Materials

13 pages, 4497 KiB

Open AccessEditor’s ChoiceArticle

The Effect of Microstructural Changes on Mechanical and Electrochemical Corrosion Properties of Duplex Stainless Steel Aged for Short Periods

by David D. S. Silva, Lindolpho S. D. C. Lima, Allan J. M. Araújo, Vinícius D. Silva, Rafael A. Raimundo, Igor Z. Damasceno, Thiago A. Simões and Rodinei M. Gomes

Materials 2020, 13(23), 5511; https://doi.org/10.3390/ma13235511 - 3 Dec 2020

Cited by 16 | Viewed by 3672

Abstract

This work reports the effects of microstructural changes due to the secondary phases, in particular sigma (σ), on the mechanical properties and electrochemical behavior of thermally aged duplex stainless steel (DSS). Structural, morphological, mechanical, and electrochemical characterizations were performed. Sigma phase [...] Read more.

This work reports the effects of microstructural changes due to the secondary phases, in particular sigma (σ), on the mechanical properties and electrochemical behavior of thermally aged duplex stainless steel (DSS). Structural, morphological, mechanical, and electrochemical characterizations were performed. Sigma phase content increased with increasing aging treatment time. It had a net-like shape, as observed by electron backscatter diffractometry (EBSD). Its presence directly damaged mechanical properties. The corrosion assessment included electrochemical impedance spectroscopy (EIS) in 1 M NaCl solution at temperatures of 25, 40, and 65 °C. EIS results demonstrate that an increase in the σ phase content decreased the corrosion resistance (21.1–0.8, 3.5–0.3, and 3.1–0.2 kΩ cm² at 25, 40, and 60 °C, respectively). Full article

(This article belongs to the Special Issue Corrosion and Corrosion Inhibition of Metals and Their Alloys)

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23 pages, 3873 KiB

Open AccessEditor’s ChoiceArticle

Effective and Apparent Diffusion Coefficients of Chloride Ions and Chloride Binding Kinetics Parameters in Mortars: Non-Stationary Diffusion–Reaction Model and the Inverse Problem

by Jerzy J. Jasielec, Jakub Stec, Krzysztof Szyszkiewicz-Warzecha, Artur Łagosz, Jan Deja, Andrzej Lewenstam and Robert Filipek

Materials 2020, 13(23), 5522; https://doi.org/10.3390/ma13235522 - 3 Dec 2020

Cited by 17 | Viewed by 3147

Abstract

A non-equilibrium diffusion–reaction model is proposed to describe chloride transport and binding in cementitious materials. A numerical solution for this non-linear transport with reaction problem is obtained using the finite element method. The effective chloride diffusion coefficients and parameters of the chloride binding [...] Read more.

A non-equilibrium diffusion–reaction model is proposed to describe chloride transport and binding in cementitious materials. A numerical solution for this non-linear transport with reaction problem is obtained using the finite element method. The effective chloride diffusion coefficients and parameters of the chloride binding are determined using the inverse method based on a diffusion–reaction model and experimentally measured chloride concentrations. The investigations are performed for two significantly different cements: ordinary Portland and blast furnace cements. The results are compared with the classical diffusion model and appropriate apparent diffusion coefficients. The role of chloride binding, with respect to the different binding isotherms applied, in the overall transport of chlorides is discussed, along with the applicability of the two models. The proposed work allows the determination of important parameters that influence the longevity of concrete structures. The developed methodology can be extended to include more ions, electrostatic interactions, and activity coefficients for even more accurate estimation of the longevity. Full article

(This article belongs to the Special Issue Long-Term Behavior of Cementitious Materials and Reinforced Concrete Structures)

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13 pages, 28378 KiB

Open AccessEditor’s ChoiceArticle

Relationship of Surface and Bulk Resistivity in the Case of Mechanically Damaged Fibre Reinforced Red Ceramic Waste Aggregate Concrete

by Marie Horňáková and Petr Lehner

Materials 2020, 13(23), 5501; https://doi.org/10.3390/ma13235501 - 2 Dec 2020

Cited by 27 | Viewed by 2583

Abstract

Electrical resistivity is an important physical property of concrete, directly related to the chloride-induced corrosion process. This paper analyses the surface resistivity (SR) and bulk resistivity (BR) of structural lightweight waste aggregate concrete (SLWAC). The studied concrete mixture contained waste material—red ceramics fine [...] Read more.

Electrical resistivity is an important physical property of concrete, directly related to the chloride-induced corrosion process. This paper analyses the surface resistivity (SR) and bulk resistivity (BR) of structural lightweight waste aggregate concrete (SLWAC). The studied concrete mixture contained waste material—red ceramics fine aggregate and artificial expanded clay coarse aggregate. Red ceramic is a frequent waste material remaining after the demolition of buildings or unsatisfactory building material production and is among the least used construction waste. Therefore, its use is desirable in terms of sustainability; in some cases, it can reliably replace the conventional aggregate in a concrete mixture. The relationship between SR and BR was determined in the case of standard specimens and mechanically damaged specimens (to 50% and 100% of ultimate strength capacity—USC). Two different instruments were utilised for the investigation—a 4-point Wenner probe meter and an RCON tester. The results of standard specimens support the theoretically derived correction ratio, but in the case of mechanically damaged specimens, the ratio is more scattered, which is related to the mechanical damage and the amount of fibre. Full article

(This article belongs to the Special Issue Research of Structure and Properties of Concretes Based on Non-conventional Aggregates)

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16 pages, 8335 KiB

Open AccessEditor’s ChoiceArticle

Study of the Stiffness of the Bitumen Emulsion Based Cold Recycling Mixes for Road Base Courses

by Katarzyna Konieczna, Piotr Pokorski, Wojciech Sorociak, Piotr Radziszewski, Dawid Żymełka and Jan Bolesław Król

Materials 2020, 13(23), 5473; https://doi.org/10.3390/ma13235473 - 1 Dec 2020

Cited by 7 | Viewed by 2487

Abstract

The benefits of the use of cold recycling mixtures (CRMs) in pavement rehabilitation are associated with both the reduction of natural resource consumption by replacing them with recycled materials and the reduction of energy consumption during their production and paving. The evolution of [...] Read more.

The benefits of the use of cold recycling mixtures (CRMs) in pavement rehabilitation are associated with both the reduction of natural resource consumption by replacing them with recycled materials and the reduction of energy consumption during their production and paving. The evolution of the stiffness of CRMs in road construction and the fatigue life of pavements with CRM base layers are still being investigated. In this paper, CRMs with 1% cement content, called bitumen-stabilized materials with bitumen emulsion (BSM-Es), were examined. Mixtures that were differentiated in terms of Reclaimed Asphalt Pavement (RAP) content, as well as the amount and type of bitumen emulsions, were subjected to indirect tensile stiffness modulus (ITSM) tests at 5 °C, 13 °C, and 20 °C. The thermal sensitivities of the BSM-E mixtures were analyzed. BSM-E mixture stiffness modulus levels at various temperatures were determined using a statistical approach. On the basis of the results obtained, a discussion on the mechanistic-empirical design of flexible pavements with BSM-E base layers is presented. The potential benefits of using BSM-E materials in road construction in certain aspects of pavement life are indicated. Full article

(This article belongs to the Special Issue Asphalt Road Paving Materials)

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15 pages, 6544 KiB

Open AccessEditor’s ChoiceArticle

Regional Waste Streams as Potential Raw Materials for Immediate Implementation in Cement Production

by Matea Flegar, Marijana Serdar, Diana Londono-Zuluaga and Karen Scrivener

Materials 2020, 13(23), 5456; https://doi.org/10.3390/ma13235456 - 30 Nov 2020

Cited by 18 | Viewed by 3283

Abstract

There is an urgent need to apply available technologies to reduce the environmental impact of the construction industry. One of the possible solutions that can be implemented immediately is the industrial symbiosis between the waste-producing industries on the one hand and the cement [...] Read more.

There is an urgent need to apply available technologies to reduce the environmental impact of the construction industry. One of the possible solutions that can be implemented immediately is the industrial symbiosis between the waste-producing industries on the one hand and the cement industry, which consumes enormous amounts of raw materials for its production, on the other. In order for the industry to accelerate the use of these available materials and technologies, the potential of these materials must be disclosed. The present study shows a systematic approach to assess the potential of waste materials, by-products, and other raw materials available in the South East Europe that can be used in cement production. Their evaluation included the analysis of their availability, their chemical and physical properties, their chemical reactivity, and their contribution to the mortar’s strength. Based on the results and the analyses carried out, a recommendation for immediate use in the construction sector is given for each of the materials collected. Full article

(This article belongs to the Special Issue Sustainability in Construction and Building Materials)

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17 pages, 6348 KiB

Open AccessEditor’s ChoiceArticle

Development and Characterization of “Green Open-Cell Polyurethane Foams” with Reduced Flammability

by Maria Kurańska, Hynek Beneš, Kamila Sałasińska, Aleksander Prociak, Elżbieta Malewska and Krzysztof Polaczek

Materials 2020, 13(23), 5459; https://doi.org/10.3390/ma13235459 - 30 Nov 2020

Cited by 24 | Viewed by 3079

Abstract

This work presents the cell structure and selected properties of polyurethane (PUR) foams, based on two types of hydroxylated used cooking oil and additionally modified with three different flame retardants. Bio-polyols from municipal waste oil with different chemical structures were obtained by transesterification [...] Read more.

This work presents the cell structure and selected properties of polyurethane (PUR) foams, based on two types of hydroxylated used cooking oil and additionally modified with three different flame retardants. Bio-polyols from municipal waste oil with different chemical structures were obtained by transesterification with triethanolamine (UCO_TEA) and diethylene glycol (UCO_DEG). Next, these bio-polyols were used to prepare open-cell polyurethane foams of very low apparent densities for thermal insulation applications. In order to obtain foams with reduced flammability, the PUR systems were modified with different amounts (10–30 parts per hundred polyol by weight—php) of flame retardants: TCPP (tris(1-chloro-2-propyl)phosphate), TEP (triethyl phosphate), and DMPP (dimethyl propylphosphonate). The flame retardants caused a decrease of the PUR formulations reactivity. The apparent densities of all the foams were comparable in the range 12–15 kg/m³. The lowest coefficients of thermal conductivity were measured for the open-cell PUR foams modified with DMPP. The lowest values of heat release rate were found for the foams based on the UCO_TEA and UCO_DEG bio-polyols that were modified with 30 php of DMPP. Full article

(This article belongs to the Special Issue Environmentally Friendly Materials in Construction)

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19 pages, 5828 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Analysis of the Calcium Phosphate-Based Hybrid Layer Formed on a Ti-6Al-7Nb Alloy to Enhance the Ossseointegration Process

by Alicja Kazek-Kęsik, David Djurado, Stéphanie Pouget, Agata Blacha-Grzechnik, Izabela Kalemba-Rec and Wojciech Simka

Materials 2020, 13(23), 5468; https://doi.org/10.3390/ma13235468 - 30 Nov 2020

Cited by 9 | Viewed by 2375

Abstract

This paper reports on hybrid, bioactive ceramic Ca-P-based coating formation on a Ti-6Al-7Nb alloy substrate to enhance the osseointegration process. The Ti alloy was anodized in a Ca₃(PO₄)₂ suspension and then the additional layer was formed by the [...] Read more.

