Materials

35 pages, 8763 KiB

Open AccessEditor’s ChoiceArticle

New Types and Dosages for the Manufacture of Low-Energy Cements from Raw Materials and Industrial Waste under the Principles of the Circular Economy and Low-Carbon Economy

by Sergio Martínez-Martínez, Luis Pérez-Villarejo, Dolores Eliche-Quesada and Pedro J. Sánchez-Soto

Materials 2023, 16(2), 802; https://doi.org/10.3390/ma16020802 - 13 Jan 2023

Cited by 19 | Viewed by 2372

Abstract

The cement manufacturing industry is one of the main greenhouse gas emission producers and also consumes a large quantity of raw materials. It is essential to reduce these emissions in order to comply with the Paris Agreement and the principles of the circular [...] Read more.

The cement manufacturing industry is one of the main greenhouse gas emission producers and also consumes a large quantity of raw materials. It is essential to reduce these emissions in order to comply with the Paris Agreement and the principles of the circular economy. The objective of this research was to develop different types of cement clinker blends using industrial waste and innovative design to produce low-energy cement. Several types of waste have been studied as alternative raw materials. Their main characteristics have been analyzed via X-ray fluorescence (XRF), X-ray diffraction (XRD), Attenuated total reflectance Fourier trans-form infrared spectroscopy (ATR-FTIR), thermal analysis (TG-DTG-DSC) and scanning electron microscopy and energy dispersive X-ray spectroscopy analysis (SEM-EDS). The results obtained from the experimental work carried out in this research focused on the study of crude blends for low-energy cement created from industrial waste. The effect of the addition of different industrial waste types, as a substitution for raw materials, in the production of low-energy cement with high dicalcium silicate content has been investigated. Thus, the dosage design has been performed using modified Bogue equations and quality indexes (LSF, AM, and SM). The calculations of both the modified Bogue equations and quality indexes necessitate knowledge of the weight percentages of CaO, SiO₂, Al₂O₃, and Fe₂O₃, determined via XRF. In this theoretical design of the different blends, it has been established that a dicalcium silicate ratio of 60–65 wt % and an LSF of 78–83% as the limit are values common to all of them. The calculation basis for the crude blends has been based on calcined materials. Therefore, the chemical composition was established, following this premise. Thus, it was possible to develop cement clinker blends with compositions of 50 wt % and 100 wt % using industrial wastes. This research has shown that the clinkerization process is one of the main options for the valorization of waste and its consideration for inclusion as a raw material within the circularity of the cement industry’s production process. Thus, waste is used as a raw material for the production of a more useful substance, taking into account the fundamental principles of the circular economy. Full article

(This article belongs to the Special Issue Recycling and Development of New Building Materials or Products)

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14 pages, 2567 KiB

Open AccessEditor’s ChoiceArticle

Mechanical Properties of a Bone-like Bioceramic–Epoxy-Based Composite Material with Nanocellulose Fibers

by Young-Seong Kim, Jin Woo Baek, Zhengyun Jin, Hee Chang Jeon, Min-Woo Han and Joong Yeon Lim

Materials 2023, 16(2), 739; https://doi.org/10.3390/ma16020739 - 12 Jan 2023

Cited by 3 | Viewed by 2719

Abstract

Several composite materials are being investigated as reinforcement fillers for surgery simulations. This study presents an artificial composite material with properties similar to those of the human bone, which may be used in surgery simulations. Moreover, considering the potential toxicity of debris generated [...] Read more.

Several composite materials are being investigated as reinforcement fillers for surgery simulations. This study presents an artificial composite material with properties similar to those of the human bone, which may be used in surgery simulations. Moreover, considering the potential toxicity of debris generated during sawing, a safe epoxy-based composite material was synthesized using cellulose nanocrystals (CNCs) and bioceramics (i.e., hydroxyapatite, Yttria stabilized zirconia oxide, Zirconia oxide), which were used to mimic the stiffness of human bone. To examine the change in mechanical properties according to the composition, 1, 3, and 5 wt% of CNCs were mixed with 5 wt% of the bioceramics. When CNCs were added at 1 wt%, there was a confirmed change in the non-linear stiffness and ductility. The CNC-added specimen fractured when forming a nano-network around the local CNCs during curing. In contrast, the specimen without CNCs was more densely structured, and combined to form a network of all specimens such that a plastic region could exist. Thus, this study successfully manufactured a material that could mimic longitudinal and transverse characteristics similar to those of real human bone, as well as exhibit mechanical properties such as strength and stiffness. Bioceramics are harmless to the human body, and can be used by controlling the added quantity of CNCs. We expect that this material will be suitable for use in surgery simulations. Full article

(This article belongs to the Section Advanced Composites)

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13 pages, 4380 KiB

Open AccessEditor’s ChoiceArticle

The Impact of Different Parameters on the Formwork Pressure Exerted by Self-Compacting Concrete

by Yaser Gamil, Andrzej Cwirzen, Jonny Nilimaa and Mats Emborg

Materials 2023, 16(2), 759; https://doi.org/10.3390/ma16020759 - 12 Jan 2023

Cited by 9 | Viewed by 2229

Abstract

Despite the advantageous benefits offered by self-compacting concrete, its uses are still limited due to the high pressure exerted on the formwork. Different parameters, such as those related to concrete mix design, the properties of newly poured concrete, and placement method, have an [...] Read more.

Despite the advantageous benefits offered by self-compacting concrete, its uses are still limited due to the high pressure exerted on the formwork. Different parameters, such as those related to concrete mix design, the properties of newly poured concrete, and placement method, have an impact on form pressure. The question remains unanswered on the degree of the impact for each parameter. Therefore, this study aims to study the level of impact of these parameters, including slump flow, T500 time, fresh concrete density, air content, static yield stress, concrete setting time, and concrete temperature. To mimic the casting scenario, 2 m columns were cast at various casting rates and a laboratory setup was developed. A pressure system that can wirelessly and continuously record pressure was used to monitor the pressure. Each parameter’s impact on the level of pressure was examined separately. Casting rate and slump flow were shown to have a greater influence on pressure. The results also demonstrated that, while higher thixotropy causes form pressure to rapidly decrease, a high casting rate and high slump flow lead to high pressure. This study suggests that more thorough analysis should be conducted of additional factors that may have an impact, such as the placement method, which was not included in this publication. Full article

(This article belongs to the Special Issue Numerical and Experimental Analysis of Advanced Concrete Materials)

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21 pages, 6540 KiB

Open AccessEditor’s ChoiceReview

Review on Mechanoresponsive Smart Windows: Structures and Driving Modes

by Bo Chen, Qi Feng, Weiwei Liu, Yang Liu, Lili Yang and Dengteng Ge

Materials 2023, 16(2), 779; https://doi.org/10.3390/ma16020779 - 12 Jan 2023

Cited by 7 | Viewed by 3327

Abstract

The growing awareness about the global energy crisis and extreme weather from global warming drives the development of smart windows market. Compared to conventional electrochromic, photochromic, or thermochromic smart windows, mechanoresponsive smart windows present advantages of simple construction, low cost, and excellent stability. [...] Read more.

The growing awareness about the global energy crisis and extreme weather from global warming drives the development of smart windows market. Compared to conventional electrochromic, photochromic, or thermochromic smart windows, mechanoresponsive smart windows present advantages of simple construction, low cost, and excellent stability. In this review, we summarize recent developments in mechanoresponsive smart windows with a focus on the structures and properties. We outline the categories and discuss the advantages and disadvantages. Especially, we also summarize six unconventional driving modes to generate mechanical strain, including pneumatic, optical, thermal, electric, magnetic, and humidity modes. Lastly, we provide practical recommendations in prospects for future development. This review aims to provide a useful reference for the design of novel mechanoresponsive smart windows and accelerate their practical applications. Full article

(This article belongs to the Special Issue Recent Trends in Functional Nanocomposites: Synthesis and Performance)

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18 pages, 9080 KiB

Open AccessEditor’s ChoiceArticle

Design and Optimization of Thermal Field for PVT Method 8-Inch SiC Crystal Growth

by Shengtao Zhang, Guoqing Fu, Hongda Cai, Junzhi Yang, Guofeng Fan, Yanyu Chen, Tie Li and Lili Zhao

Materials 2023, 16(2), 767; https://doi.org/10.3390/ma16020767 - 12 Jan 2023

Cited by 9 | Viewed by 4300

Abstract

As a wide bandgap semiconductor material, silicon carbide has promising prospects for application. However, its commercial production size is currently 6 inches, and the difficulty in preparing larger single crystals increases exponentially with size increasing. Large-size single crystal growth is faced with the [...] Read more.

As a wide bandgap semiconductor material, silicon carbide has promising prospects for application. However, its commercial production size is currently 6 inches, and the difficulty in preparing larger single crystals increases exponentially with size increasing. Large-size single crystal growth is faced with the enormous problem of radial growth conditions deteriorating. Based on simulation tools, the physical field of 8-inch crystal growth is modeled and studied. By introducing the design of the seed cavity, the radial temperature difference in the seed crystal surface is reduced by 88% from 93 K of a basic scheme to 11 K, and the thermal field conditions with uniform radial temperature and moderate temperature gradient are obtained. Meanwhile, the effects of different processing conditions and relative positions of key structures on the surface temperature and axial temperature gradients of the seed crystals are analyzed in terms of new thermal field design, including induction power, frequency, diameter and height of coils, the distance between raw materials and the seed crystal. Meanwhiles, better process conditions and relative positions under experimental conditions are obtained. Based on the optimized conditions, the thermal field verification under seedless conditions is carried out, discovering that the single crystal deposition rate is 90% of that of polycrystalline deposition under the experimental conditions. Meanwhile, an 8-inch polycrystalline with 9.6 mm uniform deposition was successfully obtained after 120 h crystal growth, whose convexity is reduced from 13 mm to 6.4 mm compared with the original scheme. The results indicate that the optimized conditions can be used for single-crystal growth. Full article

(This article belongs to the Section Electronic Materials)

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19 pages, 2238 KiB

Open AccessEditor’s ChoiceReview

Latent Potential of Multifunctional Selenium Nanoparticles in Neurological Diseases and Altered Gut Microbiota

by Hajra Ashraf, Davide Cossu, Stefano Ruberto, Marta Noli, Seyedesomaye Jasemi, Elena Rita Simula and Leonardo A. Sechi

Materials 2023, 16(2), 699; https://doi.org/10.3390/ma16020699 - 11 Jan 2023

Cited by 17 | Viewed by 3944

Abstract

Neurological diseases remain a major concern due to the high world mortality rate and the absence of appropriate therapies to cross the blood–brain barrier (BBB). Therefore, the major focus is on the development of such strategies that not only enhance the efficacy of [...] Read more.

Neurological diseases remain a major concern due to the high world mortality rate and the absence of appropriate therapies to cross the blood–brain barrier (BBB). Therefore, the major focus is on the development of such strategies that not only enhance the efficacy of drugs but also increase their permeability in the BBB. Currently, nano-scale materials seem to be an appropriate approach to treating neurological diseases based on their drug-loading capacity, reduced toxicity, targeted delivery, and enhanced therapeutic effect. Selenium (Se) is an essential micronutrient and has been of remarkable interest owing to its essential role in the physiological activity of the nervous system, i.e., signal transmission, memory, coordination, and locomotor activity. A deficiency of Se leads to various neurological diseases such as Parkinson’s disease, epilepsy, and Alzheimer’s disease. Therefore, owing to the neuroprotective role of Se (selenium) nanoparticles (SeNPs) are of particular interest to treat neurological diseases. To date, many studies investigate the role of altered microbiota with neurological diseases; thus, the current review focused not only on the recent advancement in the field of nanotechnology, considering SeNPs to cure neurological diseases, but also on investigating the potential role of SeNPs in altered microbiota. Full article

(This article belongs to the Special Issue Functionalized Nanomaterials and Structures for Biomedical Applications)

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17 pages, 7297 KiB

Open AccessEditor’s ChoiceArticle

Phase-Field Simulation of Temperature-Dependent Thermal Shock Fracture of Al₂O₃/ZrO₂ Multilayer Ceramics with Phase Transition Residual Stress

by Yong Pang, Dingyu Li, Xin Li, Ruzhuan Wang and Xiang Ao

Materials 2023, 16(2), 734; https://doi.org/10.3390/ma16020734 - 11 Jan 2023

Cited by 6 | Viewed by 2482

Abstract

Compared with single-phase ceramics, the thermal shock crack propagation mechanism of multiphase layered ceramics is more complex. There is no experimental method and theoretical framework that can fully reveal the thermal shock damage mechanism of ceramic materials. Therefore, a multiphase phase-field fracture model [...] Read more.

