pHs. Amazingly, the swelling ratio of M-BFA/DMAA was 10% higher than that of DMAA with the water retention time from 100 to 1500 min. Although M-BFA/DMAA and DMAA had similar temperature sensitivities, the pH sensitivity of M-BFA/DMAA was 0.9 higher than that of DMAA. The results proved that M-BFA/DMAA delivered superior water retention when compared to the pristine DMAA. Therefore, the resultant materials are expected to be efficient absorbent materials that can be widely used in water-deficient regions. Full article

(This article belongs to the Section Polymeric Materials)

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13 pages, 7655 KiB

Open AccessArticle

Influence of Annealing Process on Soft Magnetic Properties of Fe-B-C-Si-P Amorphous Alloys

by Jili Jia, You Wu, Lingxiang Shi, Ranbin Wang, Wenhui Guo, Hengtong Bu, Yang Shao, Na Chen and Kefu Yao

Materials 2024, 17(6), 1447; https://doi.org/10.3390/ma17061447 - 21 Mar 2024

Cited by 3 | Viewed by 1361

Abstract

It is well known that the annealing process plays a key role in tuning the properties of Fe-based amorphous soft magnetic alloys. However, the optimal annealing process for a particular amorphous alloy is often difficult to determine. Here, Fe_81.4B_13.2C [...] Read more.

It is well known that the annealing process plays a key role in tuning the properties of Fe-based amorphous soft magnetic alloys. However, the optimal annealing process for a particular amorphous alloy is often difficult to determine. Here, Fe_81.4B_13.2C_2.8Si_1.8P_0.8 and Fe_82.2B_12.4C_2.8Si_1.8P_0.8 amorphous alloys (denoted as Fe_81.4 and Fe_82.2) were prepared to systematically study the effects of the annealing temperature and time on the soft magnetic properties. The results show that the optimum annealing temperature ranges of the Fe_81.4 and Fe_82.2 amorphous alloys were 623 K to 653 K and 593 K to 623 K, and their coercivity (H_c) values were only 2.0–2.5 A/m and 1.3–2.7 A/m, respectively. Furthermore, a characteristic temperature T_ai was obtained to guide the choosing of the annealing temperature at which the dB_s/dT begins to decrease rapidly. Based on the theory of spontaneous magnetization, the relationship between T_ai and the optimum annealing temperature ranges was analyzed. When the annealing temperature was higher than T_ai, the effect of the internal magnetic field generated by spontaneous magnetization on the relaxation behavior was significantly reduced, and the alloys exhibited excellent soft magnetic properties. It is worth indicating that when annealed at 603 K (slightly higher than T_ai), the Fe_82.2 amorphous alloys exhibited excellent and stable soft magnetic properties even if annealed for a long time. The H_c of Fe_82.2B_12.4C_2.8Si_1.8P_0.8 amorphous alloys was only 1.9 A/m when annealed at 603 K for 330 min. This value of T_ai is expected to provide a suggestion for the proper annealing temperature of other amorphous soft magnetic alloys. Full article

(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Progresses in Advanced and Functional Ceramics and Glasses)

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17 pages, 7704 KiB

Open AccessArticle

Effect of PVA Fiber on the Mechanical Properties of Seawater Coral Sand Engineered Cementitious Composites

by Hongwei Han, Gongwen Gao, Yu Li, Dongxu Hou and Yudong Han

Materials 2024, 17(6), 1446; https://doi.org/10.3390/ma17061446 - 21 Mar 2024

Cited by 1 | Viewed by 1115

Abstract

The physical and mechanical characteristics of seawater coral sand engineered cementitious composites (SCECC) were examined through uniaxial compression, three-point bending, and splitting tensile tests. The mechanical properties were scrutinized under varying fiber volume fraction conditions (V = 0%, 0.575%, 1.150%, 1.725%, and 2.300%). [...] Read more.

The physical and mechanical characteristics of seawater coral sand engineered cementitious composites (SCECC) were examined through uniaxial compression, three-point bending, and splitting tensile tests. The mechanical properties were scrutinized under varying fiber volume fraction conditions (V = 0%, 0.575%, 1.150%, 1.725%, and 2.300%). The experimental results indicated that the compressive strength, three-point bending strength, and split tensile strength of SCECC tended to increase with the rise in fiber volume fraction. The strengths attained their maximum values of 45.88, 12.56, and 3.03 MPa when the fiber volume fraction reached 2.300%. In the compression test, the compressive strength of the 7-day specimen can achieve more than 78.50% of that observed in the 28-day specimen. Three-point bending test has revealed that SCECC exhibits favorable strain-hardening and multi-crack cracking characteristics. Fracture patterns of SCECC exhibited variations corresponding to changes in fiber content, as illustrated by their load–deformation curves, the addition of PVA fibers can change the damage mode of cementitious composites from brittle to ductile. The fracture energy of SCECC further attests to its elevated toughness. This is due to the fact that the fibers delay the formation of microcracks and prevent crack expansion, thus significantly increasing the deformability of the material. By verifying its strength, deformability, fracture energy, and other key performance indicators, the feasibility of SCECC in coastal construction projects has been clarified. The successful development of SCECC provides an innovative and high-performance option for the construction of future island projects. Full article

(This article belongs to the Special Issue Multifunctional Cementitious Composites: Manufacturing and Characterization)

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19 pages, 7460 KiB

Open AccessArticle

Influence of Graphene Oxide on Mechanical Properties and Durability of Cement Mortar

by Lounis Djenaoucine, Álvaro Picazo, Miguel Ángel de la Rubia, Amparo Moragues and Jaime C. Gálvez

Materials 2024, 17(6), 1445; https://doi.org/10.3390/ma17061445 - 21 Mar 2024

Viewed by 1312

Abstract

The effect of graphene oxide (GO) on the mechanical strengths and durability of cement composites was researched by preparing GO-modified cement mortars. Thermogravimetric analysis (TGA) and nuclear magnetic resonance (²⁹Si MAS-NMR) were performed on the cement paste to evaluate the influence [...] Read more.

