Materials

2 pages, 157 KiB

Open AccessEditorial

Silicon Carbide: Material Growth, Device Processing, and Applications

by Marilena Vivona and Mike Jennings

Materials 2024, 17(18), 4571; https://doi.org/10.3390/ma17184571 - 18 Sep 2024

The continuous demand for electronic devices operating at increasing current and power levels, as well as at high temperatures and in harsh environments, has driven research into wide-band gap (WBG) semiconductors over the last three decades [...] Full article

(This article belongs to the Special Issue Silicon Carbide: Material Growth, Device Processing and Applications)

13 pages, 1895 KiB

Open AccessArticle

Numerical Fatigue Crack Growth on Compact Tension Specimens under Mode I and Mixed-Mode (I+II) Loading

by Rui F. Martins, José Xavier and João Caldeira

Materials 2024, 17(18), 4570; https://doi.org/10.3390/ma17184570 - 18 Sep 2024

Abstract

This study focused on standard Compact Tension (CT) specimens and two loading modes during the numerical analyses carried out, namely: pure mode I and mixed-mode loading (Modes I+II). Numerical stress intensity factors, K_I, were calculated using Abaqus^® 2022 and compared [...] Read more.

This study focused on standard Compact Tension (CT) specimens and two loading modes during the numerical analyses carried out, namely: pure mode I and mixed-mode loading (Modes I+II). Numerical stress intensity factors, K_I, were calculated using Abaqus^® 2022 and compared with those given analytically under pure mode I loading, showing very good agreement. Additionally, K_I, K_II, and K_III results obtained from Abaqus^® were presented for mixed-mode loading, analyzing crack growth and variation through the thickness of the CT specimen. Moreover, fatigue crack growth simulations under mode I loading were conducted on standard CT specimens using the Extended Finite Element Method (XFEM) and the Paris Law parameters of an AISI 316L stainless steel. It was shown that XFEM effectively determines crack propagation direction and growth, provided that an appropriate mesh is implemented. Full article

(This article belongs to the Special Issue Fatigue Crack Growth in Metallic Materials (Volume II))

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19 pages, 5101 KiB

Open AccessArticle

The Effect of Dense and Hollow Aggregates on the Properties of Lightweight Self-Compacting Concrete

by Aleksandr Sergeevich Inozemtcev and Sergey Dmitrievich Epikhin

Materials 2024, 17(18), 4569; https://doi.org/10.3390/ma17184569 - 17 Sep 2024

Abstract

The development of self-compacting lightweight concretes is associated with solving two conflicting tasks: achieving a structure with both high flowability and homogeneity. This study aimed to identify the technological and rheological characteristics of the flow of concrete mixtures D1400…D1600 based on hollow microspheres [...] Read more.

The development of self-compacting lightweight concretes is associated with solving two conflicting tasks: achieving a structure with both high flowability and homogeneity. This study aimed to identify the technological and rheological characteristics of the flow of concrete mixtures D1400…D1600 based on hollow microspheres in comparison with heavy fine-grained D2200 concrete and to establish their structural and physico-mechanical characteristics. The study of the concrete mixtures was carried out using the slump flow test and the rotational viscometry method. The physical and mechanical properties were studied using standard methods for determining average density and flexural and compressive strength. According to the results of the research conducted, differences in the flow behaviors of concrete mixtures on dense and hollow aggregates were found. Lightweight concretes on hollow microspheres exhibited better mobility than heavy concretes. It was shown that the self-compacting coefficients of the lightweight D1400...D1600 concrete mixtures were comparable with that of the heavy D2200 concrete. The rheological curves described by the Ostwald–de Waele equation showed a dilatant flow behavior of the D1400 concrete mixtures, regardless of the ratio of quartz powder to fractionated sand. For D1500 and D1600, the dilatant flow behavior changed to pseudoplastic, with a ratio of quartz powder to fractional sand of 25/75. The studied compositions of lightweight concrete can be described as homogeneous at any ratio of quartz powder to fractional sand. It was shown that concrete mixtures with a pronounced dilatant flow character had higher resistance to segregation. The value of the ratio of quartz powder to fractional sand had a statistically insignificant effect on the average density of the studied concretes. However, the flexural and compressive strengths varied significantly more in heavy concretes (up to 38%) than in lightweight concretes (up to 18%) when this factor was varied. The specific strength of lightweight and heavy concrete compositions with a ratio of quartz powder to fractional sand of 0/100 had close values in the range of 20.4...22.9 MPa, and increasing the share of quartz powder increased the difference between compositions of different densities. Full article