Compared with single-phase ceramics, the thermal shock crack propagation mechanism of multiphase layered ceramics is more complex. There is no experimental method and theoretical framework that can fully reveal the thermal shock damage mechanism of ceramic materials. Therefore, a multiphase phase-field fracture model including the temperature dependence of material for thermal shock-induced fracture of multilayer ceramics is established. In this study, the effects of residual stress on the crack propagation of ATZ (Al₂O₃-5%tZrO₂)/AMZ (Al₂O₃-30%mZrO₂) layered ceramics with different layer thickness ratios, layers, and initial temperatures under bending and thermal shock were investigated. Simulation results of the fracture phase field under four-point bending are in good agreement with the experimental results, and the crack propagation shows a step shape, which verifies the effectiveness of the proposed method. With constant thickness, high-strength compressive stress positively changes with the layer thickness ratio, which contributes to crack deflection. The cracks of the ceramic material under thermal shock have hierarchy and regularity. When the layer thickness ratio is constant, the compressive residual stress decreases with the increase in the layer number, and the degree of thermal shock crack deflection decreases. Full article

(This article belongs to the Special Issue Recent Studies in Advanced Structural Ceramics)

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32 pages, 2590 KiB

Open AccessEditor’s ChoiceReview

Microplastics Derived from Food Packaging Waste—Their Origin and Health Risks

by Kornelia Kadac-Czapska, Eliza Knez, Magdalena Gierszewska, Ewa Olewnik-Kruszkowska and Małgorzata Grembecka

Materials 2023, 16(2), 674; https://doi.org/10.3390/ma16020674 - 10 Jan 2023

Cited by 56 | Viewed by 10868

Abstract

Plastics are commonly used for packaging in the food industry. The most popular thermoplastic materials that have found such applications are polyethylene (PE), polypropylene (PP), poly(ethylene terephthalate) (PET), and polystyrene (PS). Unfortunately, most plastic packaging is disposable. As a consequence, significant amounts of [...] Read more.

Plastics are commonly used for packaging in the food industry. The most popular thermoplastic materials that have found such applications are polyethylene (PE), polypropylene (PP), poly(ethylene terephthalate) (PET), and polystyrene (PS). Unfortunately, most plastic packaging is disposable. As a consequence, significant amounts of waste are generated, entering the environment, and undergoing degradation processes. They can occur under the influence of mechanical forces, temperature, light, chemical, and biological factors. These factors can present synergistic or antagonistic effects. As a result of their action, microplastics are formed, which can undergo further fragmentation and decomposition into small-molecule compounds. During the degradation process, various additives used at the plastics’ processing stage can also be released. Both microplastics and additives can negatively affect human and animal health. Determination of the negative consequences of microplastics on the environment and health is not possible without knowing the course of degradation processes of packaging waste and their products. In this article, we present the sources of microplastics, the causes and places of their formation, the transport of such particles, the degradation of plastics most often used in the production of packaging for food storage, the factors affecting the said process, and its effects. Full article

(This article belongs to the Special Issue Sustainability, Circular Economy and Waste Recycling: Advances in Materials Research)

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14 pages, 4377 KiB

Open AccessEditor’s ChoiceArticle

Characterization of Filigree Additively Manufactured NiTi Structures Using Micro Tomography and Micromechanical Testing for Metamaterial Material Models

by Thomas Straub, Jonas Fell, Simon Zabler, Tobias Gustmann, Hannes Korn and Sarah C. L. Fischer

Materials 2023, 16(2), 676; https://doi.org/10.3390/ma16020676 - 10 Jan 2023

Cited by 5 | Viewed by 2405

Abstract

This study focuses on the influence of additive manufacturing process strategies on the specimen geometry, porosity, microstructure and mechanical properties as well as their impacts on the design of metamaterials. Filigree additively manufactured NiTi specimens with diameters between 180 and 350 µm and [...] Read more.

This study focuses on the influence of additive manufacturing process strategies on the specimen geometry, porosity, microstructure and mechanical properties as well as their impacts on the design of metamaterials. Filigree additively manufactured NiTi specimens with diameters between 180 and 350 µm and a nominal composition of Ni_50.9Ti_49.1 (at %) were processed by laser powder bed fusion in a first step. Secondly, they structures were characterized by optical and electron microscopy as well as micro tomography to investigate the interrelations between the process parameters, specimen diameters and microstructure. Each specimen was finally tested in a micro tensile machine to acquire the mechanical performance. The process strategy had, besides the resulting specimen diameter, an impact on the microstructure (grain size) without negatively influencing its quality (porosity). All specimens revealed a superelastic response while the critical martensitic phase transition stress decreased with the applied vector length. As a conclusion, and since the design of programmable metamaterials relies on the accuracy of FEM simulations, precise and resource-efficient testing of filigree and complex structures remains an important part of creating a new type of metamaterials with locally adjusted material behavior. Full article

(This article belongs to the Special Issue Advances in Metamaterials: Structure, Properties and Applications)

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14 pages, 1717 KiB

Open AccessEditor’s ChoiceArticle

A Novel Chitosan Composite Biomaterial with Drug Eluting Capacity for Maxillary Bone Regeneration

by Barbara Giordano-Kelhoffer, Raquel Rodríguez-Gonzalez, Marina Perpiñan-Blasco, Jenifer O. Buitrago, Begoña M. Bosch and Roman A. Perez

Materials 2023, 16(2), 685; https://doi.org/10.3390/ma16020685 - 10 Jan 2023

Cited by 8 | Viewed by 2439

Abstract

Bone grafting is one of the most commonly performed treatments for bone healing or repair. Autografts, grafts from the same patient, are the most frequently used bone grafts because they can provide osteogenic cells and growth factors at the site of the implant [...] Read more.

Bone grafting is one of the most commonly performed treatments for bone healing or repair. Autografts, grafts from the same patient, are the most frequently used bone grafts because they can provide osteogenic cells and growth factors at the site of the implant with reduced risk of rejection or transfer of diseases. Nevertheless, this type of graft presents some drawbacks, such as pain, risk of infection, and limited availability. For this reason, synthetic bone grafts are among the main proposals in regenerative medicine. This branch of medicine is based on the development of new biomaterials with the goal of increasing bone healing capacity and, more specifically in dentistry, they aim at simultaneously preventing or eliminating bacterial infections. The use of fibers made of chitosan (CS) and hydroxyapatite (HA) loaded with an antibiotic (doxycycline, DX) and fabricated with the help of an injection pump is presented as a new strategy for improving maxillary bone regeneration. In vitro characterization of the DX controlled released from the fibers was quantified after mixing different amounts of HA (10–75%). The 1% CS concentration was stable, easy to manipulate and exhibited adequate cuttability and pH parameters. The hydroxyapatite concentration dictated the combined fast and controlled release profile of CSHA50DX. Our findings demonstrate that the CS-HA-DX complex may be a promising candidate graft material for enhancing bone tissue regeneration in dental clinical practice. Full article

(This article belongs to the Section Biomaterials)

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10 pages, 1835 KiB

Open AccessEditor’s ChoiceArticle

Preparation and Performance of AgNWs/PDMS Film-Based Flexible Strain Sensor

by Xiaoxin Zhu, Yimin Zhou and Cui Ye

Materials 2023, 16(2), 641; https://doi.org/10.3390/ma16020641 - 9 Jan 2023

Cited by 19 | Viewed by 3847

Abstract

Flexible strain sensors are widely used in the fields of personal electronic equipment and health monitoring to promote the rapid development of modern social science and technology. In this paper, silver nanowires (AgNWs) prepared via the polyol reduction method were used to construct [...] Read more.

Flexible strain sensors are widely used in the fields of personal electronic equipment and health monitoring to promote the rapid development of modern social science and technology. In this paper, silver nanowires (AgNWs) prepared via the polyol reduction method were used to construct a flexible strain sensor. The AgNWs/PDMS film was obtained by transfer printing using AgNWs as a conductive layer and polydimethylsiloxane (PDMS) as a flexible substrate. The morphology of AgNWs was characterized by SEM and TEM. The aspect ratio of the AgNWs was more than 700. The strain sensitivity factor of the sensor was 2.8757, with a good linear relationship between the resistance and the strain. Moreover, the strain sensor showed good response results in human activity monitoring and the LED lamp response test, which provides a new idea for the construction of flexible wearable devices. Full article

(This article belongs to the Special Issue Flexible Transparent Conductive Films: Design and Applications)

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33 pages, 19137 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Structured Catalytic Materials Development for Conversion of Liquid Hydrocarbons into Synthesis Gas for Fuel Cell Power Generators

by Vladislav Shilov, Dmitriy Potemkin, Vladimir Rogozhnikov and Pavel Snytnikov

Materials 2023, 16(2), 599; https://doi.org/10.3390/ma16020599 - 8 Jan 2023

Cited by 11 | Viewed by 2717

Abstract

The paper considers the current state of research and development of composite structured catalysts for the oxidative conversion of liquid hydrocarbons into synthesis gas for fuel cell feeding and gives more detailed information about recent advances in the Boreskov Institute of Catalysis. The [...] Read more.

The paper considers the current state of research and development of composite structured catalysts for the oxidative conversion of liquid hydrocarbons into synthesis gas for fuel cell feeding and gives more detailed information about recent advances in the Boreskov Institute of Catalysis. The main factors affecting the progress of the target reaction and side reactions leading to catalyst deactivation are discussed. The properties of the Rh/Ce_0.75Zr_0.25O₂/Al₂O₃/FeCrAl composite multifunctional catalyst for the conversion of diesel fuel into synthesis gas are described. The results of the catalyst testing and mathematical modeling of the process of diesel fuel steam–air conversion into synthesis gas are reported. Full article

(This article belongs to the Special Issue Advanced Materials in Catalysis and Adsorption)

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16 pages, 8358 KiB

Open AccessEditor’s ChoiceArticle

Creep Crack Growth Behavior during Hot Water Immersion of an Epoxy Adhesive Using a Spring-Loaded Double Cantilever Beam Test Method

by Kota Nakamura, Yu Sekiguchi, Kazumasa Shimamoto, Keiji Houjou, Haruhisa Akiyama and Chiaki Sato

Materials 2023, 16(2), 607; https://doi.org/10.3390/ma16020607 - 8 Jan 2023

Cited by 9 | Viewed by 3366

Abstract

Double cantilever beam (DCB) tests were conducted by immersing the specimens in temperature-controlled water while applying a creep load using a spring. By introducing a data reduction scheme to the spring-loaded DCB test method, it was confirmed that only a single parameter measurement [...] Read more.

Double cantilever beam (DCB) tests were conducted by immersing the specimens in temperature-controlled water while applying a creep load using a spring. By introducing a data reduction scheme to the spring-loaded DCB test method, it was confirmed that only a single parameter measurement was sufficient to calculate the energy release rate (ERR). Aluminum alloy substrates bonded with an epoxy adhesive were used, and DCB tests were performed by changing the initial load values, spring constants, and immersion temperatures for two types of surface treatment. The initial applied load and spring constant had no effect on the ERR threshold. In contrast, the threshold decreased with the increasing immersion temperature, but even in the worst case, it was 15% of the critical ERR in the static tests. Using the creep crack growth relationship, it was revealed that there were three phases of creep immersion crack growth in the adhesive joints, and each phase was affected by the temperature. The spring-loaded DCB test method has great potential for investigating the combined effects of creep, moisture, and temperature, and this study has demonstrated the validity of the test method. The long-term durability of adhesive joints becomes increasingly important, and this test method is expected to become widespread. Full article

(This article belongs to the Special Issue Mechanical Properties and Application of Adhesive Materials)

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11 pages, 2457 KiB

Open AccessEditor’s ChoiceArticle

Nanocomposite Electrode of Titanium Dioxide Nanoribbons and Multiwalled Carbon Nanotubes for Energy Storage

by Mohammad BinSabt, Mohamed Shaban and Ahmed Gamal

Materials 2023, 16(2), 595; https://doi.org/10.3390/ma16020595 - 7 Jan 2023

Cited by 8 | Viewed by 2497

Abstract

TiO₂ is one of the most investigated materials due to its abundance, lack of toxicity, high faradaic capacitance, and high chemical and physical stability; however, its potential use in energy storage devices is constrained by its high internal resistance and weak van [...] Read more.