The effect of graphene oxide (GO) on the mechanical strengths and durability of cement composites was researched by preparing GO-modified cement mortars. Thermogravimetric analysis (TGA) and nuclear magnetic resonance (²⁹Si MAS-NMR) were performed on the cement paste to evaluate the influence of GO on the hydration process and chain structure of calcium-silicate-hydrate (C–S–H) gels. TGA revealed that the high GO dosage increased the content of C–S–H by 5.46% compared with the control at 28 days. Similarly, ²⁹Si-NMR improved the hydration degree and main chain length (MCL) in GO-modified samples at 28 days. The GO led to increases of 2.54% and 7.01% in the hydration degree and MCL, respectively, compared with the control at 28 days. These findings underscore the multifaceted role of GO in improving the mechanical properties and durability of cement composites. Mechanical strength tests, such as compressive and flexural tests, were conducted on cement mortars. The optimal dosage of GO increased the compressive strength by 9.02% after 28 days. Furthermore, the flexural strength of cement mortars with the combination of GO and superplasticizer (SP) after 28 days increased by 21.86%, compared with reference mortar. The impact of GO proved to be more pronounced and beneficial in the durability tests, suggesting that GO can enhance the microstructure through hydration products to create a dense and interconnected microstructure. Full article

(This article belongs to the Special Issue Microstructural, Mechanical, and Durability Characteristics of Cementitious Materials (2nd Edition))

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15 pages, 10554 KiB

Open AccessArticle

MOP−18−Derived CuO Fiber for Hybrid Supercapacitor Electrodes

by Syed Fahad Bin Haque, Kenneth J. Balkus, Jr. and John P. Ferraris

Materials 2024, 17(6), 1444; https://doi.org/10.3390/ma17061444 - 21 Mar 2024

Cited by 1 | Viewed by 1463

Abstract

This study explores a simple method of fabricating hybrid supercapacitor electrodes, which could potentially broaden the application of this technology. The method involves electrospinning a uniform solution of Matrimid/Metal−Organic Polyhedra 18 (MOP−18) followed by carbonization at a relatively low temperature of 700 °C [...] Read more.

This study explores a simple method of fabricating hybrid supercapacitor electrodes, which could potentially broaden the application of this technology. The method involves electrospinning a uniform solution of Matrimid/Metal−Organic Polyhedra 18 (MOP−18) followed by carbonization at a relatively low temperature of 700 °C in air, rather than in an inert atmosphere, to create free−standing, redox−active hybrid supercapacitor electrodes. Additionally, the synthesis procedure requires no stabilization or activation steps, which enhances the cost effectiveness of the synthesized electrode materials. The resulting C/CuO composite was used as the working electrode, with a polyacrylonitrile (PAN)/Poly(methyl methacrylate) (PMMA) carbon nanofiber (CNF) electrode as the counter and 6 M KOH as the electrolyte in a T−cell configuration. The cell performance and redox activity were evaluated using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), electrochemical impedance spectroscopy (EIS) and cycling stability tests. Additionally, the physical and chemical structures of the electrode materials were assessed using X−ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron spectroscopy (TEM), X−ray diffractometry (PXRD), surface area analysis and other characterization techniques. The electrode material demonstrated a specific capacitance of up to 206 F/g. Supercapacitors utilizing this material display an energy density of 10.3 Wh/kg (active material) at a current density of 1 A/g in electrochemical testing. Full article

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21 pages, 8587 KiB

Open AccessArticle

Vaporization Phase Transition in Cryogenic Liquid Oxygen Sealing Film on Spiral Groove Faces

by Junjie Chen, Chunhong Ma, Shaoxian Bai and Jing Yang

Materials 2024, 17(6), 1443; https://doi.org/10.3390/ma17061443 - 21 Mar 2024

Viewed by 983

Abstract

The property of vaporization phase transition in liquid oxygen face seals is a key factor affecting the stability of mechanical face seals in many fields, especially under cryogenic conditions. Here, a numerical model based on the saturated vapor pressure is established to investigate [...] Read more.

The property of vaporization phase transition in liquid oxygen face seals is a key factor affecting the stability of mechanical face seals in many fields, especially under cryogenic conditions. Here, a numerical model based on the saturated vapor pressure is established to investigate the vaporization phase transition property of liquid oxygen sealing film. The novelty of this model is to take the influence of heat transfer and face distortions into consideration at the same time. The pressure and temperature distributions as well as face distortions are calculated, and then the property of vaporization phase transition and sealing performance are analyzed. It is found that spiral grooves may lead to the complex film temperature distributions and irregular vaporization distributions. With the increase in seal temperature and decrease in seal pressure, the vaporization area extends from the low-pressure side to the grooves area, and the vaporization rate increases rapidly. The more important thing is that the vaporization often brings a drastic fluctuation and non-monotonic change in opening force. Specifically, with the increase inin seal temperature from 55 K to 140 K, the opening force fluctuates violently, and the fluctuation range is more than 50%, showing an obvious instability. Finally, this study provides a design range of pressure and temperature values for liquid oxygen face seals. In these ranges, this kind of face seals can have a stable operation, which is beneficial to the practice engineering related to the complex properties of sealing fluid. Full article

(This article belongs to the Topic Research on the Mechanical Wear of Gear-Shaped Parts)

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20 pages, 4198 KiB

Open AccessArticle

Effects of Ultrafine Fly Ash against Sulphate Reaction in Concrete Structures

by Demet Demir Şahin and Hasan Eker

Materials 2024, 17(6), 1442; https://doi.org/10.3390/ma17061442 - 21 Mar 2024

Cited by 1 | Viewed by 1157

Abstract

In this study, Afşin Elbistan C-type fly ash (FA) was used, which protects against the sulphate reaction that damages concrete. The detrimental effects of post-reaction decrease with increasing fly ash fineness. The study used 10%, 30%, and 50% weight substitutes of cement. The [...] Read more.

In this study, Afşin Elbistan C-type fly ash (FA) was used, which protects against the sulphate reaction that damages concrete. The detrimental effects of post-reaction decrease with increasing fly ash fineness. The study used 10%, 30%, and 50% weight substitutes of cement. The fly ash was ground in a ball mill for 0, 10, 20, 30, 45, and 60 min, and Blaine fineness values of 1555, 1632, 2347, 2589, 2766, and 3433 cm²/g were obtained, respectively. The effect of the samples on the sulphate resistance was investigated by exposing the samples to 5% or 10% added sulphate solutions, and the compressive strength and ultrasonic pulse velocity of the concrete were tested. The compressive strength values obtained decreased with the increase in sulphate content, and the increase in the grinding time and the amount of substituted FA increased the compressive strength values. It was observed that weight loss increased with increasing sulphate content and decreased with the addition of FA with a high Blaine fineness. It was determined that as the Blaine fineness value increased, the sulphate content, FA substitution amount, and ultrasonic pulse speed decreased. This study was carried out to determine the effects of fly ash used at different fineness and replacement ratios on the performance and strength of concrete after exposure to external influences such as sulphate. The use of fly ash instead of cement will reduce the use of waste materials and natural resources and prevent environmental pollution. The cost of cement and concrete will be reduced. Full article

(This article belongs to the Special Issue New Trends in Sustainable Building Materials)

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13 pages, 9722 KiB

Open AccessArticle

Effect of Secondary Phase on Electroless Ni Plating Behaviour of Super Duplex Stainless Steel SAF2507 for Advanced Li-Ion Battery Case

by Byung-Hyun Shin, Seongjun Kim, Jinyong Park, Jung-Woo Ok, Doo-In Kim, Dohyung Kim and Jang-Hee Yoon

Materials 2024, 17(6), 1441; https://doi.org/10.3390/ma17061441 - 21 Mar 2024

Cited by 5 | Viewed by 1073

Abstract

The development of Li-ion battery cases requires superior electrical conductivity, strength, and corrosion resistance for both cathode and anode to enhance safety and performance. Among the various battery case materials, super duplex stainless steel (SDSS), which is composed of austenite and ferrite as [...] Read more.

