Materials

10 pages, 14826 KiB

Open AccessArticle

Osteoblast Growth in Quaternized Silicon Carbon Nitride Coatings for Dental Implants

by Haochen Zhu, Xinyi Xia, Chao-Ching Chiang, Rachael S. Watson Levings, Justin Correa, Fernanda Regina Godoy Rocha, Steve C. Ghivizzani, Fan Ren, Dan Neal, Patricia dos Santos Calderon and Josephine F. Esquivel-Upshaw

Materials 2024, 17(21), 5392; https://doi.org/10.3390/ma17215392 - 4 Nov 2024

Viewed by 450

Abstract

The demand for dental implants has increased, establishing them as the standard of care for replacing missing teeth. Several factors contribute to the success or failure of an implant post-placement. Modifications to implant surfaces can enhance the biological interactions between bone cells and [...] Read more.

The demand for dental implants has increased, establishing them as the standard of care for replacing missing teeth. Several factors contribute to the success or failure of an implant post-placement. Modifications to implant surfaces can enhance the biological interactions between bone cells and the implant, promoting better outcomes. Surface coatings have been developed to electrochemically alter implant surfaces, aiming to reduce healing time, enhance bone growth, and prevent bacterial adhesion. Quaternized silicon carbon nitride (QSiCN) is a novel material with unique electrochemical and biological properties. This study aimed to assess the influence of QSiCN, silicon carbide nitride (SiCN), and silicon carbide (SiC) coatings on the viability of osteoblast cells on nanostructured titanium surfaces. The experiment utilized thirty-two titanium sheets with anodized TiO₂ nanotubes featuring nanotube diameters of 50 nm and 150 nm. These sheets were divided into eight groups (n = 4): QSiCN-coated 50 nm, QSiCN-coated 150 nm, SiCN-coated 50 nm, SiCN-coated 150 nm, SiC-coated 50 nm, SiC-coated 150 nm, non-coated 50 nm, and non-coated 150 nm. Preosteoblast MC3T3-E1 Subclone 4 cells (ATCC, USA) were used to evaluate osteoblast viability. After three days of cell growth, samples were assessed using scanning electron microscopy (SEM). The results indicated that QSiCN coatings significantly increased osteoblast proliferation (p < 0.005) compared to other groups. The enhanced cell adhesion observed with QSiCN coatings is likely due to the positive surface charge imparted by N⁺. Full article

(This article belongs to the Special Issue Materials for Hard Tissue Repair and Regeneration (Third Edition))

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11 pages, 2751 KiB

Open AccessArticle

Study on Welding Characteristics and Parameters of Gas Metal Arc Welding for A516 Grade 70 Steel with ER70S-6 and ER308LSi Filler Materials

by Kahwai Chong, Ervina Efzan Mhd Noor, Amalina Amir and Mirza Farrukh Baig

Materials 2024, 17(21), 5391; https://doi.org/10.3390/ma17215391 - 4 Nov 2024

Viewed by 572

Abstract

Welding is a crucial process in joining metals, especially in the fabrication industry. Thisresearch aimed to investigate the effects of using two different filler materials, ER70S-6 and ER308LSi, with nine combinations of wire feeder speed (WFS) and shielding gas flow rate (GFR), on [...] Read more.

Welding is a crucial process in joining metals, especially in the fabrication industry. Thisresearch aimed to investigate the effects of using two different filler materials, ER70S-6 and ER308LSi, with nine combinations of wire feeder speed (WFS) and shielding gas flow rate (GFR), on weld joints. The study focused on the weld quality and material properties of Gas Metal Arc Welded (GMAW) butt joints of ASTM A516 G70 plates, characterized through visual inspection, liquid penetrant testing, tensile testing, hardness testing, and optical microscopy. Results indicated that the highest ultimate tensile strength and hardness were achieved at 4 m/min WFS and 15 L/min GFR with ER70S-6, and 5 m/min WFS and 20 L/min GFR with ER308LSi. The specimens welded with ER308LSi demonstrated superior mechanical properties compared to those welded with ER70S-6. Additionally, the study revealed the influence of microstructural changes from the base metal (BM) to the heat-affected zone (HAZ) and fusion zone (FZ), with finer and more compact grain structures contributing to higher hardness values. These findings underscore the importance of selecting appropriate filler materials, WFS, and GFR to achieve the desired weld quality and material properties for A516 G70 low-carbon steel welded joints. Full article

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21 pages, 8600 KiB

Open AccessArticle

Influence of Detonation Spraying Parameters on the Microstructure and Mechanical Properties of Hydroxyapatite Coatings

by Zhuldyz Sagdoldina, Marcin Kot, Daryn Baizhan, Dastan Buitkenov and Laila Sulyubayeva

Materials 2024, 17(21), 5390; https://doi.org/10.3390/ma17215390 - 4 Nov 2024

Viewed by 537

Abstract

The process of osteointegration depends significantly on the surface roughness, structure, chemical composition, and mechanical characteristics of the coating. In this regard, an important direction in the development of medical materials is the development of new techniques of surface modification and the creation [...] Read more.

The process of osteointegration depends significantly on the surface roughness, structure, chemical composition, and mechanical characteristics of the coating. In this regard, an important direction in the development of medical materials is the development of new techniques of surface modification and the creation of bioactive ceramic coatings. Calcium-phosphate materials based on hydroxyapatite have been proposed as bioactive ceramic coatings on titanium implants for the effective acceleration of bone tissue healing. To obtain bioactive ceramic coatings, pulse power sources are best suited, namely detonation spraying, in which the energy of the explosion of gas mixtures is used as a source of pulse action. The pulse mode of operation in the detonation spraying method is preferable for the formation of bioactive ceramic coatings. It provides a high velocity of hydroxyapatite particles, which promotes their effective fixation on the titanium substrate, while minimizing the heating of the material. This approach preserves the substrate structure and improves the coating adhesion. Four different types of coatings with varying O₂/C₂H₂ molar ratios, ranging from 2.6 to 3.7, were obtained using detonation spraying. Powders and obtained coatings of hydroxyapatite were studied by Raman spectroscopy and XRD structural analysis. The results of XRD phase analysis showed the partial conversion of the hydroxyapatite phase to the α-tricalcium phosphate (α-TCP) phase during the detonation spraying process. The results obtained by Raman spectroscopy indicate that hydroxyapatite is the main phase in coatings. All hydroxyapatite-based coatings exhibited hydrophobic properties, which was confirmed by contact-angle values above 90° in wettability tests, characteristic of hydrophobic surfaces. The adhesive strength of the coatings was measured by the scratch test method. Tribological tests were conducted using the ball-on-disk method under both dry conditions and in Ringer’s solution. This approach enabled the evaluation of wear resistance and friction coefficient of the coatings in different environments, simulating both lubrication-free conditions and those resembling physiological environments. Full article

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

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21 pages, 5933 KiB

Open AccessArticle

Adsorption of Lufenuron 50-EC Pesticide from Aqueous Solution Using Oil Palm Shell-Derived Activated Carbon

by David Nuñez, Juan Barraza, Juan Guerrero, Luis Díaz, Ajay K. Dalai and Venu Babu Borugadda

Materials 2024, 17(21), 5389; https://doi.org/10.3390/ma17215389 - 4 Nov 2024

Viewed by 505

Abstract

The use of Lufenuron 50-EC pesticide in oil palm crops affects water quality and aquatic life. This study investigated the adsorption of Lufenuron 50-EC from an aqueous solution using activated carbon derived from oil palm shells (OPSs). Activated carbon (AC) was prepared through [...] Read more.