TiO₂ is one of the most investigated materials due to its abundance, lack of toxicity, high faradaic capacitance, and high chemical and physical stability; however, its potential use in energy storage devices is constrained by its high internal resistance and weak van der Waals interaction between the particles. Carbon nanotubes are especially well suited for solving these issues due to their strong mechanical strength, superior electrical conductivity, high electron mobilities, excellent chemical and thermal stability, and enormous specific nanoporous surface. The hydrothermal approach was followed by chemical vapor deposition to produce a network composite of titanium dioxide nanoribbons (TNRs) and multi-walled carbon nanotubes (MWCNTs). The nanocomposite was characterized using a variety of methods. One phase of TiO₂-B nanoribbons has porous pits on its surface, and MWCNTs are grown in these pits to produce a network-like structure in the nanocomposite. With a two-electrode supercapacitor configuration, the TNR/CNT gave a gravimetric capacitance of 33.33 F g⁻¹, which was enhanced to 68.18 F g⁻¹ in a redox-active electrolyte containing hydroquinone (HQ). Additionally, the areal capacitance per footprint was increased from 80 mF cm⁻² in H₂SO₄ to 163.63 mF cm⁻² in H₂SO₄/HQ. The TNR/CNT supercapacitor has superior cyclic stability than the previously reported TiO₂-based electrodes, with 97.5% capacitance retention after 5000 cycles. Based on these results, it looks like the TNR/CNT supercapacitor could provide portable electronic power supplies with new ways to work in the future. Full article

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

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14 pages, 6103 KiB

Open AccessEditor’s ChoiceArticle

Manganese Luminescent Centers of Different Valence in Yttrium Aluminum Borate Crystals

by Anastasiia Molchanova, Kirill Boldyrev, Nikolai Kuzmin, Alexey Veligzhanin, Kirill Khaydukov, Evgeniy Khaydukov, Oleg Kondratev, Irina Gudim, Elizaveta Mikliaeva and Marina Popova

Materials 2023, 16(2), 537; https://doi.org/10.3390/ma16020537 - 5 Jan 2023

Cited by 2 | Viewed by 1993

Abstract

We present an extensive study of the luminescence characteristics of Mn impurity ions in a YAl₃(BO₃)₄:Mn crystal, in combination with X-ray fluorescence analysis and determination of the valence state of Mn by XANES (X-ray absorption near-edge structure) [...] Read more.

We present an extensive study of the luminescence characteristics of Mn impurity ions in a YAl₃(BO₃)₄:Mn crystal, in combination with X-ray fluorescence analysis and determination of the valence state of Mn by XANES (X-ray absorption near-edge structure) spectroscopy. The valences of manganese Mn²⁺(d⁵) and Mn³⁺(d⁴) were determined by the XANES and high-resolution optical spectroscopy methods shown to be complementary. We observe the R₁ and R₂ luminescence and absorption lines characteristic of the ²E ↔ ⁴A₂ transitions in d³ ions (such as Mn⁴⁺ and Cr³⁺) and show that they arise due to uncontrolled admixture of Cr³⁺ ions. A broad luminescent band in the green part of the spectrum is attributed to transitions in Mn²⁺. Narrow zero-phonon infrared luminescence lines near 1060 nm (9400 cm⁻¹) and 760 nm (13,160 cm⁻¹) are associated with spin-forbidden transitions in Mn³⁺: ¹T₂ → ³T₁ (between excited triplets) and ¹T₂ → ⁵E (to the ground state). Spin-allowed ⁵T₂ → ⁵E Mn³⁺ transitions show up as a broad band in the orange region of the spectrum. Using the data of optical spectroscopy and Tanabe–Sugano diagrams we estimated the crystal-field parameter Dq and Racah parameter B for Mn³⁺ in YAB:Mn as Dq = 1785 cm⁻¹ and B = 800 cm⁻¹. Our work can serve as a basis for further study of YAB:Mn for the purposes of luminescent thermometry, as well as other applications. Full article

(This article belongs to the Special Issue Advanced Luminescent Materials and Devices)

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13 pages, 3959 KiB

Open AccessEditor’s ChoiceArticle

Smart PEG-Block-PLA/PLA Nanosystems: Impact of the Characteristics of the Polymer Blend on the Redox Responsiveness

by Louise Van Gheluwe, Stephanie David, Eric Buchy, Igor Chourpa and Emilie Munnier

Materials 2023, 16(2), 539; https://doi.org/10.3390/ma16020539 - 5 Jan 2023

Cited by 1 | Viewed by 1968

Abstract

Nanocarriers (NCs) were designed from three polymer blends (B1, B2 and B3) and investigated as smart drug delivery systems (SDDS). The blends are composed of a “smart” copolymer, where methoxy poly(ethylene glycol) and poly(lactic acid) are connected via a redox-responsive disulfide bond (mPEG-SS-PLA), [...] Read more.

Nanocarriers (NCs) were designed from three polymer blends (B1, B2 and B3) and investigated as smart drug delivery systems (SDDS). The blends are composed of a “smart” copolymer, where methoxy poly(ethylene glycol) and poly(lactic acid) are connected via a redox-responsive disulfide bond (mPEG-SS-PLA), and of a “conventional” polymer, poly(lactic acid) (PLA). They differ by mPEG-SS-PLA/PLA ratio and PLA molecular weight. Nanoprecipitation was used to prepare NCs. Three concentrations were tested, and fluorescent dye Nile red (NR) was used as a model payload. The results show that the characteristics of the NCs, such as size and drug release kinetics, are influenced by the type of blend and the concentration used during the nanoprecipitation process. The more redox-responsive blend was B2 (ratio 1:3, PLA 5 kDa) at 16 mg/mL: the quantity of NR released was tripled upon 24 h of incubation in a reducing medium. This study reveals that the amount of disulfide bonds present in a NC is not the only parameter to be considered to design an SDDS. The stability of the SDDS in a presumably non-stimulating environment is also important to limit uncontrolled release during storage or in the body before the biological target is reached. Full article

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

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6 pages, 1804 KiB

Open AccessEditor’s ChoiceArticle

Dispersion of Long and Isolated Single-Wall Carbon Nanotubes by Using a Hydrodynamic Cavitation Method

by Shunjiro Fujii, Shin-ichi Honda, Yoshihiro Oka, Yuki Kuwahara and Takeshi Saito

Materials 2023, 16(2), 466; https://doi.org/10.3390/ma16020466 - 4 Jan 2023

Cited by 2 | Viewed by 2529

Abstract

Single-wall carbon nanotubes (SWCNTs) are promising materials for electronic applications, such as transparent electrodes and thin-film transistors. However, the dispersion of isolated SWCNTs into solvents remains an important issue for their practical applications. SWCNTs are commonly dispersed in solvents via ultrasonication. However, ultrasonication [...] Read more.

Single-wall carbon nanotubes (SWCNTs) are promising materials for electronic applications, such as transparent electrodes and thin-film transistors. However, the dispersion of isolated SWCNTs into solvents remains an important issue for their practical applications. SWCNTs are commonly dispersed in solvents via ultrasonication. However, ultrasonication damages SWCNTs, forming defects and cutting them into short pieces, which significantly degrade their electrical and mechanical properties. Herein, we demonstrate a novel approach toward the large-scale dispersion of long and isolated SWCNTs by using hydrodynamic cavitation. Considering the results of atomic force microscopy and dynamic light-scattering measurements, the average length of the SWCNTs dispersed via the hydrodynamic cavitation method is larger than that of the SWCNTs dispersed by using an ultrasonic homogenizer. Full article

(This article belongs to the Special Issue Anisotropic Functional Nanomaterials: Preparations, Characterizations, and Applications)

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21 pages, 5122 KiB

Open AccessEditor’s ChoiceArticle

Surface Modification and Properties of Thin Ink Films with Added TiO₂ and ZnO Nanoparticles Applied on Paperboard Substrates

by Sanja Mahović Poljaček, Tamara Tomašegović, Maja Strižić Jakovljević and Davor Donevski

Materials 2023, 16(2), 478; https://doi.org/10.3390/ma16020478 - 4 Jan 2023

Cited by 3 | Viewed by 1987

Abstract

In this study, the surface modification of thin ink films with added nanoparticles was used to improve the functional properties of ink applied on paperboard substrates. The surface modification was performed by additional exposure of the samples to xenon radiation. Anatase TiO₂ [...] Read more.

In this study, the surface modification of thin ink films with added nanoparticles was used to improve the functional properties of ink applied on paperboard substrates. The surface modification was performed by additional exposure of the samples to xenon radiation. Anatase TiO₂, rutile TiO₂ and ZnO were added to the base ink. The effect of surface modification on the surface, structural, and mechanical properties of the printed ink films was determined by FTIR-ATR spectroscopy, calculating the surface free energy and adhesion parameters, performing the rub resistance test of the printed samples, and by measuring the resistance to bending. Color measurements on the ink films were performed in order to observe the optical properties of unmodified and modified samples. The results showed that surface modification significantly improved the adhesion properties of the thin ink films and the mechanical properties of the samples. The results obtained on uncoated and coated paperboard showed that the addition of rutile TiO₂ and ZnO nanoparticles had the greatest effect on the rub resistance of the ink films. The results of the color analysis showed that the addition of nanoparticles did not change the optical properties of the modified ink films and that rutile TiO₂ and ZnO nanoparticles improved the lightfastness of the applied ink films. Full article

(This article belongs to the Special Issue Feature Papers in Thin Films and Interfaces)

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12 pages, 1624 KiB

Open AccessEditor’s ChoiceArticle

Binding of Ca²⁺ Ions to Alkylbenzene Sulfonates: Micelle Formation, Second Critical Concentration and Precipitation

by Adél Anna Ádám, Szilveszter Ziegenheim, László Janovák, Márton Szabados, Csaba Bús, Ákos Kukovecz, Zoltán Kónya, Imre Dékány, Pál Sipos and Bence Kutus

Materials 2023, 16(2), 494; https://doi.org/10.3390/ma16020494 - 4 Jan 2023

Cited by 2 | Viewed by 2450

Abstract

Anionic surfactants, such as sodium linear alkylbenzene sulfonates (NaLAS), are utilized in various fields, including industry, household, and agriculture. The efficiency of their use in aqueous environments is significantly affected by the presence of cations, Ca²⁺ and Mg²⁺ in particular, as [...] Read more.

Anionic surfactants, such as sodium linear alkylbenzene sulfonates (NaLAS), are utilized in various fields, including industry, household, and agriculture. The efficiency of their use in aqueous environments is significantly affected by the presence of cations, Ca²⁺ and Mg²⁺ in particular, as they can decrease the concentration of the surfactant due to precipitation. To understand cation–sulfonate interactions better, we study both NaLAS colloidal solutions in the presence of CaCl₂ and precipitates forming at higher salt concentrations. Upon addition of CaCl₂, we find the surface tension and critical micelle concentration of NaLAS to decrease significantly, in line with earlier findings for alkylbenzylsulfonates in the presence of divalent cations. Strikingly, an increase in the surface tension is discernible above 0.6 g L^–1 NaLAS, accompanied by the decrease of apparent micelle sizes, which in turn gives rise to transparent systems. Thus, there appears to be a second critical concentration indicating another micellar equilibrium. Furthermore, the maximum salt tolerance of the surfactant is 0.1 g L^–1 Ca²⁺, above which rapid precipitation occurs yielding sparingly soluble CaLAS₂∙2H₂O. Full article

(This article belongs to the Section Soft Matter)

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20 pages, 4964 KiB

Open AccessEditor’s ChoiceReview

A Review of Cu–Ni–Sn Alloys: Processing, Microstructure, Properties, and Developing Trends

by Lang Guo, Pengcheng Zuo, Zequn Zhang, Qianwen Zhang, Mengya Zhao, Xinyu Hou, Junsheng Wu and Bowei Zhang

Materials 2023, 16(1), 444; https://doi.org/10.3390/ma16010444 - 3 Jan 2023

Cited by 22 | Viewed by 5741

Abstract

Cu–Ni–Sn alloys have been widely used in the aerospace industry, the electronics industry, and other fields due to their excellent electrical and thermal conductivity, high strength, corrosion and wear resistance, etc., which make Cu–15Ni–8Sn alloys the perfect alternative to Cu–Be alloys. This paper [...] Read more.