The development of Li-ion battery cases requires superior electrical conductivity, strength, and corrosion resistance for both cathode and anode to enhance safety and performance. Among the various battery case materials, super duplex stainless steel (SDSS), which is composed of austenite and ferrite as two-phase stainless steel, exhibits outstanding strength and corrosion resistance. However, stainless steel, which is an iron-based material, tends to have lower electrical conductivity. Nevertheless, nickel-plating SDSS can achieve excellent electrical conductivity, making it suitable for Li-ion battery cases. Therefore, this study analysed the plating behaviour of SDSS plates after nickel plating to leverage their exceptional strength and corrosion resistance. Electroless Ni plating was performed to analyse the plating behaviour, and the plating behaviour was studied with reference to different plating durations. Heat treatment was conducted at 1000 °C for one hour, followed by cooling at 50 °C/s. Post-heat treatment, the analysis of phases was executed using FE-SEM, EDS, and EPMA. Electroless Ni plating was performed at 60–300 s. The plating duration after the heat treatment was up to 300 s, and the behaviour of the materials was observed using FE-SEM. The phase analysis concerning different plating durations was conducted using XRD. Post-heat treatment, the precipitated secondary phases in SAF2507 were identified as Sigma, Chi, and CrN, approximating a 13% distribution. During the electroless Ni plating, the secondary phase exhibited a plating rate equivalent to that of ferrite, entirely plating at around 180 s. Further increments in plating time displayed growth of the plating layer from the austenite direction towards the ferrite, accompanied by a reduced influence from the substrate. Despite the differences in composition, both the secondary phase and austenite demonstrated comparable plating rates, showing that electroless Ni plating on SDSS was primarily influenced by the substrate, a finding which was primarily confirmed through phase analysis. Full article

(This article belongs to the Special Issue Heat Treatment of Metallic Materials in Modern Industry—Volume II)

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14 pages, 6419 KiB

Open AccessEditor’s ChoiceArticle

Tailoring Iridium Valence States on ZSM-5 for Enhanced Catalytic Performance in CO Selective Catalytic Reduction of NO under Oxygen-Enriched Environments

by Yarong Bai, Chuhan Miao, Weilong Ouyang, Lang Wang, Haiqiang Wang and Zhongbiao Wu

Materials 2024, 17(6), 1440; https://doi.org/10.3390/ma17061440 - 21 Mar 2024

Viewed by 1049

Abstract

Barium and iridium supported on Zeolite Socony Mobil-5 (ZSM-5) are efficient catalysts for the selective catalytic reduction of nitric oxide by carbon monoxide (CO-SCR), with enhanced cyclic stability. The introduction of Ba hindered the oxidation of metallic Ir active species and enabled Ir [...] Read more.

Barium and iridium supported on Zeolite Socony Mobil-5 (ZSM-5) are efficient catalysts for the selective catalytic reduction of nitric oxide by carbon monoxide (CO-SCR), with enhanced cyclic stability. The introduction of Ba hindered the oxidation of metallic Ir active species and enabled Ir to maintain an active metallic state, thereby preventing a decrease in catalytic activity in the CO-SCR reaction. Moreover, the Ba modification increased the NO adsorption of the catalyst, further improving the catalytic activity. Owing to the better anti-oxidation ability of Ir⁰ in IrBa0.2/ZSM-5(27) than in Ir/ZSM-5(27), IrBa0.2/ZSM-5(27) showed better stability than Ir/ZSM-5(27). Considering that all samples in the present study were tested to simulate actual flue gases (such as sintering flue gas and coke oven flue gas), NH₃ was introduced into the reaction system to serve as an extra reductant for NO_x. The NO_x conversion to N₂ (77.1%) was substantially improved using the NH₃-CO-SCR system. The proposed catalysts and reaction systems are promising alternatives for treating flue gas, which contains considerable amounts of NO_x and CO in oxygen-enriched environments. Full article

(This article belongs to the Section Catalytic Materials)

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15 pages, 6351 KiB

Open AccessArticle

Exploration of Textile–Silicone Composites and Materials for Personal Impact-Resistant Protection

by Mei-Ki Chan, Pui-Ling Li, Kit-Lun Yick, Joanne Yip and Sun-Pui Ng

Materials 2024, 17(6), 1439; https://doi.org/10.3390/ma17061439 - 21 Mar 2024

Viewed by 1329

Abstract

Conventional cushioning materials such as silicone sheets which have been recommended for resisting impact generally cause discomfort to the wearer from heat and perspiration. With the increasing need for personal protective equipment, textile–silicone composite structures are proposed in this study to reduce acute [...] Read more.

Conventional cushioning materials such as silicone sheets which have been recommended for resisting impact generally cause discomfort to the wearer from heat and perspiration. With the increasing need for personal protective equipment, textile–silicone composite structures are proposed in this study to reduce acute impact and moisture while enhancing thermal comfort. The influence of the composite structure and thickness on the mechanical and thermal properties of textile–silicone materials are systematically investigated. The results show that an additional knitted powernet fabric as a composite material can significantly improve the tensile properties of silicone rubber by up to 315%. However, only a slight improvement is found in the thermal conductivity (up to 16%), compression elasticity (up to 18%) and force reduction performance (up to 3.6%). As compared to inlaid spacer fabric, which has also been used for cushioning and preserving thermal comfort, the textile–silicone composites have higher tensile and compression elasticity, exhibit force reduction with the largest difference of 43% and are more thermally conductive, with increases more than 38%. The findings of this study introduced a cost-effective new silicone–textile composite for optimal impact protection and wear comfort for protective applications. Full article

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

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12 pages, 7962 KiB

Open AccessArticle

Fixed Yellow-to-Blue Intensity Ratio of Dy³⁺ in KY(CO₃)₂ Host for Emission Color Tuning

by Lei Huang, Jian Qian, Shijian Sun and Dechuan Li

Materials 2024, 17(6), 1438; https://doi.org/10.3390/ma17061438 - 21 Mar 2024

Viewed by 861

Abstract

Dy³⁺, Ce³⁺ co-doped KY(CO₃)₂ phosphors with a monoclinic structure were synthesized using the hydrothermal method to create a fixed yellow-to-blue ratio emission. The [YO₈] polyhedron, consisting of a Y atom and eight oxygen atoms, forms [...] Read more.