The use of Lufenuron 50-EC pesticide in oil palm crops affects water quality and aquatic life. This study investigated the adsorption of Lufenuron 50-EC from an aqueous solution using activated carbon derived from oil palm shells (OPSs). Activated carbon (AC) was prepared through physical and chemical activation processes in carbon dioxide environments, using potassium hydroxide (KOH) as a chemical activating agent. The resulting AC was characterized using standard techniques. The most favorable operating parameters were physical activation at 900 °C for 2 h, achieving a BET surface area of 548 m²/g. For chemical activation, at 800 °C, 1 h, and an impregnation ratio (KOH/biochar) of 2:1 (w/w), a BET surface area of 90 m²/g was obtained, which was smaller than that achieved by physical activation. The use of KOH reduced the surface area but generated a high presence of functional groups on the AC surface, which is important for adsorption processes. The AC produced achieved high Lufenuron adsorption yields, reaching a maximum of 96.93%. AC produced at 900 °C with 2 h showed the best performance. Therefore, OPS is an excellent precursor for producing AC with favorable characteristics for pollutant adsorption in aqueous solutions, especially for the insecticide Lufenuron. Full article

(This article belongs to the Section Biomaterials)

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26 pages, 10736 KiB

Open AccessArticle

Experimental Evaluation of Under Slab Mats (USMs) Made from End-of-Life Tires for Ballastless Tram Track Applications

by Cezary Kraśkiewicz, Piotr Majnert, Anna Al Sabouni-Zawadzka, Przemysław Mossakowski and Marcin Zarzycki

Materials 2024, 17(21), 5388; https://doi.org/10.3390/ma17215388 - 4 Nov 2024

Viewed by 468

Abstract

The growing population of urban areas results in the need to deal with the noise pollution from the transportation system. This study presents experimental test results of static and dynamic elastic characteristics of under slab mats (USMs) according to the procedure of DIN [...] Read more.

The growing population of urban areas results in the need to deal with the noise pollution from the transportation system. This study presents experimental test results of static and dynamic elastic characteristics of under slab mats (USMs) according to the procedure of DIN 45673-7. Prototype USMs based on recycled elastomeric materials, i.e., SBR granules and fibres produced from waste car tires, are analysed. Vibration isolation mats with different thicknesses (10, 15, 20, 25, 30, and 40 mm), densities (500 and 600 kg/m³), and different degrees of space filling (no holes, medium holes, large holes) are considered. Moreover, a practical application of the laboratory test results of USMs in the design of ballastless track structures of two different types (with a concrete slab and longitudinal beams) is presented. Deflections of the rail and the floating slab system, as well as stresses acting on the mat, are determined according to EN 16432-2. The use of shredded rubber from recycled car tires as a material component of sustainable and environmentally friendly tram track structures may be one of the most effective ways to manage rubber waste within the current trend toward a circular economy, and this study intends to introduce methods for experimental identification and analytical selection of basic static and dynamic parameters of prototype USMs. Full article

(This article belongs to the Special Issue Advance in Sustainable Construction and Building Materials (2nd Edition))

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31 pages, 10630 KiB

Open AccessArticle

Fracture Toughness of Ordinary Plain Concrete Under Three-Point Bending Based on Double-K and Boundary Effect Fracture Models

by Huating Chen, Yifan Zhuo, Dewang Li and Yan Huang

Materials 2024, 17(21), 5387; https://doi.org/10.3390/ma17215387 - 4 Nov 2024

Viewed by 409

Abstract

Fracture tests are a necessary means to obtain the fracture properties of concrete, which are crucial material parameters for the fracture analysis of concrete structures. This study aims to fill the gap of insufficient test results on the fracture toughness of widely used [...] Read more.

Fracture tests are a necessary means to obtain the fracture properties of concrete, which are crucial material parameters for the fracture analysis of concrete structures. This study aims to fill the gap of insufficient test results on the fracture toughness of widely used ordinary C40~C60 concrete. A three-point bending fracture test was conducted on 28 plain concrete and 6 reinforced concrete single-edge notched beam specimens with various depths of prefabricated notches. The results are reported, including the failure pattern, crack initiation load, peak load, and complete load versus crack mouth opening displacement curves. The cracking load showed significant variation due to differences in notch prefabrication and aggregate distribution, while the peak load decreased nonlinearly with an increase in the notch-to-height ratio. The reinforced concrete beams showed a significantly higher peak load than the plain concrete beams, attributed to the restraint of steel reinforcement, but the measured cracking load was comparable. A compliance versus notch-to-height ratio curve was derived for future applications, such as estimating crack length in crack growth rate tests. Finally, fracture toughness was determined based on the double-K fracture model and the boundary effect model. The average fracture toughness value for C50 concrete from this study was 2.0

M P a \cdot \sqrt{m}

, slightly smaller than that of lower-strength concrete, indicating the strength and ductility dependency of concrete fracture toughness. The fracture toughness calculated from the two models is consistent, and both methods employ a closed-form solution and are practical to use. The derived fracture toughness was insensitive to the discrete parameters in the boundary effect model. The insights gained from this study significantly contribute to our understanding of the fracture toughness properties of ordinary structural concrete, highlighting its potential to shape future studies and applications in the field. Full article

(This article belongs to the Special Issue Mechanical Research of Reinforced Concrete Materials (2nd Edition))

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20 pages, 11517 KiB

Open AccessArticle

Study on Springback Behavior in Hydroforming of Micro Channels for a Metal Bipolar Plate

by Zonghui Su, Wenlong Xie, Yong Xu, Changsheng Li, Liangliang Xia, Baocheng Yang, Mingyu Gao, Hongwu Song and Shihong Zhang

Materials 2024, 17(21), 5386; https://doi.org/10.3390/ma17215386 - 4 Nov 2024

Viewed by 532

Abstract

Bipolar plates are one of the most important components of proton exchange membrane fuel cells. With the miniaturization of bipolar plate flow channel sizes and the increasing demand for precision, springback has become a key focus of research in the bipolar plate forming [...] Read more.