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31 pages, 3833 KiB

Open AccessReview

Recent Advances in the Development of 1,4-Cyclohexanedimethanol (CHDM) and Cyclic-Monomer-Based Advanced Amorphous and Semi-Crystalline Polyesters for Smart Film Applications

by Farida Irshad, Nayab Khan, Haidar Howari, Mahvish Fatima, Assad Farooq, Muhammad Awais, Muhammad Ayyoob, Muhammad Qamar Tusief, Razia Virk and Fiaz Hussain

Materials 2024, 17(18), 4568; https://doi.org/10.3390/ma17184568 (registering DOI) - 17 Sep 2024

Abstract

Polyester-based advanced thin films have versatile industrial applications, especially in the fields of textiles, packaging, and electronics. Recent advances in polymer science and engineering have resulted in the development of advanced amorphous and semi-crystalline polyesters with exceptional performance compared to those of conventional [...] Read more.

Polyester-based advanced thin films have versatile industrial applications, especially in the fields of textiles, packaging, and electronics. Recent advances in polymer science and engineering have resulted in the development of advanced amorphous and semi-crystalline polyesters with exceptional performance compared to those of conventional polymeric films. Among these, 1,4-cyclohexanedimethanol (CHDM) and cyclic-monomer-based polyesters have gained considerable attention for their exceptional characteristics and potential applications in smart films. This review article provides a comprehensive overview of the recent advances in the synthesis, characterization, and applications of CHDM and cyclic-monomer-based advanced polymers for smart film applications. It discusses the structure–property relationships of these innovative polyesters and highlights their unique characteristics, including thermal, mechanical, and barrier characteristics. Furthermore, this article also emphasizes the solution, melt, and solid-state polymerizations of the polymers. Special emphasis is placed on the influence of the addition of a second diol or second diacid on the performance characteristics of synthesized polyesters/copolyesters to explore their versatile industrial applications. Additionally, the impact of the stereochemistry of the monomers is explored to optimize the characterization of polyesters suitable for industrial applications. Furthermore, this article explores the potential of these advanced polyesters to be considered as materials for smart film applications, especially in the field of flexible electronics. Finally, this article examines the challenges and future recommendations for the development of CHDM and cyclic-monomer-based polyesters for smart film applications. It discusses potential avenues for further research, including in-depth studies for the synthesis and characterization of polyesters, the development of sustainable and biodegradable alternatives to cyclic monomers, alternative green approaches for the synthesis of polymers, etc. This review article provides valuable insight for researchers in academia and industry who are working in the fields of polymer science and materials engineering. Full article

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15 pages, 8569 KiB

Open AccessArticle

The Effects of Metakaolin on the Properties of Magnesium Sulphoaluminate Cement

by Lili Jiang, Zhuhui Li, Zhenguo Li and Dongye Wang

Materials 2024, 17(18), 4567; https://doi.org/10.3390/ma17184567 - 17 Sep 2024

Abstract

Magnesium sulphoaluminate (MSA) cement has good bonding properties and is suitable as an inorganic adhesive for repairing materials in civil engineering. However, there are still some problems with its use, such as its insufficient 1 day (d) strength and poor volumetric stability. This [...] Read more.

Magnesium sulphoaluminate (MSA) cement has good bonding properties and is suitable as an inorganic adhesive for repairing materials in civil engineering. However, there are still some problems with its use, such as its insufficient 1 day (d) strength and poor volumetric stability. This paper aims to investigate the influences of metakaolin (MK) on the physical and mechanical properties of magnesium sulphoaluminate (MSA) cement. The hydration products and microstructures of typical MSA cement samples were also analysed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The results showed that the addition of metakaolin reduces the fluidity and shortens the setting time of the MSA cement. The initial setting time and final setting time shortened maximally by 15–27 min and 25–48 min, respectively, with the addition of 10–30% metakaolin. Moreover, the compressive strength and flexural strength of the MSA cement improved significantly with the addition of 10–30% metakaolin at a curing age of 1 d. Compared with the compressive and flexural strengths of the control sample at 1 d, the compressive strengths of the modified samples showed obvious increases of 98%, 101%, and 109%, and the flexural strengths increased by 39%, 31%, and 26%, respectively, although they decreased slightly when the curing ages were 7 d, 14 d, and 28 d. The addition of 10% metakaolin improved the water resistance of the MSA cement immersed in water for 7 d and resulted in even higher water resistance at 28 d. The addition of 10–30% metakaolin improved the volumetric stability of the MSA cement with increasing dosages before 28 d of ageing. XRD and SEM-EDS analyses showed that the metakaolin accelerated the early hydration reaction and optimised the phase composition of the MSA cement. The results indicate that the addition of 10–20% metakaolin improved the strength after 1 d of ageing, water resistance, and volumetric stability of the MSA cement, providing theoretical support for the application of MAS cement as an inorganic bonding agent for repairing materials. Full article