Dy³⁺, Ce³⁺ co-doped KY(CO₃)₂ phosphors with a monoclinic structure were synthesized using the hydrothermal method to create a fixed yellow-to-blue ratio emission. The [YO₈] polyhedron, consisting of a Y atom and eight oxygen atoms, forms a relatively independent microstructure within the KY(CO₃)₂ host. Y³⁺ ions are partially replaced by Ce³⁺ or Dy³⁺ ions to construct the [CeO₈] or [DyO₈] polyhedral fluorescence emission unit. The spectral measurements indicate that Ce³⁺ and Dy³⁺ can maintain relatively independent fluorescence emission characteristics in the KY(CO₃)₂ host. The yellow-to-blue intensity ratio of Dy³⁺ remains close to 1 and does not change with the variation in the doping concentration of KY(CO₃)₂:Dy³⁺ and KY(CO₃)₂:Dy³⁺,Ce³⁺ phosphors. When Ce³⁺ and Dy³⁺ are co-doped with KY(CO₃)₂, the emission intensities of Dy³⁺ under 339 nm and 365 nm excitation increase by 8.43 and 2.32 times, respectively, through resonance energy transfer and cross-relaxation. All Ce³⁺-doped KY(CO₃)₂:Dy³⁺ phosphors can emit white light. Among them, the emitted light of KY(CO₃)₂:3%Dy³⁺,5%Ce³⁺ is closest to standard daylight. Therefore, a stable [YO₈] polyhedral structure can be used to achieve more color tuning of light. Full article

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

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24 pages, 13388 KiB

Open AccessArticle

Dimensional Characterization and Hybrid Manufacturing of Copper Parts Obtained by Atomic Diffusion Additive Manufacturing, and CNC Machining

by Elena Monzón, Pablo Bordón, Rubén Paz and Mario Monzón

Materials 2024, 17(6), 1437; https://doi.org/10.3390/ma17061437 - 21 Mar 2024

Cited by 1 | Viewed by 1090

Abstract

The combination of Atomic Diffusion Additive Manufacturing (ADAM) and traditional CNC machining allows manufacturers to leverage the advantages of both technologies in the production of functional metal parts. This study presents the methodological development of hybrid manufacturing for solid copper parts, initially produced [...] Read more.

The combination of Atomic Diffusion Additive Manufacturing (ADAM) and traditional CNC machining allows manufacturers to leverage the advantages of both technologies in the production of functional metal parts. This study presents the methodological development of hybrid manufacturing for solid copper parts, initially produced using ADAM technology and subsequently machined using a 5-axis CNC system. The ADAM technology was dimensionally characterized by adapting and manufacturing the seven types of test artifacts standardized by ISO/ASTM 52902:2019. The results showed that slender geometries suffered warpage and detachment during sintering despite complying with the design guidelines. ADAM technology undersizes cylinders and oversizes circular holes and linear lengths. In terms of roughness, the lowest results were obtained for horizontal flat surfaces, while 15° inclined surfaces exhibited the highest roughness due to the stair-stepping effect. The dimensional deviation results for each type of geometry were used to determine the specific and global oversize factors necessary to compensate for major dimensional defects. This also involved generating appropriate over-thicknesses for subsequent CNC machining. The experimental validation of this process, conducted on a validation part, demonstrated final deviations lower than 0.5% with respect to the desired final part, affirming the feasibility of achieving copper parts with a high degree of dimensional accuracy through the hybridization of ADAM and CNC machining technologies. Full article

(This article belongs to the Special Issue Design and Application of Additive Manufacturing: Volume II)

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32 pages, 4547 KiB

Open AccessReview

Modeling of Magnetic Films: A Scientific Perspective

by Denis Misiurev and Vladimír Holcman

Materials 2024, 17(6), 1436; https://doi.org/10.3390/ma17061436 - 21 Mar 2024

Viewed by 1208

Abstract

Magnetic thin-film modeling stands as a dynamic nexus of scientific inquiry and technological advancement, poised at the vanguard of materials science exploration. Leveraging a diverse suite of computational methodologies, including Monte Carlo simulations and molecular dynamics, researchers meticulously dissect the intricate interplay governing [...] Read more.

Magnetic thin-film modeling stands as a dynamic nexus of scientific inquiry and technological advancement, poised at the vanguard of materials science exploration. Leveraging a diverse suite of computational methodologies, including Monte Carlo simulations and molecular dynamics, researchers meticulously dissect the intricate interplay governing magnetism and thin-film growth across heterogeneous substrates. Recent strides, notably in multiscale modeling and machine learning paradigms, have engendered a paradigm shift in predictive capabilities, facilitating a nuanced understanding of thin-film dynamics spanning disparate spatiotemporal regimes. This interdisciplinary synergy, complemented by avantgarde experimental modalities such as in situ microscopy, promises a tapestry of transformative advancements in magnetic materials with far-reaching implications across multifaceted domains including magnetic data storage, spintronics, and magnetic sensing technologies. The confluence of computational modeling and experimental validation heralds a new era of scientific rigor, affording unparalleled insights into the real-time dynamics of magnetic films and bolstering the fidelity of predictive models. As researchers chart an ambitiously uncharted trajectory, the burgeoning realm of magnetic thin-film modeling burgeons with promise, poised to unlock novel paradigms in materials science and engineering. Through this intricate nexus of theoretical elucidation and empirical validation, magnetic thin-film modeling heralds a future replete with innovation, catalyzing a renaissance in technological possibilities across diverse industrial landscapes. Full article

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12 pages, 8384 KiB

Open AccessArticle

Investigation of Mold Flux Entrapment in Deep Oscillation Mark of Interstitial-Free Steel Shell Using Mold Simulator

by Xiong Yan, Wanlin Wang, Lejun Zhou, Xiaocan Zhong, Hongliang Lin, Xiaokang Liu, Sibao Zeng and Liwu Zhang

Materials 2024, 17(6), 1435; https://doi.org/10.3390/ma17061435 - 21 Mar 2024

Viewed by 973

Abstract

The slag entrapment defect has become a big issue for the IF steel casting process. In this study, the mechanism of mold flux entrapment in deep oscillation mark of an IF steel shell was studied by a high-temperature mold simulator. Results show that [...] Read more.

The slag entrapment defect has become a big issue for the IF steel casting process. In this study, the mechanism of mold flux entrapment in deep oscillation mark of an IF steel shell was studied by a high-temperature mold simulator. Results show that both temperature and heat flux in a copper mold become lower when mold flux B with lower melting and viscosity is used, compared with these when mold flux A with higher melting and viscosity is used. The average thickness of the slag film for mold fluxes A and B is 1.31 mm and 1.63 mm, and the consumption of them is 0.33 kg/m² and 0.35 kg/m², respectively. The shell for mold flux A exhibits sharper oscillation marks, while the shell for mold flux B has shallower oscillation marks. These deeper oscillation marks capture the mold flux by overflow of molten steel at the meniscus, which finally produces the slag entrapment defect in the shell. Full article

(This article belongs to the Special Issue Casting and Electromagnetic Treatment of Steel and Metals: Modeling and Simulation)

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21 pages, 14780 KiB

Open AccessArticle

The Influence of an Unsupported Sleeper on the Vertical Bearing Characteristics of Heavy-Haul Railway Ballast

by Dan Liu, Chengguang Su, Dawei Zhang and Caihao Lan

Materials 2024, 17(6), 1434; https://doi.org/10.3390/ma17061434 - 21 Mar 2024

Viewed by 1023

Abstract

In order to study the influence of an unsupported sleeper on the vertical bearing characteristics of heavy-haul railway ballast, a three-dimensional discrete element model (DEM) was established for a ballasted track, by removing ballast particles that come into contact with the bottom of [...] Read more.