This paper reports on hybrid, bioactive ceramic Ca-P-based coating formation on a Ti-6Al-7Nb alloy substrate to enhance the osseointegration process. The Ti alloy was anodized in a Ca₃(PO₄)₂ suspension and then the additional layer was formed by the sol-gel technique to obtain a mixture of the calcium phosphate compounds. The oxide layer was porous and additional ceramic particles were formed after sol-gel treatment (scanning electron microscopy analysis coupled with energy-dispersive x-ray spectroscopy). The ceramic particles were formed on some parts of the oxide layer and did not completely fill the pores. The layer thickness of the anodized Ti alloy was comprised between 3.01 and 5.03 µm and increased to 7.52–12.30 µm after the formation of an additional layer. Post-treatment of the anodized Ti alloys caused a decrease in surface roughness, and the layer became strongly hydrophilic. Crystalline phase analysis (X-ray diffraction, XRD) showed that the hybrid layer was composed of TiO₂ (anatase), Ca₃(PO₄)₂, Ca₁₀(PO₄)₆(OH)₂ and a partially amorphous phase; thus, the layer was also analyzed by Raman spectroscopy. The hybrid layer showed worse adhesion to the substrate than the anodized layer only; however, the coating was not brittle, and the first delamination of the layer was determined at 1.84 ± 0.11 N during scratch-test measurement. The hybrid coating was favorable for collagen type I and lactoferrin adsorption, strongly influencing the proliferation of osteoblast-like MG-63 cells. The coatings were cytocompatible and may find applications in formation of the functional layers on long-term implants’ surface after. Full article

(This article belongs to the Special Issue Corrosion and Corrosion Inhibition of Metals and Their Alloys)

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12 pages, 5254 KiB

Open AccessEditor’s ChoiceArticle

The Effect of pH on the Size of Silver Nanoparticles Obtained in the Reduction Reaction with Citric and Malic Acids

by Lukasz Marciniak, Martyna Nowak, Anna Trojanowska, Bartosz Tylkowski and Renata Jastrzab

Materials 2020, 13(23), 5444; https://doi.org/10.3390/ma13235444 - 29 Nov 2020

Cited by 87 | Viewed by 6771

Abstract

In colloidal methods, the morphology of nanoparticles (size and shape) as well as their stability can be controlled by changing the concentration of the substrate, stabilizer, adding inorganic salts, changing the reducer/substrate molar ratio, and changing the pH and reaction time. The synthesis [...] Read more.

In colloidal methods, the morphology of nanoparticles (size and shape) as well as their stability can be controlled by changing the concentration of the substrate, stabilizer, adding inorganic salts, changing the reducer/substrate molar ratio, and changing the pH and reaction time. The synthesis of silver nanoparticles was carried out according to the modified Lee and Meisel method in a wide pH range (from 2.0 to 11.0) using citric acid and malic acid, without adding any additives or stabilizers. Keeping the same reaction conditions as the concentration of acid and silver ions, temperature, and heating time, it was possible to determine the relationship between the reaction pH, the type of acid, and the size of the silver nanoparticles formed. Obtained colloids were analyzed by UV-Vis spectroscopy and investigated by means of Transmission Electron Microscope (TEM). The study showed that the colloids reduced with citric acid and malic acid are stable over time for a minimum of seven weeks. We observed that reactions occurred for citric acid from pH 6.0 to 11.0 and for malic acid from pH 7.0 to 11.0. The average size of the quasi-spherical nanoparticles changed with pH due to the increase of reaction rate. Full article

(This article belongs to the Section Materials Chemistry)

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15 pages, 5400 KiB

Open AccessEditor’s ChoiceArticle

Photocatalytic Performance Evaluation of Titanium Dioxide Nanotube-Reinforced Cement Paste

by Junxing Liu, Hyeonseok Jee, Myungkwan Lim, Joo Hyung Kim, Seung Jun Kwon, Kwang Myong Lee, Erfan Zal Nezhad and Sungchul Bae

Materials 2020, 13(23), 5423; https://doi.org/10.3390/ma13235423 - 28 Nov 2020

Cited by 18 | Viewed by 3849

Abstract

Considering the increase in research regarding environmental pollution reduction, the utilization of cementitious material, a commonly used construction material, in photocatalysts has become a desirable research field for the widespread application of photocatalytic degradation technology. Nano-reinforcement technology for cementitious materials has been extensively [...] Read more.

Considering the increase in research regarding environmental pollution reduction, the utilization of cementitious material, a commonly used construction material, in photocatalysts has become a desirable research field for the widespread application of photocatalytic degradation technology. Nano-reinforcement technology for cementitious materials has been extensively researched and developed. In this work, as a new and promising reinforcing agent for cementitious materials, the photocatalytic performance of titanium dioxide nanotube (TNT) was investigated. The degradation of methylene blue was used to evaluate the photocatalytic performance of the TNT-reinforced cement paste. In addition, cement paste containing micro-TiO₂ (m-TiO₂) and nano-TiO₂ (n-TiO₂) particles were used for comparison. Moreover, the effect of these TiO₂-based photocatalytic materials on the cement hydration products was monitored via X-ray diffraction (XRD) and thermogravimetric analysis (TG). The results indicated that all the TiO₂ based materials promoted the formation of hydration products. After 28 days of curing, the TNT-reinforced cement paste contained the maximum amount of hydration products (Ca(OH)₂). Furthermore, the cement paste containing TNT exhibited better photocatalytic effects than that containing n-TiO₂, but worse than that containing m-TiO₂. Full article

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

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24 pages, 14185 KiB

Open AccessEditor’s ChoiceArticle

Effect of Jute Fibres on the Process of MICP and Properties of Biocemented Sand

by Christine Ann Spencer, Leon van Paassen and Henrik Sass

Materials 2020, 13(23), 5429; https://doi.org/10.3390/ma13235429 - 28 Nov 2020

Cited by 24 | Viewed by 4132

Abstract

There has been increasing interest, in the past decade, in bio-mediated approaches to soil improvement for geotechnical applications. Microbially induced calcium carbonate precipitation (MICP) has been investigated as a potentially sustainable method for the strengthening and stabilisation of soil structures. This paper presents [...] Read more.

There has been increasing interest, in the past decade, in bio-mediated approaches to soil improvement for geotechnical applications. Microbially induced calcium carbonate precipitation (MICP) has been investigated as a potentially sustainable method for the strengthening and stabilisation of soil structures. This paper presents the results of a study on the effect of jute fibres on both the MICP process and properties of biocemented sand. Ureolytic Sporosarcina pasteurii has been used to produce biocemented soil columns via MICP in the laboratory. Results showed that columns containing 0.75% (by weight of sand) untreated jute fibres had unconfined compressive strengths approximately six times greater on average compared to biocemented sand columns without jute fibres. Furthermore, efficiency of chemical conversion was found to be higher in columns containing jute fibres, as measured using ion chromatography. Columns containing jute had calcimeter measured CaCO₃ contents at least three times those containing sand only. The results showed that incorporation of jute fibres into the biocemented sand material had a beneficial effect, resulting in stimulation of bacterial activity, thus sustaining the MICP process during the twelve-day treatment process. This study also explores the potential of jute fibres in self-healing MICP systems. Full article

(This article belongs to the Special Issue Textile-Based Advanced Materials: Construction, Properties and Applications)

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20 pages, 4810 KiB

Open AccessEditor’s ChoiceArticle

Physico-Mechanical and Rheological Properties of Epoxy Adhesives Modified by Microsilica and Sonication Process

by Andrzej Szewczak and Maciej Szeląg

Materials 2020, 13(23), 5310; https://doi.org/10.3390/ma13235310 - 24 Nov 2020

Cited by 30 | Viewed by 2691

Abstract

Industrial waste from the production of metallic silicon and silicon–iron alloys, which includes silica fumes (microsilica), is subject to numerous applications aiming at its reuse in concrete and polymeric composites. Recycling solves the problem of their storage and adverse environmental impact. Six different [...] Read more.

Industrial waste from the production of metallic silicon and silicon–iron alloys, which includes silica fumes (microsilica), is subject to numerous applications aiming at its reuse in concrete and polymeric composites. Recycling solves the problem of their storage and adverse environmental impact. Six different formulas of epoxy resins were tested, differing in the type of polymer, the mixing process (sonication or not) and the presence of microsilica. The study showed that microsilica added to the epoxy resin changes its viscosity and free surface energy, and these are the parameters that determine the adhesion of the polymer to the concrete surface. Strength tests and SEM analysis have determined how microsilica molecules can penetrate the structure of polymer macromolecules by filling and forming temporary chemical bonds. Mixing the fillers with the adhesive was achieved by using a sonication process. The analysis of the obtained results showed that, depending on the initial composition of the polymer, the addition of microsilica can change the chemical, physical and mechanical properties of the hardened adhesive to varying degrees. In the case of adhesives used in the construction industry to strengthen and glue structural elements, these changes significantly affect the durability of the adhesive joints. Full article

(This article belongs to the Special Issue Durability of Concrete or Mineral-Asphalt Mixtures with Recycled Aggregates)

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21 pages, 1348 KiB

Open AccessEditor’s ChoiceReview

Systematic Review on the Effects, Roles and Methods of Magnetic Particle Coatings in Magnetorheological Materials

by Siti Khumaira Mohd Jamari, Nur Azmah Nordin, Ubaidillah, Siti Aishah Abdul Aziz, Nurhazimah Nazmi and Saiful Amri Mazlan

Materials 2020, 13(23), 5317; https://doi.org/10.3390/ma13235317 - 24 Nov 2020

Cited by 10 | Viewed by 3137

Abstract

Magnetorheological (MR) material is a type of magneto-sensitive smart materials which consists of magnetizable particles dispersed in a carrier medium. Throughout the years, coating on the surface of the magnetic particles has been developed by researchers to enhance the performance of MR materials, [...] Read more.

Magnetorheological (MR) material is a type of magneto-sensitive smart materials which consists of magnetizable particles dispersed in a carrier medium. Throughout the years, coating on the surface of the magnetic particles has been developed by researchers to enhance the performance of MR materials, which include the improvement of sedimentation stability, enhancement of the interaction between the particles and matrix mediums, and improving rheological properties as well as providing extra protection against oxidative environments. There are a few coating methods that have been employed to graft the coating layer on the surface of the magnetic particles, such as atomic transfer radical polymerization (ATRP), chemical oxidative polymerization, and dispersion polymerization. This paper investigates the role of particle coating in MR materials with the effects gained from grafting the magnetic particles. This paper also discusses the coating methods employed in some of the works that have been established by researchers in the particle coating of MR materials. Full article

(This article belongs to the Special Issue Advances in Elastomers)

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11 pages, 3041 KiB

Open AccessEditor’s ChoiceArticle

Investigation of Moisture Dissipation of Water-Foamed Asphalt and Its Influence on the Viscosity

by Ning Li, Wei Tang, Xin Yu, He Zhan, Hui Ma, Gongying Ding and Yu Zhang

Materials 2020, 13(23), 5325; https://doi.org/10.3390/ma13235325 - 24 Nov 2020

Cited by 19 | Viewed by 2312

Abstract

Water-foamed asphalt is capable of improving the workability of asphalt mixture. It has been extensively used for its energy-saving and emission-reducing features. Water plays an essential part in improving the workability of water-foamed asphalt mixture. However, there is still lack in profound studies [...] Read more.