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14 pages, 1540 KiB

Open AccessArticle

Vision Inspection Method for the Quality Assessment of Paint Coatings on Glassware

by Damian Dubis, Andrzej Chochół, Izabela Betlej, Piotr Boruszewski and Piotr Borysiuk

Materials 2024, 17(18), 4566; https://doi.org/10.3390/ma17184566 - 17 Sep 2024

Abstract

Image analysis is becoming increasingly popular in many industries. Its use is perfect for, among other things, assessing the quality of products on or off the production line. Highly automated, high-performance systems can be used for this purpose. However, there are situations in [...] Read more.

Image analysis is becoming increasingly popular in many industries. Its use is perfect for, among other things, assessing the quality of products on or off the production line. Highly automated, high-performance systems can be used for this purpose. However, there are situations in which automated vision systems cannot be used on the production line due to the specific nature of the process. One such situation is testing the resistance of paint applied to glass when washing in automatic dishwashers. It is carried out outside the production line, and typical production vision systems are not used here. An attempt was made to develop a cheap and easy-to-implement research method enabling quantitative measurement of paint loss on glass when testing the coating’s resistance to automatic washing. For this purpose, analysis of images taken during the study was carried out. The developed method is based on taking a series of photos of the tested object between each stage of the wash resistance test. The obtained photographic material is then analyzed by measuring the size of paint losses expressed in the number of pixels. Then, the percentage of paint loss is calculated. This method is cheap to implement and highly accurate. Statistical analysis of the results confirmed the method’s accuracy at 98%. Full article

(This article belongs to the Special Issue Manufacturing, Heat Treatment and Forming of Advanced Metallic and Ceramic Materials (2nd Edition))

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13 pages, 3702 KiB

Open AccessArticle

Ceramic Matrix Composite Cyclic Ablation Behavior under Oxyacetylene Torch

by Hailang Ge, Xianqing Chen, Guangyu Li and Lu Zhang

Materials 2024, 17(18), 4565; https://doi.org/10.3390/ma17184565 - 17 Sep 2024

Abstract

To study the ablation properties and differences of plain-woven SiC/SiC composites under single and cyclic ablation. The ablation test of plain-woven SiC/SiC composites was conducted under an oxyacetylene torch. The results indicate that the mass ablation rate of cyclic ablation is lower than [...] Read more.

To study the ablation properties and differences of plain-woven SiC/SiC composites under single and cyclic ablation. The ablation test of plain-woven SiC/SiC composites was conducted under an oxyacetylene torch. The results indicate that the mass ablation rate of cyclic ablation is lower than that of single ablation, whereas the line ablation rate is higher. Macro-microstructural characterization revealed the presence of white oxide formed by silica on the surface of the ablation center region. The fibers in the central region of the ablation were ablated layer by layer, and the broken fiber bundles exhibited a spiky morphology with numerous silica particles attached. The oxide layer on the surface and the silica particles on the fibers, which are in the molten state formed in the high-temperature ablation environment, contribute to resisting ablation. Thermal shock during cyclic ablation also played a role in the ablation process. The thermal shock causes cracks in the fiber bundles and matrix of the SiC/SiC composites. This study helps to apply SiC/SiC composite to complex thermal shock environments. Full article

(This article belongs to the Special Issue Damage, Fracture and Fatigue of Ceramic Matrix Composites (CMCs))

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14 pages, 13110 KiB

Open AccessArticle

Auxeticity Tuning by Nanolayer Inclusion Ordering in Hard Sphere Crystals

by Jakub W. Narojczyk, Krzysztof W. Wojciechowski, Jerzy Smardzewski and Konstantin V. Tretiakov

Materials 2024, 17(18), 4564; https://doi.org/10.3390/ma17184564 - 17 Sep 2024

Abstract

Designing a particular change in a system structure to achieve the desired elastic properties of materials for a given task is challenging. Recent studies of purely geometrical atomic models have shown that structural modifications on a molecular level can lead to interesting and [...] Read more.