In order to study the influence of an unsupported sleeper on the vertical bearing characteristics of heavy-haul railway ballast, a three-dimensional discrete element model (DEM) was established for a ballasted track, by removing ballast particles that come into contact with the bottom of the sleeper from the model to simulate the unsupported sleeper. Vertical bearing characteristics for ballast on different types of unsupported sleepers were studied. The results showed that an unsupported sleeper could reduce the bearing area of the ballast below the sleeper and reduce the number of ballast particles that were in contact. It could also lead to an increase in the maximum contact force between the particles, accelerating the deterioration of the particles (thus affecting the overall performance of the ballast) and reducing the vertical stiffness of the ballast. As the unsupported length and width increased, vertical stiffness gradually decreased. The vertical ballast stiffness for an unsupported sleeper was then used in a dynamic coupled vehicle/track model, and the effect of the unsupported sleeper on wheel/rail interaction was analyzed. Results showed that increasing the unsupported length and width leads to a decrease in the supporting force on the unsupported sleeper and to an increase in the supporting force on the adjacent sleepers. Full article

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

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18 pages, 3365 KiB

Open AccessArticle

Analysis of Selected Properties of Polymer Mixtures Derived from Virgin and Re-Granulated PP with Glass Fibers

by Tomasz Stachowiak, Dariusz Kwiatkowski, Marcin Chmielarz and Dominik Grzesiczak

Materials 2024, 17(6), 1433; https://doi.org/10.3390/ma17061433 - 21 Mar 2024

Cited by 1 | Viewed by 1209

Abstract

The problem of the growing amount of waste polymer materials currently affects virtually every area of the global economy. New actions taken by the E.U. and member states could lead to a reduction in the burden on the natural environment, as well as [...] Read more.

The problem of the growing amount of waste polymer materials currently affects virtually every area of the global economy. New actions taken by the E.U. and member states could lead to a reduction in the burden on the natural environment, as well as the reuse of thermoplastic waste. The aim of this study was to analyze the possibility of reusing post-industrial waste (recycled polypropylene—rPP) in order to produce mixtures with original polypropylene (PP) and glass fibers. The research undertaken is characterized by a high level of innovation and was carried out on an industrial scale from industrial waste. The primary goal of the analyses was to determine changes in the properties of the polymer mixtures depending on the amount of recycled polymers. For this purpose, four types of mixtures were prepared, characterized by different degrees of filling with recycled material obtained from big-bag packaging (the filling levels were 0 wt.%, 20 wt.%, 30 wt.%, and 70 wt.%). A detailed analysis of the physical properties of the obtained mixtures was carried out to determine changes in the densities depending on the amount of rPP material. In addition, changes in the MFIs (melt flow indexes), characterizing viscosity changes, were analyzed depending on the amount of secondary raw material used. An analysis of the mechanical properties was also carried out based on static tensile testing, the impact strength (the Charpy method), and the Rockwell hardness test (the M method). The analysis of the thermal changes was performed using the DSC method. The results showed that the composites made of virgin polypropylene (PP GF30) and those made from re-granulates and glass fibers (rPP GF30) are characterized by similar mechanical properties and significantly different processing properties, determined by MFI. This means that the addition of re-granulates significantly affects the processability of the obtained materials, while the addition of glass fibers maintains the basic mechanical properties. Full article

(This article belongs to the Section Polymeric Materials)

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15 pages, 3178 KiB

Open AccessArticle

Effect of Dentin Irrigants on Push-Out Bond Strength in Resin Cementation Protocols for Fiber Posts in Endodontically Treated Teeth: An In Vitro Study

by Sandra García-Varela, João Carlos Ramos, María José Ginzo-Villamayor, Pablo Castelo-Baz, Ramón Méndez-Díaz, Marcos Aníbal Anache-D’Abate, Tania Gancedo-Gancedo, Manuel Ruíz-Piñón, Soledad Mareque-Bueno and Benjamín José Martín-Biedma

Materials 2024, 17(6), 1432; https://doi.org/10.3390/ma17061432 - 21 Mar 2024

Cited by 1 | Viewed by 1212

Abstract

The aim of this study is to analyze the effects of different endodontic irrigants and adhesive systems on the resin bond strength of fiber post cementation. In total, 144 single-rooted, unrestored human teeth were endodontically treated and randomly divided into 12 groups according [...] Read more.

The aim of this study is to analyze the effects of different endodontic irrigants and adhesive systems on the resin bond strength of fiber post cementation. In total, 144 single-rooted, unrestored human teeth were endodontically treated and randomly divided into 12 groups according to four endodontic irrigants (distilled water as control; EDTA 17%; NaOCl 5%; chlorhexidine digluconate 2%) and three different adhesive/resin cement systems (etch-and-rinse: orthophosphoric acid, Parabond^® A+B/Paracore^®; self-etch: ParaBond^® Non-Rinse Conditioner, Parabond^® A+B/Paracore^®; Universal: Clearfil^TM Universal Bond/Clearfil^TM DC Core Plus). Forty-eight hours after post cementation, ten teeth from each group were cross-sectioned into three discs (cervical, middle and apical regions). Thirty specimens of each group (n = 30) were submitted to a push-out test at a crosshead speed of 1 mm/min. The remaining two teeth of each group were sectioned in the same manner, and the resin–dentin interface was evaluated using scanning electron microscopy (SEM). The results were statistically analyzed with the ANOVA test and Tukey’s test (p < 0,01). The adhesive protocols and post space region showed no significant effect on bond strength (p > 0.01). The combination of NaOCl 5% and ClearfilTM Universal Bond reduced the adhesive strength (p < 0.01). The NaOCl 5%, in relation to other irrigants, significantly decreased the push-out bond strength. Full article

(This article belongs to the Topic Clinical and Experimental Research in Dentistry and Bioactive Materials)

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16 pages, 5040 KiB

Open AccessArticle

Synthesis of Electrolytic Manganese Slag–Solid Waste-Based Geopolymers: Compressive Strength and Mn Immobilization

by Bao Mi, Hui Zhao, Meng Lu, Yi Zhou and Yongjie Xue

Materials 2024, 17(6), 1431; https://doi.org/10.3390/ma17061431 - 21 Mar 2024

Cited by 2 | Viewed by 1189

Abstract

The massive stockpiling of electrolytic manganese residue (EMR) has caused serious environmental pollution. In this study, EMR, coal gangue (CG), and fly ash (FA) were used as raw materials to obtain the optimal mix ratio based on Design-Expert mixture design. The effects of [...] Read more.