Water-foamed asphalt is capable of improving the workability of asphalt mixture. It has been extensively used for its energy-saving and emission-reducing features. Water plays an essential part in improving the workability of water-foamed asphalt mixture. However, there is still lack in profound studies of moisture dissipation of the water-foamed asphalt over time and its influence on workability. In this study, the evolutions of residual water content and rotational viscosity of the water-foamed asphalt with time were respectively measured by the analytical balance and modified rotational viscometer (RV). The atomic force microscopy (AFM) analysis was conducted to discuss the mechanism of viscosity reduction of water-foamed asphalt. The results showed that moisture evaporation is significantly influenced by the foaming water content and ambient temperature, which results in the different stabilizing time of water-foamed asphalt. When water-foamed asphalt was stabilized, the residual water inside the asphalt was less than 0.01% relative to the asphalt mass. The AFM analysis showed that the foaming process changed the distribution of wax in the water-foamed asphalt resulting in reduction of viscosity. The viscosity reduction of asphalt is highly related to the initial foaming water content. After the foaming process, the viscosity keeps stable and is independent of moisture dissipation. Full article

(This article belongs to the Special Issue Sustainable Asphalt Pavements: Materials, Design Methods, and Characterization Techniques)

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31 pages, 3353 KiB

Open AccessEditor’s ChoiceReview

A Review on Cementitious Self-Healing and the Potential of Phase-Field Methods for Modeling Crack-Closing and Fracture Recovery

by Sha Yang, Fadi Aldakheel, Antonio Caggiano, Peter Wriggers and Eddie Koenders

Materials 2020, 13(22), 5265; https://doi.org/10.3390/ma13225265 - 21 Nov 2020

Cited by 29 | Viewed by 5778

Abstract

Improving the durability and sustainability of concrete structures has been driving the enormous number of research papers on self-healing mechanisms that have been published in the past decades. The vast developments of computer science significantly contributed to this and enhanced the various possibilities [...] Read more.

Improving the durability and sustainability of concrete structures has been driving the enormous number of research papers on self-healing mechanisms that have been published in the past decades. The vast developments of computer science significantly contributed to this and enhanced the various possibilities numerical simulations can offer to predict the entire service life, with emphasis on crack development and cementitious self-healing. The aim of this paper is to review the currently available literature on numerical methods for cementitious self-healing and fracture development using Phase-Field (PF) methods. The PF method is a computational method that has been frequently used for modeling and predicting the evolution of meso- and microstructural morphology of cementitious materials. It uses a set of conservative and non-conservative field variables to describe the phase evolutions. Unlike traditional sharp interface models, these field variables are continuous in the interfacial region, which is typical for PF methods. The present study first summarizes the various principles of self-healing mechanisms for cementitious materials, followed by the application of PF methods for simulating microscopic phase transformations. Then, a review on the various PF approaches for precipitation reaction and fracture mechanisms is reported, where the final section addresses potential key issues that may be considered in future developments of self-healing models. This also includes unified, combined and coupled multi-field models, which allow a comprehensive simulation of self-healing processes in cementitious materials. Full article

(This article belongs to the Special Issue Feature Papers in Construction and Building Materials)

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17 pages, 7067 KiB

Open AccessEditor’s ChoiceArticle

Chloride-Induced Corrosion of Steel in Alkali-Activated Mortars Based on Different Precursors

by Antonino Runci and Marijana Serdar

Materials 2020, 13(22), 5244; https://doi.org/10.3390/ma13225244 - 20 Nov 2020

Cited by 10 | Viewed by 2686

Abstract

The low environmental impact and high long-term performance of products are becoming imperative for the sustainable development of the construction industry. Alkali-activated materials (AAMs) are one of the available low-embodied-carbon alternatives to Portland cement (OPC). For their application in the marine environment or [...] Read more.

The low environmental impact and high long-term performance of products are becoming imperative for the sustainable development of the construction industry. Alkali-activated materials (AAMs) are one of the available low-embodied-carbon alternatives to Portland cement (OPC). For their application in the marine environment or where de-icing salts are used, it is of utmost importance to demonstrate their equal or better performance compared to OPC. The aim of this study was to compare the corrosion behaviour of the steel in AAMs based on different regionally available by-products with the behaviour of the steel in OPC. The by-products used were fly ash, slag, silica fume, and iron-silica fines. The corrosion process of each system was monitored by the corrosion potential and polarisation resistance during exposure to tap water and chloride solution over a period of almost one year. Certain AAMs showed a higher resistance to chloride penetration compared to OPC, which was attributed to the smaller number of capillary pores and higher gel phase precipitation. The same corrosion resistance compared to OPC was achieved with alkali-activated fly ash and alkali-activated slag mortars. The stability of the systems in tap water and chloride solution was confirmed by the visual assessment of the steel surface at the end of the test period. Full article

(This article belongs to the Special Issue Long-Term Behavior of Cementitious Materials and Reinforced Concrete Structures)

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20 pages, 7480 KiB

Open AccessEditor’s ChoiceArticle

Application of Ultraviolet Laser Working in Cold Ablation Conditions for Cutting Labels Used in Packaging in the Food Industry

by Łukasz Bohdal, Leon Kukiełka, Radosław Patyk, Rafał Gryglicki and Piotr Kasprzak

Materials 2020, 13(22), 5245; https://doi.org/10.3390/ma13225245 - 20 Nov 2020

Cited by 2 | Viewed by 2396

Abstract

This work presents experimental studies aiming at the development of new technology and guidelines for shaping labels from polypropylene multilayer foil using an ultraviolet (UV) laser cutting operation. Currently on production lines, the shaping of labels is undertaken by mechanical cutting or laser [...] Read more.

This work presents experimental studies aiming at the development of new technology and guidelines for shaping labels from polypropylene multilayer foil using an ultraviolet (UV) laser cutting operation. Currently on production lines, the shaping of labels is undertaken by mechanical cutting or laser cutting, taking into account the phenomenon of hot ablation. These technologies cause many problems such as burr formation on labels sheared edges, rapid tool wear, or heat-affected zone (HAZ) formation. The experimental tests were carried out on a specially designed laser system for cutting polypropylene foil using the phenomenon of cold ablation. Parametric analyses were conducted for several foil thicknesses t = 50, 60, 70 and 80 µm. The process parameters were optimized in terms of high efficiency and high labels-cut surface quality. A new criterion has been developed for assessing the quality of UV laser cutting of polypropylene foils. The results indicate a significant effect of the cutting speed and laser frequency on the width of the degraded zone on the sheet cut edge. As a result of a developed optimization task and reverse task solution it is possible to cut labels at high speeds (v = 1.5 m/s) while maintaining a high quality of cut edge free of carbon, delamination and color changes. A degraded zone does not exceed in the examined cases s ≤ 0.17 mm. Full article

(This article belongs to the Special Issue Trends and Prospects in Surface Engineering)

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12 pages, 1463 KiB

Open AccessEditor’s ChoiceArticle

A New Viscoelasticity Dynamic Fitting Method Applied for Polymeric and Polymer-Based Composite Materials

by Vitor Dacol, Elsa Caetano and João R. Correia

Materials 2020, 13(22), 5213; https://doi.org/10.3390/ma13225213 - 18 Nov 2020

Cited by 10 | Viewed by 2595

Abstract

The accurate analysis of the behaviour of a polymeric composite structure, including the determination of its deformation over time and also the evaluation of its dynamic behaviour under service conditions, demands the characterisation of the viscoelastic properties of the constituent materials. Linear viscoelastic [...] Read more.

The accurate analysis of the behaviour of a polymeric composite structure, including the determination of its deformation over time and also the evaluation of its dynamic behaviour under service conditions, demands the characterisation of the viscoelastic properties of the constituent materials. Linear viscoelastic materials should be experimentally characterised under (i) constant static load and/or (ii) harmonic load. In the first load case, the viscoelastic behaviour is characterised through the creep compliance or the relaxation modulus. In the second load case, the viscoelastic behaviour is characterised by the complex modulus,

E^{*}

, and the loss factor,

η

. In the present paper, a powerful and simple implementing technique is proposed for the processing and analysis of dynamic mechanical data. The idea is to obtain the dynamic moduli expressions from the Exponential-Power Law Method (EPL) of the creep compliance and the relaxation modulus functions, by applying the Carson and Laplace transform functions and their relationship to the Fourier transform, and the Theorem of Moivre. Reciprocally, once the complex moduli have been obtained from a dynamic test, it becomes advantageous to use mathematical interconversion techniques to obtain the time-domain function of the relaxation modulus,

E (t)

, and the creep compliance,

D (t)

. This paper demonstrates the advantages of the EPL method, namely its simplicity and straightforwardness in performing the desirable interconversion between quasi-static and dynamic behaviour of polymeric and polymer-composite materials. The EPL approximate interconversion scheme to convert the measured creep compliance to relaxation modulus is derived to obtain the complex moduli. Finally, the EPL Method is successfully assessed using experimental data from the literature. Full article

(This article belongs to the Special Issue Advanced Composite Materials: Theory, Design and Applications)

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12 pages, 2806 KiB

Open AccessEditor’s ChoiceArticle

A Study on the Utilization of Coal Fly Ash Derived Grog in Clay Ceramics

by Thye Foo Choo, Mohamad Amran Mohd Salleh, Kuan Ying Kok, Khamirul Amin Matori and Suraya Abdul Rashid

Materials 2020, 13(22), 5218; https://doi.org/10.3390/ma13225218 - 18 Nov 2020

Cited by 8 | Viewed by 2623

Abstract

Grog is an additive material that plays important roles in ceramic making. It improves the fabrication process of green bodies as well as the physical properties of fired bodies. Few low-cost materials and wastes have found their application as grog in recent years, [...] Read more.

Grog is an additive material that plays important roles in ceramic making. It improves the fabrication process of green bodies as well as the physical properties of fired bodies. Few low-cost materials and wastes have found their application as grog in recent years, thus encouraging the replacement of commercial grogs with cost-saving materials. Coal fly ash, a combustion waste produced by coal-fired power plant, has the potential to be converted into grog owing to its small particle sizes and high content of silica and alumina. In this study, grog was derived from coal fly ash and mixed with kaolin clay to produce ceramics. Effects of the grog addition on the resultant ceramics were investigated. It was found that, to a certain extent, the grog addition reduced the firing shrinkage and increased the total porosity of the ceramics. The dimensional stability of the ceramics at a firing temperature of 1200 °C was also not noticeably affected by the grog. However, the grog addition in general had negative effects on the biaxial flexural strength and refractoriness of the ceramics. Full article

(This article belongs to the Special Issue Silicate Solid Waste Recycling)

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23 pages, 4050 KiB

Open AccessEditor’s ChoiceArticle

Scaled Approach to Designing the Minimum Hybrid Reinforcement of Concrete Beams

by Andrea Gorino and Alessandro P. Fantilli

Materials 2020, 13(22), 5166; https://doi.org/10.3390/ma13225166 - 16 Nov 2020

Cited by 8 | Viewed by 1875

Abstract

To study the brittle/ductile behavior of concrete beams reinforced with low amounts of rebar and fibers, a new multi-scale model is presented. It is used to predict the flexural response of an ideal Hybrid Reinforced Concrete (HRC) beam in bending, and it is [...] Read more.