Designing a particular change in a system structure to achieve the desired elastic properties of materials for a given task is challenging. Recent studies of purely geometrical atomic models have shown that structural modifications on a molecular level can lead to interesting and desirable elastic properties. Still, the result of such changes is usually difficult to predict. The present work concerns the impact of nanolayer inclusion ordering in hard sphere crystals on their elastic properties, with special attention devoted to their auxetic properties. Two sets of representative models, based on cubic crystals consisting of

6 \times 6 \times 6

unit cells of hard spheres and containing either neighboring or separated layers of spheres of another diameter, oriented orthogonally to the [001] direction, have been studied by Monte Carlo simulations in the isothermal–isobaric (NpT) ensemble. Their elastic constants have been evaluated using the Parinello–Rahman approach. The Monte Carlo simulations showed that introducing the layer inclusions into a pure face-centered cubic (FCC) structure leads to the system’s symmetry changes from cubic symmetry to tetragonal in both cases. Essential changes in the elastic properties of the systems due to layer ordering were found both for neighboring and separated inclusions. It has been found that the choice of a set of layer inclusions allows one to tune the auxetic properties in two crystallographic directions (

[110] [1 \bar{1} 0]

and

[101] [\bar{1} 01]

). In particular, this study revealed that the change in layer ordering (from six separated layers to six neighboring ones) allows for, respectively: (i) enhancing auxeticity of the system in the

[101] [\bar{1} 01]

direction with almost loss of auxetic properties in the

[110] [1 \bar{1} 0]

direction in the case of six separated layers, while (ii) in the case of six neighboring layers, keeping the auxetic properties in both auxetic directions independently of the size of spheres constituting inclusions. Full article

(This article belongs to the Special Issue Innovations in Modelling and Simulations: Bridging Microstructures to Macroscopic Properties in Advanced Materials)

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Graphical abstract

23 pages, 5690 KiB

Open AccessReview

Ionic Liquid Crystals as Chromogenic Materials

by Andreia F. M. Santos, João L. Figueirinhas, Madalena Dionísio, Maria H. Godinho and Luis C. Branco

Materials 2024, 17(18), 4563; https://doi.org/10.3390/ma17184563 - 17 Sep 2024

Abstract

Ionic liquid crystals (ILCs), a class of soft matter materials whose properties can be tuned by the wise pairing of the cation and anion, have recently emerged as promising candidates for different applications, combining the characteristics of ionic liquids and liquid crystals. Among [...] Read more.

Ionic liquid crystals (ILCs), a class of soft matter materials whose properties can be tuned by the wise pairing of the cation and anion, have recently emerged as promising candidates for different applications, combining the characteristics of ionic liquids and liquid crystals. Among those potential uses, this review aims to cover chromogenic ILCs. In this context, examples of photo-, electro- and thermochromism based on ILCs are provided. Furthermore, thermotropic and lyotropic ionic liquid crystals are also summarised, including the most common chemical and phase structures, as well as the advantages of confining these materials. This manuscript also comprises the following main experimental techniques used to characterise ILCs: Differential Scanning Calorimetry (DSC), Polarised Optical Microscopy (POM) and X-Ray Powder Diffraction (XRD). Chromogenic ILCs can be interesting smart materials for energy and health purposes. Full article

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

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15 pages, 4909 KiB

Open AccessArticle

Investigating the Effects of Transition Metals and Activated Carbon on Hydrogenation Characteristics of Severely Deformed ZK60 Processed by High-Energy Ball Milling

by Aqeel Abbas, Tzu-Chieh Hsu, Jhe-Yi Lin, Hung-Cheng Ho, Kun-Ming Lin and Hsin-Chih Lin

Materials 2024, 17(18), 4562; https://doi.org/10.3390/ma17184562 - 17 Sep 2024

Abstract

The synergic effects of activated carbon and transition metals on the hydrogenation characteristics of commercial ZK60 magnesium alloy were investigated. Severe plastic deformation was performed using equal-channel angular pressing with an internal die angle of 120° and preheating at 300 °C. The ZK60 [...] Read more.