Bipolar plates are one of the most important components of proton exchange membrane fuel cells. With the miniaturization of bipolar plate flow channel sizes and the increasing demand for precision, springback has become a key focus of research in the bipolar plate forming process. In this paper, the hydroforming process for 316L stainless steel bipolar plates was studied, and an FEM model was built to examine the stress and strain at various locations on the longitudinal section of the plate. Modeling accuracy was validated by the comparison of experimental profile and thickness distribution. The effects of forming pressure and grain size on springback behavior are discussed. The results show that with increasing forming pressure, the springback value decreases initially, followed by an increase, but then again decreases. When the forming pressure is 80 MPa–100 MPa, the deformation of the lower element of the upper rounded corner is not uniform with more elastic regions, and the springback is positively correlated with forming pressure. The springback distribution pattern on the cross-section of the bipolar plate changes from a normal distribution to a distribution of “M” shape with increased pressure. The larger the grain size, the lower the yield strength elastic proportion, resulting in a decrease in springback of the sheet. The maximum amount of springback of the bipolar plate is 3.1 μm when the grain size is 60.7 μm. The research results provide a reference for improving the forming quality of metal bipolar plates with different flow channel shapes. Full article

(This article belongs to the Special Issue Advanced Materials, Machinability and Intelligent Manufacturing Systems)

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11 pages, 3623 KiB

Open AccessArticle

Hybrid Functional ITO/Silver Nanowire Transparent Conductive Electrodes for Enhanced Output Efficiency of Ultraviolet GaN-Based Light-Emitting Diodes

by Munsik Oh, Mun Seok Jeong, Jaehee Cho and Hyunsoo Kim

Materials 2024, 17(21), 5385; https://doi.org/10.3390/ma17215385 - 4 Nov 2024

Viewed by 478

Abstract

We investigated hybrid functional transparent conductive electrodes (HFTCEs) composed of indium-tin-oxide (ITO) and silver nanowires (AgNWs) for the enhancement of output efficiency in GaN-based ultraviolet light-emitting diodes (UVLEDs). The HFTCEs demonstrated an optical transmittance of 69.5% at a wavelength of 380 nm and [...] Read more.

We investigated hybrid functional transparent conductive electrodes (HFTCEs) composed of indium-tin-oxide (ITO) and silver nanowires (AgNWs) for the enhancement of output efficiency in GaN-based ultraviolet light-emitting diodes (UVLEDs). The HFTCEs demonstrated an optical transmittance of 69.5% at a wavelength of 380 nm and a sheet resistance of 16.4 Ω/sq, while the reference ITO TCE exhibited a transmittance of 76.4% and a sheet resistance of 18.7 Ω/sq. Despite the 8.9% lower optical transmittance, the UVLEDs fabricated with HFTCEs achieved a 25% increase in output efficiency compared to reference UVLEDs. This improvement is attributed to the HFTCE’s twofold longer current spreading length under operating forward voltages, and more significantly, the enhanced out-coupling of localized surface plasmon (LSP) resonance with the trapped wave-guided light modes. Full article

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15 pages, 4033 KiB

Open AccessArticle

In Vivo and In Vitro Response to a Regenerative Dental Scaffold

by Maree L. Gould, Xiaoxuan Deng, Karl Lyons and Azam Ali

Materials 2024, 17(21), 5384; https://doi.org/10.3390/ma17215384 - 4 Nov 2024

Viewed by 437

Abstract

As dental pulp contains the stem cells necessary for regeneration, the tooth should hold the intrinsic capacity for self-repair. A triphasic hybrid dental biocomposite (3HB) composed of biocompatible biopolymers to provide strength, antibacterial properties and protein-based cell support could provide a conducive microenvironment [...] Read more.

As dental pulp contains the stem cells necessary for regeneration, the tooth should hold the intrinsic capacity for self-repair. A triphasic hybrid dental biocomposite (3HB) composed of biocompatible biopolymers to provide strength, antibacterial properties and protein-based cell support could provide a conducive microenvironment for the regeneration of dental structures. 3HB was incorporated into Mineral Trioxide Aggregate (ProRoot MTA) to construct a malleable injectable implant. Human tooth pulp cells (hDPCs) significantly increased proliferation in the presence of 3HB+MTA compared to 3HB or MTA alone. Cell viability decreased with MTA alone but increased with 3HB and 3HB+MTA. 3HB+MTA was implanted into the residual tooth of drilled Wistar rat M2 molars for up to 45 days. Stereological analysis from micro-CT images showed the volume of the tooth remaining. Histologically, regenerative pulpal architecture was seen invading 3HB. A continuous odontoblastic profile lined a deposit of dentin-like material suggesting reparative dentinogenesis. Overall, no infection or encapsulation was seen. Immunohistochemically, odontoblasts were seen along the margins of the wounded tooth undergoing repair. Mesenchymal cells (MSCs) were seen at the base of the drilled tooth and by 21 days had translocated into the implant itself. Cells stimulating remineralization were highly expressed in the tooth undergoing repair. CD146-positive MSCs were seen in the center of the implant, possibly stimulating remineralization. In conclusion, behavior of 3HB⁺ in vitro and in vivo provided a promising start as 3HB+MTA may serve as a viable regenerative scaffold for pulp regeneration; however, this should be further studied before clinical use can be considered. Full article

(This article belongs to the Special Issue Advances in Implant Materials and Biocompatibility)

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35 pages, 2178 KiB

Open AccessReview

Review of the Anti-Candida albicans Activity and Physical Properties of Soft Lining Materials Modified with Polyene Antibiotics, Azole Drugs, and Chlorohexidine Salts

by Izabela Barszczewska-Rybarek, Patrycja Kula and Grzegorz Chladek

Materials 2024, 17(21), 5383; https://doi.org/10.3390/ma17215383 - 4 Nov 2024

Viewed by 755

Abstract

This review examined the current state of knowledge on the modifications of commercial soft lining materials (SLMs) with a variety of antifungal compounds: (i) polyene antibiotics, including nystatin and amphotericin B, (ii) azole drugs, including fluconazole, itraconazole, clotrimazole, ketoconazole, and miconazole, and (iii) [...] Read more.

This review examined the current state of knowledge on the modifications of commercial soft lining materials (SLMs) with a variety of antifungal compounds: (i) polyene antibiotics, including nystatin and amphotericin B, (ii) azole drugs, including fluconazole, itraconazole, clotrimazole, ketoconazole, and miconazole, and (iii) antiseptics, including chlorhexidine salts to give them anti-Candida albicans properties. The effect of such modifications on the SLMs’ physical properties, such as drug release, water sorption, surface properties, bond strength, tensile strength, and hardness, was also analyzed. In effect, this study provided a unique compilation of research results obtained for numerous properties of SLM modified with antifungal compounds that differ in their chemical structure and mechanism of antifungal action. These results might also be useful for prosthetic dentistry, where SLMs are used to prevent and treat candidiasis, the most common disease among denture wearers. Full article

(This article belongs to the Special Issue Novel Antimicrobial Polymers: Synthesis, Properties and Applications)

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16 pages, 9230 KiB

Open AccessArticle

Influence of Reclaimed Water on the Visual Quality of Automotive Coating

by Piotr Woźniak and Marek Gryta

Materials 2024, 17(21), 5382; https://doi.org/10.3390/ma17215382 - 4 Nov 2024

Viewed by 522

Abstract

In the present study, the possibility of recovering water in a car wash station was presented. The resistance of automotive coatings to washing water recovered at 50% and 70% from wastewater generated at car wash was tested. Wastewater treatment was carried out by [...] Read more.