To study the brittle/ductile behavior of concrete beams reinforced with low amounts of rebar and fibers, a new multi-scale model is presented. It is used to predict the flexural response of an ideal Hybrid Reinforced Concrete (HRC) beam in bending, and it is validated with the results of a specific experimental campaign, and some tests available in the technical literature. Both the numerical and the experimental measurements define a linear relationship between the amount of reinforcement and the Ductility Index (DI). The latter is a non-dimensional function depending on the difference between the ultimate load and the effective cracking load of a concrete beam. As a result, a new design-by-testing procedure can be established to determine the minimum reinforcement of HRC elements. It corresponds to DI = 0, and can be considered as a linear combination of the minimum area of rebar (of the same reinforced concrete beam) and the minimum fiber volume fraction (of the same fiber-reinforced concrete beam), respectively. Full article

(This article belongs to the Special Issue Fracture Mechanics of Fiber Reinforced Concrete)

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14 pages, 3402 KiB

Open AccessEditor’s ChoiceArticle

Dansyl-Labelled Ag@SiO₂ Core-Shell Nanostructures—Synthesis, Characterization, and Metal-Enhanced Fluorescence

by Elżbieta Szczepańska, Anna Synak, Piotr Bojarski, Paweł Niedziałkowski, Anna Wcisło, Tadeusz Ossowski and Beata Grobelna

Materials 2020, 13(22), 5168; https://doi.org/10.3390/ma13225168 - 16 Nov 2020

Cited by 12 | Viewed by 3261

Abstract

The present work describes synthesis, characterization, and use of a new dansyl-labelled Ag@SiO₂ nanocomposite as an element of a new plasmonic platform to enhance the fluorescence intensity. Keeping in mind that typical surface plasmon resonance (SPR) characteristics of silver nanoparticles coincide well [...] Read more.

The present work describes synthesis, characterization, and use of a new dansyl-labelled Ag@SiO₂ nanocomposite as an element of a new plasmonic platform to enhance the fluorescence intensity. Keeping in mind that typical surface plasmon resonance (SPR) characteristics of silver nanoparticles coincide well enough with the absorption of dansyl molecules, we used them to build the core of the nanocomposite. Moreover, we utilized 10 nm amino-functionalized silica shell as a separator between silver nanoparticles and the dansyl dye to prevent the dye-to-metal energy transfer. The dansyl group was incorporated into Ag@SiO₂ core-shell nanostructures by the reaction of aminopropyltrimethoxysilane with dansyl chloride and we characterized the new dansyl-labelled Ag@SiO₂ nanocomposite using transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FTIR). Additionally, water wettability measurements (WWM) were carried out to assess the hydrophobicity and hydrophilicity of the studied surface. We found that the nanocomposite deposited on a semitransparent silver mirror strongly increased the fluorescence intensity of dansyl dye (about 87-fold) compared with the control sample on the glass, proving that the system is a perfect candidate for a sensitive plasmonic platform. Full article

(This article belongs to the Section Materials Chemistry)

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28 pages, 4126 KiB

Open AccessEditor’s ChoiceReview

Sustainable Use of Nanomaterials in Textiles and Their Environmental Impact

by Haleema Saleem and Syed Javaid Zaidi

Materials 2020, 13(22), 5134; https://doi.org/10.3390/ma13225134 - 13 Nov 2020

Cited by 129 | Viewed by 14338

Abstract

At present, nanotechnology is a priority in research in several nations due to its massive capability and financial impact. However, due to the uncertainties and abnormalities in shape, size, and chemical compositions, the existence of certain nanomaterials may lead to dangerous effects on [...] Read more.

At present, nanotechnology is a priority in research in several nations due to its massive capability and financial impact. However, due to the uncertainties and abnormalities in shape, size, and chemical compositions, the existence of certain nanomaterials may lead to dangerous effects on the human health and environment. The present review includes the different advanced applications of nanomaterials in textiles industries, as well as their associated environmental and health risks. The four main textile industry fields using nanomaterials, nanofinishing, nanocoatings, nanofibers, and nanocomposites, are analyzed. Different functional textiles with nanomaterials are also briefly reviewed. Most textile materials are in direct and prolonged contact with our skin. Hence, the influence of carcinogenic and toxic substances that are available in textiles must be comprehensively examined. Proper recognition of the conceivable benefits and accidental hazards of nanomaterials to our surroundings is significant for pursuing its development in the forthcoming years. The conclusions of the current paper are anticipated to increase awareness on the possible influence of nanomaterial-containing textile wastes and the significance of better regulations in regards to the ultimate disposal of these wastes. Full article

(This article belongs to the Special Issue Textile-Based Advanced Materials: Construction, Properties and Applications)

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15 pages, 2244 KiB

Open AccessEditor’s ChoiceArticle

New Polyphenol-Containing LDL Nano-Preparations in Oxidative Stress and DNA Damage: A Potential Route for Cell-Targeted PP Delivery

by Hanna Lewandowska and Monika Kalinowska

Materials 2020, 13(22), 5106; https://doi.org/10.3390/ma13225106 - 12 Nov 2020

Cited by 5 | Viewed by 2126

Abstract

Low-density lipoprotein (LDL) preparations of the chosen polyphenols (PPs) were prepared for the first time in the literature. The solubility of the PPs in the lipidic core of the LDL increased with the increase of their lipophilicity. The anti-/pro-oxidative properties and toxicity of [...] Read more.

Low-density lipoprotein (LDL) preparations of the chosen polyphenols (PPs) were prepared for the first time in the literature. The solubility of the PPs in the lipidic core of the LDL increased with the increase of their lipophilicity. The anti-/pro-oxidative properties and toxicity of LDL-entrapped PPs toward A 2780 human ovarian cancer cells were examined. The obtained preparations were found to be stable in PBS, and characterized by low toxicity. A binding affinity study revealed that the uptake of PP-loaded LDL particles is non-receptor-specific under experimental conditions. The antioxidative potential of the obtained PPs-doped LDL preparations was shown to be higher than for the PPs themselves, probably due to facilitating transport of LDL preparations into the cellular milieu, where they can interact with the cellular systems and change the redox status of the cell. The PPs-loaded LDL displayed the highest protective effect against Fenton-type reaction induced oxidative DNA damage. Full article

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

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13 pages, 14406 KiB

Open AccessEditor’s ChoiceArticle

Enhanced Magneto-Optic Properties in Sputtered Bi- Containing Ferrite Garnet Thin Films Fabricated Using Oxygen Plasma Treatment and Metal Oxide Protective Layers

by V. A. Kotov, M. Nur-E-Alam, M. Vasiliev, K. Alameh, D. E. Balabanov and V. I. Burkov

Materials 2020, 13(22), 5113; https://doi.org/10.3390/ma13225113 - 12 Nov 2020

Cited by 5 | Viewed by 2428

Abstract

Magneto-optic (MO) imaging and sensing are at present the most developed practical applications of thin-film MO garnet materials. However, in order to improve sensitivity for a range of established and forward-looking applications, the technology and component-related advances are still necessary. These improvements are [...] Read more.

Magneto-optic (MO) imaging and sensing are at present the most developed practical applications of thin-film MO garnet materials. However, in order to improve sensitivity for a range of established and forward-looking applications, the technology and component-related advances are still necessary. These improvements are expected to originate from new material system development. We propose a set of technological modifications for the RF-magnetron sputtering deposition and crystallization annealing of magneto-optic bismuth-substituted iron-garnet films and investigate the improved material properties. Results show that standard crystallization annealing for the as-deposited ultrathin (sputtered 10 nm thick, amorphous phase) films resulted in more than a factor of two loss in the magneto-optical activity of the films in the visible spectral region, compared to the liquid-phase grown epitaxial films. Results also show that an additional 10 nm-thick metal-oxide (Bi₂O₃) protective layer above the amorphous film results in ~2.7 times increase in the magneto-optical quality of crystallized iron-garnet films. On the other hand, the effects of post-deposition oxygen (O₂) plasma treatment on the magneto-optical (MO) properties of Bismuth substituted iron garnet thin film materials are investigated. Results show that in the visible part of the electromagnetic spectrum (at 532 nm), the O₂ treated (up to 3 min) garnet films retain higher specific Faraday rotation and figures of merit compared to non-treated garnet films. Full article

(This article belongs to the Special Issue Photoactive Materials: Synthesis, Applications and Technology)

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12 pages, 4420 KiB

Open AccessEditor’s ChoiceArticle

Embedded NiTi Wires for Improved Dynamic Thermomechanical Performance of Silicone Elastomers

by Umut D. Çakmak, Ingrid Graz, Richard Moser, Michael Fischlschweiger and Zoltán Major

Materials 2020, 13(22), 5076; https://doi.org/10.3390/ma13225076 - 11 Nov 2020

Cited by 6 | Viewed by 2086

Abstract

The extraordinary properties of shape memory NiTi alloy are combined with the inherent viscoelastic behavior of a silicon elastomer. NiTi wires are incorporated in a silicon elastomer matrix. Benefits include features as electrical/thermal conductivity, reinforcement along with enhanced damping performance and flexibility. To [...] Read more.

The extraordinary properties of shape memory NiTi alloy are combined with the inherent viscoelastic behavior of a silicon elastomer. NiTi wires are incorporated in a silicon elastomer matrix. Benefits include features as electrical/thermal conductivity, reinforcement along with enhanced damping performance and flexibility. To gain more insight of this composite, a comprehensive dynamic thermomechanical analysis is performed and the temperature- as well as frequency-dependent storage modulus and the mechanical loss factor are obtained. The analyses are realized for the composite and single components. Moreover, the models to express the examined properties and their temperature along with the frequency dependencies are also presented. Full article

(This article belongs to the Special Issue Shape Memory Alloys (SMAs) for Engineering Applications)

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18 pages, 5019 KiB

Open AccessEditor’s ChoiceArticle

The Formation of Perovskite during the Combustion of an Energy-Rich Glycine–Nitrate Precursor

by Oksana V. Komova, Svetlana A. Mukha, Anna M. Ozerova, Galina V. Odegova, Valentina I. Simagina, Olga A. Bulavchenko, Arcady V. Ishchenko and Olga V. Netskina

Materials 2020, 13(22), 5091; https://doi.org/10.3390/ma13225091 - 11 Nov 2020

Cited by 13 | Viewed by 2297

Abstract

The effect of different regimes of combustion of glycine–nitrate precursors on the formation of perovskite phases (LaMnO₃ and LaCrO₃) without additional heat treatment was studied. The following three combustion regimes were compared: the traditional solution combustion synthesis (SCS), volume combustion [...] Read more.

The effect of different regimes of combustion of glycine–nitrate precursors on the formation of perovskite phases (LaMnO₃ and LaCrO₃) without additional heat treatment was studied. The following three combustion regimes were compared: the traditional solution combustion synthesis (SCS), volume combustion synthesis (VCS) using a powdered precursor, and self-propagating high-temperature synthesis (SHS) using a precursor pellet. The products of combustion were studied using a series of physicochemical methods (attenuated total reflection infrared spectroscopy (ATR FTIR), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and thermal analysis). SHS was found to be the most productive regime for the formation of perovskite because of its ability to develop high temperatures in the reaction zone, which led to a reduced content of the thermally stable lanthanum carbonate impurities and to an increased yield and crystallite size of the perovskite phase. The reasons for the better crystallinity and purity of LaCrO₃ as compared with LaMnO₃ is also discussed, namely the low temperatures of the onset of the thermolysis, the fast rate of combustion, and the favorable thermodynamics for the achievement of high temperatures in the reaction zone. Full article

(This article belongs to the Section Catalytic Materials)

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23 pages, 9714 KiB

Open AccessEditor’s ChoiceArticle

Molecular Dynamic Investigations on the Adhesion Behaviors of Asphalt Mastic–Aggregate Interface

by Wenyi Xu, Xin Qiu, Shanglin Xiao, Ganghua Hu, Feng Wang and Jie Yuan

Materials 2020, 13(22), 5061; https://doi.org/10.3390/ma13225061 - 10 Nov 2020

Cited by 32 | Viewed by 3534

Abstract

The asphalt mastic–aggregate interface plays an essential role in determining the service performance of asphalt mixtures. The objective of this paper was to investigate the adhesion behaviors and mechanism between asphalt mastic and aggregate based on molecular dynamic (MD) simulations. First, the asphalt [...] Read more.