The synergic effects of activated carbon and transition metals on the hydrogenation characteristics of commercial ZK60 magnesium alloy were investigated. Severe plastic deformation was performed using equal-channel angular pressing with an internal die angle of 120° and preheating at 300 °C. The ZK60 alloy samples were processed for 12 passes using route B_A. The deformed ZK60 alloy powder was blended with activated carbon and different concentrations of transition metals (Ag, Pd, Co, Ti, V, Ti) using high-energy ball milling for 20 h at a speed of 1725 rpm. The amount of hydrogen absorbed and its kinetics were calculated using Sievert’s apparatus at the higher number of cycles at a 300 °C ab/desorption temperature. The microstructure of the powder was analyzed using an X-ray diffractometer and scanning electron microscope. The results indicated that 5 wt% activated carbon presented the maximum hydrogen absorption capacity of 6.2 wt%. The optimal hydrogen absorption capacities were 7.1 wt%, 6.8 wt%, 6.7 wt%, 6.64 wt%, 6.65 wt%, and 7.06 wt% for 0.5 Ag, 0.3 Co, 0.1 Al, 0.5 Pd, 2 Ti, and 0.5 V, respectively. The hydrogen absorption capacities were reduced by 35.21%, 26.47%, 41.79%, 21.68%, 26.31%, and 26.34% after 100 cycles for 5C0.5Ag, 5C0.3Co, 5C0.1Al, 5C0.5Pd, 2Ti, and 5C0.5V, respectively. Hydrogen absorption kinetics were significantly improved so that more than 90% of hydrogen was absorbed within five minutes. Full article

(This article belongs to the Section Energy Materials)

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17 pages, 6692 KiB

Open AccessArticle

Detecting the Sigma Phase in Duplex Stainless Steel by Magnetic Noise and First Harmonic Analysis

by João Silva, Edgard Silva, Augusto Sampaio, Rayssa Lins, Josinaldo Leite, Victor Albuquerque Silva and João Manuel R. S. Tavares

Materials 2024, 17(18), 4561; https://doi.org/10.3390/ma17184561 - 17 Sep 2024

Abstract

Non-destructive electromagnetic tests based on magnetic noise analysis have been developed to study, among others, residual stress, heat treatment outcomes, and harmful microstructures in terms of toughness. When subjected to thermal cycles above 550 °C, duplex stainless steels form an extremely hard and [...] Read more.

Non-destructive electromagnetic tests based on magnetic noise analysis have been developed to study, among others, residual stress, heat treatment outcomes, and harmful microstructures in terms of toughness. When subjected to thermal cycles above 550 °C, duplex stainless steels form an extremely hard and chromium-rich constituent that, if it is superior to 5%, compromises the steel’s corrosion resistance and toughness. In the present work, a study was carried out concerning the interaction of excitation waves with duplex stainless steel. Hence, by analyzing the magnetic noise and variations in the amplitude of the first harmonic of the excitation waves, the detection of the deleterious sigma phase in SAF 2205 steel is studied. To simplify the test, a Hall effect sensor replaced the pick-up coil placed on the opposite surface of the excitation coil. Sinusoidal excitation waves of 5 Hz and 25 Hz with amplitudes ranging from 0.25 V to 9 V were applied to samples with different amounts of the sigma phase, and the microstructures were characterized by scanning electron microscopy. The results show that the best testing condition consists of applying waves with amplitudes from 1 V to 2 V and using the first harmonic amplitude. Thus, the test proved effective for detecting the formation of the deleterious sigma phase and can follow the ability to absorb energy by impact and, thus, the material embrittlement. Full article

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

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13 pages, 2228 KiB

Open AccessArticle

Optimization of Ceramic Paste Composition for 3D Printing via Robocasting

by Szymon Przybyła, Maciej Kwiatkowski, Michał Kwiatkowski and Marek Hebda

Materials 2024, 17(18), 4560; https://doi.org/10.3390/ma17184560 - 17 Sep 2024

Abstract

This article presents a procedure for selecting optimal ceramic paste formulations dedicated to the 3D printing process using robocasting technology. This study investigated pastes with varying ceramic powder particle sizes and different proportions of additives, such as ceramic microspheres and nutshells. This selection [...] Read more.