In the present study, the possibility of recovering water in a car wash station was presented. The resistance of automotive coatings to washing water recovered at 50% and 70% from wastewater generated at car wash was tested. Wastewater treatment was carried out by ultrafiltration (UF) using tubular polyvinylidene fluoride (PVDF) membranes (100 and 200 kDa) manufactured by the PCI company. The membranes retained oil contamination, suspended solids, and over 60% of surfactants. For comparison, the 0.5% Turbo Active Green solution, used at professional car washes, was also applied in paint resistance studies. The tested solutions washed the painted surfaces of samples taken from car doors for 8 days. The resistance of automotive coatings to washing solutions was assessed by measuring gloss, Log Haze, RIQ, and Rspec parameters. Scratch resistance was also assessed. The results obtained in the current study indicated that the use of water recovered from wastewater did not deteriorate the quality of the car paint coating. Full article

(This article belongs to the Special Issue Sustainable Materials for Engineering Applications)

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31 pages, 16794 KiB

Open AccessArticle

Effective Concrete Failure Area for SC Structures Using Stud and Tie Bar Under Performance Tests

by Yeongun Kim and Byong J. Choi

Materials 2024, 17(21), 5381; https://doi.org/10.3390/ma17215381 - 4 Nov 2024

Viewed by 608

Abstract

Nuclear power plants, where steel-plate concrete (SC) structures are commonly adopted, require large-scale components to withstand significant loads, such as those caused by sudden explosions. As a result, SC modular members used in nuclear power plants must have thicker walls filled with concrete [...] Read more.

Nuclear power plants, where steel-plate concrete (SC) structures are commonly adopted, require large-scale components to withstand significant loads, such as those caused by sudden explosions. As a result, SC modular members used in nuclear power plants must have thicker walls filled with concrete compared to standard-sized ones. These large walls also require additional components, such as tie bars and H-shaped steel sections, to reinforce adhesion and resist shear stresses. This study focuses on tie bars placed adjacent to studs and evaluates their influence on the tensile strength of wall structures. To investigate this, we conducted experimental tests using full-scale specimens, including various combinations ranging from single stud to combined stud-tie configurations. Based on the results of these performance tests, we propose a design recommendation for estimating the tensile capacity of SC structures, considering the influence of tie bars. Full article

(This article belongs to the Special Issue New Findings in Cementitious Materials (2nd Edition))

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15 pages, 5543 KiB

Open AccessArticle

Low-Velocity Impact Behaviour of Titanium-Based Carbon-Fibre/Epoxy Laminate

by Jing Sun, Weilin Chen, Hongjie Luo, Xingfang Xie, Jingzhou Zhang and Chao Ding

Materials 2024, 17(21), 5380; https://doi.org/10.3390/ma17215380 - 4 Nov 2024

Viewed by 462

Abstract

This study investigated the low-velocity impact response of titanium-based carbon-fibre/epoxy laminate (TI-CF FML). A comprehensive experimental study was carried out with impact energies ranging from 16.9 J to 91.9 J. Finite element analysis, performed using ABAQUS, was employed to elucidate the failure mechanisms [...] Read more.

This study investigated the low-velocity impact response of titanium-based carbon-fibre/epoxy laminate (TI-CF FML). A comprehensive experimental study was carried out with impact energies ranging from 16.9 J to 91.9 J. Finite element analysis, performed using ABAQUS, was employed to elucidate the failure mechanisms of the laminate. Three distinct damage modes were identified based on the impact energy levels. The energy absorption characteristics of the TI-CF FML were analysed, revealing that maximum energy absorption is achieved and remains constant after penetration occurs. The relationship between impact force and displacement was also explored, showing that the laminate can withstand a peak force of 13.1 kN. The research on the impact resistance, damage mechanisms and energy absorption capacity of TI-CF FML provides an in-depth understanding of the impact behaviour of the laminate and its suitability for various industrial applications. Full article

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30 pages, 20096 KiB

Open AccessReview

Core–Sheath Fibers via Single-Nozzle Spinneret Electrospinning of Emulsions and Homogeneous Blend Solutions

by Selin Kyuchyuk, Dilyana Paneva, Nevena Manolova and Iliya Rashkov

Materials 2024, 17(21), 5379; https://doi.org/10.3390/ma17215379 - 4 Nov 2024

Viewed by 708

Abstract

The preparation of core–sheath fibers by electrospinning is a topic of significant interest for producing composite fibers with distinct core and sheath functionalities. Moreover, in core–sheath fibers, low-molecular-weight substances or nanosized inorganic additives can be deposited in a targeted manner within the core [...] Read more.

The preparation of core–sheath fibers by electrospinning is a topic of significant interest for producing composite fibers with distinct core and sheath functionalities. Moreover, in core–sheath fibers, low-molecular-weight substances or nanosized inorganic additives can be deposited in a targeted manner within the core or the sheath. Commonly, for obtaining a core–sheath structure, coaxial electrospinning is used. It requires a coaxial spinneret and suitable immiscible solvents for the inner and outer solutions. The single-nozzle spinneret electrospinning of emulsions can address these issues, but use of a stabilizing agent is needed. A third approach—preparation of core–sheath fibers by single-nozzle spinneret electrospinning of homogeneous blend solutions of two polymers or of a polymer/low-molecular-weight substance—has been much less studied. It circumvents the difficulties associated with the coaxial and the emulsion electrospinning and is thoroughly discussed in this review. The formation of core–sheath fibers in this case is attributed to phase-separation-driven self-organization during the electrospinning process. Some possibilities for obtaining core–double sheath fibers using the same method are also indicated. The gained knowledge on potential applications of core–sheath fibers prepared by single-nozzle spinneret electrospinning of emulsions and homogeneous blend solutions is also discussed. Full article

(This article belongs to the Special Issue Design and Development of Polymer-Based Drug Carriers for Biomedical Applications)

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15 pages, 1249 KiB

Open AccessArticle

Physical–Mechanical Properties and Mineral Deposition of a Pit-and-Fissure Sealant Containing Niobium–Fluoride Nanoparticles—An In Vitro Study

by Alyssa Teixeira Obeid, Tatiana Rita de Lima Nascimento, Carlos Alberto Spironelli Ramos, Rafael Francisco Lia Mondelli, Alessandra Nara de Souza Rastelli, Abdulaziz Alhotan, Marilia Mattar de Amoêdo Campos Velo and Juliana Fraga Soares Bombonatti

Materials 2024, 17(21), 5378; https://doi.org/10.3390/ma17215378 - 4 Nov 2024

Viewed by 734

Abstract

This study investigated the combined effects of adding niobium–fluoride (NbF₅) nanoparticles to a pit-and-fissure sealant. One resin sealant was reinforced with varying amounts of nanoparticles (0.3, 0.6, and 0.9 wt%). The surface hardness (SH), energy-dispersive X-ray spectroscopy (EDX), surface roughness (Ra), [...] Read more.

