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Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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18 pages, 22445 KiB  
Article
Features of Electrostatic Fields and Their Force Action When Using Micro- and Nanosized Inter-Electrode Gaps
by Nikolai Pshchelko and Ekaterina Vodkailo
Materials 2020, 13(24), 5669; https://doi.org/10.3390/ma13245669 - 11 Dec 2020
Cited by 1 | Viewed by 1660
Abstract
The present work is devoted to assessing the influence of discreteness of electric charge distribution in the double electric layer on the characteristics of the electric fields and their force action in capacitor structures with small interelectrode gaps. Due to the fact that [...] Read more.
The present work is devoted to assessing the influence of discreteness of electric charge distribution in the double electric layer on the characteristics of the electric fields and their force action in capacitor structures with small interelectrode gaps. Due to the fact that modern technologies often use submicron-sized interelectrode gaps, it is no longer possible to consider the electrodes uniformly charged because of the discreteness of the electric charge. The corresponding development of a mathematical and physical model for the study of a non-uniform electric field is suggested. Numerical calculations are carried out, expressions, criteria, and results that are convenient for practical evaluations are obtained. The physical and mathematical model for force characteristics of a non-uniform electric field is developed. With a sufficiently small size of the interelectrode gap, the integral force effect of discretely distributed charges can be significantly higher than with a uniform distribution of the same charge. At reasonable surface charge densities, these phenomena are usually observed at interelectrode gaps less than tenths of a micrometer. Full article
(This article belongs to the Section Materials Physics)
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16 pages, 3686 KiB  
Article
An Experimental Assessment of the Water Permeability of Concrete with a Superplasticizer and Admixtures
by Zdzisław Skutnik, Mariusz Sobolewski and Eugeniusz Koda
Materials 2020, 13(24), 5624; https://doi.org/10.3390/ma13245624 - 10 Dec 2020
Cited by 22 | Viewed by 7616
Abstract
This study presents a flow pump technique usually used for evaluating the permeability of soils, which was, for first time, applied to measure the water permeability of concrete. Additionally, a new easy-to-apply method to determine permeability is proposed, based on a modification of [...] Read more.
This study presents a flow pump technique usually used for evaluating the permeability of soils, which was, for first time, applied to measure the water permeability of concrete. Additionally, a new easy-to-apply method to determine permeability is proposed, based on a modification of Valenta’s formula. In the calculations, the apparent air content of concrete mixes was taken into account. An additional purpose of the conducted research was to determine the influence of a new generation of polycarboxylate superplasticizer and chemically active admixtures on the permeability, compressive strength, and other properties of concrete. The following four types of concrete were tested: concrete without admixtures, concrete with an admixture to increase the compressive strength, concrete with a superplasticizer, and concrete containing two admixtures simultaneously. The results showed that the proposed method allows to obtain reliable measurements within a very short period of time. The obtained results confirmed that new method may be very useful in engineering practice, particularly in terms of the watertightness of hydrotechnical concretes and the properties of the concretes used in bridge construction, underground parts of office buildings, or sealed tanks. Full article
(This article belongs to the Special Issue Properties and Applications of Cement-based Composites)
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17 pages, 7053 KiB  
Article
Analysis of Deformation and Prediction of Cracks in the Cogging Process for Die Steel at Elevated Temperatures
by Marcin Kukuryk
Materials 2020, 13(24), 5589; https://doi.org/10.3390/ma13245589 - 8 Dec 2020
Cited by 5 | Viewed by 2393
Abstract
In this paper, an analysis of a three-dimensional state of strain and stress in the case of the hot cogging process of X32CrMoV12-28 die steel with the application of the finite element method is presented. The results of the investigations connected with the [...] Read more.