Cu–Ni–Sn alloys have been widely used in the aerospace industry, the electronics industry, and other fields due to their excellent electrical and thermal conductivity, high strength, corrosion and wear resistance, etc., which make Cu–15Ni–8Sn alloys the perfect alternative to Cu–Be alloys. This paper begins with how Cu–Ni–Sn alloys are prepared. Then, the microstructural features, especially the precipitation order of each phase, are described. In addition, the influence of alloying elements, such as Si, Ti, and Nb, on its microstructure and properties is discussed. Finally, the effects of plastic deformation and heat treatment on Cu–Ni–Sn alloys are discussed. This review is able to provide insight into the development of novel Cu–Ni–Sn alloys with a high performance. Full article

(This article belongs to the Special Issue Feature Papers in "Metals and Alloys" Section)

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12 pages, 1550 KiB

Open AccessEditor’s ChoiceArticle

Effect of Blend Composition on Barrier Properties of Insulating Mats Produced from Local Wool and Waste Bast Fibres

by Anna Kicińska-Jakubowska, Jan Broda, Małgorzata Zimniewska, Marcin Bączek and Jerzy Mańkowski

Materials 2023, 16(1), 459; https://doi.org/10.3390/ma16010459 - 3 Jan 2023

Cited by 10 | Viewed by 2274

Abstract

This paper concerns the management of natural waste fibres. The aim of this research was the production of multifunctional acoustic and thermal insulation materials from natural protein and lignocellulosic fibre wastes, according to a circular bioeconomy. For the manufacture of the materials, local [...] Read more.

This paper concerns the management of natural waste fibres. The aim of this research was the production of multifunctional acoustic and thermal insulation materials from natural protein and lignocellulosic fibre wastes, according to a circular bioeconomy. For the manufacture of the materials, local mountain sheep wool and a mixture of bast fibre waste generated by string production were used. Insulating materials in the form of mats produced by the needle-punching technique with different fibre contents were obtained. The basic parameters of the mats, i.e., the thickness, surface weight and air permeability were determined. To assess barrier properties, sound absorption and noise reduction coefficients, as well as thermal resistance and thermal conductivity, were measured. It was shown that the mats exhibit barrier properties in terms of thermal and acoustic insulation related to the composition of the mat. It was found that mats with a higher content of the bast fibres possess a greater ability to absorb sounds, while mats with higher wool contents exhibit better thermal insulation properties. The produced mats can serve as a good alternative to commonly used acoustic and thermal insulating materials. The production of the described materials allows for a reduction in the amount of natural fibre waste and achieves the goal of “zero waste” according to the European Green Deal strategy. Full article

(This article belongs to the Special Issue Advances in Multifunctional Textiles: Materials, Technologies and Production Processes)

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12 pages, 3006 KiB

Open AccessEditor’s ChoiceArticle

One-Step Synthesis of Sulfur-Doped Nanoporous Carbons from Lignin with Ultra-High Surface Area, Sulfur Content and CO₂ Adsorption Capacity

by Dipendu Saha, Gerassimos Orkoulas and Dean Bates

Materials 2023, 16(1), 455; https://doi.org/10.3390/ma16010455 - 3 Jan 2023

Cited by 10 | Viewed by 2855

Abstract

Lignin is the second-most available biopolymer in nature. In this work, lignin was employed as the carbon precursor for the one-step synthesis of sulfur-doped nanoporous carbons. Sulfur-doped nanoporous carbons have several applications in scientific and technological sectors. In order to synthesize sulfur-doped nanoporous [...] Read more.

Lignin is the second-most available biopolymer in nature. In this work, lignin was employed as the carbon precursor for the one-step synthesis of sulfur-doped nanoporous carbons. Sulfur-doped nanoporous carbons have several applications in scientific and technological sectors. In order to synthesize sulfur-doped nanoporous carbons from lignin, sodium thiosulfate was employed as a sulfurizing agent and potassium hydroxide as the activating agent to create porosity. The resultant carbons were characterized by pore textural properties, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The nanoporous carbons possess BET surface areas of 741–3626 m²/g and a total pore volume of 0.5–1.74 cm³/g. The BET surface area of the carbon was one of the highest that was reported for any carbon-based materials. The sulfur contents of the carbons are 1–12.6 at.%, and the key functionalities include S=C, S-C=O, and SO_x. The adsorption isotherms of three gases, CO₂, CH₄, and N₂, were measured at 298 K, with pressure up to 1 bar. In all the carbons, the adsorbed amount was highest for CO₂, followed by CH₄ and N₂. The equilibrium uptake capacity for CO₂ was as high as ~11 mmol/g at 298 K and 760 torr, which is likely the highest among all the porous carbon-based materials reported so far. Ideally adsorbed solution theory (IAST) was employed to calculate the selectivity for CO₂/N₂, CO₂/CH₄, and CH₄/N₂, and some of the carbons reported a very high selectivity value. The overall results suggest that these carbons can potentially be used for gas separation purposes. Full article

(This article belongs to the Special Issue Synthesis, Characterization and Applications of Sustainable Advanced Nanomaterials)

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14 pages, 4604 KiB

Open AccessEditor’s ChoiceArticle

Towards Room Temperature Phase Transition of W-Doped VO₂ Thin Films Deposited by Pulsed Laser Deposition: Thermochromic, Surface, and Structural Analysis

by Yannick Bleu, Florent Bourquard, Vincent Barnier, Anne-Sophie Loir, Florence Garrelie and Christophe Donnet

Materials 2023, 16(1), 461; https://doi.org/10.3390/ma16010461 - 3 Jan 2023

Cited by 25 | Viewed by 5011

Abstract

Vanadium dioxide (VO₂) with an insulator-to-metal (IMT) transition (∼68 °C) is considered a very attractive thermochromic material for smart window applications. Indeed, tailoring and understanding the thermochromic and surface properties at lower temperatures can enable room-temperature applications. The effect of W [...] Read more.

Vanadium dioxide (VO₂) with an insulator-to-metal (IMT) transition (∼68 °C) is considered a very attractive thermochromic material for smart window applications. Indeed, tailoring and understanding the thermochromic and surface properties at lower temperatures can enable room-temperature applications. The effect of W doping on the thermochromic, surface, and nanostructure properties of VO₂ thin film was investigated in the present proof. W-doped VO₂ thin films with different W contents were deposited by pulsed laser deposition (PLD) using V/W (+O₂) and V₂O₅/W multilayers. Rapid thermal annealing at 400–450 °C under oxygen flow was performed to crystallize the as-deposited films. The thermochromic, surface chemistry, structural, and morphological properties of the thin films obtained were investigated. The results showed that the V⁵⁺ was more surface sensitive and W distribution was homogeneous in all samples. Moreover, the V₂O₅ acted as a W diffusion barrier during the annealing stage, whereas the V+O₂ environment favored W surface diffusion. The phase transition temperature gradually decreased with increasing W content with a high efficiency of −26 °C per at. % W. For the highest doping concentration of 1.7 at. %, VO₂ showed room-temperature transition (26 °C) with high luminous transmittance (62%), indicating great potential for optical applications. Full article

(This article belongs to the Special Issue Structural, Morphological, and Optical Properties of Functional Thin Films)

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17 pages, 1378 KiB

Open AccessEditor’s ChoiceReview

Research Progress of Ba(Zn_1/3Nb_2/3)O₃ Microwave Dielectric Ceramics: A Review

by Sen Peng, Yu Zhang and Tulin Yi

Materials 2023, 16(1), 423; https://doi.org/10.3390/ma16010423 - 2 Jan 2023

Cited by 7 | Viewed by 2849

Abstract

Ba(Zn_1/3Nb_2/3)O₃ (BZN) microwave dielectric ceramics have attracted great attention due to their high-quality factor (Q), near-zero temperature coefficient of resonant frequency (τ_f), and suitable dielectric constant (ε_r), making them promising materials for [...] Read more.

Ba(Zn_1/3Nb_2/3)O₃ (BZN) microwave dielectric ceramics have attracted great attention due to their high-quality factor (Q), near-zero temperature coefficient of resonant frequency (τ_f), and suitable dielectric constant (ε_r), making them promising materials for application in microwave devices. Due to their superior dielectric properties, composite perovskite ceramics are widely used in the field of microwave communication, base stations, navigation, radar, etc. This article summarized the latest research progress of BZN ceramics and discusses the main preparation methods and performance modifications. Furthermore, the problems faced by BZN ceramics and solutions to improve their performance, as well as their potential applications, are analyzed. This article provides a reference for the design and preparation of BZN ceramics. Full article

(This article belongs to the Special Issue Advances in Dielectric Ceramics and Their Applications)

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14 pages, 4451 KiB

Open AccessEditor’s ChoiceArticle

The Influence of Atmospheric Oxygen Content on the Mechanical Properties of Selectively Laser Melted AlSi10Mg TPMS-Based Lattice

by Ahmad Baroutaji, Arun Arjunan, James Beal, John Robinson and Julio Coroado

Materials 2023, 16(1), 430; https://doi.org/10.3390/ma16010430 - 2 Jan 2023

Cited by 12 | Viewed by 4089

Abstract

Selective Laser Melting (SLM) is an emerging Additive Manufacturing (AM) technique for the on-demand fabrication of metal parts. The mechanical properties of Selectively Laser Melted (SLMed) parts are sensitive to oxygen concentration within the SLM build chamber due to the formation of oxides, [...] Read more.

Selective Laser Melting (SLM) is an emerging Additive Manufacturing (AM) technique for the on-demand fabrication of metal parts. The mechanical properties of Selectively Laser Melted (SLMed) parts are sensitive to oxygen concentration within the SLM build chamber due to the formation of oxides, which may lead to various negative consequences. As such, this work explores the influence of SLM atmospheric Oxygen Content (OC) on the macroscopic mechanical properties of SLMed AlSi10Mg bulk material and Triply Periodic Minimal Surface (TPMS) lattices namely primitive, gyroid, and diamond. Standard quasi-static tensile and crushing tests were conducted to evaluate the bulk properties of AlSi10Mg and the compressive metrics of TPMS-lattices. Two oxygen concentrations of 100 ppm and 1000 were used during the SLM fabrication of the experimental specimens. The tensile test data revealed a small influence of the oxygen content on the bulk properties. The low oxygen concentration improved the elongation while slightly reduced the ultimate tensile strength and yield stress. Similarly, the influence of the oxygen content on the compressive responses of TPMS-lattices was generally limited and primarily depended on their geometrical configuration. This study elucidates the role of SLM atmospheric oxygen content on the macroscopic behaviour of SLMed AlSi10Mg parts. Full article

(This article belongs to the Special Issue Recent Advances in the Field of Mechanical Metamaterials and Their Associated Applications and Fabrication Techniques)

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32 pages, 7038 KiB

Open AccessEditor’s ChoiceReview

Recent Progress in Electrochemical Upgrading of Bio-Oil Model Compounds and Bio-Oils to Renewable Fuels and Platform Chemicals

by Jeffrey R. Page, Zachary Manfredi, Stoyan Bliznakov and Julia A. Valla

Materials 2023, 16(1), 394; https://doi.org/10.3390/ma16010394 - 1 Jan 2023

Cited by 18 | Viewed by 7020

Abstract

Sustainable production of renewable carbon-based fuels and chemicals remains a necessary but immense challenge in the fight against climate change. Bio-oil derived from lignocellulosic biomass requires energy-intense upgrading to produce usable fuels or chemicals. Traditional upgrading methods such as hydrodeoxygenation (HDO) require high [...] Read more.