This article presents a procedure for selecting optimal ceramic paste formulations dedicated to the 3D printing process using robocasting technology. This study investigated pastes with varying ceramic powder particle sizes and different proportions of additives, such as ceramic microspheres and nutshells. This selection process allowed for the classification of ceramic mixtures into those suitable and unsuitable for this additive manufacturing technique. Subsequently, the viscosity of the pastes was measured, and extrudability tests were performed to determine the force required for extrusion and evaluate the quality of the extruded material. In the final stage, the setting time of the ceramic pastes was assessed to establish the drying time of the printed elements. It was found that the length of the extruded band of ceramic paste was inversely proportional to the Al₂O₃ content. Moreover, the extrusion force for samples with varying ceramic powder particle sizes (MG1–MG5) ranged from 133 to 166 N, compared to 77 N for the base sample (BM1). The obtained results enable further development in robocasting additive technology, including the development of a rapid and effective method for validating ceramic pastes used in this process. Full article

(This article belongs to the Special Issue Advances in Materials Processing (3rd Edition))

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147 pages, 9004 KiB

Open AccessReview

Thin Conducting Films: Preparation Methods, Optical and Electrical Properties, and Emerging Trends, Challenges, and Opportunities

by Razia Khan Sharme, Manuel Quijada, Mauricio Terrones and Mukti M. Rana

Materials 2024, 17(18), 4559; https://doi.org/10.3390/ma17184559 - 17 Sep 2024

Abstract

Thin conducting films are distinct from bulk materials and have become prevalent over the past decades as they possess unique physical, electrical, optical, and mechanical characteristics. Comprehending these essential properties for developing novel materials with tailored features for various applications is very important. [...] Read more.

Thin conducting films are distinct from bulk materials and have become prevalent over the past decades as they possess unique physical, electrical, optical, and mechanical characteristics. Comprehending these essential properties for developing novel materials with tailored features for various applications is very important. Research on these conductive thin films provides us insights into the fundamental principles, behavior at different dimensions, interface phenomena, etc. This study comprehensively analyzes the intricacies of numerous commonly used thin conducting films, covering from the fundamentals to their advanced preparation methods. Moreover, the article discusses the impact of different parameters on those thin conducting films’ electronic and optical properties. Finally, the recent future trends along with challenges are also highlighted to address the direction the field is heading towards. It is imperative to review the study to gain insight into the future development and advancing materials science, thus extending innovation and addressing vital challenges in diverse technological domains. Full article

(This article belongs to the Section Thin Films and Interfaces)

23 pages, 9628 KiB

Open AccessArticle

The Influence of the Parameters of the Skew Rolling Process for Bimetallic Elements on the Mechanical Properties and Structure of Materials

by Tomasz Kusiak, Janusz Tomczak and Jarosław Wójcik

Materials 2024, 17(18), 4558; https://doi.org/10.3390/ma17184558 - 17 Sep 2024

Abstract

This paper presents selected results of theoretical and experimental research into the manufacture of axisymmetric bimetallic components using three-tool skew rolling technology. In the tests, it was assumed that the outer layer would be a material intended for heat treatment. However, low-carbon steel [...] Read more.

This paper presents selected results of theoretical and experimental research into the manufacture of axisymmetric bimetallic components using three-tool skew rolling technology. In the tests, it was assumed that the outer layer would be a material intended for heat treatment. However, low-carbon steel was used for the core. Experimental investigations were carried out in an innovative CNC skew rolling mill. Tests were carried out at different technological parameters of the process. In addition, the geometric parameters of the billet and the way it was heated were analyzed in relation to the quality of the resulting weld between the two materials. The quality of the weld was assessed based on metallographic observation and on strength tests (shear method). On the other hand, theoretical studies were based on numerical modeling (FEM). The numerical analysis made it possible to determine the distribution of temperature, deformation and stress in the rolling bimetallic component. The results obtained indicated that it is possible to produce bimetallic materials from the proposed steel grades. In addition, a significant effect of the method of heating the billet in the chamber furnace on the microstructure in the joining zone and the shear strength was found. There was an increase in Rc strength of about 35% when using oxidation protection. The results indicated better strength when the billet is rolling with a smaller outer layer thickness (about 50 MPa). This was confirmed by the results obtained from the FEM analysis, which indicated higher values of plastic strain and the occurrence of higher compressive stresses in the near-surface zones of the rolled bimetallic forging, both of which facilitate the welding process. From the temperature distribution (in the range of (600–1200) °C) obtained during the rolling of the bimetal forging, it can be seen that contact with cold tools does not affect the temperature in the welding zone. Full article

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

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20 pages, 7162 KiB

Open AccessArticle

Homogenization of Thermal Properties in Metaplates

by David Faraci and Claudia Comi

Materials 2024, 17(18), 4557; https://doi.org/10.3390/ma17184557 - 17 Sep 2024

Abstract

Three-dimensional metamaterials endowed with two-dimensional in-plane periodicity exhibit peculiar thermoelastic behaviour when heated or cooled. By proper design of the unit cell, the equivalent thermal expansion coefficient can be programmed and can also reach negative values. The heterogeneity in the third direction of [...] Read more.