In this paper, an analysis of a three-dimensional state of strain and stress in the case of the hot cogging process of X32CrMoV12-28 die steel with the application of the finite element method is presented. The results of the investigations connected with the simulation of the kinematics of metal flow and thermal phenomena are presented, accompanied by prognosing the formation of ductile fractures in the course of the hot cogging process conducted with the application of three different shape tools and of a proposed deformation criterion of the loss of cohesion. The applied anvils were found to be highly effective in the aspects of distribution of effective strains and stresses, absence of tensile stresses in the axial zones of a forging, and also of a significant thermal stability in the internal layers of a deformed material. The developed course of changes in the deformation of the damage factor in the case of forging in the investigated anvils renders it possible to predict the situation and the phase of deformation in which the loss of cohesion by a deformed material will occur. The comparison between the predicted and the experimental results showed a good agreement. Full article
(This article belongs to the Special Issue Forging Processes of Materials)
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43 pages, 8119 KiB  
Review
Review on Adhesives and Surface Treatments for Structural Applications: Recent Developments on Sustainability and Implementation for Metal and Composite Substrates
by Ana C. Marques, Alexandra Mocanu, Nataša Z. Tomić, Sebastian Balos, Elisabeth Stammen, Asa Lundevall, Shoshan T. Abrahami, Roman Günther, John M. M. de Kok and Sofia Teixeira de Freitas
Materials 2020, 13(24), 5590; https://doi.org/10.3390/ma13245590 - 8 Dec 2020
Cited by 122 | Viewed by 17345
Abstract
Using adhesives for connection technology has many benefits. It is cost-efficient, fast, and allows homogeneous stress distribution between the bonded surfaces. This paper gives an overview on the current state of knowledge regarding the technologically important area of adhesive materials, as well as [...] Read more.
Using adhesives for connection technology has many benefits. It is cost-efficient, fast, and allows homogeneous stress distribution between the bonded surfaces. This paper gives an overview on the current state of knowledge regarding the technologically important area of adhesive materials, as well as on emergent related technologies. It is expected to fill some of the technological gaps between the existing literature and industrial reality, by focusing at opportunities and challenges in the adhesives sector, on sustainable and eco-friendly chemistries that enable bio-derived adhesives, recycling and debonding, as well as giving a brief overview on the surface treatment approaches involved in the adhesive application process, with major focus on metal and polymer matrix composites. Finally, some thoughts on the connection between research and development (R&D) efforts, industry standards and regulatory aspects are given. It contributes to bridge the gap between industry and research institutes/academy. Examples from the aeronautics industry are often used since many technological advances in this industry are innovation precursors for other industries. This paper is mainly addressed to chemists, materials scientists, materials engineers, and decision-makers. Full article
(This article belongs to the Special Issue Welding and Joining of Materials for Advanced Aerospace Applications)
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17 pages, 5665 KiB  
Article
Use of Coal Bottom Ash and CaO-CaCl2-Activated GGBFS Binder in the Manufacturing of Artificial Fine Aggregates through Cold-Bonded Pelletization
by Dongho Jeon, Woo Sung Yum, Haemin Song, Seyoon Yoon, Younghoon Bae and Jae Eun Oh
Materials 2020, 13(24), 5598; https://doi.org/10.3390/ma13245598 - 8 Dec 2020
Cited by 11 | Viewed by 2673
Abstract
This study investigated the use of coal bottom ash (bottom ash) and CaO-CaCl2-activated ground granulated blast furnace slag (GGBFS) binder in the manufacturing of artificial fine aggregates using cold-bonded pelletization. Mixture samples were prepared with varying added contents of bottom ash [...] Read more.
This study investigated the use of coal bottom ash (bottom ash) and CaO-CaCl2-activated ground granulated blast furnace slag (GGBFS) binder in the manufacturing of artificial fine aggregates using cold-bonded pelletization. Mixture samples were prepared with varying added contents of bottom ash of varying added contents of bottom ash relative to the weight of the cementless binder (= GGBFS + quicklime (CaO) + calcium chloride (CaCl2)). In the system, the added bottom ash was not simply an inert filler but was dissolved at an early stage. As the ionic concentrations of Ca and Si increased due to dissolved bottom ash, calcium silicate hydrate (C-S-H) formed both earlier and at higher levels, which increased the strength of the earlier stages. However, the added bottom ash did not affect the total quantities of main reaction products, C-S-H and hydrocalumite, in later phases (e.g., 28 days), but simply accelerated the binder reaction until it had occurred for 14 days. After considering both the mechanical strength and the pelletizing formability of all the mixtures, the proportion with 40 relative weight of bottom ash was selected for the manufacturing of pilot samples of aggregates. The produced fine aggregates had a water absorption rate of 9.83% and demonstrated a much smaller amount of heavy metal leaching than the raw bottom ash. Full article
(This article belongs to the Special Issue Sustainable Construction Materials: From Paste to Concrete)
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17 pages, 5959 KiB  
Article
Comparison of Long-Term Strength Development of Steel Fiber Shotcrete with Cast Concrete Based on Accelerator Type
by Kyong Ku Yun, Seunghak Choi, Taeho Ha, Mohammad Shakhawat Hossain and Seungyeon Han
Materials 2020, 13(24), 5599; https://doi.org/10.3390/ma13245599 - 8 Dec 2020
Cited by 10 | Viewed by 2515
Abstract
This study analyzed the effect of accelerating agents, such as aluminate, cement mineral, and alkali-free accelerators, on the long-term performance of steel-fiber-reinforced shotcrete. The shotcrete performance was studied based on the type and amount of steel fiber added. Performance tests were performed to [...] Read more.