Sustainable production of renewable carbon-based fuels and chemicals remains a necessary but immense challenge in the fight against climate change. Bio-oil derived from lignocellulosic biomass requires energy-intense upgrading to produce usable fuels or chemicals. Traditional upgrading methods such as hydrodeoxygenation (HDO) require high temperatures (200–400 °C) and 200 bar of external hydrogen. Electrochemical hydrogenation (ECH), on the other hand, operates at low temperatures (<80 °C), ambient pressure, and does not require an external hydrogen source. These environmental and economically favorable conditions make ECH a promising alternative to conventional thermochemical upgrading processes. ECH combines renewable electricity with biomass conversion and harnesses intermediately generated electricity to produce drop-in biofuels. This review aims to summarize recent studies on bio-oil upgrading using ECH focusing on the development of novel catalytic materials and factors impacting ECH efficiency and products. Here, electrode design, reaction temperature, applied overpotential, and electrolytes are analyzed for their impacts on overall ECH performance. We find that through careful reaction optimization and electrode design, ECH reactions can be tailored to be efficient and selective for the production of renewable fuels and chemicals. Preliminary economic and environmental assessments have shown that ECH can be viable alternative to convention upgrading technologies with the potential to reduce CO₂ emissions by 3 times compared to thermochemical upgrading. While the field of electrochemical upgrading of bio-oil has additional challenges before commercialization, this review finds ECH a promising avenue to produce renewable carbon-based drop-in biofuels. Finally, based on the analyses presented in this review, directions for future research areas and optimization are suggested. Full article

(This article belongs to the Section Catalytic Materials)

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22 pages, 5956 KiB

Open AccessEditor’s ChoiceArticle

The Spray-Dried Alginate/Gelatin Microparticles with Luliconazole as Mucoadhesive Drug Delivery System

by Marta Szekalska, Magdalena Wróblewska, Anna Czajkowska-Kośnik, Katarzyna Sosnowska, Paweł Misiak, Agnieszka Zofia Wilczewska and Katarzyna Winnicka

Materials 2023, 16(1), 403; https://doi.org/10.3390/ma16010403 - 1 Jan 2023

Cited by 21 | Viewed by 3675

Abstract

Candida species are opportunistic fungi, which are primary causative agents of vulvovaginal candidiasis. The cure of candidiasis is difficult, lengthy, and associated with the fungi resistivity. Therefore, the research for novel active substances and unconventional drug delivery systems providing effective and safe treatment [...] Read more.

Candida species are opportunistic fungi, which are primary causative agents of vulvovaginal candidiasis. The cure of candidiasis is difficult, lengthy, and associated with the fungi resistivity. Therefore, the research for novel active substances and unconventional drug delivery systems providing effective and safe treatment is still an active subject. Microparticles, as multicompartment dosage forms due to larger areas, provide short passage of drug diffusion, which might improve drug therapeutic efficiency. Sodium alginate is a natural polymer from a polysaccharide group, possessing swelling, mucoadhesive, and gelling properties. Gelatin A is a natural high-molecular-weight polypeptide obtained from porcine collagen. The purpose of this study was to prepare microparticles by the spray-drying of alginate/gelatin polyelectrolyte complex mixture, with a novel antifungal drug—luliconazole. In the next stage of research, the effect of gelatin presence on pharmaceutical properties of designed formulations was assessed. Interrelations among polymers were evaluated with thermal analysis and Fourier transform infrared spectroscopy. A valid aspect of this research was the in vitro antifungal activity estimation of designed microparticles using Candida species: C. albicans, C. krusei, and C. parapsilosis. It was shown that the gelatin addition affected the particles size, improved encapsulation efficiency and mucoadhesiveness, and prolonged the drug release. Moreover, gelatin addition to the formulations improved the antifungal effect against Candida species. Full article

(This article belongs to the Special Issue Advanced Materials in Drug Release and Drug Delivery Systems (Second Volume))

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15 pages, 2943 KiB

Open AccessEditor’s ChoiceArticle

Improvement of the Thermal Conductivity and Mechanical Properties of 3D-Printed Polyurethane Composites by Incorporating Hydroxylated Boron Nitride Functional Fillers

by Kai-Han Su, Cherng-Yuh Su, Wei-Ling Shih and Fang-Ting Lee

Materials 2023, 16(1), 356; https://doi.org/10.3390/ma16010356 - 30 Dec 2022

Cited by 16 | Viewed by 4178

Abstract

Recently, the use of fused deposition modeling (FDM) in the three-dimensional (3D) printing of thermal interface materials (TIMs) has garnered increasing attention. Because fillers orient themselves along the direction of the melt flow during printing, this method could effectively enhance the thermal conductivity [...] Read more.

Recently, the use of fused deposition modeling (FDM) in the three-dimensional (3D) printing of thermal interface materials (TIMs) has garnered increasing attention. Because fillers orient themselves along the direction of the melt flow during printing, this method could effectively enhance the thermal conductivity of existing composite materials. However, the poor compatibility and intensive aggregation of h-BN fillers in polymer composites are still detrimental to their practical application in thermally conductive materials. In this study, hydroxyl-functionalized boron nitride (OH-BN) particles were prepared by chemical modification and ultrasonic-assisted liquid-phase exfoliation to explore their impact on the surface compatibility, mechanical properties and the final anisotropic thermal conductivity of thermoplastic polyurethane (TPU) composites fabricated by FDM printing. The results show that the surface-functionalized OH-BN fillers are homogeneously dispersed in the TPU matrix via hydrogen bonding interactions, which improve the interfacial adhesion between the filler and matrix. For the same concentration of loaded filler, the OH-BN/TPU composites exhibit better mechanical properties and thermal conductivities than composites incorporating non-modified h-BN. These composites also show higher heat conduction along the stand-vertical direction, while simultaneously exhibiting a low dielectric constant and dielectric loss. This work therefore provides a possible strategy for the fabrication of thermal management polymers using 3D-printing methods. Full article

(This article belongs to the Special Issue 3D Printing and Additive Manufacturing of Polymer and Composites)

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20 pages, 4520 KiB

Open AccessEditor’s ChoiceArticle

Effect of Solution-to-Binder Ratio and Alkalinity on Setting and Early-Age Properties of Alkali-Activated Slag-Fly Ash Binders

by Ali Naqi, Brice Delsaute, Markus Königsberger and Stéphanie Staquet

Materials 2023, 16(1), 373; https://doi.org/10.3390/ma16010373 - 30 Dec 2022

Cited by 10 | Viewed by 2317

Abstract

The growing use of blends of low- and high-calcium solid precursors in combination with different alkaline activators requires simple, efficient, and accurate experimental means to characterize their behavior, particularly during the liquid-to-solid transition (setting) at early material ages. This research investigates slag-fly ash [...] Read more.

The growing use of blends of low- and high-calcium solid precursors in combination with different alkaline activators requires simple, efficient, and accurate experimental means to characterize their behavior, particularly during the liquid-to-solid transition (setting) at early material ages. This research investigates slag-fly ash systems mixed at different solution-to-binder (s/b) ratios with sodium silicate/sodium hydroxide-based activator solutions of varying concentrations. Therefore, continuous non-destructive tests—namely ultrasonic pulse velocity (UPV) measurements and isothermal calorimetry tests—are combined with classical slump flow, Vicat, and uniaxial compressive strength tests. The experimental results highlight that high alkali and silica contents and a low s/b ratio benefit the early-age hydration, lead to a faster setting, and improve the early-age strength. The loss of workability, determined from the time when the slump flow becomes negligible, correlates well with ultrasonic P-wave velocity evolutions. This is, however, not the case for Vicat or calorimetry tests. Full article

(This article belongs to the Special Issue Sustainable Construction Materials: From Paste to Concrete)

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24 pages, 4088 KiB

Open AccessEditor’s ChoiceArticle

Modeling Analysis of a Polygeneration Plant Using a CeO₂/Ce₂O₃ Chemical Looping

by Greta Magnolia, Massimo Santarelli, Domenico Ferrero and Davide Papurello

Materials 2023, 16(1), 315; https://doi.org/10.3390/ma16010315 - 29 Dec 2022

Viewed by 2586

Abstract

In the current context of complexity between climate change, environmental sustainability, resource scarcity, and geopolitical aspects of energy resources, a polygenerative system with a circular approach is considered to generate energy (thermal, electrical, and fuel), contributing to the control of CO₂ emissions. [...] Read more.

In the current context of complexity between climate change, environmental sustainability, resource scarcity, and geopolitical aspects of energy resources, a polygenerative system with a circular approach is considered to generate energy (thermal, electrical, and fuel), contributing to the control of CO₂ emissions. A plant for the multiple productions of electrical energy, thermal heat, DME, syngas, and methanol is discussed and analyzed, integrating a chemical cycle for CO₂/H₂O splitting driven using concentrated solar energy and biomethane. Two-stage chemical looping is the central part of the plant, operating with the CeO₂/Ce₂O₃ redox couple and operating at 1.2 bar and 900 °C. The system is coupled to biomethane reforming. The chemical loop generates fuel for the plant’s secondary units: a DME synthesis and distillation unit and a solid oxide fuel cell (SOFC). The DME synthesis and distillation unit are integrated with a biomethane reforming reactor powered by concentrated solar energy to produce syngas at 800 °C. The technical feasibility in terms of performance is presented in this paper, both with and without solar irradiation, with the following results, respectively: overall efficiencies of 62.56% and 59.08%, electricity production of 6.17 MWe and 28.96 MWe, and heat production of 111.97 MWt and 35.82 MWt. The fuel production, which occurs only at high irradiance, is 0.71 kg/s methanol, 6.18 kg/s DME, and 19.68 kg/s for the syngas. The increase in plant productivity is studied by decoupling the operation of the chemical looping with a biomethane reformer from intermittent solar energy using the heat from the SOFC unit. Full article

(This article belongs to the Special Issue Sustainable Solar Energy Technologies and Materials for Solar Thermal and Power Generation)

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17 pages, 4673 KiB

Open AccessEditor’s ChoiceArticle

Synthesis, Characterization, and Electronic Properties of ZnO/ZnS Core/Shell Nanostructures Investigated Using a Multidisciplinary Approach

by Jelena Zagorac, Dejan Zagorac, Vesna Šrot, Marjan Ranđelović, Milan Pejić, Peter A. van Aken, Branko Matović and J. Christian Schön

Materials 2023, 16(1), 326; https://doi.org/10.3390/ma16010326 - 29 Dec 2022

Cited by 8 | Viewed by 2893

Abstract

ZnO/ZnS core/shell nanostructures, which are studied for diverse possible applications, ranging from semiconductors, photovoltaics, and light-emitting diodes (LED), to solar cells, infrared detectors, and thermoelectrics, were synthesized and characterized by XRD, HR-(S)TEM, and analytical TEM (EDX and EELS). Moreover, band-gap measurements of the [...] Read more.

ZnO/ZnS core/shell nanostructures, which are studied for diverse possible applications, ranging from semiconductors, photovoltaics, and light-emitting diodes (LED), to solar cells, infrared detectors, and thermoelectrics, were synthesized and characterized by XRD, HR-(S)TEM, and analytical TEM (EDX and EELS). Moreover, band-gap measurements of the ZnO/ZnS core/shell nanostructures have been performed using UV/Vis DRS. The experimental results were combined with theoretical modeling of ZnO/ZnS (hetero)structures and band structure calculations for ZnO/ZnS systems, yielding more insights into the properties of the nanoparticles. The ab initio calculations were performed using hybrid PBE0 and HSE06 functionals. The synthesized and characterized ZnO/ZnS core/shell materials show a unique three-phase composition, where the ZnO phase is dominant in the core region and, interestingly, the auxiliary ZnS compound occurs in two phases as wurtzite and sphalerite in the shell region. Moreover, theoretical ab initio calculations show advanced semiconducting properties and possible band-gap tuning in such ZnO/ZnS structures. Full article

(This article belongs to the Special Issue ZnO Materials: Synthesis, Properties and Applications (Second Volume))

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8 pages, 2126 KiB

Open AccessEditor’s ChoiceArticle

Macrophage Polarization Related to Biomimetic Calcium Phosphate Coatings: A Preliminary Study

by Jiping Chen, Yiwen Zhou, Xingnan Lin and Huang Li

Materials 2023, 16(1), 332; https://doi.org/10.3390/ma16010332 - 29 Dec 2022

Cited by 7 | Viewed by 2193

Abstract

Biomimetic calcium phosphate (BioCaP) coatings were used to deliver bone morphogenetic protein 2 (BMP2), and enhance osteogenesis. However, the mechanism for BioCaP coatings interacting with the immune response during bone regeneration remains unclear. In this preliminary study, the effect of BioCaP coatings on [...] Read more.