This study investigated the combined effects of adding niobium–fluoride (NbF₅) nanoparticles to a pit-and-fissure sealant. One resin sealant was reinforced with varying amounts of nanoparticles (0.3, 0.6, and 0.9 wt%). The surface hardness (SH), energy-dispersive X-ray spectroscopy (EDX), surface roughness (Ra), color change (ΔE), and mineral deposition were assessed. Bovine enamel blocks were subjected to demineralization and pH-cycling for SH. The elemental composition and Ca/P ratio were evaluated using EDX, while the mineral deposition was measured using Fourier transform infrared spectroscopy (FTIR). Data were analyzed using ANOVA and Tukey’s test for the SH and EDX, ΔE, and Kruskal–Wallis for the Ra. The NbF₅ modification increased the SH, with the 0.9 wt% sealant exhibiting higher SH values, and the 0.3 wt% one exhibiting significant differences compared to the control and the 0.9 wt% (p = 0.00) samples, even after pH-cycling. For the EDX analysis, the 0.3 and 0.6 wt% samples exhibited higher Ca/P ratios, with the 0.3% one showing evidence of P-O crystal formation. There was no significant difference in the Ra (p = 0.458), and the 0.6 and 0.9 wt% ones showed lower ΔE values compared to the control. The 0.3 wt% NbF₅ demonstrated improved overall properties, making these results particularly promising for preventing tooth decay, reducing demineralization through increased ions release and promoting remineralization in posterior teeth. Full article

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24 pages, 5195 KiB

Open AccessArticle

Fixation of Tripotassium Citrate Flame Retardant Using a Sorbitol and Citric Acid Wood-Modification Treatment

by Sanghun Yun, Adèle Jane Chabert and Holger Militz

Materials 2024, 17(21), 5377; https://doi.org/10.3390/ma17215377 - 4 Nov 2024

Viewed by 599

Abstract

Wood modification has been explored in various ways to enhance dimensional stability and reduce flammability, with a focus on environmentally friendly treatments to meet market demands. This study aimed to investigate the efficacy of new, potential fire-retardant materials. Specifically, the study examined the [...] Read more.

Wood modification has been explored in various ways to enhance dimensional stability and reduce flammability, with a focus on environmentally friendly treatments to meet market demands. This study aimed to investigate the efficacy of new, potential fire-retardant materials. Specifically, the study examined the combination of tripotassium citrate (TPC), a water-soluble and bio-based fire retardant, with sorbitol and citric acid (SorCA), an eco-friendly thermosetting resin previously studied. While TPC is known to control combustion, its application in wood modification has not been thoroughly researched. To assess the fixation and flammability of these fire retardants, tests were conducted on Scots Pine (Pinus sylvestris L.), including chemical analysis, dimensional stability, mechanical properties, flame retardancy, and leaching tests. The combination of SorCA and TPC showed high weight percent gain (WPG) values; however, leaching and anti-swelling efficiency (ASE) tests revealed challenges in fixation stability. The dynamic mechanical properties were reduced, whereas the static strength values were in the same range compared with untreated wood. While TPC exhibited high flame retardancy prior to leaching, its efficacy diminished post-leaching, underscoring challenges in fixation and the need for improved retention strategies. Bunsen burner tests conducted on leached specimens indicated enhanced performance even under severe leaching conditions as per the EN 84:2020 procedure. However, cone calorimetry measurements showed less favorable outcomes, emphasizing the necessity for further investigation into optimizing TPC retention and enhancing treatment efficacy. Full article

(This article belongs to the Special Issue Advanced Materials and Composites for Flame-Resistant Applications)

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14 pages, 9428 KiB

Open AccessArticle

Effect of Interlayer Temperature on Microstructure and Properties of High-Strength Low-Alloy Steel Manufactured Using Submerged-Arc Additive Manufacturing (SAAM)

by Meijuan Hu, Qiang Chi, Lingkang Ji, Weiwei Li, Shuai Yan and Fangjie Cheng

Materials 2024, 17(21), 5376; https://doi.org/10.3390/ma17215376 - 3 Nov 2024

Viewed by 861

Abstract

Controlled interlayer temperature has a profound impact on both the microstructure and mechanical properties of the deposited components. In this study, thin-walled structures made of high-strength low-alloy steel were fabricated using the submerged-arc additive manufacturing process. The effects of varying temperature on the [...] Read more.

Controlled interlayer temperature has a profound impact on both the microstructure and mechanical properties of the deposited components. In this study, thin-walled structures made of high-strength low-alloy steel were fabricated using the submerged-arc additive manufacturing process. The effects of varying temperature on the microstructure and mechanical properties of the components were studied. The results showed that the cooling rate within T_8/5 decreased as the interlayer temperature increased, which caused the microstructure to transition from a fine-grained structure dominated by bainitic ferrite and granular bainite to a coarse-grained structure dominated by polygonal ferrite. The measurement of mechanical properties showed that due to the influence of the fine-grained structure, the components with low interlayer temperatures exhibit excellent hardness, high strength, and outstanding ductility and toughness. Furthermore, a faster cooling rate disrupts the stability of carbon diffusion, resulting in the development of increased quantities of residual austenitic films within the components with controlled low interlayer temperatures. This augmentation in residual austenite films strengthens the components’ ductility and toughness, enabling the deposited components to exhibit exceptional impact toughness in low-temperature environments. Full article

(This article belongs to the Special Issue Microstructure Engineering of Metals and Alloys, 3rd Edition)

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12 pages, 6244 KiB

Open AccessArticle

Effects of Nitrogen on Microstructure and Properties of SDSS 2507 Weld Joints by Gas Focusing Plasma Arc Welding

by Tianqing Li, Kai Wang and Yucheng Lei

Materials 2024, 17(21), 5375; https://doi.org/10.3390/ma17215375 - 3 Nov 2024

Viewed by 608

Abstract

Regulating the phase ratio between austenite and ferrite in welded joints is crucial for welding super duplex stainless steel. Nitrogen plays a significant role in maintaining an optimal phase ratio. In this study, the focusing gas channel of gas-focused plasma arc welding was [...] Read more.

Regulating the phase ratio between austenite and ferrite in welded joints is crucial for welding super duplex stainless steel. Nitrogen plays a significant role in maintaining an optimal phase ratio. In this study, the focusing gas channel of gas-focused plasma arc welding was utilized to introduce nitrogen into the arc plasma, which was then transferred to the weld pool. Experiments with and without nitrogen addition were designed and conducted to examine the effects of nitrogen on the microstructure and properties of SDSS 2507 weld joints. The results show that nitrogen addition increased the austenite content in the weld metal from 22.2% to 40.2%. Nitrogen also altered the microstructure of the austenite, changing it from thin grain boundary austenite and small intragranular austenite to a large volume of coarse, side-plate Widmanstätten austenite. The ferrite in the weld metal exhibited a preferred orientation during growth, while the austenite showed a disordered orientation. Additionally, the maximum texture intensity of the ferrite decreased with nitrogen addition. Nitrogen addition led to an increase in the microhardness of the austenite in the weld metal, attributed to the solid solution strengthening effect of nitrogen and increased dislocation tangling, while it decreased the microhardness of the ferrite. This study enhances the welding theory of 2507 super duplex stainless steel and guides the practical application of gas-focused plasma arc welding for 2507 super duplex stainless steel. Full article

(This article belongs to the Special Issue Advances in Welding Process and Materials (2nd Edition))

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30 pages, 5136 KiB

Open AccessReview

A Review on Friction Stir Welding of Copper: Tool Geometry, Process Parameters, and Joint Properties

by Răducu Nicolae Bulacu, Matthieu Dhondt, Younes Demmouche, Claudiu Bădulescu, Eduard Laurențiu Nițu and Daniela Monica Iordache

Materials 2024, 17(21), 5374; https://doi.org/10.3390/ma17215374 - 3 Nov 2024

Viewed by 904

Abstract

This paper comprehensively reviews friction stir welding (FSW) as applied to copper and its alloys. FSW is a solid-state joining process that offers significant advantages over traditional fusion welding methods, particularly for materials like copper that are difficult to weld conventionally due to [...] Read more.