Three-dimensional metamaterials endowed with two-dimensional in-plane periodicity exhibit peculiar thermoelastic behaviour when heated or cooled. By proper design of the unit cell, the equivalent thermal expansion coefficient can be programmed and can also reach negative values. The heterogeneity in the third direction of such metamaterials also causes, in general, a thermal-induced deflection. The prediction of the equivalent thermal properties is important to design the metamaterial suitable for a specific application. Under the hypothesis of small thickness with respect to the global in-plane dimensions, we make use of asymptotic homogenization to describe the thermoelastic behaviour of these metamaterials as that of an equivalent homogenous plate. The method provides explicit expressions for the effective thermal properties, which allow for a cost-effective prediction of the thermoelastic response of these metaplates. Full article

(This article belongs to the Special Issue Advanced Mechanical Design and Applications of Metamaterials)

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48 pages, 10113 KiB

Open AccessReview

The Development of Poly(lactic acid) (PLA)-Based Blends and Modification Strategies: Methods of Improving Key Properties towards Technical Applications—Review

by Jacek Andrzejewski, Subhasis Das, Vitali Lipik, Amar K. Mohanty, Manjusri Misra, Xiangyu You, Lay Poh Tan and Boon Peng Chang

Materials 2024, 17(18), 4556; https://doi.org/10.3390/ma17184556 - 17 Sep 2024

Abstract

The widespread use of poly(lactic acid) (PLA) from packaging to engineering applications seems to follow the current global trend. The development of high-performance PLA-based blends has led to the commercial introduction of various PLA-based resins with excellent thermomechanical properties. The reason for this [...] Read more.

The widespread use of poly(lactic acid) (PLA) from packaging to engineering applications seems to follow the current global trend. The development of high-performance PLA-based blends has led to the commercial introduction of various PLA-based resins with excellent thermomechanical properties. The reason for this is the progress in the field of major PLA limitations such as low thermal resistance and poor impact strength. The main purpose of using biobased polymers in polymer blends is to increase the share of renewable raw materials in the final product rather than its possible biodegradation. However, in the case of engineering applications, the focus is on achieving the required properties rather than maximizing the percentage of biopolymer. The presented review article discusses the current strategies to optimize the balance of the key features such as stiffness, toughness, and heat resistance of PLA-based blends. Improving of these properties requires molecular structural changes, which together with morphology, crystallinity, and the influence of the processing conditions are the main subjects of this article. The latest research in this field clearly indicates the high potential of using PLA-based materials in highly demanding applications. In the case of impact strength modification, it is possible to obtain values close to 800 J/m, which is a value comparable to polycarbonate. Significant improvement can also be confirmed for thermal resistance results, where heat deflection temperatures for selected types of PLA blends can reach even 130 °C after modification. The modification strategies discussed in this article confirm that a properly conducted process of selecting the blend components and the conditions of the processing technique allows for revealing the potential of PLA as an engineering plastic. Full article

(This article belongs to the Special Issue Preparation and Microstructural Analysis of Polymer-Based Nanocomposites)

14 pages, 3515 KiB

Open AccessArticle

Physico-Mechanical Characteristics of Gypsum–Fiber Boards Manufactured with Hydrophobically Impregnated Fibers

by Adrian Trociński, Dorota Dziurka, Marta Thomas and Radosław Mirski

Materials 2024, 17(18), 4555; https://doi.org/10.3390/ma17184555 - 17 Sep 2024

Abstract

Although gypsum-based building materials exhibit many positive characteristics, solutions are still being searched for to reduce the use of gypsum or improve the physico-mechanical properties of board materials. In this study, an attempt was made to produce gypsum boards with hemp fibers. Although [...] Read more.

Although gypsum-based building materials exhibit many positive characteristics, solutions are still being searched for to reduce the use of gypsum or improve the physico-mechanical properties of board materials. In this study, an attempt was made to produce gypsum boards with hemp fibers. Although hemp fibers can be a specific reinforcement for gypsum-based board materials, they negatively affect the gypsum setting process due to their hygroscopic characteristics. Fibers impregnated with derivatives based on polyvinyl acetate, styrene–acrylic copolymer and pMDI (polymeric diphenylmethane diisocyanate) were used in this study. Gypsum–fiber boards produced with impregnated fibers showed approximately 30% higher mechanical properties as determined by the 3-point bending test. The positive effect of the impregnates on the hemp fibers was confirmed by FTIR (Fourier-transform infrared spectroscopy) and TG/DTA (thermogravimetric analysis/thermal gravimetric analysis) analysis. Full article