Biomimetic calcium phosphate (BioCaP) coatings were used to deliver bone morphogenetic protein 2 (BMP2), and enhance osteogenesis. However, the mechanism for BioCaP coatings interacting with the immune response during bone regeneration remains unclear. In this preliminary study, the effect of BioCaP coatings on macrophage polarization without (BioCaP group) or with BMP2 (BioCaP+Inc.BMP2 group) was investigated. RAW 264.7 cells were cultured on the rough and platelike surfaces of coatings in BioCaP and BioCaP+Inc.BMP2 groups, while cultured on smooth surfaces in the group without material for 5 days. The BioCaP coatings per se modulated the switch of M1 to M2 phenotype from day 3, which promoted the expressions of Arg1 and CD 206 but reduced the expression of TNF-α compared with No material group. To detect the microenvironmental changes, the concentrations of calcium ion (Ca²⁺) and inorganic phosphate (Pi), pH values, as well as calcium phosphate crystal pattern were examined. The trends of ionic environmental changes were closely related with macrophage phenotype switch. These results suggest that BioCaP coating itself may affect the macrophage polarization through surface topography, surrounding ionic environment and calcium phosphate crystal pattern. Full article

(This article belongs to the Special Issue Drug Delivery Carriers and Application of Nanomaterials)

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11 pages, 4497 KiB

Open AccessEditor’s ChoiceArticle

Facile Synthesis of Island-like ZrO₂-VO₂ Composite Films with Enhanced Thermochromic Performance for Smart Windows

by Jiahao Wu, Zhe Wang, Bin Li, Baoshun Liu, Xiujian Zhao, Gen Tang, Dawen Zeng and Shouqin Tian

Materials 2023, 16(1), 273; https://doi.org/10.3390/ma16010273 - 28 Dec 2022

Cited by 11 | Viewed by 2125

Abstract

VO₂-based film, as a very promising thermochromic material for smart windows, has attracted extensive attention but has not been widely applied because it is difficult to simultaneously improve in terms of both solar-modulation efficiency (ΔT_sol) and visible transmittance [...] Read more.

VO₂-based film, as a very promising thermochromic material for smart windows, has attracted extensive attention but has not been widely applied because it is difficult to simultaneously improve in terms of both solar-modulation efficiency (ΔT_sol) and visible transmittance (T_lum) when made using the magnetron-sputtering method, and it has poor durability when made using the wet chemical method. Herein, island-like ZrO₂-VO₂ composite films with improved thermochromic performance (ΔT_sol: 12.6%, T_lum: 45.0%) were created using a simple approach combining a dual magnetron-sputtering and acid-solution procedure. The film’s ΔT_sol and T_lum values were increased initially and subsequently declined as the sputtering power of the ZrO₂ target was raised from 30 W to 120 W. ΔT_sol achieved its maximum of 12.6% at 60 W, and T_lum reached its maximum of 51.1% at 90 W. This is likely the result of the interaction of two opposing effects: Some VO₂ nanocrystals in the composite film were isolated by a few ZrO₂ grains, and some pores could utilize their surface-plasmon-resonance effect at high temperature to absorb some near-infrared light for an enhanced ΔT_sol and T_lum. More ZrO₂ grains means fewer VO₂ grains in the composite film and increased film thickness, which also results in a decrease in ΔT_sol and T_lum. As a result, this work may offer a facile strategy to prepare VO₂-based films with high thermochromic performance and promote their application in smart windows. Full article

(This article belongs to the Section Smart Materials)

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15 pages, 2801 KiB

Open AccessEditor’s ChoiceArticle

Tuning of the Titanium Oxide Surface to Control Magnetic Properties of Thin Iron Films

by Juliusz Chojenka, Arkadiusz Zarzycki, Marcin Perzanowski, Michał Krupiński, Tamás Fodor, Kálmán Vad and Marta Marszałek

Materials 2023, 16(1), 289; https://doi.org/10.3390/ma16010289 - 28 Dec 2022

Cited by 3 | Viewed by 2125

Abstract

We describe the magnetic properties of thin iron films deposited on the nanoporous titanium oxide templates and analyze their dependance on nanopore radius. We then compare the results to a continuous iron film of the same thickness. Additionally, we investigate the evolution of [...] Read more.

We describe the magnetic properties of thin iron films deposited on the nanoporous titanium oxide templates and analyze their dependance on nanopore radius. We then compare the results to a continuous iron film of the same thickness. Additionally, we investigate the evolution of the magnetic properties of these films after annealing. We demonstrate that the M(H) loops consist of two magnetic phases originating from the iron layer and iron oxides formed at the titanium oxide/iron interface. We perform deconvolution of hysteresis loops to extract information for each magnetic phase. Finally, we investigate the magnetic interactions between the phases and verify the presence of exchange coupling between them. We observe the altering of the magnetic properties by the nanopores as a magnetic hardening of the magnetic material. The ZFC-FC (Zero-field cooled/field cooled) measurements indicate the presence of a disordered glass state below 50 K, which can be explained by the formation of iron oxide at the titanium oxide-iron interface with a short-range magnetic order. Full article

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

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16 pages, 477 KiB

Open AccessEditor’s ChoiceReview

UV-A,B,C Emitting Persistent Luminescent Materials

by Suchinder K. Sharma, Jinu James, Shailendra Kumar Gupta and Shamima Hussain

Materials 2023, 16(1), 236; https://doi.org/10.3390/ma16010236 - 27 Dec 2022

Cited by 26 | Viewed by 3600

Abstract

The nearly dormant field of persistent luminescence has gained fresh impetus after the discovery of strontium aluminate persistent luminescence phosphor in 1996. Several efforts have been put in to prepare efficient, long decay, persistent luminescent materials which can be used for different applications. [...] Read more.

The nearly dormant field of persistent luminescence has gained fresh impetus after the discovery of strontium aluminate persistent luminescence phosphor in 1996. Several efforts have been put in to prepare efficient, long decay, persistent luminescent materials which can be used for different applications. The most explored among all are the materials which emit in the visible wavelength region, 400–650 nm, of the electromagnetic spectrum. However, since 2014, the wavelength range is extended further above 650 nm for biological applications due to easily distinguishable signal between luminescent probe and the auto-fluorescence. Recently, UV-emitting persistent materials have gained interest among researchers’ due to their possible application in information storage, phototherapy and photocatalysis. In the present review, we summarize these recent developments on the UV-emitting persistent luminescent materials to motivate young minds working in the field of luminescent materials. Full article

(This article belongs to the Special Issue Advanced Luminescent Materials and Devices)

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15 pages, 4517 KiB

Open AccessEditor’s ChoiceArticle

Investigation of PbSnTeSe High-Entropy Thermoelectric Alloy: A DFT Approach

by Ming Xia, Marie-Christine Record and Pascal Boulet

Materials 2023, 16(1), 235; https://doi.org/10.3390/ma16010235 - 27 Dec 2022

Cited by 7 | Viewed by 3592

Abstract

Thermoelectric materials have attracted extensive attention because they can directly convert waste heat into electric energy. As a brand-new method of alloying, high-entropy alloys (HEAs) have attracted much attention in the fields of materials science and engineering. Recent researches have found that HEAs [...] Read more.

Thermoelectric materials have attracted extensive attention because they can directly convert waste heat into electric energy. As a brand-new method of alloying, high-entropy alloys (HEAs) have attracted much attention in the fields of materials science and engineering. Recent researches have found that HEAs could be potentially good thermoelectric (TE) materials. In this study, special quasi-random structures (SQS) of PbSnTeSe high-entropy alloys consisting of 64 atoms have been generated. The thermoelectric transport properties of the highest-entropy PbSnTeSe-optimized structure were investigated by combining calculations from first-principles density-functional theory and on-the-fly machine learning with the semiclassical Boltzmann transport theory and Green–Kubo theory. The results demonstrate that PbSnTeSe HEA has a very low lattice thermal conductivity. The electrical conductivity, thermal electronic conductivity and Seebeck coefficient have been evaluated for both n-type and p-type doping. N-type PbSnTeSe exhibits better power factor (PF = S²σ) than p-type PbSnTeSe because of larger electrical conductivity for n-type doping. Despite high electrical thermal conductivities, the calculated ZT are satisfactory. The maximum ZT (about 1.1) is found at 500 K for n-type doping. These results confirm that PbSnTeSe HEA is a promising thermoelectric material. Full article

(This article belongs to the Special Issue Recent Advances in Thermoelectricity: Materials Processing, Characterization and Modelling)

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21 pages, 5105 KiB

Open AccessEditor’s ChoiceReview

Metal Oxide Heterostructures for Improving Gas Sensing Properties: A Review

by Fan-Jian Meng, Rui-Feng Xin and Shan-Xin Li

Materials 2023, 16(1), 263; https://doi.org/10.3390/ma16010263 - 27 Dec 2022

Cited by 38 | Viewed by 4168

Abstract

Metal oxide semiconductor gas sensors are widely used to detect toxic and inflammable gases in industrial production and daily life. The main research hotspot in this field is the synthesis of gas sensing materials. Previous studies have shown that incorporating two or more [...] Read more.

Metal oxide semiconductor gas sensors are widely used to detect toxic and inflammable gases in industrial production and daily life. The main research hotspot in this field is the synthesis of gas sensing materials. Previous studies have shown that incorporating two or more metal oxides to form a heterojunction interface can exhibit superior gas sensing performance in response and selectivity compared with single phase. This review focuses on mainly the synthesis methods and gas sensing mechanisms of metal oxide heterostructures. A significant number of heterostructures with different morphologies and shapes have been fabricated, which exhibit specific sensing performance toward a specific target gas. Among these synthesis methods, the hydrothermal method is noteworthy due to the fabrication of diverse structures, such as nanorod-like, nanoflower-like, and hollow sphere structures with enhanced sensing properties. In addition, it should be noted that the combination of different synthesis methods is also an efficient way to obtain metal oxide heterostructures with novel morphologies. Despite advanced methods in the metal oxide semiconductors and nanotechnology field, there are still some new issues which deserve further investigation, such as long-term chemical stability of sensing materials, reproducibility of the fabrication process, and selectivity toward homogeneous gases. Moreover, the gas sensing mechanism of metal oxide heterostructures is controversial. It should be clarified so as to further integrate laboratory theory research with practical exploitation. Full article

(This article belongs to the Special Issue Advances in Dielectric Ceramics and Their Applications)

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24 pages, 2755 KiB

Open AccessEditor’s ChoiceArticle

In-Service Delaminations in FRP Structures under Operational Loading Conditions: Are Current Fracture Testing and Analysis on Coupons Sufficient for Capturing the Essential Effects for Reliable Predictions?

by Andreas J. Brunner, René Alderliesten and John-Alan Pascoe

Materials 2023, 16(1), 248; https://doi.org/10.3390/ma16010248 - 27 Dec 2022

Cited by 7 | Viewed by 2388

Abstract

Quasi-static or cyclic loading of an artificial starter crack in unidirectionally fibre-reinforced composite test coupons yields fracture mechanics data—the toughness or strain-energy release rate (labelled G)—for characterising delamination initiation and propagation. Thus far, the reproducibility of these tests is typically between 10 and [...] Read more.