This paper comprehensively reviews friction stir welding (FSW) as applied to copper and its alloys. FSW is a solid-state joining process that offers significant advantages over traditional fusion welding methods, particularly for materials like copper that are difficult to weld conventionally due to their high thermal conductivity and oxidation issues. Over time, the FSW process has been developed for different industries. Copper structures joined through FSW are utilized for nuclear waste storage, electrical connectors, chemical and petrochemical storage, refrigeration systems, heat exchangers, and the aerospace industry. This covers recent advancements in FSW technology, the geometry of the tools used, the process parameters, and the microstructural characteristics and mechanical properties of the joints. It examines the shapes, sizes, and materials of the tools used for welding copper and its alloys, along with process parameters such as rotational speed and traverse speed, and their influence on the quality of the joints. Additionally, the paper presents syntheses of previously published results, highlighting the values of parameters that indicate the quality of the welds, including grain size, microhardness, mechanical strength, and elongation. The challenges and potential solutions in applying FSW to copper are also discussed, providing a starting point for future research and industrial applications. Full article

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15 pages, 5780 KiB

Open AccessArticle

Coupling CALPHAD Method and Entropy-Driven Design for the Development of an Advanced Lightweight High-Temperature Al-Ti-Ta Alloy

by Gourav Mundhra, Jien-Wei Yeh and B. S. Murty

Materials 2024, 17(21), 5373; https://doi.org/10.3390/ma17215373 - 3 Nov 2024

Viewed by 925

Abstract

In this study, a new lightweight Al-Ti-Ta alloy was developed through a synergistic approach, combining CALPHAD methodology and entropy-driven design. Following compositional optimization, the Al_87.5Ti_6.25Ta_6.25 (at.%) alloy was fabricated and isothermally heat-treated at 475 °C for 24 h [...] Read more.

In this study, a new lightweight Al-Ti-Ta alloy was developed through a synergistic approach, combining CALPHAD methodology and entropy-driven design. Following compositional optimization, the Al_87.5Ti_6.25Ta_6.25 (at.%) alloy was fabricated and isothermally heat-treated at 475 °C for 24 h to attain equilibrium. X-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) analyses revealed a dual-phase microstructure comprising a 50 vol.% FCC matrix enriched in Al and 50 vol.% Al₃(Ti,Ta)-type intermetallic phase (IP). Notably, the FCC phase exhibited a high-melting transition temperature of 660 °C, surpassing conventional Al-Si cast alloys. Phase-specific nanomechanical properties were evaluated using Nanoindentation. Microindentation tests demonstrated exceptional microhardness of approximately 3300 MPa. These results indicate the alloy’s superior hardness compared to conventional alloys such as Al-Si (A390), 7075 Al alloy, and CP-Ti, even exceeding Ti-64 alloy at a 15% lower density. The alloy’s stability under prolonged heat treatment at 475 °C, reflected by stable phases, microstructure, and mechanical properties, highlights its enhanced thermal stability, which can be attributed to entropy-driven phase stabilization. This study underscores the effectiveness of integrating entropy-driven design strategy with CALPHAD predictions for the accelerated development of advanced Al-based alloys. Full article

(This article belongs to the Section Metals and Alloys)

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13 pages, 5427 KiB

Open AccessArticle

Machine Learning and First-Principle Predictions of Materials with Low Lattice Thermal Conductivity

by Chia-Min Lin, Abishek Khatri, Da Yan and Cheng-Chien Chen

Materials 2024, 17(21), 5372; https://doi.org/10.3390/ma17215372 - 2 Nov 2024

Viewed by 723

Abstract

We performed machine learning (ML) simulations and density functional theory (DFT) calculations to search for materials with low lattice thermal conductivity,

κ_{L}

. Several cadmium (Cd) compounds containing elements from the alkali metal and carbon groups including A₂CdX (A = [...] Read more.

We performed machine learning (ML) simulations and density functional theory (DFT) calculations to search for materials with low lattice thermal conductivity,

κ_{L}

. Several cadmium (Cd) compounds containing elements from the alkali metal and carbon groups including A₂CdX (A = Li, Na, and K; X = Pb, Sn, and Ge) are predicted by our ML models to exhibit very low

κ_{L}

values (<1.0 W/mK), rendering these materials suitable for potential thermal management and insulation applications. Further DFT calculations of electronic and transport properties indicate that the figure of merit,

Z T

, for the thermoelectric performance can exceed 1.0 in compounds such as K₂CdPb, K₂CdSn, and K₂CdGe, which are therefore also promising thermoelectric materials. Full article

(This article belongs to the Special Issue Research Progress of Thermoelectric Materials, Modules and Applications)

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28 pages, 14019 KiB

Open AccessReview

Surface Quality as a Factor Affecting the Functionality of Products Manufactured with Metal and 3D Printing Technologies

by Maria Richert, Marek Dudek and Dariusz Sala

Materials 2024, 17(21), 5371; https://doi.org/10.3390/ma17215371 - 2 Nov 2024

Viewed by 1536

Abstract

Surface engineering is one of the most extensive industries. Virtually all areas of the economy benefit from the achievements of surface engineering. Surface quality affects the quality of finished products as well as the quality of manufactured parts. It affects both functional qualities [...] Read more.

Surface engineering is one of the most extensive industries. Virtually all areas of the economy benefit from the achievements of surface engineering. Surface quality affects the quality of finished products as well as the quality of manufactured parts. It affects both functional qualities and esthetics. Surface quality affects the image and reputation of a brand. This is particularly true for cars and household appliances. Surface modification of products is also aimed at improving their functional and protective properties. This applies to surfaces for producing hydrophobic surfaces, anti-wear protection of friction pairs, corrosion protection, and others. Metal technologies and 3D printing benefit from surface technologies that improve their functionality and facilitate the operation of products. Surface engineering offers a range of different coating and layering methods from varnishing and painting to sophisticated nanometric coatings. This paper presents an overview of selected surface engineering issues pertaining to metal products, with a particular focus on surface modification of products manufactured by 3D printing technology. It evaluates the impact of the surface quality of products on their functional and performance qualities. Full article

(This article belongs to the Special Issue Surface Engineering in Materials (2nd Edition))

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13 pages, 5451 KiB

Open AccessFeature PaperArticle

Super Tough PA6/PP/ABS/SEBS Blends Compatibilized by a Combination of Multi-Phase Compatibilizers

by Jianhui Yan, Cuifang Wang, Tongyu Zhang, Zijian Xiao and Xuming Xie

Materials 2024, 17(21), 5370; https://doi.org/10.3390/ma17215370 - 2 Nov 2024

Viewed by 638

Abstract

Development of multi-component blends to prepare high-performance polymer materials is still challenging, and is a key technology for mechanical recycling of waste plastics. However, a multi-phase compatibilizer is prerequisite to create high-performance multi-component blends. In this study, POE-g-(MAH-co-St) and [...] Read more.