This study analyzed the effect of accelerating agents, such as aluminate, cement mineral, and alkali-free accelerators, on the long-term performance of steel-fiber-reinforced shotcrete. The shotcrete performance was studied based on the type and amount of steel fiber added. Performance tests were performed to identify the accelerator providing better long-term performance to the steel-fiber-reinforced shotcrete. Changes in strength and flexural performance over time were investigated. The compressive strength and flexural strength tests on 1-, 3-, 6-, 12-, and 24-month-old test specimens were performed, wherein 37 kg of steel fiber was added to the cement mineral and aluminate mixes, and 40 kg of steel fiber was added to the alkali-free mix. The 1-month compressive strength result of all the test variables satisfied the Korea Expressway Corporation standard. The compressive strength of the cast concrete and shotcrete specimens increased with age, demonstrating a strength reduction, particularly in the 24-month-old shotcrete specimens. Thus, the shotcrete performance may deteriorate in the long-term. In the 24-month-old specimen, substantial flexural strength reduction was observed, particularly in the aluminate and alkali-free specimens. The relative strength of the specimens was compared with that of the cast concrete mold specimens. The results suggest the use of alkali-free accelerators, considering the long-term performance of tunnels and safety of workers. Moreover, increasing the steel fiber performance rather than the amount of low-performance steel fiber must be considered. Full article
(This article belongs to the Special Issue Concrete and Construction Materials)
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17 pages, 7612 KiB  
Article
Analysis on the Effects of External Temperature and Welding Speed on the Safety of EVA Waterproofing Sheet Joints by Hot Air Welding
by Wan-Goo Park, Su-Young Choi, Jin-Sang Park, Dong-Bum Kim, Xing-Yang He and Sang-Keun Oh
Materials 2020, 13(23), 5586; https://doi.org/10.3390/ma13235586 - 7 Dec 2020
Cited by 5 | Viewed by 2519
Abstract
This study analyzes the optimal seasonal ambient temperature during welding and welding speed conditions for securing high tensile strength of ethylene vinyl acetate (EVA) waterproofing sheets bonded for roofing, installed by hot air welded joints (overlaps). Seven separate ambient temperature conditions (−10, −5, [...] Read more.
This study analyzes the optimal seasonal ambient temperature during welding and welding speed conditions for securing high tensile strength of ethylene vinyl acetate (EVA) waterproofing sheets bonded for roofing, installed by hot air welded joints (overlaps). Seven separate ambient temperature conditions (−10, −5, and 0 °C for winter conditions, 20 °C for the normal condition, and 25, 30, and 35 °C for summer conditions) were set for the test variable and seven speed conditions (3, 4, 5, 6, 7, 8, and 9 m/min) for hot air welding. Based on these conditions, EVA sheet joint specimens were prepared, and the tensile strength of the joint sections was tested and measured. Tensile strength results, compared to normal temperature conditions (20 °C) showed an increase in the summer temperature condition but a decrease during winter temperature conditions. The analysis on the effects of the welding speed showed that in summer temperature conditions (25, 30, and 35 °C), the optimum hot air welding speed is 4.3~9.0 m/min at 25 °C, 4.7~8.7 m/min at 30 °C and 5.2~8.6 m/min at 35 °C, whereas in winter (−10, −5, and 0 °C), the optimum hot air welding temperature is 3~4.1 m/min at −10 °C, 3~4.6 m/min at −5 °C and 3~4.9 m/min at 0 °C. Research results demonstrate that it is imperative to consider the welding speed in accordance to the respective seasonal temperature conditions to secure construction quality of the EVA joints for roofing. Full article
(This article belongs to the Special Issue Concrete and Waterproofing Materials: Development of Waterproofing Technology for Buildings and Civil Concrete Structures)
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15 pages, 938 KiB  
Review
A Review of Polarization-Sensitive Materials for Polarization Holography
by Yueyang Zhai, Li Cao, Ying Liu and Xiaodi Tan
Materials 2020, 13(23), 5562; https://doi.org/10.3390/ma13235562 - 6 Dec 2020
Cited by 48 | Viewed by 4525
Abstract
Polarization holography has the unique capacity to record and retrieve the amplitude, phase, and polarization of light simultaneously in a polarization-sensitive recording material and has attracted widespread attention. Polarization holography is a noteworthy technology with potential applications in the fields of high-capacity data [...] Read more.