The asphalt mastic–aggregate interface plays an essential role in determining the service performance of asphalt mixtures. The objective of this paper was to investigate the adhesion behaviors and mechanism between asphalt mastic and aggregate based on molecular dynamic (MD) simulations. First, the asphalt mastic model considering the actual mass ratio of filler to asphalt (F/A) condition was established and validated in terms of thermodynamic properties. Second, the molecular arrangement characteristics of polar components on the aggregate substrate were analyzed by radial distribution function (RDF), relative concentration (RC), and mean square displacement (MSD). Third, the interfacial adhesion ability between asphalt and aggregate was quantitively evaluated based on the work of adhesion. Finally, the coupling effect of moisture and temperature on interfacial adhesion behaviors was investigated to explore the adhesion failure characteristics of the asphalt–aggregate interface. The results demonstrate that the thermodynamic properties could be employed to validate the reliability of the asphalt mastic model. The self-aggregation degree of polar components in base asphalt could be significantly increased with the addition of silica particles, exhibiting a change of configuration from “parallel arrangement” into “stack distribution” due to the high polarity of silica particles. The polar components in asphalt mastic exhibit a more uniform distribution state and lower mobility capability than base asphalt owing to the adsorption effect of silica particles. Silica particles with amounts of residual charges could significantly increase the electrostatic energy of the asphalt mastic–aggregate interface, contributing to an improvement of the adhesion between asphalt mastic and aggregate. The increase of temperature enhances the work of adhesion of the asphalt mastic–aggregate interface, which is opposite to that of the base asphalt–aggregate interface. The asphalt mastic exhibits a greater sensitivity to interfacial moisture damage than base asphalt. The findings would provide insights into a better understanding on the micro adhesion mechanism of the asphalt mastic–aggregate interface. Full article

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

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11 pages, 21216 KiB

Open AccessEditor’s ChoiceArticle

Fibre-Reinforced Composite for Protection against Shark Bites

by Thomas Fiedler and Trent Verstegen

Materials 2020, 13(22), 5065; https://doi.org/10.3390/ma13225065 - 10 Nov 2020

Cited by 1 | Viewed by 3514

Abstract

The number of shark attacks resulting in fatalities and severe injuries has increased steadily over recent years. This is mainly attributed to a growing population participating in ocean sports such as swimming, diving, and surfing. To mitigate the severity of shark attacks, the [...] Read more.

The number of shark attacks resulting in fatalities and severe injuries has increased steadily over recent years. This is mainly attributed to a growing population participating in ocean sports such as swimming, diving, and surfing. To mitigate the severity of shark attacks, the current study presents a novel fibre-reinforced composite for bite protection. This material is intended for integration into neoprene wetsuits, e.g., in the form of protective pads. A suitable material must be able to withstand significant bite forces, which are concentrated within a small contact area at the tips of the shark teeth. At the same time, the material should not hinder the complex motion sequences of aquatic sports. To this end, a novel fibre-reinforced composite was created by integrating Kevlar fibres into an elastic matrix. Uni-axial testing using shark teeth replicas was conducted on a specially designed test rig to quantify the effectiveness of the novel protective material. Full article

(This article belongs to the Section Advanced Composites)

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26 pages, 5596 KiB

Open AccessEditor’s ChoiceReview

Potential Application of Ionic Liquids for Electrodeposition of the Material Targets for Production of Diagnostic Radioisotopes

by Maciej Chotkowski, Damian Połomski and Kenneth Czerwinski

Materials 2020, 13(22), 5069; https://doi.org/10.3390/ma13225069 - 10 Nov 2020

Cited by 7 | Viewed by 3656

Abstract

An overview of the reported electrochemistry studies on the chemistry of the element for targets for isotope production in ionic liquids (ILs) is provided. The majority of investigations have been dedicated to two aspects of the reactive element chemistry. The first part of [...] Read more.

An overview of the reported electrochemistry studies on the chemistry of the element for targets for isotope production in ionic liquids (ILs) is provided. The majority of investigations have been dedicated to two aspects of the reactive element chemistry. The first part of this review presents description of the cyclotron targets properties, especially physicochemical characterization of irradiated elements. The second part is devoted to description of the electrodeposition procedures leading to obtain elements or their alloys coatings (e.g., nickel, uranium) as the targets for cyclotron and reactor generation of the radioisotopes. This review provides an evaluation of the role ILs can have in the production of isotopes. Full article

(This article belongs to the Special Issue Properties and Applications of Ionic Liquids)

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15 pages, 4072 KiB

Open AccessEditor’s ChoiceArticle

Characteristics of Interfacial Shear Bonding Between Basalt Fiber and Mortar Matrix

by Li Hong, Tadan Li, Yadi Chen, Peng Gao and Lizhi Sun

Materials 2020, 13(21), 5037; https://doi.org/10.3390/ma13215037 - 9 Nov 2020

Cited by 6 | Viewed by 2613

Abstract

Basalt fibers have been adopted as reinforcements to improve mechanical performance of concrete materials and structures due to their excellent corrosion resistance, affordable cost, and environmental-friendly nature. While the reinforcing efficiency is significantly dependent on fiber–matrix interfacial properties, there is a lack of [...] Read more.

Basalt fibers have been adopted as reinforcements to improve mechanical performance of concrete materials and structures due to their excellent corrosion resistance, affordable cost, and environmental-friendly nature. While the reinforcing efficiency is significantly dependent on fiber–matrix interfacial properties, there is a lack of studies focusing on the bonding behavior of basalt fibers in the mortar matrix. In this paper, a series of experiments were carried out to investigate the characteristics of single basalt fiber pulled out from the mortar matrix. Three embedment lengths and three types of mortar strength were considered. As references, the pull-out behavior of single polyvinyl alcohol (PVA) fiber and glass fiber in mortar matrix were also tested for comparison. Results from the pull-out test revealed that the average bonding strength is more effective than the equivalent shear bonding strength to illustrate the interfacial bond behavior of single basalt fiber in mortar matrix, which can be improved by either longer embedment length or the stronger mortar matrix. Finally, the tensile and compressive strengths of basalt/PVA/glass fiber-reinforced concrete (FRC) were measured to investigate the influence of interfacial shear bonding strengths. It was shown that, while PVA fiber developed the highest shear bonding strength with mortar, the basalt fiber exhibited the best reinforcing efficiency of FRC. Full article

(This article belongs to the Special Issue Advances in Construction and Building Materials)

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11 pages, 2782 KiB

Open AccessEditor’s ChoiceArticle

Effect of Time-Dependent Characteristics of ZnO Nanoparticles Electron Transport Layer Improved by Intense-Pulsed Light Post-Treatment on Hole-Electron Injection Balance of Quantum-Dot Light-Emitting Diodes

by Young Joon Han, Kyung-Tae Kang, Byeong-Kwon Ju and Kwan Hyun Cho

Materials 2020, 13(21), 5041; https://doi.org/10.3390/ma13215041 - 9 Nov 2020

Cited by 8 | Viewed by 3462

Abstract

We investigated the effect of intense-pulsed light (IPL) post-treatment on the time-dependent characteristics of ZnO nanoparticles (NPs) used as an electron transport layer (ETL) of quantum-dot light-emitting diodes (QLEDs). The time-dependent characteristics of the charge injection balance in QLEDs was observed by fabrication [...] Read more.

We investigated the effect of intense-pulsed light (IPL) post-treatment on the time-dependent characteristics of ZnO nanoparticles (NPs) used as an electron transport layer (ETL) of quantum-dot light-emitting diodes (QLEDs). The time-dependent characteristics of the charge injection balance in QLEDs was observed by fabrication and analysis of single carrier devices (SCDs), and it was confirmed that the time-dependent characteristics of the ZnO NPs affect the device characteristics of QLEDs. Stabilization of the ZnO NPs film properties for improvement of the charge injection balance in QLEDs was achieved by controlling the current density characteristics via filling of the oxygen vacancies by IPL post-treatment. Full article

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

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17 pages, 5317 KiB

Open AccessEditor’s ChoiceArticle

Equivalent Cement Clinker Obtained by Indirect Mechanosynthesis Process

by Rabah Hamzaoui and Othmane Bouchenafa

Materials 2020, 13(21), 5045; https://doi.org/10.3390/ma13215045 - 9 Nov 2020

Cited by 9 | Viewed by 2706

Abstract

The aim of this work is to study the heat treatment effect, milling time effect and indirect mechanosynthesis effect on the structure of the mixture limestone/clay (kaolinite). Indirect mechanosynthesis is a process that combines between mechanical activation and heat treatment at 900 °C. [...] Read more.

The aim of this work is to study the heat treatment effect, milling time effect and indirect mechanosynthesis effect on the structure of the mixture limestone/clay (kaolinite). Indirect mechanosynthesis is a process that combines between mechanical activation and heat treatment at 900 °C. XRD, TGA, FTIR and particle size distribution analysis and SEM micrograph are used in order to follow thermal properties and structural modification changes that occur. It is shown that the indirect mechanosynthesis process allows the formation of the equivalent clinker in powder with the main constituents of the clinker (Alite C₃S, belite C₂S, tricalcium aluminate C₃A and tetracalcium aluminoferrite C₄AF) at 900 °C, whereas, these constituents in the conventional clinker are obtained at 1450 °C. Full article

(This article belongs to the Special Issue The Impact of Nanomaterials in Smart Construction Materials)

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17 pages, 10805 KiB

Open AccessEditor’s ChoiceArticle

Functionally Graded Scaffolds with Programmable Pore Size Distribution Based on Triply Periodic Minimal Surface Fabricated by Selective Laser Melting

by Xueyong Zhou, Yuan Jin and Jianke Du

Materials 2020, 13(21), 5046; https://doi.org/10.3390/ma13215046 - 9 Nov 2020

Cited by 44 | Viewed by 4960

Abstract

Functional graded materials are gaining increasing attention in tissue engineering (TE) due to their superior mechanical properties and high biocompatibility. Triply periodic minimal surface (TPMS) has the capability to produce smooth surfaces and interconnectivity, which are very essential for bone scaffolds. To further [...] Read more.