Development of multi-component blends to prepare high-performance polymer materials is still challenging, and is a key technology for mechanical recycling of waste plastics. However, a multi-phase compatibilizer is prerequisite to create high-performance multi-component blends. In this study, POE-g-(MAH-co-St) and SEBS-g-(MAH-co-St) compatibilizers are prepared via melt-grafting of maleic anhydride (MAH) and styrene (St) dual monomers to polyolefin elastomer (POE) and poly [styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS), respectively. Subsequently, these compatibilizers are utilized to compatibilize the PA6/PP/ABS/SEBS quaternary blends through melt-blending. When POE-g-(MAH-co-St) and SEBS-g-(MAH-co-St) are added, respectively, both can promote the distribution of the dispersed phases, significantly reducing the dispersed phase size. When adding 10 wt% POE-g-(MAH-co-St) and 10 wt% SEBS-g-(MAH-co-St) together, compared to the non-compatibilized blend, the fracture strength, fracture elongation, and impact strength surprisingly increased by 106%, 593%, and 823%, respectively. It can be attributed to the hierarchical interfacial interactions which facilitate gradual energy dissipation from weak to strong interfaces, resulting in the improvement of mechanical properties. The synergistic effect of the enhanced phase interfacial interactions and toughening effect of elastomer compatibilizer achieved simultaneous growth in strength and toughness. Full article

(This article belongs to the Special Issue Feature Paper in the Section 'Polymeric Materials' (3rd Edition))

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16 pages, 3045 KiB

Open AccessArticle

Application of Sound Waves During the Curing of an Acrylic Resin and Its Composites Based on Short Carbon Fibers and Carbon Nanofibers

by Braian Uribe, Joana Rodrigues, Pedro Costa and Maria C. Paiva

Materials 2024, 17(21), 5369; https://doi.org/10.3390/ma17215369 - 2 Nov 2024

Viewed by 910

Abstract

Research into particulate polymer composites is of significant interest due to their potential for enhancing material properties, such as strength, thermal stability, and conductivity while maintaining low weight and cost. Among the various techniques for preparing particle-based composites, ultrasonic wave stimulation is one [...] Read more.

Research into particulate polymer composites is of significant interest due to their potential for enhancing material properties, such as strength, thermal stability, and conductivity while maintaining low weight and cost. Among the various techniques for preparing particle-based composites, ultrasonic wave stimulation is one of the principal laboratory-scale methods for enhancing the dispersion of the discontinuous phase. Nevertheless, there is a scarcity of empirical evidence to substantiate the impact of stimulating materials with natural sound frequencies within the acoustic spectrum, ranging from 20 Hz to 20 kHz, during their formation process. The present work investigates the effect of acoustic stimuli with frequencies of 56, 111, and 180 Hz on the properties of an acrylic-based polymer and its discontinuous carbon-based composites. The results indicated that the stimulus frequency affects the cure time of the studied systems, with a notable reduction of 31% and 21% in the cure times of the neat polymer and carbon-nanofiber-based composites, respectively, after applying a frequency of 180 Hz. Additionally, the higher stimulation frequencies reduced porosity in the samples, increased the degree of dispersion of the discontinuous phase, and altered the composite materials’ thermal, optical, and electrical behavior. Full article

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12 pages, 8484 KiB

Open AccessArticle

Fracture Toughness of Short Fibre-Reinforced Composites—In Vitro Study

by Noor Kamourieh, Maurice Faigenblum, Robert Blizard, Albert Leung and Peter Fine

Materials 2024, 17(21), 5368; https://doi.org/10.3390/ma17215368 - 2 Nov 2024

Viewed by 855

Abstract

The development of dental materials needs to be supported with sound evidence. This in vitro study aimed to measure the fracture toughness of a short fibre-reinforced composite (sFRC), at differing thicknesses. In this study, 2 mm, 3 mm and 4 mm depths of [...] Read more.

The development of dental materials needs to be supported with sound evidence. This in vitro study aimed to measure the fracture toughness of a short fibre-reinforced composite (sFRC), at differing thicknesses. In this study, 2 mm, 3 mm and 4 mm depths of sFRC were prepared. Using ISO4049, each preparation was tested to failure. A total of 60 samples were tested: 10 samples for each combination of sFRC and depth. Fractured samples were viewed, and outcomes were analysed. EXF showed greater toughness than EXP, with a mean of 2.49 (95%CI: 2.25, 2.73) MPa.m^1/2 compared to a mean of 2.13 (95%CI: 1.95, 2.31) MPa.m^1/2, (F(1,54) = 21.28; p < 0.001). This difference was particularly pronounced at 2 mm depths where the mean (95%CI) values were 2.72 (2.49, 2.95) for EXF and 1.90 (1.78, 2.02) for EXP (Interaction F(2,54) = 7.93; p < 0.001). Both materials performed similarly at the depths of 3 mm and 4 mm. The results for both materials were within the accepted fracture toughness values of dentine of 1.79–3.08 MPa.m^1/2. Analysis showed crack deflection and bridging fibre behaviour. The optimal thickness at the cavity base for EXF was 2 mm and for EXP 4 mm. Crack deflection and bridging behaviour indicated that restorations incorporating sFRCs are not prone to catastrophic failure and confirmed that sFRCs have similar fracture toughness to dentine. sFRCs could be a suitable biomimetic material to replace dentine. Full article

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13 pages, 5319 KiB

Open AccessArticle

Preparation of Purpurin–Fe²⁺ Complex Natural Dye and Its Printing Performance on Silk Fabrics

by Xiaojia Huang, Jie Luo, Xiangrong Wang, Xianwei Cheng and Xueni Hou

Materials 2024, 17(21), 5367; https://doi.org/10.3390/ma17215367 - 2 Nov 2024

Viewed by 707

Abstract

In order to shorten the process of textile printing with natural dyes, develop new methods, and improve the color fastness and quality of printed products, this study presents a novel approach by synthesizing a natural complex dye through the interaction between purpurin and [...] Read more.

In order to shorten the process of textile printing with natural dyes, develop new methods, and improve the color fastness and quality of printed products, this study presents a novel approach by synthesizing a natural complex dye through the interaction between purpurin and Fe²⁺ ions, resulting in a compound named purpurin–Fe²⁺ (P-Fe). This synthesized complex dye was meticulously characterized using state-of-the-art analytical techniques, including Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible (UV–Vis) spectrophotometry, and scanning electron microscopy energy-dispersive spectroscopy (EDS). The characterization confirmed the successful complexation of purpurin with Fe²⁺ ions. The prepared complex dye P-Fe was used for the printing of silk fabric. The optimized printing process involves steaming at a temperature of 100 °C for a duration of 20 min. In comparison to fabrics printed using direct dyes, the K/S values of the fabric printed with the P-Fe complex showed a significant enhancement, with all color fastness ratings achieving grade four. Furthermore, the proportion of metal elements on the white background of the printed fabric was found to be less than 0.180%, and the level of whiteness was above 50. The application of the P-Fe dye in silk fabric printing not only streamlines the printing process but also enhances the depth and speed of the printed color, effectively addressing the issue of color transfer onto a white background, which is commonly associated with natural dyes. Full article

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13 pages, 4702 KiB

Open AccessArticle

Ultra-Short Pulses Laser Heating of Dielectrics: A Semi-Classical Analytical Model

by Liviu Badea, Liviu Duta, Cristian N. Mihailescu, Mihai Oane, Alexandra M. I. Trefilov, Andrei Popescu, Claudiu Hapenciuc, Muhammad Arif Mahmood, Dorina Ticos, Natalia Mihailescu, Carmen Ristoscu, Sinziana A. Anghel and Ion N. Mihailescu

Materials 2024, 17(21), 5366; https://doi.org/10.3390/ma17215366 - 2 Nov 2024

Viewed by 545

Abstract

Femtosecond laser pulses are currently regarded as an emerging and promising tool for processing wide bandgap dielectric materials across a variety of high-end applications, although the associated physical phenomena are not yet fully understood. To address these challenges, we propose an original, fully [...] Read more.