Quasi-static or cyclic loading of an artificial starter crack in unidirectionally fibre-reinforced composite test coupons yields fracture mechanics data—the toughness or strain-energy release rate (labelled G)—for characterising delamination initiation and propagation. Thus far, the reproducibility of these tests is typically between 10 and 20%. However, differences in the size and possibly the shape, but also in the fibre lay-up, between test coupons and components or structures raise additional questions: Is G from a coupon test a suitable parameter for describing the behaviour of delaminations in composite structures? Can planar, two-dimensional, delamination propagation in composite plates or shells be properly predicted from essentially one-dimensional propagation in coupons? How does fibre bridging in unidirectionally reinforced test coupons relate to delamination propagation in multidirectional lay-ups of components and structures? How can multiple, localised delaminations—often created by impact in composite structures—and their interaction under service loads with constant or variable amplitudes be accounted for? Does planar delamination propagation depend on laminate thickness, thickness variation or the overall shape of the structure? How does exposure to different, variable service environments affect delamination initiation and propagation? Is the microscopic and mesoscopic morphology of FRP composite structures sufficiently understood for accurate predictive modelling and simulation of delamination behaviour? This contribution will examine selected issues and discuss the consequences for test development and analysis. The discussion indicates that current coupon testing and analysis are unlikely to provide the data for reliable long-term predictions of delamination behaviour in FRP composite structures. The attempts to make the building block design methodology for composite structures more efficient via combinations of experiments and related modelling look promising, but models require input data with low scatter and, even more importantly, insight into the physics of the microscopic damage processes yielding delamination initiation and propagation. Full article

(This article belongs to the Special Issue Damage Analysis and Reliability Assessment for Composite Materials)

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16 pages, 5853 KiB

Open AccessEditor’s ChoiceArticle

One Pot Synthesis of Copper Oxide Nanoparticles for Efficient Antibacterial Activity

by Rajaram Rajamohan, Chaitany Jayprakash Raorane, Seong-Cheol Kim and Yong Rok Lee

Materials 2023, 16(1), 217; https://doi.org/10.3390/ma16010217 - 26 Dec 2022

Cited by 28 | Viewed by 4029

Abstract

The unique semiconductor and optical properties of copper oxides have attracted researchers for decades. However, using fruit waste materials such as peels to synthesize the nanoparticles of copper oxide (CuO NPs) has been rarely described in literature reviews. The main purpose of this [...] Read more.

The unique semiconductor and optical properties of copper oxides have attracted researchers for decades. However, using fruit waste materials such as peels to synthesize the nanoparticles of copper oxide (CuO NPs) has been rarely described in literature reviews. The main purpose of this part of the research was to report on the CuO NPs with the help of apple peel extract under microwave irradiation. Metal salts and extracts were irradiated at 540 W for 5 min in a microwave in a 1:2 ratio. The crystallinity of the NPs was confirmed by the XRD patterns and the crystallite size of the NPs was found to be 41.6 nm. Elemental mapping of NPs showed homogeneous distributions of Cu and O. The NPs were found to contain Cu and O by EDX and XPS analysis. In a test involving two human pathogenic microbes, NPs showed antibacterial activity and the results revealed that the zone of inhibition grew significantly with respect to the concentration of CuO NPs. In a biofilm, more specifically, NPs at 25.0 µg/mL reduced mean thickness and biomass values of S. aureus and E. coli biofilms by >85.0 and 65.0%, respectively, with respect to untreated controls. In addition, environmentally benign materials offer a number of benefits for pharmaceuticals and other biomedical applications as they are eco-friendly and compatible. Full article

(This article belongs to the Special Issue Functionalized Nanomaterials and Structures for Biomedical Applications)

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13 pages, 3868 KiB

Open AccessEditor’s ChoiceArticle

Microstructural Characterization and Property of Carbon Fiber Reinforced High-Density Polyethylene Composites Fabricated by Fused Deposition Modeling

by Partha Pratim Pandit, Chang Liu, Scott Iacono, Giancarlo Corti and Yingbin Hu

Materials 2023, 16(1), 180; https://doi.org/10.3390/ma16010180 - 25 Dec 2022

Cited by 7 | Viewed by 3204

Abstract

As a promising industrial thermoplastic polymer material, high-density polyethylene (HDPE) possesses distinct properties of ease to process, good biocompatibility, high recyclability, etc. and has been widely used to make packaging, prostheses and implants, and liquid-permeable membranes. Traditional manufacturing processes for HDPE, including injection [...] Read more.

As a promising industrial thermoplastic polymer material, high-density polyethylene (HDPE) possesses distinct properties of ease to process, good biocompatibility, high recyclability, etc. and has been widely used to make packaging, prostheses and implants, and liquid-permeable membranes. Traditional manufacturing processes for HDPE, including injection molding, thermoforming, and rotational molding, require molds or post processing. In addition, part shapes are highly restricted., Thus, fused deposition modeling (FDM) is introduced to process HDPE materials to take advantage of FDM’s free of design, no mold requirement, ease and low cost of processing. To improve the mechanical properties (such as stiffness and strength) and thermal resistance of HDPE, carbon fiber (CF) was incorporated into HDPE, and CF-reinforced HDPE composites were successfully fabricated using FDM process. In addition, the effects of CF content on surface quality, microstructure characterizations, tensile properties, dynamic mechanical properties, and thermal properties have been investigated. Experimental results show that an appropriate CF content addition is beneficial for improving surface quality, and mechanical and thermal properties. Full article

(This article belongs to the Special Issue 3D Printing and Additive Manufacturing of Polymer and Composites)

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20 pages, 9290 KiB

Open AccessEditor’s ChoiceArticle

Polymer Composites with Self-Regulating Temperature Behavior: Properties and Characterization

by Radu Setnescu, Eduard-Marius Lungulescu and Virgil Emanuel Marinescu

Materials 2023, 16(1), 157; https://doi.org/10.3390/ma16010157 - 24 Dec 2022

Cited by 5 | Viewed by 2214

Abstract

A novel conductive composite material with homogeneous binary polymer matrix of HDPE (HD) and LLDPE (LLD), mixed with conductive filler consisting of carbon black (CB) and graphite (Gr), was tested against a HDPE composite with a similar conductive filler. Even the concentration of [...] Read more.

A novel conductive composite material with homogeneous binary polymer matrix of HDPE (HD) and LLDPE (LLD), mixed with conductive filler consisting of carbon black (CB) and graphite (Gr), was tested against a HDPE composite with a similar conductive filler. Even the concentration of the conductive filler was deliberately lower for (CB + Gr)/(LLD + HD), and the properties of this composite are comparable or better to those of (CB + Gr)/HD. The kinetic parameters of the ρ-T curves and from the DSC curves indicate that the resistivity peak is obtained when the polymer matrix is fully melted. When subjected to repeated thermal cycles, the composite (CB + Gr)/(LLD + HD) presented a better electrical behavior than composite CB + Gr)/HD, with an increase in resistivity (ρ_max) values with the number of cycles, as well as less intense NTC (Negative Temperature Coefficient) effects, both for the crosslinked and thermoplastic samples. Radiation crosslinking led to increased ρ_max values, as well as to inhibition of NTC effects in both cases, thus having a clear beneficial effect. Limitation effects of surface temperature and current intensity through the sample were observed at different voltages, enabling the use of these materials as self-regulating heating elements at various temperatures below the melting temperature. The procedure based on physical mixing of the components appears more efficient in imparting lower resistivity in solid state and high PTC (Positive Temperature Coefficient) effects to the composites. This effect is probably due to the concentration of the conductive particles at the surface of the polymer domains, which would facilitate the formation of the conductive paths. Further work is still necessary to optimize both the procedure of composite preparation and the properties of such materials. Full article

(This article belongs to the Special Issue Advances in Polymer Blends and Composites)

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22 pages, 8780 KiB

Open AccessEditor’s ChoiceArticle

Effective Halogen-Free Flame-Retardant Additives for Crosslinked Rigid Polyisocyanurate Foams: Comparison of Chemical Structures

by Johannes U. Lenz, Doris Pospiech, Hartmut Komber, Andreas Korwitz, Oliver Kobsch, Maxime Paven, Rolf W. Albach, Martin Günther and Bernhard Schartel

Materials 2023, 16(1), 172; https://doi.org/10.3390/ma16010172 - 24 Dec 2022

Cited by 4 | Viewed by 3085

Abstract

The impact of phosphorus-containing flame retardants (FR) on rigid polyisocyanurate (PIR) foams is studied by systematic variation of the chemical structure of the FR, including non-NCO-reactive and NCO-reactive dibenzo[d,f][1,3,2]dioxaphosphepine 6-oxide (BPPO)- and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-containing compounds, among them a number of compounds not reported [...] Read more.

The impact of phosphorus-containing flame retardants (FR) on rigid polyisocyanurate (PIR) foams is studied by systematic variation of the chemical structure of the FR, including non-NCO-reactive and NCO-reactive dibenzo[d,f][1,3,2]dioxaphosphepine 6-oxide (BPPO)- and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-containing compounds, among them a number of compounds not reported so far. These PIR foams are compared with PIR foams without FR and with standard FRs with respect to foam properties, thermal decomposition, and fire behavior. Although BPPO and DOPO differ by just one oxygen atom, the impact on the FR properties is very significant: when the FR is a filler or a dangling (dead) end in the PIR polymer network, DOPO is more effective than BPPO. When the FR is a subunit of a diol and it is fully incorporated in the PIR network, BPPO delivers superior results. Full article

(This article belongs to the Special Issue Flame Retardants for Polymeric Materials (Second Volume))

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18 pages, 4962 KiB

Open AccessEditor’s ChoiceArticle

Novel Electrospun Polycaprolactone/Calcium Alginate Scaffolds for Skin Tissue Engineering

by Maria I. Echeverria Molina, Chi-An Chen, Jeniree Martinez, Perry Tran and Kyriakos Komvopoulos

Materials 2023, 16(1), 136; https://doi.org/10.3390/ma16010136 - 23 Dec 2022

Cited by 8 | Viewed by 2995

Abstract

After decades of research, fully functional skin regeneration is still a challenge. Skin is a multilayered complex organ exhibiting a cascading healing process affected by various mechanisms. Specifically, nutrients, oxygen, and biochemical signals can lead to specific cell behavior, ultimately conducive to the [...] Read more.

After decades of research, fully functional skin regeneration is still a challenge. Skin is a multilayered complex organ exhibiting a cascading healing process affected by various mechanisms. Specifically, nutrients, oxygen, and biochemical signals can lead to specific cell behavior, ultimately conducive to the formation of high-quality tissue. This biomolecular exchange can be tuned through scaffold engineering, one of the leading fields in skin substitutes and equivalents. The principal objective of this investigation was the design, fabrication, and evaluation of a new class of three-dimensional fibrous scaffolds consisting of poly(ε-caprolactone) (PCL)/calcium alginate (CA), with the goal to induce keratinocyte differentiation through the action of calcium leaching. Scaffolds fabricated by electrospinning using a PCL/sodium alginate solution were treated by immersion in a calcium chloride solution to replace alginate-linked sodium ions by calcium ions. This treatment not only provided ion replacement, but also induced fiber crosslinking. The scaffold morphology was examined by scanning electron microscopy and systematically assessed by measurements of the pore size and the diameter, alignment, and crosslinking of the fibers. The hydrophilicity of the scaffolds was quantified by contact angle measurements and was correlated to the augmentation of cell attachment in the presence of CA. The in vitro performance of the scaffolds was investigated by seeding and staining fibroblasts and keratinocytes and using differentiation markers to detect the evolution of basal, spinous, and granular keratinocytes. The results of this study illuminate the potential of the PCL/CA scaffolds for tissue engineering and suggest that calcium leaching out from the scaffolds might have contributed to the development of a desirable biological environment for the attachment, proliferation, and differentiation of the main skin cells (i.e., fibroblasts and keratinocytes). Full article

(This article belongs to the Special Issue Advances in Biomaterials towards Tissue Engineering)

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11 pages, 1388 KiB

Open AccessEditor’s ChoiceArticle

Biomechanical Comparison of WE43-Based Magnesium vs. Titanium Miniplates in a Mandible Fracture Model in Sheep

by Heilwig Fischer, Oskar Schmidt-Bleek, Vincenzo Orassi, Dag Wulsten, Katharina Schmidt-Bleek, Max Heiland, Claudius Steffen and Carsten Rendenbach

Materials 2023, 16(1), 102; https://doi.org/10.3390/ma16010102 - 22 Dec 2022

Cited by 9 | Viewed by 2702

Abstract

In fractures of the mandible, osteosynthesis with titanium plates is considered the gold standard. Titanium is an established and reliable material, its main disadvantages being metal artefacts and the need for removal in case of osteosynthesis complications. Magnesium, as a resorbable material with [...] Read more.