The massive stockpiling of electrolytic manganese residue (EMR) has caused serious environmental pollution. In this study, EMR, coal gangue (CG), and fly ash (FA) were used as raw materials to obtain the optimal mix ratio based on Design-Expert mixture design. The effects of activator modulus, liquid–solid (L/S) ratio, and curing temperature on the mechanical properties of geopolymers were investigated. The results showed that the compressive strength of the prepared geopolymer was 12.0 MPa, and the 28d leaching of Mn was 0.123 mg/L under the conditions of EMR:CG:FA = 0.43:0.34:0.23, L/S = 0.9, a curing temperature of 60 °C, and a curing time of 24 h. This indicates that the geopolymer is an environmentally friendly material with high compressive strength. The mineral composition of the geopolymer is mainly hydrated calcium silicate and geopolymer gel. In addition, a more stable new mineral phase, MnSiO₃, was generated. The Fourier transform infrared (FTIR) spectrogram showed that the peak at 1100 m⁻¹ was shifted to 1112 cm⁻¹, which indicated that a geopolymerization reaction had occurred. Through scanning electron microscopy (SEM) and energy dispersive spectrum (EDS) analysis, it was identified that the geopolymerization produced a large amount of amorphous gelatinous substances with a relatively dense structure, the major elements being oxygen, silicon, aluminum, calcium, and sodium. Full article

(This article belongs to the Special Issue Processing of End-of-Life Materials and Industrial Wastes–Volume 2)

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13 pages, 3364 KiB

Open AccessArticle

Research on Performance Improvement of Emulsified Asphalt Mixture Based on Innovative Forming Process

by Ke Xiao, Xin Qu, Yong Jiang, Wenyang Yun, Pengfei Zheng and Weicheng Li

Materials 2024, 17(6), 1430; https://doi.org/10.3390/ma17061430 - 21 Mar 2024

Viewed by 1090

Abstract

Bulk density and porosity have great influence on the technical performance of an emulsified asphalt mixture, so in order to enhance the strength of the asphalt mixture, bulk density should be improved and porosity should be reduced. Considering the forming process of the [...] Read more.

Bulk density and porosity have great influence on the technical performance of an emulsified asphalt mixture, so in order to enhance the strength of the asphalt mixture, bulk density should be improved and porosity should be reduced. Considering the forming process of the emulsified asphalt mixture, the decrease in porosity can ensure the state of the mixture. In order to reduce the porosity of the emulsified asphalt mixture, an innovative forming process is proposed to improve the performance of the emulsified asphalt mixture, and its strength formation mechanism is explored in this paper. Three groups of emulsified asphalt mixtures (ARC-8 + SBR, SMA-5 + EVA, SMA-5 + SBR) were prepared by a conventional mixing process and novel mixing process. Marshall test of the emulsified asphalt mixture, CT scanning test of the emulsified asphalt mixture, workability test and analysis were manufactured and tested. The results show that, compared with conventional methods, the innovative forming method can increase the bulk density of the mixture and reduce the porosity, and thus improve its technical performance. The reason is that most of the water in the mixture of the innovative forming method sticks to the outer surface of the fine aggregate, and the water is more easily discharged. Secondly, the fine aggregate of the innovative forming method is directly mixed with the emulsion, and the volume is smaller. The emulsion wraps the fine aggregate in it due to the surface tension, which enhances the adhesion effect, thus improving the strength of the mixture. Full article

(This article belongs to the Special Issue Sustainable Materials and Structures Used in Pavement Engineering)

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8 pages, 4805 KiB

Open AccessCommunication

Fe_70−xNd₇B₂₁Zr₂Nb_x (x = 0–3.0) Permanent Magnets Produced by Crystallizing Amorphous Precursors

by Yong Gu, Zili Wang, Hui Xu and Zhong Li

Materials 2024, 17(6), 1429; https://doi.org/10.3390/ma17061429 - 20 Mar 2024

Viewed by 1015

Abstract

The phase evolution, magnetic properties and microstructure of rod-shaped permanent magnets prepared by annealing the amorphous precursor Fe_70−xNd₇B₂₁Zr₂Nb_x (x = 0–3.0) were systematically studied. X-ray diffraction analysis, magnetometer, microstructure and δM-plots studies [...] Read more.

The phase evolution, magnetic properties and microstructure of rod-shaped permanent magnets prepared by annealing the amorphous precursor Fe_70−xNd₇B₂₁Zr₂Nb_x (x = 0–3.0) were systematically studied. X-ray diffraction analysis, magnetometer, microstructure and δM-plots studies show that the good magnetic properties of the magnet are attributed to the uniform microstructure composed of exchange-coupled α-Fe and Nd₂Fe₁₄B phases. Nb addition to Fe_67.5Nd₇B₂₁Zr₂Nb_2.5 alloy led to an increase in the volume fraction of the soft magnetic phase, reinforced exchange coupling and improved magnetic properties. The magnetic properties of the optimized annealed Fe_67.5Nd₇B₂₁Zr₂Nb_2.5 rod are: coercivity (H_ci) = 513.92 kA/m, remanence (B_r) = 0.58 T, squareness (H_k/H_ci) = 0.24 and magnetic energy product ((BH)_max) = 37.59 kJ/m³. Full article

(This article belongs to the Section Metals and Alloys)

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12 pages, 8092 KiB

Open AccessEditor’s ChoiceArticle

A Study of the Adsorption Properties of Individual Atoms on the Graphene Surface: Density Functional Theory Calculations Assisted by Machine Learning Techniques

by Jingtao Huang, Mo Chen, Jingteng Xue, Mingwei Li, Yuan Cheng, Zhonghong Lai, Jin Hu, Fei Zhou, Nan Qu, Yong Liu and Jingchuan Zhu

Materials 2024, 17(6), 1428; https://doi.org/10.3390/ma17061428 - 20 Mar 2024

Cited by 1 | Viewed by 1168

Abstract

In this research, the adsorption performance of individual atoms on the surface of monolayer graphene surface was systematically investigated using machine learning methods to accelerate density functional theory. The adsorption behaviors of over thirty different atoms on the graphene surface were computationally analyzed. [...] Read more.