Femtosecond laser pulses are currently regarded as an emerging and promising tool for processing wide bandgap dielectric materials across a variety of high-end applications, although the associated physical phenomena are not yet fully understood. To address these challenges, we propose an original, fully analytical model combined with Two Temperatures Model (TTM) formalism. The model is applied to describe the interaction of fs laser pulses with a typical dielectric target (e.g., Sapphire). It describes the heating of dielectrics, such as Sapphire, under irradiation by fs laser pulses in the range of (10¹²–10¹⁴) W/cm². The proposed formalism was implemented to calculate the free electron density, while numerical simulations of temperature field evolution within the dielectrics were conducted using the TTM. Mathematical models have rarely been used to solve the TTM in the context of laser–dielectric interactions. Unlike the TTM applied to metals, which requires solving two heat equations, for dielectrics the free electron density must first be determined. We propose an analytical model to solve the TTM equations using this parameter. A new simulation model was developed, combining the equations for non-equilibrium electron density determination with the TTM equations. Our analyses revealed the non-linear nature of the physical phenomena involved and the inapplicability of the Beer–Lambert law for fs laser pulse interactions with dielectric targets at incident laser fluences ranging from 6 to 20 J/cm². Full article

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

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41 pages, 36184 KiB

Open AccessReview

Adiabatic Shear Localization in Metallic Materials: Review

by Xinran Guan, Shoujiang Qu, Hao Wang, Guojian Cao, Aihan Feng and Daolun Chen

Materials 2024, 17(21), 5365; https://doi.org/10.3390/ma17215365 - 1 Nov 2024

Viewed by 641

Abstract

In advanced engineering applications, there has been an increasing demand for the service performance of materials under high-strain-rate conditions where a key phenomenon of adiabatic shear instability is inevitably involved. The presence of adiabatic shear instability is typically associated with large shear strains, [...] Read more.

In advanced engineering applications, there has been an increasing demand for the service performance of materials under high-strain-rate conditions where a key phenomenon of adiabatic shear instability is inevitably involved. The presence of adiabatic shear instability is typically associated with large shear strains, high strain rates, and elevated temperatures. Significant plastic deformation that concentrates within a adiabatic shear band (ASB) often results in catastrophic failure, and it is necessary to avoid the occurrence of such a phenomenon in most areas. However, in certain areas, such as high-speed machining and self-sharpening projectile penetration, this phenomenon can be exploited. The thermal softening effect and microstructural softening effect are widely recognized as the foundational theories for the formation of ASB. Thus, elucidating various complex deformation mechanisms under thermomechanical coupling along with changes in temperatures in the shear instability process has become a focal point of research. This review highlights these two important aspects and examines the development of relevant theories and experimental results, identifying key challenges faced in this field of study. Furthermore, advancements in modern experimental characterization and computational technologies, which lead to a deeper understanding of the adiabatic shear instability phenomenon, have also been summarized. Full article

(This article belongs to the Special Issue Plastic Deformation, Strengthening and Toughening of Advanced Metallic Materials (2nd Edition))

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11 pages, 5008 KiB

Open AccessArticle

Study on High-Temperature Activated Products and Hydration Properties of Aga Soil in Tibet for Cement Concrete

by Lihui Li, Kaiming Niu, Jianrui Ji, Panpan Zhang and Jilin Zhang

Materials 2024, 17(21), 5364; https://doi.org/10.3390/ma17215364 - 1 Nov 2024

Viewed by 423

Abstract

In order to impart the properties of cementitious material to the Tibetan Agar soil, two high-temperature activation mechanisms (HTMA, HTMB) were designed in this study, and the products and hydration-hardening properties of Tibetan Agar soil high-temperature activation mechanism were analyzed by means of [...] Read more.

In order to impart the properties of cementitious material to the Tibetan Agar soil, two high-temperature activation mechanisms (HTMA, HTMB) were designed in this study, and the products and hydration-hardening properties of Tibetan Agar soil high-temperature activation mechanism were analyzed by means of SEM, XRD, and XRF. The results show that the main components of Tibetan Aga soil are calcite and quartz; Aga soil is activated by HTMA high-temperature activation, forming the main products of CaO, C₂S, CaSiO₃, and CaAl₂Si₂O₈, and its products have both air-hardening and water-hardening characteristics; Aga soil is activated by HTMB high-temperature activation, and when the temperature reaches 1250 °C when the clinker is not found in the CaO, the generation of C₂S, C₃S, C₃A, C₄AF, and Mg₂SiO₄ minerals with good water-hardening cementitious properties occurs when the temperature rises to 1350 °C, although the formation of some inert minerals that do not have the cementitious properties, but this temperature activation products of the thermodynamic properties of the best; Enhancing the value of lime saturation degree (KH) and silicon rate (SM) can promote the formation of the products of the C₂S and C₃S, increase the reactivity of the Aga soil activation products, and increase the hydration heat as well as compressive and flexural strength, combined with the results of the hydration heat and mechanical test, KH is recommended to be 0.9~0.94, SM is recommended to be 1.8~2.4, and alumina ratio (IM) is recommended to be 1.8~2.4 when Aga soil is used with raw materials. Full article

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

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32 pages, 8634 KiB

Open AccessReview

Fractal Modelling of Heterogeneous Catalytic Materials and Processes

by Suleiman Mousa and Sean P. Rigby

Materials 2024, 17(21), 5363; https://doi.org/10.3390/ma17215363 - 1 Nov 2024

Viewed by 382

Abstract

This review considers the use of fractal concepts to improve the development, fabrication, and characterisation of catalytic materials and supports. First, the theory of fractals is discussed, as well as how it can be used to better describe often highly complex catalytic materials [...] Read more.

This review considers the use of fractal concepts to improve the development, fabrication, and characterisation of catalytic materials and supports. First, the theory of fractals is discussed, as well as how it can be used to better describe often highly complex catalytic materials and enhance structural characterisation via a variety of different methods, including gas sorption, mercury porosimetry, NMR, and several imaging modalities. The review then surveys various synthesis and fabrication methods that can be used to create catalytic materials that are fractals or possess fractal character. It then goes on to consider how the fractal properties of catalysts affect their performance, especially their overall activity, selectivity for desired products, and resistance to deactivation. Finally, this review describes how the optimum fractal catalyst material for a given reaction system can be designed on a computer. Full article

(This article belongs to the Special Issue Featured Reviews in Catalytic Materials)

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