Functional graded materials are gaining increasing attention in tissue engineering (TE) due to their superior mechanical properties and high biocompatibility. Triply periodic minimal surface (TPMS) has the capability to produce smooth surfaces and interconnectivity, which are very essential for bone scaffolds. To further enhance the versatility of TPMS, a parametric design method for functionally graded scaffold (FGS) with programmable pore size distribution is proposed in this study. Combining the relative density and unit cell size, the effect of design parameters on the pore size was also considered to effectively govern the distribution of pores in generating FGS. We made use of Gyroid to generate different types of FGS, which were then fabricated using selective laser melting (SLM), followed by investigation and comparison of their structural characteristics and mechanical properties. Their morphological features could be effectively controlled, indicating that TPMS was an effective way to achieve functional gradients which had bone-mimicking architectures. In terms of mechanical performance, the proposed FGS could achieve similar mechanical response under compression tests compared to the reference FGS with the same range of density gradient. The proposed method with control over pore size allows for effectively generating porous scaffolds with tailored properties which are potentially adopted in various fields. Full article

(This article belongs to the Section Porous Materials)

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24 pages, 8707 KiB

Open AccessEditor’s ChoiceArticle

UV-Cured Poly(Siloxane-Urethane)-Based Polymer Composite Materials for Lithium Ion Batteries—The Effect of Modification with Ionic Liquids

by Janusz Kozakiewicz, Jarosław Przybylski, Bartosz Hamankiewicz, Krystyna Sylwestrzak, Joanna Trzaskowska, Michal Krajewski, Maciej Ratyński, Witold Sarna and Andrzej Czerwiński

Materials 2020, 13(21), 4978; https://doi.org/10.3390/ma13214978 - 5 Nov 2020

Cited by 10 | Viewed by 3620

Abstract

The results of studies on the synthesis and characterization of conductive polymer composite materials designed as potential separators for lithium ion batteries are presented. The conductive polymer composites were prepared from UV-cured poly(siloxane-urethanes)s (PSURs) containing poly(ethylene oxide) (PEO) segments and modified with lithium [...] Read more.

The results of studies on the synthesis and characterization of conductive polymer composite materials designed as potential separators for lithium ion batteries are presented. The conductive polymer composites were prepared from UV-cured poly(siloxane-urethanes)s (PSURs) containing poly(ethylene oxide) (PEO) segments and modified with lithium salts and ionic liquids (ILs). The most encouraging results in terms of specific conductivity and mechanical properties of the composite were obtained when part of UV-curable PSUR prepolymer was replaced with a reactive UV-curable IL. Morphology of the composites modified with ILs or containing a standard ethylene carbonate/dimethyl carbonate mixture (EC/DMC) as solvent was compared. It was found that the composites showed a two-phase structure that did not change when non-reactive ILs were applied instead of EC/DMC but was much affected when reactive UV-curable ILs were used. The selected IL-modified UV-cured PSUR composite that did not contain flammable EC/DMC solvent was preliminarily tested as gel polymer electrolyte and separator for lithium ion batteries. Full article

(This article belongs to the Special Issue Properties and Applications of Ionic Liquids)

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12 pages, 3607 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Triboelectric Energy Harvesting Response of Different Polymer-Based Materials

by Tiago Rodrigues-Marinho, Nelson Castro, Vitor Correia, Pedro Costa and Senentxu Lanceros-Méndez

Materials 2020, 13(21), 4980; https://doi.org/10.3390/ma13214980 - 5 Nov 2020

Cited by 22 | Viewed by 3909

Abstract

Energy harvesting systems for low-power devices are increasingly being a requirement within the context of the Internet of Things and, in particular, for self-powered sensors in remote or inaccessible locations. Triboelectric nanogenerators are a suitable approach for harvesting environmental mechanical energy otherwise wasted [...] Read more.

Energy harvesting systems for low-power devices are increasingly being a requirement within the context of the Internet of Things and, in particular, for self-powered sensors in remote or inaccessible locations. Triboelectric nanogenerators are a suitable approach for harvesting environmental mechanical energy otherwise wasted in nature. This work reports on the evaluation of the output power of different polymer and polymer composites, by using the triboelectric contact-separation systems (10 N of force followed by 5 cm of separation per cycle). Different materials were used as positive (Mica, polyamide (PA66) and styrene/ethylene-butadiene/styrene (SEBS)) and negative (polyvinylidene fluoride (PVDF), polyurethane (PU), polypropylene (PP) and Kapton) charge materials. The obtained output power ranges from 0.2 to 5.9 mW, depending on the pair of materials, for an active area of 46.4 cm². The highest response was obtained for Mica with PVDF composites with 30 wt.% of barium titanate (BT) and PA66 with PU pairs. A simple application has been developed based on vertical contact-separation mode, able to power up light emission diodes (LEDs) with around 30 cycles to charge a capacitor. Further, the capacitor can be charged in one triboelectric cycle if an area of 0.14 m² is used. Full article

(This article belongs to the Special Issue Smart Materials and Devices for Energy Harvesting)

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17 pages, 15297 KiB

Open AccessEditor’s ChoiceArticle

Cementitious Composites with High Compaction Potential: Modeling and Calibration

by Giao Vu, Tagir Iskhakov, Jithender J. Timothy, Christoph Schulte-Schrepping, Rolf Breitenbücher and Günther Meschke

Materials 2020, 13(21), 4989; https://doi.org/10.3390/ma13214989 - 5 Nov 2020

Cited by 13 | Viewed by 3126

Abstract

There is an increasing need for the development of novel technologies for tunnel construction in difficult geological conditions to protect segmental linings from unexpected large deformations. In the context of mechanized tunneling, one method to increase the damage tolerance of tunnel linings in [...] Read more.

There is an increasing need for the development of novel technologies for tunnel construction in difficult geological conditions to protect segmental linings from unexpected large deformations. In the context of mechanized tunneling, one method to increase the damage tolerance of tunnel linings in such conditions is the integration of a compressible two-component grout for the annular gap between the segmental linings and the deformable ground. In this regard, expanded polystyrene (EPS) lightweight concrete/mortar has received increasing interest as a potential “candidate material” for the aforementioned application. In particular, the behavior of the EPS lightweight composites can be customized by modifying their pore structure to accommodate deformations due to specific geological conditions such as squeezing rocks. To this end, novel compressible cementitious EPS-based composite materials with high compaction potential have been developed. Specimens prepared from these composites have been subjected to compressive loads with and without lateral confinement. Based on these experimental data a computational model based on the Discrete Element Method (DEM) has been calibrated and validated. The proposed calibration procedure allows for modeling and prognosis of a wide variety of composite materials with a high compaction potential. The calibration procedure is characterized by the identification of physically quantifiable parameters and the use of phenomenological submodels. Model prognoses show excellent agreement with new experimental measurements that were not incorporated in the calibration procedure. Full article

(This article belongs to the Special Issue Concrete and Construction Materials)

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16 pages, 4700 KiB

Open AccessEditor’s ChoiceArticle

Interlayer Hybridization of Virgin Carbon, Recycled Carbon and Natural Fiber Laminates

by Peter R. Wilson, Alon Ratner, Gary Stocker, Frank Syred, Kerry Kirwan and Stuart R. Coles

Materials 2020, 13(21), 4955; https://doi.org/10.3390/ma13214955 - 4 Nov 2020

Cited by 8 | Viewed by 2673

Abstract

To meet sustainability objectives in the transport sector, natural fiber (NF) and recycled carbon fiber (RCF) have been developed, although they have been typically limited to low to medium performance components. This work has considered the effect of interlayer hybridization of woven NF [...] Read more.

To meet sustainability objectives in the transport sector, natural fiber (NF) and recycled carbon fiber (RCF) have been developed, although they have been typically limited to low to medium performance components. This work has considered the effect of interlayer hybridization of woven NF and non-woven RCF with woven virgin carbon fibers (VCF) on the mechanical and damping performance of hybrid laminates, produced using double bag vacuum infusion (DBVI). The mean damping ratio of the pure laminates showed a trend of NF>RCF>VCF, which was inversely proportional to their modulus. The tensile, flexural and damping properties of hybrid laminates were dominated by the outermost ply. The VCF-RCF and VCF-NF hybrid laminates showed a comparatively greater mean damping ratio. The results of this work demonstrate a method for the uptake of alternative materials with a minimal impact on the mechanical properties and improved damping performance. Full article

(This article belongs to the Section Advanced Composites)

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16 pages, 4488 KiB

Open AccessEditor’s ChoiceArticle

Influence of Tea Tree Essential Oil and Poly(ethylene glycol) on Antibacterial and Physicochemical Properties of Polylactide-Based Films

by Iwona Tarach, Ewa Olewnik-Kruszkowska, Agnieszka Richert, Magdalena Gierszewska and Anna Rudawska

Materials 2020, 13(21), 4953; https://doi.org/10.3390/ma13214953 - 4 Nov 2020

Cited by 31 | Viewed by 3508

Abstract

The aim of the study was to establish the influence of poly(ethylene glycol) (PEG) on the properties of potential biodegradable packaging materials with antibacterial properties, based on polylactide (PLA) and tea tree essential oil (TTO). The obtained polymeric films consisted of PLA, a [...] Read more.

The aim of the study was to establish the influence of poly(ethylene glycol) (PEG) on the properties of potential biodegradable packaging materials with antibacterial properties, based on polylactide (PLA) and tea tree essential oil (TTO). The obtained polymeric films consisted of PLA, a natural biocide, and tea tree essential oil (5–20 wt. %) was prepared with or without an addition of 5 wt. % PEG. The PLA-based materials have been tested, taking into account their morphology, and their thermal, mechanical and antibacterial properties against Staphylococcus aureus and Escherichia coli. It was established that the introduction of a plasticizer into the PLA–TTO systems leads to an increase in tensile strength, resistance to deformation, as well an increased thermal stability, in comparison to films modified using only TTO. The incorporation of 5 wt. % PEG in the PLA solution containing 5 wt. % TTO allowed us to obtain a material exhibiting a satisfactory antibacterial effect on both groups of representative bacteria. The presented results indicated a beneficial effect of PEG on the antibacterial and functional properties of materials with the addition of TTO. Full article

(This article belongs to the Special Issue Modification and Processing of Biodegradable Polymers)

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16 pages, 6328 KiB

Open AccessEditor’s ChoiceArticle

Evolution of Corrosion Products Formed during the Corrosion of MgZr Alloy in Poral Solutions Extracted from Na-Geopolymers Used as Conditioning Matrix for Nuclear Waste

by Rémi Boubon, Xavier Deschanels, Martiane Cabié and Diane Rébiscoul

Materials 2020, 13(21), 4958; https://doi.org/10.3390/ma13214958 - 4 Nov 2020

Cited by 5 | Viewed by 2001

Abstract

Geopolymer, a nanoporous aluminosilicate filled with water and ions, has been selected as a potential matrix to encapsulate MgZr alloy fuel cladding. In this study, we investigate the evolution of the corrosion products formed during the corrosion of MgZr in poral solutions extracted [...] Read more.