In this research, the adsorption performance of individual atoms on the surface of monolayer graphene surface was systematically investigated using machine learning methods to accelerate density functional theory. The adsorption behaviors of over thirty different atoms on the graphene surface were computationally analyzed. The adsorption energy and distance were extracted as the research targets, and the basic information of atoms (such as atomic radius, ionic radius, etc.) were used as the feature values to establish the dataset. Through feature engineering selection, the corresponding input feature values for the input-output relationship were determined. By comparing different models on the dataset using five-fold cross-validation, the mathematical model that best fits the dataset was identified. The optimal model was further fine-tuned by adjusting of the best mathematical ML model. Subsequently, we verified the accuracy of the established machine learning model. Finally, the precision of the machine learning model forecasts was verified by the method of comparing and contrasting machine learning results with density functional theory. The results suggest that elements such as Zr, Ti, Sc, and Si possess some potential in controlling the interfacial reaction of graphene/aluminum composites. By using machine learning to accelerate first-principles calculations, we have further expanded our choice of research methods and accelerated the pace of studying element–graphene interactions. Full article

(This article belongs to the Special Issue Adsorption Materials and Their Applications)

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14 pages, 16731 KiB

Open AccessArticle

The Influence of the Modification of Carbon Nanotubes on the Properties of Copper Matrix Sintered Materials

by Adam Piasecki, Julia Sobkowiak, Dariusz Boroński, Katarzyna Siwińska-Ciesielczyk and Piotr Paczos

Materials 2024, 17(6), 1427; https://doi.org/10.3390/ma17061427 - 20 Mar 2024

Cited by 1 | Viewed by 1127

Abstract

This paper presents the results of research on the microstructure, mechanical, and tribological properties of Cu/0.5 wt.% MWCNT (multi-walled carbon nanotube) sintered composite materials produced by powder metallurgy. The purpose of this research was to investigate the impact of carbon nanotube modifications on [...] Read more.

This paper presents the results of research on the microstructure, mechanical, and tribological properties of Cu/0.5 wt.% MWCNT (multi-walled carbon nanotube) sintered composite materials produced by powder metallurgy. The purpose of this research was to investigate the impact of carbon nanotube modifications on the uniformity of their dispersion and the effectiveness of their bonding with the matrix. The MWCNTs were modified by chemical oxidation. Additionally, a modification of the ingredient mixing method utilizing ultrasonic frequencies was employed. The tests were carried out using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Vickers hardness tests, static compression tests, and wear tests using the pin-on-disc method. Furthermore, mechanical properties and strain distribution analyses of the micro-specimens were conducted using the Micro-Fatigue System (MFS). The implemented modifications had a positive effect on the dispersion of MWCNTs in the copper matrix and on the mechanical and tribological properties of the sinters. Full article

(This article belongs to the Section Carbon Materials)

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14 pages, 3729 KiB

Open AccessArticle

Antifungal Susceptibility Assessment of Innovative and Non-Conventional Lime Mortars Incorporating Almond-Shell Powder Bio-Waste Subjected to Particle-Dispersion Technique

by Alexandre Jerónimo, Mafalda Loureiro, Mariana Fernandes, Verónica De Zea Bermudez and Ana Briga-Sá

Materials 2024, 17(6), 1426; https://doi.org/10.3390/ma17061426 - 20 Mar 2024

Viewed by 1712

Abstract

A favorable environment for fungi colonization in building materials’ surfaces can emerge when certain hygrothermal conditions occur. Thus, reducing fungal growth susceptibility is of major interest. Furthermore, if the integration of bio-wastes is performed in parallel with the development of innovative materials for [...] Read more.

A favorable environment for fungi colonization in building materials’ surfaces can emerge when certain hygrothermal conditions occur. Thus, reducing fungal growth susceptibility is of major interest. Furthermore, if the integration of bio-wastes is performed in parallel with the development of innovative materials for this purpose, a more sustainable and environmentally friendly material can be obtained. In this study, the fungal susceptibility of lime mortars incorporating almond-shell powder (ASP) microparticles (2 and 4%, wt.–wt. in relation to the binder content) was evaluated. The particle-dispersion technique was employed to prepare the bio-waste introduced in the mixtures. The fungal susceptibility of ASP samples was compared with nanotitania (n-TiO₂) with recognized antifungal properties. Mechanical strength, water absorption, and wettability tests were also performed for a better characterization of the composites. Although the addition of 2% ASP led to mechanical properties reduction, an increase in the compressive and flexural strength resulted for 4% of the ASP content. Difficulties in fungal growth were observed for the samples incorporating ASP. No fungal development was detected in the mortar with 2% of ASP, which may be correlated with an increase in the surface hydrophobic behavior. Furthermore, mortars with ASP revealed a reduction in water absorption by capillarity ability, especially with 4% content, suggesting changes in the microstructure and pore characteristics. The results also demonstrated that an improvement in the physical and mechanical properties of the lime mortars can be achieved when ASP microparticles are previously subjected to dispersion techniques. Full article

(This article belongs to the Special Issue Trends in the Development of Building Materials with Recycled Waste)

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25 pages, 17845 KiB

Open AccessArticle

A Study of 2D Roughness Periodical Profiles on a Flat Surface Generated by Milling with a Ball Nose End Mill

by Mihaita Horodinca, Florin Chifan, Emilian Paduraru, Catalin Gabriel Dumitras, Adriana Munteanu and Dragos-Florin Chitariu

Materials 2024, 17(6), 1425; https://doi.org/10.3390/ma17061425 - 20 Mar 2024

Cited by 1 | Viewed by 968

Abstract

This paper presents a study of 2D roughness profiles on a flat surface generated on a steel workpiece by ball nose end milling with linear equidistant tool paths (pick-intervals). The exploration of the milled surface with a surface roughness tester (on the pick [...] Read more.

This paper presents a study of 2D roughness profiles on a flat surface generated on a steel workpiece by ball nose end milling with linear equidistant tool paths (pick-intervals). The exploration of the milled surface with a surface roughness tester (on the pick and feed directions) produces 2D roughness profiles that usually have periodic evolutions. These evolutions can be considered as time-dependent signals, which can be described as a sum of sinusoidal components (the wavelength of each component is considered as a period). In order to obtain a good approximate description of these sinusoidal components, two suitable signal processing techniques are used in this work: the first technique provides a direct mathematical (analytical) description and is based on computer-aided curve (signal) fitting (more accurate); the second technique (synthetic, less accurate, providing an indirect and incomplete description) is based on the spectrum generated by fast Fourier transform. This study can be seen as a way to better understand the interaction between the tool and the workpiece or to achieve a mathematical characterisation of the machined surface microgeometry in terms of roughness (e.g., its description as a collection of closely spaced 2D roughness profiles) and to characterise the workpiece material in terms of machinability by cutting. Full article

(This article belongs to the Special Issue Cutting Processes for Materials in Manufacturing)

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22 pages, 8759 KiB

Open AccessArticle

Compression–Shear Specimen Stress-State Response and Distribution Characteristics with Wide Stress Triaxiality

by Yiwei Xu, Chunjiang Zhao, Chen Wang, Yunlong Qiu, Xiaosong Zhao, Shaolu Li and Ning Zhao

Materials 2024, 17(6), 1424; https://doi.org/10.3390/ma17061424 - 20 Mar 2024

Viewed by 1326

Abstract

Conventional methods for studying the plastic behavior of materials involve uniaxial tension and uniaxial compression. However, in the metal rolling process, the deformation zone undergoes a complex loading of multidirectional compression and shear. Characterizing the corresponding plastic evolution process online poses challenges, and [...] Read more.