In fractures of the mandible, osteosynthesis with titanium plates is considered the gold standard. Titanium is an established and reliable material, its main disadvantages being metal artefacts and the need for removal in case of osteosynthesis complications. Magnesium, as a resorbable material with an elastic modulus close to cortical bone, offers a resorbable alternative osteosynthesis material, yet mechanical studies in mandible fracture fixation are still missing. The hypothesis of this study was that magnesium miniplates show no significant difference in the mechanical integrity provided for fracture fixation in mandible fractures under load-sharing indications. In a non-inferiority test, a continuous load was applied to a sheep mandible fracture model with osteosynthesis using either titanium miniplates of 1.0 mm thickness (Ti1.0), magnesium plates of 1.75 mm (Mg1.75), or magnesium plates of 1.5 mm thickness (Mg1.5). No significant difference (p > 0.05) was found in the peak force at failure, stiffness, or force at vertical displacement of 1.0 mm between Mg1.75, Mg1.5, and Ti1.0. This study shows the non-inferiority of WE43 magnesium miniplates compared to the clinical gold standard titanium miniplates. Full article

(This article belongs to the Section Biomaterials)

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17 pages, 3629 KiB

Open AccessEditor’s ChoiceArticle

Synthesis, Structural and Magnetic Properties of Cobalt-Doped GaN Nanowires on Si by Atmospheric Pressure Chemical Vapor Deposition

by Zhe Chuan Feng, Yu-Lun Liu, Jeffrey Yiin, Li-Chyong Chen, Kuei-Hsien Chen, Benjamin Klein and Ian T. Ferguson

Materials 2023, 16(1), 97; https://doi.org/10.3390/ma16010097 - 22 Dec 2022

Cited by 3 | Viewed by 2704

Abstract

GaN nanowires (NWs) grown on silicon via atmospheric pressure chemical vapor deposition were doped with Cobalt (Co) by ion implantation, with a high dose concentration of 4 × 10¹⁶ cm⁻², corresponding to an average atomic percentage of ~3.85%, and annealed [...] Read more.

GaN nanowires (NWs) grown on silicon via atmospheric pressure chemical vapor deposition were doped with Cobalt (Co) by ion implantation, with a high dose concentration of 4 × 10¹⁶ cm⁻², corresponding to an average atomic percentage of ~3.85%, and annealed after the implantation. Co-doped GaN showed optimum structural properties when annealed at 700 °C for 6 min in NH₃ ambience. From scanning electron microscopy, X-ray diffraction, high resolution transmission electron microscope, and energy dispersive X-ray spectroscopy measurements and analyses, the single crystalline nature of Co-GaN NWs was identified. Slight expansion in the lattice constant of Co-GaN NWs due to the implantation-induced stress effect was observed, which was recovered by thermal annealing. Co-GaN NWs exhibited ferromagnetism as per the superconducting quantum interference device (SQUID) measurement. Hysteretic curves with Hc (coercivity) of 502.5 Oe at 5 K and 201.3 Oe at 300 K were obtained. Applied with a magnetic field of 100 Oe, the transition point between paramagnetic property and ferromagnetic property was determined at 332 K. Interesting structural and conducive magnetic properties show the potential of Co-doped GaN nanowires for the next optoelectronic, electronic, spintronic, sensing, optical, and related applications. Full article

(This article belongs to the Special Issue III-V Semiconductor Optoelectronics: Materials and Devices)

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18 pages, 4408 KiB

Open AccessEditor’s ChoiceArticle

Solid-State Dewetting as a Driving Force for Structural Transformation and Magnetization Reversal Mechanism in FePd Thin Films

by Arkadiusz Zarzycki, Marcin Perzanowski, Michal Krupinski and Marta Marszalek

Materials 2023, 16(1), 92; https://doi.org/10.3390/ma16010092 - 22 Dec 2022

Cited by 5 | Viewed by 2190

Abstract

In this work, the process of solid-state dewetting in FePd thin films and its influence on structural transformation and magnetic properties is presented. The morphology, structure and magnetic properties of the FePd system subjected to annealing at 600 °C for different times were [...] Read more.

In this work, the process of solid-state dewetting in FePd thin films and its influence on structural transformation and magnetic properties is presented. The morphology, structure and magnetic properties of the FePd system subjected to annealing at 600 °C for different times were studied. The analysis showed a strong correlation between the dewetting process and various physical phenomena. In particular, the transition between the A1 phase and L1₀ phase is strongly influenced by and inextricably connected with solid-state dewetting. Major changes were observed when the film lost its continuity, including a fast growth of the L1₀ phase, changes in the magnetization reversal behavior or the induction of magnetic spring-like behavior. Full article

(This article belongs to the Special Issue Modeling and Characterization of Materials with Unique Magnetic, Electric and Mechanical Properties (Second Volume))

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28 pages, 13676 KiB

Open AccessEditor’s ChoiceArticle

Growth Kinetics, Microstructure Evolution, and Some Mechanical Properties of Boride Layers Produced on X165CrV12 Tool Steel

by Natalia Makuch, Michał Kulka, Mourad Keddam and Adam Piasecki

Materials 2023, 16(1), 26; https://doi.org/10.3390/ma16010026 - 21 Dec 2022

Cited by 11 | Viewed by 2129

Abstract

The powder-pack boriding technique with an open retort was used to form borided layers on X165CrV12 tool steel. The process was carried out at 1123, 1173, and 1223 K for 3, 6, and 9 h. As a result of boriding the high-chromium substrate, [...] Read more.

The powder-pack boriding technique with an open retort was used to form borided layers on X165CrV12 tool steel. The process was carried out at 1123, 1173, and 1223 K for 3, 6, and 9 h. As a result of boriding the high-chromium substrate, the produced layers consisted of three zones: an outer FeB layer, an inner Fe₂B layer, and a transition zone, below which the substrate material was present. Depending on the applied parameters of boriding, the total thickness of the borided layers ranged from 12.45 to 78.76 µm. The increased temperature, as well as longer duration, was accompanied by an increase in the thickness of the FeB zone and the total layer thickness. The integral diffusion model was utilized to kinetically describe the time evolution of the thickness of the FeB and (FeB + Fe₂B) layers grown on the surface of powder-pack borided X165CrV12 steel. The activation energy of boron for the FeB phase was lower than that for the Fe₂B phase. This suggested that the FeB phase could be formed before the Fe₂B phase appeared in the microstructure. The high chromium concentration in X165CrV12 steel led to the formation of chromium borides in the borided layer, which increased the hardness (21.88 ± 1.35 GPa for FeB zone, 17.45 ± 1.20 GPa for Fe₂B zone) and Young’s modulus (386.27 ± 27.04 GPa for FeB zone, 339.75 ± 17.44 GPa for Fe₂B zone). The presence of the transition zone resulted from the accumulation of chromium and carbon atoms at the interface between the tips of Fe₂B needles and the substrate material. The presence of hard iron and chromium borides provided significant improvement in the wear resistance of X165CrV12 steel. The powder-pack borided steel was characterized by a four times lower mass wear intensity factor and nine times lower ratio of mass loss to the length or wear path compared to the non-borided material. Full article

(This article belongs to the Special Issue Precision and Ultra-Precision Subtractive and Additive Manufacturing Processes of Alloys and Steels)

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8 pages, 2202 KiB

Open AccessEditor’s ChoiceArticle

Deformable Photonic Crystals Based on Chiral Liquid Crystals with Thermal-Mediative Shape Memory Effect

by Min-Seok Park, Kitae Kim, Young-Joo Lee, Jun-Hee Na and Se-Um Kim

Materials 2023, 16(1), 35; https://doi.org/10.3390/ma16010035 - 21 Dec 2022

Cited by 4 | Viewed by 2084

Abstract

We propose a deformable photonic crystal that exhibits the thermal-mediative shape memory effect. The chiral liquid crystalline polymeric scaffold, which produces the structural colors from a helical twist of the liquid crystal director, is prepared through phase-stabilization of a reactive mesogen in a [...] Read more.

We propose a deformable photonic crystal that exhibits the thermal-mediative shape memory effect. The chiral liquid crystalline polymeric scaffold, which produces the structural colors from a helical twist of the liquid crystal director, is prepared through phase-stabilization of a reactive mesogen in a small molecular chiral liquid crystal (CLC), polymerization, and removal of the CLC. The prepolymer of polyurethane acrylate (PUA) is then infiltrated in the prepared scaffold and subsequently photo-polymerized to form a CLC-PUA composite film. Upon compression, this film shows the blue shift of the structural color and retains this color-shift as released from compression. As the temperature increases, the color is recovered to a pristine state. The concept proposed in this study will be useful for designing mechanochromic soft materials. Full article

(This article belongs to the Special Issue Soft Materials and Optical Devices)

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9 pages, 4904 KiB

Open AccessEditor’s ChoiceArticle

Theoretical Study of Dynamical and Electronic Properties of Noncentrosymmetric Superconductor NbReSi

by Surajit Basak and Andrzej Ptok

Materials 2023, 16(1), 78; https://doi.org/10.3390/ma16010078 - 21 Dec 2022

Cited by 6 | Viewed by 2436

Abstract

The noncentrosymmetric NbReSi superconductor with

T_{c} ≃ 6.5

K is characterized by the relatively large upper critical magnetic field. Its multigap features were observed experimentally. Recent studies suggested the realization of P

\bar{6}

2m or Ima2 symmetry. We discuss the dynamical [...] Read more.

The noncentrosymmetric NbReSi superconductor with

T_{c} ≃ 6.5

K is characterized by the relatively large upper critical magnetic field. Its multigap features were observed experimentally. Recent studies suggested the realization of P

\bar{6}

2m or Ima2 symmetry. We discuss the dynamical properties of both symmetries (e.g., phonon spectra). In this paper, using the ab initio techniques, we clarify this ambiguity, and conclude that the Ima2 symmetry is unstable, and P

\bar{6}

2m should be realized. The P

\bar{6}

2m symmetry is also stable in the presence of external hydrostatic pressure. We show that NbReSi with the P

\bar{6}

2m symmetry should host phonon surface states for (100) and (110) surfaces. Additionally, we discuss the main electronic properties of the system with the stable symmetry. Full article

(This article belongs to the Special Issue Engineering Properties of Superconducting Materials (Second Volume))

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12 pages, 3151 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Nd³⁺, Yb³⁺:YF₃ Optical Temperature Nanosensors Operating in the Biological Windows

by Maksim Pudovkin, Ekaterina Oleynikova, Airat Kiiamov, Mikhail Cherosov and Marat Gafurov

Materials 2023, 16(1), 39; https://doi.org/10.3390/ma16010039 - 21 Dec 2022

Cited by 9 | Viewed by 2005

Abstract

This work is devoted to the study of thermometric performances of Nd³⁺ (0.1 or 0.5 mol.%), Yb³⁺ (X%):YF₃ nanoparticles. Temperature sensitivity of spectral shape is related to the phonon-assisted nature of energy transfer (PAET) between Nd³⁺ and Yb³⁺ [...] Read more.

This work is devoted to the study of thermometric performances of Nd³⁺ (0.1 or 0.5 mol.%), Yb³⁺ (X%):YF₃ nanoparticles. Temperature sensitivity of spectral shape is related to the phonon-assisted nature of energy transfer (PAET) between Nd³⁺ and Yb³⁺). However, in the case of single-doped Nd³⁺ (0.1 or 0.5 mol.%):YF₃ nanoparticles, luminescence decay time (LDT) of ⁴F_3/2 level of Nd³⁺ in Nd³⁺ (0.5 mol.%):YF₃ decreases with the temperature decrease. In turn, luminescence decay time in Nd³⁺ (0.1 mol.%):YF₃ sample remains constant. It was proposed, that at 0.5 mol.% the cross-relaxation (CR) between Nd³⁺ ions takes place in contradistinction from 0.1 mol.% Nd³⁺ concentration. The decrease of LDT with temperature is explained by the decrease of distances between Nd³⁺ with temperature that leads to the increase of cross-relaxation efficiency. It was suggested, that the presence of both CR and PAET processes in the studied system (Nd³⁺ (0.5 mol.%), Yb³⁺ (X%):YF₃) nanoparticles provides higher temperature sensitivity compared to the systems having one process (Nd³⁺ (0.1 mol.%), Yb³⁺ (X%):YF₃). The experimental results confirmed this suggestion. The maximum relative temperature sensitivity was 0.9%·K⁻¹ at 80 K. Full article

(This article belongs to the Collection Luminescent Materials)

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