Geopolymer, a nanoporous aluminosilicate filled with water and ions, has been selected as a potential matrix to encapsulate MgZr alloy fuel cladding. In this study, we investigate the evolution of the corrosion products formed during the corrosion of MgZr in poral solutions extracted from geopolymers with and without NaF as corrosion inhibitor. Using various characterization techniques such as Scanning Electron and Scanning Transmission Electron Microscopies coupled to Energy Dispersive X-ray spectroscopy and Grazing Incidence X-ray Diffraction, we show that the amounts of dissolved silica and fluoride species in solution are the key parameters driving the nature of corrosion products and probably their passivating properties regarding MgZr corrosion. Full article

(This article belongs to the Special Issue Film Composition and Characteristics on Non-ferrous Corroded Metals and Alloys)

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11 pages, 17163 KiB

Open AccessEditor’s ChoiceArticle

Hollow Gold-Silver Nanoshells Coated with Ultrathin SiO₂ Shells for Plasmon-Enhanced Photocatalytic Applications

by Pannaree Srinoi, Maria D. Marquez, Tai-Chou Lee and T. Randall Lee

Materials 2020, 13(21), 4967; https://doi.org/10.3390/ma13214967 - 4 Nov 2020

Cited by 6 | Viewed by 3094

Abstract

This article details the preparation of hollow gold-silver nanoshells (GS-NSs) coated with tunably thin silica shells for use in plasmon-enhanced photocatalytic applications. Hollow GS-NSs were synthesized via the galvanic replacement of silver nanoparticles. The localized surface plasmon resonance (LSPR) peaks of the GS-NSs [...] Read more.

This article details the preparation of hollow gold-silver nanoshells (GS-NSs) coated with tunably thin silica shells for use in plasmon-enhanced photocatalytic applications. Hollow GS-NSs were synthesized via the galvanic replacement of silver nanoparticles. The localized surface plasmon resonance (LSPR) peaks of the GS-NSs were tuned over the range of visible light to near-infrared (NIR) wavelengths by adjusting the ratio of silver nanoparticles to gold salt solution to obtain three distinct types of GS-NSs with LSPR peaks centered near 500, 700, and 900 nm. Varying concentrations of (3-aminopropyl)trimethoxysilane and sodium silicate solution afforded silica shell coatings of controllable thicknesses on the GS-NS cores. For each type of GS-NS, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images verified our ability to grow thin silica shells having three different thicknesses of silica shell (~2, ~10, and ~15 nm) on the GS-NS cores. Additionally, energy-dispersive X-ray (EDX) spectra confirmed the successful coating of the GS-NSs with SiO₂ shells having controlled thicknesses. Extinction spectra of the as-prepared nanoparticles indicated that the silica shell has a minimal effect on the LSPR peak of the gold-silver nanoshells. Full article

(This article belongs to the Special Issue Photoactive Materials: Synthesis, Applications and Technology)

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12 pages, 1005 KiB

Open AccessEditor’s ChoiceArticle

The Use of De-Vulcanized Recycled Rubber in the Modification of Road Bitumen

by Barbara Gawdzik, Tadeusz Matynia and Krzysztof Błażejowski

Materials 2020, 13(21), 4864; https://doi.org/10.3390/ma13214864 - 30 Oct 2020

Cited by 13 | Viewed by 2767

Abstract

Rubber from recycled car tires and styrene-butadiene-styrene (SBS) were used for the chemical modification of commercially available road bitumen 50/70 (EN 12591). The modification process began with the addition of rubber into asphalt and heating the whole amount at the temperature of 190 [...] Read more.

Rubber from recycled car tires and styrene-butadiene-styrene (SBS) were used for the chemical modification of commercially available road bitumen 50/70 (EN 12591). The modification process began with the addition of rubber into asphalt and heating the whole amount at the temperature of 190 °C or 220 °C. Under such conditions, de-vulcanization of rubber took place. Next, SBS and sulfur as a cross-linker were added and the heating was continued so that cross-linking of SBS and the de-vulcanized rubber proceeded. In the studies on the influence of rubber concentration on the final properties of asphalt 10% or 15% of rubber was considered. Chemical modification reactions were performed within 2, 4, and 8 h. The results showed that both the modification at 190 °C and 220 °C affected the properties of the base asphalt efficiently, although the asphalt modified at 190 °C contained more non-degraded rubber. Increasing the modification time led to dissolution of the rubber crumbs and its de-vulcanization. Bitumens modified in this way are characterized by high storage stabilities. Their behavior at low temperatures also deserves attention. Full article

(This article belongs to the Special Issue Characterization of Innovative Asphalt Materials for Use in Pavement Design and Analysis)

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19 pages, 4332 KiB

Open AccessEditor’s ChoiceArticle

Sustainable Development of Innovative Green Construction Materials: A Study for Economical Eco-Friendly Recycled Aggregate Based Geopolymer Concrete

by Hatem Alhazmi, Syyed Adnan Raheel Shah and Atif Mahmood

Materials 2020, 13(21), 4881; https://doi.org/10.3390/ma13214881 - 30 Oct 2020

Cited by 8 | Viewed by 3618

Abstract

Green revolution and high carbon footprint concepts have attracted the development of a green and sustainable environment. This work endeavors to investigate the behavior of recycled aggregate geopolymer concrete (RAGC) developed with four different types of effluents to develop sustainability in the construction [...] Read more.

Green revolution and high carbon footprint concepts have attracted the development of a green and sustainable environment. This work endeavors to investigate the behavior of recycled aggregate geopolymer concrete (RAGC) developed with four different types of effluents to develop sustainability in the construction industry and to produce an eco-friendly environment. Each of the types of effluents was used by completely replacing the freshwater in RAGC to examine its influence on compressive strength (CS), chloride ion migration (CIM), split tensile strength (STS), and resistance to the sulfuric acid attack of RAGC at various testing ages. The test outputs portray that the effluent obtained from the textile mill performed well for the CS (25% higher than the control mix) and STS (17% higher than the control mix) of RAGC. Similarly, the highest mass loss of RAGC due to the acid attack (41% higher than control mix) and the highest CIM (29% higher than control mix) were represented by the RAGC mix made with effluent obtained from fertilizer mill. The statistical analysis indicated no significant influence of using textile mill effluent (TE), fertilizer mill effluent (FE), and sugar mill effluent (SE) on the STS, CIM, and mass loss due to acid attack while it presented a significant influence on the CS of various mixes. Therefore, this investigation solidly substantiates the acceptability of studied types of effluents for the fabrication of eco-friendly green materials. Full article

(This article belongs to the Special Issue Recent Research in the Design of New Sustainable Building Materials)

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10 pages, 3567 KiB

Open AccessEditor’s ChoiceArticle

Vanadium Chemical Compounds Forms in Wastes of Vanadium Pentoxide Production

by Anton Volkov, Ulyana Kologrieva, Anatoly Kovalev, Dmitry Wainstein and Vladimir Vakhrushev

Materials 2020, 13(21), 4889; https://doi.org/10.3390/ma13214889 - 30 Oct 2020

Cited by 13 | Viewed by 2831

Abstract

A big amount of solid wastes or dump sludges is generated after leaching vanadium (V) from a roasted mixture. As the vanadium content in these tailings is comparable to its concentration in traditional vanadium sources such as titanomagnetite ores or a vanadium converter [...] Read more.

A big amount of solid wastes or dump sludges is generated after leaching vanadium (V) from a roasted mixture. As the vanadium content in these tailings is comparable to its concentration in traditional vanadium sources such as titanomagnetite ores or a vanadium converter slag, these wastes could be recycled to extract additional vanadium. Therefore, this research was aimed on studies of vanadium-containing sludges resulting from hydrometallurgical production of vanadium pentoxide to find an optimal technology for V extraction. The material composition of industrial and synthetic sludge samples was studied by X-ray fluorescence analysis (XRF), X-ray diffraction (XRD), secondary ions mass spectroscopy (SIMS), and X-ray photoelectron spectroscopy (XPS, ESCA). The paper demonstrates the presence of vanadium in sludges, not only in spinels in 3+ oxidation degree, but also in other compounds containing V⁴⁺ and V⁵⁺. It was found that vanadium substitutes a set of elements in minerals except spinel. The dependence between the content of insoluble vanadium compounds and V oxidation degree was determined. Full article

(This article belongs to the Section Materials Chemistry)

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16 pages, 7292 KiB

Open AccessEditor’s ChoiceArticle

Surface Crack Detection in Precasted Slab Track in High-Speed Rail via Infrared Thermography

by Zai-Wei Li, Xiao-Zhou Liu, Hong-Yao Lu, Yue-Lei He and Yun‐Lai Zhou

Materials 2020, 13(21), 4837; https://doi.org/10.3390/ma13214837 - 29 Oct 2020

Cited by 31 | Viewed by 3672

Abstract

The surface crack of ballastless track slab can seriously reduce the serviceability and durability of high-speed railway (HSR). Aiming at accurately and efficiently detecting the slab cracks, this research proposes an infrared thermography (IRT)-based method for the surface crack, which is the most [...] Read more.

The surface crack of ballastless track slab can seriously reduce the serviceability and durability of high-speed railway (HSR). Aiming at accurately and efficiently detecting the slab cracks, this research proposes an infrared thermography (IRT)-based method for the surface crack, which is the most serious and common crack type in track slab. A three dimensional finite element (FE) model of IRT detection of concrete slab with surface cracks is established. The relation between the width of detectable cracks and the ambient temperature can be thereby obtained by inputting the measured thermodynamic parameters in the model. Parametric study shows that with ambient temperature higher than 15 °C, cracks with a width of no less than 0.2 mm can be well detected. Scale model test and field test are conducted, IRT method can effectively locate the slab surface cracks with width as small as 0.14 mm when ambient temperature is no less than 20 °C. Full article

(This article belongs to the Section Smart Materials)

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19 pages, 7745 KiB

Open AccessEditor’s ChoiceArticle

Research Summary on Characterizing Impact of Environment on Adhesion of Sealed Joints in Façade Applications

by Barbora Nečasová and Pavel Liška

Materials 2020, 13(21), 4847; https://doi.org/10.3390/ma13214847 - 29 Oct 2020

Cited by 2 | Viewed by 2748

Abstract

The presented paper summarizes the main research findings on the impact of the environment concerning the durability and service life of building joint sealants. The focus is placed on sealed joints in façade applications, which can serve different purposes and can also be [...] Read more.

The presented paper summarizes the main research findings on the impact of the environment concerning the durability and service life of building joint sealants. The focus is placed on sealed joints in façade applications, which can serve different purposes and can also be several meters long which often intensifies the stresses that the joint needs to withstand and therefore its service life can be significantly shortened. Different approaches, test sample geometries and high-performance sealants, were used in this context to determine the most critical aspects for the studied application sector. The research was divided into three phases where the joints were subjected to (I) artificial weathering in a laboratory environment, (II) real weathering in an external environment, and (III) weathering via a real application that was monitored for almost 4 years. The extensive research scope confirmed one commonly known presumption, that standardized artificial weathering/aging methods are not able, from a long-term perspective, to simulate the impact of a real environment. The most valuable results were obtained in the third phase of the research, where the monitoring of a real façade brought to light completely different conclusions. The joints exposed to the real environment were either completely deteriorated or showed signs of advanced aging. Full article

(This article belongs to the Special Issue Advances in Construction and Building Materials)

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17 pages, 5134 KiB

Open AccessEditor’s ChoiceArticle

Experimental and Numerical Study of Vacuum Resin Infusion of Stiffened Carbon Fiber Reinforced Panels

by Francesca Lionetto, Anna Moscatello, Giuseppe Totaro, Marco Raffone and Alfonso Maffezzoli

Materials 2020, 13(21), 4800; https://doi.org/10.3390/ma13214800 - 28 Oct 2020

Cited by 33 | Viewed by 4462

Abstract

Liquid resin infusion processes are becoming attractive for aeronautic applications as an alternative to conventional autoclave-based processes. They still present several challenges, which can be faced only with an accurate simulation able to optimize the process parameters and to replace traditional time-consuming trial-and-error [...] Read more.