Conventional methods for studying the plastic behavior of materials involve uniaxial tension and uniaxial compression. However, in the metal rolling process, the deformation zone undergoes a complex loading of multidirectional compression and shear. Characterizing the corresponding plastic evolution process online poses challenges, and the existing specimen structures struggle to accurately replicate the deformation-induced loading characteristics. In this study, we aimed to design a compression–shear composite loading specimen that closely mimics the actual processing conditions. The goal was to investigate how the specimen structure influences the stress–strain response in the deformation zone. Using commercial finite element software, a compression–shear composite loading specimen was meticulously designed. Five 304 stainless steel specimens underwent uniaxial compressive loading, with variation angles between the preset notch angle (PNA) of the specimen and compression direction. We employed digital image correlation methods to capture the impact of the PNA on the strain field during compression. Additionally, we aimed to elucidate the plastic response resulting from the stress state of the specimen, particularly in relation to specimen fracture and microstructural evolution. Full article

(This article belongs to the Section Mechanics of Materials)

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35 pages, 4279 KiB

Open AccessReview

Nano-Innovations in Cancer Therapy: The Unparalleled Potential of MXene Conjugates

by Sanjay Kulkarni, Soji Soman, Prerana D. Navti, Amrita Arup Roy, Ajinkya Nitin Nikam, P. Vineeth, Jahnavi Kulkarni, Krishnaraj Somayaji Shirur, Abhijeet Pandey, Sajan D. George and Srinivas Mutalik

Materials 2024, 17(6), 1423; https://doi.org/10.3390/ma17061423 - 20 Mar 2024

Cited by 4 | Viewed by 2220

Abstract

MXenes are two-dimensional transition metal carbides, nitrides, and carbonitrides that have become important materials in nanotechnology because of their remarkable mechanical, electrical, and thermal characteristics. This review emphasizes how crucial MXene conjugates are for several biomedical applications, especially in the field of cancer. [...] Read more.

MXenes are two-dimensional transition metal carbides, nitrides, and carbonitrides that have become important materials in nanotechnology because of their remarkable mechanical, electrical, and thermal characteristics. This review emphasizes how crucial MXene conjugates are for several biomedical applications, especially in the field of cancer. These two-dimensional (2D) nanoconjugates with photothermal, chemotherapeutic, and photodynamic activities have demonstrated promise for highly effective and noninvasive anticancer therapy. MXene conjugates, with their distinctive optical capabilities, have been employed for bioimaging and biosensing, and their excellent light-to-heat conversion efficiency makes them perfect biocompatible and notably proficient nanoscale agents for photothermal applications. The synthesis and characterization of MXenes provide a framework for an in-depth understanding of various fabrication techniques and their importance in the customized formation of MXene conjugates. The following sections explore MXene-based conjugates for nanotheranostics and demonstrate their enormous potential for biomedical applications. Nanoconjugates, such as polymers, metals, graphene, hydrogels, biomimetics, quantum dots, and radio conjugates, exhibit unique properties that can be used for various therapeutic and diagnostic applications in the field of cancer nanotheranostics. An additional layer of understanding into the safety concerns of MXene nanoconjugates is provided by detailing their toxicity viewpoints. Furthermore, the review concludes by addressing the opportunities and challenges in the clinical translation of MXene-based nanoconjugates, emphasizing their potential in real-world medical practices. Full article

(This article belongs to the Special Issue Advances in Nanomaterials for Medical Application, Drug Delivery and Bone Tissue Engineering)

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15 pages, 6598 KiB

Open AccessArticle

Using the Spark Plasma Sintering System for Fabrication of Advanced Semiconductor Materials

by Kamil Kaszyca, Marcin Chmielewski, Bartosz Bucholc, Piotr Błyskun, Fatima Nisar, Jerzy Rojek and Rafał Zybała

Materials 2024, 17(6), 1422; https://doi.org/10.3390/ma17061422 - 20 Mar 2024

Viewed by 1145

Abstract

The interest in the Spark Plasma Sintering (SPS) technique has continuously increased over the last few years. This article shows the possibility of the development of an SPS device used for material processing and synthesis in both scientific and industrial applications and aims [...] Read more.

The interest in the Spark Plasma Sintering (SPS) technique has continuously increased over the last few years. This article shows the possibility of the development of an SPS device used for material processing and synthesis in both scientific and industrial applications and aims to present manufacturing methods and the versatility of an SPS device, presenting examples of processing Arc-Melted- (half-Heusler, cobalt triantimonide) and Self-propagating High-temperature Synthesis (SHS)-synthesized semiconductor (bismuth telluride) materials. The SPS system functionality development is presented, the purpose of which was to broaden the knowledge of the nature of SPS processes. This approach enabled the precise design of material sintering processes and also contributed to increasing the repeatability and accuracy of sintering conditions. Full article

(This article belongs to the Special Issue Functional Materials Sintered by FAST/SPS—From Research to Industry)

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15 pages, 3405 KiB

Open AccessArticle

Valorization of Agro-Wastes as Fillers in PLA-Based Biocomposites for Increasing Sustainability in Fused Deposition Modeling Additive Manufacturing

by Niccolò Giani, Emanuele Maccaferri, Tiziana Benelli, Marco Bovo, Daniele Torreggiani, Enrico Gianfranco Campari, Patrizia Tassinari, Loris Giorgini and Laura Mazzocchetti

Materials 2024, 17(6), 1421; https://doi.org/10.3390/ma17061421 - 20 Mar 2024

Cited by 2 | Viewed by 1212

Abstract

The use of wheat middlings (WM) and rice husks (RH) as biofillers for mixing with poly(lactic acid) (PLA) matrix to produce new 3D-printable biocomposites was assessed. Filaments containing 10 and 20 wt.% agro-waste-derived biofillers were manufactured and, for the sake of comparison, filaments [...] Read more.

The use of wheat middlings (WM) and rice husks (RH) as biofillers for mixing with poly(lactic acid) (PLA) matrix to produce new 3D-printable biocomposites was assessed. Filaments containing 10 and 20 wt.% agro-waste-derived biofillers were manufactured and, for the sake of comparison, filaments of neat PLA were also produced. The obtained filaments were characterized via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), showing potential for further application in additive manufacturing processing. Three-dimensionally printed specimens were thus produced and characterized via: DSC, also evaluating the specific heat capacity (CP) of specific 3D-printed specimens; dynamic mechanical analysis (DMA), also applied for determining the coefficient of linear thermal expansion (CLTE) measured on 3D-printed specimens in two different directions (X and Y); and tensile tests. The latter testing campaign was carried out along three printing directions (X, Y, and Z axes) to test the intrinsic biocomposite features (X-printed samples) as well as interbead and interlayer adhesion (Y- and Z-printed specimens, respectively). All samples demonstrated acceptable properties. The inclusion of a cost-free natural material leads to a strong reduction of the whole material cost. Implementing this new class of composite material to an additive manufacturing technique can significantly reduce the environmental impact of 3D-printed products. Full article

(This article belongs to the Special Issue Additive Manufacturing of Smart Polymers and Composites)

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