Polarization holography has the unique capacity to record and retrieve the amplitude, phase, and polarization of light simultaneously in a polarization-sensitive recording material and has attracted widespread attention. Polarization holography is a noteworthy technology with potential applications in the fields of high-capacity data storage, polarization-controlled optical elements, and other related fields. The choice of its high-performance materials is particularly important. To further develop polarization holography applications and improve the quality of the information recorded (i.e., material sensitivity and resolution), a deeper understanding of such materials is needed. We present an overview of the polarization-sensitive materials, which introduced polarization holographic technology and the development of polarization holographic materials. The three main types of polarization holographic materials are described, including azopolymer materials, photopolymer material, and photorefractive polymer material. We examine the key contributions of each work and present many of the suggestions that have been made to improve the different polarization-sensitive photopolymer materials. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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13 pages, 5272 KiB  
Article
Characterization and Optimization of Elastomeric Electrodes for Dielectric Elastomer Artificial Muscles
by Guangqiang Ma, Xiaojun Wu, Lijin Chen, Xin Tong and Weiwei Zhao
Materials 2020, 13(23), 5542; https://doi.org/10.3390/ma13235542 - 4 Dec 2020
Cited by 11 | Viewed by 3077
Abstract
Dielectric elastomer actuators (DEAs) are an emerging type of soft actuation technology. As a fundamental unit of a DEA, the characteristics of compliant electrodes play a crucial role in the actuation performances of DEAs. Generally, the compliant electrodes can be categorized into uncured [...] Read more.
Dielectric elastomer actuators (DEAs) are an emerging type of soft actuation technology. As a fundamental unit of a DEA, the characteristics of compliant electrodes play a crucial role in the actuation performances of DEAs. Generally, the compliant electrodes can be categorized into uncured and cured types, of which the cured one commonly involves mixing conductive particles into an elastomeric matrix before curing, thus demonstrating a better long-term performance. Along with the increasing proportion of conductive particles, the electrical conductivity increases at the cost of a stiffer electrode and lower elongation at break ratio. For different DEA applications, it can be more desirable to minimize the electrode stiffness or to maximize its conductivity. In examination of the papers published in recent years, few works have characterized the effects of elastomeric electrodes on the outputs of DEAs, or of their optimizations under different application scenarios. In this work, we propose an experimental framework to characterize the performances of elastomeric electrodes with different formulas based on the two key parameters of stiffness and conductivity. An optimizing method is developed and verified by two different application cases (e.g., quasi-static and dynamic). The findings and the methods developed in this work can offer potential approaches for developing high-performance DEAs. Full article
(This article belongs to the Section Smart Materials)
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13 pages, 4497 KiB  
Article
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 3738
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  
Article
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 20 | Viewed by 3242
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  
Article
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 2635
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  
Article
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 2538
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  
Article
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 19 | Viewed by 3342
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  
Article
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 27 | Viewed by 3147
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  
Article
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 2437
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  
Article
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 92 | Viewed by 7042
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  
Article
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 3922
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  
Article
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 26 | Viewed by 4204
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  
Article
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 31 | Viewed by 2781
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  
Review
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 12 | Viewed by 3240
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  
Article
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 2382
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  
Review
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 31 | Viewed by 5944
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  
Article
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 2755
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  
Article
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 2437
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  
Article
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 11 | Viewed by 2685
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  
Article
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 2690
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  
Article
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 1924
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  
Article
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 3344
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  
Review
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 139 | Viewed by 14851
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  
Article
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 6 | Viewed by 2177
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  
Article
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 2488
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  
Article
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 2118
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  
Article
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 2403
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  
Article
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 35 | Viewed by 3615
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  
Article
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 3581
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  
Review
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 3767
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  
Article
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 2686
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  
Article
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 9 | Viewed by 3519
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  
Article
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 10 | Viewed by 2759
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  
Article
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 45 | Viewed by 5055
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  
Article
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 3700
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  
Article
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 3991
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  
Article
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 3191
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  
Article
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 2746
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  
Article
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 32 | Viewed by 3572
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  
Article
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 2040
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  
Article
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 3208
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  
Article
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 2848
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  
Article
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 3692
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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