Liquid resin infusion processes are becoming attractive for aeronautic applications as an alternative to conventional autoclave-based processes. They still present several challenges, which can be faced only with an accurate simulation able to optimize the process parameters and to replace traditional time-consuming trial-and-error procedures. This paper presents an experimentally validated model to simulate the resin infusion process of an aeronautical component by accounting for the anisotropic permeability of the reinforcement and the chemophysical and rheological changes in the crosslinking resin. The input parameters of the model have been experimentally determined. The experimental work has been devoted to the study of the curing kinetics and chemorheological behavior of the thermosetting epoxy matrix and to the determination of both the in-plane and out-of-plane permeability of two carbon fiber preforms using an ultrasonic-based method, recently developed by the authors. The numerical simulation of the resin infusion process involved the modeling of the resin flow through the reinforcement, the heat exchange in the part and within the mold, and the crosslinking reaction of the resin. The time necessary to fill the component has been measured by an optical fiber-based equipment and compared with the simulation results. Full article

(This article belongs to the Special Issue Carbon Fiber Reinforced Polymers)

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25 pages, 4959 KiB

Open AccessEditor’s ChoiceReview

Corrosion and Corrosion Protection of Additively Manufactured Aluminium Alloys—A Critical Review

by Reynier I. Revilla, Donovan Verkens, Tim Rubben and Iris De Graeve

Materials 2020, 13(21), 4804; https://doi.org/10.3390/ma13214804 - 28 Oct 2020

Cited by 50 | Viewed by 5898

Abstract

Metal additive manufacturing (MAM), also known as metal 3D printing, is a rapidly growing industry based on the fabrication of complex metal parts with improved functionalities. During MAM, metal parts are produced in a layer by layer fashion using 3D computer-aided design models. [...] Read more.

Metal additive manufacturing (MAM), also known as metal 3D printing, is a rapidly growing industry based on the fabrication of complex metal parts with improved functionalities. During MAM, metal parts are produced in a layer by layer fashion using 3D computer-aided design models. The advantages of using this technology include the reduction of materials waste, high efficiency for small production runs, near net shape manufacturing, ease of change or revision of versions of a product, support of lattice structures, and rapid prototyping. Numerous metals and alloys can nowadays be processed by additive manufacturing techniques. Among them, Al-based alloys are of great interest in the automotive and aeronautic industry due to their relatively high strength and stiffness to weight ratio, good wear and corrosion resistance, and recycling potential. The special conditions associated with the MAM processes are known to produce in these materials a fine microstructure with unique directional growth features far from equilibrium. This distinctive microstructure, together with other special features and microstructural defects originating from the additive manufacturing process, is known to greatly influence the corrosion behaviour of these materials. Several works have already been conducted in this direction. However, several issues concerning the corrosion and corrosion protection of these materials are still not well understood. This work reviews the main studies to date investigating the corrosion aspects of additively manufactured aluminium alloys. It also provides a summary and outlook of relevant directions to be explored in future research. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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15 pages, 3762 KiB

Open AccessEditor’s ChoiceArticle

Dual-Mode Solution Plasma Processing for the Production of Chitosan/Ag Composites with the Antibacterial Effect

by Valerii Titov, Daniil Nikitin, Irina Naumova, Nikolay Losev, Irina Lipatova, Dmitry Kosterin, Pavel Pleskunov, Roman Perekrestov, Nikolay Sirotkin, Anna Khlyustova, Alexander Agafonov and Andrei Choukourov

Materials 2020, 13(21), 4821; https://doi.org/10.3390/ma13214821 - 28 Oct 2020

Cited by 15 | Viewed by 3315

Abstract

The development of novel biocompatible and biodegradable materials for medical applications has been drawing significant interest in the scientific community for years. Particularly, chitosan loaded with silver nanoparticles (Ag NPs) has a strong antimicrobial potential and could be applied, for example, as wound [...] Read more.

The development of novel biocompatible and biodegradable materials for medical applications has been drawing significant interest in the scientific community for years. Particularly, chitosan loaded with silver nanoparticles (Ag NPs) has a strong antimicrobial potential and could be applied, for example, as wound dressing material. In this work, chitosan/Ag NP composites were produced utilizing a single-step plasma-solution process, which is simple and environmentally friendly. An acetic solution of chitosan containing AgNO₃ was treated by the direct current (DC) atmospheric pressure glow discharge, with the liquid serving as either cathode or anode. The plasma-solution system with liquid anode is more useful for the production of Ag NPs. Nevertheless, the NP size is comparable for both cases. The plasma treatment with both polarities led to chitosan degradation. The cleavage of glucosidic chains mostly occurred in the system with the liquid cathode, whereas the side oxidation reactions took place when the solution served as the anode. The oxidation processes were possibly induced by the hydrogen peroxide H₂O₂ efficiently formed in the last case. The composite materials produced with both polarities of liquid electrode demonstrated the bactericidal action against Gram-negative Escherichia coli, Gram-positive Staphylococcus aureus, and Gram-positive Bacillus subtilis. Full article

(This article belongs to the Special Issue Innovative Plasma-Based Deposition Techniques for the Production of Functional Materials)

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13 pages, 1354 KiB

Open AccessEditor’s ChoiceArticle

Melt-Spinning of an Intrinsically Flame-Retardant Polyacrylonitrile Copolymer

by Simon König, Philipp Kreis, Christian Herbert, Andreas Wego, Mark Steinmann, Dongren Wang, Erik Frank and Michael R. Buchmeiser

Materials 2020, 13(21), 4826; https://doi.org/10.3390/ma13214826 - 28 Oct 2020

Cited by 13 | Viewed by 4970

Abstract

Poly(acrylonitrile) (PAN) fibers have two essential drawbacks: they are usually processed by solution-spinning, which is inferior to melt spinning in terms of productivity and costs, and they are flammable in air. Here, we report on the synthesis and melt-spinning of an intrinsically flame-retardant [...] Read more.

Poly(acrylonitrile) (PAN) fibers have two essential drawbacks: they are usually processed by solution-spinning, which is inferior to melt spinning in terms of productivity and costs, and they are flammable in air. Here, we report on the synthesis and melt-spinning of an intrinsically flame-retardant PAN-copolymer with phosphorus-containing dimethylphosphonomethyl acrylate (DPA) as primary comonomer. Furthermore, the copolymerization parameters of the aqueous suspension polymerization of acrylonitrile (AN) and DPA were determined applying both the Fineman and Ross and Kelen and Tüdõs methods. For flame retardancy and melt-spinning tests, multiple PAN copolymers with different amounts of DPA and, in some cases, methyl acrylate (MA) have been synthesized. One of the synthesized PAN-copolymers has been melt-spun with propylene carbonate (PC) as plasticizer; the resulting PAN-fibers had a tenacity of 195 ± 40 MPa and a Young’s modulus of 5.2 ± 0.7 GPa. The flame-retardant properties have been determined by Limiting Oxygen Index (LOI) flame tests. The LOI value of the melt-spinnable PAN was 25.1; it therefore meets the flame retardancy criteria for many applications. In short, the reported method shows that the disadvantage of high comonomer content necessary for flame retardation can be turned into an advantage by enabling melt spinning. Full article

(This article belongs to the Special Issue Novel Synthetic Fibers for Textile Applications)

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45 pages, 40454 KiB

Open AccessEditor’s ChoiceArticle

Determining the Damage and Failure Behaviour of Textile Reinforced Composites under Combined In-Plane and Out-of-Plane Loading

by Christian Düreth, Daniel Weck, Robert Böhm, Mike Thieme, Maik Gude, Sebastian Henkel, Carl H. Wolf and Horst Biermann

Materials 2020, 13(21), 4772; https://doi.org/10.3390/ma13214772 - 26 Oct 2020

Cited by 7 | Viewed by 3923

Abstract

The absence of sufficient knowledge of the heterogeneous damage behaviour of textile reinforced composites, especially under combined in-plane and out-of-plane loadings, requires the development of multi-scale experimental and numerical methods. In the scope of this paper, three different types of plain weave fabrics [...] Read more.

The absence of sufficient knowledge of the heterogeneous damage behaviour of textile reinforced composites, especially under combined in-plane and out-of-plane loadings, requires the development of multi-scale experimental and numerical methods. In the scope of this paper, three different types of plain weave fabrics with increasing areal weight were considered to characterise the influence of ondulation and nesting effects on the damage behaviour. Therefore an advanced new biaxial testing method has been elaborated to experimentally determine the fracture resistance at the combined biaxial loads. Methods in image processing of the acquired in-situ CT data and micrographs have been utilised to obtain profound knowledge of the textile geometry and the distribution of the fibre volume content of each type. Combining the derived data of the idealised geometry with a numerical multi-scale approach was sufficient to determine the fracture resistances of predefined uniaxial and biaxial load paths. Thereby, Cuntze’s three-dimensional failure mode concept was incorporated to predict damage and failure. The embedded element method was used to obtain a structured mesh of the complex textile geometries. The usage of statistical and visualisation methods contributed to a profound comprehension of the ondulation and nesting effects. Full article

(This article belongs to the Special Issue Tailored Textile-Reinforced Composite Materials)

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19 pages, 9067 KiB

Open AccessEditor’s ChoiceArticle

Research on the Influence of the Manufacturing Process Conditions of Iron Sintered with the Addition of Layered Lubricating Materials on its Selected Properties

by Wieslaw Urbaniak, Tomasz Majewski, Ryszard Wozniak, Judyta Sienkiewicz, Jozef Kubik and Aneta D. Petelska

Materials 2020, 13(21), 4782; https://doi.org/10.3390/ma13214782 - 26 Oct 2020

Cited by 3 | Viewed by 2113

Abstract

The purpose of the conducted experiments was to test the selected properties of materials intended for porous sintered bearings containing layered materials in the form of powders with an average particle size of 0.5–1.5 μm, with very good tribological properties. The subject of [...] Read more.

The purpose of the conducted experiments was to test the selected properties of materials intended for porous sintered bearings containing layered materials in the form of powders with an average particle size of 0.5–1.5 μm, with very good tribological properties. The subject of the research was a sinter based on iron powder with the addition of layered materials; molybdenum disulfide MoS₂ (average particle size 1.5 μm), tungsten disulfide WS₂ (average particle size 0.6 μm), hexagonal boron nitride, h-BN (average particle size 0.5 and 1.5 μm) with two different porosities. The article presents the results of density and porosity tests, compressive strength, metallographic and tribological tests and the assessment of changes in the surface condition occurring during the long storage period. The use of layered additives allows for an approximately 20% lower coefficient of friction. In the case of sulfides, the technological process of pressing 250 MPa, 350 MPa, and sintering at a temperature of 1120 °C allows us to obtain a material with good strength and tribological properties, better than in the case of h-BN. However, the main problem is the appearance of elements from the decomposition of sulfide compounds in the material matrix, which results in rapid material degradation. In hexagonal boron nitride, such disintegration under these conditions does not occur; the material as observed does not degrade. In this case, the material is characterized by lower hardness, resulting from a different behavior of hexagonal boron nitride in the pressing and sintering process; in this case, pressing at a pressure of 350 MPa seems to be too low. However, taking into account that even with these technological parameters, the obtained material containing 2.5% h-BN with an average grain size of 1.5 μm allowed obtaining a coefficient of friction at the level of 0.41, which, with very good material durability, seems to be very positive news before further tests. Full article

(This article belongs to the Section Materials Chemistry)

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