(This article belongs to the Special Issue Advanced Fiber-Reinforced Composites: Design, Properties and Applications (Second Edition))

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19 pages, 10170 KiB

Open AccessArticle

Challenges of a Circular Economy: The Example of Raw Recycled Tyre Steel Fibres Added to Concrete

by Agnieszka Michalik, Filip Chyliński, Jacek Zychowicz and Waldemar Pichór

Materials 2024, 17(18), 4554; https://doi.org/10.3390/ma17184554 - 17 Sep 2024

Abstract

This research was conducted to analyse the possibility of using raw, untreated recycled tyre fibres as an effective concrete reinforcement according to circular economy principles. The aim of the article was also to develop a method for dispensing tire fibres on a real [...] Read more.

This research was conducted to analyse the possibility of using raw, untreated recycled tyre fibres as an effective concrete reinforcement according to circular economy principles. The aim of the article was also to develop a method for dispensing tire fibres on a real scale. Additional treatment and homogenisation of recycled steel fibres entail higher energy consumption, emissions of greenhouse gases, and increased costs. However, obtaining durable and safe concrete effectively reinforced with steel fibres is critical. Finding a balance between environmental friendliness and product durability is a circular economic challenge. Reference concrete with commercial steel fibres (15 kg/m³) and two concretes containing various quantities of non-treated, raw tyre recycled fibres (25 kg/m³ and 45 kg/m³) were industrially produced. Tests were carried out on the properties of the concrete mixture and hardened concrete, such as compressive strength, flexural strength, splitting strength, modulus of elasticity, residual flexural tensile strength, and fibre distribution in concrete. Tests revealed that increasing the amount of raw tyre fibres disturbs the structure and causes air entrainment and the formation of fibre clusters. Smaller quantities of raw tyre fibres turn out an effective concrete reinforcement. The use of non-treated tyre fibres as concrete reinforcement is possible but requires more stringent control of the concrete parameters. Implementation tests on an industrial scale are a novelty in this study, presenting an analysis of the possible dispensing of tyre fibres in a ready-mixed concrete production plant and testing the characteristics of manufactured concrete. Full article

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

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19 pages, 1285 KiB

Open AccessArticle

Boosting Flame Retardancy of Polypropylene/Calcium Carbonate Composites with Inorganic Flame Retardants

by Antonio Benjamim Mapossa, Erick Gabriel Ribeiro dos Anjos and Uttandaraman Sundararaj

Materials 2024, 17(18), 4553; https://doi.org/10.3390/ma17184553 - 16 Sep 2024

Abstract

This study investigates the effects of inorganic flame retardants, zinc borate, and magnesium hydroxide, on the thermal, morphological, flame retardancy, and mechanical properties of polypropylene (PP)/calcium carbonate composites for potential construction industry applications. Polypropylene/calcium carbonate (50 wt.%) composites containing 5 and 10 wt.% [...] Read more.

This study investigates the effects of inorganic flame retardants, zinc borate, and magnesium hydroxide, on the thermal, morphological, flame retardancy, and mechanical properties of polypropylene (PP)/calcium carbonate composites for potential construction industry applications. Polypropylene/calcium carbonate (50 wt.%) composites containing 5 and 10 wt.% flame retardants were prepared using a batch mixer, followed by compression moulding. The results demonstrated enhanced thermal stability, with the highest char residue reaching 47.2% for polypropylene/calcium carbonate/zinc borate (10 wt.%)/magnesium hydroxide (10 wt.%) composite, a notably strong outcome. Additionally, the composite exhibited an elevated limited oxygen index (LOI) of 29.4%, indicating a synergistic effect between zinc borate and magnesium hydroxide. The proposed flame retardancy mechanism suggests that the flammability performance is driven by the interaction between the flame retardants within the polypropylene/calcium carbonate matrix. Magnesium hydroxide contributes to smoke suppression by releasing water, while zinc borate forms a protective glassy foam that covers the burning surface, promoting char formation and acting as a physical barrier to heat transmission and fire spread. Scanning electron microscopy confirmed good dispersion of the additives alongside calcium carbonate within the polymer matrix. Despite the addition of up to 10 wt.% flame retardants, the composites maintained high-notched impact strength. Full article

(This article belongs to the Special Issue Design and Development of Flame-Retardant Polymer Materials)

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